AMDGPU: Don't use InstVisitor for AMDGPUPromoteAlloca

Frontend authors are strongly encouraged to keep allocas
in the entry block, so don't bother visiting every instruction
in the other blocks of the function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263206 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed