InstructionCombining.cpp revision f1ec4e4123a8e6d811c072f383399781cfeaa9aa
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/DataLayout.h" 44#include "llvm/Target/TargetLibraryInfo.h" 45#include "llvm/Transforms/Utils/Local.h" 46#include "llvm/Support/CFG.h" 47#include "llvm/Support/Debug.h" 48#include "llvm/Support/GetElementPtrTypeIterator.h" 49#include "llvm/Support/PatternMatch.h" 50#include "llvm/Support/ValueHandle.h" 51#include "llvm/ADT/SmallPtrSet.h" 52#include "llvm/ADT/Statistic.h" 53#include "llvm/ADT/StringSwitch.h" 54#include "llvm-c/Initialization.h" 55#include <algorithm> 56#include <climits> 57using namespace llvm; 58using namespace llvm::PatternMatch; 59 60STATISTIC(NumCombined , "Number of insts combined"); 61STATISTIC(NumConstProp, "Number of constant folds"); 62STATISTIC(NumDeadInst , "Number of dead inst eliminated"); 63STATISTIC(NumSunkInst , "Number of instructions sunk"); 64STATISTIC(NumExpand, "Number of expansions"); 65STATISTIC(NumFactor , "Number of factorizations"); 66STATISTIC(NumReassoc , "Number of reassociations"); 67 68// Initialization Routines 69void llvm::initializeInstCombine(PassRegistry &Registry) { 70 initializeInstCombinerPass(Registry); 71} 72 73void LLVMInitializeInstCombine(LLVMPassRegistryRef R) { 74 initializeInstCombine(*unwrap(R)); 75} 76 77char InstCombiner::ID = 0; 78INITIALIZE_PASS_BEGIN(InstCombiner, "instcombine", 79 "Combine redundant instructions", false, false) 80INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) 81INITIALIZE_PASS_END(InstCombiner, "instcombine", 82 "Combine redundant instructions", false, false) 83 84void InstCombiner::getAnalysisUsage(AnalysisUsage &AU) const { 85 AU.setPreservesCFG(); 86 AU.addRequired<TargetLibraryInfo>(); 87} 88 89 90Value *InstCombiner::EmitGEPOffset(User *GEP) { 91 return llvm::EmitGEPOffset(Builder, *getDataLayout(), GEP); 92} 93 94/// ShouldChangeType - Return true if it is desirable to convert a computation 95/// from 'From' to 'To'. We don't want to convert from a legal to an illegal 96/// type for example, or from a smaller to a larger illegal type. 97bool InstCombiner::ShouldChangeType(Type *From, Type *To) const { 98 assert(From->isIntegerTy() && To->isIntegerTy()); 99 100 // If we don't have TD, we don't know if the source/dest are legal. 101 if (!TD) return false; 102 103 unsigned FromWidth = From->getPrimitiveSizeInBits(); 104 unsigned ToWidth = To->getPrimitiveSizeInBits(); 105 bool FromLegal = TD->isLegalInteger(FromWidth); 106 bool ToLegal = TD->isLegalInteger(ToWidth); 107 108 // If this is a legal integer from type, and the result would be an illegal 109 // type, don't do the transformation. 110 if (FromLegal && !ToLegal) 111 return false; 112 113 // Otherwise, if both are illegal, do not increase the size of the result. We 114 // do allow things like i160 -> i64, but not i64 -> i160. 115 if (!FromLegal && !ToLegal && ToWidth > FromWidth) 116 return false; 117 118 return true; 119} 120 121// Return true, if No Signed Wrap should be maintained for I. 122// The No Signed Wrap flag can be kept if the operation "B (I.getOpcode) C", 123// where both B and C should be ConstantInts, results in a constant that does 124// not overflow. This function only handles the Add and Sub opcodes. For 125// all other opcodes, the function conservatively returns false. 126static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) { 127 OverflowingBinaryOperator *OBO = dyn_cast<OverflowingBinaryOperator>(&I); 128 if (!OBO || !OBO->hasNoSignedWrap()) { 129 return false; 130 } 131 132 // We reason about Add and Sub Only. 133 Instruction::BinaryOps Opcode = I.getOpcode(); 134 if (Opcode != Instruction::Add && 135 Opcode != Instruction::Sub) { 136 return false; 137 } 138 139 ConstantInt *CB = dyn_cast<ConstantInt>(B); 140 ConstantInt *CC = dyn_cast<ConstantInt>(C); 141 142 if (!CB || !CC) { 143 return false; 144 } 145 146 const APInt &BVal = CB->getValue(); 147 const APInt &CVal = CC->getValue(); 148 bool Overflow = false; 149 150 if (Opcode == Instruction::Add) { 151 BVal.sadd_ov(CVal, Overflow); 152 } else { 153 BVal.ssub_ov(CVal, Overflow); 154 } 155 156 return !Overflow; 157} 158 159/// SimplifyAssociativeOrCommutative - This performs a few simplifications for 160/// operators which are associative or commutative: 161// 162// Commutative operators: 163// 164// 1. Order operands such that they are listed from right (least complex) to 165// left (most complex). This puts constants before unary operators before 166// binary operators. 167// 168// Associative operators: 169// 170// 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. 171// 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. 172// 173// Associative and commutative operators: 174// 175// 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. 176// 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. 177// 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" 178// if C1 and C2 are constants. 179// 180bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) { 181 Instruction::BinaryOps Opcode = I.getOpcode(); 182 bool Changed = false; 183 184 do { 185 // Order operands such that they are listed from right (least complex) to 186 // left (most complex). This puts constants before unary operators before 187 // binary operators. 188 if (I.isCommutative() && getComplexity(I.getOperand(0)) < 189 getComplexity(I.getOperand(1))) 190 Changed = !I.swapOperands(); 191 192 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0)); 193 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1)); 194 195 if (I.isAssociative()) { 196 // Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. 197 if (Op0 && Op0->getOpcode() == Opcode) { 198 Value *A = Op0->getOperand(0); 199 Value *B = Op0->getOperand(1); 200 Value *C = I.getOperand(1); 201 202 // Does "B op C" simplify? 203 if (Value *V = SimplifyBinOp(Opcode, B, C, TD)) { 204 // It simplifies to V. Form "A op V". 205 I.setOperand(0, A); 206 I.setOperand(1, V); 207 // Conservatively clear the optional flags, since they may not be 208 // preserved by the reassociation. 209 if (MaintainNoSignedWrap(I, B, C) && 210 (!Op0 || (isa<BinaryOperator>(Op0) && Op0->hasNoSignedWrap()))) { 211 // Note: this is only valid because SimplifyBinOp doesn't look at 212 // the operands to Op0. 213 I.clearSubclassOptionalData(); 214 I.setHasNoSignedWrap(true); 215 } else { 216 I.clearSubclassOptionalData(); 217 } 218 219 Changed = true; 220 ++NumReassoc; 221 continue; 222 } 223 } 224 225 // Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. 226 if (Op1 && Op1->getOpcode() == Opcode) { 227 Value *A = I.getOperand(0); 228 Value *B = Op1->getOperand(0); 229 Value *C = Op1->getOperand(1); 230 231 // Does "A op B" simplify? 232 if (Value *V = SimplifyBinOp(Opcode, A, B, TD)) { 233 // It simplifies to V. Form "V op C". 234 I.setOperand(0, V); 235 I.setOperand(1, C); 236 // Conservatively clear the optional flags, since they may not be 237 // preserved by the reassociation. 238 I.clearSubclassOptionalData(); 239 Changed = true; 240 ++NumReassoc; 241 continue; 242 } 243 } 244 } 245 246 if (I.isAssociative() && I.isCommutative()) { 247 // Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. 248 if (Op0 && Op0->getOpcode() == Opcode) { 249 Value *A = Op0->getOperand(0); 250 Value *B = Op0->getOperand(1); 251 Value *C = I.getOperand(1); 252 253 // Does "C op A" simplify? 254 if (Value *V = SimplifyBinOp(Opcode, C, A, TD)) { 255 // It simplifies to V. Form "V op B". 256 I.setOperand(0, V); 257 I.setOperand(1, B); 258 // Conservatively clear the optional flags, since they may not be 259 // preserved by the reassociation. 260 I.clearSubclassOptionalData(); 261 Changed = true; 262 ++NumReassoc; 263 continue; 264 } 265 } 266 267 // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. 268 if (Op1 && Op1->getOpcode() == Opcode) { 269 Value *A = I.getOperand(0); 270 Value *B = Op1->getOperand(0); 271 Value *C = Op1->getOperand(1); 272 273 // Does "C op A" simplify? 274 if (Value *V = SimplifyBinOp(Opcode, C, A, TD)) { 275 // It simplifies to V. Form "B op V". 276 I.setOperand(0, B); 277 I.setOperand(1, V); 278 // Conservatively clear the optional flags, since they may not be 279 // preserved by the reassociation. 280 I.clearSubclassOptionalData(); 281 Changed = true; 282 ++NumReassoc; 283 continue; 284 } 285 } 286 287 // Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" 288 // if C1 and C2 are constants. 289 if (Op0 && Op1 && 290 Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode && 291 isa<Constant>(Op0->getOperand(1)) && 292 isa<Constant>(Op1->getOperand(1)) && 293 Op0->hasOneUse() && Op1->hasOneUse()) { 294 Value *A = Op0->getOperand(0); 295 Constant *C1 = cast<Constant>(Op0->getOperand(1)); 296 Value *B = Op1->getOperand(0); 297 Constant *C2 = cast<Constant>(Op1->getOperand(1)); 298 299 Constant *Folded = ConstantExpr::get(Opcode, C1, C2); 300 BinaryOperator *New = BinaryOperator::Create(Opcode, A, B); 301 InsertNewInstWith(New, I); 302 New->takeName(Op1); 303 I.setOperand(0, New); 304 I.setOperand(1, Folded); 305 // Conservatively clear the optional flags, since they may not be 306 // preserved by the reassociation. 307 I.clearSubclassOptionalData(); 308 309 Changed = true; 310 continue; 311 } 312 } 313 314 // No further simplifications. 315 return Changed; 316 } while (1); 317} 318 319/// LeftDistributesOverRight - Whether "X LOp (Y ROp Z)" is always equal to 320/// "(X LOp Y) ROp (X LOp Z)". 321static bool LeftDistributesOverRight(Instruction::BinaryOps LOp, 322 Instruction::BinaryOps ROp) { 323 switch (LOp) { 324 default: 325 return false; 326 327 case Instruction::And: 328 // And distributes over Or and Xor. 329 switch (ROp) { 330 default: 331 return false; 332 case Instruction::Or: 333 case Instruction::Xor: 334 return true; 335 } 336 337 case Instruction::Mul: 338 // Multiplication distributes over addition and subtraction. 339 switch (ROp) { 340 default: 341 return false; 342 case Instruction::Add: 343 case Instruction::Sub: 344 return true; 345 } 346 347 case Instruction::Or: 348 // Or distributes over And. 349 switch (ROp) { 350 default: 351 return false; 352 case Instruction::And: 353 return true; 354 } 355 } 356} 357 358/// RightDistributesOverLeft - Whether "(X LOp Y) ROp Z" is always equal to 359/// "(X ROp Z) LOp (Y ROp Z)". 360static bool RightDistributesOverLeft(Instruction::BinaryOps LOp, 361 Instruction::BinaryOps ROp) { 362 if (Instruction::isCommutative(ROp)) 363 return LeftDistributesOverRight(ROp, LOp); 364 // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z", 365 // but this requires knowing that the addition does not overflow and other 366 // such subtleties. 367 return false; 368} 369 370/// SimplifyUsingDistributiveLaws - This tries to simplify binary operations 371/// which some other binary operation distributes over either by factorizing 372/// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this 373/// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is 374/// a win). Returns the simplified value, or null if it didn't simplify. 375Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) { 376 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 377 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 378 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 379 Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); // op 380 381 // Factorization. 382 if (Op0 && Op1 && Op0->getOpcode() == Op1->getOpcode()) { 383 // The instruction has the form "(A op' B) op (C op' D)". Try to factorize 384 // a common term. 385 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1); 386 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1); 387 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' 388 389 // Does "X op' Y" always equal "Y op' X"? 390 bool InnerCommutative = Instruction::isCommutative(InnerOpcode); 391 392 // Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"? 393 if (LeftDistributesOverRight(InnerOpcode, TopLevelOpcode)) 394 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the 395 // commutative case, "(A op' B) op (C op' A)"? 396 if (A == C || (InnerCommutative && A == D)) { 397 if (A != C) 398 std::swap(C, D); 399 // Consider forming "A op' (B op D)". 400 // If "B op D" simplifies then it can be formed with no cost. 401 Value *V = SimplifyBinOp(TopLevelOpcode, B, D, TD); 402 // If "B op D" doesn't simplify then only go on if both of the existing 403 // operations "A op' B" and "C op' D" will be zapped as no longer used. 404 if (!V && Op0->hasOneUse() && Op1->hasOneUse()) 405 V = Builder->CreateBinOp(TopLevelOpcode, B, D, Op1->getName()); 406 if (V) { 407 ++NumFactor; 408 V = Builder->CreateBinOp(InnerOpcode, A, V); 409 V->takeName(&I); 410 return V; 411 } 412 } 413 414 // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"? 415 if (RightDistributesOverLeft(TopLevelOpcode, InnerOpcode)) 416 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the 417 // commutative case, "(A op' B) op (B op' D)"? 418 if (B == D || (InnerCommutative && B == C)) { 419 if (B != D) 420 std::swap(C, D); 421 // Consider forming "(A op C) op' B". 422 // If "A op C" simplifies then it can be formed with no cost. 423 Value *V = SimplifyBinOp(TopLevelOpcode, A, C, TD); 424 // If "A op C" doesn't simplify then only go on if both of the existing 425 // operations "A op' B" and "C op' D" will be zapped as no longer used. 426 if (!V && Op0->hasOneUse() && Op1->hasOneUse()) 427 V = Builder->CreateBinOp(TopLevelOpcode, A, C, Op0->getName()); 428 if (V) { 429 ++NumFactor; 430 V = Builder->CreateBinOp(InnerOpcode, V, B); 431 V->takeName(&I); 432 return V; 433 } 434 } 435 } 436 437 // Expansion. 438 if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) { 439 // The instruction has the form "(A op' B) op C". See if expanding it out 440 // to "(A op C) op' (B op C)" results in simplifications. 441 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; 442 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' 443 444 // Do "A op C" and "B op C" both simplify? 445 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, C, TD)) 446 if (Value *R = SimplifyBinOp(TopLevelOpcode, B, C, TD)) { 447 // They do! Return "L op' R". 448 ++NumExpand; 449 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. 450 if ((L == A && R == B) || 451 (Instruction::isCommutative(InnerOpcode) && L == B && R == A)) 452 return Op0; 453 // Otherwise return "L op' R" if it simplifies. 454 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, TD)) 455 return V; 456 // Otherwise, create a new instruction. 457 C = Builder->CreateBinOp(InnerOpcode, L, R); 458 C->takeName(&I); 459 return C; 460 } 461 } 462 463 if (Op1 && LeftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) { 464 // The instruction has the form "A op (B op' C)". See if expanding it out 465 // to "(A op B) op' (A op C)" results in simplifications. 466 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); 467 Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op' 468 469 // Do "A op B" and "A op C" both simplify? 470 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, B, TD)) 471 if (Value *R = SimplifyBinOp(TopLevelOpcode, A, C, TD)) { 472 // They do! Return "L op' R". 473 ++NumExpand; 474 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. 475 if ((L == B && R == C) || 476 (Instruction::isCommutative(InnerOpcode) && L == C && R == B)) 477 return Op1; 478 // Otherwise return "L op' R" if it simplifies. 479 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, TD)) 480 return V; 481 // Otherwise, create a new instruction. 482 A = Builder->CreateBinOp(InnerOpcode, L, R); 483 A->takeName(&I); 484 return A; 485 } 486 } 487 488 return 0; 489} 490 491// dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction 492// if the LHS is a constant zero (which is the 'negate' form). 493// 494Value *InstCombiner::dyn_castNegVal(Value *V) const { 495 if (BinaryOperator::isNeg(V)) 496 return BinaryOperator::getNegArgument(V); 497 498 // Constants can be considered to be negated values if they can be folded. 499 if (ConstantInt *C = dyn_cast<ConstantInt>(V)) 500 return ConstantExpr::getNeg(C); 501 502 if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) 503 if (C->getType()->getElementType()->isIntegerTy()) 504 return ConstantExpr::getNeg(C); 505 506 return 0; 507} 508 509// dyn_castFNegVal - Given a 'fsub' instruction, return the RHS of the 510// instruction if the LHS is a constant negative zero (which is the 'negate' 511// form). 512// 513Value *InstCombiner::dyn_castFNegVal(Value *V) const { 514 if (BinaryOperator::isFNeg(V)) 515 return BinaryOperator::getFNegArgument(V); 516 517 // Constants can be considered to be negated values if they can be folded. 518 if (ConstantFP *C = dyn_cast<ConstantFP>(V)) 519 return ConstantExpr::getFNeg(C); 520 521 if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) 522 if (C->getType()->getElementType()->isFloatingPointTy()) 523 return ConstantExpr::getFNeg(C); 524 525 return 0; 526} 527 528static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO, 529 InstCombiner *IC) { 530 if (CastInst *CI = dyn_cast<CastInst>(&I)) { 531 return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType()); 532 } 533 534 // Figure out if the constant is the left or the right argument. 535 bool ConstIsRHS = isa<Constant>(I.getOperand(1)); 536 Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS)); 537 538 if (Constant *SOC = dyn_cast<Constant>(SO)) { 539 if (ConstIsRHS) 540 return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand); 541 return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC); 542 } 543 544 Value *Op0 = SO, *Op1 = ConstOperand; 545 if (!ConstIsRHS) 546 std::swap(Op0, Op1); 547 548 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I)) 549 return IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1, 550 SO->getName()+".op"); 551 if (ICmpInst *CI = dyn_cast<ICmpInst>(&I)) 552 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, 553 SO->getName()+".cmp"); 554 if (FCmpInst *CI = dyn_cast<FCmpInst>(&I)) 555 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, 556 SO->getName()+".cmp"); 557 llvm_unreachable("Unknown binary instruction type!"); 558} 559 560// FoldOpIntoSelect - Given an instruction with a select as one operand and a 561// constant as the other operand, try to fold the binary operator into the 562// select arguments. This also works for Cast instructions, which obviously do 563// not have a second operand. 564Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) { 565 // Don't modify shared select instructions 566 if (!SI->hasOneUse()) return 0; 567 Value *TV = SI->getOperand(1); 568 Value *FV = SI->getOperand(2); 569 570 if (isa<Constant>(TV) || isa<Constant>(FV)) { 571 // Bool selects with constant operands can be folded to logical ops. 572 if (SI->getType()->isIntegerTy(1)) return 0; 573 574 // If it's a bitcast involving vectors, make sure it has the same number of 575 // elements on both sides. 576 if (BitCastInst *BC = dyn_cast<BitCastInst>(&Op)) { 577 VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy()); 578 VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy()); 579 580 // Verify that either both or neither are vectors. 581 if ((SrcTy == NULL) != (DestTy == NULL)) return 0; 582 // If vectors, verify that they have the same number of elements. 583 if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements()) 584 return 0; 585 } 586 587 Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this); 588 Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this); 589 590 return SelectInst::Create(SI->getCondition(), 591 SelectTrueVal, SelectFalseVal); 592 } 593 return 0; 594} 595 596 597/// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which 598/// has a PHI node as operand #0, see if we can fold the instruction into the 599/// PHI (which is only possible if all operands to the PHI are constants). 600/// 601Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) { 602 PHINode *PN = cast<PHINode>(I.getOperand(0)); 603 unsigned NumPHIValues = PN->getNumIncomingValues(); 604 if (NumPHIValues == 0) 605 return 0; 606 607 // We normally only transform phis with a single use. However, if a PHI has 608 // multiple uses and they are all the same operation, we can fold *all* of the 609 // uses into the PHI. 610 if (!PN->hasOneUse()) { 611 // Walk the use list for the instruction, comparing them to I. 612 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); 613 UI != E; ++UI) { 614 Instruction *User = cast<Instruction>(*UI); 615 if (User != &I && !I.isIdenticalTo(User)) 616 return 0; 617 } 618 // Otherwise, we can replace *all* users with the new PHI we form. 619 } 620 621 // Check to see if all of the operands of the PHI are simple constants 622 // (constantint/constantfp/undef). If there is one non-constant value, 623 // remember the BB it is in. If there is more than one or if *it* is a PHI, 624 // bail out. We don't do arbitrary constant expressions here because moving 625 // their computation can be expensive without a cost model. 626 BasicBlock *NonConstBB = 0; 627 for (unsigned i = 0; i != NumPHIValues; ++i) { 628 Value *InVal = PN->getIncomingValue(i); 629 if (isa<Constant>(InVal) && !isa<ConstantExpr>(InVal)) 630 continue; 631 632 if (isa<PHINode>(InVal)) return 0; // Itself a phi. 633 if (NonConstBB) return 0; // More than one non-const value. 634 635 NonConstBB = PN->getIncomingBlock(i); 636 637 // If the InVal is an invoke at the end of the pred block, then we can't 638 // insert a computation after it without breaking the edge. 639 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) 640 if (II->getParent() == NonConstBB) 641 return 0; 642 643 // If the incoming non-constant value is in I's block, we will remove one 644 // instruction, but insert another equivalent one, leading to infinite 645 // instcombine. 646 if (NonConstBB == I.getParent()) 647 return 0; 648 } 649 650 // If there is exactly one non-constant value, we can insert a copy of the 651 // operation in that block. However, if this is a critical edge, we would be 652 // inserting the computation one some other paths (e.g. inside a loop). Only 653 // do this if the pred block is unconditionally branching into the phi block. 654 if (NonConstBB != 0) { 655 BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator()); 656 if (!BI || !BI->isUnconditional()) return 0; 657 } 658 659 // Okay, we can do the transformation: create the new PHI node. 660 PHINode *NewPN = PHINode::Create(I.getType(), PN->getNumIncomingValues()); 661 InsertNewInstBefore(NewPN, *PN); 662 NewPN->takeName(PN); 663 664 // If we are going to have to insert a new computation, do so right before the 665 // predecessors terminator. 666 if (NonConstBB) 667 Builder->SetInsertPoint(NonConstBB->getTerminator()); 668 669 // Next, add all of the operands to the PHI. 670 if (SelectInst *SI = dyn_cast<SelectInst>(&I)) { 671 // We only currently try to fold the condition of a select when it is a phi, 672 // not the true/false values. 673 Value *TrueV = SI->getTrueValue(); 674 Value *FalseV = SI->getFalseValue(); 675 BasicBlock *PhiTransBB = PN->getParent(); 676 for (unsigned i = 0; i != NumPHIValues; ++i) { 677 BasicBlock *ThisBB = PN->getIncomingBlock(i); 678 Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB); 679 Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB); 680 Value *InV = 0; 681 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 682 InV = InC->isNullValue() ? FalseVInPred : TrueVInPred; 683 else 684 InV = Builder->CreateSelect(PN->getIncomingValue(i), 685 TrueVInPred, FalseVInPred, "phitmp"); 686 NewPN->addIncoming(InV, ThisBB); 687 } 688 } else if (CmpInst *CI = dyn_cast<CmpInst>(&I)) { 689 Constant *C = cast<Constant>(I.getOperand(1)); 690 for (unsigned i = 0; i != NumPHIValues; ++i) { 691 Value *InV = 0; 692 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 693 InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C); 694 else if (isa<ICmpInst>(CI)) 695 InV = Builder->CreateICmp(CI->getPredicate(), PN->getIncomingValue(i), 696 C, "phitmp"); 697 else 698 InV = Builder->CreateFCmp(CI->getPredicate(), PN->getIncomingValue(i), 699 C, "phitmp"); 700 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 701 } 702 } else if (I.getNumOperands() == 2) { 703 Constant *C = cast<Constant>(I.getOperand(1)); 704 for (unsigned i = 0; i != NumPHIValues; ++i) { 705 Value *InV = 0; 706 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 707 InV = ConstantExpr::get(I.getOpcode(), InC, C); 708 else 709 InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(), 710 PN->getIncomingValue(i), C, "phitmp"); 711 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 712 } 713 } else { 714 CastInst *CI = cast<CastInst>(&I); 715 Type *RetTy = CI->getType(); 716 for (unsigned i = 0; i != NumPHIValues; ++i) { 717 Value *InV; 718 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 719 InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy); 720 else 721 InV = Builder->CreateCast(CI->getOpcode(), 722 PN->getIncomingValue(i), I.getType(), "phitmp"); 723 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 724 } 725 } 726 727 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); 728 UI != E; ) { 729 Instruction *User = cast<Instruction>(*UI++); 730 if (User == &I) continue; 731 ReplaceInstUsesWith(*User, NewPN); 732 EraseInstFromFunction(*User); 733 } 734 return ReplaceInstUsesWith(I, NewPN); 735} 736 737/// FindElementAtOffset - Given a type and a constant offset, determine whether 738/// or not there is a sequence of GEP indices into the type that will land us at 739/// the specified offset. If so, fill them into NewIndices and return the 740/// resultant element type, otherwise return null. 741Type *InstCombiner::FindElementAtOffset(Type *Ty, int64_t Offset, 742 SmallVectorImpl<Value*> &NewIndices) { 743 if (!TD) return 0; 744 if (!Ty->isSized()) return 0; 745 746 // Start with the index over the outer type. Note that the type size 747 // might be zero (even if the offset isn't zero) if the indexed type 748 // is something like [0 x {int, int}] 749 Type *IntPtrTy = TD->getIntPtrType(Ty->getContext()); 750 int64_t FirstIdx = 0; 751 if (int64_t TySize = TD->getTypeAllocSize(Ty)) { 752 FirstIdx = Offset/TySize; 753 Offset -= FirstIdx*TySize; 754 755 // Handle hosts where % returns negative instead of values [0..TySize). 756 if (Offset < 0) { 757 --FirstIdx; 758 Offset += TySize; 759 assert(Offset >= 0); 760 } 761 assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset"); 762 } 763 764 NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx)); 765 766 // Index into the types. If we fail, set OrigBase to null. 767 while (Offset) { 768 // Indexing into tail padding between struct/array elements. 769 if (uint64_t(Offset*8) >= TD->getTypeSizeInBits(Ty)) 770 return 0; 771 772 if (StructType *STy = dyn_cast<StructType>(Ty)) { 773 const StructLayout *SL = TD->getStructLayout(STy); 774 assert(Offset < (int64_t)SL->getSizeInBytes() && 775 "Offset must stay within the indexed type"); 776 777 unsigned Elt = SL->getElementContainingOffset(Offset); 778 NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 779 Elt)); 780 781 Offset -= SL->getElementOffset(Elt); 782 Ty = STy->getElementType(Elt); 783 } else if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) { 784 uint64_t EltSize = TD->getTypeAllocSize(AT->getElementType()); 785 assert(EltSize && "Cannot index into a zero-sized array"); 786 NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize)); 787 Offset %= EltSize; 788 Ty = AT->getElementType(); 789 } else { 790 // Otherwise, we can't index into the middle of this atomic type, bail. 791 return 0; 792 } 793 } 794 795 return Ty; 796} 797 798static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) { 799 // If this GEP has only 0 indices, it is the same pointer as 800 // Src. If Src is not a trivial GEP too, don't combine 801 // the indices. 802 if (GEP.hasAllZeroIndices() && !Src.hasAllZeroIndices() && 803 !Src.hasOneUse()) 804 return false; 805 return true; 806} 807 808/// Descale - Return a value X such that Val = X * Scale, or null if none. If 809/// the multiplication is known not to overflow then NoSignedWrap is set. 810Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) { 811 assert(isa<IntegerType>(Val->getType()) && "Can only descale integers!"); 812 assert(cast<IntegerType>(Val->getType())->getBitWidth() == 813 Scale.getBitWidth() && "Scale not compatible with value!"); 814 815 // If Val is zero or Scale is one then Val = Val * Scale. 816 if (match(Val, m_Zero()) || Scale == 1) { 817 NoSignedWrap = true; 818 return Val; 819 } 820 821 // If Scale is zero then it does not divide Val. 822 if (Scale.isMinValue()) 823 return 0; 824 825 // Look through chains of multiplications, searching for a constant that is 826 // divisible by Scale. For example, descaling X*(Y*(Z*4)) by a factor of 4 827 // will find the constant factor 4 and produce X*(Y*Z). Descaling X*(Y*8) by 828 // a factor of 4 will produce X*(Y*2). The principle of operation is to bore 829 // down from Val: 830 // 831 // Val = M1 * X || Analysis starts here and works down 832 // M1 = M2 * Y || Doesn't descend into terms with more 833 // M2 = Z * 4 \/ than one use 834 // 835 // Then to modify a term at the bottom: 836 // 837 // Val = M1 * X 838 // M1 = Z * Y || Replaced M2 with Z 839 // 840 // Then to work back up correcting nsw flags. 841 842 // Op - the term we are currently analyzing. Starts at Val then drills down. 843 // Replaced with its descaled value before exiting from the drill down loop. 844 Value *Op = Val; 845 846 // Parent - initially null, but after drilling down notes where Op came from. 847 // In the example above, Parent is (Val, 0) when Op is M1, because M1 is the 848 // 0'th operand of Val. 849 std::pair<Instruction*, unsigned> Parent; 850 851 // RequireNoSignedWrap - Set if the transform requires a descaling at deeper 852 // levels that doesn't overflow. 853 bool RequireNoSignedWrap = false; 854 855 // logScale - log base 2 of the scale. Negative if not a power of 2. 856 int32_t logScale = Scale.exactLogBase2(); 857 858 for (;; Op = Parent.first->getOperand(Parent.second)) { // Drill down 859 860 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) { 861 // If Op is a constant divisible by Scale then descale to the quotient. 862 APInt Quotient(Scale), Remainder(Scale); // Init ensures right bitwidth. 863 APInt::sdivrem(CI->getValue(), Scale, Quotient, Remainder); 864 if (!Remainder.isMinValue()) 865 // Not divisible by Scale. 866 return 0; 867 // Replace with the quotient in the parent. 868 Op = ConstantInt::get(CI->getType(), Quotient); 869 NoSignedWrap = true; 870 break; 871 } 872 873 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op)) { 874 875 if (BO->getOpcode() == Instruction::Mul) { 876 // Multiplication. 877 NoSignedWrap = BO->hasNoSignedWrap(); 878 if (RequireNoSignedWrap && !NoSignedWrap) 879 return 0; 880 881 // There are three cases for multiplication: multiplication by exactly 882 // the scale, multiplication by a constant different to the scale, and 883 // multiplication by something else. 884 Value *LHS = BO->getOperand(0); 885 Value *RHS = BO->getOperand(1); 886 887 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 888 // Multiplication by a constant. 889 if (CI->getValue() == Scale) { 890 // Multiplication by exactly the scale, replace the multiplication 891 // by its left-hand side in the parent. 892 Op = LHS; 893 break; 894 } 895 896 // Otherwise drill down into the constant. 897 if (!Op->hasOneUse()) 898 return 0; 899 900 Parent = std::make_pair(BO, 1); 901 continue; 902 } 903 904 // Multiplication by something else. Drill down into the left-hand side 905 // since that's where the reassociate pass puts the good stuff. 906 if (!Op->hasOneUse()) 907 return 0; 908 909 Parent = std::make_pair(BO, 0); 910 continue; 911 } 912 913 if (logScale > 0 && BO->getOpcode() == Instruction::Shl && 914 isa<ConstantInt>(BO->getOperand(1))) { 915 // Multiplication by a power of 2. 916 NoSignedWrap = BO->hasNoSignedWrap(); 917 if (RequireNoSignedWrap && !NoSignedWrap) 918 return 0; 919 920 Value *LHS = BO->getOperand(0); 921 int32_t Amt = cast<ConstantInt>(BO->getOperand(1))-> 922 getLimitedValue(Scale.getBitWidth()); 923 // Op = LHS << Amt. 924 925 if (Amt == logScale) { 926 // Multiplication by exactly the scale, replace the multiplication 927 // by its left-hand side in the parent. 928 Op = LHS; 929 break; 930 } 931 if (Amt < logScale || !Op->hasOneUse()) 932 return 0; 933 934 // Multiplication by more than the scale. Reduce the multiplying amount 935 // by the scale in the parent. 936 Parent = std::make_pair(BO, 1); 937 Op = ConstantInt::get(BO->getType(), Amt - logScale); 938 break; 939 } 940 } 941 942 if (!Op->hasOneUse()) 943 return 0; 944 945 if (CastInst *Cast = dyn_cast<CastInst>(Op)) { 946 if (Cast->getOpcode() == Instruction::SExt) { 947 // Op is sign-extended from a smaller type, descale in the smaller type. 948 unsigned SmallSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); 949 APInt SmallScale = Scale.trunc(SmallSize); 950 // Suppose Op = sext X, and we descale X as Y * SmallScale. We want to 951 // descale Op as (sext Y) * Scale. In order to have 952 // sext (Y * SmallScale) = (sext Y) * Scale 953 // some conditions need to hold however: SmallScale must sign-extend to 954 // Scale and the multiplication Y * SmallScale should not overflow. 955 if (SmallScale.sext(Scale.getBitWidth()) != Scale) 956 // SmallScale does not sign-extend to Scale. 957 return 0; 958 assert(SmallScale.exactLogBase2() == logScale); 959 // Require that Y * SmallScale must not overflow. 