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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+ <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+ <title>Source Level Debugging with LLVM</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+</head>
+<body>
+
+<div class="doc_title">Source Level Debugging with LLVM</div>
+
+<table class="layout" style="width:100%">
+ <tr class="layout">
+ <td class="left">
+<ul>
+ <li><a href="#introduction">Introduction</a>
+ <ol>
+ <li><a href="#phil">Philosophy behind LLVM debugging information</a></li>
+ <li><a href="#consumers">Debug information consumers</a></li>
+ <li><a href="#debugopt">Debugging optimized code</a></li>
+ </ol></li>
+ <li><a href="#format">Debugging information format</a>
+ <ol>
+ <li><a href="#debug_info_descriptors">Debug information descriptors</a>
+ <ul>
+ <li><a href="#format_anchors">Anchor descriptors</a></li>
+ <li><a href="#format_compile_units">Compile unit descriptors</a></li>
+ <li><a href="#format_global_variables">Global variable descriptors</a></li>
+ <li><a href="#format_subprograms">Subprogram descriptors</a></li>
+ <li><a href="#format_blocks">Block descriptors</a></li>
+ <li><a href="#format_basic_type">Basic type descriptors</a></li>
+ <li><a href="#format_derived_type">Derived type descriptors</a></li>
+ <li><a href="#format_composite_type">Composite type descriptors</a></li>
+ <li><a href="#format_subrange">Subrange descriptors</a></li>
+ <li><a href="#format_enumeration">Enumerator descriptors</a></li>
+ <li><a href="#format_variables">Local variables</a></li>
+ </ul></li>
+ <li><a href="#format_common_intrinsics">Debugger intrinsic functions</a>
+ <ul>
+ <li><a href="#format_common_stoppoint">llvm.dbg.stoppoint</a></li>
+ <li><a href="#format_common_func_start">llvm.dbg.func.start</a></li>
+ <li><a href="#format_common_region_start">llvm.dbg.region.start</a></li>
+ <li><a href="#format_common_region_end">llvm.dbg.region.end</a></li>
+ <li><a href="#format_common_declare">llvm.dbg.declare</a></li>
+ </ul></li>
+ <li><a href="#format_common_stoppoints">Representing stopping points in the
+ source program</a></li>
+ </ol></li>
+ <li><a href="#ccxx_frontend">C/C++ front-end specific debug information</a>
+ <ol>
+ <li><a href="#ccxx_compile_units">C/C++ source file information</a></li>
+ <li><a href="#ccxx_global_variable">C/C++ global variable information</a></li>
+ <li><a href="#ccxx_subprogram">C/C++ function information</a></li>
+ <li><a href="#ccxx_basic_types">C/C++ basic types</a></li>
+ <li><a href="#ccxx_derived_types">C/C++ derived types</a></li>
+ <li><a href="#ccxx_composite_types">C/C++ struct/union types</a></li>
+ <li><a href="#ccxx_enumeration_types">C/C++ enumeration types</a></li>
+ </ol></li>
+</ul>
+</td>
+<td class="right">
+<img src="img/venusflytrap.jpg" alt="A leafy and green bug eater" width="247"
+height="369">
+</td>
+</tr></table>
+
+<div class="doc_author">
+ <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>
+ and <a href="mailto:jlaskey@mac.com">Jim Laskey</a></p>
+</div>
+
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="introduction">Introduction</a></div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>This document is the central repository for all information pertaining to
+ debug information in LLVM. It describes the <a href="#format">actual format
+ that the LLVM debug information</a> takes, which is useful for those
+ interested in creating front-ends or dealing directly with the information.
+ Further, this document provides specifc examples of what debug information
+ for C/C++.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="phil">Philosophy behind LLVM debugging information</a>
+</div>
+
+<div class="doc_text">
+
+<p>The idea of the LLVM debugging information is to capture how the important
+ pieces of the source-language's Abstract Syntax Tree map onto LLVM code.
+ Several design aspects have shaped the solution that appears here. The
+ important ones are:</p>
+
+<ul>
+ <li>Debugging information should have very little impact on the rest of the
+ compiler. No transformations, analyses, or code generators should need to
+ be modified because of debugging information.</li>
+
+ <li>LLVM optimizations should interact in <a href="#debugopt">well-defined and
+ easily described ways</a> with the debugging information.</li>
+
+ <li>Because LLVM is designed to support arbitrary programming languages,
+ LLVM-to-LLVM tools should not need to know anything about the semantics of
+ the source-level-language.</li>
+
+ <li>Source-level languages are often <b>widely</b> different from one another.
+ LLVM should not put any restrictions of the flavor of the source-language,
+ and the debugging information should work with any language.</li>
+
+ <li>With code generator support, it should be possible to use an LLVM compiler
+ to compile a program to native machine code and standard debugging
+ formats. This allows compatibility with traditional machine-code level
+ debuggers, like GDB or DBX.</li>
+</ul>
+
+<p>The approach used by the LLVM implementation is to use a small set
+ of <a href="#format_common_intrinsics">intrinsic functions</a> to define a
+ mapping between LLVM program objects and the source-level objects. The
+ description of the source-level program is maintained in LLVM global
+ variables in an <a href="#ccxx_frontend">implementation-defined format</a>
+ (the C/C++ front-end currently uses working draft 7 of
+ the <a href="http://www.eagercon.com/dwarf/dwarf3std.htm">DWARF 3
+ standard</a>).</p>
+
+<p>When a program is being debugged, a debugger interacts with the user and
+ turns the stored debug information into source-language specific information.
