GVN.cpp revision 1440ac54176cff6cf5ac917ea29ef9adb90b5f6d
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 } 465 466 if (Instruction *LocalDepInst = local_dep.getInst()) { 467 if (!isa<CallInst>(LocalDepInst)) { 468 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 469 return nextValueNumber++; 470 } 471 472 CallInst* local_cdep = cast<CallInst>(LocalDepInst); 473 474 if (local_cdep->getCalledFunction() != C->getCalledFunction() || 475 local_cdep->getNumOperands() != C->getNumOperands()) { 476 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 477 return nextValueNumber++; 478 } 479 480 if (!C->getCalledFunction()) { 481 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 482 return nextValueNumber++; 483 } 484 485 for (unsigned i = 1; i < C->getNumOperands(); ++i) { 486 uint32_t c_vn = lookup_or_add(C->getOperand(i)); 487 uint32_t cd_vn = lookup_or_add(local_cdep->getOperand(i)); 488 if (c_vn != cd_vn) { 489 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 490 return nextValueNumber++; 491 } 492 } 493 494 uint32_t v = lookup_or_add(local_cdep); 495 valueNumbering.insert(std::make_pair(V, v)); 496 return v; 497 } 498 499 500 SmallVector<std::pair<BasicBlock*, MemDepResult>, 32> deps; 501 MD->getNonLocalDependency(C, deps); 502 CallInst* cdep = 0; 503 504 // Check to see if we have a single dominating call instruction that is 505 // identical to C. 506 for (SmallVector<std::pair<BasicBlock*, MemDepResult>, 32> 507 ::iterator I = deps.begin(), E = deps.end(); I != E; ++I) { 508 // Ignore non-local dependencies. 509 if (I->second.isNonLocal()) 510 continue; 511 512 // We don't handle non-depedencies. If we already have a call, reject 513 // instruction dependencies. 514 if (I->second.isNone() || cdep != 0) { 515 cdep = 0; 516 break; 517 } 518 519 CallInst *NonLocalDepCall = dyn_cast<CallInst>(I->second.getInst()); 520 // FIXME: All duplicated with non-local case. 521 if (NonLocalDepCall && DT->properlyDominates(I->first, C->getParent())){ 522 cdep = NonLocalDepCall; 523 continue; 524 } 525 526 cdep = 0; 527 break; 528 } 529 530 if (!cdep) { 531 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 532 return nextValueNumber++; 533 } 534 535 if (cdep->getCalledFunction() != C->getCalledFunction() || 536 cdep->getNumOperands() != C->getNumOperands()) { 537 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 538 return nextValueNumber++; 539 } 540 if (!C->getCalledFunction()) { 541 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 542 return nextValueNumber++; 543 } 544 for (unsigned i = 1; i < C->getNumOperands(); ++i) { 545 uint32_t c_vn = lookup_or_add(C->getOperand(i)); 546 uint32_t cd_vn = lookup_or_add(cdep->getOperand(i)); 547 if (c_vn != cd_vn) { 548 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 549 return nextValueNumber++; 550 } 551 } 552 553 uint32_t v = lookup_or_add(cdep); 554 valueNumbering.insert(std::make_pair(V, v)); 555 return v; 556 557 } else { 558 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 559 return nextValueNumber++; 560 } 561 } else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) { 562 Expression e = create_expression(BO); 563 564 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 565 if (EI != expressionNumbering.end()) { 566 valueNumbering.insert(std::make_pair(V, EI->second)); 567 return EI->second; 568 } else { 569 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 570 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 571 572 return nextValueNumber++; 573 } 574 } else if (CmpInst* C = dyn_cast<CmpInst>(V)) { 575 Expression e = create_expression(C); 576 577 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 578 if (EI != expressionNumbering.end()) { 579 valueNumbering.insert(std::make_pair(V, EI->second)); 580 return EI->second; 581 } else { 582 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 583 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 