X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FPostRASchedulerList.cpp;h=c73e87733cb4212421bb9e7a90084c51212baebc;hb=340d596509129de8c3fa9dbe4184a2b148b78757;hp=dc11400094cc4ca1ef9e779bc5455901c7d3247d;hpb=c9a5b9e38b442c2ae6b115213a07df3fcd14708d;p=oota-llvm.git diff --git a/lib/CodeGen/PostRASchedulerList.cpp b/lib/CodeGen/PostRASchedulerList.cpp index dc11400094c..c73e87733cb 100644 --- a/lib/CodeGen/PostRASchedulerList.cpp +++ b/lib/CodeGen/PostRASchedulerList.cpp @@ -19,39 +19,79 @@ //===----------------------------------------------------------------------===// #define DEBUG_TYPE "post-RA-sched" +#include "AntiDepBreaker.h" +#include "AggressiveAntiDepBreaker.h" +#include "CriticalAntiDepBreaker.h" +#include "RegisterClassInfo.h" +#include "ScheduleDAGInstrs.h" #include "llvm/CodeGen/Passes.h" -#include "llvm/CodeGen/ScheduleDAGInstrs.h" #include "llvm/CodeGen/LatencyPriorityQueue.h" #include "llvm/CodeGen/SchedulerRegistry.h" #include "llvm/CodeGen/MachineDominators.h" +#include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineLoopInfo.h" #include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/ScheduleHazardRecognizer.h" +#include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Target/TargetLowering.h" +#include "llvm/Target/TargetMachine.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetRegisterInfo.h" -#include "llvm/Support/Compiler.h" +#include "llvm/Target/TargetSubtargetInfo.h" +#include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/ADT/BitVector.h" #include "llvm/ADT/Statistic.h" -#include "llvm/ADT/DenseSet.h" -#include "llvm/ADT/SmallVector.h" -#include -#include +#include using namespace llvm; +STATISTIC(NumNoops, "Number of noops inserted"); STATISTIC(NumStalls, "Number of pipeline stalls"); +STATISTIC(NumFixedAnti, "Number of fixed anti-dependencies"); +// Post-RA scheduling is enabled with +// TargetSubtargetInfo.enablePostRAScheduler(). This flag can be used to +// override the target. static cl::opt +EnablePostRAScheduler("post-RA-scheduler", + cl::desc("Enable scheduling after register allocation"), + cl::init(false), cl::Hidden); +static cl::opt EnableAntiDepBreaking("break-anti-dependencies", - cl::desc("Break post-RA scheduling anti-dependencies"), - cl::init(true), cl::Hidden); + cl::desc("Break post-RA scheduling anti-dependencies: " + "\"critical\", \"all\", or \"none\""), + cl::init("none"), cl::Hidden); + +// If DebugDiv > 0 then only schedule MBB with (ID % DebugDiv) == DebugMod +static cl::opt +DebugDiv("postra-sched-debugdiv", + cl::desc("Debug control MBBs that are scheduled"), + cl::init(0), cl::Hidden); +static cl::opt +DebugMod("postra-sched-debugmod", + cl::desc("Debug control MBBs that are scheduled"), + cl::init(0), cl::Hidden); + +AntiDepBreaker::~AntiDepBreaker() { } namespace { - class VISIBILITY_HIDDEN PostRAScheduler : public MachineFunctionPass { + class PostRAScheduler : public MachineFunctionPass { + AliasAnalysis *AA; + const TargetInstrInfo *TII; + RegisterClassInfo RegClassInfo; + CodeGenOpt::Level OptLevel; + public: static char ID; - PostRAScheduler() : MachineFunctionPass(&ID) {} + PostRAScheduler(CodeGenOpt::Level ol) : + MachineFunctionPass(ID), OptLevel(ol) {} void getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesCFG(); + AU.addRequired(); AU.addRequired(); AU.addPreserved(); AU.addRequired(); @@ -67,11 +107,11 @@ namespace { }; char PostRAScheduler::ID = 0; - class VISIBILITY_HIDDEN SchedulePostRATDList : public ScheduleDAGInstrs { + class SchedulePostRATDList : public ScheduleDAGInstrs { /// AvailableQueue - The priority queue to use for the available SUnits. /// LatencyPriorityQueue AvailableQueue; - + /// PendingQueue - This contains all of the instructions whose operands have /// been issued, but their results are not ready yet (due to the latency of /// the operation). Once the operands becomes available, the instruction is @@ -81,51 +121,198 @@ namespace { /// Topo - A topological ordering for SUnits. ScheduleDAGTopologicalSort Topo; + /// HazardRec - The hazard recognizer to use. + ScheduleHazardRecognizer *HazardRec; + + /// AntiDepBreak - Anti-dependence breaking object, or NULL if none + AntiDepBreaker *AntiDepBreak; + + /// AA - AliasAnalysis for making memory reference queries. + AliasAnalysis *AA; + + /// KillIndices - The index of the most recent kill (proceding bottom-up), + /// or ~0u if the register is not live. + std::vector KillIndices; + public: - SchedulePostRATDList(MachineBasicBlock *mbb, const TargetMachine &tm, - const MachineLoopInfo &MLI, - const MachineDominatorTree &MDT) - : ScheduleDAGInstrs(mbb, tm, MLI, MDT), Topo(SUnits) {} + SchedulePostRATDList( + MachineFunction &MF, MachineLoopInfo &MLI, MachineDominatorTree &MDT, + AliasAnalysis *AA, const RegisterClassInfo&, + TargetSubtargetInfo::AntiDepBreakMode AntiDepMode, + SmallVectorImpl &CriticalPathRCs); + + ~SchedulePostRATDList(); + + /// StartBlock - Initialize register live-range state for scheduling in + /// this block. + /// + void StartBlock(MachineBasicBlock *BB); + /// Schedule - Schedule the instruction range using list scheduling. + /// void Schedule(); + /// Observe - Update liveness information to account for the current + /// instruction, which will not be scheduled. + /// + void Observe(MachineInstr *MI, unsigned Count); + + /// FinishBlock - Clean up register live-range state. + /// + void FinishBlock(); + + /// FixupKills - Fix register kill flags that have been made + /// invalid due to scheduling + /// + void FixupKills(MachineBasicBlock *MBB); + private: void ReleaseSucc(SUnit *SU, SDep *SuccEdge); + void ReleaseSuccessors(SUnit *SU); void ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle); void ListScheduleTopDown(); - bool BreakAntiDependencies(); + void StartBlockForKills(MachineBasicBlock *BB); + + // ToggleKillFlag - Toggle a register operand kill flag. Other + // adjustments may be made to the instruction if necessary. Return + // true if the operand has been deleted, false if not. + bool ToggleKillFlag(MachineInstr *MI, MachineOperand &MO); }; } +SchedulePostRATDList::SchedulePostRATDList( + MachineFunction &MF, MachineLoopInfo &MLI, MachineDominatorTree &MDT, + AliasAnalysis *AA, const RegisterClassInfo &RCI, + TargetSubtargetInfo::AntiDepBreakMode AntiDepMode, + SmallVectorImpl &CriticalPathRCs) + : ScheduleDAGInstrs(MF, MLI, MDT), Topo(SUnits), AA(AA), + KillIndices(TRI->getNumRegs()) +{ + const TargetMachine &TM = MF.getTarget(); + const InstrItineraryData *InstrItins = TM.getInstrItineraryData(); + HazardRec = + TM.getInstrInfo()->CreateTargetPostRAHazardRecognizer(InstrItins, this); + AntiDepBreak = + ((AntiDepMode == TargetSubtargetInfo::ANTIDEP_ALL) ? + (AntiDepBreaker *)new AggressiveAntiDepBreaker(MF, RCI, CriticalPathRCs) : + ((AntiDepMode == TargetSubtargetInfo::ANTIDEP_CRITICAL) ? + (AntiDepBreaker *)new CriticalAntiDepBreaker(MF, RCI) : NULL)); +} + +SchedulePostRATDList::~SchedulePostRATDList() { + delete HazardRec; + delete AntiDepBreak; +} + bool PostRAScheduler::runOnMachineFunction(MachineFunction &Fn) { - DOUT << "PostRAScheduler\n"; + TII = Fn.getTarget().getInstrInfo(); + MachineLoopInfo &MLI = getAnalysis(); + MachineDominatorTree &MDT = getAnalysis(); + AliasAnalysis *AA = &getAnalysis(); + RegClassInfo.runOnMachineFunction(Fn); + + // Check for explicit enable/disable of post-ra scheduling. + TargetSubtargetInfo::AntiDepBreakMode AntiDepMode = TargetSubtargetInfo::ANTIDEP_NONE; + SmallVector CriticalPathRCs; + if (EnablePostRAScheduler.getPosition() > 0) { + if (!EnablePostRAScheduler) + return false; + } else { + // Check that post-RA scheduling is enabled for this target. + // This may upgrade the AntiDepMode. + const TargetSubtargetInfo &ST = Fn.getTarget().getSubtarget(); + if (!ST.enablePostRAScheduler(OptLevel, AntiDepMode, CriticalPathRCs)) + return false; + } - const MachineLoopInfo &MLI = getAnalysis(); - const MachineDominatorTree &MDT = getAnalysis(); + // Check for antidep breaking override... + if (EnableAntiDepBreaking.getPosition() > 0) { + AntiDepMode = (EnableAntiDepBreaking == "all") + ? TargetSubtargetInfo::ANTIDEP_ALL + : ((EnableAntiDepBreaking == "critical") + ? TargetSubtargetInfo::ANTIDEP_CRITICAL + : TargetSubtargetInfo::ANTIDEP_NONE); + } + + DEBUG(dbgs() << "PostRAScheduler\n"); + + SchedulePostRATDList Scheduler(Fn, MLI, MDT, AA, RegClassInfo, AntiDepMode, + CriticalPathRCs); // Loop over all of the basic blocks for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end(); MBB != MBBe; ++MBB) { +#ifndef NDEBUG + // If DebugDiv > 0 then only schedule MBB with (ID % DebugDiv) == DebugMod + if (DebugDiv > 0) { + static int bbcnt = 0; + if (bbcnt++ % DebugDiv != DebugMod) + continue; + dbgs() << "*** DEBUG scheduling " << Fn.getFunction()->getNameStr() << + ":BB#" << MBB->getNumber() << " ***\n"; + } +#endif - SchedulePostRATDList Scheduler(MBB, Fn.getTarget(), MLI, MDT); + // Initialize register live-range state for scheduling in this block. + Scheduler.StartBlock(MBB); + + // Schedule each sequence of instructions not interrupted by a label + // or anything else that effectively needs to shut down scheduling. + MachineBasicBlock::iterator Current = MBB->end(); + unsigned Count = MBB->size(), CurrentCount = Count; + for (MachineBasicBlock::iterator I = Current; I != MBB->begin(); ) { + MachineInstr *MI = llvm::prior(I); + if (TII->isSchedulingBoundary(MI, MBB, Fn)) { + Scheduler.Run(MBB, I, Current, CurrentCount); + Scheduler.EmitSchedule(); + Current = MI; + CurrentCount = Count - 1; + Scheduler.Observe(MI, CurrentCount); + } + I = MI; + --Count; + } + assert(Count == 0 && "Instruction count mismatch!"); + assert((MBB->begin() == Current || CurrentCount != 0) && + "Instruction count mismatch!"); + Scheduler.Run(MBB, MBB->begin(), Current, CurrentCount); + Scheduler.EmitSchedule(); - Scheduler.Run(); + // Clean up register live-range state. + Scheduler.FinishBlock(); - Scheduler.EmitSchedule(); + // Update register kills + Scheduler.FixupKills(MBB); } return true; } - -/// Schedule - Schedule the DAG using list scheduling. + +/// StartBlock - Initialize register live-range state for scheduling in +/// this block. +/// +void SchedulePostRATDList::StartBlock(MachineBasicBlock *BB) { + // Call the superclass. + ScheduleDAGInstrs::StartBlock(BB); + + // Reset the hazard recognizer and anti-dep breaker. + HazardRec->Reset(); + if (AntiDepBreak != NULL) + AntiDepBreak->StartBlock(BB); +} + +/// Schedule - Schedule the instruction range using list scheduling. +/// void SchedulePostRATDList::Schedule() { - DOUT << "********** List Scheduling **********\n"; - // Build the scheduling graph. - BuildSchedGraph(); + BuildSchedGraph(AA); + + if (AntiDepBreak != NULL) { + unsigned Broken = + AntiDepBreak->BreakAntiDependencies(SUnits, Begin, InsertPos, + InsertPosIndex, DbgValues); - if (EnableAntiDepBreaking) { - if (BreakAntiDependencies()) { + if (Broken != 0) { // We made changes. Update the dependency graph. // Theoretically we could update the graph in place: // When a live range is changed to use a different register, remove @@ -133,374 +320,139 @@ void SchedulePostRATDList::Schedule() { // that register, and add new anti-dependence and output-dependence // edges based on the next live range of the register. SUnits.clear(); - BuildSchedGraph(); + Sequence.clear(); + EntrySU = SUnit(); + ExitSU = SUnit(); + BuildSchedGraph(AA); + + NumFixedAnti += Broken; } } - AvailableQueue.initNodes(SUnits); + DEBUG(dbgs() << "********** List Scheduling **********\n"); + DEBUG(for (unsigned su = 0, e = SUnits.size(); su != e; ++su) + SUnits[su].dumpAll(this)); + AvailableQueue.initNodes(SUnits); ListScheduleTopDown(); - AvailableQueue.releaseState(); } -/// getInstrOperandRegClass - Return register class of the operand of an -/// instruction of the specified TargetInstrDesc. -static const TargetRegisterClass* -getInstrOperandRegClass(const TargetRegisterInfo *TRI, - const TargetInstrInfo *TII, const TargetInstrDesc &II, - unsigned Op) { - if (Op >= II.getNumOperands()) - return NULL; - if (II.OpInfo[Op].isLookupPtrRegClass()) - return TII->getPointerRegClass(); - return TRI->getRegClass(II.OpInfo[Op].RegClass); -} - -/// CriticalPathStep - Return the next SUnit after SU on the bottom-up -/// critical path. -static SDep *CriticalPathStep(SUnit *SU) { - SDep *Next = 0; - unsigned NextDepth = 0; - // Find the predecessor edge with the greatest depth. - for (SUnit::pred_iterator P = SU->Preds.begin(), PE = SU->Preds.end(); - P != PE; ++P) { - SUnit *PredSU = P->getSUnit(); - unsigned PredLatency = P->getLatency(); - unsigned PredTotalLatency = PredSU->getDepth() + PredLatency; - // In the case of a latency tie, prefer an anti-dependency edge over - // other types of edges. - if (NextDepth < PredTotalLatency || - (NextDepth == PredTotalLatency && P->getKind() == SDep::Anti)) { - NextDepth = PredTotalLatency; - Next = &*P; - } - } - return Next; +/// Observe - Update liveness information to account for the current +/// instruction, which will not be scheduled. +/// +void SchedulePostRATDList::Observe(MachineInstr *MI, unsigned Count) { + if (AntiDepBreak != NULL) + AntiDepBreak->Observe(MI, Count, InsertPosIndex); } -/// BreakAntiDependencies - Identifiy anti-dependencies along the critical path -/// of the ScheduleDAG and break them by renaming registers. +/// FinishBlock - Clean up register live-range state. /// -bool SchedulePostRATDList::BreakAntiDependencies() { - // The code below assumes that there is at least one instruction, - // so just duck out immediately if the block is empty. - if (BB->empty()) return false; +void SchedulePostRATDList::FinishBlock() { + if (AntiDepBreak != NULL) + AntiDepBreak->FinishBlock(); - // Find the node at the bottom of the critical path. - SUnit *Max = 