GVN.cpp revision f2204d7bb103b1d23c910efc678d5303003635bb
1//===- GVN.cpp - Eliminate redundant values and loads ------------===// 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 pass performs global value numbering to eliminate fully redundant 11// instructions. It also performs simple dead load elimination. 12// 13// Note that this pass does the value numbering itself, it does not use the 14// ValueNumbering analysis passes. 15// 16//===----------------------------------------------------------------------===// 17 18#define DEBUG_TYPE "gvn" 19#include "llvm/Transforms/Scalar.h" 20#include "llvm/BasicBlock.h" 21#include "llvm/Constants.h" 22#include "llvm/DerivedTypes.h" 23#include "llvm/Function.h" 24#include "llvm/Instructions.h" 25#include "llvm/Value.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/Dominators.h" 32#include "llvm/Analysis/AliasAnalysis.h" 33#include "llvm/Analysis/MemoryDependenceAnalysis.h" 34#include "llvm/Support/CFG.h" 35#include "llvm/Support/CommandLine.h" 36#include "llvm/Support/Compiler.h" 37#include "llvm/Support/Debug.h" 38#include "llvm/Transforms/Utils/BasicBlockUtils.h" 39using namespace llvm; 40 41STATISTIC(NumGVNInstr, "Number of instructions deleted"); 42STATISTIC(NumGVNLoad, "Number of loads deleted"); 43STATISTIC(NumGVNPRE, "Number of instructions PRE'd"); 44 45static cl::opt<bool> EnablePRE("enable-pre", 46 cl::init(false), cl::Hidden); 47 48//===----------------------------------------------------------------------===// 49// ValueTable Class 50//===----------------------------------------------------------------------===// 51 52/// This class holds the mapping between values and value numbers. It is used 53/// as an efficient mechanism to determine the expression-wise equivalence of 54/// two values. 55namespace { 56 struct VISIBILITY_HIDDEN Expression { 57 enum ExpressionOpcode { ADD, SUB, MUL, UDIV, SDIV, FDIV, UREM, SREM, 58 FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ, 59 ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE, 60 ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ, 61 FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE, 62 FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE, 63 FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT, 64 SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI, 65 FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT, 66 PTRTOINT, INTTOPTR, BITCAST, GEP, CALL, CONSTANT, 67 EMPTY, TOMBSTONE }; 68 69 ExpressionOpcode opcode; 70 const Type* type; 71 uint32_t firstVN; 72 uint32_t secondVN; 73 uint32_t thirdVN; 74 SmallVector<uint32_t, 4> varargs; 75 Value* function; 76 77 Expression() { } 78 Expression(ExpressionOpcode o) : opcode(o) { } 79 80 bool operator==(const Expression &other) const { 81 if (opcode != other.opcode) 82 return false; 83 else if (opcode == EMPTY || opcode == TOMBSTONE) 84 return true; 85 else if (type != other.type) 86 return false; 87 else if (function != other.function) 88 return false; 89 else if (firstVN != other.firstVN) 90 return false; 91 else if (secondVN != other.secondVN) 92 return false; 93 else if (thirdVN != other.thirdVN) 94 return false; 95 else { 96 if (varargs.size() != other.varargs.size()) 97 return false; 98 99 for (size_t i = 0; i < varargs.size(); ++i) 100 if (varargs[i] != other.varargs[i]) 101 return false; 102 103 return true; 104 } 105 } 106 107 bool operator!=(const Expression &other) const { 108 if (opcode != other.opcode) 109 return true; 110 else if (opcode == EMPTY || opcode == TOMBSTONE) 111 return false; 112 else if (type != other.type) 113 return true; 114 else if (function != other.function) 115 return true; 116 else if (firstVN != other.firstVN) 117 return true; 118 else if (secondVN != other.secondVN) 119 return true; 120 else if (thirdVN != other.thirdVN) 121 return true; 122 else { 123 if (varargs.size() != other.varargs.size()) 124 return true; 125 126 for (size_t i = 0; i < varargs.size(); ++i) 127 if (varargs[i] != other.varargs[i]) 128 return true; 129 130 return false; 131 } 132 } 133 }; 134 135 class VISIBILITY_HIDDEN ValueTable { 136 private: 137 DenseMap<Value*, uint32_t> valueNumbering; 138 DenseMap<Expression, uint32_t> expressionNumbering; 139 AliasAnalysis* AA; 140 MemoryDependenceAnalysis* MD; 141 DominatorTree* DT; 142 143 uint32_t nextValueNumber; 144 145 Expression::ExpressionOpcode getOpcode(BinaryOperator* BO); 146 Expression::ExpressionOpcode getOpcode(CmpInst* C); 147 Expression::ExpressionOpcode getOpcode(CastInst* C); 148 Expression create_expression(BinaryOperator* BO); 149 Expression create_expression(CmpInst* C); 150 Expression create_expression(ShuffleVectorInst* V); 151 Expression create_expression(ExtractElementInst* C); 152 Expression create_expression(InsertElementInst* V); 153 Expression create_expression(SelectInst* V); 154 Expression create_expression(CastInst* C); 155 Expression create_expression(GetElementPtrInst* G); 156 Expression create_expression(CallInst* C); 157 Expression create_expression(Constant* C); 158 public: 159 ValueTable() : nextValueNumber(1) { } 160 uint32_t lookup_or_add(Value* V); 161 uint32_t lookup(Value* V) const; 162 void add(Value* V, uint32_t num); 163 void clear(); 164 void erase(Value* v); 165 unsigned size(); 166 void setAliasAnalysis(AliasAnalysis* A) { AA = A; } 167 void