584 585 return nextValueNumber++; 586 } 587 } else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) { 588 Expression e = create_expression(U); 589 590 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 591 if (EI != expressionNumbering.end()) { 592 valueNumbering.insert(std::make_pair(V, EI->second)); 593 return EI->second; 594 } else { 595 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 596 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 597 598 return nextValueNumber++; 599 } 600 } else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) { 601 Expression e = create_expression(U); 602 603 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 604 if (EI != expressionNumbering.end()) { 605 valueNumbering.insert(std::make_pair(V, EI->second)); 606 return EI->second; 607 } else { 608 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 609 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 610 611 return nextValueNumber++; 612 } 613 } else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) { 614 Expression e = create_expression(U); 615 616 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 617 if (EI != expressionNumbering.end()) { 618 valueNumbering.insert(std::make_pair(V, EI->second)); 619 return EI->second; 620 } else { 621 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 622 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 623 624 return nextValueNumber++; 625 } 626 } else if (SelectInst* U = dyn_cast<SelectInst>(V)) { 627 Expression e = create_expression(U); 628 629 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 630 if (EI != expressionNumbering.end()) { 631 valueNumbering.insert(std::make_pair(V, EI->second)); 632 return EI->second; 633 } else { 634 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 635 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 636 637 return nextValueNumber++; 638 } 639 } else if (CastInst* U = dyn_cast<CastInst>(V)) { 640 Expression e = create_expression(U); 641 642 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 643 if (EI != expressionNumbering.end()) { 644 valueNumbering.insert(std::make_pair(V, EI->second)); 645 return EI->second; 646 } else { 647 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 648 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 649 650 return nextValueNumber++; 651 } 652 } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) { 653 Expression e = create_expression(U); 654 655 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); 656 if (EI != expressionNumbering.end()) { 657 valueNumbering.insert(std::make_pair(V, EI->second)); 658 return EI->second; 659 } else { 660 expressionNumbering.insert(std::make_pair(e, nextValueNumber)); 661 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 662 663 return nextValueNumber++; 664 } 665 } else { 666 valueNumbering.insert(std::make_pair(V, nextValueNumber)); 667 return nextValueNumber++; 668 } 669} 670 671/// lookup - Returns the value number of the specified value. Fails if 672/// the value has not yet been numbered. 673uint32_t ValueTable::lookup(Value* V) const { 674 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); 675 assert(VI != valueNumbering.end() && "Value not numbered?"); 676 return VI->second; 677} 678 679/// clear - Remove all entries from the ValueTable 680void ValueTable::clear() { 681 valueNumbering.clear(); 682 expressionNumbering.clear(); 683 nextValueNumber = 1; 684} 685 686/// erase - Remove a value from the value numbering 687void ValueTable::erase(Value* V) { 688 valueNumbering.erase(V); 689} 690 691//===----------------------------------------------------------------------===// 692// GVN Pass 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(&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.addRequired<DominatorTree>(); 723 AU.addRequired<MemoryDependenceAnalysis>(); 724 