ScheduleDAG.cpp revision 3f0e83067d7938f742d21e14fc87c006d2fc3161
1//===---- ScheduleDAG.cpp - Implement the ScheduleDAG class ---------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This implements the ScheduleDAG class, which is a base class used by 11// scheduling implementation classes. 12// 13//===----------------------------------------------------------------------===// 14 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" 23#include <climits> 24using namespace llvm; 25 26ScheduleDAG::ScheduleDAG(MachineFunction &mf) 27 : TM(mf.getTarget()), 28 TII(TM.getInstrInfo()), 29 TRI(TM.getRegisterInfo()), 30 TLI(TM.getTargetLowering()), 31 MF(mf), MRI(mf.getRegInfo()), 32 ConstPool(MF.getConstantPool()), 33 EntrySU(), ExitSU() { 34} 35 36ScheduleDAG::~ScheduleDAG() {} 37 38/// dump - dump the schedule. 39void ScheduleDAG::dumpSchedule() const { 40 for (unsigned i = 0, e = Sequence.size(); i != e; i++) { 41 if (SUnit *SU = Sequence[i]) 42 SU->dump(this); 43 else 44 errs() << "**** NOOP ****\n"; 45 } 46} 47 48 49/// Run - perform scheduling. 50/// 51void ScheduleDAG::Run(MachineBasicBlock *bb, 52 MachineBasicBlock::iterator insertPos) { 53 BB = bb; 54 InsertPos = insertPos; 55 56 SUnits.clear(); 57 Sequence.clear(); 58 EntrySU = SUnit(); 59 ExitSU = SUnit(); 60 61 Schedule(); 62 63 DOUT << "*** Final schedule ***\n"; 64 DEBUG(dumpSchedule()); 65 DOUT << "\n"; 66} 67 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 70/// specified node. 71void 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(); 74 I != E; ++I) 75 if (*I == D) 76 return; 77 // Now add a corresponding succ to N. 78 SDep P = D; 79 P.setSUnit(this); 80 SUnit *N = D.getSUnit(); 81 // Update the bookkeeping. 82 if (D.getKind() == SDep::Data) { 83 ++NumPreds; 84 ++N->NumSuccs; 85 } 86 if (!N->isScheduled) 87 ++NumPredsLeft; 88 if (!isScheduled) 89 ++N->NumSuccsLeft; 90 Preds.push_back(D); 91 N->Succs.push_back(P); 92 if (P.getLatency() != 0) { 93 this->setDepthDirty(); 94 N->setHeightDirty(); 95 } 96} 97 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. 101void SUnit::removePred(const SDep &D) { 102 // Find the matching predecessor. 103 for (SmallVector<SDep, 4>::iterator I = Preds.begin(), E = Preds.end(); 104 I != E; ++I) 105 if (*I == D) { 106 bool FoundSucc = false; 107 // Find the corresponding successor in N. 108 SDep P = D; 109 P.setSUnit(this); 110 SUnit *N = D.getSUnit(); 111 for (SmallVector<SDep, 4>::iterator II = N->Succs.begin(), 112 EE = N->Succs.end(); II != EE; ++II) 113 if (*II == P) { 114 FoundSucc = true; 115 N->Succs.erase(II); 116 break; 117 } 118 assert(FoundSucc && "Mismatching preds / succs lists!"); 119 Preds.erase(I); 120 // Update the bookkeeping. 121 if (P.getKind() == SDep::Data) { 122 --NumPreds; 123 --N->NumSuccs; 124 } 125 if (!N->isScheduled) 126 --NumPredsLeft; 127 if (!isScheduled) 128 --N->NumSuccsLeft; 129 if (P.getLatency() != 0) { 130 this->setDepthDirty(); 131 N->setHeightDirty(); 132 } 133 return; 134 } 135} 136 137void SUnit::setDepthDirty() { 138 if (!isDepthCurrent) return; 139 SmallVector<SUnit*, 8> WorkList; 140 WorkList.push_back(this); 141 do { 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); 149 } 150 } while (!WorkList.empty()); 151} 152 153void SUnit::setHeightDirty() { 154 if (!isHeightCurrent) return; 155 SmallVector<SUnit*, 8> WorkList; 156 WorkList.push_back(this); 157 do { 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); 165 } 166 } while (!WorkList.empty()); 167} 168 169/// setDepthToAtLeast - Update this node's successors to reflect the 170/// fact that this node's depth just increased. 171/// 172void SUnit::setDepthToAtLeast(unsigned NewDepth) { 173 if (NewDepth <= getDepth()) 174 return; 175 setDepthDirty(); 176 Depth = NewDepth; 177 isDepthCurrent = true; 178} 179 180/// setHeightToAtLeast - Update this node's predecessors to reflect the 181/// fact that this node's height just increased. 182/// 183void SUnit::setHeightToAtLeast(unsigned NewHeight) { 184 if (NewHeight <= getHeight()) 185 return; 186 setHeightDirty(); 187 Height = NewHeight; 188 isHeightCurrent = true; 189} 190 191/// ComputeDepth - Calculate the maximal path from the node to the exit. 192/// 193void SUnit::ComputeDepth() { 194 SmallVector<SUnit*, 8> WorkList; 195 WorkList.push_back(this); 196 do { 197 SUnit *Cur = WorkList.back(); 198 199 bool Done = true; 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()); 207 else { 208 Done = false; 209 WorkList.push_back(PredSU); 210 } 211 } 212 213 if (Done) { 214 WorkList.pop_back(); 215 if (MaxPredDepth != Cur->Depth) { 216 Cur->setDepthDirty(); 217 Cur->Depth = MaxPredDepth; 218 } 219 Cur->isDepthCurrent = true; 220 } 221 } while (!WorkList.empty()); 222} 223 224/// ComputeHeight - Calculate the maximal path from the node to the entry. 225/// 226void SUnit::ComputeHeight() { 227 SmallVector<SUnit*, 8> WorkList; 228 WorkList.push_back(this); 229 do { 230 SUnit *Cur = WorkList.back(); 231 232 bool Done = true; 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()); 240 else { 241 Done = false; 242 WorkList.push_back(SuccSU); 243 } 244 } 245 246 if (Done) { 247 WorkList.pop_back(); 248 if (MaxSuccHeight != Cur->Height) { 249 Cur->setHeightDirty(); 250 Cur->Height = MaxSuccHeight; 251 } 252 Cur->isHeightCurrent = true; 253 } 254 } while (!WorkList.empty()); 255} 256 257/// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or 258/// a group of nodes flagged together. 259void SUnit::dump(const ScheduleDAG *G) const { 260 errs() << "SU(" << NodeNum << "): "; 261 G->dumpNode(this); 262} 263 264void SUnit::dumpAll(const ScheduleDAG *G) const { 265 dump(G); 266 267 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"; 272 273 if (Preds.size() != 0) { 274 errs() << " Predecessors:\n"; 275 for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end(); 276 I != E; ++I) { 277 errs() << " "; 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; 283 } 284 errs() << "#"; 285 errs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")"; 286 if (I->isArtificial()) 287 errs() << " *"; 288 errs() << "\n"; 289 } 290 } 291 if (Succs.size() != 0) { 292 errs() << " Successors:\n"; 293 for (SUnit::const_succ_iterator I = Succs.begin(), E = Succs.end(); 294 I != E; ++I) { 295 errs() << " "; 296 switch (I->getKind()) { 297 case SDep::Data: errs() << "val "; break; 298 case SDep::Anti: errs() << "anti"; break; 299 case SDep::Output: errs() << "out "; break; 300 case SDep::Order: errs() << "ch "; break; 301 } 302 errs() << "#"; 303 errs() << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")"; 304 if (I->isArtificial()) 305 errs() << " *"; 306 errs() << "\n"; 307 } 308 } 309 errs() << "\n"; 310} 311 312#ifndef NDEBUG 313/// VerifySchedule - Verify that all SUnits were scheduled and that 314/// their state is consistent. 315/// 316void ScheduleDAG::VerifySchedule(bool isBottomUp) { 317 bool AnyNotSched = false; 318 unsigned DeadNodes = 0; 319 unsigned Noops = 0; 320 for (unsigned i = 0, e = SUnits.size(); i != e; ++i) { 321 if (!SUnits[i].isScheduled) { 322 if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) { 323 ++DeadNodes; 324 continue; 325 } 326 if (!AnyNotSched) 327 errs() << "*** Scheduling failed! ***\n"; 328 SUnits[i].dump(this); 329 errs() << "has not been scheduled!\n"; 330 AnyNotSched = true; 331 } 332 if (SUnits[i].isScheduled && 333 (isBottomUp ? SUnits[i].getHeight() : SUnits[i].getHeight()) > 334 unsigned(INT_MAX)) { 335 if (!AnyNotSched) 336 errs() << "*** Scheduling failed! ***\n"; 337 SUnits[i].dump(this); 338 errs() << "has an unexpected " 339 << (isBottomUp ? "Height" : "Depth") << " value!