1 //===- MachineScheduler.cpp - Machine Instruction Scheduler ---------------===//
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 // MachineScheduler schedules machine instructions after phi elimination. It
11 // preserves LiveIntervals so it can be invoked before register allocation.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/CodeGen/MachineScheduler.h"
16 #include "llvm/ADT/PriorityQueue.h"
17 #include "llvm/Analysis/AliasAnalysis.h"
18 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
19 #include "llvm/CodeGen/MachineDominators.h"
20 #include "llvm/CodeGen/MachineLoopInfo.h"
21 #include "llvm/CodeGen/MachineRegisterInfo.h"
22 #include "llvm/CodeGen/Passes.h"
23 #include "llvm/CodeGen/RegisterClassInfo.h"
24 #include "llvm/CodeGen/ScheduleDFS.h"
25 #include "llvm/CodeGen/ScheduleHazardRecognizer.h"
26 #include "llvm/Support/CommandLine.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/GraphWriter.h"
30 #include "llvm/Support/raw_ostream.h"
31 #include "llvm/Target/TargetInstrInfo.h"
36 #define DEBUG_TYPE "misched"
39 cl::opt<bool> ForceTopDown("misched-topdown", cl::Hidden,
40 cl::desc("Force top-down list scheduling"));
41 cl::opt<bool> ForceBottomUp("misched-bottomup", cl::Hidden,
42 cl::desc("Force bottom-up list scheduling"));
44 DumpCriticalPathLength("misched-dcpl", cl::Hidden,
45 cl::desc("Print critical path length to stdout"));
49 static cl::opt<bool> ViewMISchedDAGs("view-misched-dags", cl::Hidden,
50 cl::desc("Pop up a window to show MISched dags after they are processed"));
52 /// In some situations a few uninteresting nodes depend on nearly all other
53 /// nodes in the graph, provide a cutoff to hide them.
54 static cl::opt<unsigned> ViewMISchedCutoff("view-misched-cutoff", cl::Hidden,
55 cl::desc("Hide nodes with more predecessor/successor than cutoff"));
57 static cl::opt<unsigned> MISchedCutoff("misched-cutoff", cl::Hidden,
58 cl::desc("Stop scheduling after N instructions"), cl::init(~0U));
60 static cl::opt<std::string> SchedOnlyFunc("misched-only-func", cl::Hidden,
61 cl::desc("Only schedule this function"));
62 static cl::opt<unsigned> SchedOnlyBlock("misched-only-block", cl::Hidden,
63 cl::desc("Only schedule this MBB#"));
65 static bool ViewMISchedDAGs = false;
68 static cl::opt<bool> EnableRegPressure("misched-regpressure", cl::Hidden,
69 cl::desc("Enable register pressure scheduling."), cl::init(true));
71 static cl::opt<bool> EnableCyclicPath("misched-cyclicpath", cl::Hidden,
72 cl::desc("Enable cyclic critical path analysis."), cl::init(true));
74 static cl::opt<bool> EnableLoadCluster("misched-cluster", cl::Hidden,
75 cl::desc("Enable load clustering."), cl::init(true));
77 // Experimental heuristics
78 static cl::opt<bool> EnableMacroFusion("misched-fusion", cl::Hidden,
79 cl::desc("Enable scheduling for macro fusion."), cl::init(true));
81 static cl::opt<bool> VerifyScheduling("verify-misched", cl::Hidden,
82 cl::desc("Verify machine instrs before and after machine scheduling"));
84 // DAG subtrees must have at least this many nodes.
85 static const unsigned MinSubtreeSize = 8;
87 // Pin the vtables to this file.
88 void MachineSchedStrategy::anchor() {}
89 void ScheduleDAGMutation::anchor() {}
91 //===----------------------------------------------------------------------===//
92 // Machine Instruction Scheduling Pass and Registry
93 //===----------------------------------------------------------------------===//
95 MachineSchedContext::MachineSchedContext():
96 MF(nullptr), MLI(nullptr), MDT(nullptr), PassConfig(nullptr), AA(nullptr), LIS(nullptr) {
97 RegClassInfo = new RegisterClassInfo();
100 MachineSchedContext::~MachineSchedContext() {
105 /// Base class for a machine scheduler class that can run at any point.
106 class MachineSchedulerBase : public MachineSchedContext,
107 public MachineFunctionPass {
109 MachineSchedulerBase(char &ID): MachineFunctionPass(ID) {}
111 void print(raw_ostream &O, const Module* = nullptr) const override;
114 void scheduleRegions(ScheduleDAGInstrs &Scheduler, bool FixKillFlags);
117 /// MachineScheduler runs after coalescing and before register allocation.
118 class MachineScheduler : public MachineSchedulerBase {
122 void getAnalysisUsage(AnalysisUsage &AU) const override;
124 bool runOnMachineFunction(MachineFunction&) override;
126 static char ID; // Class identification, replacement for typeinfo
129 ScheduleDAGInstrs *createMachineScheduler();
132 /// PostMachineScheduler runs after shortly before code emission.
133 class PostMachineScheduler : public MachineSchedulerBase {
135 PostMachineScheduler();
137 void getAnalysisUsage(AnalysisUsage &AU) const override;
139 bool runOnMachineFunction(MachineFunction&) override;
141 static char ID; // Class identification, replacement for typeinfo
144 ScheduleDAGInstrs *createPostMachineScheduler();
148 char MachineScheduler::ID = 0;
150 char &llvm::MachineSchedulerID = MachineScheduler::ID;
152 INITIALIZE_PASS_BEGIN(MachineScheduler, "machine-scheduler",
153 "Machine Instruction Scheduler", false, false)
154 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
155 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
156 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
157 INITIALIZE_PASS_END(MachineScheduler, "machine-scheduler",
158 "Machine Instruction Scheduler", false, false)
160 MachineScheduler::MachineScheduler()
161 : MachineSchedulerBase(ID) {
162 initializeMachineSchedulerPass(*PassRegistry::getPassRegistry());
165 void MachineScheduler::getAnalysisUsage(AnalysisUsage &AU) const {
166 AU.setPreservesCFG();
167 AU.addRequiredID(MachineDominatorsID);
168 AU.addRequired<MachineLoopInfo>();
169 AU.addRequired<AAResultsWrapperPass>();
170 AU.addRequired<TargetPassConfig>();
171 AU.addRequired<SlotIndexes>();
172 AU.addPreserved<SlotIndexes>();
173 AU.addRequired<LiveIntervals>();
174 AU.addPreserved<LiveIntervals>();
175 MachineFunctionPass::getAnalysisUsage(AU);
178 char PostMachineScheduler::ID = 0;
180 char &llvm::PostMachineSchedulerID = PostMachineScheduler::ID;
182 INITIALIZE_PASS(PostMachineScheduler, "postmisched",
183 "PostRA Machine Instruction Scheduler", false, false)
185 PostMachineScheduler::PostMachineScheduler()
186 : MachineSchedulerBase(ID) {
187 initializePostMachineSchedulerPass(*PassRegistry::getPassRegistry());
190 void PostMachineScheduler::getAnalysisUsage(AnalysisUsage &AU) const {
191 AU.setPreservesCFG();
192 AU.addRequiredID(MachineDominatorsID);
193 AU.addRequired<MachineLoopInfo>();
194 AU.addRequired<TargetPassConfig>();
195 MachineFunctionPass::getAnalysisUsage(AU);
198 MachinePassRegistry MachineSchedRegistry::Registry;
200 /// A dummy default scheduler factory indicates whether the scheduler
201 /// is overridden on the command line.
202 static ScheduleDAGInstrs *useDefaultMachineSched(MachineSchedContext *C) {
206 /// MachineSchedOpt allows command line selection of the scheduler.
207 static cl::opt<MachineSchedRegistry::ScheduleDAGCtor, false,
208 RegisterPassParser<MachineSchedRegistry> >
209 MachineSchedOpt("misched",
210 cl::init(&useDefaultMachineSched), cl::Hidden,
211 cl::desc("Machine instruction scheduler to use"));
213 static MachineSchedRegistry
214 DefaultSchedRegistry("default", "Use the target's default scheduler choice.",
215 useDefaultMachineSched);
217 static cl::opt<bool> EnableMachineSched(
219 cl::desc("Enable the machine instruction scheduling pass."), cl::init(true),
222 /// Forward declare the standard machine scheduler. This will be used as the
223 /// default scheduler if the target does not set a default.
224 static ScheduleDAGInstrs *createGenericSchedLive(MachineSchedContext *C);
225 static ScheduleDAGInstrs *createGenericSchedPostRA(MachineSchedContext *C);
227 /// Decrement this iterator until reaching the top or a non-debug instr.
228 static MachineBasicBlock::const_iterator
229 priorNonDebug(MachineBasicBlock::const_iterator I,
230 MachineBasicBlock::const_iterator Beg) {
231 assert(I != Beg && "reached the top of the region, cannot decrement");
233 if (!I->isDebugValue())
239 /// Non-const version.
240 static MachineBasicBlock::iterator
241 priorNonDebug(MachineBasicBlock::iterator I,
242 MachineBasicBlock::const_iterator Beg) {
243 return const_cast<MachineInstr*>(
244 &*priorNonDebug(MachineBasicBlock::const_iterator(I), Beg));
247 /// If this iterator is a debug value, increment until reaching the End or a
248 /// non-debug instruction.
249 static MachineBasicBlock::const_iterator
250 nextIfDebug(MachineBasicBlock::const_iterator I,
251 MachineBasicBlock::const_iterator End) {
252 for(; I != End; ++I) {
253 if (!I->isDebugValue())
259 /// Non-const version.
260 static MachineBasicBlock::iterator
261 nextIfDebug(MachineBasicBlock::iterator I,
262 MachineBasicBlock::const_iterator End) {
263 // Cast the return value to nonconst MachineInstr, then cast to an
264 // instr_iterator, which does not check for null, finally return a
266 return MachineBasicBlock::instr_iterator(
267 const_cast<MachineInstr*>(
268 &*nextIfDebug(MachineBasicBlock::const_iterator(I), End)));
271 /// Instantiate a ScheduleDAGInstrs that will be owned by the caller.
272 ScheduleDAGInstrs *MachineScheduler::createMachineScheduler() {
273 // Select the scheduler, or set the default.
274 MachineSchedRegistry::ScheduleDAGCtor Ctor = MachineSchedOpt;
275 if (Ctor != useDefaultMachineSched)
278 // Get the default scheduler set by the target for this function.
279 ScheduleDAGInstrs *Scheduler = PassConfig->createMachineScheduler(this);
283 // Default to GenericScheduler.
284 return createGenericSchedLive(this);
287 /// Instantiate a ScheduleDAGInstrs for PostRA scheduling that will be owned by
288 /// the caller. We don't have a command line option to override the postRA
289 /// scheduler. The Target must configure it.
290 ScheduleDAGInstrs *PostMachineScheduler::createPostMachineScheduler() {
291 // Get the postRA scheduler set by the target for this function.
292 ScheduleDAGInstrs *Scheduler = PassConfig->createPostMachineScheduler(this);
296 // Default to GenericScheduler.
297 return createGenericSchedPostRA(this);
300 /// Top-level MachineScheduler pass driver.
302 /// Visit blocks in function order. Divide each block into scheduling regions
303 /// and visit them bottom-up. Visiting regions bottom-up is not required, but is
304 /// consistent with the DAG builder, which traverses the interior of the
305 /// scheduling regions bottom-up.
307 /// This design avoids exposing scheduling boundaries to the DAG builder,
308 /// simplifying the DAG builder's support for "special" target instructions.
309 /// At the same time the design allows target schedulers to operate across
310 /// scheduling boundaries, for example to bundle the boudary instructions
311 /// without reordering them. This creates complexity, because the target
312 /// scheduler must update the RegionBegin and RegionEnd positions cached by
313 /// ScheduleDAGInstrs whenever adding or removing instructions. A much simpler
314 /// design would be to split blocks at scheduling boundaries, but LLVM has a
315 /// general bias against block splitting purely for implementation simplicity.
316 bool MachineScheduler::runOnMachineFunction(MachineFunction &mf) {
317 if (EnableMachineSched.getNumOccurrences()) {
318 if (!EnableMachineSched)
320 } else if (!mf.getSubtarget().enableMachineScheduler())
323 DEBUG(dbgs() << "Before MISched:\n"; mf.print(dbgs()));
325 // Initialize the context of the pass.
327 MLI = &getAnalysis<MachineLoopInfo>();
328 MDT = &getAnalysis<MachineDominatorTree>();
329 PassConfig = &getAnalysis<TargetPassConfig>();
330 AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
332 LIS = &getAnalysis<LiveIntervals>();
334 if (VerifyScheduling) {
336 MF->verify(this, "Before machine scheduling.");
338 RegClassInfo->runOnMachineFunction(*MF);
340 // Instantiate the selected scheduler for this target, function, and
341 // optimization level.
342 std::unique_ptr<ScheduleDAGInstrs> Scheduler(createMachineScheduler());
343 scheduleRegions(*Scheduler, false);
346 if (VerifyScheduling)
347 MF->verify(this, "After machine scheduling.");
351 bool PostMachineScheduler::runOnMachineFunction(MachineFunction &mf) {
352 if (skipOptnoneFunction(*mf.getFunction()))
355 if (!mf.getSubtarget().enablePostRAScheduler()) {
356 DEBUG(dbgs() << "Subtarget disables post-MI-sched.\n");
359 DEBUG(dbgs() << "Before post-MI-sched:\n"; mf.print(dbgs()));
361 // Initialize the context of the pass.
363 PassConfig = &getAnalysis<TargetPassConfig>();
365 if (VerifyScheduling)
366 MF->verify(this, "Before post machine scheduling.");
368 // Instantiate the selected scheduler for this target, function, and
369 // optimization level.
370 std::unique_ptr<ScheduleDAGInstrs> Scheduler(createPostMachineScheduler());
371 scheduleRegions(*Scheduler, true);
373 if (VerifyScheduling)
374 MF->verify(this, "After post machine scheduling.");
378 /// Return true of the given instruction should not be included in a scheduling
381 /// MachineScheduler does not currently support scheduling across calls. To
382 /// handle calls, the DAG builder needs to be modified to create register
383 /// anti/output dependencies on the registers clobbered by the call's regmask
384 /// operand. In PreRA scheduling, the stack pointer adjustment already prevents
385 /// scheduling across calls. In PostRA scheduling, we need the isCall to enforce
386 /// the boundary, but there would be no benefit to postRA scheduling across
387 /// calls this late anyway.
388 static bool isSchedBoundary(MachineBasicBlock::iterator MI,
389 MachineBasicBlock *MBB,
391 const TargetInstrInfo *TII) {
392 return MI->isCall() || TII->isSchedulingBoundary(MI, MBB, *MF);
395 /// Main driver for both MachineScheduler and PostMachineScheduler.
396 void MachineSchedulerBase::scheduleRegions(ScheduleDAGInstrs &Scheduler,
398 const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
400 // Visit all machine basic blocks.
402 // TODO: Visit blocks in global postorder or postorder within the bottom-up
403 // loop tree. Then we can optionally compute global RegPressure.
404 for (MachineFunction::iterator MBB = MF->begin(), MBBEnd = MF->end();
405 MBB != MBBEnd; ++MBB) {
407 Scheduler.startBlock(&*MBB);
410 if (SchedOnlyFunc.getNumOccurrences() && SchedOnlyFunc != MF->getName())
412 if (SchedOnlyBlock.getNumOccurrences()
413 && (int)SchedOnlyBlock != MBB->getNumber())
417 // Break the block into scheduling regions [I, RegionEnd), and schedule each
418 // region as soon as it is discovered. RegionEnd points the scheduling
419 // boundary at the bottom of the region. The DAG does not include RegionEnd,
420 // but the region does (i.e. the next RegionEnd is above the previous
421 // RegionBegin). If the current block has no terminator then RegionEnd ==
422 // MBB->end() for the bottom region.
424 // The Scheduler may insert instructions during either schedule() or
425 // exitRegion(), even for empty regions. So the local iterators 'I' and
426 // 'RegionEnd' are invalid across these calls.
428 // MBB::size() uses instr_iterator to count. Here we need a bundle to count
429 // as a single instruction.
430 unsigned RemainingInstrs = std::distance(MBB->begin(), MBB->end());
431 for(MachineBasicBlock::iterator RegionEnd = MBB->end();
432 RegionEnd != MBB->begin(); RegionEnd = Scheduler.begin()) {
434 // Avoid decrementing RegionEnd for blocks with no terminator.
435 if (RegionEnd != MBB->end() ||
436 isSchedBoundary(&*std::prev(RegionEnd), &*MBB, MF, TII)) {
438 // Count the boundary instruction.
442 // The next region starts above the previous region. Look backward in the
443 // instruction stream until we find the nearest boundary.