AU.addRequired<AliasAnalysis>(); 725 726 AU.addPreserved<DominatorTree>(); 727 AU.addPreserved<AliasAnalysis>(); 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 bool mergeBlockIntoPredecessor(BasicBlock* BB); 751 void cleanupGlobalSets(); 752 }; 753 754 char GVN::ID = 0; 755} 756 757// createGVNPass - The public interface to this file... 758FunctionPass *llvm::createGVNPass() { return new GVN(); } 759 760static RegisterPass<GVN> X("gvn", 761 "Global Value Numbering"); 762 763void GVN::dump(DenseMap<uint32_t, Value*>& d) { 764 printf("{\n"); 765 for (DenseMap<uint32_t, Value*>::iterator I = d.begin(), 766 E = d.end(); I != E; ++I) { 767 printf("%d\n", I->first); 768 I->second->dump(); 769 } 770 printf("}\n"); 771} 772 773Value* GVN::CollapsePhi(PHINode* p) { 774 DominatorTree &DT = getAnalysis<DominatorTree>(); 775 Value* constVal = p->hasConstantValue(); 776 777 if (!constVal) return 0; 778 779 Instruction* inst = dyn_cast<Instruction>(constVal); 780 if (!inst) 781 return constVal; 782 783 if (DT.dominates(inst, p)) 784 if (isSafeReplacement(p, inst)) 785 return inst; 786 return 0; 787} 788 789bool GVN::isSafeReplacement(PHINode* p, Instruction* inst) { 790 if (!isa<PHINode>(inst)) 791 return true; 792 793 for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end(); 794 UI != E; ++UI) 795 if (PHINode* use_phi = dyn_cast<PHINode>(UI)) 796 if (use_phi->getParent() == inst->getParent()) 797 return false; 798 799 return true; 800} 801 802/// GetValueForBlock - Get the value to use within the specified basic block. 803/// available values are in Phis. 804Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig, 805 DenseMap<BasicBlock*, Value*> &Phis, 806 bool top_level) { 807 808 // If we have already computed this value, return the previously computed val. 809 DenseMap<BasicBlock*, Value*>::iterator V = Phis.find(BB); 810 if (V != Phis.end() && !top_level) return V->second; 811 812 // If the block is unreachable, just return undef, since this path 813 // can't actually occur at runtime. 814 if (!getAnalysis<DominatorTree>().isReachableFromEntry(BB)) 815 return Phis[BB] = UndefValue::get(orig->getType()); 816 817 BasicBlock* singlePred = BB->getSinglePredecessor(); 818 if (singlePred) { 819 Value *ret = GetValueForBlock(singlePred, orig, Phis); 820 Phis[BB] = ret; 821 return ret; 822 } 823 824 // Otherwise, the idom is the loop, so we need to insert a PHI node. Do so 825 // now, then get values to fill in the incoming values for the PHI. 826 PHINode *PN = PHINode::Create(orig->getType(), orig->getName()+".rle", 827 BB->begin()); 828 PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB))); 829 830 if (Phis.count(BB) == 0) 831 Phis.insert(std::make_pair(BB, PN)); 832 833 // Fill in the incoming values for the block. 834 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { 835 Value* val = GetValueForBlock(*PI, orig, Phis); 836 PN->addIncoming(val, *PI); 837 } 838 839 AliasAnalysis& AA = getAnalysis<AliasAnalysis>(); 840 AA.copyValue(orig, PN); 841 842 // Attempt to collapse PHI nodes that are trivially redundant 843 Value* v = CollapsePhi(PN); 844 if (!v) { 845 // Cache our phi construction results 846 phiMap[orig->getPointerOperand()].insert(PN); 847 return PN; 848 } 849 850 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 851 852 MD.removeInstruction(PN); 853 PN->replaceAllUsesWith(v); 854 855 for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(), 856 E = Phis.end(); I != E; ++I) 857 if (I->second == PN) 858 I->second = v; 859 860 PN->eraseFromParent(); 861 862 Phis[BB] = v; 863 return v; 864} 865 866/// processNonLocalLoad - Attempt to eliminate a load whose dependencies are 867/// non-local by performing PHI construction. 