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| author | ed <ed@FreeBSD.org> | 2009-06-22 08:08:12 +0000 |
|---|---|---|
| committer | ed <ed@FreeBSD.org> | 2009-06-22 08:08:12 +0000 |
| commit | a4c19d68f13cf0a83bc0da53bd6d547fcaf635fe (patch) | |
| tree | 86c1bc482baa6c81fc70b8d715153bfa93377186 /docs/ProgrammersManual.html | |
| parent | db89e312d968c258aba3c79c1c398f5fb19267a3 (diff) | |
| download | FreeBSD-src-a4c19d68f13cf0a83bc0da53bd6d547fcaf635fe.zip FreeBSD-src-a4c19d68f13cf0a83bc0da53bd6d547fcaf635fe.tar.gz | |
Update LLVM sources to r73879.
Diffstat (limited to 'docs/ProgrammersManual.html')
| -rw-r--r-- | docs/ProgrammersManual.html | 138 |
1 files changed, 133 insertions, 5 deletions
diff --git a/docs/ProgrammersManual.html b/docs/ProgrammersManual.html index e7b2ad0..b45a60b 100644 --- a/docs/ProgrammersManual.html +++ b/docs/ProgrammersManual.html @@ -2,6 +2,7 @@ "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> + <meta http-equiv="Content-type" content="text/html;charset=UTF-8"> <title>LLVM Programmer's Manual</title> <link rel="stylesheet" href="llvm.css" type="text/css"> </head> @@ -129,6 +130,15 @@ with another <tt>Value</tt></a> </li> </ul> </li> + <li><a href="#threading">Threads and LLVM</a> + <ul> + <li><a href="#startmultithreaded">Entering and Exiting Multithreaded Mode + </a></li> + <li><a href="#shutdown">Ending execution with <tt>llvm_shutdown()</tt></a></li> + <li><a href="#managedstatic">Lazy initialization with <tt>ManagedStatic</tt></a></li> + </ul> + </li> + <li><a href="#advanced">Advanced Topics</a> <ul> <li><a href="#TypeResolve">LLVM Type Resolution</a> @@ -176,8 +186,9 @@ with another <tt>Value</tt></a> </li> <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>, <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>, <a href="mailto:ggreif@gmail.com">Gabor Greif</a>, - <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a> and - <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p> + <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, + <a href="mailto:rspencer@x10sys.com">Reid Spencer</a> and + <a href="mailto:owen@apple.com">Owen Anderson</a></p> </div> <!-- *********************************************************************** --> @@ -2118,7 +2129,7 @@ FunctionType *ft = TypeBuilder<types::i<8>(types::i<32>*), true&g <div class="doc_code"> <pre> -std::vector<const Type*> params; +std::vector<const Type*> params; params.push_back(PointerType::getUnqual(Type::Int32Ty)); FunctionType *ft = FunctionType::get(Type::Int8Ty, params, false); </pre> @@ -2131,6 +2142,123 @@ comment</a> for more details.</p> <!-- *********************************************************************** --> <div class="doc_section"> + <a name="threading">Threads and LLVM</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> +<p> +This section describes the interaction of the LLVM APIs with multithreading, +both on the part of client applications, and in the JIT, in the hosted +application. +</p> + +<p> +Note that LLVM's support for multithreading is still relatively young. Up +through version 2.5, the execution of threaded hosted applications was +supported, but not threaded client access to the APIs. While this use case is +now supported, clients <em>must</em> adhere to the guidelines specified below to +ensure proper operation in multithreaded mode. +</p> + +<p> +Note that, on Unix-like platforms, LLVM requires the presence of GCC's atomic +intrinsics in order to support threaded operation. If you need a +multhreading-capable LLVM on a platform without a suitably modern system +compiler, consider compiling LLVM and LLVM-GCC in single-threaded mode, and +using the resultant compiler to build a copy of LLVM with multithreading +support. +</p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="startmultithreaded">Entering and Exiting Multithreaded Mode</a> +</div> + +<div class="doc_text"> + +<p> +In order to properly protect its internal data