1 //===- MachineScheduler.h - MachineInstr Scheduling Pass --------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file provides an interface for customizing the standard MachineScheduler
11 // pass. Note that the entire pass may be replaced as follows:
13 // <Target>TargetMachine::createPassConfig(PassManagerBase &PM) {
14 // PM.substitutePass(&MachineSchedulerID, &CustomSchedulerPassID);
17 // The MachineScheduler pass is only responsible for choosing the regions to be
18 // scheduled. Targets can override the DAG builder and scheduler without
19 // replacing the pass as follows:
21 // ScheduleDAGInstrs *<Target>PassConfig::
22 // createMachineScheduler(MachineSchedContext *C) {
23 // return new CustomMachineScheduler(C);
26 // The default scheduler, ScheduleDAGMILive, builds the DAG and drives list
27 // scheduling while updating the instruction stream, register pressure, and live
28 // intervals. Most targets don't need to override the DAG builder and list
29 // scheduler, but subtargets that require custom scheduling heuristics may
30 // plugin an alternate MachineSchedStrategy. The strategy is responsible for
31 // selecting the highest priority node from the list:
33 // ScheduleDAGInstrs *<Target>PassConfig::
34 // createMachineScheduler(MachineSchedContext *C) {
35 // return new ScheduleDAGMILive(C, CustomStrategy(C));
38 // The DAG builder can also be customized in a sense by adding DAG mutations
39 // that will run after DAG building and before list scheduling. DAG mutations
40 // can adjust dependencies based on target-specific knowledge or add weak edges
43 // ScheduleDAGInstrs *<Target>PassConfig::
44 // createMachineScheduler(MachineSchedContext *C) {
45 // ScheduleDAGMI *DAG = createGenericSchedLive(C);
46 // DAG->addMutation(new CustomDAGMutation(...));
50 // A target that supports alternative schedulers can use the
51 // MachineSchedRegistry to allow command line selection. This can be done by
52 // implementing the following boilerplate:
54 // static ScheduleDAGInstrs *createCustomMachineSched(MachineSchedContext *C) {
55 // return new CustomMachineScheduler(C);
57 // static MachineSchedRegistry
58 // SchedCustomRegistry("custom", "Run my target's custom scheduler",
59 // createCustomMachineSched);
62 // Finally, subtargets that don't need to implement custom heuristics but would
63 // like to configure the GenericScheduler's policy for a given scheduler region,
64 // including scheduling direction and register pressure tracking policy, can do
67 // void <SubTarget>Subtarget::
68 // overrideSchedPolicy(MachineSchedPolicy &Policy,
69 // unsigned NumRegionInstrs) const {
70 // Policy.<Flag> = true;
73 //===----------------------------------------------------------------------===//
75 #ifndef LLVM_CODEGEN_MACHINESCHEDULER_H
76 #define LLVM_CODEGEN_MACHINESCHEDULER_H
78 #include "llvm/ADT/ArrayRef.h"
79 #include "llvm/ADT/BitVector.h"
80 #include "llvm/ADT/STLExtras.h"
81 #include "llvm/ADT/SmallVector.h"
82 #include "llvm/ADT/StringRef.h"
83 #include "llvm/ADT/Twine.h"
84 #include "llvm/Analysis/AliasAnalysis.h"
85 #include "llvm/CodeGen/MachineBasicBlock.h"
86 #include "llvm/CodeGen/MachinePassRegistry.h"
87 #include "llvm/CodeGen/RegisterPressure.h"
88 #include "llvm/CodeGen/ScheduleDAG.h"
89 #include "llvm/CodeGen/ScheduleDAGInstrs.h"
90 #include "llvm/CodeGen/ScheduleDAGMutation.h"
91 #include "llvm/CodeGen/TargetSchedule.h"
92 #include "llvm/Support/CommandLine.h"
93 #include "llvm/Support/ErrorHandling.h"
102 extern cl::opt<bool> ForceTopDown;
103 extern cl::opt<bool> ForceBottomUp;
106 class MachineDominatorTree;
107 class MachineFunction;
109 class MachineLoopInfo;
110 class RegisterClassInfo;
111 class SchedDFSResult;
112 class ScheduleHazardRecognizer;
113 class TargetInstrInfo;
114 class TargetPassConfig;
115 class TargetRegisterInfo;
117 /// MachineSchedContext provides enough context from the MachineScheduler pass
118 /// for the target to instantiate a scheduler.
