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/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index ed74301..5dd6569 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -947,6 +947,7 @@
     case lltok::kw_noinline:        Attrs |= Attribute::NoInline; break;
     case lltok::kw_readnone:        Attrs |= Attribute::ReadNone; break;
     case lltok::kw_readonly:        Attrs |= Attribute::ReadOnly; break;
+    case lltok::kw_inlinehint:      Attrs |= Attribute::InlineHint; break;
     case lltok::kw_alwaysinline:    Attrs |= Attribute::AlwaysInline; break;
     case lltok::kw_optsize:         Attrs |= Attribute::OptimizeForSize; break;
     case lltok::kw_ssp:             Attrs |= Attribute::StackProtect; break;