868bool GVN::processNonLocalLoad(LoadInst* L, 869 SmallVectorImpl<Instruction*> &toErase) { 870 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 871 872 // Find the non-local dependencies of the load 873 SmallVector<std::pair<BasicBlock*, MemDepResult>, 32> deps; 874 MD.getNonLocalDependency(L, deps); 875 876 // If we had to process more than one hundred blocks to find the 877 // dependencies, this load isn't worth worrying about. Optimizing 878 // it will be too expensive. 879 if (deps.size() > 100) 880 return false; 881 882 BasicBlock *EntryBlock = &L->getParent()->getParent()->getEntryBlock(); 883 884 DenseMap<BasicBlock*, Value*> repl; 885 886 // Filter out useless results (non-locals, etc) 887 for (SmallVector<std::pair<BasicBlock*, MemDepResult>, 32>::iterator 888 I = deps.begin(), E = deps.end(); I != E; ++I) { 889 if (I->second.isNone()) { 890 repl[I->first] = UndefValue::get(L->getType()); 891 continue; 892 } 893 894 if (I->second.isNonLocal()) { 895 // If this is a non-local dependency in the entry block, then we depend on 896 // the value live-in at the start of the function. We could insert a load 897 // in the entry block to get this, but for now we'll just bail out. 898 // FIXME: Consider emitting a load in the entry block to catch this case! 899 if (I->first == EntryBlock) 900 return false; 901 continue; 902 } 903 904 if (StoreInst* S = dyn_cast<StoreInst>(I->second.getInst())) { 905 if (S->getPointerOperand() != L->getPointerOperand()) 906 return false; 907 repl[I->first] = S->getOperand(0); 908 } else if (LoadInst* LD = dyn_cast<LoadInst>(I->second.getInst())) { 909 if (LD->getPointerOperand() != L->getPointerOperand()) 910 return false; 911 repl[I->first] = LD; 912 } else { 913 return false; 914 } 915 } 916 917 // Use cached PHI construction information from previous runs 918 SmallPtrSet<Instruction*, 4>& p = phiMap[L->getPointerOperand()]; 919 for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end(); 920 I != E; ++I) { 921 if ((*I)->getParent() == L->getParent()) { 922 MD.removeInstruction(L); 923 L->replaceAllUsesWith(*I); 924 toErase.push_back(L); 925 NumGVNLoad++; 926 return true; 927 } 928 929 repl.insert(std::make_pair((*I)->getParent(), *I)); 930 } 931 932 // Perform PHI construction 933 SmallPtrSet<BasicBlock*, 4> visited; 934 Value* v = GetValueForBlock(L->getParent(), L, repl, true); 935 936 MD.removeInstruction(L); 937 L->replaceAllUsesWith(v); 938 toErase.push_back(L); 939 NumGVNLoad++; 940 941 return true; 942} 943 944/// processLoad - Attempt to eliminate a load, first by eliminating it 945/// locally, and then attempting non-local elimination if that fails. 946bool GVN::processLoad(LoadInst *L, DenseMap<Value*, LoadInst*> &lastLoad, 947 SmallVectorImpl<Instruction*> &toErase) { 948 if (L->isVolatile()) { 949 lastLoad[L->getPointerOperand()] = L; 950 return false; 951 } 952 953 Value* pointer = L->getPointerOperand(); 954 LoadInst*& last = lastLoad[pointer]; 955 956 // ... to a pointer that has been loaded from before... 957 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 958 bool removedNonLocal = false; 959 MemDepResult dep = MD.getDependency(L); 960 if (dep.isNonLocal() && 961 L->getParent() != &L->getParent()->getParent()->getEntryBlock()) { 962 removedNonLocal = processNonLocalLoad(L, toErase); 963 964 if (!removedNonLocal) 965 last = L; 966 967 return removedNonLocal; 968 } 969 970 971 bool deletedLoad = false; 972 973 // Walk up the dependency chain until we either find 974 // a dependency we can use, or we can't walk any further 975 while (Instruction *DepInst = dep.getInst()) { 976 // ... that depends on a store ... 977 if (StoreInst* S = dyn_cast<StoreInst>(DepInst)) { 978 if (S->getPointerOperand() == pointer) { 979 // Remove it! 980 MD.removeInstruction(L); 981 982 L->replaceAllUsesWith(S->getOperand(0)); 983 toErase.push_back(L); 984 deletedLoad = true; 985 NumGVNLoad++; 986 } 987 988 // Whether we removed it or not, we can't 989 // go any further 990 break; 991 } else if (!isa<LoadInst>(DepInst)) { 992 // Only want to handle loads below. 