119 struct MachineSchedContext {
120 MachineFunction *MF = nullptr;
121 const MachineLoopInfo *MLI = nullptr;
122 const MachineDominatorTree *MDT = nullptr;
123 const TargetPassConfig *PassConfig = nullptr;
124 AliasAnalysis *AA = nullptr;
125 LiveIntervals *LIS = nullptr;
127 RegisterClassInfo *RegClassInfo;
129 MachineSchedContext();
130 virtual ~MachineSchedContext();
133 /// MachineSchedRegistry provides a selection of available machine instruction
135 class MachineSchedRegistry : public MachinePassRegistryNode {
137 using ScheduleDAGCtor = ScheduleDAGInstrs *(*)(MachineSchedContext *);
139 // RegisterPassParser requires a (misnamed) FunctionPassCtor type.
140 using FunctionPassCtor = ScheduleDAGCtor;
142 static MachinePassRegistry Registry;
144 MachineSchedRegistry(const char *N, const char *D, ScheduleDAGCtor C)
145 : MachinePassRegistryNode(N, D, (MachinePassCtor)C) {
149 ~MachineSchedRegistry() { Registry.Remove(this); }
153 MachineSchedRegistry *getNext() const {
154 return (MachineSchedRegistry *)MachinePassRegistryNode::getNext();
157 static MachineSchedRegistry *getList() {
158 return (MachineSchedRegistry *)Registry.getList();
161 static void setListener(MachinePassRegistryListener *L) {
162 Registry.setListener(L);
168 /// Define a generic scheduling policy for targets that don't provide their own
169 /// MachineSchedStrategy. This can be overriden for each scheduling region
170 /// before building the DAG.
171 struct MachineSchedPolicy {
172 // Allow the scheduler to disable register pressure tracking.
173 bool ShouldTrackPressure = false;
174 /// Track LaneMasks to allow reordering of independent subregister writes
175 /// of the same vreg. \sa MachineSchedStrategy::shouldTrackLaneMasks()
176 bool ShouldTrackLaneMasks = false;
178 // Allow the scheduler to force top-down or bottom-up scheduling. If neither
179 // is true, the scheduler runs in both directions and converges.
180 bool OnlyTopDown = false;
181 bool OnlyBottomUp = false;
183 // Disable heuristic that tries to fetch nodes from long dependency chains
185 bool DisableLatencyHeuristic = false;
187 MachineSchedPolicy() = default;
190 /// MachineSchedStrategy - Interface to the scheduling algorithm used by
193 /// Initialization sequence:
194 /// initPolicy -> shouldTrackPressure -> initialize(DAG) -> registerRoots
195 class MachineSchedStrategy {
196 virtual void anchor();
199 virtual ~MachineSchedStrategy() = default;
201 /// Optionally override the per-region scheduling policy.
202 virtual void initPolicy(MachineBasicBlock::iterator Begin,
203 MachineBasicBlock::iterator End,
204 unsigned NumRegionInstrs) {}
206 virtual void dumpPolicy() const {}
208 /// Check if pressure tracking is needed before building the DAG and
209 /// initializing this strategy. Called after initPolicy.
210 virtual bool shouldTrackPressure() const { return true; }
212 /// Returns true if lanemasks should be tracked. LaneMask tracking is
213 /// necessary to reorder independent subregister defs for the same vreg.
214 /// This has to be enabled in combination with shouldTrackPressure().
215 virtual bool shouldTrackLaneMasks() const { return false; }
217 // If this method returns true, handling of the scheduling regions
218 // themselves (in case of a scheduling boundary in MBB) will be done
219 // beginning with the topmost region of MBB.
220 virtual bool doMBBSchedRegionsTopDown() const { return false; }
222 /// Initialize the strategy after building the DAG for a new region.
223 virtual void initialize(ScheduleDAGMI *DAG) = 0;
225 /// Tell the strategy that MBB is about to be processed.
226 virtual void enterMBB(MachineBasicBlock *MBB) {};
228 /// Tell the strategy that current MBB is done.
229 virtual void leaveMBB() {};
231 /// Notify this strategy that all roots have been released (including those
232 /// that depend on EntrySU or ExitSU).
233 virtual void registerRoots() {}
235 /// Pick the next node to schedule, or return NULL. Set IsTopNode to true to
236 /// schedule the node at the top of the unscheduled region. Otherwise it will
237 /// be scheduled at the bottom.
238 virtual SUnit *pickNode(bool &IsTopNode) = 0;
240 /// \brief Scheduler callback to notify that a new subtree is scheduled.
241 virtual void scheduleTree(unsigned SubtreeID) {}
243 /// Notify MachineSchedStrategy that ScheduleDAGMI has scheduled an
244 /// instruction and updated scheduled/remaining flags in the DAG nodes.
245 virtual void schedNode(SUnit *SU, bool IsTopNode) = 0;
247 /// When all predecessor dependencies have been resolved, free this node for
248 /// top-down scheduling.