+ As such, a debugger must be aware of the source-language, and is thus tied to
+ a specific language or family of languages.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="consumers">Debug information consumers</a>
+</div>
+
+<div class="doc_text">
+
+<p>The role of debug information is to provide meta information normally
+ stripped away during the compilation process. This meta information provides
+ an LLVM user a relationship between generated code and the original program
+ source code.</p>
+
+<p>Currently, debug information is consumed by the DwarfWriter to produce dwarf
+ information used by the gdb debugger. Other targets could use the same
+ information to produce stabs or other debug forms.</p>
+
+<p>It would also be reasonable to use debug information to feed profiling tools
+ for analysis of generated code, or, tools for reconstructing the original
+ source from generated code.</p>
+
+<p>TODO - expound a bit more.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="debugopt">Debugging optimized code</a>
+</div>
+
+<div class="doc_text">
+
+<p>An extremely high priority of LLVM debugging information is to make it
+ interact well with optimizations and analysis. In particular, the LLVM debug
+ information provides the following guarantees:</p>
+
+<ul>
+ <li>LLVM debug information <b>always provides information to accurately read
+ the source-level state of the program</b>, regardless of which LLVM
+ optimizations have been run, and without any modification to the
+ optimizations themselves. However, some optimizations may impact the
+ ability to modify the current state of the program with a debugger, such
+ as setting program variables, or calling functions that have been
+ deleted.</li>
+
+ <li>LLVM optimizations gracefully interact with debugging information. If
+ they are not aware of debug information, they are automatically disabled
+ as necessary in the cases that would invalidate the debug info. This
+ retains the LLVM features, making it easy to write new
+ transformations.</li>
+
+ <li>As desired, LLVM optimizations can be upgraded to be aware of the LLVM
+ debugging information, allowing them to update the debugging information
+ as they perform aggressive optimizations. This means that, with effort,
+ the LLVM optimizers could optimize debug code just as well as non-debug
+ code.</li>
+
+ <li>LLVM debug information does not prevent many important optimizations from
+ happening (for example inlining, basic block reordering/merging/cleanup,
+ tail duplication, etc), further reducing the amount of the compiler that
+ eventually is "aware" of debugging information.</li>
+
+ <li>LLVM debug information is automatically optimized along with the rest of
+ the program, using existing facilities. For example, duplicate
+ information is automatically merged by the linker, and unused information
+ is automatically removed.</li>
+</ul>
+
+<p>Basically, the debug information allows you to compile a program with
+ "<tt>-O0 -g</tt>" and get full debug information, allowing you to arbitrarily
+ modify the program as it executes from a debugger. Compiling a program with
+ "<tt>-O3 -g</tt>" gives you full debug information that is always available
+ and accurate for reading (e.g., you get accurate stack traces despite tail
+ call elimination and inlining), but you might lose the ability to modify the
+ program and call functions where were optimized out of the program, or
+ inlined away completely.</p>
+
+<p><a href="TestingGuide.html#quicktestsuite">LLVM test suite</a> provides a
+ framework to test optimizer's handling of debugging information. It can be
+ run like this:</p>
+
+<div class="doc_code">
+<pre>
+% cd llvm/projects/test-suite/MultiSource/Benchmarks # or some other level
+% make TEST=dbgopt
+</pre>
+</div>
+
+<p>This will test impact of debugging information on optimization passes. If
+ debugging information influences optimization passes then it will be reported
+ as a failure. See <a href="TestingGuide.html">TestingGuide</a> for more
+ information on LLVM test infrastructure and how to run various tests.</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="format">Debugging information format</a>
+</div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>LLVM debugging information has been carefully designed to make it possible
+ for the optimizer to optimize the program and debugging information without
+ necessarily having to know anything about debugging information. In
+ particular, the global constant merging pass automatically eliminates
+ duplicated debugging information (often caused by header files), the global
+ dead code elimination pass automatically deletes debugging information for a
+ function if it decides to delete the function, and the linker eliminates
+ debug information when it merges <tt>linkonce</tt> functions.</p>
+
+<p>To do this, most of the debugging information (descriptors for types,
+ variables, functions, source files, etc) is inserted by the language
+ front-end in the form of LLVM global variables. These LLVM global variables
+ are no different from any other global variables, except that they have a web
+ of LLVM intrinsic functions that point to them. If the last references to a
+ particular piece of debugging information are deleted (for example, by the
+ <tt>-globaldce</tt> pass), the extraneous debug information will
+ automatically become dead and be removed by the optimizer.</p>
+
+<p>Debug information is designed to be agnostic about the target debugger and
+ debugging information representation (e.g. DWARF/Stabs/etc). It uses a
+ generic machine debug information pass to decode the information that
+ represents variables, types, functions, namespaces, etc: this allows for
+ arbitrary source-language semantics and type-systems to be used, as long as
+ there is a module written for the target debugger to interpret the
+ information. In addition, debug global variables are declared in
+ the <tt>"llvm.metadata"</tt> section. All values declared in this section
+ are stripped away after target debug information is constructed and before
+ the program object is emitted.</p>
+
+<p>To provide basic functionality, the LLVM debugger does have to make some
+ assumptions about the source-level language being debugged, though it keeps
+ these to a minimum. The only common features that the LLVM debugger assumes
+ exist are <a href="#format_compile_units">source files</a>,
+ and <a href="#format_global_variables">program objects</a>. These abstract
+ objects are used by a debugger to form stack traces, show information about
+ local variables, etc.</p>
+
+<p>This section of the documentation first describes the representation aspects
+ common to any source-language. The <a href="#ccxx_frontend">next section</a>
+ describes the data layout conventions used by the C and C++ front-ends.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="debug_info_descriptors">Debug information descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<p>In consideration of the complexity and volume of debug information, LLVM
+ provides a specification for well formed debug global variables. The
+ constant value of each of these globals is one of a limited set of
+ structures, known as debug descriptors.</p>
+
+<p>Consumers of LLVM debug information expect the descriptors for program
+ objects to start in a canonical format, but the descriptors can include
+ additional information appended at the end that is source-language
+ specific. All LLVM debugging information is versioned, allowing backwards
+ compatibility in the case that the core structures need to change in some
+ way. Also, all debugging information objects start with a tag to indicate
+ what type of object it is. The source-language is allowed to define its own
+ objects, by using unreserved tag numbers. We recommend using with tags in
+ the range 0x1000 thru 0x2000 (there is a defined enum DW_TAG_user_base =
+ 0x1000.)</p>
+
+<p>The fields of debug descriptors used internally by LLVM (MachineModuleInfo)
+ are restricted to only the simple data types <tt>int</tt>, <tt>uint</tt>,
+ <tt>bool</tt>, <tt>float</tt>, <tt>double</tt>, <tt>i8*</tt> and
+ <tt>{&nbsp;}*</tt>. References to arbitrary values are handled using a
+ <tt>{&nbsp;}*</tt> and a cast to <tt>{&nbsp;}*</tt> expression; typically
+ references to other field descriptors, arrays of descriptors or global
+ variables.</p>
+
+<div class="doc_code">
+<pre>
+%llvm.dbg.object.type = type {
+ uint, ;; A tag
+ ...
+}
+</pre>
+</div>
+
+<p><a name="LLVMDebugVersion">The first field of a descriptor is always an
+ <tt>uint</tt> containing a tag value identifying the content of the
+ descriptor. The remaining fields are specific to the descriptor. The values
+ of tags are loosely bound to the tag values of DWARF information entries.
+ However, that does not restrict the use of the information supplied to DWARF
+ targets. To facilitate versioning of debug information, the tag is augmented
+ with the current debug version (LLVMDebugVersion = 4 << 16 or 0x40000 or
+ 262144.)</a></p>
+
+<p>The details of the various descriptors follow.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_anchors">Anchor descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_anchors">llvm.dbg.anchor.type</a> = type {
+ i32, ;; Tag = 0 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a>
+ i32 ;; Tag of descriptors grouped by the anchor
+}
+</pre>
+</div>
+
+<p>One important aspect of the LLVM debug representation is that it allows the
+ LLVM debugger to efficiently index all of the global objects without having
+ to scan the program. To do this, all of the global objects use "anchor"
+ descriptors with designated names. All of the global objects of a particular
+ type (e.g., compile units) contain a pointer to the anchor. This pointer
+ allows a debugger to use def-use chains to find all global objects of that
+ type.</p>
+
+<p>The following names are recognized as anchors by LLVM:</p>
+
+<div class="doc_code">
+<pre>
+%<a href="#format_compile_units">llvm.dbg.compile_units</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> {
+ i32 0,
+ i32 17
+} ;; DW_TAG_compile_unit
+%<a href="#format_global_variables">llvm.dbg.global_variables</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> {
+ i32 0,
+ i32 52
+} ;; DW_TAG_variable
+%<a href="#format_subprograms">llvm.dbg.subprograms</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> {
+ i32 0,
+ i32 46
+} ;; DW_TAG_subprogram
+</pre>
+</div>
+
+<p>Using anchors in this way (where the compile unit descriptor points to the
+ anchors, as opposed to having a list of compile unit descriptors) allows for
+ the standard dead global elimination and merging passes to automatically
+ remove unused debugging information. If the globals were kept track of
+ through lists, there would always be an object pointing to the descriptors,
+ thus would never be deleted.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_compile_units">Compile unit descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type {
+ i32, ;; Tag = 17 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_compile_unit)
+ { }*, ;; Compile unit anchor = cast = (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*)
+ i32, ;; DWARF language identifier (ex. DW_LANG_C89)
+ i8*, ;; Source file name
+ i8*, ;; Source file directory (includes trailing slash)
+ i8* ;; Producer (ex. "4.0.1 LLVM (LLVM research group)")
+ i1, ;; True if this is a main compile unit.