993 break; 994 } else if (!last) { 995 // If we don't depend on a store, and we haven't 996 // been loaded before, bail. 997 break; 998 } else if (DepInst == last) { 999 // Remove it! 1000 MD.removeInstruction(L); 1001 1002 L->replaceAllUsesWith(last); 1003 toErase.push_back(L); 1004 deletedLoad = true; 1005 NumGVNLoad++; 1006 break; 1007 } else { 1008 dep = MD.getDependencyFrom(L, DepInst, DepInst->getParent()); 1009 } 1010 } 1011 1012 // If this load really doesn't depend on anything, then we must be loading an 1013 // undef value. This can happen when loading for a fresh allocation with no 1014 // intervening stores, for example. 1015 if (dep.isNone()) { 1016 // If this load depends directly on an allocation, there isn't 1017 // anything stored there; therefore, we can optimize this load 1018 // to undef. 1019 MD.removeInstruction(L); 1020 L->replaceAllUsesWith(UndefValue::get(L->getType())); 1021 toErase.push_back(L); 1022 deletedLoad = true; 1023 NumGVNLoad++; 1024 } 1025 1026 if (!deletedLoad) 1027 last = L; 1028 1029 return deletedLoad; 1030} 1031 1032Value* GVN::lookupNumber(BasicBlock* BB, uint32_t num) { 1033 DenseMap<BasicBlock*, ValueNumberScope*>::iterator I = localAvail.find(BB); 1034 if (I == localAvail.end()) 1035 return 0; 1036 1037 ValueNumberScope* locals = I->second; 1038 1039 while (locals) { 1040 DenseMap<uint32_t, Value*>::iterator I = locals->table.find(num); 1041 if (I != locals->table.end()) 1042 return I->second; 1043 else 1044 locals = locals->parent; 1045 } 1046 1047 return 0; 1048} 1049 1050/// processInstruction - When calculating availability, handle an instruction 1051/// by inserting it into the appropriate sets 1052bool GVN::processInstruction(Instruction *I, 1053 DenseMap<Value*, LoadInst*> &lastSeenLoad, 1054 SmallVectorImpl<Instruction*> &toErase) { 1055 if (LoadInst* L = dyn_cast<LoadInst>(I)) { 1056 bool changed = processLoad(L, lastSeenLoad, toErase); 1057 1058 if (!changed) { 1059 unsigned num = VN.lookup_or_add(L); 1060 localAvail[I->getParent()]->table.insert(std::make_pair(num, L)); 1061 } 1062 1063 return changed; 1064 } 1065 1066 uint32_t nextNum = VN.getNextUnusedValueNumber(); 1067 unsigned num = VN.lookup_or_add(I); 1068 1069 // Allocations are always uniquely numbered, so we can save time and memory 1070 // by fast failing them. 1071 if (isa<AllocationInst>(I) || isa<TerminatorInst>(I)) { 1072 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1073 return false; 1074 } 1075 1076 // Collapse PHI nodes 1077 if (PHINode* p = dyn_cast<PHINode>(I)) { 1078 Value* constVal = CollapsePhi(p); 1079 1080 if (constVal) { 1081 for (PhiMapType::iterator PI = phiMap.begin(), PE = phiMap.end(); 1082 PI != PE; ++PI) 1083 if (PI->second.count(p)) 1084 PI->second.erase(p); 1085 1086 p->replaceAllUsesWith(constVal); 1087 toErase.push_back(p); 1088 } else { 1089 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1090 } 1091 1092 // If the number we were assigned was a brand new VN, then we don't 1093 // need to do a lookup to see if the number already exists 1094 // somewhere in the domtree: it can't! 1095 } else if (num == nextNum) { 1096 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1097 1098 // Perform value-number based elimination 1099 } else if (Value* repl = lookupNumber(I->getParent(), num)) { 1100 // Remove it! 1101 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); 1102 MD.removeInstruction(I); 1103 1104 VN.erase(I); 1105 I->replaceAllUsesWith(repl); 1106 toErase.push_back(I); 1107 return true; 1108 } else { 1109 localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); 1110 } 1111 1112 return false; 1113} 1114 1115// GVN::runOnFunction - This is the main transformation entry point for a 1116// function. 