GVN.cpp revision 4f9ba7c40c41cae3d9730c5416a2750dea4f0ff4
1//===- GVN.cpp - Eliminate redundant values and loads ------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the Owen Anderson and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This pass performs global value numbering to eliminate fully redundant 11// instructions. It also performs simple dead load elimination. 12// 13//===----------------------------------------------------------------------===// 14 15#define DEBUG_TYPE "gvn" 16 17#include "llvm/Transforms/Scalar.h" 18#include "llvm/BasicBlock.h" 19#include "llvm/Constants.h" 20#include "llvm/DerivedTypes.h" 21#include "llvm/Function.h" 22#include "llvm/Instructions.h" 23#include "llvm/Value.h" 24#include "llvm/Analysis/Dominators.h" 25#include "llvm/ADT/BitVector.h" 26#include "llvm/ADT/DenseMap.h" 27#include "llvm/ADT/DepthFirstIterator.h" 28#include "llvm/ADT/SmallPtrSet.h" 29#include "llvm/ADT/SmallVector.h" 30#include "llvm/ADT/Statistic.h" 31#include "llvm/Analysis/MemoryDependenceAnalysis.h" 32#include "llvm/Support/CFG.h" 33#include "llvm/Support/Compiler.h" 34using namespace llvm; 35 36//===----------------------------------------------------------------------===// 37// ValueTable Class 38//===----------------------------------------------------------------------===// 39 40/// This class holds the mapping between values and value numbers. It is used 41/// as an efficient mechanism to determine the expression-wise equivalence of 42/// two values. 43namespace { 44 struct VISIBILITY_HIDDEN Expression { 45 enum ExpressionOpcode { ADD, SUB, MUL, UDIV, SDIV, FDIV, UREM, SREM, 46 FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ, 47 ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE, 48 ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ, 49 FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE, 50 FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE, 51 FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT, 52 SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI, 53 FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT, 54 PTRTOINT, INTTOPTR, BITCAST, GEP, EMPTY, 55 TOMBSTONE }; 56 57 ExpressionOpcode opcode; 58 const Type* type; 59 uint32_t firstVN; 60 uint32_t secondVN; 61 uint32_t thirdVN; 62 SmallVector<uint32_t, 4> varargs; 63 64 Expression() { } 65 Expression(ExpressionOpcode o) : opcode(o) { } 66 67 bool operator==(const Expression &other) const { 68 if (opcode != other.opcode) 69 return false; 70 else if (opcode == EMPTY || opcode == TOMBSTONE) 71 return true; 72 else if (type != other.type) 73 return false; 74 else if (firstVN != other.firstVN) 75 return false; 76 else if (secondVN != other.secondVN) 77 return false; 78 else if (thirdVN != other.thirdVN) 79 return false; 80 else { 81 if (varargs.size() != other.varargs.size()) 82 return false; 83 84 for (size_t i = 0; i < varargs.size(); ++i) 85 if (varargs[i] != other.varargs[i]) 86 return false; 87 88 return true; 89 } 90 } 91 92 bool operator!=(const Expression &other) const { 93 if (opcode != other.opcode) 94 return true; 95 else if (opcode == EMPTY || opcode == TOMBSTONE) 96 return false; 97 else if (type != other.type) 98 return true; 99 else if (firstVN != other.firstVN) 100 return true; 101 else if (secondVN != other.secondVN) 102 return true; 103 else if (thirdVN != other.thirdVN) 104 return true; 105 else { 106 if (varargs.size() != other.varargs.size()) 107 return true; 108 109 for (size_t i = 0; i < varargs.size(); ++i) 110 if (varargs[i] != other.varargs[i]) 111 return true; 112 113 return false; 114 } 115 } 116 }; 117 118 class VISIBILITY_HIDDEN ValueTable { 119 private: 120 DenseMap<Value*, uint32_t> valueNumbering; 121 DenseMap<Expression, uint32_t> expressionNumbering; 122 123 uint32_t nextValueNumber; 124 125 Expression::ExpressionOpcode getOpcode(BinaryOperator* BO); 126 Expression::ExpressionOpcode getOpcode(CmpInst* C); 127 