InstructionCombining.cpp revision 9381dd1ac9ac8a4020cd0dd03323a26f1ae5587f
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-c/Initialization.h" 40#include "llvm/ADT/SmallPtrSet.h" 41#include "llvm/ADT/Statistic.h" 42#include "llvm/ADT/StringSwitch.h" 43#include "llvm/Analysis/ConstantFolding.h" 44#include "llvm/Analysis/InstructionSimplify.h" 45#include "llvm/Analysis/MemoryBuiltins.h" 46#include "llvm/IR/DataLayout.h" 47#include "llvm/IR/IntrinsicInst.h" 48#include "llvm/Support/CFG.h" 49#include "llvm/Support/CommandLine.h" 50#include "llvm/Support/Debug.h" 51#include "llvm/Support/GetElementPtrTypeIterator.h" 52#include "llvm/Support/PatternMatch.h" 53#include "llvm/Support/ValueHandle.h" 54#include "llvm/Target/TargetLibraryInfo.h" 55#include "llvm/Transforms/Utils/Local.h" 56#include <algorithm> 57#include <climits> 58using namespace llvm; 59using namespace llvm::PatternMatch; 60 61STATISTIC(NumCombined , "Number of insts combined"); 62STATISTIC(NumConstProp, "Number of constant folds"); 63STATISTIC(NumDeadInst , "Number of dead inst eliminated"); 64STATISTIC(NumSunkInst , "Number of instructions sunk"); 65STATISTIC(NumExpand, "Number of expansions"); 66STATISTIC(NumFactor , "Number of factorizations"); 67STATISTIC(NumReassoc , "Number of reassociations"); 68 69static cl::opt<bool> UnsafeFPShrink("enable-double-float-shrink", cl::Hidden, 70 cl::init(false), 71 cl::desc("Enable unsafe double to float " 72 "shrinking for math lib calls")); 73 74// Initialization Routines 75void llvm::initializeInstCombine(PassRegistry &Registry) { 76 initializeInstCombinerPass(Registry); 77} 78 79void LLVMInitializeInstCombine(LLVMPassRegistryRef R) { 80 initializeInstCombine(*unwrap(R)); 81} 82 83char InstCombiner::ID = 0; 84INITIALIZE_PASS_BEGIN(InstCombiner, "instcombine", 85 "Combine redundant instructions", false, false) 86INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) 87INITIALIZE_PASS_END(InstCombiner, "instcombine", 88 "Combine redundant instructions", false, false) 89 90void InstCombiner::getAnalysisUsage(AnalysisUsage &AU) const { 91 AU.setPreservesCFG(); 92 AU.addRequired<TargetLibraryInfo>(); 93} 94 95 96Value *InstCombiner::EmitGEPOffset(User *GEP) { 97 return llvm::EmitGEPOffset(Builder, *getDataLayout(), GEP); 98} 99 100/// ShouldChangeType - Return true if it is desirable to convert a computation 101/// from 'From' to 'To'. We don't want to convert from a legal to an illegal 102/// type for example, or from a smaller to a larger illegal type. 103bool InstCombiner::ShouldChangeType(Type *From, Type *To) const { 104 assert(From->isIntegerTy() && To->isIntegerTy()); 105 106 // If we don't have TD, we don't know if the source/dest are legal. 107 if (!TD) return false; 108 109 unsigned FromWidth = From->getPrimitiveSizeInBits(); 110 unsigned ToWidth = To->getPrimitiveSizeInBits(); 111 bool FromLegal = TD->isLegalInteger(FromWidth); 112 bool ToLegal = TD->isLegalInteger(ToWidth); 113 114 // If this is a legal integer from type, and the result would be an illegal 115 // type, don't do the transformation. 116 if (FromLegal && !ToLegal) 117 return false; 118 119 // Otherwise, if both are illegal, do not increase the size of the result. We 120 // do allow things like i160 -> i64, but not i64 -> i160. 121 if (!FromLegal && !ToLegal && ToWidth > FromWidth) 122 return false; 123 124 return true; 125} 126 127// Return true, if No Signed Wrap should be maintained for I. 128// The No Signed Wrap flag can be kept if the operation "B (I.getOpcode) C", 129// where both B and C should be ConstantInts, results in a constant that does 130// not overflow. This function only handles the Add and Sub opcodes. For 131// all other opcodes, the function conservatively returns false. 132static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) { 133 OverflowingBinaryOperator *OBO = dyn_cast<OverflowingBinaryOperator>(&I); 134 if (!OBO || !OBO->hasNoSignedWrap()) { 135 return false; 136 } 137 138 // We reason about Add and Sub Only. 139 Instruction::BinaryOps Opcode = I.getOpcode(); 140 if (Opcode != Instruction::Add && 141 Opcode != Instruction::Sub) { 142 return false; 143 } 144 145 ConstantInt *CB = dyn_cast<ConstantInt>(B); 146 ConstantInt *CC = dyn_cast<ConstantInt>(C); 147 148 if (!CB || !CC) { 149 return false; 150 } 151 152 const APInt &BVal = CB->getValue(); 153 const APInt &CVal = CC->getValue(); 154 bool Overflow = false; 155 156 if (Opcode == Instruction::Add) { 157 BVal.sadd_ov(CVal, Overflow); 158 } else { 159 BVal.ssub_ov(CVal, Overflow); 160 } 161 162 return !Overflow; 163} 164 165/// SimplifyAssociativeOrCommutative - This performs a few simplifications for 166/// operators which are associative or commutative: 167// 168// Commutative operators: 169// 170// 1. Order operands such that they are listed from right (least complex) to 171// left (most complex). This puts constants before unary operators before 172// binary operators. 173// 174// Associative operators: 175// 176// 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. 177// 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. 178// 179// Associative and commutative operators: 180// 181// 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. 182// 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. 183// 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" 184// if C1 and C2 are constants. 185// 186bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) { 187 Instruction::BinaryOps Opcode = I.getOpcode(); 188 bool Changed = false; 189 190 do { 191 // Order operands such that they are listed from right (least complex) to 192 // left (most complex). This puts constants before unary operators before 193 // binary operators. 194 if (I.isCommutative() && getComplexity(I.getOperand(0)) < 195 getComplexity(I.getOperand(1))) 196 Changed = !I.swapOperands(); 197 198 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0)); 199 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1)); 200 201 if (I.isAssociative()) { 202 // Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. 203 if (Op0 && Op0->getOpcode() == Opcode) { 204 Value *A = Op0->getOperand(0); 205 Value *B = Op0->getOperand(1); 206 Value *C = I.getOperand(1); 207 208 // Does "B op C" simplify? 209 if (Value *V = SimplifyBinOp(Opcode, B, C, TD)) { 210 // It simplifies to V. Form "A op V". 211 I.setOperand(0, A); 212 I.setOperand(1, V); 213 // Conservatively clear the optional flags, since they may not be 214 // preserved by the reassociation. 215 if (MaintainNoSignedWrap(I, B, C) && 216 (!Op0 || (isa<BinaryOperator>(Op0) && Op0->hasNoSignedWrap()))) { 217 // Note: this is only valid because SimplifyBinOp doesn't look at 218 // the operands to Op0. 219 I.clearSubclassOptionalData(); 220 I.setHasNoSignedWrap(true); 221 } else { 222 I.clearSubclassOptionalData(); 223 } 224 225 Changed = true; 226 ++NumReassoc; 227 continue; 228 } 229 } 230 231 // Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. 232 if (Op1 && Op1->getOpcode() == Opcode) { 233 Value *A = I.getOperand(0); 234 Value *B = Op1->getOperand(0); 235 Value *C = Op1->getOperand(1); 236 237 // Does "A op B" simplify? 238 if (Value *V = SimplifyBinOp(Opcode, A, B, TD)) { 239 // It simplifies to V. Form "V op C". 240 I.setOperand(0, V); 241 I.setOperand(1, C); 242 // Conservatively clear the optional flags, since they may not be 243 // preserved by the reassociation. 244 I.clearSubclassOptionalData(); 245 Changed = true; 246 ++NumReassoc; 247 continue; 248 } 249 } 250 } 251 252 if (I.isAssociative() && I.isCommutative()) { 253 // Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. 254 if (Op0 && Op0->getOpcode() == Opcode) { 255 Value *A = Op0->getOperand(0); 256 Value *B = Op0->getOperand(1); 257 Value *C = I.getOperand(1); 258 259 // Does "C op A" simplify? 260 if (Value *V = SimplifyBinOp(Opcode, C, A, TD)) { 261 // It simplifies to V. Form "V op B". 262 I.setOperand(0, V); 263 I.setOperand(1, B); 264 // Conservatively clear the optional flags, since they may not be 265 // preserved by the reassociation. 266 I.clearSubclassOptionalData(); 267 Changed = true; 268 ++NumReassoc; 269 continue; 270 } 271 } 272 273 // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. 274 if (Op1 && Op1->getOpcode() == Opcode) { 275 Value *A = I.getOperand(0); 276 Value *B = Op1->getOperand(0); 277 Value *C = Op1->getOperand(1); 278 279 // Does "C op A" simplify? 280 if (Value *V = SimplifyBinOp(Opcode, C, A, TD)) { 281 // It simplifies to V. Form "B op V". 282 I.setOperand(0, B); 283 I.setOperand(1, V); 284 // Conservatively clear the optional flags, since they may not be 285 // preserved by the reassociation. 286 I.clearSubclassOptionalData(); 287 Changed = true; 288 ++NumReassoc; 289 continue; 290 } 291 } 292 293 // Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" 294 // if C1 and C2 are constants. 295 if (Op0 && Op1 && 296 Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode && 297 isa<Constant>(Op0->getOperand(1)) && 298 isa<Constant>(Op1->getOperand(1)) && 299 Op0->hasOneUse() && Op1->hasOneUse()) { 300 Value *A = Op0->getOperand(0); 301 Constant *C1 = cast<Constant>(Op0->getOperand(1)); 302 Value *B = Op1->getOperand(0); 303 Constant *C2 = cast<Constant>(Op1->getOperand(1)); 304 305 Constant *Folded = ConstantExpr::get(Opcode, C1, C2); 306 BinaryOperator *New = BinaryOperator::Create(Opcode, A, B); 307 InsertNewInstWith(New, I); 308 New->takeName(Op1); 309 I.setOperand(0, New); 310 I.setOperand(1, Folded); 311 // Conservatively clear the optional flags, since they may not be 312 // preserved by the reassociation. 313 I.clearSubclassOptionalData(); 314 315 Changed = true; 316 continue; 317 } 318 } 319 320 // No further simplifications. 321 return Changed; 322 } while (1); 323} 324 325/// LeftDistributesOverRight - Whether "X LOp (Y ROp Z)" is always equal to 326/// "(X LOp Y) ROp (X LOp Z)". 327static bool LeftDistributesOverRight(Instruction::BinaryOps LOp, 328 Instruction::BinaryOps ROp) { 329 switch (LOp) { 330 default: 331 return false; 332 333 case Instruction::And: 334 // And distributes over Or and Xor. 335 switch (ROp) { 336 default: 337 return false; 338 case Instruction::Or: 339 case Instruction::Xor: 340 return true; 341 } 342 343 case Instruction::Mul: 344 // Multiplication distributes over addition and subtraction. 345 switch (ROp) { 346 default: 347 return false; 348 case Instruction::Add: 349 case Instruction::Sub: 350 return true; 351 } 352 353 case Instruction::Or: 354 // Or distributes over And. 355 switch (ROp) { 356 default: 357 return false; 358 case Instruction::And: 359 return true; 360 } 361 } 362} 363 364/// RightDistributesOverLeft - Whether "(X LOp Y) ROp Z" is always equal to 365/// "(X ROp Z) LOp (Y ROp Z)". 366static bool RightDistributesOverLeft(Instruction::BinaryOps LOp, 367 Instruction::BinaryOps ROp) { 368 if (Instruction::isCommutative(ROp)) 369 return LeftDistributesOverRight(ROp, LOp); 370 // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z", 371 // but this requires knowing that the addition does not overflow and other 372 // such subtleties. 373 return false; 374} 375 376/// SimplifyUsingDistributiveLaws - This tries to simplify binary operations 377/// which some other binary operation distributes over either by factorizing 378/// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this 379/// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is 380/// a win). Returns the simplified value, or null if it didn't simplify. 381Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) { 382 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 383 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 384 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 385 Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); // op 386 387 // Factorization. 