1 //==- MachineScheduler.h - MachineInstr Scheduling Pass ----------*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file provides a MachineSchedRegistry for registering alternative machine
11 // schedulers. A Target may provide an alternative scheduler implementation by
12 // implementing the following boilerplate:
14 // static ScheduleDAGInstrs *createCustomMachineSched(MachineSchedContext *C) {
15 // return new CustomMachineScheduler(C);
17 // static MachineSchedRegistry
18 // SchedCustomRegistry("custom", "Run my target's custom scheduler",
19 // createCustomMachineSched);
21 // Inside <Target>PassConfig:
22 // enablePass(&MachineSchedulerID);
23 // MachineSchedRegistry::setDefault(createCustomMachineSched);
25 //===----------------------------------------------------------------------===//
27 #ifndef LLVM_CODEGEN_MACHINESCHEDULER_H
28 #define LLVM_CODEGEN_MACHINESCHEDULER_H
30 #include "llvm/CodeGen/MachinePassRegistry.h"
31 #include "llvm/CodeGen/RegisterPressure.h"
32 #include "llvm/CodeGen/ScheduleDAGInstrs.h"
36 extern cl::opt<bool> ForceTopDown;
37 extern cl::opt<bool> ForceBottomUp;
41 class MachineDominatorTree;
42 class MachineLoopInfo;
43 class RegisterClassInfo;
44 class ScheduleDAGInstrs;
47 /// MachineSchedContext provides enough context from the MachineScheduler pass
48 /// for the target to instantiate a scheduler.
49 struct MachineSchedContext {
51 const MachineLoopInfo *MLI;
52 const MachineDominatorTree *MDT;
53 const TargetPassConfig *PassConfig;
57 RegisterClassInfo *RegClassInfo;
59 MachineSchedContext();
60 virtual ~MachineSchedContext();
63 /// MachineSchedRegistry provides a selection of available machine instruction
65 class MachineSchedRegistry : public MachinePassRegistryNode {
67 typedef ScheduleDAGInstrs *(*ScheduleDAGCtor)(MachineSchedContext *);
69 // RegisterPassParser requires a (misnamed) FunctionPassCtor type.
70 typedef ScheduleDAGCtor FunctionPassCtor;
72 static MachinePassRegistry Registry;
74 MachineSchedRegistry(const char *N, const char *D, ScheduleDAGCtor C)
75 : MachinePassRegistryNode(N, D, (MachinePassCtor)C) {
78 ~MachineSchedRegistry() { Registry.Remove(this); }
82 MachineSchedRegistry *getNext() const {
83 return (MachineSchedRegistry *)MachinePassRegistryNode::getNext();
85 static MachineSchedRegistry *getList() {
86 return (MachineSchedRegistry *)Registry.getList();
88 static ScheduleDAGCtor getDefault() {
89 return (ScheduleDAGCtor)Registry.getDefault();
91 static void setDefault(ScheduleDAGCtor C) {
92 Registry.setDefault((MachinePassCtor)C);
94 static void setDefault(StringRef Name) {
95 Registry.setDefault(Name);
97 static void setListener(MachinePassRegistryListener *L) {
98 Registry.setListener(L);
104 /// MachineSchedStrategy - Interface to the scheduling algorithm used by
106 class MachineSchedStrategy {
108 virtual ~MachineSchedStrategy() {}
110 /// Check if pressure tracking is needed before building the DAG and
111 /// initializing this strategy.
112 virtual bool shouldTrackPressure(unsigned NumRegionInstrs) { return true; }
114 /// Initialize the strategy after building the DAG for a new region.
115 virtual void initialize(ScheduleDAGMI *DAG) = 0;
117 /// Notify this strategy that all roots have been released (including those
118 /// that depend on EntrySU or ExitSU).
119 virtual void registerRoots() {}
121 /// Pick the next node to schedule, or return NULL. Set IsTopNode to true to
122 /// schedule the node at the top of the unscheduled region. Otherwise it will
123 /// be scheduled at the bottom.
124 virtual SUnit *pickNode(bool &IsTopNode) = 0;
126 /// \brief Scheduler callback to notify that a new subtree is scheduled.
127 virtual void scheduleTree(unsigned SubtreeID) {}
129 /// Notify MachineSchedStrategy that ScheduleDAGMI has scheduled an
130 /// instruction and updated scheduled/remaining flags in the DAG nodes.
131 virtual void schedNode(SUnit *SU, bool IsTopNode) = 0;
133 /// When all predecessor dependencies have been resolved, free this node for
134 /// top-down scheduling.
135 virtual void releaseTopNode(SUnit *SU) = 0;
136 /// When all successor dependencies have been resolved, free this node for
137 /// bottom-up scheduling.
138 virtual void releaseBottomNode(SUnit *SU) = 0;
141 /// ReadyQueue encapsulates vector of "ready" SUnits with basic convenience
142 /// methods for pushing and removing nodes. ReadyQueue's are uniquely identified
143 /// by an ID. SUnit::NodeQueueId is a mask of the ReadyQueues the SUnit is in.
