lib/Transforms/Scalar/GVNPRE.cpp

   1 //===- GVNPRE.cpp - Eliminate redundant values and expressions ------------===//
   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 a hybrid of global value numbering and partial redundancy
  11 // elimination, known as GVN-PRE.  It performs partial redundancy elimination on
  12 // values, rather than lexical expressions, allowing a more comprehensive view
  13 // the optimization.  It replaces redundant values with uses of earlier
  14 // occurences of the same value.  While this is beneficial in that it eliminates
  15 // unneeded computation, it also increases register pressure by creating large
  16 // live ranges, and should be used with caution on platforms that are very
  17 // sensitive to register pressure.
  18 //
  19 // Note that this pass does the value numbering itself, it does not use the
  20 // ValueNumbering analysis passes.
  21 //
  22 //===----------------------------------------------------------------------===//
  23
  24 #define DEBUG_TYPE "gvnpre"
  25 #include "llvm/Value.h"
  26 #include "llvm/Transforms/Scalar.h"
  27 #include "llvm/Instructions.h"
  28 #include "llvm/Function.h"
  29 #include "llvm/DerivedTypes.h"
  30 #include "llvm/Analysis/Dominators.h"
  31 #include "llvm/ADT/BitVector.h"
  32 #include "llvm/ADT/DenseMap.h"
  33 #include "llvm/ADT/DepthFirstIterator.h"
  34 #include "llvm/ADT/PostOrderIterator.h"
  35 #include "llvm/ADT/SmallPtrSet.h"
  36 #include "llvm/ADT/SmallVector.h"
  37 #include "llvm/ADT/Statistic.h"
  38 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
  39 #include "llvm/Support/CFG.h"
  40 #include "llvm/Support/Compiler.h"
  41 #include "llvm/Support/Debug.h"
  42 #include <algorithm>
  43 #include <deque>
  44 #include <map>
  45 using namespace llvm;
  46
  47 //===----------------------------------------------------------------------===//
  48 //                         ValueTable Class
  49 //===----------------------------------------------------------------------===//
  50
  51 namespace {
  52
  53 /// This class holds the mapping between values and value numbers.  It is used
  54 /// as an efficient mechanism to determine the expression-wise equivalence of
  55 /// two values.
  56
  57 struct Expression {
  58   enum ExpressionOpcode { ADD, SUB, MUL, UDIV, SDIV, FDIV, UREM, SREM,
  59                           FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ,
  60                           ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE,
  61                           ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ,
  62                           FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE,
  63                           FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE,
  64                           FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT,
  65                           SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI,
  66                           FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT,
  67                           PTRTOINT, INTTOPTR, BITCAST, GEP, EMPTY,
  68                           TOMBSTONE };
  69
  70   ExpressionOpcode opcode;
  71   const Type* type;
  72   uint32_t firstVN;
  73   uint32_t secondVN;
  74   uint32_t thirdVN;
  75   SmallVector<uint32_t, 4> varargs;
  76
  77   Expression() { }
  78   explicit 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 (firstVN != other.firstVN)
  88       return false;
  89     else if (secondVN != other.secondVN)
  90       return false;
  91     else if (thirdVN != other.thirdVN)
  92       return false;
  93     else {
  94       if (varargs.size() != other.varargs.size())
  95         return false;
  96
  97       for (size_t i = 0; i < varargs.size(); ++i)
  98         if (varargs[i] != other.varargs[i])
  99           return false;
 100
 101       return true;
 102     }
 103   }
 104
 105   bool operator!=(const Expression &other) const {
 106     if (opcode != other.opcode)
 107       return true;
 108     else if (opcode == EMPTY || opcode == TOMBSTONE)
 109       return false;
 110     else if (type != other.type)
 111       return true;
 112     else if (firstVN != other.firstVN)
 113       return true;
 114     else if (secondVN != other.secondVN)
 115       return true;
 116     else if (thirdVN != other.thirdVN)
 117       return true;
 118     else {
 119       if (varargs.size() != other.varargs.size())
 120         return true;
 121
 122       for (size_t i = 0; i < varargs.size(); ++i)
 123         if (varargs[i] != other.varargs[i])
 124           return true;
 125
 126       return false;
 127     }
 128   }
 129 };
 130
 131 }
 132
 133 namespace {
 134   class VISIBILITY_HIDDEN ValueTable {
 135     private:
 136       DenseMap<Value*, uint32_t> valueNumbering;
 137       DenseMap<Expression, uint32_t> expressionNumbering;
 138
 139       uint32_t nextValueNumber;
 140
 141       Expression::ExpressionOpcode getOpcode(BinaryOperator* BO);
 142       Expression::ExpressionOpcode getOpcode(CmpInst* C);
 143       Expression::ExpressionOpcode getOpcode(CastInst* C);
 144       Expression create_expression(BinaryOperator* BO);
 145       Expression create_expression(CmpInst* C);
 146       Expression create_expression(ShuffleVectorInst* V);
 147       Expression create_expression(ExtractElementInst* C);
 148       Expression create_expression(InsertElementInst* V);
 149       Expression create_expression(SelectInst* V);
 150       Expression create_expression(CastInst* C);
 151       Expression create_expression(GetElementPtrInst* G);
 152     public:
 153       ValueTable() { nextValueNumber = 1; }
 154       uint32_t lookup_or_add(Value* V);
 155       uint32_t lookup(Value* V) const;
 156       void add(Value* V, uint32_t num);
 157       void clear();
 158       void erase(Value* v);
 159       unsigned size();
 160   };
 161 }
 162
 163 namespace llvm {
 164 template <> struct DenseMapInfo<Expression> {
 165   static inline Expression getEmptyKey() {
 166     return Expression(Expression::EMPTY);
 167   }
 168
 169   static inline Expression getTombstoneKey() {
 170     return Expression(Expression::TOMBSTONE);
 171   }
 172
 173   static unsigned getHashValue(const Expression e) {
 174     unsigned hash = e.opcode;
 175
 176     hash = e.firstVN + hash * 37;
 177     hash = e.secondVN + hash * 37;
 178     hash = e.thirdVN + hash * 37;
 179
 180     hash = ((unsigned)((uintptr_t)e.type >> 4) ^
 181             (unsigned)((uintptr_t)e.type >> 9)) +
 182            hash * 37;
 183
 184     for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(),
 185          E = e.varargs.end(); I != E; ++I)
 186       hash = *I + hash * 37;
 187
 188     return hash;
 189   }
 190   static bool isEqual(const Expression &LHS, const Expression &RHS) {
 191     return LHS == RHS;
 192   }
 193   static bool isPod() { return true; }
 194 };
 195 }
 196
 197 //===----------------------------------------------------------------------===//
 198 //                     ValueTable Internal Functions
 199 //===----------------------------------------------------------------------===//
 200 Expression::ExpressionOpcode
 201                              ValueTable::getOpcode(BinaryOperator* BO) {
 202   switch(BO->getOpcode()) {
 203     case Instruction::Add:
 204       return Expression::ADD;
 205     case Instruction::Sub:
 206       return Expression::SUB;
 207     case Instruction::Mul:
 208       return Expression::MUL;
 209     case Instruction::UDiv:
 210       return Expression::UDIV;
 211     case Instruction::SDiv:
 212       return Expression::SDIV;
 213     case Instruction::FDiv:
 214       return Expression::FDIV;
 215     case Instruction::URem:
 216       return Expression::UREM;
 217     case Instruction::SRem:
 218       return Expression::SREM;
 219     case Instruction::FRem:
 220       return Expression::FREM;
 221     case Instruction::Shl:
 222       return Expression::SHL;
 223     case Instruction::LShr:
 224       return Expression::LSHR;
 225     case Instruction::AShr:
 226       return Expression::ASHR;
 227     case Instruction::And:
 228       return Expression::AND;
 229     case Instruction::Or:
 230       return Expression::OR;
 231     case Instruction::Xor:
 232       return Expression::XOR;
 233
 234     // THIS SHOULD NEVER HAPPEN
 235     default:
 236       assert(0 && "Binary operator with unknown opcode?");
 237       return Expression::ADD;
 238   }
 239 }
 240
 241 Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) {
 242   if (C->getOpcode() == Instruction::ICmp) {
 243     switch (C->getPredicate()) {
 244       case ICmpInst::ICMP_EQ:
 245         return Expression::ICMPEQ;
 246       case ICmpInst::ICMP_NE:
 247         return Expression::ICMPNE;
 248       case ICmpInst::ICMP_UGT:
 249         return Expression::ICMPUGT;
 250       case ICmpInst::ICMP_UGE:
 251         return Expression::ICMPUGE;
 252       case ICmpInst::ICMP_ULT:
 253         return Expression::ICMPULT;
 254       case ICmpInst::ICMP_ULE:
 255         return Expression::ICMPULE;
 256       case ICmpInst::ICMP_SGT:
 257         return Expression::ICMPSGT;
 258       case ICmpInst::ICMP_SGE:
 259         return Expression::ICMPSGE;
 260       case ICmpInst::ICMP_SLT:
 261         return Expression::ICMPSLT;
 262       case ICmpInst::ICMP_SLE:
 263         return Expression::ICMPSLE;
 264
 265       // THIS SHOULD NEVER HAPPEN
 266       default:
 267         assert(0 && "Comparison with unknown predicate?");
 268         return Expression::ICMPEQ;
 269     }
 270   } else {
 271     switch (C->getPredicate()) {
 272       case FCmpInst::FCMP_OEQ:
 273         return Expression::FCMPOEQ;
 274       case FCmpInst::FCMP_OGT:
 275         return Expression::FCMPOGT;
 276       case FCmpInst::FCMP_OGE:
 277         return Expression::FCMPOGE;
 278       case FCmpInst::FCMP_OLT:
 279         return Expression::FCMPOLT;
 280       case FCmpInst::FCMP_OLE:
