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 /// Initialize the strategy after building the DAG for a new region.
111 virtual void initialize(ScheduleDAGMI *DAG) = 0;
113 /// Notify this strategy that all roots have been released (including those
114 /// that depend on EntrySU or ExitSU).
115 virtual void registerRoots() {}
117 /// Pick the next node to schedule, or return NULL. Set IsTopNode to true to
118 /// schedule the node at the top of the unscheduled region. Otherwise it will
119 /// be scheduled at the bottom.
120 virtual SUnit *pickNode(bool &IsTopNode) = 0;
122 /// \brief Scheduler callback to notify that a new subtree is scheduled.
123 virtual void scheduleTree(unsigned SubtreeID) {}
125 /// Notify MachineSchedStrategy that ScheduleDAGMI has scheduled an
126 /// instruction and updated scheduled/remaining flags in the DAG nodes.
127 virtual void schedNode(SUnit *SU, bool IsTopNode) = 0;
129 /// When all predecessor dependencies have been resolved, free this node for
130 /// top-down scheduling.
131 virtual void releaseTopNode(SUnit *SU) = 0;
132 /// When all successor dependencies have been resolved, free this node for
133 /// bottom-up scheduling.
134 virtual void releaseBottomNode(SUnit *SU) = 0;
137 /// ReadyQueue encapsulates vector of "ready" SUnits with basic convenience
138 /// methods for pushing and removing nodes. ReadyQueue's are uniquely identified
139 /// by an ID. SUnit::NodeQueueId is a mask of the ReadyQueues the SUnit is in.
141 /// This is a convenience class that may be used by implementations of
142 /// MachineSchedStrategy.
146 std::vector<SUnit*> Queue;
149 ReadyQueue(unsigned id, const Twine &name): ID(id), Name(name.str()) {}
151 unsigned getID() const { return ID; }
153 StringRef getName() const { return Name; }
155 // SU is in this queue if it's NodeQueueID is a superset of this ID.
156 bool isInQueue(SUnit *SU) const { return (SU->NodeQueueId & ID); }
158 bool empty() const { return Queue.empty(); }
160 void clear() { Queue.clear(); }
162 unsigned size() const { return Queue.size(); }
164 typedef std::vector<SUnit*>::iterator iterator;
166 iterator begin() { return Queue.begin(); }
168 iterator end() { return Queue.end(); }
170 ArrayRef<SUnit*> elements() { return Queue; }
172 iterator find(SUnit *SU) {
173 return std::find(Queue.begin(), Queue.end(), SU);
176 void push(SUnit *SU) {
178 SU->NodeQueueId |= ID;
181 iterator remove(iterator I) {
182 (*I)->NodeQueueId &= ~ID;
184 unsigned idx = I - Queue.begin();
186 return Queue.begin() + idx;
189 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
194 /// Mutate the DAG as a postpass after normal DAG building.
195 class ScheduleDAGMutation {
197 virtual ~ScheduleDAGMutation() {}
199 virtual void apply(ScheduleDAGMI *DAG) = 0;
202 /// ScheduleDAGMI is an implementation of ScheduleDAGInstrs that schedules
203 /// machine instructions while updating LiveIntervals and tracking regpressure.
204 class ScheduleDAGMI : public ScheduleDAGInstrs {
207 RegisterClassInfo *RegClassInfo;
208 MachineSchedStrategy *SchedImpl;
210 /// Information about DAG subtrees. If DFSResult is NULL, then SchedulerTrees
212 SchedDFSResult *DFSResult;
213 BitVector ScheduledTrees;
215 /// Topo - A topological ordering for SUnits which permits fast IsReachable
216 /// and similar queries.
217 ScheduleDAGTopologicalSort Topo;
219 /// Ordered list of DAG postprocessing steps.
220 std::vector<ScheduleDAGMutation*> Mutations;
222 MachineBasicBlock::iterator LiveRegionEnd;
224 // Map each SU to its summary of pressure changes. This array is updated for
225 // liveness during bottom-up scheduling. Top-down scheduling may proceed but
226 // has no affect on the pressure diffs.
227 PressureDiffs SUPressureDiffs;
229 /// Register pressure in this region computed by initRegPressure.
230 IntervalPressure RegPressure;
231 RegPressureTracker RPTracker;
233 /// List of pressure sets that exceed the target's pressure limit before
234 /// scheduling, listed in increasing set ID order. Each pressure set is paired
235 /// with its max pressure in the currently scheduled regions.
236 std::vector<PressureChange> RegionCriticalPSets;
238 /// The top of the unscheduled zone.
239 MachineBasicBlock::iterator CurrentTop;
240 IntervalPressure TopPressure;
241 RegPressureTracker TopRPTracker;
243 /// The bottom of the unscheduled zone.
244 MachineBasicBlock::iterator CurrentBottom;
245 IntervalPressure BotPressure;
246 RegPressureTracker BotRPTracker;
248 /// Record the next node in a scheduled cluster.
249 const SUnit *NextClusterPred;
250 const SUnit *NextClusterSucc;
253 /// The number of instructions scheduled so far. Used to cut off the
254 /// scheduler at the point determined by misched-cutoff.
