AMDGPU: Add support pattern for SUB of one bit

Summary:
  Add selection patterns to support one bit Sub.

Reviewers:
  rampitec, arsenm

Differential Revision:
  https://reviews.llvm.org/D52946

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@344815 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed