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* Fix several comments

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* Update LiveVar info better, fixing bug: Jello/2003-05-11-PHIRegAllocBug.ll

llvm-svn: 6110
This commit is contained in:
Chris Lattner 2003-05-12 03:55:21 +00:00
parent 738ee6f0fd
commit 30e6616afa
1 changed files with 37 additions and 6 deletions
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43
lib/CodeGen/PHIElimination.cpp
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@ -71,7 +71,7 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(DestReg);
unsigned IncomingReg = MF.getSSARegMap()->createVirtualRegister(RC);
// Insert a register to register copy in the top of the current block (by
// Insert a register to register copy in the top of the current block (but
// after any remaining phi nodes) which copies the new incoming register
// into the phi node destination.
//
@ -79,18 +79,47 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
if (AfterPHIsIt != MBB.end())
while ((*AfterPHIsIt)->getOpcode() == TargetInstrInfo::PHI) ++AfterPHIsIt;
RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC);
// Update live variable information if there is any...
if (LV) {
MachineInstr *PHICopy = *(AfterPHIsIt-1);
// Add information to LiveVariables to know that the incoming value is dead
if (LV) LV->addVirtualRegisterKill(IncomingReg, *(AfterPHIsIt-1));
// Add information to LiveVariables to know that the incoming value is
// dead. This says that the register is dead, not killed, because we
// cannot use the live variable information to indicate that the variable
// is defined in multiple entry blocks. Instead, we pretend that this
// instruction defined it and killed it at the same time.
//
LV->addVirtualRegisterDead(IncomingReg, PHICopy);
// Now loop over all of the incoming arguments turning them into copies into
// Since we are going to be deleting the PHI node, if it is the last use
// of any registers, or if the value itself is dead, we need to move this
// information over to the new copy we just inserted...
//
std::pair<LiveVariables::killed_iterator, LiveVariables::killed_iterator>
RKs = LV->killed_range(MI);
if (RKs.first != RKs.second) {
for (LiveVariables::killed_iterator I = RKs.first; I != RKs.second; ++I)
LV->addVirtualRegisterKilled(I->second, PHICopy);
LV->removeVirtualRegistersKilled(RKs.first, RKs.second);
}
RKs = LV->dead_range(MI);
if (RKs.first != RKs.second) {
for (LiveVariables::killed_iterator I = RKs.first; I != RKs.second; ++I)
LV->addVirtualRegisterDead(I->second, PHICopy);
LV->removeVirtualRegistersDead(RKs.first, RKs.second);
}
}
// Now loop over all of the incoming arguments, changing them to copy into
// the IncomingReg register in the corresponding predecessor basic block.
//
for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) {
MachineOperand &opVal = MI->getOperand(i-1);
// Get the MachineBasicBlock equivalent of the BasicBlock that is the
// source path the phi
// source path the PHI.
MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock();
// Check to make sure we haven't already emitted the copy for this block.
@ -99,7 +128,9 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
// all incoming values are guaranteed to be the same for a particular bb.
//
// Note that this is N^2 in the number of phi node entries, but since the
// # of entries is tiny, this is not a problem.
// # of entries is usually small, this is not a problem. FIXME: this
// should just check to see if there is already a copy in the bottom of
// this basic block!
//
bool HaveNotEmitted = true;
for (int op = MI->getNumOperands() - 1; op != i; op -= 2)