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| author | ed <ed@FreeBSD.org> | 2009-06-02 17:52:33 +0000 |
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| committer | ed <ed@FreeBSD.org> | 2009-06-02 17:52:33 +0000 |
| commit | 3277b69d734b9c90b44ebde4ede005717e2c3b2e (patch) | |
| tree | 64ba909838c23261cace781ece27d106134ea451 /docs/LangRef.html | |
| download | FreeBSD-src-3277b69d734b9c90b44ebde4ede005717e2c3b2e.zip FreeBSD-src-3277b69d734b9c90b44ebde4ede005717e2c3b2e.tar.gz | |
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diff --git a/docs/LangRef.html b/docs/LangRef.html new file mode 100644 index 0000000..32441cc --- /dev/null +++ b/docs/LangRef.html @@ -0,0 +1,7111 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" + "http://www.w3.org/TR/html4/strict.dtd"> +<html> +<head> + <title>LLVM Assembly Language Reference Manual</title> + <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> + <meta name="author" content="Chris Lattner"> + <meta name="description" + content="LLVM Assembly Language Reference Manual."> + <link rel="stylesheet" href="llvm.css" type="text/css"> +</head> + +<body> + +<div class="doc_title"> LLVM Language Reference Manual </div> +<ol> + <li><a href="#abstract">Abstract</a></li> + <li><a href="#introduction">Introduction</a></li> + <li><a href="#identifiers">Identifiers</a></li> + <li><a href="#highlevel">High Level Structure</a> + <ol> + <li><a href="#modulestructure">Module Structure</a></li> + <li><a href="#linkage">Linkage Types</a></li> + <li><a href="#callingconv">Calling Conventions</a></li> + <li><a href="#namedtypes">Named Types</a></li> + <li><a href="#globalvars">Global Variables</a></li> + <li><a href="#functionstructure">Functions</a></li> + <li><a href="#aliasstructure">Aliases</a></li> + <li><a href="#paramattrs">Parameter Attributes</a></li> + <li><a href="#fnattrs">Function Attributes</a></li> + <li><a href="#gc">Garbage Collector Names</a></li> + <li><a href="#moduleasm">Module-Level Inline Assembly</a></li> + <li><a href="#datalayout">Data Layout</a></li> + </ol> + </li> + <li><a href="#typesystem">Type System</a> + <ol> + <li><a href="#t_classifications">Type Classifications</a></li> + <li><a href="#t_primitive">Primitive Types</a> + <ol> + <li><a href="#t_floating">Floating Point Types</a></li> + <li><a href="#t_void">Void Type</a></li> + <li><a href="#t_label">Label Type</a></li> + <li><a href="#t_metadata">Metadata Type</a></li> + </ol> + </li> + <li><a href="#t_derived">Derived Types</a> + <ol> + <li><a href="#t_integer">Integer Type</a></li> + <li><a href="#t_array">Array Type</a></li> + <li><a href="#t_function">Function Type</a></li> + <li><a href="#t_pointer">Pointer Type</a></li> + <li><a href="#t_struct">Structure Type</a></li> + <li><a href="#t_pstruct">Packed Structure Type</a></li> + <li><a href="#t_vector">Vector Type</a></li> + <li><a href="#t_opaque">Opaque Type</a></li> + </ol> + </li> + <li><a href="#t_uprefs">Type Up-references</a></li> + </ol> + </li> + <li><a href="#constants">Constants</a> + <ol> + <li><a href="#simpleconstants">Simple Constants</a></li> + <li><a href="#complexconstants">Complex Constants</a></li> + <li><a href="#globalconstants">Global Variable and Function Addresses</a></li> + <li><a href="#undefvalues">Undefined Values</a></li> + <li><a href="#constantexprs">Constant Expressions</a></li> + <li><a href="#metadata">Embedded Metadata</a></li> + </ol> + </li> + <li><a href="#othervalues">Other Values</a> + <ol> + <li><a href="#inlineasm">Inline Assembler Expressions</a></li> + </ol> + </li> + <li><a href="#instref">Instruction Reference</a> + <ol> + <li><a href="#terminators">Terminator Instructions</a> + <ol> + <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li> + <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li> + <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li> + <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li> + <li><a href="#i_unwind">'<tt>unwind</tt>' Instruction</a></li> + <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li> + </ol> + </li> + <li><a href="#binaryops">Binary Operations</a> + <ol> + <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li> + <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li> + <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li> + <li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li> + <li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li> + <li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li> + <li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li> + <li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li> + <li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li> + </ol> + </li> + <li><a href="#bitwiseops">Bitwise Binary Operations</a> + <ol> + <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li> + <li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li> + <li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li> + <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li> + <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li> + <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li> + </ol> + </li> + <li><a href="#vectorops">Vector Operations</a> + <ol> + <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li> + <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li> + <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li> + </ol> + </li> + <li><a href="#aggregateops">Aggregate Operations</a> + <ol> + <li><a href="#i_extractvalue">'<tt>extractvalue</tt>' Instruction</a></li> + <li><a href="#i_insertvalue">'<tt>insertvalue</tt>' Instruction</a></li> + </ol> + </li> + <li><a href="#memoryops">Memory Access and Addressing Operations</a> + <ol> + <li><a href="#i_malloc">'<tt>malloc</tt>' Instruction</a></li> + <li><a href="#i_free">'<tt>free</tt>' Instruction</a></li> + <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li> + <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li> + <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li> + <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li> + </ol> + </li> + <li><a href="#convertops">Conversion Operations</a> + <ol> + <li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li> + <li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li> + <li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li> + <li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li> + <li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li> + <li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li> + <li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li> + <li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li> + <li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li> + <li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li> + <li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li> + <li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li> + </ol> + </li> + <li><a href="#otherops">Other Operations</a> + <ol> + <li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li> + <li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li> + <li><a href="#i_vicmp">'<tt>vicmp</tt>' Instruction</a></li> + <li><a href="#i_vfcmp">'<tt>vfcmp</tt>' Instruction</a></li> + <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li> + <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li> + <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li> + <li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li> + </ol> + </li> + </ol> + </li> + <li><a href="#intrinsics">Intrinsic Functions</a> + <ol> + <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a> + <ol> + <li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li> + <li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li> + <li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li> + </ol> + </li> + <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a> + <ol> + <li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li> + <li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li> + <li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li> + </ol> + </li> + <li><a href="#int_codegen">Code Generator Intrinsics</a> + <ol> + <li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li> + <li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li> + <li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li> + <li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li> + <li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li> + <li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li> + <li><a href="#int_readcyclecounter"><tt>llvm.readcyclecounter</tt>' Intrinsic</a></li> + </ol> + </li> + <li><a href="#int_libc">Standard C Library Intrinsics</a> + <ol> + <li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li> + <li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li> + <li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li> + <li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li> + <li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li> + <li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li> + <li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li> + <li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li> + </ol> + </li> + <li><a href="#int_manip">Bit Manipulation Intrinsics</a> + <ol> + <li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li> + <li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li> + <li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li> + <li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li> + <li><a href="#int_part_select">'<tt>llvm.part.select.*</tt>' Intrinsic </a></li> + <li><a href="#int_part_set">'<tt>llvm.part.set.*</tt>' Intrinsic </a></li> + </ol> + </li> + <li><a href="#int_overflow">Arithmetic with Overflow Intrinsics</a> + <ol> + <li><a href="#int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt> Intrinsics</a></li> + <li><a href="#int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt> Intrinsics</a></li> + <li><a href="#int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt> Intrinsics</a></li> + <li><a href="#int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt> Intrinsics</a></li> + <li><a href="#int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt> Intrinsics</a></li> + <li><a href="#int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt> Intrinsics</a></li> + </ol> + </li> + <li><a href="#int_debugger">Debugger intrinsics</a></li> + <li><a href="#int_eh">Exception Handling intrinsics</a></li> + <li><a href="#int_trampoline">Trampoline Intrinsic</a> + <ol> + <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li> + </ol> + </li> + <li><a href="#int_atomics">Atomic intrinsics</a> + <ol> + <li><a href="#int_memory_barrier"><tt>llvm.memory_barrier</tt></a></li> + <li><a href="#int_atomic_cmp_swap"><tt>llvm.atomic.cmp.swap</tt></a></li> + <li><a href="#int_atomic_swap"><tt>llvm.atomic.swap</tt></a></li> + <li><a href="#int_atomic_load_add"><tt>llvm.atomic.load.add</tt></a></li> + <li><a href="#int_atomic_load_sub"><tt>llvm.atomic.load.sub</tt></a></li> + <li><a href="#int_atomic_load_and"><tt>llvm.atomic.load.and</tt></a></li> + <li><a href="#int_atomic_load_nand"><tt>llvm.atomic.load.nand</tt></a></li> + <li><a href="#int_atomic_load_or"><tt>llvm.atomic.load.or</tt></a></li> + <li><a href="#int_atomic_load_xor"><tt>llvm.atomic.load.xor</tt></a></li> + <li><a href="#int_atomic_load_max"><tt>llvm.atomic.load.max</tt></a></li> + <li><a href="#int_atomic_load_min"><tt>llvm.atomic.load.min</tt></a></li> + <li><a href="#int_atomic_load_umax"><tt>llvm.atomic.load.umax</tt></a></li> + <li><a href="#int_atomic_load_umin"><tt>llvm.atomic.load.umin</tt></a></li> + </ol> + </li> + <li><a href="#int_general">General intrinsics</a> + <ol> + <li><a href="#int_var_annotation"> + '<tt>llvm.var.annotation</tt>' Intrinsic</a></li> + <li><a href="#int_annotation"> + '<tt>llvm.annotation.*</tt>' Intrinsic</a></li> + <li><a href="#int_trap"> + '<tt>llvm.trap</tt>' Intrinsic</a></li> + <li><a href="#int_stackprotector"> + '<tt>llvm.stackprotector</tt>' Intrinsic</a></li> + </ol> + </li> + </ol> + </li> +</ol> + +<div class="doc_author"> + <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a> + and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="abstract">Abstract </a></div> +<!-- *********************************************************************** --> + +<div class="doc_text"> +<p>This document is a reference manual for the LLVM assembly language. +LLVM is a Static Single Assignment (SSA) based representation that provides +type safety, low-level operations, flexibility, and the capability of +representing 'all' high-level languages cleanly. It is the common code +representation used throughout all phases of the LLVM compilation +strategy.</p> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="introduction">Introduction</a> </div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>The LLVM code representation is designed to be used in three +different forms: as an in-memory compiler IR, as an on-disk bitcode +representation (suitable for fast loading by a Just-In-Time compiler), +and as a human readable assembly language representation. This allows +LLVM to provide a powerful intermediate representation for efficient +compiler transformations and analysis, while providing a natural means +to debug and visualize the transformations. The three different forms +of LLVM are all equivalent. This document describes the human readable +representation and notation.</p> + +<p>The LLVM representation aims to be light-weight and low-level +while being expressive, typed, and extensible at the same time. It +aims to be a "universal IR" of sorts, by being at a low enough level +that high-level ideas may be cleanly mapped to it (similar to how +microprocessors are "universal IR's", allowing many source languages to +be mapped to them). By providing type information, LLVM can be used as +the target of optimizations: for example, through pointer analysis, it +can be proven that a C automatic variable is never accessed outside of +the current function... allowing it to be promoted to a simple SSA +value instead of a memory location.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div> + +<div class="doc_text"> + +<p>It is important to note that this document describes 'well formed' +LLVM assembly language. There is a difference between what the parser +accepts and what is considered 'well formed'. For example, the +following instruction is syntactically okay, but not well formed:</p> + +<div class="doc_code"> +<pre> +%x = <a href="#i_add">add</a> i32 1, %x +</pre> +</div> + +<p>...because the definition of <tt>%x</tt> does not dominate all of +its uses. The LLVM infrastructure provides a verification pass that may +be used to verify that an LLVM module is well formed. This pass is +automatically run by the parser after parsing input assembly and by +the optimizer before it outputs bitcode. The violations pointed out +by the verifier pass indicate bugs in transformation passes or input to +the parser.</p> +</div> + +<!-- Describe the typesetting conventions here. --> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="identifiers">Identifiers</a> </div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + + <p>LLVM identifiers come in two basic types: global and local. Global + identifiers (functions, global variables) begin with the @ character. Local + identifiers (register names, types) begin with the % character. Additionally, + there are three different formats for identifiers, for different purposes:</p> + +<ol> + <li>Named values are represented as a string of characters with their prefix. + For example, %foo, @DivisionByZero, %a.really.long.identifier. The actual + regular expression used is '<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'. + Identifiers which require other characters in their names can be surrounded + with quotes. Special characters may be escaped using "\xx" where xx is the + ASCII code for the character in hexadecimal. In this way, any character can + be used in a name value, even quotes themselves. + + <li>Unnamed values are represented as an unsigned numeric value with their + prefix. For example, %12, @2, %44.</li> + + <li>Constants, which are described in a <a href="#constants">section about + constants</a>, below.</li> +</ol> + +<p>LLVM requires that values start with a prefix for two reasons: Compilers +don't need to worry about name clashes with reserved words, and the set of +reserved words may be expanded in the future without penalty. Additionally, +unnamed identifiers allow a compiler to quickly come up with a temporary +variable without having to avoid symbol table conflicts.</p> + +<p>Reserved words in LLVM are very similar to reserved words in other +languages. There are keywords for different opcodes +('<tt><a href="#i_add">add</a></tt>', + '<tt><a href="#i_bitcast">bitcast</a></tt>', + '<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names ('<tt><a +href="#t_void">void</a></tt>', '<tt><a href="#t_primitive">i32</a></tt>', etc...), +and others. These reserved words cannot conflict with variable names, because +none of them start with a prefix character ('%' or '@').</p> + +<p>Here is an example of LLVM code to multiply the integer variable +'<tt>%X</tt>' by 8:</p> + +<p>The easy way:</p> + +<div class="doc_code"> +<pre> +%result = <a href="#i_mul">mul</a> i32 %X, 8 +</pre> +</div> + +<p>After strength reduction:</p> + +<div class="doc_code"> +<pre> +%result = <a href="#i_shl">shl</a> i32 %X, i8 3 +</pre> +</div> + +<p>And the hard way:</p> + +<div class="doc_code"> +<pre> +<a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i> +<a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i> +%result = <a href="#i_add">add</a> i32 %1, %1 +</pre> +</div> + +<p>This last way of multiplying <tt>%X</tt> by 8 illustrates several +important lexical features of LLVM:</p> + +<ol> + + <li>Comments are delimited with a '<tt>;</tt>' and go until the end of + line.</li> + + <li>Unnamed temporaries are created when the result of a computation is not + assigned to a named value.</li> + + <li>Unnamed temporaries are numbered sequentially</li> + +</ol> + +<p>...and it also shows a convention that we follow in this document. When +demonstrating instructions, we will follow an instruction with a comment that +defines the type and name of value produced. Comments are shown in italic +text.</p> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="highlevel">High Level Structure</a> </div> +<!-- *********************************************************************** --> + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="modulestructure">Module Structure</a> +</div> + +<div class="doc_text"> + +<p>LLVM programs are composed of "Module"s, each of which is a +translation unit of the input programs. Each module consists of +functions, global variables, and symbol table entries. Modules may be +combined together with the LLVM linker, which merges function (and +global variable) definitions, resolves forward declarations, and merges +symbol table entries. Here is an example of the "hello world" module:</p> + +<div class="doc_code"> +<pre><i>; Declare the string constant as a global constant...</i> +<a href="#identifiers">@.LC0</a> = <a href="#linkage_internal">internal</a> <a + href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" <i>; [13 x i8]*</i> + +<i>; External declaration of the puts function</i> +<a href="#functionstructure">declare</a> i32 @puts(i8 *) <i>; i32(i8 *)* </i> + +<i>; Definition of main function</i> +define i32 @main() { <i>; i32()* </i> + <i>; Convert [13 x i8]* to i8 *...</i> + %cast210 = <a + href="#i_getelementptr">getelementptr</a> [13 x i8]* @.LC0, i64 0, i64 0 <i>; i8 *</i> + + <i>; Call puts function to write out the string to stdout...</i> + <a + href="#i_call">call</a> i32 @puts(i8 * %cast210) <i>; i32</i> + <a + href="#i_ret">ret</a> i32 0<br>}<br> +</pre> +</div> + +<p>This example is made up of a <a href="#globalvars">global variable</a> +named "<tt>.LC0</tt>", an external declaration of the "<tt>puts</tt>" +function, and a <a href="#functionstructure">function definition</a> +for "<tt>main</tt>".</p> + +<p>In general, a module is made up of a list of global values, +where both functions and global variables are global values. Global values are +represented by a pointer to a memory location (in this case, a pointer to an +array of char, and a pointer to a function), and have one of the following <a +href="#linkage">linkage types</a>.</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="linkage">Linkage Types</a> +</div> + +<div class="doc_text"> + +<p> +All Global Variables and Functions have one of the following types of linkage: +</p> + +<dl> + + <dt><tt><b><a name="linkage_private">private</a></b></tt>: </dt> + + <dd>Global values with private linkage are only directly accessible by + objects in the current module. In particular, linking code into a module with + an private global value may cause the private to be renamed as necessary to + avoid collisions. Because the symbol is private to the module, all + references can be updated. This doesn't show up in any symbol table in the + object file. + </dd> + + <dt><tt><b><a name="linkage_internal">internal</a></b></tt>: </dt> + + <dd> Similar to private, but the value shows as a local symbol (STB_LOCAL in + the case of ELF) in the object file. This corresponds to the notion of the + '<tt>static</tt>' keyword in C. + </dd> + + <dt><tt><b><a name="available_externally">available_externally</a></b></tt>: + </dt> + + <dd>Globals with "<tt>available_externally</tt>" linkage are never emitted + into the object file corresponding to the LLVM module. They exist to + allow inlining and other optimizations to take place given knowledge of the + definition of the global, which is known to be somewhere outside the module. + Globals with <tt>available_externally</tt> linkage are allowed to be discarded + at will, and are otherwise the same as <tt>linkonce_odr</tt>. This linkage + type is only allowed on definitions, not declarations.</dd> + + <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt> + + <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of + the same name when linkage occurs. This is typically used to implement + inline functions, templates, or other code which must be generated in each + translation unit that uses it. Unreferenced <tt>linkonce</tt> globals are + allowed to be discarded. + </dd> + + <dt><tt><b><a name="linkage_common">common</a></b></tt>: </dt> + + <dd>"<tt>common</tt>" linkage is exactly the same as <tt>linkonce</tt> + linkage, except that unreferenced <tt>common</tt> globals may not be + discarded. This is used for globals that may be emitted in multiple + translation units, but that are not guaranteed to be emitted into every + translation unit that uses them. One example of this is tentative + definitions in C, such as "<tt>int X;</tt>" at global scope. + </dd> + + <dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt> + + <dd>"<tt>weak</tt>" linkage is the same as <tt>common</tt> linkage, except + that some targets may choose to emit different assembly sequences for them + for target-dependent reasons. This is used for globals that are declared + "weak" in C source code. + </dd> + + <dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt> + + <dd>"<tt>appending</tt>" linkage may only be applied to global variables of + pointer to array type. When two global variables with appending linkage are + linked together, the two global arrays are appended together. This is the + LLVM, typesafe, equivalent of having the system linker append together + "sections" with identical names when .o files are linked. + </dd> + + <dt><tt><b><a name="linkage_externweak">extern_weak</a></b></tt>: </dt> + + <dd>The semantics of this linkage follow the ELF object file model: the + symbol is weak until linked, if not linked, the symbol becomes null instead + of being an undefined reference. + </dd> + + <dt><tt><b><a name="linkage_linkonce">linkonce_odr</a></b></tt>: </dt> + <dt><tt><b><a name="linkage_weak">weak_odr</a></b></tt>: </dt> + <dd>Some languages allow differing globals to be merged, such as two + functions with different semantics. Other languages, such as <tt>C++</tt>, + ensure that only equivalent globals are ever merged (the "one definition + rule" - "ODR"). Such languages can use the <tt>linkonce_odr</tt> + and <tt>weak_odr</tt> linkage types to indicate that the global will only + be merged with equivalent globals. These linkage types are otherwise the + same as their non-<tt>odr</tt> versions. + </dd> + + <dt><tt><b><a name="linkage_external">externally visible</a></b></tt>:</dt> + + <dd>If none of the above identifiers are used, the global is externally + visible, meaning that it participates in linkage and can be used to resolve + external symbol references. + </dd> +</dl> + + <p> + The next two types of linkage are targeted for Microsoft Windows platform + only. They are designed to support importing (exporting) symbols from (to) + DLLs (Dynamic Link Libraries). + </p> + + <dl> + <dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt>: </dt> + + <dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function + or variable via a global pointer to a pointer that is set up by the DLL + exporting the symbol. On Microsoft Windows targets, the pointer name is + formed by combining <code>__imp_</code> and the function or variable name. + </dd> + + <dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt>: </dt> + + <dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global + pointer to a pointer in a DLL, so that it can be referenced with the + <tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer + name is formed by combining <code>__imp_</code> and the function or variable + name. + </dd> + +</dl> + +<p>For example, since the "<tt>.LC0</tt>" +variable is defined to be internal, if another module defined a "<tt>.LC0</tt>" +variable and was linked with this one, one of the two would be renamed, +preventing a collision. Since "<tt>main</tt>" and "<tt>puts</tt>" are +external (i.e., lacking any linkage declarations), they are accessible +outside of the current module.</p> +<p>It is illegal for a function <i>declaration</i> +to have any linkage type other than "externally visible", <tt>dllimport</tt> +or <tt>extern_weak</tt>.</p> +<p>Aliases can have only <tt>external</tt>, <tt>internal</tt>, <tt>weak</tt> +or <tt>weak_odr</tt> linkages.</p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="callingconv">Calling Conventions</a> +</div> + +<div class="doc_text"> + +<p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a> +and <a href="#i_invoke">invokes</a> can all have an optional calling convention +specified for the call. The calling convention of any pair of dynamic +caller/callee must match, or the behavior of the program is undefined. The +following calling conventions are supported by LLVM, and more may be added in +the future:</p> + +<dl> + <dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt> + + <dd>This calling convention (the default if no other calling convention is + specified) matches the target C calling conventions. This calling convention + supports varargs function calls and tolerates some mismatch in the declared + prototype and implemented declaration of the function (as does normal C). + </dd> + + <dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt> + + <dd>This calling convention attempts to make calls as fast as possible + (e.g. by passing things in registers). This calling convention allows the + target to use whatever tricks it wants to produce fast code for the target, + without having to conform to an externally specified ABI (Application Binary + Interface). Implementations of this convention should allow arbitrary + <a href="CodeGenerator.html#tailcallopt">tail call optimization</a> to be + supported. This calling convention does not support varargs and requires the + prototype of all callees to exactly match the prototype of the function + definition. + </dd> + + <dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt> + + <dd>This calling convention attempts to make code in the caller as efficient + as possible under the assumption that the call is not commonly executed. As + such, these calls often preserve all registers so that the call does not break + any live ranges in the caller side. This calling convention does not support + varargs and requires the prototype of all callees to exactly match the + prototype of the function definition. + </dd> + + <dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt> + + <dd>Any calling convention may be specified by number, allowing + target-specific calling conventions to be used. Target specific calling + conventions start at 64. + </dd> +</dl> + +<p>More calling conventions can be added/defined on an as-needed basis, to +support pascal conventions or any other well-known target-independent +convention.