GVN.cpp revision 4c724006256032e827177afeae04ea62436796e7
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" 39#include <cstdio> 40using namespace llvm; 41 42STATISTIC(NumGVNInstr, "Number of instructions deleted"); 43STATISTIC(NumGVNLoad, "Number of loads deleted"); 44STATISTIC(NumGVNPRE, "Number of instructions PRE'd"); 45STATISTIC(NumGVNBlocks, "Number of blocks merged"); 46 47static cl::opt<bool> EnablePRE("enable-pre", 48 cl::init(true), cl::Hidden); 49 50//===----------------------------------------------------------------------===// 51// ValueTable Class 52//===----------------------------------------------------------------------===// 53 54/// This class holds the mapping between values and value numbers. It is used 55/// as an efficient mechanism to determine the expression-wise equivalence of 56/// two values. 57namespace { 58 struct VISIBILITY_HIDDEN Expression { 59 enum ExpressionOpcode { ADD, SUB, MUL, UDIV, SDIV, FDIV, UREM, SREM, 60 FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ, 61 ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE, 62 ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ, 63 FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE, 64 FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE, 65 FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT, 66 SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI, 67 FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT, 68 PTRTOINT, INTTOPTR, BITCAST, GEP, CALL, CONSTANT, 69 EMPTY, TOMBSTONE }; 70 71 ExpressionOpcode opcode; 72 const Type* type; 73 uint32_t firstVN; 74 uint32_t secondVN; 75 uint32_t thirdVN; 76 SmallVector<uint32_t, 4> varargs; 77 Value* function; 78 79 Expression() { } 80 Expression(ExpressionOpcode o) : opcode(o) { } 81 82 bool operator==(const Expression &other) const { 83 if (opcode != other.opcode) 84 return false; 85 else if (opcode == EMPTY || opcode == TOMBSTONE) 86 return true; 87 else if (type != other.type) 88 return false; 89 else if (function != other.function) 90 return false; 91 else if (firstVN != other.firstVN) 92 return false; 93 else if (secondVN != other.secondVN) 94 return false; 95 else if (thirdVN != other.thirdVN) 96 return false; 97 else { 98 if (varargs.size() != other.varargs.size()) 99 return false; 100 101 for (size_t i = 0; i < varargs.size(); ++i) 102 if (varargs[i] != other.varargs[i]) 103 return false; 104 105 return true; 106 } 107 } 108 109 bool operator!=(const Expression &other) const { 110 if (opcode != other.opcode) 111 return true; 112 else if (opcode == EMPTY || opcode == TOMBSTONE) 113 return false; 114 else if (type != other.type) 115 return true; 116 else if (function != other.function) 117 return true; 118 else if (firstVN != other.firstVN) 119 return true; 120 else if (secondVN != other.secondVN) 121 return true; 122 else if (thirdVN != other.thirdVN) 123 return true; 124 else { 125 if (varargs.size() != other.varargs.size()) 126 return true; 127 128 for (size_t i = 0; i < varargs.size(); ++i) 129 if (varargs[i] != other.varargs[i]) 130 return true; 131 132 return false; 133 } 134 } 135 }; 136 137 class VISIBILITY_HIDDEN ValueTable { 138 private: 139 DenseMap<Value*, uint32_t> valueNumbering; 140 DenseMap<Expression, uint32_t> expressionNumbering; 141 AliasAnalysis* AA; 142 MemoryDependenceAnalysis* MD; 143 DominatorTree* DT; 144 145 uint32_t nextValueNumber; 146 147 Expression::ExpressionOpcode getOpcode(BinaryOperator* BO); 148 Expression::ExpressionOpcode getOpcode(CmpInst* C); 149 Expression::ExpressionOpcode getOpcode(CastInst* C); 150 Expression create_expression(BinaryOperator* BO); 151 Expression create_expression(CmpInst* C); 152 Expression create_expression(ShuffleVectorInst* V); 153 Expression create_expression(ExtractElementInst* C); 154 Expression create_expression(InsertElementInst* V); 155 Expression create_expression(SelectInst* V); 156 Expression create_expression(CastInst* C); 157 Expression create_expression(GetElementPtrInst* G); 158 Expression create_expression(CallInst* C); 159 Expression create_expression(Constant* C); 160 public: 161 ValueTable() : nextValueNumber(1) { } 162 uint32_t lookup_or_add(Value* V); 163 uint32_t lookup(Value* V) const; 164 void add(Value* V, uint32_t num); 165 void clear(); 166 void erase(Value* v); 167 unsigned size(); 168 void setAliasAnalysis(AliasAnalysis* A) { AA = A; } 169 void setMemDep(MemoryDependenceAnalysis* M) { MD = M; } 170 void setDomTree(DominatorTree* D) { DT = D; } 171 uint32_t getNextUnusedValueNumber() { return nextValueNumber; } 172 }; 173} 174 175namespace llvm { 176template <> struct DenseMapInfo<Expression> { 177 static inline Expression getEmptyKey() { 178 return Expression(Expression::EMPTY); 179 } 180 181 static inline Expression getTombstoneKey() { 182 return Expression(Expression::TOMBSTONE); 183 } 184 185 static unsigned getHashValue(const Expression e) { 186 unsigned hash = e.opcode; 187 188 hash = e.firstVN + hash * 37; 189 hash = e.secondVN + hash * 37; 190 hash = e.thirdVN + hash * 37; 191 192 hash = ((unsigned)((uintptr_t)e.type >> 4) ^ 193 (unsigned)((uintptr_t)e.type >> 9)) + 194 hash * 37; 195 196 for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(), 197 E = e.varargs.end(); I != E; ++I) 198 