 281         return Expression::FCMPOLE;
 282       case FCmpInst::FCMP_ONE:
 283         return Expression::FCMPONE;
 284       case FCmpInst::FCMP_ORD:
 285         return Expression::FCMPORD;
 286       case FCmpInst::FCMP_UNO:
 287         return Expression::FCMPUNO;
 288       case FCmpInst::FCMP_UEQ:
 289         return Expression::FCMPUEQ;
 290       case FCmpInst::FCMP_UGT:
 291         return Expression::FCMPUGT;
 292       case FCmpInst::FCMP_UGE:
 293         return Expression::FCMPUGE;
 294       case FCmpInst::FCMP_ULT:
 295         return Expression::FCMPULT;
 296       case FCmpInst::FCMP_ULE:
 297         return Expression::FCMPULE;
 298       case FCmpInst::FCMP_UNE:
 299         return Expression::FCMPUNE;
 300
 301       // THIS SHOULD NEVER HAPPEN
 302       default:
 303         assert(0 && "Comparison with unknown predicate?");
 304         return Expression::FCMPOEQ;
 305     }
 306   }
 307 }
 308
 309 Expression::ExpressionOpcode
 310                              ValueTable::getOpcode(CastInst* C) {
 311   switch(C->getOpcode()) {
 312     case Instruction::Trunc:
 313       return Expression::TRUNC;
 314     case Instruction::ZExt:
 315       return Expression::ZEXT;
 316     case Instruction::SExt:
 317       return Expression::SEXT;
 318     case Instruction::FPToUI:
 319       return Expression::FPTOUI;
 320     case Instruction::FPToSI:
 321       return Expression::FPTOSI;
 322     case Instruction::UIToFP:
 323       return Expression::UITOFP;
 324     case Instruction::SIToFP:
 325       return Expression::SITOFP;
 326     case Instruction::FPTrunc:
 327       return Expression::FPTRUNC;
 328     case Instruction::FPExt:
 329       return Expression::FPEXT;
 330     case Instruction::PtrToInt:
 331       return Expression::PTRTOINT;
 332     case Instruction::IntToPtr:
 333       return Expression::INTTOPTR;
 334     case Instruction::BitCast:
 335       return Expression::BITCAST;
 336
 337     // THIS SHOULD NEVER HAPPEN
 338     default:
 339       assert(0 && "Cast operator with unknown opcode?");
 340       return Expression::BITCAST;
 341   }
 342 }
 343
 344 Expression ValueTable::create_expression(BinaryOperator* BO) {
 345   Expression e;
 346
 347   e.firstVN = lookup_or_add(BO->getOperand(0));
 348   e.secondVN = lookup_or_add(BO->getOperand(1));
 349   e.thirdVN = 0;
 350   e.type = BO->getType();
 351   e.opcode = getOpcode(BO);
 352
 353   return e;
 354 }
 355
 356 Expression ValueTable::create_expression(CmpInst* C) {
 357   Expression e;
 358
 359   e.firstVN = lookup_or_add(C->getOperand(0));
 360   e.secondVN = lookup_or_add(C->getOperand(1));
 361   e.thirdVN = 0;
 362   e.type = C->getType();
 363   e.opcode = getOpcode(C);
 364
 365   return e;
 366 }
 367
 368 Expression ValueTable::create_expression(CastInst* C) {
 369   Expression e;
 370
 371   e.firstVN = lookup_or_add(C->getOperand(0));
 372   e.secondVN = 0;
 373   e.thirdVN = 0;
 374   e.type = C->getType();
 375   e.opcode = getOpcode(C);
 376
 377   return e;
 378 }
 379
 380 Expression ValueTable::create_expression(ShuffleVectorInst* S) {
 381   Expression e;
 382
 383   e.firstVN = lookup_or_add(S->getOperand(0));
 384   e.secondVN = lookup_or_add(S->getOperand(1));
 385   e.thirdVN = lookup_or_add(S->getOperand(2));
 386   e.type = S->getType();
 387   e.opcode = Expression::SHUFFLE;
 388
 389   return e;
 390 }
 391
 392 Expression ValueTable::create_expression(ExtractElementInst* E) {
 393   Expression e;
 394
 395   e.firstVN = lookup_or_add(E->getOperand(0));
 396   e.secondVN = lookup_or_add(E->getOperand(1));
 397   e.thirdVN = 0;
 398   e.type = E->getType();
 399   e.opcode = Expression::EXTRACT;
 400
 401   return e;
 402 }
 403
 404 Expression ValueTable::create_expression(InsertElementInst* I) {
 405   Expression e;
 406
 407   e.firstVN = lookup_or_add(I->getOperand(0));
 408   e.secondVN = lookup_or_add(I->getOperand(1));
 409   e.thirdVN = lookup_or_add(I->getOperand(2));
 410   e.type = I->getType();
 411   e.opcode = Expression::INSERT;
 412
 413   return e;
 414 }
 415
 416 Expression ValueTable::create_expression(SelectInst* I) {
 417   Expression e;
 418
 419   e.firstVN = lookup_or_add(I->getCondition());
 420   e.secondVN = lookup_or_add(I->getTrueValue());
 421   e.thirdVN = lookup_or_add(I->getFalseValue());
 422   e.type = I->getType();
 423   e.opcode = Expression::SELECT;
 424
 425   return e;
 426 }
 427
 428 Expression ValueTable::create_expression(GetElementPtrInst* G) {
 429   Expression e;
 430
 431   e.firstVN = lookup_or_add(G->getPointerOperand());
 432   e.secondVN = 0;
 433   e.thirdVN = 0;
 434   e.type = G->getType();
 435   e.opcode = Expression::GEP;
 436
 437   for (GetElementPtrInst::op_iterator I = G->idx_begin(), E = G->idx_end();
 438        I != E; ++I)
 439     e.varargs.push_back(lookup_or_add(*I));
 440
 441   return e;
 442 }
 443
 444 //===----------------------------------------------------------------------===//
 445 //                     ValueTable External Functions
 446 //===----------------------------------------------------------------------===//
 447
 448 /// lookup_or_add - Returns the value number for the specified value, assigning
 449 /// it a new number if it did not have one before.
 450 uint32_t ValueTable::lookup_or_add(Value* V) {
 451   DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
 452   if (VI != valueNumbering.end())
 453     return VI->second;
 454
 455
 456   if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
 457     Expression e = create_expression(BO);
 458
 459     DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
 460     if (EI != expressionNumbering.end()) {
 461       valueNumbering.insert(std::make_pair(V, EI->second));
 462       return EI->second;
 463     } else {
 464       expressionNumbering.insert(std::make_pair(e, nextValueNumber));
 465       valueNumbering.insert(std::make_pair(V, nextValueNumber));
 466
 467       return nextValueNumber++;
 468     }
 469   } else if (CmpInst* C = dyn_cast<CmpInst>(V)) {
 470     Expression e = create_expression(C);
 471
 472     DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
 473     if (EI != expressionNumbering.end()) {
 474       valueNumbering.insert(std::make_pair(V, EI->second));
 475       return EI->second;
 476     } else {
 477       expressionNumbering.insert(std::make_pair(e, nextValueNumber));
 478       valueNumbering.insert(std::make_pair(V, nextValueNumber));
 479
 480       return nextValueNumber++;
 481     }
 482   } else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) {
 483     Expression e = create_expression(U);
 484
 485     DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
 486     if (EI != expressionNumbering.end()) {
 487       valueNumbering.insert(std::make_pair(V, EI->second));
 488       return EI->second;
 489     } else {
 490       expressionNumbering.insert(std::make_pair(e, nextValueNumber));
 491       valueNumbering.insert(std::make_pair(V, nextValueNumber));
 492
 493       return nextValueNumber++;
 494     }
 495   } else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) {
 496     Expression e = create_expression(U);
 497
 498     DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
 499     if (EI != expressionNumbering.end()) {
 500       valueNumbering.insert(std::make_pair(V, EI->second));
 501       return EI->second;
 502     } else {
 503       expressionNumbering.insert(std::make_pair(e, nextValueNumber));
 504       valueNumbering.insert(std::make_pair(V, nextValueNumber));
 505
 506       return nextValueNumber++;
 507     }
 508   } else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) {
 509     Expression e = create_expression(U);
 510
 511     DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
 512     if (EI != expressionNumbering.end()) {
 513       valueNumbering.insert(std::make_pair(V, EI->second));
 514       return EI->second;
 515     } else {
 516       expressionNumbering.insert(std::make_pair(e, nextValueNumber));
 517       valueNumbering.insert(std::make_pair(V, nextValueNumber));
 518
 519       return nextValueNumber++;
 520     }
 521   } else if (SelectInst* U = dyn_cast<SelectInst>(V)) {
 522     Expression e = create_expression(U);
 523
 524     DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
 525     if (EI != expressionNumbering.end()) {
 526       valueNumbering.insert(std::make_pair(V, EI->second));
 527       return EI->second;
 528     } else {
 529       expressionNumbering.insert(std::make_pair(e, nextValueNumber));
 530       valueNumbering.insert(std::make_pair(V, nextValueNumber));
 531
 532       return nextValueNumber++;
 533     }
 534   } else if (CastInst* U = dyn_cast<CastInst>(V)) {
 535     Expression e = create_expression(U);
 536
 537     DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
 538     if (EI != expressionNumbering.end()) {
 539       valueNumbering.insert(std::make_pair(V, EI->second));
 540       return EI->second;
 541     } else {
 542       expressionNumbering.insert(std::make_pair(e, nextValueNumber));
 543       valueNumbering.insert(std::make_pair(V, nextValueNumber));
 544
 545       return nextValueNumber++;
 546     }
 547   } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) {
 548     Expression e = create_expression(U);
 549
 550     DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
 551     if (EI != expressionNumbering.end()) {
 552       valueNumbering.insert(std::make_pair(V, EI->second));
 553       return EI->second;
 554     } else {
 555       expressionNumbering.insert(std::make_pair(e, nextValueNumber));
 556       valueNumbering.insert(std::make_pair(V, nextValueNumber));
 557
 558       return nextValueNumber++;
 559     }
 560   } else {
 561     valueNumbering.insert(std::make_pair(V, nextValueNumber));
 562     return nextValueNumber++;
 563   }
 564 }
 565
 566 /// lookup - Returns the value number of the specified value. Fails if
 567 /// the value has not yet been numbered.