Expression::ExpressionOpcode getOpcode(CastInst* C); 128 Expression create_expression(BinaryOperator* BO); 129 Expression create_expression(CmpInst* C); 130 Expression create_expression(ShuffleVectorInst* V); 131 Expression create_expression(ExtractElementInst* C); 132 Expression create_expression(InsertElementInst* V); 133 Expression create_expression(SelectInst* V); 134 Expression create_expression(CastInst* C); 135 Expression create_expression(GetElementPtrInst* G); 136 public: 137 ValueTable() { nextValueNumber = 1; } 138 uint32_t lookup_or_add(Value* V); 139 uint32_t lookup(Value* V) const; 140 void add(Value* V, uint32_t num); 141 void clear(); 142 void erase(Value* v); 143 unsigned size(); 144 }; 145} 146 147namespace llvm { 148template <> struct DenseMapKeyInfo<Expression> { 149 static inline Expression getEmptyKey() { return Expression(Expression::EMPTY); } 150 static inline Expression getTombstoneKey() { return Expression(Expression::TOMBSTONE); } 151 152 static unsigned getHashValue(const Expression e) { 153 unsigned hash = e.opcode; 154 155 hash = e.firstVN + hash * 37; 156 hash = e.secondVN + hash * 37; 157 hash = e.thirdVN + hash * 37; 158 159 hash = (unsigned)((uintptr_t)e.type >> 4) ^ 160 (unsigned)((uintptr_t)e.type >> 9) + 161 hash * 37; 162 163 for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(), E = e.varargs.end(); 164 I != E; ++I) 165 hash = *I + hash * 37; 166 167 return hash; 168 } 169 static bool isPod() { return true; } 170}; 171} 172 173//===----------------------------------------------------------------------===// 174// ValueTable Internal Functions 175//===----------------------------------------------------------------------===// 176Expression::ExpressionOpcode 177 ValueTable::getOpcode(BinaryOperator* BO) { 178 switch(BO->getOpcode()) { 179 case Instruction::Add: 180 return Expression::ADD; 181 case Instruction::Sub: 182 return Expression::SUB; 183 case Instruction::Mul: 184 return Expression::MUL; 185 case Instruction::UDiv: 186 return Expression::UDIV; 187 case Instruction::SDiv: 188 return Expression::SDIV; 189 case Instruction::FDiv: 190 return Expression::FDIV; 191 case Instruction::URem: 192 return Expression::UREM; 193 case Instruction::SRem: 194 return Expression::SREM; 195 case Instruction::FRem: 196 return Expression::FREM; 197 case Instruction::Shl: 198 return Expression::SHL; 199 case Instruction::LShr: 200 return Expression::LSHR; 201 case Instruction::AShr: 202 return Expression::ASHR; 203 case Instruction::And: 204 return Expression::AND; 205 case Instruction::Or: 206 return Expression::OR; 207 case Instruction::Xor: 208 return Expression::XOR; 209 210 // THIS SHOULD NEVER HAPPEN 211 default: 212 assert(0 && "Binary operator with unknown opcode?"); 213 return Expression::ADD; 214 } 215} 216 217Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) { 218 if (C->getOpcode() == Instruction::ICmp) { 219 switch (C->getPredicate()) { 220 case ICmpInst::ICMP_EQ: 221 return Expression::ICMPEQ; 222 case ICmpInst::ICMP_NE: 223 return Expression::ICMPNE; 224 case ICmpInst::ICMP_UGT: 225 return Expression::ICMPUGT; 226 case ICmpInst::ICMP_UGE: 227 return Expression::ICMPUGE; 228 case ICmpInst::ICMP_ULT: 229 return Expression::ICMPULT; 230 case ICmpInst::ICMP_ULE: 231 return Expression::ICMPULE; 232 case ICmpInst::ICMP_SGT: 233 return Expression::ICMPSGT; 234 case ICmpInst::ICMP_SGE: 235 return Expression::ICMPSGE; 236 case ICmpInst::ICMP_SLT: 237 return Expression::ICMPSLT; 238 case ICmpInst::ICMP_SLE: 239 return Expression::ICMPSLE; 240 241 // THIS SHOULD NEVER HAPPEN 242 default: 243 assert(0 && "Comparison with unknown predicate?"); 244 return Expression::ICMPEQ; 245 } 246 } else { 247 switch (C->getPredicate()) { 248 case FCmpInst::FCMP_OEQ: 249 return Expression::FCMPOEQ; 250 case FCmpInst::FCMP_OGT: 251 return Expression::FCMPOGT; 252 case FCmpInst::FCMP_OGE: 253 return Expression::FCMPOGE; 254 case FCmpInst::FCMP_OLT: 