setMemDep(MemoryDependenceAnalysis* M) { MD = M; } 168 void setDomTree(DominatorTree* D) { DT = D; } 169 }; 170} 171 172namespace llvm { 173template <> struct DenseMapInfo<Expression> { 174 static inline Expression getEmptyKey() { 175 return Expression(Expression::EMPTY); 176 } 177 178 static inline Expression getTombstoneKey() { 179 return Expression(Expression::TOMBSTONE); 180 } 181 182 static unsigned getHashValue(const Expression e) { 183 unsigned hash = e.opcode; 184 185 hash = e.firstVN + hash * 37; 186 hash = e.secondVN + hash * 37; 187 hash = e.thirdVN + hash * 37; 188 189 hash = ((unsigned)((uintptr_t)e.type >> 4) ^ 190 (unsigned)((uintptr_t)e.type >> 9)) + 191 hash * 37; 192 193 for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(), 194 E = e.varargs.end(); I != E; ++I) 195 hash = *I + hash * 37; 196 197 hash = ((unsigned)((uintptr_t)e.function >> 4) ^ 198 (unsigned)((uintptr_t)e.function >> 9)) + 199 hash * 37; 200 201 return hash; 202 } 203 static bool isEqual(const Expression &LHS, const Expression &RHS) { 204 return LHS == RHS; 205 } 206 static bool isPod() { return true; } 207}; 208} 209 210//===----------------------------------------------------------------------===// 211// ValueTable Internal Functions 212//===----------------------------------------------------------------------===// 213Expression::ExpressionOpcode ValueTable::getOpcode(BinaryOperator* BO) { 214 switch(BO->getOpcode()) { 215 default: // THIS SHOULD NEVER HAPPEN 216 assert(0 && "Binary operator with unknown opcode?"); 217 case Instruction::Add: return Expression::ADD; 218 case Instruction::Sub: return Expression::SUB; 219 case Instruction::Mul: return Expression::MUL; 220 case Instruction::UDiv: return Expression::UDIV; 221 case Instruction::SDiv: return Expression::SDIV; 222 case Instruction::FDiv: return Expression::FDIV; 223 case Instruction::URem: return Expression::UREM; 224 case Instruction::SRem: return Expression::SREM; 225 case Instruction::FRem: return Expression::FREM; 226 case Instruction::Shl: return Expression::SHL; 227 case Instruction::LShr: return Expression::LSHR; 228 case Instruction::AShr: return Expression::ASHR; 229 case Instruction::And: return Expression::AND; 230 case Instruction::Or: return Expression::OR; 231 case Instruction::Xor: return Expression::XOR; 232 } 233} 234 235Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) { 236 if (isa<ICmpInst>(C) || isa<VICmpInst>(C)) { 237 switch (C->getPredicate()) { 238 default: // THIS SHOULD NEVER HAPPEN 239 assert(0 && "Comparison with unknown predicate?"); 240 case ICmpInst::ICMP_EQ: return Expression::ICMPEQ; 241 case ICmpInst::ICMP_NE: return Expression::ICMPNE; 242 case ICmpInst::ICMP_UGT: return Expression::ICMPUGT; 243 case ICmpInst::ICMP_UGE: return Expression::ICMPUGE; 244 case ICmpInst::ICMP_ULT: return Expression::ICMPULT; 245 case ICmpInst::ICMP_ULE: return Expression::ICMPULE; 246 case ICmpInst::ICMP_SGT: return Expression::ICMPSGT; 247 case ICmpInst::ICMP_SGE: return Expression::ICMPSGE; 248 case ICmpInst::ICMP_SLT: return Expression::ICMPSLT; 249 case ICmpInst::ICMP_SLE: return Expression::ICMPSLE; 250 } 251 } 252 assert((isa<FCmpInst>(C) || isa<VFCmpInst>(C)) && "Unknown compare"); 253 switch (C->getPredicate()) { 254 default: // THIS SHOULD NEVER HAPPEN 255 assert(0 && "Comparison with unknown predicate?"); 256 case FCmpInst::FCMP_OEQ: return Expression::FCMPOEQ; 257 case FCmpInst::FCMP_OGT: return Expression::FCMPOGT; 258 case FCmpInst::FCMP_OGE: return Expression::FCMPOGE; 259 case FCmpInst::FCMP_OLT: return Expression::FCMPOLT; 260 case FCmpInst::FCMP_OLE: return Expression::FCMPOLE; 261 case FCmpInst::FCMP_ONE: return Expression::FCMPONE; 262 case FCmpInst::FCMP_ORD: return Expression::FCMPORD; 263 case FCmpInst::FCMP_UNO: return Expression::FCMPUNO; 264 case FCmpInst::FCMP_UEQ: return Expression::FCMPUEQ; 265 case FCmpInst::FCMP_UGT: return Expression::FCMPUGT; 266 case FCmpInst::FCMP_UGE: return Expression::FCMPUGE; 267 case FCmpInst::FCMP_ULT: return Expression::FCMPULT; 268 case FCmpInst::FCMP_ULE: return Expression::FCMPULE; 269 case FCmpInst::FCMP_UNE: return Expression::FCMPUNE; 270 } 271} 272 273Expression::ExpressionOpcode ValueTable::getOpcode(CastInst* C) { 274 switch(C->getOpcode()) { 275 default: // THIS SHOULD NEVER HAPPEN 276 assert(0 && "Cast operator with unknown opcode?"); 277 case Instruction::Trunc: return Expression::TRUNC; 278 case Instruction::ZExt: return Expression::ZEXT; 279 case Instruction::SExt: return Expression::SEXT; 280 case Instruction::FPToUI: return Expression::FPTOUI; 281 case Instruction::FPToSI: return Expression::FPTOSI; 282 case Instruction::UIToFP: return Expression::UITOFP; 283 case Instruction::SIToFP: return Expression::SITOFP; 284 case Instruction::FPTrunc: return Expression::FPTRUNC; 285 case Instruction::FPExt: return Expression::FPEXT; 286 case Instruction::PtrToInt: return Expression::PTRTOINT; 287 case Instruction::IntToPtr: return Expression::INTTOPTR; 288 case Instruction::BitCast: return Expression::BITCAST; 289 } 290} 291 292Expression ValueTable::create_expression(CallInst* C) { 293 Expression e; 294 295 e.type = C->getType(); 296 e.firstVN = 0; 297 e.secondVN = 0; 298 e.thirdVN = 0; 299 e.function = C->getCalledFunction(); 300 e.opcode = Expression::CALL; 301 302 for (CallInst::op_iterator I = C->op_begin()+1, E = C->op_end(); 303 I != E; ++I) 304 e.varargs.push_back(lookup_or_add(*I)); 305 306 return e; 307} 308 309Expression ValueTable::create_expression(BinaryOperator* BO) { 310 Expression e; 311 312 e.firstVN = lookup_or_add(BO->getOperand(0)); 313 e.secondVN = lookup_or_add(BO->getOperand(1)); 314 e.thirdVN = 0; 315 e.function = 0; 316 e.type = BO->getType(); 317 e.opcode = getOpcode(BO); 318 319 return e; 320} 321 322Expression ValueTable::create_expression(CmpInst* C) { 323 Expression e; 324 325 e.firstVN = lookup_or_add(C->getOperand(0)); 326 e.secondVN = lookup_or_add(C->getOperand(1)); 327 e.thirdVN = 0; 328 e.function = 0; 329 e.type = C->getType(); 330 e.opcode = getOpcode(C); 331 332 return e; 333} 334 335Expression ValueTable::create_expression(CastInst* C) { 336 Expression e; 337 338 e.firstVN = lookup_or_add(C->getOperand(0)); 339 e.secondVN = 0; 340 e.thirdVN = 0; 341 e.function = 0; 342 e.type = C->getType(); 343 e.opcode = getOpcode(C); 344 345 return e; 346} 347 348Expression ValueTable::create_expression(ShuffleVectorInst* S) { 349 Expression e; 350 351 e.firstVN = lookup_or_add(S->getOperand(0)); 352 e.secondVN = lookup_or_add(S->getOperand(1)); 353 e.thirdVN = lookup_or_add(S->getOperand(2)); 354 e.function = 0; 355 e.type = S->getType(); 356 e.opcode = Expression::SHUFFLE; 357 358 return e; 359} 360 361Expression ValueTable::create_expression(ExtractElementInst* E) { 362 Expression e; 363 364 e.firstVN = lookup_or_add(E->getOperand(0)); 365 e.secondVN = lookup_or_add(E->getOperand(1)); 366 e.thirdVN = 0; 367 e.function = 0; 368 e.type = E->getType(); 369 e.opcode = Expression::EXTRACT; 370 371 return e; 372} 373 374Expression ValueTable::create_expression(InsertElementInst* I) { 375 Expression e; 376 377 e.firstVN = lookup_or_add(I->getOperand(0)); 378 e.secondVN = lookup_or_add(I->getOperand(1)); 379 e.thirdVN = lookup_or_add(I->getOperand(2)); 380 e.function = 0; 381 e.type = I->getType(); 382 e.opcode = Expression::INSERT; 383 384 return e; 385} 386 387Expression ValueTable::create_expression(SelectInst* I) { 388 Expression e; 389 390 e.firstVN = lookup_or_add(I->getCondition()); 391 e.secondVN = lookup_or_add(I->getTrueValue()); 392 e.thirdVN = lookup_or_add(I->getFalseValue()); 393 e.function = 0; 394 e.type = I->getType(); 395 e.opcode = Expression::SELECT; 396 397 return e; 398} 399 400Expression ValueTable::create_expression(GetElementPtrInst* G) { 401 Expression e; 402 403 e.firstVN = lookup_or_add(G->getPointerOperand()); 404 e.secondVN = 0; 405 e.thirdVN = 0; 406 e.function = 0; 407 e.type = G->getType(); 408 e.opcode = Expression::GEP; 409 410 for (GetElementPtrInst::op_iterator I = G->idx_begin(), E = G->idx_end(); 411 I != E; ++I) 412 e.varargs.push_back(lookup_or_add(*I)); 413 414 return e; 415} 416 417//===----------------------------------------------------------------------===// 418// ValueTable External Functions 419//===----------------------------------------------------------------------===// 420 421/// add - Insert a value into the table with a specified value number. 422void ValueTable::add(Value* V, uint32_t num) { 423 valueNumbering.insert(std::make_pair(V, num)); 424} 425 426/// lookup_or_add - Returns the value number for the specified value, assigning 427/// it a new number if it did not have one before. 428uint32_t ValueTable::lookup_or_add(Value* V) { 429 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); 430 if (VI != valueNumbering.end()) 431 return VI->second; 432 433 if (CallInst* C = dyn_cast<CallInst>(V)) { 434 if (AA->doesNotAccessMemory(C)) { 435 Expression e = create_expression(C); 436 437 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 438 if (EI != expressionNumbering.end()) { 439 valueNumbering.insert(std::make_pair(V, EI->second)); 440 return EI->second; 441 } else { 442 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 443 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 444 445 return nextValueNumber++; 446 } 447 } else if (AA->onlyReadsMemory(C)) { 448 Expression e = create_expression(C); 449 450 if (expressionNumbering.find(e) == expressionNumbering.end()) { 451 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 452 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 453 return nextValueNumber++; 454 } 455 456 Instruction* local_dep = MD->getDependency(C); 457 458 if (local_dep == MemoryDependenceAnalysis::None) { 459 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 460 return nextValueNumber++; 461 } else if (local_dep != MemoryDependenceAnalysis::NonLocal) { 462 if (!isa<CallInst>(local_dep)) { 463 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 464 return nextValueNumber++; 465 } 466 467 CallInst* local_cdep = cast<CallInst>(local_dep); 468 469 if (local_cdep->getCalledFunction() != C->getCalledFunction() || 470 local_cdep->getNumOperands() != C->getNumOperands()) { 471 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 472 return nextValueNumber++; 473 } else if (!C->getCalledFunction()) { 474 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 475 return nextValueNumber++; 476 } else { 477 for (unsigned i = 1; i < C->getNumOperands(); ++i) { 478 uint32_t c_vn = lookup_or_add(C->getOperand(i)); 479 uint32_t cd_vn = lookup_or_add(local_cdep->getOperand(i)); 480 if (c_vn != cd_vn) { 481 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 