1 //===- InstructionSimplify.cpp - Fold instruction operands ----------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements routines for folding instructions into simpler forms 11 // that do not require creating new instructions. This does constant folding 12 // ("add i32 1, 1" -> "2") but can also handle non-constant operands, either 13 // returning a constant ("and i32 %x, 0" -> "0") or an already existing value 14 // ("and i32 %x, %x" -> "%x"). All operands are assumed to have already been 15 // simplified: This is usually true and assuming it simplifies the logic (if 16 // they have not been simplified then results are correct but maybe suboptimal). 17 // 18 //===----------------------------------------------------------------------===// 19 20 #define DEBUG_TYPE "instsimplify" 21 #include "llvm/GlobalAlias.h" 22 #include "llvm/Operator.h" 23 #include "llvm/ADT/Statistic.h" 24 #include "llvm/ADT/SetVector.h" 25 #include "llvm/Analysis/InstructionSimplify.h" 26 #include "llvm/Analysis/AliasAnalysis.h" 27 #include "llvm/Analysis/ConstantFolding.h" 28 #include "llvm/Analysis/Dominators.h" 29 #include "llvm/Analysis/ValueTracking.h" 30 #include "llvm/Support/ConstantRange.h" 31 #include "llvm/Support/GetElementPtrTypeIterator.h" 32 #include "llvm/Support/PatternMatch.h" 33 #include "llvm/Support/ValueHandle.h" 34 #include "llvm/Target/TargetData.h" 35 using namespace llvm; 36 using namespace llvm::PatternMatch; 37 38 enum { RecursionLimit = 3 }; 39 40 STATISTIC(NumExpand, "Number of expansions"); 41 STATISTIC(NumFactor , "Number of factorizations"); 42 STATISTIC(NumReassoc, "Number of reassociations"); 43 44 struct Query { 45 const TargetData *TD; 46 const TargetLibraryInfo *TLI; 47 const DominatorTree *DT; 48 49 Query(const TargetData *td, const TargetLibraryInfo *tli, 50 const DominatorTree *dt) : TD(td), TLI(tli), DT(dt) {}; 51 }; 52 53 static Value *SimplifyAndInst(Value *, Value *, const Query &, unsigned); 54 static Value *SimplifyBinOp(unsigned, Value *, Value *, const Query &, 55 unsigned); 56 static Value *SimplifyCmpInst(unsigned, Value *, Value *, const Query &, 57 unsigned); 58 static Value *SimplifyOrInst(Value *, Value *, const Query &, unsigned); 59 static Value *SimplifyXorInst(Value *, Value *, const Query &, unsigned); 60 static Value *SimplifyTruncInst(Value *, Type *, const Query &, unsigned); 61 62 /// getFalse - For a boolean type, or a vector of boolean type, return false, or 63 /// a vector with every element false, as appropriate for the type. 64 static Constant *getFalse(Type *Ty) { 65 assert(Ty->getScalarType()->isIntegerTy(1) && 66 "Expected i1 type or a vector of i1!"); 67 return Constant::getNullValue(Ty); 68 } 69 70 /// getTrue - For a boolean type, or a vector of boolean type, return true, or 71 /// a vector with every element true, as appropriate for the type. 72 static Constant *getTrue(Type *Ty) { 73 assert(Ty->getScalarType()->isIntegerTy(1) && 74 "Expected i1 type or a vector of i1!"); 75 return Constant::getAllOnesValue(Ty); 76 } 77 78 /// isSameCompare - Is V equivalent to the comparison "LHS Pred RHS"? 79 static bool isSameCompare(Value *V, CmpInst::Predicate Pred, Value *LHS, 80 Value *RHS) { 81 CmpInst *Cmp = dyn_cast<CmpInst>(V); 82 if (!Cmp) 83 return false; 84 CmpInst::Predicate CPred = Cmp->getPredicate(); 85 Value *CLHS = Cmp->getOperand(0), *CRHS = Cmp->getOperand(1); 86 if (CPred == Pred && CLHS == LHS && CRHS == RHS) 87 return true; 88 return CPred == CmpInst::getSwappedPredicate(Pred) && CLHS == RHS && 89 CRHS == LHS; 90 } 91 92 /// ValueDominatesPHI - Does the given value dominate the specified phi node? 93 static bool ValueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) { 94 Instruction *I = dyn_cast<Instruction>(V); 95 if (!I) 96 // Arguments and constants dominate all instructions. 97 return true; 98 99 // If we are processing instructions (and/or basic blocks) that have not been 100 // fully added to a function, the parent nodes may still be null. Simply 101 // return the conservative answer in these cases. 