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Do not insert multiple initializations for the same value in a PHI node

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llvm-svn: 6113
This commit is contained in:
Chris Lattner 2003-05-12 14:22:21 +00:00
parent 3ab77b0589
commit 56f8186e3e
1 changed files with 29 additions and 9 deletions
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38
lib/Target/X86/InstSelectSimple.cpp
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@ -493,18 +493,38 @@ void ISel::SelectPHINodes() {
MBB->insert(MBB->begin()+NumPHIs++, LongPhiMI);
}
// PHIValues - Map of blocks to incoming virtual registers. We use this
// so that we only initialize one incoming value for a particular block,
// even if the block has multiple entries in the PHI node.
//
std::map<MachineBasicBlock*, unsigned> PHIValues;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
MachineBasicBlock *PredMBB = MBBMap[PN->getIncomingBlock(i)];
unsigned ValReg;
std::map<MachineBasicBlock*, unsigned>::iterator EntryIt =
PHIValues.lower_bound(PredMBB);
if (EntryIt != PHIValues.end() && EntryIt->first == PredMBB) {
// We already inserted an initialization of the register for this
// predecessor. Recycle it.
ValReg = EntryIt->second;
} else {
// Get the incoming value into a virtual register. If it is not
// already available in a virtual register, insert the computation
// code into PredMBB
//
MachineBasicBlock::iterator PI = PredMBB->end();
while (PI != PredMBB->begin() &&
TII.isTerminatorInstr((*(PI-1))->getOpcode()))
--PI;
ValReg = getReg(PN->getIncomingValue(i), PredMBB, PI);
// Remember that we inserted a value for this PHI for this predecessor
PHIValues.insert(EntryIt, std::make_pair(PredMBB, ValReg));
}
// Get the incoming value into a virtual register. If it is not already
// available in a virtual register, insert the computation code into
// PredMBB
//
MachineBasicBlock::iterator PI = PredMBB->end();
while (PI != PredMBB->begin() &&
TII.isTerminatorInstr((*(PI-1))->getOpcode()))
--PI;
unsigned ValReg = getReg(PN->getIncomingValue(i), PredMBB, PI);
PhiMI->addRegOperand(ValReg);
PhiMI->addMachineBasicBlockOperand(PredMBB);
if (LongPhiMI) {