255 return Expression::FCMPOLT; 256 case FCmpInst::FCMP_OLE: 257 return Expression::FCMPOLE; 258 case FCmpInst::FCMP_ONE: 259 return Expression::FCMPONE; 260 case FCmpInst::FCMP_ORD: 261 return Expression::FCMPORD; 262 case FCmpInst::FCMP_UNO: 263 return Expression::FCMPUNO; 264 case FCmpInst::FCMP_UEQ: 265 return Expression::FCMPUEQ; 266 case FCmpInst::FCMP_UGT: 267 return Expression::FCMPUGT; 268 case FCmpInst::FCMP_UGE: 269 return Expression::FCMPUGE; 270 case FCmpInst::FCMP_ULT: 271 return Expression::FCMPULT; 272 case FCmpInst::FCMP_ULE: 273 return Expression::FCMPULE; 274 case FCmpInst::FCMP_UNE: 275 return Expression::FCMPUNE; 276 277 // THIS SHOULD NEVER HAPPEN 278 default: 279 assert(0 && "Comparison with unknown predicate?"); 280 return Expression::FCMPOEQ; 281 } 282 } 283} 284 285Expression::ExpressionOpcode 286 ValueTable::getOpcode(CastInst* C) { 287 switch(C->getOpcode()) { 288 case Instruction::Trunc: 289 return Expression::TRUNC; 290 case Instruction::ZExt: 291 return Expression::ZEXT; 292 case Instruction::SExt: 293 return Expression::SEXT; 294 case Instruction::FPToUI: 295 return Expression::FPTOUI; 296 case Instruction::FPToSI: 297 return Expression::FPTOSI; 298 case Instruction::UIToFP: 299 return Expression::UITOFP; 300 case Instruction::SIToFP: 301 return Expression::SITOFP; 302 case Instruction::FPTrunc: 303 return Expression::FPTRUNC; 304 case Instruction::FPExt: 305 return Expression::FPEXT; 306 case Instruction::PtrToInt: 307 return Expression::PTRTOINT; 308 case Instruction::IntToPtr: 309 return Expression::INTTOPTR; 310 case Instruction::BitCast: 311 return Expression::BITCAST; 312 313 // THIS SHOULD NEVER HAPPEN 314 default: 315 assert(0 && "Cast operator with unknown opcode?"); 316 return Expression::BITCAST; 317 } 318} 319 320Expression ValueTable::create_expression(BinaryOperator* BO) { 321 Expression e; 322 323 e.firstVN = lookup_or_add(BO->getOperand(0)); 324 e.secondVN = lookup_or_add(BO->getOperand(1)); 325 e.thirdVN = 0; 326 e.type = BO->getType(); 327 e.opcode = getOpcode(BO); 328 329 return e; 330} 331 332Expression ValueTable::create_expression(CmpInst* C) { 333 Expression e; 334 335 e.firstVN = lookup_or_add(C->getOperand(0)); 336 e.secondVN = lookup_or_add(C->getOperand(1)); 337 e.thirdVN = 0; 338 e.type = C->getType(); 339 e.opcode = getOpcode(C); 340 341 return e; 342} 343 344Expression ValueTable::create_expression(CastInst* C) { 345 Expression e; 346 347 e.firstVN = lookup_or_add(C->getOperand(0)); 348 e.secondVN = 0; 349 e.thirdVN = 0; 350 e.type = C->getType(); 351 e.opcode = getOpcode(C); 352 353 return e; 354} 355 356Expression ValueTable::create_expression(ShuffleVectorInst* S) { 357 Expression e; 358 359 e.firstVN = lookup_or_add(S->getOperand(0)); 360 e.secondVN = lookup_or_add(S->getOperand(1)); 361 e.thirdVN = lookup_or_add(S->getOperand(2)); 362 e.type = S->getType(); 363 e.opcode = Expression::SHUFFLE; 364 365 return e; 366} 367 368Expression ValueTable::create_expression(ExtractElementInst* E) { 369 Expression e; 370 371 e.firstVN = lookup_or_add(E->getOperand(0)); 372 e.secondVN = lookup_or_add(E->getOperand(1)); 373 e.thirdVN = 0; 374 e.type = E->getType(); 375 e.opcode = Expression::EXTRACT; 376 377 return e; 378} 379 380Expression ValueTable::create_expression(InsertElementInst* I) { 381 Expression e; 382 383 e.firstVN = lookup_or_add(I->getOperand(0)); 384 e.secondVN = lookup_or_add(I->getOperand(1)); 385 e.thirdVN = lookup_or_add(I->getOperand(2)); 386 e.type = I->getType(); 387 e.opcode = Expression::INSERT; 388 389 return e; 390} 391 392Expression ValueTable::create_expression(SelectInst* I) { 393 Expression e; 394 395 e.firstVN = lookup_or_add(I->getCondition()); 396 e.secondVN = lookup_or_add(I->getTrueValue()); 397 e.thirdVN = lookup_or_add(I->getFalseValue()); 398 e.type = I->getType(); 399 e.opcode = Expression::SELECT; 400 401 return e; 402} 403 404Expression