CriticalAntiDepBreaker.cpp [plain text]
#define DEBUG_TYPE "post-RA-sched"
#include "CriticalAntiDepBreaker.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
CriticalAntiDepBreaker::
CriticalAntiDepBreaker(MachineFunction& MFi, const RegisterClassInfo &RCI) :
AntiDepBreaker(), MF(MFi),
MRI(MF.getRegInfo()),
TII(MF.getTarget().getInstrInfo()),
TRI(MF.getTarget().getRegisterInfo()),
RegClassInfo(RCI),
Classes(TRI->getNumRegs(), static_cast<const TargetRegisterClass *>(0)),
KillIndices(TRI->getNumRegs(), 0),
DefIndices(TRI->getNumRegs(), 0) {}
CriticalAntiDepBreaker::~CriticalAntiDepBreaker() {
}
void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) {
const unsigned BBSize = BB->size();
for (unsigned i = 0, e = TRI->getNumRegs(); i != e; ++i) {
Classes[i] = static_cast<const TargetRegisterClass *>(0);
KillIndices[i] = ~0u;
DefIndices[i] = BBSize;
}
KeepRegs.clear();
bool IsReturnBlock = (!BB->empty() && BB->back().isReturn());
if (IsReturnBlock) {
for (MachineRegisterInfo::liveout_iterator I = MRI.liveout_begin(),
E = MRI.liveout_end(); I != E; ++I) {
unsigned Reg = *I;
Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
KillIndices[Reg] = BB->size();
DefIndices[Reg] = ~0u;
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
unsigned AliasReg = *Alias;
Classes[AliasReg] = reinterpret_cast<TargetRegisterClass *>(-1);
KillIndices[AliasReg] = BB->size();
DefIndices[AliasReg] = ~0u;
}
}
}
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
SE = BB->succ_end(); SI != SE; ++SI)
for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
E = (*SI)->livein_end(); I != E; ++I) {
unsigned Reg = *I;
Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
KillIndices[Reg] = BB->size();
DefIndices[Reg] = ~0u;
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
unsigned AliasReg = *Alias;
Classes[AliasReg] = reinterpret_cast<TargetRegisterClass *>(-1);
KillIndices[AliasReg] = BB->size();
DefIndices[AliasReg] = ~0u;
}
}
const MachineFrameInfo *MFI = MF.getFrameInfo();
BitVector Pristine = MFI->getPristineRegs(BB);
for (const unsigned *I = TRI->getCalleeSavedRegs(); *I; ++I) {
unsigned Reg = *I;
if (!IsReturnBlock && !Pristine.test(Reg)) continue;
Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
KillIndices[Reg] = BB->size();
DefIndices[Reg] = ~0u;
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
unsigned AliasReg = *Alias;
Classes[AliasReg] = reinterpret_cast<TargetRegisterClass *>(-1);
KillIndices[AliasReg] = BB->size();
DefIndices[AliasReg] = ~0u;
}
}
}
void CriticalAntiDepBreaker::FinishBlock() {
RegRefs.clear();
KeepRegs.clear();
}
void CriticalAntiDepBreaker::Observe(MachineInstr *MI, unsigned Count,
unsigned InsertPosIndex) {
if (MI->isDebugValue())
return;
assert(Count < InsertPosIndex && "Instruction index out of expected range!");
for (unsigned Reg = 0; Reg != TRI->getNumRegs(); ++Reg) {
if (KillIndices[Reg] != ~0u) {
Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
KillIndices[Reg] = Count;
} else if (DefIndices[Reg] < InsertPosIndex && DefIndices[Reg] >= Count) {
Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
DefIndices[Reg] = InsertPosIndex;
}
}
PrescanInstruction(MI);
ScanInstruction(MI, Count);
}
static const SDep *CriticalPathStep(const SUnit *SU) {
const SDep *Next = 0;
unsigned NextDepth = 0;
for (SUnit::const_pred_iterator P = SU->Preds.begin(), PE = SU->Preds.end();
P != PE; ++P) {
const SUnit *PredSU = P->getSUnit();
unsigned PredLatency = P->getLatency();
unsigned PredTotalLatency = PredSU->getDepth() + PredLatency;
if (NextDepth < PredTotalLatency ||
(NextDepth == PredTotalLatency && P->getKind() == SDep::Anti)) {
NextDepth = PredTotalLatency;
Next = &*P;
}
}
return Next;
}
void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) {
bool Special = MI->isCall() ||
MI->hasExtraSrcRegAllocReq() ||
TII->isPredicated(MI);
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
const TargetRegisterClass *NewRC = 0;