960 RequireNoSignedWrap = true; 961 962 // Drill down through the cast. 963 Parent = std::make_pair(Cast, 0); 964 Scale = SmallScale; 965 continue; 966 } 967 968 if (Cast->getOpcode() == Instruction::Trunc) { 969 // Op is truncated from a larger type, descale in the larger type. 970 // Suppose Op = trunc X, and we descale X as Y * sext Scale. Then 971 // trunc (Y * sext Scale) = (trunc Y) * Scale 972 // always holds. However (trunc Y) * Scale may overflow even if 973 // trunc (Y * sext Scale) does not, so nsw flags need to be cleared 974 // from this point up in the expression (see later). 975 if (RequireNoSignedWrap) 976 return 0; 977 978 // Drill down through the cast. 979 unsigned LargeSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); 980 Parent = std::make_pair(Cast, 0); 981 Scale = Scale.sext(LargeSize); 982 if (logScale + 1 == (int32_t)Cast->getType()->getPrimitiveSizeInBits()) 983 logScale = -1; 984 assert(Scale.exactLogBase2() == logScale); 985 continue; 986 } 987 } 988 989 // Unsupported expression, bail out. 990 return 0; 991 } 992 993 // We know that we can successfully descale, so from here on we can safely 994 // modify the IR. Op holds the descaled version of the deepest term in the 995 // expression. NoSignedWrap is 'true' if multiplying Op by Scale is known 996 // not to overflow. 997 998 if (!Parent.first) 999 // The expression only had one term. 1000 return Op; 1001 1002 // Rewrite the parent using the descaled version of its operand. 1003 assert(Parent.first->hasOneUse() && "Drilled down when more than one use!"); 1004 assert(Op != Parent.first->getOperand(Parent.second) && 1005 "Descaling was a no-op?"); 1006 Parent.first->setOperand(Parent.second, Op); 1007 Worklist.Add(Parent.first); 1008 1009 // Now work back up the expression correcting nsw flags. The logic is based 1010 // on the following observation: if X * Y is known not to overflow as a signed 1011 // multiplication, and Y is replaced by a value Z with smaller absolute value, 1012 // then X * Z will not overflow as a signed multiplication either. As we work 1013 // our way up, having NoSignedWrap 'true' means that the descaled value at the 1014 // current level has strictly smaller absolute value than the original. 1015 Instruction *Ancestor = Parent.first; 1016 do { 1017 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Ancestor)) { 1018 // If the multiplication wasn't nsw then we can't say anything about the 1019 // value of the descaled multiplication, and we have to clear nsw flags 1020 // from this point on up. 1021 bool OpNoSignedWrap = BO->hasNoSignedWrap(); 1022 NoSignedWrap &= OpNoSignedWrap; 1023 if (NoSignedWrap != OpNoSignedWrap) { 1024 BO->setHasNoSignedWrap(NoSignedWrap); 1025 Worklist.Add(Ancestor); 1026 } 1027 } else if (Ancestor->getOpcode() == Instruction::Trunc) { 1028 // The fact that the descaled input to the trunc has smaller absolute 1029 // value than the original input doesn't tell us anything useful about 1030 // the absolute values of the truncations. 1031 NoSignedWrap = false; 1032 } 1033 assert((Ancestor->getOpcode() != Instruction::SExt || NoSignedWrap) && 1034 "Failed to keep proper track of nsw flags while drilling down?"); 1035 1036 if (Ancestor == Val) 1037 // Got to the top, all done! 1038 return Val; 1039 1040 // Move up one level in the expression. 1041 assert(Ancestor->hasOneUse() && "Drilled down when more than one use!"); 1042 Ancestor = Ancestor->use_back(); 1043 } while (1); 1044} 1045 1046Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { 1047 SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end()); 1048 1049 if (Value *V = SimplifyGEPInst(Ops, TD)) 1050 return ReplaceInstUsesWith(GEP, V); 1051 1052 Value *PtrOp = GEP.getOperand(0); 1053 1054 // Eliminate unneeded casts for indices, and replace indices which displace 1055 // by multiples of a zero size type with zero. 1056 if (TD) { 1057 bool MadeChange = false; 1058 Type *IntPtrTy = TD->getIntPtrType(GEP.getContext()); 1059 1060 gep_type_iterator GTI = gep_type_begin(GEP); 1061 for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); 1062 I != E; ++I, ++GTI) { 1063 // Skip indices into struct types. 1064 SequentialType *SeqTy = dyn_cast<SequentialType>(*GTI); 1065 if (!SeqTy) continue; 1066 1067 // If the element type has zero size then any index over it is equivalent 1068 // to an index of zero, so replace it with zero if it is not zero already. 1069 if (SeqTy->getElementType()->isSized() && 1070 TD->getTypeAllocSize(SeqTy->getElementType()) == 0) 1071 if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) { 1072 *I = Constant::getNullValue(IntPtrTy); 1073 MadeChange = true; 1074 } 1075 1076 Type *IndexTy = (*I)->getType(); 1077 if (IndexTy != IntPtrTy && !IndexTy->isVectorTy()) { 1078 // If we are using a wider index than needed for this platform, shrink 1079 // it to what we need. If narrower, sign-extend it to what we need. 1080 // This explicit cast can make subsequent optimizations more obvious. 1081 *I = Builder->CreateIntCast(*I, IntPtrTy, true); 1082 MadeChange = true; 1083 } 1084 } 1085 if (MadeChange) return &GEP; 1086 } 1087 1088 // Combine Indices - If the source pointer to this getelementptr instruction 1089 // is a getelementptr instruction, combine the indices of the two 1090 // getelementptr instructions into a single instruction. 1091 // 1092 if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) { 1093 if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src)) 1094 return 0; 1095 1096 // Note that if our source is a gep chain itself then we wait for that 1097 // chain to be resolved before we perform this transformation. This 1098 // avoids us creating a TON of code in some cases. 1099 if (GEPOperator *SrcGEP = 1100 dyn_cast<GEPOperator>(Src->getOperand(0))) 1101 if (SrcGEP->getNumOperands() == 2 && shouldMergeGEPs(*Src, *SrcGEP)) 1102 return 0; // Wait until our source is folded to completion. 1103 1104 SmallVector<Value*, 8> Indices; 1105 1106 // Find out whether the last index in the source GEP is a sequential idx. 1107 bool EndsWithSequential = false; 1108 for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src); 1109 I != E; ++I) 1110 EndsWithSequential = !(*I)->isStructTy(); 1111 1112 // Can we combine the two pointer arithmetics offsets? 1113 if (EndsWithSequential) { 1114 // Replace: gep (gep %P, long B), long A, ... 1115 // With: T = long A+B; gep %P, T, ... 1116 // 1117 Value *Sum; 1118 Value *SO1 = Src->getOperand(Src->getNumOperands()-1); 1119 Value *GO1 = GEP.getOperand(1); 1120 if (SO1 == Constant::getNullValue(SO1->getType())) { 1121 Sum = GO1; 1122 } else if (GO1 == Constant::getNullValue(GO1->getType())) { 1123 Sum = SO1; 1124 } else { 1125 // If they aren't the same type, then the input hasn't been processed 1126 // by the loop above yet (which canonicalizes sequential index types to 1127 // intptr_t). Just avoid transforming this until the input has been 1128 // normalized. 1129 if (SO1->getType() != GO1->getType()) 1130 return 0; 1131 Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum"); 1132 } 1133 1134 // Update the GEP in place if possible. 1135 if (Src->getNumOperands() == 2) { 1136 GEP.setOperand(0, Src->getOperand(0)); 1137 GEP.setOperand(1, Sum); 1138 return &GEP; 1139 } 1140 Indices.append(Src->op_begin()+1, Src->op_end()-1); 1141 Indices.push_back(Sum); 1142 Indices.append(GEP.op_begin()+2, GEP.op_end()); 1143 } else if (isa<Constant>(*GEP.idx_begin()) && 1144 cast<Constant>(*GEP.idx_begin())->isNullValue() && 1145 Src->getNumOperands() != 1) { 1146 // Otherwise we can do the fold if the first index of the GEP is a zero 1147 Indices.append(Src->op_begin()+1, Src->op_end()); 1148 Indices.append(GEP.idx_begin()+1, GEP.idx_end()); 1149 } 1150 1151 if (!Indices.empty()) 1152 return (GEP.isInBounds() && Src->isInBounds()) ? 1153 GetElementPtrInst::CreateInBounds(Src->getOperand(0), Indices, 1154 GEP.getName()) : 1155 GetElementPtrInst::Create(Src->getOperand(0), Indices, GEP.getName()); 1156 } 1157 1158 // Handle gep(bitcast x) and gep(gep x, 0, 0, 0). 1159 Value *StrippedPtr = PtrOp->stripPointerCasts(); 1160 PointerType *StrippedPtrTy = dyn_cast<PointerType>(StrippedPtr->getType()); 1161 1162 // We do not handle pointer-vector geps here. 1163 if (!StrippedPtrTy) 1164 return 0; 1165 1166 if (StrippedPtr != PtrOp && 1167 StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) { 1168 1169 bool HasZeroPointerIndex = false; 1170 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1))) 1171 HasZeroPointerIndex = C->isZero(); 1172 1173 // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... 1174 // into : GEP [10 x i8]* X, i32 0, ... 1175 // 1176 // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ... 1177 // into : GEP i8* X, ... 1178 // 1179 // This occurs when the program declares an array extern like "int X[];" 1180 if (HasZeroPointerIndex) { 1181 PointerType *CPTy = cast<PointerType>(PtrOp->getType()); 1182 if (ArrayType *CATy = 1183 dyn_cast<ArrayType>(CPTy->getElementType())) { 1184 // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ? 1185 if (CATy->getElementType() == StrippedPtrTy->getElementType()) { 1186 // -> GEP i8* X, ... 1187 SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end()); 1188 GetElementPtrInst *Res = 1189 GetElementPtrInst::Create(StrippedPtr, Idx, GEP.getName()); 1190 Res->setIsInBounds(GEP.isInBounds()); 1191 return Res; 1192 } 1193 1194 if (ArrayType *XATy = 1195 dyn_cast<ArrayType>(StrippedPtrTy->getElementType())){ 1196 // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ? 1197 if (CATy->getElementType() == XATy->getElementType()) { 1198 // -> GEP [10 x i8]* X, i32 0, ... 1199 // At this point, we know that the cast source type is a pointer 1200 // to an array of the same type as the destination pointer 1201 // array. Because the array type is never stepped over (there 1202 // is a leading zero) we can fold the cast into this GEP. 1203 GEP.setOperand(0, StrippedPtr); 1204 return &GEP; 1205 } 1206 } 1207 } 1208 } else if (GEP.getNumOperands() == 2) { 1209 // Transform things like: 1210 // %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V 1211 // into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast 1212 Type *SrcElTy = StrippedPtrTy->getElementType(); 1213 Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType(); 1214 if (TD && SrcElTy->isArrayTy() && 1215 TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()) == 1216 TD->getTypeAllocSize(ResElTy)) { 1217 Value *Idx[2]; 1218 Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); 1219 Idx[1] = GEP.getOperand(1); 1220 Value *NewGEP = GEP.isInBounds() ? 1221 Builder->CreateInBoundsGEP(StrippedPtr, Idx, GEP.getName()) : 1222 Builder->CreateGEP(StrippedPtr, Idx, GEP.getName()); 1223 // V and GEP are both pointer types --> BitCast 1224 return new BitCastInst(NewGEP, GEP.getType()); 1225 } 1226 1227 // Transform things like: 1228 // %V = mul i64 %N, 4 1229 // %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V 1230 // into: %t1 = getelementptr i32* %arr, i32 %N; bitcast 1231 if (TD && ResElTy->isSized() && SrcElTy->isSized()) { 1232 // Check that changing the type amounts to dividing the index by a scale 1233 // factor. 