void SplitEditor::deleteRematVictims() {
SmallVector<MachineInstr*, 8> Dead;
for (LiveRangeEdit::iterator I = Edit->begin(), E = Edit->end(); I != E; ++I){
LiveInterval *LI = *I;
for (LiveInterval::const_iterator LII = LI->begin(), LIE = LI->end();
LII != LIE; ++LII) {
// Dead defs end at the store slot.
if (LII->end != LII->valno->def.getNextSlot())
continue;
MachineInstr *MI = LIS.getInstructionFromIndex(LII->valno->def);
assert(MI && "Missing instruction for dead def");
MI->addRegisterDead(LI->reg, &TRI);
if (!MI->allDefsAreDead())
continue;
DEBUG(dbgs() << "All defs dead: " << *MI);
Dead.push_back(MI);
}
}
if (Dead.empty())
return;
Edit->eliminateDeadDefs(Dead, LIS, VRM, TII);
}
bool LiveIntervals::computeDeadValues(LiveInterval &LI,
SmallVectorImpl<MachineInstr*> *dead) {
bool PHIRemoved = false;
for (auto VNI : LI.valnos) {
if (VNI->isUnused())
continue;
SlotIndex Def = VNI->def;
LiveRange::iterator I = LI.FindSegmentContaining(Def);
assert(I != LI.end() && "Missing segment for VNI");
// Is the register live before? Otherwise we may have to add a read-undef
// flag for subregister defs.
if (MRI->tracksSubRegLiveness()) {
if ((I == LI.begin() || std::prev(I)->end < Def) && !VNI->isPHIDef()) {
MachineInstr *MI = getInstructionFromIndex(Def);
MI->addRegisterDefReadUndef(LI.reg);
}
}
if (I->end != Def.getDeadSlot())
continue;
if (VNI->isPHIDef()) {
// This is a dead PHI. Remove it.
VNI->markUnused();
LI.removeSegment(I);
DEBUG(dbgs() << "Dead PHI at " << Def << " may separate interval\n");
PHIRemoved = true;
} else {
// This is a dead def. Make sure the instruction knows.
MachineInstr *MI = getInstructionFromIndex(Def);
assert(MI && "No instruction defining live value");
MI->addRegisterDead(LI.reg, TRI);
if (dead && MI->allDefsAreDead()) {
DEBUG(dbgs() << "All defs dead: " << Def << '\t' << *MI);
dead->push_back(MI);
}
}
}
return PHIRemoved;
}
/// reMaterializeAll - Try to rematerialize as many uses as possible,
/// and trim the live ranges after.
void InlineSpiller::reMaterializeAll() {
// analyzeSiblingValues has already tested all relevant defining instructions.
if (!Edit->anyRematerializable(AA))
return;
UsedValues.clear();
// Try to remat before all uses of snippets.
bool anyRemat = false;
for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i) {
unsigned Reg = RegsToSpill[i];
LiveInterval &LI = LIS.getInterval(Reg);
for (MachineRegisterInfo::use_nodbg_iterator
RI = MRI.use_nodbg_begin(Reg);
MachineInstr *MI = RI.skipBundle();)
anyRemat |= reMaterializeFor(LI, MI);
}
if (!anyRemat)
return;
// Remove any values that were completely rematted.
for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i) {
unsigned Reg = RegsToSpill[i];
LiveInterval &LI = LIS.getInterval(Reg);
for (LiveInterval::vni_iterator I = LI.vni_begin(), E = LI.vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused() || VNI->isPHIDef() || UsedValues.count(VNI))
continue;
MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
MI->addRegisterDead(Reg, &TRI);
if (!MI->allDefsAreDead())
continue;
DEBUG(dbgs() << "All defs dead: " << *MI);
DeadDefs.push_back(MI);
}
}
// Eliminate dead code after remat. Note that some snippet copies may be
// deleted here.
if (DeadDefs.empty())
return;
DEBUG(dbgs() << "Remat created " << DeadDefs.size() << " dead defs.\n");
Edit->eliminateDeadDefs(DeadDefs, RegsToSpill);
// Get rid of deleted and empty intervals.
unsigned ResultPos = 0;
for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i) {
unsigned Reg = RegsToSpill[i];
if (!LIS.hasInterval(Reg))
continue;
LiveInterval &LI = LIS.getInterval(Reg);
if (LI.empty()) {
Edit->eraseVirtReg(Reg);
continue;
}
RegsToSpill[ResultPos++] = Reg;
}
RegsToSpill.erase(RegsToSpill.begin() + ResultPos, RegsToSpill.end());
DEBUG(dbgs() << RegsToSpill.size() << " registers to spill after remat.\n");
}
/// shrinkToUses - After removing some uses of a register, shrink its live
/// range to just the remaining uses. This method does not compute reaching
/// defs for new uses, and it doesn't remove dead defs.
bool LiveIntervals::shrinkToUses(LiveInterval *li,
SmallVectorImpl<MachineInstr*> *dead) {
DEBUG(dbgs() << "Shrink: " << *li << '\n');
assert(TargetRegisterInfo::isVirtualRegister(li->reg)
&& "Can only shrink virtual registers");
// Find all the values used, including PHI kills.
