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[CodeGen] TailDuplicator should remove PHI when single predecessor block remains #158533

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[CodeGen] TailDuplicator should remove PHI when single predecessor block remains #158533

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10 changes: 10 additions & 0 deletions llvm/lib/CodeGen/TailDuplicator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -387,6 +387,16 @@ void TailDuplicator::processPHI(
MI->eraseFromParent();
else if (MI->getNumOperands() == 1)
MI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF));
else if (TailBB->pred_size() == 2) {
// According to callers implementation, PredBB has not yet been removed from
// TailBB predecessors list. After removal TailBB will have the only one
// predecessor and all phi instructions should be replaced with copies.
assert(PredBB->isSuccessor(TailBB));
BuildMI(*TailBB, MI->getIterator(), MI->getDebugLoc(),
TII->get(TargetOpcode::COPY), MI->getOperand(0).getReg())
.add(MI->getOperand(1));
MI->eraseFromParent();
}
}

/// Duplicate a TailBB instruction to PredBB and update
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