</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="visibility">Visibility Styles</a> +</div> + +<div class="doc_text"> + +<p> +All Global Variables and Functions have one of the following visibility styles: +</p> + +<dl> + <dt><b>"<tt>default</tt>" - Default style</b>:</dt> + + <dd>On targets that use the ELF object file format, default visibility means + that the declaration is visible to other + modules and, in shared libraries, means that the declared entity may be + overridden. On Darwin, default visibility means that the declaration is + visible to other modules. Default visibility corresponds to "external + linkage" in the language. + </dd> + + <dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt> + + <dd>Two declarations of an object with hidden visibility refer to the same + object if they are in the same shared object. Usually, hidden visibility + indicates that the symbol will not be placed into the dynamic symbol table, + so no other module (executable or shared library) can reference it + directly. + </dd> + + <dt><b>"<tt>protected</tt>" - Protected style</b>:</dt> + + <dd>On ELF, protected visibility indicates that the symbol will be placed in + the dynamic symbol table, but that references within the defining module will + bind to the local symbol. That is, the symbol cannot be overridden by another + module. + </dd> +</dl> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="namedtypes">Named Types</a> +</div> + +<div class="doc_text"> + +<p>LLVM IR allows you to specify name aliases for certain types. This can make +it easier to read the IR and make the IR more condensed (particularly when +recursive types are involved). An example of a name specification is: +</p> + +<div class="doc_code"> +<pre> +%mytype = type { %mytype*, i32 } +</pre> +</div> + +<p>You may give a name to any <a href="#typesystem">type</a> except "<a +href="t_void">void</a>". Type name aliases may be used anywhere a type is +expected with the syntax "%mytype".</p> + +<p>Note that type names are aliases for the structural type that they indicate, +and that you can therefore specify multiple names for the same type. This often +leads to confusing behavior when dumping out a .ll file. Since LLVM IR uses +structural typing, the name is not part of the type. When printing out LLVM IR, +the printer will pick <em>one name</em> to render all types of a particular +shape. This means that if you have code where two different source types end up +having the same LLVM type, that the dumper will sometimes print the "wrong" or +unexpected type. This is an important design point and isn't going to +change.</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="globalvars">Global Variables</a> +</div> + +<div class="doc_text"> + +<p>Global variables define regions of memory allocated at compilation time +instead of run-time. Global variables may optionally be initialized, may have +an explicit section to be placed in, and may have an optional explicit alignment +specified. A variable may be defined as "thread_local", which means that it +will not be shared by threads (each thread will have a separated copy of the +variable). A variable may be defined as a global "constant," which indicates +that the contents of the variable will <b>never</b> be modified (enabling better +optimization, allowing the global data to be placed in the read-only section of +an executable, etc). Note that variables that need runtime initialization +cannot be marked "constant" as there is a store to the variable.</p> + +<p> +LLVM explicitly allows <em>declarations</em> of global variables to be marked +constant, even if the final definition of the global is not. This capability +can be used to enable slightly better optimization of the program, but requires +the language definition to guarantee that optimizations based on the +'constantness' are valid for the translation units that do not include the +definition. +</p> + +<p>As SSA values, global variables define pointer values that are in +scope (i.e. they dominate) all basic blocks in the program. Global +variables always define a pointer to their "content" type because they +describe a region of memory, and all memory objects in LLVM are +accessed through pointers.</p> + +<p>A global variable may be declared to reside in a target-specifc numbered +address space. For targets that support them, address spaces may affect how +optimizations are performed and/or what target instructions are used to access +the variable. The default address space is zero. The address space qualifier +must precede any other attributes.</p> + +<p>LLVM allows an explicit section to be specified for globals. If the target +supports it, it will emit globals to the section specified.</p> + +<p>An explicit alignment may be specified for a global. If not present, or if +the alignment is set to zero, the alignment of the global is set by the target +to whatever it feels convenient. If an explicit alignment is specified, the +global is forced to have at least that much alignment. All alignments must be +a power of 2.</p> + +<p>For example, the following defines a global in a numbered address space with +an initializer, section, and alignment:</p> + +<div class="doc_code"> +<pre> +@G = addrspace(5) constant float 1.0, section "foo", align 4 +</pre> +</div> + +</div> + + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="functionstructure">Functions</a> +</div> + +<div class="doc_text"> + +<p>LLVM function definitions consist of the "<tt>define</tt>" keyord, +an optional <a href="#linkage">linkage type</a>, an optional +<a href="#visibility">visibility style</a>, an optional +<a href="#callingconv">calling convention</a>, a return type, an optional +<a href="#paramattrs">parameter attribute</a> for the return type, a function +name, a (possibly empty) argument list (each with optional +<a href="#paramattrs">parameter attributes</a>), optional +<a href="#fnattrs">function attributes</a>, an optional section, +an optional alignment, an optional <a href="#gc">garbage collector name</a>, +an opening curly brace, a list of basic blocks, and a closing curly brace. + +LLVM function declarations consist of the "<tt>declare</tt>" keyword, an +optional <a href="#linkage">linkage type</a>, an optional +<a href="#visibility">visibility style</a>, an optional +<a href="#callingconv">calling convention</a>, a return type, an optional +<a href="#paramattrs">parameter attribute</a> for the return type, a function +name, a possibly empty list of arguments, an optional alignment, and an optional +<a href="#gc">garbage collector name</a>.</p> + +<p>A function definition contains a list of basic blocks, forming the CFG +(Control Flow Graph) for +the function. Each basic block may optionally start with a label (giving the +basic block a symbol table entry), contains a list of instructions, and ends +with a <a href="#terminators">terminator</a> instruction (such as a branch or +function return).</p> + +<p>The first basic block in a function is special in two ways: it is immediately +executed on entrance to the function, and it is not allowed to have predecessor +basic blocks (i.e. there can not be any branches to the entry block of a +function). Because the block can have no predecessors, it also cannot have any +<a href="#i_phi">PHI nodes</a>.</p> + +<p>LLVM allows an explicit section to be specified for functions. If the target +supports it, it will emit functions to the section specified.</p> + +<p>An explicit alignment may be specified for a function. If not present, or if +the alignment is set to zero, the alignment of the function is set by the target +to whatever it feels convenient. If an explicit alignment is specified, the +function is forced to have at least that much alignment. All alignments must be +a power of 2.</p> + + <h5>Syntax:</h5> + +<div class="doc_code"> +<tt> +define [<a href="#linkage">linkage</a>] [<a href="#visibility">visibility</a>] + [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] + <ResultType> @<FunctionName> ([argument list]) + [<a href="#fnattrs">fn Attrs</a>] [section "name"] [align N] + [<a href="#gc">gc</a>] { ... } +</tt> +</div> + +</div> + + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="aliasstructure">Aliases</a> +</div> +<div class="doc_text"> + <p>Aliases act as "second name" for the aliasee value (which can be either + function, global variable, another alias or bitcast of global value). Aliases + may have an optional <a href="#linkage">linkage type</a>, and an + optional <a href="#visibility">visibility style</a>.</p> + + <h5>Syntax:</h5> + +<div class="doc_code"> +<pre> +@<Name> = alias [Linkage] [Visibility] <AliaseeTy> @<Aliasee> +</pre> +</div> + +</div> + + + +<!-- ======================================================================= --> +<div class="doc_subsection"><a name="paramattrs">Parameter Attributes</a></div> +<div class="doc_text"> + <p>The return type and each parameter of a function type may have a set of + <i>parameter attributes</i> associated with them. Parameter attributes are + used to communicate additional information about the result or parameters of + a function. Parameter attributes are considered to be part of the function, + not of the function type, so functions with different parameter attributes + can have the same function type.</p> + + <p>Parameter attributes are simple keywords that follow the type specified. If + multiple parameter attributes are needed, they are space separated. For + example:</p> + +<div class="doc_code"> +<pre> +declare i32 @printf(i8* noalias nocapture, ...) +declare i32 @atoi(i8 zeroext) +declare signext i8 @returns_signed_char() +</pre> +</div> + + <p>Note that any attributes for the function result (<tt>nounwind</tt>, + <tt>readonly</tt>) come immediately after the argument list.</p> + + <p>Currently, only the following parameter attributes are defined:</p> + <dl> + <dt><tt>zeroext</tt></dt> + <dd>This indicates to the code generator that the parameter or return value + should be zero-extended to a 32-bit value by the caller (for a parameter) + or the callee (for a return value).</dd> + + <dt><tt>signext</tt></dt> + <dd>This indicates to the code generator that the parameter or return value + should be sign-extended to a 32-bit value by the caller (for a parameter) + or the callee (for a return value).</dd> + + <dt><tt>inreg</tt></dt> + <dd>This indicates that this parameter or return value should be treated + in a special target-dependent fashion during while emitting code for a + function call or return (usually, by putting it in a register as opposed + to memory, though some targets use it to distinguish between two different + kinds of registers). Use of this attribute is target-specific.</dd> + + <dt><tt><a name="byval">byval</a></tt></dt> + <dd>This indicates that the pointer parameter should really be passed by + value to the function. The attribute implies that a hidden copy of the + pointee is made between the caller and the callee, so the callee is unable + to modify the value in the callee. This attribute is only valid on LLVM + pointer arguments. It is generally used to pass structs and arrays by + value, but is also valid on pointers to scalars. The copy is considered to + belong to the caller not the callee (for example, + <tt><a href="#readonly">readonly</a></tt> functions should not write to + <tt>byval</tt> parameters). This is not a valid attribute for return + values. The byval attribute also supports specifying an alignment with the + align attribute. This has a target-specific effect on the code generator + that usually indicates a desired alignment for the synthesized stack + slot.</dd> + + <dt><tt>sret</tt></dt> + <dd>This indicates that the pointer parameter specifies the address of a + structure that is the return value of the function in the source program. + This pointer must be guaranteed by the caller to be valid: loads and stores + to the structure may be assumed by the callee to not to trap. This may only + be applied to the first parameter. This is not a valid attribute for + return values. </dd> + + <dt><tt>noalias</tt></dt> + <dd>This indicates that the pointer does not alias any global or any other + parameter. The caller is responsible for ensuring that this is the + case. On a function return value, <tt>noalias</tt> additionally indicates + that the pointer does not alias any other pointers visible to the + caller. For further details, please see the discussion of the NoAlias + response in + <a href="http://llvm.org/docs/AliasAnalysis.html#MustMayNo">alias + analysis</a>.</dd> + + <dt><tt>nocapture</tt></dt> + <dd>This indicates that the callee does not make any copies of the pointer + that outlive the callee itself. This is not a valid attribute for return + values.</dd> + + <dt><tt>nest</tt></dt> + <dd>This indicates that the pointer parameter can be excised using the + <a href="#int_trampoline">trampoline intrinsics</a>. This is not a valid + attribute for return values.</dd> + </dl> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="gc">Garbage Collector Names</a> +</div> + +<div class="doc_text"> +<p>Each function may specify a garbage collector name, which is simply a +string.</p> + +<div class="doc_code"><pre +>define void @f() gc "name" { ...</pre></div> + +<p>The compiler declares the supported values of <i>name</i>. Specifying a +collector which will cause the compiler to alter its output in order to support +the named garbage collection algorithm.</p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="fnattrs">Function Attributes</a> +</div> + +<div class="doc_text"> + +<p>Function attributes are set to communicate additional information about + a function. Function attributes are considered to be part of the function, + not of the function type, so functions with different parameter attributes + can have the same function type.</p> + + <p>Function attributes are simple keywords that follow the type specified. If + multiple attributes are needed, they are space separated. For + example:</p> + +<div class="doc_code"> +<pre> +define void @f() noinline { ... } +define void @f() alwaysinline { ... } +define void @f() alwaysinline optsize { ... } +define void @f() optsize +</pre> +</div> + +<dl> +<dt><tt>alwaysinline</tt></dt> +<dd>This attribute indicates that the inliner should attempt to inline this +function into callers whenever possible, ignoring any active inlining size +threshold for this caller.</dd> + +<dt><tt>noinline</tt></dt> +<dd>This attribute indicates that the inliner should never inline this function +in any situation. This attribute may not be used together with the +<tt>alwaysinline</tt> attribute.</dd> + +<dt><tt>optsize</tt></dt> +<dd>This attribute suggests that optimization passes and code generator passes +make choices that keep the code size of this function low, and otherwise do +optimizations specifically to reduce code size.</dd> + +<dt><tt>noreturn</tt></dt> +<dd>This function attribute indicates that the function never returns normally. +This produces undefined behavior at runtime if the function ever does +dynamically return.</dd> + +<dt><tt>nounwind</tt></dt> +<dd>This function attribute indicates that the function never returns with an +unwind or exceptional control flow. If the function does unwind, its runtime +behavior is undefined.</dd> + +<dt><tt>readnone</tt></dt> +<dd>This attribute indicates that the function computes its result (or decides to +unwind an exception) based strictly on its arguments, without dereferencing any +pointer arguments or otherwise accessing any mutable state (e.g. memory, control +registers, etc) visible to caller functions. It does not write through any +pointer arguments (including <tt><a href="#byval">byval</a></tt> arguments) and +never changes any state visible to callers. This means that it cannot unwind +exceptions by calling the <tt>C++</tt> exception throwing methods, but could +use the <tt>unwind</tt> instruction.</dd> + +<dt><tt><a name="readonly">readonly</a></tt></dt> +<dd>This attribute indicates that the function does not write through any +pointer arguments (including <tt><a href="#byval">byval</a></tt> arguments) +or otherwise modify any state (e.g. memory, control registers, etc) visible to +caller functions. It may dereference pointer arguments and read state that may +be set in the caller. A readonly function always returns the same value (or +unwinds an exception identically) when called with the same set of arguments +and global state. It cannot unwind an exception by calling the <tt>C++</tt> +exception throwing methods, but may use the <tt>unwind</tt> instruction.</dd> + +<dt><tt><a name="ssp">ssp</a></tt></dt> +<dd>This attribute indicates that the function should emit a stack smashing +protector. It is in the form of a "canary"—a random value placed on the +stack before the local variables that's checked upon return from the function to +see if it has been overwritten. A heuristic is used to determine if a function +needs stack protectors or not. + +<p>If a function that has an <tt>ssp</tt> attribute is inlined into a function +that doesn't have an <tt>ssp</tt> attribute, then the resulting function will +have an <tt>ssp</tt> attribute.</p></dd> + +<dt><tt>sspreq</tt></dt> +<dd>This attribute indicates that the function should <em>always</em> emit a +stack smashing protector. This overrides the <tt><a href="#ssp">ssp</a></tt> +function attribute. + +<p>If a function that has an <tt>sspreq</tt> attribute is inlined into a +function that doesn't have an <tt>sspreq</tt> attribute or which has +an <tt>ssp</tt> attribute, then the resulting function will have +an <tt>sspreq</tt> attribute.</p></dd> +</dl> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="moduleasm">Module-Level Inline Assembly</a> +</div> + +<div class="doc_text"> +<p> +Modules may contain "module-level inline asm" blocks, which corresponds to the +GCC "file scope inline asm" blocks. These blocks are internally concatenated by +LLVM and treated as a single unit, but may be separated in the .ll file if +desired. The syntax is very simple: +</p> + +<div class="doc_code"> +<pre> +module asm "inline asm code goes here" +module asm "more can go here" +</pre> +</div> + +<p>The strings can contain any character by escaping non-printable characters. + The escape sequence used is simply "\xx" where "xx" is the two digit hex code + for the number. +</p> + +<p> + The inline asm code is simply printed to the machine code .s file when + assembly code is generated. +</p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="datalayout">Data Layout</a> +</div> + +<div class="doc_text"> +<p>A module may specify a target specific data layout string that specifies how +data is to be laid out in memory. The syntax for the data layout is simply:</p> +<pre> target datalayout = "<i>layout specification</i>"</pre> +<p>The <i>layout specification</i> consists of a list of specifications +separated by the minus sign character ('-'). Each specification starts with a +letter and may include other information after the letter to define some +aspect of the data layout. The specifications accepted are as follows: </p> +<dl> + <dt><tt>E</tt></dt> + <dd>Specifies that the target lays out data in big-endian form. That is, the + bits with the most significance have the lowest address location.</dd> + <dt><tt>e</tt></dt> + <dd>Specifies that the target lays out data in little-endian form. That is, + the bits with the least significance have the lowest address location.</dd> + <dt><tt>p:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> + <dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and + <i>preferred</i> alignments. All sizes are in bits. Specifying the <i>pref</i> + alignment is optional. If omitted, the preceding <tt>:</tt> should be omitted + too.</dd> + <dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> + <dd>This specifies the alignment for an integer type of a given bit + <i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd> + <dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> + <dd>This specifies the alignment for a vector type of a given bit + <i>size</i>.</dd> + <dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> + <dd>This specifies the alignment for a floating point type of a given bit + <i>size</i>. The value of <i>size</i> must be either 32 (float) or 64 + (double).</dd> + <dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> + <dd>This specifies the alignment for an aggregate type of a given bit + <i>size</i>.</dd> +</dl> +<p>When constructing the data layout for a given target, LLVM starts with a +default set of specifications which are then (possibly) overriden by the +specifications in the <tt>datalayout</tt> keyword. The default specifications +are given in this list:</p> +<ul> + <li><tt>E</tt> - big endian</li> + <li><tt>p:32:64:64</tt> - 32-bit pointers with 64-bit alignment</li> + <li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li> + <li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li> + <li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li> + <li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li> + <li><tt>i64:32:64</tt> - i64 has ABI alignment of 32-bits but preferred + alignment of 64-bits</li> + <li><tt>f32:32:32</tt> - float is 32-bit aligned</li> + <li><tt>f64:64:64</tt> - double is 64-bit aligned</li> + <li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li> + <li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li> + <li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li> +</ul> +<p>When LLVM is determining the alignment for a given type, it uses the +following rules:</p> +<ol> + <li>If the type sought is an exact match for one of the specifications, that + specification is used.</li> + <li>If no match is found, and the type sought is an integer type, then the + smallest integer type that is larger than the bitwidth of the sought type is + used. If none of the specifications are larger than the bitwidth then the the + largest integer type is used. For example, given the default specifications + above, the i7 type will use the alignment of i8 (next largest) while both + i65 and i256 will use the alignment of i64 (largest specified).</li> + <li>If no match is found, and the type sought is a vector type, then the + largest vector type that is smaller than the sought vector type will be used + as a fall back. This happens because <128 x double> can be implemented + in terms of 64 <2 x double>, for example.</li> +</ol> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="typesystem">Type System</a> </div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>The LLVM type system is one of the most important features of the +intermediate representation. Being typed enables a number of +optimizations to be performed on the intermediate representation directly, +without having to do +extra analyses on the side before the transformation. A strong type +system makes it easier to read the generated code and enables novel +analyses and transformations that are not feasible to perform on normal +three address code representations.</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="t_classifications">Type +Classifications</a> </div> +<div class="doc_text"> +<p>The types fall into a few useful +classifications:</p> + +<table border="1" cellspacing="0" cellpadding="4"> + <tbody> + <tr><th>Classification</th><th>Types</th></tr> + <tr> + <td><a href="#t_integer">integer</a></td> + <td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td> + </tr> + <tr> + <td><a href="#t_floating">floating point</a></td> + <td><tt>float, double, x86_fp80, fp128, ppc_fp128</tt></td> + </tr> + <tr> + <td><a name="t_firstclass">first class</a></td> + <td><a href="#t_integer">integer</a>, + <a href="#t_floating">floating point</a>, + <a href="#t_pointer">pointer</a>, + <a href="#t_vector">vector</a>, + <a href="#t_struct">structure</a>, + <a href="#t_array">array</a>, + <a href="#t_label">label</a>, + <a href="#t_metadata">metadata</a>. + </td> + </tr> + <tr> + <td><a href="#t_primitive">primitive</a></td> + <td><a href="#t_label">label</a>, + <a href="#t_void">void</a>, + <a href="#t_floating">floating point</a>, + <a href="#t_metadata">metadata</a>.</td> + </tr> + <tr> + <td><a href="#t_derived">derived</a></td> + <td><a href="#t_integer">integer</a>, + <a href="#t_array">array</a>, + <a href="#t_function">function</a>, + <a href="#t_pointer">pointer</a>, + <a href="#t_struct">structure</a>, + <a href="#t_pstruct">packed structure</a>, + <a href="#t_vector">vector</a>, + <a href="#t_opaque">opaque</a>. + </td> + </tr> + </tbody> +</table> + +<p>The <a href="#t_firstclass">first class</a> types are perhaps the +most important. Values of these types are the only ones which can be +produced by instructions, passed as arguments, or used as operands to +instructions.</p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="t_primitive">Primitive Types</a> </div> + +<div class="doc_text"> +<p>The primitive types are the fundamental building blocks of the LLVM +system.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_floating">Floating Point Types</a> </div> + +<div class="doc_text"> + <table> + <tbody> + <tr><th>Type</th><th>Description</th></tr> + <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr> + <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr> + <tr><td><tt>fp128</tt></td><td>128-bit floating point value (112-bit mantissa)</td></tr> + <tr><td><tt>x86_fp80</tt></td><td>80-bit floating point value (X87)</td></tr> + <tr><td><tt>ppc_fp128</tt></td><td>128-bit floating point value (two 64-bits)</td></tr> + </tbody> + </table> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_void">Void Type</a> </div> + +<div class="doc_text"> +<h5>Overview:</h5> +<p>The void type does not represent any value and has no size.</p> + +<h5>Syntax:</h5> + +<pre> + void +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_label">Label Type</a> </div> + +<div class="doc_text"> +<h5>Overview:</h5> +<p>The label type represents code labels.</p> + +<h5>Syntax:</h5> + +<pre> + label +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_metadata">Metadata Type</a> </div> + +<div class="doc_text"> +<h5>Overview:</h5> +<p>The metadata type represents embedded metadata. The only derived type that +may contain metadata is <tt>metadata*</tt> or a function type that returns or +takes metadata typed parameters, but not pointer to metadata types.</p> + +<h5>Syntax:</h5> + +<pre> + metadata +</pre> +</div> + + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="t_derived">Derived Types</a> </div> + +<div class="doc_text"> + +<p>The real power in LLVM comes from the derived types in the system. +This is what allows a programmer to represent arrays, functions, +pointers, and other useful types. Note that these derived types may be +recursive: For example, it is possible to have a two dimensional array.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_integer">Integer Type</a> </div> + +<div class="doc_text"> + +<h5>Overview:</h5> +<p>The integer type is a very simple derived type that simply specifies an +arbitrary bit width for the integer type desired. Any bit width from 1 bit to +2^23-1 (about 8 million) can be specified.</p> + +<h5>Syntax:</h5> + +<pre> + iN +</pre> + +<p>The number of bits the integer will occupy is specified by the <tt>N</tt> +value.</p> + +<h5>Examples:</h5> +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>i1</tt></td> + <td class="left">a single-bit integer.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>i32</tt></td> + <td class="left">a 32-bit integer.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>i1942652</tt></td> + <td class="left">a really big integer of over 1 million bits.</td> + </tr> +</table> + +<p>Note that the code generator does not yet support large integer types +to be used as function return types. The specific limit on how large a +return type the code generator can currently handle is target-dependent; +currently it's often 64 bits for 32-bit targets and 128 bits for 64-bit +targets.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_array">Array Type</a> </div> + +<div class="doc_text"> + +<h5>Overview:</h5> + +<p>The array type is a very simple derived type that arranges elements +sequentially in memory. The array type requires a size (number of +elements) and an underlying data type.</p> + +<h5>Syntax:</h5> + +<pre> + [<# elements> x <elementtype>] +</pre> + +<p>The number of elements is a constant integer value; elementtype may +be any type with a size.</p> + +<h5>Examples:</h5> +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>[40 x i32]</tt></td> + <td class="left">Array of 40 32-bit integer values.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>[41 x i32]</tt></td> + <td class="left">Array of 41 32-bit integer values.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>[4 x i8]</tt></td> + <td class="left">Array of 4 8-bit integer values.</td> + </tr> +</table> +<p>Here are some examples of multidimensional arrays:</p> +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>[3 x [4 x i32]]</tt></td> + <td class="left">3x4 array of 32-bit integer values.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>[12 x [10 x float]]</tt></td> + <td class="left">12x10 array of single precision floating point values.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>[2 x [3 x [4 x i16]]]</tt></td> + <td class="left">2x3x4 array of 16-bit integer values.</td> + </tr> +</table> + +<p>Note that 'variable sized arrays' can be implemented in LLVM with a zero +length array. Normally, accesses past the end of an array are undefined in +LLVM (e.g. it is illegal to access the 5th element of a 3 element array). +As a special case, however, zero length arrays are recognized to be variable +length. This allows implementation of 'pascal style arrays' with the LLVM +type "{ i32, [0 x float]}", for example.