482 return nextValueNumber++; 483 } 484 } 485 486 uint32_t v = lookup_or_add(local_cdep); 487 valueNumbering.insert(std::make_pair(V, v)); 488 return v; 489 } 490 } 491 492 493 DenseMap<BasicBlock*, Value*> deps; 494 MD->getNonLocalDependency(C, deps); 495 CallInst* cdep = 0; 496 497 for (DenseMap<BasicBlock*, Value*>::iterator I = deps.begin(), 498 E = deps.end(); I != E; ++I) { 499 if (I->second == MemoryDependenceAnalysis::None) { 500 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 501 502 return nextValueNumber++; 503 } else if (I->second != MemoryDependenceAnalysis::NonLocal) { 504 if (DT->properlyDominates(I->first, C->getParent())) { 505 if (CallInst* CD = dyn_cast<CallInst>(I->second)) 506 cdep = CD; 507 else { 508 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 509 return nextValueNumber++; 510 } 511 } else { 512 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 513 return nextValueNumber++; 514 } 515 } 516 } 517 518 if (!cdep) { 519 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 520 return nextValueNumber++; 521 } 522 523 if (cdep->getCalledFunction() != C->getCalledFunction() || 524 cdep->getNumOperands() != C->getNumOperands()) { 525 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 526 return nextValueNumber++; 527 } else if (!C->getCalledFunction()) { 528 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 529 return nextValueNumber++; 530 } else { 531 for (unsigned i = 1; i < C->getNumOperands(); ++i) { 532 uint32_t c_vn = lookup_or_add(C->getOperand(i)); 533 uint32_t cd_vn = lookup_or_add(cdep->getOperand(i)); 534 if (c_vn != cd_vn) { 535 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 536 return nextValueNumber++; 537 } 538 } 539 540 uint32_t v = lookup_or_add(cdep); 541 valueNumbering.insert(std::make_pair(V, v)); 542 return v; 543 } 544 545 } else { 546 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 547 return nextValueNumber++; 548 } 549 } else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) { 550 Expression e = create_expression(BO); 551 552 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 553 if (EI != expressionNumbering.end()) { 554 valueNumbering.insert(std::make_pair(V, EI->second)); 555 return EI->second; 556 } else { 557 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 558 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 559 560 return nextValueNumber++; 561 } 562 } else if (CmpInst* C = dyn_cast<CmpInst>(V)) { 563 Expression e = create_expression(C); 564 565 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 566 if (EI != expressionNumbering.end()) { 567 valueNumbering.insert(std::make_pair(V, EI->second)); 568 return EI->second; 569 } else { 570 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 571 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 572 573 return nextValueNumber++; 574 } 575 } else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) { 576 Expression e = create_expression(U); 577 578 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 579 if (EI != expressionNumbering.end()) { 580 valueNumbering.insert(std::make_pair(V, EI->second)); 581 return EI->second; 582 } else { 583 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 584 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 585 586 return nextValueNumber++; 587 } 588 } else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) { 589 Expression e = create_expression(U); 590 591 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 592 if (EI != expressionNumbering.end()) { 593 valueNumbering.insert(std::make_pair(V, EI->second)); 594 return EI->second; 595 } else { 596 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 597 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 598 599 return nextValueNumber++; 600 } 601 } else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) { 602 Expression e = create_expression(U); 603 604 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 605 if (EI != expressionNumbering.end()) { 606 valueNumbering.insert(std::make_pair(V, EI->second)); 607 return EI->second; 608 } else { 609 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 610 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 611 612 return nextValueNumber++; 613 } 614 } else if (SelectInst* U = dyn_cast<SelectInst>(V)) { 615 Expression e = create_expression(U); 616 617 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 618 if (EI != expressionNumbering.end()) { 619 valueNumbering.insert(std::make_pair(V, EI->second)); 620 return EI->second; 621 } else { 622 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 623 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 624 625 return nextValueNumber++; 626 } 627 } else if (CastInst* U = dyn_cast<CastInst>(V)) { 628 Expression e = create_expression(U); 629 630 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 631 if (EI != expressionNumbering.end()) { 632 valueNumbering.insert(std::make_pair(V, EI->second)); 633 return EI->second; 634 } else { 635 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 636 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 637 638 return nextValueNumber++; 639 } 640 } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) { 641 Expression e = create_expression(U); 642 643 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 644 if (EI != expressionNumbering.end()) { 645 valueNumbering.insert(std::make_pair(V, EI->second)); 646 return EI->second; 647 } else { 648 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 649 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 650 651 return nextValueNumber++; 652 } 653 } else { 654 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 655 return nextValueNumber++; 656 } 657} 658 659/// lookup - Returns the value number of the specified value. Fails if 660/// the value has not yet been numbered. 