This is based on Justin's testcase and checking whether BFI is not populated
in case hotness is off.
This is a patch meant on top of Justin's patch to enable Machine opt-remarks
in the
AsmPrinter (http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20170130/426595.html)
Do you need -debug-only=block-freq here? Does it work with release build?