ValueTable::create_expression(GetElementPtrInst* G) { 405 Expression e; 406 407 e.firstVN = lookup_or_add(G->getPointerOperand()); 408 e.secondVN = 0; 409 e.thirdVN = 0; 410 e.type = G->getType(); 411 e.opcode = Expression::GEP; 412 413 for (GetElementPtrInst::op_iterator I = G->idx_begin(), E = G->idx_end(); 414 I != E; ++I) 415 e.varargs.push_back(lookup_or_add(*I)); 416 417 return e; 418} 419 420//===----------------------------------------------------------------------===// 421// ValueTable External Functions 422//===----------------------------------------------------------------------===// 423 424/// lookup_or_add - Returns the value number for the specified value, assigning 425/// it a new number if it did not have one before. 426uint32_t ValueTable::lookup_or_add(Value* V) { 427 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); 428 if (VI != valueNumbering.end()) 429 return VI->second; 430 431 432 if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) { 433 Expression e = create_expression(BO); 434 435 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 436 if (EI != expressionNumbering.end()) { 437 valueNumbering.insert(std::make_pair(V, EI->second)); 438 return EI->second; 439 } else { 440 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 441 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 442 443 return nextValueNumber++; 444 } 445 } else if (CmpInst* C = dyn_cast<CmpInst>(V)) { 446 Expression e = create_expression(C); 447 448 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 449 if (EI != expressionNumbering.end()) { 450 valueNumbering.insert(std::make_pair(V, EI->second)); 451 return EI->second; 452 } else { 453 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 454 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 455 456 return nextValueNumber++; 457 } 458 } else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) { 459 Expression e = create_expression(U); 460 461 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 462 if (EI != expressionNumbering.end()) { 463 valueNumbering.insert(std::make_pair(V, EI->second)); 464 return EI->second; 465 } else { 466 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 467 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 468 469 return nextValueNumber++; 470 } 471 } else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) { 472 Expression e = create_expression(U); 473 474 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 475 if (EI != expressionNumbering.end()) { 476 valueNumbering.insert(std::make_pair(V, EI->second)); 477 return EI->second; 478 } else { 479 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 480 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 481 482 return nextValueNumber++; 483 } 484 } else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) { 485 Expression e = create_expression(U); 486 487 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 488 if (EI != expressionNumbering.end()) { 489 valueNumbering.insert(std::make_pair(V, EI->second)); 490 return EI->second; 491 } else { 492 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 493 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 494 495 return nextValueNumber++; 496 } 497 } else if (SelectInst* U = dyn_cast<SelectInst>(V)) { 498 Expression e = create_expression(U); 499 500 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 501 if (EI != expressionNumbering.end()) { 502 valueNumbering.insert(std::make_pair(V, EI->second)); 503 return EI->second; 504 } else { 505 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 506 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 507 508 return nextValueNumber++; 509 } 510 } else if (CastInst* U = dyn_cast<CastInst>(V)) { 511 Expression e = create_expression(U); 512 513 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 514 if (EI != expressionNumbering.end()) { 515 valueNumbering.insert(std::make_pair(V, EI->second)); 516 return EI->second; 