[PATCH] D152810: [RISCV] Fix IMPLICIT_DEF check in doPeepholeMaskedRVV

[Luke Lau via Phabricator via llvm-commits]

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An IMPLICIT_DEF is different from an undef node, so this patch fixes the
check for it.
It doesn't actually change any test output, as previously it was
conservatively emitting tail undisturbed with an IMPLICIT_DEF passthru,
which ultimately got selected as tail agnostic anyway.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D152810

Files:
  llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp


Index: llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -3194,7 +3194,9 @@
       if (!(N->getConstantOperandVal(*TailPolicyOpIdx) &
             RISCVII::TAIL_AGNOSTIC)) {
         // We can't use TA if the tie-operand is not IMPLICIT_DEF
-        if (!N->getOperand(0).isUndef()) {
+        if (!(N->getOperand(0).isMachineOpcode() &&
+              N->getOperand(0).getMachineOpcode() ==
+                  TargetOpcode::IMPLICIT_DEF)) {
           // Keep the true-masked instruction when there is no unmasked TU
           // instruction
           if (I->UnmaskedTUPseudo == I->MaskedPseudo)


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