+ i1, ;; True if this is optimized.
+ i8*, ;; Flags
+ i32 ;; Runtime version
+}
+</pre>
+</div>
+
+<p>These descriptors contain a source language ID for the file (we use the DWARF
+ 3.0 ID numbers, such as <tt>DW_LANG_C89</tt>, <tt>DW_LANG_C_plus_plus</tt>,
+ <tt>DW_LANG_Cobol74</tt>, etc), three strings describing the filename,
+ working directory of the compiler, and an identifier string for the compiler
+ that produced it.</p>
+
+<p>Compile unit descriptors provide the root context for objects declared in a
+ specific source file. Global variables and top level functions would be
+ defined using this context. Compile unit descriptors also provide context
+ for source line correspondence.</p>
+
+<p>Each input file is encoded as a separate compile unit in LLVM debugging
+ information output. However, many target specific tool chains prefer to
+ encode only one compile unit in an object file. In this situation, the LLVM
+ code generator will include debugging information entities in the compile
+ unit that is marked as main compile unit. The code generator accepts maximum
+ one main compile unit per module. If a module does not contain any main
+ compile unit then the code generator will emit multiple compile units in the
+ output object file.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_global_variables">Global variable descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type {
+ i32, ;; Tag = 52 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_variable)
+ { }*, ;; Global variable anchor = cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_global_variables">llvm.dbg.global_variables</a> to { }*),
+ { }*, ;; Reference to context descriptor
+ i8*, ;; Name
+ i8*, ;; Display name (fully qualified C++ name)
+ i8*, ;; MIPS linkage name (for C++)
+ { }*, ;; Reference to compile unit where defined
+ i32, ;; Line number where defined
+ { }*, ;; Reference to type descriptor
+ i1, ;; True if the global is local to compile unit (static)
+ i1, ;; True if the global is defined in the compile unit (not extern)
+ { }* ;; Reference to the global variable
+}
+</pre>
+</div>
+
+<p>These descriptors provide debug information about globals variables. The
+provide details such as name, type and where the variable is defined.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_subprograms">Subprogram descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type {
+ i32, ;; Tag = 46 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subprogram)
+ { }*, ;; Subprogram anchor = cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_subprograms">llvm.dbg.subprograms</a> to { }*),
+ { }*, ;; Reference to context descriptor
+ i8*, ;; Name
+ i8*, ;; Display name (fully qualified C++ name)
+ i8*, ;; MIPS linkage name (for C++)
+ { }*, ;; Reference to compile unit where defined
+ i32, ;; Line number where defined
+ { }*, ;; Reference to type descriptor
+ i1, ;; True if the global is local to compile unit (static)
+ i1 ;; True if the global is defined in the compile unit (not extern)
+}
+</pre>
+</div>
+
+<p>These descriptors provide debug information about functions, methods and
+ subprograms. They provide details such as name, return types and the source
+ location where the subprogram is defined.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_blocks">Block descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_blocks">llvm.dbg.block</a> = type {
+ i32, ;; Tag = 13 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_lexical_block)
+ { }* ;; Reference to context descriptor
+}
+</pre>
+</div>
+
+<p>These descriptors provide debug information about nested blocks within a
+ subprogram. The array of member descriptors is used to define local
+ variables and deeper nested blocks.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_basic_type">Basic type descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type {
+ i32, ;; Tag = 36 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_base_type)
+ { }*, ;; Reference to context (typically a compile unit)
+ i8*, ;; Name (may be "" for anonymous types)
+ { }*, ;; Reference to compile unit where defined (may be NULL)
+ i32, ;; Line number where defined (may be 0)
+ i64, ;; Size in bits
+ i64, ;; Alignment in bits
+ i64, ;; Offset in bits
+ i32, ;; Flags
+ i32 ;; DWARF type encoding
+}
+</pre>
+</div>
+
+<p>These descriptors define primitive types used in the code. Example int, bool
+ and float. The context provides the scope of the type, which is usually the
+ top level. Since basic types are not usually user defined the compile unit
+ and line number can be left as NULL and 0. The size, alignment and offset
+ are expressed in bits and can be 64 bit values. The alignment is used to
+ round the offset when embedded in a
+ <a href="#format_composite_type">composite type</a> (example to keep float
+ doubles on 64 bit boundaries.) The offset is the bit offset if embedded in
+ a <a href="#format_composite_type">composite type</a>.</p>
+
+<p>The type encoding provides the details of the type. The values are typically
+ one of the following:</p>
+
+<div class="doc_code">
+<pre>
+DW_ATE_address = 1
+DW_ATE_boolean = 2
+DW_ATE_float = 4
+DW_ATE_signed = 5
+DW_ATE_signed_char = 6
+DW_ATE_unsigned = 7
+DW_ATE_unsigned_char = 8
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_derived_type">Derived type descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> = type {
+ i32, ;; Tag (see below)
+ { }*, ;; Reference to context
+ i8*, ;; Name (may be "" for anonymous types)
+ { }*, ;; Reference to compile unit where defined (may be NULL)
+ i32, ;; Line number where defined (may be 0)
+ i32, ;; Size in bits
+ i32, ;; Alignment in bits
+ i32, ;; Offset in bits
+ { }* ;; Reference to type derived from
+}
+</pre>
+</div>
+
+<p>These descriptors are used to define types derived from other types. The
+value of the tag varies depending on the meaning. The following are possible
+tag values:</p>
+
+<div class="doc_code">
+<pre>
+DW_TAG_formal_parameter = 5
+DW_TAG_member = 13
+DW_TAG_pointer_type = 15
+DW_TAG_reference_type = 16
+DW_TAG_typedef = 22
+DW_TAG_const_type = 38
+DW_TAG_volatile_type = 53
+DW_TAG_restrict_type = 55
+</pre>
+</div>
+
+<p><tt>DW_TAG_member</tt> is used to define a member of
+ a <a href="#format_composite_type">composite type</a>
+ or <a href="#format_subprograms">subprogram</a>. The type of the member is
+ the <a href="#format_derived_type">derived
+ type</a>. <tt>DW_TAG_formal_parameter</tt> is used to define a member which
+ is a formal argument of a subprogram.</p>
+