444 unsigned NumRegionInstrs = 0;
445 MachineBasicBlock::iterator I = RegionEnd;
446 for(;I != MBB->begin(); --I, --RemainingInstrs) {
447 if (isSchedBoundary(&*std::prev(I), &*MBB, MF, TII))
449 if (!I->isDebugValue())
452 // Notify the scheduler of the region, even if we may skip scheduling
453 // it. Perhaps it still needs to be bundled.
454 Scheduler.enterRegion(&*MBB, I, RegionEnd, NumRegionInstrs);
456 // Skip empty scheduling regions (0 or 1 schedulable instructions).
457 if (I == RegionEnd || I == std::prev(RegionEnd)) {
458 // Close the current region. Bundle the terminator if needed.
459 // This invalidates 'RegionEnd' and 'I'.
460 Scheduler.exitRegion();
463 DEBUG(dbgs() << "********** MI Scheduling **********\n");
464 DEBUG(dbgs() << MF->getName()
465 << ":BB#" << MBB->getNumber() << " " << MBB->getName()
466 << "\n From: " << *I << " To: ";
467 if (RegionEnd != MBB->end()) dbgs() << *RegionEnd;
468 else dbgs() << "End";
469 dbgs() << " RegionInstrs: " << NumRegionInstrs
470 << " Remaining: " << RemainingInstrs << "\n");
471 if (DumpCriticalPathLength) {
472 errs() << MF->getName();
473 errs() << ":BB# " << MBB->getNumber();
474 errs() << " " << MBB->getName() << " \n";
477 // Schedule a region: possibly reorder instructions.
478 // This invalidates 'RegionEnd' and 'I'.
479 Scheduler.schedule();
481 // Close the current region.
482 Scheduler.exitRegion();
484 // Scheduling has invalidated the current iterator 'I'. Ask the
485 // scheduler for the top of it's scheduled region.
486 RegionEnd = Scheduler.begin();
488 assert(RemainingInstrs == 0 && "Instruction count mismatch!");
489 Scheduler.finishBlock();
490 // FIXME: Ideally, no further passes should rely on kill flags. However,
491 // thumb2 size reduction is currently an exception, so the PostMIScheduler
494 Scheduler.fixupKills(&*MBB);
496 Scheduler.finalizeSchedule();
499 void MachineSchedulerBase::print(raw_ostream &O, const Module* m) const {
504 void ReadyQueue::dump() {
505 dbgs() << "Queue " << Name << ": ";
506 for (unsigned i = 0, e = Queue.size(); i < e; ++i)
507 dbgs() << Queue[i]->NodeNum << " ";
511 //===----------------------------------------------------------------------===//
512 // ScheduleDAGMI - Basic machine instruction scheduling. This is
513 // independent of PreRA/PostRA scheduling and involves no extra book-keeping for
514 // virtual registers.
515 // ===----------------------------------------------------------------------===/
517 // Provide a vtable anchor.
518 ScheduleDAGMI::~ScheduleDAGMI() {
521 bool ScheduleDAGMI::canAddEdge(SUnit *SuccSU, SUnit *PredSU) {
522 return SuccSU == &ExitSU || !Topo.IsReachable(PredSU, SuccSU);
525 bool ScheduleDAGMI::addEdge(SUnit *SuccSU, const SDep &PredDep) {
526 if (SuccSU != &ExitSU) {
527 // Do not use WillCreateCycle, it assumes SD scheduling.
528 // If Pred is reachable from Succ, then the edge creates a cycle.
529 if (Topo.IsReachable(PredDep.getSUnit(), SuccSU))
531 Topo.AddPred(SuccSU, PredDep.getSUnit());
533 SuccSU->addPred(PredDep, /*Required=*/!PredDep.isArtificial());
534 // Return true regardless of whether a new edge needed to be inserted.
538 /// ReleaseSucc - Decrement the NumPredsLeft count of a successor. When
539 /// NumPredsLeft reaches zero, release the successor node.
541 /// FIXME: Adjust SuccSU height based on MinLatency.
542 void ScheduleDAGMI::releaseSucc(SUnit *SU, SDep *SuccEdge) {
543 SUnit *SuccSU = SuccEdge->getSUnit();
545 if (SuccEdge->isWeak()) {
546 --SuccSU->WeakPredsLeft;
547 if (SuccEdge->isCluster())
548 NextClusterSucc = SuccSU;
552 if (SuccSU->NumPredsLeft == 0) {
553 dbgs() << "*** Scheduling failed! ***\n";
555 dbgs() << " has been released too many times!\n";
556 llvm_unreachable(nullptr);
559 // SU->TopReadyCycle was set to CurrCycle when it was scheduled. However,
560 // CurrCycle may have advanced since then.
561 if (SuccSU->TopReadyCycle < SU->TopReadyCycle + SuccEdge->getLatency())
562 SuccSU->TopReadyCycle = SU->TopReadyCycle + SuccEdge->getLatency();
564 --SuccSU->NumPredsLeft;
565 if (SuccSU->NumPredsLeft == 0 && SuccSU != &ExitSU)
566 SchedImpl->releaseTopNode(SuccSU);
569 /// releaseSuccessors - Call releaseSucc on each of SU's successors.
570 void ScheduleDAGMI::releaseSuccessors(SUnit *SU) {
571 for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
573 releaseSucc(SU, &*I);
577 /// ReleasePred - Decrement the NumSuccsLeft count of a predecessor. When
578 /// NumSuccsLeft reaches zero, release the predecessor node.
580 /// FIXME: Adjust PredSU height based on MinLatency.
581 void ScheduleDAGMI::releasePred(SUnit *SU, SDep *PredEdge) {
582 SUnit *PredSU = PredEdge->getSUnit();
584 if (PredEdge->isWeak()) {
585 --PredSU->WeakSuccsLeft;
586 if (PredEdge->isCluster())
587 NextClusterPred = PredSU;
591 if (PredSU->NumSuccsLeft == 0) {
592 dbgs() << "*** Scheduling failed! ***\n";
594 dbgs() << " has been released too many times!\n";
595 llvm_unreachable(nullptr);
598 // SU->BotReadyCycle was set to CurrCycle when it was scheduled. However,
599 // CurrCycle may have advanced since then.
600 if (PredSU->BotReadyCycle < SU->BotReadyCycle + PredEdge->getLatency())
601 PredSU->BotReadyCycle = SU->BotReadyCycle + PredEdge->getLatency();
603 --PredSU->NumSuccsLeft;
604 if (PredSU->NumSuccsLeft == 0 && PredSU != &EntrySU)
605 SchedImpl->releaseBottomNode(PredSU);
608 /// releasePredecessors - Call releasePred on each of SU's predecessors.
609 void ScheduleDAGMI::releasePredecessors(SUnit *SU) {
610 for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
612 releasePred(SU, &*I);
616 /// enterRegion - Called back from MachineScheduler::runOnMachineFunction after
617 /// crossing a scheduling boundary. [begin, end) includes all instructions in
618 /// the region, including the boundary itself and single-instruction regions
619 /// that don't get scheduled.
620 void ScheduleDAGMI::enterRegion(MachineBasicBlock *bb,
621 MachineBasicBlock::iterator begin,
622 MachineBasicBlock::iterator end,
623 unsigned regioninstrs)
625 ScheduleDAGInstrs::enterRegion(bb, begin, end, regioninstrs);
627 SchedImpl->initPolicy(begin, end, regioninstrs);
630 /// This is normally called from the main scheduler loop but may also be invoked
631 /// by the scheduling strategy to perform additional code motion.
632 void ScheduleDAGMI::moveInstruction(
633 MachineInstr *MI, MachineBasicBlock::iterator InsertPos) {
634 // Advance RegionBegin if the first instruction moves down.
635 if (&*RegionBegin == MI)
638 // Update the instruction stream.
639 BB->splice(InsertPos, BB, MI);
641 // Update LiveIntervals
643 LIS->handleMove(MI, /*UpdateFlags=*/true);
645 // Recede RegionBegin if an instruction moves above the first.
646 if (RegionBegin == InsertPos)
650 bool ScheduleDAGMI::checkSchedLimit() {
652 if (NumInstrsScheduled == MISchedCutoff && MISchedCutoff != ~0U) {
653 CurrentTop = CurrentBottom;
656 ++NumInstrsScheduled;
661 /// Per-region scheduling driver, called back from
662 /// MachineScheduler::runOnMachineFunction. This is a simplified driver that
663 /// does not consider liveness or register pressure. It is useful for PostRA
664 /// scheduling and potentially other custom schedulers.
665 void ScheduleDAGMI::schedule() {
666 DEBUG(dbgs() << "ScheduleDAGMI::schedule starting\n");
667 DEBUG(SchedImpl->dumpPolicy());
672 Topo.InitDAGTopologicalSorting();
676 SmallVector<SUnit*, 8> TopRoots, BotRoots;
677 findRootsAndBiasEdges(TopRoots, BotRoots);
679 // Initialize the strategy before modifying the DAG.
680 // This may initialize a DFSResult to be used for queue priority.
681 SchedImpl->initialize(this);
683 DEBUG(for (unsigned su = 0, e = SUnits.size(); su != e; ++su)
684 SUnits[su].dumpAll(this));
685 if (ViewMISchedDAGs) viewGraph();
687 // Initialize ready queues now that the DAG and priority data are finalized.
688 initQueues(TopRoots, BotRoots);
690 bool IsTopNode = false;
692 DEBUG(dbgs() << "** ScheduleDAGMI::schedule picking next node\n");
693 SUnit *SU = SchedImpl->pickNode(IsTopNode);
696 assert(!SU->isScheduled && "Node already scheduled");
697 if (!checkSchedLimit())
700 MachineInstr *MI = SU->getInstr();
702 assert(SU->isTopReady() && "node still has unscheduled dependencies");
703 if (&*CurrentTop == MI)
704 CurrentTop = nextIfDebug(++CurrentTop, CurrentBottom);
706 moveInstruction(MI, CurrentTop);
709 assert(SU->isBottomReady() && "node still has unscheduled dependencies");
710 MachineBasicBlock::iterator priorII =
711 priorNonDebug(CurrentBottom, CurrentTop);
713 CurrentBottom = priorII;
715 if (&*CurrentTop == MI)
716 CurrentTop = nextIfDebug(++CurrentTop, priorII);
717 moveInstruction(MI, CurrentBottom);
721 // Notify the scheduling strategy before updating the DAG.
722 // This sets the scheduled node's ReadyCycle to CurrCycle. When updateQueues
723 // runs, it can then use the accurate ReadyCycle time to determine whether
724 // newly released nodes can move to the readyQ.
725 SchedImpl->schedNode(SU, IsTopNode);
727 updateQueues(SU, IsTopNode);
729 assert(CurrentTop == CurrentBottom && "Nonempty unscheduled zone.");
734 unsigned BBNum = begin()->getParent()->getNumber();
735 dbgs() << "*** Final schedule for BB#" << BBNum << " ***\n";
741 /// Apply each ScheduleDAGMutation step in order.
742 void ScheduleDAGMI::postprocessDAG() {
743 for (unsigned i = 0, e = Mutations.size(); i < e; ++i) {
744 Mutations[i]->apply(this);
749 findRootsAndBiasEdges(SmallVectorImpl<SUnit*> &TopRoots,
750 SmallVectorImpl<SUnit*> &BotRoots) {
751 for (std::vector<SUnit>::iterator
752 I = SUnits.begin(), E = SUnits.end(); I != E; ++I) {
754 assert(!SU->isBoundaryNode() && "Boundary node should not be in SUnits");
756 // Order predecessors so DFSResult follows the critical path.
757 SU->biasCriticalPath();
759 // A SUnit is ready to top schedule if it has no predecessors.
760 if (!I->NumPredsLeft)
761 TopRoots.push_back(SU);
762 // A SUnit is ready to bottom schedule if it has no successors.
763 if (!I->NumSuccsLeft)
764 BotRoots.push_back(SU);
766 ExitSU.biasCriticalPath();
769 /// Identify DAG roots and setup scheduler queues.
770 void ScheduleDAGMI::initQueues(ArrayRef<SUnit*> TopRoots,
771 ArrayRef<SUnit*> BotRoots) {
772 NextClusterSucc = nullptr;
773 NextClusterPred = nullptr;
775 // Release all DAG roots for scheduling, not including EntrySU/ExitSU.
777 // Nodes with unreleased weak edges can still be roots.
778 // Release top roots in forward order.
779 for (SmallVectorImpl<SUnit*>::const_iterator
780 I = TopRoots.begin(), E = TopRoots.end(); I != E; ++I) {
781 SchedImpl->releaseTopNode(*I);
783 // Release bottom roots in reverse order so the higher priority nodes appear
784 // first. This is more natural and slightly more efficient.
785 for (SmallVectorImpl<SUnit*>::const_reverse_iterator
786 I = BotRoots.rbegin(), E = BotRoots.rend(); I != E; ++I) {
787 SchedImpl->releaseBottomNode(*I);
790 releaseSuccessors(&EntrySU);
791 releasePredecessors(&ExitSU);
793 SchedImpl->registerRoots();
795 // Advance past initial DebugValues.
796 CurrentTop = nextIfDebug(RegionBegin, RegionEnd);
797 CurrentBottom = RegionEnd;
800 /// Update scheduler queues after scheduling an instruction.
801 void ScheduleDAGMI::updateQueues(SUnit *SU, bool IsTopNode) {
802 // Release dependent instructions for scheduling.
804 releaseSuccessors(SU);
806 releasePredecessors(SU);
808 SU->isScheduled = true;
811 /// Reinsert any remaining debug_values, just like the PostRA scheduler.
812 void ScheduleDAGMI::placeDebugValues() {
813 // If first instruction was a DBG_VALUE then put it back.
815 BB->splice(RegionBegin, BB, FirstDbgValue);
816 RegionBegin = FirstDbgValue;
819 for (std::vector<std::pair<MachineInstr *, MachineInstr *> >::iterator
820 DI = DbgValues.end(), DE = DbgValues.begin(); DI != DE; --DI) {
821 std::pair<MachineInstr *, MachineInstr *> P = *std::prev(DI);
822 MachineInstr *DbgValue = P.first;
823 MachineBasicBlock::iterator OrigPrevMI = P.second;
824 if (&*RegionBegin == DbgValue)
826 BB->splice(++OrigPrevMI, BB, DbgValue);
827 if (OrigPrevMI == std::prev(RegionEnd))
828 RegionEnd = DbgValue;
831 FirstDbgValue = nullptr;
834 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
835 void ScheduleDAGMI::dumpSchedule() const {
836 for (MachineBasicBlock::iterator MI = begin(), ME = end(); MI != ME; ++MI) {
837 if (SUnit *SU = getSUnit(&(*MI)))
840 dbgs() << "Missing SUnit\n";
845 //===----------------------------------------------------------------------===//
846 // ScheduleDAGMILive - Base class for MachineInstr scheduling with LiveIntervals
848 //===----------------------------------------------------------------------===//
850 ScheduleDAGMILive::~ScheduleDAGMILive() {
854 /// enterRegion - Called back from MachineScheduler::runOnMachineFunction after
855 /// crossing a scheduling boundary. [begin, end) includes all instructions in
856 /// the region, including the boundary itself and single-instruction regions
857 /// that don't get scheduled.
858 void ScheduleDAGMILive::enterRegion(MachineBasicBlock *bb,
859 MachineBasicBlock::iterator begin,
860 MachineBasicBlock::iterator end,
861 unsigned regioninstrs)
863 // ScheduleDAGMI initializes SchedImpl's per-region policy.
864 ScheduleDAGMI::enterRegion(bb, begin, end, regioninstrs);
866 // For convenience remember the end of the liveness region.
867 LiveRegionEnd = (RegionEnd == bb->end()) ? RegionEnd : std::next(RegionEnd);
869 SUPressureDiffs.clear();
871 ShouldTrackPressure = SchedImpl->shouldTrackPressure();
874 // Setup the register pressure trackers for the top scheduled top and bottom
875 // scheduled regions.
876 void ScheduleDAGMILive::initRegPressure() {
877 TopRPTracker.init(&MF, RegClassInfo, LIS, BB, RegionBegin);
878 BotRPTracker.init(&MF, RegClassInfo, LIS, BB, LiveRegionEnd);
880 // Close the RPTracker to finalize live ins.
881 RPTracker.closeRegion();
883 DEBUG(RPTracker.dump());
885 // Initialize the live ins and live outs.
886 TopRPTracker.addLiveRegs(RPTracker.getPressure().LiveInRegs);
887 BotRPTracker.addLiveRegs(RPTracker.getPressure().LiveOutRegs);
889 // Close one end of the tracker so we can call
890 // getMaxUpward/DownwardPressureDelta before advancing across any
891 // instructions. This converts currently live regs into live ins/outs.
892 TopRPTracker.closeTop();
893 BotRPTracker.closeBottom();
895 BotRPTracker.initLiveThru(RPTracker);
896 if (!BotRPTracker.getLiveThru().empty()) {
897 TopRPTracker.initLiveThru(BotRPTracker.getLiveThru());
898 DEBUG(dbgs() << "Live Thru: ";
899 dumpRegSetPressure(BotRPTracker.getLiveThru(), TRI));
902 // For each live out vreg reduce the pressure change associated with other
903 // uses of the same vreg below the live-out reaching def.
