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SDISel's constant branch folding can fold away self-loops, which doesn't result in any dead blocks, but

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rather an incorrect phi input.  Add code to UnreachableMachineBlockElim to get rid of these entries.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54432 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2008-08-06 23:16:52 +00:00
parent 883771f86a
commit 9200e81a18
1 changed files with 40 additions and 15 deletions
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55
lib/CodeGen/UnreachableBlockElim.cpp
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@ -111,9 +111,11 @@ bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
// Loop over all dead blocks, remembering them and deleting all instructions
// in them.
std::vector<MachineBasicBlock*> DeadBlocks;
for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I)
if (!Reachable.count(I)) {
MachineBasicBlock *BB = I;
for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
MachineBasicBlock *BB = I;
// Test for deadness.
if (!Reachable.count(BB)) {
DeadBlocks.push_back(BB);
while (BB->succ_begin() != BB->succ_end()) {
@ -129,28 +131,51 @@ bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
start->RemoveOperand(i-1);
}
if (start->getNumOperands() == 3) {
MachineInstr* phi = start;
unsigned Input = phi->getOperand(1).getReg();
unsigned Output = phi->getOperand(0).getReg();
start++;
phi->eraseFromParent();
if (Input != Output)
F.getRegInfo().replaceRegWith(Output, Input);
} else
start++;
start++;
}
BB->removeSuccessor(BB->succ_begin());
}
}
}
// Actually remove the blocks now.
for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i)
DeadBlocks[i]->eraseFromParent();
// Cleanup PHI nodes.
for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
MachineBasicBlock *BB = I;
// Prune unneeded PHI entries.
SmallPtrSet<MachineBasicBlock*, 8> preds(BB->pred_begin(),
BB->pred_end());
MachineBasicBlock::iterator phi = BB->begin();
while (phi != BB->end() &&
phi->getOpcode() == TargetInstrInfo::PHI) {
if (phi->getNumOperands() == 3) {
unsigned Input = phi->getOperand(1).getReg();
unsigned Output = phi->getOperand(0).getReg();
MachineInstr* temp = phi;
++phi;
temp->eraseFromParent();
if (Input != Output)
F.getRegInfo().replaceRegWith(Output, Input);
continue;
}
for (unsigned i = phi->getNumOperands() - 1; i >= 2; i-=2)
if (!preds.count(phi->getOperand(i).getMBB())) {
phi->RemoveOperand(i);
phi->RemoveOperand(i-1);
}
++phi;
}
}
F.RenumberBlocks();
return DeadBlocks.size();