AMDGPU: Materialize sign bits with bfrev

If a constant is the same as the reverse of an inline immediate,
this is 4 bytes smaller than having to embed a 32-bit literal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263201 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed