Refactor PGO code in preparation for handling non-C/C++ code.
Move the PGO.assignRegionCounters() call out of StartFunction, because that
function is called from many places where it does not make sense to do PGO
instrumentation (e.g., compiler-generated helper functions). Change several
functions to take a StringRef argument for the unique name associated with
a function, so that the name can be set differently for things like Objective-C
methods and block literals.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203073
91177308-0d34-0410-b5e6-
96231b3b80d8