388 if (Op0 && Op1 && Op0->getOpcode() == Op1->getOpcode()) { 389 // The instruction has the form "(A op' B) op (C op' D)". Try to factorize 390 // a common term. 391 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1); 392 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1); 393 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' 394 395 // Does "X op' Y" always equal "Y op' X"? 396 bool InnerCommutative = Instruction::isCommutative(InnerOpcode); 397 398 // Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"? 399 if (LeftDistributesOverRight(InnerOpcode, TopLevelOpcode)) 400 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the 401 // commutative case, "(A op' B) op (C op' A)"? 402 if (A == C || (InnerCommutative && A == D)) { 403 if (A != C) 404 std::swap(C, D); 405 // Consider forming "A op' (B op D)". 406 // If "B op D" simplifies then it can be formed with no cost. 407 Value *V = SimplifyBinOp(TopLevelOpcode, B, D, TD); 408 // If "B op D" doesn't simplify then only go on if both of the existing 409 // operations "A op' B" and "C op' D" will be zapped as no longer used. 410 if (!V && Op0->hasOneUse() && Op1->hasOneUse()) 411 V = Builder->CreateBinOp(TopLevelOpcode, B, D, Op1->getName()); 412 if (V) { 413 ++NumFactor; 414 V = Builder->CreateBinOp(InnerOpcode, A, V); 415 V->takeName(&I); 416 return V; 417 } 418 } 419 420 // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"? 421 if (RightDistributesOverLeft(TopLevelOpcode, InnerOpcode)) 422 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the 423 // commutative case, "(A op' B) op (B op' D)"? 424 if (B == D || (InnerCommutative && B == C)) { 425 if (B != D) 426 std::swap(C, D); 427 // Consider forming "(A op C) op' B". 428 // If "A op C" simplifies then it can be formed with no cost. 429 Value *V = SimplifyBinOp(TopLevelOpcode, A, C, TD); 430 // If "A op C" doesn't simplify then only go on if both of the existing 431 // operations "A op' B" and "C op' D" will be zapped as no longer used. 432 if (!V && Op0->hasOneUse() && Op1->hasOneUse()) 433 V = Builder->CreateBinOp(TopLevelOpcode, A, C, Op0->getName()); 434 if (V) { 435 ++NumFactor; 436 V = Builder->CreateBinOp(InnerOpcode, V, B); 437 V->takeName(&I); 438 return V; 439 } 440 } 441 } 442 443 // Expansion. 444 if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) { 445 // The instruction has the form "(A op' B) op C". See if expanding it out 446 // to "(A op C) op' (B op C)" results in simplifications. 447 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; 448 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' 449 450 // Do "A op C" and "B op C" both simplify? 451 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, C, TD)) 452 if (Value *R = SimplifyBinOp(TopLevelOpcode, B, C, TD)) { 453 // They do! Return "L op' R". 454 ++NumExpand; 455 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. 456 if ((L == A && R == B) || 457 (Instruction::isCommutative(InnerOpcode) && L == B && R == A)) 458 return Op0; 459 // Otherwise return "L op' R" if it simplifies. 460 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, TD)) 461 return V; 462 // Otherwise, create a new instruction. 463 C = Builder->CreateBinOp(InnerOpcode, L, R); 464 C->takeName(&I); 465 return C; 466 } 467 } 468 469 if (Op1 && LeftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) { 470 // The instruction has the form "A op (B op' C)". See if expanding it out 471 // to "(A op B) op' (A op C)" results in simplifications. 472 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); 473 Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op' 474 475 // Do "A op B" and "A op C" both simplify? 476 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, B, TD)) 477 if (Value *R = SimplifyBinOp(TopLevelOpcode, A, C, TD)) { 478 // They do! Return "L op' R". 479 ++NumExpand; 480 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. 481 if ((L == B && R == C) || 482 (Instruction::isCommutative(InnerOpcode) && L == C && R == B)) 483 return Op1; 484 // Otherwise return "L op' R" if it simplifies. 485 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, TD)) 486 return V; 487 // Otherwise, create a new instruction. 488 A = Builder->CreateBinOp(InnerOpcode, L, R); 489 A->takeName(&I); 490 return A; 491 } 492 } 493 494 return 0; 495} 496 497// dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction 498// if the LHS is a constant zero (which is the 'negate' form). 499// 500Value *InstCombiner::dyn_castNegVal(Value *V) const { 501 if (BinaryOperator::isNeg(V)) 502 return BinaryOperator::getNegArgument(V); 503 504 // Constants can be considered to be negated values if they can be folded. 505 if (ConstantInt *C = dyn_cast<ConstantInt>(V)) 506 return ConstantExpr::getNeg(C); 507 508 if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) 509 if (C->getType()->getElementType()->isIntegerTy()) 510 return ConstantExpr::getNeg(C); 511 512 return 0; 513} 514 515// dyn_castFNegVal - Given a 'fsub' instruction, return the RHS of the 516// instruction if the LHS is a constant negative zero (which is the 'negate' 517// form). 518// 519Value *InstCombiner::dyn_castFNegVal(Value *V, bool IgnoreZeroSign) const { 520 if (BinaryOperator::isFNeg(V, IgnoreZeroSign)) 521 return BinaryOperator::getFNegArgument(V); 522 523 // Constants can be considered to be negated values if they can be folded. 524 if (ConstantFP *C = dyn_cast<ConstantFP>(V)) 525 return ConstantExpr::getFNeg(C); 526 527 if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) 528 if (C->getType()->getElementType()->isFloatingPointTy()) 529 return ConstantExpr::getFNeg(C); 530 531 return 0; 532} 533 534static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO, 535 InstCombiner *IC) { 536 if (CastInst *CI = dyn_cast<CastInst>(&I)) { 537 return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType()); 538 } 539 540 // Figure out if the constant is the left or the right argument. 541 bool ConstIsRHS = isa<Constant>(I.getOperand(1)); 542 Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS)); 543 544 if (Constant *SOC = dyn_cast<Constant>(SO)) { 545 if (ConstIsRHS) 546 return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand); 547 return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC); 548 } 549 550 Value *Op0 = SO, *Op1 = ConstOperand; 551 if (!ConstIsRHS) 552 std::swap(Op0, Op1); 553 554 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I)) 555 return IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1, 556 SO->getName()+".op"); 557 if (ICmpInst *CI = dyn_cast<ICmpInst>(&I)) 558 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, 559 SO->getName()+".cmp"); 560 if (FCmpInst *CI = dyn_cast<FCmpInst>(&I)) 561 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, 562 SO->getName()+".cmp"); 563 llvm_unreachable("Unknown binary instruction type!"); 564} 565 566// FoldOpIntoSelect - Given an instruction with a select as one operand and a 567// constant as the other operand, try to fold the binary operator into the 568// select arguments. This also works for Cast instructions, which obviously do 569// not have a second operand. 570Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) { 571 // Don't modify shared select instructions 572 if (!SI->hasOneUse()) return 0; 573 Value *TV = SI->getOperand(1); 574 Value *FV = SI->getOperand(2); 575 576 if (isa<Constant>(TV) || isa<Constant>(FV)) { 577 // Bool selects with constant operands can be folded to logical ops. 578 if (SI->getType()->isIntegerTy(1)) return 0; 579 580 // If it's a bitcast involving vectors, make sure it has the same number of 581 // elements on both sides. 582 if (BitCastInst *BC = dyn_cast<BitCastInst>(&Op)) { 583 VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy()); 584 VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy()); 585 586 // Verify that either both or neither are vectors. 587 if ((SrcTy == NULL) != (DestTy == NULL)) return 0; 588 // If vectors, verify that they have the same number of elements. 589 if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements()) 590 return 0; 591 } 592 593 Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this); 594 Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this); 595 596 return SelectInst::Create(SI->getCondition(), 597 SelectTrueVal, SelectFalseVal); 598 } 599 return 0; 600} 601 602 603/// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which 604/// has a PHI node as operand #0, see if we can fold the instruction into the 605/// PHI (which is only possible if all operands to the PHI are constants). 606/// 607Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) { 608 PHINode *PN = cast<PHINode>(I.getOperand(0)); 609 unsigned NumPHIValues = PN->getNumIncomingValues(); 610 if (NumPHIValues == 0) 611 return 0; 612 613 // We normally only transform phis with a single use. However, if a PHI has 614 // multiple uses and they are all the same operation, we can fold *all* of the 615 // uses into the PHI. 616 if (!PN->hasOneUse()) { 617 // Walk the use list for the instruction, comparing them to I. 618 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); 619 UI != E; ++UI) { 620 Instruction *User = cast<Instruction>(*UI); 621 if (User != &I && !I.isIdenticalTo(User)) 622 return 0; 623 } 624 // Otherwise, we can replace *all* users with the new PHI we form. 625 } 626 627 // Check to see if all of the operands of the PHI are simple constants 628 // (constantint/constantfp/undef). If there is one non-constant value, 629 // remember the BB it is in. If there is more than one or if *it* is a PHI, 630 // bail out. We don't do arbitrary constant expressions here because moving 631 // their computation can be expensive without a cost model. 632 BasicBlock *NonConstBB = 0; 633 for (unsigned i = 0; i != NumPHIValues; ++i) { 634 Value *InVal = PN->getIncomingValue(i); 635 if (isa<Constant>(InVal) && !isa<ConstantExpr>(InVal)) 636 continue; 637 638 if (isa<PHINode>(InVal)) return 0; // Itself a phi. 639 if (NonConstBB) return 0; // More than one non-const value. 640 641 NonConstBB = PN->getIncomingBlock(i); 642 643 // If the InVal is an invoke at the end of the pred block, then we can't 644 // insert a computation after it without breaking the edge. 645 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) 646 if (II->getParent() == NonConstBB) 647 return 0; 648 649 // If the incoming non-constant value is in I's block, we will remove one 650 // instruction, but insert another equivalent one, leading to infinite 651 // instcombine. 652 if (NonConstBB == I.getParent()) 653 return 0; 654 } 655 656 // If there is exactly one non-constant value, we can insert a copy of the 657 // operation in that block. However, if this is a critical edge, we would be 658 // inserting the computation one some other paths (e.g. inside a loop). Only 659 // do this if the pred block is unconditionally branching into the phi block. 660 if (NonConstBB != 0) { 661 BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator()); 662 if (!BI || !BI->isUnconditional()) return 0; 663 } 664 665 // Okay, we can do the transformation: create the new PHI node. 666 PHINode *NewPN = PHINode::Create(I.getType(), PN->getNumIncomingValues()); 667 InsertNewInstBefore(NewPN, *PN); 668 NewPN->takeName(PN); 669 670 // If we are going to have to insert a new computation, do so right before the 671 // predecessors terminator. 672 if (NonConstBB) 673 Builder->SetInsertPoint(NonConstBB->getTerminator()); 674 675 // Next, add all of the operands to the PHI. 676 if (SelectInst *SI = dyn_cast<SelectInst>(&I)) { 677 // We only currently try to fold the condition of a select when it is a phi, 678 // not the true/false values. 