llvm.memory.barrier, and impl for x86 and alpha

llvm-svn: 47204

1 files changed, 106 insertions, 0 deletions

diff --git a/llvm/docs/LangRef.html b/llvm/docs/LangRef.html
index d9d5ca83735..6267cf806cc 100644
--- a/llvm/docs/LangRef.html
+++ b/llvm/docs/LangRef.html
@@ -204,6 +204,11 @@
           <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></li>
+            </ol>
+          </li>
       <li><a href="#int_general">General intrinsics</a>
         <ol>
           <li><a href="#int_var_annotation">
@@ -5234,6 +5239,107 @@ declare i8* @llvm.init.trampoline(i8* &lt;tramp&gt;, i8* &lt;func&gt;, i8* &lt;n
 
 <!-- ======================================================================= -->
 <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 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 &lt;ll&gt;, i1 &lt;ls&gt;, i1 &lt;sl&gt;, i1 &lt;ss&gt;, 
+i1 &lt;device&gt; )
+
+</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.
+  </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_subsection">
   <a name="int_general">General Intrinsics</a>
 </div>