1234 uint64_t ResSize = TD->getTypeAllocSize(ResElTy); 1235 uint64_t SrcSize = TD->getTypeAllocSize(SrcElTy); 1236 if (ResSize && SrcSize % ResSize == 0) { 1237 Value *Idx = GEP.getOperand(1); 1238 unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); 1239 uint64_t Scale = SrcSize / ResSize; 1240 1241 // Earlier transforms ensure that the index has type IntPtrType, which 1242 // considerably simplifies the logic by eliminating implicit casts. 1243 assert(Idx->getType() == TD->getIntPtrType(GEP.getContext()) && 1244 "Index not cast to pointer width?"); 1245 1246 bool NSW; 1247 if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { 1248 // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. 1249 // If the multiplication NewIdx * Scale may overflow then the new 1250 // GEP may not be "inbounds". 1251 Value *NewGEP = GEP.isInBounds() && NSW ? 1252 Builder->CreateInBoundsGEP(StrippedPtr, NewIdx, GEP.getName()) : 1253 Builder->CreateGEP(StrippedPtr, NewIdx, GEP.getName()); 1254 // The NewGEP must be pointer typed, so must the old one -> BitCast 1255 return new BitCastInst(NewGEP, GEP.getType()); 1256 } 1257 } 1258 } 1259 1260 // Similarly, transform things like: 1261 // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp 1262 // (where tmp = 8*tmp2) into: 1263 // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast 1264 if (TD && ResElTy->isSized() && SrcElTy->isSized() && 1265 SrcElTy->isArrayTy()) { 1266 // Check that changing to the array element type amounts to dividing the 1267 // index by a scale factor. 1268 uint64_t ResSize = TD->getTypeAllocSize(ResElTy); 1269 uint64_t ArrayEltSize = 1270 TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()); 1271 if (ResSize && ArrayEltSize % ResSize == 0) { 1272 Value *Idx = GEP.getOperand(1); 1273 unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); 1274 uint64_t Scale = ArrayEltSize / ResSize; 1275 1276 // Earlier transforms ensure that the index has type IntPtrType, which 1277 // considerably simplifies the logic by eliminating implicit casts. 1278 assert(Idx->getType() == TD->getIntPtrType(GEP.getContext()) && 1279 "Index not cast to pointer width?"); 1280 1281 bool NSW; 1282 if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { 1283 // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. 1284 // If the multiplication NewIdx * Scale may overflow then the new 1285 // GEP may not be "inbounds". 1286 Value *Off[2]; 1287 Off[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); 1288 Off[1] = NewIdx; 1289 Value *NewGEP = GEP.isInBounds() && NSW ? 1290 Builder->CreateInBoundsGEP(StrippedPtr, Off, GEP.getName()) : 1291 Builder->CreateGEP(StrippedPtr, Off, GEP.getName()); 1292 // The NewGEP must be pointer typed, so must the old one -> BitCast 1293 return new BitCastInst(NewGEP, GEP.getType()); 1294 } 1295 } 1296 } 1297 } 1298 } 1299 1300 /// See if we can simplify: 1301 /// X = bitcast A* to B* 1302 /// Y = gep X, <...constant indices...> 1303 /// into a gep of the original struct. This is important for SROA and alias 1304 /// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged. 1305 if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) { 1306 if (TD && 1307 !isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices() && 1308 StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) { 1309 1310 // Determine how much the GEP moves the pointer. 1311 SmallVector<Value*, 8> Ops(GEP.idx_begin(), GEP.idx_end()); 1312 int64_t Offset = TD->getIndexedOffset(GEP.getPointerOperandType(), Ops); 1313 1314 // If this GEP instruction doesn't move the pointer, just replace the GEP 1315 // with a bitcast of the real input to the dest type. 1316 if (Offset == 0) { 1317 // If the bitcast is of an allocation, and the allocation will be 1318 // converted to match the type of the cast, don't touch this. 1319 if (isa<AllocaInst>(BCI->getOperand(0)) || 1320 isAllocationFn(BCI->getOperand(0), TLI)) { 1321 // See if the bitcast simplifies, if so, don't nuke this GEP yet. 1322 if (Instruction *I = visitBitCast(*BCI)) { 1323 if (I != BCI) { 1324 I->takeName(BCI); 1325 BCI->getParent()->getInstList().insert(BCI, I); 1326 ReplaceInstUsesWith(*BCI, I); 1327 } 1328 return &GEP; 1329 } 1330 } 1331 return new BitCastInst(BCI->getOperand(0), GEP.getType()); 1332 } 1333 1334 // Otherwise, if the offset is non-zero, we need to find out if there is a 1335 // field at Offset in 'A's type. If so, we can pull the cast through the 1336 // GEP. 1337 SmallVector<Value*, 8> NewIndices; 1338 Type *InTy = 1339 cast<PointerType>(BCI->getOperand(0)->getType())->getElementType(); 1340 if (FindElementAtOffset(InTy, Offset, NewIndices)) { 1341 Value *NGEP = GEP.isInBounds() ? 1342 Builder->CreateInBoundsGEP(BCI->getOperand(0), NewIndices) : 1343 Builder->CreateGEP(BCI->getOperand(0), NewIndices); 1344 1345 if (NGEP->getType() == GEP.getType()) 1346 return ReplaceInstUsesWith(GEP, NGEP); 1347 NGEP->takeName(&GEP); 1348 return new BitCastInst(NGEP, GEP.getType()); 1349 } 1350 } 1351 } 1352 1353 return 0; 1354} 1355 1356 1357 1358static bool 1359isAllocSiteRemovable(Instruction *AI, SmallVectorImpl<WeakVH> &Users, 1360 const TargetLibraryInfo *TLI) { 1361 SmallVector<Instruction*, 4> Worklist; 1362 Worklist.push_back(AI); 1363 1364 do { 1365 Instruction *PI = Worklist.pop_back_val(); 1366 for (Value::use_iterator UI = PI->use_begin(), UE = PI->use_end(); UI != UE; 1367 ++UI) { 1368 Instruction *I = cast<Instruction>(*UI); 1369 switch (I->getOpcode()) { 1370 default: 1371 // Give up the moment we see something we can't handle. 1372 return false; 1373 1374 case Instruction::BitCast: 1375 case Instruction::GetElementPtr: 1376 Users.push_back(I); 1377 Worklist.push_back(I); 1378 continue; 1379 1380 case Instruction::ICmp: { 1381 ICmpInst *ICI = cast<ICmpInst>(I); 1382 // We can fold eq/ne comparisons with null to false/true, respectively. 1383 if (!ICI->isEquality() || !isa<ConstantPointerNull>(ICI->getOperand(1))) 1384 return false; 1385 Users.push_back(I); 1386 continue; 1387 } 1388 1389 case Instruction::Call: 1390 // Ignore no-op and store intrinsics. 1391 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 1392 switch (II->getIntrinsicID()) { 1393 default: 1394 return false; 1395 1396 case Intrinsic::memmove: 1397 case Intrinsic::memcpy: 1398 case Intrinsic::memset: { 1399 MemIntrinsic *MI = cast<MemIntrinsic>(II); 1400 if (MI->isVolatile() || MI->getRawDest() != PI) 1401 return false; 1402 } 1403 // fall through 1404 case Intrinsic::dbg_declare: 1405 case Intrinsic::dbg_value: 1406 case Intrinsic::invariant_start: 1407 case Intrinsic::invariant_end: 1408 case Intrinsic::lifetime_start: 1409 case Intrinsic::lifetime_end: 1410 case Intrinsic::objectsize: 1411 Users.push_back(I); 1412 continue; 1413 } 1414 } 1415 1416 if (isFreeCall(I, TLI)) { 1417 Users.push_back(I); 1418 continue; 1419 } 1420 return false; 1421 1422 case Instruction::Store: { 1423 StoreInst *SI = cast<StoreInst>(I); 1424 if (SI->isVolatile() || SI->getPointerOperand() != PI) 1425 return false; 1426 Users.push_back(I); 1427 continue; 1428 } 1429 } 1430 llvm_unreachable("missing a return?"); 1431 } 1432 } while (!Worklist.empty()); 1433 return true; 1434} 1435 1436Instruction *InstCombiner::visitAllocSite(Instruction &MI) { 1437 // If we have a malloc call which is only used in any amount of comparisons 1438 // to null and free calls, delete the calls and replace the comparisons with 1439 // true or false as appropriate. 1440 SmallVector<WeakVH, 64> Users; 1441 if (isAllocSiteRemovable(&MI, Users, TLI)) { 1442 for (unsigned i = 0, e = Users.size(); i != e; ++i) { 1443 Instruction *I = cast_or_null<Instruction>(&*Users[i]); 1444 if (!I) continue; 1445 1446 if (ICmpInst *C = dyn_cast<ICmpInst>(I)) { 1447 ReplaceInstUsesWith(*C, 1448 ConstantInt::get(Type::getInt1Ty(C->getContext()), 1449 C->isFalseWhenEqual())); 1450 } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) { 1451 ReplaceInstUsesWith(*I, UndefValue::get(I->getType())); 1452 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 1453 if (II->getIntrinsicID() == Intrinsic::objectsize) { 1454 ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1)); 1455 uint64_t DontKnow = CI->isZero() ? -1ULL : 0; 1456 ReplaceInstUsesWith(*I, ConstantInt::get(I->getType(), DontKnow)); 1457 } 1458 } 1459 EraseInstFromFunction(*I); 1460 } 1461 1462 if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) { 1463 // Replace invoke with a NOP intrinsic to maintain the original CFG 1464 Module *M = II->getParent()->getParent()->getParent(); 1465 Function *F = Intrinsic::getDeclaration(M, Intrinsic::donothing); 1466 InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(), 1467 ArrayRef<Value *>(), "", II->getParent()); 1468 } 1469 return EraseInstFromFunction(MI); 1470 } 1471 return 0; 1472} 1473 1474 1475 1476Instruction *InstCombiner::visitFree(CallInst &FI) { 1477 Value *Op = FI.getArgOperand(0); 1478 1479 // free undef -> unreachable. 1480 if (isa<UndefValue>(Op)) { 1481 // Insert a new store to null because we cannot modify the CFG here. 1482 Builder->CreateStore(ConstantInt::getTrue(FI.getContext()), 1483 UndefValue::get(Type::getInt1PtrTy(FI.getContext()))); 1484 return EraseInstFromFunction(FI); 1485 } 1486 1487 // If we have 'free null' delete the instruction. This can happen in stl code 1488 // when lots of inlining happens. 1489 if (isa<ConstantPointerNull>(Op)) 1490 return EraseInstFromFunction(FI); 1491 1492 return 0; 1493} 1494 1495 1496 1497Instruction *InstCombiner::visitBranchInst(BranchInst &BI) { 1498 // Change br (not X), label True, label False to: br X, label False, True 1499 Value *X = 0; 1500 BasicBlock *TrueDest; 1501 BasicBlock *FalseDest; 1502 if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) && 1503 !isa<Constant>(X)) { 1504 // Swap Destinations and condition... 1505 BI.setCondition(X); 1506 BI.swapSuccessors(); 1507 return &BI; 1508 } 1509 1510 // Cannonicalize fcmp_one -> fcmp_oeq 1511 FCmpInst::Predicate FPred; Value *Y; 1512 if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)), 1513 TrueDest, FalseDest)) && 1514 BI.getCondition()->hasOneUse()) 1515 if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE || 1516 FPred == FCmpInst::FCMP_OGE) { 1517 FCmpInst *Cond = cast<FCmpInst>(BI.getCondition()); 1518 Cond->setPredicate(FCmpInst::getInversePredicate(FPred)); 1519 1520 // Swap Destinations and condition. 1521 BI.swapSuccessors(); 1522 Worklist.Add(Cond); 1523 return &BI; 1524 } 1525 1526 // Cannonicalize icmp_ne -> icmp_eq 1527 ICmpInst::Predicate IPred; 1528 if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)), 1529 TrueDest, FalseDest)) && 1530 BI.getCondition()->hasOneUse()) 1531 if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE || 1532 IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE || 1533 IPred == ICmpInst::ICMP_SGE) { 1534 ICmpInst *Cond = cast<ICmpInst>(BI.getCondition()); 1535 Cond->setPredicate(ICmpInst::getInversePredicate(IPred)); 1536 // Swap Destinations and condition. 