145 /// This is a convenience class that may be used by implementations of
146 /// MachineSchedStrategy.
150 std::vector<SUnit*> Queue;
153 ReadyQueue(unsigned id, const Twine &name): ID(id), Name(name.str()) {}
155 unsigned getID() const { return ID; }
157 StringRef getName() const { return Name; }
159 // SU is in this queue if it's NodeQueueID is a superset of this ID.
160 bool isInQueue(SUnit *SU) const { return (SU->NodeQueueId & ID); }
162 bool empty() const { return Queue.empty(); }
164 void clear() { Queue.clear(); }
166 unsigned size() const { return Queue.size(); }
168 typedef std::vector<SUnit*>::iterator iterator;
170 iterator begin() { return Queue.begin(); }
172 iterator end() { return Queue.end(); }
174 ArrayRef<SUnit*> elements() { return Queue; }
176 iterator find(SUnit *SU) {
177 return std::find(Queue.begin(), Queue.end(), SU);
180 void push(SUnit *SU) {
182 SU->NodeQueueId |= ID;
185 iterator remove(iterator I) {
186 (*I)->NodeQueueId &= ~ID;
188 unsigned idx = I - Queue.begin();
190 return Queue.begin() + idx;
193 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
198 /// Mutate the DAG as a postpass after normal DAG building.
199 class ScheduleDAGMutation {
201 virtual ~ScheduleDAGMutation() {}
203 virtual void apply(ScheduleDAGMI *DAG) = 0;
206 /// ScheduleDAGMI is an implementation of ScheduleDAGInstrs that schedules
207 /// machine instructions while updating LiveIntervals and tracking regpressure.
208 class ScheduleDAGMI : public ScheduleDAGInstrs {
211 RegisterClassInfo *RegClassInfo;
212 MachineSchedStrategy *SchedImpl;
214 /// Information about DAG subtrees. If DFSResult is NULL, then SchedulerTrees
216 SchedDFSResult *DFSResult;
217 BitVector ScheduledTrees;
219 /// Topo - A topological ordering for SUnits which permits fast IsReachable
220 /// and similar queries.
221 ScheduleDAGTopologicalSort Topo;
223 /// Ordered list of DAG postprocessing steps.
224 std::vector<ScheduleDAGMutation*> Mutations;
226 MachineBasicBlock::iterator LiveRegionEnd;
228 // Map each SU to its summary of pressure changes. This array is updated for
229 // liveness during bottom-up scheduling. Top-down scheduling may proceed but
230 // has no affect on the pressure diffs.
231 PressureDiffs SUPressureDiffs;
233 /// Register pressure in this region computed by initRegPressure.
234 bool ShouldTrackPressure;
235 IntervalPressure RegPressure;
236 RegPressureTracker RPTracker;
238 /// List of pressure sets that exceed the target's pressure limit before
239 /// scheduling, listed in increasing set ID order. Each pressure set is paired
240 /// with its max pressure in the currently scheduled regions.
241 std::vector<PressureChange> RegionCriticalPSets;
243 /// The top of the unscheduled zone.
244 MachineBasicBlock::iterator CurrentTop;
245 IntervalPressure TopPressure;
246 RegPressureTracker TopRPTracker;
248 /// The bottom of the unscheduled zone.
249 MachineBasicBlock::iterator CurrentBottom;
250 IntervalPressure BotPressure;
251 RegPressureTracker BotRPTracker;
253 /// Record the next node in a scheduled cluster.
254 const SUnit *NextClusterPred;
255 const SUnit *NextClusterSucc;
258 /// The number of instructions scheduled so far. Used to cut off the
259 /// scheduler at the point determined by misched-cutoff.
260 unsigned NumInstrsScheduled;
264 ScheduleDAGMI(MachineSchedContext *C, MachineSchedStrategy *S):
265 ScheduleDAGInstrs(*C->MF, *C->MLI, *C->MDT, /*IsPostRA=*/false, C->LIS),
266 AA(C->AA), RegClassInfo(C->RegClassInfo), SchedImpl(S), DFSResult(0),
267 Topo(SUnits, &ExitSU), ShouldTrackPressure(false),
268 RPTracker(RegPressure), CurrentTop(), TopRPTracker(TopPressure),
269 CurrentBottom(), BotRPTracker(BotPressure),
270 NextClusterPred(NULL), NextClusterSucc(NULL) {
272 NumInstrsScheduled = 0;
276 virtual ~ScheduleDAGMI();
278 /// \brief Return true if register pressure tracking is enabled.
279 bool isTrackingPressure() const { return ShouldTrackPressure; }
281 /// Add a postprocessing step to the DAG builder.
282 /// Mutations are applied in the order that they are added after normal DAG
283 /// building and before MachineSchedStrategy initialization.
