Reintroduce the InlineHint function attribute.

This time it's for real! I am going to hook this up in the frontends as well.

The inliner has some experimental heuristics for dealing with the inline hint.
When given a -respect-inlinehint option, functions marked with the inline
keyword are given a threshold just above the default for -O3.

We need some experiments to determine if that is the right thing to do.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95466 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/LangRef.html b/docs/LangRef.html
index c028f6b..fed2f80 100644
--- a/docs/LangRef.html
+++ b/docs/LangRef.html
@@ -1083,6 +1083,11 @@
       function into callers whenever possible, ignoring any active inlining size
       threshold for this caller.</dd>
 
+  <dt><tt><b>inlinehint</b></tt></dt>
+  <dd>This attribute indicates that the source code contained a hint that inlining
+      this function is desirable (such as the "inline" keyword in C/C++).  It
+      is just a hint; it imposes no requirements on the inliner.</dd>
+
   <dt><tt><b>noinline</b></tt></dt>
   <dd>This attribute indicates that the inliner should never inline this
       function in any situation. This attribute may not be used together with