+<p><tt>DW_TAG_typedef</tt> is used to provide a name for the derived type.</p>
+
+<p><tt>DW_TAG_pointer_type</tt>,<tt>DW_TAG_reference_type</tt>,
+ <tt>DW_TAG_const_type</tt>, <tt>DW_TAG_volatile_type</tt>
+ and <tt>DW_TAG_restrict_type</tt> are used to qualify
+ the <a href="#format_derived_type">derived type</a>. </p>
+
+<p><a href="#format_derived_type">Derived type</a> location can be determined
+ from the compile unit and line number. The size, alignment and offset are
+ expressed in bits and can be 64 bit values. The alignment is used to round
+ the offset when embedded in a <a href="#format_composite_type">composite
+ type</a> (example to keep float doubles on 64 bit boundaries.) The offset is
+ the bit offset if embedded in a <a href="#format_composite_type">composite
+ type</a>.</p>
+
+<p>Note that the <tt>void *</tt> type is expressed as a
+ <tt>llvm.dbg.derivedtype.type</tt> with tag of <tt>DW_TAG_pointer_type</tt>
+ and <tt>NULL</tt> derived type.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_composite_type">Composite type descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_composite_type">llvm.dbg.compositetype.type</a> = type {
+ i32, ;; Tag (see below)
+ { }*, ;; Reference to context
+ i8*, ;; Name (may be "" for anonymous types)
+ { }*, ;; Reference to compile unit where defined (may be NULL)
+ i32, ;; Line number where defined (may be 0)
+ i64, ;; Size in bits
+ i64, ;; Alignment in bits
+ i64, ;; Offset in bits
+ i32, ;; Flags
+ { }*, ;; Reference to type derived from
+ { }*, ;; Reference to array of member descriptors
+ i32 ;; Runtime languages
+}
+</pre>
+</div>
+
+<p>These descriptors are used to define types that are composed of 0 or more
+elements. The value of the tag varies depending on the meaning. The following
+are possible tag values:</p>
+
+<div class="doc_code">
+<pre>
+DW_TAG_array_type = 1
+DW_TAG_enumeration_type = 4
+DW_TAG_structure_type = 19
+DW_TAG_union_type = 23
+DW_TAG_vector_type = 259
+DW_TAG_subroutine_type = 21
+DW_TAG_inheritance = 28
+</pre>
+</div>
+
+<p>The vector flag indicates that an array type is a native packed vector.</p>
+
+<p>The members of array types (tag = <tt>DW_TAG_array_type</tt>) or vector types
+ (tag = <tt>DW_TAG_vector_type</tt>) are <a href="#format_subrange">subrange
+ descriptors</a>, each representing the range of subscripts at that level of
+ indexing.</p>
+
+<p>The members of enumeration types (tag = <tt>DW_TAG_enumeration_type</tt>) are
+ <a href="#format_enumeration">enumerator descriptors</a>, each representing
+ the definition of enumeration value for the set.</p>
+
+<p>The members of structure (tag = <tt>DW_TAG_structure_type</tt>) or union (tag
+ = <tt>DW_TAG_union_type</tt>) types are any one of
+ the <a href="#format_basic_type">basic</a>,
+ <a href="#format_derived_type">derived</a>
+ or <a href="#format_composite_type">composite</a> type descriptors, each
+ representing a field member of the structure or union.</p>
+
+<p>For C++ classes (tag = <tt>DW_TAG_structure_type</tt>), member descriptors
+ provide information about base classes, static members and member
+ functions. If a member is a <a href="#format_derived_type">derived type
+ descriptor</a> and has a tag of <tt>DW_TAG_inheritance</tt>, then the type
+ represents a base class. If the member of is
+ a <a href="#format_global_variables">global variable descriptor</a> then it
+ represents a static member. And, if the member is
+ a <a href="#format_subprograms">subprogram descriptor</a> then it represents
+ a member function. For static members and member
+ functions, <tt>getName()</tt> returns the members link or the C++ mangled
+ name. <tt>getDisplayName()</tt> the simplied version of the name.</p>
+
+<p>The first member of subroutine (tag = <tt>DW_TAG_subroutine_type</tt>) type
+ elements is the return type for the subroutine. The remaining elements are
+ the formal arguments to the subroutine.</p>
+
+<p><a href="#format_composite_type">Composite type</a> location can be
+ determined from the compile unit and line number. The size, alignment and
+ offset are expressed in bits and can be 64 bit values. The alignment is used
+ to round the offset when embedded in
+ a <a href="#format_composite_type">composite type</a> (as an example, to keep
+ float doubles on 64 bit boundaries.) The offset is the bit offset if embedded
+ in a <a href="#format_composite_type">composite type</a>.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_subrange">Subrange descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_subrange">llvm.dbg.subrange.type</a> = type {
+ i32, ;; Tag = 33 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subrange_type)
+ i64, ;; Low value
+ i64 ;; High value
+}
+</pre>
+</div>
+
+<p>These descriptors are used to define ranges of array subscripts for an array
+ <a href="#format_composite_type">composite type</a>. The low value defines
+ the lower bounds typically zero for C/C++. The high value is the upper
+ bounds. Values are 64 bit. High - low + 1 is the size of the array. If low
+ == high the array will be unbounded.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_enumeration">Enumerator descriptors</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_enumeration">llvm.dbg.enumerator.type</a> = type {
+ i32, ;; Tag = 40 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_enumerator)
+ i8*, ;; Name
+ i64 ;; Value
+}
+</pre>
+</div>
+
+<p>These descriptors are used to define members of an
+ enumeration <a href="#format_composite_type">composite type</a>, it
+ associates the name to the value.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_variables">Local variables</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_variables">llvm.dbg.variable.type</a> = type {
+ i32, ;; Tag (see below)
+ { }*, ;; Context
+ i8*, ;; Name
+ { }*, ;; Reference to compile unit where defined
+ i32, ;; Line number where defined
+ { }* ;; Type descriptor
+}
+</pre>
+</div>
+
+<p>These descriptors are used to define variables local to a sub program. The
+ value of the tag depends on the usage of the variable:</p>
+
+<div class="doc_code">
+<pre>
+DW_TAG_auto_variable = 256
+DW_TAG_arg_variable = 257
+DW_TAG_return_variable = 258
+</pre>
+</div>
+
+<p>An auto variable is any variable declared in the body of the function. An
+ argument variable is any variable that appears as a formal argument to the
+ function. A return variable is used to track the result of a function and
+ has no source correspondent.</p>
+
+<p>The context is either the subprogram or block where the variable is defined.