255 unsigned NumInstrsScheduled;
259 ScheduleDAGMI(MachineSchedContext *C, MachineSchedStrategy *S):
260 ScheduleDAGInstrs(*C->MF, *C->MLI, *C->MDT, /*IsPostRA=*/false, C->LIS),
261 AA(C->AA), RegClassInfo(C->RegClassInfo), SchedImpl(S), DFSResult(0),
262 Topo(SUnits, &ExitSU), RPTracker(RegPressure), CurrentTop(),
263 TopRPTracker(TopPressure), CurrentBottom(), BotRPTracker(BotPressure),
264 NextClusterPred(NULL), NextClusterSucc(NULL) {
266 NumInstrsScheduled = 0;
270 virtual ~ScheduleDAGMI();
272 /// Add a postprocessing step to the DAG builder.
273 /// Mutations are applied in the order that they are added after normal DAG
274 /// building and before MachineSchedStrategy initialization.
276 /// ScheduleDAGMI takes ownership of the Mutation object.
277 void addMutation(ScheduleDAGMutation *Mutation) {
278 Mutations.push_back(Mutation);
281 /// \brief True if an edge can be added from PredSU to SuccSU without creating
283 bool canAddEdge(SUnit *SuccSU, SUnit *PredSU);
285 /// \brief Add a DAG edge to the given SU with the given predecessor
288 /// \returns true if the edge may be added without creating a cycle OR if an
289 /// equivalent edge already existed (false indicates failure).
290 bool addEdge(SUnit *SuccSU, const SDep &PredDep);
292 MachineBasicBlock::iterator top() const { return CurrentTop; }
293 MachineBasicBlock::iterator bottom() const { return CurrentBottom; }
295 /// Implement the ScheduleDAGInstrs interface for handling the next scheduling
296 /// region. This covers all instructions in a block, while schedule() may only
298 void enterRegion(MachineBasicBlock *bb,
299 MachineBasicBlock::iterator begin,
300 MachineBasicBlock::iterator end,
301 unsigned regioninstrs) LLVM_OVERRIDE;
303 /// Implement ScheduleDAGInstrs interface for scheduling a sequence of
304 /// reorderable instructions.
305 virtual void schedule();
307 /// Change the position of an instruction within the basic block and update
308 /// live ranges and region boundary iterators.
309 void moveInstruction(MachineInstr *MI, MachineBasicBlock::iterator InsertPos);
311 /// Get current register pressure for the top scheduled instructions.
312 const IntervalPressure &getTopPressure() const { return TopPressure; }
313 const RegPressureTracker &getTopRPTracker() const { return TopRPTracker; }
315 /// Get current register pressure for the bottom scheduled instructions.
316 const IntervalPressure &getBotPressure() const { return BotPressure; }
317 const RegPressureTracker &getBotRPTracker() const { return BotRPTracker; }
319 /// Get register pressure for the entire scheduling region before scheduling.
320 const IntervalPressure &getRegPressure() const { return RegPressure; }
322 const std::vector<PressureChange> &getRegionCriticalPSets() const {
323 return RegionCriticalPSets;
326 PressureDiff &getPressureDiff(const SUnit *SU) {
327 return SUPressureDiffs[SU->NodeNum];
330 const SUnit *getNextClusterPred() const { return NextClusterPred; }
332 const SUnit *getNextClusterSucc() const { return NextClusterSucc; }
334 /// Compute a DFSResult after DAG building is complete, and before any
335 /// queue comparisons.
336 void computeDFSResult();
338 /// Return a non-null DFS result if the scheduling strategy initialized it.
339 const SchedDFSResult *getDFSResult() const { return DFSResult; }
341 BitVector &getScheduledTrees() { return ScheduledTrees; }
343 /// Compute the cyclic critical path through the DAG.
344 unsigned computeCyclicCriticalPath();
346 void viewGraph(const Twine &Name, const Twine &Title) LLVM_OVERRIDE;
347 void viewGraph() LLVM_OVERRIDE;
350 // Top-Level entry points for the schedule() driver...
352 /// Call ScheduleDAGInstrs::buildSchedGraph with register pressure tracking
353 /// enabled. This sets up three trackers. RPTracker will cover the entire DAG
354 /// region, TopTracker and BottomTracker will be initialized to the top and
355 /// bottom of the DAG region without covereing any unscheduled instruction.
356 void buildDAGWithRegPressure();
358 /// Apply each ScheduleDAGMutation step in order. This allows different
359 /// instances of ScheduleDAGMI to perform custom DAG postprocessing.
360 void postprocessDAG();
362 /// Release ExitSU predecessors and setup scheduler queues.
363 void initQueues(ArrayRef<SUnit*> TopRoots, ArrayRef<SUnit*> BotRoots);
365 /// Move an instruction and update register pressure.
366 void scheduleMI(SUnit *SU, bool IsTopNode);
368 /// Update scheduler DAG and queues after scheduling an instruction.
369 void updateQueues(SUnit *SU, bool IsTopNode);
371 /// Reinsert debug_values recorded in ScheduleDAGInstrs::DbgValues.
372 void placeDebugValues();
374 /// \brief dump the scheduled Sequence.
375 void dumpSchedule() const;
379 void initRegPressure();
381 void updatePressureDiffs(ArrayRef<unsigned> LiveUses);
383 void updateScheduledPressure(const std::vector<unsigned> &NewMaxPressure);
385 bool checkSchedLimit();
387 void findRootsAndBiasEdges(SmallVectorImpl<SUnit*> &TopRoots,
388 SmallVectorImpl<SUnit*> &BotRoots);
390 void releaseSucc(SUnit *SU, SDep *SuccEdge);
391 void releaseSuccessors(SUnit *SU);
392 void releasePred(SUnit *SU, SDep *PredEdge);
393 void releasePredecessors(SUnit *SU);