SmallVector<std::pair<SlotIndex, VNInfo*>, 16> WorkList;
// Blocks that have already been added to WorkList as live-out.
SmallPtrSet<MachineBasicBlock*, 16> LiveOut;
// Visit all instructions reading li->reg.
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(li->reg);
MachineInstr *UseMI = I.skipInstruction();) {
if (UseMI->isDebugValue() || !UseMI->readsVirtualRegister(li->reg))
continue;
SlotIndex Idx = getInstructionIndex(UseMI).getRegSlot();
LiveRangeQuery LRQ(*li, Idx);
VNInfo *VNI = LRQ.valueIn();
if (!VNI) {
// This shouldn't happen: readsVirtualRegister returns true, but there is
// no live value. It is likely caused by a target getting <undef> flags
// wrong.
DEBUG(dbgs() << Idx << '\t' << *UseMI
<< "Warning: Instr claims to read non-existent value in "
<< *li << '\n');
continue;
}
// Special case: An early-clobber tied operand reads and writes the
// register one slot early.
if (VNInfo *DefVNI = LRQ.valueDefined())
Idx = DefVNI->def;
WorkList.push_back(std::make_pair(Idx, VNI));
}
// Create a new live interval with only minimal live segments per def.
LiveInterval NewLI(li->reg, 0);
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
NewLI.addRange(LiveRange(VNI->def, VNI->def.getDeadSlot(), VNI));
}
// Keep track of the PHIs that are in use.
SmallPtrSet<VNInfo*, 8> UsedPHIs;
// Extend intervals to reach all uses in WorkList.
while (!WorkList.empty()) {
SlotIndex Idx = WorkList.back().first;
VNInfo *VNI = WorkList.back().second;
WorkList.pop_back();
const MachineBasicBlock *MBB = getMBBFromIndex(Idx.getPrevSlot());
SlotIndex BlockStart = getMBBStartIdx(MBB);
// Extend the live range for VNI to be live at Idx.
if (VNInfo *ExtVNI = NewLI.extendInBlock(BlockStart, Idx)) {
(void)ExtVNI;
assert(ExtVNI == VNI && "Unexpected existing value number");
// Is this a PHIDef we haven't seen before?
if (!VNI->isPHIDef() || VNI->def != BlockStart || !UsedPHIs.insert(VNI))
continue;
// The PHI is live, make sure the predecessors are live-out.
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
if (!LiveOut.insert(*PI))
continue;
SlotIndex Stop = getMBBEndIdx(*PI);
// A predecessor is not required to have a live-out value for a PHI.
if (VNInfo *PVNI = li->getVNInfoBefore(Stop))
WorkList.push_back(std::make_pair(Stop, PVNI));
}
continue;
}
// VNI is live-in to MBB.
DEBUG(dbgs() << " live-in at " << BlockStart << '\n');
NewLI.addRange(LiveRange(BlockStart, Idx, VNI));
// Make sure VNI is live-out from the predecessors.
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
if (!LiveOut.insert(*PI))
continue;
SlotIndex Stop = getMBBEndIdx(*PI);
assert(li->getVNInfoBefore(Stop) == VNI &&
"Wrong value out of predecessor");
WorkList.push_back(std::make_pair(Stop, VNI));
}
}
// Handle dead values.
bool CanSeparate = false;
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
LiveInterval::iterator LII = NewLI.FindLiveRangeContaining(VNI->def);
assert(LII != NewLI.end() && "Missing live range for PHI");
if (LII->end != VNI->def.getDeadSlot())
continue;
if (VNI->isPHIDef()) {
// This is a dead PHI. Remove it.
VNI->markUnused();
NewLI.removeRange(*LII);
DEBUG(dbgs() << "Dead PHI at " << VNI->def << " may separate interval\n");
CanSeparate = true;
} else {
// This is a dead def. Make sure the instruction knows.