hash = *I + hash * 37; 199 200 hash = ((unsigned)((uintptr_t)e.function >> 4) ^ 201 (unsigned)((uintptr_t)e.function >> 9)) + 202 hash * 37; 203 204 return hash; 205 } 206 static bool isEqual(const Expression &LHS, const Expression &RHS) { 207 return LHS == RHS; 208 } 209 static bool isPod() { return true; } 210}; 211} 212 213//===----------------------------------------------------------------------===// 214// ValueTable Internal Functions 215//===----------------------------------------------------------------------===// 216Expression::ExpressionOpcode ValueTable::getOpcode(BinaryOperator* BO) { 217 switch(BO->getOpcode()) { 218 default: // THIS SHOULD NEVER HAPPEN 219 assert(0 && "Binary operator with unknown opcode?"); 220 case Instruction::Add: return Expression::ADD; 221 case Instruction::Sub: return Expression::SUB; 222 case Instruction::Mul: return Expression::MUL; 223 case Instruction::UDiv: return Expression::UDIV; 224 case Instruction::SDiv: return Expression::SDIV; 225 case Instruction::FDiv: return Expression::FDIV; 226 case Instruction::URem: return Expression::UREM; 227 case Instruction::SRem: return Expression::SREM; 228 case Instruction::FRem: return Expression::FREM; 229 case Instruction::Shl: return Expression::SHL; 230 case Instruction::LShr: return Expression::LSHR; 231 case Instruction::AShr: return Expression::ASHR; 232 case Instruction::And: return Expression::AND; 233 case Instruction::Or: return Expression::OR; 234 case Instruction::Xor: return Expression::XOR; 235 } 236} 237 238Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) { 239 if (isa<ICmpInst>(C) || isa<VICmpInst>(C)) { 240 switch (C->getPredicate()) { 241 default: // THIS SHOULD NEVER HAPPEN 242 assert(0 && "Comparison with unknown predicate?"); 243 case ICmpInst::ICMP_EQ: return Expression::ICMPEQ; 244 case ICmpInst::ICMP_NE: return Expression::ICMPNE; 245 case ICmpInst::ICMP_UGT: return Expression::ICMPUGT; 246 case ICmpInst::ICMP_UGE: return Expression::ICMPUGE; 247 case ICmpInst::ICMP_ULT: return Expression::ICMPULT; 248 case ICmpInst::ICMP_ULE: return Expression::ICMPULE; 249 case ICmpInst::ICMP_SGT: return Expression::ICMPSGT; 250 case ICmpInst::ICMP_SGE: return Expression::ICMPSGE; 251 case ICmpInst::ICMP_SLT: return Expression::ICMPSLT; 252 case ICmpInst::ICMP_SLE: return Expression::ICMPSLE; 253 } 254 } 255 assert((isa<FCmpInst>(C) || isa<VFCmpInst>(C)) && "Unknown compare"); 256 switch (C->getPredicate()) { 257 default: // THIS SHOULD NEVER HAPPEN 258 assert(0 && "Comparison with unknown predicate?"); 259 case FCmpInst::FCMP_OEQ: return Expression::FCMPOEQ; 260 case FCmpInst::FCMP_OGT: return Expression::FCMPOGT; 261 case FCmpInst::FCMP_OGE: return Expression::FCMPOGE; 262 case FCmpInst::FCMP_OLT: return Expression::FCMPOLT; 263 case FCmpInst::FCMP_OLE: return Expression::FCMPOLE; 264 case FCmpInst::FCMP_ONE: return Expression::FCMPONE; 265 case FCmpInst::FCMP_ORD: return Expression::FCMPORD; 266 case FCmpInst::FCMP_UNO: return Expression::FCMPUNO; 267 case FCmpInst::FCMP_UEQ: return Expression::FCMPUEQ; 268 case FCmpInst::FCMP_UGT: return Expression::FCMPUGT; 269 case FCmpInst::FCMP_UGE: return Expression::FCMPUGE; 270 case FCmpInst::FCMP_ULT: return Expression::FCMPULT; 271 case FCmpInst::FCMP_ULE: return Expression::FCMPULE; 272 case FCmpInst::FCMP_UNE: return Expression::FCMPUNE; 273 } 274} 275 276Expression::ExpressionOpcode ValueTable::getOpcode(CastInst* C) { 277 switch(C->getOpcode()) { 278 default: // THIS SHOULD NEVER HAPPEN 279 assert(0 && "Cast operator with unknown opcode?"); 280 case Instruction::Trunc: return Expression::TRUNC; 281 case Instruction::ZExt: return Expression::ZEXT; 282 case Instruction::SExt: return Expression::SEXT; 283 case Instruction::FPToUI: return Expression::FPTOUI; 284 case Instruction::FPToSI: return Expression::FPTOSI; 285 case Instruction::UIToFP: return Expression::UITOFP; 286 case Instruction::SIToFP: return Expression::SITOFP; 287 case Instruction::FPTrunc: return Expression::FPTRUNC; 288 case Instruction::FPExt: return Expression::FPEXT; 289 case Instruction::PtrToInt: return Expression::PTRTOINT; 290 case Instruction::IntToPtr: return Expression::INTTOPTR; 291 case Instruction::BitCast: return Expression::BITCAST; 292 } 293} 294 295Expression ValueTable::create_expression(CallInst* C) { 296 Expression e; 297 298 e.type = C->getType(); 299 e.firstVN = 0; 300 e.secondVN = 0; 301 e.thirdVN = 0; 302 e.function = C->getCalledFunction(); 303 e.opcode = Expression::CALL; 304 305 for (CallInst::op_iterator I = C->op_begin()+1, E = C->op_end(); 306 I != E; ++I) 307 e.varargs.push_back(lookup_or_add(*I)); 308 309 return e; 310} 311 312Expression ValueTable::create_expression(BinaryOperator* BO) { 313 Expression e; 314 315 e.firstVN = lookup_or_add(BO->getOperand(0)); 316 e.secondVN = lookup_or_add(BO->getOperand(1)); 317 e.thirdVN = 0; 318 e.function = 0; 319 e.type = BO->getType(); 320 e.opcode = getOpcode(BO); 321 322 return e; 323} 324 325Expression ValueTable::create_expression(CmpInst* C) { 326 Expression e; 327 328 e.firstVN = lookup_or_add(C->getOperand(0)); 329 e.secondVN = lookup_or_add(C->getOperand(1)); 330 e.thirdVN = 0; 331 e.function = 0; 332 e.type = C->getType(); 333 e.opcode = getOpcode(C); 334 