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Fixes <rdar://problem/8612856>: During postRAsched, the antidependence

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breaker needs to check all definitions of the antidepenent register to
avoid multiple defs of the same new register.

llvm-svn: 118032
This commit is contained in:
Andrew Trick 2010-11-02 18:16:45 +00:00
parent 8759d96b7a
commit f861447393
2 changed files with 35 additions and 11 deletions
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36
lib/CodeGen/CriticalAntiDepBreaker.cpp
View File

@ -325,8 +325,25 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI,
}
}
// Check all machine instructions that define the antidependent register.
// Return true if any of these instructions define the new register.
bool
CriticalAntiDepBreaker::isNewRegModifiedByRefs(RegRefIter RegRefBegin,
RegRefIter RegRefEnd,
unsigned NewReg)
{
for (RegRefIter I = RegRefBegin; I != RegRefEnd; ++I ) {
MachineOperand *MO = I->second;
if (MO->isDef()) continue;
if (MO->getParent()->modifiesRegister(NewReg, TRI))
return true;
}
return false;
}
unsigned
CriticalAntiDepBreaker::findSuitableFreeRegister(MachineInstr *MI,
CriticalAntiDepBreaker::findSuitableFreeRegister(RegRefIter RegRefBegin,
RegRefIter RegRefEnd,
unsigned AntiDepReg,
unsigned LastNewReg,
const TargetRegisterClass *RC)
@ -342,10 +359,10 @@ CriticalAntiDepBreaker::findSuitableFreeRegister(MachineInstr *MI,
// an anti-dependence with this AntiDepReg, because that would
// re-introduce that anti-dependence.
if (NewReg == LastNewReg) continue;
// If the instruction already has a def of the NewReg, it's not suitable.
// For example, Instruction with multiple definitions can result in this
// condition.
if (MI->modifiesRegister(NewReg, TRI)) continue;
// If any instructions that define AntiDepReg also define the NewReg, it's
// not suitable. For example, Instruction with multiple definitions can
// result in this condition.
if (isNewRegModifiedByRefs(RegRefBegin, RegRefEnd, NewReg)) continue;
// If NewReg is dead and NewReg's most recent def is not before
// AntiDepReg's kill, it's safe to replace AntiDepReg with NewReg.
assert(((KillIndices[AntiDepReg] == ~0u) != (DefIndices[AntiDepReg] == ~0u))
@ -552,7 +569,11 @@ BreakAntiDependencies(const std::vector<SUnit>& SUnits,
// TODO: Instead of picking the first free register, consider which might
// be the best.
if (AntiDepReg != 0) {
if (unsigned NewReg = findSuitableFreeRegister(MI, AntiDepReg,
std::pair<std::multimap<unsigned, MachineOperand *>::iterator,
std::multimap<unsigned, MachineOperand *>::iterator>
Range = RegRefs.equal_range(AntiDepReg);
if (unsigned NewReg = findSuitableFreeRegister(Range.first, Range.second,
AntiDepReg,
LastNewReg[AntiDepReg],
RC)) {
DEBUG(dbgs() << "Breaking anti-dependence edge on "
@ -562,9 +583,6 @@ BreakAntiDependencies(const std::vector<SUnit>& SUnits,
// Update the references to the old register to refer to the new
// register.
std::pair<std::multimap<unsigned, MachineOperand *>::iterator,
std::multimap<unsigned, MachineOperand *>::iterator>
Range = RegRefs.equal_range(AntiDepReg);
for (std::multimap<unsigned, MachineOperand *>::iterator
Q = Range.first, QE = Range.second; Q != QE; ++Q) {
Q->second->setReg(NewReg);

10
lib/CodeGen/CriticalAntiDepBreaker.h
View File

@ -50,6 +50,8 @@ class TargetRegisterInfo;
/// RegRegs - Map registers to all their references within a live range.
std::multimap<unsigned, MachineOperand *> RegRefs;
typedef std::multimap<unsigned, MachineOperand *>::const_iterator
RegRefIter;
/// KillIndices - The index of the most recent kill (proceding bottom-up),
/// or ~0u if the register is not live.
@ -90,10 +92,14 @@ class TargetRegisterInfo;
private:
void PrescanInstruction(MachineInstr *MI);
void ScanInstruction(MachineInstr *MI, unsigned Count);
unsigned findSuitableFreeRegister(MachineInstr *MI,
bool isNewRegModifiedByRefs(RegRefIter RegRefBegin,
RegRefIter RegRefEnd,
unsigned NewReg);
unsigned findSuitableFreeRegister(RegRefIter RegRefBegin,
RegRefIter RegRefEnd,
unsigned AntiDepReg,
unsigned LastNewReg,
const TargetRegisterClass *);
const TargetRegisterClass *RC);
};
}