+ Name the source variable name. Compile unit and line indicate where the
+ variable was defined. Type descriptor defines the declared type of the
+ variable.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="format_common_intrinsics">Debugger intrinsic functions</a>
+</div>
+
+<div class="doc_text">
+
+<p>LLVM uses several intrinsic functions (name prefixed with "llvm.dbg") to
+ provide debug information at various points in generated code.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_common_stoppoint">llvm.dbg.stoppoint</a>
+</div>
+
+<div class="doc_text">
+<pre>
+ void %<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint, uint, { }* )
+</pre>
+
+<p>This intrinsic is used to provide correspondence between the source file and
+ the generated code. The first argument is the line number (base 1), second
+ argument is the column number (0 if unknown) and the third argument the
+ source <tt>%<a href="#format_compile_units">llvm.dbg.compile_unit</a>*</tt>
+ cast to a <tt>{&nbsp;}*</tt>. Code following a call to this intrinsic will
+ have been defined in close proximity of the line, column and file. This
+ information holds until the next call
+ to <tt>%<a href="#format_common_stoppoint">lvm.dbg.stoppoint</a></tt>.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_common_func_start">llvm.dbg.func.start</a>
+</div>
+
+<div class="doc_text">
+<pre>
+ void %<a href="#format_common_func_start">llvm.dbg.func.start</a>( { }* )
+</pre>
+
+<p>This intrinsic is used to link the debug information
+ in <tt>%<a href="#format_subprograms">llvm.dbg.subprogram</a></tt> to the
+ function. It defines the beginning of the function's declarative region
+ (scope). It also implies a call to
+ %<tt><a href="#format_common_stoppoint">llvm.dbg.stoppoint</a></tt> which
+ defines a source line "stop point". The intrinsic should be called early in
+ the function after the all the alloca instructions. It should be paired off
+ with a closing
+ <tt>%<a href="#format_common_region_end">llvm.dbg.region.end</a></tt>.
+ The function's single argument is
+ the <tt>%<a href="#format_subprograms">llvm.dbg.subprogram.type</a></tt>.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_common_region_start">llvm.dbg.region.start</a>
+</div>
+
+<div class="doc_text">
+<pre>
+ void %<a href="#format_common_region_start">llvm.dbg.region.start</a>( { }* )
+</pre>
+
+<p>This intrinsic is used to define the beginning of a declarative scope (ex.
+ block) for local language elements. It should be paired off with a closing
+ <tt>%<a href="#format_common_region_end">llvm.dbg.region.end</a></tt>. The
+ function's single argument is
+ the <tt>%<a href="#format_blocks">llvm.dbg.block</a></tt> which is
+ starting.</p>
+
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_common_region_end">llvm.dbg.region.end</a>
+</div>
+
+<div class="doc_text">
+<pre>
+ void %<a href="#format_common_region_end">llvm.dbg.region.end</a>( { }* )
+</pre>
+
+<p>This intrinsic is used to define the end of a declarative scope (ex. block)
+ for local language elements. It should be paired off with an
+ opening <tt>%<a href="#format_common_region_start">llvm.dbg.region.start</a></tt>
+ or <tt>%<a href="#format_common_func_start">llvm.dbg.func.start</a></tt>.
+ The function's single argument is either
+ the <tt>%<a href="#format_blocks">llvm.dbg.block</a></tt> or
+ the <tt>%<a href="#format_subprograms">llvm.dbg.subprogram.type</a></tt>
+ which is ending.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="format_common_declare">llvm.dbg.declare</a>
+</div>
+
+<div class="doc_text">
+<pre>
+ void %<a href="#format_common_declare">llvm.dbg.declare</a>( { } *, { }* )
+</pre>
+
+<p>This intrinsic provides information about a local element (ex. variable.) The
+ first argument is the alloca for the variable, cast to a <tt>{ }*</tt>. The
+ second argument is
+ the <tt>%<a href="#format_variables">llvm.dbg.variable</a></tt> containing
+ the description of the variable, also cast to a <tt>{ }*</tt>.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="format_common_stoppoints">
+ Representing stopping points in the source program
+ </a>
+</div>
+
+<div class="doc_text">
+
+<p>LLVM debugger "stop points" are a key part of the debugging representation
+ that allows the LLVM to maintain simple semantics
+ for <a href="#debugopt">debugging optimized code</a>. The basic idea is that
+ the front-end inserts calls to
+ the <a href="#format_common_stoppoint">%<tt>llvm.dbg.stoppoint</tt></a>
+ intrinsic function at every point in the program where a debugger should be
+ able to inspect the program (these correspond to places a debugger stops when
+ you "<tt>step</tt>" through it). The front-end can choose to place these as
+ fine-grained as it would like (for example, before every subexpression
+ evaluated), but it is recommended to only put them after every source
+ statement that includes executable code.</p>
+
+<p>Using calls to this intrinsic function to demark legal points for the
+ debugger to inspect the program automatically disables any optimizations that
+ could potentially confuse debugging information. To
+ non-debug-information-aware transformations, these calls simply look like
+ calls to an external function, which they must assume to do anything
+ (including reading or writing to any part of reachable memory). On the other
+ hand, it does not impact many optimizations, such as code motion of
+ non-trapping instructions, nor does it impact optimization of subexpressions,
+ code duplication transformations, or basic-block reordering
+ transformations.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="format_common_lifetime">Object lifetimes and scoping</a>
+</div>
+
+<div class="doc_text">
+<p>In many languages, the local variables in functions can have their lifetime
+ or scope limited to a subset of a function. In the C family of languages,
+ for example, variables are only live (readable and writable) within the
+ source block that they are defined in. In functional languages, values are
+ only readable after they have been defined. Though this is a very obvious
+ concept, it is also non-trivial to model in LLVM, because it has no notion of
+ scoping in this sense, and does not want to be tied to a language's scoping
+ rules.</p>
+
+<p>In order to handle this, the LLVM debug format uses the notion of "regions"
+ of a function, delineated by calls to intrinsic functions. These intrinsic
+ functions define new regions of the program and indicate when the region
+ lifetime expires. Consider the following C fragment, for example:</p>
+
+<div class="doc_code">
+<pre>
+1. void foo() {
+2. int X = ...;
+3. int Y = ...;
+4. {
+5. int Z = ...;
+6. ...
+7. }
+8. ...
+9. }
+</pre>
+</div>
+
+<p>Compiled to LLVM, this function would be represented like this:</p>
+
+<div class="doc_code">
+<pre>
+void %foo() {
+entry:
+ %X = alloca int
+ %Y = alloca int
+ %Z = alloca int
+
+ ...
+
+ call void @<a href="#format_common_func_start">llvm.dbg.func.start</a>( %<a href="#format_subprograms">llvm.dbg.subprogram.type</a>* @llvm.dbg.subprogram )
+
+ call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 2, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
+
+ call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %X, ...)
+ call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %Y, ...)
+
+ <i>;; Evaluate expression on line 2, assigning to X.</i>
+
+ call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 3, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
+
+ <i>;; Evaluate expression on line 3, assigning to Y.</i>
+
+ call void @<a href="#format_common_stoppoint">llvm.region.start</a>()
+ call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 5, uint 4, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
+ call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %X, ...)