661uint32_t ValueTable::lookup(Value* V) const { 662 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); 663 assert(VI != valueNumbering.end() && "Value not numbered?"); 664 return VI->second; 665} 666 667/// clear - Remove all entries from the ValueTable 668void ValueTable::clear() { 669 valueNumbering.clear(); 670 expressionNumbering.clear(); 671 nextValueNumber = 1; 672} 673 674/// erase - Remove a value from the value numbering 675void ValueTable::erase(Value* V) { 676 valueNumbering.erase(V); 677} 678 679//===----------------------------------------------------------------------===// 680// GVN Pass 681//===----------------------------------------------------------------------===// 682 683namespace llvm { 684 template<> struct DenseMapInfo<uint32_t> { 685 static inline uint32_t getEmptyKey() { return ~0; } 686 static inline uint32_t getTombstoneKey() { return ~0 - 1; } 687 static unsigned getHashValue(const uint32_t& Val) { return Val * 37; } 688 static bool isPod() { return true; } 689 static bool isEqual(const uint32_t& LHS, const uint32_t& RHS) { 690 return LHS == RHS; 691 } 692 }; 693} 694 695namespace { 696 struct VISIBILITY_HIDDEN ValueNumberScope { 697 ValueNumberScope* parent; 698 DenseMap<uint32_t, Value*> table; 699 700 ValueNumberScope(ValueNumberScope* p) : parent(p) { } 701 }; 702} 703 704namespace { 705 706 class VISIBILITY_HIDDEN GVN : public FunctionPass { 707 bool runOnFunction(Function &F); 708 public: 709 static char ID; // Pass identification, replacement for typeid 710 GVN() : FunctionPass((intptr_t)&ID) { } 711 712 private: 713 ValueTable VN; 714 DenseMap<BasicBlock*, ValueNumberScope*> localAvail; 715 716 typedef DenseMap<Value*, SmallPtrSet<Instruction*, 4> > PhiMapType; 717 PhiMapType phiMap; 718 719 720 // This transformation requires dominator postdominator info 721 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 722 AU.setPreservesCFG(); 723 AU.addRequired<DominatorTree>(); 724 AU.addRequired<MemoryDependenceAnalysis>(); 725 AU.addRequired<AliasAnalysis>(); 726 AU.addPreserved<AliasAnalysis>(); 727 AU.addPreserved<MemoryDependenceAnalysis>(); 728 } 729 730 // Helper fuctions 731 // FIXME: eliminate or document these better 732 bool processLoad(LoadInst* L, 733 DenseMap<Value*, LoadInst*> &lastLoad, 734 SmallVectorImpl<Instruction*> &toErase); 735 bool processInstruction(Instruction* I, 736 DenseMap<Value*, LoadInst*>& lastSeenLoad, 737 SmallVectorImpl<Instruction*> &toErase); 738 bool processNonLocalLoad(LoadInst* L, 739 SmallVectorImpl<Instruction*> &toErase); 740 bool processBlock(DomTreeNode* DTN); 741 Value *GetValueForBlock(BasicBlock *BB, LoadInst* orig, 742 DenseMap<BasicBlock*, Value*> &Phis, 743 bool top_level = false); 744 void dump(DenseMap<uint32_t, Value*>& d); 745 bool iterateOnFunction(Function &F); 746 Value* CollapsePhi(PHINode* p); 747 bool isSafeReplacement(PHINode* p, Instruction* inst); 748 bool performPRE(Function& F); 749 Value* lookupNumber(BasicBlock* BB, uint32_t num); 750 }; 751 752 char GVN::ID = 0; 753} 754 755// createGVNPass - The public interface to this file... 756FunctionPass *llvm::createGVNPass() { return new GVN(); } 757 758static RegisterPass<GVN> X("gvn", 759 "Global Value Numbering"); 760 761void GVN::dump(DenseMap<uint32_t, Value*>& d) { 762 printf("{\n"); 763 for (DenseMap<uint32_t, Value*>::iterator I = d.begin(), 764 E = d.end(); I != E; ++I) { 765 printf("%d\n", I->first); 766 I->second->dump(); 767 } 768 printf("}\n"); 769} 770 771Value* GVN::CollapsePhi(PHINode* p) { 772 DominatorTree &DT = getAnalysis<DominatorTree>(); 773 Value* constVal = p->hasConstantValue(); 774 775 if (!constVal) return 0; 776 777 Instruction* inst = dyn_cast<Instruction>(constVal); 778 if (!inst) 779 return constVal; 780 781 if (DT.dominates(inst, p)) 782 if (isSafeReplacement(p, inst)) 783 return inst; 784 return 0; 785} 786 787bool GVN::isSafeReplacement(PHINode* p, Instruction* inst) { 788 if (!isa<PHINode>(inst)) 789 return true; 790 791 for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end(); 792 UI != E; ++UI) 793 if (PHINode* use_phi = dyn_cast<PHINode>(UI)) 794 if (use_phi->getParent() == inst->getParent()) 795 return false; 796 797 return true; 798} 799 800/// GetValueForBlock - Get the value to use within the specified basic block. 801/// available values are in Phis. 802Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig, 803 DenseMap<BasicBlock*, Value*> &Phis, 804 bool top_level) { 805 806 // If we have already computed this value, return the previously computed val. 807 DenseMap<BasicBlock*, Value*>::iterator V = Phis.find(BB); 808 if (V != Phis.end() && !top_level) return V->second; 809 810 BasicBlock* singlePred = BB->getSinglePredecessor(); 811 if (singlePred) { 812 Value *ret = GetValueForBlock(singlePred, orig, Phis); 813 Phis[BB] = ret; 814 return ret; 815 } 816 817 // Otherwise, the idom is the loop, so we need to insert a PHI node. Do so 818 // now, then get values to fill in the incoming values for the PHI. 819 PHINode *PN = PHINode::Create(orig->getType(), orig->getName()+".rle", 820 BB->begin()); 821 PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB))); 822 823 if (Phis.count(BB) == 0) 824 Phis.insert(std::make_pair(BB, PN)); 825 826 // Fill in the incoming values for the block. 