335 return e; 336} 337 338Expression ValueTable::create_expression(CastInst* C) { 339 Expression e; 340 341 e.firstVN = lookup_or_add(C->getOperand(0)); 342 e.secondVN = 0; 343 e.thirdVN = 0; 344 e.function = 0; 345 e.type = C->getType(); 346 e.opcode = getOpcode(C); 347 348 return e; 349} 350 351Expression ValueTable::create_expression(ShuffleVectorInst* S) { 352 Expression e; 353 354 e.firstVN = lookup_or_add(S->getOperand(0)); 355 e.secondVN = lookup_or_add(S->getOperand(1)); 356 e.thirdVN = lookup_or_add(S->getOperand(2)); 357 e.function = 0; 358 e.type = S->getType(); 359 e.opcode = Expression::SHUFFLE; 360 361 return e; 362} 363 364Expression ValueTable::create_expression(ExtractElementInst* E) { 365 Expression e; 366 367 e.firstVN = lookup_or_add(E->getOperand(0)); 368 e.secondVN = lookup_or_add(E->getOperand(1)); 369 e.thirdVN = 0; 370 e.function = 0; 371 e.type = E->getType(); 372 e.opcode = Expression::EXTRACT; 373 374 return e; 375} 376 377Expression ValueTable::create_expression(InsertElementInst* I) { 378 Expression e; 379 380 e.firstVN = lookup_or_add(I->getOperand(0)); 381 e.secondVN = lookup_or_add(I->getOperand(1)); 382 e.thirdVN = lookup_or_add(I->getOperand(2)); 383 e.function = 0; 384 e.type = I->getType(); 385 e.opcode = Expression::INSERT; 386 387 return e; 388} 389 390Expression ValueTable::create_expression(SelectInst* I) { 391 Expression e; 392 393 e.firstVN = lookup_or_add(I->getCondition()); 394 e.secondVN = lookup_or_add(I->getTrueValue()); 395 e.thirdVN = lookup_or_add(I->getFalseValue()); 396 e.function = 0; 397 e.type = I->getType(); 398 e.opcode = Expression::SELECT; 399 400 return e; 401} 402 403Expression ValueTable::create_expression(GetElementPtrInst* G) { 404 Expression e; 405 406 e.firstVN = lookup_or_add(G->getPointerOperand()); 407 e.secondVN = 0; 408 e.thirdVN = 0; 409 e.function = 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/// add - Insert a value into the table with a specified value number. 425void ValueTable::add(Value* V, uint32_t num) { 426 valueNumbering.insert(std::make_pair(V, num)); 427} 428 429/// lookup_or_add - Returns the value number for the specified value, assigning 430/// it a new number if it did not have one before. 431uint32_t ValueTable::lookup_or_add(Value* V) { 432 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); 433 if (VI != valueNumbering.end()) 434 return VI->second; 435 436 if (CallInst* C = dyn_cast<CallInst>(V)) { 437 if (AA->doesNotAccessMemory(C)) { 438 Expression e = create_expression(C); 439 440 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 441 if (EI != expressionNumbering.end()) { 442 valueNumbering.insert(std::make_pair(V, EI->second)); 443 return EI->second; 444 } else { 445 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 446 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 447 448 return nextValueNumber++; 449 } 450 } else if (AA->onlyReadsMemory(C)) { 451 Expression e = create_expression(C); 452 453 if (expressionNumbering.find(e) == expressionNumbering.end()) { 454 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 455 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 456 return nextValueNumber++; 457 } 458 459 MemDepResult local_dep = MD->getDependency(C); 460 461 if (local_dep.isNone()) { 462 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 463 return nextValueNumber++; 464 } else if (Instruction *LocalDepInst = local_dep.getInst()) { 465 // FIXME: INDENT PROPERLY! 466 if (!isa<CallInst>(LocalDepInst)) { 467 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 468 return nextValueNumber++; 469 } 470 471 CallInst* local_cdep = cast<CallInst>(LocalDepInst); 472 473 // FIXME: INDENT PROPERLY. 474 if (local_cdep->getCalledFunction() != C->getCalledFunction() || 475 local_cdep->getNumOperands() != C->getNumOperands()) { 476 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 477 return nextValueNumber++; 478 } else if (!C->getCalledFunction()) { 479 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 480 return nextValueNumber++; 481 } else { 482 for (unsigned i = 1; i < C->getNumOperands(); ++i) { 483 uint32_t c_vn = lookup_or_add(C->getOperand(i)); 484 uint32_t cd_vn = lookup_or_add(local_cdep->getOperand(i)); 485 if (c_vn != cd_vn) { 486 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 487 return nextValueNumber++; 488 } 489 } 490 491 uint32_t v = lookup_or_add(local_cdep); 492 valueNumbering.insert(std::make_pair(V, v)); 493 return v; 494 } 495 } 496 497 498 DenseMap<BasicBlock*, MemDepResult> deps; 499 MD->getNonLocalDependency(C, deps); 500 CallInst* cdep = 0; 501 502 for (DenseMap<BasicBlock*, MemDepResult> 503 ::iterator I = deps.begin(), E = deps.end(); I != E; ++I) { 504 if (I->second.isNone()) { 505 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 506 507 return nextValueNumber++; 508 } else if (Instruction *NonLocalDepInst = I->second.getInst()) { 509 // FIXME: INDENT PROPERLY 510 // FIXME: All duplicated with non-local case. 511 if (DT->properlyDominates(I->first, C->getParent())) { 512 if (CallInst* CD = dyn_cast<CallInst>(NonLocalDepInst)) 513 cdep = CD; 514 else { 515 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 516 return nextValueNumber++; 517 } 518 } else { 519 