+
+ <i>;; Evaluate expression on line 5, assigning to Z.</i>
+
+ call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 7, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
+ call void @<a href="#format_common_region_end">llvm.region.end</a>()
+
+ call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 9, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )
+
+ call void @<a href="#format_common_region_end">llvm.region.end</a>()
+
+ ret void
+}
+</pre>
+</div>
+
+<p>This example illustrates a few important details about the LLVM debugging
+ information. In particular, it shows how the various intrinsics are applied
+ together to allow a debugger to analyze the relationship between statements,
+ variable definitions, and the code used to implement the function.</p>
+
+<p>The first
+ intrinsic <tt>%<a href="#format_common_func_start">llvm.dbg.func.start</a></tt>
+ provides a link with the <a href="#format_subprograms">subprogram
+ descriptor</a> containing the details of this function. This call also
+ defines the beginning of the function region, bounded by
+ the <tt>%<a href="#format_common_region_end">llvm.region.end</a></tt> at the
+ end of the function. This region is used to bracket the lifetime of
+ variables declared within. For a function, this outer region defines a new
+ stack frame whose lifetime ends when the region is ended.</p>
+
+<p>It is possible to define inner regions for short term variables by using the
+ %<a href="#format_common_stoppoint"><tt>llvm.region.start</tt></a>
+ and <a href="#format_common_region_end"><tt>%llvm.region.end</tt></a> to
+ bound a region. The inner region in this example would be for the block
+ containing the declaration of Z.</p>
+
+<p>Using regions to represent the boundaries of source-level functions allow
+ LLVM interprocedural optimizations to arbitrarily modify LLVM functions
+ without having to worry about breaking mapping information between the LLVM
+ code and the and source-level program. In particular, the inliner requires
+ no modification to support inlining with debugging information: there is no
+ explicit correlation drawn between LLVM functions and their source-level
+ counterparts (note however, that if the inliner inlines all instances of a
+ non-strong-linkage function into its caller that it will not be possible for
+ the user to manually invoke the inlined function from a debugger).</p>
+
+<p>Once the function has been defined,
+ the <a href="#format_common_stoppoint"><tt>stopping point</tt></a>
+ corresponding to line #2 (column #2) of the function is encountered. At this
+ point in the function, <b>no</b> local variables are live. As lines 2 and 3
+ of the example are executed, their variable definitions are introduced into
+ the program using
+ %<a href="#format_common_declare"><tt>llvm.dbg.declare</tt></a>, without the
+ need to specify a new region. These variables do not require new regions to
+ be introduced because they go out of scope at the same point in the program:
+ line 9.</p>
+
+<p>In contrast, the <tt>Z</tt> variable goes out of scope at a different time,
+ on line 7. For this reason, it is defined within the inner region, which
+ kills the availability of <tt>Z</tt> before the code for line 8 is executed.
+ In this way, regions can support arbitrary source-language scoping rules, as
+ long as they can only be nested (ie, one scope cannot partially overlap with
+ a part of another scope).</p>
+
+<p>It is worth noting that this scoping mechanism is used to control scoping of
+ all declarations, not just variable declarations. For example, the scope of
+ a C++ using declaration is controlled with this and could change how name
+ lookup is performed.</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="ccxx_frontend">C/C++ front-end specific debug information</a>
+</div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>The C and C++ front-ends represent information about the program in a format
+ that is effectively identical
+ to <a href="http://www.eagercon.com/dwarf/dwarf3std.htm">DWARF 3.0</a> in
+ terms of information content. This allows code generators to trivially
+ support native debuggers by generating standard dwarf information, and
+ contains enough information for non-dwarf targets to translate it as
+ needed.</p>
+
+<p>This section describes the forms used to represent C and C++ programs. Other
+ languages could pattern themselves after this (which itself is tuned to
+ representing programs in the same way that DWARF 3 does), or they could
+ choose to provide completely different forms if they don't fit into the DWARF
+ model. As support for debugging information gets added to the various LLVM
+ source-language front-ends, the information used should be documented
+ here.</p>
+
+<p>The following sections provide examples of various C/C++ constructs and the
+ debug information that would best describe those constructs.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="ccxx_compile_units">C/C++ source file information</a>
+</div>
+
+<div class="doc_text">
+
+<p>Given the source files <tt>MySource.cpp</tt> and <tt>MyHeader.h</tt> located
+ in the directory <tt>/Users/mine/sources</tt>, the following code:</p>
+
+<div class="doc_code">
+<pre>
+#include "MyHeader.h"
+
+int main(int argc, char *argv[]) {
+ return 0;
+}
+</pre>
+</div>
+
+<p>a C/C++ front-end would generate the following descriptors:</p>
+
+<div class="doc_code">
+<pre>
+...
+;;
+;; Define types used. In this case we need one for compile unit anchors and one
+;; for compile units.
+;;
+%<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
+%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type { uint, { }*, uint, uint, i8*, i8*, i8* }
+...
+;;
+;; Define the anchor for compile units. Note that the second field of the
+;; anchor is 17, which is the same as the tag for compile units
+;; (17 = DW_TAG_compile_unit.)
+;;
+%<a href="#format_compile_units">llvm.dbg.compile_units</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 17 }, section "llvm.metadata"
+
+;;
+;; Define the compile unit for the source file "/Users/mine/sources/MySource.cpp".
+;;
+%<a href="#format_compile_units">llvm.dbg.compile_unit1</a> = internal constant %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> {
+ uint add(uint 17, uint 262144),
+ { }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*),
+ uint 1,
+ uint 1,
+ i8* getelementptr ([13 x i8]* %str1, i32 0, i32 0),
+ i8* getelementptr ([21 x i8]* %str2, i32 0, i32 0),
+ i8* getelementptr ([33 x i8]* %str3, i32 0, i32 0) }, section "llvm.metadata"
+
+;;
+;; Define the compile unit for the header file "/Users/mine/sources/MyHeader.h".
+;;
+%<a href="#format_compile_units">llvm.dbg.compile_unit2</a> = internal constant %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> {
+ uint add(uint 17, uint 262144),
+ { }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to { }*),
+ uint 1,
+ uint 1,
+ i8* getelementptr ([11 x i8]* %str4, int 0, int 0),
+ i8* getelementptr ([21 x i8]* %str2, int 0, int 0),
+ i8* getelementptr ([33 x i8]* %str3, int 0, int 0) }, section "llvm.metadata"
+
+;;
+;; Define each of the strings used in the compile units.
+;;
+%str1 = internal constant [13 x i8] c"MySource.cpp\00", section "llvm.metadata";
+%str2 = internal constant [21 x i8] c"/Users/mine/sources/\00", section "llvm.metadata";
+%str3 = internal constant [33 x i8] c"4.0.1 LLVM (LLVM research group)\00", section "llvm.metadata";
+%str4 = internal constant [11 x i8] c"MyHeader.h\00", section "llvm.metadata";
+...
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="ccxx_global_variable">C/C++ global variable information</a>
+</div>
+
+<div class="doc_text">
+
+<p>Given an integer global variable declared as follows:</p>
+
+<div class="doc_code">
+<pre>
+int MyGlobal = 100;
+</pre>
+</div>
+
+<p>a C/C++ front-end would generate the following descriptors:</p>
+
+<div class="doc_code">
+<pre>
+;;
+;; Define types used. One for global variable anchors, one for the global
+;; variable descriptor, one for the global's basic type and one for the global's
+;; compile unit.