if (i < MI->getDesc().getNumOperands())
NewRC = TII->getRegClass(MI->getDesc(), i, TRI);
if (!Classes[Reg] && NewRC)
Classes[Reg] = NewRC;
else if (!NewRC || Classes[Reg] != NewRC)
Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
unsigned AliasReg = *Alias;
if (Classes[AliasReg]) {
Classes[AliasReg] = reinterpret_cast<TargetRegisterClass *>(-1);
Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
}
}
if (Classes[Reg] != reinterpret_cast<TargetRegisterClass *>(-1))
RegRefs.insert(std::make_pair(Reg, &MO));
if (MO.isUse() && Special) {
if (KeepRegs.insert(Reg)) {
for (const unsigned *Subreg = TRI->getSubRegisters(Reg);
*Subreg; ++Subreg)
KeepRegs.insert(*Subreg);
}
}
}
}
void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI,
unsigned Count) {
if (!TII->isPredicated(MI)) {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (!MO.isDef()) continue;
if (MI->isRegTiedToUseOperand(i)) continue;
DefIndices[Reg] = Count;
KillIndices[Reg] = ~0u;
assert(((KillIndices[Reg] == ~0u) !=
(DefIndices[Reg] == ~0u)) &&
"Kill and Def maps aren't consistent for Reg!");
KeepRegs.erase(Reg);
Classes[Reg] = 0;
RegRefs.erase(Reg);
for (const unsigned *Subreg = TRI->getSubRegisters(Reg);
*Subreg; ++Subreg) {
unsigned SubregReg = *Subreg;
DefIndices[SubregReg] = Count;
KillIndices[SubregReg] = ~0u;
KeepRegs.erase(SubregReg);
Classes[SubregReg] = 0;
RegRefs.erase(SubregReg);
}
for (const unsigned *Super = TRI->getSuperRegisters(Reg);
*Super; ++Super) {
unsigned SuperReg = *Super;
Classes[SuperReg] = reinterpret_cast<TargetRegisterClass *>(-1);
}
}
}
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (!MO.isUse()) continue;
const TargetRegisterClass *NewRC = 0;
if (i < MI->getDesc().getNumOperands())
NewRC = TII->getRegClass(MI->getDesc(), i, TRI);
if (!Classes[Reg] && NewRC)
Classes[Reg] = NewRC;
else if (!NewRC || Classes[Reg] != NewRC)
Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
RegRefs.insert(std::make_pair(Reg, &MO));
if (KillIndices[Reg] == ~0u) {
KillIndices[Reg] = Count;
DefIndices[Reg] = ~0u;
assert(((KillIndices[Reg] == ~0u) !=
(DefIndices[Reg] == ~0u)) &&
"Kill and Def maps aren't consistent for Reg!");
}
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
unsigned AliasReg = *Alias;
if (KillIndices[AliasReg] == ~0u) {
KillIndices[AliasReg] = Count;
DefIndices[AliasReg] = ~0u;
}
}
}
}
bool
CriticalAntiDepBreaker::isNewRegClobberedByRefs(RegRefIter RegRefBegin,
RegRefIter RegRefEnd,
unsigned NewReg)
{
for (RegRefIter I = RegRefBegin; I != RegRefEnd; ++I ) {
MachineOperand *RefOper = I->second;
if (RefOper->isDef() && RefOper->isEarlyClobber())
return true;
MachineInstr *MI = RefOper->getParent();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &CheckOper = MI->getOperand(i);
if (!CheckOper.isReg() || !CheckOper.isDef() ||
CheckOper.getReg() != NewReg)
continue;
if (RefOper->isDef())
return true;
if (CheckOper.isEarlyClobber())
return true;
if (MI->isInlineAsm())
return true;
}
}
return false;
}
unsigned
CriticalAntiDepBreaker::findSuitableFreeRegister(RegRefIter RegRefBegin,
RegRefIter RegRefEnd,
unsigned AntiDepReg,
unsigned LastNewReg,
const TargetRegisterClass *RC)
{
ArrayRef<unsigned> Order = RegClassInfo.getOrder(RC);
for (unsigned i = 0; i != Order.size(); ++i) {
unsigned NewReg = Order[i];
if (NewReg == AntiDepReg) continue;
if (NewReg == LastNewReg) continue;
if (isNewRegClobberedByRefs(RegRefBegin, RegRefEnd, NewReg)) continue;
assert(((KillIndices[AntiDepReg] == ~0u) != (DefIndices[AntiDepReg] == ~0u))
&& "Kill and Def maps aren't consistent for AntiDepReg!");
assert(((KillIndices[NewReg] == ~0u) != (DefIndices[NewReg] == ~0u))
&& "Kill and Def maps aren't consistent for NewReg!");
if (KillIndices[NewReg] != ~0u ||
Classes[NewReg] == reinterpret_cast<TargetRegisterClass *>(-1) ||
KillIndices[AntiDepReg] > DefIndices[NewReg])
continue;
return NewReg;
}
return 0;
}
unsigned CriticalAntiDepBreaker::
BreakAntiDependencies(const std::vector<SUnit>& SUnits,