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 520 return nextValueNumber++; 521 } 522 } 523 } 524 525 if (!cdep) { 526 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 527 return nextValueNumber++; 528 } 529 530 if (cdep->getCalledFunction() != C->getCalledFunction() || 531 cdep->getNumOperands() != C->getNumOperands()) { 532 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 533 return nextValueNumber++; 534 } else if (!C->getCalledFunction()) { 535 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 536 return nextValueNumber++; 537 } else { 538 for (unsigned i = 1; i < C->getNumOperands(); ++i) { 539 uint32_t c_vn = lookup_or_add(C->getOperand(i)); 540 uint32_t cd_vn = lookup_or_add(cdep->getOperand(i)); 541 if (c_vn != cd_vn) { 542 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 543 return nextValueNumber++; 544 } 545 } 546 547 uint32_t v = lookup_or_add(cdep); 548 valueNumbering.insert(std::make_pair(V, v)); 549 return v; 550 } 551 552 } else { 553 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 554 return nextValueNumber++; 555 } 556 } else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) { 557 Expression e = create_expression(BO); 558 559 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 560 if (EI != expressionNumbering.end()) { 561 valueNumbering.insert(std::make_pair(V, EI->second)); 562 return EI->second; 563 } else { 564 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 565 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 566 567 return nextValueNumber++; 568 } 569 } else if (CmpInst* C = dyn_cast<CmpInst>(V)) { 570 Expression e = create_expression(C); 571 572 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 573 if (EI != expressionNumbering.end()) { 574 valueNumbering.insert(std::make_pair(V, EI->second)); 575 return EI->second; 576 } else { 577 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 578 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 579 580 return nextValueNumber++; 581 } 582 } else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) { 583 Expression e = create_expression(U); 584 585 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 586 if (EI != expressionNumbering.end()) { 587 valueNumbering.insert(std::make_pair(V, EI->second)); 588 return EI->second; 589 } else { 590 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 591 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 592 593 return nextValueNumber++; 594 } 595 } else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) { 596 Expression e = create_expression(U); 597 598 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 599 if (EI != expressionNumbering.end()) { 600 valueNumbering.insert(std::make_pair(V, EI->second)); 601 return EI->second; 602 } else { 603 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 604 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 605 606 return nextValueNumber++; 607 } 608 } else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) { 609 Expression e = create_expression(U); 610 611 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 612 if (EI != expressionNumbering.end()) { 613 valueNumbering.insert(std::make_pair(V, EI->second)); 614 return EI->second; 615 } else { 616 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 617 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 618 619 return nextValueNumber++; 620 } 621 } else if (SelectInst* U = dyn_cast<SelectInst>(V)) { 622 Expression e = create_expression(U); 623 624 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 625 if (EI != expressionNumbering.end()) { 626 valueNumbering.insert(std::make_pair(V, EI->second)); 627 return EI->second; 628 } else { 629 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 630 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 631 632 return nextValueNumber++; 633 } 634 } else if (CastInst* U = dyn_cast<CastInst>(V)) { 635 Expression e = create_expression(U); 636 637 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 638 if (EI != expressionNumbering.end()) { 639 valueNumbering.insert(std::make_pair(V, EI->second)); 640 return EI->second; 641 } else { 642 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 643 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 644 645 return nextValueNumber++; 646 } 647 } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) { 648 Expression e = create_expression(U); 649 650 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 651 if (EI != expressionNumbering.end()) { 652 valueNumbering.insert(std::make_pair(V, EI->second)); 653 return EI->second; 654 } else { 655 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 656 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 657 658 return nextValueNumber++; 659 } 660 } else { 661 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 662 return nextValueNumber++; 663 } 664} 665 666/// lookup - Returns the value number of the specified value. Fails if 667/// the value has not yet been numbered. 