1 //===---- ScheduleDAG.cpp - Implement the ScheduleDAG class ---------------===//
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 implements the ScheduleDAG class, which is a base class used by
11 // scheduling implementation classes.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "pre-RA-sched"
16 #include "llvm/CodeGen/ScheduleDAG.h"
17 #include "llvm/CodeGen/ScheduleHazardRecognizer.h"
18 #include "llvm/Target/TargetMachine.h"
19 #include "llvm/Target/TargetInstrInfo.h"
20 #include "llvm/Target/TargetRegisterInfo.h"
21 #include "llvm/Support/Debug.h"
22 #include "llvm/Support/raw_ostream.h"
26 ScheduleDAG::ScheduleDAG(MachineFunction &mf)
28 TII(TM.getInstrInfo()),
29 TRI(TM.getRegisterInfo()),
30 TLI(TM.getTargetLowering()),
31 MF(mf), MRI(mf.getRegInfo()),
32 ConstPool(MF.getConstantPool()),
36 ScheduleDAG::~ScheduleDAG() {}
38 /// dump - dump the schedule.
39 void ScheduleDAG::dumpSchedule() const {
40 for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
41 if (SUnit *SU = Sequence[i])
44 errs() << "**** NOOP ****\n";
49 /// Run - perform scheduling.
51 void ScheduleDAG::Run(MachineBasicBlock *bb,
52 MachineBasicBlock::iterator insertPos) {
54 InsertPos = insertPos;
63 DOUT << "*** Final schedule ***\n";
64 DEBUG(dumpSchedule());
68 /// addPred - This adds the specified edge as a pred of the current node if
69 /// not already. It also adds the current node as a successor of the
71 void SUnit::addPred(const SDep &D) {
72 // If this node already has this depenence, don't add a redundant one.
73 for (SmallVector<SDep, 4>::const_iterator I = Preds.begin(), E = Preds.end();
77 // Now add a corresponding succ to N.
80 SUnit *N = D.getSUnit();
81 // Update the bookkeeping.
82 if (D.getKind() == SDep::Data) {
91 N->Succs.push_back(P);
92 if (P.getLatency() != 0) {
93 this->setDepthDirty();
98 /// removePred - This removes the specified edge as a pred of the current
99 /// node if it exists. It also removes the current node as a successor of
100 /// the specified node.
101 void SUnit::removePred(const SDep &D) {
102 // Find the matching predecessor.
103 for (SmallVector<SDep, 4>::iterator I = Preds.begin(), E = Preds.end();
106 bool FoundSucc = false;
107 // Find the corresponding successor in N.
110 SUnit *N = D.getSUnit();
111 for (SmallVector<SDep, 4>::iterator II = N->Succs.begin(),
112 EE = N->Succs.end(); II != EE; ++II)
118 assert(FoundSucc && "Mismatching preds / succs lists!");
120 // Update the bookkeeping.
121 if (P.getKind() == SDep::Data) {
129 if (P.getLatency() != 0) {
130 this->setDepthDirty();
137 void SUnit::setDepthDirty() {
138 if (!isDepthCurrent) return;
139 SmallVector<SUnit*, 8> WorkList;
140 WorkList.push_back(this);
142 SUnit *SU = WorkList.pop_back_val();
143 SU->isDepthCurrent = false;
144 for (SUnit::const_succ_iterator I = SU->Succs.begin(),
145 E = SU->Succs.end(); I != E; ++I) {
146 SUnit *SuccSU = I->getSUnit();
147 if (SuccSU->isDepthCurrent)
148 WorkList.push_back(SuccSU);
150 } while (!WorkList.empty());
153 void SUnit::setHeightDirty() {
154 if (!isHeightCurrent) return;
155 SmallVector<SUnit*, 8> WorkList;
156 WorkList.push_back(this);
158 SUnit *SU = WorkList.pop_back_val();
159 SU->isHeightCurrent = false;
160 for (SUnit::const_pred_iterator I = SU->Preds.begin(),
161 E = SU->Preds.end(); I != E; ++I) {
162 SUnit *PredSU = I->getSUnit();
163 if (PredSU->isHeightCurrent)
164 WorkList.push_back(PredSU);
166 } while (!WorkList.empty());
169 /// setDepthToAtLeast - Update this node's successors to reflect the
170 /// fact that this node's depth just increased.
