InstructionCombining.cpp revision 218893
1//===- InstructionCombining.cpp - Combine multiple instructions -----------===// 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// InstructionCombining - Combine instructions to form fewer, simple 11// instructions. This pass does not modify the CFG. This pass is where 12// algebraic simplification happens. 13// 14// This pass combines things like: 15// %Y = add i32 %X, 1 16// %Z = add i32 %Y, 1 17// into: 18// %Z = add i32 %X, 2 19// 20// This is a simple worklist driven algorithm. 21// 22// This pass guarantees that the following canonicalizations are performed on 23// the program: 24// 1. If a binary operator has a constant operand, it is moved to the RHS 25// 2. Bitwise operators with constant operands are always grouped so that 26// shifts are performed first, then or's, then and's, then xor's. 27// 3. Compare instructions are converted from <,>,<=,>= to ==,!= if possible 28// 4. All cmp instructions on boolean values are replaced with logical ops 29// 5. add X, X is represented as (X*2) => (X << 1) 30// 6. Multiplies with a power-of-two constant argument are transformed into 31// shifts. 32// ... etc. 33// 34//===----------------------------------------------------------------------===// 35 36#define DEBUG_TYPE "instcombine" 37#include "llvm/Transforms/Scalar.h" 38#include "InstCombine.h" 39#include "llvm/IntrinsicInst.h" 40#include "llvm/Analysis/ConstantFolding.h" 41#include "llvm/Analysis/InstructionSimplify.h" 42#include "llvm/Analysis/MemoryBuiltins.h" 43#include "llvm/Target/TargetData.h" 44#include "llvm/Transforms/Utils/Local.h" 45#include "llvm/Support/CFG.h" 46#include "llvm/Support/Debug.h" 47#include "llvm/Support/GetElementPtrTypeIterator.h" 48#include "llvm/Support/PatternMatch.h" 49#include "llvm/ADT/SmallPtrSet.h" 50#include "llvm/ADT/Statistic.h" 51#include "llvm-c/Initialization.h" 52#include <algorithm> 53#include <climits> 54using namespace llvm; 55using namespace llvm::PatternMatch; 56 57STATISTIC(NumCombined , "Number of insts combined"); 58STATISTIC(NumConstProp, "Number of constant folds"); 59STATISTIC(NumDeadInst , "Number of dead inst eliminated"); 60STATISTIC(NumSunkInst , "Number of instructions sunk"); 61STATISTIC(NumExpand, "Number of expansions"); 62STATISTIC(NumFactor , "Number of factorizations"); 63STATISTIC(NumReassoc , "Number of reassociations"); 64 65// Initialization Routines 66void llvm::initializeInstCombine(PassRegistry &Registry) { 67 initializeInstCombinerPass(Registry); 68} 69 70void LLVMInitializeInstCombine(LLVMPassRegistryRef R) { 71 initializeInstCombine(*unwrap(R)); 72} 73 74char InstCombiner::ID = 0; 75INITIALIZE_PASS(InstCombiner, "instcombine", 76 "Combine redundant instructions", false, false) 77 78void InstCombiner::getAnalysisUsage(AnalysisUsage &AU) const { 79 AU.addPreservedID(LCSSAID); 80 AU.setPreservesCFG(); 81} 82 83 84/// ShouldChangeType - Return true if it is desirable to convert a computation 85/// from 'From' to 'To'. We don't want to convert from a legal to an illegal 86/// type for example, or from a smaller to a larger illegal type. 87bool InstCombiner::ShouldChangeType(const Type *From, const Type *To) const { 88 assert(From->isIntegerTy() && To->isIntegerTy()); 89 90 // If we don't have TD, we don't know if the source/dest are legal. 91 if (!TD) return false; 92 93 unsigned FromWidth = From->getPrimitiveSizeInBits(); 94 unsigned ToWidth = To->getPrimitiveSizeInBits(); 95 bool FromLegal = TD->isLegalInteger(FromWidth); 96 bool ToLegal = TD->isLegalInteger(ToWidth); 97 98 // If this is a legal integer from type, and the result would be an illegal 99 // type, don't do the transformation. 100 if (FromLegal && !ToLegal) 101 return false; 102 103 // Otherwise, if both are illegal, do not increase the size of the result. We 104 // do allow things like i160 -> i64, but not i64 -> i160. 105 if (!FromLegal && !ToLegal && ToWidth > FromWidth) 106 return false; 107 108 return true; 109} 110 111 112/// SimplifyAssociativeOrCommutative - This performs a few simplifications for 113/// operators which are associative or commutative: 114// 115// Commutative operators: 116// 117// 1. Order operands such that they are listed from right (least complex) to 118// left (most complex). This puts constants before unary operators before 119// binary operators. 120// 121// Associative operators: 122// 123// 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. 124// 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. 125// 126// Associative and commutative operators: 127// 128// 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. 129// 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. 130// 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" 131// if C1 and C2 are constants. 132// 133bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) { 134 Instruction::BinaryOps Opcode = I.getOpcode(); 135 bool Changed = false; 136 137 do { 138 // Order operands such that they are listed from right (least complex) to 139 // left (most complex). This puts constants before unary operators before 140 // binary operators. 141 if (I.isCommutative() && getComplexity(I.getOperand(0)) < 142 getComplexity(I.getOperand(1))) 143 Changed = !I.swapOperands(); 144 145 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0)); 146 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1)); 147 148 if (I.isAssociative()) { 149 // Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. 150 if (Op0 && Op0->getOpcode() == Opcode) { 151 Value *A = Op0->getOperand(0); 152 Value *B = Op0->getOperand(1); 153 Value *C = I.getOperand(1); 154 155 // Does "B op C" simplify? 156 if (Value *V = SimplifyBinOp(Opcode, B, C, TD)) { 157 // It simplifies to V. Form "A op V". 158 I.setOperand(0, A); 159 I.setOperand(1, V); 160 // Conservatively clear the optional flags, since they may not be 161 // preserved by the reassociation. 162 I.clearSubclassOptionalData(); 163 Changed = true; 164 ++NumReassoc; 165 continue; 166 } 167 } 168 169 // Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. 170 if (Op1 && Op1->getOpcode() == Opcode) { 171 Value *A = I.getOperand(0); 172 Value *B = Op1->getOperand(0); 173 Value *C = Op1->getOperand(1); 174 175 // Does "A op B" simplify? 176 if (Value *V = SimplifyBinOp(Opcode, A, B, TD)) { 177 // It simplifies to V. Form "V op C". 178 I.setOperand(0, V); 179 I.setOperand(1, C); 180 // Conservatively clear the optional flags, since they may not be 181 // preserved by the reassociation. 182 I.clearSubclassOptionalData(); 183 Changed = true; 184 ++NumReassoc; 185 continue; 186 } 187 } 188 } 189 190 if (I.isAssociative() && I.isCommutative()) { 191 // Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. 192 if (Op0 && Op0->getOpcode() == Opcode) { 193 Value *A = Op0->getOperand(0); 194 Value *B = Op0->getOperand(1); 195 Value *C = I.getOperand(1); 196 197 // Does "C op A" simplify? 198 if (Value *V = SimplifyBinOp(Opcode, C, A, TD)) { 199 // It simplifies to V. Form "V op B". 200 I.setOperand(0, V); 201 I.setOperand(1, B); 202 // Conservatively clear the optional flags, since they may not be 203 // preserved by the reassociation. 204 I.clearSubclassOptionalData(); 205 Changed = true; 206 ++NumReassoc; 207 continue; 208 } 209 } 210 211 // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. 212 if (Op1 && Op1->getOpcode() == Opcode) { 213 Value *A = I.getOperand(0); 214 Value *B = Op1->getOperand(0); 215 Value *C = Op1->getOperand(1); 216 217 // Does "C op A" simplify? 218 if (Value *V = SimplifyBinOp(Opcode, C, A, TD)) { 219 // It simplifies to V. Form "B op V". 220 I.setOperand(0, B); 221 I.setOperand(1, V); 222 // Conservatively clear the optional flags, since they may not be 223 // preserved by the reassociation. 