[PATCH] D57653: GlobalISel: Combine g_extract with g_merge_values

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: aemerson, aditya_nandakumar, volkan, dsanders, paquette, t.p.northover.
Herald added subscribers: Petar.Avramovic, kristof.beyls, javed.absar, rovka, nhaehnle, wdng, jvesely.

Try to use the underlying source registers.

      

This enables legalization in more cases where some irregular
operations are widened and others narrowed.

      

This seems to make the test_combines_2 AArch64 test worse, since the
MERGE_VALUES has multiple uses. Since this should be required for
legalization, a hasOneUse check is probably inappropriate (or maybe
should only be used if the merge is legal?).


https://reviews.llvm.org/D57653

Files:
  include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
  lib/CodeGen/GlobalISel/Legalizer.cpp
  test/CodeGen/AArch64/GlobalISel/legalize-combines.mir
  test/CodeGen/AArch64/GlobalISel/legalize-extracts.mir
  test/CodeGen/AMDGPU/GlobalISel/artifact-combiner-extract.mir

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