172 void SUnit::setDepthToAtLeast(unsigned NewDepth) {
173 if (NewDepth <= getDepth())
177 isDepthCurrent = true;
180 /// setHeightToAtLeast - Update this node's predecessors to reflect the
181 /// fact that this node's height just increased.
183 void SUnit::setHeightToAtLeast(unsigned NewHeight) {
184 if (NewHeight <= getHeight())
188 isHeightCurrent = true;
191 /// ComputeDepth - Calculate the maximal path from the node to the exit.
193 void SUnit::ComputeDepth() {
194 SmallVector<SUnit*, 8> WorkList;
195 WorkList.push_back(this);
197 SUnit *Cur = WorkList.back();
200 unsigned MaxPredDepth = 0;
201 for (SUnit::const_pred_iterator I = Cur->Preds.begin(),
202 E = Cur->Preds.end(); I != E; ++I) {
203 SUnit *PredSU = I->getSUnit();
204 if (PredSU->isDepthCurrent)
205 MaxPredDepth = std::max(MaxPredDepth,
206 PredSU->Depth + I->getLatency());
209 WorkList.push_back(PredSU);
215 if (MaxPredDepth != Cur->Depth) {
216 Cur->setDepthDirty();
217 Cur->Depth = MaxPredDepth;
219 Cur->isDepthCurrent = true;
221 } while (!WorkList.empty());
224 /// ComputeHeight - Calculate the maximal path from the node to the entry.
226 void SUnit::ComputeHeight() {
227 SmallVector<SUnit*, 8> WorkList;
228 WorkList.push_back(this);
230 SUnit *Cur = WorkList.back();
233 unsigned MaxSuccHeight = 0;
234 for (SUnit::const_succ_iterator I = Cur->Succs.begin(),
235 E = Cur->Succs.end(); I != E; ++I) {
236 SUnit *SuccSU = I->getSUnit();
237 if (SuccSU->isHeightCurrent)
238 MaxSuccHeight = std::max(MaxSuccHeight,
239 SuccSU->Height + I->getLatency());
242 WorkList.push_back(SuccSU);
248 if (MaxSuccHeight != Cur->Height) {
249 Cur->setHeightDirty();
250 Cur->Height = MaxSuccHeight;
252 Cur->isHeightCurrent = true;
254 } while (!WorkList.empty());
257 /// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or
258 /// a group of nodes flagged together.
259 void SUnit::dump(const ScheduleDAG *G) const {
260 errs() << "SU(" << NodeNum << "): ";
264 void SUnit::dumpAll(const ScheduleDAG *G) const {
267 errs() << " # preds left : " << NumPredsLeft << "\n";
268 errs() << " # succs left : " << NumSuccsLeft << "\n";
269 errs() << " Latency : " << Latency << "\n";
270 errs() << " Depth : " << Depth << "\n";
271 errs() << " Height : " << Height << "\n";
273 if (Preds.size() != 0) {
274 errs() << " Predecessors:\n";
275 for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end();
278 switch (I->getKind()) {
279 case SDep::Data: errs() << "val "; break;
280 case SDep::Anti: errs() << "anti"; break;
281 case SDep::Output: errs() << "out "; break;
282 case SDep::Order: errs() << "ch "; break;
285 errs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
286 if (I->isArtificial())
288 errs() << ": Latency=" << I->getLatency();
292 if (Succs.size() != 0) {
293 errs() << " Successors:\n";
294 for (SUnit::const_succ_iterator I = Succs.begin(), E = Succs.end();
297 switch (I->getKind()) {
298 case SDep::Data: errs() << "val "; break;
299 case SDep::Anti: errs() << "anti"; break;
300 case SDep::Output: errs() << "out "; break;
301 case SDep::Order: errs() << "ch "; break;
304 errs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
305 if (I->isArtificial())
307 errs() << ": Latency=" << I->getLatency();
315 /// VerifySchedule - Verify that all SUnits were scheduled and that
316 /// their state is consistent.
