#include "llvm/CodeGen/LiveRangeEdit.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/VirtRegMap.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
using namespace llvm;
#define DEBUG_TYPE "regalloc"
STATISTIC(NumDCEDeleted, "Number of instructions deleted by DCE");
STATISTIC(NumDCEFoldedLoads, "Number of single use loads folded after DCE");
STATISTIC(NumFracRanges, "Number of live ranges fractured by DCE");
void LiveRangeEdit::Delegate::anchor() { }
LiveInterval &LiveRangeEdit::createEmptyIntervalFrom(unsigned OldReg) {
unsigned VReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
if (VRM) {
VRM->setIsSplitFromReg(VReg, VRM->getOriginal(OldReg));
}
LiveInterval &LI = LIS.createEmptyInterval(VReg);
return LI;
}
unsigned LiveRangeEdit::createFrom(unsigned OldReg) {
unsigned VReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
if (VRM) {
VRM->setIsSplitFromReg(VReg, VRM->getOriginal(OldReg));
}
return VReg;
}
bool LiveRangeEdit::checkRematerializable(VNInfo *VNI,
const MachineInstr *DefMI,
AliasAnalysis *aa) {
assert(DefMI && "Missing instruction");
ScannedRemattable = true;
if (!TII.isTriviallyReMaterializable(DefMI, aa))
return false;
Remattable.insert(VNI);
return true;
}
void LiveRangeEdit::scanRemattable(AliasAnalysis *aa) {
for (VNInfo *VNI : getParent().valnos) {
if (VNI->isUnused())
continue;
MachineInstr *DefMI = LIS.getInstructionFromIndex(VNI->def);
if (!DefMI)
continue;
checkRematerializable(VNI, DefMI, aa);
}
ScannedRemattable = true;
}
bool LiveRangeEdit::anyRematerializable(AliasAnalysis *aa) {
if (!ScannedRemattable)
scanRemattable(aa);
return !Remattable.empty();
}
bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
SlotIndex OrigIdx,
SlotIndex UseIdx) const {
OrigIdx = OrigIdx.getRegSlot(true);
UseIdx = UseIdx.getRegSlot(true);
for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = OrigMI->getOperand(i);
if (!MO.isReg() || !MO.getReg() || !MO.readsReg())
continue;
if (TargetRegisterInfo::isPhysicalRegister(MO.getReg())) {
if (MRI.isConstantPhysReg(MO.getReg(), *OrigMI->getParent()->getParent()))
continue;
return false;
}
LiveInterval &li = LIS.getInterval(MO.getReg());
const VNInfo *OVNI = li.getVNInfoAt(OrigIdx);
if (!OVNI)
continue;
if (SlotIndex::isSameInstr(OrigIdx, UseIdx))
return false;
if (OVNI != li.getVNInfoAt(UseIdx))
return false;
}
return true;
}
bool LiveRangeEdit::canRematerializeAt(Remat &RM,
SlotIndex UseIdx,
bool cheapAsAMove) {
assert(ScannedRemattable && "Call anyRematerializable first");
if (!Remattable.count(RM.ParentVNI))
return false;
SlotIndex DefIdx;
if (RM.OrigMI)
DefIdx = LIS.getInstructionIndex(RM.OrigMI);
else {
DefIdx = RM.ParentVNI->def;
RM.OrigMI = LIS.getInstructionFromIndex(DefIdx);
assert(RM.OrigMI && "No defining instruction for remattable value");
}
if (cheapAsAMove && !TII.isAsCheapAsAMove(RM.OrigMI))
return false;
if (!allUsesAvailableAt(RM.OrigMI, DefIdx, UseIdx))
return false;
return true;
}
SlotIndex LiveRangeEdit::rematerializeAt(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned DestReg,
const Remat &RM,
const TargetRegisterInfo &tri,
bool Late) {
assert(RM.OrigMI && "Invalid remat");
TII.reMaterialize(MBB, MI, DestReg, 0, RM.OrigMI, tri);
Rematted.insert(RM.ParentVNI);
return LIS.getSlotIndexes()->insertMachineInstrInMaps(--MI, Late)
.getRegSlot();
}
void LiveRangeEdit::eraseVirtReg(unsigned Reg) {
if (TheDelegate && TheDelegate->LRE_CanEraseVirtReg(Reg))
LIS.removeInterval(Reg);
}
bool LiveRangeEdit::foldAsLoad(LiveInterval *LI,
SmallVectorImpl<MachineInstr*> &Dead) {
MachineInstr *DefMI = nullptr, *UseMI = nullptr;
for (MachineOperand &MO : MRI.reg_nodbg_operands(LI->reg)) {
MachineInstr *MI = MO.getParent();
if (MO.isDef()) {
if (DefMI && DefMI != MI)
return false;
if (!MI->canFoldAsLoad())
return false;
DefMI = MI;
} else if (!MO.isUndef()) {
if (UseMI && UseMI != MI)
return false;
if (MO.getSubReg())
return false;
UseMI = MI;
}
}
if (!DefMI || !UseMI)
return false;
if (!allUsesAvailableAt(DefMI,
LIS.getInstructionIndex(DefMI),
LIS.getInstructionIndex(UseMI)))
return false;
bool SawStore = true;
if (!DefMI->isSafeToMove(nullptr, SawStore))
return false;
DEBUG(dbgs() << "Try to fold single def: " << *DefMI
<< " into single use: " << *UseMI);
SmallVector<unsigned, 8> Ops;
if (UseMI->readsWritesVirtualRegister(LI->reg, &Ops).second)
return false;