679 Value *TrueV = SI->getTrueValue(); 680 Value *FalseV = SI->getFalseValue(); 681 BasicBlock *PhiTransBB = PN->getParent(); 682 for (unsigned i = 0; i != NumPHIValues; ++i) { 683 BasicBlock *ThisBB = PN->getIncomingBlock(i); 684 Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB); 685 Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB); 686 Value *InV = 0; 687 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 688 InV = InC->isNullValue() ? FalseVInPred : TrueVInPred; 689 else 690 InV = Builder->CreateSelect(PN->getIncomingValue(i), 691 TrueVInPred, FalseVInPred, "phitmp"); 692 NewPN->addIncoming(InV, ThisBB); 693 } 694 } else if (CmpInst *CI = dyn_cast<CmpInst>(&I)) { 695 Constant *C = cast<Constant>(I.getOperand(1)); 696 for (unsigned i = 0; i != NumPHIValues; ++i) { 697 Value *InV = 0; 698 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 699 InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C); 700 else if (isa<ICmpInst>(CI)) 701 InV = Builder->CreateICmp(CI->getPredicate(), PN->getIncomingValue(i), 702 C, "phitmp"); 703 else 704 InV = Builder->CreateFCmp(CI->getPredicate(), PN->getIncomingValue(i), 705 C, "phitmp"); 706 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 707 } 708 } else if (I.getNumOperands() == 2) { 709 Constant *C = cast<Constant>(I.getOperand(1)); 710 for (unsigned i = 0; i != NumPHIValues; ++i) { 711 Value *InV = 0; 712 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 713 InV = ConstantExpr::get(I.getOpcode(), InC, C); 714 else 715 InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(), 716 PN->getIncomingValue(i), C, "phitmp"); 717 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 718 } 719 } else { 720 CastInst *CI = cast<CastInst>(&I); 721 Type *RetTy = CI->getType(); 722 for (unsigned i = 0; i != NumPHIValues; ++i) { 723 Value *InV; 724 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) 725 InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy); 726 else 727 InV = Builder->CreateCast(CI->getOpcode(), 728 PN->getIncomingValue(i), I.getType(), "phitmp"); 729 NewPN->addIncoming(InV, PN->getIncomingBlock(i)); 730 } 731 } 732 733 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); 734 UI != E; ) { 735 Instruction *User = cast<Instruction>(*UI++); 736 if (User == &I) continue; 737 ReplaceInstUsesWith(*User, NewPN); 738 EraseInstFromFunction(*User); 739 } 740 return ReplaceInstUsesWith(I, NewPN); 741} 742 743/// FindElementAtOffset - Given a type and a constant offset, determine whether 744/// or not there is a sequence of GEP indices into the type that will land us at 745/// the specified offset. If so, fill them into NewIndices and return the 746/// resultant element type, otherwise return null. 747Type *InstCombiner::FindElementAtOffset(Type *Ty, int64_t Offset, 748 SmallVectorImpl<Value*> &NewIndices) { 749 if (!TD) return 0; 750 if (!Ty->isSized()) return 0; 751 752 // Start with the index over the outer type. Note that the type size 753 // might be zero (even if the offset isn't zero) if the indexed type 754 // is something like [0 x {int, int}] 755 Type *IntPtrTy = TD->getIntPtrType(Ty->getContext()); 756 int64_t FirstIdx = 0; 757 if (int64_t TySize = TD->getTypeAllocSize(Ty)) { 758 FirstIdx = Offset/TySize; 759 Offset -= FirstIdx*TySize; 760 761 assert(Offset >= 0 && "Offset should never be negative!"); 762 assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset"); 763 } 764 765 NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx)); 766 767 // Index into the types. If we fail, set OrigBase to null. 768 while (Offset) { 769 // Indexing into tail padding between struct/array elements. 770 if (uint64_t(Offset*8) >= TD->getTypeSizeInBits(Ty)) 771 return 0; 772 773 if (StructType *STy = dyn_cast<StructType>(Ty)) { 774 const StructLayout *SL = TD->getStructLayout(STy); 775 assert(Offset < (int64_t)SL->getSizeInBytes() && 776 "Offset must stay within the indexed type"); 777 778 unsigned Elt = SL->getElementContainingOffset(Offset); 779 NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 780 Elt)); 781 782 Offset -= SL->getElementOffset(Elt); 783 Ty = STy->getElementType(Elt); 784 } else if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) { 785 uint64_t EltSize = TD->getTypeAllocSize(AT->getElementType()); 786 assert(EltSize && "Cannot index into a zero-sized array"); 787 NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize)); 788 Offset %= EltSize; 789 Ty = AT->getElementType(); 790 } else { 791 // Otherwise, we can't index into the middle of this atomic type, bail. 792 return 0; 793 } 794 } 795 796 return Ty; 797} 798 799static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) { 800 // If this GEP has only 0 indices, it is the same pointer as 801 // Src. If Src is not a trivial GEP too, don't combine 802 // the indices. 803 if (GEP.hasAllZeroIndices() && !Src.hasAllZeroIndices() && 804 !Src.hasOneUse()) 805 return false; 806 return true; 807} 808 809/// Descale - Return a value X such that Val = X * Scale, or null if none. If 810/// the multiplication is known not to overflow then NoSignedWrap is set. 811Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) { 812 assert(isa<IntegerType>(Val->getType()) && "Can only descale integers!"); 813 assert(cast<IntegerType>(Val->getType())->getBitWidth() == 814 Scale.getBitWidth() && "Scale not compatible with value!"); 815 816 // If Val is zero or Scale is one then Val = Val * Scale. 817 if (match(Val, m_Zero()) || Scale == 1) { 818 NoSignedWrap = true; 819 return Val; 820 } 821 822 // If Scale is zero then it does not divide Val. 823 if (Scale.isMinValue()) 824 return 0; 825 826 // Look through chains of multiplications, searching for a constant that is 827 // divisible by Scale. For example, descaling X*(Y*(Z*4)) by a factor of 4 828 // will find the constant factor 4 and produce X*(Y*Z). Descaling X*(Y*8) by 829 // a factor of 4 will produce X*(Y*2). The principle of operation is to bore 830 // down from Val: 831 // 832 // Val = M1 * X || Analysis starts here and works down 833 // M1 = M2 * Y || Doesn't descend into terms with more 834 // M2 = Z * 4 \/ than one use 835 // 836 // Then to modify a term at the bottom: 837 // 838 // Val = M1 * X 839 // M1 = Z * Y || Replaced M2 with Z 840 // 841 // Then to work back up correcting nsw flags. 842 843 // Op - the term we are currently analyzing. Starts at Val then drills down. 844 // Replaced with its descaled value before exiting from the drill down loop. 845 Value *Op = Val; 846 847 // Parent - initially null, but after drilling down notes where Op came from. 848 // In the example above, Parent is (Val, 0) when Op is M1, because M1 is the 849 // 0'th operand of Val. 850 std::pair<Instruction*, unsigned> Parent; 851 852 // RequireNoSignedWrap - Set if the transform requires a descaling at deeper 853 // levels that doesn't overflow. 854 bool RequireNoSignedWrap = false; 855 856 // logScale - log base 2 of the scale. Negative if not a power of 2. 857 int32_t logScale = Scale.exactLogBase2(); 858 859 for (;; Op = Parent.first->getOperand(Parent.second)) { // Drill down 860 861 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) { 862 // If Op is a constant divisible by Scale then descale to the quotient. 863 APInt Quotient(Scale), Remainder(Scale); // Init ensures right bitwidth. 864 APInt::sdivrem(CI->getValue(), Scale, Quotient, Remainder); 865 if (!Remainder.isMinValue()) 866 // Not divisible by Scale. 867 return 0; 868 // Replace with the quotient in the parent. 869 Op = ConstantInt::get(CI->getType(), Quotient); 870 NoSignedWrap = true; 871 break; 872 } 873 874 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op)) { 875 876 if (BO->getOpcode() == Instruction::Mul) { 877 // Multiplication. 878 NoSignedWrap = BO->hasNoSignedWrap(); 879 if (RequireNoSignedWrap && !NoSignedWrap) 880 return 0; 881 882 // There are three cases for multiplication: multiplication by exactly 883 // the scale, multiplication by a constant different to the scale, and 884 // multiplication by something else. 885 Value *LHS = BO->getOperand(0); 886 Value *RHS = BO->getOperand(1); 887 888 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 889 // Multiplication by a constant. 890 if (CI->getValue() == Scale) { 891 // Multiplication by exactly the scale, replace the multiplication 892 // by its left-hand side in the parent. 893 Op = LHS; 894 break; 895 } 896 897 // Otherwise drill down into the constant. 898 if (!Op->hasOneUse()) 899 return 0; 900 901 Parent = std::make_pair(BO, 1); 902 continue; 903 } 904 905 // Multiplication by something else. Drill down into the left-hand side 906 // since that's where the reassociate pass puts the good stuff. 907 if (!Op->hasOneUse()) 908 return 0; 909 910 Parent = std::make_pair(BO, 0); 911 continue; 912 } 913 914 if (logScale > 0 && BO->getOpcode() == Instruction::Shl && 915 isa<ConstantInt>(BO->getOperand(1))) { 916 // Multiplication by a power of 2. 917 NoSignedWrap = BO->hasNoSignedWrap(); 918 if (RequireNoSignedWrap && !NoSignedWrap) 919 return 0; 920 921 Value *LHS = BO->getOperand(0); 922 int32_t Amt = cast<ConstantInt>(BO->getOperand(1))-> 923 getLimitedValue(Scale.getBitWidth()); 924 // Op = LHS << Amt. 925 926 if (Amt == logScale) { 927 // Multiplication by exactly the scale, replace the multiplication 928 // by its left-hand side in the parent. 929 Op = LHS; 930 break; 931 } 932 if (Amt < logScale || !Op->hasOneUse()) 933 return 0; 934 935 // Multiplication by more than the scale. Reduce the multiplying amount 936 // by the scale in the parent. 937 Parent = std::make_pair(BO, 1); 938 Op = ConstantInt::get(BO->getType(), Amt - logScale); 939 break; 940 } 941 } 942 943 if (!Op->hasOneUse()) 944 return 0; 945 946 if (CastInst *Cast = dyn_cast<CastInst>(Op)) { 947 if (Cast->getOpcode() == Instruction::SExt) { 948 // Op is sign-extended from a smaller type, descale in the smaller type. 949 unsigned SmallSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); 950 APInt SmallScale = Scale.trunc(SmallSize); 951 // Suppose Op = sext X, and we descale X as Y * SmallScale. We want to 952 // descale Op as (sext Y) * Scale. In order to have 953 // sext (Y * SmallScale) = (sext Y) * Scale 954 // some conditions need to hold however: SmallScale must sign-extend to 955 // Scale and the multiplication Y * SmallScale should not overflow. 956 if (SmallScale.sext(Scale.getBitWidth()) != Scale) 957 // SmallScale does not sign-extend to Scale. 958 return 0; 959 assert(SmallScale.exactLogBase2() == logScale); 960 // Require that Y * SmallScale must not overflow. 961 RequireNoSignedWrap = true; 962 963 // Drill down through the cast. 964 Parent = std::make_pair(Cast, 0); 965 Scale = SmallScale; 966 continue; 967 } 968 969 if (Cast->getOpcode() == Instruction::Trunc) { 970 // Op is truncated from a larger type, descale in the larger type. 971 // Suppose Op = trunc X, and we descale X as Y * sext Scale. Then 972 // trunc (Y * sext Scale) = (trunc Y) * Scale 973 // always holds. However (trunc Y) * Scale may overflow even if 974 // trunc (Y * sext Scale) does not, so nsw flags need to be cleared 975 // from this point up in the expression (see later). 976 if (RequireNoSignedWrap) 977 return 0; 978 979 // Drill down through the cast. 980 unsigned LargeSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); 981 Parent = std::make_pair(Cast, 0); 982 Scale = Scale.sext(LargeSize); 983 if (logScale + 1 == (int32_t)Cast->getType()->getPrimitiveSizeInBits()) 984 logScale = -1; 985 assert(Scale.exactLogBase2() == logScale); 986 continue; 987 } 988 } 989 990 // Unsupported expression, bail out. 991 return 0; 992 } 993 994 // We know that we can successfully descale, so from here on we can safely 995 // modify the IR. Op holds the descaled version of the deepest term in the 996 // expression. NoSignedWrap is 'true' if multiplying Op by Scale is known 997 // not to overflow. 