224 I.clearSubclassOptionalData(); 225 Changed = true; 226 ++NumReassoc; 227 continue; 228 } 229 } 230 231 // Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" 232 // if C1 and C2 are constants. 233 if (Op0 && Op1 && 234 Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode && 235 isa<Constant>(Op0->getOperand(1)) && 236 isa<Constant>(Op1->getOperand(1)) && 237 Op0->hasOneUse() && Op1->hasOneUse()) { 238 Value *A = Op0->getOperand(0); 239 Constant *C1 = cast<Constant>(Op0->getOperand(1)); 240 Value *B = Op1->getOperand(0); 241 Constant *C2 = cast<Constant>(Op1->getOperand(1)); 242 243 Constant *Folded = ConstantExpr::get(Opcode, C1, C2); 244 Instruction *New = BinaryOperator::Create(Opcode, A, B, Op1->getName(), 245 &I); 246 Worklist.Add(New); 247 I.setOperand(0, New); 248 I.setOperand(1, Folded); 249 // Conservatively clear the optional flags, since they may not be 250 // preserved by the reassociation. 251 I.clearSubclassOptionalData(); 252 Changed = true; 253 continue; 254 } 255 } 256 257 // No further simplifications. 258 return Changed; 259 } while (1); 260} 261 262/// LeftDistributesOverRight - Whether "X LOp (Y ROp Z)" is always equal to 263/// "(X LOp Y) ROp (X LOp Z)". 264static bool LeftDistributesOverRight(Instruction::BinaryOps LOp, 265 Instruction::BinaryOps ROp) { 266 switch (LOp) { 267 default: 268 return false; 269 270 case Instruction::And: 271 // And distributes over Or and Xor. 272 switch (ROp) { 273 default: 274 return false; 275 case Instruction::Or: 276 case Instruction::Xor: 277 return true; 278 } 279 280 case Instruction::Mul: 281 // Multiplication distributes over addition and subtraction. 282 switch (ROp) { 283 default: 284 return false; 285 case Instruction::Add: 286 case Instruction::Sub: 287 return true; 288 } 289 290 case Instruction::Or: 291 // Or distributes over And. 292 switch (ROp) { 293 default: 294 return false; 295 case Instruction::And: 296 return true; 297 } 298 } 299} 300 301/// RightDistributesOverLeft - Whether "(X LOp Y) ROp Z" is always equal to 302/// "(X ROp Z) LOp (Y ROp Z)". 303static bool RightDistributesOverLeft(Instruction::BinaryOps LOp, 304 Instruction::BinaryOps ROp) { 305 if (Instruction::isCommutative(ROp)) 306 return LeftDistributesOverRight(ROp, LOp); 307 // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z", 308 // but this requires knowing that the addition does not overflow and other 309 // such subtleties. 310 return false; 311} 312 313/// SimplifyUsingDistributiveLaws - This tries to simplify binary operations 314/// which some other binary operation distributes over either by factorizing 315/// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this 316/// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is 317/// a win). Returns the simplified value, or null if it didn't simplify. 318Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) { 319 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 320 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 321 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 322 Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); // op 323 324 // Factorization. 325 if (Op0 && Op1 && Op0->getOpcode() == Op1->getOpcode()) { 326 // The instruction has the form "(A op' B) op (C op' D)". Try to factorize 327 // a common term. 328 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1); 329 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1); 330 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' 331 332 // Does "X op' Y" always equal "Y op' X"? 333 bool InnerCommutative = Instruction::isCommutative(InnerOpcode); 334 335 // Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"? 336 if (LeftDistributesOverRight(InnerOpcode, TopLevelOpcode)) 337 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the 338 // commutative case, "(A op' B) op (C op' A)"? 339 if (A == C || (InnerCommutative && A == D)) { 340 if (A != C) 341 std::swap(C, D); 342 // Consider forming "A op' (B op D)". 343 // If "B op D" simplifies then it can be formed with no cost. 344 Value *V = SimplifyBinOp(TopLevelOpcode, B, D, TD); 345 // If "B op D" doesn't simplify then only go on if both of the existing 346 // operations "A op' B" and "C op' D" will be zapped as no longer used. 347 if (!V && Op0->hasOneUse() && Op1->hasOneUse()) 348 V = Builder->CreateBinOp(TopLevelOpcode, B, D, Op1->getName()); 349 if (V) { 350 ++NumFactor; 351 V = Builder->CreateBinOp(InnerOpcode, A, V); 352 V->takeName(&I); 353 return V; 354 } 355 } 356 357 // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"? 358 if (RightDistributesOverLeft(TopLevelOpcode, InnerOpcode)) 359 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the 360 // commutative case, "(A op' B) op (B op' D)"? 361 if (B == D || (InnerCommutative && B == C)) { 362 if (B != D) 363 std::swap(C, D); 364 // Consider forming "(A op C) op' B". 365 // If "A op C" simplifies then it can be formed with no cost. 366 Value *V = SimplifyBinOp(TopLevelOpcode, A, C, TD); 367 // If "A op C" doesn't simplify then only go on if both of the existing 368 // operations "A op' B" and "C op' D" will be zapped as no longer used. 369 if (!V && Op0->hasOneUse() && Op1->hasOneUse()) 370 V = Builder->CreateBinOp(TopLevelOpcode, A, C, Op0->getName()); 371 if (V) { 372 ++NumFactor; 373 V = Builder->CreateBinOp(InnerOpcode, V, B); 374 V->takeName(&I); 375 return V; 376 } 377 } 378 } 379 380 // Expansion. 381 if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) { 382 // The instruction has the form "(A op' B) op C". See if expanding it out 383 // to "(A op C) op' (B op C)" results in simplifications. 384 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; 385 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' 386 387 // Do "A op C" and "B op C" both simplify? 388 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, C, TD)) 389 if (Value *R = SimplifyBinOp(TopLevelOpcode, B, C, TD)) { 390 // They do! Return "L op' R". 391 ++NumExpand; 392 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. 393 if ((L == A && R == B) || 394 (Instruction::isCommutative(InnerOpcode) && L == B && R == A)) 395 return Op0; 396 // Otherwise return "L op' R" if it simplifies. 397 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, TD)) 398 return V; 399 // Otherwise, create a new instruction. 400 C = Builder->CreateBinOp(InnerOpcode, L, R); 401 C->takeName(&I); 402 return C; 403 } 404 } 405 406 if (Op1 && LeftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) { 407 // The instruction has the form "A op (B op' C)". See if expanding it out 408 // to "(A op B) op' (A op C)" results in simplifications. 409 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); 410 Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op' 411 412 // Do "A op B" and "A op C" both simplify? 413 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, B, TD)) 414 if (Value *R = SimplifyBinOp(TopLevelOpcode, A, C, TD)) { 415 // They do! Return "L op' R". 416 ++NumExpand; 417 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. 418 if ((L == B && R == C) || 419 (Instruction::isCommutative(InnerOpcode) && L == C && R == B)) 420 return Op1; 421 // Otherwise return "L op' R" if it simplifies. 422 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, TD)) 423 return V; 424 // Otherwise, create a new instruction. 425 A = Builder->CreateBinOp(InnerOpcode, L, R); 426 A->takeName(&I); 427 return A; 428 } 429 } 430 431 return 0; 432} 433 434// dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction 435// if the LHS is a constant zero (which is the 'negate' form). 436// 437Value *InstCombiner::dyn_castNegVal(Value *V) const { 438 if (BinaryOperator::isNeg(V)) 439 return BinaryOperator::getNegArgument(V); 440 441 // Constants can be considered to be negated values if they can be folded. 