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Fix inverted conflict test in -early-coalesce. 

A non-identity copy cannot be coalesced when the phi join destination register
is live at the copy site.

Also verify the condition that the PHI join source register is only used in
the PHI join. Otherwise the coalescing is invalid.

llvm-svn: 86322
This commit is contained in:
Jakob Stoklund Olesen 2009-11-07 01:58:40 +00:00
parent 3a42e7ac65
commit 4141d8ee92
2 changed files with 19 additions and 17 deletions
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7
llvm/include/llvm/CodeGen/LiveIntervalAnalysis.h
View File

@ -290,9 +290,10 @@ namespace llvm {
/// computeIntervals - Compute live intervals.
void computeIntervals();
bool isProfitableToCoalesce(LiveInterval &DstInt, LiveInterval &SrcInt,
SmallVector<MachineInstr*,16> &IdentCopies,
SmallVector<MachineInstr*,16> &OtherCopies);
bool isSafeAndProfitableToCoalesce(LiveInterval &DstInt,
LiveInterval &SrcInt,
SmallVector<MachineInstr*,16> &IdentCopies,
SmallVector<MachineInstr*,16> &OtherCopies);
void performEarlyCoalescing();

29
llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
View File

@ -646,17 +646,17 @@ void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB,
0, false, VNInfoAllocator);
vni->setIsPHIDef(true);
LiveRange LR(start, end, vni);
interval.addRange(LR);
LR.valno->addKill(end);
DEBUG(errs() << " +" << LR << '\n');
}
bool
LiveIntervals::isProfitableToCoalesce(LiveInterval &DstInt, LiveInterval &SrcInt,
SmallVector<MachineInstr*,16> &IdentCopies,
SmallVector<MachineInstr*,16> &OtherCopies) {
bool HaveConflict = false;
bool LiveIntervals::
isSafeAndProfitableToCoalesce(LiveInterval &DstInt,
LiveInterval &SrcInt,
SmallVector<MachineInstr*,16> &IdentCopies,
SmallVector<MachineInstr*,16> &OtherCopies) {
unsigned NumIdent = 0;
for (MachineRegisterInfo::def_iterator ri = mri_->def_begin(SrcInt.reg),
re = mri_->def_end(); ri != re; ++ri) {
@ -665,16 +665,16 @@ LiveIntervals::isProfitableToCoalesce(LiveInterval &DstInt, LiveInterval &SrcInt
if (!tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubReg, DstSubReg))
return false;
if (SrcReg != DstInt.reg) {
// Non-identity copy - we cannot handle overlapping intervals
if (DstInt.liveAt(getInstructionIndex(MI)))
return false;
OtherCopies.push_back(MI);
HaveConflict |= DstInt.liveAt(getInstructionIndex(MI));
} else {
IdentCopies.push_back(MI);
++NumIdent;
}
}
if (!HaveConflict)
return false; // Let coalescer handle it
return IdentCopies.size() > OtherCopies.size();
}
@ -701,19 +701,21 @@ void LiveIntervals::performEarlyCoalescing() {
LiveInterval &SrcInt = getInterval(PHISrc);
SmallVector<MachineInstr*, 16> IdentCopies;
SmallVector<MachineInstr*, 16> OtherCopies;
if (!isProfitableToCoalesce(DstInt, SrcInt, IdentCopies, OtherCopies))
if (!isSafeAndProfitableToCoalesce(DstInt, SrcInt,
IdentCopies, OtherCopies))
continue;
DEBUG(errs() << "PHI Join: " << *Join);
assert(DstInt.containsOneValue() && "PHI join should have just one val#!");
assert(std::distance(mri_->use_begin(PHISrc), mri_->use_end()) == 1 &&
"PHI join src should not be used elsewhere");
VNInfo *VNI = DstInt.getValNumInfo(0);
// Change the non-identity copies to directly target the phi destination.
for (unsigned i = 0, e = OtherCopies.size(); i != e; ++i) {
MachineInstr *PHICopy = OtherCopies[i];
DEBUG(errs() << "Moving: " << *PHICopy);
SlotIndex MIIndex = getInstructionIndex(PHICopy);
DEBUG(errs() << "Moving: " << MIIndex << ' ' << *PHICopy);
SlotIndex DefIndex = MIIndex.getDefIndex();
LiveRange *SLR = SrcInt.getLiveRangeContaining(DefIndex);
SlotIndex StartIndex = SLR->start;
@ -724,8 +726,7 @@ void LiveIntervals::performEarlyCoalescing() {
SrcInt.removeValNo(SLR->valno);
DEBUG(errs() << " added range [" << StartIndex << ','
<< EndIndex << "] to reg" << DstInt.reg << '\n');
if (DstInt.liveAt(StartIndex))
DstInt.removeRange(StartIndex, EndIndex);
assert (!DstInt.liveAt(StartIndex) && "Cannot coalesce when dst live!");
VNInfo *NewVNI = DstInt.getNextValue(DefIndex, PHICopy, true,
VNInfoAllocator);
NewVNI->setHasPHIKill(true);