AMDGPU/SI: Avoid creating unnecessary copies in the SIFixSGPRCopies pass
Summary:
1. Don't try to copy values to and from the same register class.
2. Replace copies with of registers with immediate values with v_mov/s_mov
instructions.
The main purpose of this change is to make MachineSink do a better job of
determining when it is beneficial to split a critical edge, since the pass
assumes that copies will become move instructions.
This prevents a regression in uniform-cfg.ll if we enable critical edge
splitting for AMDGPU.
Reviewers: arsenm
Subscribers: arsenm, kzhuravl, llvm-commits
Differential Revision: https://reviews.llvm.org/D23408
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@287131
91177308-0d34-0410-b5e6-
96231b3b80d8
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