442 if (ConstantInt *C = dyn_cast<ConstantInt>(V)) 443 return ConstantExpr::getNeg(C); 444 445 if (ConstantVector *C = dyn_cast<ConstantVector>(V)) 446 if (C->getType()->getElementType()->isIntegerTy()) 447 return ConstantExpr::getNeg(C); 448 449 return 0; 450} 451 452// dyn_castFNegVal - Given a 'fsub' instruction, return the RHS of the 453// instruction if the LHS is a constant negative zero (which is the 'negate' 454// form). 455// 456Value *InstCombiner::dyn_castFNegVal(Value *V) const { 457 if (BinaryOperator::isFNeg(V)) 458 return BinaryOperator::getFNegArgument(V); 459 460 // Constants can be considered to be negated values if they can be folded. 461 if (ConstantFP *C = dyn_cast<ConstantFP>(V)) 462 return ConstantExpr::getFNeg(C); 463 464 if (ConstantVector *C = dyn_cast<ConstantVector>(V)) 465 if (C->getType()->getElementType()->isFloatingPointTy()) 466 return ConstantExpr::getFNeg(C); 467 468 return 0; 469} 470 471static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO, 472 InstCombiner *IC) { 473 if (CastInst *CI = dyn_cast<CastInst>(&I)) { 474 return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType()); 475 } 476 477 // Figure out if the constant is the left or the right argument. 478 bool ConstIsRHS = isa<Constant>(I.getOperand(1)); 479 Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS)); 480 481 if (Constant *SOC = dyn_cast<Constant>(SO)) { 482 if (ConstIsRHS) 483 return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand); 484 return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC); 485 } 486 487 Value *Op0 = SO, *Op1 = ConstOperand; 488 if (!ConstIsRHS) 489 std::swap(Op0, Op1); 490 491 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I)) 492 return IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1, 493 SO->getName()+".op"); 494 if (ICmpInst *CI = dyn_cast<ICmpInst>(&I)) 495 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, 496 SO->getName()+".cmp"); 497 if (FCmpInst *CI = dyn_cast<FCmpInst>(&I)) 498 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, 499 SO->getName()+".cmp"); 500 llvm_unreachable("Unknown binary instruction type!"); 501} 502 503// FoldOpIntoSelect - Given an instruction with a select as one operand and a 504// constant as the other operand, try to fold the binary operator into the 505// select arguments. This also works for Cast instructions, which obviously do 506// not have a second operand. 507Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) { 508 // Don't modify shared select instructions 509 if (!SI->hasOneUse()) return 0; 510 Value *TV = SI->getOperand(1); 511 Value *FV = SI->getOperand(2); 512 513 if (isa<Constant>(TV) || isa<Constant>(FV)) { 514 // Bool selects with constant operands can be folded to logical ops. 515 if (SI->getType()->isIntegerTy(1)) return 0; 516 517 // If it's a bitcast involving vectors, make sure it has the same number of 518 // elements on both sides. 519 if (BitCastInst *BC = dyn_cast<BitCastInst>(&Op)) { 520 const VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy()); 521 const VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy()); 522 523 // Verify that either both or neither are vectors. 524 if ((SrcTy == NULL) != (DestTy == NULL)) return 0; 525 // If vectors, verify that they have the same number of elements. 526 if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements()) 527 return 0; 528 } 529 530 Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this); 531 Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this); 532 533 return SelectInst::Create(SI->getCondition(), 534 SelectTrueVal, SelectFalseVal); 535 } 536 return 0; 537} 538 539 540/// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which 541/// has a PHI node as operand #0, see if we can fold the instruction into the 542/// PHI (which is only possible if all operands to the PHI are constants). 543/// 544Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) { 545 PHINode *PN = cast<PHINode>(I.getOperand(0)); 546 unsigned NumPHIValues = PN->getNumIncomingValues(); 547 if (NumPHIValues == 0) 548 return 0; 549 550 // We normally only transform phis with a single use. However, if a PHI has 551 // multiple uses and they are all the same operation, we can fold *all* of the 552 // uses into the PHI. 553 if (!PN->hasOneUse()) { 554 // Walk the use list for the instruction, comparing them to I. 555 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); 556 UI != E; ++UI) { 557 Instruction *User = cast<Instruction>(*UI); 558 if (User != &I && !I.isIdenticalTo(User)) 559 return 0; 560 } 561 // Otherwise, we can replace *all* users with the new PHI we form. 562 } 563 564 // Check to see if all of the operands of the PHI are simple constants 565 // (constantint/constantfp/undef). If there is one non-constant value, 566 // remember the BB it is in. If there is more than one or if *it* is a PHI, 567 // bail out. We don't do arbitrary constant expressions here because moving 568 // their computation can be expensive without a cost model. 569 BasicBlock *NonConstBB = 0; 570 for (unsigned i = 0; i != NumPHIValues; ++i) { 571 Value *InVal = PN->getIncomingValue(i); 572 if (isa<Constant>(InVal) && !isa<ConstantExpr>(InVal)) 573 continue; 574 575 if (isa<PHINode>(InVal)) return 0; // Itself a phi. 576 if (NonConstBB) return 0; // More than one non-const value. 577 578 NonConstBB = PN->getIncomingBlock(i); 579 580 // If the InVal is an invoke at the end of the pred block, then we can't 581 // insert a computation after it without breaking the edge. 582 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) 583 if (II->getParent() == NonConstBB) 584 return 0; 585 586 // If the incoming non-constant value is in I's block, we will remove one 587 // instruction, but insert another equivalent one, leading to infinite 588 // instcombine. 589 if (NonConstBB == I.getParent()) 590 return 0; 591 } 592 593 // If there is exactly one non-constant value, we can insert a copy of the 594 // operation in that block. However, if this is a critical edge, we would be 595 // inserting the computation one some other paths (e.g. inside a loop). Only 596 // do this if the pred block is unconditionally branching into the phi block. 597 if (NonConstBB != 0) { 598 BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator()); 599 if (!BI || !BI->isUnconditional()) return 0; 600 } 601 602 // Okay, we can do the transformation: create the new PHI node. 603 PHINode *NewPN = PHINode::Create(I.getType(), ""); 604 NewPN->reserveOperandSpace(PN->getNumOperands()/2); 605 InsertNewInstBefore(NewPN, *PN); 606 NewPN->takeName(PN); 607 608 // If we are going to have to insert a new computation, do so right before the 609 // predecessors terminator. 610 if (NonConstBB) 611 Builder->SetInsertPoint(NonConstBB->getTerminator()); 612 613 // Next, add all of the operands to the PHI. 614 if (SelectInst *SI = dyn_cast<SelectInst>(&I)) { 615 // We only currently try to fold the condition of a select when it is a phi, 616 // not the true/false values. 