249 virtual void releaseTopNode(SUnit *SU) = 0;
251 /// When all successor dependencies have been resolved, free this node for
252 /// bottom-up scheduling.
253 virtual void releaseBottomNode(SUnit *SU) = 0;
256 /// ScheduleDAGMI is an implementation of ScheduleDAGInstrs that simply
257 /// schedules machine instructions according to the given MachineSchedStrategy
258 /// without much extra book-keeping. This is the common functionality between
259 /// PreRA and PostRA MachineScheduler.
260 class ScheduleDAGMI : public ScheduleDAGInstrs {
264 std::unique_ptr<MachineSchedStrategy> SchedImpl;
266 /// Topo - A topological ordering for SUnits which permits fast IsReachable
267 /// and similar queries.
268 ScheduleDAGTopologicalSort Topo;
270 /// Ordered list of DAG postprocessing steps.
271 std::vector<std::unique_ptr<ScheduleDAGMutation>> Mutations;
273 /// The top of the unscheduled zone.
274 MachineBasicBlock::iterator CurrentTop;
276 /// The bottom of the unscheduled zone.
277 MachineBasicBlock::iterator CurrentBottom;
279 /// Record the next node in a scheduled cluster.
280 const SUnit *NextClusterPred = nullptr;
281 const SUnit *NextClusterSucc = nullptr;
284 /// The number of instructions scheduled so far. Used to cut off the
285 /// scheduler at the point determined by misched-cutoff.
286 unsigned NumInstrsScheduled = 0;
290 ScheduleDAGMI(MachineSchedContext *C, std::unique_ptr<MachineSchedStrategy> S,
291 bool RemoveKillFlags)
292 : ScheduleDAGInstrs(*C->MF, C->MLI, RemoveKillFlags), AA(C->AA),
293 LIS(C->LIS), SchedImpl(std::move(S)), Topo(SUnits, &ExitSU) {}
295 // Provide a vtable anchor
296 ~ScheduleDAGMI() override;
298 /// If this method returns true, handling of the scheduling regions
299 /// themselves (in case of a scheduling boundary in MBB) will be done
300 /// beginning with the topmost region of MBB.
301 bool doMBBSchedRegionsTopDown() const override {
302 return SchedImpl->doMBBSchedRegionsTopDown();
305 // Returns LiveIntervals instance for use in DAG mutators and such.
306 LiveIntervals *getLIS() const { return LIS; }
308 /// Return true if this DAG supports VReg liveness and RegPressure.
309 virtual bool hasVRegLiveness() const { return false; }
311 /// Add a postprocessing step to the DAG builder.
312 /// Mutations are applied in the order that they are added after normal DAG
313 /// building and before MachineSchedStrategy initialization.
315 /// ScheduleDAGMI takes ownership of the Mutation object.
316 void addMutation(std::unique_ptr<ScheduleDAGMutation> Mutation) {
318 Mutations.push_back(std::move(Mutation));
321 /// \brief True if an edge can be added from PredSU to SuccSU without creating
323 bool canAddEdge(SUnit *SuccSU, SUnit *PredSU);
325 /// \brief Add a DAG edge to the given SU with the given predecessor
328 /// \returns true if the edge may be added without creating a cycle OR if an
329 /// equivalent edge already existed (false indicates failure).
330 bool addEdge(SUnit *SuccSU, const SDep &PredDep);
332 MachineBasicBlock::iterator top() const { return CurrentTop; }
333 MachineBasicBlock::iterator bottom() const { return CurrentBottom; }
335 /// Implement the ScheduleDAGInstrs interface for handling the next scheduling
336 /// region. This covers all instructions in a block, while schedule() may only
338 void enterRegion(MachineBasicBlock *bb,
339 MachineBasicBlock::iterator begin,
340 MachineBasicBlock::iterator end,
341 unsigned regioninstrs) override;
343 /// Implement ScheduleDAGInstrs interface for scheduling a sequence of
344 /// reorderable instructions.
345 void schedule() override;
347 void startBlock(MachineBasicBlock *bb) override;
348 void finishBlock() override;
350 /// Change the position of an instruction within the basic block and update
351 /// live ranges and region boundary iterators.
352 void moveInstruction(MachineInstr *MI, MachineBasicBlock::iterator InsertPos);
354 const SUnit *getNextClusterPred() const { return NextClusterPred; }
356 const SUnit *getNextClusterSucc() const { return NextClusterSucc; }
358 void viewGraph(const Twine &Name, const Twine &Title) override;
359 void viewGraph() override;
362 // Top-Level entry points for the schedule() driver...