668uint32_t ValueTable::lookup(Value* V) const { 669 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); 670 assert(VI != valueNumbering.end() && "Value not numbered?"); 671 return VI->second; 672} 673 674/// clear - Remove all entries from the ValueTable 675void ValueTable::clear() { 676 valueNumbering.clear(); 677 expressionNumbering.clear(); 678 nextValueNumber = 1; 679} 680 681/// erase - Remove a value from the value numbering 682void ValueTable::erase(Value* V) { 683 valueNumbering.erase(V); 684} 685 686//===----------------------------------------------------------------------===// 687// GVN Pass 688//===----------------------------------------------------------------------===// 689 690namespace { 691 struct VISIBILITY_HIDDEN ValueNumberScope { 692 ValueNumberScope* parent; 693 DenseMap<uint32_t, Value*> table; 694 695 ValueNumberScope(ValueNumberScope* p) : parent(p) { } 696 }; 697} 698 699namespace { 700 701 class VISIBILITY_HIDDEN GVN : public FunctionPass { 702 bool runOnFunction(Function &F); 703 public: 704 static char ID; // Pass identification, replacement for typeid 705 GVN() : FunctionPass(&ID) { } 706 707 private: 708 ValueTable VN; 709 DenseMap<BasicBlock*, ValueNumberScope*> localAvail; 710 711 typedef DenseMap<Value*, SmallPtrSet<Instruction*, 4> > PhiMapType; 712 PhiMapType phiMap; 713 714 715 // This transformation requires dominator postdominator info 716 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 717 AU.addRequired<DominatorTree>(); 718 AU.addRequired<MemoryDependenceAnalysis>(); 719 AU.addRequired<AliasAnalysis>(); 720 721 AU.addPreserved<DominatorTree>(); 722 AU.addPreserved<AliasAnalysis>(); 723 } 724 725 // Helper fuctions 726 // FIXME: eliminate or document these better 727 bool processLoad(LoadInst* L, 728 DenseMap<Value*, LoadInst*> &lastLoad, 729 SmallVectorImpl<Instruction*> &toErase); 730 bool processInstruction(Instruction* I, 731 DenseMap<Value*, LoadInst*>& lastSeenLoad, 732 SmallVectorImpl<Instruction*> &toErase); 733 bool processNonLocalLoad(LoadInst* L, 734 SmallVectorImpl<Instruction*> &toErase); 735 bool processBlock(DomTreeNode* DTN); 736 Value *GetValueForBlock(BasicBlock *BB, LoadInst* orig, 737 DenseMap<BasicBlock*, Value*> &Phis, 738 bool top_level = false); 739 void dump(DenseMap<uint32_t, Value*>& d); 740 bool iterateOnFunction(Function &F); 741 Value* CollapsePhi(PHINode* p); 742 bool isSafeReplacement(PHINode* p, Instruction* inst); 743 bool performPRE(Function& F); 744 Value* lookupNumber(BasicBlock* BB, uint32_t num); 745 bool mergeBlockIntoPredecessor(BasicBlock* BB); 746 void cleanupGlobalSets(); 747 }; 748 749 char GVN::ID = 0; 750} 751 752// createGVNPass - The public interface to this file... 753FunctionPass *llvm::createGVNPass() { return new GVN(); } 754 755static RegisterPass<GVN> X("gvn", 756 "Global Value Numbering"); 757 758void GVN::dump(DenseMap<uint32_t, Value*>& d) { 759 printf("{\n"); 760 for (DenseMap<uint32_t, Value*>::iterator I = d.begin(), 761 E = d.end(); I != E; ++I) { 762 printf("%d\n", I->first); 763 I->second->dump(); 764 } 765 printf("}\n"); 766} 767 768Value* GVN::CollapsePhi(PHINode* p) { 769 DominatorTree &DT = getAnalysis<DominatorTree>(); 770 Value* constVal = p->hasConstantValue(); 771 772 if (!constVal) return 0; 773 774 Instruction* inst = dyn_cast<Instruction>(constVal); 775 if (!inst) 776 return constVal; 777 778 if (DT.dominates(inst, p)) 779 if (isSafeReplacement(p, inst)) 780 return inst; 781 return 0; 782} 783 784bool GVN::isSafeReplacement(PHINode* p, Instruction* inst) { 785 if (!isa<PHINode>(inst)) 786 return true; 787 788 for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end(); 789 UI != E; ++UI) 790 if (PHINode* use_phi = dyn_cast<PHINode>(UI)) 791 if (use_phi->getParent() == inst->getParent()) 792 return false; 793 794 return true; 795} 796 797/// GetValueForBlock - Get the value to use within the specified basic block. 798/// available values are in Phis. 799Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig, 800 DenseMap<BasicBlock*, Value*> &Phis, 801 bool top_level) { 802 803 // If we have already computed this value, return the previously computed val. 804 DenseMap<BasicBlock*, Value*>::iterator V = Phis.find(BB); 805 if (V != Phis.end() && !top_level) return V->second; 806 807 // If the block is unreachable, just return undef, since this path 808 // can't actually occur at runtime. 809 if (!getAnalysis<DominatorTree>().isReachableFromEntry(BB)) 810 return Phis[BB] = UndefValue::get(orig->getType()); 811 812 BasicBlock* singlePred = BB->getSinglePredecessor(); 813 if (singlePred) { 814 Value *ret = GetValueForBlock(singlePred, orig, Phis); 815 Phis[BB] = ret; 816 return ret; 817 } 818 819 // Otherwise, the idom is the loop, so we need to insert a PHI node. Do so 820 // now, then get values to fill in the incoming values for the PHI. 821 PHINode *PN = PHINode::Create(orig->getType(), orig->getName()+".rle", 822 BB->begin()); 823 PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB))); 824 825 if (Phis.count(BB) == 0) 826 Phis.insert(std::make_pair(BB, PN)); 827 828 // Fill in the incoming values for the block. 