617 Value *TrueV = SI->getTrueValue(); 618 Value *FalseV = SI->getFalseValue(); 619 BasicBlock *PhiTransBB = PN->getParent(); 620 for (unsigned i = 0; i != NumPHIValues; ++i) { 621 BasicBlock *ThisBB = PN->getIncomingBlock(i); 622 Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB); 623 Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB); 624 Value *InV = 0; 625 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 626 InV = InC->isNullValue() ? FalseVInPred : TrueVInPred; 627 else 628 InV = Builder->CreateSelect(PN->getIncomingValue(i), 629 TrueVInPred, FalseVInPred, "phitmp"); 630 NewPN->addIncoming(InV, ThisBB); 631 } 632 } else if (CmpInst *CI = dyn_cast<CmpInst>(&I)) { 633 Constant *C = cast<Constant>(I.getOperand(1)); 634 for (unsigned i = 0; i != NumPHIValues; ++i) { 635 Value *InV = 0; 636 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 637 InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C); 638 else if (isa<ICmpInst>(CI)) 639 InV = Builder->CreateICmp(CI->getPredicate(), PN->getIncomingValue(i), 640 C, "phitmp"); 641 else 642 InV = Builder->CreateFCmp(CI->getPredicate(), PN->getIncomingValue(i), 643 C, "phitmp"); 644 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 645 } 646 } else if (I.getNumOperands() == 2) { 647 Constant *C = cast<Constant>(I.getOperand(1)); 648 for (unsigned i = 0; i != NumPHIValues; ++i) { 649 Value *InV = 0; 650 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 651 InV = ConstantExpr::get(I.getOpcode(), InC, C); 652 else 653 InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(), 654 PN->getIncomingValue(i), C, "phitmp"); 655 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 656 } 657 } else { 658 CastInst *CI = cast<CastInst>(&I); 659 const Type *RetTy = CI->getType(); 660 for (unsigned i = 0; i != NumPHIValues; ++i) { 661 Value *InV; 662 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 663 InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy); 664 else 665 InV = Builder->CreateCast(CI->getOpcode(), 666 PN->getIncomingValue(i), I.getType(), "phitmp"); 667 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 668 } 669 } 670 671 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); 672 UI != E; ) { 673 Instruction *User = cast<Instruction>(*UI++); 674 if (User == &I) continue; 675 ReplaceInstUsesWith(*User, NewPN); 676 EraseInstFromFunction(*User); 677 } 678 return ReplaceInstUsesWith(I, NewPN); 679} 680 681/// FindElementAtOffset - Given a type and a constant offset, determine whether 682/// or not there is a sequence of GEP indices into the type that will land us at 683/// the specified offset. If so, fill them into NewIndices and return the 684/// resultant element type, otherwise return null. 685const Type *InstCombiner::FindElementAtOffset(const Type *Ty, int64_t Offset, 686 SmallVectorImpl<Value*> &NewIndices) { 687 if (!TD) return 0; 688 if (!Ty->isSized()) return 0; 689 690 // Start with the index over the outer type. Note that the type size 691 // might be zero (even if the offset isn't zero) if the indexed type 692 // is something like [0 x {int, int}] 693 const Type *IntPtrTy = TD->getIntPtrType(Ty->getContext()); 694 int64_t FirstIdx = 0; 695 if (int64_t TySize = TD->getTypeAllocSize(Ty)) { 696 FirstIdx = Offset/TySize; 697 Offset -= FirstIdx*TySize; 698 699 // Handle hosts where % returns negative instead of values [0..TySize). 700 if (Offset < 0) { 701 --FirstIdx; 702 Offset += TySize; 703 assert(Offset >= 0); 704 } 705 assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset"); 706 } 707 708 NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx)); 709 710 // Index into the types. If we fail, set OrigBase to null. 711 while (Offset) { 712 // Indexing into tail padding between struct/array elements. 713 if (uint64_t(Offset*8) >= TD->getTypeSizeInBits(Ty)) 714 return 0; 715 716 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 717 const StructLayout *SL = TD->getStructLayout(STy); 718 assert(Offset < (int64_t)SL->getSizeInBytes() && 719 "Offset must stay within the indexed type"); 720 721 unsigned Elt = SL->getElementContainingOffset(Offset); 722 NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 723 Elt)); 724 725 Offset -= SL->getElementOffset(Elt); 726 Ty = STy->getElementType(Elt); 727 } else if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) { 728 uint64_t EltSize = TD->getTypeAllocSize(AT->getElementType()); 729 assert(EltSize && "Cannot index into a zero-sized array"); 730 NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize)); 731 Offset %= EltSize; 732 Ty = AT->getElementType(); 733 } else { 734 // Otherwise, we can't index into the middle of this atomic type, bail. 735 return 0; 736 } 737 } 738 739 return Ty; 740} 741 742 743 744Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { 745 SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end()); 746 747 if (Value *V = SimplifyGEPInst(&Ops[0], Ops.size(), TD)) 748 return ReplaceInstUsesWith(GEP, V); 749 750 Value *PtrOp = GEP.getOperand(0); 751 752 // Eliminate unneeded casts for indices, and replace indices which displace 753 // by multiples of a zero size type with zero. 754 if (TD) { 755 bool MadeChange = false; 756 const Type *IntPtrTy = TD->getIntPtrType(GEP.getContext()); 757 758 gep_type_iterator GTI = gep_type_begin(GEP); 759 for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); 760 I != E; ++I, ++GTI) { 761 // Skip indices into struct types. 762 const SequentialType *SeqTy = dyn_cast<SequentialType>(*GTI); 763 if (!SeqTy) continue; 764 765 // If the element type has zero size then any index over it is equivalent 766 // to an index of zero, so replace it with zero if it is not zero already. 767 if (SeqTy->getElementType()->isSized() && 768 TD->getTypeAllocSize(SeqTy->getElementType()) == 0) 769 if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) { 770 *I = Constant::getNullValue(IntPtrTy); 771 MadeChange = true; 772 } 773 774 if ((*I)->getType() != IntPtrTy) { 775 // If we are using a wider index than needed for this platform, shrink 776 // it to what we need. If narrower, sign-extend it to what we need. 777 // This explicit cast can make subsequent optimizations more obvious. 778 *I = Builder->CreateIntCast(*I, IntPtrTy, true); 779 MadeChange = true; 780 } 781 } 782 if (MadeChange) return &GEP; 783 } 784 785 // Combine Indices - If the source pointer to this getelementptr instruction 786 // is a getelementptr instruction, combine the indices of the two 787 // getelementptr instructions into a single instruction. 788 // 789 if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) { 790 // Note that if our source is a gep chain itself that we wait for that 791 // chain to be resolved before we perform this transformation. This 792 // avoids us creating a TON of code in some cases. 793 // 794 if (GetElementPtrInst *SrcGEP = 795 dyn_cast<GetElementPtrInst>(Src->getOperand(0))) 796 if (SrcGEP->getNumOperands() == 2) 797 return 0; // Wait until our source is folded to completion. 798 799 SmallVector<Value*, 8> Indices; 800 801 // Find out whether the last index in the source GEP is a sequential idx. 802 bool EndsWithSequential = false; 803 for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src); 804 I != E; ++I) 805 EndsWithSequential = !(*I)->isStructTy(); 806 807 // Can we combine the two pointer arithmetics offsets? 808 if (EndsWithSequential) { 809 // Replace: gep (gep %P, long B), long A, ... 810 // With: T = long A+B; gep %P, T, ... 811 // 812 Value *Sum; 813 Value *SO1 = Src->getOperand(Src->getNumOperands()-1); 814 Value *GO1 = GEP.getOperand(1); 815 if (SO1 == Constant::getNullValue(SO1->getType())) { 816 Sum = GO1; 817 } else if (GO1 == Constant::getNullValue(GO1->getType())) { 818 Sum = SO1; 819 } else { 820 // If they aren't the same type, then the input hasn't been processed 821 // by the loop above yet (which canonicalizes sequential index types to 822 // intptr_t). Just avoid transforming this until the input has been 823 // normalized. 824 if (SO1->getType() != GO1->getType()) 825 return 0; 826 Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum"); 827 } 828 829 // Update the GEP in place if possible. 830 if (Src->getNumOperands() == 2) { 831 GEP.setOperand(0, Src->getOperand(0)); 832 GEP.setOperand(1, Sum); 833 return &GEP; 834 } 835 Indices.append(Src->op_begin()+1, Src->op_end()-1); 836 Indices.push_back(Sum); 837 Indices.append(GEP.op_begin()+2, GEP.op_end()); 838 } else if (isa<Constant>(*GEP.idx_begin()) && 839 cast<Constant>(*GEP.idx_begin())->isNullValue() && 840 Src->getNumOperands() != 1) { 841 // Otherwise we can do the fold if the first index of the GEP is a zero 842 Indices.append(Src->op_begin()+1, Src->op_end()); 843 Indices.append(GEP.idx_begin()+1, GEP.idx_end()); 844 } 845 846 if (!Indices.empty()) 847 return (GEP.isInBounds() && Src->isInBounds()) ? 