</p> + +<p>Note that the code generator does not yet support large aggregate types +to be used as function return types. The specific limit on how large an +aggregate return type the code generator can currently handle is +target-dependent, and also dependent on the aggregate element types.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div> +<div class="doc_text"> + +<h5>Overview:</h5> + +<p>The function type can be thought of as a function signature. It +consists of a return type and a list of formal parameter types. The +return type of a function type is a scalar type, a void type, or a struct type. +If the return type is a struct type then all struct elements must be of first +class types, and the struct must have at least one element.</p> + +<h5>Syntax:</h5> + +<pre> + <returntype list> (<parameter list>) +</pre> + +<p>...where '<tt><parameter list></tt>' is a comma-separated list of type +specifiers. Optionally, the parameter list may include a type <tt>...</tt>, +which indicates that the function takes a variable number of arguments. +Variable argument functions can access their arguments with the <a + href="#int_varargs">variable argument handling intrinsic</a> functions. +'<tt><returntype list></tt>' is a comma-separated list of +<a href="#t_firstclass">first class</a> type specifiers.</p> + +<h5>Examples:</h5> +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>i32 (i32)</tt></td> + <td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt> + </td> + </tr><tr class="layout"> + <td class="left"><tt>float (i16 signext, i32 *) * + </tt></td> + <td class="left"><a href="#t_pointer">Pointer</a> to a function that takes + an <tt>i16</tt> that should be sign extended and a + <a href="#t_pointer">pointer</a> to <tt>i32</tt>, returning + <tt>float</tt>. + </td> + </tr><tr class="layout"> + <td class="left"><tt>i32 (i8*, ...)</tt></td> + <td class="left">A vararg function that takes at least one + <a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C), + which returns an integer. This is the signature for <tt>printf</tt> in + LLVM. + </td> + </tr><tr class="layout"> + <td class="left"><tt>{i32, i32} (i32)</tt></td> + <td class="left">A function taking an <tt>i32</tt>, returning two + <tt>i32</tt> values as an aggregate of type <tt>{ i32, i32 }</tt> + </td> + </tr> +</table> + +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_struct">Structure Type</a> </div> +<div class="doc_text"> +<h5>Overview:</h5> +<p>The structure type is used to represent a collection of data members +together in memory. The packing of the field types is defined to match +the ABI of the underlying processor. The elements of a structure may +be any type that has a size.</p> +<p>Structures are accessed using '<tt><a href="#i_load">load</a></tt> +and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a +field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' +instruction.</p> +<h5>Syntax:</h5> +<pre> { <type list> }<br></pre> +<h5>Examples:</h5> +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>{ i32, i32, i32 }</tt></td> + <td class="left">A triple of three <tt>i32</tt> values</td> + </tr><tr class="layout"> + <td class="left"><tt>{ float, i32 (i32) * }</tt></td> + <td class="left">A pair, where the first element is a <tt>float</tt> and the + second element is a <a href="#t_pointer">pointer</a> to a + <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning + an <tt>i32</tt>.</td> + </tr> +</table> + +<p>Note that the code generator does not yet support large aggregate types +to be used as function return types. The specific limit on how large an +aggregate return type the code generator can currently handle is +target-dependent, and also dependent on the aggregate element types.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_pstruct">Packed Structure Type</a> +</div> +<div class="doc_text"> +<h5>Overview:</h5> +<p>The packed structure type is used to represent a collection of data members +together in memory. There is no padding between fields. Further, the alignment +of a packed structure is 1 byte. The elements of a packed structure may +be any type that has a size.</p> +<p>Structures are accessed using '<tt><a href="#i_load">load</a></tt> +and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a +field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' +instruction.</p> +<h5>Syntax:</h5> +<pre> < { <type list> } > <br></pre> +<h5>Examples:</h5> +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>< { i32, i32, i32 } ></tt></td> + <td class="left">A triple of three <tt>i32</tt> values</td> + </tr><tr class="layout"> + <td class="left"> +<tt>< { float, i32 (i32)* } ></tt></td> + <td class="left">A pair, where the first element is a <tt>float</tt> and the + second element is a <a href="#t_pointer">pointer</a> to a + <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning + an <tt>i32</tt>.</td> + </tr> +</table> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div> +<div class="doc_text"> +<h5>Overview:</h5> +<p>As in many languages, the pointer type represents a pointer or +reference to another object, which must live in memory. Pointer types may have +an optional address space attribute defining the target-specific numbered +address space where the pointed-to object resides. The default address space is +zero.</p> + +<p>Note that LLVM does not permit pointers to void (<tt>void*</tt>) nor does +it permit pointers to labels (<tt>label*</tt>). Use <tt>i8*</tt> instead.</p> + +<h5>Syntax:</h5> +<pre> <type> *<br></pre> +<h5>Examples:</h5> +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>[4 x i32]*</tt></td> + <td class="left">A <a href="#t_pointer">pointer</a> to <a + href="#t_array">array</a> of four <tt>i32</tt> values.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>i32 (i32 *) *</tt></td> + <td class="left"> A <a href="#t_pointer">pointer</a> to a <a + href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an + <tt>i32</tt>.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>i32 addrspace(5)*</tt></td> + <td class="left">A <a href="#t_pointer">pointer</a> to an <tt>i32</tt> value + that resides in address space #5.</td> + </tr> +</table> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_vector">Vector Type</a> </div> +<div class="doc_text"> + +<h5>Overview:</h5> + +<p>A vector type is a simple derived type that represents a vector +of elements. Vector types are used when multiple primitive data +are operated in parallel using a single instruction (SIMD). +A vector type requires a size (number of +elements) and an underlying primitive data type. Vectors must have a power +of two length (1, 2, 4, 8, 16 ...). Vector types are +considered <a href="#t_firstclass">first class</a>.</p> + +<h5>Syntax:</h5> + +<pre> + < <# elements> x <elementtype> > +</pre> + +<p>The number of elements is a constant integer value; elementtype may +be any integer or floating point type.</p> + +<h5>Examples:</h5> + +<table class="layout"> + <tr class="layout"> + <td class="left"><tt><4 x i32></tt></td> + <td class="left">Vector of 4 32-bit integer values.</td> + </tr> + <tr class="layout"> + <td class="left"><tt><8 x float></tt></td> + <td class="left">Vector of 8 32-bit floating-point values.</td> + </tr> + <tr class="layout"> + <td class="left"><tt><2 x i64></tt></td> + <td class="left">Vector of 2 64-bit integer values.</td> + </tr> +</table> + +<p>Note that the code generator does not yet support large vector types +to be used as function return types. The specific limit on how large a +vector return type codegen can currently handle is target-dependent; +currently it's often a few times longer than a hardware vector register.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="t_opaque">Opaque Type</a> </div> +<div class="doc_text"> + +<h5>Overview:</h5> + +<p>Opaque types are used to represent unknown types in the system. This +corresponds (for example) to the C notion of a forward declared structure type. +In LLVM, opaque types can eventually be resolved to any type (not just a +structure type).</p> + +<h5>Syntax:</h5> + +<pre> + opaque +</pre> + +<h5>Examples:</h5> + +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>opaque</tt></td> + <td class="left">An opaque type.</td> + </tr> +</table> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="t_uprefs">Type Up-references</a> +</div> + +<div class="doc_text"> +<h5>Overview:</h5> +<p> +An "up reference" allows you to refer to a lexically enclosing type without +requiring it to have a name. For instance, a structure declaration may contain a +pointer to any of the types it is lexically a member of. Example of up +references (with their equivalent as named type declarations) include:</p> + +<pre> + { \2 * } %x = type { %x* } + { \2 }* %y = type { %y }* + \1* %z = type %z* +</pre> + +<p> +An up reference is needed by the asmprinter for printing out cyclic types when +there is no declared name for a type in the cycle. Because the asmprinter does +not want to print out an infinite type string, it needs a syntax to handle +recursive types that have no names (all names are optional in llvm IR). +</p> + +<h5>Syntax:</h5> +<pre> + \<level> +</pre> + +<p> +The level is the count of the lexical type that is being referred to. +</p> + +<h5>Examples:</h5> + +<table class="layout"> + <tr class="layout"> + <td class="left"><tt>\1*</tt></td> + <td class="left">Self-referential pointer.</td> + </tr> + <tr class="layout"> + <td class="left"><tt>{ { \3*, i8 }, i32 }</tt></td> + <td class="left">Recursive structure where the upref refers to the out-most + structure.</td> + </tr> +</table> +</div> + + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="constants">Constants</a> </div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>LLVM has several different basic types of constants. This section describes +them all and their syntax.</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"><a name="simpleconstants">Simple Constants</a></div> + +<div class="doc_text"> + +<dl> + <dt><b>Boolean constants</b></dt> + + <dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid + constants of the <tt><a href="#t_primitive">i1</a></tt> type. + </dd> + + <dt><b>Integer constants</b></dt> + + <dd>Standard integers (such as '4') are constants of the <a + href="#t_integer">integer</a> type. Negative numbers may be used with + integer types. + </dd> + + <dt><b>Floating point constants</b></dt> + + <dd>Floating point constants use standard decimal notation (e.g. 123.421), + exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal + notation (see below). The assembler requires the exact decimal value of + a floating-point constant. For example, the assembler accepts 1.25 but + rejects 1.3 because 1.3 is a repeating decimal in binary. Floating point + constants must have a <a href="#t_floating">floating point</a> type. </dd> + + <dt><b>Null pointer constants</b></dt> + + <dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant + and must be of <a href="#t_pointer">pointer type</a>.</dd> + +</dl> + +<p>The one non-intuitive notation for constants is the hexadecimal form +of floating point constants. For example, the form '<tt>double +0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) '<tt>double +4.5e+15</tt>'. The only time hexadecimal floating point constants are required +(and the only time that they are generated by the disassembler) is when a +floating point constant must be emitted but it cannot be represented as a +decimal floating point number in a reasonable number of digits. For example, +NaN's, infinities, and other +special values are represented in their IEEE hexadecimal format so that +assembly and disassembly do not cause any bits to change in the constants.</p> +<p>When using the hexadecimal form, constants of types float and double are +represented using the 16-digit form shown above (which matches the IEEE754 +representation for double); float values must, however, be exactly representable +as IEE754 single precision. +Hexadecimal format is always used for long +double, and there are three forms of long double. The 80-bit +format used by x86 is represented as <tt>0xK</tt> +followed by 20 hexadecimal digits. +The 128-bit format used by PowerPC (two adjacent doubles) is represented +by <tt>0xM</tt> followed by 32 hexadecimal digits. The IEEE 128-bit +format is represented +by <tt>0xL</tt> followed by 32 hexadecimal digits; no currently supported +target uses this format. Long doubles will only work if they match +the long double format on your target. All hexadecimal formats are big-endian +(sign bit at the left).</p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> +<a name="aggregateconstants"> <!-- old anchor --> +<a name="complexconstants">Complex Constants</a></a> +</div> + +<div class="doc_text"> +<p>Complex constants are a (potentially recursive) combination of simple +constants and smaller complex constants.</p> + +<dl> + <dt><b>Structure constants</b></dt> + + <dd>Structure constants are represented with notation similar to structure + type definitions (a comma separated list of elements, surrounded by braces + (<tt>{}</tt>)). For example: "<tt>{ i32 4, float 17.0, i32* @G }</tt>", + where "<tt>@G</tt>" is declared as "<tt>@G = external global i32</tt>". Structure constants + must have <a href="#t_struct">structure type</a>, and the number and + types of elements must match those specified by the type. + </dd> + + <dt><b>Array constants</b></dt> + + <dd>Array constants are represented with notation similar to array type + definitions (a comma separated list of elements, surrounded by square brackets + (<tt>[]</tt>)). For example: "<tt>[ i32 42, i32 11, i32 74 ]</tt>". Array + constants must have <a href="#t_array">array type</a>, and the number and + types of elements must match those specified by the type. + </dd> + + <dt><b>Vector constants</b></dt> + + <dd>Vector constants are represented with notation similar to vector type + definitions (a comma separated list of elements, surrounded by + less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32 42, + i32 11, i32 74, i32 100 ></tt>". Vector constants must have <a + href="#t_vector">vector type</a>, and the number and types of elements must + match those specified by the type. + </dd> + + <dt><b>Zero initialization</b></dt> + + <dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a + value to zero of <em>any</em> type, including scalar and aggregate types. + This is often used to avoid having to print large zero initializers (e.g. for + large arrays) and is always exactly equivalent to using explicit zero + initializers. + </dd> + + <dt><b>Metadata node</b></dt> + + <dd>A metadata node is a structure-like constant with + <a href="#t_metadata">metadata type</a>. For example: + "<tt>metadata !{ i32 0, metadata !"test" }</tt>". Unlike other constants + that are meant to be interpreted as part of the instruction stream, metadata + is a place to attach additional information such as debug info. + </dd> +</dl> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="globalconstants">Global Variable and Function Addresses</a> +</div> + +<div class="doc_text"> + +<p>The addresses of <a href="#globalvars">global variables</a> and <a +href="#functionstructure">functions</a> are always implicitly valid (link-time) +constants. These constants are explicitly referenced when the <a +href="#identifiers">identifier for the global</a> is used and always have <a +href="#t_pointer">pointer</a> type. For example, the following is a legal LLVM +file:</p> + +<div class="doc_code"> +<pre> +@X = global i32 17 +@Y = global i32 42 +@Z = global [2 x i32*] [ i32* @X, i32* @Y ] +</pre> +</div> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"><a name="undefvalues">Undefined Values</a></div> +<div class="doc_text"> + <p>The string '<tt>undef</tt>' is recognized as a type-less constant that has + no specific value. Undefined values may be of any type and be used anywhere + a constant is permitted.</p> + + <p>Undefined values indicate to the compiler that the program is well defined + no matter what value is used, giving the compiler more freedom to optimize. + </p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"><a name="constantexprs">Constant Expressions</a> +</div> + +<div class="doc_text"> + +<p>Constant expressions are used to allow expressions involving other constants +to be used as constants. Constant expressions may be of any <a +href="#t_firstclass">first class</a> type and may involve any LLVM operation +that does not have side effects (e.g. load and call are not supported). The +following is the syntax for constant expressions:</p> + +<dl> + <dt><b><tt>trunc ( CST to TYPE )</tt></b></dt> + <dd>Truncate a constant to another type. The bit size of CST must be larger + than the bit size of TYPE. Both types must be integers.</dd> + + <dt><b><tt>zext ( CST to TYPE )</tt></b></dt> + <dd>Zero extend a constant to another type. The bit size of CST must be + smaller or equal to the bit size of TYPE. Both types must be integers.</dd> + + <dt><b><tt>sext ( CST to TYPE )</tt></b></dt> + <dd>Sign extend a constant to another type. The bit size of CST must be + smaller or equal to the bit size of TYPE. Both types must be integers.</dd> + + <dt><b><tt>fptrunc ( CST to TYPE )</tt></b></dt> + <dd>Truncate a floating point constant to another floating point type. The + size of CST must be larger than the size of TYPE. Both types must be + floating point.</dd> + + <dt><b><tt>fpext ( CST to TYPE )</tt></b></dt> + <dd>Floating point extend a constant to another type. The size of CST must be + smaller or equal to the size of TYPE. Both types must be floating point.</dd> + + <dt><b><tt>fptoui ( CST to TYPE )</tt></b></dt> + <dd>Convert a floating point constant to the corresponding unsigned integer + constant. TYPE must be a scalar or vector integer type. CST must be of scalar + or vector floating point type. Both CST and TYPE must be scalars, or vectors + of the same number of elements. If the value won't fit in the integer type, + the results are undefined.</dd> + + <dt><b><tt>fptosi ( CST to TYPE )</tt></b></dt> + <dd>Convert a floating point constant to the corresponding signed integer + constant. TYPE must be a scalar or vector integer type. CST must be of scalar + or vector floating point type. Both CST and TYPE must be scalars, or vectors + of the same number of elements. If the value won't fit in the integer type, + the results are undefined.</dd> + + <dt><b><tt>uitofp ( CST to TYPE )</tt></b></dt> + <dd>Convert an unsigned integer constant to the corresponding floating point + constant. TYPE must be a scalar or vector floating point type. CST must be of + scalar or vector integer type. Both CST and TYPE must be scalars, or vectors + of the same number of elements. If the value won't fit in the floating point + type, the results are undefined.</dd> + + <dt><b><tt>sitofp ( CST to TYPE )</tt></b></dt> + <dd>Convert a signed integer constant to the corresponding floating point + constant. TYPE must be a scalar or vector floating point type. CST must be of + scalar or vector integer type. Both CST and TYPE must be scalars, or vectors + of the same number of elements. If the value won't fit in the floating point + type, the results are undefined.</dd> + + <dt><b><tt>ptrtoint ( CST to TYPE )</tt></b></dt> + <dd>Convert a pointer typed constant to the corresponding integer constant + TYPE must be an integer type. CST must be of pointer type. The CST value is + zero extended, truncated, or unchanged to make it fit in TYPE.</dd> + + <dt><b><tt>inttoptr ( CST to TYPE )</tt></b></dt> + <dd>Convert a integer constant to a pointer constant. TYPE must be a + pointer type. CST must be of integer type. The CST value is zero extended, + truncated, or unchanged to make it fit in a pointer size. This one is + <i>really</i> dangerous!</dd> + + <dt><b><tt>bitcast ( CST to TYPE )</tt></b></dt> + <dd>Convert a constant, CST, to another TYPE. The constraints of the operands + are the same as those for the <a href="#i_bitcast">bitcast + instruction</a>.</dd> + + <dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt> + + <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on + constants. As with the <a href="#i_getelementptr">getelementptr</a> + instruction, the index list may have zero or more indexes, which are required + to make sense for the type of "CSTPTR".</dd> + + <dt><b><tt>select ( COND, VAL1, VAL2 )</tt></b></dt> + + <dd>Perform the <a href="#i_select">select operation</a> on + constants.</dd> + + <dt><b><tt>icmp COND ( VAL1, VAL2 )</tt></b></dt> + <dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd> + + <dt><b><tt>fcmp COND ( VAL1, VAL2 )</tt></b></dt> + <dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd> + + <dt><b><tt>vicmp COND ( VAL1, VAL2 )</tt></b></dt> + <dd>Performs the <a href="#i_vicmp">vicmp operation</a> on constants.</dd> + + <dt><b><tt>vfcmp COND ( VAL1, VAL2 )</tt></b></dt> + <dd>Performs the <a href="#i_vfcmp">vfcmp operation</a> on constants.</dd> + + <dt><b><tt>extractelement ( VAL, IDX )</tt></b></dt> + + <dd>Perform the <a href="#i_extractelement">extractelement + operation</a> on constants.</dd> + + <dt><b><tt>insertelement ( VAL, ELT, IDX )</tt></b></dt> + + <dd>Perform the <a href="#i_insertelement">insertelement + operation</a> on constants.</dd> + + + <dt><b><tt>shufflevector ( VEC1, VEC2, IDXMASK )</tt></b></dt> + + <dd>Perform the <a href="#i_shufflevector">shufflevector + operation</a> on constants.</dd> + + <dt><b><tt>OPCODE ( LHS, RHS )</tt></b></dt> + + <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may + be any of the <a href="#binaryops">binary</a> or <a href="#bitwiseops">bitwise + binary</a> operations. The constraints on operands are the same as those for + the corresponding instruction (e.g. no bitwise operations on floating point + values are allowed).</dd> +</dl> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"><a name="metadata">Embedded Metadata</a> +</div> + +<div class="doc_text"> + +<p>Embedded metadata provides a way to attach arbitrary data to the +instruction stream without affecting the behaviour of the program. There are +two metadata primitives, strings and nodes. All metadata has the +<tt>metadata</tt> type and is identified in syntax by a preceding exclamation +point ('<tt>!</tt>'). +</p> + +<p>A metadata string is a string surrounded by double quotes. It can contain +any character by escaping non-printable characters with "\xx" where "xx" is +the two digit hex code. For example: "<tt>!"test\00"</tt>". +</p> + +<p>Metadata nodes are represented with notation similar to structure constants +(a comma separated list of elements, surrounded by braces and preceeded by an +exclamation point). For example: "<tt>!{ metadata !"test\00", i32 10}</tt>". +</p> + +<p>A metadata node will attempt to track changes to the values it holds. In +the event that a value is deleted, it will be replaced with a typeless +"<tt>null</tt>", such as "<tt>metadata !{null, i32 10}</tt>".</p> + +<p>Optimizations may rely on metadata to provide additional information about +the program that isn't available in the instructions, or that isn't easily +computable. Similarly, the code generator may expect a certain metadata format +to be used to express debugging information.</p> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="othervalues">Other Values</a> </div> +<!-- *********************************************************************** --> + +<!-- ======================================================================= --> +<div class="doc_subsection"> +<a name="inlineasm">Inline Assembler Expressions</a> +</div> + +<div class="doc_text"> + +<p> +LLVM supports inline assembler expressions (as opposed to <a href="#moduleasm"> +Module-Level Inline Assembly</a>) through the use of a special value. This +value represents the inline assembler as a string (containing the instructions +to emit), a list of operand constraints (stored as a string), and a flag that +indicates whether or not the inline asm expression has side effects. An example +inline assembler expression is: +</p> + +<div class="doc_code"> +<pre> +i32 (i32) asm "bswap $0", "=r,r" +</pre> +</div> + +<p> +Inline assembler expressions may <b>only</b> be used as the callee operand of +a <a href="#i_call"><tt>call</tt> instruction</a>. Thus, typically we have: +</p> + +<div class="doc_code"> +<pre> +%X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y) +</pre> +</div> + +<p> +Inline asms with side effects not visible in the constraint list must be marked +as having side effects. This is done through the use of the +'<tt>sideeffect</tt>' keyword, like so: +</p> + +<div class="doc_code"> +<pre> +call void asm sideeffect "eieio", ""() +</pre> +</div> + +<p>TODO: The format of the asm and constraints string still need to be +documented here. Constraints on what can be done (e.g. duplication, moving, etc +need to be documented). This is probably best done by reference to another +document that covers inline asm from a holistic perspective. +</p> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="instref">Instruction Reference</a> </div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>The LLVM instruction set consists of several different +classifications of instructions: <a href="#terminators">terminator +instructions</a>, <a href="#binaryops">binary instructions</a>, +<a href="#bitwiseops">bitwise binary instructions</a>, <a + href="#memoryops">memory instructions</a>, and <a href="#otherops">other +instructions</a>.</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="terminators">Terminator +Instructions</a> </div> + +<div class="doc_text"> + +<p>As mentioned <a href="#functionstructure">previously</a>, every +basic block in a program ends with a "Terminator" instruction, which +indicates which block should be executed after the current block is +finished. These terminator instructions typically yield a '<tt>void</tt>' +value: they produce control flow, not values (the one exception being +the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p> +<p>There are six different terminator instructions: the '<a + href="#i_ret"><tt>ret</tt></a>' instruction, the '<a href="#i_br"><tt>br</tt></a>' +instruction, the '<a href="#i_switch"><tt>switch</tt></a>' instruction, +the '<a href="#i_invoke"><tt>invoke</tt></a>' instruction, the '<a + href="#i_unwind"><tt>unwind</tt></a>' instruction, and the '<a + href="#i_unreachable"><tt>unreachable</tt></a>' instruction.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_ret">'<tt>ret</tt>' +Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> + ret <type> <value> <i>; Return a value from a non-void function</i> + ret void <i>; Return from void function</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>ret</tt>' instruction is used to return control flow (and +optionally a value) from a function back to the caller.</p> +<p>There are two forms of the '<tt>ret</tt>' instruction: one that +returns a value and then causes control flow, and one that just causes +control flow to occur.</p> + +<h5>Arguments:</h5> + +<p>The '<tt>ret</tt>' instruction optionally accepts a single argument, +the return value. The type of the return value must be a +'<a href="#t_firstclass">first class</a>' type.</p> + +<p>A function is not <a href="#wellformed">well formed</a> if +it it has a non-void return type and contains a '<tt>ret</tt>' +instruction with no return value or a return value with a type that +does not match its type, or if it has a void return type and contains +a '<tt>ret</tt>' instruction with a return value.</p> + +<h5>Semantics:</h5> + +<p>When the '<tt>ret</tt>' instruction is executed, control flow +returns back to the calling function's context. If the caller is a "<a + href="#i_call"><tt>call</tt></a>" instruction, execution continues at +the instruction after the call. If the caller was an "<a + href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues +at the beginning of the "normal" destination block. If the instruction +returns a value, that value shall set the call or invoke instruction's +return value.</p> + +<h5>Example:</h5> + +<pre> + ret i32 5 <i>; Return an integer value of 5</i> + ret void <i>; Return from a void function</i> + ret { i32, i8 } { i32 4, i8 2 } <i>; Return a struct of values 4 and 2</i> +</pre> + +<p>Note that the code generator does not yet fully support large + return values. The specific sizes that are currently supported are + dependent on the target. For integers, on 32-bit targets the limit + is often 64 bits, and on 64-bit targets the limit is often 128 bits. + For aggregate types, the current limits are dependent on the element + types; for example targets are often limited to 2 total integer + elements and 2 total floating-point elements.</p> + +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_br">'<tt>br</tt>' Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> br i1 <cond>, label <iftrue>, label <iffalse><br> br label <dest> <i>; Unconditional branch</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>br</tt>' instruction is used to cause control flow to +transfer to a different basic block in the current function. There are +two forms of this instruction, corresponding to a conditional branch +and an unconditional branch.</p> +<h5>Arguments:</h5> +<p>The conditional branch form of the '<tt>br</tt>' instruction takes a +single '<tt>i1</tt>' value and two '<tt>label</tt>' values. The +unconditional form of the '<tt>br</tt>' instruction takes a single +'<tt>label</tt>' value as a target.