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Reuse operand location when updating PHI instructions. 

Calling RemoveOperand is very expensive on huge PHI instructions. This makes
early tail duplication run twice as fast on the Firefox JavaScript
interpreter.

llvm-svn: 95832
This commit is contained in:
Jakob Stoklund Olesen 2010-02-11 00:34:33 +00:00
parent 896428d630
commit 75521cab3e
1 changed files with 26 additions and 7 deletions
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33
llvm/lib/CodeGen/TailDuplication.cpp
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@ -403,26 +403,45 @@ TailDuplicatePass::UpdateSuccessorsPHIs(MachineBasicBlock *FromBB, bool isDead,
II->RemoveOperand(i);
}
}
II->RemoveOperand(Idx+1);
II->RemoveOperand(Idx);
}
} else
Idx = 0;
// If Idx is set, the operands at Idx and Idx+1 must be removed.
// We reuse the location to avoid expensive RemoveOperand calls.
DenseMap<unsigned,AvailableValsTy>::iterator LI=SSAUpdateVals.find(Reg);
if (LI != SSAUpdateVals.end()) {
// This register is defined in the tail block.
for (unsigned j = 0, ee = LI->second.size(); j != ee; ++j) {
MachineBasicBlock *SrcBB = LI->second[j].first;
unsigned SrcReg = LI->second[j].second;
II->addOperand(MachineOperand::CreateReg(SrcReg, false));
II->addOperand(MachineOperand::CreateMBB(SrcBB));
if (Idx != 0) {
II->getOperand(Idx).setReg(SrcReg);
II->getOperand(Idx+1).setMBB(SrcBB);
Idx = 0;
} else {
II->addOperand(MachineOperand::CreateReg(SrcReg, false));
II->addOperand(MachineOperand::CreateMBB(SrcBB));
}
}
} else {
// Live in tail block, must also be live in predecessors.
for (unsigned j = 0, ee = TDBBs.size(); j != ee; ++j) {
MachineBasicBlock *SrcBB = TDBBs[j];
II->addOperand(MachineOperand::CreateReg(Reg, false));
II->addOperand(MachineOperand::CreateMBB(SrcBB));
if (Idx != 0) {
II->getOperand(Idx).setReg(Reg);
II->getOperand(Idx+1).setMBB(SrcBB);
Idx = 0;
} else {
II->addOperand(MachineOperand::CreateReg(Reg, false));
II->addOperand(MachineOperand::CreateMBB(SrcBB));
}
}
}
if (Idx != 0) {
II->RemoveOperand(Idx+1);
II->RemoveOperand(Idx);
}
}
}
}