102 if (!I->getParent() || !P->getParent() || !I->getParent()->getParent()) 103 return false; 104 105 // If we have a DominatorTree then do a precise test. 106 if (DT) { 107 if (!DT->isReachableFromEntry(P->getParent())) 108 return true; 109 if (!DT->isReachableFromEntry(I->getParent())) 110 return false; 111 return DT->dominates(I, P); 112 } 113 114 // Otherwise, if the instruction is in the entry block, and is not an invoke, 115 // then it obviously dominates all phi nodes. 116 if (I->getParent() == &I->getParent()->getParent()->getEntryBlock() && 117 !isa<InvokeInst>(I)) 118 return true; 119 120 return false; 121 } 122 123 /// ExpandBinOp - Simplify "A op (B op' C)" by distributing op over op', turning 124 /// it into "(A op B) op' (A op C)". Here "op" is given by Opcode and "op'" is 125 /// given by OpcodeToExpand, while "A" corresponds to LHS and "B op' C" to RHS. 126 /// Also performs the transform "(A op' B) op C" -> "(A op C) op' (B op C)". 127 /// Returns the simplified value, or null if no simplification was performed. 128 static Value *ExpandBinOp(unsigned Opcode, Value *LHS, Value *RHS, 129 unsigned OpcToExpand, const Query &Q, 130 unsigned MaxRecurse) { 131 Instruction::BinaryOps OpcodeToExpand = (Instruction::BinaryOps)OpcToExpand; 132 // Recursion is always used, so bail out at once if we already hit the limit. 133 if (!MaxRecurse--) 134 return 0; 135 136 // Check whether the expression has the form "(A op' B) op C". 137 if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS)) 138 if (Op0->getOpcode() == OpcodeToExpand) { 139 // It does! Try turning it into "(A op C) op' (B op C)". 140 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; 141 // Do "A op C" and "B op C" both simplify? 142 if (Value *L = SimplifyBinOp(Opcode, A, C, Q, MaxRecurse)) 143 if (Value *R = SimplifyBinOp(Opcode, B, C, Q, MaxRecurse)) { 144 // They do! Return "L op' R" if it simplifies or is already available. 145 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. 146 if ((L == A && R == B) || (Instruction::isCommutative(OpcodeToExpand) 147 && L == B && R == A)) { 148 ++NumExpand; 149 return LHS; 150 } 151 // Otherwise return "L op' R" if it simplifies. 152 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, Q, MaxRecurse)) { 153 ++NumExpand; 154 return V; 155 } 156 } 157 } 158 159 // Check whether the expression has the form "A op (B op' C)". 160 if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS)) 161 if (Op1->getOpcode() == OpcodeToExpand) { 162 // It does! Try turning it into "(A op B) op' (A op C)". 163 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); 164 // Do "A op B" and "A op C" both simplify? 165 if (Value *L = SimplifyBinOp(Opcode, A, B, Q, MaxRecurse)) 166 if (Value *R = SimplifyBinOp(Opcode, A, C, Q, MaxRecurse)) { 167 // They do! Return "L op' R" if it simplifies or is already available. 168 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. 169 if ((L == B && R == C) || (Instruction::isCommutative(OpcodeToExpand) 170 && L == C && R == B)) { 171 ++NumExpand; 172 return RHS; 173 } 174 // Otherwise return "L op' R" if it simplifies. 175 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, Q, MaxRecurse)) { 176 ++NumExpand; 177 return V; 178 } 179 } 180 } 181 182 return 0; 183 } 184 185 /// FactorizeBinOp - Simplify "LHS Opcode RHS" by factorizing out a common term 186 /// using the operation OpCodeToExtract. For example, when Opcode is Add and 187 /// OpCodeToExtract is Mul then this tries to turn "(A*B)+(A*C)" into "A*(B+C)". 188 /// Returns the simplified value, or null if no simplification was performed. 189 static Value *FactorizeBinOp(unsigned Opcode, Value *LHS, Value *RHS, 190 unsigned OpcToExtract, const Query &Q, 191 unsigned MaxRecurse) { 192 Instruction::BinaryOps OpcodeToExtract = (Instruction::BinaryOps)OpcToExtract; 193 // Recursion is always used, so bail out at once if we already hit the limit. 