1117// 1118bool GVN::runOnFunction(Function& F) { 1119 VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>()); 1120 VN.setMemDep(&getAnalysis<MemoryDependenceAnalysis>()); 1121 VN.setDomTree(&getAnalysis<DominatorTree>()); 1122 1123 bool changed = false; 1124 bool shouldContinue = true; 1125 1126 // Merge unconditional branches, allowing PRE to catch more 1127 // optimization opportunities. 1128 for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) { 1129 BasicBlock* BB = FI; 1130 ++FI; 1131 bool removedBlock = MergeBlockIntoPredecessor(BB, this); 1132 if (removedBlock) NumGVNBlocks++; 1133 1134 changed |= removedBlock; 1135 } 1136 1137 while (shouldContinue) { 1138 shouldContinue = iterateOnFunction(F); 1139 changed |= shouldContinue; 1140 } 1141 1142 if (EnablePRE) { 1143 bool PREChanged = true; 1144 while (PREChanged) { 1145 PREChanged = performPRE(F); 1146 changed |= PREChanged; 1147 } 1148 } 1149 1150 cleanupGlobalSets(); 1151 1152 return changed; 1153} 1154 1155 1156bool GVN::processBlock(DomTreeNode* DTN) { 1157 BasicBlock* BB = DTN->getBlock(); 1158 1159 SmallVector<Instruction*, 8> toErase; 1160 DenseMap<Value*, LoadInst*> lastSeenLoad; 1161 bool changed_function = false; 1162 1163 if (DTN->getIDom()) 1164 localAvail[BB] = 1165 new ValueNumberScope(localAvail[DTN->getIDom()->getBlock()]); 1166 else 1167 localAvail[BB] = new ValueNumberScope(0); 1168 1169 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); 1170 BI != BE;) { 1171 changed_function |= processInstruction(BI, lastSeenLoad, toErase); 1172 if (toErase.empty()) { 1173 ++BI; 1174 continue; 1175 } 1176 1177 // If we need some instructions deleted, do it now. 1178 NumGVNInstr += toErase.size(); 1179 1180 // Avoid iterator invalidation. 1181 bool AtStart = BI == BB->begin(); 1182 if (!AtStart) 1183 --BI; 1184 1185 for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(), 1186 E = toErase.end(); I != E; ++I) 1187 (*I)->eraseFromParent(); 1188 1189 if (AtStart) 1190 BI = BB->begin(); 1191 else 1192 ++BI; 1193 1194 toErase.clear(); 1195 } 1196 1197 return changed_function; 1198} 1199 1200/// performPRE - Perform a purely local form of PRE that looks for diamond 1201/// control flow patterns and attempts to perform simple PRE at the join point. 1202bool GVN::performPRE(Function& F) { 1203 bool changed = false; 1204 SmallVector<std::pair<TerminatorInst*, unsigned>, 4> toSplit; 1205 for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()), 1206 DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) { 1207 BasicBlock* CurrentBlock = *DI; 1208 1209 // Nothing to PRE in the entry block. 1210 if (CurrentBlock == &F.getEntryBlock()) continue; 1211 1212 for (BasicBlock::iterator BI = CurrentBlock->begin(), 1213 BE = CurrentBlock->end(); BI != BE; ) { 1214 if (isa<AllocationInst>(BI) || isa<TerminatorInst>(BI) || 1215 isa<PHINode>(BI) || BI->mayReadFromMemory() || 1216 BI->mayWriteToMemory()) { 1217 BI++; 1218 continue; 1219 } 1220 1221 uint32_t valno = VN.lookup(BI); 1222 1223 // Look for the predecessors for PRE opportunities. We're 1224 // only trying to solve the basic diamond case, where 1225 // a value is computed in the successor and one predecessor, 1226 // but not the other. We also explicitly disallow cases 1227 // where the successor is its own predecessor, because they're 1228 // more complicated to get right. 1229 unsigned numWith = 0; 1230 unsigned numWithout = 0; 1231 BasicBlock* PREPred = 0; 1232 DenseMap<BasicBlock*, Value*> predMap; 1233 for (pred_iterator PI = pred_begin(CurrentBlock), 1234 PE = pred_end(CurrentBlock); PI != PE; ++PI) { 1235 // We're not interested in PRE where the block is its 1236 // own predecessor, on in blocks with predecessors 1237 // that are not reachable. 