318 void ScheduleDAG::VerifySchedule(bool isBottomUp) {
319 bool AnyNotSched = false;
320 unsigned DeadNodes = 0;
322 for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
323 if (!SUnits[i].isScheduled) {
324 if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) {
329 errs() << "*** Scheduling failed! ***\n";
330 SUnits[i].dump(this);
331 errs() << "has not been scheduled!\n";
334 if (SUnits[i].isScheduled &&
335 (isBottomUp ? SUnits[i].getHeight() : SUnits[i].getHeight()) >
338 errs() << "*** Scheduling failed! ***\n";
339 SUnits[i].dump(this);
340 errs() << "has an unexpected "
341 << (isBottomUp ? "Height" : "Depth") << " value!\n";
345 if (SUnits[i].NumSuccsLeft != 0) {
347 errs() << "*** Scheduling failed! ***\n";
348 SUnits[i].dump(this);
349 errs() << "has successors left!\n";
353 if (SUnits[i].NumPredsLeft != 0) {
355 errs() << "*** Scheduling failed! ***\n";
356 SUnits[i].dump(this);
357 errs() << "has predecessors left!\n";
362 for (unsigned i = 0, e = Sequence.size(); i != e; ++i)
365 assert(!AnyNotSched);
366 assert(Sequence.size() + DeadNodes - Noops == SUnits.size() &&
367 "The number of nodes scheduled doesn't match the expected number!");
371 /// InitDAGTopologicalSorting - create the initial topological
372 /// ordering from the DAG to be scheduled.
374 /// The idea of the algorithm is taken from
375 /// "Online algorithms for managing the topological order of
376 /// a directed acyclic graph" by David J. Pearce and Paul H.J. Kelly
377 /// This is the MNR algorithm, which was first introduced by
378 /// A. Marchetti-Spaccamela, U. Nanni and H. Rohnert in
379 /// "Maintaining a topological order under edge insertions".
381 /// Short description of the algorithm:
383 /// Topological ordering, ord, of a DAG maps each node to a topological
384 /// index so that for all edges X->Y it is the case that ord(X) < ord(Y).
386 /// This means that if there is a path from the node X to the node Z,
387 /// then ord(X) < ord(Z).
389 /// This property can be used to check for reachability of nodes:
390 /// if Z is reachable from X, then an insertion of the edge Z->X would
393 /// The algorithm first computes a topological ordering for the DAG by
394 /// initializing the Index2Node and Node2Index arrays and then tries to keep
395 /// the ordering up-to-date after edge insertions by reordering the DAG.
397 /// On insertion of the edge X->Y, the algorithm first marks by calling DFS
398 /// the nodes reachable from Y, and then shifts them using Shift to lie
399 /// immediately after X in Index2Node.
400 void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
401 unsigned DAGSize = SUnits.size();
402 std::vector<SUnit*> WorkList;
403 WorkList.reserve(DAGSize);
405 Index2Node.resize(DAGSize);
406 Node2Index.resize(DAGSize);
408 // Initialize the data structures.
409 for (unsigned i = 0, e = DAGSize; i != e; ++i) {
410 SUnit *SU = &SUnits[i];
411 int NodeNum = SU->NodeNum;
412 unsigned Degree = SU->Succs.size();
413 // Temporarily use the Node2Index array as scratch space for degree counts.
414 Node2Index[NodeNum] = Degree;
416 // Is it a node without dependencies?
418 assert(SU->Succs.empty() && "SUnit should have no successors");
419 // Collect leaf nodes.
420 WorkList.push_back(SU);
425 while (!WorkList.empty()) {
426 SUnit *SU = WorkList.back();
428 Allocate(SU->NodeNum, --Id);
429 for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
431 SUnit *SU = I->getSUnit();
432 if (!--Node2Index[SU->NodeNum])
433 // If all dependencies of the node are processed already,
434 // then the node can be computed now.
