[PATCH] D117328: GlobalISel: Add bitcast to tryFoldUnmergeCast

Mon Feb 21 18:29:02 PST 2022

arsenm added inline comments.

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Comment at: llvm/include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h:373

-    if (!isArtifactCast(CastOpc))
+    if (!isArtifactCast(CastOpc) && CastOpc != TargetOpcode::G_BITCAST)
       return false;
----------------
It feels inappropriate for the artifact combiner to operate on something that isn't defined as a legalization artifact. We currently don't call G_BITCAST a legalization artifact, but is there any real reason for that? Should we just start treating it as one? It gets murky because we currently lower G_BITCAST into merge+unmerge, so that sort of implies it's not fundamentally an artifact.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D117328/new/

https://reviews.llvm.org/D117328