364 /// Apply each ScheduleDAGMutation step in order. This allows different
365 /// instances of ScheduleDAGMI to perform custom DAG postprocessing.
366 void postprocessDAG();
368 /// Release ExitSU predecessors and setup scheduler queues.
369 void initQueues(ArrayRef<SUnit*> TopRoots, ArrayRef<SUnit*> BotRoots);
371 /// Update scheduler DAG and queues after scheduling an instruction.
372 void updateQueues(SUnit *SU, bool IsTopNode);
374 /// Reinsert debug_values recorded in ScheduleDAGInstrs::DbgValues.
375 void placeDebugValues();
377 /// \brief dump the scheduled Sequence.
378 void dumpSchedule() const;
381 bool checkSchedLimit();
383 void findRootsAndBiasEdges(SmallVectorImpl<SUnit*> &TopRoots,
384 SmallVectorImpl<SUnit*> &BotRoots);
386 void releaseSucc(SUnit *SU, SDep *SuccEdge);
387 void releaseSuccessors(SUnit *SU);
388 void releasePred(SUnit *SU, SDep *PredEdge);
389 void releasePredecessors(SUnit *SU);
392 /// ScheduleDAGMILive is an implementation of ScheduleDAGInstrs that schedules
393 /// machine instructions while updating LiveIntervals and tracking regpressure.
394 class ScheduleDAGMILive : public ScheduleDAGMI {
396 RegisterClassInfo *RegClassInfo;
398 /// Information about DAG subtrees. If DFSResult is NULL, then SchedulerTrees
400 SchedDFSResult *DFSResult = nullptr;
401 BitVector ScheduledTrees;
403 MachineBasicBlock::iterator LiveRegionEnd;
405 /// Maps vregs to the SUnits of their uses in the current scheduling region.
406 VReg2SUnitMultiMap VRegUses;
408 // Map each SU to its summary of pressure changes. This array is updated for
409 // liveness during bottom-up scheduling. Top-down scheduling may proceed but
410 // has no affect on the pressure diffs.
411 PressureDiffs SUPressureDiffs;
413 /// Register pressure in this region computed by initRegPressure.
414 bool ShouldTrackPressure = false;
415 bool ShouldTrackLaneMasks = false;
416 IntervalPressure RegPressure;
417 RegPressureTracker RPTracker;
419 /// List of pressure sets that exceed the target's pressure limit before
420 /// scheduling, listed in increasing set ID order. Each pressure set is paired
421 /// with its max pressure in the currently scheduled regions.
422 std::vector<PressureChange> RegionCriticalPSets;
424 /// The top of the unscheduled zone.
425 IntervalPressure TopPressure;
426 RegPressureTracker TopRPTracker;
428 /// The bottom of the unscheduled zone.
429 IntervalPressure BotPressure;
430 RegPressureTracker BotRPTracker;
432 /// True if disconnected subregister components are already renamed.
433 /// The renaming is only done on demand if lane masks are tracked.
434 bool DisconnectedComponentsRenamed = false;
437 ScheduleDAGMILive(MachineSchedContext *C,
438 std::unique_ptr<MachineSchedStrategy> S)
439 : ScheduleDAGMI(C, std::move(S), /*RemoveKillFlags=*/false),
440 RegClassInfo(C->RegClassInfo), RPTracker(RegPressure),
441 TopRPTracker(TopPressure), BotRPTracker(BotPressure) {}
443 ~ScheduleDAGMILive() override;
445 /// Return true if this DAG supports VReg liveness and RegPressure.
446 bool hasVRegLiveness() const override { return true; }
448 /// \brief Return true if register pressure tracking is enabled.
449 bool isTrackingPressure() const { return ShouldTrackPressure; }
451 /// Get current register pressure for the top scheduled instructions.
452 const IntervalPressure &getTopPressure() const { return TopPressure; }
453 const RegPressureTracker &getTopRPTracker() const { return TopRPTracker; }
455 /// Get current register pressure for the bottom scheduled instructions.
456 const IntervalPressure &getBotPressure() const { return BotPressure; }
457 const RegPressureTracker &getBotRPTracker() const { return BotRPTracker; }
459 /// Get register pressure for the entire scheduling region before scheduling.
460 const IntervalPressure &getRegPressure() const { return RegPressure; }
462 const std::vector<PressureChange> &getRegionCriticalPSets() const {
463 return RegionCriticalPSets;
466 PressureDiff &getPressureDiff(const SUnit *SU) {
467 return SUPressureDiffs[SU->NodeNum];
470 /// Compute a DFSResult after DAG building is complete, and before any
471 /// queue comparisons.
472 void computeDFSResult();
474 /// Return a non-null DFS result if the scheduling strategy initialized it.