904 updatePressureDiffs(RPTracker.getPressure().LiveOutRegs);
906 // Account for liveness generated by the region boundary.
907 if (LiveRegionEnd != RegionEnd) {
908 SmallVector<unsigned, 8> LiveUses;
909 BotRPTracker.recede(&LiveUses);
910 updatePressureDiffs(LiveUses);
913 assert(BotRPTracker.getPos() == RegionEnd && "Can't find the region bottom");
915 // Cache the list of excess pressure sets in this region. This will also track
916 // the max pressure in the scheduled code for these sets.
917 RegionCriticalPSets.clear();
918 const std::vector<unsigned> &RegionPressure =
919 RPTracker.getPressure().MaxSetPressure;
920 for (unsigned i = 0, e = RegionPressure.size(); i < e; ++i) {
921 unsigned Limit = RegClassInfo->getRegPressureSetLimit(i);
922 if (RegionPressure[i] > Limit) {
923 DEBUG(dbgs() << TRI->getRegPressureSetName(i)
924 << " Limit " << Limit
925 << " Actual " << RegionPressure[i] << "\n");
926 RegionCriticalPSets.push_back(PressureChange(i));
929 DEBUG(dbgs() << "Excess PSets: ";
930 for (unsigned i = 0, e = RegionCriticalPSets.size(); i != e; ++i)
931 dbgs() << TRI->getRegPressureSetName(
932 RegionCriticalPSets[i].getPSet()) << " ";
936 void ScheduleDAGMILive::
937 updateScheduledPressure(const SUnit *SU,
938 const std::vector<unsigned> &NewMaxPressure) {
939 const PressureDiff &PDiff = getPressureDiff(SU);
940 unsigned CritIdx = 0, CritEnd = RegionCriticalPSets.size();
941 for (PressureDiff::const_iterator I = PDiff.begin(), E = PDiff.end();
945 unsigned ID = I->getPSet();
946 while (CritIdx != CritEnd && RegionCriticalPSets[CritIdx].getPSet() < ID)
948 if (CritIdx != CritEnd && RegionCriticalPSets[CritIdx].getPSet() == ID) {
949 if ((int)NewMaxPressure[ID] > RegionCriticalPSets[CritIdx].getUnitInc()
950 && NewMaxPressure[ID] <= INT16_MAX)
951 RegionCriticalPSets[CritIdx].setUnitInc(NewMaxPressure[ID]);
953 unsigned Limit = RegClassInfo->getRegPressureSetLimit(ID);
954 if (NewMaxPressure[ID] >= Limit - 2) {
955 DEBUG(dbgs() << " " << TRI->getRegPressureSetName(ID) << ": "
956 << NewMaxPressure[ID]
957 << ((NewMaxPressure[ID] > Limit) ? " > " : " <= ") << Limit
958 << "(+ " << BotRPTracker.getLiveThru()[ID] << " livethru)\n");
963 /// Update the PressureDiff array for liveness after scheduling this
965 void ScheduleDAGMILive::updatePressureDiffs(ArrayRef<unsigned> LiveUses) {
966 for (unsigned LUIdx = 0, LUEnd = LiveUses.size(); LUIdx != LUEnd; ++LUIdx) {
967 /// FIXME: Currently assuming single-use physregs.
968 unsigned Reg = LiveUses[LUIdx];
969 DEBUG(dbgs() << " LiveReg: " << PrintVRegOrUnit(Reg, TRI) << "\n");
970 if (!TRI->isVirtualRegister(Reg))
973 // This may be called before CurrentBottom has been initialized. However,
974 // BotRPTracker must have a valid position. We want the value live into the
975 // instruction or live out of the block, so ask for the previous
976 // instruction's live-out.
977 const LiveInterval &LI = LIS->getInterval(Reg);
979 MachineBasicBlock::const_iterator I =
980 nextIfDebug(BotRPTracker.getPos(), BB->end());
982 VNI = LI.getVNInfoBefore(LIS->getMBBEndIdx(BB));
984 LiveQueryResult LRQ = LI.Query(LIS->getInstructionIndex(I));
987 // RegisterPressureTracker guarantees that readsReg is true for LiveUses.
988 assert(VNI && "No live value at use.");
989 for (const VReg2SUnit &V2SU
990 : make_range(VRegUses.find(Reg), VRegUses.end())) {
992 // If this use comes before the reaching def, it cannot be a last use, so
993 // descrease its pressure change.
994 if (!SU->isScheduled && SU != &ExitSU) {
996 = LI.Query(LIS->getInstructionIndex(SU->getInstr()));
997 if (LRQ.valueIn() == VNI) {
998 PressureDiff &PDiff = getPressureDiff(SU);
999 PDiff.addPressureChange(Reg, true, &MRI);
1001 dbgs() << " UpdateRegP: SU(" << SU->NodeNum << ") "
1012 /// schedule - Called back from MachineScheduler::runOnMachineFunction
1013 /// after setting up the current scheduling region. [RegionBegin, RegionEnd)
1014 /// only includes instructions that have DAG nodes, not scheduling boundaries.
1016 /// This is a skeletal driver, with all the functionality pushed into helpers,
1017 /// so that it can be easily extended by experimental schedulers. Generally,
1018 /// implementing MachineSchedStrategy should be sufficient to implement a new
1019 /// scheduling algorithm. However, if a scheduler further subclasses
1020 /// ScheduleDAGMILive then it will want to override this virtual method in order
1021 /// to update any specialized state.
1022 void ScheduleDAGMILive::schedule() {
1023 DEBUG(dbgs() << "ScheduleDAGMILive::schedule starting\n");
1024 DEBUG(SchedImpl->dumpPolicy());
1025 buildDAGWithRegPressure();
1027 Topo.InitDAGTopologicalSorting();
1031 SmallVector<SUnit*, 8> TopRoots, BotRoots;
1032 findRootsAndBiasEdges(TopRoots, BotRoots);
1034 // Initialize the strategy before modifying the DAG.
1035 // This may initialize a DFSResult to be used for queue priority.
1036 SchedImpl->initialize(this);
1039 for (const SUnit &SU : SUnits) {
1041 if (ShouldTrackPressure) {
1042 dbgs() << " Pressure Diff : ";
1043 getPressureDiff(&SU).dump(*TRI);
1048 if (ViewMISchedDAGs) viewGraph();
1050 // Initialize ready queues now that the DAG and priority data are finalized.
1051 initQueues(TopRoots, BotRoots);
1053 if (ShouldTrackPressure) {
1054 assert(TopRPTracker.getPos() == RegionBegin && "bad initial Top tracker");
1055 TopRPTracker.setPos(CurrentTop);
1058 bool IsTopNode = false;
1060 DEBUG(dbgs() << "** ScheduleDAGMILive::schedule picking next node\n");
1061 SUnit *SU = SchedImpl->pickNode(IsTopNode);
1064 assert(!SU->isScheduled && "Node already scheduled");
1065 if (!checkSchedLimit())
1068 scheduleMI(SU, IsTopNode);
1071 unsigned SubtreeID = DFSResult->getSubtreeID(SU);
1072 if (!ScheduledTrees.test(SubtreeID)) {
1073 ScheduledTrees.set(SubtreeID);
1074 DFSResult->scheduleTree(SubtreeID);
1075 SchedImpl->scheduleTree(SubtreeID);
1079 // Notify the scheduling strategy after updating the DAG.
1080 SchedImpl->schedNode(SU, IsTopNode);
1082 updateQueues(SU, IsTopNode);
1084 assert(CurrentTop == CurrentBottom && "Nonempty unscheduled zone.");
1089 unsigned BBNum = begin()->getParent()->getNumber();
1090 dbgs() << "*** Final schedule for BB#" << BBNum << " ***\n";
1096 /// Build the DAG and setup three register pressure trackers.
1097 void ScheduleDAGMILive::buildDAGWithRegPressure() {
1098 if (!ShouldTrackPressure) {
1100 RegionCriticalPSets.clear();
1101 buildSchedGraph(AA);
1105 // Initialize the register pressure tracker used by buildSchedGraph.
1106 RPTracker.init(&MF, RegClassInfo, LIS, BB, LiveRegionEnd,
1107 /*TrackUntiedDefs=*/true);
1109 // Account for liveness generate by the region boundary.
1110 if (LiveRegionEnd != RegionEnd)
1113 // Build the DAG, and compute current register pressure.
1114 buildSchedGraph(AA, &RPTracker, &SUPressureDiffs);
1116 // Initialize top/bottom trackers after computing region pressure.
1120 void ScheduleDAGMILive::computeDFSResult() {
1122 DFSResult = new SchedDFSResult(/*BottomU*/true, MinSubtreeSize);
1124 ScheduledTrees.clear();
1125 DFSResult->resize(SUnits.size());
1126 DFSResult->compute(SUnits);
1127 ScheduledTrees.resize(DFSResult->getNumSubtrees());
1130 /// Compute the max cyclic critical path through the DAG. The scheduling DAG
1131 /// only provides the critical path for single block loops. To handle loops that
1132 /// span blocks, we could use the vreg path latencies provided by
1133 /// MachineTraceMetrics instead. However, MachineTraceMetrics is not currently
1134 /// available for use in the scheduler.
1136 /// The cyclic path estimation identifies a def-use pair that crosses the back
1137 /// edge and considers the depth and height of the nodes. For example, consider
1138 /// the following instruction sequence where each instruction has unit latency
1139 /// and defines an epomymous virtual register:
1141 /// a->b(a,c)->c(b)->d(c)->exit
1143 /// The cyclic critical path is a two cycles: b->c->b
1144 /// The acyclic critical path is four cycles: a->b->c->d->exit
1145 /// LiveOutHeight = height(c) = len(c->d->exit) = 2
1146 /// LiveOutDepth = depth(c) + 1 = len(a->b->c) + 1 = 3
1147 /// LiveInHeight = height(b) + 1 = len(b->c->d->exit) + 1 = 4
1148 /// LiveInDepth = depth(b) = len(a->b) = 1
1150 /// LiveOutDepth - LiveInDepth = 3 - 1 = 2
1151 /// LiveInHeight - LiveOutHeight = 4 - 2 = 2
1152 /// CyclicCriticalPath = min(2, 2) = 2
1154 /// This could be relevant to PostRA scheduling, but is currently implemented
1155 /// assuming LiveIntervals.
1156 unsigned ScheduleDAGMILive::computeCyclicCriticalPath() {
1157 // This only applies to single block loop.
1158 if (!BB->isSuccessor(BB))
1161 unsigned MaxCyclicLatency = 0;
1162 // Visit each live out vreg def to find def/use pairs that cross iterations.
1163 ArrayRef<unsigned> LiveOuts = RPTracker.getPressure().LiveOutRegs;
1164 for (ArrayRef<unsigned>::iterator RI = LiveOuts.begin(), RE = LiveOuts.end();
1167 if (!TRI->isVirtualRegister(Reg))
1169 const LiveInterval &LI = LIS->getInterval(Reg);
1170 const VNInfo *DefVNI = LI.getVNInfoBefore(LIS->getMBBEndIdx(BB));
1174 MachineInstr *DefMI = LIS->getInstructionFromIndex(DefVNI->def);
1175 const SUnit *DefSU = getSUnit(DefMI);
1179 unsigned LiveOutHeight = DefSU->getHeight();
1180 unsigned LiveOutDepth = DefSU->getDepth() + DefSU->Latency;
1181 // Visit all local users of the vreg def.
1182 for (const VReg2SUnit &V2SU
1183 : make_range(VRegUses.find(Reg), VRegUses.end())) {
1184 SUnit *SU = V2SU.SU;
1188 // Only consider uses of the phi.
1189 LiveQueryResult LRQ =
1190 LI.Query(LIS->getInstructionIndex(SU->getInstr()));
1191 if (!LRQ.valueIn()->isPHIDef())
1194 // Assume that a path spanning two iterations is a cycle, which could
1195 // overestimate in strange cases. This allows cyclic latency to be
1196 // estimated as the minimum slack of the vreg's depth or height.
1197 unsigned CyclicLatency = 0;
1198 if (LiveOutDepth > SU->getDepth())
1199 CyclicLatency = LiveOutDepth - SU->getDepth();
1201 unsigned LiveInHeight = SU->getHeight() + DefSU->Latency;
1202 if (LiveInHeight > LiveOutHeight) {
1203 if (LiveInHeight - LiveOutHeight < CyclicLatency)
1204 CyclicLatency = LiveInHeight - LiveOutHeight;
1209 DEBUG(dbgs() << "Cyclic Path: SU(" << DefSU->NodeNum << ") -> SU("
1210 << SU->NodeNum << ") = " << CyclicLatency << "c\n");
1211 if (CyclicLatency > MaxCyclicLatency)
1212 MaxCyclicLatency = CyclicLatency;
1215 DEBUG(dbgs() << "Cyclic Critical Path: " << MaxCyclicLatency << "c\n");
1216 return MaxCyclicLatency;
1219 /// Move an instruction and update register pressure.
1220 void ScheduleDAGMILive::scheduleMI(SUnit *SU, bool IsTopNode) {
1221 // Move the instruction to its new location in the instruction stream.
1222 MachineInstr *MI = SU->getInstr();
1225 assert(SU->isTopReady() && "node still has unscheduled dependencies");
1226 if (&*CurrentTop == MI)
1227 CurrentTop = nextIfDebug(++CurrentTop, CurrentBottom);
1229 moveInstruction(MI, CurrentTop);
1230 TopRPTracker.setPos(MI);
1233 if (ShouldTrackPressure) {
1234 // Update top scheduled pressure.
1235 TopRPTracker.advance();
1236 assert(TopRPTracker.getPos() == CurrentTop && "out of sync");
1238 dbgs() << "Top Pressure:\n";
1239 dumpRegSetPressure(TopRPTracker.getRegSetPressureAtPos(), TRI);
1242 updateScheduledPressure(SU, TopRPTracker.getPressure().MaxSetPressure);
1246 assert(SU->isBottomReady() && "node still has unscheduled dependencies");
1247 MachineBasicBlock::iterator priorII =
1248 priorNonDebug(CurrentBottom, CurrentTop);
1249 if (&*priorII == MI)
1250 CurrentBottom = priorII;
1252 if (&*CurrentTop == MI) {
1253 CurrentTop = nextIfDebug(++CurrentTop, priorII);
1254 TopRPTracker.setPos(CurrentTop);
1256 moveInstruction(MI, CurrentBottom);
1259 if (ShouldTrackPressure) {
1260 // Update bottom scheduled pressure.
1261 SmallVector<unsigned, 8> LiveUses;
1262 BotRPTracker.recede(&LiveUses);
1263 assert(BotRPTracker.getPos() == CurrentBottom && "out of sync");
1265 dbgs() << "Bottom Pressure:\n";
1266 dumpRegSetPressure(BotRPTracker.getRegSetPressureAtPos(), TRI);
1269 updateScheduledPressure(SU, BotRPTracker.getPressure().MaxSetPressure);
1270 updatePressureDiffs(LiveUses);
1275 //===----------------------------------------------------------------------===//
1276 // LoadClusterMutation - DAG post-processing to cluster loads.
1277 //===----------------------------------------------------------------------===//
1280 /// \brief Post-process the DAG to create cluster edges between neighboring
1282 class LoadClusterMutation : public ScheduleDAGMutation {
1287 LoadInfo(SUnit *su, unsigned reg, unsigned ofs)
1288 : SU(su), BaseReg(reg), Offset(ofs) {}
1290 bool operator<(const LoadInfo &RHS) const {
1291 return std::tie(BaseReg, Offset) < std::tie(RHS.BaseReg, RHS.Offset);
1295 const TargetInstrInfo *TII;
1296 const TargetRegisterInfo *TRI;
1298 LoadClusterMutation(const TargetInstrInfo *tii,
1299 const TargetRegisterInfo *tri)
1300 : TII(tii), TRI(tri) {}
1302 void apply(ScheduleDAGMI *DAG) override;
1304 void clusterNeighboringLoads(ArrayRef<SUnit*> Loads, ScheduleDAGMI *DAG);
1308 void LoadClusterMutation::clusterNeighboringLoads(ArrayRef<SUnit*> Loads,
1309 ScheduleDAGMI *DAG) {
1310 SmallVector<LoadClusterMutation::LoadInfo,32> LoadRecords;
1311 for (unsigned Idx = 0, End = Loads.size(); Idx != End; ++Idx) {
1312 SUnit *SU = Loads[Idx];
1315 if (TII->getMemOpBaseRegImmOfs(SU->getInstr(), BaseReg, Offset, TRI))
1316 LoadRecords.push_back(LoadInfo(SU, BaseReg, Offset));
1318 if (LoadRecords.size() < 2)
1320 std::sort(LoadRecords.begin(), LoadRecords.end());
1321 unsigned ClusterLength = 1;
1322 for (unsigned Idx = 0, End = LoadRecords.size(); Idx < (End - 1); ++Idx) {
1323 if (LoadRecords[Idx].BaseReg != LoadRecords[Idx+1].BaseReg) {
1328 SUnit *SUa = LoadRecords[Idx].SU;
1329 SUnit *SUb = LoadRecords[Idx+1].SU;
1330 if (TII->shouldClusterLoads(SUa->getInstr(), SUb->getInstr(), ClusterLength)
1331 && DAG->addEdge(SUb, SDep(SUa, SDep::Cluster))) {
1333 DEBUG(dbgs() << "Cluster loads SU(" << SUa->NodeNum << ") - SU("
1334 << SUb->NodeNum << ")\n");
1335 // Copy successor edges from SUa to SUb. Interleaving computation
1336 // dependent on SUa can prevent load combining due to register reuse.
