PNaCl documentation: improve some of the SIMD documentation.

native_client_sdk/doc_generated/reference/pnacl-c-cpp-language-support.html

 {{+bindTo:partials.standard_nacl_article}}
 
 <section id="pnacl-c-c-language-support">
 <h1 id="pnacl-c-c-language-support">PNaCl C/C++ Language Support</h1>
 <div class="contents local" id="contents" style="display: none">
 <ul class="small-gap">
 <li><p class="first"><a class="reference internal" href="#source-language-support" id="id3">Source language support</a></p>
 <ul class="small-gap">
 <li><a class="reference internal" href="#versions" id="id4">Versions</a></li>
 <li><a class="reference internal" href="#preprocessor-definitions" id="id5">Preprocessor definitions</a></li>
@@ skipping 164 matching lines @@
 <p>NaCl supports full zero-cost C++ exception handling.</p>
 </section><section id="inline-assembly">
 <h2 id="inline-assembly">Inline Assembly</h2>
 <p>Inline assembly isn&#8217;t supported by PNaCl because it isn&#8217;t portable. The
 one current exception is the common compiler barrier idiom
 <code>asm(&quot;&quot;:::&quot;memory&quot;)</code>, which gets transformed to a sequentially
 consistent memory barrier (equivalent to <code>__sync_synchronize()</code>). In
 PNaCl this barrier is only guaranteed to order <code>volatile</code> and atomic
 memory accesses, though in practice the implementation attempts to also
 prevent reordering of memory accesses to objects which may escape.</p>
+<p>PNaCl supports <a class="reference internal" href="#portable-simd-vectors"><em>Portable SIMD Vectors</em></a>,
+which are traditionally expressed through target-specific intrinsics or
+inline assembly.</p>
 <p>NaCl supports a fairly wide subset of inline assembly through GCC&#8217;s
 inline assembly syntax, with the restriction that the sandboxing model
 for the target architecture has to be respected.</p>
 </section><section id="portable-simd-vectors">
 <span id="id2"></span><h2 id="portable-simd-vectors"><span id="id2"></span>Portable SIMD Vectors</h2>
 <p>SIMD vectors aren&#8217;t part of the C/C++ standards and are traditionally
 very hardware-specific. Portable Native Client offers a portable version
 of SIMD vector datatypes and operations which map well to modern
 architectures and offer performance which matches or approaches
 hardware-specific uses.</p>
-<p>SIMD vector support was added to Portable Native Client for version 36
-of Chrome, and more features are expected to be added in subsequent
-releases.</p>
+<p>SIMD vector support was added to Portable Native Client for version 37
+of Chrome and more features, including performance enhancements, are
+expected to be added in subsequent releases.</p>
 <section id="hand-coding-vector-extensions">
 <h3 id="hand-coding-vector-extensions">Hand-Coding Vector Extensions</h3>
 <p>The initial vector support in Portable Native Client adds <a class="reference external" href="http://clang.llvm.org/docs/LanguageExtensions.html#vectors-and-extended-vectors">LLVM vectors</a>
 and <a class="reference external" href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html">GCC vectors</a> since these
 are well supported by different hardware platforms and don&#8217;t require any
 new compiler intrinsics.</p>
 <p>Vector types can be used through the <code>vector_size</code> attribute:</p>
 <pre class="prettyprint">
 #define VECTOR_BYTES 16
 typedef int v4s __attribute__((vector_size(VECTOR_BYTES)));
@@ skipping 215 matching lines @@
 <p>Neither PNaCl nor NaCl currently support asynchronous interruption
 or suspension of threads.</p>
 </li>
 </ul>
 <p>If PNaCl were to support either of these, the interaction of
 <code>volatile</code> and atomics with same-thread signal handling would need
 to be carefully detailed.</p>
 </section></section></section>
 
 {{/partials.standard_nacl_article}}