517 } else { 518 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 519 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 520 521 return nextValueNumber++; 522 } 523 } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) { 524 Expression e = create_expression(U); 525 526 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 527 if (EI != expressionNumbering.end()) { 528 valueNumbering.insert(std::make_pair(V, EI->second)); 529 return EI->second; 530 } else { 531 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 532 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 533 534 return nextValueNumber++; 535 } 536 } else { 537 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 538 return nextValueNumber++; 539 } 540} 541 542/// lookup - Returns the value number of the specified value. Fails if 543/// the value has not yet been numbered. 544uint32_t ValueTable::lookup(Value* V) const { 545 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); 546 if (VI != valueNumbering.end()) 547 return VI->second; 548 else 549 assert(0 && "Value not numbered?"); 550 551 return 0; 552} 553 554/// clear - Remove all entries from the ValueTable 555void ValueTable::clear() { 556 valueNumbering.clear(); 557 expressionNumbering.clear(); 558 nextValueNumber = 1; 559} 560 561//===----------------------------------------------------------------------===// 562// ValueNumberedSet Class 563//===----------------------------------------------------------------------===// 564namespace { 565class ValueNumberedSet { 566 private: 567 SmallPtrSet<Value*, 8> contents; 568 BitVector numbers; 569 public: 570 ValueNumberedSet() { numbers.resize(1); } 571 ValueNumberedSet(const ValueNumberedSet& other) { 572 numbers = other.numbers; 573 contents = other.contents; 574 } 575 576 typedef SmallPtrSet<Value*, 8>::iterator iterator; 577 578 iterator begin() { return contents.begin(); } 579 iterator end() { return contents.end(); } 580 581 bool insert(Value* v) { return contents.insert(v); } 582 void insert(iterator I, iterator E) { contents.insert(I, E); } 583 void erase(Value* v) { contents.erase(v); } 584 unsigned count(Value* v) { return contents.count(v); } 585 size_t size() { return contents.size(); } 586 587 void set(unsigned i) { 588 if (i >= numbers.size()) 589 numbers.resize(i+1); 590 591 numbers.set(i); 592 } 593 594 void operator=(const ValueNumberedSet& other) { 595 contents = other.contents; 596 numbers = other.numbers; 597 } 598 599 void reset(unsigned i) { 600 if (i < numbers.size()) 601 numbers.reset(i); 602 } 603 604 bool test(unsigned i) { 605 if (i >= numbers.size()) 606 return false; 607 608 return numbers.test(i); 609 } 610 611 void clear() { 612 contents.clear(); 613 numbers.clear(); 614 } 615}; 616} 617 618//===----------------------------------------------------------------------===// 619// GVN Pass 620//===----------------------------------------------------------------------===// 621 622namespace { 623 624 class VISIBILITY_HIDDEN GVN : public FunctionPass { 625 bool runOnFunction(Function &F); 626 public: 627 static char ID; // Pass identification, replacement for typeid 628 GVN() : FunctionPass((intptr_t)&ID) { } 629 630 private: 631 ValueTable VN; 632 633 DenseMap<BasicBlock*, ValueNumberedSet> availableOut; 634 635 // This transformation requires dominator postdominator info 636 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 637 AU.setPreservesCFG(); 638 AU.addRequired<DominatorTree>(); 639 AU.addRequired<MemoryDependenceAnalysis>(); 640 AU.addPreserved<MemoryDependenceAnalysis>(); 641 } 642 643 // Helper fuctions 644 // FIXME: eliminate or document these better 645 Value* find_leader(ValueNumberedSet& vals, uint32_t v) ; 646 void val_insert(ValueNumberedSet& s, Value* v); 647 bool processLoad(LoadInst* L, 648 DenseMap<Value*, LoadInst*>& lastLoad, 649 SmallVector<Instruction*, 4>& toErase); 650 bool processInstruction(Instruction* I, 651 