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disable some objectionable code, maybe we can bring this pass to life

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30939 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-10-13 20:43:10 +00:00
parent d77ddbc0ba
commit eb15eeec39
1 changed files with 42 additions and 7 deletions
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49
lib/CodeGen/BranchFolding.cpp
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@ -94,11 +94,7 @@ static void ReplaceUsesOfBlockWith(MachineBasicBlock *BB,
I->getOperand(i).setMachineBasicBlock(New); I->getOperand(i).setMachineBasicBlock(New);
} }
// If BB falls through into Old, insert an unconditional branch to New. // Update the successor information.
MachineFunction::iterator BBSucc = BB; ++BBSucc;
if (BBSucc != BB->getParent()->end() && &*BBSucc == Old)
TII.insertGoto(*BB, *New);
std::vector<MachineBasicBlock*> Succs(BB->succ_begin(), BB->succ_end()); std::vector<MachineBasicBlock*> Succs(BB->succ_begin(), BB->succ_end());
for (int i = Succs.size()-1; i >= 0; --i) for (int i = Succs.size()-1; i >= 0; --i)
if (Succs[i] == Old) { if (Succs[i] == Old) {
@ -110,7 +106,7 @@ static void ReplaceUsesOfBlockWith(MachineBasicBlock *BB,
bool BranchFolder::OptimizeBlock(MachineFunction::iterator MBB, bool BranchFolder::OptimizeBlock(MachineFunction::iterator MBB,
const TargetInstrInfo &TII) { const TargetInstrInfo &TII) {
// If this block is empty, make everyone use it's fall-through, not the block // If this block is empty, make everyone use its fall-through, not the block
// explicitly. // explicitly.
if (MBB->empty()) { if (MBB->empty()) {
if (MBB->pred_empty()) return false; if (MBB->pred_empty()) return false;
@ -124,6 +120,8 @@ bool BranchFolder::OptimizeBlock(MachineFunction::iterator MBB,
return true; return true;
} }
#if 0
if (MBB->pred_size() == 1) { if (MBB->pred_size() == 1) {
// If this block has a single predecessor, and if that block has a single // If this block has a single predecessor, and if that block has a single
// successor, merge this block into that block. // successor, merge this block into that block.
@ -131,6 +129,43 @@ bool BranchFolder::OptimizeBlock(MachineFunction::iterator MBB,
if (Pred->succ_size() == 1) { if (Pred->succ_size() == 1) {
// Delete all of the terminators from end of the pred block. NOTE, this // Delete all of the terminators from end of the pred block. NOTE, this
// assumes that terminators do not have side effects! // assumes that terminators do not have side effects!
// FIXME: This doesn't work for FP_REG_KILL.
while (!Pred->empty() && TII.isTerminatorInstr(Pred->back().getOpcode()))
Pred->pop_back();
// Splice the instructions over.
Pred->splice(Pred->end(), MBB, MBB->begin(), MBB->end());
// If MBB does not end with a barrier, add a goto instruction to the end.
if (Pred->empty() || !TII.isBarrier(Pred->back().getOpcode()))
TII.insertGoto(*Pred, *next(MBB));
// Update the CFG now.
Pred->removeSuccessor(Pred->succ_begin());
while (!MBB->succ_empty()) {
Pred->addSuccessor(*(MBB->succ_end()-1));
MBB->removeSuccessor(MBB->succ_end()-1);
}
return true;
}
}
// If BB falls through into Old, insert an unconditional branch to New.
MachineFunction::iterator BBSucc = BB; ++BBSucc;
if (BBSucc != BB->getParent()->end() && &*BBSucc == Old)
TII.insertGoto(*BB, *New);
if (MBB->pred_size() == 1) {
// If this block has a single predecessor, and if that block has a single
// successor, merge this block into that block.
MachineBasicBlock *Pred = *MBB->pred_begin();
if (Pred->succ_size() == 1) {
// Delete all of the terminators from end of the pred block. NOTE, this
// assumes that terminators do not have side effects!
// FIXME: This doesn't work for FP_REG_KILL.
while (!Pred->empty() && TII.isTerminatorInstr(Pred->back().getOpcode())) while (!Pred->empty() && TII.isTerminatorInstr(Pred->back().getOpcode()))
Pred->pop_back(); Pred->pop_back();
@ -199,6 +234,6 @@ bool BranchFolder::OptimizeBlock(MachineFunction::iterator MBB,
} }
} }
} }
#endif
return false; return false;
} }