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/Target/TargetMachine.h"
18 #include "llvm/Target/TargetInstrInfo.h"
19 #include "llvm/Target/TargetRegisterInfo.h"
20 #include "llvm/Support/Debug.h"
24 ScheduleDAG::ScheduleDAG(SelectionDAG *dag, MachineBasicBlock *bb,
25 const TargetMachine &tm)
26 : DAG(dag), BB(bb), TM(tm), MRI(BB->getParent()->getRegInfo()) {
27 TII = TM.getInstrInfo();
29 TRI = TM.getRegisterInfo();
30 TLI = TM.getTargetLowering();
31 ConstPool = MF->getConstantPool();
34 ScheduleDAG::~ScheduleDAG() {}
36 /// CalculateDepths - compute depths using algorithms for the longest
38 void ScheduleDAG::CalculateDepths() {
39 unsigned DAGSize = SUnits.size();
40 std::vector<SUnit*> WorkList;
41 WorkList.reserve(DAGSize);
43 // Initialize the data structures
44 for (unsigned i = 0, e = DAGSize; i != e; ++i) {
45 SUnit *SU = &SUnits[i];
46 unsigned Degree = SU->Preds.size();
47 // Temporarily use the Depth field as scratch space for the degree count.
50 // Is it a node without dependencies?
52 assert(SU->Preds.empty() && "SUnit should have no predecessors");
54 WorkList.push_back(SU);
58 // Process nodes in the topological order
59 while (!WorkList.empty()) {
60 SUnit *SU = WorkList.back();
64 // Use dynamic programming:
65 // When current node is being processed, all of its dependencies
66 // are already processed.
67 // So, just iterate over all predecessors and take the longest path
68 for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
70 unsigned PredDepth = I->getSUnit()->Depth;
71 if (PredDepth+1 > SUDepth) {
72 SUDepth = PredDepth + 1;
78 // Update degrees of all nodes depending on current SUnit
79 for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
81 SUnit *SU = I->getSUnit();
83 // If all dependencies of the node are processed already,
84 // then the longest path for the node can be computed now
85 WorkList.push_back(SU);
90 /// CalculateHeights - compute heights using algorithms for the longest
92 void ScheduleDAG::CalculateHeights() {
93 unsigned DAGSize = SUnits.size();
94 std::vector<SUnit*> WorkList;
95 WorkList.reserve(DAGSize);
97 // Initialize the data structures
98 for (unsigned i = 0, e = DAGSize; i != e; ++i) {
99 SUnit *SU = &SUnits[i];
100 unsigned Degree = SU->Succs.size();
101 // Temporarily use the Height field as scratch space for the degree count.
104 // Is it a node without dependencies?
106 assert(SU->Succs.empty() && "Something wrong");
107 assert(WorkList.empty() && "Should be empty");
108 // Collect leaf nodes
109 WorkList.push_back(SU);
113 // Process nodes in the topological order
114 while (!WorkList.empty()) {
115 SUnit *SU = WorkList.back();
117 unsigned SUHeight = 0;
119 // Use dynamic programming:
120 // When current node is being processed, all of its dependencies
121 // are already processed.
122 // So, just iterate over all successors and take the longest path
123 for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
125 unsigned SuccHeight = I->getSUnit()->Height;
126 if (SuccHeight+1 > SUHeight) {
127 SUHeight = SuccHeight + 1;
131 SU->Height = SUHeight;
133 // Update degrees of all nodes depending on current SUnit
134 for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
136 SUnit *SU = I->getSUnit();
138 // If all dependencies of the node are processed already,
139 // then the longest path for the node can be computed now
140 WorkList.push_back(SU);
145 /// dump - dump the schedule.
146 void ScheduleDAG::dumpSchedule() const {
147 for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
148 if (SUnit *SU = Sequence[i])
151 cerr << "**** NOOP ****\n";
156 /// Run - perform scheduling.
158 void ScheduleDAG::Run() {
161 DOUT << "*** Final schedule ***\n";
162 DEBUG(dumpSchedule());
166 /// addPred - This adds the specified edge as a pred of the current node if
167 /// not already. It also adds the current node as a successor of the
169 void SUnit::addPred(const SDep &D) {
170 // If this node already has this depenence, don't add a redundant one.
171 for (unsigned i = 0, e = (unsigned)Preds.size(); i != e; ++i)
174 // Add a pred to this SUnit.
176 // Now add a corresponding succ to N.
179 SUnit *N = D.getSUnit();
180 N->Succs.push_back(P);
181 // Update the bookkeeping.
182 if (D.getKind() == SDep::Data) {
192 /// removePred - This removes the specified edge as a pred of the current
193 /// node if it exists. It also removes the current node as a successor of
194 /// the specified node.
195 void SUnit::removePred(const SDep &D) {
196 // Find the matching predecessor.
