X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FCriticalAntiDepBreaker.cpp;h=84c4d59c0e41bb99cd69c3705e5dedd51edbc5a7;hb=d61c34ba30888c49f4f223422f30b018a41594da;hp=e3746a985644708c406513028c2c3076058469b2;hpb=46df4eb46e784036cf895db271fe29e1cf2a975a;p=oota-llvm.git diff --git a/lib/CodeGen/CriticalAntiDepBreaker.cpp b/lib/CodeGen/CriticalAntiDepBreaker.cpp index e3746a98564..84c4d59c0e4 100644 --- a/lib/CodeGen/CriticalAntiDepBreaker.cpp +++ b/lib/CodeGen/CriticalAntiDepBreaker.cpp @@ -27,26 +27,26 @@ using namespace llvm; CriticalAntiDepBreaker:: -CriticalAntiDepBreaker(MachineFunction& MFi) : +CriticalAntiDepBreaker(MachineFunction& MFi, const RegisterClassInfo &RCI) : AntiDepBreaker(), MF(MFi), MRI(MF.getRegInfo()), TII(MF.getTarget().getInstrInfo()), TRI(MF.getTarget().getRegisterInfo()), - AllocatableSet(TRI->getAllocatableSet(MF)) -{ -} + RegClassInfo(RCI), + Classes(TRI->getNumRegs(), static_cast(0)), + KillIndices(TRI->getNumRegs(), 0), + DefIndices(TRI->getNumRegs(), 0) {} CriticalAntiDepBreaker::~CriticalAntiDepBreaker() { } void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) { - // Clear out the register class data. - std::fill(Classes, array_endof(Classes), - static_cast(0)); - - // Initialize the indices to indicate that no registers are live. const unsigned BBSize = BB->size(); - for (unsigned i = 0; i < TRI->getNumRegs(); ++i) { + for (unsigned i = 0, e = TRI->getNumRegs(); i != e; ++i) { + // Clear out the register class data. + Classes[i] = static_cast(0); + + // Initialize the indices to indicate that no registers are live. KillIndices[i] = ~0u; DefIndices[i] = BBSize; } @@ -65,6 +65,7 @@ void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) { Classes[Reg] = reinterpret_cast(-1); KillIndices[Reg] = BB->size(); DefIndices[Reg] = ~0u; + // Repeat, for all aliases. for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) { unsigned AliasReg = *Alias; @@ -86,6 +87,7 @@ void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) { Classes[Reg] = reinterpret_cast(-1); KillIndices[Reg] = BB->size(); DefIndices[Reg] = ~0u; + // Repeat, for all aliases. for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) { unsigned AliasReg = *Alias; @@ -106,6 +108,7 @@ void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) { Classes[Reg] = reinterpret_cast(-1); KillIndices[Reg] = BB->size(); DefIndices[Reg] = ~0u; + // Repeat, for all aliases. for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) { unsigned AliasReg = *Alias; @@ -127,19 +130,25 @@ void CriticalAntiDepBreaker::Observe(MachineInstr *MI, unsigned Count, return; assert(Count < InsertPosIndex && "Instruction index out of expected range!"); - // Any register which was defined within the previous scheduling region - // may have been rescheduled and its lifetime may overlap with registers - // in ways not reflected in our current liveness state. For each such - // register, adjust the liveness state to be conservatively correct. - for (unsigned Reg = 0; Reg != TRI->getNumRegs(); ++Reg) - if (DefIndices[Reg] < InsertPosIndex && DefIndices[Reg] >= Count) { - assert(KillIndices[Reg] == ~0u && "Clobbered register is live!"); - // Mark this register to be non-renamable. + for (unsigned Reg = 0; Reg != TRI->getNumRegs(); ++Reg) { + if (KillIndices[Reg] != ~0u) { + // If Reg is currently live, then mark that it can't be renamed as + // we don't know the extent of its live-range anymore (now that it + // has been scheduled). + Classes[Reg] = reinterpret_cast(-1); + KillIndices[Reg] = Count; + } else if (DefIndices[Reg] < InsertPosIndex && DefIndices[Reg] >= Count) { + // Any register which was defined within the previous scheduling region + // may have been rescheduled and its lifetime may overlap with registers + // in ways not reflected in our current liveness state. For each such + // register, adjust the liveness state to be conservatively correct. Classes[Reg] = reinterpret_cast(-1); + // Move