0; - for (unsigned i = 0, e = SUnits.size(); i != e; ++i) { - SUnit *SU = &SUnits[i]; - if (!Max || SU->getDepth() + SU->Latency > Max->getDepth() + Max->Latency) - Max = SU; - } + // Call the superclass. + ScheduleDAGInstrs::FinishBlock(); +} - DOUT << "Critical path has total latency " - << (Max ? Max->getDepth() + Max->Latency : 0) << "\n"; - - // We'll be ignoring anti-dependencies on non-allocatable registers, because - // they may not be safe to break. - const BitVector AllocatableSet = TRI->getAllocatableSet(*MF); - - // Track progress along the critical path through the SUnit graph as we walk - // the instructions. - SUnit *CriticalPathSU = Max; - MachineInstr *CriticalPathMI = CriticalPathSU->getInstr(); - - // For live regs that are only used in one register class in a live range, - // the register class. If the register is not live, the corresponding value - // is null. If the register is live but used in multiple register classes, - // the corresponding value is -1 casted to a pointer. - const TargetRegisterClass * - Classes[TargetRegisterInfo::FirstVirtualRegister] = {}; - - // Map registers to all their references within a live range. - std::multimap RegRefs; - - // The index of the most recent kill (proceding bottom-up), or ~0u if - // the register is not live. - unsigned KillIndices[TargetRegisterInfo::FirstVirtualRegister]; - std::fill(KillIndices, array_endof(KillIndices), ~0u); - // The index of the most recent complete def (proceding bottom up), or ~0u if - // the register is live. - unsigned DefIndices[TargetRegisterInfo::FirstVirtualRegister]; - std::fill(DefIndices, array_endof(DefIndices), BB->size()); +/// StartBlockForKills - Initialize register live-range state for updating kills +/// +void SchedulePostRATDList::StartBlockForKills(MachineBasicBlock *BB) { + // Initialize the indices to indicate that no registers are live. + for (unsigned i = 0; i < TRI->getNumRegs(); ++i) + KillIndices[i] = ~0u; // Determine the live-out physregs for this block. - if (BB->back().getDesc().isReturn()) + if (!BB->empty() && BB->back().getDesc().isReturn()) { // In a return block, examine the function live-out regs. for (MachineRegisterInfo::liveout_iterator I = MRI.liveout_begin(), - E = MRI.liveout_end(); I != E; ++I) { + E = MRI.liveout_end(); I != E; ++I) { unsigned Reg = *I; - 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; - Classes[AliasReg] = reinterpret_cast(-1); - KillIndices[AliasReg] = BB->size(); - DefIndices[AliasReg] = ~0u; + // Repeat, for all subregs. + for (const unsigned *Subreg = TRI->getSubRegisters(Reg); + *Subreg; ++Subreg) { + KillIndices[*Subreg] = BB->size(); } } - else + } + else { // In a non-return block, examine the live-in regs of all successors. for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), - SE = BB->succ_end(); SI != SE; ++SI) + SE = BB->succ_end(); SI != SE; ++SI) { for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(), - E = (*SI)->livein_end(); I != E; ++I) { + E = (*SI)->livein_end(); I != E; ++I) { unsigned Reg = *I; - 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; - Classes[AliasReg] = reinterpret_cast(-1); - KillIndices[AliasReg] = BB->size(); - DefIndices[AliasReg] = ~0u; + // Repeat, for all subregs. + for (const unsigned *Subreg = TRI->getSubRegisters(Reg); + *Subreg; ++Subreg) { + KillIndices[*Subreg] = BB->size(); } } - - // Consider callee-saved registers as live-out, since we're running after - // prologue/epilogue insertion so there's no way to add additional - // saved registers. - // - // TODO: If the callee saves and restores these, then we can potentially - // use them between the save and the restore. To do that, we could scan - // the exit blocks to see which of these registers are defined. - // Alternatively, callee-saved registers that aren't saved and restored - // could be marked live-in in every block. - for (const unsigned *I = TRI->getCalleeSavedRegs(); *I; ++I) { - unsigned Reg = *I; - 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; - Classes[AliasReg] = reinterpret_cast(-1); - KillIndices[AliasReg] = BB->size(); - DefIndices[AliasReg] = ~0u; } } +} - // Consider this pattern: - // A = ... - // ... = A - // A = ... - // ... = A - // A = ... - // ... = A - // A = ... - // ... = A - // There are three anti-dependencies here, and without special care, - // we'd break all of them using the same register: - // A = ... - // ... = A - // B = ... - // ... = B - // B = ... - // ... = B - // B = ... - // ... = B - // because at each anti-dependence, B is the first register that - // isn't A which is free. This