475 const SchedDFSResult *getDFSResult() const { return DFSResult; }
477 BitVector &getScheduledTrees() { return ScheduledTrees; }
479 /// Implement the ScheduleDAGInstrs interface for handling the next scheduling
480 /// region. This covers all instructions in a block, while schedule() may only
482 void enterRegion(MachineBasicBlock *bb,
483 MachineBasicBlock::iterator begin,
484 MachineBasicBlock::iterator end,
485 unsigned regioninstrs) override;
487 /// Implement ScheduleDAGInstrs interface for scheduling a sequence of
488 /// reorderable instructions.
489 void schedule() override;
491 /// Compute the cyclic critical path through the DAG.
492 unsigned computeCyclicCriticalPath();
495 // Top-Level entry points for the schedule() driver...
497 /// Call ScheduleDAGInstrs::buildSchedGraph with register pressure tracking
498 /// enabled. This sets up three trackers. RPTracker will cover the entire DAG
499 /// region, TopTracker and BottomTracker will be initialized to the top and
500 /// bottom of the DAG region without covereing any unscheduled instruction.
501 void buildDAGWithRegPressure();
503 /// Release ExitSU predecessors and setup scheduler queues. Re-position
504 /// the Top RP tracker in case the region beginning has changed.
505 void initQueues(ArrayRef<SUnit*> TopRoots, ArrayRef<SUnit*> BotRoots);
507 /// Move an instruction and update register pressure.
508 void scheduleMI(SUnit *SU, bool IsTopNode);
512 void initRegPressure();
514 void updatePressureDiffs(ArrayRef<RegisterMaskPair> LiveUses);
516 void updateScheduledPressure(const SUnit *SU,
517 const std::vector<unsigned> &NewMaxPressure);
519 void collectVRegUses(SUnit &SU);
522 //===----------------------------------------------------------------------===//
524 /// Helpers for implementing custom MachineSchedStrategy classes. These take
525 /// care of the book-keeping associated with list scheduling heuristics.
527 //===----------------------------------------------------------------------===//
529 /// ReadyQueue encapsulates vector of "ready" SUnits with basic convenience
530 /// methods for pushing and removing nodes. ReadyQueue's are uniquely identified
531 /// by an ID. SUnit::NodeQueueId is a mask of the ReadyQueues the SUnit is in.
533 /// This is a convenience class that may be used by implementations of
534 /// MachineSchedStrategy.
538 std::vector<SUnit*> Queue;
541 ReadyQueue(unsigned id, const Twine &name): ID(id), Name(name.str()) {}
543 unsigned getID() const { return ID; }
545 StringRef getName() const { return Name; }
547 // SU is in this queue if it's NodeQueueID is a superset of this ID.
548 bool isInQueue(SUnit *SU) const { return (SU->NodeQueueId & ID); }
550 bool empty() const { return Queue.empty(); }
552 void clear() { Queue.clear(); }
554 unsigned size() const { return Queue.size(); }
556 using iterator = std::vector<SUnit*>::iterator;
558 iterator begin() { return Queue.begin(); }
560 iterator end() { return Queue.end(); }
562 ArrayRef<SUnit*> elements() { return Queue; }
564 iterator find(SUnit *SU) { return llvm::find(Queue, SU); }
566 void push(SUnit *SU) {
568 SU->NodeQueueId |= ID;
571 iterator remove(iterator I) {
572 (*I)->NodeQueueId &= ~ID;
574 unsigned idx = I - Queue.begin();
576 return Queue.begin() + idx;
582 /// Summarize the unscheduled region.
583 struct SchedRemainder {
584 // Critical path through the DAG in expected latency.
585 unsigned CriticalPath;
586 unsigned CyclicCritPath;
588 // Scaled count of micro-ops left to schedule.
589 unsigned RemIssueCount;
591 bool IsAcyclicLatencyLimited;
593 // Unscheduled resources
594 SmallVector<unsigned, 16> RemainingCounts;
596 SchedRemainder() { reset(); }
602 IsAcyclicLatencyLimited = false;
603 RemainingCounts.clear();
606 void init(ScheduleDAGMI *DAG, const TargetSchedModel *SchedModel);
609 /// Each Scheduling boundary is associated with ready queues. It tracks the
610 /// current cycle in the direction of movement, and maintains the state
611 /// of "hazards" and other interlocks at the current cycle.
