[PATCH] D12588: PeepholeOptimizer: Look through simple extracts of reg_sequence

[Matt Arsenault via llvm-commits]

arsenm created this revision.
arsenm added reviewers: MatzeB, tstellarAMD.
arsenm added a subscriber: llvm-commits.
Herald added a subscriber: arsenm.

If a copy is a subregister extract of a reg_sequence, use
the original source to the reg_sequence.
    
This only looks at simple cases where the subreg index matches,
but could probably do something for extracting subregisters
of subregisters as well.
    
Change one motivating case where AMDGPU emitted sequences
of reg_sequence and copy to a pattern more amenable
to the simple case by extracting the full 64-bit subregister
instead of 2 32-bit components from the 128-bit register
separately.


http://reviews.llvm.org/D12588

Files:
  lib/CodeGen/PeepholeOptimizer.cpp
  lib/Target/AMDGPU/SIInstrInfo.cpp
  test/CodeGen/AMDGPU/ds_read2_superreg.ll
  test/CodeGen/AMDGPU/half.ll
  test/CodeGen/AMDGPU/llvm.round.f64.ll
  test/CodeGen/AMDGPU/move-addr64-rsrc-dead-subreg-writes.ll

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