1537 BI.swapSuccessors(); 1538 Worklist.Add(Cond); 1539 return &BI; 1540 } 1541 1542 return 0; 1543} 1544 1545Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) { 1546 Value *Cond = SI.getCondition(); 1547 if (Instruction *I = dyn_cast<Instruction>(Cond)) { 1548 if (I->getOpcode() == Instruction::Add) 1549 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) { 1550 // change 'switch (X+4) case 1:' into 'switch (X) case -3' 1551 // Skip the first item since that's the default case. 1552 for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end(); 1553 i != e; ++i) { 1554 ConstantInt* CaseVal = i.getCaseValue(); 1555 Constant* NewCaseVal = ConstantExpr::getSub(cast<Constant>(CaseVal), 1556 AddRHS); 1557 assert(isa<ConstantInt>(NewCaseVal) && 1558 "Result of expression should be constant"); 1559 i.setValue(cast<ConstantInt>(NewCaseVal)); 1560 } 1561 SI.setCondition(I->getOperand(0)); 1562 Worklist.Add(I); 1563 return &SI; 1564 } 1565 } 1566 return 0; 1567} 1568 1569Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) { 1570 Value *Agg = EV.getAggregateOperand(); 1571 1572 if (!EV.hasIndices()) 1573 return ReplaceInstUsesWith(EV, Agg); 1574 1575 if (Constant *C = dyn_cast<Constant>(Agg)) { 1576 if (Constant *C2 = C->getAggregateElement(*EV.idx_begin())) { 1577 if (EV.getNumIndices() == 0) 1578 return ReplaceInstUsesWith(EV, C2); 1579 // Extract the remaining indices out of the constant indexed by the 1580 // first index 1581 return ExtractValueInst::Create(C2, EV.getIndices().slice(1)); 1582 } 1583 return 0; // Can't handle other constants 1584 } 1585 1586 if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) { 1587 // We're extracting from an insertvalue instruction, compare the indices 1588 const unsigned *exti, *exte, *insi, *inse; 1589 for (exti = EV.idx_begin(), insi = IV->idx_begin(), 1590 exte = EV.idx_end(), inse = IV->idx_end(); 1591 exti != exte && insi != inse; 1592 ++exti, ++insi) { 1593 if (*insi != *exti) 1594 // The insert and extract both reference distinctly different elements. 1595 // This means the extract is not influenced by the insert, and we can 1596 // replace the aggregate operand of the extract with the aggregate 1597 // operand of the insert. i.e., replace 1598 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 1599 // %E = extractvalue { i32, { i32 } } %I, 0 1600 // with 1601 // %E = extractvalue { i32, { i32 } } %A, 0 1602 return ExtractValueInst::Create(IV->getAggregateOperand(), 1603 EV.getIndices()); 1604 } 1605 if (exti == exte && insi == inse) 1606 // Both iterators are at the end: Index lists are identical. Replace 1607 // %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 1608 // %C = extractvalue { i32, { i32 } } %B, 1, 0 1609 // with "i32 42" 1610 return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand()); 1611 if (exti == exte) { 1612 // The extract list is a prefix of the insert list. i.e. replace 1613 // %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 1614 // %E = extractvalue { i32, { i32 } } %I, 1 1615 // with 1616 // %X = extractvalue { i32, { i32 } } %A, 1 1617 // %E = insertvalue { i32 } %X, i32 42, 0 1618 // by switching the order of the insert and extract (though the 1619 // insertvalue should be left in, since it may have other uses). 1620 Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(), 1621 EV.getIndices()); 1622 return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(), 1623 makeArrayRef(insi, inse)); 1624 } 1625 if (insi == inse) 1626 // The insert list is a prefix of the extract list 1627 // We can simply remove the common indices from the extract and make it 1628 // operate on the inserted value instead of the insertvalue result. 1629 // i.e., replace 1630 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 1631 // %E = extractvalue { i32, { i32 } } %I, 1, 0 1632 // with 1633 // %E extractvalue { i32 } { i32 42 }, 0 1634 return ExtractValueInst::Create(IV->getInsertedValueOperand(), 1635 makeArrayRef(exti, exte)); 1636 } 1637 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) { 1638 // We're extracting from an intrinsic, see if we're the only user, which 1639 // allows us to simplify multiple result intrinsics to simpler things that 1640 // just get one value. 1641 if (II->hasOneUse()) { 1642 // Check if we're grabbing the overflow bit or the result of a 'with 1643 // overflow' intrinsic. If it's the latter we can remove the intrinsic 1644 // and replace it with a traditional binary instruction. 1645 switch (II->getIntrinsicID()) { 1646 case Intrinsic::uadd_with_overflow: 1647 case Intrinsic::sadd_with_overflow: 1648 if (*EV.idx_begin() == 0) { // Normal result. 1649 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1650 ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); 1651 EraseInstFromFunction(*II); 1652 return BinaryOperator::CreateAdd(LHS, RHS); 1653 } 1654 1655 // If the normal result of the add is dead, and the RHS is a constant, 1656 // we can transform this into a range comparison. 1657 // overflow = uadd a, -4 --> overflow = icmp ugt a, 3 1658 if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow) 1659 if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1))) 1660 return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0), 1661 ConstantExpr::getNot(CI)); 1662 break; 1663 case Intrinsic::usub_with_overflow: 1664 case Intrinsic::ssub_with_overflow: 1665 if (*EV.idx_begin() == 0) { // Normal result. 1666 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1667 ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); 1668 EraseInstFromFunction(*II); 1669 return BinaryOperator::CreateSub(LHS, RHS); 1670 } 1671 break; 1672 case Intrinsic::umul_with_overflow: 1673 case Intrinsic::smul_with_overflow: 1674 if (*EV.idx_begin() == 0) { // Normal result. 1675 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1676 ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); 1677 EraseInstFromFunction(*II); 1678 return BinaryOperator::CreateMul(LHS, RHS); 1679 } 1680 break; 1681 default: 1682 break; 1683 } 1684 } 1685 } 1686 if (LoadInst *L = dyn_cast<LoadInst>(Agg)) 1687 // If the (non-volatile) load only has one use, we can rewrite this to a 1688 // load from a GEP. This reduces the size of the load. 1689 // FIXME: If a load is used only by extractvalue instructions then this 1690 // could be done regardless of having multiple uses. 1691 if (L->isSimple() && L->hasOneUse()) { 1692 // extractvalue has integer indices, getelementptr has Value*s. Convert. 1693 SmallVector<Value*, 4> Indices; 1694 // Prefix an i32 0 since we need the first element. 1695 Indices.push_back(Builder->getInt32(0)); 1696 for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end(); 1697 I != E; ++I) 1698 Indices.push_back(Builder->getInt32(*I)); 1699 1700 // We need to insert these at the location of the old load, not at that of 1701 // the extractvalue. 1702 Builder->SetInsertPoint(L->getParent(), L); 1703 Value *GEP = Builder->CreateInBoundsGEP(L->getPointerOperand(), Indices); 1704 // Returning the load directly will cause the main loop to insert it in 1705 // the wrong spot, so use ReplaceInstUsesWith(). 1706 return ReplaceInstUsesWith(EV, Builder->CreateLoad(GEP)); 1707 } 1708 // We could simplify extracts from other values. Note that nested extracts may 1709 // already be simplified implicitly by the above: extract (extract (insert) ) 1710 // will be translated into extract ( insert ( extract ) ) first and then just 1711 // the value inserted, if appropriate. Similarly for extracts from single-use 1712 // loads: extract (extract (load)) will be translated to extract (load (gep)) 1713 // and if again single-use then via load (gep (gep)) to load (gep). 1714 // However, double extracts from e.g. function arguments or return values 1715 // aren't handled yet. 1716 return 0; 1717} 1718 1719enum Personality_Type { 1720 Unknown_Personality, 1721 GNU_Ada_Personality, 1722 GNU_CXX_Personality, 1723 GNU_ObjC_Personality 1724}; 1725 1726/// RecognizePersonality - See if the given exception handling personality 1727/// function is one that we understand. If so, return a description of it; 1728/// otherwise return Unknown_Personality. 1729static Personality_Type RecognizePersonality(Value *Pers) { 1730 Function *F = dyn_cast<Function>(Pers->stripPointerCasts()); 1731 if (!F) 1732 return Unknown_Personality; 1733 return StringSwitch<Personality_Type>(F->getName()) 1734 .Case("__gnat_eh_personality", GNU_Ada_Personality) 1735 .Case("__gxx_personality_v0", GNU_CXX_Personality) 1736 .Case("__objc_personality_v0", GNU_ObjC_Personality) 1737 .Default(Unknown_Personality); 1738} 1739 1740/// isCatchAll - Return 'true' if the given typeinfo will match anything. 1741static bool isCatchAll(Personality_Type Personality, Constant *TypeInfo) { 1742 switch (Personality) { 1743 case Unknown_Personality: 1744 return false; 1745 case GNU_Ada_Personality: 1746 // While __gnat_all_others_value will match any Ada exception, it doesn't 1747 // match foreign exceptions (or didn't, before gcc-4.7). 1748 return false; 1749 case GNU_CXX_Personality: 1750 case GNU_ObjC_Personality: 1751 return TypeInfo->isNullValue(); 1752 } 1753 llvm_unreachable("Unknown personality!"); 1754} 1755 1756static bool shorter_filter(const Value *LHS, const Value *RHS) { 1757 return 1758 cast<ArrayType>(LHS->getType())->getNumElements() 1759 < 1760 cast<ArrayType>(RHS->getType())->getNumElements(); 1761} 1762 1763Instruction *InstCombiner::visitLandingPadInst(LandingPadInst &LI) { 1764 // The logic here should be correct for any real-world personality function. 1765 // However if that turns out not to be true, the offending logic can always 1766 // be conditioned on the personality function, like the catch-all logic is. 1767 Personality_Type Personality = RecognizePersonality(LI.getPersonalityFn()); 1768 1769 // Simplify the list of clauses, eg by removing repeated catch clauses 1770 // (these are often created by inlining). 1771 bool MakeNewInstruction = false; // If true, recreate using the following: 1772 SmallVector<Value *, 16> NewClauses; // - Clauses for the new instruction; 1773 bool CleanupFlag = LI.isCleanup(); // - The new instruction is a cleanup. 1774 1775 SmallPtrSet<Value *, 16> AlreadyCaught; // Typeinfos known caught already. 1776 for (unsigned i = 0, e = LI.getNumClauses(); i != e; ++i) { 1777 bool isLastClause = i + 1 == e; 1778 if (LI.isCatch(i)) { 1779 // A catch clause. 1780 Value *CatchClause = LI.getClause(i); 1781 Constant *TypeInfo = cast<Constant>(CatchClause->stripPointerCasts()); 1782 1783 // If we already saw this clause, there is no point in having a second 1784 // copy of it. 1785 if (AlreadyCaught.insert(TypeInfo)) { 1786 // This catch clause was not already seen. 1787 NewClauses.push_back(CatchClause); 1788 } else { 1789 // Repeated catch clause - drop the redundant copy. 1790 MakeNewInstruction = true; 1791 } 1792 1793 // If this is a catch-all then there is no point in keeping any following 1794 // clauses or marking the landingpad as having a cleanup. 1795 if (isCatchAll(Personality, TypeInfo)) { 1796 if (!isLastClause) 1797 MakeNewInstruction = true; 1798 CleanupFlag = false; 1799 break; 1800 } 1801 } else { 1802 // A filter clause. If any of the filter elements were already caught 1803 // then they can be dropped from the filter. It is tempting to try to 1804 // exploit the filter further by saying that any typeinfo that does not 1805 // occur in the filter can't be caught later (and thus can be dropped). 