MachineBasicBlock::iterator Begin,
MachineBasicBlock::iterator End,
unsigned InsertPosIndex,
DbgValueVector &DbgValues) {
if (SUnits.empty()) return 0;
DenseMap<MachineInstr*,const SUnit*> MISUnitMap;
const SUnit *Max = 0;
for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
const SUnit *SU = &SUnits[i];
MISUnitMap[SU->getInstr()] = SU;
if (!Max || SU->getDepth() + SU->Latency > Max->getDepth() + Max->Latency)
Max = SU;
}
#ifndef NDEBUG
{
DEBUG(dbgs() << "Critical path has total latency "
<< (Max->getDepth() + Max->Latency) << "\n");
DEBUG(dbgs() << "Available regs:");
for (unsigned Reg = 0; Reg < TRI->getNumRegs(); ++Reg) {
if (KillIndices[Reg] == ~0u)
DEBUG(dbgs() << " " << TRI->getName(Reg));
}
DEBUG(dbgs() << '\n');
}
#endif
const SUnit *CriticalPathSU = Max;
MachineInstr *CriticalPathMI = CriticalPathSU->getInstr();
std::vector<unsigned> LastNewReg(TRI->getNumRegs(), 0);
unsigned Broken = 0;
unsigned Count = InsertPosIndex - 1;
for (MachineBasicBlock::iterator I = End, E = Begin;
I != E; --Count) {
MachineInstr *MI = --I;
if (MI->isDebugValue())
continue;
unsigned AntiDepReg = 0;
if (MI == CriticalPathMI) {
if (const SDep *Edge = CriticalPathStep(CriticalPathSU)) {
const SUnit *NextSU = Edge->getSUnit();
if (Edge->getKind() == SDep::Anti) {
AntiDepReg = Edge->getReg();
assert(AntiDepReg != 0 && "Anti-dependence on reg0?");
if (!RegClassInfo.isAllocatable(AntiDepReg))
AntiDepReg = 0;
else if (KeepRegs.count(AntiDepReg))
AntiDepReg = 0;
else {
for (SUnit::const_pred_iterator P = CriticalPathSU->Preds.begin(),
PE = CriticalPathSU->Preds.end(); P != PE; ++P)
if (P->getSUnit() == NextSU ?
(P->getKind() != SDep::Anti || P->getReg() != AntiDepReg) :
(P->getKind() == SDep::Data && P->getReg() == AntiDepReg)) {
AntiDepReg = 0;
break;
}
}
}
CriticalPathSU = NextSU;
CriticalPathMI = CriticalPathSU->getInstr();
} else {
CriticalPathSU = 0;
CriticalPathMI = 0;
}
}
PrescanInstruction(MI);
if (MI->isCall() || MI->hasExtraDefRegAllocReq() ||
TII->isPredicated(MI))
AntiDepReg = 0;
else if (AntiDepReg) {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (MO.isUse() && TRI->regsOverlap(AntiDepReg, Reg)) {
AntiDepReg = 0;
break;
}
}
}
const TargetRegisterClass *RC = AntiDepReg != 0 ? Classes[AntiDepReg] : 0;
assert((AntiDepReg == 0 || RC != NULL) &&
"Register should be live if it's causing an anti-dependence!");
if (RC == reinterpret_cast<TargetRegisterClass *>(-1))
AntiDepReg = 0;
if (AntiDepReg != 0) {
std::pair<std::multimap<unsigned, MachineOperand *>::iterator,
std::multimap<unsigned, MachineOperand *>::iterator>
Range = RegRefs.equal_range(AntiDepReg);
if (unsigned NewReg = findSuitableFreeRegister(Range.first, Range.second,
AntiDepReg,
LastNewReg[AntiDepReg],
RC)) {
DEBUG(dbgs() << "Breaking anti-dependence edge on "
<< TRI->getName(AntiDepReg)
<< " with " << RegRefs.count(AntiDepReg) << " references"
<< " using " << TRI->getName(NewReg) << "!\n");
for (std::multimap<unsigned, MachineOperand *>::iterator
Q = Range.first, QE = Range.second; Q != QE; ++Q) {
Q->second->setReg(NewReg);
const SUnit *SU = MISUnitMap[Q->second->getParent()];
if (!SU) continue;
for (DbgValueVector::iterator DVI = DbgValues.begin(),
DVE = DbgValues.end(); DVI != DVE; ++DVI)
if (DVI->second == Q->second->getParent())
UpdateDbgValue(DVI->first, AntiDepReg, NewReg);
}
Classes[NewReg] = Classes[AntiDepReg];
DefIndices[NewReg] = DefIndices[AntiDepReg];
KillIndices[NewReg] = KillIndices[AntiDepReg];
assert(((KillIndices[NewReg] == ~0u) !=
(DefIndices[NewReg] == ~0u)) &&
"Kill and Def maps aren't consistent for NewReg!");
Classes[AntiDepReg] = 0;
DefIndices[AntiDepReg] = KillIndices[AntiDepReg];
KillIndices[AntiDepReg] = ~0u;
assert(((KillIndices[AntiDepReg] == ~0u) !=
(DefIndices[AntiDepReg] == ~0u)) &&
"Kill and Def maps aren't consistent for AntiDepReg!");
RegRefs.erase(AntiDepReg);
LastNewReg[AntiDepReg] = NewReg;
++Broken;
}
}
ScanInstruction(MI, Count);
}
return Broken;
}