[NaClDocs] Add documentation for the PNaCl fabs intrinsic.

native_client_sdk/doc_generated/reference/pnacl-bitcode-abi.html

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 <section id="pnacl-bitcode-reference-manual">
 <h1 id="pnacl-bitcode-reference-manual">PNaCl Bitcode Reference Manual</h1>
 <div class="contents local" id="contents" style="display: none">
 <ul class="small-gap">
 <li><a class="reference internal" href="#introduction" id="id1">Introduction</a></li>
 <li><p class="first"><a class="reference internal" href="#high-level-structure" id="id2">High Level Structure</a></p>
 <ul class="small-gap">
 <li><a class="reference internal" href="#data-model" id="id3">Data Model</a></li>
@@ skipping 309 matching lines @@
 <li><p class="first"><code>llvm.memset</code></p>
 <p>These intrinsics are only supported with an i32 <code>len</code> argument.</p>
 </li>
 <li><p class="first"><code>llvm.bswap</code></p>
 <p>The overloaded <code>llvm.bswap</code> intrinsic is only supported with the following
 argument types: i16, i32, i64 (the types supported by C-style GCC builtins).</p>
 </li>
 <li><code>llvm.ctlz</code></li>
 <li><code>llvm.cttz</code></li>
 <li><p class="first"><code>llvm.ctpop</code></p>
-<p>The overloaded llvm.ctlz, llvm.cttz, and llvm.ctpop intrinsics are only
-supported with the i32 and i64 argument types (the types supported by
-C-style GCC builtins).</p>
+<p>The overloaded <code>llvm.ctlz</code>, <code>llvm.cttz</code>, and <code>llvm.ctpop</code> intrinsics
+are only supported with the i32 and i64 argument types (the types
+supported by C-style GCC builtins).</p>
+</li>
+<li><p class="first"><code>llvm.fabs</code></p>
+<p>The overloaded <code>llvm.fabs</code> intrinsic is supported for float, double and
+<code>&lt;4 x float&gt;</code> argument types. It returns the absolute value of
+the argument. Some notable points: it returns <code>+0.0</code> when given <code>-0.0</code>,
+<code>+inf</code> when given <code>-inf</code>, and a positive <code>NaN</code> when given any
+signed <code>NaN</code>.</p>
+<p>NOTE: This intrinsic was introduced in the pepper_42 SDK.</p>
 </li>
 <li><p class="first"><code>llvm.sqrt</code></p>
 <p>The overloaded <code>llvm.sqrt</code> intrinsic is only supported for float
 and double arguments types. This has the same semantics as the libc
-sqrt function, returning NaN for values less than -0.0. However, this
-does not set <code>errno</code> when the result is NaN (see the
+sqrt function, returning <code>NaN</code> for values less than <code>-0.0</code>.
+However, this does not set <code>errno</code> when the result is NaN (see the
 <a class="reference internal" href="#ir-and-errno"><em>instructions and errno</em></a> section).</p>
 </li>
 <li><code>llvm.stacksave</code></li>
 <li><p class="first"><code>llvm.stackrestore</code></p>
 <p>These intrinsics are used to implement language features like scoped automatic
 variable sized arrays in C99. <code>llvm.stacksave</code> returns a value that
 represents the current state of the stack. This value may only be used as the
 argument to <code>llvm.stackrestore</code>, which restores the stack to the given
 state.</p>
 </li>
@@ skipping 87 matching lines @@
 <p>The <code>llvm.nacl.atomic.is.lock.free</code> intrinsic is designed to
 determine at translation time whether atomic operations of a certain
 <code>byte_size</code> (a compile-time constant), at a particular <code>address</code>,
 are lock-free or not. This reflects the C11 <code>atomic_is_lock_free</code>
 function from header <code>&lt;stdatomic.h&gt;</code> and the C++11 <code>is_lock_free</code>
 member function in header <code>&lt;atomic&gt;</code>. It can be used through the
 <code>__nacl_atomic_is_lock_free</code> builtin.</p>
 </section>
 
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