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[CodeGen] Fix partial phi input removal in TailDuplicator. #158265

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Merged
merged 1 commit into from
Sep 13, 2025
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[CodeGen] Fix partial phi input removal in TailDuplicator. #158265

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11 changes: 8 additions & 3 deletions llvm/lib/CodeGen/TailDuplicator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -375,9 +375,14 @@ void TailDuplicator::processPHI(
if (!Remove)
return;

// Remove PredBB from the PHI node.
MI->removeOperand(SrcOpIdx + 1);
MI->removeOperand(SrcOpIdx);
// MI might have multiple entries for PredBB. Need to remove them all.
for (unsigned N = MI->getNumOperands(); N > 2; N -= 2) {
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I thought there was a helper for this somewhere? The IR has one, and isn't there one used in the MachineBasicBlock CFG helpers?

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I've run grep by getMBB() and seems like there is no helper. PHI input removal code is seems to be re-implemented from scratch each time (or copy-pasted)

if (MI->getOperand(N - 1).getMBB() == PredBB) {
MI->removeOperand(N - 1);
MI->removeOperand(N - 2);
}
}

if (MI->getNumOperands() == 1 && !TailBB->hasAddressTaken())
MI->eraseFromParent();
else if (MI->getNumOperands() == 1)
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