</p> +<h5>Semantics:</h5> +<p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>i1</tt>' +argument is evaluated. If the value is <tt>true</tt>, control flows +to the '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>, +control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p> +<h5>Example:</h5> +<pre>Test:<br> %cond = <a href="#i_icmp">icmp</a> eq i32 %a, %b<br> br i1 %cond, label %IfEqual, label %IfUnequal<br>IfEqual:<br> <a + href="#i_ret">ret</a> i32 1<br>IfUnequal:<br> <a href="#i_ret">ret</a> i32 0<br></pre> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_switch">'<tt>switch</tt>' Instruction</a> +</div> + +<div class="doc_text"> +<h5>Syntax:</h5> + +<pre> + switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ] +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of +several different places. It is a generalization of the '<tt>br</tt>' +instruction, allowing a branch to occur to one of many possible +destinations.</p> + + +<h5>Arguments:</h5> + +<p>The '<tt>switch</tt>' instruction uses three parameters: an integer +comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, and +an array of pairs of comparison value constants and '<tt>label</tt>'s. The +table is not allowed to contain duplicate constant entries.</p> + +<h5>Semantics:</h5> + +<p>The <tt>switch</tt> instruction specifies a table of values and +destinations. When the '<tt>switch</tt>' instruction is executed, this +table is searched for the given value. If the value is found, control flow is +transfered to the corresponding destination; otherwise, control flow is +transfered to the default destination.</p> + +<h5>Implementation:</h5> + +<p>Depending on properties of the target machine and the particular +<tt>switch</tt> instruction, this instruction may be code generated in different +ways. For example, it could be generated as a series of chained conditional +branches or with a lookup table.</p> + +<h5>Example:</h5> + +<pre> + <i>; Emulate a conditional br instruction</i> + %Val = <a href="#i_zext">zext</a> i1 %value to i32 + switch i32 %Val, label %truedest [ i32 0, label %falsedest ] + + <i>; Emulate an unconditional br instruction</i> + switch i32 0, label %dest [ ] + + <i>; Implement a jump table:</i> + switch i32 %val, label %otherwise [ i32 0, label %onzero + i32 1, label %onone + i32 2, label %ontwo ] +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_invoke">'<tt>invoke</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = invoke [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ptr to function ty> <function ptr val>(<function args>) [<a href="#fnattrs">fn attrs</a>] + to label <normal label> unwind label <exception label> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified +function, with the possibility of control flow transfer to either the +'<tt>normal</tt>' label or the +'<tt>exception</tt>' label. If the callee function returns with the +"<tt><a href="#i_ret">ret</a></tt>" instruction, control flow will return to the +"normal" label. If the callee (or any indirect callees) returns with the "<a +href="#i_unwind"><tt>unwind</tt></a>" instruction, control is interrupted and +continued at the dynamically nearest "exception" label.</p> + +<h5>Arguments:</h5> + +<p>This instruction requires several arguments:</p> + +<ol> + <li> + The optional "cconv" marker indicates which <a href="#callingconv">calling + convention</a> the call should use. If none is specified, the call defaults + to using C calling conventions. + </li> + + <li>The optional <a href="#paramattrs">Parameter Attributes</a> list for + return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', + and '<tt>inreg</tt>' attributes are valid here.</li> + + <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to + function value being invoked. In most cases, this is a direct function + invocation, but indirect <tt>invoke</tt>s are just as possible, branching off + an arbitrary pointer to function value. + </li> + + <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a + function to be invoked. </li> + + <li>'<tt>function args</tt>': argument list whose types match the function + signature argument types. If the function signature indicates the function + accepts a variable number of arguments, the extra arguments can be + specified. </li> + + <li>'<tt>normal label</tt>': the label reached when the called function + executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li> + + <li>'<tt>exception label</tt>': the label reached when a callee returns with + the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li> + + <li>The optional <a href="#fnattrs">function attributes</a> list. Only + '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and + '<tt>readnone</tt>' attributes are valid here.</li> +</ol> + +<h5>Semantics:</h5> + +<p>This instruction is designed to operate as a standard '<tt><a +href="#i_call">call</a></tt>' instruction in most regards. The primary +difference is that it establishes an association with a label, which is used by +the runtime library to unwind the stack.</p> + +<p>This instruction is used in languages with destructors to ensure that proper +cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown +exception. Additionally, this is important for implementation of +'<tt>catch</tt>' clauses in high-level languages that support them.</p> + +<p>It is not valid to reference the return value of an invoke call from +anywhere not dominated by the normal label, since an unwind does not +provide a return value.</p> + +<h5>Example:</h5> +<pre> + %retval = invoke i32 @Test(i32 15) to label %Continue + unwind label %TestCleanup <i>; {i32}:retval set</i> + %retval = invoke <a href="#callingconv">coldcc</a> i32 %Testfnptr(i32 15) to label %Continue + unwind label %TestCleanup <i>; {i32}:retval set</i> +</pre> +</div> + + +<!-- _______________________________________________________________________ --> + +<div class="doc_subsubsection"> <a name="i_unwind">'<tt>unwind</tt>' +Instruction</a> </div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + unwind +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>unwind</tt>' instruction unwinds the stack, continuing control flow +at the first callee in the dynamic call stack which used an <a +href="#i_invoke"><tt>invoke</tt></a> instruction to perform the call. This is +primarily used to implement exception handling.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>unwind</tt>' instruction causes execution of the current function to +immediately halt. The dynamic call stack is then searched for the first <a +href="#i_invoke"><tt>invoke</tt></a> instruction on the call stack. Once found, +execution continues at the "exceptional" destination block specified by the +<tt>invoke</tt> instruction. If there is no <tt>invoke</tt> instruction in the +dynamic call chain, undefined behavior results.</p> +</div> + +<!-- _______________________________________________________________________ --> + +<div class="doc_subsubsection"> <a name="i_unreachable">'<tt>unreachable</tt>' +Instruction</a> </div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + unreachable +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>unreachable</tt>' instruction has no defined semantics. This +instruction is used to inform the optimizer that a particular portion of the +code is not reachable. This can be used to indicate that the code after a +no-return function cannot be reached, and other facts.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p> +</div> + + + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="binaryops">Binary Operations</a> </div> +<div class="doc_text"> +<p>Binary operators are used to do most of the computation in a +program. They require two operands of the same type, execute an operation on them, and +produce a single value. The operands might represent +multiple data, as is the case with the <a href="#t_vector">vector</a> data type. +The result value has the same type as its operands.</p> +<p>There are several different binary operators:</p> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_add">'<tt>add</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = add <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p> + +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>add</tt>' instruction must be <a + href="#t_integer">integer</a>, <a href="#t_floating">floating point</a>, or + <a href="#t_vector">vector</a> values. Both arguments must have identical + types.</p> + +<h5>Semantics:</h5> + +<p>The value produced is the integer or floating point sum of the two +operands.</p> + +<p>If an integer sum has unsigned overflow, the result returned is the +mathematical result modulo 2<sup>n</sup>, where n is the bit width of +the result.</p> + +<p>Because LLVM integers use a two's complement representation, this +instruction is appropriate for both signed and unsigned integers.</p> + +<h5>Example:</h5> + +<pre> + <result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i> +</pre> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_sub">'<tt>sub</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = sub <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>sub</tt>' instruction returns the difference of its two +operands.</p> + +<p>Note that the '<tt>sub</tt>' instruction is used to represent the +'<tt>neg</tt>' instruction present in most other intermediate +representations.</p> + +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>sub</tt>' instruction must be <a + href="#t_integer">integer</a>, <a href="#t_floating">floating point</a>, + or <a href="#t_vector">vector</a> values. Both arguments must have identical + types.</p> + +<h5>Semantics:</h5> + +<p>The value produced is the integer or floating point difference of +the two operands.</p> + +<p>If an integer difference has unsigned overflow, the result returned is the +mathematical result modulo 2<sup>n</sup>, where n is the bit width of +the result.</p> + +<p>Because LLVM integers use a two's complement representation, this +instruction is appropriate for both signed and unsigned integers.</p> + +<h5>Example:</h5> +<pre> + <result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i> + <result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_mul">'<tt>mul</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> <result> = mul <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>mul</tt>' instruction returns the product of its two +operands.</p> + +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>mul</tt>' instruction must be <a +href="#t_integer">integer</a>, <a href="#t_floating">floating point</a>, +or <a href="#t_vector">vector</a> values. Both arguments must have identical +types.</p> + +<h5>Semantics:</h5> + +<p>The value produced is the integer or floating point product of the +two operands.</p> + +<p>If the result of an integer multiplication has unsigned overflow, +the result returned is the mathematical result modulo +2<sup>n</sup>, where n is the bit width of the result.</p> +<p>Because LLVM integers use a two's complement representation, and the +result is the same width as the operands, this instruction returns the +correct result for both signed and unsigned integers. If a full product +(e.g. <tt>i32</tt>x<tt>i32</tt>-><tt>i64</tt>) is needed, the operands +should be sign-extended or zero-extended as appropriate to the +width of the full product.</p> +<h5>Example:</h5> +<pre> <result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_udiv">'<tt>udiv</tt>' Instruction +</a></div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = udiv <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>udiv</tt>' instruction returns the quotient of its two +operands.</p> + +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>udiv</tt>' instruction must be +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +values. Both arguments must have identical types.</p> + +<h5>Semantics:</h5> + +<p>The value produced is the unsigned integer quotient of the two operands.</p> +<p>Note that unsigned integer division and signed integer division are distinct +operations; for signed integer division, use '<tt>sdiv</tt>'.</p> +<p>Division by zero leads to undefined behavior.</p> +<h5>Example:</h5> +<pre> <result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i> +</pre> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_sdiv">'<tt>sdiv</tt>' Instruction +</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> + <result> = sdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>sdiv</tt>' instruction returns the quotient of its two +operands.</p> + +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>sdiv</tt>' instruction must be +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +values. Both arguments must have identical types.</p> + +<h5>Semantics:</h5> +<p>The value produced is the signed integer quotient of the two operands rounded towards zero.</p> +<p>Note that signed integer division and unsigned integer division are distinct +operations; for unsigned integer division, use '<tt>udiv</tt>'.</p> +<p>Division by zero leads to undefined behavior. Overflow also leads to +undefined behavior; this is a rare case, but can occur, for example, +by doing a 32-bit division of -2147483648 by -1.</p> +<h5>Example:</h5> +<pre> <result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i> +</pre> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_fdiv">'<tt>fdiv</tt>' +Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> + <result> = fdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> +<h5>Overview:</h5> + +<p>The '<tt>fdiv</tt>' instruction returns the quotient of its two +operands.</p> + +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>fdiv</tt>' instruction must be +<a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> +of floating point values. Both arguments must have identical types.</p> + +<h5>Semantics:</h5> + +<p>The value produced is the floating point quotient of the two operands.</p> + +<h5>Example:</h5> + +<pre> + <result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_urem">'<tt>urem</tt>' Instruction</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = urem <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>urem</tt>' instruction returns the remainder from the +unsigned division of its two arguments.</p> +<h5>Arguments:</h5> +<p>The two arguments to the '<tt>urem</tt>' instruction must be +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +values. Both arguments must have identical types.</p> +<h5>Semantics:</h5> +<p>This instruction returns the unsigned integer <i>remainder</i> of a division. +This instruction always performs an unsigned division to get the remainder.</p> +<p>Note that unsigned integer remainder and signed integer remainder are +distinct operations; for signed integer remainder, use '<tt>srem</tt>'.</p> +<p>Taking the remainder of a division by zero leads to undefined behavior.</p> +<h5>Example:</h5> +<pre> <result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i> +</pre> + +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_srem">'<tt>srem</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = srem <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>srem</tt>' instruction returns the remainder from the +signed division of its two operands. This instruction can also take +<a href="#t_vector">vector</a> versions of the values in which case +the elements must be integers.</p> + +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>srem</tt>' instruction must be +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +values. Both arguments must have identical types.</p> + +<h5>Semantics:</h5> + +<p>This instruction returns the <i>remainder</i> of a division (where the result +has the same sign as the dividend, <tt>op1</tt>), not the <i>modulo</i> +operator (where the result has the same sign as the divisor, <tt>op2</tt>) of +a value. For more information about the difference, see <a + href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The +Math Forum</a>. For a table of how this is implemented in various languages, +please see <a href="http://en.wikipedia.org/wiki/Modulo_operation"> +Wikipedia: modulo operation</a>.</p> +<p>Note that signed integer remainder and unsigned integer remainder are +distinct operations; for unsigned integer remainder, use '<tt>urem</tt>'.</p> +<p>Taking the remainder of a division by zero leads to undefined behavior. +Overflow also leads to undefined behavior; this is a rare case, but can occur, +for example, by taking the remainder of a 32-bit division of -2147483648 by -1. +(The remainder doesn't actually overflow, but this rule lets srem be +implemented using instructions that return both the result of the division +and the remainder.)</p> +<h5>Example:</h5> +<pre> <result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i> +</pre> + +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_frem">'<tt>frem</tt>' Instruction</a> </div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> <result> = frem <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>frem</tt>' instruction returns the remainder from the +division of its two operands.</p> +<h5>Arguments:</h5> +<p>The two arguments to the '<tt>frem</tt>' instruction must be +<a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> +of floating point values. Both arguments must have identical types.</p> + +<h5>Semantics:</h5> + +<p>This instruction returns the <i>remainder</i> of a division. +The remainder has the same sign as the dividend.</p> + +<h5>Example:</h5> + +<pre> + <result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</i> +</pre> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="bitwiseops">Bitwise Binary +Operations</a> </div> +<div class="doc_text"> +<p>Bitwise binary operators are used to do various forms of +bit-twiddling in a program. They are generally very efficient +instructions and can commonly be strength reduced from other +instructions. They require two operands of the same type, execute an operation on them, +and produce a single value. The resulting value is the same type as its operands.</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_shl">'<tt>shl</tt>' +Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = shl <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>shl</tt>' instruction returns the first operand shifted to +the left a specified number of bits.</p> + +<h5>Arguments:</h5> + +<p>Both arguments to the '<tt>shl</tt>' instruction must be the same <a + href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +type. '<tt>op2</tt>' is treated as an unsigned value.</p> + +<h5>Semantics:</h5> + +<p>The value produced is <tt>op1</tt> * 2<sup><tt>op2</tt></sup> mod 2<sup>n</sup>, +where n is the width of the result. If <tt>op2</tt> is (statically or dynamically) negative or +equal to or larger than the number of bits in <tt>op1</tt>, the result is undefined. +If the arguments are vectors, each vector element of <tt>op1</tt> is shifted by the +corresponding shift amount in <tt>op2</tt>.</p> + +<h5>Example:</h5><pre> + <result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i> + <result> = shl i32 4, 2 <i>; yields {i32}: 16</i> + <result> = shl i32 1, 10 <i>; yields {i32}: 1024</i> + <result> = shl i32 1, 32 <i>; undefined</i> + <result> = shl <2 x i32> < i32 1, i32 1>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 2, i32 4></i> +</pre> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_lshr">'<tt>lshr</tt>' +Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = lshr <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first +operand shifted to the right a specified number of bits with zero fill.</p> + +<h5>Arguments:</h5> +<p>Both arguments to the '<tt>lshr</tt>' instruction must be the same +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +type. '<tt>op2</tt>' is treated as an unsigned value.</p> + +<h5>Semantics:</h5> + +<p>This instruction always performs a logical shift right operation. The most +significant bits of the result will be filled with zero bits after the +shift. If <tt>op2</tt> is (statically or dynamically) equal to or larger than +the number of bits in <tt>op1</tt>, the result is undefined. If the arguments are +vectors, each vector element of <tt>op1</tt> is shifted by the corresponding shift +amount in <tt>op2</tt>.</p> + +<h5>Example:</h5> +<pre> + <result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i> + <result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i> + <result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i> + <result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i> + <result> = lshr i32 1, 32 <i>; undefined</i> + <result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1></i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_ashr">'<tt>ashr</tt>' +Instruction</a> </div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> <result> = ashr <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first +operand shifted to the right a specified number of bits with sign extension.</p> + +<h5>Arguments:</h5> +<p>Both arguments to the '<tt>ashr</tt>' instruction must be the same +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +type. '<tt>op2</tt>' is treated as an unsigned value.</p> + +<h5>Semantics:</h5> +<p>This instruction always performs an arithmetic shift right operation, +The most significant bits of the result will be filled with the sign bit +of <tt>op1</tt>. If <tt>op2</tt> is (statically or dynamically) equal to or +larger than the number of bits in <tt>op1</tt>, the result is undefined. If the +arguments are vectors, each vector element of <tt>op1</tt> is shifted by the +corresponding shift amount in <tt>op2</tt>.</p> + +<h5>Example:</h5> +<pre> + <result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i> + <result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i> + <result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i> + <result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i> + <result> = ashr i32 1, 32 <i>; undefined</i> + <result> = ashr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 3> <i>; yields: result=<2 x i32> < i32 -1, i32 0></i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_and">'<tt>and</tt>' +Instruction</a> </div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = and <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>and</tt>' instruction returns the bitwise logical and of +its two operands.</p> + +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>and</tt>' instruction must be +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +values. Both arguments must have identical types.</p> + +<h5>Semantics:</h5> +<p>The truth table used for the '<tt>and</tt>' instruction is:</p> +<p> </p> +<div> +<table border="1" cellspacing="0" cellpadding="4"> + <tbody> + <tr> + <td>In0</td> + <td>In1</td> + <td>Out</td> + </tr> + <tr> + <td>0</td> + <td>0</td> + <td>0</td> + </tr> + <tr> + <td>0</td> + <td>1</td> + <td>0</td> + </tr> + <tr> + <td>1</td> + <td>0</td> + <td>0</td> + </tr> + <tr> + <td>1</td> + <td>1</td> + <td>1</td> + </tr> + </tbody> +</table> +</div> +<h5>Example:</h5> +<pre> + <result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i> + <result> = and i32 15, 40 <i>; yields {i32}:result = 8</i> + <result> = and i32 4, 8 <i>; yields {i32}:result = 0</i> +</pre> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_or">'<tt>or</tt>' Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = or <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive +or of its two operands.</p> +<h5>Arguments:</h5> + +<p>The two arguments to the '<tt>or</tt>' instruction must be +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +values. Both arguments must have identical types.</p> +<h5>Semantics:</h5> +<p>The truth table used for the '<tt>or</tt>' instruction is:</p> +<p> </p> +<div> +<table border="1" cellspacing="0" cellpadding="4"> + <tbody> + <tr> + <td>In0</td> + <td>In1</td> + <td>Out</td> + </tr> + <tr> + <td>0</td> + <td>0</td> + <td>0</td> + </tr> + <tr> + <td>0</td> + <td>1</td> + <td>1</td> + </tr> + <tr> + <td>1</td> + <td>0</td> + <td>1</td> + </tr> + <tr> + <td>1</td> + <td>1</td> + <td>1</td> + </tr> + </tbody> +</table> +</div> +<h5>Example:</h5> +<pre> <result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i> + <result> = or i32 15, 40 <i>; yields {i32}:result = 47</i> + <result> = or i32 4, 8 <i>; yields {i32}:result = 12</i> +</pre> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_xor">'<tt>xor</tt>' +Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = xor <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive +or of its two operands. The <tt>xor</tt> is used to implement the +"one's complement" operation, which is the "~" operator in C.</p> +<h5>Arguments:</h5> +<p>The two arguments to the '<tt>xor</tt>' instruction must be +<a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer +values. Both arguments must have identical types.</p> + +<h5>Semantics:</h5> + +<p>The truth table used for the '<tt>xor</tt>' instruction is:</p> +<p> </p> +<div> +<table border="1" cellspacing="0" cellpadding="4"> + <tbody> + <tr> + <td>In0</td> + <td>In1</td> + <td>Out</td> + </tr> + <tr> + <td>0</td> + <td>0</td> + <td>0</td> + </tr> + <tr> + <td>0</td> + <td>1</td> + <td>1</td> + </tr> + <tr> + <td>1</td> + <td>0</td> + <td>1</td> + </tr> + <tr> + <td>1</td> + <td>1</td> + <td>0</td> + </tr> + </tbody> +</table> +</div> +<p> </p> +<h5>Example:</h5> +<pre> <result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i> + <result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i> + <result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i> + <result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i> +</pre> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="vectorops">Vector Operations</a> +</div> + +<div class="doc_text"> + +<p>LLVM supports several instructions to represent vector operations in a +target-independent manner. These instructions cover the element-access and +vector-specific operations needed to process vectors effectively. While LLVM +does directly support these vector operations, many sophisticated algorithms +will want to use target-specific intrinsics to take full advantage of a specific +target.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i> +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>extractelement</tt>' instruction extracts a single scalar +element from a vector at a specified index. +</p> + + +<h5>Arguments:</h5> + +<p> +The first operand of an '<tt>extractelement</tt>' instruction is a +value of <a href="#t_vector">vector</a> type. The second operand is +an index indicating the position from which to extract the element. +The index may be a variable.</p> + +<h5>Semantics:</h5> + +<p> +The result is a scalar of the same type as the element type of +<tt>val</tt>. Its value is the value at position <tt>idx</tt> of +<tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the +results are undefined. +</p> + +<h5>Example:</h5> + +<pre> + %result = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i> +</pre> +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i> +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>insertelement</tt>' instruction inserts a scalar +element into a vector at a specified index. +</p> + + +<h5>Arguments:</h5> + +<p> +The first operand of an '<tt>insertelement</tt>' instruction is a +value of <a href="#t_vector">vector</a> type. The second operand is a +scalar value whose type must equal the element type of the first +operand. The third operand is an index indicating the position at +which to insert the value. The index may be a variable.</p> + +<h5>Semantics:</h5> + +<p> +The result is a vector of the same type as <tt>val</tt>. Its +element values are those of <tt>val</tt> except at position +<tt>idx</tt>, where it gets the value <tt>elt</tt>. If <tt>idx</tt> +exceeds the length of <tt>val</tt>, the results are undefined. +</p> + +<h5>Example:</h5> + +<pre> + %result = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <m x i32> <mask> <i>; yields <m x <ty>></i> +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>shufflevector</tt>' instruction constructs a permutation of elements +from two input vectors, returning a vector with the same element type as +the input and length that is the same as the shuffle mask. +</p> + +<h5>Arguments:</h5> + +<p> +The first two operands of a '<tt>shufflevector</tt>' instruction are vectors +with types that match each other. The third argument is a shuffle mask whose +element type is always 'i32'. The result of the instruction is a vector whose +length is the same as the shuffle mask and whose element type is the same as +the element type of the first two operands. +</p> + +<p> +The shuffle mask operand is required to be a constant vector with either +constant integer or undef values. +</p> + +<h5>Semantics:</h5> + +<p> +The elements of the two input vectors are numbered from left to right across +both of the vectors. The shuffle mask operand specifies, for each element of +the result vector, which element of the two input vectors the result element +gets. The element selector may be undef (meaning "don't care") and the second +operand may be undef if performing a shuffle from only one vector. +</p> + +<h5>Example:</h5> + +<pre> + %result = shufflevector <4 x i32> %v1, <4 x i32> %v2, + <4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i> + %result = shufflevector <4 x i32> %v1, <4 x i32> undef, + <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle. + %result = shufflevector <8 x i32> %v1, <8 x i32> undef, + <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> + %result = shufflevector <4 x i32> %v1, <4 x i32> %v2, + <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7 > <i>; yields <8 x i32></i> +</pre> +</div> + + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="aggregateops">Aggregate Operations</a> +</div> + +<div class="doc_text"> + +<p>LLVM supports several instructions for working with aggregate values. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_extractvalue">'<tt>extractvalue</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = extractvalue <aggregate type> <val>, <idx>{, <idx>}* +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>extractvalue</tt>' instruction extracts the value of a struct field +or array element from an aggregate value. +</p> + + +<h5>Arguments:</h5> + +<p> +The first operand of an '<tt>extractvalue</tt>' instruction is a +value of <a href="#t_struct">struct</a> or <a href="#t_array">array</a> +type. The operands are constant indices to specify which value to extract +in a similar manner as indices in a +'<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction. +</p> + +<h5>Semantics:</h5> + +<p> +The result is the value at the position in the aggregate specified by +the index operands. +</p> + +<h5>Example:</h5> + +<pre> + %result = extractvalue {i32, float} %agg, 0 <i>; yields i32</i> +</pre> +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_insertvalue">'<tt>insertvalue</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = insertvalue <aggregate type> <val>, <ty> <val>, <idx> <i>; yields <n x <ty>></i> +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>insertvalue</tt>' instruction inserts a value +into a struct field or array element in an aggregate. +</p> + + +<h5>Arguments:</h5> + +<p> +The first operand of an '<tt>insertvalue</tt>' instruction is a +value of <a href="#t_struct">struct</a> or <a href="#t_array">array</a> type. +The second operand is a first-class value to insert. +The following operands are constant indices +indicating the position at which to insert the value in a similar manner as +indices in a +'<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction. +The value to insert must have the same type as the value identified +by the indices. +</p> + +<h5>Semantics:</h5> + +<p> +The result is an aggregate of the same type as <tt>val</tt>. Its +value is that of <tt>val</tt> except that the value at the position +specified by the indices is that of <tt>elt</tt>. +</p> + +<h5>Example:</h5> + +<pre> + %result = insertvalue {i32, float} %agg, i32 1, 0 <i>; yields {i32, float}</i> +</pre> +</div> + + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="memoryops">Memory Access and Addressing Operations</a> +</div> + +<div class="doc_text"> + +<p>A key design point of an SSA-based representation is how it +represents memory. In LLVM, no memory locations are in SSA form, which +makes things very simple. This section describes how to read, write, +allocate, and free memory in LLVM.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_malloc">'<tt>malloc</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = malloc <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>malloc</tt>' instruction allocates memory from the system +heap and returns a pointer to it. The object is always allocated in the generic +address space (address space zero).</p> + +<h5>Arguments:</h5> + +<p>The '<tt>malloc</tt>' instruction allocates +<tt>sizeof(<type>)*NumElements</tt> +bytes of memory from the operating system and returns a pointer of the +appropriate type to the program. If "NumElements" is specified, it is the +number of elements allocated, otherwise "NumElements" is defaulted to be one. +If a constant alignment is specified, the value result of the allocation is guaranteed to +be aligned to at least that boundary. If not specified, or if zero, the target can +choose to align the allocation on any convenient boundary.</p> + +<p>'<tt>type</tt>' must be a sized type.</p> + +<h5>Semantics:</h5> + +<p>Memory is allocated using the system "<tt>malloc</tt>" function, and +a pointer is returned. The result of a zero byte allocation is undefined. The +result is null if there is insufficient memory available.</p> + +<h5>Example:</h5> + +<pre> + %array = malloc [4 x i8] <i>; yields {[%4 x i8]*}:array</i> + + %size = <a href="#i_add">add</a> i32 2, 2 <i>; yields {i32}:size = i32 4</i> + %array1 = malloc i8, i32 4 <i>; yields {i8*}:array1</i> + %array2 = malloc [12 x i8], i32 %size <i>; yields {[12 x i8]*}:array2</i> + %array3 = malloc i32, i32 4, align 1024 <i>; yields {i32*}:array3</i> + %array4 = malloc i32, align 1024 <i>; yields {i32*}:array4</i> +</pre> + +<p>Note that the code generator does not yet respect the + alignment value.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_free">'<tt>free</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + free <type> <value> <i>; yields {void}</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>free</tt>' instruction returns memory back to the unused +memory heap to be reallocated in the future.</p> + +<h5>Arguments:</h5> + +<p>'<tt>value</tt>' shall be a pointer value that points to a value +that was allocated with the '<tt><a href="#i_malloc">malloc</a></tt>' +instruction.</p> + +<h5>Semantics:</h5> + +<p>Access to the memory pointed to by the pointer is no longer defined +after this instruction executes. If the pointer is null, the operation +is a noop.</p> + +<h5>Example:</h5> + +<pre> + %array = <a href="#i_malloc">malloc</a> [4 x i8] <i>; yields {[4 x i8]*}:array</i> + free [4 x i8]* %array +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_alloca">'<tt>alloca</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = alloca <type>[, i32 <NumElements>][, align <alignment>] <i>; yields {type*}:result</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the +currently executing function, to be automatically released when this function +returns to its caller. The object is always allocated in the generic address +space (address space zero).</p> + +<h5>Arguments:</h5> + +<p>The '<tt>alloca</tt>' instruction allocates <tt>sizeof(<type>)*NumElements</tt> +bytes of memory on the runtime stack, returning a pointer of the +appropriate type to the program. If "NumElements" is specified, it is the +number of elements allocated, otherwise "NumElements" is defaulted to be one. +If a constant alignment is specified, the value result of the allocation is guaranteed +to be aligned to at least that boundary. If not specified, or if zero, the target +can choose to align the allocation on any convenient boundary.</p> + +<p>'<tt>type</tt>' may be any sized type.</p> + +<h5>Semantics:</h5> + +<p>Memory is allocated; a pointer is returned. The operation is undefined if +there is insufficient stack space for the allocation. '<tt>alloca</tt>'d +memory is automatically released when the function returns. The '<tt>alloca</tt>' +instruction is commonly used to represent automatic variables that must +have an address available. When the function returns (either with the <tt><a + href="#i_ret">ret</a></tt> or <tt><a href="#i_unwind">unwind</a></tt> +instructions), the memory is reclaimed. Allocating zero bytes +is legal, but the result is undefined.</p> + +<h5>Example:</h5> + +<pre> + %ptr = alloca i32 <i>; yields {i32*}:ptr</i> + %ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i> + %ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i> + %ptr = alloca i32, align 1024 <i>; yields {i32*}:ptr</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_load">'<tt>load</tt>' +Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = load <ty>* <pointer>[, align <alignment>]<br> <result> = volatile load <ty>* <pointer>[, align <alignment>]<br></pre> +<h5>Overview:</h5> +<p>The '<tt>load</tt>' instruction is used to read from memory.</p> +<h5>Arguments:</h5> +<p>The argument to the '<tt>load</tt>' instruction specifies the memory +address from which to load. The pointer must point to a <a + href="#t_firstclass">first class</a> type. If the <tt>load</tt> is +marked as <tt>volatile</tt>, then the optimizer is not allowed to modify +the number or order of execution of this <tt>load</tt> with other +volatile <tt>load</tt> and <tt><a href="#i_store">store</a></tt> +instructions. </p> +<p> +The optional constant "align" argument specifies the alignment of the operation +(that is, the alignment of the memory address). A value of 0 or an +omitted "align" argument means that the operation has the preferential +alignment for the target. It is the responsibility of the code emitter +to ensure that the alignment information is correct. Overestimating +the alignment results in an undefined behavior. Underestimating the +alignment may produce less efficient code. An alignment of 1 is always +safe. +</p> +<h5>Semantics:</h5> +<p>The location of memory pointed to is loaded. If the value being loaded +is of scalar type then the number of bytes read does not exceed the minimum +number of bytes needed to hold all bits of the type. For example, loading an +<tt>i24</tt> reads at most three bytes. When loading a value of a type like +<tt>i20</tt> with a size that is not an integral number of bytes, the result +is undefined if the value was not originally written using a store of the +same type.</p> +<h5>Examples:</h5> +<pre> %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i> + <a + href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i> + %val = load i32* %ptr <i>; yields {i32}:val = i32 3</i> +</pre> +</div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="i_store">'<tt>store</tt>' +Instruction</a> </div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i> + volatile store <ty> <value>, <ty>* <pointer>[, align <alignment>] <i>; yields {void}</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>store</tt>' instruction is used to write to memory.</p> +<h5>Arguments:</h5> +<p>There are two arguments to the '<tt>store</tt>' instruction: a value +to store and an address at which to store it. The type of the '<tt><pointer></tt>' +operand must be a pointer to the <a href="#t_firstclass">first class</a> type +of the '<tt><value></tt>' +operand. If the <tt>store</tt> is marked as <tt>volatile</tt>, then the +optimizer is not allowed to modify the number or order of execution of +this <tt>store</tt> with other volatile <tt>load</tt> and <tt><a + href="#i_store">store</a></tt> instructions.</p> +<p> +The optional constant "align" argument specifies the alignment of the operation +(that is, the alignment of the memory address). A value of 0 or an +omitted "align" argument means that the operation has the preferential +alignment for the target. It is the responsibility of the code emitter +to ensure that the alignment information is correct. Overestimating +the alignment results in an undefined behavior. Underestimating the +alignment may produce less efficient code. An alignment of 1 is always +safe. +</p> +<h5>Semantics:</h5> +<p>The contents of memory are updated to contain '<tt><value></tt>' +at the location specified by the '<tt><pointer></tt>' operand. +If '<tt><value></tt>' is of scalar type then the number of bytes +written does not exceed the minimum number of bytes needed to hold all +bits of the type. For example, storing an <tt>i24</tt> writes at most +three bytes. When writing a value of a type like <tt>i20</tt> with a +size that is not an integral number of bytes, it is unspecified what +happens to the extra bits that do not belong to the type, but they will +typically be overwritten.</p> +<h5>Example:</h5> +<pre> %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i> + store i32 3, i32* %ptr <i>; yields {void}</i> + %val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a> +</div> + +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> + <result> = getelementptr <pty>* <ptrval>{, <ty> <idx>}* +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>getelementptr</tt>' instruction is used to get the address of a +subelement of an aggregate data structure. It performs address calculation only +and does not access memory.</p> + +<h5>Arguments:</h5> + +<p>The first argument is always a pointer, and forms the basis of the +calculation. The remaining arguments are indices, that indicate which of the +elements of the aggregate object are indexed. The interpretation of each index +is dependent on the type being indexed into. The first index always indexes the +pointer value given as the first argument, the second index indexes a value of +the type pointed to (not necessarily the value directly pointed to, since the +first index can be non-zero), etc. The first type indexed into must be a pointer +value, subsequent types can be arrays, vectors and structs. Note that subsequent +types being indexed into can never be pointers, since that would require loading +the pointer before continuing calculation.</p> + +<p>The type of each index argument depends on the type it is indexing into. +When indexing into a (packed) structure, only <tt>i32</tt> integer +<b>constants</b> are allowed. When indexing into an array, pointer or vector, +integers of any width are allowed (also non-constants).</p> + +<p>For example, let's consider a C code fragment and how it gets +compiled to LLVM:</p> + +<div class="doc_code"> +<pre> +struct RT { + char A; + int B[10][20]; + char C; +}; +struct ST { + int X; + double Y; + struct RT Z; +}; + +int *foo(struct ST *s) { + return &s[1].Z.B[5][13]; +} +</pre> +</div> + +<p>The LLVM code generated by the GCC frontend is:</p> + +<div class="doc_code"> +<pre> +%RT = <a href="#namedtypes">type</a> { i8 , [10 x [20 x i32]], i8 } +%ST = <a href="#namedtypes">type</a> { i32, double, %RT } + +define i32* %foo(%ST* %s) { +entry: + %reg = getelementptr %ST* %s, i32 1, i32 2, i32 1, i32 5, i32 13 + ret i32* %reg +} +</pre> +</div> + +<h5>Semantics:</h5> + +<p>In the example above, the first index is indexing into the '<tt>%ST*</tt>' +type, which is a pointer, yielding a '<tt>%ST</tt>' = '<tt>{ i32, double, %RT +}</tt>' type, a structure. The second index indexes into the third element of +the structure, yielding a '<tt>%RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]], +i8 }</tt>' type, another structure. The third index indexes into the second +element of the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an +array. The two dimensions of the array are subscripted into, yielding an +'<tt>i32</tt>' type. The '<tt>getelementptr</tt>' instruction returns a pointer +to this element, thus computing a value of '<tt>i32*</tt>' type.</p> + +<p>Note that it is perfectly legal to index partially through a +structure, returning a pointer to an inner element. Because of this, +the LLVM code for the given testcase is equivalent to:</p> + +<pre> + define i32* %foo(%ST* %s) { + %t1 = getelementptr %ST* %s, i32 1 <i>; yields %ST*:%t1</i> + %t2 = getelementptr %ST* %t1, i32 0, i32 2 <i>; yields %RT*:%t2</i> + %t3 = getelementptr %RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i> + %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i> + %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i> + ret i32* %t5 + } +</pre> + +<p>Note that it is undefined to access an array out of bounds: array +and pointer indexes must always be within the defined bounds of the +array type when accessed with an instruction that dereferences the +pointer (e.g. a load or store instruction). The one exception for +this rule is zero length arrays. These arrays are defined to be +accessible as variable length arrays, which requires access beyond the +zero'th element.</p> + +<p>The getelementptr instruction is often confusing. For some more insight +into how it works, see <a href="GetElementPtr.html">the getelementptr +FAQ</a>.</p> + +<h5>Example:</h5> + +<pre> + <i>; yields [12 x i8]*:aptr</i> + %aptr = getelementptr {i32, [12 x i8]}* %saptr, i64 0, i32 1 + <i>; yields i8*:vptr</i> + %vptr = getelementptr {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1 + <i>; yields i8*:eptr</i> + %eptr = getelementptr [12 x i8]* %aptr, i64 0, i32 1 + <i>; yields i32*:iptr</i> + %iptr = getelementptr [10 x i32]* @arr, i16 0, i16 0 +</pre> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="convertops">Conversion Operations</a> +</div> +<div class="doc_text"> +<p>The instructions in this category are the conversion instructions (casting) +which all take a single operand and a type. They perform various bit conversions +on the operand.</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p> +The '<tt>trunc</tt>' instruction truncates its operand to the type <tt>ty2</tt>. +</p> + +<h5>Arguments:</h5> +<p> +The '<tt>trunc</tt>' instruction takes a <tt>value</tt> to trunc, which must +be an <a href="#t_integer">integer</a> type, and a type that specifies the size +and type of the result, which must be an <a href="#t_integer">integer</a> +type. The bit size of <tt>value</tt> must be larger than the bit size of +<tt>ty2</tt>. Equal sized types are not allowed.</p> + +<h5>Semantics:</h5> +<p> +The '<tt>trunc</tt>' instruction truncates the high order bits in <tt>value</tt> +and converts the remaining bits to <tt>ty2</tt>. Since the source size must be +larger than the destination size, <tt>trunc</tt> cannot be a <i>no-op cast</i>. +It will always truncate bits.</p> + +<h5>Example:</h5> +<pre> + %X = trunc i32 257 to i8 <i>; yields i8:1</i> + %Y = trunc i32 123 to i1 <i>; yields i1:true</i> + %Y = trunc i32 122 to i1 <i>; yields i1:false</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_zext">'<tt>zext .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = zext <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>zext</tt>' instruction zero extends its operand to type +<tt>ty2</tt>.</p> + + +<h5>Arguments:</h5> +<p>The '<tt>zext</tt>' instruction takes a value to cast, which must be of +<a href="#t_integer">integer</a> type, and a type to cast it to, which must +also be of <a href="#t_integer">integer</a> type. The bit size of the +<tt>value</tt> must be smaller than the bit size of the destination type, +<tt>ty2</tt>.</p> + +<h5>Semantics:</h5> +<p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero +bits until it reaches the size of the destination type, <tt>ty2</tt>.</p> + +<p>When zero extending from i1, the result will always be either 0 or 1.</p> + +<h5>Example:</h5> +<pre> + %X = zext i32 257 to i64 <i>; yields i64:257</i> + %Y = zext i1 true to i32 <i>; yields i32:1</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_sext">'<tt>sext .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = sext <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p> + +<h5>Arguments:</h5> +<p> +The '<tt>sext</tt>' instruction takes a value to cast, which must be of +<a href="#t_integer">integer</a> type, and a type to cast it to, which must +also be of <a href="#t_integer">integer</a> type. The bit size of the +<tt>value</tt> must be smaller than the bit size of the destination type, +<tt>ty2</tt>.</p> + +<h5>Semantics:</h5> +<p> +The '<tt>sext</tt>' instruction performs a sign extension by copying the sign +bit (highest order bit) of the <tt>value</tt> until it reaches the bit size of +the type <tt>ty2</tt>.</p> + +<p>When sign extending from i1, the extension always results in -1 or 0.</p> + +<h5>Example:</h5> +<pre> + %X = sext i8 -1 to i16 <i>; yields i16 :65535</i> + %Y = sext i1 true to i32 <i>; yields i32:-1</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type +<tt>ty2</tt>.</p> + + +<h5>Arguments:</h5> +<p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating + point</a> value to cast and a <a href="#t_floating">floating point</a> type to +cast it to. The size of <tt>value</tt> must be larger than the size of +<tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a +<i>no-op cast</i>.</p> + +<h5>Semantics:</h5> +<p> The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger +<a href="#t_floating">floating point</a> type to a smaller +<a href="#t_floating">floating point</a> type. If the value cannot fit within +the destination type, <tt>ty2</tt>, then the results are undefined.</p> + +<h5>Example:</h5> +<pre> + %X = fptrunc double 123.0 to float <i>; yields float:123.0</i> + %Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger +floating point value.</p> + +<h5>Arguments:</h5> +<p>The '<tt>fpext</tt>' instruction takes a +<a href="#t_floating">floating point</a> <tt>value</tt> to cast, +and a <a href="#t_floating">floating point</a> type to cast it to. The source +type must be smaller than the destination type.</p> + +<h5>Semantics:</h5> +<p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller +<a href="#t_floating">floating point</a> type to a larger +<a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be +used to make a <i>no-op cast</i> because it always changes bits. Use +<tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p> + +<h5>Example:</h5> +<pre> + %X = fpext float 3.1415 to double <i>; yields double:3.1415</i> + %Y = fpext float 1.0 to float <i>; yields float:1.0 (no-op)</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its +unsigned integer equivalent of type <tt>ty2</tt>. +</p> + +<h5>Arguments:</h5> +<p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a +scalar or vector <a href="#t_floating">floating point</a> value, and a type +to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> +type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a +vector integer type with the same number of elements as <tt>ty</tt></p> + +<h5>Semantics:</h5> +<p> The '<tt>fptoui</tt>' instruction converts its +<a href="#t_floating">floating point</a> operand into the nearest (rounding +towards zero) unsigned integer value. If the value cannot fit in <tt>ty2</tt>, +the results are undefined.</p> + +<h5>Example:</h5> +<pre> + %X = fptoui double 123.0 to i32 <i>; yields i32:123</i> + %Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i> + %X = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>fptosi</tt>' instruction converts +<a href="#t_floating">floating point</a> <tt>value</tt> to type <tt>ty2</tt>. +</p> + +<h5>Arguments:</h5> +<p> The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a +scalar or vector <a href="#t_floating">floating point</a> value, and a type +to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> +type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a +vector integer type with the same number of elements as <tt>ty</tt></p> + +<h5>Semantics:</h5> +<p>The '<tt>fptosi</tt>' instruction converts its +<a href="#t_floating">floating point</a> operand into the nearest (rounding +towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>, +the results are undefined.</p> + +<h5>Example:</h5> +<pre> + %X = fptosi double -123.0 to i32 <i>; yields i32:-123</i> + %Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i> + %X = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned +integer and converts that value to the <tt>ty2</tt> type.</p> + +<h5>Arguments:</h5> +<p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be a +scalar or vector <a href="#t_integer">integer</a> value, and a type to cast it +to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a> +type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector +floating point type with the same number of elements as <tt>ty</tt></p> + +<h5>Semantics:</h5> +<p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned +integer quantity and converts it to the corresponding floating point value. If +the value cannot fit in the floating point value, the results are undefined.</p> + +<h5>Example:</h5> +<pre> + %X = uitofp i32 257 to float <i>; yields float:257.0</i> + %Y = uitofp i8 -1 to double <i>; yields double:255.0</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed +integer and converts that value to the <tt>ty2</tt> type.</p> + +<h5>Arguments:</h5> +<p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be a +scalar or vector <a href="#t_integer">integer</a> value, and a type to cast it +to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a> +type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector +floating point type with the same number of elements as <tt>ty</tt></p> + +<h5>Semantics:</h5> +<p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed +integer quantity and converts it to the corresponding floating point value. If +the value cannot fit in the floating point value, the results are undefined.</p> + +<h5>Example:</h5> +<pre> + %X = sitofp i32 257 to float <i>; yields float:257.0</i> + %Y = sitofp i8 -1 to double <i>; yields double:-1.0</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>ptrtoint</tt>' instruction converts the pointer <tt>value</tt> to +the integer type <tt>ty2</tt>.</p> + +<h5>Arguments:</h5> +<p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which +must be a <a href="#t_pointer">pointer</a> value, and a type to cast it to +<tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> type.</p> + +<h5>Semantics:</h5> +<p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type +<tt>ty2</tt> by interpreting the pointer value as an integer and either +truncating or zero extending that value to the size of the integer type. If +<tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If +<tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they +are the same size, then nothing is done (<i>no-op cast</i>) other than a type +change.</p> + +<h5>Example:</h5> +<pre> + %X = ptrtoint i32* %X to i8 <i>; yields truncation on 32-bit architecture</i> + %Y = ptrtoint i32* %x to i64 <i>; yields zero extension on 32-bit architecture</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> +<p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to +a pointer type, <tt>ty2</tt>.</p> + +<h5>Arguments:</h5> +<p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a> +value to cast, and a type to cast it to, which must be a +<a href="#t_pointer">pointer</a> type.</p> + +<h5>Semantics:</h5> +<p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type +<tt>ty2</tt> by applying either a zero extension or a truncation depending on +the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the +size of a pointer then a truncation is done. If <tt>value</tt> is smaller than +the size of a pointer then a zero extension is done. If they are the same size, +nothing is done (<i>no-op cast</i>).</p> + +<h5>Example:</h5> +<pre> + %X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i> + %X = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i> + %Y = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a> +</div> +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type +<tt>ty2</tt> without changing any bits.</p> + +<h5>Arguments:</h5> + +<p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be +a non-aggregate first class value, and a type to cast it to, which must also be +a non-aggregate <a href="#t_firstclass">first class</a> type. The bit sizes of +<tt>value</tt> +and the destination type, <tt>ty2</tt>, must be identical. If the source +type is a pointer, the destination type must also be a pointer. This +instruction supports bitwise conversion of vectors to integers and to vectors +of other types (as long as they have the same size).</p> + +<h5>Semantics:</h5> +<p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type +<tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with +this conversion. The conversion is done as if the <tt>value</tt> had been +stored to memory and read back as type <tt>ty2</tt>. Pointer types may only be +converted to other pointer types with this instruction. To convert pointers to +other types, use the <a href="#i_inttoptr">inttoptr</a> or +<a href="#i_ptrtoint">ptrtoint</a> instructions first.</p> + +<h5>Example:</h5> +<pre> + %X = bitcast i8 255 to i8 <i>; yields i8 :-1</i> + %Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i> + %Z = bitcast <2 x int> %V to i64; <i>; yields i64: %V</i> +</pre> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="otherops">Other Operations</a> </div> +<div class="doc_text"> +<p>The instructions in this category are the "miscellaneous" +instructions, which defy better classification.</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"><a name="i_icmp">'<tt>icmp</tt>' Instruction</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = icmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>icmp</tt>' instruction returns a boolean value or +a vector of boolean values based on comparison +of its two integer, integer vector, or pointer operands.</p> +<h5>Arguments:</h5> +<p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is +the condition code indicating the kind of comparison to perform. It is not +a value, just a keyword. The possible condition code are: +</p> +<ol> + <li><tt>eq</tt>: equal</li> + <li><tt>ne</tt>: not equal </li> + <li><tt>ugt</tt>: unsigned greater than</li> + <li><tt>uge</tt>: unsigned greater or equal</li> + <li><tt>ult</tt>: unsigned less than</li> + <li><tt>ule</tt>: unsigned less or equal</li> + <li><tt>sgt</tt>: signed greater than</li> + <li><tt>sge</tt>: signed greater or equal</li> + <li><tt>slt</tt>: signed less than</li> + <li><tt>sle</tt>: signed less or equal</li> +</ol> +<p>The remaining two arguments must be <a href="#t_integer">integer</a> or +<a href="#t_pointer">pointer</a> +or integer <a href="#t_vector">vector</a> typed. +They must also be identical types.