194 if (!MaxRecurse--) 195 return 0; 196 197 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 198 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 199 200 if (!Op0 || Op0->getOpcode() != OpcodeToExtract || 201 !Op1 || Op1->getOpcode() != OpcodeToExtract) 202 return 0; 203 204 // The expression has the form "(A op' B) op (C op' D)". 205 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1); 206 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1); 207 208 // Use left distributivity, i.e. "X op' (Y op Z) = (X op' Y) op (X op' Z)". 209 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the 210 // commutative case, "(A op' B) op (C op' A)"? 211 if (A == C || (Instruction::isCommutative(OpcodeToExtract) && A == D)) { 212 Value *DD = A == C ? D : C; 213 // Form "A op' (B op DD)" if it simplifies completely. 214 // Does "B op DD" simplify? 215 if (Value *V = SimplifyBinOp(Opcode, B, DD, Q, MaxRecurse)) { 216 // It does! Return "A op' V" if it simplifies or is already available. 217 // If V equals B then "A op' V" is just the LHS. If V equals DD then 218 // "A op' V" is just the RHS. 219 if (V == B || V == DD) { 220 ++NumFactor; 221 return V == B ? LHS : RHS; 222 } 223 // Otherwise return "A op' V" if it simplifies. 224 if (Value *W = SimplifyBinOp(OpcodeToExtract, A, V, Q, MaxRecurse)) { 225 ++NumFactor; 226 return W; 227 } 228 } 229 } 230 231 // Use right distributivity, i.e. "(X op Y) op' Z = (X op' Z) op (Y op' Z)". 232 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the 233 // commutative case, "(A op' B) op (B op' D)"? 234 if (B == D || (Instruction::isCommutative(OpcodeToExtract) && B == C)) { 235 Value *CC = B == D ? C : D; 236 // Form "(A op CC) op' B" if it simplifies completely.. 237 // Does "A op CC" simplify? 238 if (Value *V = SimplifyBinOp(Opcode, A, CC, Q, MaxRecurse)) { 239 // It does! Return "V op' B" if it simplifies or is already available. 240 // If V equals A then "V op' B" is just the LHS. If V equals CC then 241 // "V op' B" is just the RHS. 242 if (V == A || V == CC) { 243 ++NumFactor; 244 return V == A ? LHS : RHS; 245 } 246 // Otherwise return "V op' B" if it simplifies. 247 if (Value *W = SimplifyBinOp(OpcodeToExtract, V, B, Q, MaxRecurse)) { 248 ++NumFactor; 249 return W; 250 } 251 } 252 } 253 254 return 0; 255 } 256 257 /// SimplifyAssociativeBinOp - Generic simplifications for associative binary 258 /// operations. Returns the simpler value, or null if none was found. 259 static Value *SimplifyAssociativeBinOp(unsigned Opc, Value *LHS, Value *RHS, 260 const Query &Q, unsigned MaxRecurse) { 261 Instruction::BinaryOps Opcode = (Instruction::BinaryOps)Opc; 262 assert(Instruction::isAssociative(Opcode) && "Not an associative operation!"); 263 264 // Recursion is always used, so bail out at once if we already hit the limit. 265 if (!MaxRecurse--) 266 return 0; 267 268 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 269 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 270 271 // Transform: "(A op B) op C" ==> "A op (B op C)" if it simplifies completely. 272 if (Op0 && Op0->getOpcode() == Opcode) { 273 Value *A = Op0->getOperand(0); 274 Value *B = Op0->getOperand(1); 275 Value *C = RHS; 276 277 // Does "B op C" simplify? 278 if (Value *V = SimplifyBinOp(Opcode, B, C, Q, MaxRecurse)) { 279 // It does! Return "A op V" if it simplifies or is already available. 280 // If V equals B then "A op V" is just the LHS. 281 if (V == B) return LHS; 282 // Otherwise return "A op V" if it simplifies. 283 if (Value *W = SimplifyBinOp(Opcode, A, V, Q, MaxRecurse)) { 284 ++NumReassoc; 285 return W; 286 } 287 } 288 } 289 290 // Transform: "A op (B op C)" ==> "(A op B) op C" if it simplifies completely. 291 if (Op1 && Op1->getOpcode() == Opcode) { 292 Value *A = LHS; 293 Value *B = Op1->getOperand(0); 294 Value *C = Op1->getOperand(1); 295 296 // Does "A op B" simplify? 297 if (Value *V = SimplifyBinOp(Opcode, A, B, Q, MaxRecurse)) { 298 // It does! Return "V op C" if it simplifies or is already available. 299 // If V equals B then "V op C" is just the RHS. 300 if (V == B) return RHS; 301 // Otherwise return "V op C" if it simplifies. 