827 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { 828 Value* val = GetValueForBlock(*PI, orig, Phis); 829 PN->addIncoming(val, *PI); 830 } 831 832 AliasAnalysis& AA = getAnalysis<AliasAnalysis>(); 833 AA.copyValue(orig, PN); 834 835 // Attempt to collapse PHI nodes that are trivially redundant 836 Value* v = CollapsePhi(PN); 837 if (!v) { 838 // Cache our phi construction results 839 phiMap[orig->getPointerOperand()].insert(PN); 840 return PN; 841 } 842 843 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 844 845 MD.removeInstruction(PN); 846 PN->replaceAllUsesWith(v); 847 848 for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(), 849 E = Phis.end(); I != E; ++I) 850 if (I->second == PN) 851 I->second = v; 852 853 PN->eraseFromParent(); 854 855 Phis[BB] = v; 856 return v; 857} 858 859/// processNonLocalLoad - Attempt to eliminate a load whose dependencies are 860/// non-local by performing PHI construction. 861bool GVN::processNonLocalLoad(LoadInst* L, 862 SmallVectorImpl<Instruction*> &toErase) { 863 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 864 865 // Find the non-local dependencies of the load 866 DenseMap<BasicBlock*, Value*> deps; 867 MD.getNonLocalDependency(L, deps); 868 869 DenseMap<BasicBlock*, Value*> repl; 870 871 // Filter out useless results (non-locals, etc) 872 for (DenseMap<BasicBlock*, Value*>::iterator I = deps.begin(), E = deps.end(); 873 I != E; ++I) { 874 if (I->second == MemoryDependenceAnalysis::None) 875 return false; 876 877 if (I->second == MemoryDependenceAnalysis::NonLocal) 878 continue; 879 880 if (StoreInst* S = dyn_cast<StoreInst>(I->second)) { 881 if (S->getPointerOperand() != L->getPointerOperand()) 882 return false; 883 repl[I->first] = S->getOperand(0); 884 } else if (LoadInst* LD = dyn_cast<LoadInst>(I->second)) { 885 if (LD->getPointerOperand() != L->getPointerOperand()) 886 return false; 887 repl[I->first] = LD; 888 } else { 889 return false; 890 } 891 } 892 893 // Use cached PHI construction information from previous runs 894 SmallPtrSet<Instruction*, 4>& p = phiMap[L->getPointerOperand()]; 895 for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end(); 896 I != E; ++I) { 897 if ((*I)->getParent() == L->getParent()) { 898 MD.removeInstruction(L); 899 L->replaceAllUsesWith(*I); 900 toErase.push_back(L); 901 NumGVNLoad++; 902 return true; 903 } 904 905 repl.insert(std::make_pair((*I)->getParent(), *I)); 906 } 907 908 // Perform PHI construction 909 SmallPtrSet<BasicBlock*, 4> visited; 910 Value* v = GetValueForBlock(L->getParent(), L, repl, true); 911 912 MD.removeInstruction(L); 913 L->replaceAllUsesWith(v); 914 toErase.push_back(L); 915 NumGVNLoad++; 916 917 return true; 918} 919 920/// processLoad - Attempt to eliminate a load, first by eliminating it 921/// locally, and then attempting non-local elimination if that fails. 922bool GVN::processLoad(LoadInst *L, DenseMap<Value*, LoadInst*> &lastLoad, 923 SmallVectorImpl<Instruction*> &toErase) { 924 if (L->isVolatile()) { 925 lastLoad[L->getPointerOperand()] = L; 926 return false; 927 } 928 929 Value* pointer = L->getPointerOperand(); 930 LoadInst*& last = lastLoad[pointer]; 931 932 // ... to a pointer that has been loaded from before... 933 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 934 bool removedNonLocal = false; 935 Instruction* dep = MD.getDependency(L); 936 if (dep == MemoryDependenceAnalysis::NonLocal && 937 L->getParent() != &L->getParent()->getParent()->getEntryBlock()) { 938 removedNonLocal = processNonLocalLoad(L, toErase); 939 940 if (!removedNonLocal) 941 last = L; 942 943 return removedNonLocal; 944 } 945 946 947 bool deletedLoad = false; 948 949 // Walk up the dependency chain until we either find 950 // a dependency we can use, or we can't walk any further 951 while (dep != MemoryDependenceAnalysis::None && 952 dep != MemoryDependenceAnalysis::NonLocal && 953 (isa<LoadInst>(dep) || isa<StoreInst>(dep))) { 954 // ... that depends on a store ... 955 if (StoreInst* S = dyn_cast<StoreInst>(dep)) { 956 if (S->getPointerOperand() == pointer) { 957 // Remove it! 958 MD.removeInstruction(L); 959 960 L->replaceAllUsesWith(S->getOperand(0)); 961 toErase.push_back(L); 962 deletedLoad = true; 963 NumGVNLoad++; 964 } 965 966 // Whether we removed it or not, we can't 967 // go any further 968 break; 969 } else if (!last) { 970 // If we don't depend on a store, and we haven't 971 // been loaded before, bail. 972 break; 973 } else if (dep == last) { 974 // Remove it! 975 MD.removeInstruction(L); 976 977 L->replaceAllUsesWith(last); 978 toErase.push_back(L); 979 deletedLoad = true; 980 NumGVNLoad++; 981 982 break; 983 } else { 984 dep = MD.getDependency(L, dep); 985 } 986 } 987 988 if (dep != MemoryDependenceAnalysis::None && 989 dep != MemoryDependenceAnalysis::NonLocal && 990 isa<AllocationInst>(dep)) { 991 // Check that this load is actually from the 992 // allocation we found 993 Value* v = L->getOperand(0); 994 while (true) { 995 if (BitCastInst *BC = dyn_cast<BitCastInst>(v)) 996 v = BC->getOperand(0); 997 else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(v)) 998 v = GEP->getOperand(0); 999 else 1000 break; 1001 } 1002 if (v == dep) { 1003 // If this load depends directly on an allocation, there isn't 1004 // anything stored there; therefore, we can optimize this load 1005 // to undef. 