[PGO] More comments how function pointers for indirect calls are mapped to function names
[PGO] More comments how function pointers for indirect calls are mapped
to function names

Summary:
Hopefully this will make it easier for the next person to figure all
this out...

Reviewers: bogner, davidxl

Subscribers: davidxl, cfe-commits

Differential Revision: http://reviews.llvm.org/D18489

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@264681 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang