[PATCH] D72636: Cancelling out G_MERGE_VALUES/G_UNMERGE pairs sometimes needs a copy

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

Needs tests



================
Comment at: llvm/include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h:402
+        auto *NewRC = MRI.getRegClassOrNull(NewDef);
+        if ((!OldRC && !NewRC) || (OldRC && NewRC && OldRC == NewRC))
+          MRI.replaceRegWith(OldReg, NewDef);
----------------
This is just OldRC == NewRC


================
Comment at: llvm/include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h:406
+          Builder.setInstr(MI);
+          Builder.buildInstr(TargetOpcode::COPY, {OldReg}, {NewDef});
+        }
----------------
buildCopy


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D72636/new/

https://reviews.llvm.org/D72636