1806 // However this would be wrong, since typeinfos can match without being 1807 // equal (for example if one represents a C++ class, and the other some 1808 // class derived from it). 1809 assert(LI.isFilter(i) && "Unsupported landingpad clause!"); 1810 Value *FilterClause = LI.getClause(i); 1811 ArrayType *FilterType = cast<ArrayType>(FilterClause->getType()); 1812 unsigned NumTypeInfos = FilterType->getNumElements(); 1813 1814 // An empty filter catches everything, so there is no point in keeping any 1815 // following clauses or marking the landingpad as having a cleanup. By 1816 // dealing with this case here the following code is made a bit simpler. 1817 if (!NumTypeInfos) { 1818 NewClauses.push_back(FilterClause); 1819 if (!isLastClause) 1820 MakeNewInstruction = true; 1821 CleanupFlag = false; 1822 break; 1823 } 1824 1825 bool MakeNewFilter = false; // If true, make a new filter. 1826 SmallVector<Constant *, 16> NewFilterElts; // New elements. 1827 if (isa<ConstantAggregateZero>(FilterClause)) { 1828 // Not an empty filter - it contains at least one null typeinfo. 1829 assert(NumTypeInfos > 0 && "Should have handled empty filter already!"); 1830 Constant *TypeInfo = 1831 Constant::getNullValue(FilterType->getElementType()); 1832 // If this typeinfo is a catch-all then the filter can never match. 1833 if (isCatchAll(Personality, TypeInfo)) { 1834 // Throw the filter away. 1835 MakeNewInstruction = true; 1836 continue; 1837 } 1838 1839 // There is no point in having multiple copies of this typeinfo, so 1840 // discard all but the first copy if there is more than one. 1841 NewFilterElts.push_back(TypeInfo); 1842 if (NumTypeInfos > 1) 1843 MakeNewFilter = true; 1844 } else { 1845 ConstantArray *Filter = cast<ConstantArray>(FilterClause); 1846 SmallPtrSet<Value *, 16> SeenInFilter; // For uniquing the elements. 1847 NewFilterElts.reserve(NumTypeInfos); 1848 1849 // Remove any filter elements that were already caught or that already 1850 // occurred in the filter. While there, see if any of the elements are 1851 // catch-alls. If so, the filter can be discarded. 1852 bool SawCatchAll = false; 1853 for (unsigned j = 0; j != NumTypeInfos; ++j) { 1854 Value *Elt = Filter->getOperand(j); 1855 Constant *TypeInfo = cast<Constant>(Elt->stripPointerCasts()); 1856 if (isCatchAll(Personality, TypeInfo)) { 1857 // This element is a catch-all. Bail out, noting this fact. 1858 SawCatchAll = true; 1859 break; 1860 } 1861 if (AlreadyCaught.count(TypeInfo)) 1862 // Already caught by an earlier clause, so having it in the filter 1863 // is pointless. 1864 continue; 1865 // There is no point in having multiple copies of the same typeinfo in 1866 // a filter, so only add it if we didn't already. 1867 if (SeenInFilter.insert(TypeInfo)) 1868 NewFilterElts.push_back(cast<Constant>(Elt)); 1869 } 1870 // A filter containing a catch-all cannot match anything by definition. 1871 if (SawCatchAll) { 1872 // Throw the filter away. 1873 MakeNewInstruction = true; 1874 continue; 1875 } 1876 1877 // If we dropped something from the filter, make a new one. 1878 if (NewFilterElts.size() < NumTypeInfos) 1879 MakeNewFilter = true; 1880 } 1881 if (MakeNewFilter) { 1882 FilterType = ArrayType::get(FilterType->getElementType(), 1883 NewFilterElts.size()); 1884 FilterClause = ConstantArray::get(FilterType, NewFilterElts); 1885 MakeNewInstruction = true; 1886 } 1887 1888 NewClauses.push_back(FilterClause); 1889 1890 // If the new filter is empty then it will catch everything so there is 1891 // no point in keeping any following clauses or marking the landingpad 1892 // as having a cleanup. The case of the original filter being empty was 1893 // already handled above. 1894 if (MakeNewFilter && !NewFilterElts.size()) { 1895 assert(MakeNewInstruction && "New filter but not a new instruction!"); 1896 CleanupFlag = false; 1897 break; 1898 } 1899 } 1900 } 1901 1902 // If several filters occur in a row then reorder them so that the shortest 1903 // filters come first (those with the smallest number of elements). This is 1904 // advantageous because shorter filters are more likely to match, speeding up 1905 // unwinding, but mostly because it increases the effectiveness of the other 1906 // filter optimizations below. 1907 for (unsigned i = 0, e = NewClauses.size(); i + 1 < e; ) { 1908 unsigned j; 1909 // Find the maximal 'j' s.t. the range [i, j) consists entirely of filters. 1910 for (j = i; j != e; ++j) 1911 if (!isa<ArrayType>(NewClauses[j]->getType())) 1912 break; 1913 1914 // Check whether the filters are already sorted by length. We need to know 1915 // if sorting them is actually going to do anything so that we only make a 1916 // new landingpad instruction if it does. 1917 for (unsigned k = i; k + 1 < j; ++k) 1918 if (shorter_filter(NewClauses[k+1], NewClauses[k])) { 1919 // Not sorted, so sort the filters now. Doing an unstable sort would be 1920 // correct too but reordering filters pointlessly might confuse users. 1921 std::stable_sort(NewClauses.begin() + i, NewClauses.begin() + j, 1922 shorter_filter); 1923 MakeNewInstruction = true; 1924 break; 1925 } 1926 1927 // Look for the next batch of filters. 1928 i = j + 1; 1929 } 1930 1931 // If typeinfos matched if and only if equal, then the elements of a filter L 1932 // that occurs later than a filter F could be replaced by the intersection of 1933 // the elements of F and L. In reality two typeinfos can match without being 1934 // equal (for example if one represents a C++ class, and the other some class 1935 // derived from it) so it would be wrong to perform this transform in general. 1936 // However the transform is correct and useful if F is a subset of L. In that 1937 // case L can be replaced by F, and thus removed altogether since repeating a 1938 // filter is pointless. So here we look at all pairs of filters F and L where 1939 // L follows F in the list of clauses, and remove L if every element of F is 1940 // an element of L. This can occur when inlining C++ functions with exception 1941 // specifications. 1942 for (unsigned i = 0; i + 1 < NewClauses.size(); ++i) { 1943 // Examine each filter in turn. 1944 Value *Filter = NewClauses[i]; 1945 ArrayType *FTy = dyn_cast<ArrayType>(Filter->getType()); 1946 if (!FTy) 1947 // Not a filter - skip it. 1948 continue; 1949 unsigned FElts = FTy->getNumElements(); 1950 // Examine each filter following this one. Doing this backwards means that 1951 // we don't have to worry about filters disappearing under us when removed. 1952 for (unsigned j = NewClauses.size() - 1; j != i; --j) { 1953 Value *LFilter = NewClauses[j]; 1954 ArrayType *LTy = dyn_cast<ArrayType>(LFilter->getType()); 1955 if (!LTy) 1956 // Not a filter - skip it. 1957 continue; 1958 // If Filter is a subset of LFilter, i.e. every element of Filter is also 1959 // an element of LFilter, then discard LFilter. 1960 SmallVector<Value *, 16>::iterator J = NewClauses.begin() + j; 1961 // If Filter is empty then it is a subset of LFilter. 1962 if (!FElts) { 1963 // Discard LFilter. 1964 NewClauses.erase(J); 1965 MakeNewInstruction = true; 1966 // Move on to the next filter. 1967 continue; 1968 } 1969 unsigned LElts = LTy->getNumElements(); 1970 // If Filter is longer than LFilter then it cannot be a subset of it. 1971 if (FElts > LElts) 1972 // Move on to the next filter. 1973 continue; 1974 // At this point we know that LFilter has at least one element. 1975 if (isa<ConstantAggregateZero>(LFilter)) { // LFilter only contains zeros. 1976 // Filter is a subset of LFilter iff Filter contains only zeros (as we 1977 // already know that Filter is not longer than LFilter). 1978 if (isa<ConstantAggregateZero>(Filter)) { 1979 assert(FElts <= LElts && "Should have handled this case earlier!"); 1980 // Discard LFilter. 1981 NewClauses.erase(J); 1982 MakeNewInstruction = true; 1983 } 1984 // Move on to the next filter. 1985 continue; 1986 } 1987 ConstantArray *LArray = cast<ConstantArray>(LFilter); 1988 if (isa<ConstantAggregateZero>(Filter)) { // Filter only contains zeros. 1989 // Since Filter is non-empty and contains only zeros, it is a subset of 1990 // LFilter iff LFilter contains a zero. 1991 assert(FElts > 0 && "Should have eliminated the empty filter earlier!"); 1992 for (unsigned l = 0; l != LElts; ++l) 1993 if (LArray->getOperand(l)->isNullValue()) { 1994 // LFilter contains a zero - discard it. 1995 NewClauses.erase(J); 1996 MakeNewInstruction = true; 1997 break; 1998 } 1999 // Move on to the next filter. 2000 continue; 2001 } 2002 // At this point we know that both filters are ConstantArrays. Loop over 2003 // operands to see whether every element of Filter is also an element of 2004 // LFilter. Since filters tend to be short this is probably faster than 2005 // using a method that scales nicely. 2006 ConstantArray *FArray = cast<ConstantArray>(Filter); 2007 bool AllFound = true; 2008 for (unsigned f = 0; f != FElts; ++f) { 2009 Value *FTypeInfo = FArray->getOperand(f)->stripPointerCasts(); 2010 AllFound = false; 2011 for (unsigned l = 0; l != LElts; ++l) { 2012 Value *LTypeInfo = LArray->getOperand(l)->stripPointerCasts(); 2013 if (LTypeInfo == FTypeInfo) { 2014 AllFound = true; 2015 break; 2016 } 2017 } 2018 if (!AllFound) 2019 break; 2020 } 2021 if (AllFound) { 2022 // Discard LFilter. 2023 NewClauses.erase(J); 2024 MakeNewInstruction = true; 2025 } 2026 // Move on to the next filter. 2027 } 2028 } 2029 2030 // If we changed any of the clauses, replace the old landingpad instruction 2031 // with a new one. 2032 if (MakeNewInstruction) { 2033 LandingPadInst *NLI = LandingPadInst::Create(LI.getType(), 2034 LI.getPersonalityFn(), 2035 NewClauses.size()); 2036 for (unsigned i = 0, e = NewClauses.size(); i != e; ++i) 2037 NLI->addClause(NewClauses[i]); 2038 // A landing pad with no clauses must have the cleanup flag set. It is 2039 // theoretically possible, though highly unlikely, that we eliminated all 2040 // clauses. If so, force the cleanup flag to true. 2041 if (NewClauses.empty()) 2042 CleanupFlag = true; 2043 NLI->setCleanup(CleanupFlag); 2044 return NLI; 2045 } 2046 2047 // Even if none of the clauses changed, we may nonetheless have understood 2048 // that the cleanup flag is pointless. Clear it if so. 2049 if (LI.isCleanup() != CleanupFlag) { 2050 assert(!CleanupFlag && "Adding a cleanup, not removing one?!"); 2051 LI.setCleanup(CleanupFlag); 2052 return &LI; 2053 } 2054 2055 return 0; 2056} 2057 2058 2059 2060 2061/// TryToSinkInstruction - Try to move the specified instruction from its 2062/// current block into the beginning of DestBlock, which can only happen if it's 2063/// safe to move the instruction past all of the instructions between it and the 2064/// end of its block. 2065static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) { 2066 assert(I->hasOneUse() && "Invariants didn't hold!"); 2067 2068 // Cannot move control-flow-involving, volatile loads, vaarg, etc. 2069 if (isa<PHINode>(I) || isa<LandingPadInst>(I) || I->mayHaveSideEffects() || 2070 isa<TerminatorInst>(I)) 2071 return false; 2072 2073 // Do not sink alloca instructions out of the entry block. 