MachineInstr *FoldMI = TII.foldMemoryOperand(UseMI, Ops, DefMI);
if (!FoldMI)
return false;
DEBUG(dbgs() << " folded: " << *FoldMI);
LIS.ReplaceMachineInstrInMaps(UseMI, FoldMI);
UseMI->eraseFromParent();
DefMI->addRegisterDead(LI->reg, nullptr);
Dead.push_back(DefMI);
++NumDCEFoldedLoads;
return true;
}
bool LiveRangeEdit::useIsKill(const LiveInterval &LI,
const MachineOperand &MO) const {
const MachineInstr *MI = MO.getParent();
SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
if (LI.Query(Idx).isKill())
return true;
const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
unsigned SubReg = MO.getSubReg();
LaneBitmask LaneMask = TRI.getSubRegIndexLaneMask(SubReg);
for (const LiveInterval::SubRange &S : LI.subranges()) {
if ((S.LaneMask & LaneMask) != 0 && S.Query(Idx).isKill())
return true;
}
return false;
}
void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink) {
assert(MI->allDefsAreDead() && "Def isn't really dead");
SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
if (MI->isBundled()) {
return;
}
if (MI->isInlineAsm()) {
DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
return;
}
bool SawStore = false;
if (!MI->isSafeToMove(nullptr, SawStore)) {
DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
return;
}
DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
SmallVector<unsigned, 8> RegsToErase;
bool ReadsPhysRegs = false;
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)) {
if (Reg && MOI->readsReg() && !MRI.isReserved(Reg))
ReadsPhysRegs = true;
else if (MOI->isDef())
LIS.removePhysRegDefAt(Reg, Idx);
continue;
}
LiveInterval &LI = LIS.getInterval(Reg);
if ((MI->readsVirtualRegister(Reg) && (MI->isCopy() || MOI->isDef())) ||
(MOI->readsReg() && (MRI.hasOneNonDBGUse(Reg) || useIsKill(LI, *MOI))))
ToShrink.insert(&LI);
if (MOI->isDef()) {
if (TheDelegate && LI.getVNInfoAt(Idx) != nullptr)
TheDelegate->LRE_WillShrinkVirtReg(LI.reg);
LIS.removeVRegDefAt(LI, Idx);
if (LI.empty())
RegsToErase.push_back(Reg);
}
}
if (ReadsPhysRegs) {
MI->setDesc(TII.get(TargetOpcode::KILL));
for (unsigned i = MI->getNumOperands(); i; --i) {
const MachineOperand &MO = MI->getOperand(i-1);
if (MO.isReg() && TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
continue;
MI->RemoveOperand(i-1);
}
DEBUG(dbgs() << "Converted physregs to:\t" << *MI);
} else {
if (TheDelegate)
TheDelegate->LRE_WillEraseInstruction(MI);
LIS.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
++NumDCEDeleted;
}
for (unsigned i = 0, e = RegsToErase.size(); i != e; ++i) {
unsigned Reg = RegsToErase[i];
if (LIS.hasInterval(Reg) && MRI.reg_nodbg_empty(Reg)) {
ToShrink.remove(&LIS.getInterval(Reg));
eraseVirtReg(Reg);
}
}
}
void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
ArrayRef<unsigned> RegsBeingSpilled) {
ToShrinkSet ToShrink;
for (;;) {
while (!Dead.empty())
eliminateDeadDef(Dead.pop_back_val(), ToShrink);
if (ToShrink.empty())
break;
LiveInterval *LI = ToShrink.back();
ToShrink.pop_back();
if (foldAsLoad(LI, Dead))
continue;
unsigned VReg = LI->reg;
if (TheDelegate)
TheDelegate->LRE_WillShrinkVirtReg(VReg);
if (!LIS.shrinkToUses(LI, &Dead))
continue;
bool BeingSpilled = false;
for (unsigned i = 0, e = RegsBeingSpilled.size(); i != e; ++i) {
if (VReg == RegsBeingSpilled[i]) {
BeingSpilled = true;
break;
}
}
if (BeingSpilled) continue;
LI->RenumberValues();
SmallVector<LiveInterval*, 8> SplitLIs;
LIS.splitSeparateComponents(*LI, SplitLIs);
if (!SplitLIs.empty())
++NumFracRanges;
unsigned Original = VRM ? VRM->getOriginal(VReg) : 0;
for (const LiveInterval *SplitLI : SplitLIs) {
if (Original != VReg && Original != 0)
VRM->setIsSplitFromReg(SplitLI->reg, Original);
if (TheDelegate)
TheDelegate->LRE_DidCloneVirtReg(SplitLI->reg, VReg);
}
}
}
void
LiveRangeEdit::MRI_NoteNewVirtualRegister(unsigned VReg)
{
if (VRM)
VRM->grow();
NewRegs.push_back(VReg);
}
void
LiveRangeEdit::calculateRegClassAndHint(MachineFunction &MF,
const MachineLoopInfo &Loops,
const MachineBlockFrequencyInfo &MBFI) {
VirtRegAuxInfo VRAI(MF, LIS, VRM, Loops, MBFI);
for (unsigned I = 0, Size = size(); I < Size; ++I) {
LiveInterval &LI = LIS.getInterval(get(I));
if (MRI.recomputeRegClass(LI.reg))
DEBUG({
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
dbgs() << "Inflated " << PrintReg(LI.reg) << " to "
<< TRI->getRegClassName(MRI.getRegClass(LI.reg)) << '\n';
});
VRAI.calculateSpillWeightAndHint(LI);
}
}