 568 uint32_t ValueTable::lookup(Value* V) const {
 569   DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
 570   if (VI != valueNumbering.end())
 571     return VI->second;
 572   else
 573     assert(0 && "Value not numbered?");
 574
 575   return 0;
 576 }
 577
 578 /// add - Add the specified value with the given value number, removing
 579 /// its old number, if any
 580 void ValueTable::add(Value* V, uint32_t num) {
 581   DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
 582   if (VI != valueNumbering.end())
 583     valueNumbering.erase(VI);
 584   valueNumbering.insert(std::make_pair(V, num));
 585 }
 586
 587 /// clear - Remove all entries from the ValueTable
 588 void ValueTable::clear() {
 589   valueNumbering.clear();
 590   expressionNumbering.clear();
 591   nextValueNumber = 1;
 592 }
 593
 594 /// erase - Remove a value from the value numbering
 595 void ValueTable::erase(Value* V) {
 596   valueNumbering.erase(V);
 597 }
 598
 599 /// size - Return the number of assigned value numbers
 600 unsigned ValueTable::size() {
 601   // NOTE: zero is never assigned
 602   return nextValueNumber;
 603 }
 604
 605 namespace {
 606
 607 //===----------------------------------------------------------------------===//
 608 //                       ValueNumberedSet Class
 609 //===----------------------------------------------------------------------===//
 610
 611 class ValueNumberedSet {
 612   private:
 613     SmallPtrSet<Value*, 8> contents;
 614     BitVector numbers;
 615   public:
 616     ValueNumberedSet() { numbers.resize(1); }
 617     ValueNumberedSet(const ValueNumberedSet& other) {
 618       numbers = other.numbers;
 619       contents = other.contents;
 620     }
 621
 622     typedef SmallPtrSet<Value*, 8>::iterator iterator;
 623
 624     iterator begin() { return contents.begin(); }
 625     iterator end() { return contents.end(); }
 626
 627     bool insert(Value* v) { return contents.insert(v); }
 628     void insert(iterator I, iterator E) { contents.insert(I, E); }
 629     void erase(Value* v) { contents.erase(v); }
 630     unsigned count(Value* v) { return contents.count(v); }
 631     size_t size() { return contents.size(); }
 632
 633     void set(unsigned i)  {
 634       if (i >= numbers.size())
 635         numbers.resize(i+1);
 636
 637       numbers.set(i);
 638     }
 639
 640     void operator=(const ValueNumberedSet& other) {
 641       contents = other.contents;
 642       numbers = other.numbers;
 643     }
 644
 645     void reset(unsigned i)  {
 646       if (i < numbers.size())
 647         numbers.reset(i);
 648     }
 649
 650     bool test(unsigned i)  {
 651       if (i >= numbers.size())
 652         return false;
 653
 654       return numbers.test(i);
 655     }
 656
 657     void clear() {
 658       contents.clear();
 659       numbers.clear();
 660     }
 661 };
 662
 663 }
 664
 665 //===----------------------------------------------------------------------===//
 666 //                         GVNPRE Pass
 667 //===----------------------------------------------------------------------===//
 668
 669 namespace {
 670
 671   class VISIBILITY_HIDDEN GVNPRE : public FunctionPass {
 672     bool runOnFunction(Function &F);
 673   public:
 674     static char ID; // Pass identification, replacement for typeid
 675     GVNPRE() : FunctionPass(&ID) {}
 676
 677   private:
 678     ValueTable VN;
 679     SmallVector<Instruction*, 8> createdExpressions;
 680
 681     DenseMap<BasicBlock*, ValueNumberedSet> availableOut;
 682     DenseMap<BasicBlock*, ValueNumberedSet> anticipatedIn;
 683     DenseMap<BasicBlock*, ValueNumberedSet> generatedPhis;
 684
 685     // This transformation requires dominator postdominator info
 686     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
 687       AU.setPreservesCFG();
 688       AU.addRequiredID(BreakCriticalEdgesID);
 689       AU.addRequired<UnifyFunctionExitNodes>();
 690       AU.addRequired<DominatorTree>();
 691     }
 692
 693     // Helper fuctions
 694     // FIXME: eliminate or document these better
 695     void dump(ValueNumberedSet& s) const ;
 696     void clean(ValueNumberedSet& set) ;
 697     Value* find_leader(ValueNumberedSet& vals, uint32_t v) ;
 698     Value* phi_translate(Value* V, BasicBlock* pred, BasicBlock* succ) ;
 699     void phi_translate_set(ValueNumberedSet& anticIn, BasicBlock* pred,
 700                            BasicBlock* succ, ValueNumberedSet& out) ;
 701
 702     void topo_sort(ValueNumberedSet& set,
 703                    SmallVector<Value*, 8>& vec) ;
 704
 705     void cleanup() ;
 706     bool elimination() ;
 707
 708     void val_insert(ValueNumberedSet& s, Value* v) ;
 709     void val_replace(ValueNumberedSet& s, Value* v) ;
 710     bool dependsOnInvoke(Value* V) ;
 711     void buildsets_availout(BasicBlock::iterator I,
 712                             ValueNumberedSet& currAvail,
 713                             ValueNumberedSet& currPhis,
 714                             ValueNumberedSet& currExps,
 715                             SmallPtrSet<Value*, 16>& currTemps);
 716     bool buildsets_anticout(BasicBlock* BB,
 717                             ValueNumberedSet& anticOut,
 718                             SmallPtrSet<BasicBlock*, 8>& visited);
 719     unsigned buildsets_anticin(BasicBlock* BB,
 720                            ValueNumberedSet& anticOut,
 721                            ValueNumberedSet& currExps,
 722                            SmallPtrSet<Value*, 16>& currTemps,
 723                            SmallPtrSet<BasicBlock*, 8>& visited);
 724     void buildsets(Function& F) ;
 725
 726     void insertion_pre(Value* e, BasicBlock* BB,
 727                        DenseMap<BasicBlock*, Value*>& avail,
 728                        std::map<BasicBlock*,ValueNumberedSet>& new_set);
 729     unsigned insertion_mergepoint(SmallVector<Value*, 8>& workList,
 730                                   df_iterator<DomTreeNode*>& D,
 731                       std::map<BasicBlock*, ValueNumberedSet>& new_set);
 732     bool insertion(Function& F) ;
 733
 734   };
 735
 736   char GVNPRE::ID = 0;
 737
 738 }
 739
 740 // createGVNPREPass - The public interface to this file...