612 class SchedBoundary {
614 /// SUnit::NodeQueueId: 0 (none), 1 (top), 2 (bot), 3 (both)
621 ScheduleDAGMI *DAG = nullptr;
622 const TargetSchedModel *SchedModel = nullptr;
623 SchedRemainder *Rem = nullptr;
625 ReadyQueue Available;
628 ScheduleHazardRecognizer *HazardRec = nullptr;
631 /// True if the pending Q should be checked/updated before scheduling another
635 /// Number of cycles it takes to issue the instructions scheduled in this
636 /// zone. It is defined as: scheduled-micro-ops / issue-width + stalls.
640 /// Micro-ops issued in the current cycle
643 /// MinReadyCycle - Cycle of the soonest available instruction.
644 unsigned MinReadyCycle;
646 // The expected latency of the critical path in this scheduled zone.
647 unsigned ExpectedLatency;
649 // The latency of dependence chains leading into this zone.
650 // For each node scheduled bottom-up: DLat = max DLat, N.Depth.
651 // For each cycle scheduled: DLat -= 1.
652 unsigned DependentLatency;
654 /// Count the scheduled (issued) micro-ops that can be retired by
655 /// time=CurrCycle assuming the first scheduled instr is retired at time=0.
656 unsigned RetiredMOps;
658 // Count scheduled resources that have been executed. Resources are
659 // considered executed if they become ready in the time that it takes to
660 // saturate any resource including the one in question. Counts are scaled
661 // for direct comparison with other resources. Counts can be compared with
662 // MOps * getMicroOpFactor and Latency * getLatencyFactor.
663 SmallVector<unsigned, 16> ExecutedResCounts;
665 /// Cache the max count for a single resource.
666 unsigned MaxExecutedResCount;
668 // Cache the critical resources ID in this scheduled zone.
669 unsigned ZoneCritResIdx;
671 // Is the scheduled region resource limited vs. latency limited.
672 bool IsResourceLimited;
674 // Record the highest cycle at which each resource has been reserved by a
675 // scheduled instruction.
676 SmallVector<unsigned, 16> ReservedCycles;
679 // Remember the greatest possible stall as an upper bound on the number of
680 // times we should retry the pending queue because of a hazard.
681 unsigned MaxObservedStall;
685 /// Pending queues extend the ready queues with the same ID and the
687 SchedBoundary(unsigned ID, const Twine &Name):
688 Available(ID, Name+".A"), Pending(ID << LogMaxQID, Name+".P") {
696 void init(ScheduleDAGMI *dag, const TargetSchedModel *smodel,
697 SchedRemainder *rem);
700 return Available.getID() == TopQID;
703 /// Number of cycles to issue the instructions scheduled in this zone.
704 unsigned getCurrCycle() const { return CurrCycle; }
706 /// Micro-ops issued in the current cycle
707 unsigned getCurrMOps() const { return CurrMOps; }
709 // The latency of dependence chains leading into this zone.
710 unsigned getDependentLatency() const { return DependentLatency; }
712 /// Get the number of latency cycles "covered" by the scheduled
713 /// instructions. This is the larger of the critical path within the zone
714 /// and the number of cycles required to issue the instructions.
715 unsigned getScheduledLatency() const {
716 return std::max(ExpectedLatency, CurrCycle);
719 unsigned getUnscheduledLatency(SUnit *SU) const {
720 return isTop() ? SU->getHeight() : SU->getDepth();
723 unsigned getResourceCount(unsigned ResIdx) const {
724 return ExecutedResCounts[ResIdx];
727 /// Get the scaled count of scheduled micro-ops and resources, including
728 /// executed resources.
729 unsigned getCriticalCount() const {
731 return RetiredMOps * SchedModel->getMicroOpFactor();
732 return getResourceCount(ZoneCritResIdx);
735 /// Get a scaled count for the minimum execution time of the scheduled
736 /// micro-ops that are ready to execute by getExecutedCount. Notice the
738 unsigned getExecutedCount() const {
739 return std::max(CurrCycle * SchedModel->getLatencyFactor(),
740 MaxExecutedResCount);
743 unsigned getZoneCritResIdx() const { return ZoneCritResIdx; }
745 // Is the scheduled region resource limited vs. latency limited.
746 bool isResourceLimited() const { return IsResourceLimited; }
748 /// Get the difference between the given SUnit's ready time and the current
750 unsigned getLatencyStallCycles(SUnit *SU);
752 unsigned getNextResourceCycle(unsigned PIdx, unsigned Cycles);
754 bool checkHazard(SUnit *SU);
756 unsigned findMaxLatency(ArrayRef<SUnit*> ReadySUs);
758 unsigned getOtherResourceCount(unsigned &OtherCritIdx);
760 void releaseNode(SUnit *SU, unsigned ReadyCycle);
762 void bumpCycle(unsigned NextCycle);
764 void incExecutedResources(unsigned PIdx, unsigned Count);
766 unsigned countResource(unsigned PIdx, unsigned Cycles, unsigned ReadyCycle);
768 void bumpNode(SUnit *SU);
770 void releasePending();
772 void removeReady(SUnit *SU);
774 /// Call this before applying any other heuristics to the Available queue.