1337 // Predecessor edges do not need to be copied from SUb to SUa since nearby
1338 // loads should have effectively the same inputs.
1339 for (SUnit::const_succ_iterator
1340 SI = SUa->Succs.begin(), SE = SUa->Succs.end(); SI != SE; ++SI) {
1341 if (SI->getSUnit() == SUb)
1343 DEBUG(dbgs() << " Copy Succ SU(" << SI->getSUnit()->NodeNum << ")\n");
1344 DAG->addEdge(SI->getSUnit(), SDep(SUb, SDep::Artificial));
1353 /// \brief Callback from DAG postProcessing to create cluster edges for loads.
1354 void LoadClusterMutation::apply(ScheduleDAGMI *DAG) {
1355 // Map DAG NodeNum to store chain ID.
1356 DenseMap<unsigned, unsigned> StoreChainIDs;
1357 // Map each store chain to a set of dependent loads.
1358 SmallVector<SmallVector<SUnit*,4>, 32> StoreChainDependents;
1359 for (unsigned Idx = 0, End = DAG->SUnits.size(); Idx != End; ++Idx) {
1360 SUnit *SU = &DAG->SUnits[Idx];
1361 if (!SU->getInstr()->mayLoad())
1363 unsigned ChainPredID = DAG->SUnits.size();
1364 for (SUnit::const_pred_iterator
1365 PI = SU->Preds.begin(), PE = SU->Preds.end(); PI != PE; ++PI) {
1367 ChainPredID = PI->getSUnit()->NodeNum;
1371 // Check if this chain-like pred has been seen
1372 // before. ChainPredID==MaxNodeID for loads at the top of the schedule.
1373 unsigned NumChains = StoreChainDependents.size();
1374 std::pair<DenseMap<unsigned, unsigned>::iterator, bool> Result =
1375 StoreChainIDs.insert(std::make_pair(ChainPredID, NumChains));
1377 StoreChainDependents.resize(NumChains + 1);
1378 StoreChainDependents[Result.first->second].push_back(SU);
1380 // Iterate over the store chains.
1381 for (unsigned Idx = 0, End = StoreChainDependents.size(); Idx != End; ++Idx)
1382 clusterNeighboringLoads(StoreChainDependents[Idx], DAG);
1385 //===----------------------------------------------------------------------===//
1386 // MacroFusion - DAG post-processing to encourage fusion of macro ops.
1387 //===----------------------------------------------------------------------===//
1390 /// \brief Post-process the DAG to create cluster edges between instructions
1391 /// that may be fused by the processor into a single operation.
1392 class MacroFusion : public ScheduleDAGMutation {
1393 const TargetInstrInfo &TII;
1394 const TargetRegisterInfo &TRI;
1396 MacroFusion(const TargetInstrInfo &TII, const TargetRegisterInfo &TRI)
1397 : TII(TII), TRI(TRI) {}
1399 void apply(ScheduleDAGMI *DAG) override;
1403 /// Returns true if \p MI reads a register written by \p Other.
1404 static bool HasDataDep(const TargetRegisterInfo &TRI, const MachineInstr &MI,
1405 const MachineInstr &Other) {
1406 for (const MachineOperand &MO : MI.uses()) {
1407 if (!MO.isReg() || !MO.readsReg())
1410 unsigned Reg = MO.getReg();
1411 if (Other.modifiesRegister(Reg, &TRI))
1417 /// \brief Callback from DAG postProcessing to create cluster edges to encourage
1418 /// fused operations.
1419 void MacroFusion::apply(ScheduleDAGMI *DAG) {
1420 // For now, assume targets can only fuse with the branch.
1421 SUnit &ExitSU = DAG->ExitSU;
1422 MachineInstr *Branch = ExitSU.getInstr();
1426 for (SUnit &SU : DAG->SUnits) {
1427 // SUnits with successors can't be schedule in front of the ExitSU.
1428 if (!SU.Succs.empty())
1430 // We only care if the node writes to a register that the branch reads.
1431 MachineInstr *Pred = SU.getInstr();
1432 if (!HasDataDep(TRI, *Branch, *Pred))
1435 if (!TII.shouldScheduleAdjacent(Pred, Branch))
1438 // Create a single weak edge from SU to ExitSU. The only effect is to cause
1439 // bottom-up scheduling to heavily prioritize the clustered SU. There is no
1440 // need to copy predecessor edges from ExitSU to SU, since top-down
1441 // scheduling cannot prioritize ExitSU anyway. To defer top-down scheduling
1442 // of SU, we could create an artificial edge from the deepest root, but it
1443 // hasn't been needed yet.
1444 bool Success = DAG->addEdge(&ExitSU, SDep(&SU, SDep::Cluster));
1446 assert(Success && "No DAG nodes should be reachable from ExitSU");
1448 DEBUG(dbgs() << "Macro Fuse SU(" << SU.NodeNum << ")\n");
1453 //===----------------------------------------------------------------------===//
1454 // CopyConstrain - DAG post-processing to encourage copy elimination.
1455 //===----------------------------------------------------------------------===//
1458 /// \brief Post-process the DAG to create weak edges from all uses of a copy to
1459 /// the one use that defines the copy's source vreg, most likely an induction
1460 /// variable increment.
1461 class CopyConstrain : public ScheduleDAGMutation {
1463 SlotIndex RegionBeginIdx;
1464 // RegionEndIdx is the slot index of the last non-debug instruction in the
1465 // scheduling region. So we may have RegionBeginIdx == RegionEndIdx.
1466 SlotIndex RegionEndIdx;
1468 CopyConstrain(const TargetInstrInfo *, const TargetRegisterInfo *) {}
1470 void apply(ScheduleDAGMI *DAG) override;
1473 void constrainLocalCopy(SUnit *CopySU, ScheduleDAGMILive *DAG);
1477 /// constrainLocalCopy handles two possibilities:
1482 /// I3: dst = src (copy)
1483 /// (create pred->succ edges I0->I1, I2->I1)
1486 /// I0: dst = src (copy)
1490 /// (create pred->succ edges I1->I2, I3->I2)
1492 /// Although the MachineScheduler is currently constrained to single blocks,
1493 /// this algorithm should handle extended blocks. An EBB is a set of
1494 /// contiguously numbered blocks such that the previous block in the EBB is
1495 /// always the single predecessor.
1496 void CopyConstrain::constrainLocalCopy(SUnit *CopySU, ScheduleDAGMILive *DAG) {
1497 LiveIntervals *LIS = DAG->getLIS();
1498 MachineInstr *Copy = CopySU->getInstr();
1500 // Check for pure vreg copies.
1501 unsigned SrcReg = Copy->getOperand(1).getReg();
1502 if (!TargetRegisterInfo::isVirtualRegister(SrcReg))
1505 unsigned DstReg = Copy->getOperand(0).getReg();
1506 if (!TargetRegisterInfo::isVirtualRegister(DstReg))
1509 // Check if either the dest or source is local. If it's live across a back
1510 // edge, it's not local. Note that if both vregs are live across the back
1511 // edge, we cannot successfully contrain the copy without cyclic scheduling.
1512 // If both the copy's source and dest are local live intervals, then we
1513 // should treat the dest as the global for the purpose of adding
1514 // constraints. This adds edges from source's other uses to the copy.
1515 unsigned LocalReg = SrcReg;
1516 unsigned GlobalReg = DstReg;
1517 LiveInterval *LocalLI = &LIS->getInterval(LocalReg);
1518 if (!LocalLI->isLocal(RegionBeginIdx, RegionEndIdx)) {
1521 LocalLI = &LIS->getInterval(LocalReg);
1522 if (!LocalLI->isLocal(RegionBeginIdx, RegionEndIdx))
1525 LiveInterval *GlobalLI = &LIS->getInterval(GlobalReg);
1527 // Find the global segment after the start of the local LI.
1528 LiveInterval::iterator GlobalSegment = GlobalLI->find(LocalLI->beginIndex());
1529 // If GlobalLI does not overlap LocalLI->start, then a copy directly feeds a
1530 // local live range. We could create edges from other global uses to the local
1531 // start, but the coalescer should have already eliminated these cases, so
1532 // don't bother dealing with it.
1533 if (GlobalSegment == GlobalLI->end())
1536 // If GlobalSegment is killed at the LocalLI->start, the call to find()
1537 // returned the next global segment. But if GlobalSegment overlaps with
1538 // LocalLI->start, then advance to the next segement. If a hole in GlobalLI
1539 // exists in LocalLI's vicinity, GlobalSegment will be the end of the hole.
1540 if (GlobalSegment->contains(LocalLI->beginIndex()))
1543 if (GlobalSegment == GlobalLI->end())
1546 // Check if GlobalLI contains a hole in the vicinity of LocalLI.
1547 if (GlobalSegment != GlobalLI->begin()) {
1548 // Two address defs have no hole.
1549 if (SlotIndex::isSameInstr(std::prev(GlobalSegment)->end,
1550 GlobalSegment->start)) {
1553 // If the prior global segment may be defined by the same two-address
1554 // instruction that also defines LocalLI, then can't make a hole here.
1555 if (SlotIndex::isSameInstr(std::prev(GlobalSegment)->start,
1556 LocalLI->beginIndex())) {
1559 // If GlobalLI has a prior segment, it must be live into the EBB. Otherwise
1560 // it would be a disconnected component in the live range.
1561 assert(std::prev(GlobalSegment)->start < LocalLI->beginIndex() &&
1562 "Disconnected LRG within the scheduling region.");
1564 MachineInstr *GlobalDef = LIS->getInstructionFromIndex(GlobalSegment->start);
1568 SUnit *GlobalSU = DAG->getSUnit(GlobalDef);
1572 // GlobalDef is the bottom of the GlobalLI hole. Open the hole by
1573 // constraining the uses of the last local def to precede GlobalDef.
1574 SmallVector<SUnit*,8> LocalUses;
1575 const VNInfo *LastLocalVN = LocalLI->getVNInfoBefore(LocalLI->endIndex());
1576 MachineInstr *LastLocalDef = LIS->getInstructionFromIndex(LastLocalVN->def);
1577 SUnit *LastLocalSU = DAG->getSUnit(LastLocalDef);
1578 for (SUnit::const_succ_iterator
1579 I = LastLocalSU->Succs.begin(), E = LastLocalSU->Succs.end();
1581 if (I->getKind() != SDep::Data || I->getReg() != LocalReg)
1583 if (I->getSUnit() == GlobalSU)
1585 if (!DAG->canAddEdge(GlobalSU, I->getSUnit()))
1587 LocalUses.push_back(I->getSUnit());
1589 // Open the top of the GlobalLI hole by constraining any earlier global uses
1590 // to precede the start of LocalLI.
1591 SmallVector<SUnit*,8> GlobalUses;
1592 MachineInstr *FirstLocalDef =
1593 LIS->getInstructionFromIndex(LocalLI->beginIndex());
1594 SUnit *FirstLocalSU = DAG->getSUnit(FirstLocalDef);
1595 for (SUnit::const_pred_iterator
1596 I = GlobalSU->Preds.begin(), E = GlobalSU->Preds.end(); I != E; ++I) {
1597 if (I->getKind() != SDep::Anti || I->getReg() != GlobalReg)
1599 if (I->getSUnit() == FirstLocalSU)
1601 if (!DAG->canAddEdge(FirstLocalSU, I->getSUnit()))
1603 GlobalUses.push_back(I->getSUnit());
1605 DEBUG(dbgs() << "Constraining copy SU(" << CopySU->NodeNum << ")\n");
1606 // Add the weak edges.
1607 for (SmallVectorImpl<SUnit*>::const_iterator
1608 I = LocalUses.begin(), E = LocalUses.end(); I != E; ++I) {
1609 DEBUG(dbgs() << " Local use SU(" << (*I)->NodeNum << ") -> SU("
1610 << GlobalSU->NodeNum << ")\n");
1611 DAG->addEdge(GlobalSU, SDep(*I, SDep::Weak));
1613 for (SmallVectorImpl<SUnit*>::const_iterator
1614 I = GlobalUses.begin(), E = GlobalUses.end(); I != E; ++I) {
1615 DEBUG(dbgs() << " Global use SU(" << (*I)->NodeNum << ") -> SU("
1616 << FirstLocalSU->NodeNum << ")\n");
1617 DAG->addEdge(FirstLocalSU, SDep(*I, SDep::Weak));
1621 /// \brief Callback from DAG postProcessing to create weak edges to encourage
1622 /// copy elimination.
1623 void CopyConstrain::apply(ScheduleDAGMI *DAG) {
1624 assert(DAG->hasVRegLiveness() && "Expect VRegs with LiveIntervals");
1626 MachineBasicBlock::iterator FirstPos = nextIfDebug(DAG->begin(), DAG->end());
1627 if (FirstPos == DAG->end())
1629 RegionBeginIdx = DAG->getLIS()->getInstructionIndex(&*FirstPos);
1630 RegionEndIdx = DAG->getLIS()->getInstructionIndex(
1631 &*priorNonDebug(DAG->end(), DAG->begin()));
1633 for (unsigned Idx = 0, End = DAG->SUnits.size(); Idx != End; ++Idx) {
1634 SUnit *SU = &DAG->SUnits[Idx];
1635 if (!SU->getInstr()->isCopy())
1638 constrainLocalCopy(SU, static_cast<ScheduleDAGMILive*>(DAG));
1642 //===----------------------------------------------------------------------===//
1643 // MachineSchedStrategy helpers used by GenericScheduler, GenericPostScheduler
1644 // and possibly other custom schedulers.
1645 //===----------------------------------------------------------------------===//
1647 static const unsigned InvalidCycle = ~0U;
1649 SchedBoundary::~SchedBoundary() { delete HazardRec; }
1651 void SchedBoundary::reset() {
1652 // A new HazardRec is created for each DAG and owned by SchedBoundary.
1653 // Destroying and reconstructing it is very expensive though. So keep
1654 // invalid, placeholder HazardRecs.
1655 if (HazardRec && HazardRec->isEnabled()) {
1657 HazardRec = nullptr;
1661 CheckPending = false;
1665 MinReadyCycle = UINT_MAX;
1666 ExpectedLatency = 0;
1667 DependentLatency = 0;
1669 MaxExecutedResCount = 0;
1671 IsResourceLimited = false;
1672 ReservedCycles.clear();
1674 // Track the maximum number of stall cycles that could arise either from the
1675 // latency of a DAG edge or the number of cycles that a processor resource is
1676 // reserved (SchedBoundary::ReservedCycles).
1677 MaxObservedStall = 0;
1679 // Reserve a zero-count for invalid CritResIdx.
1680 ExecutedResCounts.resize(1);
1681 assert(!ExecutedResCounts[0] && "nonzero count for bad resource");
1684 void SchedRemainder::
1685 init(ScheduleDAGMI *DAG, const TargetSchedModel *SchedModel) {
1687 if (!SchedModel->hasInstrSchedModel())
1689 RemainingCounts.resize(SchedModel->getNumProcResourceKinds());
1690 for (std::vector<SUnit>::iterator
1691 I = DAG->SUnits.begin(), E = DAG->SUnits.end(); I != E; ++I) {
1692 const MCSchedClassDesc *SC = DAG->getSchedClass(&*I);
1693 RemIssueCount += SchedModel->getNumMicroOps(I->getInstr(), SC)
1694 * SchedModel->getMicroOpFactor();
1695 for (TargetSchedModel::ProcResIter
1696 PI = SchedModel->getWriteProcResBegin(SC),
1697 PE = SchedModel->getWriteProcResEnd(SC); PI != PE; ++PI) {
1698 unsigned PIdx = PI->ProcResourceIdx;
1699 unsigned Factor = SchedModel->getResourceFactor(PIdx);
1700 RemainingCounts[PIdx] += (Factor * PI->Cycles);
1705 void SchedBoundary::
1706 init(ScheduleDAGMI *dag, const TargetSchedModel *smodel, SchedRemainder *rem) {
1709 SchedModel = smodel;
1711 if (SchedModel->hasInstrSchedModel()) {
1712 ExecutedResCounts.resize(SchedModel->getNumProcResourceKinds());
1713 ReservedCycles.resize(SchedModel->getNumProcResourceKinds(), InvalidCycle);
1717 /// Compute the stall cycles based on this SUnit's ready time. Heuristics treat
1718 /// these "soft stalls" differently than the hard stall cycles based on CPU
1719 /// resources and computed by checkHazard(). A fully in-order model
1720 /// (MicroOpBufferSize==0) will not make use of this since instructions are not
1721 /// available for scheduling until they are ready. However, a weaker in-order
1722 /// model may use this for heuristics. For example, if a processor has in-order
1723 /// behavior when reading certain resources, this may come into play.