197 for (SmallVector<SDep, 4>::iterator I = Preds.begin(), E = Preds.end();
200 bool FoundSucc = false;
201 // Find the corresponding successor in N.
204 SUnit *N = D.getSUnit();
205 for (SmallVector<SDep, 4>::iterator II = N->Succs.begin(),
206 EE = N->Succs.end(); II != EE; ++II)
212 assert(FoundSucc && "Mismatching preds / succs lists!");
214 // Update the bookkeeping;
215 if (D.getKind() == SDep::Data) {
227 /// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or
228 /// a group of nodes flagged together.
229 void SUnit::dump(const ScheduleDAG *G) const {
230 cerr << "SU(" << NodeNum << "): ";
234 void SUnit::dumpAll(const ScheduleDAG *G) const {
237 cerr << " # preds left : " << NumPredsLeft << "\n";
238 cerr << " # succs left : " << NumSuccsLeft << "\n";
239 cerr << " Latency : " << Latency << "\n";
240 cerr << " Depth : " << Depth << "\n";
241 cerr << " Height : " << Height << "\n";
243 if (Preds.size() != 0) {
244 cerr << " Predecessors:\n";
245 for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end();
248 switch (I->getKind()) {
249 case SDep::Data: cerr << "val "; break;
250 case SDep::Anti: cerr << "anti"; break;
251 case SDep::Output: cerr << "out "; break;
252 case SDep::Order: cerr << "ch "; break;
255 cerr << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
256 if (I->isArtificial())
261 if (Succs.size() != 0) {
262 cerr << " Successors:\n";
263 for (SUnit::const_succ_iterator I = Succs.begin(), E = Succs.end();
266 switch (I->getKind()) {
267 case SDep::Data: cerr << "val "; break;
268 case SDep::Anti: cerr << "anti"; break;
269 case SDep::Output: cerr << "out "; break;
270 case SDep::Order: cerr << "ch "; break;
273 cerr << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
274 if (I->isArtificial())
283 /// VerifySchedule - Verify that all SUnits were scheduled and that
284 /// their state is consistent.
286 void ScheduleDAG::VerifySchedule(bool isBottomUp) {
287 bool AnyNotSched = false;
288 unsigned DeadNodes = 0;
290 for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
291 if (!SUnits[i].isScheduled) {
292 if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) {
297 cerr << "*** Scheduling failed! ***\n";
298 SUnits[i].dump(this);
299 cerr << "has not been scheduled!\n";
302 if (SUnits[i].isScheduled && SUnits[i].Cycle > (unsigned)INT_MAX) {
304 cerr << "*** Scheduling failed! ***\n";
305 SUnits[i].dump(this);
306 cerr << "has an unexpected Cycle value!\n";
310 if (SUnits[i].NumSuccsLeft != 0) {
312 cerr << "*** Scheduling failed! ***\n";
313 SUnits[i].dump(this);
314 cerr << "has successors left!\n";
318 if (SUnits[i].NumPredsLeft != 0) {
320 cerr << "*** Scheduling failed! ***\n";
321 SUnits[i].dump(this);
322 cerr << "has predecessors left!\n";
327 for (unsigned i = 0, e = Sequence.size(); i != e; ++i)
330 assert(!AnyNotSched);
331 assert(Sequence.size() + DeadNodes - Noops == SUnits.size() &&
332 "The number of nodes scheduled doesn't match the expected number!");
336 /// InitDAGTopologicalSorting - create the initial topological
337 /// ordering from the DAG to be scheduled.
339 /// The idea of the algorithm is taken from
340 /// "Online algorithms for managing the topological order of
341 /// a directed acyclic graph" by David J. Pearce and Paul H.J. Kelly
342 /// This is the MNR algorithm, which was first introduced by
343 /// A. Marchetti-Spaccamela, U. Nanni and H. Rohnert in
344 /// "Maintaining a topological order under edge insertions".
346 /// Short description of the algorithm:
348 /// Topological ordering, ord, of a DAG maps each node to a topological
349 /// index so that for all edges X->Y it is the case that ord(X) < ord(Y).
351 /// This means that if there is a path from the node X to the node Z,
352 /// then ord(X) < ord(Z).
354 /// This property can be used to check for reachability of nodes:
355 /// if Z is reachable from X, then an insertion of the edge Z->X would
358 /// The algorithm first computes a topological ordering for the DAG by
359 /// initializing the Index2Node and Node2Index arrays and then tries to keep
360 /// the ordering up-to-date after edge insertions by reordering the DAG.
362 /// On insertion of the edge X->Y, the algorithm first marks by calling DFS
363 /// the nodes reachable from Y, and then shifts them using Shift to lie
364 /// immediately after X in Index2Node.
365 void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
366 unsigned DAGSize = SUnits.size();
367 std::vector<SUnit*> WorkList;
368 WorkList.reserve(DAGSize);
370 Index2Node.resize(DAGSize);
371 Node2Index.resize(DAGSize);
373 // Initialize the data structures.