302 if (Value *W = SimplifyBinOp(Opcode, V, C, Q, MaxRecurse)) { 303 ++NumReassoc; 304 return W; 305 } 306 } 307 } 308 309 // The remaining transforms require commutativity as well as associativity. 310 if (!Instruction::isCommutative(Opcode)) 311 return 0; 312 313 // Transform: "(A op B) op C" ==> "(C op A) op B" if it simplifies completely. 314 if (Op0 && Op0->getOpcode() == Opcode) { 315 Value *A = Op0->getOperand(0); 316 Value *B = Op0->getOperand(1); 317 Value *C = RHS; 318 319 // Does "C op A" simplify? 320 if (Value *V = SimplifyBinOp(Opcode, C, A, Q, MaxRecurse)) { 321 // It does! Return "V op B" if it simplifies or is already available. 322 // If V equals A then "V op B" is just the LHS. 323 if (V == A) return LHS; 324 // Otherwise return "V op B" if it simplifies. 325 if (Value *W = SimplifyBinOp(Opcode, V, B, Q, MaxRecurse)) { 326 ++NumReassoc; 327 return W; 328 } 329 } 330 } 331 332 // Transform: "A op (B op C)" ==> "B op (C op A)" if it simplifies completely. 333 if (Op1 && Op1->getOpcode() == Opcode) { 334 Value *A = LHS; 335 Value *B = Op1->getOperand(0); 336 Value *C = Op1->getOperand(1); 337 338 // Does "C op A" simplify? 339 if (Value *V = SimplifyBinOp(Opcode, C, A, Q, MaxRecurse)) { 340 // It does! Return "B op V" if it simplifies or is already available. 341 // If V equals C then "B op V" is just the RHS. 342 if (V == C) return RHS; 343 // Otherwise return "B op V" if it simplifies. 344 if (Value *W = SimplifyBinOp(Opcode, B, V, Q, MaxRecurse)) { 345 ++NumReassoc; 346 return W; 347 } 348 } 349 } 350 351 return 0; 352 } 353 354 /// ThreadBinOpOverSelect - In the case of a binary operation with a select 355 /// instruction as an operand, try to simplify the binop by seeing whether 356 /// evaluating it on both branches of the select results in the same value. 357 /// Returns the common value if so, otherwise returns null. 358 static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS, 359 const Query &Q, unsigned MaxRecurse) { 360 // Recursion is always used, so bail out at once if we already hit the limit. 361 if (!MaxRecurse--) 362 return 0; 363 364 SelectInst *SI; 365 if (isa<SelectInst>(LHS)) { 366 SI = cast<SelectInst>(LHS); 367 } else { 368 assert(isa<SelectInst>(RHS) && "No select instruction operand!"); 369 SI = cast<SelectInst>(RHS); 370 } 371 372 // Evaluate the BinOp on the true and false branches of the select. 373 Value *TV; 374 Value *FV; 375 if (SI == LHS) { 376 TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, Q, MaxRecurse); 377 FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, Q, MaxRecurse); 378 } else { 379 TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), Q, MaxRecurse); 380 FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), Q, MaxRecurse); 381 } 382 383 // If they simplified to the same value, then return the common value. 384 // If they both failed to simplify then return null. 385 if (TV == FV) 386 return TV; 387 388 // If one branch simplified to undef, return the other one. 389 if (TV && isa<UndefValue>(TV)) 390 return FV; 391 if (FV && isa<UndefValue>(FV)) 392 return TV; 393 394 // If applying the operation did not change the true and false select values, 395 // then the result of the binop is the select itself. 396 if (TV == SI->getTrueValue() && FV == SI->getFalseValue()) 397 return SI; 398 399 // If one branch simplified and the other did not, and the simplified 400 // value is equal to the unsimplified one, return the simplified value. 401 // For example, select (cond, X, X & Z) & Z -> X & Z. 402 if ((FV && !TV) || (TV && !FV)) { 403 // Check that the simplified value has the form "X op Y" where "op" is the 404 // same as the original operation. 405 Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV); 406 if (Simplified && Simplified->getOpcode() == Opcode) { 407 // The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS". 408 // We already know that "op" is the same as for the simplified value. See 409 // if the operands match too. If so, return the simplified value. 