the def index to the end of the previous region, to reflect // that the def could theoretically have been scheduled at the end. DefIndices[Reg] = InsertPosIndex; } + } PrescanInstruction(MI); ScanInstruction(MI, Count); @@ -172,7 +181,7 @@ void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) { // that have special allocation requirements. Also assume all registers // used in a call must not be changed (ABI). // FIXME: The issue with predicated instruction is more complex. We are being - // conservatively here because the kill markers cannot be trusted after + // conservative here because the kill markers cannot be trusted after // if-conversion: // %R6 = LDR %SP, %reg0, 92, pred:14, pred:%reg0; mem:LD4[FixedStack14] // ... @@ -198,7 +207,7 @@ void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) { const TargetRegisterClass *NewRC = 0; if (i < MI->getDesc().getNumOperands()) - NewRC = MI->getDesc().OpInfo[i].getRegClass(TRI); + NewRC = TII->getRegClass(MI->getDesc(), i, TRI); // For now, only allow the register to be changed if its register // class is consistent across all uses. @@ -286,7 +295,7 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI, const TargetRegisterClass *NewRC = 0; if (i < MI->getDesc().getNumOperands()) - NewRC = MI->getDesc().OpInfo[i].getRegClass(TRI); + NewRC = TII->getRegClass(MI->getDesc(), i, TRI); // For now, only allow the register to be changed if its register // class is consistent across all uses. @@ -316,25 +325,79 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI, } } +// Check all machine operands that reference the antidependent register and must +// be replaced by NewReg. Return true if any of their parent instructions may +// clobber the new register. +// +// Note: AntiDepReg may be referenced by a two-address instruction such that +// it's use operand is tied to a def operand. We guard against the case in which +// the two-address instruction also defines NewReg, as may happen with +// pre/postincrement loads. In this case, both the use and def operands are in +// RegRefs because the def is inserted by PrescanInstruction and not erased +// during ScanInstruction. So checking for an instructions with definitions of +// both NewReg and AntiDepReg covers it. +bool +CriticalAntiDepBreaker::isNewRegClobberedByRefs(RegRefIter RegRefBegin, + RegRefIter RegRefEnd, + unsigned NewReg) +{ + for (RegRefIter I = RegRefBegin; I != RegRefEnd; ++I ) { + MachineOperand *RefOper = I->second; + + // Don't allow the instruction defining AntiDepReg to earlyclobber its + // operands, in case they may be assigned to NewReg. In this case antidep + // breaking must fail, but it's too rare to bother optimizing. + if (RefOper->isDef() && RefOper->isEarlyClobber()) + return true; + + // Handle cases in which this instructions defines NewReg. + 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; + + // Don't allow the instruction to define NewReg and AntiDepReg. + // When AntiDepReg is renamed it will be an illegal op. + if (RefOper->isDef()) + return true; + + // Don't allow an instruction using AntiDepReg to be earlyclobbered by + // NewReg + if (CheckOper.isEarlyClobber()) + return true; + + // Don't allow inline asm to define NewReg at all. Who know what it's + // doing with it. + if (MI->isInlineAsm()) + return true; + } + } + return false; +} + unsigned -CriticalAntiDepBreaker::findSuitableFreeRegister(MachineInstr *MI, +CriticalAntiDepBreaker::findSuitableFreeRegister(RegRefIter RegRefBegin, + RegRefIter RegRefEnd, unsigned AntiDepReg, unsigned LastNewReg, const TargetRegisterClass *RC) { - for (TargetRegisterClass::iterator R = RC->allocation_order_begin(MF), - RE = RC->allocation_order_end(MF); R != RE; ++R) { - unsigned NewReg = *R; + ArrayRef Order = RegClassInfo.getOrder(RC); + for (unsigned i = 0; i != Order.size(); ++i) { + unsigned NewReg = Order[i]; // Don't replace a register with itself. if (NewReg == AntiDepReg) continue; // Don't