\n"; 340 AnyNotSched = true; 341 } 342 if (isBottomUp) { 343 if (SUnits[i].NumSuccsLeft != 0) { 344 if (!AnyNotSched) 345 errs() << "*** Scheduling failed! ***\n"; 346 SUnits[i].dump(this); 347 errs() << "has successors left!\n"; 348 AnyNotSched = true; 349 } 350 } else { 351 if (SUnits[i].NumPredsLeft != 0) { 352 if (!AnyNotSched) 353 errs() << "*** Scheduling failed! ***\n"; 354 SUnits[i].dump(this); 355 errs() << "has predecessors left!\n"; 356 AnyNotSched = true; 357 } 358 } 359 } 360 for (unsigned i = 0, e = Sequence.size(); i != e; ++i) 361 if (!Sequence[i]) 362 ++Noops; 363 assert(!AnyNotSched); 364 assert(Sequence.size() + DeadNodes - Noops == SUnits.size() && 365 "The number of nodes scheduled doesn't match the expected number!"); 366} 367#endif 368 369/// InitDAGTopologicalSorting - create the initial topological 370/// ordering from the DAG to be scheduled. 371/// 372/// The idea of the algorithm is taken from 373/// "Online algorithms for managing the topological order of 374/// a directed acyclic graph" by David J. Pearce and Paul H.J. Kelly 375/// This is the MNR algorithm, which was first introduced by 376/// A. Marchetti-Spaccamela, U. Nanni and H. Rohnert in 377/// "Maintaining a topological order under edge insertions". 378/// 379/// Short description of the algorithm: 380/// 381/// Topological ordering, ord, of a DAG maps each node to a topological 382/// index so that for all edges X->Y it is the case that ord(X) < ord(Y). 383/// 384/// This means that if there is a path from the node X to the node Z, 385/// then ord(X) < ord(Z). 386/// 387/// This property can be used to check for reachability of nodes: 388/// if Z is reachable from X, then an insertion of the edge Z->X would 389/// create a cycle. 390/// 391/// The algorithm first computes a topological ordering for the DAG by 392/// initializing the Index2Node and Node2Index arrays and then tries to keep 393/// the ordering up-to-date after edge insertions by reordering the DAG. 394/// 395/// On insertion of the edge X->Y, the algorithm first marks by calling DFS 396/// the nodes reachable from Y, and then shifts them using Shift to lie 397/// immediately after X in Index2Node. 398void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() { 399 unsigned DAGSize = SUnits.size(); 400 std::vector<SUnit*> WorkList; 401 WorkList.reserve(DAGSize); 402 403 Index2Node.resize(DAGSize); 404 Node2Index.resize(DAGSize); 405 406 // Initialize the data structures. 407 for (unsigned i = 0, e = DAGSize; i != e; ++i) { 408 SUnit *SU = &SUnits[i]; 409 int NodeNum = SU->NodeNum; 410 unsigned Degree = SU->Succs.size(); 411 // Temporarily use the Node2Index array as scratch space for degree counts. 412 Node2Index[NodeNum] = Degree; 413 414 // Is it a node without dependencies? 415 if (Degree == 0) { 416 assert(SU->Succs.empty() && "SUnit should have no successors"); 417 // Collect leaf nodes. 418 WorkList.push_back(SU); 419 } 420 } 421 422 int Id = DAGSize; 423 while (!WorkList.empty()) { 424 SUnit *SU = WorkList.back(); 425 WorkList.pop_back(); 426 Allocate(SU->NodeNum, --Id); 427 for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); 428 I != E; ++I) { 429 SUnit *SU = I->getSUnit(); 430 if (!--Node2Index[SU->NodeNum]) 431 // If all dependencies of the node are processed already, 432 // then the node can be computed now. 433 WorkList.push_back(SU); 434 } 435 } 436 437 Visited.resize(DAGSize); 438 439#ifndef NDEBUG 440 // Check correctness of the ordering 441 for (unsigned i = 0, e = DAGSize; i != e; ++i) { 442 SUnit *SU = &SUnits[i]; 443 for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); 444 I != E; ++I) { 445 assert(Node2Index[SU->NodeNum] > Node2Index[I->getSUnit()->NodeNum] && 446 "Wrong topological sorting"); 447 } 448 } 449#endif 450} 451 452/// AddPred - Updates the topological ordering to accomodate an edge 453/// to be added from SUnit X to SUnit Y. 454void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) { 455 int UpperBound, LowerBound; 456 LowerBound = Node2Index[Y->NodeNum]; 457 UpperBound = Node2Index[X->NodeNum]; 458 bool HasLoop = false; 459 // Is Ord(X) < Ord(Y) ? 