410 Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue(); 411 Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS; 412 Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch; 413 if (Simplified->getOperand(0) == UnsimplifiedLHS && 414 Simplified->getOperand(1) == UnsimplifiedRHS) 415 return Simplified; 416 if (Simplified->isCommutative() && 417 Simplified->getOperand(1) == UnsimplifiedLHS && 418 Simplified->getOperand(0) == UnsimplifiedRHS) 419 return Simplified; 420 } 421 } 422 423 return 0; 424 } 425 426 /// ThreadCmpOverSelect - In the case of a comparison with a select instruction, 427 /// try to simplify the comparison by seeing whether both branches of the select 428 /// result in the same value. Returns the common value if so, otherwise returns 429 /// null. 430 static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS, 431 Value *RHS, const Query &Q, 432 unsigned MaxRecurse) { 433 // Recursion is always used, so bail out at once if we already hit the limit. 434 if (!MaxRecurse--) 435 return 0; 436 437 // Make sure the select is on the LHS. 438 if (!isa<SelectInst>(LHS)) { 439 std::swap(LHS, RHS); 440 Pred = CmpInst::getSwappedPredicate(Pred); 441 } 442 assert(isa<SelectInst>(LHS) && "Not comparing with a select instruction!"); 443 SelectInst *SI = cast<SelectInst>(LHS); 444 Value *Cond = SI->getCondition(); 445 Value *TV = SI->getTrueValue(); 446 Value *FV = SI->getFalseValue(); 447 448 // Now that we have "cmp select(Cond, TV, FV), RHS", analyse it. 449 // Does "cmp TV, RHS" simplify? 450 Value *TCmp = SimplifyCmpInst(Pred, TV, RHS, Q, MaxRecurse); 451 if (TCmp == Cond) { 452 // It not only simplified, it simplified to the select condition. Replace 453 // it with 'true'. 454 TCmp = getTrue(Cond->getType()); 455 } else if (!TCmp) { 456 // It didn't simplify. However if "cmp TV, RHS" is equal to the select 457 // condition then we can replace it with 'true'. Otherwise give up. 458 if (!isSameCompare(Cond, Pred, TV, RHS)) 459 return 0; 460 TCmp = getTrue(Cond->getType()); 461 } 462 463 // Does "cmp FV, RHS" simplify? 464 Value *FCmp = SimplifyCmpInst(Pred, FV, RHS, Q, MaxRecurse); 465 if (FCmp == Cond) { 466 // It not only simplified, it simplified to the select condition. Replace 467 // it with 'false'. 468 FCmp = getFalse(Cond->getType()); 469 } else if (!FCmp) { 470 // It didn't simplify. However if "cmp FV, RHS" is equal to the select 471 // condition then we can replace it with 'false'. Otherwise give up. 472 if (!isSameCompare(Cond, Pred, FV, RHS)) 473 return 0; 474 FCmp = getFalse(Cond->getType()); 475 } 476 477 // If both sides simplified to the same value, then use it as the result of 478 // the original comparison. 479 if (TCmp == FCmp) 480 return TCmp; 481 482 // The remaining cases only make sense if the select condition has the same 483 // type as the result of the comparison, so bail out if this is not so. 484 if (Cond->getType()->isVectorTy() != RHS->getType()->isVectorTy()) 485 return 0; 486 // If the false value simplified to false, then the result of the compare 487 // is equal to "Cond && TCmp". This also catches the case when the false 488 // value simplified to false and the true value to true, returning "Cond". 489 if (match(FCmp, m_Zero())) 490 if (Value *V = SimplifyAndInst(Cond, TCmp, Q, MaxRecurse)) 491 return V; 492 // If the true value simplified to true, then the result of the compare 493 // is equal to "Cond || FCmp". 494 if (match(TCmp, m_One())) 495 if (Value *V = SimplifyOrInst(Cond, FCmp, Q, MaxRecurse)) 496 return V; 497 // Finally, if the false value simplified to true and the true value to 498 // false, then the result of the compare is equal to "!Cond". 