Make it possible to indicate relaxed floating point requirements at the IR level

through the use of 'fpmath' metadata.  Currently this only provides a 'fpaccuracy'
value, which may be a number in ULPs or the keyword 'fast', however the intent is
that this will be extended with additional information about NaN's, infinities
etc later.  No optimizations have been hooked up to this so far.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154822 91177308-0d34-0410-b5e6-96231b3b80d8

docs/ReleaseNotes.html

@@ -489,6 +489,9 @@ syntax, there are still significant gaps in that support.</p>
   <li>The <tt>unwind</tt> instruction is now gone. With the introduction of the
       new exception handling system in LLVM 3.0, the <tt>unwind</tt> instruction
       became obsolete.</li>
+  <li>Floating point instructions can be annotated with <tt>fpmath</tt> metadata
+      to indicate relaxed precision requirements, such as those corresponding to
+      "fast math".</li>
   <li>....</li>
 </ul>