structures while avoiding +excessive locking overhead in the single-threaded case, the LLVM must intialize +certain data structures necessary to provide guards around its internals. To do +so, the client program must invoke <tt>llvm_start_multithreaded()</tt> before +making any concurrent LLVM API calls. To subsequently tear down these +structures, use the <tt>llvm_stop_multithreaded()</tt> call. You can also use +the <tt>llvm_is_multithreaded()</tt> call to check the status of multithreaded +mode. +</p> + +<p> +Note that both of these calls must be made <em>in isolation</em>. That is to +say that no other LLVM API calls may be executing at any time during the +execution of <tt>llvm_start_multithreaded()</tt> or <tt>llvm_stop_multithreaded +</tt>. It's is the client's responsibility to enforce this isolation. +</p> + +<p> +The return value of <tt>llvm_start_multithreaded()</tt> indicates the success or +failure of the initialization. Failure typically indicates that your copy of +LLVM was built without multithreading support, typically because GCC atomic +intrinsics were not found in your system compiler. In this case, the LLVM API +will not be safe for concurrent calls. However, it <em>will</em> be safe for +hosting threaded applications in the JIT, though care must be taken to ensure +that side exits and the like do not accidentally result in concurrent LLVM API +calls. +</p> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="shutdown">Ending Execution with <tt>llvm_shutdown()</tt></a> +</div> + +<div class="doc_text"> +<p> +When you are done using the LLVM APIs, you should call <tt>llvm_shutdown()</tt> +to deallocate memory used for internal structures. This will also invoke +<tt>llvm_stop_multithreaded()</tt> if LLVM is operating in multithreaded mode. +As such, <tt>llvm_shutdown()</tt> requires the same isolation guarantees as +<tt>llvm_stop_multithreaded()</tt>. +</p> + +<p> +Note that, if you use scope-based shutdown, you can use the +<tt>llvm_shutdown_obj</tt> class, which calls <tt>llvm_shutdown()</tt> in its +destructor. +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="managedstatic">Lazy Initialization with <tt>ManagedStatic</tt></a> +</div> + +<div class="doc_text"> +<p> +<tt>ManagedStatic</tt> is a utility class in LLVM used to implement static +initialization of static resources, such as the global type tables. Before the +invocation of <tt>llvm_shutdown()</tt>, it implements a simple lazy +initialization scheme. Once <tt>llvm_start_multithreaded()</tt> returns, +however, it uses double-checked locking to implement thread-safe lazy +initialization. +</p> + +<p> +Note that, because no other threads are allowed to issue LLVM API calls before +<tt>llvm_start_multithreaded()</tt> returns, it is possible to have +<tt>ManagedStatic</tt>s of <tt>llvm::sys::Mutex</tt>s. +</p> + +<p> +The <tt>llvm_acquire_global_lock()</tt> and <tt>llvm_release_global_lock</tt> +APIs provide access to the global lock used to implement the double-checked +locking for lazy initialization. These should only be used internally to LLVM, +and only if you know what you're doing! +</p> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> <a name="advanced">Advanced Topics</a> </div> <!-- *********************************************************************** --> @@ -3430,7 +3558,7 @@ never change at runtime).</p> <p><tt>#include "<a href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br> -doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock +doxygen info: <a href="/doxygen/classllvm_1_1BasicBlock.html">BasicBlock Class</a><br> Superclass: <a href="#Value"><tt>Value</tt></a></p> @@ -3536,7 +3664,7 @@ arguments. An argument has a pointer to the parent Function.</p> <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br> - Last modified: $Date: 2009-05-01 22:40:51 +0200 (Fri, 01 May 2009) $ + Last modified: $Date: 2009-06-17 21:12:26 +0000 (Wed, 17 Jun 2009) $ </address> </body> |
