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SDISel's constant branch folding can fold away self-loops, which doesn't result in any dead blocks, but
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
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@ -111,9 +111,11 @@ bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
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// Loop over all dead blocks, remembering them and deleting all instructions
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// in them.
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std::vector<MachineBasicBlock*> DeadBlocks;
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for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (!Reachable.count(I)) {
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for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
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MachineBasicBlock *BB = I;
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// Test for deadness.
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if (!Reachable.count(BB)) {
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DeadBlocks.push_back(BB);
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while (BB->succ_begin() != BB->succ_end()) {
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@ -129,28 +131,51 @@ bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
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start->RemoveOperand(i-1);
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}
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if (start->getNumOperands() == 3) {
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MachineInstr* phi = start;
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unsigned Input = phi->getOperand(1).getReg();
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unsigned Output = phi->getOperand(0).getReg();
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start++;
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phi->eraseFromParent();
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if (Input != Output)
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F.getRegInfo().replaceRegWith(Output, Input);
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} else
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start++;
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}
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BB->removeSuccessor(BB->succ_begin());
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}
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}
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}
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// Actually remove the blocks now.
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for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i)
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DeadBlocks[i]->eraseFromParent();
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// Cleanup PHI nodes.
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for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
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MachineBasicBlock *BB = I;
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// Prune unneeded PHI entries.
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SmallPtrSet<MachineBasicBlock*, 8> preds(BB->pred_begin(),
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BB->pred_end());
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MachineBasicBlock::iterator phi = BB->begin();
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while (phi != BB->end() &&
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phi->getOpcode() == TargetInstrInfo::PHI) {
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if (phi->getNumOperands() == 3) {
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unsigned Input = phi->getOperand(1).getReg();
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unsigned Output = phi->getOperand(0).getReg();
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MachineInstr* temp = phi;
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++phi;
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temp->eraseFromParent();
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if (Input != Output)
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F.getRegInfo().replaceRegWith(Output, Input);
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continue;
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}
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for (unsigned i = phi->getNumOperands() - 1; i >= 2; i-=2)
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if (!preds.count(phi->getOperand(i).getMBB())) {
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phi->RemoveOperand(i);
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phi->RemoveOperand(i-1);
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}
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++phi;
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}
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}
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F.RenumberBlocks();
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return DeadBlocks.size();
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