 741 FunctionPass *llvm::createGVNPREPass() { return new GVNPRE(); }
 742
 743 static RegisterPass<GVNPRE> X("gvnpre",
 744                       "Global Value Numbering/Partial Redundancy Elimination");
 745
 746
 747 STATISTIC(NumInsertedVals, "Number of values inserted");
 748 STATISTIC(NumInsertedPhis, "Number of PHI nodes inserted");
 749 STATISTIC(NumEliminated, "Number of redundant instructions eliminated");
 750
 751 /// find_leader - Given a set and a value number, return the first
 752 /// element of the set with that value number, or 0 if no such element
 753 /// is present
 754 Value* GVNPRE::find_leader(ValueNumberedSet& vals, uint32_t v) {
 755   if (!vals.test(v))
 756     return 0;
 757
 758   for (ValueNumberedSet::iterator I = vals.begin(), E = vals.end();
 759        I != E; ++I)
 760     if (v == VN.lookup(*I))
 761       return *I;
 762
 763   assert(0 && "No leader found, but present bit is set?");
 764   return 0;
 765 }
 766
 767 /// val_insert - Insert a value into a set only if there is not a value
 768 /// with the same value number already in the set
 769 void GVNPRE::val_insert(ValueNumberedSet& s, Value* v) {
 770   uint32_t num = VN.lookup(v);
 771   if (!s.test(num))
 772     s.insert(v);
 773 }
 774
 775 /// val_replace - Insert a value into a set, replacing any values already in
 776 /// the set that have the same value number
 777 void GVNPRE::val_replace(ValueNumberedSet& s, Value* v) {
 778   if (s.count(v)) return;
 779
 780   uint32_t num = VN.lookup(v);
 781   Value* leader = find_leader(s, num);
 782   if (leader != 0)
 783     s.erase(leader);
 784   s.insert(v);
 785   s.set(num);
 786 }
 787
 788 /// phi_translate - Given a value, its parent block, and a predecessor of its
 789 /// parent, translate the value into legal for the predecessor block.  This
 790 /// means translating its operands (and recursively, their operands) through
 791 /// any phi nodes in the parent into values available in the predecessor
 792 Value* GVNPRE::phi_translate(Value* V, BasicBlock* pred, BasicBlock* succ) {
 793   if (V == 0)
 794     return 0;
 795
 796   // Unary Operations
 797   if (CastInst* U = dyn_cast<CastInst>(V)) {
 798     Value* newOp1 = 0;
 799     if (isa<Instruction>(U->getOperand(0)))
 800       newOp1 = phi_translate(U->getOperand(0), pred, succ);
 801     else
 802       newOp1 = U->getOperand(0);
 803
 804     if (newOp1 == 0)
 805       return 0;
 806
 807     if (newOp1 != U->getOperand(0)) {
 808       Instruction* newVal = 0;
 809       if (CastInst* C = dyn_cast<CastInst>(U))
 810         newVal = CastInst::Create(C->getOpcode(),
 811                                   newOp1, C->getType(),
 812                                   C->getName()+".expr");
 813
 814       uint32_t v = VN.lookup_or_add(newVal);
 815
 816       Value* leader = find_leader(availableOut[pred], v);
 817       if (leader == 0) {
 818         createdExpressions.push_back(newVal);
 819         return newVal;
 820       } else {
 821         VN.erase(newVal);
 822         delete newVal;
 823         return leader;
 824       }
 825     }
 826
 827   // Binary Operations
 828   } if (isa<BinaryOperator>(V) || isa<CmpInst>(V) ||
 829       isa<ExtractElementInst>(V)) {
 830     User* U = cast<User>(V);
 831
 832     Value* newOp1 = 0;
 833     if (isa<Instruction>(U->getOperand(0)))
 834       newOp1 = phi_translate(U->getOperand(0), pred, succ);
 835     else
 836       newOp1 = U->getOperand(0);
 837
 838     if (newOp1 == 0)
 839       return 0;
 840
 841     Value* newOp2 = 0;
 842     if (isa<Instruction>(U->getOperand(1)))
 843       newOp2 = phi_translate(U->getOperand(1), pred, succ);
 844     else
 845       newOp2 = U->getOperand(1);
 846
 847     if (newOp2 == 0)
 848       return 0;
 849
 850     if (newOp1 != U->getOperand(0) || newOp2 != U->getOperand(1)) {
 851       Instruction* newVal = 0;
 852       if (BinaryOperator* BO = dyn_cast<BinaryOperator>(U))
 853         newVal = BinaryOperator::Create(BO->getOpcode(),
 854                                         newOp1, newOp2,
 855                                         BO->getName()+".expr");
 856       else if (CmpInst* C = dyn_cast<CmpInst>(U))
 857         newVal = CmpInst::Create(C->getOpcode(),
 858                                  C->getPredicate(),
 859                                  newOp1, newOp2,
 860                                  C->getName()+".expr");
 861       else if (ExtractElementInst* E = dyn_cast<ExtractElementInst>(U))
 862         newVal = new ExtractElementInst(newOp1, newOp2, E->getName()+".expr");
 863
 864       uint32_t v = VN.lookup_or_add(newVal);
 865
 866       Value* leader = find_leader(availableOut[pred], v);
 867       if (leader == 0) {
 868         createdExpressions.push_back(newVal);
 869         return newVal;
 870       } else {
 871         VN.erase(newVal);
 872         delete newVal;
 873         return leader;
 874       }
 875     }
 876
 877   // Ternary Operations
 878   } else if (isa<ShuffleVectorInst>(V) || isa<InsertElementInst>(V) ||
 879              isa<SelectInst>(V)) {
 880     User* U = cast<User>(V);
 881
 882     Value* newOp1 = 0;
 883     if (isa<Instruction>(U->getOperand(0)))
 884       newOp1 = phi_translate(U->getOperand(0), pred, succ);
 885     else
 886       newOp1 = U->getOperand(0);
 887
 888     if (newOp1 == 0)
 889       return 0;
 890
 891     Value* newOp2 = 0;
 892     if (isa<Instruction>(U->getOperand(1)))
 893       newOp2 = phi_translate(U->getOperand(1), pred, succ);
 894     else
 895       newOp2 = U->getOperand(1);
 896
 897     if (newOp2 == 0)
 898       return 0;
 899
 900     Value* newOp3 = 0;
 901     if (isa<Instruction>(U->getOperand(2)))
 902       newOp3 = phi_translate(U->getOperand(2), pred, succ);
 903     else
 904       newOp3 = U->getOperand(2);
 905
 906     if (newOp3 == 0)
 907       return 0;
 908
 909     if (newOp1 != U->getOperand(0) ||
 910         newOp2 != U->getOperand(1) ||
 911         newOp3 != U->getOperand(2)) {
 912       Instruction* newVal = 0;
 913       if (ShuffleVectorInst* S = dyn_cast<ShuffleVectorInst>(U))
 914         newVal = new ShuffleVectorInst(newOp1, newOp2, newOp3,
 915                                        S->getName() + ".expr");
 916       else if (InsertElementInst* I = dyn_cast<InsertElementInst>(U))
 917         newVal = InsertElementInst::Create(newOp1, newOp2, newOp3,
 918                                            I->getName() + ".expr");
 919       else if (SelectInst* I = dyn_cast<SelectInst>(U))
 920         newVal = SelectInst::Create(newOp1, newOp2, newOp3,
 921                                     I->getName() + ".expr");
 922
 923       uint32_t v = VN.lookup_or_add(newVal);
 924
 925       Value* leader = find_leader(availableOut[pred], v);
 926       if (leader == 0) {
 927         createdExpressions.push_back(newVal);
 928         return newVal;
 929       } else {
 930         VN.erase(newVal);
 931         delete newVal;
 932         return leader;
 933       }
 934     }
 935
 936   // Varargs operators
 937   } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) {
 938     Value* newOp1 = 0;
 939     if (isa<Instruction>(U->getPointerOperand()))
 940       newOp1 = phi_translate(U->getPointerOperand(), pred, succ);
 941     else
 942       newOp1 = U->getPointerOperand();
 943
 944     if (newOp1 == 0)
 945       return 0;
 946
 947     bool changed_idx = false;
 948     SmallVector<Value*, 4> newIdx;
 949     for (GetElementPtrInst::op_iterator I = U->idx_begin(), E = U->idx_end();
 950          I != E; ++I)
 951       if (isa<Instruction>(*I)) {
 952         Value* newVal = phi_translate(*I, pred, succ);
 953         newIdx.push_back(newVal);
 954         if (newVal != *I)
 955           changed_idx = true;
 956       } else {
 957         newIdx.push_back(*I);
 958       }
 959
 960     if (newOp1 != U->getPointerOperand() || changed_idx) {
 961       Instruction* newVal =
 962           GetElementPtrInst::Create(newOp1,
 963                                     newIdx.begin(), newIdx.end(),
 964                                     U->getName()+".expr");
 965
 966       uint32_t v = VN.lookup_or_add(newVal);
 967
 968       Value* leader = find_leader(availableOut[pred], v);
 969       if (leader == 0) {
 970         createdExpressions.push_back(newVal);
 971         return newVal;
 972       } else {
 973         VN.erase(newVal);
 974         delete newVal;
 975         return leader;
 976       }
 977     }
 978
 979   // PHI Nodes
 980   } else if (PHINode* P = dyn_cast<PHINode>(V)) {
 981     if (P->getParent() == succ)
 982       return P->getIncomingValueForBlock(pred);
 983   }
 984
 985   return V;
 986 }
 987
 988 /// phi_translate_set - Perform phi translation on every element of a set
 989 void GVNPRE::phi_translate_set(ValueNumberedSet& anticIn,
 990                               BasicBlock* pred, BasicBlock* succ,
 991                               ValueNumberedSet& out) {
 992   for (ValueNumberedSet::iterator I = anticIn.begin(),
 993        E = anticIn.end(); I != E; ++I) {
 994     Value* V = phi_translate(*I, pred, succ);
 995     if (V != 0 && !out.test(VN.lookup_or_add(V))) {
 996       out.insert(V);
 997       out.set(VN.lookup(V));
 998     }
 999   }
1000 }
1001
1002 /// dependsOnInvoke - Test if a value has an phi node as an operand, any of
1003 /// whose inputs is an invoke instruction.  If this is true, we cannot safely
1004 /// PRE the instruction or anything that depends on it.