460 if (LowerBound < UpperBound) { 461 // Update the topological order. 462 Visited.reset(); 463 DFS(Y, UpperBound, HasLoop); 464 assert(!HasLoop && "Inserted edge creates a loop!"); 465 // Recompute topological indexes. 466 Shift(Visited, LowerBound, UpperBound); 467 } 468} 469 470/// RemovePred - Updates the topological ordering to accomodate an 471/// an edge to be removed from the specified node N from the predecessors 472/// of the current node M. 473void ScheduleDAGTopologicalSort::RemovePred(SUnit *M, SUnit *N) { 474 // InitDAGTopologicalSorting(); 475} 476 477/// DFS - Make a DFS traversal to mark all nodes reachable from SU and mark 478/// all nodes affected by the edge insertion. These nodes will later get new 479/// topological indexes by means of the Shift method. 480void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound, 481 bool& HasLoop) { 482 std::vector<const SUnit*> WorkList; 483 WorkList.reserve(SUnits.size()); 484 485 WorkList.push_back(SU); 486 do { 487 SU = WorkList.back(); 488 WorkList.pop_back(); 489 Visited.set(SU->NodeNum); 490 for (int I = SU->Succs.size()-1; I >= 0; --I) { 491 int s = SU->Succs[I].getSUnit()->NodeNum; 492 if (Node2Index[s] == UpperBound) { 493 HasLoop = true; 494 return; 495 } 496 // Visit successors if not already and in affected region. 497 if (!Visited.test(s) && Node2Index[s] < UpperBound) { 498 WorkList.push_back(SU->Succs[I].getSUnit()); 499 } 500 } 501 } while (!WorkList.empty()); 502} 503 504/// Shift - Renumber the nodes so that the topological ordering is 505/// preserved. 506void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound, 507 int UpperBound) { 508 std::vector<int> L; 509 int shift = 0; 510 int i; 511 512 for (i = LowerBound; i <= UpperBound; ++i) { 513 // w is node at topological index i. 514 int w = Index2Node[i]; 515 if (Visited.test(w)) { 516 // Unmark. 517 Visited.reset(w); 518 L.push_back(w); 519 shift = shift + 1; 520 } else { 521 Allocate(w, i - shift); 522 } 523 } 524 525 for (unsigned j = 0; j < L.size(); ++j) { 526 Allocate(L[j], i - shift); 527 i = i + 1; 528 } 529} 530 531 532/// WillCreateCycle - Returns true if adding an edge from SU to TargetSU will 533/// create a cycle. 534bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *SU, SUnit *TargetSU) { 535 if (IsReachable(TargetSU, SU)) 536 return true; 537 for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); 538 I != E; ++I) 539 if (I->isAssignedRegDep() && 540 IsReachable(TargetSU, I->getSUnit())) 541 return true; 542 return false; 543} 544 545/// IsReachable - Checks if SU is reachable from TargetSU. 546bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU, 547 const SUnit *TargetSU) { 548 // If insertion of the edge SU->TargetSU would create a cycle 549 // then there is a path from TargetSU to SU. 550 int UpperBound, LowerBound; 551 LowerBound = Node2Index[TargetSU->NodeNum]; 552 UpperBound = Node2Index[SU->NodeNum]; 553 bool HasLoop = false; 554 // Is Ord(TargetSU) < Ord(SU) ? 555 if (LowerBound < UpperBound) { 556 Visited.reset(); 557 // There may be a path from TargetSU to SU. Check for it. 558 DFS(TargetSU, UpperBound, HasLoop); 559 } 560 return HasLoop; 561} 562 563/// Allocate - assign the topological index to the node n. 564void ScheduleDAGTopologicalSort::Allocate(int n, int index) { 565 Node2Index[n] = index; 566 Index2Node[index] = n; 567} 568 569ScheduleDAGTopologicalSort::ScheduleDAGTopologicalSort( 570 std::vector<SUnit> &sunits) 571 : SUnits(sunits) {} 572 573ScheduleHazardRecognizer::~ScheduleHazardRecognizer() {} 574