998 999 if (!Parent.first) 1000 // The expression only had one term. 1001 return Op; 1002 1003 // Rewrite the parent using the descaled version of its operand. 1004 assert(Parent.first->hasOneUse() && "Drilled down when more than one use!"); 1005 assert(Op != Parent.first->getOperand(Parent.second) && 1006 "Descaling was a no-op?"); 1007 Parent.first->setOperand(Parent.second, Op); 1008 Worklist.Add(Parent.first); 1009 1010 // Now work back up the expression correcting nsw flags. The logic is based 1011 // on the following observation: if X * Y is known not to overflow as a signed 1012 // multiplication, and Y is replaced by a value Z with smaller absolute value, 1013 // then X * Z will not overflow as a signed multiplication either. As we work 1014 // our way up, having NoSignedWrap 'true' means that the descaled value at the 1015 // current level has strictly smaller absolute value than the original. 1016 Instruction *Ancestor = Parent.first; 1017 do { 1018 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Ancestor)) { 1019 // If the multiplication wasn't nsw then we can't say anything about the 1020 // value of the descaled multiplication, and we have to clear nsw flags 1021 // from this point on up. 1022 bool OpNoSignedWrap = BO->hasNoSignedWrap(); 1023 NoSignedWrap &= OpNoSignedWrap; 1024 if (NoSignedWrap != OpNoSignedWrap) { 1025 BO->setHasNoSignedWrap(NoSignedWrap); 1026 Worklist.Add(Ancestor); 1027 } 1028 } else if (Ancestor->getOpcode() == Instruction::Trunc) { 1029 // The fact that the descaled input to the trunc has smaller absolute 1030 // value than the original input doesn't tell us anything useful about 1031 // the absolute values of the truncations. 1032 NoSignedWrap = false; 1033 } 1034 assert((Ancestor->getOpcode() != Instruction::SExt || NoSignedWrap) && 1035 "Failed to keep proper track of nsw flags while drilling down?"); 1036 1037 if (Ancestor == Val) 1038 // Got to the top, all done! 1039 return Val; 1040 1041 // Move up one level in the expression. 1042 assert(Ancestor->hasOneUse() && "Drilled down when more than one use!"); 1043 Ancestor = Ancestor->use_back(); 1044 } while (1); 1045} 1046 1047Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { 1048 SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end()); 1049 1050 if (Value *V = SimplifyGEPInst(Ops, TD)) 1051 return ReplaceInstUsesWith(GEP, V); 1052 1053 Value *PtrOp = GEP.getOperand(0); 1054 1055 // Eliminate unneeded casts for indices, and replace indices which displace 1056 // by multiples of a zero size type with zero. 1057 if (TD) { 1058 bool MadeChange = false; 1059 Type *IntPtrTy = TD->getIntPtrType(GEP.getPointerOperandType()); 1060 1061 gep_type_iterator GTI = gep_type_begin(GEP); 1062 for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); 1063 I != E; ++I, ++GTI) { 1064 // Skip indices into struct types. 1065 SequentialType *SeqTy = dyn_cast<SequentialType>(*GTI); 1066 if (!SeqTy) continue; 1067 1068 // If the element type has zero size then any index over it is equivalent 1069 // to an index of zero, so replace it with zero if it is not zero already. 1070 if (SeqTy->getElementType()->isSized() && 1071 TD->getTypeAllocSize(SeqTy->getElementType()) == 0) 1072 if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) { 1073 *I = Constant::getNullValue(IntPtrTy); 1074 MadeChange = true; 1075 } 1076 1077 Type *IndexTy = (*I)->getType(); 1078 if (IndexTy != IntPtrTy) { 1079 // If we are using a wider index than needed for this platform, shrink 1080 // it to what we need. If narrower, sign-extend it to what we need. 1081 // This explicit cast can make subsequent optimizations more obvious. 1082 *I = Builder->CreateIntCast(*I, IntPtrTy, true); 1083 MadeChange = true; 1084 } 1085 } 1086 if (MadeChange) return &GEP; 1087 } 1088 1089 // Combine Indices - If the source pointer to this getelementptr instruction 1090 // is a getelementptr instruction, combine the indices of the two 1091 // getelementptr instructions into a single instruction. 1092 // 1093 if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) { 1094 if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src)) 1095 return 0; 1096 1097 // Note that if our source is a gep chain itself then we wait for that 1098 // chain to be resolved before we perform this transformation. This 1099 // avoids us creating a TON of code in some cases. 1100 if (GEPOperator *SrcGEP = 1101 dyn_cast<GEPOperator>(Src->getOperand(0))) 1102 if (SrcGEP->getNumOperands() == 2 && shouldMergeGEPs(*Src, *SrcGEP)) 1103 return 0; // Wait until our source is folded to completion. 1104 1105 SmallVector<Value*, 8> Indices; 1106 1107 // Find out whether the last index in the source GEP is a sequential idx. 1108 bool EndsWithSequential = false; 1109 for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src); 1110 I != E; ++I) 1111 EndsWithSequential = !(*I)->isStructTy(); 1112 1113 // Can we combine the two pointer arithmetics offsets? 1114 if (EndsWithSequential) { 1115 // Replace: gep (gep %P, long B), long A, ... 1116 // With: T = long A+B; gep %P, T, ... 1117 // 1118 Value *Sum; 1119 Value *SO1 = Src->getOperand(Src->getNumOperands()-1); 1120 Value *GO1 = GEP.getOperand(1); 1121 if (SO1 == Constant::getNullValue(SO1->getType())) { 1122 Sum = GO1; 1123 } else if (GO1 == Constant::getNullValue(GO1->getType())) { 1124 Sum = SO1; 1125 } else { 1126 // If they aren't the same type, then the input hasn't been processed 1127 // by the loop above yet (which canonicalizes sequential index types to 1128 // intptr_t). Just avoid transforming this until the input has been 1129 // normalized. 1130 if (SO1->getType() != GO1->getType()) 1131 return 0; 1132 Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum"); 1133 } 1134 1135 // Update the GEP in place if possible. 1136 if (Src->getNumOperands() == 2) { 1137 GEP.setOperand(0, Src->getOperand(0)); 1138 GEP.setOperand(1, Sum); 1139 return &GEP; 1140 } 1141 Indices.append(Src->op_begin()+1, Src->op_end()-1); 1142 Indices.push_back(Sum); 1143 Indices.append(GEP.op_begin()+2, GEP.op_end()); 1144 } else if (isa<Constant>(*GEP.idx_begin()) && 1145 cast<Constant>(*GEP.idx_begin())->isNullValue() && 1146 Src->getNumOperands() != 1) { 1147 // Otherwise we can do the fold if the first index of the GEP is a zero 1148 Indices.append(Src->op_begin()+1, Src->op_end()); 1149 Indices.append(GEP.idx_begin()+1, GEP.idx_end()); 1150 } 1151 1152 if (!Indices.empty()) 1153 return (GEP.isInBounds() && Src->isInBounds()) ? 1154 GetElementPtrInst::CreateInBounds(Src->getOperand(0), Indices, 1155 GEP.getName()) : 1156 GetElementPtrInst::Create(Src->getOperand(0), Indices, GEP.getName()); 1157 } 1158 1159 // Handle gep(bitcast x) and gep(gep x, 0, 0, 0). 1160 Value *StrippedPtr = PtrOp->stripPointerCasts(); 1161 PointerType *StrippedPtrTy = dyn_cast<PointerType>(StrippedPtr->getType()); 1162 1163 // We do not handle pointer-vector geps here. 1164 if (!StrippedPtrTy) 1165 return 0; 1166 1167 if (StrippedPtr != PtrOp && 1168 StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) { 1169 1170 bool HasZeroPointerIndex = false; 1171 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1))) 1172 HasZeroPointerIndex = C->isZero(); 1173 1174 // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... 1175 // into : GEP [10 x i8]* X, i32 0, ... 1176 // 1177 // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ... 1178 // into : GEP i8* X, ... 1179 // 1180 // This occurs when the program declares an array extern like "int X[];" 1181 if (HasZeroPointerIndex) { 1182 PointerType *CPTy = cast<PointerType>(PtrOp->getType()); 1183 if (ArrayType *CATy = 1184 dyn_cast<ArrayType>(CPTy->getElementType())) { 1185 // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ? 1186 if (CATy->getElementType() == StrippedPtrTy->getElementType()) { 1187 // -> GEP i8* X, ... 1188 SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end()); 1189 GetElementPtrInst *Res = 1190 GetElementPtrInst::Create(StrippedPtr, Idx, GEP.getName()); 1191 Res->setIsInBounds(GEP.isInBounds()); 1192 return Res; 1193 } 1194 1195 if (ArrayType *XATy = 1196 dyn_cast<ArrayType>(StrippedPtrTy->getElementType())){ 1197 // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ? 1198 if (CATy->getElementType() == XATy->getElementType()) { 1199 // -> GEP [10 x i8]* X, i32 0, ... 1200 // At this point, we know that the cast source type is a pointer 1201 // to an array of the same type as the destination pointer 1202 // array. Because the array type is never stepped over (there 1203 // is a leading zero) we can fold the cast into this GEP. 1204 GEP.setOperand(0, StrippedPtr); 1205 return &GEP; 1206 } 1207 } 1208 } 1209 } else if (GEP.getNumOperands() == 2) { 1210 // Transform things like: 1211 // %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V 1212 // into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast 1213 Type *SrcElTy = StrippedPtrTy->getElementType(); 1214 Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType(); 1215 if (TD && SrcElTy->isArrayTy() && 1216 TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()) == 1217 TD->getTypeAllocSize(ResElTy)) { 1218 Value *Idx[2]; 1219 Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); 1220 Idx[1] = GEP.getOperand(1); 1221 Value *NewGEP = GEP.isInBounds() ? 1222 Builder->CreateInBoundsGEP(StrippedPtr, Idx, GEP.getName()) : 1223 Builder->CreateGEP(StrippedPtr, Idx, GEP.getName()); 1224 // V and GEP are both pointer types --> BitCast 1225 return new BitCastInst(NewGEP, GEP.getType()); 1226 } 1227 1228 // Transform things like: 1229 // %V = mul i64 %N, 4 1230 // %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V 1231 // into: %t1 = getelementptr i32* %arr, i32 %N; bitcast 1232 if (TD && ResElTy->isSized() && SrcElTy->isSized()) { 1233 // Check that changing the type amounts to dividing the index by a scale 1234 // factor. 1235 uint64_t ResSize = TD->getTypeAllocSize(ResElTy); 1236 uint64_t SrcSize = TD->getTypeAllocSize(SrcElTy); 1237 if (ResSize && SrcSize % ResSize == 0) { 1238 Value *Idx = GEP.getOperand(1); 1239 unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); 1240 uint64_t Scale = SrcSize / ResSize; 1241 1242 // Earlier transforms ensure that the index has type IntPtrType, which 1243 // considerably simplifies the logic by eliminating implicit casts. 1244 assert(Idx->getType() == TD->getIntPtrType(GEP.getContext()) && 1245 "Index not cast to pointer width?"); 1246 1247 bool NSW; 1248 if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { 1249 // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. 1250 // If the multiplication NewIdx * Scale may overflow then the new 1251 // GEP may not be "inbounds". 1252 Value *NewGEP = GEP.isInBounds() && NSW ? 1253 Builder->CreateInBoundsGEP(StrippedPtr, NewIdx, GEP.getName()) : 1254 Builder->CreateGEP(StrippedPtr, NewIdx, GEP.getName()); 1255 // The NewGEP must be pointer typed, so must the old one -> BitCast 1256 return new BitCastInst(NewGEP, GEP.getType()); 1257 } 1258 } 1259 } 1260 1261 // Similarly, transform things like: 1262 // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp 1263 // (where tmp = 8*tmp2) into: 1264 // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast 1265 if (TD && ResElTy->isSized() && SrcElTy->isSized() && 1266 SrcElTy->isArrayTy()) { 1267 // Check that changing to the array element type amounts to dividing the 1268 // index by a scale factor. 