1005 bool GVNPRE::dependsOnInvoke(Value* V) {
1006   if (PHINode* p = dyn_cast<PHINode>(V)) {
1007     for (PHINode::op_iterator I = p->op_begin(), E = p->op_end(); I != E; ++I)
1008       if (isa<InvokeInst>(*I))
1009         return true;
1010     return false;
1011   } else {
1012     return false;
1013   }
1014 }
1015
1016 /// clean - Remove all non-opaque values from the set whose operands are not
1017 /// themselves in the set, as well as all values that depend on invokes (see
1018 /// above)
1019 void GVNPRE::clean(ValueNumberedSet& set) {
1020   SmallVector<Value*, 8> worklist;
1021   worklist.reserve(set.size());
1022   topo_sort(set, worklist);
1023
1024   for (unsigned i = 0; i < worklist.size(); ++i) {
1025     Value* v = worklist[i];
1026
1027     // Handle unary ops
1028     if (CastInst* U = dyn_cast<CastInst>(v)) {
1029       bool lhsValid = !isa<Instruction>(U->getOperand(0));
1030       lhsValid |= set.test(VN.lookup(U->getOperand(0)));
1031       if (lhsValid)
1032         lhsValid = !dependsOnInvoke(U->getOperand(0));
1033
1034       if (!lhsValid) {
1035         set.erase(U);
1036         set.reset(VN.lookup(U));
1037       }
1038
1039     // Handle binary ops
1040     } else if (isa<BinaryOperator>(v) || isa<CmpInst>(v) ||
1041         isa<ExtractElementInst>(v)) {
1042       User* U = cast<User>(v);
1043
1044       bool lhsValid = !isa<Instruction>(U->getOperand(0));
1045       lhsValid |= set.test(VN.lookup(U->getOperand(0)));
1046       if (lhsValid)
1047         lhsValid = !dependsOnInvoke(U->getOperand(0));
1048
1049       bool rhsValid = !isa<Instruction>(U->getOperand(1));
1050       rhsValid |= set.test(VN.lookup(U->getOperand(1)));
1051       if (rhsValid)
1052         rhsValid = !dependsOnInvoke(U->getOperand(1));
1053
1054       if (!lhsValid || !rhsValid) {
1055         set.erase(U);
1056         set.reset(VN.lookup(U));
1057       }
1058
1059     // Handle ternary ops
1060     } else if (isa<ShuffleVectorInst>(v) || isa<InsertElementInst>(v) ||
1061                isa<SelectInst>(v)) {
1062       User* U = cast<User>(v);
1063
1064       bool lhsValid = !isa<Instruction>(U->getOperand(0));
1065       lhsValid |= set.test(VN.lookup(U->getOperand(0)));
1066       if (lhsValid)
1067         lhsValid = !dependsOnInvoke(U->getOperand(0));
1068
1069       bool rhsValid = !isa<Instruction>(U->getOperand(1));
1070       rhsValid |= set.test(VN.lookup(U->getOperand(1)));
1071       if (rhsValid)
1072         rhsValid = !dependsOnInvoke(U->getOperand(1));
1073
1074       bool thirdValid = !isa<Instruction>(U->getOperand(2));
1075       thirdValid |= set.test(VN.lookup(U->getOperand(2)));
1076       if (thirdValid)
1077         thirdValid = !dependsOnInvoke(U->getOperand(2));
1078
1079       if (!lhsValid || !rhsValid || !thirdValid) {
1080         set.erase(U);
1081         set.reset(VN.lookup(U));
1082       }
1083
1084     // Handle varargs ops
1085     } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(v)) {
1086       bool ptrValid = !isa<Instruction>(U->getPointerOperand());
1087       ptrValid |= set.test(VN.lookup(U->getPointerOperand()));
1088       if (ptrValid)
1089         ptrValid = !dependsOnInvoke(U->getPointerOperand());
1090
1091       bool varValid = true;
1092       for (GetElementPtrInst::op_iterator I = U->idx_begin(), E = U->idx_end();
1093            I != E; ++I)
1094         if (varValid) {
1095           varValid &= !isa<Instruction>(*I) || set.test(VN.lookup(*I));
1096           varValid &= !dependsOnInvoke(*I);
1097         }
1098
1099       if (!ptrValid || !varValid) {
1100         set.erase(U);
1101         set.reset(VN.lookup(U));
1102       }
1103     }
1104   }
1105 }
1106
1107 /// topo_sort - Given a set of values, sort them by topological
1108 /// order into the provided vector.
1109 void GVNPRE::topo_sort(ValueNumberedSet& set, SmallVector<Value*, 8>& vec) {
1110   SmallPtrSet<Value*, 16> visited;
1111   SmallVector<Value*, 8> stack;
1112   for (ValueNumberedSet::iterator I = set.begin(), E = set.end();
1113        I != E; ++I) {
1114     if (visited.count(*I) == 0)
1115       stack.push_back(*I);
1116
1117     while (!stack.empty()) {
1118       Value* e = stack.back();
1119
1120       // Handle unary ops
1121       if (CastInst* U = dyn_cast<CastInst>(e)) {
1122         Value* l = find_leader(set, VN.lookup(U->getOperand(0)));
1123
1124         if (l != 0 && isa<Instruction>(l) &&
1125             visited.count(l) == 0)
1126           stack.push_back(l);
1127         else {
1128           vec.push_back(e);
1129           visited.insert(e);
1130           stack.pop_back();
1131         }
1132
1133       // Handle binary ops
1134       } else if (isa<BinaryOperator>(e) || isa<CmpInst>(e) ||
1135           isa<ExtractElementInst>(e)) {
1136         User* U = cast<User>(e);
1137         Value* l = find_leader(set, VN.lookup(U->getOperand(0)));
1138         Value* r = find_leader(set, VN.lookup(U->getOperand(1)));
1139
1140         if (l != 0 && isa<Instruction>(l) &&
1141             visited.count(l) == 0)
1142           stack.push_back(l);
1143         else if (r != 0 && isa<Instruction>(r) &&
1144                  visited.count(r) == 0)
1145           stack.push_back(r);
1146         else {
1147           vec.push_back(e);
1148           visited.insert(e);
1149           stack.pop_back();
1150         }
1151
1152       // Handle ternary ops
1153       } else if (isa<InsertElementInst>(e) || isa<ShuffleVectorInst>(e) ||
1154                  isa<SelectInst>(e)) {
1155         User* U = cast<User>(e);
1156         Value* l = find_leader(set, VN.lookup(U->getOperand(0)));
1157         Value* r = find_leader(set, VN.lookup(U->getOperand(1)));
1158         Value* m = find_leader(set, VN.lookup(U->getOperand(2)));
1159
1160         if (l != 0 && isa<Instruction>(l) &&
1161             visited.count(l) == 0)
1162           stack.push_back(l);
1163         else if (r != 0 && isa<Instruction>(r) &&
1164                  visited.count(r) == 0)
1165           stack.push_back(r);
1166         else if (m != 0 && isa<Instruction>(m) &&
1167                  visited.count(m) == 0)
1168           stack.push_back(m);
1169         else {
1170           vec.push_back(e);
1171           visited.insert(e);
1172           stack.pop_back();
1173         }
1174
1175       // Handle vararg ops
1176       } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(e)) {
1177         Value* p = find_leader(set, VN.lookup(U->getPointerOperand()));
1178
1179         if (p != 0 && isa<Instruction>(p) &&
1180             visited.count(p) == 0)
1181           stack.push_back(p);
1182         else {
1183           bool push_va = false;
1184           for (GetElementPtrInst::op_iterator I = U->idx_begin(),
1185                E = U->idx_end(); I != E; ++I) {
1186             Value * v = find_leader(set, VN.lookup(*I));
1187             if (v != 0 && isa<Instruction>(v) && visited.count(v) == 0) {
1188               stack.push_back(v);
1189               push_va = true;
1190             }
1191           }
1192
1193           if (!push_va) {
1194             vec.push_back(e);
1195             visited.insert(e);
1196             stack.pop_back();
1197           }
1198         }
1199
1200       // Handle opaque ops
1201       } else {
1202         visited.insert(e);
1203         vec.push_back(e);
1204         stack.pop_back();
1205       }
1206     }
1207
1208     stack.clear();
1209   }
1210 }
1211
1212 /// dump - Dump a set of values to standard error
1213 void GVNPRE::dump(ValueNumberedSet& s) const {
1214   DOUT << "{ ";
1215   for (ValueNumberedSet::iterator I = s.begin(), E = s.end();
1216        I != E; ++I) {
1217     DOUT << "" << VN.lookup(*I) << ": ";
1218     DEBUG((*I)->dump());
1219   }
1220   DOUT << "}\n\n";
1221 }
1222
1223 /// elimination - Phase 3 of the main algorithm.  Perform full redundancy
1224 /// elimination by walking the dominator tree and removing any instruction that
1225 /// is dominated by another instruction with the same value number.
