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If there are multiple unconditional branches terminating a block, eliminate all 

but the first one. Those will never be executed. There was logic to do this
but it was faulty.

llvm-svn: 114632
This commit is contained in:
Evan Cheng 2010-09-23 06:54:40 +00:00
parent d4b31a7630
commit 66c8cd2b32
1 changed files with 17 additions and 1 deletions
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18
llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
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@ -275,13 +275,29 @@ ARMBaseInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,MachineBasicBlock *&TBB,
// Get the instruction before it if it is a terminator.
MachineInstr *SecondLastInst = I;
unsigned SecondLastOpc = SecondLastInst->getOpcode();
// If AllowModify is true and the block ends with two or more unconditional
// branches, delete all but the first unconditional branch.
if (AllowModify && isUncondBranchOpcode(LastOpc)) {
while (isUncondBranchOpcode(SecondLastOpc)) {
LastInst->eraseFromParent();
LastInst = SecondLastInst;
LastOpc = LastInst->getOpcode();
if (I == MBB.begin() || !isUnpredicatedTerminator(--I))
break;
else {
SecondLastInst = I;
SecondLastOpc = SecondLastInst->getOpcode();
}
}
}
// If there are three terminators, we don't know what sort of block this is.
if (SecondLastInst && I != MBB.begin() && isUnpredicatedTerminator(--I))
return true;
// If the block ends with a B and a Bcc, handle it.
unsigned SecondLastOpc = SecondLastInst->getOpcode();
if (isCondBranchOpcode(SecondLastOpc) && isUncondBranchOpcode(LastOpc)) {
TBB = SecondLastInst->getOperand(0).getMBB();
Cond.push_back(SecondLastInst->getOperand(1));