285 /// ScheduleDAGMI takes ownership of the Mutation object.
286 void addMutation(ScheduleDAGMutation *Mutation) {
287 Mutations.push_back(Mutation);
290 /// \brief True if an edge can be added from PredSU to SuccSU without creating
292 bool canAddEdge(SUnit *SuccSU, SUnit *PredSU);
294 /// \brief Add a DAG edge to the given SU with the given predecessor
297 /// \returns true if the edge may be added without creating a cycle OR if an
298 /// equivalent edge already existed (false indicates failure).
299 bool addEdge(SUnit *SuccSU, const SDep &PredDep);
301 MachineBasicBlock::iterator top() const { return CurrentTop; }
302 MachineBasicBlock::iterator bottom() const { return CurrentBottom; }
304 /// Implement the ScheduleDAGInstrs interface for handling the next scheduling
305 /// region. This covers all instructions in a block, while schedule() may only
307 void enterRegion(MachineBasicBlock *bb,
308 MachineBasicBlock::iterator begin,
309 MachineBasicBlock::iterator end,
310 unsigned regioninstrs) LLVM_OVERRIDE;
312 /// Implement ScheduleDAGInstrs interface for scheduling a sequence of
313 /// reorderable instructions.
314 virtual void schedule();
316 /// Change the position of an instruction within the basic block and update
317 /// live ranges and region boundary iterators.
318 void moveInstruction(MachineInstr *MI, MachineBasicBlock::iterator InsertPos);
320 /// Get current register pressure for the top scheduled instructions.
321 const IntervalPressure &getTopPressure() const { return TopPressure; }
322 const RegPressureTracker &getTopRPTracker() const { return TopRPTracker; }
324 /// Get current register pressure for the bottom scheduled instructions.
325 const IntervalPressure &getBotPressure() const { return BotPressure; }
326 const RegPressureTracker &getBotRPTracker() const { return BotRPTracker; }
328 /// Get register pressure for the entire scheduling region before scheduling.
329 const IntervalPressure &getRegPressure() const { return RegPressure; }
331 const std::vector<PressureChange> &getRegionCriticalPSets() const {
332 return RegionCriticalPSets;
335 PressureDiff &getPressureDiff(const SUnit *SU) {
336 return SUPressureDiffs[SU->NodeNum];
339 const SUnit *getNextClusterPred() const { return NextClusterPred; }
341 const SUnit *getNextClusterSucc() const { return NextClusterSucc; }
343 /// Compute a DFSResult after DAG building is complete, and before any
344 /// queue comparisons.
345 void computeDFSResult();
347 /// Return a non-null DFS result if the scheduling strategy initialized it.
348 const SchedDFSResult *getDFSResult() const { return DFSResult; }
350 BitVector &getScheduledTrees() { return ScheduledTrees; }
352 /// Compute the cyclic critical path through the DAG.
353 unsigned computeCyclicCriticalPath();
355 void viewGraph(const Twine &Name, const Twine &Title) LLVM_OVERRIDE;
356 void viewGraph() LLVM_OVERRIDE;
359 // Top-Level entry points for the schedule() driver...
361 /// Call ScheduleDAGInstrs::buildSchedGraph with register pressure tracking
362 /// enabled. This sets up three trackers. RPTracker will cover the entire DAG
363 /// region, TopTracker and BottomTracker will be initialized to the top and
364 /// bottom of the DAG region without covereing any unscheduled instruction.
365 void buildDAGWithRegPressure();
367 /// Apply each ScheduleDAGMutation step in order. This allows different
368 /// instances of ScheduleDAGMI to perform custom DAG postprocessing.
369 void postprocessDAG();
371 /// Release ExitSU predecessors and setup scheduler queues.
372 void initQueues(ArrayRef<SUnit*> TopRoots, ArrayRef<SUnit*> BotRoots);
374 /// Move an instruction and update register pressure.
375 void scheduleMI(SUnit *SU, bool IsTopNode);
377 /// Update scheduler DAG and queues after scheduling an instruction.
378 void updateQueues(SUnit *SU, bool IsTopNode);
380 /// Reinsert debug_values recorded in ScheduleDAGInstrs::DbgValues.
381 void placeDebugValues();
383 /// \brief dump the scheduled Sequence.
384 void dumpSchedule() const;
388 void initRegPressure();
390 void updatePressureDiffs(ArrayRef<unsigned> LiveUses);
392 void updateScheduledPressure(const std::vector<unsigned> &NewMaxPressure);
394 bool checkSchedLimit();
396 void findRootsAndBiasEdges(SmallVectorImpl<SUnit*> &TopRoots,
397 SmallVectorImpl<SUnit*> &BotRoots);
399 void releaseSucc(SUnit *SU, SDep *SuccEdge);
400 void releaseSuccessors(SUnit *SU);
401 void releasePred(SUnit *SU, SDep *PredEdge);
402 void releasePredecessors(SUnit *SU);