1724 unsigned SchedBoundary::getLatencyStallCycles(SUnit *SU) {
1725 if (!SU->isUnbuffered)
1728 unsigned ReadyCycle = (isTop() ? SU->TopReadyCycle : SU->BotReadyCycle);
1729 if (ReadyCycle > CurrCycle)
1730 return ReadyCycle - CurrCycle;
1734 /// Compute the next cycle at which the given processor resource can be
1736 unsigned SchedBoundary::
1737 getNextResourceCycle(unsigned PIdx, unsigned Cycles) {
1738 unsigned NextUnreserved = ReservedCycles[PIdx];
1739 // If this resource has never been used, always return cycle zero.
1740 if (NextUnreserved == InvalidCycle)
1742 // For bottom-up scheduling add the cycles needed for the current operation.
1744 NextUnreserved += Cycles;
1745 return NextUnreserved;
1748 /// Does this SU have a hazard within the current instruction group.
1750 /// The scheduler supports two modes of hazard recognition. The first is the
1751 /// ScheduleHazardRecognizer API. It is a fully general hazard recognizer that
1752 /// supports highly complicated in-order reservation tables
1753 /// (ScoreboardHazardRecognizer) and arbitraty target-specific logic.
1755 /// The second is a streamlined mechanism that checks for hazards based on
1756 /// simple counters that the scheduler itself maintains. It explicitly checks
1757 /// for instruction dispatch limitations, including the number of micro-ops that
1758 /// can dispatch per cycle.
1760 /// TODO: Also check whether the SU must start a new group.
1761 bool SchedBoundary::checkHazard(SUnit *SU) {
1762 if (HazardRec->isEnabled()
1763 && HazardRec->getHazardType(SU) != ScheduleHazardRecognizer::NoHazard) {
1766 unsigned uops = SchedModel->getNumMicroOps(SU->getInstr());
1767 if ((CurrMOps > 0) && (CurrMOps + uops > SchedModel->getIssueWidth())) {
1768 DEBUG(dbgs() << " SU(" << SU->NodeNum << ") uops="
1769 << SchedModel->getNumMicroOps(SU->getInstr()) << '\n');
1772 if (SchedModel->hasInstrSchedModel() && SU->hasReservedResource) {
1773 const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
1774 for (TargetSchedModel::ProcResIter
1775 PI = SchedModel->getWriteProcResBegin(SC),
1776 PE = SchedModel->getWriteProcResEnd(SC); PI != PE; ++PI) {
1777 unsigned NRCycle = getNextResourceCycle(PI->ProcResourceIdx, PI->Cycles);
1778 if (NRCycle > CurrCycle) {
1780 MaxObservedStall = std::max(PI->Cycles, MaxObservedStall);
1782 DEBUG(dbgs() << " SU(" << SU->NodeNum << ") "
1783 << SchedModel->getResourceName(PI->ProcResourceIdx)
1784 << "=" << NRCycle << "c\n");
1792 // Find the unscheduled node in ReadySUs with the highest latency.
1793 unsigned SchedBoundary::
1794 findMaxLatency(ArrayRef<SUnit*> ReadySUs) {
1795 SUnit *LateSU = nullptr;
1796 unsigned RemLatency = 0;
1797 for (ArrayRef<SUnit*>::iterator I = ReadySUs.begin(), E = ReadySUs.end();
1799 unsigned L = getUnscheduledLatency(*I);
1800 if (L > RemLatency) {
1806 DEBUG(dbgs() << Available.getName() << " RemLatency SU("
1807 << LateSU->NodeNum << ") " << RemLatency << "c\n");
1812 // Count resources in this zone and the remaining unscheduled
1813 // instruction. Return the max count, scaled. Set OtherCritIdx to the critical
1814 // resource index, or zero if the zone is issue limited.
1815 unsigned SchedBoundary::
1816 getOtherResourceCount(unsigned &OtherCritIdx) {
1818 if (!SchedModel->hasInstrSchedModel())
1821 unsigned OtherCritCount = Rem->RemIssueCount
1822 + (RetiredMOps * SchedModel->getMicroOpFactor());
1823 DEBUG(dbgs() << " " << Available.getName() << " + Remain MOps: "
1824 << OtherCritCount / SchedModel->getMicroOpFactor() << '\n');
1825 for (unsigned PIdx = 1, PEnd = SchedModel->getNumProcResourceKinds();
1826 PIdx != PEnd; ++PIdx) {
1827 unsigned OtherCount = getResourceCount(PIdx) + Rem->RemainingCounts[PIdx];
1828 if (OtherCount > OtherCritCount) {
1829 OtherCritCount = OtherCount;
1830 OtherCritIdx = PIdx;
1834 DEBUG(dbgs() << " " << Available.getName() << " + Remain CritRes: "
1835 << OtherCritCount / SchedModel->getResourceFactor(OtherCritIdx)
1836 << " " << SchedModel->getResourceName(OtherCritIdx) << "\n");
1838 return OtherCritCount;
1841 void SchedBoundary::releaseNode(SUnit *SU, unsigned ReadyCycle) {
1842 assert(SU->getInstr() && "Scheduled SUnit must have instr");
1845 // ReadyCycle was been bumped up to the CurrCycle when this node was
1846 // scheduled, but CurrCycle may have been eagerly advanced immediately after
1847 // scheduling, so may now be greater than ReadyCycle.
1848 if (ReadyCycle > CurrCycle)
1849 MaxObservedStall = std::max(ReadyCycle - CurrCycle, MaxObservedStall);
1852 if (ReadyCycle < MinReadyCycle)
1853 MinReadyCycle = ReadyCycle;
1855 // Check for interlocks first. For the purpose of other heuristics, an
1856 // instruction that cannot issue appears as if it's not in the ReadyQueue.
1857 bool IsBuffered = SchedModel->getMicroOpBufferSize() != 0;
1858 if ((!IsBuffered && ReadyCycle > CurrCycle) || checkHazard(SU))
1863 // Record this node as an immediate dependent of the scheduled node.
1867 void SchedBoundary::releaseTopNode(SUnit *SU) {
1868 if (SU->isScheduled)
1871 releaseNode(SU, SU->TopReadyCycle);
1874 void SchedBoundary::releaseBottomNode(SUnit *SU) {
1875 if (SU->isScheduled)
1878 releaseNode(SU, SU->BotReadyCycle);
1881 /// Move the boundary of scheduled code by one cycle.
1882 void SchedBoundary::bumpCycle(unsigned NextCycle) {
1883 if (SchedModel->getMicroOpBufferSize() == 0) {
1884 assert(MinReadyCycle < UINT_MAX && "MinReadyCycle uninitialized");
1885 if (MinReadyCycle > NextCycle)
1886 NextCycle = MinReadyCycle;
1888 // Update the current micro-ops, which will issue in the next cycle.
1889 unsigned DecMOps = SchedModel->getIssueWidth() * (NextCycle - CurrCycle);
1890 CurrMOps = (CurrMOps <= DecMOps) ? 0 : CurrMOps - DecMOps;
1892 // Decrement DependentLatency based on the next cycle.
1893 if ((NextCycle - CurrCycle) > DependentLatency)
1894 DependentLatency = 0;
1896 DependentLatency -= (NextCycle - CurrCycle);
1898 if (!HazardRec->isEnabled()) {
1899 // Bypass HazardRec virtual calls.
1900 CurrCycle = NextCycle;
1903 // Bypass getHazardType calls in case of long latency.
1904 for (; CurrCycle != NextCycle; ++CurrCycle) {
1906 HazardRec->AdvanceCycle();
1908 HazardRec->RecedeCycle();
1911 CheckPending = true;
1912 unsigned LFactor = SchedModel->getLatencyFactor();
1914 (int)(getCriticalCount() - (getScheduledLatency() * LFactor))
1917 DEBUG(dbgs() << "Cycle: " << CurrCycle << ' ' << Available.getName() << '\n');
1920 void SchedBoundary::incExecutedResources(unsigned PIdx, unsigned Count) {
1921 ExecutedResCounts[PIdx] += Count;
1922 if (ExecutedResCounts[PIdx] > MaxExecutedResCount)
1923 MaxExecutedResCount = ExecutedResCounts[PIdx];
1926 /// Add the given processor resource to this scheduled zone.
1928 /// \param Cycles indicates the number of consecutive (non-pipelined) cycles
1929 /// during which this resource is consumed.
1931 /// \return the next cycle at which the instruction may execute without
1932 /// oversubscribing resources.
1933 unsigned SchedBoundary::
1934 countResource(unsigned PIdx, unsigned Cycles, unsigned NextCycle) {
1935 unsigned Factor = SchedModel->getResourceFactor(PIdx);
1936 unsigned Count = Factor * Cycles;
1937 DEBUG(dbgs() << " " << SchedModel->getResourceName(PIdx)
1938 << " +" << Cycles << "x" << Factor << "u\n");
1940 // Update Executed resources counts.
1941 incExecutedResources(PIdx, Count);
1942 assert(Rem->RemainingCounts[PIdx] >= Count && "resource double counted");
1943 Rem->RemainingCounts[PIdx] -= Count;
1945 // Check if this resource exceeds the current critical resource. If so, it
1946 // becomes the critical resource.
1947 if (ZoneCritResIdx != PIdx && (getResourceCount(PIdx) > getCriticalCount())) {
1948 ZoneCritResIdx = PIdx;
1949 DEBUG(dbgs() << " *** Critical resource "
1950 << SchedModel->getResourceName(PIdx) << ": "
1951 << getResourceCount(PIdx) / SchedModel->getLatencyFactor() << "c\n");
1953 // For reserved resources, record the highest cycle using the resource.
1954 unsigned NextAvailable = getNextResourceCycle(PIdx, Cycles);
1955 if (NextAvailable > CurrCycle) {
1956 DEBUG(dbgs() << " Resource conflict: "
1957 << SchedModel->getProcResource(PIdx)->Name << " reserved until @"
1958 << NextAvailable << "\n");
1960 return NextAvailable;
1963 /// Move the boundary of scheduled code by one SUnit.
1964 void SchedBoundary::bumpNode(SUnit *SU) {
1965 // Update the reservation table.
1966 if (HazardRec->isEnabled()) {
1967 if (!isTop() && SU->isCall) {
1968 // Calls are scheduled with their preceding instructions. For bottom-up
1969 // scheduling, clear the pipeline state before emitting.
1972 HazardRec->EmitInstruction(SU);
1974 // checkHazard should prevent scheduling multiple instructions per cycle that
1975 // exceed the issue width.
1976 const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
1977 unsigned IncMOps = SchedModel->getNumMicroOps(SU->getInstr());
1979 (CurrMOps == 0 || (CurrMOps + IncMOps) <= SchedModel->getIssueWidth()) &&
1980 "Cannot schedule this instruction's MicroOps in the current cycle.");
1982 unsigned ReadyCycle = (isTop() ? SU->TopReadyCycle : SU->BotReadyCycle);
1983 DEBUG(dbgs() << " Ready @" << ReadyCycle << "c\n");
1985 unsigned NextCycle = CurrCycle;
1986 switch (SchedModel->getMicroOpBufferSize()) {
1988 assert(ReadyCycle <= CurrCycle && "Broken PendingQueue");
1991 if (ReadyCycle > NextCycle) {
1992 NextCycle = ReadyCycle;
1993 DEBUG(dbgs() << " *** Stall until: " << ReadyCycle << "\n");
1997 // We don't currently model the OOO reorder buffer, so consider all
1998 // scheduled MOps to be "retired". We do loosely model in-order resource
1999 // latency. If this instruction uses an in-order resource, account for any
2000 // likely stall cycles.
2001 if (SU->isUnbuffered && ReadyCycle > NextCycle)
2002 NextCycle = ReadyCycle;
2005 RetiredMOps += IncMOps;
2007 // Update resource counts and critical resource.
2008 if (SchedModel->hasInstrSchedModel()) {
2009 unsigned DecRemIssue = IncMOps * SchedModel->getMicroOpFactor();
2010 assert(Rem->RemIssueCount >= DecRemIssue && "MOps double counted");
2011 Rem->RemIssueCount -= DecRemIssue;
2012 if (ZoneCritResIdx) {
2013 // Scale scheduled micro-ops for comparing with the critical resource.
2014 unsigned ScaledMOps =
2015 RetiredMOps * SchedModel->getMicroOpFactor();
2017 // If scaled micro-ops are now more than the previous critical resource by
2018 // a full cycle, then micro-ops issue becomes critical.
2019 if ((int)(ScaledMOps - getResourceCount(ZoneCritResIdx))
2020 >= (int)SchedModel->getLatencyFactor()) {
2022 DEBUG(dbgs() << " *** Critical resource NumMicroOps: "
2023 << ScaledMOps / SchedModel->getLatencyFactor() << "c\n");
2026 for (TargetSchedModel::ProcResIter
2027 PI = SchedModel->getWriteProcResBegin(SC),
2028 PE = SchedModel->getWriteProcResEnd(SC); PI != PE; ++PI) {
2030 countResource(PI->ProcResourceIdx, PI->Cycles, NextCycle);
2031 if (RCycle > NextCycle)
2034 if (SU->hasReservedResource) {
2035 // For reserved resources, record the highest cycle using the resource.
2036 // For top-down scheduling, this is the cycle in which we schedule this
2037 // instruction plus the number of cycles the operations reserves the
2038 // resource. For bottom-up is it simply the instruction's cycle.
2039 for (TargetSchedModel::ProcResIter
2040 PI = SchedModel->getWriteProcResBegin(SC),
2041 PE = SchedModel->getWriteProcResEnd(SC); PI != PE; ++PI) {
2042 unsigned PIdx = PI->ProcResourceIdx;
2043 if (SchedModel->getProcResource(PIdx)->BufferSize == 0) {
2045 ReservedCycles[PIdx] =
2046 std::max(getNextResourceCycle(PIdx, 0), NextCycle + PI->Cycles);
2049 ReservedCycles[PIdx] = NextCycle;
2054 // Update ExpectedLatency and DependentLatency.
2055 unsigned &TopLatency = isTop() ? ExpectedLatency : DependentLatency;
2056 unsigned &BotLatency = isTop() ? DependentLatency : ExpectedLatency;
2057 if (SU->getDepth() > TopLatency) {
2058 TopLatency = SU->getDepth();
2059 DEBUG(dbgs() << " " << Available.getName()
2060 << " TopLatency SU(" << SU->NodeNum << ") " << TopLatency << "c\n");
2062 if (SU->getHeight() > BotLatency) {
2063 BotLatency = SU->getHeight();
2064 DEBUG(dbgs() << " " << Available.getName()
2065 << " BotLatency SU(" << SU->NodeNum << ") " << BotLatency << "c\n");
2067 // If we stall for any reason, bump the cycle.
2068 if (NextCycle > CurrCycle) {
2069 bumpCycle(NextCycle);
2072 // After updating ZoneCritResIdx and ExpectedLatency, check if we're
2073 // resource limited. If a stall occurred, bumpCycle does this.
2074 unsigned LFactor = SchedModel->getLatencyFactor();
2076 (int)(getCriticalCount() - (getScheduledLatency() * LFactor))
2079 // Update CurrMOps after calling bumpCycle to handle stalls, since bumpCycle
2080 // resets CurrMOps. Loop to handle instructions with more MOps than issue in
2081 // one cycle. Since we commonly reach the max MOps here, opportunistically
2082 // bump the cycle to avoid uselessly checking everything in the readyQ.
2083 CurrMOps += IncMOps;
2084 while (CurrMOps >= SchedModel->getIssueWidth()) {
2085 DEBUG(dbgs() << " *** Max MOps " << CurrMOps
2086 << " at cycle " << CurrCycle << '\n');
2087 bumpCycle(++NextCycle);
2089 DEBUG(dumpScheduledState());
2092 /// Release pending ready nodes in to the available queue. This makes them
2093 /// visible to heuristics.
2094 void SchedBoundary::releasePending() {
2095 // If the available queue is empty, it is safe to reset MinReadyCycle.
2096 if (Available.empty())
2097 MinReadyCycle = UINT_MAX;
2099 // Check to see if any of the pending instructions are ready to issue. If
2100 // so, add them to the available queue.
2101 bool IsBuffered = SchedModel->getMicroOpBufferSize() != 0;
2102 for (unsigned i = 0, e = Pending.size(); i != e; ++i) {
2103 SUnit *SU = *(Pending.begin()+i);
2104 unsigned ReadyCycle = isTop() ? SU->TopReadyCycle : SU->BotReadyCycle;
2106 if (ReadyCycle < MinReadyCycle)
2107 MinReadyCycle = ReadyCycle;
2109 if (!IsBuffered && ReadyCycle > CurrCycle)
2112 if (checkHazard(SU))
2116 Pending.remove(Pending.begin()+i);
2119 DEBUG(if (!Pending.empty()) Pending.dump());
2120 CheckPending = false;
2123 /// Remove SU from the ready set for this boundary.