848 GetElementPtrInst::CreateInBounds(Src->getOperand(0), Indices.begin(), 849 Indices.end(), GEP.getName()) : 850 GetElementPtrInst::Create(Src->getOperand(0), Indices.begin(), 851 Indices.end(), GEP.getName()); 852 } 853 854 // Handle gep(bitcast x) and gep(gep x, 0, 0, 0). 855 Value *StrippedPtr = PtrOp->stripPointerCasts(); 856 if (StrippedPtr != PtrOp) { 857 const PointerType *StrippedPtrTy =cast<PointerType>(StrippedPtr->getType()); 858 859 bool HasZeroPointerIndex = false; 860 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1))) 861 HasZeroPointerIndex = C->isZero(); 862 863 // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... 864 // into : GEP [10 x i8]* X, i32 0, ... 865 // 866 // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ... 867 // into : GEP i8* X, ... 868 // 869 // This occurs when the program declares an array extern like "int X[];" 870 if (HasZeroPointerIndex) { 871 const PointerType *CPTy = cast<PointerType>(PtrOp->getType()); 872 if (const ArrayType *CATy = 873 dyn_cast<ArrayType>(CPTy->getElementType())) { 874 // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ? 875 if (CATy->getElementType() == StrippedPtrTy->getElementType()) { 876 // -> GEP i8* X, ... 877 SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end()); 878 GetElementPtrInst *Res = 879 GetElementPtrInst::Create(StrippedPtr, Idx.begin(), 880 Idx.end(), GEP.getName()); 881 Res->setIsInBounds(GEP.isInBounds()); 882 return Res; 883 } 884 885 if (const ArrayType *XATy = 886 dyn_cast<ArrayType>(StrippedPtrTy->getElementType())){ 887 // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ? 888 if (CATy->getElementType() == XATy->getElementType()) { 889 // -> GEP [10 x i8]* X, i32 0, ... 890 // At this point, we know that the cast source type is a pointer 891 // to an array of the same type as the destination pointer 892 // array. Because the array type is never stepped over (there 893 // is a leading zero) we can fold the cast into this GEP. 894 GEP.setOperand(0, StrippedPtr); 895 return &GEP; 896 } 897 } 898 } 899 } else if (GEP.getNumOperands() == 2) { 900 // Transform things like: 901 // %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V 902 // into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast 903 const Type *SrcElTy = StrippedPtrTy->getElementType(); 904 const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType(); 905 if (TD && SrcElTy->isArrayTy() && 906 TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()) == 907 TD->getTypeAllocSize(ResElTy)) { 908 Value *Idx[2]; 909 Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); 910 Idx[1] = GEP.getOperand(1); 911 Value *NewGEP = GEP.isInBounds() ? 912 Builder->CreateInBoundsGEP(StrippedPtr, Idx, Idx + 2, GEP.getName()) : 913 Builder->CreateGEP(StrippedPtr, Idx, Idx + 2, GEP.getName()); 914 // V and GEP are both pointer types --> BitCast 915 return new BitCastInst(NewGEP, GEP.getType()); 916 } 917 918 // Transform things like: 919 // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp 920 // (where tmp = 8*tmp2) into: 921 // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast 922 923 if (TD && SrcElTy->isArrayTy() && ResElTy->isIntegerTy(8)) { 924 uint64_t ArrayEltSize = 925 TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()); 926 927 // Check to see if "tmp" is a scale by a multiple of ArrayEltSize. We 928 // allow either a mul, shift, or constant here. 929 Value *NewIdx = 0; 930 ConstantInt *Scale = 0; 931 if (ArrayEltSize == 1) { 932 NewIdx = GEP.getOperand(1); 933 Scale = ConstantInt::get(cast<IntegerType>(NewIdx->getType()), 1); 934 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(1))) { 935 NewIdx = ConstantInt::get(CI->getType(), 1); 936 Scale = CI; 937 } else if (Instruction *Inst =dyn_cast<Instruction>(GEP.getOperand(1))){ 938 if (Inst->getOpcode() == Instruction::Shl && 939 isa<ConstantInt>(Inst->getOperand(1))) { 940 ConstantInt *ShAmt = cast<ConstantInt>(Inst->getOperand(1)); 941 uint32_t ShAmtVal = ShAmt->getLimitedValue(64); 942 Scale = ConstantInt::get(cast<IntegerType>(Inst->getType()), 943 1ULL << ShAmtVal); 944 NewIdx = Inst->getOperand(0); 945 } else if (Inst->getOpcode() == Instruction::Mul && 946 isa<ConstantInt>(Inst->getOperand(1))) { 947 Scale = cast<ConstantInt>(Inst->getOperand(1)); 948 NewIdx = Inst->getOperand(0); 949 } 950 } 951 952 // If the index will be to exactly the right offset with the scale taken 953 // out, perform the transformation. Note, we don't know whether Scale is 954 // signed or not. We'll use unsigned version of division/modulo 955 // operation after making sure Scale doesn't have the sign bit set. 956 if (ArrayEltSize && Scale && Scale->getSExtValue() >= 0LL && 957 Scale->getZExtValue() % ArrayEltSize == 0) { 958 Scale = ConstantInt::get(Scale->getType(), 959 Scale->getZExtValue() / ArrayEltSize); 960 if (Scale->getZExtValue() != 1) { 961 Constant *C = ConstantExpr::getIntegerCast(Scale, NewIdx->getType(), 962 false /*ZExt*/); 963 NewIdx = Builder->CreateMul(NewIdx, C, "idxscale"); 964 } 965 966 // Insert the new GEP instruction. 967 Value *Idx[2]; 968 Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); 969 Idx[1] = NewIdx; 970 Value *NewGEP = GEP.isInBounds() ? 971 Builder->CreateInBoundsGEP(StrippedPtr, Idx, Idx + 2,GEP.getName()): 972 Builder->CreateGEP(StrippedPtr, Idx, Idx + 2, GEP.getName()); 973 // The NewGEP must be pointer typed, so must the old one -> BitCast 974 return new BitCastInst(NewGEP, GEP.getType()); 975 } 976 } 977 } 978 } 979 980 /// See if we can simplify: 981 /// X = bitcast A* to B* 982 /// Y = gep X, <...constant indices...> 983 /// into a gep of the original struct. This is important for SROA and alias 984 /// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged. 985 if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) { 986 if (TD && 987 !isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices()) { 988 // Determine how much the GEP moves the pointer. We are guaranteed to get 989 // a constant back from EmitGEPOffset. 990 ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(&GEP)); 991 int64_t Offset = OffsetV->getSExtValue(); 992 993 // If this GEP instruction doesn't move the pointer, just replace the GEP 994 // with a bitcast of the real input to the dest type. 995 if (Offset == 0) { 996 // If the bitcast is of an allocation, and the allocation will be 997 // converted to match the type of the cast, don't touch this. 998 if (isa<AllocaInst>(BCI->getOperand(0)) || 999 isMalloc(BCI->getOperand(0))) { 1000 // See if the bitcast simplifies, if so, don't nuke this GEP yet. 1001 if (Instruction *I = visitBitCast(*BCI)) { 1002 if (I != BCI) { 1003 I->takeName(BCI); 1004 BCI->getParent()->getInstList().insert(BCI, I); 1005 ReplaceInstUsesWith(*BCI, I); 1006 } 1007 return &GEP; 1008 } 1009 } 1010 return new BitCastInst(BCI->getOperand(0), GEP.getType()); 1011 } 1012 1013 // Otherwise, if the offset is non-zero, we need to find out if there is a 1014 // field at Offset in 'A's type. If so, we can pull the cast through the 1015 // GEP. 1016 SmallVector<Value*, 8> NewIndices; 1017 const Type *InTy = 1018 cast<PointerType>(BCI->getOperand(0)->getType())->getElementType(); 1019 if (FindElementAtOffset(InTy, Offset, NewIndices)) { 1020 Value *NGEP = GEP.isInBounds() ? 