1269 uint64_t ResSize = TD->getTypeAllocSize(ResElTy); 1270 uint64_t ArrayEltSize = 1271 TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()); 1272 if (ResSize && ArrayEltSize % ResSize == 0) { 1273 Value *Idx = GEP.getOperand(1); 1274 unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); 1275 uint64_t Scale = ArrayEltSize / ResSize; 1276 1277 // Earlier transforms ensure that the index has type IntPtrType, which 1278 // considerably simplifies the logic by eliminating implicit casts. 1279 assert(Idx->getType() == TD->getIntPtrType(GEP.getContext()) && 1280 "Index not cast to pointer width?"); 1281 1282 bool NSW; 1283 if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { 1284 // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. 1285 // If the multiplication NewIdx * Scale may overflow then the new 1286 // GEP may not be "inbounds". 1287 Value *Off[2]; 1288 Off[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); 1289 Off[1] = NewIdx; 1290 Value *NewGEP = GEP.isInBounds() && NSW ? 1291 Builder->CreateInBoundsGEP(StrippedPtr, Off, GEP.getName()) : 1292 Builder->CreateGEP(StrippedPtr, Off, GEP.getName()); 1293 // The NewGEP must be pointer typed, so must the old one -> BitCast 1294 return new BitCastInst(NewGEP, GEP.getType()); 1295 } 1296 } 1297 } 1298 } 1299 } 1300 1301 /// See if we can simplify: 1302 /// X = bitcast A* to B* 1303 /// Y = gep X, <...constant indices...> 1304 /// into a gep of the original struct. This is important for SROA and alias 1305 /// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged. 1306 if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) { 1307 APInt Offset(TD ? TD->getPointerSizeInBits() : 1, 0); 1308 if (TD && 1309 !isa<BitCastInst>(BCI->getOperand(0)) && 1310 GEP.accumulateConstantOffset(*TD, Offset) && 1311 StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) { 1312 1313 // If this GEP instruction doesn't move the pointer, just replace the GEP 1314 // with a bitcast of the real input to the dest type. 1315 if (!Offset) { 1316 // If the bitcast is of an allocation, and the allocation will be 1317 // converted to match the type of the cast, don't touch this. 1318 if (isa<AllocaInst>(BCI->getOperand(0)) || 1319 isAllocationFn(BCI->getOperand(0), TLI)) { 1320 // See if the bitcast simplifies, if so, don't nuke this GEP yet. 1321 if (Instruction *I = visitBitCast(*BCI)) { 1322 if (I != BCI) { 1323 I->takeName(BCI); 1324 BCI->getParent()->getInstList().insert(BCI, I); 1325 ReplaceInstUsesWith(*BCI, I); 1326 } 1327 return &GEP; 1328 } 1329 } 1330 return new BitCastInst(BCI->getOperand(0), GEP.getType()); 1331 } 1332 1333 // Otherwise, if the offset is non-zero, we need to find out if there is a 1334 // field at Offset in 'A's type. If so, we can pull the cast through the 1335 // GEP. 1336 SmallVector<Value*, 8> NewIndices; 1337 Type *InTy = 1338 cast<PointerType>(BCI->getOperand(0)->getType())->getElementType(); 1339 if (FindElementAtOffset(InTy, Offset.getSExtValue(), NewIndices)) { 1340 Value *NGEP = GEP.isInBounds() ? 1341 Builder->CreateInBoundsGEP(BCI->getOperand(0), NewIndices) : 1342 Builder->CreateGEP(BCI->getOperand(0), NewIndices); 1343 1344 if (NGEP->getType() == GEP.getType()) 1345 return ReplaceInstUsesWith(GEP, NGEP); 1346 NGEP->takeName(&GEP); 1347 return new BitCastInst(NGEP, GEP.getType()); 1348 } 1349 } 1350 } 1351 1352 return 0; 1353} 1354 1355 1356 1357static bool 1358isAllocSiteRemovable(Instruction *AI, SmallVectorImpl<WeakVH> &Users, 1359 const TargetLibraryInfo *TLI) { 1360 SmallVector<Instruction*, 4> Worklist; 1361 Worklist.push_back(AI); 1362 1363 do { 1364 Instruction *PI = Worklist.pop_back_val(); 1365 for (Value::use_iterator UI = PI->use_begin(), UE = PI->use_end(); UI != UE; 1366 ++UI) { 1367 Instruction *I = cast<Instruction>(*UI); 1368 switch (I->getOpcode()) { 1369 default: 1370 // Give up the moment we see something we can't handle. 1371 return false; 1372 1373 case Instruction::BitCast: 1374 case Instruction::GetElementPtr: 1375 Users.push_back(I); 1376 Worklist.push_back(I); 1377 continue; 1378 1379 case Instruction::ICmp: { 1380 ICmpInst *ICI = cast<ICmpInst>(I); 1381 // We can fold eq/ne comparisons with null to false/true, respectively. 1382 if (!ICI->isEquality() || !isa<ConstantPointerNull>(ICI->getOperand(1))) 1383 return false; 1384 Users.push_back(I); 1385 continue; 1386 } 1387 1388 case Instruction::Call: 1389 // Ignore no-op and store intrinsics. 1390 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 1391 switch (II->getIntrinsicID()) { 1392 default: 1393 return false; 1394 1395 case Intrinsic::memmove: 1396 case Intrinsic::memcpy: 1397 case Intrinsic::memset: { 1398 MemIntrinsic *MI = cast<MemIntrinsic>(II); 1399 if (MI->isVolatile() || MI->getRawDest() != PI) 1400 return false; 1401 } 1402 // fall through 1403 case Intrinsic::dbg_declare: 1404 case Intrinsic::dbg_value: 1405 case Intrinsic::invariant_start: 1406 case Intrinsic::invariant_end: 1407 case Intrinsic::lifetime_start: 1408 case Intrinsic::lifetime_end: 1409 case Intrinsic::objectsize: 1410 Users.push_back(I); 1411 continue; 1412 } 1413 } 1414 1415 if (isFreeCall(I, TLI)) { 1416 Users.push_back(I); 1417 continue; 1418 } 1419 return false; 1420 1421 case Instruction::Store: { 1422 StoreInst *SI = cast<StoreInst>(I); 1423 if (SI->isVolatile() || SI->getPointerOperand() != PI) 1424 return false; 1425 Users.push_back(I); 1426 continue; 1427 } 1428 } 1429 llvm_unreachable("missing a return?"); 1430 } 1431 } while (!Worklist.empty()); 1432 return true; 1433} 1434 1435Instruction *InstCombiner::visitAllocSite(Instruction &MI) { 1436 // If we have a malloc call which is only used in any amount of comparisons 1437 // to null and free calls, delete the calls and replace the comparisons with 1438 // true or false as appropriate. 1439 SmallVector<WeakVH, 64> Users; 1440 if (isAllocSiteRemovable(&MI, Users, TLI)) { 1441 for (unsigned i = 0, e = Users.size(); i != e; ++i) { 1442 Instruction *I = cast_or_null<Instruction>(&*Users[i]); 1443 if (!I) continue; 1444 1445 if (ICmpInst *C = dyn_cast<ICmpInst>(I)) { 1446 ReplaceInstUsesWith(*C, 1447 ConstantInt::get(Type::getInt1Ty(C->getContext()), 1448 C->isFalseWhenEqual())); 1449 } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) { 1450 ReplaceInstUsesWith(*I, UndefValue::get(I->getType())); 1451 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 1452 if (II->getIntrinsicID() == Intrinsic::objectsize) { 1453 ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1)); 1454 uint64_t DontKnow = CI->isZero() ? -1ULL : 0; 1455 ReplaceInstUsesWith(*I, ConstantInt::get(I->getType(), DontKnow)); 1456 } 1457 } 1458 EraseInstFromFunction(*I); 1459 } 1460 1461 if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) { 1462 // Replace invoke with a NOP intrinsic to maintain the original CFG 1463 Module *M = II->getParent()->getParent()->getParent(); 1464 Function *F = Intrinsic::getDeclaration(M, Intrinsic::donothing); 1465 InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(), 1466 ArrayRef<Value *>(), "", II->getParent()); 1467 } 1468 return EraseInstFromFunction(MI); 1469 } 1470 return 0; 1471} 1472 1473/// \brief Move the call to free before a NULL test. 1474/// 1475/// Check if this free is accessed after its argument has been test 1476/// against NULL (property 0). 1477/// If yes, it is legal to move this call in its predecessor block. 1478/// 1479/// The move is performed only if the block containing the call to free 1480/// will be removed, i.e.: 1481/// 1. it has only one predecessor P, and P has two successors 1482/// 2. it contains the call and an unconditional branch 1483/// 3. its successor is the same as its predecessor's successor 1484/// 1485/// The profitability is out-of concern here and this function should 1486/// be called only if the caller knows this transformation would be 1487/// profitable (e.g., for code size). 1488static Instruction * 1489tryToMoveFreeBeforeNullTest(CallInst &FI) { 1490 Value *Op = FI.getArgOperand(0); 1491 BasicBlock *FreeInstrBB = FI.getParent(); 1492 BasicBlock *PredBB = FreeInstrBB->getSinglePredecessor(); 1493 1494 // Validate part of constraint #1: Only one predecessor 1495 // FIXME: We can extend the number of predecessor, but in that case, we 1496 // would duplicate the call to free in each predecessor and it may 1497 // not be profitable even for code size. 1498 if (!PredBB) 1499 return 0; 1500 1501 // Validate constraint #2: Does this block contains only the call to 1502 // free and an unconditional branch? 1503 // FIXME: We could check if we can speculate everything in the 1504 // predecessor block 1505 if (FreeInstrBB->size() != 2) 1506 return 0; 1507 BasicBlock *SuccBB; 1508 if (!match(FreeInstrBB->getTerminator(), m_UnconditionalBr(SuccBB))) 1509 return 0; 1510 1511 // Validate the rest of constraint #1 by matching on the pred branch. 1512 TerminatorInst *TI = PredBB->getTerminator(); 1513 BasicBlock *TrueBB, *FalseBB; 1514 ICmpInst::Predicate Pred; 1515 if (!match(TI, m_Br(m_ICmp(Pred, m_Specific(Op), m_Zero()), TrueBB, FalseBB))) 1516 return 0; 1517 if (Pred != ICmpInst::ICMP_EQ && Pred != ICmpInst::ICMP_NE) 1518 return 0; 1519 1520 // Validate constraint #3: Ensure the null case just falls through. 1521 if (SuccBB != (Pred == ICmpInst::ICMP_EQ ? TrueBB : FalseBB)) 1522 return 0; 1523 assert(FreeInstrBB == (Pred == ICmpInst::ICMP_EQ ? FalseBB : TrueBB) && 1524 "Broken CFG: missing edge from predecessor to successor"); 1525 1526 FI.moveBefore(TI); 1527 return &FI; 1528} 1529 1530 1531Instruction *InstCombiner::visitFree(CallInst &FI) { 1532 Value *Op = FI.getArgOperand(0); 1533 1534 // free undef -> unreachable. 1535 if (isa<UndefValue>(Op)) { 1536 // Insert a new store to null because we cannot modify the CFG here. 1537 Builder->CreateStore(ConstantInt::getTrue(FI.getContext()), 1538 UndefValue::get(Type::getInt1PtrTy(FI.getContext()))); 1539 return EraseInstFromFunction(FI); 1540 } 1541 1542 // If we have 'free null' delete the instruction. This can happen in stl code 1543 // when lots of inlining happens. 1544 if (isa<ConstantPointerNull>(Op)) 1545 return EraseInstFromFunction(FI); 1546 1547 // If we optimize for code size, try to move the call to free before the null 1548 // test so that simplify cfg can remove the empty block and dead code 1549 // elimination the branch. I.e., helps to turn something like: 1550 // if (foo) free(foo); 1551 // into 1552 // free(foo); 1553 if (MinimizeSize) 1554 if (Instruction *I = tryToMoveFreeBeforeNullTest(FI)) 1555 return I; 1556 1557 return 0; 1558} 1559 1560 1561 1562Instruction *InstCombiner::visitBranchInst(BranchInst &BI) { 1563 // Change br (not X), label True, label False to: br X, label False, True 1564 Value *X = 0; 1565 BasicBlock *TrueDest; 1566 BasicBlock *FalseDest; 1567 if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) && 1568 !isa<Constant>(X)) { 1569 // Swap Destinations and condition... 1570 BI.setCondition(X); 1571 BI.swapSuccessors(); 1572 return &BI; 1573 } 1574 1575 // Cannonicalize fcmp_one -> fcmp_oeq 1576 FCmpInst::Predicate FPred; Value *Y; 1577 if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)), 1578 TrueDest, FalseDest)) && 1579 BI.getCondition()->hasOneUse()) 1580 if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE || 1581 FPred == FCmpInst::FCMP_OGE) { 1582 FCmpInst *Cond = cast<FCmpInst>(BI.getCondition()); 1583 Cond->setPredicate(FCmpInst::getInversePredicate(FPred)); 1584 1585 // Swap Destinations and condition. 