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Factor out the code for finding an available register for use

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in breaking an anti-dependence into a separate function.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78767 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-08-12 01:33:27 +00:00
parent 428473bf21
commit 26255adcaa
1 changed files with 66 additions and 50 deletions
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116
lib/CodeGen/PostRASchedulerList.cpp
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@ -158,6 +158,9 @@ namespace {
void ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle);
void ListScheduleTopDown();
bool BreakAntiDependencies();
unsigned findSuitableFreeRegister(unsigned AntiDepReg,
unsigned LastNewReg,
const TargetRegisterClass *);
};
}
@ -510,6 +513,36 @@ void SchedulePostRATDList::ScanInstruction(MachineInstr *MI,
}
}
unsigned
SchedulePostRATDList::findSuitableFreeRegister(unsigned AntiDepReg,
unsigned LastNewReg,
const TargetRegisterClass *RC) {
for (TargetRegisterClass::iterator R = RC->allocation_order_begin(MF),
RE = RC->allocation_order_end(MF); R != RE; ++R) {
unsigned NewReg = *R;
// Don't replace a register with itself.
if (NewReg == AntiDepReg) continue;
// Don't replace a register with one that was recently used to repair
// an anti-dependence with this AntiDepReg, because that would
// re-introduce that anti-dependence.
if (NewReg == LastNewReg) 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)) &&
"Kill and Def maps aren't consistent for AntiDepReg!");
assert(((KillIndices[NewReg] == ~0u) != (DefIndices[NewReg] == ~0u)) &&
"Kill and Def maps aren't consistent for NewReg!");
if (KillIndices[NewReg] == ~0u &&
Classes[NewReg] != reinterpret_cast<TargetRegisterClass *>(-1) &&
KillIndices[AntiDepReg] <= DefIndices[NewReg])
continue;
return NewReg;
}
// No registers are free and available!
return 0;
}
/// BreakAntiDependencies - Identifiy anti-dependencies along the critical path
/// of the ScheduleDAG and break them by renaming registers.
///
@ -674,60 +707,43 @@ bool SchedulePostRATDList::BreakAntiDependencies() {
// TODO: Instead of picking the first free register, consider which might
// be the best.
if (AntiDepReg != 0) {
for (TargetRegisterClass::iterator R = RC->allocation_order_begin(MF),
RE = RC->allocation_order_end(MF); R != RE; ++R) {
unsigned NewReg = *R;
// Don't replace a register with itself.
if (NewReg == AntiDepReg) continue;
// Don't replace a register with one that was recently used to repair
// an anti-dependence with this AntiDepReg, because that would
// re-introduce that anti-dependence.
if (NewReg == LastNewReg[AntiDepReg]) 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)) &&
"Kill and Def maps aren't consistent for AntiDepReg!");
assert(((KillIndices[NewReg] == ~0u) != (DefIndices[NewReg] == ~0u)) &&
"Kill and Def maps aren't consistent for NewReg!");
if (KillIndices[NewReg] == ~0u &&
Classes[NewReg] != reinterpret_cast<TargetRegisterClass *>(-1) &&
KillIndices[AntiDepReg] <= DefIndices[NewReg]) {
DEBUG(errs() << "Breaking anti-dependence edge on "
<< TRI->getName(AntiDepReg)
<< " with " << RegRefs.count(AntiDepReg) << " references"
<< " using " << TRI->getName(NewReg) << "!\n");
if (unsigned NewReg = findSuitableFreeRegister(AntiDepReg,
LastNewReg[AntiDepReg],
RC)) {
DEBUG(errs() << "Breaking anti-dependence edge on "
<< TRI->getName(AntiDepReg)
<< " with " << RegRefs.count(AntiDepReg) << " references"
<< " using " << TRI->getName(NewReg) << "!\n");
// 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);
// 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);
// We just went back in time and modified history; the
// liveness information for the anti-depenence reg is now
// inconsistent. Set the state as if it were dead.
Classes[NewReg] = Classes[AntiDepReg];
DefIndices[NewReg] = DefIndices[AntiDepReg];
KillIndices[NewReg] = KillIndices[AntiDepReg];
assert(((KillIndices[NewReg] == ~0u) !=
(DefIndices[NewReg] == ~0u)) &&
"Kill and Def maps aren't consistent for NewReg!");
// We just went back in time and modified history; the
// liveness information for the anti-depenence reg is now
// inconsistent. Set the state as if it were dead.
Classes[NewReg] = Classes[AntiDepReg];
DefIndices[NewReg] = DefIndices[AntiDepReg];
KillIndices[NewReg] = KillIndices[AntiDepReg];
assert(((KillIndices[NewReg] == ~0u) !=
(DefIndices[NewReg] == ~0u)) &&
"Kill and Def maps aren't consistent for NewReg!");
Classes[AntiDepReg] = 0;
DefIndices[AntiDepReg] = KillIndices[AntiDepReg];
KillIndices[AntiDepReg] = ~0u;
assert(((KillIndices[AntiDepReg] == ~0u) !=
(DefIndices[AntiDepReg] == ~0u)) &&
"Kill and Def maps aren't consistent for AntiDepReg!");
Classes[AntiDepReg] = 0;
DefIndices[AntiDepReg] = KillIndices[AntiDepReg];
KillIndices[AntiDepReg] = ~0u;
assert(((KillIndices[AntiDepReg] == ~0u) !=
(DefIndices[AntiDepReg] == ~0u)) &&
"Kill and Def maps aren't consistent for AntiDepReg!");
RegRefs.erase(AntiDepReg);
Changed = true;
LastNewReg[AntiDepReg] = NewReg;
break;
}
RegRefs.erase(AntiDepReg);
Changed = true;
LastNewReg[AntiDepReg] = NewReg;
}
}