1021 Builder->CreateInBoundsGEP(BCI->getOperand(0), NewIndices.begin(), 1022 NewIndices.end()) : 1023 Builder->CreateGEP(BCI->getOperand(0), NewIndices.begin(), 1024 NewIndices.end()); 1025 1026 if (NGEP->getType() == GEP.getType()) 1027 return ReplaceInstUsesWith(GEP, NGEP); 1028 NGEP->takeName(&GEP); 1029 return new BitCastInst(NGEP, GEP.getType()); 1030 } 1031 } 1032 } 1033 1034 return 0; 1035} 1036 1037 1038 1039static bool IsOnlyNullComparedAndFreed(const Value &V) { 1040 for (Value::const_use_iterator UI = V.use_begin(), UE = V.use_end(); 1041 UI != UE; ++UI) { 1042 const User *U = *UI; 1043 if (isFreeCall(U)) 1044 continue; 1045 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(U)) 1046 if (ICI->isEquality() && isa<ConstantPointerNull>(ICI->getOperand(1))) 1047 continue; 1048 return false; 1049 } 1050 return true; 1051} 1052 1053Instruction *InstCombiner::visitMalloc(Instruction &MI) { 1054 // If we have a malloc call which is only used in any amount of comparisons 1055 // to null and free calls, delete the calls and replace the comparisons with 1056 // true or false as appropriate. 1057 if (IsOnlyNullComparedAndFreed(MI)) { 1058 for (Value::use_iterator UI = MI.use_begin(), UE = MI.use_end(); 1059 UI != UE;) { 1060 // We can assume that every remaining use is a free call or an icmp eq/ne 1061 // to null, so the cast is safe. 1062 Instruction *I = cast<Instruction>(*UI); 1063 1064 // Early increment here, as we're about to get rid of the user. 1065 ++UI; 1066 1067 if (isFreeCall(I)) { 1068 EraseInstFromFunction(*cast<CallInst>(I)); 1069 continue; 1070 } 1071 // Again, the cast is safe. 1072 ICmpInst *C = cast<ICmpInst>(I); 1073 ReplaceInstUsesWith(*C, ConstantInt::get(Type::getInt1Ty(C->getContext()), 1074 C->isFalseWhenEqual())); 1075 EraseInstFromFunction(*C); 1076 } 1077 return EraseInstFromFunction(MI); 1078 } 1079 return 0; 1080} 1081 1082 1083 1084Instruction *InstCombiner::visitFree(CallInst &FI) { 1085 Value *Op = FI.getArgOperand(0); 1086 1087 // free undef -> unreachable. 1088 if (isa<UndefValue>(Op)) { 1089 // Insert a new store to null because we cannot modify the CFG here. 1090 new StoreInst(ConstantInt::getTrue(FI.getContext()), 1091 UndefValue::get(Type::getInt1PtrTy(FI.getContext())), &FI); 1092 return EraseInstFromFunction(FI); 1093 } 1094 1095 // If we have 'free null' delete the instruction. This can happen in stl code 1096 // when lots of inlining happens. 1097 if (isa<ConstantPointerNull>(Op)) 1098 return EraseInstFromFunction(FI); 1099 1100 return 0; 1101} 1102 1103 1104 1105Instruction *InstCombiner::visitBranchInst(BranchInst &BI) { 1106 // Change br (not X), label True, label False to: br X, label False, True 1107 Value *X = 0; 1108 BasicBlock *TrueDest; 1109 BasicBlock *FalseDest; 1110 if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) && 1111 !isa<Constant>(X)) { 1112 // Swap Destinations and condition... 1113 BI.setCondition(X); 1114 BI.setSuccessor(0, FalseDest); 1115 BI.setSuccessor(1, TrueDest); 1116 return &BI; 1117 } 1118 1119 // Cannonicalize fcmp_one -> fcmp_oeq 1120 FCmpInst::Predicate FPred; Value *Y; 1121 if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)), 1122 TrueDest, FalseDest)) && 1123 BI.getCondition()->hasOneUse()) 1124 if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE || 1125 FPred == FCmpInst::FCMP_OGE) { 1126 FCmpInst *Cond = cast<FCmpInst>(BI.getCondition()); 1127 Cond->setPredicate(FCmpInst::getInversePredicate(FPred)); 1128 1129 // Swap Destinations and condition. 1130 BI.setSuccessor(0, FalseDest); 1131 BI.setSuccessor(1, TrueDest); 1132 Worklist.Add(Cond); 1133 return &BI; 1134 } 1135 1136 // Cannonicalize icmp_ne -> icmp_eq 1137 ICmpInst::Predicate IPred; 1138 if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)), 1139 TrueDest, FalseDest)) && 1140 BI.getCondition()->hasOneUse()) 1141 if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE || 1142 IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE || 1143 IPred == ICmpInst::ICMP_SGE) { 1144 ICmpInst *Cond = cast<ICmpInst>(BI.getCondition()); 1145 Cond->setPredicate(ICmpInst::getInversePredicate(IPred)); 1146 // Swap Destinations and condition. 1147 BI.setSuccessor(0, FalseDest); 1148 BI.setSuccessor(1, TrueDest); 1149 Worklist.Add(Cond); 1150 return &BI; 1151 } 1152 1153 return 0; 1154} 1155 1156Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) { 1157 Value *Cond = SI.getCondition(); 1158 if (Instruction *I = dyn_cast<Instruction>(Cond)) { 1159 if (I->getOpcode() == Instruction::Add) 1160 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) { 1161 // change 'switch (X+4) case 1:' into 'switch (X) case -3' 1162 for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2) 1163 SI.setOperand(i, 1164 ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)), 1165 AddRHS)); 1166 SI.setOperand(0, I->getOperand(0)); 1167 Worklist.Add(I); 1168 return &SI; 1169 } 1170 } 1171 return 0; 1172} 1173 1174Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) { 1175 Value *Agg = EV.getAggregateOperand(); 1176 1177 if (!EV.hasIndices()) 1178 return ReplaceInstUsesWith(EV, Agg); 1179 1180 if (Constant *C = dyn_cast<Constant>(Agg)) { 1181 if (isa<UndefValue>(C)) 1182 return ReplaceInstUsesWith(EV, UndefValue::get(EV.getType())); 1183 1184 if (isa<ConstantAggregateZero>(C)) 1185 return ReplaceInstUsesWith(EV, Constant::getNullValue(EV.getType())); 1186 1187 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) { 1188 // Extract the element indexed by the first index out of the constant 1189 Value *V = C->getOperand(*EV.idx_begin()); 1190 if (EV.getNumIndices() > 1) 1191 // Extract the remaining indices out of the constant indexed by the 1192 // first index 1193 return ExtractValueInst::Create(V, EV.idx_begin() + 1, EV.idx_end()); 1194 else 1195 return ReplaceInstUsesWith(EV, V); 1196 } 1197 return 0; // Can't handle other constants 1198 } 1199 if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) { 1200 // We're extracting from an insertvalue instruction, compare the indices 1201 const unsigned *exti, *exte, *insi, *inse; 1202 for (exti = EV.idx_begin(), insi = IV->idx_begin(), 1203 exte = EV.idx_end(), inse = IV->idx_end(); 1204 exti != exte && insi != inse; 1205 ++exti, ++insi) { 1206 if (*insi != *exti) 1207 // The insert and extract both reference distinctly different elements. 1208 // This means the extract is not influenced by the insert, and we can 1209 // replace the aggregate operand of the extract with the aggregate 1210 // operand of the insert. i.e., replace 1211 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 1212 // %E = extractvalue { i32, { i32 } } %I, 0 1213 // with 1214 // %E = extractvalue { i32, { i32 } } %A, 0 1215 return ExtractValueInst::Create(IV->getAggregateOperand(), 1216 EV.idx_begin(), EV.idx_end()); 1217 } 1218 if (exti == exte && insi == inse) 1219 // Both iterators are at the end: Index lists are identical. Replace 1220 // %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 1221 // %C = extractvalue { i32, { i32 } } %B, 1, 0 1222 // with "i32 42" 1223 return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand()); 1224 if (exti == exte) { 1225 // The extract list is a prefix of the insert list. i.e. replace 1226 // %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 1227 // %E = extractvalue { i32, { i32 } } %I, 1 1228 // with 1229 // %X = extractvalue { i32, { i32 } } %A, 1 1230 // %E = insertvalue { i32 } %X, i32 42, 0 1231 // by switching the order of the insert and extract (though the 1232 // insertvalue should be left in, since it may have other uses). 1233 Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(), 1234 EV.idx_begin(), EV.idx_end()); 1235 return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(), 1236 insi, inse); 1237 } 1238 if (insi == inse) 1239 // The insert list is a prefix of the extract list 1240 // We can simply remove the common indices from the extract and make it 1241 // operate on the inserted value instead of the insertvalue result. 