re-introduces anti-dependencies - // at all but one of the original anti-dependencies that we were - // trying to break. To avoid this, keep track of the most recent - // register that each register was replaced with, avoid avoid - // using it to repair an anti-dependence on the same register. - // This lets us produce this: - // A = ... - // ... = A - // B = ... - // ... = B - // C = ... - // ... = C - // B = ... - // ... = B - // This still has an anti-dependence on B, but at least it isn't on the - // original critical path. - // - // TODO: If we tracked more than one register here, we could potentially - // 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] = {}; - - // Attempt to break anti-dependence edges on the critical path. Walk the - // instructions from the bottom up, tracking information about liveness - // as we go to help determine which registers are available. - bool Changed = false; - unsigned Count = BB->size() - 1; - for (MachineBasicBlock::reverse_iterator I = BB->rbegin(), E = BB->rend(); - I != E; ++I, --Count) { - MachineInstr *MI = &*I; - - // After regalloc, IMPLICIT_DEF instructions aren't safe to treat as - // dependence-breaking. In the case of an INSERT_SUBREG, the IMPLICIT_DEF - // is left behind appearing to clobber the super-register, while the - // subregister needs to remain live. So we just ignore them. - if (MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) - continue; +bool SchedulePostRATDList::ToggleKillFlag(MachineInstr *MI, + MachineOperand &MO) { + // Setting kill flag... + if (!MO.isKill()) { + MO.setIsKill(true); + return false; + } - // Check if this instruction has a dependence on the critical path that - // is an anti-dependence that we may be able to break. If it is, set - // AntiDepReg to the non-zero register associated with the anti-dependence. - // - // We limit our attention to the critical path as a heuristic to avoid - // breaking anti-dependence edges that aren't going to significantly - // impact the overall schedule. There are a limited number of registers - // and we want to save them for the important edges. - // - // TODO: Instructions with multiple defs could have multiple - // anti-dependencies. The current code here only knows how to break one - // edge per instruction. Note that we'd have to be able to break all of - // the anti-dependencies in an instruction in order to be effective. - unsigned AntiDepReg = 0; - if (MI == CriticalPathMI) { - if (SDep *Edge = CriticalPathStep(CriticalPathSU)) { - SUnit *NextSU = Edge->getSUnit(); - - // Only consider anti-dependence edges. - if (Edge->getKind() == SDep::Anti) { - AntiDepReg = Edge->getReg(); - assert(AntiDepReg != 0 && "Anti-dependence on reg0?"); - // Don't break anti-dependencies on non-allocatable registers. - if (AllocatableSet.test(AntiDepReg)) { - // If the SUnit has other dependencies on the SUnit that it - // anti-depends on, don't bother breaking the anti-dependency - // since those edges would prevent such units from being - // scheduled past each other regardless. - // - // Also, if there are dependencies on other SUnits with the - // same register as the anti-dependency, don't attempt to - // break it. - for (SUnit::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 { - // We've reached the end of the critical path. - CriticalPathSU = 0; - CriticalPathMI = 0; - } + // If MO itself is live, clear the kill flag... + if (KillIndices[MO.getReg()] != ~0u) { + MO.setIsKill(false); + return false; + } + + // If any subreg of MO is live, then create an imp-def for that + // subreg and keep MO marked as killed. + MO.setIsKill(false); + bool AllDead = true; + const unsigned SuperReg = MO.getReg(); + for (const unsigned *Subreg = TRI->getSubRegisters(SuperReg); + *Subreg; ++Subreg) { + if (KillIndices[*Subreg] != ~0u) { + MI->addOperand(MachineOperand::CreateReg(*Subreg, + true /*IsDef*/, + true /*IsImp*/, + false /*IsKill*/, + false /*IsDead*/)); + AllDead = false; } + } - // Scan the register operands for this instruction and update - // Classes and RegRefs. - 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 = - getInstrOperandRegClass(TRI, TII, MI->getDesc(), i); - - // If this instruction has a use of AntiDepReg, breaking it - // is invalid. - if (MO.isUse() && AntiDepReg == Reg) - AntiDepReg = 0; - - // For now, only allow the register to be changed if its register - // class is consistent across all uses. - if (!Classes[Reg] && NewRC) - Classes[Reg] = NewRC; - else if (!NewRC || Classes[Reg] != NewRC) - Classes[Reg] = reinterpret_cast(-1); - - // Now check for