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/lib/AsmParser/LLLexer.cpp b/lib/AsmParser/LLLexer.cpp
index 2a926d2..8ad658d 100644
--- a/lib/AsmParser/LLLexer.cpp
+++ b/lib/AsmParser/LLLexer.cpp
@@ -558,6 +558,7 @@
   KEYWORD(readnone);
   KEYWORD(readonly);
 
+  KEYWORD(inlinehint);
   KEYWORD(noinline);
   KEYWORD(alwaysinline);
   KEYWORD(optsize);