499 if (match(FCmp, m_One()) && match(TCmp, m_Zero())) 500 if (Value *V = 501 SimplifyXorInst(Cond, Constant::getAllOnesValue(Cond->getType()), 502 Q, MaxRecurse)) 503 return V; 504 505 return 0; 506 } 507 508 /// ThreadBinOpOverPHI - In the case of a binary operation with an operand that 509 /// is a PHI instruction, try to simplify the binop by seeing whether evaluating 510 /// it on the incoming phi values yields the same result for every value. If so 511 /// returns the common value, otherwise returns null. 512 static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS, 513 const Query &Q, unsigned MaxRecurse) { 514 // Recursion is always used, so bail out at once if we already hit the limit. 515 if (!MaxRecurse--) 516 return 0; 517 518 PHINode *PI; 519 if (isa<PHINode>(LHS)) { 520 PI = cast<PHINode>(LHS); 521 // Bail out if RHS and the phi may be mutually interdependent due to a loop. 522 if (!ValueDominatesPHI(RHS, PI, Q.DT)) 523 return 0; 524 } else { 525 assert(isa<PHINode>(RHS) && "No PHI instruction operand!"); 526 PI = cast<PHINode>(RHS); 527 // Bail out if LHS and the phi may be mutually interdependent due to a loop. 528 if (!ValueDominatesPHI(LHS, PI, Q.DT)) 529 return 0; 530 } 531 532 // Evaluate the BinOp on the incoming phi values. 533 Value *CommonValue = 0; 534 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) { 535 Value *Incoming = PI->getIncomingValue(i); 536 // If the incoming value is the phi node itself, it can safely be skipped. 537 if (Incoming == PI) continue; 538 Value *V = PI == LHS ? 539 SimplifyBinOp(Opcode, Incoming, RHS, Q, MaxRecurse) : 540 SimplifyBinOp(Opcode, LHS, Incoming, Q, MaxRecurse); 541 // If the operation failed to simplify, or simplified to a different value 542 // to previously, then give up. 543 if (!V || (CommonValue && V != CommonValue)) 544 return 0; 545 CommonValue = V; 546 } 547 548 return CommonValue; 549 } 550 551 /// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try 552 /// try to simplify the comparison by seeing whether comparing with all of the 553 /// incoming phi values yields the same result every time. If so returns the 554 /// common result, otherwise returns null. 555 static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS, 556 const Query &Q, unsigned MaxRecurse) { 557 // Recursion is always used, so bail out at once if we already hit the limit. 558 if (!MaxRecurse--) 559 return 0; 560 561 // Make sure the phi is on the LHS. 562 if (!isa<PHINode>(LHS)) { 563 std::swap(LHS, RHS); 564 Pred = CmpInst::getSwappedPredicate(Pred); 565 } 566 assert(isa<PHINode>(LHS) && "Not comparing with a phi instruction!"); 567 PHINode *PI = cast<PHINode>(LHS); 568 569 // Bail out if RHS and the phi may be mutually interdependent due to a loop. 570 if (!ValueDominatesPHI(RHS, PI, Q.DT)) 571 return 0; 572 573 // Evaluate the BinOp on the incoming phi values. 574 Value *CommonValue = 0; 575 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) { 576 Value *Incoming = PI->getIncomingValue(i); 577 // If the incoming value is the phi node itself, it can safely be skipped. 578 if (Incoming == PI) continue; 579 Value *V = SimplifyCmpInst(Pred, Incoming, RHS, Q, MaxRecurse); 580 // If the operation failed to simplify, or simplified to a different value 581 // to previously, then give up. 582 if (!V || (CommonValue && V != CommonValue)) 583 return 0; 584 CommonValue = V; 585 } 586 587 return CommonValue; 588 } 589 590 /// SimplifyAddInst - Given operands for an Add, see if we can 591 /// fold the result. If not, this returns null. 592 static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 593 const Query &Q, unsigned MaxRecurse) { 594 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 595 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 596 Constant *Ops[] = { CLHS, CRHS }; 597 return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(), Ops, 598 Q.TD, Q.TLI); 599 } 600 601 // Canonicalize the constant to the RHS. 602 std::swap(Op0, Op1); 603 } 604 605 // X + undef -> undef 606 if (match(Op1, m_Undef())) 607 return Op1; 608 609 // X + 0 -> X 610 if (match(Op1, m_Zero())) 611 return Op0; 612 613 // X + (Y - X) -> Y 614 // (Y - X) + X -> Y 615 // Eg: X + -X -> 0 616 Value *Y = 0; 617 if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) || 618 match(Op0, m_Sub(m_Value(Y), m_Specific(Op1)))) 619 return Y; 620 621 // X + ~X -> -1 since ~X = -X-1 622 if (match(Op0, m_Not(m_Specific(Op1))) || 623 match(Op1, m_Not(m_Specific(Op0)))) 624 return Constant::getAllOnesValue(Op0->getType()); 625 626 /// i1 add -> xor. 627 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 628 if (Value *V = SimplifyXorInst(Op0, Op1, Q, MaxRecurse-1)) 629 return V; 630 631 // Try some generic simplifications for associative operations. 