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When the scavenger is looking for a good candidate location to restore from a 

spill, it should avoid doing so inside the live range of a virtual register.

llvm-svn: 85026
This commit is contained in:
Jim Grosbach 2009-10-25 00:45:07 +00:00
parent 7f2413f18b
commit 5027d359e7
1 changed files with 27 additions and 5 deletions
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32
llvm/lib/CodeGen/RegisterScavenging.cpp
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@ -227,7 +227,7 @@ unsigned RegScavenger::FindUnusedReg(const TargetRegisterClass *RC) const {
/// ///
/// No more than InstrLimit instructions are inspected. /// No more than InstrLimit instructions are inspected.
/// ///
unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator MI, unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator StartMI,
BitVector &Candidates, BitVector &Candidates,
unsigned InstrLimit, unsigned InstrLimit,
MachineBasicBlock::iterator &UseMI) { MachineBasicBlock::iterator &UseMI) {
@ -235,19 +235,37 @@ unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator MI,
assert(Survivor > 0 && "No candidates for scavenging"); assert(Survivor > 0 && "No candidates for scavenging");
MachineBasicBlock::iterator ME = MBB->getFirstTerminator(); MachineBasicBlock::iterator ME = MBB->getFirstTerminator();
assert(MI != ME && "MI already at terminator"); assert(StartMI != ME && "MI already at terminator");
MachineBasicBlock::iterator RestorePointMI = StartMI;
MachineBasicBlock::iterator MI = StartMI;
bool inVirtLiveRange = false;
for (++MI; InstrLimit > 0 && MI != ME; ++MI, --InstrLimit) { for (++MI; InstrLimit > 0 && MI != ME; ++MI, --InstrLimit) {
bool isVirtKillInsn = false;
bool isVirtDefInsn = false;
// Remove any candidates touched by instruction. // Remove any candidates touched by instruction.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i); const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || MO.isUndef() || !MO.getReg() || if (!MO.isReg() || MO.isUndef() || !MO.getReg())
TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue; continue;
if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
if (MO.isDef())
isVirtDefInsn = true;
else if (MO.isKill())
isVirtKillInsn = true;
continue;
}
Candidates.reset(MO.getReg()); Candidates.reset(MO.getReg());
for (const unsigned *R = TRI->getAliasSet(MO.getReg()); *R; R++) for (const unsigned *R = TRI->getAliasSet(MO.getReg()); *R; R++)
Candidates.reset(*R); Candidates.reset(*R);
} }
// If we're not in a virtual reg's live range, this is a valid
// restore point.
if (!inVirtLiveRange) RestorePointMI = MI;
// Update whether we're in the live range of a virtual register
if (isVirtKillInsn) inVirtLiveRange = false;
if (isVirtDefInsn) inVirtLiveRange = true;
// Was our survivor untouched by this instruction? // Was our survivor untouched by this instruction?
if (Candidates.test(Survivor)) if (Candidates.test(Survivor))
@ -259,9 +277,13 @@ unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator MI,
Survivor = Candidates.find_first(); Survivor = Candidates.find_first();
} }
// If we ran off the end, that's where we want to restore.
if (MI == ME) RestorePointMI = ME;
assert (RestorePointMI != StartMI &&
"No available scavenger restore location!");
// We ran out of candidates, so stop the search. // We ran out of candidates, so stop the search.
UseMI = MI; UseMI = RestorePointMI;
return Survivor; return Survivor;
} }