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[RISCV] Reverse iteration/deletion structure in vsetvli coalescing [NFC] #98936

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Merged
merged 1 commit into from
Jul 23, 2024
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[RISCV] Reverse iteration/deletion structure in vsetvli coalescing [NFC] #98936

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55 changes: 29 additions & 26 deletions llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1645,24 +1645,23 @@ void RISCVInsertVSETVLI::coalesceVSETVLIs(MachineBasicBlock &MBB) const {
Used.demandVTYPE();
SmallVector<MachineInstr*> ToDelete;

// Update LIS and cleanup dead AVLs given a value which has
// has had one use (as an AVL) removed.
auto afterDroppedAVLUse = [&](Register OldVLReg) {
auto dropAVLUse = [&](MachineOperand &MO) {
if (!MO.isReg() || !MO.getReg().isVirtual())
return;
Register OldVLReg = MO.getReg();
MO.setReg(RISCV::NoRegister);

if (LIS)
LIS->shrinkToUses(&LIS->getInterval(OldVLReg));

MachineInstr *VLOpDef = MRI->getUniqueVRegDef(OldVLReg);
if (VLOpDef && TII->isAddImmediate(*VLOpDef, OldVLReg) &&
MRI->use_nodbg_empty(OldVLReg)) {
if (LIS) {
LIS->removeInterval(OldVLReg);
LIS->RemoveMachineInstrFromMaps(*VLOpDef);
}
VLOpDef->eraseFromParent();
}
MRI->use_nodbg_empty(OldVLReg))
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Not something introduced by this patch, but is it safe to delete a LiveInterval which still might have a debug use?

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I believe so. RegAllocBase.cpp does so, and if that wasn't valid, I imagine we'd have figured that out by now.

ToDelete.push_back(VLOpDef);
};

for (MachineInstr &MI : make_range(MBB.rbegin(), MBB.rend())) {
for (MachineInstr &MI :
make_early_inc_range(make_range(MBB.rbegin(), MBB.rend()))) {

if (!isVectorConfigInstr(MI)) {
Used.doUnion(getDemanded(MI, ST));
Expand All @@ -1678,7 +1677,11 @@ void RISCVInsertVSETVLI::coalesceVSETVLIs(MachineBasicBlock &MBB) const {

if (NextMI) {
if (!Used.usedVL() && !Used.usedVTYPE()) {
ToDelete.push_back(&MI);
dropAVLUse(MI.getOperand(1));
if (LIS)
LIS->RemoveMachineInstrFromMaps(MI);
MI.eraseFromParent();
NumCoalescedVSETVL++;
// Leave NextMI unchanged
continue;
}
Expand Down Expand Up @@ -1707,37 +1710,37 @@ void RISCVInsertVSETVLI::coalesceVSETVLIs(MachineBasicBlock &MBB) const {
LIS->shrinkToUses(&DefLI);
}

Register OldVLReg;
if (MI.getOperand(1).isReg())
OldVLReg = MI.getOperand(1).getReg();
dropAVLUse(MI.getOperand(1));
if (NextMI->getOperand(1).isImm())
MI.getOperand(1).ChangeToImmediate(NextMI->getOperand(1).getImm());
else
MI.getOperand(1).ChangeToRegister(NextMI->getOperand(1).getReg(), false);
if (OldVLReg && OldVLReg.isVirtual())
afterDroppedAVLUse(OldVLReg);
MI.getOperand(1).ChangeToRegister(NextMI->getOperand(1).getReg(),
false);

MI.setDesc(NextMI->getDesc());
}
MI.getOperand(2).setImm(NextMI->getOperand(2).getImm());
ToDelete.push_back(NextMI);

dropAVLUse(NextMI->getOperand(1));
if (LIS)
LIS->RemoveMachineInstrFromMaps(*NextMI);
NextMI->eraseFromParent();
NumCoalescedVSETVL++;
// fallthrough
}
}
NextMI = &MI;
Used = getDemanded(MI, ST);
}

NumCoalescedVSETVL += ToDelete.size();
// Loop over the dead AVL values, and delete them now. This has
// to be outside the above loop to avoid invalidating iterators.
for (auto *MI : ToDelete) {
if (LIS)
if (LIS) {
LIS->removeInterval(MI->getOperand(0).getReg());
LIS->RemoveMachineInstrFromMaps(*MI);
Register OldAVLReg;
if (MI->getOperand(1).isReg())
OldAVLReg = MI->getOperand(1).getReg();
}
MI->eraseFromParent();
if (OldAVLReg && OldAVLReg.isVirtual())
afterDroppedAVLUse(OldAVLReg);
}
}

Expand Down
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