1586 BI.swapSuccessors(); 1587 Worklist.Add(Cond); 1588 return &BI; 1589 } 1590 1591 // Cannonicalize icmp_ne -> icmp_eq 1592 ICmpInst::Predicate IPred; 1593 if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)), 1594 TrueDest, FalseDest)) && 1595 BI.getCondition()->hasOneUse()) 1596 if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE || 1597 IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE || 1598 IPred == ICmpInst::ICMP_SGE) { 1599 ICmpInst *Cond = cast<ICmpInst>(BI.getCondition()); 1600 Cond->setPredicate(ICmpInst::getInversePredicate(IPred)); 1601 // Swap Destinations and condition. 1602 BI.swapSuccessors(); 1603 Worklist.Add(Cond); 1604 return &BI; 1605 } 1606 1607 return 0; 1608} 1609 1610Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) { 1611 Value *Cond = SI.getCondition(); 1612 if (Instruction *I = dyn_cast<Instruction>(Cond)) { 1613 if (I->getOpcode() == Instruction::Add) 1614 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) { 1615 // change 'switch (X+4) case 1:' into 'switch (X) case -3' 1616 // Skip the first item since that's the default case. 1617 for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end(); 1618 i != e; ++i) { 1619 ConstantInt* CaseVal = i.getCaseValue(); 1620 Constant* NewCaseVal = ConstantExpr::getSub(cast<Constant>(CaseVal), 1621 AddRHS); 1622 assert(isa<ConstantInt>(NewCaseVal) && 1623 "Result of expression should be constant"); 1624 i.setValue(cast<ConstantInt>(NewCaseVal)); 1625 } 1626 SI.setCondition(I->getOperand(0)); 1627 Worklist.Add(I); 1628 return &SI; 1629 } 1630 } 1631 return 0; 1632} 1633 1634Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) { 1635 Value *Agg = EV.getAggregateOperand(); 1636 1637 if (!EV.hasIndices()) 1638 return ReplaceInstUsesWith(EV, Agg); 1639 1640 if (Constant *C = dyn_cast<Constant>(Agg)) { 1641 if (Constant *C2 = C->getAggregateElement(*EV.idx_begin())) { 1642 if (EV.getNumIndices() == 0) 1643 return ReplaceInstUsesWith(EV, C2); 1644 // Extract the remaining indices out of the constant indexed by the 1645 // first index 1646 return ExtractValueInst::Create(C2, EV.getIndices().slice(1)); 1647 } 1648 return 0; // Can't handle other constants 1649 } 1650 1651 if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) { 1652 // We're extracting from an insertvalue instruction, compare the indices 1653 const unsigned *exti, *exte, *insi, *inse; 1654 for (exti = EV.idx_begin(), insi = IV->idx_begin(), 1655 exte = EV.idx_end(), inse = IV->idx_end(); 1656 exti != exte && insi != inse; 1657 ++exti, ++insi) { 1658 if (*insi != *exti) 1659 // The insert and extract both reference distinctly different elements. 1660 // This means the extract is not influenced by the insert, and we can 1661 // replace the aggregate operand of the extract with the aggregate 1662 // operand of the insert. i.e., replace 1663 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 1664 // %E = extractvalue { i32, { i32 } } %I, 0 1665 // with 1666 // %E = extractvalue { i32, { i32 } } %A, 0 1667 return ExtractValueInst::Create(IV->getAggregateOperand(), 1668 EV.getIndices()); 1669 } 1670 if (exti == exte && insi == inse) 1671 // Both iterators are at the end: Index lists are identical. Replace 1672 // %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 1673 // %C = extractvalue { i32, { i32 } } %B, 1, 0 1674 // with "i32 42" 1675 return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand()); 1676 if (exti == exte) { 1677 // The extract list is a prefix of the insert list. i.e. replace 1678 // %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 1679 // %E = extractvalue { i32, { i32 } } %I, 1 1680 // with 1681 // %X = extractvalue { i32, { i32 } } %A, 1 1682 // %E = insertvalue { i32 } %X, i32 42, 0 1683 // by switching the order of the insert and extract (though the 1684 // insertvalue should be left in, since it may have other uses). 1685 Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(), 1686 EV.getIndices()); 1687 return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(), 1688 makeArrayRef(insi, inse)); 1689 } 1690 if (insi == inse) 1691 // The insert list is a prefix of the extract list 1692 // We can simply remove the common indices from the extract and make it 1693 // operate on the inserted value instead of the insertvalue result. 1694 // i.e., replace 1695 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 1696 // %E = extractvalue { i32, { i32 } } %I, 1, 0 1697 // with 1698 // %E extractvalue { i32 } { i32 42 }, 0 1699 return ExtractValueInst::Create(IV->getInsertedValueOperand(), 1700 makeArrayRef(exti, exte)); 1701 } 1702 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) { 1703 // We're extracting from an intrinsic, see if we're the only user, which 1704 // allows us to simplify multiple result intrinsics to simpler things that 1705 // just get one value. 1706 if (II->hasOneUse()) { 1707 // Check if we're grabbing the overflow bit or the result of a 'with 1708 // overflow' intrinsic. If it's the latter we can remove the intrinsic 1709 // and replace it with a traditional binary instruction. 1710 switch (II->getIntrinsicID()) { 1711 case Intrinsic::uadd_with_overflow: 1712 case Intrinsic::sadd_with_overflow: 1713 if (*EV.idx_begin() == 0) { // Normal result. 1714 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1715 ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); 1716 EraseInstFromFunction(*II); 1717 return BinaryOperator::CreateAdd(LHS, RHS); 1718 } 1719 1720 // If the normal result of the add is dead, and the RHS is a constant, 1721 // we can transform this into a range comparison. 1722 // overflow = uadd a, -4 --> overflow = icmp ugt a, 3 1723 if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow) 1724 if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1))) 1725 return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0), 1726 ConstantExpr::getNot(CI)); 1727 break; 1728 case Intrinsic::usub_with_overflow: 1729 case Intrinsic::ssub_with_overflow: 1730 if (*EV.idx_begin() == 0) { // Normal result. 1731 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1732 ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); 1733 EraseInstFromFunction(*II); 1734 return BinaryOperator::CreateSub(LHS, RHS); 1735 } 1736 break; 1737 case Intrinsic::umul_with_overflow: 1738 case Intrinsic::smul_with_overflow: 1739 if (*EV.idx_begin() == 0) { // Normal result. 1740 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); 1741 ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); 1742 EraseInstFromFunction(*II); 1743 return BinaryOperator::CreateMul(LHS, RHS); 1744 } 1745 break; 1746 default: 1747 break; 1748 } 1749 } 1750 } 1751 if (LoadInst *L = dyn_cast<LoadInst>(Agg)) 1752 // If the (non-volatile) load only has one use, we can rewrite this to a 1753 // load from a GEP. This reduces the size of the load. 1754 // FIXME: If a load is used only by extractvalue instructions then this 1755 // could be done regardless of having multiple uses. 1756 if (L->isSimple() && L->hasOneUse()) { 1757 // extractvalue has integer indices, getelementptr has Value*s. Convert. 1758 SmallVector<Value*, 4> Indices; 1759 // Prefix an i32 0 since we need the first element. 1760 Indices.push_back(Builder->getInt32(0)); 1761 for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end(); 1762 I != E; ++I) 1763 Indices.push_back(Builder->getInt32(*I)); 1764 1765 // We need to insert these at the location of the old load, not at that of 1766 // the extractvalue. 1767 Builder->SetInsertPoint(L->getParent(), L); 1768 Value *GEP = Builder->CreateInBoundsGEP(L->getPointerOperand(), Indices); 1769 // Returning the load directly will cause the main loop to insert it in 1770 // the wrong spot, so use ReplaceInstUsesWith(). 1771 return ReplaceInstUsesWith(EV, Builder->CreateLoad(GEP)); 1772 } 1773 // We could simplify extracts from other values. Note that nested extracts may 1774 // already be simplified implicitly by the above: extract (extract (insert) ) 1775 // will be translated into extract ( insert ( extract ) ) first and then just 1776 // the value inserted, if appropriate. Similarly for extracts from single-use 1777 // loads: extract (extract (load)) will be translated to extract (load (gep)) 1778 // and if again single-use then via load (gep (gep)) to load (gep). 1779 // However, double extracts from e.g. function arguments or return values 1780 // aren't handled yet. 1781 return 0; 1782} 1783 1784enum Personality_Type { 1785 Unknown_Personality, 1786 GNU_Ada_Personality, 1787 GNU_CXX_Personality, 1788 GNU_ObjC_Personality 1789}; 1790 1791/// RecognizePersonality - See if the given exception handling personality 1792/// function is one that we understand. If so, return a description of it; 1793/// otherwise return Unknown_Personality. 1794static Personality_Type RecognizePersonality(Value *Pers) { 1795 Function *F = dyn_cast<Function>(Pers->stripPointerCasts()); 1796 if (!F) 1797 return Unknown_Personality; 1798 return StringSwitch<Personality_Type>(F->getName()) 1799 .Case("__gnat_eh_personality", GNU_Ada_Personality) 1800 .Case("__gxx_personality_v0", GNU_CXX_Personality) 1801 .Case("__objc_personality_v0", GNU_ObjC_Personality) 1802 .Default(Unknown_Personality); 1803} 1804 1805/// isCatchAll - Return 'true' if the given typeinfo will match anything. 1806static bool isCatchAll(Personality_Type Personality, Constant *TypeInfo) { 1807 switch (Personality) { 1808 case Unknown_Personality: 1809 return false; 1810 case GNU_Ada_Personality: 1811 // While __gnat_all_others_value will match any Ada exception, it doesn't 1812 // match foreign exceptions (or didn't, before gcc-4.7). 1813 return false; 1814 case GNU_CXX_Personality: 1815 case GNU_ObjC_Personality: 1816 return TypeInfo->isNullValue(); 1817 } 1818 llvm_unreachable("Unknown personality!"); 1819} 1820 1821static bool shorter_filter(const Value *LHS, const Value *RHS) { 1822 return 1823 cast<ArrayType>(LHS->getType())->getNumElements() 1824 < 1825 cast<ArrayType>(RHS->getType())->getNumElements(); 1826} 1827 1828Instruction *InstCombiner::visitLandingPadInst(LandingPadInst &LI) { 1829 // The logic here should be correct for any real-world personality function. 1830 // However if that turns out not to be true, the offending logic can always 1831 // be conditioned on the personality function, like the catch-all logic is. 1832 Personality_Type Personality = RecognizePersonality(LI.getPersonalityFn()); 1833 1834 // Simplify the list of clauses, eg by removing repeated catch clauses 1835 // (these are often created by inlining). 1836 bool MakeNewInstruction = false; // If true, recreate using the following: 1837 SmallVector<Value *, 16> NewClauses; // - Clauses for the new instruction; 1838 bool CleanupFlag = LI.isCleanup(); // - The new instruction is a cleanup. 1839 1840 SmallPtrSet<Value *, 16> AlreadyCaught; // Typeinfos known caught already. 1841 for (unsigned i = 0, e = LI.getNumClauses(); i != e; ++i) { 1842 bool isLastClause = i + 1 == e; 1843 if (LI.isCatch(i)) { 1844 // A catch clause. 1845 Value *CatchClause = LI.getClause(i); 1846 Constant *TypeInfo = cast<Constant>(CatchClause->stripPointerCasts()); 1847 1848 // If we already saw this clause, there is no point in having a second 1849 // copy of it. 1850 if (AlreadyCaught.insert(TypeInfo)) { 1851 // This catch clause was not already seen. 1852 NewClauses.push_back(CatchClause); 1853 } else { 1854 // Repeated catch clause - drop the redundant copy. 1855 MakeNewInstruction = true; 1856 } 1857 1858 // If this is a catch-all then there is no point in keeping any following 1859 // clauses or marking the landingpad as having a cleanup. 