829 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { 830 Value* val = GetValueForBlock(*PI, orig, Phis); 831 PN->addIncoming(val, *PI); 832 } 833 834 AliasAnalysis& AA = getAnalysis<AliasAnalysis>(); 835 AA.copyValue(orig, PN); 836 837 // Attempt to collapse PHI nodes that are trivially redundant 838 Value* v = CollapsePhi(PN); 839 if (!v) { 840 // Cache our phi construction results 841 phiMap[orig->getPointerOperand()].insert(PN); 842 return PN; 843 } 844 845 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 846 847 MD.removeInstruction(PN); 848 PN->replaceAllUsesWith(v); 849 850 for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(), 851 E = Phis.end(); I != E; ++I) 852 if (I->second == PN) 853 I->second = v; 854 855 PN->eraseFromParent(); 856 857 Phis[BB] = v; 858 return v; 859} 860 861/// processNonLocalLoad - Attempt to eliminate a load whose dependencies are 862/// non-local by performing PHI construction. 863bool GVN::processNonLocalLoad(LoadInst* L, 864 SmallVectorImpl<Instruction*> &toErase) { 865 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 866 867 // Find the non-local dependencies of the load 868 DenseMap<BasicBlock*, MemDepResult> deps; 869 MD.getNonLocalDependency(L, deps); 870 871 // If we had to process more than one hundred blocks to find the 872 // dependencies, this load isn't worth worrying about. Optimizing 873 // it will be too expensive. 874 if (deps.size() > 100) 875 return false; 876 877 DenseMap<BasicBlock*, Value*> repl; 878 879 // Filter out useless results (non-locals, etc) 880 for (DenseMap<BasicBlock*, MemDepResult>::iterator I = deps.begin(), 881 E = deps.end(); I != E; ++I) { 882 if (I->second.isNone()) 883 return false; 884 885 if (I->second.isNonLocal()) 886 continue; 887 888 if (StoreInst* S = dyn_cast<StoreInst>(I->second.getInst())) { 889 if (S->getPointerOperand() != L->getPointerOperand()) 890 return false; 891 repl[I->first] = S->getOperand(0); 892 } else if (LoadInst* LD = dyn_cast<LoadInst>(I->second.getInst())) { 893 if (LD->getPointerOperand() != L->getPointerOperand()) 894 return false; 895 repl[I->first] = LD; 896 } else { 897 return false; 898 } 899 } 900 901 // Use cached PHI construction information from previous runs 902 SmallPtrSet<Instruction*, 4>& p = phiMap[L->getPointerOperand()]; 903 for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end(); 904 I != E; ++I) { 905 if ((*I)->getParent() == L->getParent()) { 906 MD.removeInstruction(L); 907 L->replaceAllUsesWith(*I); 908 toErase.push_back(L); 909 NumGVNLoad++; 910 return true; 911 } 912 913 repl.insert(std::make_pair((*I)->getParent(), *I)); 914 } 915 916 // Perform PHI construction 917 SmallPtrSet<BasicBlock*, 4> visited; 918 Value* v = GetValueForBlock(L->getParent(), L, repl, true); 919 920 MD.removeInstruction(L); 921 L->replaceAllUsesWith(v); 922 toErase.push_back(L); 923 NumGVNLoad++; 924 925 return true; 926} 927 928/// processLoad - Attempt to eliminate a load, first by eliminating it 929/// locally, and then attempting non-local elimination if that fails. 930bool GVN::processLoad(LoadInst *L, DenseMap<Value*, LoadInst*> &lastLoad, 931 SmallVectorImpl<Instruction*> &toErase) { 932 if (L->isVolatile()) { 933 lastLoad[L->getPointerOperand()] = L; 934 return false; 935 } 936 937 Value* pointer = L->getPointerOperand(); 938 LoadInst*& last = lastLoad[pointer]; 939 940 // ... to a pointer that has been loaded from before... 941 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 942 bool removedNonLocal = false; 943 MemDepResult dep = MD.getDependency(L); 944 if (dep.isNonLocal() && 945 L->getParent() != &L->getParent()->getParent()->getEntryBlock()) { 946 removedNonLocal = processNonLocalLoad(L, toErase); 947 948 if (!removedNonLocal) 949 last = L; 950 951 return removedNonLocal; 952 } 953 954 955 bool deletedLoad = false; 956 957 // Walk up the dependency chain until we either find 958 // a dependency we can use, or we can't walk any further 959 while (Instruction *DepInst = dep.getInst()) { 960 // ... that depends on a store ... 961 if (StoreInst* S = dyn_cast<StoreInst>(DepInst)) { 962 if (S->getPointerOperand() == pointer) { 963 // Remove it! 964 MD.removeInstruction(L); 965 966 L->replaceAllUsesWith(S->getOperand(0)); 967 toErase.push_back(L); 968 deletedLoad = true; 969 NumGVNLoad++; 970 } 971 972 // Whether we removed it or not, we can't 973 // go any further 974 break; 975 } else if (!isa<LoadInst>(DepInst)) { 976 // Only want to handle loads below. 977 break; 978 } else if (!last) { 979 // If we don't depend on a store, and we haven't 980 // been loaded before, bail. 981 break; 982 } else if (DepInst == last) { 983 // Remove it! 984 MD.removeInstruction(L); 985 986 L->replaceAllUsesWith(last); 987 toErase.push_back(L); 988 deletedLoad = true; 989 NumGVNLoad++; 990 991 break; 992 } else { 993 dep = MD.getDependency(L, DepInst); 994 } 995 } 996 997 if (AllocationInst *DepAI = dyn_cast_or_null<AllocationInst>(dep.getInst())) { 998 // Check that this load is actually from the 999 // allocation we found 1000 if (L->getOperand(0)->getUnderlyingObject() == DepAI) { 1001 // If this load depends directly on an allocation, there isn't 1002 // anything stored there; therefore, we can optimize this load 1003 // to undef. 