1238 if (*PI == CurrentBlock) { 1239 numWithout = 2; 1240 break; 1241 } else if (!localAvail.count(*PI)) { 1242 numWithout = 2; 1243 break; 1244 } 1245 1246 DenseMap<uint32_t, Value*>::iterator predV = 1247 localAvail[*PI]->table.find(valno); 1248 if (predV == localAvail[*PI]->table.end()) { 1249 PREPred = *PI; 1250 numWithout++; 1251 } else if (predV->second == BI) { 1252 numWithout = 2; 1253 } else { 1254 predMap[*PI] = predV->second; 1255 numWith++; 1256 } 1257 } 1258 1259 // Don't do PRE when it might increase code size, i.e. when 1260 // we would need to insert instructions in more than one pred. 1261 if (numWithout != 1 || numWith == 0) { 1262 BI++; 1263 continue; 1264 } 1265 1266 // We can't do PRE safely on a critical edge, so instead we schedule 1267 // the edge to be split and perform the PRE the next time we iterate 1268 // on the function. 1269 unsigned succNum = 0; 1270 for (unsigned i = 0, e = PREPred->getTerminator()->getNumSuccessors(); 1271 i != e; ++i) 1272 if (PREPred->getTerminator()->getSuccessor(i) == CurrentBlock) { 1273 succNum = i; 1274 break; 1275 } 1276 1277 if (isCriticalEdge(PREPred->getTerminator(), succNum)) { 1278 toSplit.push_back(std::make_pair(PREPred->getTerminator(), succNum)); 1279 changed = true; 1280 BI++; 1281 continue; 1282 } 1283 1284 // Instantiate the expression the in predecessor that lacked it. 1285 // Because we are going top-down through the block, all value numbers 1286 // will be available in the predecessor by the time we need them. Any 1287 // that weren't original present will have been instantiated earlier 1288 // in this loop. 1289 Instruction* PREInstr = BI->clone(); 1290 bool success = true; 1291 for (unsigned i = 0; i < BI->getNumOperands(); ++i) { 1292 Value* op = BI->getOperand(i); 1293 if (isa<Argument>(op) || isa<Constant>(op) || isa<GlobalValue>(op)) 1294 PREInstr->setOperand(i, op); 1295 else { 1296 Value* V = lookupNumber(PREPred, VN.lookup(op)); 1297 if (!V) { 1298 success = false; 1299 break; 1300 } else 1301 PREInstr->setOperand(i, V); 1302 } 1303 } 1304 1305 // Fail out if we encounter an operand that is not available in 1306 // the PRE predecessor. This is typically because of loads which 1307 // are not value numbered precisely. 1308 if (!success) { 1309 delete PREInstr; 1310 BI++; 1311 continue; 1312 } 1313 1314 PREInstr->insertBefore(PREPred->getTerminator()); 1315 PREInstr->setName(BI->getName() + ".pre"); 1316 predMap[PREPred] = PREInstr; 1317 VN.add(PREInstr, valno); 1318 NumGVNPRE++; 1319 1320 // Update the availability map to include the new instruction. 1321 localAvail[PREPred]->table.insert(std::make_pair(valno, PREInstr)); 1322 1323 // Create a PHI to make the value available in this block. 1324 PHINode* Phi = PHINode::Create(BI->getType(), 1325 BI->getName() + ".pre-phi", 1326 CurrentBlock->begin()); 1327 for (pred_iterator PI = pred_begin(CurrentBlock), 1328 PE = pred_end(CurrentBlock); PI != PE; ++PI) 1329 Phi->addIncoming(predMap[*PI], *PI); 1330 1331 VN.add(Phi, valno); 1332 localAvail[CurrentBlock]->table[valno] = Phi; 1333 1334 BI->replaceAllUsesWith(Phi); 1335 VN.erase(BI); 1336 1337 Instruction* erase = BI; 1338 BI++; 1339 erase->eraseFromParent(); 1340 1341 changed = true; 1342 } 1343 } 1344 1345 for (SmallVector<std::pair<TerminatorInst*, unsigned>, 4>::iterator 1346 I = toSplit.begin(), E = toSplit.end(); I != E; ++I) 1347 SplitCriticalEdge(I->first, I->second, this); 1348 1349 return changed || toSplit.size(); 1350} 1351 1352// iterateOnFunction - Executes one iteration of GVN 1353bool GVN::iterateOnFunction(Function &F) { 1354 DominatorTree &DT = getAnalysis<DominatorTree>(); 1355 1356 cleanupGlobalSets(); 1357 1358 // Top-down walk of the dominator tree 1359 bool changed = false; 1360 for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()), 1361 DE = df_end(DT.getRootNode()); DI != DE; ++DI) 1362 changed |= processBlock(*DI); 1363 1364 return changed; 1365} 1366 1367void GVN::cleanupGlobalSets() { 1368 VN.clear(); 1369 phiMap.clear(); 1370 1371 for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator 1372 I = localAvail.begin(), E = localAvail.end(); I != E; ++I) 1373 delete I->second; 1374 localAvail.clear(); 1375} 1376