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If we see a load from a stack slot into a physreg, consider it as providing

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the stack slot.  This fixes PR943.

llvm-svn: 30898
This commit is contained in:
Chris Lattner 2006-10-12 02:34:07 +00:00
parent 65264c811f
commit d781da5f26
1 changed files with 32 additions and 17 deletions
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49
lib/CodeGen/VirtRegMap.cpp
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@ -706,24 +706,25 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
int FrameIdx;
if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
// If this spill slot is available, turn it into a copy (or nothing)
// instead of leaving it as a load!
unsigned InReg;
if (FrameIdx == SS && (InReg = Spills.getSpillSlotPhysReg(SS))) {
DEBUG(std::cerr << "Promoted Load To Copy: " << MI);
MachineFunction &MF = *MBB.getParent();
if (DestReg != InReg) {
MRI->copyRegToReg(MBB, &MI, DestReg, InReg,
MF.getSSARegMap()->getRegClass(VirtReg));
// Revisit the copy so we make sure to notice the effects of the
// operation on the destreg (either needing to RA it if it's
// virtual or needing to clobber any values if it's physical).
NextMII = &MI;
--NextMII; // backtrack to the copy.
if (FrameIdx == SS) {
// If this spill slot is available, turn it into a copy (or nothing)
// instead of leaving it as a load!
if (unsigned InReg = Spills.getSpillSlotPhysReg(SS)) {
DEBUG(std::cerr << "Promoted Load To Copy: " << MI);
MachineFunction &MF = *MBB.getParent();
if (DestReg != InReg) {
MRI->copyRegToReg(MBB, &MI, DestReg, InReg,
MF.getSSARegMap()->getRegClass(VirtReg));
// Revisit the copy so we make sure to notice the effects of the
// operation on the destreg (either needing to RA it if it's
// virtual or needing to clobber any values if it's physical).
NextMII = &MI;
--NextMII; // backtrack to the copy.
}
VRM.RemoveFromFoldedVirtMap(&MI);
MBB.erase(&MI);
goto ProcessNextInst;
}
VRM.RemoveFromFoldedVirtMap(&MI);
MBB.erase(&MI);
goto ProcessNextInst;
}
}
}
@ -791,7 +792,21 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
VRM.RemoveFromFoldedVirtMap(&MI);
goto ProcessNextInst;
}
// If it's not a no-op copy, it clobbers the value in the destreg.
Spills.ClobberPhysReg(VirtReg);
// Check to see if this instruction is a load from a stack slot into
// a register. If so, this provides the stack slot value in the reg.
int FrameIdx;
if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
assert(DestReg == VirtReg && "Unknown load situation!");
// Otherwise, if it wasn't available, remember that it is now!
Spills.addAvailable(FrameIdx, DestReg);
goto ProcessNextInst;
}
continue;
}