</p> +<h5>Semantics:</h5> +<p>The '<tt>icmp</tt>' compares <tt>op1</tt> and <tt>op2</tt> according to +the condition code given as <tt>cond</tt>. The comparison performed always +yields either an <a href="#t_primitive"><tt>i1</tt></a> or vector of <tt>i1</tt> result, as follows: +</p> +<ol> + <li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal, + <tt>false</tt> otherwise. No sign interpretation is necessary or performed. + </li> + <li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal, + <tt>false</tt> otherwise. No sign interpretation is necessary or performed.</li> + <li><tt>ugt</tt>: interprets the operands as unsigned values and yields + <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li> + <li><tt>uge</tt>: interprets the operands as unsigned values and yields + <tt>true</tt> if <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li> + <li><tt>ult</tt>: interprets the operands as unsigned values and yields + <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li> + <li><tt>ule</tt>: interprets the operands as unsigned values and yields + <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> + <li><tt>sgt</tt>: interprets the operands as signed values and yields + <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li> + <li><tt>sge</tt>: interprets the operands as signed values and yields + <tt>true</tt> if <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li> + <li><tt>slt</tt>: interprets the operands as signed values and yields + <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li> + <li><tt>sle</tt>: interprets the operands as signed values and yields + <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> +</ol> +<p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer +values are compared as if they were integers.</p> +<p>If the operands are integer vectors, then they are compared +element by element. The result is an <tt>i1</tt> vector with +the same number of elements as the values being compared. +Otherwise, the result is an <tt>i1</tt>. +</p> + +<h5>Example:</h5> +<pre> <result> = icmp eq i32 4, 5 <i>; yields: result=false</i> + <result> = icmp ne float* %X, %X <i>; yields: result=false</i> + <result> = icmp ult i16 4, 5 <i>; yields: result=true</i> + <result> = icmp sgt i16 4, 5 <i>; yields: result=false</i> + <result> = icmp ule i16 -4, 5 <i>; yields: result=false</i> + <result> = icmp sge i16 4, 5 <i>; yields: result=false</i> +</pre> + +<p>Note that the code generator does not yet support vector types with + the <tt>icmp</tt> instruction.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"><a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = fcmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>fcmp</tt>' instruction returns a boolean value +or vector of boolean values based on comparison +of its operands.</p> +<p> +If the operands are floating point scalars, then the result +type is a boolean (<a href="#t_primitive"><tt>i1</tt></a>). +</p> +<p>If the operands are floating point vectors, then the result type +is a vector of boolean with the same number of elements as the +operands being compared.</p> +<h5>Arguments:</h5> +<p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is +the condition code indicating the kind of comparison to perform. It is not +a value, just a keyword. The possible condition code are:</p> +<ol> + <li><tt>false</tt>: no comparison, always returns false</li> + <li><tt>oeq</tt>: ordered and equal</li> + <li><tt>ogt</tt>: ordered and greater than </li> + <li><tt>oge</tt>: ordered and greater than or equal</li> + <li><tt>olt</tt>: ordered and less than </li> + <li><tt>ole</tt>: ordered and less than or equal</li> + <li><tt>one</tt>: ordered and not equal</li> + <li><tt>ord</tt>: ordered (no nans)</li> + <li><tt>ueq</tt>: unordered or equal</li> + <li><tt>ugt</tt>: unordered or greater than </li> + <li><tt>uge</tt>: unordered or greater than or equal</li> + <li><tt>ult</tt>: unordered or less than </li> + <li><tt>ule</tt>: unordered or less than or equal</li> + <li><tt>une</tt>: unordered or not equal</li> + <li><tt>uno</tt>: unordered (either nans)</li> + <li><tt>true</tt>: no comparison, always returns true</li> +</ol> +<p><i>Ordered</i> means that neither operand is a QNAN while +<i>unordered</i> means that either operand may be a QNAN.</p> +<p>Each of <tt>val1</tt> and <tt>val2</tt> arguments must be +either a <a href="#t_floating">floating point</a> type +or a <a href="#t_vector">vector</a> of floating point type. +They must have identical types.</p> +<h5>Semantics:</h5> +<p>The '<tt>fcmp</tt>' instruction compares <tt>op1</tt> and <tt>op2</tt> +according to the condition code given as <tt>cond</tt>. +If the operands are vectors, then the vectors are compared +element by element. +Each comparison performed +always yields an <a href="#t_primitive">i1</a> result, as follows:</p> +<ol> + <li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li> + <li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and + <tt>op1</tt> is equal to <tt>op2</tt>.</li> + <li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and + <tt>op1</tt> is greather than <tt>op2</tt>.</li> + <li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and + <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li> + <li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and + <tt>op1</tt> is less than <tt>op2</tt>.</li> + <li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and + <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> + <li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and + <tt>op1</tt> is not equal to <tt>op2</tt>.</li> + <li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li> + <li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or + <tt>op1</tt> is equal to <tt>op2</tt>.</li> + <li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or + <tt>op1</tt> is greater than <tt>op2</tt>.</li> + <li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or + <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li> + <li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or + <tt>op1</tt> is less than <tt>op2</tt>.</li> + <li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or + <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> + <li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or + <tt>op1</tt> is not equal to <tt>op2</tt>.</li> + <li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li> + <li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li> +</ol> + +<h5>Example:</h5> +<pre> <result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i> + <result> = fcmp one float 4.0, 5.0 <i>; yields: result=true</i> + <result> = fcmp olt float 4.0, 5.0 <i>; yields: result=true</i> + <result> = fcmp ueq double 1.0, 2.0 <i>; yields: result=false</i> +</pre> + +<p>Note that the code generator does not yet support vector types with + the <tt>fcmp</tt> instruction.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_vicmp">'<tt>vicmp</tt>' Instruction</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = vicmp <cond> <ty> <op1>, <op2> <i>; yields {ty}:result</i> +</pre> +<h5>Overview:</h5> +<p>The '<tt>vicmp</tt>' instruction returns an integer vector value based on +element-wise comparison of its two integer vector operands.</p> +<h5>Arguments:</h5> +<p>The '<tt>vicmp</tt>' instruction takes three operands. The first operand is +the condition code indicating the kind of comparison to perform. It is not +a value, just a keyword. The possible condition code are:</p> +<ol> + <li><tt>eq</tt>: equal</li> + <li><tt>ne</tt>: not equal </li> + <li><tt>ugt</tt>: unsigned greater than</li> + <li><tt>uge</tt>: unsigned greater or equal</li> + <li><tt>ult</tt>: unsigned less than</li> + <li><tt>ule</tt>: unsigned less or equal</li> + <li><tt>sgt</tt>: signed greater than</li> + <li><tt>sge</tt>: signed greater or equal</li> + <li><tt>slt</tt>: signed less than</li> + <li><tt>sle</tt>: signed less or equal</li> +</ol> +<p>The remaining two arguments must be <a href="#t_vector">vector</a> or +<a href="#t_integer">integer</a> typed. They must also be identical types.</p> +<h5>Semantics:</h5> +<p>The '<tt>vicmp</tt>' instruction compares <tt>op1</tt> and <tt>op2</tt> +according to the condition code given as <tt>cond</tt>. The comparison yields a +<a href="#t_vector">vector</a> of <a href="#t_integer">integer</a> result, of +identical type as the values being compared. The most significant bit in each +element is 1 if the element-wise comparison evaluates to true, and is 0 +otherwise. All other bits of the result are undefined. The condition codes +are evaluated identically to the <a href="#i_icmp">'<tt>icmp</tt>' +instruction</a>.</p> + +<h5>Example:</h5> +<pre> + <result> = vicmp eq <2 x i32> < i32 4, i32 0>, < i32 5, i32 0> <i>; yields: result=<2 x i32> < i32 0, i32 -1 ></i> + <result> = vicmp ult <2 x i8 > < i8 1, i8 2>, < i8 2, i8 2 > <i>; yields: result=<2 x i8> < i8 -1, i8 0 ></i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_vfcmp">'<tt>vfcmp</tt>' Instruction</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> <result> = vfcmp <cond> <ty> <op1>, <op2></pre> +<h5>Overview:</h5> +<p>The '<tt>vfcmp</tt>' instruction returns an integer vector value based on +element-wise comparison of its two floating point vector operands. The output +elements have the same width as the input elements.</p> +<h5>Arguments:</h5> +<p>The '<tt>vfcmp</tt>' instruction takes three operands. The first operand is +the condition code indicating the kind of comparison to perform. It is not +a value, just a keyword. The possible condition code are:</p> +<ol> + <li><tt>false</tt>: no comparison, always returns false</li> + <li><tt>oeq</tt>: ordered and equal</li> + <li><tt>ogt</tt>: ordered and greater than </li> + <li><tt>oge</tt>: ordered and greater than or equal</li> + <li><tt>olt</tt>: ordered and less than </li> + <li><tt>ole</tt>: ordered and less than or equal</li> + <li><tt>one</tt>: ordered and not equal</li> + <li><tt>ord</tt>: ordered (no nans)</li> + <li><tt>ueq</tt>: unordered or equal</li> + <li><tt>ugt</tt>: unordered or greater than </li> + <li><tt>uge</tt>: unordered or greater than or equal</li> + <li><tt>ult</tt>: unordered or less than </li> + <li><tt>ule</tt>: unordered or less than or equal</li> + <li><tt>une</tt>: unordered or not equal</li> + <li><tt>uno</tt>: unordered (either nans)</li> + <li><tt>true</tt>: no comparison, always returns true</li> +</ol> +<p>The remaining two arguments must be <a href="#t_vector">vector</a> of +<a href="#t_floating">floating point</a> typed. They must also be identical +types.</p> +<h5>Semantics:</h5> +<p>The '<tt>vfcmp</tt>' instruction compares <tt>op1</tt> and <tt>op2</tt> +according to the condition code given as <tt>cond</tt>. The comparison yields a +<a href="#t_vector">vector</a> of <a href="#t_integer">integer</a> result, with +an identical number of elements as the values being compared, and each element +having identical with to the width of the floating point elements. The most +significant bit in each element is 1 if the element-wise comparison evaluates to +true, and is 0 otherwise. All other bits of the result are undefined. The +condition codes are evaluated identically to the +<a href="#i_fcmp">'<tt>fcmp</tt>' instruction</a>.</p> + +<h5>Example:</h5> +<pre> + <i>; yields: result=<2 x i32> < i32 0, i32 -1 ></i> + <result> = vfcmp oeq <2 x float> < float 4, float 0 >, < float 5, float 0 > + + <i>; yields: result=<2 x i64> < i64 -1, i64 0 ></i> + <result> = vfcmp ult <2 x double> < double 1, double 2 >, < double 2, double 2> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_phi">'<tt>phi</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> <result> = phi <ty> [ <val0>, <label0>], ...<br></pre> +<h5>Overview:</h5> +<p>The '<tt>phi</tt>' instruction is used to implement the φ node in +the SSA graph representing the function.</p> +<h5>Arguments:</h5> + +<p>The type of the incoming values is specified with the first type +field. After this, the '<tt>phi</tt>' instruction takes a list of pairs +as arguments, with one pair for each predecessor basic block of the +current block. Only values of <a href="#t_firstclass">first class</a> +type may be used as the value arguments to the PHI node. Only labels +may be used as the label arguments.</p> + +<p>There must be no non-phi instructions between the start of a basic +block and the PHI instructions: i.e. PHI instructions must be first in +a basic block.</p> + +<h5>Semantics:</h5> + +<p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value +specified by the pair corresponding to the predecessor basic block that executed +just prior to the current block.</p> + +<h5>Example:</h5> +<pre> +Loop: ; Infinite loop that counts from 0 on up... + %indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ] + %nextindvar = add i32 %indvar, 1 + br label %Loop +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_select">'<tt>select</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <result> = select <i>selty</i> <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i> + + <i>selty</i> is either i1 or {<N x i1>} +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>select</tt>' instruction is used to choose one value based on a +condition, without branching. +</p> + + +<h5>Arguments:</h5> + +<p> +The '<tt>select</tt>' instruction requires an 'i1' value or +a vector of 'i1' values indicating the +condition, and two values of the same <a href="#t_firstclass">first class</a> +type. If the val1/val2 are vectors and +the condition is a scalar, then entire vectors are selected, not +individual elements. +</p> + +<h5>Semantics:</h5> + +<p> +If the condition is an i1 and it evaluates to 1, the instruction returns the first +value argument; otherwise, it returns the second value argument. +</p> +<p> +If the condition is a vector of i1, then the value arguments must +be vectors of the same size, and the selection is done element +by element. +</p> + +<h5>Example:</h5> + +<pre> + %X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i> +</pre> + +<p>Note that the code generator does not yet support conditions + with vector type.</p> + +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_call">'<tt>call</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + <result> = [tail] call [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ty> [<fnty>*] <fnptrval>(<function args>) [<a href="#fnattrs">fn attrs</a>] +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>call</tt>' instruction represents a simple function call.</p> + +<h5>Arguments:</h5> + +<p>This instruction requires several arguments:</p> + +<ol> + <li> + <p>The optional "tail" marker indicates whether the callee function accesses + any allocas or varargs in the caller. If the "tail" marker is present, the + function call is eligible for tail call optimization. Note that calls may + be marked "tail" even if they do not occur before a <a + href="#i_ret"><tt>ret</tt></a> instruction.</p> + </li> + <li> + <p>The optional "cconv" marker indicates which <a href="#callingconv">calling + convention</a> the call should use. If none is specified, the call defaults + to using C calling conventions.</p> + </li> + + <li> + <p>The optional <a href="#paramattrs">Parameter Attributes</a> list for + return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', + and '<tt>inreg</tt>' attributes are valid here.</p> + </li> + + <li> + <p>'<tt>ty</tt>': the type of the call instruction itself which is also + the type of the return value. Functions that return no value are marked + <tt><a href="#t_void">void</a></tt>.</p> + </li> + <li> + <p>'<tt>fnty</tt>': shall be the signature of the pointer to function + value being invoked. The argument types must match the types implied by + this signature. This type can be omitted if the function is not varargs + and if the function type does not return a pointer to a function.</p> + </li> + <li> + <p>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to + be invoked. In most cases, this is a direct function invocation, but + indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer + to function value.</p> + </li> + <li> + <p>'<tt>function args</tt>': argument list whose types match the + function signature argument types. All arguments must be of + <a href="#t_firstclass">first class</a> type. If the function signature + indicates the function accepts a variable number of arguments, the extra + arguments can be specified.</p> + </li> + <li> + <p>The optional <a href="#fnattrs">function attributes</a> list. Only + '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and + '<tt>readnone</tt>' attributes are valid here.</p> + </li> +</ol> + +<h5>Semantics:</h5> + +<p>The '<tt>call</tt>' instruction is used to cause control flow to +transfer to a specified function, with its incoming arguments bound to +the specified values. Upon a '<tt><a href="#i_ret">ret</a></tt>' +instruction in the called function, control flow continues with the +instruction after the function call, and the return value of the +function is bound to the result argument.</p> + +<h5>Example:</h5> + +<pre> + %retval = call i32 @test(i32 %argc) + call i32 (i8 *, ...)* @printf(i8 * %msg, i32 12, i8 42) <i>; yields i32</i> + %X = tail call i32 @foo() <i>; yields i32</i> + %Y = tail call <a href="#callingconv">fastcc</a> i32 @foo() <i>; yields i32</i> + call void %foo(i8 97 signext) + + %struct.A = type { i32, i8 } + %r = call %struct.A @foo() <i>; yields { 32, i8 }</i> + %gr = extractvalue %struct.A %r, 0 <i>; yields i32</i> + %gr1 = extractvalue %struct.A %r, 1 <i>; yields i8</i> + %Z = call void @foo() noreturn <i>; indicates that %foo never returns normally</i> + %ZZ = call zeroext i32 @bar() <i>; Return value is %zero extended</i> +</pre> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_va_arg">'<tt>va_arg</tt>' Instruction</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + <resultval> = va_arg <va_list*> <arglist>, <argty> +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through +the "variable argument" area of a function call. It is used to implement the +<tt>va_arg</tt> macro in C.</p> + +<h5>Arguments:</h5> + +<p>This instruction takes a <tt>va_list*</tt> value and the type of +the argument. It returns a value of the specified argument type and +increments the <tt>va_list</tt> to point to the next argument. The +actual type of <tt>va_list</tt> is target specific.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>va_arg</tt>' instruction loads an argument of the specified +type from the specified <tt>va_list</tt> and causes the +<tt>va_list</tt> to point to the next argument. For more information, +see the variable argument handling <a href="#int_varargs">Intrinsic +Functions</a>.</p> + +<p>It is legal for this instruction to be called in a function which does not +take a variable number of arguments, for example, the <tt>vfprintf</tt> +function.</p> + +<p><tt>va_arg</tt> is an LLVM instruction instead of an <a +href="#intrinsics">intrinsic function</a> because it takes a type as an +argument.</p> + +<h5>Example:</h5> + +<p>See the <a href="#int_varargs">variable argument processing</a> section.</p> + +<p>Note that the code generator does not yet fully support va_arg + on many targets. Also, it does not currently support va_arg with + aggregate types on any target.</p> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="intrinsics">Intrinsic Functions</a> </div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>LLVM supports the notion of an "intrinsic function". These functions have +well known names and semantics and are required to follow certain restrictions. +Overall, these intrinsics represent an extension mechanism for the LLVM +language that does not require changing all of the transformations in LLVM when +adding to the language (or the bitcode reader/writer, the parser, etc...).</p> + +<p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This +prefix is reserved in LLVM for intrinsic names; thus, function names may not +begin with this prefix. Intrinsic functions must always be external functions: +you cannot define the body of intrinsic functions. Intrinsic functions may +only be used in call or invoke instructions: it is illegal to take the address +of an intrinsic function. Additionally, because intrinsic functions are part +of the LLVM language, it is required if any are added that they be documented +here.</p> + +<p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents +a family of functions that perform the same operation but on different data +types. Because LLVM can represent over 8 million different integer types, +overloading is used commonly to allow an intrinsic function to operate on any +integer type. One or more of the argument types or the result type can be +overloaded to accept any integer type. Argument types may also be defined as +exactly matching a previous argument's type or the result type. This allows an +intrinsic function which accepts multiple arguments, but needs all of them to +be of the same type, to only be overloaded with respect to a single argument or +the result.</p> + +<p>Overloaded intrinsics will have the names of its overloaded argument types +encoded into its function name, each preceded by a period. Only those types +which are overloaded result in a name suffix. Arguments whose type is matched +against another type do not. For example, the <tt>llvm.ctpop</tt> function can +take an integer of any width and returns an integer of exactly the same integer +width. This leads to a family of functions such as +<tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29 %val)</tt>. +Only one type, the return type, is overloaded, and only one type suffix is +required. Because the argument's type is matched against the return type, it +does not require its own name suffix.</p> + +<p>To learn how to add an intrinsic function, please see the +<a href="ExtendingLLVM.html">Extending LLVM Guide</a>. +</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_varargs">Variable Argument Handling Intrinsics</a> +</div> + +<div class="doc_text"> + +<p>Variable argument support is defined in LLVM with the <a + href="#i_va_arg"><tt>va_arg</tt></a> instruction and these three +intrinsic functions. These functions are related to the similarly +named macros defined in the <tt><stdarg.h></tt> header file.</p> + +<p>All of these functions operate on arguments that use a +target-specific value type "<tt>va_list</tt>". The LLVM assembly +language reference manual does not define what this type is, so all +transformations should be prepared to handle these functions regardless of +the type used.</p> + +<p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a> +instruction and the variable argument handling intrinsic functions are +used.</p> + +<div class="doc_code"> +<pre> +define i32 @test(i32 %X, ...) { + ; Initialize variable argument processing + %ap = alloca i8* + %ap2 = bitcast i8** %ap to i8* + call void @llvm.va_start(i8* %ap2) + + ; Read a single integer argument + %tmp = va_arg i8** %ap, i32 + + ; Demonstrate usage of llvm.va_copy and llvm.va_end + %aq = alloca i8* + %aq2 = bitcast i8** %aq to i8* + call void @llvm.va_copy(i8* %aq2, i8* %ap2) + call void @llvm.va_end(i8* %aq2) + + ; Stop processing of arguments. + call void @llvm.va_end(i8* %ap2) + ret i32 %tmp +} + +declare void @llvm.va_start(i8*) +declare void @llvm.va_copy(i8*, i8*) +declare void @llvm.va_end(i8*) +</pre> +</div> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a> +</div> + + +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> declare void %llvm.va_start(i8* <arglist>)<br></pre> +<h5>Overview:</h5> +<p>The '<tt>llvm.va_start</tt>' intrinsic initializes +<tt>*<arglist></tt> for subsequent use by <tt><a +href="#i_va_arg">va_arg</a></tt>.</p> + +<h5>Arguments:</h5> + +<p>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt> +macro available in C. In a target-dependent way, it initializes the +<tt>va_list</tt> element to which the argument points, so that the next call to +<tt>va_arg</tt> will produce the first variable argument passed to the function. +Unlike the C <tt>va_start</tt> macro, this intrinsic does not need to know the +last argument of the function as the compiler can figure that out.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> declare void @llvm.va_end(i8* <arglist>)<br></pre> +<h5>Overview:</h5> + +<p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt>*<arglist></tt>, +which has been initialized previously with <tt><a href="#int_va_start">llvm.va_start</a></tt> +or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p> + +<h5>Arguments:</h5> + +<p>The argument is a pointer to a <tt>va_list</tt> to destroy.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt> +macro available in C. In a target-dependent way, it destroys the +<tt>va_list</tt> element to which the argument points. Calls to <a +href="#int_va_start"><tt>llvm.va_start</tt></a> and <a href="#int_va_copy"> +<tt>llvm.va_copy</tt></a> must be matched exactly with calls to +<tt>llvm.va_end</tt>.</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position +from the source argument list to the destination argument list.</p> + +<h5>Arguments:</h5> + +<p>The first argument is a pointer to a <tt>va_list</tt> element to initialize. +The second argument is a pointer to a <tt>va_list</tt> element to copy from.</p> + + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt> +macro available in C. In a target-dependent way, it copies the source +<tt>va_list</tt> element into the destination <tt>va_list</tt> element. This +intrinsic is necessary because the <tt><a href="#int_va_start"> +llvm.va_start</a></tt> intrinsic may be arbitrarily complex and require, for +example, memory allocation.</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_gc">Accurate Garbage Collection Intrinsics</a> +</div> + +<div class="doc_text"> + +<p> +LLVM support for <a href="GarbageCollection.html">Accurate Garbage +Collection</a> (GC) requires the implementation and generation of these +intrinsics. +These intrinsics allow identification of <a href="#int_gcroot">GC roots on the +stack</a>, as well as garbage collector implementations that require <a +href="#int_gcread">read</a> and <a href="#int_gcwrite">write</a> barriers. +Front-ends for type-safe garbage collected languages should generate these +intrinsics to make use of the LLVM garbage collectors. For more details, see <a +href="GarbageCollection.html">Accurate Garbage Collection with LLVM</a>. +</p> + +<p>The garbage collection intrinsics only operate on objects in the generic + address space (address space zero).</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to +the code generator, and allows some metadata to be associated with it.</p> + +<h5>Arguments:</h5> + +<p>The first argument specifies the address of a stack object that contains the +root pointer. The second pointer (which must be either a constant or a global +value address) contains the meta-data to be associated with the root.</p> + +<h5>Semantics:</h5> + +<p>At runtime, a call to this intrinsic stores a null pointer into the "ptrloc" +location. At compile-time, the code generator generates information to allow +the runtime to find the pointer at GC safe points. The '<tt>llvm.gcroot</tt>' +intrinsic may only be used in a function which <a href="#gc">specifies a GC +algorithm</a>.</p> + +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap +locations, allowing garbage collector implementations that require read +barriers.</p> + +<h5>Arguments:</h5> + +<p>The second argument is the address to read from, which should be an address +allocated from the garbage collector. The first object is a pointer to the +start of the referenced object, if needed by the language runtime (otherwise +null).</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load +instruction, but may be replaced with substantially more complex code by the +garbage collector runtime, as needed. The '<tt>llvm.gcread</tt>' intrinsic +may only be used in a function which <a href="#gc">specifies a GC +algorithm</a>.</p> + +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<pre> + declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap +locations, allowing garbage collector implementations that require write +barriers (such as generational or reference counting collectors).</p> + +<h5>Arguments:</h5> + +<p>The first argument is the reference to store, the second is the start of the +object to store it to, and the third is the address of the field of Obj to +store to. If the runtime does not require a pointer to the object, Obj may be +null.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store +instruction, but may be replaced with substantially more complex code by the +garbage collector runtime, as needed. The '<tt>llvm.gcwrite</tt>' intrinsic +may only be used in a function which <a href="#gc">specifies a GC +algorithm</a>.</p> + +</div> + + + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_codegen">Code Generator Intrinsics</a> +</div> + +<div class="doc_text"> +<p> +These intrinsics are provided by LLVM to expose special features that may only +be implemented with code generator support. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare i8 *@llvm.returnaddress(i32 <level>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute a +target-specific value indicating the return address of the current function +or one of its callers. +</p> + +<h5>Arguments:</h5> + +<p> +The argument to this intrinsic indicates which function to return the address +for. Zero indicates the calling function, one indicates its caller, etc. The +argument is <b>required</b> to be a constant integer value. +</p> + +<h5>Semantics:</h5> + +<p> +The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer indicating +the return address of the specified call frame, or zero if it cannot be +identified. The value returned by this intrinsic is likely to be incorrect or 0 +for arguments other than zero, so it should only be used for debugging purposes. +</p> + +<p> +Note that calling this intrinsic does not prevent function inlining or other +aggressive transformations, so the value returned may not be that of the obvious +source-language caller. +</p> +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare i8 *@llvm.frameaddress(i32 <level>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return the +target-specific frame pointer value for the specified stack frame. +</p> + +<h5>Arguments:</h5> + +<p> +The argument to this intrinsic indicates which function to return the frame +pointer for. Zero indicates the calling function, one indicates its caller, +etc. The argument is <b>required</b> to be a constant integer value. +</p> + +<h5>Semantics:</h5> + +<p> +The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer indicating +the frame address of the specified call frame, or zero if it cannot be +identified. The value returned by this intrinsic is likely to be incorrect or 0 +for arguments other than zero, so it should only be used for debugging purposes. +</p> + +<p> +Note that calling this intrinsic does not prevent function inlining or other +aggressive transformations, so the value returned may not be that of the obvious +source-language caller. +</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare i8 *@llvm.stacksave() +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state of +the function stack, for use with <a href="#int_stackrestore"> +<tt>llvm.stackrestore</tt></a>. This is useful for implementing language +features like scoped automatic variable sized arrays in C99. +</p> + +<h5>Semantics:</h5> + +<p> +This intrinsic returns a opaque pointer value that can be passed to <a +href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When an +<tt>llvm.stackrestore</tt> intrinsic is executed with a value saved from +<tt>llvm.stacksave</tt>, it effectively restores the state of the stack to the +state it was in when the <tt>llvm.stacksave</tt> intrinsic executed. In +practice, this pops any <a href="#i_alloca">alloca</a> blocks from the stack +that were allocated after the <tt>llvm.stacksave</tt> was executed. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare void @llvm.stackrestore(i8 * %ptr) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of +the function stack to the state it was in when the corresponding <a +href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic executed. This is +useful for implementing language features like scoped automatic variable sized +arrays in C99. +</p> + +<h5>Semantics:</h5> + +<p> +See the description for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>. +</p> + +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>) +</pre> + +<h5>Overview:</h5> + + +<p> +The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to insert +a prefetch instruction if supported; otherwise, it is a noop. Prefetches have +no +effect on the behavior of the program but can change its performance +characteristics. +</p> + +<h5>Arguments:</h5> + +<p> +<tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the specifier +determining if the fetch should be for a read (0) or write (1), and +<tt>locality</tt> is a temporal locality specifier ranging from (0) - no +locality, to (3) - extremely local keep in cache. The <tt>rw</tt> and +<tt>locality</tt> arguments must be constant integers. +</p> + +<h5>Semantics:</h5> + +<p> +This intrinsic does not modify the behavior of the program. In particular, +prefetches cannot trap and do not produce a value. On targets that support this +intrinsic, the prefetch can provide hints to the processor cache for better +performance. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare void @llvm.pcmarker(i32 <id>) +</pre> + +<h5>Overview:</h5> + + +<p> +The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program Counter +(PC) in a region of +code to simulators and other tools. The method is target specific, but it is +expected that the marker will use exported symbols to transmit the PC of the +marker. +The marker makes no guarantees that it will remain with any specific instruction +after optimizations. It is possible that the presence of a marker will inhibit +optimizations. The intended use is to be inserted after optimizations to allow +correlations of simulation runs. +</p> + +<h5>Arguments:</h5> + +<p> +<tt>id</tt> is a numerical id identifying the marker. +</p> + +<h5>Semantics:</h5> + +<p> +This intrinsic does not modify the behavior of the program. Backends that do not +support this intrinisic may ignore it. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare i64 @llvm.readcyclecounter( ) +</pre> + +<h5>Overview:</h5> + + +<p> +The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle +counter register (or similar low latency, high accuracy clocks) on those targets +that support it. On X86, it should map to RDTSC. On Alpha, it should map to RPCC. +As the backing counters overflow quickly (on the order of 9 seconds on alpha), this +should only be used for small timings. +</p> + +<h5>Semantics:</h5> + +<p> +When directly supported, reading the cycle counter should not modify any memory. +Implementations are allowed to either return a application specific value or a +system wide value. On backends without support, this is lowered to a constant 0. +</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_libc">Standard C Library Intrinsics</a> +</div> + +<div class="doc_text"> +<p> +LLVM provides intrinsics for a few important standard C library functions. +These intrinsics allow source-language front-ends to pass information about the +alignment of the pointer arguments to the code generator, providing opportunity +for more efficient code generation. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use llvm.memcpy on any integer bit +width. Not all targets support all bit widths however.</p> +<pre> + declare void @llvm.memcpy.i8(i8 * <dest>, i8 * <src>, + i8 <len>, i32 <align>) + declare void @llvm.memcpy.i16(i8 * <dest>, i8 * <src>, + i16 <len>, i32 <align>) + declare void @llvm.memcpy.i32(i8 * <dest>, i8 * <src>, + i32 <len>, i32 <align>) + declare void @llvm.memcpy.i64(i8 * <dest>, i8 * <src>, + i64 <len>, i32 <align>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the source +location to the destination location. +</p> + +<p> +Note that, unlike the standard libc function, the <tt>llvm.memcpy.*</tt> +intrinsics do not return a value, and takes an extra alignment argument. +</p> + +<h5>Arguments:</h5> + +<p> +The first argument is a pointer to the destination, the second is a pointer to +the source. The third argument is an integer argument +specifying the number of bytes to copy, and the fourth argument is the alignment +of the source and destination locations. +</p> + +<p> +If the call to this intrinisic has an alignment value that is not 0 or 1, then +the caller guarantees that both the source and destination pointers are aligned +to that boundary. +</p> + +<h5>Semantics:</h5> + +<p> +The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the source +location to the destination location, which are not allowed to overlap. It +copies "len" bytes of memory over. If the argument is known to be aligned to +some boundary, this can be specified as the fourth argument, otherwise it should +be set to 0 or 1. +</p> +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use llvm.memmove on any integer bit +width. Not all targets support all bit widths however.</p> +<pre> + declare void @llvm.memmove.i8(i8 * <dest>, i8 * <src>, + i8 <len>, i32 <align>) + declare void @llvm.memmove.i16(i8 * <dest>, i8 * <src>, + i16 <len>, i32 <align>) + declare void @llvm.memmove.i32(i8 * <dest>, i8 * <src>, + i32 <len>, i32 <align>) + declare void @llvm.memmove.i64(i8 * <dest>, i8 * <src>, + i64 <len>, i32 <align>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the source +location to the destination location. It is similar to the +'<tt>llvm.memcpy</tt>' intrinsic but allows the two memory locations to overlap. +</p> + +<p> +Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt> +intrinsics do not return a value, and takes an extra alignment argument. +</p> + +<h5>Arguments:</h5> + +<p> +The first argument is a pointer to the destination, the second is a pointer to +the source. The third argument is an integer argument +specifying the number of bytes to copy, and the fourth argument is the alignment +of the source and destination locations. +</p> + +<p> +If the call to this intrinisic has an alignment value that is not 0 or 1, then +the caller guarantees that the source and destination pointers are aligned to +that boundary. +</p> + +<h5>Semantics:</h5> + +<p> +The '<tt>llvm.memmove.*</tt>' intrinsics copy a block of memory from the source +location to the destination location, which may overlap. It +copies "len" bytes of memory over. If the argument is known to be aligned to +some boundary, this can be specified as the fourth argument, otherwise it should +be set to 0 or 1. +</p> +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use llvm.memset on any integer bit +width. Not all targets support all bit widths however.</p> +<pre> + declare void @llvm.memset.i8(i8 * <dest>, i8 <val>, + i8 <len>, i32 <align>) + declare void @llvm.memset.i16(i8 * <dest>, i8 <val>, + i16 <len>, i32 <align>) + declare void @llvm.memset.i32(i8 * <dest>, i8 <val>, + i32 <len>, i32 <align>) + declare void @llvm.memset.i64(i8 * <dest>, i8 <val>, + i64 <len>, i32 <align>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.memset.*</tt>' intrinsics fill a block of memory with a particular +byte value. +</p> + +<p> +Note that, unlike the standard libc function, the <tt>llvm.memset</tt> intrinsic +does not return a value, and takes an extra alignment argument. +</p> + +<h5>Arguments:</h5> + +<p> +The first argument is a pointer to the destination to fill, the second is the +byte value to fill it with, the third argument is an integer +argument specifying the number of bytes to fill, and the fourth argument is the +known alignment of destination location. +</p> + +<p> +If the call to this intrinisic has an alignment value that is not 0 or 1, then +the caller guarantees that the destination pointer is aligned to that boundary. +</p> + +<h5>Semantics:</h5> + +<p> +The '<tt>llvm.memset.*</tt>' intrinsics fill "len" bytes of memory starting at +the +destination location. If the argument is known to be aligned to some boundary, +this can be specified as the fourth argument, otherwise it should be set to 0 or +1. +</p> +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any +floating point or vector of floating point type. Not all targets support all +types however.</p> +<pre> + declare float @llvm.sqrt.f32(float %Val) + declare double @llvm.sqrt.f64(double %Val) + declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val) + declare fp128 @llvm.sqrt.f128(fp128 %Val) + declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand, +returning the same value as the libm '<tt>sqrt</tt>' functions would. Unlike +<tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined behavior for +negative numbers other than -0.0 (which allows for better optimization, because +there is no need to worry about errno being set). <tt>llvm.sqrt(-0.0)</tt> is +defined to return -0.0 like IEEE sqrt. +</p> + +<h5>Arguments:</h5> + +<p> +The argument and return value are floating point numbers of the same type. +</p> + +<h5>Semantics:</h5> + +<p> +This function returns the sqrt of the specified operand if it is a nonnegative +floating point number. +</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any +floating point or vector of floating point type. Not all targets support all +types however.</p> +<pre> + declare float @llvm.powi.f32(float %Val, i32 %power) + declare double @llvm.powi.f64(double %Val, i32 %power) + declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power) + declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power) + declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the +specified (positive or negative) power. The order of evaluation of +multiplications is not defined. When a vector of floating point type is +used, the second argument remains a scalar integer value. +</p> + +<h5>Arguments:</h5> + +<p> +The second argument is an integer power, and the first is a value to raise to +that power. +</p> + +<h5>Semantics:</h5> + +<p> +This function returns the first value raised to the second power with an +unspecified sequence of rounding operations.</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any +floating point or vector of floating point type. Not all targets support all +types however.</p> +<pre> + declare float @llvm.sin.f32(float %Val) + declare double @llvm.sin.f64(double %Val) + declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val) + declare fp128 @llvm.sin.f128(fp128 %Val) + declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand. +</p> + +<h5>Arguments:</h5> + +<p> +The argument and return value are floating point numbers of the same type. +</p> + +<h5>Semantics:</h5> + +<p> +This function returns the sine of the specified operand, returning the +same values as the libm <tt>sin</tt> functions would, and handles error +conditions in the same way.</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any +floating point or vector of floating point type. Not all targets support all +types however.</p> +<pre> + declare float @llvm.cos.f32(float %Val) + declare double @llvm.cos.f64(double %Val) + declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val) + declare fp128 @llvm.cos.f128(fp128 %Val) + declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand. +</p> + +<h5>Arguments:</h5> + +<p> +The argument and return value are floating point numbers of the same type. +</p> + +<h5>Semantics:</h5> + +<p> +This function returns the cosine of the specified operand, returning the +same values as the libm <tt>cos</tt> functions would, and handles error +conditions in the same way.</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any +floating point or vector of floating point type. Not all targets support all +types however.</p> +<pre> + declare float @llvm.pow.f32(float %Val, float %Power) + declare double @llvm.pow.f64(double %Val, double %Power) + declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power) + declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power) + declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the +specified (positive or negative) power. +</p> + +<h5>Arguments:</h5> + +<p> +The second argument is a floating point power, and the first is a value to +raise to that power. +</p> + +<h5>Semantics:</h5> + +<p> +This function returns the first value raised to the second power, +returning the +same values as the libm <tt>pow</tt> functions would, and handles error +conditions in the same way.</p> +</div> + + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_manip">Bit Manipulation Intrinsics</a> +</div> + +<div class="doc_text"> +<p> +LLVM provides intrinsics for a few important bit manipulation operations. +These allow efficient code generation for some algorithms. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic function. You can use bswap on any integer +type that is an even number of bytes (i.e. BitWidth % 16 == 0).</p> +<pre> + declare i16 @llvm.bswap.i16(i16 <id>) + declare i32 @llvm.bswap.i32(i32 <id>) + declare i64 @llvm.bswap.i64(i64 <id>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer +values with an even number of bytes (positive multiple of 16 bits). These are +useful for performing operations on data that is not in the target's native +byte order. +</p> + +<h5>Semantics:</h5> + +<p> +The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high +and low byte of the input i16 swapped. Similarly, the <tt>llvm.bswap.i32</tt> +intrinsic returns an i32 value that has the four bytes of the input i32 +swapped, so that if the input bytes are numbered 0, 1, 2, 3 then the returned +i32 will have its bytes in 3, 2, 1, 0 order. The <tt>llvm.bswap.i48</tt>, +<tt>llvm.bswap.i64</tt> and other intrinsics extend this concept to +additional even-byte lengths (6 bytes, 8 bytes and more, respectively). +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit +width. Not all targets support all bit widths however.</p> +<pre> + declare i8 @llvm.ctpop.i8(i8 <src>) + declare i16 @llvm.ctpop.i16(i16 <src>) + declare i32 @llvm.ctpop.i32(i32 <src>) + declare i64 @llvm.ctpop.i64(i64 <src>) + declare i256 @llvm.ctpop.i256(i256 <src>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set in a +value. +</p> + +<h5>Arguments:</h5> + +<p> +The only argument is the value to be counted. The argument may be of any +integer type. The return type must match the argument type. +</p> + +<h5>Semantics:</h5> + +<p> +The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable. +</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any +integer bit width. Not all targets support all bit widths however.</p> +<pre> + declare i8 @llvm.ctlz.i8 (i8 <src>) + declare i16 @llvm.ctlz.i16(i16 <src>) + declare i32 @llvm.ctlz.i32(i32 <src>) + declare i64 @llvm.ctlz.i64(i64 <src>) + declare i256 @llvm.ctlz.i256(i256 <src>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.ctlz</tt>' family of intrinsic functions counts the number of +leading zeros in a variable. +</p> + +<h5>Arguments:</h5> + +<p> +The only argument is the value to be counted. The argument may be of any +integer type. The return type must match the argument type. +</p> + +<h5>Semantics:</h5> + +<p> +The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant) zeros +in a variable. If the src == 0 then the result is the size in bits of the type +of src. For example, <tt>llvm.ctlz(i32 2) = 30</tt>. +</p> +</div> + + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any +integer bit width. Not all targets support all bit widths however.</p> +<pre> + declare i8 @llvm.cttz.i8 (i8 <src>) + declare i16 @llvm.cttz.i16(i16 <src>) + declare i32 @llvm.cttz.i32(i32 <src>) + declare i64 @llvm.cttz.i64(i64 <src>) + declare i256 @llvm.cttz.i256(i256 <src>) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.cttz</tt>' family of intrinsic functions counts the number of +trailing zeros. +</p> + +<h5>Arguments:</h5> + +<p> +The only argument is the value to be counted. The argument may be of any +integer type. The return type must match the argument type. +</p> + +<h5>Semantics:</h5> + +<p> +The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant) zeros +in a variable. If the src == 0 then the result is the size in bits of the type +of src. For example, <tt>llvm.cttz(2) = 1</tt>. +</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_part_select">'<tt>llvm.part.select.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.part.select</tt> +on any integer bit width.</p> +<pre> + declare i17 @llvm.part.select.i17 (i17 %val, i32 %loBit, i32 %hiBit) + declare i29 @llvm.part.select.i29 (i29 %val, i32 %loBit, i32 %hiBit) +</pre> + +<h5>Overview:</h5> +<p>The '<tt>llvm.part.select</tt>' family of intrinsic functions selects a +range of bits from an integer value and returns them in the same bit width as +the original value.</p> + +<h5>Arguments:</h5> +<p>The first argument, <tt>%val</tt> and the result may be integer types of +any bit width but they must have the same bit width. The second and third +arguments must be <tt>i32</tt> type since they specify only a bit index.</p> + +<h5>Semantics:</h5> +<p>The operation of the '<tt>llvm.part.select</tt>' intrinsic has two modes +of operation: forwards and reverse. If <tt>%loBit</tt> is greater than +<tt>%hiBits</tt> then the intrinsic operates in reverse mode. Otherwise it +operates in forward mode.</p> +<p>In forward mode, this intrinsic is the equivalent of shifting <tt>%val</tt> +right by <tt>%loBit</tt> bits and then ANDing it with a mask with +only the <tt>%hiBit - %loBit</tt> bits set, as follows:</p> +<ol> + <li>The <tt>%val</tt> is shifted right (LSHR) by the number of bits specified + by <tt>%loBits</tt>. This normalizes the value to the low order bits.</li> + <li>The <tt>%loBits</tt> value is subtracted from the <tt>%hiBits</tt> value + to determine the number of bits to retain.</li> + <li>A mask of the retained bits is created by shifting a -1 value.</li> + <li>The mask is ANDed with <tt>%val</tt> to produce the result.</li> +</ol> +<p>In reverse mode, a similar computation is made except that the bits are +returned in the reverse order. So, for example, if <tt>X</tt> has the value +<tt>i16 0x0ACF (101011001111)</tt> and we apply +<tt>part.select(i16 X, 8, 3)</tt> to it, we get back the value +<tt>i16 0x0026 (000000100110)</tt>.</p> +</div> + +<div class="doc_subsubsection"> + <a name="int_part_set">'<tt>llvm.part.set.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use <tt>llvm.part.set</tt> +on any integer bit width.</p> +<pre> + declare i17 @llvm.part.set.i17.i9 (i17 %val, i9 %repl, i32 %lo, i32 %hi) + declare i29 @llvm.part.set.i29.i9 (i29 %val, i9 %repl, i32 %lo, i32 %hi) +</pre> + +<h5>Overview:</h5> +<p>The '<tt>llvm.part.set</tt>' family of intrinsic functions replaces a range +of bits in an integer value with another integer value. It returns the integer +with the replaced bits.</p> + +<h5>Arguments:</h5> +<p>The first argument, <tt>%val</tt>, and the result may be integer types of +any bit width, but they must have the same bit width. <tt>%val</tt> is the value +whose bits will be replaced. The second argument, <tt>%repl</tt> may be an +integer of any bit width. The third and fourth arguments must be <tt>i32</tt> +type since they specify only a bit index.</p> + +<h5>Semantics:</h5> +<p>The operation of the '<tt>llvm.part.set</tt>' intrinsic has two modes +of operation: forwards and reverse. If <tt>%lo</tt> is greater than +<tt>%hi</tt> then the intrinsic operates in reverse mode. Otherwise it +operates in forward mode.</p> + +<p>For both modes, the <tt>%repl</tt> value is prepared for use by either +truncating it down to the size of the replacement area or zero extending it +up to that size.</p> + +<p>In forward mode, the bits between <tt>%lo</tt> and <tt>%hi</tt> (inclusive) +are replaced with corresponding bits from <tt>%repl</tt>. That is the 0th bit +in <tt>%repl</tt> replaces the <tt>%lo</tt>th bit in <tt>%val</tt> and etc. up +to the <tt>%hi</tt>th bit.</p> + +<p>In reverse mode, a similar computation is made except that the bits are +reversed. That is, the <tt>0</tt>th bit in <tt>%repl</tt> replaces the +<tt>%hi</tt> bit in <tt>%val</tt> and etc. down to the <tt>%lo</tt>th bit.</p> + +<h5>Examples:</h5> + +<pre> + llvm.part.set(0xFFFF, 0, 4, 7) -> 0xFF0F + llvm.part.set(0xFFFF, 0, 7, 4) -> 0xFF0F + llvm.part.set(0xFFFF, 1, 7, 4) -> 0xFF8F + llvm.part.set(0xFFFF, F, 8, 3) -> 0xFFE7 + llvm.part.set(0xFFFF, 0, 3, 8) -> 0xFE07 +</pre> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_overflow">Arithmetic with Overflow Intrinsics</a> +</div> + +<div class="doc_text"> +<p> +LLVM provides intrinsics for some arithmetic with overflow operations. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt>' Intrinsics</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<p>This is an overloaded intrinsic. You can use <tt>llvm.sadd.with.overflow</tt> +on any integer bit width.</p> + +<pre> + declare {i16, i1} @llvm.sadd.with.overflow.i16(i16 %a, i16 %b) + declare {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b) + declare {i64, i1} @llvm.sadd.with.overflow.i64(i64 %a, i64 %b) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform +a signed addition of the two arguments, and indicate whether an overflow +occurred during the signed summation.</p> + +<h5>Arguments:</h5> + +<p>The arguments (%a and %b) and the first element of the result structure may +be of integer types of any bit width, but they must have the same bit width. The +second element of the result structure must be of type <tt>i1</tt>. <tt>%a</tt> +and <tt>%b</tt> are the two values that will undergo signed addition.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform +a signed addition of the two variables. They return a structure — the +first element of which is the signed summation, and the second element of which +is a bit specifying if the signed summation resulted in an overflow.</p> + +<h5>Examples:</h5> +<pre> + %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b) + %sum = extractvalue {i32, i1} %res, 0 + %obit = extractvalue {i32, i1} %res, 1 + br i1 %obit, label %overflow, label %normal +</pre> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt>' Intrinsics</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<p>This is an overloaded intrinsic. You can use <tt>llvm.uadd.with.overflow</tt> +on any integer bit width.</p> + +<pre> + declare {i16, i1} @llvm.uadd.with.overflow.i16(i16 %a, i16 %b) + declare {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b) + declare {i64, i1} @llvm.uadd.with.overflow.i64(i64 %a, i64 %b) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform +an unsigned addition of the two arguments, and indicate whether a carry occurred +during the unsigned summation.</p> + +<h5>Arguments:</h5> + +<p>The arguments (%a and %b) and the first element of the result structure may +be of integer types of any bit width, but they must have the same bit width. The +second element of the result structure must be of type <tt>i1</tt>. <tt>%a</tt> +and <tt>%b</tt> are the two values that will undergo unsigned addition.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform +an unsigned addition of the two arguments. They return a structure — the +first element of which is the sum, and the second element of which is a bit +specifying if the unsigned summation resulted in a carry.</p> + +<h5>Examples:</h5> +<pre> + %res = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b) + %sum = extractvalue {i32, i1} %res, 0 + %obit = extractvalue {i32, i1} %res, 1 + br i1 %obit, label %carry, label %normal +</pre> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt>' Intrinsics</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<p>This is an overloaded intrinsic. You can use <tt>llvm.ssub.with.overflow</tt> +on any integer bit width.</p> + +<pre> + declare {i16, i1} @llvm.ssub.with.overflow.i16(i16 %a, i16 %b) + declare {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b) + declare {i64, i1} @llvm.ssub.with.overflow.i64(i64 %a, i64 %b) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform +a signed subtraction of the two arguments, and indicate whether an overflow +occurred during the signed subtraction.</p> + +<h5>Arguments:</h5> + +<p>The arguments (%a and %b) and the first element of the result structure may +be of integer types of any bit width, but they must have the same bit width. The +second element of the result structure must be of type <tt>i1</tt>. <tt>%a</tt> +and <tt>%b</tt> are the two values that will undergo signed subtraction.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform +a signed subtraction of the two arguments. They return a structure — the +first element of which is the subtraction, and the second element of which is a bit +specifying if the signed subtraction resulted in an overflow.</p> + +<h5>Examples:</h5> +<pre> + %res = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b) + %sum = extractvalue {i32, i1} %res, 0 + %obit = extractvalue {i32, i1} %res, 1 + br i1 %obit, label %overflow, label %normal +</pre> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt>' Intrinsics</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<p>This is an overloaded intrinsic. You can use <tt>llvm.usub.with.overflow</tt> +on any integer bit width.</p> + +<pre> + declare {i16, i1} @llvm.usub.with.overflow.i16(i16 %a, i16 %b) + declare {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b) + declare {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %b) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform +an unsigned subtraction of the two arguments, and indicate whether an overflow +occurred during the unsigned subtraction.</p> + +<h5>Arguments:</h5> + +<p>The arguments (%a and %b) and the first element of the result structure may +be of integer types of any bit width, but they must have the same bit width. The +second element of the result structure must be of type <tt>i1</tt>. <tt>%a</tt> +and <tt>%b</tt> are the two values that will undergo unsigned subtraction.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform +an unsigned subtraction of the two arguments. They return a structure — the +first element of which is the subtraction, and the second element of which is a bit +specifying if the unsigned subtraction resulted in an overflow.</p> + +<h5>Examples:</h5> +<pre> + %res = call {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b) + %sum = extractvalue {i32, i1} %res, 0 + %obit = extractvalue {i32, i1} %res, 1 + br i1 %obit, label %overflow, label %normal +</pre> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt>' Intrinsics</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<p>This is an overloaded intrinsic. You can use <tt>llvm.smul.with.overflow</tt> +on any integer bit width.