435 WorkList.push_back(SU);
439 Visited.resize(DAGSize);
442 // Check correctness of the ordering
443 for (unsigned i = 0, e = DAGSize; i != e; ++i) {
444 SUnit *SU = &SUnits[i];
445 for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
447 assert(Node2Index[SU->NodeNum] > Node2Index[I->getSUnit()->NodeNum] &&
448 "Wrong topological sorting");
454 /// AddPred - Updates the topological ordering to accomodate an edge
455 /// to be added from SUnit X to SUnit Y.
456 void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) {
457 int UpperBound, LowerBound;
458 LowerBound = Node2Index[Y->NodeNum];
459 UpperBound = Node2Index[X->NodeNum];
460 bool HasLoop = false;
461 // Is Ord(X) < Ord(Y) ?
462 if (LowerBound < UpperBound) {
463 // Update the topological order.
465 DFS(Y, UpperBound, HasLoop);
466 assert(!HasLoop && "Inserted edge creates a loop!");
467 // Recompute topological indexes.
468 Shift(Visited, LowerBound, UpperBound);
472 /// RemovePred - Updates the topological ordering to accomodate an
473 /// an edge to be removed from the specified node N from the predecessors
474 /// of the current node M.
475 void ScheduleDAGTopologicalSort::RemovePred(SUnit *M, SUnit *N) {
476 // InitDAGTopologicalSorting();
479 /// DFS - Make a DFS traversal to mark all nodes reachable from SU and mark
480 /// all nodes affected by the edge insertion. These nodes will later get new
481 /// topological indexes by means of the Shift method.
482 void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound,
484 std::vector<const SUnit*> WorkList;
485 WorkList.reserve(SUnits.size());
487 WorkList.push_back(SU);
489 SU = WorkList.back();
491 Visited.set(SU->NodeNum);
492 for (int I = SU->Succs.size()-1; I >= 0; --I) {
493 int s = SU->Succs[I].getSUnit()->NodeNum;
494 if (Node2Index[s] == UpperBound) {
498 // Visit successors if not already and in affected region.
499 if (!Visited.test(s) && Node2Index[s] < UpperBound) {
500 WorkList.push_back(SU->Succs[I].getSUnit());
503 } while (!WorkList.empty());
506 /// Shift - Renumber the nodes so that the topological ordering is
508 void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound,
514 for (i = LowerBound; i <= UpperBound; ++i) {
515 // w is node at topological index i.
516 int w = Index2Node[i];
517 if (Visited.test(w)) {
523 Allocate(w, i - shift);
527 for (unsigned j = 0; j < L.size(); ++j) {
528 Allocate(L[j], i - shift);
534 /// WillCreateCycle - Returns true if adding an edge from SU to TargetSU will
536 bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *SU, SUnit *TargetSU) {
537 if (IsReachable(TargetSU, SU))
539 for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
541 if (I->isAssignedRegDep() &&
542 IsReachable(TargetSU, I->getSUnit()))
547 /// IsReachable - Checks if SU is reachable from TargetSU.
548 bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU,
549 const SUnit *TargetSU) {
550 // If insertion of the edge SU->TargetSU would create a cycle
551 // then there is a path from TargetSU to SU.
552 int UpperBound, LowerBound;
553 LowerBound = Node2Index[TargetSU->NodeNum];
554 UpperBound = Node2Index[SU->NodeNum];
555 bool HasLoop = false;
556 // Is Ord(TargetSU) < Ord(SU) ?
557 if (LowerBound < UpperBound) {
559 // There may be a path from TargetSU to SU. Check for it.
560 DFS(TargetSU, UpperBound, HasLoop);
565 /// Allocate - assign the topological index to the node n.
566 void ScheduleDAGTopologicalSort::Allocate(int n, int index) {
567 Node2Index[n] = index;
568 Index2Node[index] = n;
571 ScheduleDAGTopologicalSort::ScheduleDAGTopologicalSort(
572 std::vector<SUnit> &sunits)
575 ScheduleHazardRecognizer::~ScheduleHazardRecognizer() {}