MachineInstr *MI = getInstructionFromIndex(VNI->def);
assert(MI && "No instruction defining live value");
MI->addRegisterDead(li->reg, TRI);
if (dead && MI->allDefsAreDead()) {
DEBUG(dbgs() << "All defs dead: " << VNI->def << '\t' << *MI);
dead->push_back(MI);
}
}
}
// Move the trimmed ranges back.
li->ranges.swap(NewLI.ranges);
DEBUG(dbgs() << "Shrunk: " << *li << '\n');
return CanSeparate;
}
void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
ArrayRef<unsigned> RegsBeingSpilled) {
SetVector<LiveInterval*,
SmallVector<LiveInterval*, 8>,
SmallPtrSet<LiveInterval*, 8> > ToShrink;
for (;;) {
// Erase all dead defs.
while (!Dead.empty()) {
MachineInstr *MI = Dead.pop_back_val();
assert(MI->allDefsAreDead() && "Def isn't really dead");
SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
// Never delete inline asm.
if (MI->isInlineAsm()) {
DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
continue;
}
// Use the same criteria as DeadMachineInstructionElim.
bool SawStore = false;
if (!MI->isSafeToMove(&TII, 0, SawStore)) {
DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
continue;
}
DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
// Check for live intervals that may shrink
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
if (!MOI->isReg())
continue;
unsigned Reg = MOI->getReg();
if (!TargetRegisterInfo::isVirtualRegister(Reg))
continue;
LiveInterval &LI = LIS.getInterval(Reg);
// Shrink read registers, unless it is likely to be expensive and
// unlikely to change anything. We typically don't want to shrink the
// PIC base register that has lots of uses everywhere.
// Always shrink COPY uses that probably come from live range splitting.
if (MI->readsVirtualRegister(Reg) &&
(MI->isCopy() || MOI->isDef() || MRI.hasOneNonDBGUse(Reg) ||
LI.killedAt(Idx)))
ToShrink.insert(&LI);
// Remove defined value.
if (MOI->isDef()) {
if (VNInfo *VNI = LI.getVNInfoAt(Idx)) {
if (TheDelegate)
TheDelegate->LRE_WillShrinkVirtReg(LI.reg);
LI.removeValNo(VNI);
if (LI.empty()) {
ToShrink.remove(&LI);
eraseVirtReg(Reg);
}
}
}
}
if (TheDelegate)
TheDelegate->LRE_WillEraseInstruction(MI);
LIS.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
++NumDCEDeleted;
}
if (ToShrink.empty())
break;
// Shrink just one live interval. Then delete new dead defs.
LiveInterval *LI = ToShrink.back();
ToShrink.pop_back();
if (foldAsLoad(LI, Dead))
continue;
if (TheDelegate)
TheDelegate->LRE_WillShrinkVirtReg(LI->reg);
if (!LIS.shrinkToUses(LI, &Dead))
continue;
// Don't create new intervals for a register being spilled.
// The new intervals would have to be spilled anyway so its not worth it.
// Also they currently aren't spilled so creating them and not spilling
// them results in incorrect code.
bool BeingSpilled = false;
for (unsigned i = 0, e = RegsBeingSpilled.size(); i != e; ++i) {
if (LI->reg == RegsBeingSpilled[i]) {
BeingSpilled = true;
break;
}
}
if (BeingSpilled) continue;
// LI may have been separated, create new intervals.
LI->RenumberValues(LIS);
ConnectedVNInfoEqClasses ConEQ(LIS);
unsigned NumComp = ConEQ.Classify(LI);
if (NumComp <= 1)
continue;
++NumFracRanges;
bool IsOriginal = VRM && VRM->getOriginal(LI->reg) == LI->reg;
DEBUG(dbgs() << NumComp << " components: " << *LI << '\n');
SmallVector<LiveInterval*, 8> Dups(1, LI);
for (unsigned i = 1; i != NumComp; ++i) {
Dups.push_back(&createFrom(LI->reg));
// If LI is an original interval that hasn't been split yet, make the new
// intervals their own originals instead of referring to LI. The original
// interval must contain all the split products, and LI doesn't.
if (IsOriginal)
VRM->setIsSplitFromReg(Dups.back()->reg, 0);
if (TheDelegate)
TheDelegate->LRE_DidCloneVirtReg(Dups.back()->reg, LI->reg);
}
ConEQ.Distribute(&Dups[0], MRI);
DEBUG({
for (unsigned i = 0; i != NumComp; ++i)
dbgs() << '\t' << *Dups[i] << '\n';
});
}