374 for (unsigned i = 0, e = DAGSize; i != e; ++i) {
375 SUnit *SU = &SUnits[i];
376 int NodeNum = SU->NodeNum;
377 unsigned Degree = SU->Succs.size();
378 // Temporarily use the Node2Index array as scratch space for degree counts.
379 Node2Index[NodeNum] = Degree;
381 // Is it a node without dependencies?
383 assert(SU->Succs.empty() && "SUnit should have no successors");
384 // Collect leaf nodes.
385 WorkList.push_back(SU);
390 while (!WorkList.empty()) {
391 SUnit *SU = WorkList.back();
393 Allocate(SU->NodeNum, --Id);
394 for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
396 SUnit *SU = I->getSUnit();
397 if (!--Node2Index[SU->NodeNum])
398 // If all dependencies of the node are processed already,
399 // then the node can be computed now.
400 WorkList.push_back(SU);
404 Visited.resize(DAGSize);
407 // Check correctness of the ordering
408 for (unsigned i = 0, e = DAGSize; i != e; ++i) {
409 SUnit *SU = &SUnits[i];
410 for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
412 assert(Node2Index[SU->NodeNum] > Node2Index[I->getSUnit()->NodeNum] &&
413 "Wrong topological sorting");
419 /// AddPred - Updates the topological ordering to accomodate an edge
420 /// to be added from SUnit X to SUnit Y.
421 void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) {
422 int UpperBound, LowerBound;
423 LowerBound = Node2Index[Y->NodeNum];
424 UpperBound = Node2Index[X->NodeNum];
425 bool HasLoop = false;
426 // Is Ord(X) < Ord(Y) ?
427 if (LowerBound < UpperBound) {
428 // Update the topological order.
430 DFS(Y, UpperBound, HasLoop);
431 assert(!HasLoop && "Inserted edge creates a loop!");
432 // Recompute topological indexes.
433 Shift(Visited, LowerBound, UpperBound);
437 /// RemovePred - Updates the topological ordering to accomodate an
438 /// an edge to be removed from the specified node N from the predecessors
439 /// of the current node M.
440 void ScheduleDAGTopologicalSort::RemovePred(SUnit *M, SUnit *N) {
441 // InitDAGTopologicalSorting();
444 /// DFS - Make a DFS traversal to mark all nodes reachable from SU and mark
445 /// all nodes affected by the edge insertion. These nodes will later get new
446 /// topological indexes by means of the Shift method.
447 void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound,
449 std::vector<const SUnit*> WorkList;
450 WorkList.reserve(SUnits.size());
452 WorkList.push_back(SU);
453 while (!WorkList.empty()) {
454 SU = WorkList.back();
456 Visited.set(SU->NodeNum);
457 for (int I = SU->Succs.size()-1; I >= 0; --I) {
458 int s = SU->Succs[I].getSUnit()->NodeNum;
459 if (Node2Index[s] == UpperBound) {
463 // Visit successors if not already and in affected region.
464 if (!Visited.test(s) && Node2Index[s] < UpperBound) {
465 WorkList.push_back(SU->Succs[I].getSUnit());
471 /// Shift - Renumber the nodes so that the topological ordering is
473 void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound,
479 for (i = LowerBound; i <= UpperBound; ++i) {
480 // w is node at topological index i.
481 int w = Index2Node[i];
482 if (Visited.test(w)) {
488 Allocate(w, i - shift);
492 for (unsigned j = 0; j < L.size(); ++j) {
493 Allocate(L[j], i - shift);
499 /// WillCreateCycle - Returns true if adding an edge from SU to TargetSU will
501 bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *SU, SUnit *TargetSU) {
502 if (IsReachable(TargetSU, SU))
504 for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
506 if (I->isAssignedRegDep() &&
507 IsReachable(TargetSU, I->getSUnit()))
512 /// IsReachable - Checks if SU is reachable from TargetSU.
513 bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU,
514 const SUnit *TargetSU) {
515 // If insertion of the edge SU->TargetSU would create a cycle
516 // then there is a path from TargetSU to SU.
517 int UpperBound, LowerBound;
518 LowerBound = Node2Index[TargetSU->NodeNum];
519 UpperBound = Node2Index[SU->NodeNum];
520 bool HasLoop = false;
521 // Is Ord(TargetSU) < Ord(SU) ?
522 if (LowerBound < UpperBound) {
524 // There may be a path from TargetSU to SU. Check for it.
525 DFS(TargetSU, UpperBound, HasLoop);
530 /// Allocate - assign the topological index to the node n.
531 void ScheduleDAGTopologicalSort::Allocate(int n, int index) {
532 Node2Index[n] = index;
533 Index2Node[index] = n;
536 ScheduleDAGTopologicalSort::ScheduleDAGTopologicalSort(
537 std::vector<SUnit> &sunits)