1226 bool GVNPRE::elimination() {
1227   bool changed_function = false;
1228
1229   SmallVector<std::pair<Instruction*, Value*>, 8> replace;
1230   SmallVector<Instruction*, 8> erase;
1231
1232   DominatorTree& DT = getAnalysis<DominatorTree>();
1233
1234   for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
1235          E = df_end(DT.getRootNode()); DI != E; ++DI) {
1236     BasicBlock* BB = DI->getBlock();
1237
1238     for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
1239          BI != BE; ++BI) {
1240
1241       if (isa<BinaryOperator>(BI) || isa<CmpInst>(BI) ||
1242           isa<ShuffleVectorInst>(BI) || isa<InsertElementInst>(BI) ||
1243           isa<ExtractElementInst>(BI) || isa<SelectInst>(BI) ||
1244           isa<CastInst>(BI) || isa<GetElementPtrInst>(BI)) {
1245
1246         if (availableOut[BB].test(VN.lookup(BI)) &&
1247             !availableOut[BB].count(BI)) {
1248           Value *leader = find_leader(availableOut[BB], VN.lookup(BI));
1249           if (Instruction* Instr = dyn_cast<Instruction>(leader))
1250             if (Instr->getParent() != 0 && Instr != BI) {
1251               replace.push_back(std::make_pair(BI, leader));
1252               erase.push_back(BI);
1253               ++NumEliminated;
1254             }
1255         }
1256       }
1257     }
1258   }
1259
1260   while (!replace.empty()) {
1261     std::pair<Instruction*, Value*> rep = replace.back();
1262     replace.pop_back();
1263     rep.first->replaceAllUsesWith(rep.second);
1264     changed_function = true;
1265   }
1266
1267   for (SmallVector<Instruction*, 8>::iterator I = erase.begin(),
1268        E = erase.end(); I != E; ++I)
1269      (*I)->eraseFromParent();
1270
1271   return changed_function;
1272 }
1273
1274 /// cleanup - Delete any extraneous values that were created to represent
1275 /// expressions without leaders.
1276 void GVNPRE::cleanup() {
1277   while (!createdExpressions.empty()) {
1278     Instruction* I = createdExpressions.back();
1279     createdExpressions.pop_back();
1280
1281     delete I;
1282   }
1283 }
1284
1285 /// buildsets_availout - When calculating availability, handle an instruction
1286 /// by inserting it into the appropriate sets
1287 void GVNPRE::buildsets_availout(BasicBlock::iterator I,
1288                                 ValueNumberedSet& currAvail,
1289                                 ValueNumberedSet& currPhis,
1290                                 ValueNumberedSet& currExps,
1291                                 SmallPtrSet<Value*, 16>& currTemps) {
1292   // Handle PHI nodes
1293   if (PHINode* p = dyn_cast<PHINode>(I)) {
1294     unsigned num = VN.lookup_or_add(p);
1295
1296     currPhis.insert(p);
1297     currPhis.set(num);
1298
1299   // Handle unary ops
1300   } else if (CastInst* U = dyn_cast<CastInst>(I)) {
1301     Value* leftValue = U->getOperand(0);
1302
1303     unsigned num = VN.lookup_or_add(U);
1304
1305     if (isa<Instruction>(leftValue))
1306       if (!currExps.test(VN.lookup(leftValue))) {
1307         currExps.insert(leftValue);
1308         currExps.set(VN.lookup(leftValue));
1309       }
1310
1311     if (!currExps.test(num)) {
1312       currExps.insert(U);
1313       currExps.set(num);
1314     }
1315
1316   // Handle binary ops
1317   } else if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
1318              isa<ExtractElementInst>(I)) {
1319     User* U = cast<User>(I);
1320     Value* leftValue = U->getOperand(0);
1321     Value* rightValue = U->getOperand(1);
1322
1323     unsigned num = VN.lookup_or_add(U);
1324
1325     if (isa<Instruction>(leftValue))
1326       if (!currExps.test(VN.lookup(leftValue))) {
1327         currExps.insert(leftValue);
1328         currExps.set(VN.lookup(leftValue));
1329       }
1330
1331     if (isa<Instruction>(rightValue))
1332       if (!currExps.test(VN.lookup(rightValue))) {
1333         currExps.insert(rightValue);
1334         currExps.set(VN.lookup(rightValue));
1335       }
1336
1337     if (!currExps.test(num)) {
1338       currExps.insert(U);
1339       currExps.set(num);
1340     }
1341
1342   // Handle ternary ops
1343   } else if (isa<InsertElementInst>(I) || isa<ShuffleVectorInst>(I) ||
1344              isa<SelectInst>(I)) {
1345     User* U = cast<User>(I);
1346     Value* leftValue = U->getOperand(0);
1347     Value* rightValue = U->getOperand(1);
1348     Value* thirdValue = U->getOperand(2);
1349
1350     VN.lookup_or_add(U);
1351
1352     unsigned num = VN.lookup_or_add(U);
1353
1354     if (isa<Instruction>(leftValue))
1355       if (!currExps.test(VN.lookup(leftValue))) {
1356         currExps.insert(leftValue);
1357         currExps.set(VN.lookup(leftValue));
1358       }
1359     if (isa<Instruction>(rightValue))
1360       if (!currExps.test(VN.lookup(rightValue))) {
1361         currExps.insert(rightValue);
1362         currExps.set(VN.lookup(rightValue));
1363       }
1364     if (isa<Instruction>(thirdValue))
1365       if (!currExps.test(VN.lookup(thirdValue))) {
1366         currExps.insert(thirdValue);
1367         currExps.set(VN.lookup(thirdValue));
1368       }
1369
1370     if (!currExps.test(num)) {
1371       currExps.insert(U);
1372       currExps.set(num);
1373     }
1374
1375   // Handle vararg ops
1376   } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(I)) {
1377     Value* ptrValue = U->getPointerOperand();
1378
1379     VN.lookup_or_add(U);
1380
1381     unsigned num = VN.lookup_or_add(U);
1382
1383     if (isa<Instruction>(ptrValue))
1384       if (!currExps.test(VN.lookup(ptrValue))) {
1385         currExps.insert(ptrValue);
1386         currExps.set(VN.lookup(ptrValue));
1387       }
1388
1389     for (GetElementPtrInst::op_iterator OI = U->idx_begin(), OE = U->idx_end();
1390          OI != OE; ++OI)
1391       if (isa<Instruction>(*OI) && !currExps.test(VN.lookup(*OI))) {
1392         currExps.insert(*OI);
1393         currExps.set(VN.lookup(*OI));
1394       }
1395
1396     if (!currExps.test(VN.lookup(U))) {
1397       currExps.insert(U);
1398       currExps.set(num);
1399     }
1400
1401   // Handle opaque ops
1402   } else if (!I->isTerminator()){
1403     VN.lookup_or_add(I);
1404
1405     currTemps.insert(I);
1406   }
1407
1408   if (!I->isTerminator())
1409     if (!currAvail.test(VN.lookup(I))) {
1410       currAvail.insert(I);
1411       currAvail.set(VN.lookup(I));
1412     }
1413 }
1414
1415 /// buildsets_anticout - When walking the postdom tree, calculate the ANTIC_OUT
1416 /// set as a function of the ANTIC_IN set of the block's predecessors
1417 bool GVNPRE::buildsets_anticout(BasicBlock* BB,
1418                                 ValueNumberedSet& anticOut,
1419                                 SmallPtrSet<BasicBlock*, 8>& visited) {
1420   if (BB->getTerminator()->getNumSuccessors() == 1) {
1421     if (BB->getTerminator()->getSuccessor(0) != BB &&
1422         visited.count(BB->getTerminator()->getSuccessor(0)) == 0) {
1423       return true;
1424     }
1425     else {
1426       phi_translate_set(anticipatedIn[BB->getTerminator()->getSuccessor(0)],
1427                         BB,  BB->getTerminator()->getSuccessor(0), anticOut);
1428     }
1429   } else if (BB->getTerminator()->getNumSuccessors() > 1) {
1430     BasicBlock* first = BB->getTerminator()->getSuccessor(0);
1431     for (ValueNumberedSet::iterator I = anticipatedIn[first].begin(),
1432          E = anticipatedIn[first].end(); I != E; ++I) {
1433       anticOut.insert(*I);
1434       anticOut.set(VN.lookup(*I));
1435     }
1436
1437     for (unsigned i = 1; i < BB->getTerminator()->getNumSuccessors(); ++i) {
1438       BasicBlock* currSucc = BB->getTerminator()->getSuccessor(i);
1439       ValueNumberedSet& succAnticIn = anticipatedIn[currSucc];
1440
1441       SmallVector<Value*, 16> temp;
1442
1443       for (ValueNumberedSet::iterator I = anticOut.begin(),
1444            E = anticOut.end(); I != E; ++I)
1445         if (!succAnticIn.test(VN.lookup(*I)))
1446           temp.push_back(*I);
1447
1448       for (SmallVector<Value*, 16>::iterator I = temp.begin(), E = temp.end();
1449            I != E; ++I) {
1450         anticOut.erase(*I);
1451         anticOut.reset(VN.lookup(*I));
1452       }
1453     }
1454   }
1455
1456   return false;
1457 }
1458
1459 /// buildsets_anticin - Walk the postdom tree, calculating ANTIC_OUT for
1460 /// each block.  ANTIC_IN is then a function of ANTIC_OUT and the GEN
1461 /// sets populated in buildsets_availout
1462 unsigned GVNPRE::buildsets_anticin(BasicBlock* BB,
1463                                ValueNumberedSet& anticOut,
1464                                ValueNumberedSet& currExps,
1465                                SmallPtrSet<Value*, 16>& currTemps,
1466                                SmallPtrSet<BasicBlock*, 8>& visited) {
1467   ValueNumberedSet& anticIn = anticipatedIn[BB];
1468   unsigned old = anticIn.size();
1469
1470   bool defer = buildsets_anticout(BB, anticOut, visited);
1471   if (defer)
1472     return 0;
1473
1474   anticIn.clear();
1475
1476   for (ValueNumberedSet::iterator I = anticOut.begin(),
1477        E = anticOut.end(); I != E; ++I) {
1478     anticIn.insert(*I);
1479     anticIn.set(VN.lookup(*I));
1480   }
1481   for (ValueNumberedSet::iterator I = currExps.begin(),
1482        E = currExps.end(); I != E; ++I) {
1483     if (!anticIn.test(VN.lookup(*I))) {
1484       anticIn.insert(*I);
1485       anticIn.set(VN.lookup(*I));
1486     }
1487   }
1488
1489   for (SmallPtrSet<Value*, 16>::iterator I = currTemps.begin(),
1490        E = currTemps.end(); I != E; ++I) {
1491     anticIn.erase(*I);
1492     anticIn.reset(VN.lookup(*I));
1493   }
1494
1495   clean(anticIn);
1496   anticOut.clear();
1497
1498   if (old != anticIn.size())
1499     return 2;
1500   else
1501     return 1;
1502 }
1503
1504 /// buildsets - Phase 1 of the main algorithm.  Construct the AVAIL_OUT
1505 /// and the ANTIC_IN sets.