1006 MD.removeInstruction(L); 1007 1008 L->replaceAllUsesWith(UndefValue::get(L->getType())); 1009 toErase.push_back(L); 1010 deletedLoad = true; 1011 NumGVNLoad++; 1012 } 1013 } 1014 1015 if (!deletedLoad) 1016 last = L; 1017 1018 return deletedLoad; 1019} 1020 1021Value* GVN::lookupNumber(BasicBlock* BB, uint32_t num) { 1022 ValueNumberScope* locals = localAvail[BB]; 1023 1024 while (locals) { 1025 DenseMap<uint32_t, Value*>::iterator I = locals->table.find(num); 1026 if (I != locals->table.end()) 1027 return I->second; 1028 else 1029 locals = locals->parent; 1030 } 1031 1032 return 0; 1033} 1034 1035/// processInstruction - When calculating availability, handle an instruction 1036/// by inserting it into the appropriate sets 1037bool GVN::processInstruction(Instruction *I, 1038 DenseMap<Value*, LoadInst*> &lastSeenLoad, 1039 SmallVectorImpl<Instruction*> &toErase) { 1040 if (LoadInst* L = dyn_cast<LoadInst>(I)) { 1041 bool changed = processLoad(L, lastSeenLoad, toErase); 1042 1043 if (!changed) { 1044 unsigned num = VN.lookup_or_add(L); 1045 localAvail[I->getParent()]->table.insert(std::make_pair(num, L)); 1046 } 1047 1048 return changed; 1049 } 1050 1051 unsigned num = VN.lookup_or_add(I); 1052 1053 // Allocations are always uniquely numbered, so we can save time and memory 1054 // by fast failing them. 1055 if (isa<AllocationInst>(I)) { 1056 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1057 return false; 1058 } 1059 1060 // Collapse PHI nodes 1061 if (PHINode* p = dyn_cast<PHINode>(I)) { 1062 Value* constVal = CollapsePhi(p); 1063 1064 if (constVal) { 1065 for (PhiMapType::iterator PI = phiMap.begin(), PE = phiMap.end(); 1066 PI != PE; ++PI) 1067 if (PI->second.count(p)) 1068 PI->second.erase(p); 1069 1070 p->replaceAllUsesWith(constVal); 1071 toErase.push_back(p); 1072 } else { 1073 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1074 } 1075 // Perform value-number based elimination 1076 } else if (Value* repl = lookupNumber(I->getParent(), num)) { 1077 // Remove it! 1078 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 1079 MD.removeInstruction(I); 1080 1081 VN.erase(I); 1082 I->replaceAllUsesWith(repl); 1083 toErase.push_back(I); 1084 return true; 1085 } else if (!I->isTerminator()) { 1086 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1087 } 1088 1089 return false; 1090} 1091 1092// GVN::runOnFunction - This is the main transformation entry point for a 1093// function. 1094// 1095bool GVN::runOnFunction(Function& F) { 1096 VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>()); 1097 VN.setMemDep(&getAnalysis<MemoryDependenceAnalysis>()); 1098 VN.setDomTree(&getAnalysis<DominatorTree>()); 1099 1100 bool changed = false; 1101 bool shouldContinue = true; 1102 1103 while (shouldContinue) { 1104 shouldContinue = iterateOnFunction(F); 1105 changed |= shouldContinue; 1106 } 1107 1108 return changed; 1109} 1110 1111 1112bool GVN::processBlock(DomTreeNode* DTN) { 1113 BasicBlock* BB = DTN->getBlock(); 1114 1115 SmallVector<Instruction*, 8> toErase; 1116 DenseMap<Value*, LoadInst*> lastSeenLoad; 1117 bool changed_function = false; 1118 1119 if (DTN->getIDom()) 1120 localAvail[BB] = 1121 new ValueNumberScope(localAvail[DTN->getIDom()->getBlock()]); 1122 else 1123 localAvail[BB] = new ValueNumberScope(0); 1124 1125 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); 1126 BI != BE;) { 1127 changed_function |= processInstruction(BI, lastSeenLoad, toErase); 1128 if (toErase.empty()) { 1129 ++BI; 1130 continue; 1131 } 1132 1133 // If we need some instructions deleted, do it now. 1134 NumGVNInstr += toErase.size(); 1135 1136 // Avoid iterator invalidation. 1137 bool AtStart = BI == BB->begin(); 1138 if (!AtStart) 1139 --BI; 1140 1141 for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(), 1142 E = toErase.end(); I != E; ++I) 1143 (*I)->eraseFromParent(); 1144 1145 if (AtStart) 1146 BI = BB->begin(); 1147 else 1148 ++BI; 1149 1150 toErase.clear(); 1151 } 1152 1153 return changed_function; 1154} 1155 1156/// performPRE - Perform a purely local form of PRE that looks for diamond 1157/// control flow patterns and attempts to perform simple PRE at the join point. 1158bool GVN::performPRE(Function& F) { 1159 bool changed = false; 1160 SmallVector<std::pair<TerminatorInst*, unsigned>, 4> toSplit; 1161 for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()), 1162 DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) { 1163 BasicBlock* CurrentBlock = *DI; 1164 1165 // Nothing to PRE in the entry block. 