775 /// Updates the Available/Pending Q's if necessary and returns the single
776 /// available instruction, or NULL if there are multiple candidates.
777 SUnit *pickOnlyChoice();
779 void dumpScheduledState() const;
782 /// Base class for GenericScheduler. This class maintains information about
783 /// scheduling candidates based on TargetSchedModel making it easy to implement
784 /// heuristics for either preRA or postRA scheduling.
785 class GenericSchedulerBase : public MachineSchedStrategy {
787 /// Represent the type of SchedCandidate found within a single queue.
788 /// pickNodeBidirectional depends on these listed by decreasing priority.
789 enum CandReason : uint8_t {
790 NoCand, Only1, PhysRegCopy, RegExcess, RegCritical, Stall, Cluster, Weak,
791 RegMax, ResourceReduce, ResourceDemand, BotHeightReduce, BotPathReduce,
792 TopDepthReduce, TopPathReduce, NextDefUse, NodeOrder};
795 static const char *getReasonStr(GenericSchedulerBase::CandReason Reason);
798 /// Policy for scheduling the next instruction in the candidate's zone.
800 bool ReduceLatency = false;
801 unsigned ReduceResIdx = 0;
802 unsigned DemandResIdx = 0;
804 CandPolicy() = default;
806 bool operator==(const CandPolicy &RHS) const {
807 return ReduceLatency == RHS.ReduceLatency &&
808 ReduceResIdx == RHS.ReduceResIdx &&
809 DemandResIdx == RHS.DemandResIdx;
811 bool operator!=(const CandPolicy &RHS) const {
812 return !(*this == RHS);
816 /// Status of an instruction's critical resource consumption.
817 struct SchedResourceDelta {
818 // Count critical resources in the scheduled region required by SU.
819 unsigned CritResources = 0;
821 // Count critical resources from another region consumed by SU.
822 unsigned DemandedResources = 0;
824 SchedResourceDelta() = default;
826 bool operator==(const SchedResourceDelta &RHS) const {
827 return CritResources == RHS.CritResources
828 && DemandedResources == RHS.DemandedResources;
830 bool operator!=(const SchedResourceDelta &RHS) const {
831 return !operator==(RHS);
835 /// Store the state used by GenericScheduler heuristics, required for the
836 /// lifetime of one invocation of pickNode().
837 struct SchedCandidate {
840 // The best SUnit candidate.
843 // The reason for this candidate.
846 // Whether this candidate should be scheduled at top/bottom.
849 // Register pressure values for the best candidate.
850 RegPressureDelta RPDelta;
852 // Critical resource consumption of the best candidate.
853 SchedResourceDelta ResDelta;
855 SchedCandidate() { reset(CandPolicy()); }
856 SchedCandidate(const CandPolicy &Policy) { reset(Policy); }
858 void reset(const CandPolicy &NewPolicy) {
863 RPDelta = RegPressureDelta();
864 ResDelta = SchedResourceDelta();
867 bool isValid() const { return SU; }
869 // Copy the status of another candidate without changing policy.
870 void setBest(SchedCandidate &Best) {
871 assert(Best.Reason != NoCand && "uninitialized Sched candidate");
873 Reason = Best.Reason;
875 RPDelta = Best.RPDelta;
876 ResDelta = Best.ResDelta;
879 void initResourceDelta(const ScheduleDAGMI *DAG,
880 const TargetSchedModel *SchedModel);
884 const MachineSchedContext *Context;
885 const TargetSchedModel *SchedModel = nullptr;
886 const TargetRegisterInfo *TRI = nullptr;
890 GenericSchedulerBase(const MachineSchedContext *C) : Context(C) {}
892 void setPolicy(CandPolicy &Policy, bool IsPostRA, SchedBoundary &CurrZone,
893 SchedBoundary *OtherZone);
896 void traceCandidate(const SchedCandidate &Cand);
900 /// GenericScheduler shrinks the unscheduled zone using heuristics to balance
902 class GenericScheduler : public GenericSchedulerBase {
904 GenericScheduler(const MachineSchedContext *C):
905 GenericSchedulerBase(C), Top(SchedBoundary::TopQID, "TopQ"),
906 Bot(SchedBoundary::BotQID, "BotQ") {}
908 void initPolicy(MachineBasicBlock::iterator Begin,
909 MachineBasicBlock::iterator End,
910 unsigned NumRegionInstrs) override;
912 void dumpPolicy() const override;
914 bool shouldTrackPressure() const override {
915 return RegionPolicy.ShouldTrackPressure;
918 bool shouldTrackLaneMasks() const override {
919 return RegionPolicy.ShouldTrackLaneMasks;
922 void initialize(ScheduleDAGMI *dag) override;
924 SUnit *pickNode(bool &IsTopNode) override;
926 void schedNode(SUnit *SU, bool IsTopNode) override;
928 void releaseTopNode(SUnit *SU) override {
932 Top.releaseNode(SU, SU->TopReadyCycle);
933 TopCand.SU = nullptr;
936 void releaseBottomNode(SUnit *SU) override {
940 Bot.releaseNode(SU, SU->BotReadyCycle);
941 BotCand.SU = nullptr;
944 void registerRoots() override;
947 ScheduleDAGMILive *DAG = nullptr;
949 MachineSchedPolicy RegionPolicy;
951 // State of the top and bottom scheduled instruction boundaries.