1506 void GVNPRE::buildsets(Function& F) {
1507   DenseMap<BasicBlock*, ValueNumberedSet> generatedExpressions;
1508   DenseMap<BasicBlock*, SmallPtrSet<Value*, 16> > generatedTemporaries;
1509
1510   DominatorTree &DT = getAnalysis<DominatorTree>();
1511
1512   // Phase 1, Part 1: calculate AVAIL_OUT
1513
1514   // Top-down walk of the dominator tree
1515   for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
1516          E = df_end(DT.getRootNode()); DI != E; ++DI) {
1517
1518     // Get the sets to update for this block
1519     ValueNumberedSet& currExps = generatedExpressions[DI->getBlock()];
1520     ValueNumberedSet& currPhis = generatedPhis[DI->getBlock()];
1521     SmallPtrSet<Value*, 16>& currTemps = generatedTemporaries[DI->getBlock()];
1522     ValueNumberedSet& currAvail = availableOut[DI->getBlock()];
1523
1524     BasicBlock* BB = DI->getBlock();
1525
1526     // A block inherits AVAIL_OUT from its dominator
1527     if (DI->getIDom() != 0)
1528       currAvail = availableOut[DI->getIDom()->getBlock()];
1529
1530     for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
1531          BI != BE; ++BI)
1532       buildsets_availout(BI, currAvail, currPhis, currExps,
1533                          currTemps);
1534
1535   }
1536
1537   // Phase 1, Part 2: calculate ANTIC_IN
1538
1539   SmallPtrSet<BasicBlock*, 8> visited;
1540   SmallPtrSet<BasicBlock*, 4> block_changed;
1541   for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
1542     block_changed.insert(FI);
1543
1544   bool changed = true;
1545   unsigned iterations = 0;
1546
1547   while (changed) {
1548     changed = false;
1549     ValueNumberedSet anticOut;
1550
1551     // Postorder walk of the CFG
1552     for (po_iterator<BasicBlock*> BBI = po_begin(&F.getEntryBlock()),
1553          BBE = po_end(&F.getEntryBlock()); BBI != BBE; ++BBI) {
1554       BasicBlock* BB = *BBI;
1555
1556       if (block_changed.count(BB) != 0) {
1557         unsigned ret = buildsets_anticin(BB, anticOut,generatedExpressions[BB],
1558                                          generatedTemporaries[BB], visited);
1559
1560         if (ret == 0) {
1561           changed = true;
1562           continue;
1563         } else {
1564           visited.insert(BB);
1565
1566           if (ret == 2)
1567            for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
1568                  PI != PE; ++PI) {
1569               block_changed.insert(*PI);
1570            }
1571           else
1572             block_changed.erase(BB);
1573
1574           changed |= (ret == 2);
1575         }
1576       }
1577     }
1578
1579     iterations++;
1580   }
1581 }
1582
1583 /// insertion_pre - When a partial redundancy has been identified, eliminate it
1584 /// by inserting appropriate values into the predecessors and a phi node in
1585 /// the main block
1586 void GVNPRE::insertion_pre(Value* e, BasicBlock* BB,
1587                            DenseMap<BasicBlock*, Value*>& avail,
1588                     std::map<BasicBlock*, ValueNumberedSet>& new_sets) {
1589   for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
1590     Value* e2 = avail[*PI];
1591     if (!availableOut[*PI].test(VN.lookup(e2))) {
1592       User* U = cast<User>(e2);
1593
1594       Value* s1 = 0;
1595       if (isa<BinaryOperator>(U->getOperand(0)) ||
1596           isa<CmpInst>(U->getOperand(0)) ||
1597           isa<ShuffleVectorInst>(U->getOperand(0)) ||
1598           isa<ExtractElementInst>(U->getOperand(0)) ||
1599           isa<InsertElementInst>(U->getOperand(0)) ||
1600           isa<SelectInst>(U->getOperand(0)) ||
1601           isa<CastInst>(U->getOperand(0)) ||
1602           isa<GetElementPtrInst>(U->getOperand(0)))
1603         s1 = find_leader(availableOut[*PI], VN.lookup(U->getOperand(0)));
1604       else
1605         s1 = U->getOperand(0);
1606
1607       Value* s2 = 0;
1608
1609       if (isa<BinaryOperator>(U) ||
1610           isa<CmpInst>(U) ||
1611           isa<ShuffleVectorInst>(U) ||
1612           isa<ExtractElementInst>(U) ||
1613           isa<InsertElementInst>(U) ||
1614           isa<SelectInst>(U)) {
1615         if (isa<BinaryOperator>(U->getOperand(1)) ||
1616             isa<CmpInst>(U->getOperand(1)) ||
1617             isa<ShuffleVectorInst>(U->getOperand(1)) ||
1618             isa<ExtractElementInst>(U->getOperand(1)) ||
1619             isa<InsertElementInst>(U->getOperand(1)) ||
1620             isa<SelectInst>(U->getOperand(1)) ||
1621             isa<CastInst>(U->getOperand(1)) ||
1622             isa<GetElementPtrInst>(U->getOperand(1))) {
1623           s2 = find_leader(availableOut[*PI], VN.lookup(U->getOperand(1)));
1624         } else {
1625           s2 = U->getOperand(1);
1626         }
1627       }
1628
1629       // Ternary Operators
1630       Value* s3 = 0;
1631       if (isa<ShuffleVectorInst>(U) ||
1632           isa<InsertElementInst>(U) ||
1633           isa<SelectInst>(U)) {
1634         if (isa<BinaryOperator>(U->getOperand(2)) ||
1635             isa<CmpInst>(U->getOperand(2)) ||
1636             isa<ShuffleVectorInst>(U->getOperand(2)) ||
1637             isa<ExtractElementInst>(U->getOperand(2)) ||
1638             isa<InsertElementInst>(U->getOperand(2)) ||
1639             isa<SelectInst>(U->getOperand(2)) ||
1640             isa<CastInst>(U->getOperand(2)) ||
1641             isa<GetElementPtrInst>(U->getOperand(2))) {
1642           s3 = find_leader(availableOut[*PI], VN.lookup(U->getOperand(2)));
1643         } else {
1644           s3 = U->getOperand(2);
1645         }
1646       }
1647
1648       // Vararg operators
1649       SmallVector<Value*, 4> sVarargs;
1650       if (GetElementPtrInst* G = dyn_cast<GetElementPtrInst>(U)) {
1651         for (GetElementPtrInst::op_iterator OI = G->idx_begin(),
1652              OE = G->idx_end(); OI != OE; ++OI) {
1653           if (isa<BinaryOperator>(*OI) ||
1654               isa<CmpInst>(*OI) ||
1655               isa<ShuffleVectorInst>(*OI) ||
1656               isa<ExtractElementInst>(*OI) ||
1657               isa<InsertElementInst>(*OI) ||
1658               isa<SelectInst>(*OI) ||
1659               isa<CastInst>(*OI) ||
1660               isa<GetElementPtrInst>(*OI)) {
1661             sVarargs.push_back(find_leader(availableOut[*PI],
1662                                VN.lookup(*OI)));
1663           } else {
1664             sVarargs.push_back(*OI);
1665           }
1666         }
1667       }
1668
1669       Value* newVal = 0;
1670       if (BinaryOperator* BO = dyn_cast<BinaryOperator>(U))
1671         newVal = BinaryOperator::Create(BO->getOpcode(), s1, s2,
1672                                         BO->getName()+".gvnpre",
1673                                         (*PI)->getTerminator());
1674       else if (CmpInst* C = dyn_cast<CmpInst>(U))
1675         newVal = CmpInst::Create(C->getOpcode(), C->getPredicate(), s1, s2,
1676                                  C->getName()+".gvnpre",
1677                                  (*PI)->getTerminator());
1678       else if (ShuffleVectorInst* S = dyn_cast<ShuffleVectorInst>(U))
1679         newVal = new ShuffleVectorInst(s1, s2, s3, S->getName()+".gvnpre",
1680                                        (*PI)->getTerminator());
1681       else if (InsertElementInst* S = dyn_cast<InsertElementInst>(U))
1682         newVal = InsertElementInst::Create(s1, s2, s3, S->getName()+".gvnpre",
1683                                            (*PI)->getTerminator());