replace a register with one that was recently used to repair // an anti-dependence with this AntiDepReg, because that would // re-introduce that anti-dependence. if (NewReg == LastNewReg) continue; - // If the instruction already has a def of the NewReg, it's not suitable. - // For example, Instruction with multiple definitions can result in this - // condition. - if (MI->modifiesRegister(NewReg, TRI)) continue; + // If any instructions that define AntiDepReg also define the NewReg, it's + // not suitable. For example, Instruction with multiple definitions can + // result in this condition. + if (isNewRegClobberedByRefs(RegRefBegin, RegRefEnd, NewReg)) continue; // If NewReg is dead and NewReg's most recent def is not before // AntiDepReg's kill, it's safe to replace AntiDepReg with NewReg. assert(((KillIndices[AntiDepReg] == ~0u) != (DefIndices[AntiDepReg] == ~0u)) @@ -356,7 +419,8 @@ unsigned CriticalAntiDepBreaker:: BreakAntiDependencies(const std::vector& SUnits, MachineBasicBlock::iterator Begin, MachineBasicBlock::iterator End, - unsigned InsertPosIndex) { + unsigned InsertPosIndex, + DbgValueVector &DbgValues) { // The code below assumes that there is at least one instruction, // so just duck out immediately if the block is empty. if (SUnits.empty()) return 0; @@ -433,7 +497,7 @@ BreakAntiDependencies(const std::vector& SUnits, // fix that remaining critical edge too. This is a little more involved, // because unlike the most recent register, less recent registers should // still be considered, though only if no other registers are available. - unsigned LastNewReg[TargetRegisterInfo::FirstVirtualRegister] = {}; + std::vector LastNewReg(TRI->getNumRegs(), 0); // Attempt to break anti-dependence edges on the critical path. Walk the // instructions from the bottom up, tracking information about liveness @@ -468,7 +532,7 @@ BreakAntiDependencies(const std::vector& SUnits, if (Edge->getKind() == SDep::Anti) { AntiDepReg = Edge->getReg(); assert(AntiDepReg != 0 && "Anti-dependence on reg0?"); - if (!AllocatableSet.test(AntiDepReg)) + if (!RegClassInfo.isAllocatable(AntiDepReg)) // Don't break anti-dependencies on non-allocatable registers. AntiDepReg = 0; else if (KeepRegs.count(AntiDepReg)) @@ -541,7 +605,11 @@ BreakAntiDependencies(const std::vector& SUnits, // TODO: Instead of picking the first free register, consider which might // be the best. if (AntiDepReg != 0) { - if (unsigned NewReg = findSuitableFreeRegister(MI, AntiDepReg, + std::pair::iterator, + std::multimap::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 " @@ -551,9 +619,6 @@ BreakAntiDependencies(const std::vector& SUnits, // Update the references to the old register to refer to the new // register. - std::pair::iterator, - std::multimap::iterator> - Range = RegRefs.equal_range(AntiDepReg); for (std::multimap::iterator Q = Range.first, QE = Range.second; Q != QE; ++Q) { Q->second->setReg(NewReg); @@ -562,18 +627,14 @@ BreakAntiDependencies(const std::vector& SUnits, // as well. const SUnit *SU = MISUnitMap[Q->second->getParent()]; if (!SU) continue; - for (unsigned i = 0, e = SU->DbgInstrList.size() ; i < e ; ++i) { - MachineInstr *DI = SU->DbgInstrList[i]; - assert (DI->getNumOperands()==3 && DI->getOperand(0).isReg() && - DI->getOperand(0).getReg() - && "Non register dbg_value attached to SUnit!"); - if (DI->getOperand(0).getReg() == AntiDepReg) - DI->getOperand(0).setReg(NewReg); - } + for (DbgValueVector::iterator DVI = DbgValues.begin(), + DVE = DbgValues.end(); DVI != DVE; ++DVI) + if (DVI->second == Q->second->getParent()) + UpdateDbgValue(DVI->first, AntiDepReg, NewReg); } // We just went back in time and modified history; the - // liveness information for the anti-depenence reg is now + // liveness information for the anti-dependence reg is now // inconsistent. Set the state as if it were dead. Classes[NewReg] = Classes[AntiDepReg]; DefIndices[NewReg] = DefIndices[AntiDepReg];