+;;
+%<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
+%<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type { uint, { }*, { }*, i8*, { }*, uint, { }*, bool, bool, { }*, uint }
+%<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type { uint, { }*, i8*, { }*, int, uint, uint, uint, uint }
+%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = ...
+...
+;;
+;; Define the global itself.
+;;
+%MyGlobal = global int 100
+...
+;;
+;; Define the anchor for global variables. Note that the second field of the
+;; anchor is 52, which is the same as the tag for global variables
+;; (52 = DW_TAG_variable.)
+;;
+%<a href="#format_global_variables">llvm.dbg.global_variables</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 52 }, section "llvm.metadata"
+
+;;
+;; Define the global variable descriptor. Note the reference to the global
+;; variable anchor and the global variable itself.
+;;
+%<a href="#format_global_variables">llvm.dbg.global_variable</a> = internal constant %<a href="#format_global_variables">llvm.dbg.global_variable.type</a> {
+ uint add(uint 52, uint 262144),
+ { }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_global_variables">llvm.dbg.global_variables</a> to { }*),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([9 x i8]* %str1, int 0, int 0),
+ i8* getelementptr ([1 x i8]* %str2, int 0, int 0),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ uint 1,
+ { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*),
+ bool false,
+ bool true,
+ { }* cast (int* %MyGlobal to { }*) }, section "llvm.metadata"
+
+;;
+;; Define the basic type of 32 bit signed integer. Note that since int is an
+;; intrinsic type the source file is NULL and line 0.
+;;
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([4 x i8]* %str3, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 32,
+ uint 32,
+ uint 0,
+ uint 5 }, section "llvm.metadata"
+
+;;
+;; Define the names of the global variable and basic type.
+;;
+%str1 = internal constant [9 x i8] c"MyGlobal\00", section "llvm.metadata"
+%str2 = internal constant [1 x i8] c"\00", section "llvm.metadata"
+%str3 = internal constant [4 x i8] c"int\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="ccxx_subprogram">C/C++ function information</a>
+</div>
+
+<div class="doc_text">
+
+<p>Given a function declared as follows:</p>
+
+<div class="doc_code">
+<pre>
+int main(int argc, char *argv[]) {
+ return 0;
+}
+</pre>
+</div>
+
+<p>a C/C++ front-end would generate the following descriptors:</p>
+
+<div class="doc_code">
+<pre>
+;;
+;; Define types used. One for subprogram anchors, one for the subprogram
+;; descriptor, one for the global's basic type and one for the subprogram's
+;; compile unit.
+;;
+%<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type { uint, { }*, { }*, i8*, { }*, bool, bool }
+%<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }
+%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = ...
+
+;;
+;; Define the anchor for subprograms. Note that the second field of the
+;; anchor is 46, which is the same as the tag for subprograms
+;; (46 = DW_TAG_subprogram.)
+;;
+%<a href="#format_subprograms">llvm.dbg.subprograms</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 46 }, section "llvm.metadata"
+
+;;
+;; Define the descriptor for the subprogram. TODO - more details.
+;;
+%<a href="#format_subprograms">llvm.dbg.subprogram</a> = internal constant %<a href="#format_subprograms">llvm.dbg.subprogram.type</a> {
+ uint add(uint 46, uint 262144),
+ { }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_subprograms">llvm.dbg.subprograms</a> to { }*),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([5 x i8]* %str1, int 0, int 0),
+ i8* getelementptr ([1 x i8]* %str2, int 0, int 0),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ uint 1,
+ { }* null,
+ bool false,
+ bool true }, section "llvm.metadata"
+
+;;
+;; Define the name of the subprogram.
+;;
+%str1 = internal constant [5 x i8] c"main\00", section "llvm.metadata"
+%str2 = internal constant [1 x i8] c"\00", section "llvm.metadata"
+
+;;
+;; Define the subprogram itself.
+;;
+int %main(int %argc, i8** %argv) {
+...
+}
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="ccxx_basic_types">C/C++ basic types</a>
+</div>
+
+<div class="doc_text">
+
+<p>The following are the basic type descriptors for C/C++ core types:</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_type_bool">bool</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([5 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 32,
+ uint 32,
+ uint 0,
+ uint 2 }, section "llvm.metadata"
+%str1 = internal constant [5 x i8] c"bool\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_char">char</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([5 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 8,
+ uint 8,
+ uint 0,
+ uint 6 }, section "llvm.metadata"
+%str1 = internal constant [5 x i8] c"char\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_unsigned_char">unsigned char</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([14 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 8,
+ uint 8,
+ uint 0,
+ uint 8 }, section "llvm.metadata"
+%str1 = internal constant [14 x i8] c"unsigned char\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_short">short</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([10 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 16,
+ uint 16,
+ uint 0,
+ uint 5 }, section "llvm.metadata"
+%str1 = internal constant [10 x i8] c"short int\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_unsigned_short">unsigned short</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([19 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 16,
+ uint 16,
+ uint 0,
+ uint 7 }, section "llvm.metadata"
+%str1 = internal constant [19 x i8] c"short unsigned int\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_int">int</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([4 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 32,
+ uint 32,
+ uint 0,
+ uint 5 }, section "llvm.metadata"
+%str1 = internal constant [4 x i8] c"int\00", section "llvm.metadata"
+</pre></div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_unsigned_int">unsigned int</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([13 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 32,
+ uint 32,
+ uint 0,
+ uint 7 }, section "llvm.metadata"
+%str1 = internal constant [13 x i8] c"unsigned int\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_long_long">long long</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([14 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 64,
+ uint 64,
+ uint 0,
+ uint 5 }, section "llvm.metadata"
+%str1 = internal constant [14 x i8] c"long long int\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_unsigned_long_long">unsigned long long</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([23 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 64,
+ uint 64,
+ uint 0,
+ uint 7 }, section "llvm.metadata"
+%str1 = internal constant [23 x 8] c"long long unsigned int\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_float">float</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([6 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 32,
+ uint 32,
+ uint 0,
+ uint 4 }, section "llvm.metadata"
+%str1 = internal constant [6 x i8] c"float\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsubsection">
+ <a name="ccxx_basic_double">double</a>
+</div>
+
+<div class="doc_text">
+
+<div class="doc_code">
+<pre>
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ 8* getelementptr ([7 x 8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 64,
+ uint 64,
+ uint 0,
+ uint 4 }, section "llvm.metadata"
+%str1 = internal constant [7 x 8] c"double\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="ccxx_derived_types">C/C++ derived types</a>
+</div>
+
+<div class="doc_text">
+
+<p>Given the following as an example of C/C++ derived type:</p>
+
+<div class="doc_code">
+<pre>
+typedef const int *IntPtr;
+</pre>
+</div>
+
+<p>a C/C++ front-end would generate the following descriptors:</p>
+
+<div class="doc_code">
+<pre>
+;;
+;; Define the typedef "IntPtr".