1860 if (isCatchAll(Personality, TypeInfo)) { 1861 if (!isLastClause) 1862 MakeNewInstruction = true; 1863 CleanupFlag = false; 1864 break; 1865 } 1866 } else { 1867 // A filter clause. If any of the filter elements were already caught 1868 // then they can be dropped from the filter. It is tempting to try to 1869 // exploit the filter further by saying that any typeinfo that does not 1870 // occur in the filter can't be caught later (and thus can be dropped). 1871 // However this would be wrong, since typeinfos can match without being 1872 // equal (for example if one represents a C++ class, and the other some 1873 // class derived from it). 1874 assert(LI.isFilter(i) && "Unsupported landingpad clause!"); 1875 Value *FilterClause = LI.getClause(i); 1876 ArrayType *FilterType = cast<ArrayType>(FilterClause->getType()); 1877 unsigned NumTypeInfos = FilterType->getNumElements(); 1878 1879 // An empty filter catches everything, so there is no point in keeping any 1880 // following clauses or marking the landingpad as having a cleanup. By 1881 // dealing with this case here the following code is made a bit simpler. 1882 if (!NumTypeInfos) { 1883 NewClauses.push_back(FilterClause); 1884 if (!isLastClause) 1885 MakeNewInstruction = true; 1886 CleanupFlag = false; 1887 break; 1888 } 1889 1890 bool MakeNewFilter = false; // If true, make a new filter. 1891 SmallVector<Constant *, 16> NewFilterElts; // New elements. 1892 if (isa<ConstantAggregateZero>(FilterClause)) { 1893 // Not an empty filter - it contains at least one null typeinfo. 1894 assert(NumTypeInfos > 0 && "Should have handled empty filter already!"); 1895 Constant *TypeInfo = 1896 Constant::getNullValue(FilterType->getElementType()); 1897 // If this typeinfo is a catch-all then the filter can never match. 1898 if (isCatchAll(Personality, TypeInfo)) { 1899 // Throw the filter away. 1900 MakeNewInstruction = true; 1901 continue; 1902 } 1903 1904 // There is no point in having multiple copies of this typeinfo, so 1905 // discard all but the first copy if there is more than one. 1906 NewFilterElts.push_back(TypeInfo); 1907 if (NumTypeInfos > 1) 1908 MakeNewFilter = true; 1909 } else { 1910 ConstantArray *Filter = cast<ConstantArray>(FilterClause); 1911 SmallPtrSet<Value *, 16> SeenInFilter; // For uniquing the elements. 1912 NewFilterElts.reserve(NumTypeInfos); 1913 1914 // Remove any filter elements that were already caught or that already 1915 // occurred in the filter. While there, see if any of the elements are 1916 // catch-alls. If so, the filter can be discarded. 1917 bool SawCatchAll = false; 1918 for (unsigned j = 0; j != NumTypeInfos; ++j) { 1919 Value *Elt = Filter->getOperand(j); 1920 Constant *TypeInfo = cast<Constant>(Elt->stripPointerCasts()); 1921 if (isCatchAll(Personality, TypeInfo)) { 1922 // This element is a catch-all. Bail out, noting this fact. 1923 SawCatchAll = true; 1924 break; 1925 } 1926 if (AlreadyCaught.count(TypeInfo)) 1927 // Already caught by an earlier clause, so having it in the filter 1928 // is pointless. 1929 continue; 1930 // There is no point in having multiple copies of the same typeinfo in 1931 // a filter, so only add it if we didn't already. 1932 if (SeenInFilter.insert(TypeInfo)) 1933 NewFilterElts.push_back(cast<Constant>(Elt)); 1934 } 1935 // A filter containing a catch-all cannot match anything by definition. 1936 if (SawCatchAll) { 1937 // Throw the filter away. 1938 MakeNewInstruction = true; 1939 continue; 1940 } 1941 1942 // If we dropped something from the filter, make a new one. 1943 if (NewFilterElts.size() < NumTypeInfos) 1944 MakeNewFilter = true; 1945 } 1946 if (MakeNewFilter) { 1947 FilterType = ArrayType::get(FilterType->getElementType(), 1948 NewFilterElts.size()); 1949 FilterClause = ConstantArray::get(FilterType, NewFilterElts); 1950 MakeNewInstruction = true; 1951 } 1952 1953 NewClauses.push_back(FilterClause); 1954 1955 // If the new filter is empty then it will catch everything so there is 1956 // no point in keeping any following clauses or marking the landingpad 1957 // as having a cleanup. The case of the original filter being empty was 1958 // already handled above. 1959 if (MakeNewFilter && !NewFilterElts.size()) { 1960 assert(MakeNewInstruction && "New filter but not a new instruction!"); 1961 CleanupFlag = false; 1962 break; 1963 } 1964 } 1965 } 1966 1967 // If several filters occur in a row then reorder them so that the shortest 1968 // filters come first (those with the smallest number of elements). This is 1969 // advantageous because shorter filters are more likely to match, speeding up 1970 // unwinding, but mostly because it increases the effectiveness of the other 1971 // filter optimizations below. 1972 for (unsigned i = 0, e = NewClauses.size(); i + 1 < e; ) { 1973 unsigned j; 1974 // Find the maximal 'j' s.t. the range [i, j) consists entirely of filters. 1975 for (j = i; j != e; ++j) 1976 if (!isa<ArrayType>(NewClauses[j]->getType())) 1977 break; 1978 1979 // Check whether the filters are already sorted by length. We need to know 1980 // if sorting them is actually going to do anything so that we only make a 1981 // new landingpad instruction if it does. 1982 for (unsigned k = i; k + 1 < j; ++k) 1983 if (shorter_filter(NewClauses[k+1], NewClauses[k])) { 1984 // Not sorted, so sort the filters now. Doing an unstable sort would be 1985 // correct too but reordering filters pointlessly might confuse users. 1986 std::stable_sort(NewClauses.begin() + i, NewClauses.begin() + j, 1987 shorter_filter); 1988 MakeNewInstruction = true; 1989 break; 1990 } 1991 1992 // Look for the next batch of filters. 1993 i = j + 1; 1994 } 1995 1996 // If typeinfos matched if and only if equal, then the elements of a filter L 1997 // that occurs later than a filter F could be replaced by the intersection of 1998 // the elements of F and L. In reality two typeinfos can match without being 1999 // equal (for example if one represents a C++ class, and the other some class 2000 // derived from it) so it would be wrong to perform this transform in general. 2001 // However the transform is correct and useful if F is a subset of L. In that 2002 // case L can be replaced by F, and thus removed altogether since repeating a 2003 // filter is pointless. So here we look at all pairs of filters F and L where 2004 // L follows F in the list of clauses, and remove L if every element of F is 2005 // an element of L. This can occur when inlining C++ functions with exception 2006 // specifications. 2007 for (unsigned i = 0; i + 1 < NewClauses.size(); ++i) { 2008 // Examine each filter in turn. 2009 Value *Filter = NewClauses[i]; 2010 ArrayType *FTy = dyn_cast<ArrayType>(Filter->getType()); 2011 if (!FTy) 2012 // Not a filter - skip it. 2013 continue; 2014 unsigned FElts = FTy->getNumElements(); 2015 // Examine each filter following this one. Doing this backwards means that 2016 // we don't have to worry about filters disappearing under us when removed. 2017 for (unsigned j = NewClauses.size() - 1; j != i; --j) { 2018 Value *LFilter = NewClauses[j]; 2019 ArrayType *LTy = dyn_cast<ArrayType>(LFilter->getType()); 2020 if (!LTy) 2021 // Not a filter - skip it. 2022 continue; 2023 // If Filter is a subset of LFilter, i.e. every element of Filter is also 2024 // an element of LFilter, then discard LFilter. 2025 SmallVector<Value *, 16>::iterator J = NewClauses.begin() + j; 2026 // If Filter is empty then it is a subset of LFilter. 2027 if (!FElts) { 2028 // Discard LFilter. 2029 NewClauses.erase(J); 2030 MakeNewInstruction = true; 2031 // Move on to the next filter. 2032 continue; 2033 } 2034 unsigned LElts = LTy->getNumElements(); 2035 // If Filter is longer than LFilter then it cannot be a subset of it. 2036 if (FElts > LElts) 2037 // Move on to the next filter. 2038 continue; 2039 // At this point we know that LFilter has at least one element. 2040 if (isa<ConstantAggregateZero>(LFilter)) { // LFilter only contains zeros. 2041 // Filter is a subset of LFilter iff Filter contains only zeros (as we 2042 // already know that Filter is not longer than LFilter). 2043 if (isa<ConstantAggregateZero>(Filter)) { 2044 assert(FElts <= LElts && "Should have handled this case earlier!"); 2045 // Discard LFilter. 2046 NewClauses.erase(J); 2047 MakeNewInstruction = true; 2048 } 2049 // Move on to the next filter. 2050 continue; 2051 } 2052 ConstantArray *LArray = cast<ConstantArray>(LFilter); 2053 if (isa<ConstantAggregateZero>(Filter)) { // Filter only contains zeros. 2054 // Since Filter is non-empty and contains only zeros, it is a subset of 2055 // LFilter iff LFilter contains a zero. 2056 assert(FElts > 0 && "Should have eliminated the empty filter earlier!"); 2057 for (unsigned l = 0; l != LElts; ++l) 2058 if (LArray->getOperand(l)->isNullValue()) { 2059 // LFilter contains a zero - discard it. 2060 NewClauses.erase(J); 2061 MakeNewInstruction = true; 2062 break; 2063 } 2064 // Move on to the next filter. 2065 continue; 2066 } 2067 // At this point we know that both filters are ConstantArrays. Loop over 2068 // operands to see whether every element of Filter is also an element of 2069 // LFilter. Since filters tend to be short this is probably faster than 2070 // using a method that scales nicely. 2071 ConstantArray *FArray = cast<ConstantArray>(Filter); 2072 bool AllFound = true; 2073 for (unsigned f = 0; f != FElts; ++f) { 2074 Value *FTypeInfo = FArray->getOperand(f)->stripPointerCasts(); 2075 AllFound = false; 2076 for (unsigned l = 0; l != LElts; ++l) { 2077 Value *LTypeInfo = LArray->getOperand(l)->stripPointerCasts(); 2078 if (LTypeInfo == FTypeInfo) { 2079 AllFound = true; 2080 break; 2081 } 2082 } 2083 if (!AllFound) 2084 break; 2085 } 2086 if (AllFound) { 2087 // Discard LFilter. 2088 NewClauses.erase(J); 2089 MakeNewInstruction = true; 2090 } 2091 // Move on to the next filter. 2092 } 2093 } 2094 2095 // If we changed any of the clauses, replace the old landingpad instruction 2096 // with a new one. 2097 if (MakeNewInstruction) { 2098 LandingPadInst *NLI = LandingPadInst::Create(LI.getType(), 2099 LI.getPersonalityFn(), 2100 NewClauses.size()); 2101 for (unsigned i = 0, e = NewClauses.size(); i != e; ++i) 2102 NLI->addClause(NewClauses[i]); 2103 // A landing pad with no clauses must have the cleanup flag set. It is 2104 // theoretically possible, though highly unlikely, that we eliminated all 2105 // clauses. If so, force the cleanup flag to true. 2106 if (NewClauses.empty()) 2107 CleanupFlag = true; 2108 NLI->setCleanup(CleanupFlag); 2109 return NLI; 2110 } 2111 2112 // Even if none of the clauses changed, we may nonetheless have understood 2113 // that the cleanup flag is pointless. Clear it if so. 2114 if (LI.isCleanup() != CleanupFlag) { 2115 assert(!CleanupFlag && "Adding a cleanup, not removing one?!"); 2116 LI.setCleanup(CleanupFlag); 2117 return &LI; 2118 } 2119 2120 return 0; 2121} 2122 2123 2124 2125 2126/// TryToSinkInstruction - Try to move the specified instruction from its 2127/// current block into the beginning of DestBlock, which can only happen if it's 2128/// safe to move the instruction past all of the instructions between it and the 2129/// end of its block. 2130static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) { 2131 assert(I->hasOneUse() && "Invariants didn't hold!"); 2132 2133 // Cannot move control-flow-involving, volatile loads, vaarg, etc. 2134 if (isa<PHINode>(I) || isa<LandingPadInst>(I) || I->mayHaveSideEffects() || 2135 isa<TerminatorInst>(I)) 2136 return false; 2137 2138 // Do not sink alloca instructions out of the entry block. 2139 if (isa<AllocaInst>(I) && I->getParent() == 2140 &DestBlock->getParent()->getEntryBlock()) 2141 return false; 2142 2143 // We can only sink load instructions if there is nothing between the load and 2144 // the end of block that could change the value. 