1004 MD.removeInstruction(L); 1005 1006 L->replaceAllUsesWith(UndefValue::get(L->getType())); 1007 toErase.push_back(L); 1008 deletedLoad = true; 1009 NumGVNLoad++; 1010 } 1011 } 1012 1013 if (!deletedLoad) 1014 last = L; 1015 1016 return deletedLoad; 1017} 1018 1019Value* GVN::lookupNumber(BasicBlock* BB, uint32_t num) { 1020 DenseMap<BasicBlock*, ValueNumberScope*>::iterator I = localAvail.find(BB); 1021 if (I == localAvail.end()) 1022 return 0; 1023 1024 ValueNumberScope* locals = I->second; 1025 1026 while (locals) { 1027 DenseMap<uint32_t, Value*>::iterator I = locals->table.find(num); 1028 if (I != locals->table.end()) 1029 return I->second; 1030 else 1031 locals = locals->parent; 1032 } 1033 1034 return 0; 1035} 1036 1037/// processInstruction - When calculating availability, handle an instruction 1038/// by inserting it into the appropriate sets 1039bool GVN::processInstruction(Instruction *I, 1040 DenseMap<Value*, LoadInst*> &lastSeenLoad, 1041 SmallVectorImpl<Instruction*> &toErase) { 1042 if (LoadInst* L = dyn_cast<LoadInst>(I)) { 1043 bool changed = processLoad(L, lastSeenLoad, toErase); 1044 1045 if (!changed) { 1046 unsigned num = VN.lookup_or_add(L); 1047 localAvail[I->getParent()]->table.insert(std::make_pair(num, L)); 1048 } 1049 1050 return changed; 1051 } 1052 1053 uint32_t nextNum = VN.getNextUnusedValueNumber(); 1054 unsigned num = VN.lookup_or_add(I); 1055 1056 // Allocations are always uniquely numbered, so we can save time and memory 1057 // by fast failing them. 1058 if (isa<AllocationInst>(I) || isa<TerminatorInst>(I)) { 1059 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1060 return false; 1061 } 1062 1063 // Collapse PHI nodes 1064 if (PHINode* p = dyn_cast<PHINode>(I)) { 1065 Value* constVal = CollapsePhi(p); 1066 1067 if (constVal) { 1068 for (PhiMapType::iterator PI = phiMap.begin(), PE = phiMap.end(); 1069 PI != PE; ++PI) 1070 if (PI->second.count(p)) 1071 PI->second.erase(p); 1072 1073 p->replaceAllUsesWith(constVal); 1074 toErase.push_back(p); 1075 } else { 1076 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1077 } 1078 1079 // If the number we were assigned was a brand new VN, then we don't 1080 // need to do a lookup to see if the number already exists 1081 // somewhere in the domtree: it can't! 1082 } else if (num == nextNum) { 1083 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1084 1085 // Perform value-number based elimination 1086 } else if (Value* repl = lookupNumber(I->getParent(), num)) { 1087 // Remove it! 1088 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 1089 MD.removeInstruction(I); 1090 1091 VN.erase(I); 1092 I->replaceAllUsesWith(repl); 1093 toErase.push_back(I); 1094 return true; 1095 } else { 1096 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1097 } 1098 1099 return false; 1100} 1101 1102// GVN::runOnFunction - This is the main transformation entry point for a 1103// function. 1104// 1105bool GVN::runOnFunction(Function& F) { 1106 VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>()); 1107 VN.setMemDep(&getAnalysis<MemoryDependenceAnalysis>()); 1108 VN.setDomTree(&getAnalysis<DominatorTree>()); 1109 1110 bool changed = false; 1111 bool shouldContinue = true; 1112 1113 // Merge unconditional branches, allowing PRE to catch more 1114 // optimization opportunities. 1115 for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) { 1116 BasicBlock* BB = FI; 1117 ++FI; 1118 bool removedBlock = MergeBlockIntoPredecessor(BB, this); 1119 if (removedBlock) NumGVNBlocks++; 1120 1121 changed |= removedBlock; 1122 } 1123 1124 while (shouldContinue) { 1125 shouldContinue = iterateOnFunction(F); 1126 changed |= shouldContinue; 1127 } 1128 1129 if (EnablePRE) { 1130 bool PREChanged = true; 1131 while (PREChanged) { 1132 PREChanged = performPRE(F); 1133 changed |= PREChanged; 1134 } 1135 } 1136 1137 cleanupGlobalSets(); 1138 1139 return changed; 1140} 1141 1142 1143bool GVN::processBlock(DomTreeNode* DTN) { 1144 BasicBlock* BB = DTN->getBlock(); 1145 1146 SmallVector<Instruction*, 8> toErase; 1147 DenseMap<Value*, LoadInst*> lastSeenLoad; 1148 bool changed_function = false; 1149 1150 if (DTN->getIDom()) 1151 localAvail[BB] = 1152 new ValueNumberScope(localAvail[DTN->getIDom()->getBlock()]); 1153 else 1154 localAvail[BB] = new ValueNumberScope(0); 1155 1156 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); 1157 BI != BE;) { 1158 changed_function |= processInstruction(BI, lastSeenLoad, toErase); 1159 if (toErase.empty()) { 1160 ++BI; 1161 continue; 1162 } 1163 1164 // If we need some instructions deleted, do it now. 1165 NumGVNInstr += toErase.size(); 1166 1167 // Avoid iterator invalidation. 1168 bool AtStart = BI == BB->begin(); 1169 if (!AtStart) 1170 --BI; 1171 1172 for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(), 1173 E = toErase.end(); I != E; ++I) 1174 (*I)->eraseFromParent(); 1175 1176 if (AtStart) 1177 BI = BB->begin(); 1178 else 1179 ++BI; 1180 1181 toErase.clear(); 1182 } 1183 1184 return changed_function; 1185} 1186 1187/// performPRE - Perform a purely local form of PRE that looks for diamond 1188/// control flow patterns and attempts to perform simple PRE at the join point. 1189bool GVN::performPRE(Function& F) { 1190 bool changed = false; 1191 SmallVector<std::pair<TerminatorInst*, unsigned>, 4> toSplit; 1192 for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()), 1193 DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) { 1194 BasicBlock* CurrentBlock = *DI; 1195 1196 // Nothing to PRE in the entry block. 