aliases. - for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) { - // If an alias of the reg is used during the live range, give up. - // Note that this allows us to skip checking if AntiDepReg - // overlaps with any of the aliases, among other things. - unsigned AliasReg = *Alias; - if (Classes[AliasReg]) { - Classes[AliasReg] = reinterpret_cast(-1); - Classes[Reg] = reinterpret_cast(-1); - } - } + if(AllDead) + MO.setIsKill(true); + return false; +} - // If we're still willing to consider this register, note the reference. - if (Classes[Reg] != reinterpret_cast(-1)) - RegRefs.insert(std::make_pair(Reg, &MO)); - } +/// FixupKills - Fix the register kill flags, they may have been made +/// incorrect by instruction reordering. +/// +void SchedulePostRATDList::FixupKills(MachineBasicBlock *MBB) { + DEBUG(dbgs() << "Fixup kills for BB#" << MBB->getNumber() << '\n'); - // Determine AntiDepReg's register class, if it is live and is - // consistently used within a single class. - 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(-1)) - AntiDepReg = 0; - - // Look for a suitable register to use to break the anti-depenence. - // - // TODO: Instead of picking the first free register, consider which might - // be the best. - if (AntiDepReg != 0) { - for (TargetRegisterClass::iterator R = RC->allocation_order_begin(*MF), - RE = RC->allocation_order_end(*MF); R != RE; ++R) { - unsigned NewReg = *R; - // 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[AntiDepReg]) 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)) && - "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(-1) && - KillIndices[AntiDepReg] <= DefIndices[NewReg]) { - DOUT << "Breaking anti-dependence edge on " - << TRI->getName(AntiDepReg) - << " with " << RegRefs.count(AntiDepReg) << " references" - << " using " << TRI->getName(NewReg) << "!\n"; - - // 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); - - // We just went back in time and modified history; the - // liveness information for the anti-depenence reg is now - // inconsistent. Set the state as if it were dead. - Classes[NewReg] = Classes[AntiDepReg]; - DefIndices[NewReg] = DefIndices[AntiDepReg]; - KillIndices[NewReg] = KillIndices[AntiDepReg]; - - Classes[AntiDepReg] = 0; - DefIndices[AntiDepReg] = KillIndices[AntiDepReg]; - KillIndices[AntiDepReg] = ~0u; - - RegRefs.erase(AntiDepReg); - Changed = true; - LastNewReg[AntiDepReg] = NewReg; - break; - } - } - } + std::set killedRegs; + BitVector ReservedRegs = TRI->getReservedRegs(MF); + + StartBlockForKills(MBB); + + // Examine block from end to start... + unsigned Count = MBB->size(); + for (MachineBasicBlock::iterator I = MBB->end(), E = MBB->begin(); + I != E; --Count) { + MachineInstr *MI = --I; + if (MI->isDebugValue()) + continue; - // Update liveness. - // Proceding upwards, registers that are defed but not used in this - // instruction are now dead. + // Update liveness. Registers that are defed but not used in this + // instruction are now dead. Mark register and all subregs as they + // are completely defined. for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { MachineOperand &MO = MI->getOperand(i); if (!MO.isReg()) continue; @@ -508,65 +460,71 @@ bool SchedulePostRATDList::BreakAntiDependencies() { if (Reg == 0) continue; if (!MO.isDef()) continue; // Ignore two-addr defs. - if (MI->isRegReDefinedByTwoAddr(i)) continue; + if (MI->isRegTiedToUseOperand(i)) continue; - DefIndices[Reg] = Count; KillIndices[Reg] = ~0u; - Classes[Reg] = 0; - RegRefs.erase(Reg); - // Repeat, for all subregs. + + // Repeat for all subregs. for (const unsigned *Subreg = TRI->getSubRegisters(Reg); *Subreg; ++Subreg) { - unsigned SubregReg = *Subreg; - DefIndices[SubregReg] = Count; - KillIndices[SubregReg] = ~0u; - Classes[SubregReg] = 0; - RegRefs.erase(SubregReg); - } - // Conservatively mark super-registers as unusable. - for (const unsigned *Super = TRI->getSuperRegisters(Reg); - *Super; ++Super) { - unsigned SuperReg = *Super; - Classes[SuperReg] = reinterpret_cast(-1); + KillIndices[*Subreg] = ~0u; } } + + // Examine all used registers and set/clear kill flag. When a + // register is used multiple times we only set the kill flag on + // the first use. + killedRegs.clear(); for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { MachineOperand &MO = MI->getOperand(i); - if (!MO.isReg()) continue; + if (!MO.isReg() || !MO.isUse()) continue; unsigned Reg = MO.getReg(); - if (Reg == 0) continue; - if (!MO.isUse()) continue; + if ((Reg == 0) || ReservedRegs.test(Reg)) continue; + + bool kill = false; + if (killedRegs.find(Reg) == killedRegs.end()) { + kill = true; + // A register is not killed if any subregs are live... + for (const unsigned *Subreg = TRI->getSubRegisters(Reg); + *Subreg; ++Subreg) { + if (KillIndices[*Subreg] != ~0u) { + kill = false; + break; + } + } - const TargetRegisterClass *NewRC = - getInstrOperandRegClass(TRI, TII, MI->getDesc(), i); + // If subreg is not live, then register is killed if it became + // live in this instruction + if (kill) + kill = (KillIndices[Reg] == ~0u); + } - // For now, only allow the register to be changed if its register - // class is consistent across all uses. - if (!Classes[Reg] && NewRC) - Classes[Reg] = NewRC; - else if (!NewRC || Classes[Reg] != NewRC) - Classes[Reg] = reinterpret_cast(-1); + if (MO.isKill() != kill) { + DEBUG(dbgs() << "Fixing " << MO << " in "); + // Warning: ToggleKillFlag may invalidate MO. + ToggleKillFlag(MI, MO); + DEBUG(MI->dump()); + } - RegRefs.insert(std::make_pair(Reg, &MO)); + killedRegs.insert(Reg); + } - // It wasn't previously live but now it is, this is a kill. - if (KillIndices[Reg] == ~0u) { - KillIndices[Reg] = Count; - DefIndices[Reg] = ~0u; - } - // Repeat, for all aliases. - for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) { - unsigned AliasReg = *Alias; - if (KillIndices[AliasReg] == ~0u) { - KillIndices[AliasReg] = Count; - DefIndices[AliasReg] = ~0u; - } + // Mark any used register (that is not using undef) and subregs as + // now live... + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI->getOperand(i); + if (!MO.isReg() || !MO.isUse() || MO.isUndef()) continue; + unsigned Reg = MO.getReg(); + if ((Reg == 0) || ReservedRegs.test(Reg)) continue; + + KillIndices[Reg] = Count; + + for (const unsigned *Subreg = TRI->getSubRegisters(Reg); + *Subreg; ++Subreg) { + KillIndices[*Subreg] = Count; } } } - assert(Count == ~0u && "Count mismatch!"); - - return Changed; } //===----------------------------------------------------------------------===// @@ -577,24 +535,39 @@ bool SchedulePostRATDList::BreakAntiDependencies() { /// the PendingQueue if the count reaches zero. Also update its cycle bound. void SchedulePostRATDList::ReleaseSucc(SUnit *SU, SDep *SuccEdge) { SUnit *SuccSU = SuccEdge->getSUnit(); - --SuccSU->NumPredsLeft; - + #ifndef NDEBUG - if (SuccSU->NumPredsLeft < 0) { - cerr << "*** Scheduling failed! ***\n"; + if (SuccSU->NumPredsLeft == 0) { + dbgs() << "*** Scheduling failed! ***\n"; SuccSU->dump(this); - cerr << " has been released too many times!\n"; - assert(0); + dbgs() << " has been released too many times!\n"; + llvm_unreachable(0); } #endif - - // Compute how many cycles it will be before this actually becomes - // available. This is the max of the start time of all predecessors plus - // their latencies. - SuccSU->setDepthToAtLeast(SU->getDepth() + SuccEdge->getLatency()); - - if (SuccSU->NumPredsLeft == 0) { + --SuccSU->NumPredsLeft; + + // Standard scheduler algorithms will recompute the depth of the successor + // here as such: + // SuccSU->setDepthToAtLeast(SU->getDepth() + SuccEdge->getLatency()); + // + // However, we lazily compute node depth instead. Note that + // ScheduleNodeTopDown has already updated the depth of this node which causes + // all descendents to be marked dirty. Setting the successor depth explicitly + // here would cause depth to be recomputed for all its ancestors. If the + // successor is not yet ready (because of a transitively redundant edge) then + // this causes depth computation to be quadratic in the size of the DAG. + + // If all the node's predecessors are scheduled, this node is ready + // to be scheduled. Ignore the special ExitSU node. + if (SuccSU->NumPredsLeft == 0 && SuccSU != &ExitSU) PendingQueue.push_back(SuccSU); +} + +/// ReleaseSuccessors - Call ReleaseSucc on each of SU's successors. +void SchedulePostRATDList::ReleaseSuccessors(SUnit *SU) { + for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end(); + I != E; ++I) { + ReleaseSucc(SU, &*I); } } @@ -602,18 +575,15 @@ void SchedulePostRATDList::ReleaseSucc(SUnit *SU, SDep *SuccEdge) { /// count of its successors. If a successor pending count is zero, add it to /// the Available queue. void SchedulePostRATDList::ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle) { - DOUT << "*** Scheduling [" << CurCycle << "]: "; + DEBUG(dbgs() << "*** Scheduling [" << CurCycle << "]: "); DEBUG(SU->dump(this)); - + Sequence.push_back(SU); - assert(CurCycle >= SU->getDepth() && "Node scheduled above its depth!"); + assert(CurCycle >= SU->getDepth() && + "Node scheduled above its depth!"); SU->setDepthToAtLeast(CurCycle); - // Top down: release