</p> + +<pre> + declare {i16, i1} @llvm.smul.with.overflow.i16(i16 %a, i16 %b) + declare {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b) + declare {i64, i1} @llvm.smul.with.overflow.i64(i64 %a, i64 %b) +</pre> + +<h5>Overview:</h5> + +<p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform +a signed multiplication of the two arguments, and indicate whether an overflow +occurred during the signed multiplication.</p> + +<h5>Arguments:</h5> + +<p>The arguments (%a and %b) and the first element of the result structure may +be of integer types of any bit width, but they must have the same bit width. The +second element of the result structure must be of type <tt>i1</tt>. <tt>%a</tt> +and <tt>%b</tt> are the two values that will undergo signed multiplication.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform +a signed multiplication of the two arguments. They return a structure — +the first element of which is the multiplication, and the second element of +which is a bit specifying if the signed multiplication resulted in an +overflow.</p> + +<h5>Examples:</h5> +<pre> + %res = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b) + %sum = extractvalue {i32, i1} %res, 0 + %obit = extractvalue {i32, i1} %res, 1 + br i1 %obit, label %overflow, label %normal +</pre> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt>' Intrinsics</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> + +<p>This is an overloaded intrinsic. You can use <tt>llvm.umul.with.overflow</tt> +on any integer bit width.</p> + +<pre> + declare {i16, i1} @llvm.umul.with.overflow.i16(i16 %a, i16 %b) + declare {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b) + declare {i64, i1} @llvm.umul.with.overflow.i64(i64 %a, i64 %b) +</pre> + +<h5>Overview:</h5> + +<p><i><b>Warning:</b> '<tt>llvm.umul.with.overflow</tt>' is badly broken. It is +actively being fixed, but it should not currently be used!</i></p> + +<p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform +a unsigned multiplication of the two arguments, and indicate whether an overflow +occurred during the unsigned multiplication.</p> + +<h5>Arguments:</h5> + +<p>The arguments (%a and %b) and the first element of the result structure may +be of integer types of any bit width, but they must have the same bit width. The +second element of the result structure must be of type <tt>i1</tt>. <tt>%a</tt> +and <tt>%b</tt> are the two values that will undergo unsigned +multiplication.</p> + +<h5>Semantics:</h5> + +<p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform +an unsigned multiplication of the two arguments. They return a structure — +the first element of which is the multiplication, and the second element of +which is a bit specifying if the unsigned multiplication resulted in an +overflow.</p> + +<h5>Examples:</h5> +<pre> + %res = call {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b) + %sum = extractvalue {i32, i1} %res, 0 + %obit = extractvalue {i32, i1} %res, 1 + br i1 %obit, label %overflow, label %normal +</pre> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_debugger">Debugger Intrinsics</a> +</div> + +<div class="doc_text"> +<p> +The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> prefix), +are described in the <a +href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source Level +Debugging</a> document. +</p> +</div> + + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_eh">Exception Handling Intrinsics</a> +</div> + +<div class="doc_text"> +<p> The LLVM exception handling intrinsics (which all start with +<tt>llvm.eh.</tt> prefix), are described in the <a +href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception +Handling</a> document. </p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_trampoline">Trampoline Intrinsic</a> +</div> + +<div class="doc_text"> +<p> + This intrinsic makes it possible to excise one parameter, marked with + the <tt>nest</tt> attribute, from a function. The result is a callable + function pointer lacking the nest parameter - the caller does not need + to provide a value for it. Instead, the value to use is stored in + advance in a "trampoline", a block of memory usually allocated + on the stack, which also contains code to splice the nest value into the + argument list. This is used to implement the GCC nested function address + extension. +</p> +<p> + For example, if the function is + <tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function + pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as follows:</p> +<pre> + %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86 + %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0 + %p = call i8* @llvm.init.trampoline( i8* %tramp1, i8* bitcast (i32 (i8* nest , i32, i32)* @f to i8*), i8* %nval ) + %fp = bitcast i8* %p to i32 (i32, i32)* +</pre> + <p>The call <tt>%val = call i32 %fp( i32 %x, i32 %y )</tt> is then equivalent + to <tt>%val = call i32 %f( i8* %nval, i32 %x, i32 %y )</tt>.</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> +declare i8* @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>) +</pre> +<h5>Overview:</h5> +<p> + This fills the memory pointed to by <tt>tramp</tt> with code + and returns a function pointer suitable for executing it. +</p> +<h5>Arguments:</h5> +<p> + The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all + pointers. The <tt>tramp</tt> argument must point to a sufficiently large + and sufficiently aligned block of memory; this memory is written to by the + intrinsic. Note that the size and the alignment are target-specific - LLVM + currently provides no portable way of determining them, so a front-end that + generates this intrinsic needs to have some target-specific knowledge. + The <tt>func</tt> argument must hold a function bitcast to an <tt>i8*</tt>. +</p> +<h5>Semantics:</h5> +<p> + The block of memory pointed to by <tt>tramp</tt> is filled with target + dependent code, turning it into a function. A pointer to this function is + returned, but needs to be bitcast to an + <a href="#int_trampoline">appropriate function pointer type</a> + before being called. The new function's signature is the same as that of + <tt>func</tt> with any arguments marked with the <tt>nest</tt> attribute + removed. At most one such <tt>nest</tt> argument is allowed, and it must be + of pointer type. Calling the new function is equivalent to calling + <tt>func</tt> with the same argument list, but with <tt>nval</tt> used for the + missing <tt>nest</tt> argument. If, after calling + <tt>llvm.init.trampoline</tt>, the memory pointed to by <tt>tramp</tt> is + modified, then the effect of any later call to the returned function pointer is + undefined. +</p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_atomics">Atomic Operations and Synchronization Intrinsics</a> +</div> + +<div class="doc_text"> +<p> + These intrinsic functions expand the "universal IR" of LLVM to represent + hardware constructs for atomic operations and memory synchronization. This + provides an interface to the hardware, not an interface to the programmer. It + is aimed at a low enough level to allow any programming models or APIs + (Application Programming Interfaces) which + need atomic behaviors to map cleanly onto it. It is also modeled primarily on + hardware behavior. Just as hardware provides a "universal IR" for source + languages, it also provides a starting point for developing a "universal" + atomic operation and synchronization IR. +</p> +<p> + These do <em>not</em> form an API such as high-level threading libraries, + software transaction memory systems, atomic primitives, and intrinsic + functions as found in BSD, GNU libc, atomic_ops, APR, and other system and + application libraries. The hardware interface provided by LLVM should allow + a clean implementation of all of these APIs and parallel programming models. + No one model or paradigm should be selected above others unless the hardware + itself ubiquitously does so. + +</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_memory_barrier">'<tt>llvm.memory.barrier</tt>' Intrinsic</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> +declare void @llvm.memory.barrier( i1 <ll>, i1 <ls>, i1 <sl>, i1 <ss>, +i1 <device> ) + +</pre> +<h5>Overview:</h5> +<p> + The <tt>llvm.memory.barrier</tt> intrinsic guarantees ordering between + specific pairs of memory access types. +</p> +<h5>Arguments:</h5> +<p> + The <tt>llvm.memory.barrier</tt> intrinsic requires five boolean arguments. + The first four arguments enables a specific barrier as listed below. The fith + argument specifies that the barrier applies to io or device or uncached memory. + +</p> + <ul> + <li><tt>ll</tt>: load-load barrier</li> + <li><tt>ls</tt>: load-store barrier</li> + <li><tt>sl</tt>: store-load barrier</li> + <li><tt>ss</tt>: store-store barrier</li> + <li><tt>device</tt>: barrier applies to device and uncached memory also.</li> + </ul> +<h5>Semantics:</h5> +<p> + This intrinsic causes the system to enforce some ordering constraints upon + the loads and stores of the program. This barrier does not indicate + <em>when</em> any events will occur, it only enforces an <em>order</em> in + which they occur. For any of the specified pairs of load and store operations + (f.ex. load-load, or store-load), all of the first operations preceding the + barrier will complete before any of the second operations succeeding the + barrier begin. Specifically the semantics for each pairing is as follows: +</p> + <ul> + <li><tt>ll</tt>: All loads before the barrier must complete before any load + after the barrier begins.</li> + + <li><tt>ls</tt>: All loads before the barrier must complete before any + store after the barrier begins.</li> + <li><tt>ss</tt>: All stores before the barrier must complete before any + store after the barrier begins.</li> + <li><tt>sl</tt>: All stores before the barrier must complete before any + load after the barrier begins.</li> + </ul> +<p> + These semantics are applied with a logical "and" behavior when more than one + is enabled in a single memory barrier intrinsic. +</p> +<p> + Backends may implement stronger barriers than those requested when they do not + support as fine grained a barrier as requested. Some architectures do not + need all types of barriers and on such architectures, these become noops. +</p> +<h5>Example:</h5> +<pre> +%ptr = malloc i32 + store i32 4, %ptr + +%result1 = load i32* %ptr <i>; yields {i32}:result1 = 4</i> + call void @llvm.memory.barrier( i1 false, i1 true, i1 false, i1 false ) + <i>; guarantee the above finishes</i> + store i32 8, %ptr <i>; before this begins</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_atomic_cmp_swap">'<tt>llvm.atomic.cmp.swap.*</tt>' Intrinsic</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<p> + This is an overloaded intrinsic. You can use <tt>llvm.atomic.cmp.swap</tt> on + any integer bit width and for different address spaces. Not all targets + support all bit widths however.</p> + +<pre> +declare i8 @llvm.atomic.cmp.swap.i8.p0i8( i8* <ptr>, i8 <cmp>, i8 <val> ) +declare i16 @llvm.atomic.cmp.swap.i16.p0i16( i16* <ptr>, i16 <cmp>, i16 <val> ) +declare i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* <ptr>, i32 <cmp>, i32 <val> ) +declare i64 @llvm.atomic.cmp.swap.i64.p0i64( i64* <ptr>, i64 <cmp>, i64 <val> ) + +</pre> +<h5>Overview:</h5> +<p> + This loads a value in memory and compares it to a given value. If they are + equal, it stores a new value into the memory. +</p> +<h5>Arguments:</h5> +<p> + The <tt>llvm.atomic.cmp.swap</tt> intrinsic takes three arguments. The result as + well as both <tt>cmp</tt> and <tt>val</tt> must be integer values with the + same bit width. The <tt>ptr</tt> argument must be a pointer to a value of + this integer type. While any bit width integer may be used, targets may only + lower representations they support in hardware. + +</p> +<h5>Semantics:</h5> +<p> + This entire intrinsic must be executed atomically. It first loads the value + in memory pointed to by <tt>ptr</tt> and compares it with the value + <tt>cmp</tt>. If they are equal, <tt>val</tt> is stored into the memory. The + loaded value is yielded in all cases. This provides the equivalent of an + atomic compare-and-swap operation within the SSA framework. +</p> +<h5>Examples:</h5> + +<pre> +%ptr = malloc i32 + store i32 4, %ptr + +%val1 = add i32 4, 4 +%result1 = call i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* %ptr, i32 4, %val1 ) + <i>; yields {i32}:result1 = 4</i> +%stored1 = icmp eq i32 %result1, 4 <i>; yields {i1}:stored1 = true</i> +%memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 8</i> + +%val2 = add i32 1, 1 +%result2 = call i32 @llvm.atomic.cmp.swap.i32.p0i32( i32* %ptr, i32 5, %val2 ) + <i>; yields {i32}:result2 = 8</i> +%stored2 = icmp eq i32 %result2, 5 <i>; yields {i1}:stored2 = false</i> + +%memval2 = load i32* %ptr <i>; yields {i32}:memval2 = 8</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_atomic_swap">'<tt>llvm.atomic.swap.*</tt>' Intrinsic</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> + +<p> + This is an overloaded intrinsic. You can use <tt>llvm.atomic.swap</tt> on any + integer bit width. Not all targets support all bit widths however.</p> +<pre> +declare i8 @llvm.atomic.swap.i8.p0i8( i8* <ptr>, i8 <val> ) +declare i16 @llvm.atomic.swap.i16.p0i16( i16* <ptr>, i16 <val> ) +declare i32 @llvm.atomic.swap.i32.p0i32( i32* <ptr>, i32 <val> ) +declare i64 @llvm.atomic.swap.i64.p0i64( i64* <ptr>, i64 <val> ) + +</pre> +<h5>Overview:</h5> +<p> + This intrinsic loads the value stored in memory at <tt>ptr</tt> and yields + the value from memory. It then stores the value in <tt>val</tt> in the memory + at <tt>ptr</tt>. +</p> +<h5>Arguments:</h5> + +<p> + The <tt>llvm.atomic.swap</tt> intrinsic takes two arguments. Both the + <tt>val</tt> argument and the result must be integers of the same bit width. + The first argument, <tt>ptr</tt>, must be a pointer to a value of this + integer type. The targets may only lower integer representations they + support. +</p> +<h5>Semantics:</h5> +<p> + This intrinsic loads the value pointed to by <tt>ptr</tt>, yields it, and + stores <tt>val</tt> back into <tt>ptr</tt> atomically. This provides the + equivalent of an atomic swap operation within the SSA framework. + +</p> +<h5>Examples:</h5> +<pre> +%ptr = malloc i32 + store i32 4, %ptr + +%val1 = add i32 4, 4 +%result1 = call i32 @llvm.atomic.swap.i32.p0i32( i32* %ptr, i32 %val1 ) + <i>; yields {i32}:result1 = 4</i> +%stored1 = icmp eq i32 %result1, 4 <i>; yields {i1}:stored1 = true</i> +%memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 8</i> + +%val2 = add i32 1, 1 +%result2 = call i32 @llvm.atomic.swap.i32.p0i32( i32* %ptr, i32 %val2 ) + <i>; yields {i32}:result2 = 8</i> + +%stored2 = icmp eq i32 %result2, 8 <i>; yields {i1}:stored2 = true</i> +%memval2 = load i32* %ptr <i>; yields {i32}:memval2 = 2</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_atomic_load_add">'<tt>llvm.atomic.load.add.*</tt>' Intrinsic</a> + +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<p> + This is an overloaded intrinsic. You can use <tt>llvm.atomic.load.add</tt> on any + integer bit width. Not all targets support all bit widths however.</p> +<pre> +declare i8 @llvm.atomic.load.add.i8..p0i8( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.add.i16..p0i16( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.add.i32..p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.add.i64..p0i64( i64* <ptr>, i64 <delta> ) + +</pre> +<h5>Overview:</h5> +<p> + This intrinsic adds <tt>delta</tt> to the value stored in memory at + <tt>ptr</tt>. It yields the original value at <tt>ptr</tt>. +</p> +<h5>Arguments:</h5> +<p> + + The intrinsic takes two arguments, the first a pointer to an integer value + and the second an integer value. The result is also an integer value. These + integer types can have any bit width, but they must all have the same bit + width. The targets may only lower integer representations they support. +</p> +<h5>Semantics:</h5> +<p> + This intrinsic does a series of operations atomically. It first loads the + value stored at <tt>ptr</tt>. It then adds <tt>delta</tt>, stores the result + to <tt>ptr</tt>. It yields the original value stored at <tt>ptr</tt>. +</p> + +<h5>Examples:</h5> +<pre> +%ptr = malloc i32 + store i32 4, %ptr +%result1 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 4 ) + <i>; yields {i32}:result1 = 4</i> +%result2 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 2 ) + <i>; yields {i32}:result2 = 8</i> +%result3 = call i32 @llvm.atomic.load.add.i32.p0i32( i32* %ptr, i32 5 ) + <i>; yields {i32}:result3 = 10</i> +%memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 15</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_atomic_load_sub">'<tt>llvm.atomic.load.sub.*</tt>' Intrinsic</a> + +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<p> + This is an overloaded intrinsic. You can use <tt>llvm.atomic.load.sub</tt> on + any integer bit width and for different address spaces. Not all targets + support all bit widths however.</p> +<pre> +declare i8 @llvm.atomic.load.sub.i8.p0i32( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.sub.i16.p0i32( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.sub.i32.p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.sub.i64.p0i32( i64* <ptr>, i64 <delta> ) + +</pre> +<h5>Overview:</h5> +<p> + This intrinsic subtracts <tt>delta</tt> to the value stored in memory at + <tt>ptr</tt>. It yields the original value at <tt>ptr</tt>. +</p> +<h5>Arguments:</h5> +<p> + + The intrinsic takes two arguments, the first a pointer to an integer value + and the second an integer value. The result is also an integer value. These + integer types can have any bit width, but they must all have the same bit + width. The targets may only lower integer representations they support. +</p> +<h5>Semantics:</h5> +<p> + This intrinsic does a series of operations atomically. It first loads the + value stored at <tt>ptr</tt>. It then subtracts <tt>delta</tt>, stores the + result to <tt>ptr</tt>. It yields the original value stored at <tt>ptr</tt>. +</p> + +<h5>Examples:</h5> +<pre> +%ptr = malloc i32 + store i32 8, %ptr +%result1 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 4 ) + <i>; yields {i32}:result1 = 8</i> +%result2 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 2 ) + <i>; yields {i32}:result2 = 4</i> +%result3 = call i32 @llvm.atomic.load.sub.i32.p0i32( i32* %ptr, i32 5 ) + <i>; yields {i32}:result3 = 2</i> +%memval1 = load i32* %ptr <i>; yields {i32}:memval1 = -3</i> +</pre> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_atomic_load_and">'<tt>llvm.atomic.load.and.*</tt>' Intrinsic</a><br> + <a name="int_atomic_load_nand">'<tt>llvm.atomic.load.nand.*</tt>' Intrinsic</a><br> + <a name="int_atomic_load_or">'<tt>llvm.atomic.load.or.*</tt>' Intrinsic</a><br> + <a name="int_atomic_load_xor">'<tt>llvm.atomic.load.xor.*</tt>' Intrinsic</a><br> + +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<p> + These are overloaded intrinsics. You can use <tt>llvm.atomic.load_and</tt>, + <tt>llvm.atomic.load_nand</tt>, <tt>llvm.atomic.load_or</tt>, and + <tt>llvm.atomic.load_xor</tt> on any integer bit width and for different + address spaces. Not all targets support all bit widths however.</p> +<pre> +declare i8 @llvm.atomic.load.and.i8.p0i8( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.and.i16.p0i16( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.and.i32.p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.and.i64.p0i64( i64* <ptr>, i64 <delta> ) + +</pre> + +<pre> +declare i8 @llvm.atomic.load.or.i8.p0i8( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.or.i16.p0i16( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.or.i32.p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.or.i64.p0i64( i64* <ptr>, i64 <delta> ) + +</pre> + +<pre> +declare i8 @llvm.atomic.load.nand.i8.p0i32( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.nand.i16.p0i32( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.nand.i32.p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.nand.i64.p0i32( i64* <ptr>, i64 <delta> ) + +</pre> + +<pre> +declare i8 @llvm.atomic.load.xor.i8.p0i32( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.xor.i16.p0i32( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.xor.i32.p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.xor.i64.p0i32( i64* <ptr>, i64 <delta> ) + +</pre> +<h5>Overview:</h5> +<p> + These intrinsics bitwise the operation (and, nand, or, xor) <tt>delta</tt> to + the value stored in memory at <tt>ptr</tt>. It yields the original value + at <tt>ptr</tt>. +</p> +<h5>Arguments:</h5> +<p> + + These intrinsics take two arguments, the first a pointer to an integer value + and the second an integer value. The result is also an integer value. These + integer types can have any bit width, but they must all have the same bit + width. The targets may only lower integer representations they support. +</p> +<h5>Semantics:</h5> +<p> + These intrinsics does a series of operations atomically. They first load the + value stored at <tt>ptr</tt>. They then do the bitwise operation + <tt>delta</tt>, store the result to <tt>ptr</tt>. They yield the original + value stored at <tt>ptr</tt>. +</p> + +<h5>Examples:</h5> +<pre> +%ptr = malloc i32 + store i32 0x0F0F, %ptr +%result0 = call i32 @llvm.atomic.load.nand.i32.p0i32( i32* %ptr, i32 0xFF ) + <i>; yields {i32}:result0 = 0x0F0F</i> +%result1 = call i32 @llvm.atomic.load.and.i32.p0i32( i32* %ptr, i32 0xFF ) + <i>; yields {i32}:result1 = 0xFFFFFFF0</i> +%result2 = call i32 @llvm.atomic.load.or.i32.p0i32( i32* %ptr, i32 0F ) + <i>; yields {i32}:result2 = 0xF0</i> +%result3 = call i32 @llvm.atomic.load.xor.i32.p0i32( i32* %ptr, i32 0F ) + <i>; yields {i32}:result3 = FF</i> +%memval1 = load i32* %ptr <i>; yields {i32}:memval1 = F0</i> +</pre> +</div> + + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_atomic_load_max">'<tt>llvm.atomic.load.max.*</tt>' Intrinsic</a><br> + <a name="int_atomic_load_min">'<tt>llvm.atomic.load.min.*</tt>' Intrinsic</a><br> + <a name="int_atomic_load_umax">'<tt>llvm.atomic.load.umax.*</tt>' Intrinsic</a><br> + <a name="int_atomic_load_umin">'<tt>llvm.atomic.load.umin.*</tt>' Intrinsic</a><br> + +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<p> + These are overloaded intrinsics. You can use <tt>llvm.atomic.load_max</tt>, + <tt>llvm.atomic.load_min</tt>, <tt>llvm.atomic.load_umax</tt>, and + <tt>llvm.atomic.load_umin</tt> on any integer bit width and for different + address spaces. Not all targets + support all bit widths however.</p> +<pre> +declare i8 @llvm.atomic.load.max.i8.p0i8( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.max.i16.p0i16( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.max.i32.p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.max.i64.p0i64( i64* <ptr>, i64 <delta> ) + +</pre> + +<pre> +declare i8 @llvm.atomic.load.min.i8.p0i8( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.min.i16.p0i16( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.min.i32..p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.min.i64..p0i64( i64* <ptr>, i64 <delta> ) + +</pre> + +<pre> +declare i8 @llvm.atomic.load.umax.i8.p0i8( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.umax.i16.p0i16( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.umax.i32.p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.umax.i64.p0i64( i64* <ptr>, i64 <delta> ) + +</pre> + +<pre> +declare i8 @llvm.atomic.load.umin.i8..p0i8( i8* <ptr>, i8 <delta> ) +declare i16 @llvm.atomic.load.umin.i16.p0i16( i16* <ptr>, i16 <delta> ) +declare i32 @llvm.atomic.load.umin.i32..p0i32( i32* <ptr>, i32 <delta> ) +declare i64 @llvm.atomic.load.umin.i64..p0i64( i64* <ptr>, i64 <delta> ) + +</pre> +<h5>Overview:</h5> +<p> + These intrinsics takes the signed or unsigned minimum or maximum of + <tt>delta</tt> and the value stored in memory at <tt>ptr</tt>. It yields the + original value at <tt>ptr</tt>. +</p> +<h5>Arguments:</h5> +<p> + + These intrinsics take two arguments, the first a pointer to an integer value + and the second an integer value. The result is also an integer value. These + integer types can have any bit width, but they must all have the same bit + width. The targets may only lower integer representations they support. +</p> +<h5>Semantics:</h5> +<p> + These intrinsics does a series of operations atomically. They first load the + value stored at <tt>ptr</tt>. They then do the signed or unsigned min or max + <tt>delta</tt> and the value, store the result to <tt>ptr</tt>. They yield + the original value stored at <tt>ptr</tt>. +</p> + +<h5>Examples:</h5> +<pre> +%ptr = malloc i32 + store i32 7, %ptr +%result0 = call i32 @llvm.atomic.load.min.i32.p0i32( i32* %ptr, i32 -2 ) + <i>; yields {i32}:result0 = 7</i> +%result1 = call i32 @llvm.atomic.load.max.i32.p0i32( i32* %ptr, i32 8 ) + <i>; yields {i32}:result1 = -2</i> +%result2 = call i32 @llvm.atomic.load.umin.i32.p0i32( i32* %ptr, i32 10 ) + <i>; yields {i32}:result2 = 8</i> +%result3 = call i32 @llvm.atomic.load.umax.i32.p0i32( i32* %ptr, i32 30 ) + <i>; yields {i32}:result3 = 8</i> +%memval1 = load i32* %ptr <i>; yields {i32}:memval1 = 30</i> +</pre> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="int_general">General Intrinsics</a> +</div> + +<div class="doc_text"> +<p> This class of intrinsics is designed to be generic and has +no specific purpose. </p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int> ) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.var.annotation</tt>' intrinsic +</p> + +<h5>Arguments:</h5> + +<p> +The first argument is a pointer to a value, the second is a pointer to a +global string, the third is a pointer to a global string which is the source +file name, and the last argument is the line number. +</p> + +<h5>Semantics:</h5> + +<p> +This intrinsic allows annotation of local variables with arbitrary strings. +This can be useful for special purpose optimizations that want to look for these +annotations. These have no other defined use, they are ignored by code +generation and optimization. +</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on +any integer bit width. +</p> +<pre> + declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int> ) + declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int> ) + declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int> ) + declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int> ) + declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int> ) +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.annotation</tt>' intrinsic. +</p> + +<h5>Arguments:</h5> + +<p> +The first argument is an integer value (result of some expression), +the second is a pointer to a global string, the third is a pointer to a global +string which is the source file name, and the last argument is the line number. +It returns the value of the first argument. +</p> + +<h5>Semantics:</h5> + +<p> +This intrinsic allows annotations to be put on arbitrary expressions +with arbitrary strings. This can be useful for special purpose optimizations +that want to look for these annotations. These have no other defined use, they +are ignored by code generation and optimization. +</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_trap">'<tt>llvm.trap</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare void @llvm.trap() +</pre> + +<h5>Overview:</h5> + +<p> +The '<tt>llvm.trap</tt>' intrinsic +</p> + +<h5>Arguments:</h5> + +<p> +None +</p> + +<h5>Semantics:</h5> + +<p> +This intrinsics is lowered to the target dependent trap instruction. If the +target does not have a trap instruction, this intrinsic will be lowered to the +call of the abort() function. +</p> +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="int_stackprotector">'<tt>llvm.stackprotector</tt>' Intrinsic</a> +</div> +<div class="doc_text"> +<h5>Syntax:</h5> +<pre> +declare void @llvm.stackprotector( i8* <guard>, i8** <slot> ) + +</pre> +<h5>Overview:</h5> +<p> + The <tt>llvm.stackprotector</tt> intrinsic takes the <tt>guard</tt> and stores + it onto the stack at <tt>slot</tt>. The stack slot is adjusted to ensure that + it is placed on the stack before local variables. +</p> +<h5>Arguments:</h5> +<p> + The <tt>llvm.stackprotector</tt> intrinsic requires two pointer arguments. The + first argument is the value loaded from the stack guard + <tt>@__stack_chk_guard</tt>. The second variable is an <tt>alloca</tt> that + has enough space to hold the value of the guard. +</p> +<h5>Semantics:</h5> +<p> + This intrinsic causes the prologue/epilogue inserter to force the position of + the <tt>AllocaInst</tt> stack slot to be before local variables on the + stack. This is to ensure that if a local variable on the stack is overwritten, + it will destroy the value of the guard. When the function exits, the guard on + the stack is checked against the original guard. If they're different, then + the program aborts by calling the <tt>__stack_chk_fail()</tt> function. +</p> +</div> + +<!-- *********************************************************************** --> +<hr> +<address> + <a href="http://jigsaw.w3.org/css-validator/check/referer"><img + src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a> + <a href="http://validator.w3.org/check/referer"><img + src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a> + + <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> + <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br> + Last modified: $Date: 2009-05-30 18:08:30 +0200 (Sat, 30 May 2009) $ +</address> + +</body> +</html> |