1197 if (CurrentBlock == &F.getEntryBlock()) continue; 1198 1199 for (BasicBlock::iterator BI = CurrentBlock->begin(), 1200 BE = CurrentBlock->end(); BI != BE; ) { 1201 if (isa<AllocationInst>(BI) || isa<TerminatorInst>(BI) || 1202 isa<PHINode>(BI) || BI->mayReadFromMemory() || 1203 BI->mayWriteToMemory()) { 1204 BI++; 1205 continue; 1206 } 1207 1208 uint32_t valno = VN.lookup(BI); 1209 1210 // Look for the predecessors for PRE opportunities. We're 1211 // only trying to solve the basic diamond case, where 1212 // a value is computed in the successor and one predecessor, 1213 // but not the other. We also explicitly disallow cases 1214 // where the successor is its own predecessor, because they're 1215 // more complicated to get right. 1216 unsigned numWith = 0; 1217 unsigned numWithout = 0; 1218 BasicBlock* PREPred = 0; 1219 DenseMap<BasicBlock*, Value*> predMap; 1220 for (pred_iterator PI = pred_begin(CurrentBlock), 1221 PE = pred_end(CurrentBlock); PI != PE; ++PI) { 1222 // We're not interested in PRE where the block is its 1223 // own predecessor, on in blocks with predecessors 1224 // that are not reachable. 1225 if (*PI == CurrentBlock) { 1226 numWithout = 2; 1227 break; 1228 } else if (!localAvail.count(*PI)) { 1229 numWithout = 2; 1230 break; 1231 } 1232 1233 DenseMap<uint32_t, Value*>::iterator predV = 1234 localAvail[*PI]->table.find(valno); 1235 if (predV == localAvail[*PI]->table.end()) { 1236 PREPred = *PI; 1237 numWithout++; 1238 } else if (predV->second == BI) { 1239 numWithout = 2; 1240 } else { 1241 predMap[*PI] = predV->second; 1242 numWith++; 1243 } 1244 } 1245 1246 // Don't do PRE when it might increase code size, i.e. when 1247 // we would need to insert instructions in more than one pred. 1248 if (numWithout != 1 || numWith == 0) { 1249 BI++; 1250 continue; 1251 } 1252 1253 // We can't do PRE safely on a critical edge, so instead we schedule 1254 // the edge to be split and perform the PRE the next time we iterate 1255 // on the function. 1256 unsigned succNum = 0; 1257 for (unsigned i = 0, e = PREPred->getTerminator()->getNumSuccessors(); 1258 i != e; ++i) 1259 if (PREPred->getTerminator()->getSuccessor(i) == CurrentBlock) { 1260 succNum = i; 1261 break; 1262 } 1263 1264 if (isCriticalEdge(PREPred->getTerminator(), succNum)) { 1265 toSplit.push_back(std::make_pair(PREPred->getTerminator(), succNum)); 1266 changed = true; 1267 BI++; 1268 continue; 1269 } 1270 1271 // Instantiate the expression the in predecessor that lacked it. 1272 // Because we are going top-down through the block, all value numbers 1273 // will be available in the predecessor by the time we need them. Any 1274 // that weren't original present will have been instantiated earlier 1275 // in this loop. 1276 Instruction* PREInstr = BI->clone(); 1277 bool success = true; 1278 for (unsigned i = 0; i < BI->getNumOperands(); ++i) { 1279 Value* op = BI->getOperand(i); 1280 if (isa<Argument>(op) || isa<Constant>(op) || isa<GlobalValue>(op)) 1281 PREInstr->setOperand(i, op); 1282 else { 1283 Value* V = lookupNumber(PREPred, VN.lookup(op)); 1284 if (!V) { 1285 success = false; 1286 break; 1287 } else 1288 PREInstr->setOperand(i, V); 1289 } 1290 } 1291 1292 // Fail out if we encounter an operand that is not available in 1293 // the PRE predecessor. This is typically because of loads which 1294 // are not value numbered precisely. 1295 if (!success) { 1296 delete PREInstr; 1297 BI++; 1298 continue; 1299 } 1300 1301 PREInstr->insertBefore(PREPred->getTerminator()); 1302 PREInstr->setName(BI->getName() + ".pre"); 1303 predMap[PREPred] = PREInstr; 1304 VN.add(PREInstr, valno); 1305 NumGVNPRE++; 1306 1307 // Update the availability map to include the new instruction. 1308 localAvail[PREPred]->table.insert(std::make_pair(valno, PREInstr)); 1309 1310 // Create a PHI to make the value available in this block. 1311 PHINode* Phi = PHINode::Create(BI->getType(), 1312 BI->getName() + ".pre-phi", 1313 CurrentBlock->begin()); 1314 for (pred_iterator PI = pred_begin(CurrentBlock), 1315 PE = pred_end(CurrentBlock); PI != PE; ++PI) 1316 Phi->addIncoming(predMap[*PI], *PI); 1317 1318 VN.add(Phi, valno); 1319 localAvail[CurrentBlock]->table[valno] = Phi; 1320 1321 BI->replaceAllUsesWith(Phi); 1322 VN.erase(BI); 1323 1324 Instruction* erase = BI; 1325 BI++; 1326 erase->eraseFromParent(); 1327 1328 changed = true; 1329 } 1330 } 1331 1332 for (SmallVector<std::pair<TerminatorInst*, unsigned>, 4>::iterator 1333 I = toSplit.begin(), E = toSplit.end(); I != E; ++I) 1334 SplitCriticalEdge(I->first, I->second, this); 1335 1336 return changed || toSplit.size(); 1337} 1338 1339// iterateOnFunction - Executes one iteration of GVN 1340bool GVN::iterateOnFunction(Function &F) { 1341 DominatorTree &DT = getAnalysis<DominatorTree>(); 1342 1343 cleanupGlobalSets(); 1344 1345 // Top-down walk of the dominator tree 1346 bool changed = false; 1347 for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()), 1348 DE = df_end(DT.getRootNode()); DI != DE; ++DI) 1349 changed |= processBlock(*DI); 1350 1351 return changed; 1352} 1353 1354void GVN::cleanupGlobalSets() { 1355 VN.clear(); 1356 phiMap.clear(); 1357 1358 for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator 1359 I = localAvail.begin(), E = localAvail.end(); I != E; ++I) 1360 delete I->second; 1361 localAvail.clear(); 1362} 1363