successors. - for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end(); - I != E; ++I) - ReleaseSucc(SU, &*I); - + ReleaseSuccessors(SU); SU->isScheduled = true; AvailableQueue.ScheduledNode(SU); } @@ -623,17 +593,32 @@ void SchedulePostRATDList::ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle) { void SchedulePostRATDList::ListScheduleTopDown() { unsigned CurCycle = 0; - // All leaves to Available queue. + // We're scheduling top-down but we're visiting the regions in + // bottom-up order, so we don't know the hazards at the start of a + // region. So assume no hazards (this should usually be ok as most + // blocks are a single region). + HazardRec->Reset(); + + // Release any successors of the special Entry node. + ReleaseSuccessors(&EntrySU); + + // Add all leaves to Available queue. for (unsigned i = 0, e = SUnits.size(); i != e; ++i) { // It is available if it has no predecessors. - if (SUnits[i].Preds.empty()) { + bool available = SUnits[i].Preds.empty(); + if (available) { AvailableQueue.push(&SUnits[i]); SUnits[i].isAvailable = true; } } - + + // In any cycle where we can't schedule any instructions, we must + // stall or emit a noop, depending on the target. + bool CycleHasInsts = false; + // While Available queue is not empty, grab the node with the highest // priority. If it is not ready put it back. Schedule the node. + std::vector NotReady; Sequence.reserve(SUnits.size()); while (!AvailableQueue.empty() || !PendingQueue.empty()) { // Check to see if any of the pending instructions are ready to issue. If @@ -649,29 +634,67 @@ void SchedulePostRATDList::ListScheduleTopDown() { } else if (PendingQueue[i]->getDepth() < MinDepth) MinDepth = PendingQueue[i]->getDepth(); } - - // If there are no instructions available, don't try to issue anything. - if (AvailableQueue.empty()) { - CurCycle = MinDepth != ~0u ? MinDepth : CurCycle + 1; - continue; + + DEBUG(dbgs() << "\n*** Examining Available\n"; AvailableQueue.dump(this)); + + SUnit *FoundSUnit = 0; + bool HasNoopHazards = false; + while (!AvailableQueue.empty()) { + SUnit *CurSUnit = AvailableQueue.pop(); + + ScheduleHazardRecognizer::HazardType HT = + HazardRec->getHazardType(CurSUnit, 0/*no stalls*/); + if (HT == ScheduleHazardRecognizer::NoHazard) { + FoundSUnit = CurSUnit; + break; + } + + // Remember if this is a noop hazard. + HasNoopHazards |= HT == ScheduleHazardRecognizer::NoopHazard; + + NotReady.push_back(CurSUnit); + } + + // Add the nodes that aren't ready back onto the available list. + if (!NotReady.empty()) { + AvailableQueue.push_all(NotReady); + NotReady.clear(); } - SUnit *FoundSUnit = AvailableQueue.pop(); - - // If we found a node to schedule, do it now. + // If we found a node to schedule... if (FoundSUnit) { + // ... schedule the node... ScheduleNodeTopDown(FoundSUnit, CurCycle); - - // If this is a pseudo-op node, we don't want to increment the current - // cycle. - if (FoundSUnit->Latency) // Don't increment CurCycle for pseudo-ops! - ++CurCycle; + HazardRec->EmitInstruction(FoundSUnit); + CycleHasInsts = true; + if (HazardRec->atIssueLimit()) { + DEBUG(dbgs() << "*** Max instructions per cycle " << CurCycle << '\n'); + HazardRec->AdvanceCycle(); + ++CurCycle; + CycleHasInsts = false; + } } else { - // Otherwise, we have a pipeline stall, but no other problem, just advance - // the current cycle and try again. - DOUT << "*** Advancing cycle, no work to do\n"; - ++NumStalls; + if (CycleHasInsts) { + DEBUG(dbgs() << "*** Finished cycle " << CurCycle << '\n'); + HazardRec->AdvanceCycle(); + } else if (!HasNoopHazards) { + // Otherwise, we have a pipeline stall, but no other problem, + // just advance the current cycle and try again. + DEBUG(dbgs() << "*** Stall in cycle " << CurCycle << '\n'); + HazardRec->AdvanceCycle(); + ++NumStalls; + } else { + // Otherwise, we have no instructions to issue and we have instructions + // that will fault if we don't do this right. This is the case for + // processors without pipeline interlocks and other cases. + DEBUG(dbgs() << "*** Emitting noop in cycle " << CurCycle << '\n'); + HazardRec->EmitNoop(); + Sequence.push_back(0); // NULL here means noop + ++NumNoops; + } + ++CurCycle; + CycleHasInsts = false; } } @@ -684,6 +707,6 @@ void SchedulePostRATDList::ListScheduleTopDown() { // Public Constructor Functions //===----------------------------------------------------------------------===// -FunctionPass *llvm::createPostRAScheduler() { - return new PostRAScheduler(); +FunctionPass *llvm::createPostRAScheduler(CodeGenOpt::Level OptLevel) { + return new PostRAScheduler(OptLevel); }