ValueNumberedSet& currAvail, 652 DenseMap<Value*, LoadInst*>& lastSeenLoad, 653 SmallVector<Instruction*, 4>& toErase); 654 bool processNonLocalLoad(LoadInst* L, SmallVector<Instruction*, 4>& toErase); 655 Value *GetValueForBlock(BasicBlock *BB, LoadInst* orig, 656 DenseMap<BasicBlock*, Value*> &Phis); 657 void dump(DenseMap<BasicBlock*, Value*>& d); 658 }; 659 660 char GVN::ID = 0; 661 662} 663 664// createGVNPass - The public interface to this file... 665FunctionPass *llvm::createGVNPass() { return new GVN(); } 666 667static RegisterPass<GVN> X("gvn", 668 "Global Value Numbering"); 669 670STATISTIC(NumGVNInstr, "Number of instructions deleted"); 671STATISTIC(NumGVNLoad, "Number of loads deleted"); 672 673/// find_leader - Given a set and a value number, return the first 674/// element of the set with that value number, or 0 if no such element 675/// is present 676Value* GVN::find_leader(ValueNumberedSet& vals, uint32_t v) { 677 if (!vals.test(v)) 678 return 0; 679 680 for (ValueNumberedSet::iterator I = vals.begin(), E = vals.end(); 681 I != E; ++I) 682 if (v == VN.lookup(*I)) 683 return *I; 684 685 assert(0 && "No leader found, but present bit is set?"); 686 return 0; 687} 688 689/// val_insert - Insert a value into a set only if there is not a value 690/// with the same value number already in the set 691void GVN::val_insert(ValueNumberedSet& s, Value* v) { 692 uint32_t num = VN.lookup(v); 693 if (!s.test(num)) 694 s.insert(v); 695} 696 697void GVN::dump(DenseMap<BasicBlock*, Value*>& d) { 698 printf("{\n"); 699 for (DenseMap<BasicBlock*, Value*>::iterator I = d.begin(), 700 E = d.end(); I != E; ++I) { 701 if (I->second == MemoryDependenceAnalysis::None) 702 printf("None\n"); 703 else 704 I->second->dump(); 705 } 706 printf("}\n"); 707} 708 709 710/// GetValueForBlock - Get the value to use within the specified basic block. 711/// available values are in Phis. 712Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig, 713 DenseMap<BasicBlock*, Value*> &Phis) { 714 DominatorTree &DT = getAnalysis<DominatorTree>(); 715 716 // If we have already computed this value, return the previously computed val. 717 Value *&V = Phis[BB]; 718 if (V) return V; 719 720 DomTreeNode *IDom = DT.getNode(BB)->getIDom(); 721 722 if (IDom && Phis.count(IDom->getBlock())) { 723 return V = GetValueForBlock(IDom->getBlock(), orig, Phis); 724 } 725 726 if (std::distance(pred_begin(BB), pred_end(BB)) == 1) 727 return V = GetValueForBlock(IDom->getBlock(), orig, Phis); 728 729 // Otherwise, the idom is the loop, so we need to insert a PHI node. Do so 730 // now, then get values to fill in the incoming values for the PHI. 731 PHINode *PN = new PHINode(orig->getType(), orig->getName()+".rle", 732 BB->begin()); 733 PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB))); 734 V = PN; 735 736 // Fill in the incoming values for the block. 737 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 738 PN->addIncoming(GetValueForBlock(*PI, orig, Phis), *PI); 739 return PN; 740} 741 742bool GVN::processNonLocalLoad(LoadInst* L, SmallVector<Instruction*, 4>& toErase) { 743 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 744 745 DenseMap<BasicBlock*, Value*> deps; 746 bool ret = MD.getNonLocalDependency(L, deps); 747 if (!ret) 748 return false; 749 750 DenseMap<BasicBlock*, Value*> repl; 751 for (DenseMap<BasicBlock*, Value*>::iterator I = deps.begin(), E = deps.end(); 752 I != E; ++I) 753 if (I->second == MemoryDependenceAnalysis::None) { 754 return false; 755 } else if (StoreInst* S = dyn_cast<StoreInst>(I->second)) { 756 if (S->getPointerOperand() == L->getPointerOperand()) 757 repl.insert(std::make_pair(I->first, S->getOperand(0))); 758 else 759 return false; 760 } else if (LoadInst* LD = dyn_cast<LoadInst>(I->second)) { 761 if (LD->getPointerOperand() == L->getPointerOperand()) 762 repl.insert(std::make_pair(I->first, LD)); 763 else 764 return false; 765 } else { 766 return false; 767 } 768 769 SmallPtrSet<BasicBlock*, 4> visited; 770 Value* v = GetValueForBlock(L->getParent(), L, repl); 771 772 MD.removeInstruction(L); 773 L->replaceAllUsesWith(v); 774 toErase.push_back(L); 775 776 return true; 777} 778 779bool GVN::processLoad(LoadInst* L, 780 DenseMap<Value*, LoadInst*>& lastLoad, 781 SmallVector<Instruction*, 4>& toErase) { 782 if (L->isVolatile()) { 783 lastLoad[L->getPointerOperand()] = L; 784 return false; 785 } 786 787 Value* pointer = L->getPointerOperand(); 788 LoadInst*& last = lastLoad[pointer]; 789 790 // ... to a pointer that has been loaded from before... 791 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 792 Instruction* dep = MD.getDependency(L); 793 if (dep == MemoryDependenceAnalysis::NonLocal && 794 L->getParent() != &L->getParent()->getParent()->getEntryBlock()) 795 processNonLocalLoad(L, toErase); 796 bool deletedLoad = false; 797 798 while (dep != MemoryDependenceAnalysis::None && 799 dep != MemoryDependenceAnalysis::NonLocal && 800 (isa<LoadInst>(dep) || isa<StoreInst>(dep))) { 801 // ... that depends on a store ... 802 if (StoreInst* S = dyn_cast<StoreInst>(dep)) { 803 if (S->getPointerOperand() == pointer) { 804 // Remove it! 805 MD.removeInstruction(L); 806 807 L->replaceAllUsesWith(S->getOperand(0)); 808 toErase.push_back(L); 809 deletedLoad = true; 810 NumGVNLoad++; 811 } 812 813 // Whether we removed it or not, we can't 814 // go any further 815 break; 816 } else if (!last) { 817 // If we don't depend on a store, and we haven't 818 // been loaded before, bail. 819 break; 820 } else if (dep == last) { 821 // Remove it! 822 MD.removeInstruction(L); 823 824 L->replaceAllUsesWith(last); 825 toErase.push_back(L); 826 deletedLoad = true; 827 NumGVNLoad++; 828 829 break; 830 } else { 831 dep = MD.getDependency(L, dep); 832 } 833 } 834 835 if (!deletedLoad) 836 last = L; 837 838 return deletedLoad; 839} 840 841/// buildsets_availout - When calculating availability, handle an instruction 842/// by inserting it into the appropriate sets 843bool GVN::processInstruction(Instruction* I, 844 ValueNumberedSet& currAvail, 845 DenseMap<Value*, LoadInst*>& lastSeenLoad, 846 SmallVector<Instruction*, 4>& toErase) { 847 if (LoadInst* L = dyn_cast<LoadInst>(I)) { 848 return processLoad(L, lastSeenLoad, toErase); 849 } 850 851 unsigned num = VN.lookup_or_add(I); 852 853 if (currAvail.test(num)) { 854 Value* repl = find_leader(currAvail, num); 855 856 I->replaceAllUsesWith(repl); 857 toErase.push_back(I); 858 return true; 859 } else if (!I->isTerminator()) { 860 currAvail.set(num); 861 currAvail.insert(I); 862 } 863 864 return false; 865} 866 867// GVN::runOnFunction - This is the main transformation entry point for a 868// function. 869// 870bool GVN::runOnFunction(Function &F) { 871 // Clean out global sets from any previous functions 872 VN.clear(); 873 availableOut.clear(); 874 875 bool changed_function = false; 876 877 DominatorTree &DT = getAnalysis<DominatorTree>(); 878 879 SmallVector<Instruction*, 4> toErase; 880 881 // Top-down walk of the dominator tree 882 for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()), 883 E = df_end(DT.getRootNode()); DI != E; ++DI) { 884 885 // Get the set to update for this block 886 ValueNumberedSet& currAvail = availableOut[DI->getBlock()]; 887 DenseMap<Value*, LoadInst*> lastSeenLoad; 888 889 BasicBlock* BB = DI->getBlock(); 890 891 // A block inherits AVAIL_OUT from its dominator 892 if (DI->getIDom() != 0) 893 currAvail = availableOut[DI->getIDom()->getBlock()]; 894 895 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); 896 BI != BE; ++BI) { 897 changed_function |= processInstruction(BI, currAvail, lastSeenLoad, toErase); 898 899 NumGVNInstr += toErase.size(); 900 901 for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(), 902 E = toErase.end(); I != E; ++I) 903 (*I)->eraseFromParent(); 904 905 toErase.clear(); 906 } 907 } 908 909 return changed_function; 910} 911