[PATCH] D118351: [AMDGPU][GlobalISel] Code quality: don't expand G_BUILD_VECTOR_TRUNC if not neccessary

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/Target/AMDGPU/AMDGPUPostLegalizerCombiner.cpp:322
+    if (MI.getOpcode() == TargetOpcode::G_LSHR) {
+      Register LshrCstReg = getDefIgnoringCopies(MI.getOperand(2).getReg(), MRI)
+                                ->getOperand(0)
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matejam wrote:
> arsenm wrote:
> > Why use getDefIgnoringCopies instead of directly using mi_match?
> In case we have a copy instruction as a second operand of G_LSHR. mi_match would return false, this way we don't have to worry about that.
Extra copies should be separately folded out by copy combines


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D118351/new/

https://reviews.llvm.org/D118351