1242 // i.e., replace 1243 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 1244 // %E = extractvalue { i32, { i32 } } %I, 1, 0 1245 // with 1246 // %E extractvalue { i32 } { i32 42 }, 0 1247 return ExtractValueInst::Create(IV->getInsertedValueOperand(), 1248 exti, exte); 1249 } 1250 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) { 1251 // We're extracting from an intrinsic, see if we're the only user, which 1252 // allows us to simplify multiple result intrinsics to simpler things that 1253 // just get one value. 1254 if (II->hasOneUse()) { 1255 // Check if we're grabbing the overflow bit or the result of a 'with 1256 // overflow' intrinsic. If it's the latter we can remove the intrinsic 1257 // and replace it with a traditional binary instruction. 1258 switch (II->getIntrinsicID()) { 1259 case Intrinsic::uadd_with_overflow: 1260 case Intrinsic::sadd_with_overflow: 1261 if (*EV.idx_begin() == 0) { // Normal result. 1262 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1263 II->replaceAllUsesWith(UndefValue::get(II->getType())); 1264 EraseInstFromFunction(*II); 1265 return BinaryOperator::CreateAdd(LHS, RHS); 1266 } 1267 1268 // If the normal result of the add is dead, and the RHS is a constant, 1269 // we can transform this into a range comparison. 1270 // overflow = uadd a, -4 --> overflow = icmp ugt a, 3 1271 if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow) 1272 if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1))) 1273 return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0), 1274 ConstantExpr::getNot(CI)); 1275 break; 1276 case Intrinsic::usub_with_overflow: 1277 case Intrinsic::ssub_with_overflow: 1278 if (*EV.idx_begin() == 0) { // Normal result. 1279 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1280 II->replaceAllUsesWith(UndefValue::get(II->getType())); 1281 EraseInstFromFunction(*II); 1282 return BinaryOperator::CreateSub(LHS, RHS); 1283 } 1284 break; 1285 case Intrinsic::umul_with_overflow: 1286 case Intrinsic::smul_with_overflow: 1287 if (*EV.idx_begin() == 0) { // Normal result. 1288 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1289 II->replaceAllUsesWith(UndefValue::get(II->getType())); 1290 EraseInstFromFunction(*II); 1291 return BinaryOperator::CreateMul(LHS, RHS); 1292 } 1293 break; 1294 default: 1295 break; 1296 } 1297 } 1298 } 1299 if (LoadInst *L = dyn_cast<LoadInst>(Agg)) 1300 // If the (non-volatile) load only has one use, we can rewrite this to a 1301 // load from a GEP. This reduces the size of the load. 1302 // FIXME: If a load is used only by extractvalue instructions then this 1303 // could be done regardless of having multiple uses. 1304 if (!L->isVolatile() && L->hasOneUse()) { 1305 // extractvalue has integer indices, getelementptr has Value*s. Convert. 1306 SmallVector<Value*, 4> Indices; 1307 // Prefix an i32 0 since we need the first element. 1308 Indices.push_back(Builder->getInt32(0)); 1309 for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end(); 1310 I != E; ++I) 1311 Indices.push_back(Builder->getInt32(*I)); 1312 1313 // We need to insert these at the location of the old load, not at that of 1314 // the extractvalue. 1315 Builder->SetInsertPoint(L->getParent(), L); 1316 Value *GEP = Builder->CreateInBoundsGEP(L->getPointerOperand(), 1317 Indices.begin(), Indices.end()); 1318 // Returning the load directly will cause the main loop to insert it in 1319 // the wrong spot, so use ReplaceInstUsesWith(). 1320 return ReplaceInstUsesWith(EV, Builder->CreateLoad(GEP)); 1321 } 1322 // We could simplify extracts from other values. Note that nested extracts may 1323 // already be simplified implicitly by the above: extract (extract (insert) ) 1324 // will be translated into extract ( insert ( extract ) ) first and then just 1325 // the value inserted, if appropriate. Similarly for extracts from single-use 1326 // loads: extract (extract (load)) will be translated to extract (load (gep)) 1327 // and if again single-use then via load (gep (gep)) to load (gep). 1328 // However, double extracts from e.g. function arguments or return values 1329 // aren't handled yet. 1330 return 0; 1331} 1332 1333 1334 1335 1336/// TryToSinkInstruction - Try to move the specified instruction from its 1337/// current block into the beginning of DestBlock, which can only happen if it's 1338/// safe to move the instruction past all of the instructions between it and the 1339/// end of its block. 1340static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) { 1341 assert(I->hasOneUse() && "Invariants didn't hold!"); 1342 1343 // Cannot move control-flow-involving, volatile loads, vaarg, etc. 1344 if (isa<PHINode>(I) || I->mayHaveSideEffects() || isa<TerminatorInst>(I)) 1345 return false; 1346 1347 // Do not sink alloca instructions out of the entry block. 1348 if (isa<AllocaInst>(I) && I->getParent() == 1349 &DestBlock->getParent()->getEntryBlock()) 1350 return false; 1351 1352 // We can only sink load instructions if there is nothing between the load and 1353 // the end of block that could change the value. 1354 if (I->mayReadFromMemory()) { 1355 for (BasicBlock::iterator Scan = I, E = I->getParent()->end(); 1356 Scan != E; ++Scan) 1357 if (Scan->mayWriteToMemory()) 1358 return false; 1359 } 1360 1361 BasicBlock::iterator InsertPos = DestBlock->getFirstNonPHI(); 1362 1363 I->moveBefore(InsertPos); 1364 ++NumSunkInst; 1365 return true; 1366} 1367 1368 1369/// AddReachableCodeToWorklist - Walk the function in depth-first order, adding 1370/// all reachable code to the worklist. 1371/// 1372/// This has a couple of tricks to make the code faster and more powerful. In 1373/// particular, we constant fold and DCE instructions as we go, to avoid adding 1374/// them to the worklist (this significantly speeds up instcombine on code where 1375/// many instructions are dead or constant). Additionally, if we find a branch 1376/// whose condition is a known constant, we only visit the reachable successors. 1377/// 1378static bool AddReachableCodeToWorklist(BasicBlock *BB, 1379 SmallPtrSet<BasicBlock*, 64> &Visited, 1380 InstCombiner &IC, 1381 const TargetData *TD) { 1382 bool MadeIRChange = false; 1383 SmallVector<BasicBlock*, 256> Worklist; 1384 Worklist.push_back(BB); 1385 1386 SmallVector<Instruction*, 128> InstrsForInstCombineWorklist; 1387 SmallPtrSet<ConstantExpr*, 64> FoldedConstants; 1388 1389 do { 1390 BB = Worklist.pop_back_val(); 1391 1392 // We have now visited this block! If we've already been here, ignore it. 1393 if (!Visited.insert(BB)) continue; 1394 1395 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { 1396 Instruction *Inst = BBI++; 1397 1398 // DCE instruction if trivially dead. 1399 if (isInstructionTriviallyDead(Inst)) { 1400 ++NumDeadInst; 1401 DEBUG(errs() << "IC: DCE: " << *Inst << '\n'); 1402 Inst->eraseFromParent(); 1403 continue; 1404 } 1405 1406 // ConstantProp instruction if trivially constant. 1407 if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0))) 1408 if (Constant *C = ConstantFoldInstruction(Inst, TD)) { 1409 DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " 1410 << *Inst << '\n'); 1411 Inst->replaceAllUsesWith(C); 1412 ++NumConstProp; 1413 Inst->eraseFromParent(); 1414 continue; 1415 } 1416 1417 if (TD) { 1418 // See if we can constant fold its operands. 1419 for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end(); 1420 i != e; ++i) { 1421 ConstantExpr *CE = dyn_cast<ConstantExpr>(i); 1422 if (CE == 0) continue; 1423 1424 // If we already folded this constant, don't try again. 1425 if (!FoldedConstants.insert(CE)) 1426 continue; 1427 1428 Constant *NewC = ConstantFoldConstantExpression(CE, TD); 1429 if (NewC && NewC != CE) { 1430 *i = NewC; 1431 MadeIRChange = true; 1432 } 1433 } 1434 } 1435 1436 InstrsForInstCombineWorklist.push_back(Inst); 1437 } 1438 1439 // Recursively visit successors. If this is a branch or switch on a 1440 // constant, only visit the reachable successor. 