Prepare for future patch which affects codegen for calls to preemptible
functions.
Differential Revision: https://reviews.llvm.org/D57605
llvm-svn: 352920
AMDGPU currently only supports direct calls, but at lower optimisation levels it
fails to lower statically direct calls which appear indirect due to a bitcast.
Add a pass to visit all CallSites and use CallPromotionUtils to "devirtualize"
calls.
Differential Revision: https://reviews.llvm.org/D52741
llvm-svn: 345382