955 /// Candidate last picked from Top boundary.
956 SchedCandidate TopCand;
957 /// Candidate last picked from Bot boundary.
958 SchedCandidate BotCand;
960 void checkAcyclicLatency();
962 void initCandidate(SchedCandidate &Cand, SUnit *SU, bool AtTop,
963 const RegPressureTracker &RPTracker,
964 RegPressureTracker &TempTracker);
966 void tryCandidate(SchedCandidate &Cand,
967 SchedCandidate &TryCand,
968 SchedBoundary *Zone);
970 SUnit *pickNodeBidirectional(bool &IsTopNode);
972 void pickNodeFromQueue(SchedBoundary &Zone,
973 const CandPolicy &ZonePolicy,
974 const RegPressureTracker &RPTracker,
975 SchedCandidate &Candidate);
977 void reschedulePhysRegCopies(SUnit *SU, bool isTop);
980 /// PostGenericScheduler - Interface to the scheduling algorithm used by
983 /// Callbacks from ScheduleDAGMI:
984 /// initPolicy -> initialize(DAG) -> registerRoots -> pickNode ...
985 class PostGenericScheduler : public GenericSchedulerBase {
988 SmallVector<SUnit*, 8> BotRoots;
991 PostGenericScheduler(const MachineSchedContext *C):
992 GenericSchedulerBase(C), Top(SchedBoundary::TopQID, "TopQ") {}
994 ~PostGenericScheduler() override = default;
996 void initPolicy(MachineBasicBlock::iterator Begin,
997 MachineBasicBlock::iterator End,
998 unsigned NumRegionInstrs) override {
999 /* no configurable policy */
1002 /// PostRA scheduling does not track pressure.
1003 bool shouldTrackPressure() const override { return false; }
1005 void initialize(ScheduleDAGMI *Dag) override;
1007 void registerRoots() override;
1009 SUnit *pickNode(bool &IsTopNode) override;
1011 void scheduleTree(unsigned SubtreeID) override {
1012 llvm_unreachable("PostRA scheduler does not support subtree analysis.");
1015 void schedNode(SUnit *SU, bool IsTopNode) override;
1017 void releaseTopNode(SUnit *SU) override {
1018 if (SU->isScheduled)
1020 Top.releaseNode(SU, SU->TopReadyCycle);
1023 // Only called for roots.
1024 void releaseBottomNode(SUnit *SU) override {
1025 BotRoots.push_back(SU);
1029 void tryCandidate(SchedCandidate &Cand, SchedCandidate &TryCand);
1031 void pickNodeFromQueue(SchedCandidate &Cand);
1034 /// Create the standard converging machine scheduler. This will be used as the
1035 /// default scheduler if the target does not set a default.
1036 /// Adds default DAG mutations.
1037 ScheduleDAGMILive *createGenericSchedLive(MachineSchedContext *C);
1039 /// Create a generic scheduler with no vreg liveness or DAG mutation passes.
1040 ScheduleDAGMI *createGenericSchedPostRA(MachineSchedContext *C);
1042 std::unique_ptr<ScheduleDAGMutation>
1043 createLoadClusterDAGMutation(const TargetInstrInfo *TII,
1044 const TargetRegisterInfo *TRI);
1046 std::unique_ptr<ScheduleDAGMutation>
1047 createStoreClusterDAGMutation(const TargetInstrInfo *TII,
1048 const TargetRegisterInfo *TRI);
1050 std::unique_ptr<ScheduleDAGMutation>
1051 createCopyConstrainDAGMutation(const TargetInstrInfo *TII,
1052 const TargetRegisterInfo *TRI);
1054 } // end namespace llvm
1056 #endif // LLVM_CODEGEN_MACHINESCHEDULER_H