1166 if (CurrentBlock == &F.getEntryBlock()) continue; 1167 1168 for (BasicBlock::iterator BI = CurrentBlock->begin(), 1169 BE = CurrentBlock->end(); BI != BE; ) { 1170 if (isa<AllocaInst>(BI) || isa<TerminatorInst>(BI) || 1171 isa<LoadInst>(BI) || isa<StoreInst>(BI) || 1172 isa<CallInst>(BI) || isa<PHINode>(BI)) { 1173 BI++; 1174 continue; 1175 } 1176 1177 uint32_t valno = VN.lookup(BI); 1178 1179 // Look for the predecessors for PRE opportunities. We're 1180 // only trying to solve the basic diamond case, where 1181 // a value is computed in the successor and one predecessor, 1182 // but not the other. We also explicitly disallow cases 1183 // where the successor is its own predecessor, because they're 1184 // more complicated to get right. 1185 unsigned numWith = 0; 1186 unsigned numWithout = 0; 1187 BasicBlock* PREPred = 0; 1188 DenseMap<BasicBlock*, Value*> predMap; 1189 for (pred_iterator PI = pred_begin(CurrentBlock), 1190 PE = pred_end(CurrentBlock); PI != PE; ++PI) { 1191 // We're not interested in PRE where the block is its 1192 // own predecessor, on in blocks with predecessors 1193 // that are not reachable. 1194 if (*PI == CurrentBlock) { 1195 numWithout = 2; 1196 break; 1197 } else if (!localAvail.count(*PI)) { 1198 numWithout = 2; 1199 break; 1200 } 1201 1202 DenseMap<uint32_t, Value*>::iterator predV = 1203 localAvail[*PI]->table.find(valno); 1204 if (predV == localAvail[*PI]->table.end()) { 1205 PREPred = *PI; 1206 numWithout++; 1207 } else if (predV->second == BI) { 1208 numWithout = 2; 1209 } else { 1210 predMap[*PI] = predV->second; 1211 numWith++; 1212 } 1213 } 1214 1215 // Don't do PRE when it might increase code size, i.e. when 1216 // we would need to insert instructions in more than one pred. 1217 if (numWithout != 1 || numWith == 0) { 1218 BI++; 1219 continue; 1220 } 1221 1222 // We can't do PRE safely on a critical edge, so instead we schedule 1223 // the edge to be split and perform the PRE the next time we iterate 1224 // on the function. 1225 unsigned succNum = 0; 1226 for (unsigned i = 0, e = PREPred->getTerminator()->getNumSuccessors(); 1227 i != e; ++i) 1228 if (PREPred->getTerminator()->getSuccessor(i) == PREPred) { 1229 succNum = i; 1230 break; 1231 } 1232 1233 if (isCriticalEdge(PREPred->getTerminator(), succNum)) { 1234 toSplit.push_back(std::make_pair(PREPred->getTerminator(), succNum)); 1235 changed = true; 1236 BI++; 1237 continue; 1238 } 1239 1240 // Instantiate the expression the in predecessor that lacked it. 1241 // Because we are going top-down through the block, all value numbers 1242 // will be available in the predecessor by the time we need them. Any 1243 // that weren't original present will have been instantiated earlier 1244 // in this loop. 1245 Instruction* PREInstr = BI->clone(); 1246 bool success = true; 1247 for (unsigned i = 0; i < BI->getNumOperands(); ++i) { 1248 Value* op = BI->getOperand(i); 1249 if (isa<Argument>(op) || isa<Constant>(op) || isa<GlobalValue>(op)) 1250 PREInstr->setOperand(i, op); 1251 else if (!lookupNumber(PREPred, VN.lookup(op))) { 1252 success = false; 1253 break; 1254 } else 1255 PREInstr->setOperand(i, lookupNumber(PREPred, VN.lookup(op))); 1256 } 1257 1258 // Fail out if we encounter an operand that is not available in 1259 // the PRE predecessor. This is typically because of loads which 1260 // are not value numbered precisely. 1261 if (!success) { 1262 delete PREInstr; 1263 BI++; 1264 continue; 1265 } 1266 1267 PREInstr->insertBefore(PREPred->getTerminator()); 1268 PREInstr->setName(BI->getName() + ".pre"); 1269 predMap[PREPred] = PREInstr; 1270 VN.add(PREInstr, valno); 1271 NumGVNPRE++; 1272 1273 // Update the availability map to include the new instruction. 1274 localAvail[PREPred]->table.insert(std::make_pair(valno, PREInstr)); 1275 1276 // Create a PHI to make the value available in this block. 1277 PHINode* Phi = PHINode::Create(BI->getType(), 1278 BI->getName() + ".pre-phi", 1279 CurrentBlock->begin()); 1280 for (pred_iterator PI = pred_begin(CurrentBlock), 1281 PE = pred_end(CurrentBlock); PI != PE; ++PI) 1282 Phi->addIncoming(predMap[*PI], *PI); 1283 1284 VN.add(Phi, valno); 1285 1286 // The newly created PHI completely replaces the old instruction, 1287 // so we need to update the maps to reflect this. 1288 DomTreeNode* DTN = getAnalysis<DominatorTree>()[CurrentBlock]; 1289 for (DomTreeNode::iterator UI = DTN->begin(), UE = DTN->end(); 1290 UI != UE; ++UI) 1291 localAvail[(*UI)->getBlock()]->table[valno] = Phi; 1292 localAvail[CurrentBlock]->table[valno] = Phi; 1293 1294 BI->replaceAllUsesWith(Phi); 1295 VN.erase(BI); 1296 1297 Instruction* erase = BI; 1298 BI++; 1299 erase->eraseFromParent(); 1300 1301 changed = true; 1302 } 1303 } 1304 1305 for (SmallVector<std::pair<TerminatorInst*, unsigned>, 4>::iterator 1306 I = toSplit.begin(), E = toSplit.end(); I != E; ++I) 1307 SplitCriticalEdge(I->first, I->second, this); 1308 1309 return changed; 1310} 1311 1312// GVN::iterateOnFunction - Executes one iteration of GVN 1313bool GVN::iterateOnFunction(Function &F) { 1314 // Clean out global sets from any previous functions 1315 VN.clear(); 1316 phiMap.clear(); 1317 1318 for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator 1319 I = localAvail.begin(), E = localAvail.end(); I != E; ++I) 1320 delete I->second; 1321 localAvail.clear(); 1322 1323 DominatorTree &DT = getAnalysis<DominatorTree>(); 1324 1325 // Top-down walk of the dominator tree 1326 bool changed = false; 1327 for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()), 1328 DE = df_end(DT.getRootNode()); DI != DE; ++DI) 1329 changed |= processBlock(*DI); 1330 1331 if (EnablePRE) 1332 changed |= performPRE(F); 1333 1334 return changed; 1335} 1336