2145 if (I->mayReadFromMemory()) { 2146 for (BasicBlock::iterator Scan = I, E = I->getParent()->end(); 2147 Scan != E; ++Scan) 2148 if (Scan->mayWriteToMemory()) 2149 return false; 2150 } 2151 2152 BasicBlock::iterator InsertPos = DestBlock->getFirstInsertionPt(); 2153 I->moveBefore(InsertPos); 2154 ++NumSunkInst; 2155 return true; 2156} 2157 2158 2159/// AddReachableCodeToWorklist - Walk the function in depth-first order, adding 2160/// all reachable code to the worklist. 2161/// 2162/// This has a couple of tricks to make the code faster and more powerful. In 2163/// particular, we constant fold and DCE instructions as we go, to avoid adding 2164/// them to the worklist (this significantly speeds up instcombine on code where 2165/// many instructions are dead or constant). Additionally, if we find a branch 2166/// whose condition is a known constant, we only visit the reachable successors. 2167/// 2168static bool AddReachableCodeToWorklist(BasicBlock *BB, 2169 SmallPtrSet<BasicBlock*, 64> &Visited, 2170 InstCombiner &IC, 2171 const DataLayout *TD, 2172 const TargetLibraryInfo *TLI) { 2173 bool MadeIRChange = false; 2174 SmallVector<BasicBlock*, 256> Worklist; 2175 Worklist.push_back(BB); 2176 2177 SmallVector<Instruction*, 128> InstrsForInstCombineWorklist; 2178 DenseMap<ConstantExpr*, Constant*> FoldedConstants; 2179 2180 do { 2181 BB = Worklist.pop_back_val(); 2182 2183 // We have now visited this block! If we've already been here, ignore it. 2184 if (!Visited.insert(BB)) continue; 2185 2186 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { 2187 Instruction *Inst = BBI++; 2188 2189 // DCE instruction if trivially dead. 2190 if (isInstructionTriviallyDead(Inst, TLI)) { 2191 ++NumDeadInst; 2192 DEBUG(errs() << "IC: DCE: " << *Inst << '\n'); 2193 Inst->eraseFromParent(); 2194 continue; 2195 } 2196 2197 // ConstantProp instruction if trivially constant. 2198 if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0))) 2199 if (Constant *C = ConstantFoldInstruction(Inst, TD, TLI)) { 2200 DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " 2201 << *Inst << '\n'); 2202 Inst->replaceAllUsesWith(C); 2203 ++NumConstProp; 2204 Inst->eraseFromParent(); 2205 continue; 2206 } 2207 2208 if (TD) { 2209 // See if we can constant fold its operands. 2210 for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end(); 2211 i != e; ++i) { 2212 ConstantExpr *CE = dyn_cast<ConstantExpr>(i); 2213 if (CE == 0) continue; 2214 2215 Constant*& FoldRes = FoldedConstants[CE]; 2216 if (!FoldRes) 2217 FoldRes = ConstantFoldConstantExpression(CE, TD, TLI); 2218 if (!FoldRes) 2219 FoldRes = CE; 2220 2221 if (FoldRes != CE) { 2222 *i = FoldRes; 2223 MadeIRChange = true; 2224 } 2225 } 2226 } 2227 2228 InstrsForInstCombineWorklist.push_back(Inst); 2229 } 2230 2231 // Recursively visit successors. If this is a branch or switch on a 2232 // constant, only visit the reachable successor. 2233 TerminatorInst *TI = BB->getTerminator(); 2234 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { 2235 if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) { 2236 bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue(); 2237 BasicBlock *ReachableBB = BI->getSuccessor(!CondVal); 2238 Worklist.push_back(ReachableBB); 2239 continue; 2240 } 2241 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { 2242 if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) { 2243 // See if this is an explicit destination. 2244 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); 2245 i != e; ++i) 2246 if (i.getCaseValue() == Cond) { 2247 BasicBlock *ReachableBB = i.getCaseSuccessor(); 2248 Worklist.push_back(ReachableBB); 2249 continue; 2250 } 2251 2252 // Otherwise it is the default destination. 2253 Worklist.push_back(SI->getDefaultDest()); 2254 continue; 2255 } 2256 } 2257 2258 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 2259 Worklist.push_back(TI->getSuccessor(i)); 2260 } while (!Worklist.empty()); 2261 2262 // Once we've found all of the instructions to add to instcombine's worklist, 2263 // add them in reverse order. This way instcombine will visit from the top 2264 // of the function down. This jives well with the way that it adds all uses 2265 // of instructions to the worklist after doing a transformation, thus avoiding 2266 // some N^2 behavior in pathological cases. 2267 IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0], 2268 InstrsForInstCombineWorklist.size()); 2269 2270 return MadeIRChange; 2271} 2272 2273bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) { 2274 MadeIRChange = false; 2275 2276 DEBUG(errs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on " 2277 << F.getName() << "\n"); 2278 2279 { 2280 // Do a depth-first traversal of the function, populate the worklist with 2281 // the reachable instructions. Ignore blocks that are not reachable. Keep 2282 // track of which blocks we visit. 2283 SmallPtrSet<BasicBlock*, 64> Visited; 2284 MadeIRChange |= AddReachableCodeToWorklist(F.begin(), Visited, *this, TD, 2285 TLI); 2286 2287 // Do a quick scan over the function. If we find any blocks that are 2288 // unreachable, remove any instructions inside of them. This prevents 2289 // the instcombine code from having to deal with some bad special cases. 2290 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { 2291 if (Visited.count(BB)) continue; 2292 2293 // Delete the instructions backwards, as it has a reduced likelihood of 2294 // having to update as many def-use and use-def chains. 2295 Instruction *EndInst = BB->getTerminator(); // Last not to be deleted. 2296 while (EndInst != BB->begin()) { 2297 // Delete the next to last instruction. 2298 BasicBlock::iterator I = EndInst; 2299 Instruction *Inst = --I; 2300 if (!Inst->use_empty()) 2301 Inst->replaceAllUsesWith(UndefValue::get(Inst->getType())); 2302 if (isa<LandingPadInst>(Inst)) { 2303 EndInst = Inst; 2304 continue; 2305 } 2306 if (!isa<DbgInfoIntrinsic>(Inst)) { 2307 ++NumDeadInst; 2308 MadeIRChange = true; 2309 } 2310 Inst->eraseFromParent(); 2311 } 2312 } 2313 } 2314 2315 while (!Worklist.isEmpty()) { 2316 Instruction *I = Worklist.RemoveOne(); 2317 if (I == 0) continue; // skip null values. 2318 2319 // Check to see if we can DCE the instruction. 2320 if (isInstructionTriviallyDead(I, TLI)) { 2321 DEBUG(errs() << "IC: DCE: " << *I << '\n'); 2322 EraseInstFromFunction(*I); 2323 ++NumDeadInst; 2324 MadeIRChange = true; 2325 continue; 2326 } 2327 2328 // Instruction isn't dead, see if we can constant propagate it. 2329 if (!I->use_empty() && isa<Constant>(I->getOperand(0))) 2330 if (Constant *C = ConstantFoldInstruction(I, TD, TLI)) { 2331 DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n'); 2332 2333 // Add operands to the worklist. 2334 ReplaceInstUsesWith(*I, C); 2335 ++NumConstProp; 2336 EraseInstFromFunction(*I); 2337 MadeIRChange = true; 2338 continue; 2339 } 2340 2341 // See if we can trivially sink this instruction to a successor basic block. 2342 if (I->hasOneUse()) { 2343 BasicBlock *BB = I->getParent(); 2344 Instruction *UserInst = cast<Instruction>(I->use_back()); 2345 BasicBlock *UserParent; 2346 2347 // Get the block the use occurs in. 2348 if (PHINode *PN = dyn_cast<PHINode>(UserInst)) 2349 UserParent = PN->getIncomingBlock(I->use_begin().getUse()); 2350 else 2351 UserParent = UserInst->getParent(); 2352 2353 if (UserParent != BB) { 2354 bool UserIsSuccessor = false; 2355 // See if the user is one of our successors. 2356 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) 2357 if (*SI == UserParent) { 2358 UserIsSuccessor = true; 2359 break; 2360 } 2361 2362 // If the user is one of our immediate successors, and if that successor 2363 // only has us as a predecessors (we'd have to split the critical edge 2364 // otherwise), we can keep going. 2365 if (UserIsSuccessor && UserParent->getSinglePredecessor()) 2366 // Okay, the CFG is simple enough, try to sink this instruction. 2367 MadeIRChange |= TryToSinkInstruction(I, UserParent); 2368 } 2369 } 2370 2371 // Now that we have an instruction, try combining it to simplify it. 2372 Builder->SetInsertPoint(I->getParent(), I); 2373 Builder->SetCurrentDebugLocation(I->getDebugLoc()); 2374 2375#ifndef NDEBUG 2376 std::string OrigI; 2377#endif 2378 DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str();); 2379 DEBUG(errs() << "IC: Visiting: " << OrigI << '\n'); 2380 2381 if (Instruction *Result = visit(*I)) { 2382 ++NumCombined; 2383 // Should we replace the old instruction with a new one? 2384 if (Result != I) { 2385 DEBUG(errs() << "IC: Old = " << *I << '\n' 2386 << " New = " << *Result << '\n'); 2387 2388 if (!I->getDebugLoc().isUnknown()) 2389 Result->setDebugLoc(I->getDebugLoc()); 2390 // Everything uses the new instruction now. 2391 I->replaceAllUsesWith(Result); 2392 2393 // Move the name to the new instruction first. 2394 Result->takeName(I); 2395 2396 // Push the new instruction and any users onto the worklist. 2397 Worklist.Add(Result); 2398 Worklist.AddUsersToWorkList(*Result); 2399 2400 // Insert the new instruction into the basic block... 2401 BasicBlock *InstParent = I->getParent(); 2402 BasicBlock::iterator InsertPos = I; 2403 2404 // If we replace a PHI with something that isn't a PHI, fix up the 2405 // insertion point. 2406 if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos)) 2407 InsertPos = InstParent->getFirstInsertionPt(); 2408 2409 InstParent->getInstList().insert(InsertPos, Result); 2410 2411 EraseInstFromFunction(*I); 2412 } else { 2413#ifndef NDEBUG 2414 DEBUG(errs() << "IC: Mod = " << OrigI << '\n' 2415 << " New = " << *I << '\n'); 2416#endif 2417 2418 // If the instruction was modified, it's possible that it is now dead. 2419 // if so, remove it. 2420 if (isInstructionTriviallyDead(I, TLI)) { 2421 EraseInstFromFunction(*I); 2422 } else { 2423 Worklist.Add(I); 2424 Worklist.AddUsersToWorkList(*I); 2425 } 2426 } 2427 MadeIRChange = true; 2428 } 2429 } 2430 2431 Worklist.Zap(); 2432 return MadeIRChange; 2433} 2434 2435namespace { 2436class InstCombinerLibCallSimplifier : public LibCallSimplifier { 2437 InstCombiner *IC; 2438public: 2439 InstCombinerLibCallSimplifier(const DataLayout *TD, 2440 const TargetLibraryInfo *TLI, 2441 InstCombiner *IC) 2442 : LibCallSimplifier(TD, TLI, UnsafeFPShrink) { 2443 this->IC = IC; 2444 } 2445 2446 /// replaceAllUsesWith - override so that instruction replacement 2447 /// can be defined in terms of the instruction combiner framework. 2448 virtual void replaceAllUsesWith(Instruction *I, Value *With) const { 2449 IC->ReplaceInstUsesWith(*I, With); 2450 } 2451}; 2452} 2453 2454bool InstCombiner::runOnFunction(Function &F) { 2455 TD = getAnalysisIfAvailable<DataLayout>(); 2456 TLI = &getAnalysis<TargetLibraryInfo>(); 2457 // Minimizing size? 2458 MinimizeSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex, 2459 Attribute::MinSize); 2460 2461 /// Builder - This is an IRBuilder that automatically inserts new 2462 /// instructions into the worklist when they are created. 2463 IRBuilder<true, TargetFolder, InstCombineIRInserter> 2464 TheBuilder(F.getContext(), TargetFolder(TD), 2465 InstCombineIRInserter(Worklist)); 2466 Builder = &TheBuilder; 2467 2468 InstCombinerLibCallSimplifier TheSimplifier(TD, TLI, this); 2469 Simplifier = &TheSimplifier; 2470 2471 bool EverMadeChange = false; 2472 2473 // Lower dbg.declare intrinsics otherwise their value may be clobbered 2474 // by instcombiner. 2475 EverMadeChange = LowerDbgDeclare(F); 2476 2477 // Iterate while there is work to do. 2478 unsigned Iteration = 0; 2479 while (DoOneIteration(F, Iteration++)) 2480 EverMadeChange = true; 2481 2482 Builder = 0; 2483 return EverMadeChange; 2484} 2485 2486FunctionPass *llvm::createInstructionCombiningPass() { 2487 return new InstCombiner(); 2488} 2489