+;;
+%<a href="#format_derived_type">llvm.dbg.derivedtype1</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
+ uint add(uint 22, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([7 x 8]* %str1, int 0, int 0),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ int 1,
+ uint 0,
+ uint 0,
+ uint 0,
+ { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> to { }*) }, section "llvm.metadata"
+%str1 = internal constant [7 x 8] c"IntPtr\00", section "llvm.metadata"
+
+;;
+;; Define the pointer type.
+;;
+%<a href="#format_derived_type">llvm.dbg.derivedtype2</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
+ uint add(uint 15, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* null,
+ { }* null,
+ int 0,
+ uint 32,
+ uint 32,
+ uint 0,
+ { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> to { }*) }, section "llvm.metadata"
+
+;;
+;; Define the const type.
+;;
+%<a href="#format_derived_type">llvm.dbg.derivedtype3</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
+ uint add(uint 38, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* null,
+ { }* null,
+ int 0,
+ uint 0,
+ uint 0,
+ uint 0,
+ { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype1</a> to { }*) }, section "llvm.metadata"
+
+;;
+;; Define the int type.
+;;
+%<a href="#format_basic_type">llvm.dbg.basictype1</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ 8* getelementptr ([4 x 8]* %str2, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 32,
+ uint 32,
+ uint 0,
+ uint 5 }, section "llvm.metadata"
+%str2 = internal constant [4 x 8] c"int\00", section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="ccxx_composite_types">C/C++ struct/union types</a>
+</div>
+
+<div class="doc_text">
+
+<p>Given the following as an example of C/C++ struct type:</p>
+
+<div class="doc_code">
+<pre>
+struct Color {
+ unsigned Red;
+ unsigned Green;
+ unsigned Blue;
+};
+</pre>
+</div>
+
+<p>a C/C++ front-end would generate the following descriptors:</p>
+
+<div class="doc_code">
+<pre>
+;;
+;; Define basic type for unsigned int.
+;;
+%<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {
+ uint add(uint 36, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([13 x i8]* %str1, int 0, int 0),
+ { }* null,
+ int 0,
+ uint 32,
+ uint 32,
+ uint 0,
+ uint 7 }, section "llvm.metadata"
+%str1 = internal constant [13 x i8] c"unsigned int\00", section "llvm.metadata"
+
+;;
+;; Define composite type for struct Color.
+;;
+%<a href="#format_composite_type">llvm.dbg.compositetype</a> = internal constant %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> {
+ uint add(uint 19, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([6 x i8]* %str2, int 0, int 0),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ int 1,
+ uint 96,
+ uint 32,
+ uint 0,
+ { }* null,
+ { }* cast ([3 x { }*]* %llvm.dbg.array to { }*) }, section "llvm.metadata"
+%str2 = internal constant [6 x i8] c"Color\00", section "llvm.metadata"
+
+;;
+;; Define the Red field.
+;;
+%<a href="#format_derived_type">llvm.dbg.derivedtype1</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
+ uint add(uint 13, uint 262144),
+ { }* null,
+ i8* getelementptr ([4 x i8]* %str3, int 0, int 0),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ int 2,
+ uint 32,
+ uint 32,
+ uint 0,
+ { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
+%str3 = internal constant [4 x i8] c"Red\00", section "llvm.metadata"
+
+;;
+;; Define the Green field.
+;;
+%<a href="#format_derived_type">llvm.dbg.derivedtype2</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
+ uint add(uint 13, uint 262144),
+ { }* null,
+ i8* getelementptr ([6 x i8]* %str4, int 0, int 0),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ int 3,
+ uint 32,
+ uint 32,
+ uint 32,
+ { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
+%str4 = internal constant [6 x i8] c"Green\00", section "llvm.metadata"
+
+;;
+;; Define the Blue field.
+;;
+%<a href="#format_derived_type">llvm.dbg.derivedtype3</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {
+ uint add(uint 13, uint 262144),
+ { }* null,
+ i8* getelementptr ([5 x i8]* %str5, int 0, int 0),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ int 4,
+ uint 32,
+ uint 32,
+ uint 64,
+ { }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to { }*) }, section "llvm.metadata"
+%str5 = internal constant [5 x 8] c"Blue\00", section "llvm.metadata"
+
+;;
+;; Define the array of fields used by the composite type Color.
+;;
+%llvm.dbg.array = internal constant [3 x { }*] [
+ { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype1</a> to { }*),
+ { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> to { }*),
+ { }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> to { }*) ], section "llvm.metadata"
+</pre>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="ccxx_enumeration_types">C/C++ enumeration types</a>
+</div>
+
+<div class="doc_text">
+
+<p>Given the following as an example of C/C++ enumeration type:</p>
+
+<div class="doc_code">
+<pre>
+enum Trees {
+ Spruce = 100,
+ Oak = 200,
+ Maple = 300
+};
+</pre>
+</div>
+
+<p>a C/C++ front-end would generate the following descriptors:</p>
+
+<div class="doc_code">
+<pre>
+;;
+;; Define composite type for enum Trees
+;;
+%<a href="#format_composite_type">llvm.dbg.compositetype</a> = internal constant %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> {
+ uint add(uint 4, uint 262144),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ i8* getelementptr ([6 x i8]* %str1, int 0, int 0),
+ { }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to { }*),
+ int 1,
+ uint 32,
+ uint 32,
+ uint 0,
+ { }* null,
+ { }* cast ([3 x { }*]* %llvm.dbg.array to { }*) }, section "llvm.metadata"
+%str1 = internal constant [6 x i8] c"Trees\00", section "llvm.metadata"
+
+;;
+;; Define Spruce enumerator.
+;;
+%<a href="#format_enumeration">llvm.dbg.enumerator1</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
+ uint add(uint 40, uint 262144),
+ i8* getelementptr ([7 x i8]* %str2, int 0, int 0),
+ int 100 }, section "llvm.metadata"
+%str2 = internal constant [7 x i8] c"Spruce\00", section "llvm.metadata"
+
+;;
+;; Define Oak enumerator.
+;;
+%<a href="#format_enumeration">llvm.dbg.enumerator2</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
+ uint add(uint 40, uint 262144),
+ i8* getelementptr ([4 x i8]* %str3, int 0, int 0),
+ int 200 }, section "llvm.metadata"
+%str3 = internal constant [4 x i8] c"Oak\00", section "llvm.metadata"
+
+;;
+;; Define Maple enumerator.
+;;
+%<a href="#format_enumeration">llvm.dbg.enumerator3</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {
+ uint add(uint 40, uint 262144),
+ i8* getelementptr ([6 x i8]* %str4, int 0, int 0),
+ int 300 }, section "llvm.metadata"
+%str4 = internal constant [6 x i8] c"Maple\00", section "llvm.metadata"
+
+;;
+;; Define the array of enumerators used by composite type Trees.
+;;
+%llvm.dbg.array = internal constant [3 x { }*] [
+ { }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator1</a> to { }*),
+ { }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator2</a> to { }*),
+ { }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator3</a> to { }*) ], section "llvm.metadata"
+</pre>
+</div>
+
+</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">LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date: 2009-05-29 19:08:57 +0200 (Fri, 29 May 2009) $
+</address>
+
+</body>
+</html>
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