2124 void SchedBoundary::removeReady(SUnit *SU) {
2125 if (Available.isInQueue(SU))
2126 Available.remove(Available.find(SU));
2128 assert(Pending.isInQueue(SU) && "bad ready count");
2129 Pending.remove(Pending.find(SU));
2133 /// If this queue only has one ready candidate, return it. As a side effect,
2134 /// defer any nodes that now hit a hazard, and advance the cycle until at least
2135 /// one node is ready. If multiple instructions are ready, return NULL.
2136 SUnit *SchedBoundary::pickOnlyChoice() {
2141 // Defer any ready instrs that now have a hazard.
2142 for (ReadyQueue::iterator I = Available.begin(); I != Available.end();) {
2143 if (checkHazard(*I)) {
2145 I = Available.remove(I);
2151 for (unsigned i = 0; Available.empty(); ++i) {
2152 // FIXME: Re-enable assert once PR20057 is resolved.
2153 // assert(i <= (HazardRec->getMaxLookAhead() + MaxObservedStall) &&
2154 // "permanent hazard");
2156 bumpCycle(CurrCycle + 1);
2159 if (Available.size() == 1)
2160 return *Available.begin();
2165 // This is useful information to dump after bumpNode.
2166 // Note that the Queue contents are more useful before pickNodeFromQueue.
2167 void SchedBoundary::dumpScheduledState() {
2170 if (ZoneCritResIdx) {
2171 ResFactor = SchedModel->getResourceFactor(ZoneCritResIdx);
2172 ResCount = getResourceCount(ZoneCritResIdx);
2175 ResFactor = SchedModel->getMicroOpFactor();
2176 ResCount = RetiredMOps * SchedModel->getMicroOpFactor();
2178 unsigned LFactor = SchedModel->getLatencyFactor();
2179 dbgs() << Available.getName() << " @" << CurrCycle << "c\n"
2180 << " Retired: " << RetiredMOps;
2181 dbgs() << "\n Executed: " << getExecutedCount() / LFactor << "c";
2182 dbgs() << "\n Critical: " << ResCount / LFactor << "c, "
2183 << ResCount / ResFactor << " "
2184 << SchedModel->getResourceName(ZoneCritResIdx)
2185 << "\n ExpectedLatency: " << ExpectedLatency << "c\n"
2186 << (IsResourceLimited ? " - Resource" : " - Latency")
2191 //===----------------------------------------------------------------------===//
2192 // GenericScheduler - Generic implementation of MachineSchedStrategy.
2193 //===----------------------------------------------------------------------===//
2195 void GenericSchedulerBase::SchedCandidate::
2196 initResourceDelta(const ScheduleDAGMI *DAG,
2197 const TargetSchedModel *SchedModel) {
2198 if (!Policy.ReduceResIdx && !Policy.DemandResIdx)
2201 const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
2202 for (TargetSchedModel::ProcResIter
2203 PI = SchedModel->getWriteProcResBegin(SC),
2204 PE = SchedModel->getWriteProcResEnd(SC); PI != PE; ++PI) {
2205 if (PI->ProcResourceIdx == Policy.ReduceResIdx)
2206 ResDelta.CritResources += PI->Cycles;
2207 if (PI->ProcResourceIdx == Policy.DemandResIdx)
2208 ResDelta.DemandedResources += PI->Cycles;
2212 /// Set the CandPolicy given a scheduling zone given the current resources and
2213 /// latencies inside and outside the zone.
2214 void GenericSchedulerBase::setPolicy(CandPolicy &Policy,
2216 SchedBoundary &CurrZone,
2217 SchedBoundary *OtherZone) {
2218 // Apply preemptive heuristics based on the total latency and resources
2219 // inside and outside this zone. Potential stalls should be considered before
2220 // following this policy.
2222 // Compute remaining latency. We need this both to determine whether the
2223 // overall schedule has become latency-limited and whether the instructions
2224 // outside this zone are resource or latency limited.
2226 // The "dependent" latency is updated incrementally during scheduling as the
2227 // max height/depth of scheduled nodes minus the cycles since it was
2229 // DLat = max (N.depth - (CurrCycle - N.ReadyCycle) for N in Zone
2231 // The "independent" latency is the max ready queue depth:
2232 // ILat = max N.depth for N in Available|Pending
2234 // RemainingLatency is the greater of independent and dependent latency.
2235 unsigned RemLatency = CurrZone.getDependentLatency();
2236 RemLatency = std::max(RemLatency,
2237 CurrZone.findMaxLatency(CurrZone.Available.elements()));
2238 RemLatency = std::max(RemLatency,
2239 CurrZone.findMaxLatency(CurrZone.Pending.elements()));
2241 // Compute the critical resource outside the zone.
2242 unsigned OtherCritIdx = 0;
2243 unsigned OtherCount =
2244 OtherZone ? OtherZone->getOtherResourceCount(OtherCritIdx) : 0;
2246 bool OtherResLimited = false;
2247 if (SchedModel->hasInstrSchedModel()) {
2248 unsigned LFactor = SchedModel->getLatencyFactor();
2249 OtherResLimited = (int)(OtherCount - (RemLatency * LFactor)) > (int)LFactor;
2251 // Schedule aggressively for latency in PostRA mode. We don't check for
2252 // acyclic latency during PostRA, and highly out-of-order processors will
2253 // skip PostRA scheduling.
2254 if (!OtherResLimited) {
2255 if (IsPostRA || (RemLatency + CurrZone.getCurrCycle() > Rem.CriticalPath)) {
2256 Policy.ReduceLatency |= true;
2257 DEBUG(dbgs() << " " << CurrZone.Available.getName()
2258 << " RemainingLatency " << RemLatency << " + "
2259 << CurrZone.getCurrCycle() << "c > CritPath "
2260 << Rem.CriticalPath << "\n");
2263 // If the same resource is limiting inside and outside the zone, do nothing.
2264 if (CurrZone.getZoneCritResIdx() == OtherCritIdx)
2268 if (CurrZone.isResourceLimited()) {
2269 dbgs() << " " << CurrZone.Available.getName() << " ResourceLimited: "
2270 << SchedModel->getResourceName(CurrZone.getZoneCritResIdx())
2273 if (OtherResLimited)
2274 dbgs() << " RemainingLimit: "
2275 << SchedModel->getResourceName(OtherCritIdx) << "\n";
2276 if (!CurrZone.isResourceLimited() && !OtherResLimited)
2277 dbgs() << " Latency limited both directions.\n");
2279 if (CurrZone.isResourceLimited() && !Policy.ReduceResIdx)
2280 Policy.ReduceResIdx = CurrZone.getZoneCritResIdx();
2282 if (OtherResLimited)
2283 Policy.DemandResIdx = OtherCritIdx;
2287 const char *GenericSchedulerBase::getReasonStr(
2288 GenericSchedulerBase::CandReason Reason) {
2290 case NoCand: return "NOCAND ";
2291 case PhysRegCopy: return "PREG-COPY";
2292 case RegExcess: return "REG-EXCESS";
2293 case RegCritical: return "REG-CRIT ";
2294 case Stall: return "STALL ";
2295 case Cluster: return "CLUSTER ";
2296 case Weak: return "WEAK ";
2297 case RegMax: return "REG-MAX ";
2298 case ResourceReduce: return "RES-REDUCE";
2299 case ResourceDemand: return "RES-DEMAND";
2300 case TopDepthReduce: return "TOP-DEPTH ";
2301 case TopPathReduce: return "TOP-PATH ";
2302 case BotHeightReduce:return "BOT-HEIGHT";
2303 case BotPathReduce: return "BOT-PATH ";
2304 case NextDefUse: return "DEF-USE ";
2305 case NodeOrder: return "ORDER ";
2307 llvm_unreachable("Unknown reason!");
2310 void GenericSchedulerBase::traceCandidate(const SchedCandidate &Cand) {
2312 unsigned ResIdx = 0;
2313 unsigned Latency = 0;
2314 switch (Cand.Reason) {
2318 P = Cand.RPDelta.Excess;
2321 P = Cand.RPDelta.CriticalMax;
2324 P = Cand.RPDelta.CurrentMax;
2326 case ResourceReduce:
2327 ResIdx = Cand.Policy.ReduceResIdx;
2329 case ResourceDemand:
2330 ResIdx = Cand.Policy.DemandResIdx;
2332 case TopDepthReduce:
2333 Latency = Cand.SU->getDepth();
2336 Latency = Cand.SU->getHeight();
2338 case BotHeightReduce:
2339 Latency = Cand.SU->getHeight();
2342 Latency = Cand.SU->getDepth();
2345 dbgs() << " Cand SU(" << Cand.SU->NodeNum << ") " << getReasonStr(Cand.Reason);
2347 dbgs() << " " << TRI->getRegPressureSetName(P.getPSet())
2348 << ":" << P.getUnitInc() << " ";
2352 dbgs() << " " << SchedModel->getProcResource(ResIdx)->Name << " ";
2356 dbgs() << " " << Latency << " cycles ";
2363 /// Return true if this heuristic determines order.
2364 static bool tryLess(int TryVal, int CandVal,
2365 GenericSchedulerBase::SchedCandidate &TryCand,
2366 GenericSchedulerBase::SchedCandidate &Cand,
2367 GenericSchedulerBase::CandReason Reason) {
2368 if (TryVal < CandVal) {
2369 TryCand.Reason = Reason;
2372 if (TryVal > CandVal) {
2373 if (Cand.Reason > Reason)
2374 Cand.Reason = Reason;
2377 Cand.setRepeat(Reason);
2381 static bool tryGreater(int TryVal, int CandVal,
2382 GenericSchedulerBase::SchedCandidate &TryCand,
2383 GenericSchedulerBase::SchedCandidate &Cand,
2384 GenericSchedulerBase::CandReason Reason) {
2385 if (TryVal > CandVal) {
2386 TryCand.Reason = Reason;
2389 if (TryVal < CandVal) {
2390 if (Cand.Reason > Reason)
2391 Cand.Reason = Reason;
2394 Cand.setRepeat(Reason);
2398 static bool tryLatency(GenericSchedulerBase::SchedCandidate &TryCand,
2399 GenericSchedulerBase::SchedCandidate &Cand,
2400 SchedBoundary &Zone) {
2402 if (Cand.SU->getDepth() > Zone.getScheduledLatency()) {
2403 if (tryLess(TryCand.SU->getDepth(), Cand.SU->getDepth(),
2404 TryCand, Cand, GenericSchedulerBase::TopDepthReduce))
2407 if (tryGreater(TryCand.SU->getHeight(), Cand.SU->getHeight(),
2408 TryCand, Cand, GenericSchedulerBase::TopPathReduce))
2412 if (Cand.SU->getHeight() > Zone.getScheduledLatency()) {
2413 if (tryLess(TryCand.SU->getHeight(), Cand.SU->getHeight(),
2414 TryCand, Cand, GenericSchedulerBase::BotHeightReduce))
2417 if (tryGreater(TryCand.SU->getDepth(), Cand.SU->getDepth(),
2418 TryCand, Cand, GenericSchedulerBase::BotPathReduce))
2424 static void tracePick(const GenericSchedulerBase::SchedCandidate &Cand,
2426 DEBUG(dbgs() << "Pick " << (IsTop ? "Top " : "Bot ")
2427 << GenericSchedulerBase::getReasonStr(Cand.Reason) << '\n');
2430 void GenericScheduler::initialize(ScheduleDAGMI *dag) {
2431 assert(dag->hasVRegLiveness() &&
2432 "(PreRA)GenericScheduler needs vreg liveness");
2433 DAG = static_cast<ScheduleDAGMILive*>(dag);
2434 SchedModel = DAG->getSchedModel();
2437 Rem.init(DAG, SchedModel);
2438 Top.init(DAG, SchedModel, &Rem);
2439 Bot.init(DAG, SchedModel, &Rem);
2441 // Initialize resource counts.
2443 // Initialize the HazardRecognizers. If itineraries don't exist, are empty, or
2444 // are disabled, then these HazardRecs will be disabled.
2445 const InstrItineraryData *Itin = SchedModel->getInstrItineraries();
2446 if (!Top.HazardRec) {
2448 DAG->MF.getSubtarget().getInstrInfo()->CreateTargetMIHazardRecognizer(
2451 if (!Bot.HazardRec) {
2453 DAG->MF.getSubtarget().getInstrInfo()->CreateTargetMIHazardRecognizer(
2458 /// Initialize the per-region scheduling policy.
2459 void GenericScheduler::initPolicy(MachineBasicBlock::iterator Begin,
2460 MachineBasicBlock::iterator End,
2461 unsigned NumRegionInstrs) {
2462 const MachineFunction &MF = *Begin->getParent()->getParent();
2463 const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
2465 // Avoid setting up the register pressure tracker for small regions to save
2466 // compile time. As a rough heuristic, only track pressure when the number of
2467 // schedulable instructions exceeds half the integer register file.
2468 RegionPolicy.ShouldTrackPressure = true;
2469 for (unsigned VT = MVT::i32; VT > (unsigned)MVT::i1; --VT) {
2470 MVT::SimpleValueType LegalIntVT = (MVT::SimpleValueType)VT;
2471 if (TLI->isTypeLegal(LegalIntVT)) {
2472 unsigned NIntRegs = Context->RegClassInfo->getNumAllocatableRegs(
2473 TLI->getRegClassFor(LegalIntVT));
2474 RegionPolicy.ShouldTrackPressure = NumRegionInstrs > (NIntRegs / 2);
2478 // For generic targets, we default to bottom-up, because it's simpler and more
2479 // compile-time optimizations have been implemented in that direction.
2480 RegionPolicy.OnlyBottomUp = true;
2482 // Allow the subtarget to override default policy.
2483 MF.getSubtarget().overrideSchedPolicy(RegionPolicy, Begin, End,
2486 // After subtarget overrides, apply command line options.
2487 if (!EnableRegPressure)
2488 RegionPolicy.ShouldTrackPressure = false;
2490 // Check -misched-topdown/bottomup can force or unforce scheduling direction.
2491 // e.g. -misched-bottomup=false allows scheduling in both directions.
2492 assert((!ForceTopDown || !ForceBottomUp) &&
2493 "-misched-topdown incompatible with -misched-bottomup");
2494 if (ForceBottomUp.getNumOccurrences() > 0) {
2495 RegionPolicy.OnlyBottomUp = ForceBottomUp;
2496 if (RegionPolicy.OnlyBottomUp)
2497 RegionPolicy.OnlyTopDown = false;
2499 if (ForceTopDown.getNumOccurrences() > 0) {
2500 RegionPolicy.OnlyTopDown = ForceTopDown;
2501 if (RegionPolicy.OnlyTopDown)
2502 RegionPolicy.OnlyBottomUp = false;
2506 void GenericScheduler::dumpPolicy() {
2507 dbgs() << "GenericScheduler RegionPolicy: "
2508 << " ShouldTrackPressure=" << RegionPolicy.ShouldTrackPressure
2509 << " OnlyTopDown=" << RegionPolicy.OnlyTopDown
2510 << " OnlyBottomUp=" << RegionPolicy.OnlyBottomUp
2514 /// Set IsAcyclicLatencyLimited if the acyclic path is longer than the cyclic
2515 /// critical path by more cycles than it takes to drain the instruction buffer.
2516 /// We estimate an upper bounds on in-flight instructions as:
2518 /// CyclesPerIteration = max( CyclicPath, Loop-Resource-Height )
2519 /// InFlightIterations = AcyclicPath / CyclesPerIteration
2520 /// InFlightResources = InFlightIterations * LoopResources
2522 /// TODO: Check execution resources in addition to IssueCount.
2523 void GenericScheduler::checkAcyclicLatency() {
2524 if (Rem.CyclicCritPath == 0 || Rem.CyclicCritPath >= Rem.CriticalPath)
2527 // Scaled number of cycles per loop iteration.
2528 unsigned IterCount =
2529 std::max(Rem.CyclicCritPath * SchedModel->getLatencyFactor(),
2531 // Scaled acyclic critical path.
2532 unsigned AcyclicCount = Rem.CriticalPath * SchedModel->getLatencyFactor();
2533 // InFlightCount = (AcyclicPath / IterCycles) * InstrPerLoop
2534 unsigned InFlightCount =
2535 (AcyclicCount * Rem.RemIssueCount + IterCount-1) / IterCount;
2536 unsigned BufferLimit =
2537 SchedModel->getMicroOpBufferSize() * SchedModel->getMicroOpFactor();
2539 Rem.IsAcyclicLatencyLimited = InFlightCount > BufferLimit;
2541 DEBUG(dbgs() << "IssueCycles="
2542 << Rem.RemIssueCount / SchedModel->getLatencyFactor() << "c "
2543 << "IterCycles=" << IterCount / SchedModel->getLatencyFactor()
2544 << "c NumIters=" << (AcyclicCount + IterCount-1) / IterCount
2545 << " InFlight=" << InFlightCount / SchedModel->getMicroOpFactor()
2546 << "m BufferLim=" << SchedModel->getMicroOpBufferSize() << "m\n";
2547 if (Rem.IsAcyclicLatencyLimited)
2548 dbgs() << " ACYCLIC LATENCY LIMIT\n");
2551 void GenericScheduler::registerRoots() {
2552 Rem.CriticalPath = DAG->ExitSU.getDepth();
2554 // Some roots may not feed into ExitSU. Check all of them in case.
2555 for (std::vector<SUnit*>::const_iterator
2556 I = Bot.Available.begin(), E = Bot.Available.end(); I != E; ++I) {
2557 if ((*I)->getDepth() > Rem.CriticalPath)
2558 Rem.CriticalPath = (*I)->getDepth();
2560 DEBUG(dbgs() << "Critical Path(GS-RR ): " << Rem.CriticalPath << '\n');
2561 if (DumpCriticalPathLength) {
2562 errs() << "Critical Path(GS-RR ): " << Rem.CriticalPath << " \n";
2565 if (EnableCyclicPath) {
2566 Rem.CyclicCritPath = DAG->computeCyclicCriticalPath();
2567 checkAcyclicLatency();
2571 static bool tryPressure(const PressureChange &TryP,
2572 const PressureChange &CandP,
2573 GenericSchedulerBase::SchedCandidate &TryCand,
2574 GenericSchedulerBase::SchedCandidate &Cand,
2575 GenericSchedulerBase::CandReason Reason) {
2576 int TryRank = TryP.getPSetOrMax();
2577 int CandRank = CandP.getPSetOrMax();
2578 // If both candidates affect the same set, go with the smallest increase.
2579 if (TryRank == CandRank) {
2580 return tryLess(TryP.getUnitInc(), CandP.getUnitInc(), TryCand, Cand,
2583 // If one candidate decreases and the other increases, go with it.
2584 // Invalid candidates have UnitInc==0.
2585 if (tryGreater(TryP.getUnitInc() < 0, CandP.getUnitInc() < 0, TryCand, Cand,
2589 // If the candidates are decreasing pressure, reverse priority.
2590 if (TryP.getUnitInc() < 0)
2591 std::swap(TryRank, CandRank);
2592 return tryGreater(TryRank, CandRank, TryCand, Cand, Reason);
2595 static unsigned getWeakLeft(const SUnit *SU, bool isTop) {
2596 return (isTop) ? SU->WeakPredsLeft : SU->WeakSuccsLeft;
2599 /// Minimize physical register live ranges. Regalloc wants them adjacent to
2600 /// their physreg def/use.
2602 /// FIXME: This is an unnecessary check on the critical path. Most are root/leaf
2603 /// copies which can be prescheduled. The rest (e.g. x86 MUL) could be bundled
2604 /// with the operation that produces or consumes the physreg. We'll do this when
2605 /// regalloc has support for parallel copies.
2606 static int biasPhysRegCopy(const SUnit *SU, bool isTop) {
2607 const MachineInstr *MI = SU->getInstr();
2611 unsigned ScheduledOper = isTop ? 1 : 0;
2612 unsigned UnscheduledOper = isTop ? 0 : 1;
2613 // If we have already scheduled the physreg produce/consumer, immediately
2614 // schedule the copy.
2615 if (TargetRegisterInfo::isPhysicalRegister(
2616 MI->getOperand(ScheduledOper).getReg()))
2618 // If the physreg is at the boundary, defer it. Otherwise schedule it
2619 // immediately to free the dependent. We can hoist the copy later.
2620 bool AtBoundary = isTop ? !SU->NumSuccsLeft : !SU->NumPredsLeft;
2621 if (TargetRegisterInfo::isPhysicalRegister(
2622 MI->getOperand(UnscheduledOper).getReg()))
2623 return AtBoundary ? -1 : 1;
2627 /// Apply a set of heursitics to a new candidate. Heuristics are currently
2628 /// hierarchical. This may be more efficient than a graduated cost model because
2629 /// we don't need to evaluate all aspects of the model for each node in the
2630 /// queue. But it's really done to make the heuristics easier to debug and
2631 /// statistically analyze.
2633 /// \param Cand provides the policy and current best candidate.
2634 /// \param TryCand refers to the next SUnit candidate, otherwise uninitialized.
2635 /// \param Zone describes the scheduled zone that we are extending.
2636 /// \param RPTracker describes reg pressure within the scheduled zone.
2637 /// \param TempTracker is a scratch pressure tracker to reuse in queries.
2638 void GenericScheduler::tryCandidate(SchedCandidate &Cand,
2639 SchedCandidate &TryCand,
2640 SchedBoundary &Zone,
2641 const RegPressureTracker &RPTracker,
2642 RegPressureTracker &TempTracker) {
2644 if (DAG->isTrackingPressure()) {
2645 // Always initialize TryCand's RPDelta.
2647 TempTracker.getMaxDownwardPressureDelta(
2648 TryCand.SU->getInstr(),
2650 DAG->getRegionCriticalPSets(),
2651 DAG->getRegPressure().MaxSetPressure);
2654 if (VerifyScheduling) {
2655 TempTracker.getMaxUpwardPressureDelta(
2656 TryCand.SU->getInstr(),
2657 &DAG->getPressureDiff(TryCand.SU),
2659 DAG->getRegionCriticalPSets(),
2660 DAG->getRegPressure().MaxSetPressure);
2663 RPTracker.getUpwardPressureDelta(
2664 TryCand.SU->getInstr(),
2665 DAG->getPressureDiff(TryCand.SU),
2667 DAG->getRegionCriticalPSets(),
2668 DAG->getRegPressure().MaxSetPressure);
2672 DEBUG(if (TryCand.RPDelta.Excess.isValid())
2673 dbgs() << " Try SU(" << TryCand.SU->NodeNum << ") "
2674 << TRI->getRegPressureSetName(TryCand.RPDelta.Excess.getPSet())
2675 << ":" << TryCand.RPDelta.Excess.getUnitInc() << "\n");
2677 // Initialize the candidate if needed.
2678 if (!Cand.isValid()) {
2679 TryCand.Reason = NodeOrder;
2683 if (tryGreater(biasPhysRegCopy(TryCand.SU, Zone.isTop()),
2684 biasPhysRegCopy(Cand.SU, Zone.isTop()),
2685 TryCand, Cand, PhysRegCopy))
2688 // Avoid exceeding the target's limit.
2689 if (DAG->isTrackingPressure() && tryPressure(TryCand.RPDelta.Excess,
2690 Cand.RPDelta.Excess,
2691 TryCand, Cand, RegExcess))
2694 // Avoid increasing the max critical pressure in the scheduled region.
2695 if (DAG->isTrackingPressure() && tryPressure(TryCand.RPDelta.CriticalMax,
2696 Cand.RPDelta.CriticalMax,
2697 TryCand, Cand, RegCritical))
2700 // For loops that are acyclic path limited, aggressively schedule for latency.
2701 // This can result in very long dependence chains scheduled in sequence, so
2702 // once every cycle (when CurrMOps == 0), switch to normal heuristics.
2703 if (Rem.IsAcyclicLatencyLimited && !Zone.getCurrMOps()
2704 && tryLatency(TryCand, Cand, Zone))
2707 // Prioritize instructions that read unbuffered resources by stall cycles.
2708 if (tryLess(Zone.getLatencyStallCycles(TryCand.SU),
2709 Zone.getLatencyStallCycles(Cand.SU), TryCand, Cand, Stall))
2712 // Keep clustered nodes together to encourage downstream peephole
2713 // optimizations which may reduce resource requirements.
2715 // This is a best effort to set things up for a post-RA pass. Optimizations
2716 // like generating loads of multiple registers should ideally be done within
2717 // the scheduler pass by combining the loads during DAG postprocessing.
2718 const SUnit *NextClusterSU =
2719 Zone.isTop() ? DAG->getNextClusterSucc() : DAG->getNextClusterPred();
2720 if (tryGreater(TryCand.SU == NextClusterSU, Cand.SU == NextClusterSU,
2721 TryCand, Cand, Cluster))
2724 // Weak edges are for clustering and other constraints.
2725 if (tryLess(getWeakLeft(TryCand.SU, Zone.isTop()),
2726 getWeakLeft(Cand.SU, Zone.isTop()),
2727 TryCand, Cand, Weak)) {
2730 // Avoid increasing the max pressure of the entire region.
2731 if (DAG->isTrackingPressure() && tryPressure(TryCand.RPDelta.CurrentMax,
2732 Cand.RPDelta.CurrentMax,
2733 TryCand, Cand, RegMax))
2736 // Avoid critical resource consumption and balance the schedule.
2737 TryCand.initResourceDelta(DAG, SchedModel);
2738 if (tryLess(TryCand.ResDelta.CritResources, Cand.ResDelta.CritResources,
2739 TryCand, Cand, ResourceReduce))
2741 if (tryGreater(TryCand.ResDelta.DemandedResources,
2742 Cand.ResDelta.DemandedResources,
2743 TryCand, Cand, ResourceDemand))
2746 // Avoid serializing long latency dependence chains.
2747 // For acyclic path limited loops, latency was already checked above.
2748 if (!RegionPolicy.DisableLatencyHeuristic && Cand.Policy.ReduceLatency &&
2749 !Rem.IsAcyclicLatencyLimited && tryLatency(TryCand, Cand, Zone)) {
2753 // Prefer immediate defs/users of the last scheduled instruction. This is a
2754 // local pressure avoidance strategy that also makes the machine code
2756 if (tryGreater(Zone.isNextSU(TryCand.SU), Zone.isNextSU(Cand.SU),
2757 TryCand, Cand, NextDefUse))
2760 // Fall through to original instruction order.
2761 if ((Zone.isTop() && TryCand.SU->NodeNum < Cand.SU->NodeNum)
2762 || (!Zone.isTop() && TryCand.SU->NodeNum > Cand.SU->NodeNum)) {
2763 TryCand.Reason = NodeOrder;
2767 /// Pick the best candidate from the queue.
2769 /// TODO: getMaxPressureDelta results can be mostly cached for each SUnit during
2770 /// DAG building. To adjust for the current scheduling location we need to
2771 /// maintain the number of vreg uses remaining to be top-scheduled.
2772 void GenericScheduler::pickNodeFromQueue(SchedBoundary &Zone,
2773 const RegPressureTracker &RPTracker,
2774 SchedCandidate &Cand) {
2775 ReadyQueue &Q = Zone.Available;
2779 // getMaxPressureDelta temporarily modifies the tracker.
2780 RegPressureTracker &TempTracker = const_cast<RegPressureTracker&>(RPTracker);
2782 for (ReadyQueue::iterator I = Q.begin(), E = Q.end(); I != E; ++I) {
2784 SchedCandidate TryCand(Cand.Policy);
2786 tryCandidate(Cand, TryCand, Zone, RPTracker, TempTracker);
2787 if (TryCand.Reason != NoCand) {
2788 // Initialize resource delta if needed in case future heuristics query it.
2789 if (TryCand.ResDelta == SchedResourceDelta())
2790 TryCand.initResourceDelta(DAG, SchedModel);
2791 Cand.setBest(TryCand);
2792 DEBUG(traceCandidate(Cand));
2797 /// Pick the best candidate node from either the top or bottom queue.
2798 SUnit *GenericScheduler::pickNodeBidirectional(bool &IsTopNode) {
2799 // Schedule as far as possible in the direction of no choice. This is most
2800 // efficient, but also provides the best heuristics for CriticalPSets.
2801 if (SUnit *SU = Bot.pickOnlyChoice()) {
2803 DEBUG(dbgs() << "Pick Bot NOCAND\n");
2806 if (SUnit *SU = Top.pickOnlyChoice()) {
2808 DEBUG(dbgs() << "Pick Top NOCAND\n");
2811 CandPolicy NoPolicy;
2812 SchedCandidate BotCand(NoPolicy);
2813 SchedCandidate TopCand(NoPolicy);
2814 // Set the bottom-up policy based on the state of the current bottom zone and
2815 // the instructions outside the zone, including the top zone.
2816 setPolicy(BotCand.Policy, /*IsPostRA=*/false, Bot, &Top);
2817 // Set the top-down policy based on the state of the current top zone and
2818 // the instructions outside the zone, including the bottom zone.
2819 setPolicy(TopCand.Policy, /*IsPostRA=*/false, Top, &Bot);
2821 // Prefer bottom scheduling when heuristics are silent.
2822 pickNodeFromQueue(Bot, DAG->getBotRPTracker(), BotCand);
2823 assert(BotCand.Reason != NoCand && "failed to find the first candidate");
2825 // If either Q has a single candidate that provides the least increase in
2826 // Excess pressure, we can immediately schedule from that Q.
2828 // RegionCriticalPSets summarizes the pressure within the scheduled region and
2829 // affects picking from either Q. If scheduling in one direction must
2830 // increase pressure for one of the excess PSets, then schedule in that
2831 // direction first to provide more freedom in the other direction.
2832 if ((BotCand.Reason == RegExcess && !BotCand.isRepeat(RegExcess))
2833 || (BotCand.Reason == RegCritical
2834 && !BotCand.isRepeat(RegCritical)))
2837 tracePick(BotCand, IsTopNode);
2840 // Check if the top Q has a better candidate.
2841 pickNodeFromQueue(Top, DAG->getTopRPTracker(), TopCand);
2842 assert(TopCand.Reason != NoCand && "failed to find the first candidate");
2844 // Choose the queue with the most important (lowest enum) reason.
2845 if (TopCand.Reason < BotCand.Reason) {
2847 tracePick(TopCand, IsTopNode);
2850 // Otherwise prefer the bottom candidate, in node order if all else failed.
2852 tracePick(BotCand, IsTopNode);
2856 /// Pick the best node to balance the schedule. Implements MachineSchedStrategy.
2857 SUnit *GenericScheduler::pickNode(bool &IsTopNode) {
2858 if (DAG->top() == DAG->bottom()) {
2859 assert(Top.Available.empty() && Top.Pending.empty() &&
2860 Bot.Available.empty() && Bot.Pending.empty() && "ReadyQ garbage");
2865 if (RegionPolicy.OnlyTopDown) {
2866 SU = Top.pickOnlyChoice();
2868 CandPolicy NoPolicy;
2869 SchedCandidate TopCand(NoPolicy);
2870 pickNodeFromQueue(Top, DAG->getTopRPTracker(), TopCand);
2871 assert(TopCand.Reason != NoCand && "failed to find a candidate");
2872 tracePick(TopCand, true);
2877 else if (RegionPolicy.OnlyBottomUp) {
2878 SU = Bot.pickOnlyChoice();
2880 CandPolicy NoPolicy;
2881 SchedCandidate BotCand(NoPolicy);
2882 pickNodeFromQueue(Bot, DAG->getBotRPTracker(), BotCand);
2883 assert(BotCand.Reason != NoCand && "failed to find a candidate");
2884 tracePick(BotCand, false);
2890 SU = pickNodeBidirectional(IsTopNode);
2892 } while (SU->isScheduled);
2894 if (SU->isTopReady())
2895 Top.removeReady(SU);
2896 if (SU->isBottomReady())
2897 Bot.removeReady(SU);
2899 DEBUG(dbgs() << "Scheduling SU(" << SU->NodeNum << ") " << *SU->getInstr());
2903 void GenericScheduler::reschedulePhysRegCopies(SUnit *SU, bool isTop) {
2905 MachineBasicBlock::iterator InsertPos = SU->getInstr();
2908 SmallVectorImpl<SDep> &Deps = isTop ? SU->Preds : SU->Succs;
2910 // Find already scheduled copies with a single physreg dependence and move
2911 // them just above the scheduled instruction.
2912 for (SmallVectorImpl<SDep>::iterator I = Deps.begin(), E = Deps.end();
2914 if (I->getKind() != SDep::Data || !TRI->isPhysicalRegister(I->getReg()))
2916 SUnit *DepSU = I->getSUnit();
2917 if (isTop ? DepSU->Succs.size() > 1 : DepSU->Preds.size() > 1)
2919 MachineInstr *Copy = DepSU->getInstr();
2920 if (!Copy->isCopy())
2922 DEBUG(dbgs() << " Rescheduling physreg copy ";
2923 I->getSUnit()->dump(DAG));
2924 DAG->moveInstruction(Copy, InsertPos);
2928 /// Update the scheduler's state after scheduling a node. This is the same node
2929 /// that was just returned by pickNode(). However, ScheduleDAGMILive needs to
2930 /// update it's state based on the current cycle before MachineSchedStrategy
2933 /// FIXME: Eventually, we may bundle physreg copies rather than rescheduling
2934 /// them here. See comments in biasPhysRegCopy.
