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When tail-merging multiple blocks, make sure to correctly update the live-in list on the merged block to correctly account for the live-outs of all the predecessors. They might not be the same in all cases (the testcase I have involves a PHI node where one of the operands is an IMPLICIT_DEF).

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Unfortunately, the testcase I have is large and confidential, so I don't have a test to commit at the moment; I'll see if I can come up with something smaller where this issue reproduces.

<rdar://problem/9716278>



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134565 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2011-07-06 23:41:48 +00:00
parent 66c9ee7e6d
commit a38cfb2fce
2 changed files with 23 additions and 10 deletions
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31
lib/CodeGen/BranchFolding.cpp
View File

@ -366,11 +366,31 @@ static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1,
return TailLen;
}
void BranchFolder::MaintainLiveIns(MachineBasicBlock *CurMBB,
MachineBasicBlock *NewMBB) {
if (RS) {
RS->enterBasicBlock(CurMBB);
if (!CurMBB->empty())
RS->forward(prior(CurMBB->end()));
BitVector RegsLiveAtExit(TRI->getNumRegs());
RS->getRegsUsed(RegsLiveAtExit, false);
for (unsigned int i = 0, e = TRI->getNumRegs(); i != e; i++)
if (RegsLiveAtExit[i])
NewMBB->addLiveIn(i);
}
}
/// ReplaceTailWithBranchTo - Delete the instruction OldInst and everything
/// after it, replacing it with an unconditional branch to NewDest.
void BranchFolder::ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst,
MachineBasicBlock *NewDest) {
MachineBasicBlock *CurMBB = OldInst->getParent();
TII->ReplaceTailWithBranchTo(OldInst, NewDest);
// For targets that use the register scavenger, we must maintain LiveIns.
MaintainLiveIns(CurMBB, NewDest);
++NumTailMerge;
}
@ -399,16 +419,7 @@ MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end());
// For targets that use the register scavenger, we must maintain LiveIns.
if (RS) {
RS->enterBasicBlock(&CurMBB);
if (!CurMBB.empty())
RS->forward(prior(CurMBB.end()));
BitVector RegsLiveAtExit(TRI->getNumRegs());
RS->getRegsUsed(RegsLiveAtExit, false);
for (unsigned int i = 0, e = TRI->getNumRegs(); i != e; i++)
if (RegsLiveAtExit[i])
NewMBB->addLiveIn(i);
}
MaintainLiveIns(&CurMBB, NewMBB);
return NewMBB;
}

2
lib/CodeGen/BranchFolding.h
View File

@ -95,6 +95,8 @@ namespace llvm {
bool TailMergeBlocks(MachineFunction &MF);
bool TryTailMergeBlocks(MachineBasicBlock* SuccBB,
MachineBasicBlock* PredBB);
void MaintainLiveIns(MachineBasicBlock *CurMBB,
MachineBasicBlock *NewMBB);
void ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst,
MachineBasicBlock *NewDest);
MachineBasicBlock *SplitMBBAt(MachineBasicBlock &CurMBB,