bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
df_iterator_default_set<MachineBasicBlock*> Reachable;
bool ModifiedPHI = false;
MMI = getAnalysisIfAvailable<MachineModuleInfo>();
MachineDominatorTree *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
// Mark all reachable blocks.
for (MachineBasicBlock *BB : depth_first_ext(&F, Reachable))
(void)BB/* Mark all reachable blocks */;
// 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) {
MachineBasicBlock *BB = &*I;
// Test for deadness.
if (!Reachable.count(BB)) {
DeadBlocks.push_back(BB);
// Update dominator and loop info.
if (MLI) MLI->removeBlock(BB);
if (MDT && MDT->getNode(BB)) MDT->eraseNode(BB);
while (BB->succ_begin() != BB->succ_end()) {
MachineBasicBlock* succ = *BB->succ_begin();
MachineBasicBlock::iterator start = succ->begin();
while (start != succ->end() && start->isPHI()) {
for (unsigned i = start->getNumOperands() - 1; i >= 2; i-=2)
if (start->getOperand(i).isMBB() &&
start->getOperand(i).getMBB() == BB) {
start->RemoveOperand(i);
start->RemoveOperand(i-1);
}
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->isPHI()) {
for (unsigned i = phi->getNumOperands() - 1; i >= 2; i-=2)
if (!preds.count(phi->getOperand(i).getMBB())) {
phi->RemoveOperand(i);
phi->RemoveOperand(i-1);
ModifiedPHI = true;
}
if (phi->getNumOperands() == 3) {
const MachineOperand &Input = phi->getOperand(1);
const MachineOperand &Output = phi->getOperand(0);
unsigned InputReg = Input.getReg();
unsigned OutputReg = Output.getReg();
assert(Output.getSubReg() == 0 && "Cannot have output subregister");
ModifiedPHI = true;
if (InputReg != OutputReg) {
MachineRegisterInfo &MRI = F.getRegInfo();
unsigned InputSub = Input.getSubReg();
if (InputSub == 0 &&
MRI.constrainRegClass(InputReg, MRI.getRegClass(OutputReg))) {
MRI.replaceRegWith(OutputReg, InputReg);
} else {
// The input register to the PHI has a subregister or it can't be
// constrained to the proper register class:
// insert a COPY instead of simply replacing the output
// with the input.
const TargetInstrInfo *TII = F.getSubtarget().getInstrInfo();
BuildMI(*BB, BB->getFirstNonPHI(), phi->getDebugLoc(),
TII->get(TargetOpcode::COPY), OutputReg)
.addReg(InputReg, getRegState(Input), InputSub);
}
phi++->eraseFromParent();
}
continue;
}
++phi;
}
}
F.RenumberBlocks();
return (!DeadBlocks.empty() || ModifiedPHI);
}
bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
SmallPtrSet<MachineBasicBlock*, 8> Reachable;
MMI = getAnalysisIfAvailable<MachineModuleInfo>();
MachineDominatorTree *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
// Mark all reachable blocks.
for (df_ext_iterator<MachineFunction*, SmallPtrSet<MachineBasicBlock*, 8> >
I = df_ext_begin(&F, Reachable), E = df_ext_end(&F, Reachable);
I != E; ++I)
/* Mark all reachable blocks */;
// 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) {
MachineBasicBlock *BB = I;
// Test for deadness.
if (!Reachable.count(BB)) {
DeadBlocks.push_back(BB);
// Update dominator and loop info.
if (MLI) MLI->removeBlock(BB);
if (MDT && MDT->getNode(BB)) MDT->eraseNode(BB);
while (BB->succ_begin() != BB->succ_end()) {
MachineBasicBlock* succ = *BB->succ_begin();
MachineBasicBlock::iterator start = succ->begin();
while (start != succ->end() && start->isPHI()) {
for (unsigned i = start->getNumOperands() - 1; i >= 2; i-=2)
if (start->getOperand(i).isMBB() &&
start->getOperand(i).getMBB() == BB) {
start->RemoveOperand(i);
start->RemoveOperand(i-1);
}
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->isPHI()) {
for (unsigned i = phi->getNumOperands() - 1; i >= 2; i-=2)
if (!preds.count(phi->getOperand(i).getMBB())) {
phi->RemoveOperand(i);
phi->RemoveOperand(i-1);
}
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;
}
++phi;
}
}
F.RenumberBlocks();
return DeadBlocks.size();
}