2935 void GenericScheduler::schedNode(SUnit *SU, bool IsTopNode) {
2937 SU->TopReadyCycle = std::max(SU->TopReadyCycle, Top.getCurrCycle());
2939 if (SU->hasPhysRegUses)
2940 reschedulePhysRegCopies(SU, true);
2943 SU->BotReadyCycle = std::max(SU->BotReadyCycle, Bot.getCurrCycle());
2945 if (SU->hasPhysRegDefs)
2946 reschedulePhysRegCopies(SU, false);
2950 /// Create the standard converging machine scheduler. This will be used as the
2951 /// default scheduler if the target does not set a default.
2952 static ScheduleDAGInstrs *createGenericSchedLive(MachineSchedContext *C) {
2953 ScheduleDAGMILive *DAG = new ScheduleDAGMILive(C, make_unique<GenericScheduler>(C));
2954 // Register DAG post-processors.
2956 // FIXME: extend the mutation API to allow earlier mutations to instantiate
2957 // data and pass it to later mutations. Have a single mutation that gathers
2958 // the interesting nodes in one pass.
2959 DAG->addMutation(make_unique<CopyConstrain>(DAG->TII, DAG->TRI));
2960 if (EnableLoadCluster && DAG->TII->enableClusterLoads())
2961 DAG->addMutation(make_unique<LoadClusterMutation>(DAG->TII, DAG->TRI));
2962 if (EnableMacroFusion)
2963 DAG->addMutation(make_unique<MacroFusion>(*DAG->TII, *DAG->TRI));
2967 static MachineSchedRegistry
2968 GenericSchedRegistry("converge", "Standard converging scheduler.",
2969 createGenericSchedLive);
2971 //===----------------------------------------------------------------------===//
2972 // PostGenericScheduler - Generic PostRA implementation of MachineSchedStrategy.
2973 //===----------------------------------------------------------------------===//
2975 void PostGenericScheduler::initialize(ScheduleDAGMI *Dag) {
2977 SchedModel = DAG->getSchedModel();
2980 Rem.init(DAG, SchedModel);
2981 Top.init(DAG, SchedModel, &Rem);
2984 // Initialize the HazardRecognizers. If itineraries don't exist, are empty,
2985 // or are disabled, then these HazardRecs will be disabled.
2986 const InstrItineraryData *Itin = SchedModel->getInstrItineraries();
2987 if (!Top.HazardRec) {
2989 DAG->MF.getSubtarget().getInstrInfo()->CreateTargetMIHazardRecognizer(
2995 void PostGenericScheduler::registerRoots() {
2996 Rem.CriticalPath = DAG->ExitSU.getDepth();
2998 // Some roots may not feed into ExitSU. Check all of them in case.
2999 for (SmallVectorImpl<SUnit*>::const_iterator
3000 I = BotRoots.begin(), E = BotRoots.end(); I != E; ++I) {
3001 if ((*I)->getDepth() > Rem.CriticalPath)
3002 Rem.CriticalPath = (*I)->getDepth();
3004 DEBUG(dbgs() << "Critical Path: (PGS-RR) " << Rem.CriticalPath << '\n');
3005 if (DumpCriticalPathLength) {
3006 errs() << "Critical Path(PGS-RR ): " << Rem.CriticalPath << " \n";
3010 /// Apply a set of heursitics to a new candidate for PostRA scheduling.
3012 /// \param Cand provides the policy and current best candidate.
3013 /// \param TryCand refers to the next SUnit candidate, otherwise uninitialized.
3014 void PostGenericScheduler::tryCandidate(SchedCandidate &Cand,
3015 SchedCandidate &TryCand) {
3017 // Initialize the candidate if needed.
3018 if (!Cand.isValid()) {
3019 TryCand.Reason = NodeOrder;
3023 // Prioritize instructions that read unbuffered resources by stall cycles.
3024 if (tryLess(Top.getLatencyStallCycles(TryCand.SU),
3025 Top.getLatencyStallCycles(Cand.SU), TryCand, Cand, Stall))
3028 // Avoid critical resource consumption and balance the schedule.
3029 if (tryLess(TryCand.ResDelta.CritResources, Cand.ResDelta.CritResources,
3030 TryCand, Cand, ResourceReduce))
3032 if (tryGreater(TryCand.ResDelta.DemandedResources,
3033 Cand.ResDelta.DemandedResources,
3034 TryCand, Cand, ResourceDemand))
3037 // Avoid serializing long latency dependence chains.
3038 if (Cand.Policy.ReduceLatency && tryLatency(TryCand, Cand, Top)) {
3042 // Fall through to original instruction order.
3043 if (TryCand.SU->NodeNum < Cand.SU->NodeNum)
3044 TryCand.Reason = NodeOrder;
3047 void PostGenericScheduler::pickNodeFromQueue(SchedCandidate &Cand) {
3048 ReadyQueue &Q = Top.Available;
3052 for (ReadyQueue::iterator I = Q.begin(), E = Q.end(); I != E; ++I) {
3053 SchedCandidate TryCand(Cand.Policy);
3055 TryCand.initResourceDelta(DAG, SchedModel);
3056 tryCandidate(Cand, TryCand);
3057 if (TryCand.Reason != NoCand) {
3058 Cand.setBest(TryCand);
3059 DEBUG(traceCandidate(Cand));
3064 /// Pick the next node to schedule.
3065 SUnit *PostGenericScheduler::pickNode(bool &IsTopNode) {
3066 if (DAG->top() == DAG->bottom()) {
3067 assert(Top.Available.empty() && Top.Pending.empty() && "ReadyQ garbage");
3072 SU = Top.pickOnlyChoice();
3074 CandPolicy NoPolicy;
3075 SchedCandidate TopCand(NoPolicy);
3076 // Set the top-down policy based on the state of the current top zone and
3077 // the instructions outside the zone, including the bottom zone.
3078 setPolicy(TopCand.Policy, /*IsPostRA=*/true, Top, nullptr);
3079 pickNodeFromQueue(TopCand);
3080 assert(TopCand.Reason != NoCand && "failed to find a candidate");
3081 tracePick(TopCand, true);
3084 } while (SU->isScheduled);
3087 Top.removeReady(SU);
3089 DEBUG(dbgs() << "Scheduling SU(" << SU->NodeNum << ") " << *SU->getInstr());
3093 /// Called after ScheduleDAGMI has scheduled an instruction and updated
3094 /// scheduled/remaining flags in the DAG nodes.
3095 void PostGenericScheduler::schedNode(SUnit *SU, bool IsTopNode) {
3096 SU->TopReadyCycle = std::max(SU->TopReadyCycle, Top.getCurrCycle());
3100 /// Create a generic scheduler with no vreg liveness or DAG mutation passes.
3101 static ScheduleDAGInstrs *createGenericSchedPostRA(MachineSchedContext *C) {
3102 return new ScheduleDAGMI(C, make_unique<PostGenericScheduler>(C), /*IsPostRA=*/true);
3105 //===----------------------------------------------------------------------===//
3106 // ILP Scheduler. Currently for experimental analysis of heuristics.
3107 //===----------------------------------------------------------------------===//
3110 /// \brief Order nodes by the ILP metric.
3112 const SchedDFSResult *DFSResult;
3113 const BitVector *ScheduledTrees;
3116 ILPOrder(bool MaxILP)
3117 : DFSResult(nullptr), ScheduledTrees(nullptr), MaximizeILP(MaxILP) {}
3119 /// \brief Apply a less-than relation on node priority.
3121 /// (Return true if A comes after B in the Q.)
3122 bool operator()(const SUnit *A, const SUnit *B) const {
3123 unsigned SchedTreeA = DFSResult->getSubtreeID(A);
3124 unsigned SchedTreeB = DFSResult->getSubtreeID(B);
3125 if (SchedTreeA != SchedTreeB) {
3126 // Unscheduled trees have lower priority.
3127 if (ScheduledTrees->test(SchedTreeA) != ScheduledTrees->test(SchedTreeB))
3128 return ScheduledTrees->test(SchedTreeB);
3130 // Trees with shallower connections have have lower priority.
3131 if (DFSResult->getSubtreeLevel(SchedTreeA)
3132 != DFSResult->getSubtreeLevel(SchedTreeB)) {
3133 return DFSResult->getSubtreeLevel(SchedTreeA)
3134 < DFSResult->getSubtreeLevel(SchedTreeB);
3138 return DFSResult->getILP(A) < DFSResult->getILP(B);
3140 return DFSResult->getILP(A) > DFSResult->getILP(B);
3144 /// \brief Schedule based on the ILP metric.
3145 class ILPScheduler : public MachineSchedStrategy {
3146 ScheduleDAGMILive *DAG;
3149 std::vector<SUnit*> ReadyQ;
3151 ILPScheduler(bool MaximizeILP): DAG(nullptr), Cmp(MaximizeILP) {}
3153 void initialize(ScheduleDAGMI *dag) override {
3154 assert(dag->hasVRegLiveness() && "ILPScheduler needs vreg liveness");
3155 DAG = static_cast<ScheduleDAGMILive*>(dag);
3156 DAG->computeDFSResult();
3157 Cmp.DFSResult = DAG->getDFSResult();
3158 Cmp.ScheduledTrees = &DAG->getScheduledTrees();
3162 void registerRoots() override {
3163 // Restore the heap in ReadyQ with the updated DFS results.
3164 std::make_heap(ReadyQ.begin(), ReadyQ.end(), Cmp);
3167 /// Implement MachineSchedStrategy interface.
3168 /// -----------------------------------------
3170 /// Callback to select the highest priority node from the ready Q.
3171 SUnit *pickNode(bool &IsTopNode) override {
3172 if (ReadyQ.empty()) return nullptr;
3173 std::pop_heap(ReadyQ.begin(), ReadyQ.end(), Cmp);
3174 SUnit *SU = ReadyQ.back();
3177 DEBUG(dbgs() << "Pick node " << "SU(" << SU->NodeNum << ") "
3178 << " ILP: " << DAG->getDFSResult()->getILP(SU)
3179 << " Tree: " << DAG->getDFSResult()->getSubtreeID(SU) << " @"
3180 << DAG->getDFSResult()->getSubtreeLevel(
3181 DAG->getDFSResult()->getSubtreeID(SU)) << '\n'
3182 << "Scheduling " << *SU->getInstr());
3186 /// \brief Scheduler callback to notify that a new subtree is scheduled.
3187 void scheduleTree(unsigned SubtreeID) override {
3188 std::make_heap(ReadyQ.begin(), ReadyQ.end(), Cmp);
3191 /// Callback after a node is scheduled. Mark a newly scheduled tree, notify
3192 /// DFSResults, and resort the priority Q.
3193 void schedNode(SUnit *SU, bool IsTopNode) override {
3194 assert(!IsTopNode && "SchedDFSResult needs bottom-up");
3197 void releaseTopNode(SUnit *) override { /*only called for top roots*/ }
3199 void releaseBottomNode(SUnit *SU) override {
3200 ReadyQ.push_back(SU);
3201 std::push_heap(ReadyQ.begin(), ReadyQ.end(), Cmp);
3206 static ScheduleDAGInstrs *createILPMaxScheduler(MachineSchedContext *C) {
3207 return new ScheduleDAGMILive(C, make_unique<ILPScheduler>(true));
3209 static ScheduleDAGInstrs *createILPMinScheduler(MachineSchedContext *C) {
3210 return new ScheduleDAGMILive(C, make_unique<ILPScheduler>(false));
3212 static MachineSchedRegistry ILPMaxRegistry(
3213 "ilpmax", "Schedule bottom-up for max ILP", createILPMaxScheduler);
3214 static MachineSchedRegistry ILPMinRegistry(
3215 "ilpmin", "Schedule bottom-up for min ILP", createILPMinScheduler);
3217 //===----------------------------------------------------------------------===//
3218 // Machine Instruction Shuffler for Correctness Testing
3219 //===----------------------------------------------------------------------===//
3223 /// Apply a less-than relation on the node order, which corresponds to the
3224 /// instruction order prior to scheduling. IsReverse implements greater-than.
3225 template<bool IsReverse>
3227 bool operator()(SUnit *A, SUnit *B) const {
3229 return A->NodeNum > B->NodeNum;
3231 return A->NodeNum < B->NodeNum;
3235 /// Reorder instructions as much as possible.
3236 class InstructionShuffler : public MachineSchedStrategy {
3240 // Using a less-than relation (SUnitOrder<false>) for the TopQ priority
3241 // gives nodes with a higher number higher priority causing the latest
3242 // instructions to be scheduled first.
3243 PriorityQueue<SUnit*, std::vector<SUnit*>, SUnitOrder<false> >
3245 // When scheduling bottom-up, use greater-than as the queue priority.
3246 PriorityQueue<SUnit*, std::vector<SUnit*>, SUnitOrder<true> >
3249 InstructionShuffler(bool alternate, bool topdown)
3250 : IsAlternating(alternate), IsTopDown(topdown) {}
3252 void initialize(ScheduleDAGMI*) override {
3257 /// Implement MachineSchedStrategy interface.
3258 /// -----------------------------------------
3260 SUnit *pickNode(bool &IsTopNode) override {
3264 if (TopQ.empty()) return nullptr;
3267 } while (SU->isScheduled);
3272 if (BottomQ.empty()) return nullptr;
3275 } while (SU->isScheduled);
3279 IsTopDown = !IsTopDown;
3283 void schedNode(SUnit *SU, bool IsTopNode) override {}
3285 void releaseTopNode(SUnit *SU) override {
3288 void releaseBottomNode(SUnit *SU) override {
3294 static ScheduleDAGInstrs *createInstructionShuffler(MachineSchedContext *C) {
3295 bool Alternate = !ForceTopDown && !ForceBottomUp;
3296 bool TopDown = !ForceBottomUp;
3297 assert((TopDown || !ForceTopDown) &&
3298 "-misched-topdown incompatible with -misched-bottomup");
3299 return new ScheduleDAGMILive(C, make_unique<InstructionShuffler>(Alternate, TopDown));
3301 static MachineSchedRegistry ShufflerRegistry(
3302 "shuffle", "Shuffle machine instructions alternating directions",
3303 createInstructionShuffler);
3306 //===----------------------------------------------------------------------===//
3307 // GraphWriter support for ScheduleDAGMILive.
3308 //===----------------------------------------------------------------------===//
3313 template<> struct GraphTraits<
3314 ScheduleDAGMI*> : public GraphTraits<ScheduleDAG*> {};
3317 struct DOTGraphTraits<ScheduleDAGMI*> : public DefaultDOTGraphTraits {
3319 DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}
3321 static std::string getGraphName(const ScheduleDAG *G) {
3322 return G->MF.getName();
3325 static bool renderGraphFromBottomUp() {
3329 static bool isNodeHidden(const SUnit *Node) {
3330 if (ViewMISchedCutoff == 0)
3332 return (Node->Preds.size() > ViewMISchedCutoff
3333 || Node->Succs.size() > ViewMISchedCutoff);
3336 /// If you want to override the dot attributes printed for a particular
3337 /// edge, override this method.
3338 static std::string getEdgeAttributes(const SUnit *Node,
3340 const ScheduleDAG *Graph) {
3341 if (EI.isArtificialDep())
3342 return "color=cyan,style=dashed";
3344 return "color=blue,style=dashed";
3348 static std::string getNodeLabel(const SUnit *SU, const ScheduleDAG *G) {
3350 raw_string_ostream SS(Str);
3351 const ScheduleDAGMI *DAG = static_cast<const ScheduleDAGMI*>(G);
3352 const SchedDFSResult *DFS = DAG->hasVRegLiveness() ?
3353 static_cast<const ScheduleDAGMILive*>(G)->getDFSResult() : nullptr;
3354 SS << "SU:" << SU->NodeNum;
3356 SS << " I:" << DFS->getNumInstrs(SU);
3359 static std::string getNodeDescription(const SUnit *SU, const ScheduleDAG *G) {
3360 return G->getGraphNodeLabel(SU);
3363 static std::string getNodeAttributes(const SUnit *N, const ScheduleDAG *G) {
3364 std::string Str("shape=Mrecord");
3365 const ScheduleDAGMI *DAG = static_cast<const ScheduleDAGMI*>(G);
3366 const SchedDFSResult *DFS = DAG->hasVRegLiveness() ?
3367 static_cast<const ScheduleDAGMILive*>(G)->getDFSResult() : nullptr;
3369 Str += ",style=filled,fillcolor=\"#";
3370 Str += DOT::getColorString(DFS->getSubtreeID(N));
3379 /// viewGraph - Pop up a ghostview window with the reachable parts of the DAG
3380 /// rendered using 'dot'.
3382 void ScheduleDAGMI::viewGraph(const Twine &Name, const Twine &Title) {
3384 ViewGraph(this, Name, false, Title);
3386 errs() << "ScheduleDAGMI::viewGraph is only available in debug builds on "
3387 << "systems with Graphviz or gv!\n";
3391 /// Out-of-line implementation with no arguments is handy for gdb.
3392 void ScheduleDAGMI::viewGraph() {
3393 viewGraph(getDAGName(), "Scheduling-Units Graph for " + getDAGName());