1684       else if (ExtractElementInst* S = dyn_cast<ExtractElementInst>(U))
1685         newVal = new ExtractElementInst(s1, s2, S->getName()+".gvnpre",
1686                                         (*PI)->getTerminator());
1687       else if (SelectInst* S = dyn_cast<SelectInst>(U))
1688         newVal = SelectInst::Create(s1, s2, s3, S->getName()+".gvnpre",
1689                                     (*PI)->getTerminator());
1690       else if (CastInst* C = dyn_cast<CastInst>(U))
1691         newVal = CastInst::Create(C->getOpcode(), s1, C->getType(),
1692                                   C->getName()+".gvnpre",
1693                                   (*PI)->getTerminator());
1694       else if (GetElementPtrInst* G = dyn_cast<GetElementPtrInst>(U))
1695         newVal = GetElementPtrInst::Create(s1, sVarargs.begin(), sVarargs.end(),
1696                                            G->getName()+".gvnpre",
1697                                            (*PI)->getTerminator());
1698
1699       VN.add(newVal, VN.lookup(U));
1700
1701       ValueNumberedSet& predAvail = availableOut[*PI];
1702       val_replace(predAvail, newVal);
1703       val_replace(new_sets[*PI], newVal);
1704       predAvail.set(VN.lookup(newVal));
1705
1706       DenseMap<BasicBlock*, Value*>::iterator av = avail.find(*PI);
1707       if (av != avail.end())
1708         avail.erase(av);
1709       avail.insert(std::make_pair(*PI, newVal));
1710
1711       ++NumInsertedVals;
1712     }
1713   }
1714
1715   PHINode* p = 0;
1716
1717   for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
1718     if (p == 0)
1719       p = PHINode::Create(avail[*PI]->getType(), "gvnpre-join", BB->begin());
1720
1721     p->addIncoming(avail[*PI], *PI);
1722   }
1723
1724   VN.add(p, VN.lookup(e));
1725   val_replace(availableOut[BB], p);
1726   availableOut[BB].set(VN.lookup(e));
1727   generatedPhis[BB].insert(p);
1728   generatedPhis[BB].set(VN.lookup(e));
1729   new_sets[BB].insert(p);
1730   new_sets[BB].set(VN.lookup(e));
1731
1732   ++NumInsertedPhis;
1733 }
1734
1735 /// insertion_mergepoint - When walking the dom tree, check at each merge
1736 /// block for the possibility of a partial redundancy.  If present, eliminate it
1737 unsigned GVNPRE::insertion_mergepoint(SmallVector<Value*, 8>& workList,
1738                                       df_iterator<DomTreeNode*>& D,
1739                     std::map<BasicBlock*, ValueNumberedSet >& new_sets) {
1740   bool changed_function = false;
1741   bool new_stuff = false;
1742
1743   BasicBlock* BB = D->getBlock();
1744   for (unsigned i = 0; i < workList.size(); ++i) {
1745     Value* e = workList[i];
1746
1747     if (isa<BinaryOperator>(e) || isa<CmpInst>(e) ||
1748         isa<ExtractElementInst>(e) || isa<InsertElementInst>(e) ||
1749         isa<ShuffleVectorInst>(e) || isa<SelectInst>(e) || isa<CastInst>(e) ||
1750         isa<GetElementPtrInst>(e)) {
1751       if (availableOut[D->getIDom()->getBlock()].test(VN.lookup(e)))
1752         continue;
1753
1754       DenseMap<BasicBlock*, Value*> avail;
1755       bool by_some = false;
1756       bool all_same = true;
1757       Value * first_s = 0;
1758
1759       for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;
1760            ++PI) {
1761         Value *e2 = phi_translate(e, *PI, BB);
1762         Value *e3 = find_leader(availableOut[*PI], VN.lookup(e2));
1763
1764         if (e3 == 0) {
1765           DenseMap<BasicBlock*, Value*>::iterator av = avail.find(*PI);
1766           if (av != avail.end())
1767             avail.erase(av);
1768           avail.insert(std::make_pair(*PI, e2));
1769           all_same = false;
1770         } else {
1771           DenseMap<BasicBlock*, Value*>::iterator av = avail.find(*PI);
1772           if (av != avail.end())
1773             avail.erase(av);
1774           avail.insert(std::make_pair(*PI, e3));
1775
1776           by_some = true;
1777           if (first_s == 0)
1778             first_s = e3;
1779           else if (first_s != e3)
1780             all_same = false;
1781         }
1782       }
1783
1784       if (by_some && !all_same &&
1785           !generatedPhis[BB].test(VN.lookup(e))) {
1786         insertion_pre(e, BB, avail, new_sets);
1787
1788         changed_function = true;
1789         new_stuff = true;
1790       }
1791     }
1792   }
1793
1794   unsigned retval = 0;
1795   if (changed_function)
1796     retval += 1;
1797   if (new_stuff)
1798     retval += 2;
1799
1800   return retval;
1801 }
1802
1803 /// insert - Phase 2 of the main algorithm.  Walk the dominator tree looking for
1804 /// merge points.  When one is found, check for a partial redundancy.  If one is
1805 /// present, eliminate it.  Repeat this walk until no changes are made.
1806 bool GVNPRE::insertion(Function& F) {
1807   bool changed_function = false;
1808
1809   DominatorTree &DT = getAnalysis<DominatorTree>();
1810
1811   std::map<BasicBlock*, ValueNumberedSet> new_sets;
1812   bool new_stuff = true;
1813   while (new_stuff) {
1814     new_stuff = false;
1815     for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
1816          E = df_end(DT.getRootNode()); DI != E; ++DI) {
1817       BasicBlock* BB = DI->getBlock();
1818
1819       if (BB == 0)
1820         continue;
1821
1822       ValueNumberedSet& availOut = availableOut[BB];
1823       ValueNumberedSet& anticIn = anticipatedIn[BB];
1824
1825       // Replace leaders with leaders inherited from dominator
1826       if (DI->getIDom() != 0) {
1827         ValueNumberedSet& dom_set = new_sets[DI->getIDom()->getBlock()];
1828         for (ValueNumberedSet::iterator I = dom_set.begin(),
1829              E = dom_set.end(); I != E; ++I) {
1830           val_replace(new_sets[BB], *I);
1831           val_replace(availOut, *I);
1832         }
1833       }
1834
1835       // If there is more than one predecessor...
1836       if (pred_begin(BB) != pred_end(BB) && ++pred_begin(BB) != pred_end(BB)) {
1837         SmallVector<Value*, 8> workList;
1838         workList.reserve(anticIn.size());
1839         topo_sort(anticIn, workList);
1840
1841         unsigned result = insertion_mergepoint(workList, DI, new_sets);
1842         if (result & 1)
1843           changed_function = true;
1844         if (result & 2)
1845           new_stuff = true;
1846       }
1847     }
1848   }
1849
1850   return changed_function;
1851 }
1852
1853 // GVNPRE::runOnFunction - This is the main transformation entry point for a
1854 // function.
1855 //
1856 bool GVNPRE::runOnFunction(Function &F) {
1857   // Clean out global sets from any previous functions
1858   VN.clear();
1859   createdExpressions.clear();
1860   availableOut.clear();
1861   anticipatedIn.clear();
1862   generatedPhis.clear();
1863
1864   bool changed_function = false;
1865
1866   // Phase 1: BuildSets
1867   // This phase calculates the AVAIL_OUT and ANTIC_IN sets
1868   buildsets(F);
1869
1870   // Phase 2: Insert
1871   // This phase inserts values to make partially redundant values
1872   // fully redundant
1873   changed_function |= insertion(F);
1874
1875   // Phase 3: Eliminate
1876   // This phase performs trivial full redundancy elimination
1877   changed_function |= elimination();
1878
1879   // Phase 4: Cleanup
1880   // This phase cleans up values that were created solely
1881   // as leaders for expressions
1882   cleanup();
1883
1884   return changed_function;
1885 }