2074 if (isa<AllocaInst>(I) && I->getParent() == 2075 &DestBlock->getParent()->getEntryBlock()) 2076 return false; 2077 2078 // We can only sink load instructions if there is nothing between the load and 2079 // the end of block that could change the value. 2080 if (I->mayReadFromMemory()) { 2081 for (BasicBlock::iterator Scan = I, E = I->getParent()->end(); 2082 Scan != E; ++Scan) 2083 if (Scan->mayWriteToMemory()) 2084 return false; 2085 } 2086 2087 BasicBlock::iterator InsertPos = DestBlock->getFirstInsertionPt(); 2088 I->moveBefore(InsertPos); 2089 ++NumSunkInst; 2090 return true; 2091} 2092 2093 2094/// AddReachableCodeToWorklist - Walk the function in depth-first order, adding 2095/// all reachable code to the worklist. 2096/// 2097/// This has a couple of tricks to make the code faster and more powerful. In 2098/// particular, we constant fold and DCE instructions as we go, to avoid adding 2099/// them to the worklist (this significantly speeds up instcombine on code where 2100/// many instructions are dead or constant). Additionally, if we find a branch 2101/// whose condition is a known constant, we only visit the reachable successors. 2102/// 2103static bool AddReachableCodeToWorklist(BasicBlock *BB, 2104 SmallPtrSet<BasicBlock*, 64> &Visited, 2105 InstCombiner &IC, 2106 const DataLayout *TD, 2107 const TargetLibraryInfo *TLI) { 2108 bool MadeIRChange = false; 2109 SmallVector<BasicBlock*, 256> Worklist; 2110 Worklist.push_back(BB); 2111 2112 SmallVector<Instruction*, 128> InstrsForInstCombineWorklist; 2113 DenseMap<ConstantExpr*, Constant*> FoldedConstants; 2114 2115 do { 2116 BB = Worklist.pop_back_val(); 2117 2118 // We have now visited this block! If we've already been here, ignore it. 2119 if (!Visited.insert(BB)) continue; 2120 2121 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { 2122 Instruction *Inst = BBI++; 2123 2124 // DCE instruction if trivially dead. 2125 if (isInstructionTriviallyDead(Inst, TLI)) { 2126 ++NumDeadInst; 2127 DEBUG(errs() << "IC: DCE: " << *Inst << '\n'); 2128 Inst->eraseFromParent(); 2129 continue; 2130 } 2131 2132 // ConstantProp instruction if trivially constant. 2133 if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0))) 2134 if (Constant *C = ConstantFoldInstruction(Inst, TD, TLI)) { 2135 DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " 2136 << *Inst << '\n'); 2137 Inst->replaceAllUsesWith(C); 2138 ++NumConstProp; 2139 Inst->eraseFromParent(); 2140 continue; 2141 } 2142 2143 if (TD) { 2144 // See if we can constant fold its operands. 2145 for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end(); 2146 i != e; ++i) { 2147 ConstantExpr *CE = dyn_cast<ConstantExpr>(i); 2148 if (CE == 0) continue; 2149 2150 Constant*& FoldRes = FoldedConstants[CE]; 2151 if (!FoldRes) 2152 FoldRes = ConstantFoldConstantExpression(CE, TD, TLI); 2153 if (!FoldRes) 2154 FoldRes = CE; 2155 2156 if (FoldRes != CE) { 2157 *i = FoldRes; 2158 MadeIRChange = true; 2159 } 2160 } 2161 } 2162 2163 InstrsForInstCombineWorklist.push_back(Inst); 2164 } 2165 2166 // Recursively visit successors. If this is a branch or switch on a 2167 // constant, only visit the reachable successor. 2168 TerminatorInst *TI = BB->getTerminator(); 2169 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { 2170 if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) { 2171 bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue(); 2172 BasicBlock *ReachableBB = BI->getSuccessor(!CondVal); 2173 Worklist.push_back(ReachableBB); 2174 continue; 2175 } 2176 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { 2177 if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) { 2178 // See if this is an explicit destination. 2179 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); 2180 i != e; ++i) 2181 if (i.getCaseValue() == Cond) { 2182 BasicBlock *ReachableBB = i.getCaseSuccessor(); 2183 Worklist.push_back(ReachableBB); 2184 continue; 2185 } 2186 2187 // Otherwise it is the default destination. 2188 Worklist.push_back(SI->getDefaultDest()); 2189 continue; 2190 } 2191 } 2192 2193 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 2194 Worklist.push_back(TI->getSuccessor(i)); 2195 } while (!Worklist.empty()); 2196 2197 // Once we've found all of the instructions to add to instcombine's worklist, 2198 // add them in reverse order. This way instcombine will visit from the top 2199 // of the function down. This jives well with the way that it adds all uses 2200 // of instructions to the worklist after doing a transformation, thus avoiding 2201 // some N^2 behavior in pathological cases. 2202 IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0], 2203 InstrsForInstCombineWorklist.size()); 2204 2205 return MadeIRChange; 2206} 2207 2208bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) { 2209 MadeIRChange = false; 2210 2211 DEBUG(errs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on " 2212 << F.getName() << "\n"); 2213 2214 { 2215 // Do a depth-first traversal of the function, populate the worklist with 2216 // the reachable instructions. Ignore blocks that are not reachable. Keep 2217 // track of which blocks we visit. 2218 SmallPtrSet<BasicBlock*, 64> Visited; 2219 MadeIRChange |= AddReachableCodeToWorklist(F.begin(), Visited, *this, TD, 2220 TLI); 2221 2222 // Do a quick scan over the function. If we find any blocks that are 2223 // unreachable, remove any instructions inside of them. This prevents 2224 // the instcombine code from having to deal with some bad special cases. 2225 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 2226 if (Visited.count(BB)) continue; 2227 2228 // Delete the instructions backwards, as it has a reduced likelihood of 2229 // having to update as many def-use and use-def chains. 2230 Instruction *EndInst = BB->getTerminator(); // Last not to be deleted. 2231 while (EndInst != BB->begin()) { 2232 // Delete the next to last instruction. 2233 BasicBlock::iterator I = EndInst; 2234 Instruction *Inst = --I; 2235 if (!Inst->use_empty()) 2236 Inst->replaceAllUsesWith(UndefValue::get(Inst->getType())); 2237 if (isa<LandingPadInst>(Inst)) { 2238 EndInst = Inst; 2239 continue; 2240 } 2241 if (!isa<DbgInfoIntrinsic>(Inst)) { 2242 ++NumDeadInst; 2243 MadeIRChange = true; 2244 } 2245 Inst->eraseFromParent(); 2246 } 2247 } 2248 } 2249 2250 while (!Worklist.isEmpty()) { 2251 Instruction *I = Worklist.RemoveOne(); 2252 if (I == 0) continue; // skip null values. 2253 2254 // Check to see if we can DCE the instruction. 2255 if (isInstructionTriviallyDead(I, TLI)) { 2256 DEBUG(errs() << "IC: DCE: " << *I << '\n'); 2257 EraseInstFromFunction(*I); 2258 ++NumDeadInst; 2259 MadeIRChange = true; 2260 continue; 2261 } 2262 2263 // Instruction isn't dead, see if we can constant propagate it. 2264 if (!I->use_empty() && isa<Constant>(I->getOperand(0))) 2265 if (Constant *C = ConstantFoldInstruction(I, TD, TLI)) { 2266 DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n'); 2267 2268 // Add operands to the worklist. 2269 ReplaceInstUsesWith(*I, C); 2270 ++NumConstProp; 2271 EraseInstFromFunction(*I); 2272 MadeIRChange = true; 2273 continue; 2274 } 2275 2276 // See if we can trivially sink this instruction to a successor basic block. 2277 if (I->hasOneUse()) { 2278 BasicBlock *BB = I->getParent(); 2279 Instruction *UserInst = cast<Instruction>(I->use_back()); 2280 BasicBlock *UserParent; 2281 2282 // Get the block the use occurs in. 2283 if (PHINode *PN = dyn_cast<PHINode>(UserInst)) 2284 UserParent = PN->getIncomingBlock(I->use_begin().getUse()); 2285 else 2286 UserParent = UserInst->getParent(); 2287 2288 if (UserParent != BB) { 2289 bool UserIsSuccessor = false; 2290 // See if the user is one of our successors. 2291 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) 2292 if (*SI == UserParent) { 2293 UserIsSuccessor = true; 2294 break; 2295 } 2296 2297 // If the user is one of our immediate successors, and if that successor 2298 // only has us as a predecessors (we'd have to split the critical edge 2299 // otherwise), we can keep going. 2300 if (UserIsSuccessor && UserParent->getSinglePredecessor()) 2301 // Okay, the CFG is simple enough, try to sink this instruction. 2302 MadeIRChange |= TryToSinkInstruction(I, UserParent); 2303 } 2304 } 2305 2306 // Now that we have an instruction, try combining it to simplify it. 2307 Builder->SetInsertPoint(I->getParent(), I); 2308 Builder->SetCurrentDebugLocation(I->getDebugLoc()); 2309 2310#ifndef NDEBUG 2311 std::string OrigI; 2312#endif 2313 DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str();); 2314 DEBUG(errs() << "IC: Visiting: " << OrigI << '\n'); 2315 2316 if (Instruction *Result = visit(*I)) { 2317 ++NumCombined; 2318 // Should we replace the old instruction with a new one? 2319 if (Result != I) { 2320 DEBUG(errs() << "IC: Old = " << *I << '\n' 2321 << " New = " << *Result << '\n'); 2322 2323 if (!I->getDebugLoc().isUnknown()) 2324 Result->setDebugLoc(I->getDebugLoc()); 2325 // Everything uses the new instruction now. 2326 I->replaceAllUsesWith(Result); 2327 2328 // Move the name to the new instruction first. 2329 Result->takeName(I); 2330 2331 // Push the new instruction and any users onto the worklist. 2332 Worklist.Add(Result); 2333 Worklist.AddUsersToWorkList(*Result); 2334 2335 // Insert the new instruction into the basic block... 2336 BasicBlock *InstParent = I->getParent(); 2337 BasicBlock::iterator InsertPos = I; 2338 2339 // If we replace a PHI with something that isn't a PHI, fix up the 2340 // insertion point. 2341 if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos)) 2342 InsertPos = InstParent->getFirstInsertionPt(); 2343 2344 InstParent->getInstList().insert(InsertPos, Result); 2345 2346 EraseInstFromFunction(*I); 2347 } else { 2348#ifndef NDEBUG 2349 DEBUG(errs() << "IC: Mod = " << OrigI << '\n' 2350 << " New = " << *I << '\n'); 2351#endif 2352 2353 // If the instruction was modified, it's possible that it is now dead. 2354 // if so, remove it. 2355 if (isInstructionTriviallyDead(I, TLI)) { 2356 EraseInstFromFunction(*I); 2357 } else { 2358 Worklist.Add(I); 2359 Worklist.AddUsersToWorkList(*I); 2360 } 2361 } 2362 MadeIRChange = true; 2363 } 2364 } 2365 2366 Worklist.Zap(); 2367 return MadeIRChange; 2368} 2369 2370 2371bool InstCombiner::runOnFunction(Function &F) { 2372 TD = getAnalysisIfAvailable<DataLayout>(); 2373 TLI = &getAnalysis<TargetLibraryInfo>(); 2374 2375 /// Builder - This is an IRBuilder that automatically inserts new 2376 /// instructions into the worklist when they are created. 2377 IRBuilder<true, TargetFolder, InstCombineIRInserter> 2378 TheBuilder(F.getContext(), TargetFolder(TD), 2379 InstCombineIRInserter(Worklist)); 2380 Builder = &TheBuilder; 2381 2382 LibCallSimplifier TheSimplifier(TD, TLI); 2383 Simplifier = &TheSimplifier; 2384 2385 bool EverMadeChange = false; 2386 2387 // Lower dbg.declare intrinsics otherwise their value may be clobbered 2388 // by instcombiner. 2389 EverMadeChange = LowerDbgDeclare(F); 2390 2391 // Iterate while there is work to do. 2392 unsigned Iteration = 0; 2393 while (DoOneIteration(F, Iteration++)) 2394 EverMadeChange = true; 2395 2396 Builder = 0; 2397 return EverMadeChange; 2398} 2399 2400FunctionPass *llvm::createInstructionCombiningPass() { 2401 return new InstCombiner(); 2402} 2403