1441 TerminatorInst *TI = BB->getTerminator(); 1442 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { 1443 if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) { 1444 bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue(); 1445 BasicBlock *ReachableBB = BI->getSuccessor(!CondVal); 1446 Worklist.push_back(ReachableBB); 1447 continue; 1448 } 1449 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { 1450 if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) { 1451 // See if this is an explicit destination. 1452 for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) 1453 if (SI->getCaseValue(i) == Cond) { 1454 BasicBlock *ReachableBB = SI->getSuccessor(i); 1455 Worklist.push_back(ReachableBB); 1456 continue; 1457 } 1458 1459 // Otherwise it is the default destination. 1460 Worklist.push_back(SI->getSuccessor(0)); 1461 continue; 1462 } 1463 } 1464 1465 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 1466 Worklist.push_back(TI->getSuccessor(i)); 1467 } while (!Worklist.empty()); 1468 1469 // Once we've found all of the instructions to add to instcombine's worklist, 1470 // add them in reverse order. This way instcombine will visit from the top 1471 // of the function down. This jives well with the way that it adds all uses 1472 // of instructions to the worklist after doing a transformation, thus avoiding 1473 // some N^2 behavior in pathological cases. 1474 IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0], 1475 InstrsForInstCombineWorklist.size()); 1476 1477 return MadeIRChange; 1478} 1479 1480bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) { 1481 MadeIRChange = false; 1482 1483 DEBUG(errs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on " 1484 << F.getNameStr() << "\n"); 1485 1486 { 1487 // Do a depth-first traversal of the function, populate the worklist with 1488 // the reachable instructions. Ignore blocks that are not reachable. Keep 1489 // track of which blocks we visit. 1490 SmallPtrSet<BasicBlock*, 64> Visited; 1491 MadeIRChange |= AddReachableCodeToWorklist(F.begin(), Visited, *this, TD); 1492 1493 // Do a quick scan over the function. If we find any blocks that are 1494 // unreachable, remove any instructions inside of them. This prevents 1495 // the instcombine code from having to deal with some bad special cases. 1496 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) 1497 if (!Visited.count(BB)) { 1498 Instruction *Term = BB->getTerminator(); 1499 while (Term != BB->begin()) { // Remove instrs bottom-up 1500 BasicBlock::iterator I = Term; --I; 1501 1502 DEBUG(errs() << "IC: DCE: " << *I << '\n'); 1503 // A debug intrinsic shouldn't force another iteration if we weren't 1504 // going to do one without it. 1505 if (!isa<DbgInfoIntrinsic>(I)) { 1506 ++NumDeadInst; 1507 MadeIRChange = true; 1508 } 1509 1510 // If I is not void type then replaceAllUsesWith undef. 1511 // This allows ValueHandlers and custom metadata to adjust itself. 1512 if (!I->getType()->isVoidTy()) 1513 I->replaceAllUsesWith(UndefValue::get(I->getType())); 1514 I->eraseFromParent(); 1515 } 1516 } 1517 } 1518 1519 while (!Worklist.isEmpty()) { 1520 Instruction *I = Worklist.RemoveOne(); 1521 if (I == 0) continue; // skip null values. 1522 1523 // Check to see if we can DCE the instruction. 1524 if (isInstructionTriviallyDead(I)) { 1525 DEBUG(errs() << "IC: DCE: " << *I << '\n'); 1526 EraseInstFromFunction(*I); 1527 ++NumDeadInst; 1528 MadeIRChange = true; 1529 continue; 1530 } 1531 1532 // Instruction isn't dead, see if we can constant propagate it. 1533 if (!I->use_empty() && isa<Constant>(I->getOperand(0))) 1534 if (Constant *C = ConstantFoldInstruction(I, TD)) { 1535 DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n'); 1536 1537 // Add operands to the worklist. 1538 ReplaceInstUsesWith(*I, C); 1539 ++NumConstProp; 1540 EraseInstFromFunction(*I); 1541 MadeIRChange = true; 1542 continue; 1543 } 1544 1545 // See if we can trivially sink this instruction to a successor basic block. 1546 if (I->hasOneUse()) { 1547 BasicBlock *BB = I->getParent(); 1548 Instruction *UserInst = cast<Instruction>(I->use_back()); 1549 BasicBlock *UserParent; 1550 1551 // Get the block the use occurs in. 1552 if (PHINode *PN = dyn_cast<PHINode>(UserInst)) 1553 UserParent = PN->getIncomingBlock(I->use_begin().getUse()); 1554 else 1555 UserParent = UserInst->getParent(); 1556 1557 if (UserParent != BB) { 1558 bool UserIsSuccessor = false; 1559 // See if the user is one of our successors. 1560 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) 1561 if (*SI == UserParent) { 1562 UserIsSuccessor = true; 1563 break; 1564 } 1565 1566 // If the user is one of our immediate successors, and if that successor 1567 // only has us as a predecessors (we'd have to split the critical edge 1568 // otherwise), we can keep going. 1569 if (UserIsSuccessor && UserParent->getSinglePredecessor()) 1570 // Okay, the CFG is simple enough, try to sink this instruction. 1571 MadeIRChange |= TryToSinkInstruction(I, UserParent); 1572 } 1573 } 1574 1575 // Now that we have an instruction, try combining it to simplify it. 1576 Builder->SetInsertPoint(I->getParent(), I); 1577 1578#ifndef NDEBUG 1579 std::string OrigI; 1580#endif 1581 DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str();); 1582 DEBUG(errs() << "IC: Visiting: " << OrigI << '\n'); 1583 1584 if (Instruction *Result = visit(*I)) { 1585 ++NumCombined; 1586 // Should we replace the old instruction with a new one? 1587 if (Result != I) { 1588 DEBUG(errs() << "IC: Old = " << *I << '\n' 1589 << " New = " << *Result << '\n'); 1590 1591 Result->setDebugLoc(I->getDebugLoc()); 1592 // Everything uses the new instruction now. 1593 I->replaceAllUsesWith(Result); 1594 1595 // Push the new instruction and any users onto the worklist. 1596 Worklist.Add(Result); 1597 Worklist.AddUsersToWorkList(*Result); 1598 1599 // Move the name to the new instruction first. 1600 Result->takeName(I); 1601 1602 // Insert the new instruction into the basic block... 1603 BasicBlock *InstParent = I->getParent(); 1604 BasicBlock::iterator InsertPos = I; 1605 1606 if (!isa<PHINode>(Result)) // If combining a PHI, don't insert 1607 while (isa<PHINode>(InsertPos)) // middle of a block of PHIs. 1608 ++InsertPos; 1609 1610 InstParent->getInstList().insert(InsertPos, Result); 1611 1612 EraseInstFromFunction(*I); 1613 } else { 1614#ifndef NDEBUG 1615 DEBUG(errs() << "IC: Mod = " << OrigI << '\n' 1616 << " New = " << *I << '\n'); 1617#endif 1618 1619 // If the instruction was modified, it's possible that it is now dead. 1620 // if so, remove it. 1621 if (isInstructionTriviallyDead(I)) { 1622 EraseInstFromFunction(*I); 1623 } else { 1624 Worklist.Add(I); 1625 Worklist.AddUsersToWorkList(*I); 1626 } 1627 } 1628 MadeIRChange = true; 1629 } 1630 } 1631 1632 Worklist.Zap(); 1633 return MadeIRChange; 1634} 1635 1636 1637bool InstCombiner::runOnFunction(Function &F) { 1638 MustPreserveLCSSA = mustPreserveAnalysisID(LCSSAID); 1639 TD = getAnalysisIfAvailable<TargetData>(); 1640 1641 1642 /// Builder - This is an IRBuilder that automatically inserts new 1643 /// instructions into the worklist when they are created. 1644 IRBuilder<true, TargetFolder, InstCombineIRInserter> 1645 TheBuilder(F.getContext(), TargetFolder(TD), 1646 InstCombineIRInserter(Worklist)); 1647 Builder = &TheBuilder; 1648 1649 bool EverMadeChange = false; 1650 1651 // Iterate while there is work to do. 1652 unsigned Iteration = 0; 1653 while (DoOneIteration(F, Iteration++)) 1654 EverMadeChange = true; 1655 1656 Builder = 0; 1657 return EverMadeChange; 1658} 1659 1660FunctionPass *llvm::createInstructionCombiningPass() { 1661 return new InstCombiner(); 1662} 1663