632 if (Value *V = SimplifyAssociativeBinOp(Instruction::Add, Op0, Op1, Q, 633 MaxRecurse)) 634 return V; 635 636 // Mul distributes over Add. Try some generic simplifications based on this. 637 if (Value *V = FactorizeBinOp(Instruction::Add, Op0, Op1, Instruction::Mul, 638 Q, MaxRecurse)) 639 return V; 640 641 // Threading Add over selects and phi nodes is pointless, so don't bother. 642 // Threading over the select in "A + select(cond, B, C)" means evaluating 643 // "A+B" and "A+C" and seeing if they are equal; but they are equal if and 644 // only if B and C are equal. If B and C are equal then (since we assume 645 // that operands have already been simplified) "select(cond, B, C)" should 646 // have been simplified to the common value of B and C already. Analysing 647 // "A+B" and "A+C" thus gains nothing, but costs compile time. Similarly 648 // for threading over phi nodes. 649 650 return 0; 651 } 652 653 Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 654 const TargetData *TD, const TargetLibraryInfo *TLI, 655 const DominatorTree *DT) { 656 return ::SimplifyAddInst(Op0, Op1, isNSW, isNUW, Query (TD, TLI, DT), 657 RecursionLimit); 658 } 659 660 /// \brief Accumulate the constant integer offset a GEP represents. 661 /// 662 /// Given a getelementptr instruction/constantexpr, accumulate the constant 663 /// offset from the base pointer into the provided APInt 'Offset'. Returns true 664 /// if the GEP has all-constant indices. Returns false if any non-constant 665 /// index is encountered leaving the 'Offset' in an undefined state. The 666 /// 'Offset' APInt must be the bitwidth of the target's pointer size. 667 static bool accumulateGEPOffset(const TargetData &TD, GEPOperator *GEP, 668 APInt &Offset) { 669 unsigned IntPtrWidth = TD.getPointerSizeInBits(); 670 assert(IntPtrWidth == Offset.getBitWidth()); 671 672 gep_type_iterator GTI = gep_type_begin(GEP); 673 for (User::op_iterator I = GEP->op_begin() + 1, E = GEP->op_end(); I != E; 674 ++I, ++GTI) { 675 ConstantInt *OpC = dyn_cast<ConstantInt>(*I); 676 if (!OpC) return false; 677 if (OpC->isZero()) continue; 678 679 // Handle a struct index, which adds its field offset to the pointer. 680 if (StructType *STy = dyn_cast<StructType>(*GTI)) { 681 unsigned ElementIdx = OpC->getZExtValue(); 682 const StructLayout *SL = TD.getStructLayout(STy); 683 Offset += APInt(IntPtrWidth, SL->getElementOffset(ElementIdx)); 684 continue; 685 } 686 687 APInt TypeSize(IntPtrWidth, TD.getTypeAllocSize(GTI.getIndexedType())); 688 Offset += OpC->getValue().sextOrTrunc(IntPtrWidth) * TypeSize; 689 } 690 return true; 691 } 692 693 /// \brief Compute the base pointer and cumulative constant offsets for V. 694 /// 695 /// This strips all constant offsets off of V, leaving it the base pointer, and 696 /// accumulates the total constant offset applied in the returned constant. It 697 /// returns 0 if V is not a pointer, and returns the constant '0' if there are 698 /// no constant offsets applied. 699 static Constant *stripAndComputeConstantOffsets(const TargetData &TD, 700 Value *&V) { 701 if (!V->getType()->isPointerTy()) 702 return 0; 703 704 unsigned IntPtrWidth = TD.getPointerSizeInBits(); 705 APInt Offset = APInt::getNullValue(IntPtrWidth); 706 707 // Even though we don't look through PHI nodes, we could be called on an 708 // instruction in an unreachable block, which may be on a cycle. 709 SmallPtrSet<Value *, 4> Visited; 710 Visited.insert(V); 711 do { 712 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { 713 if (!GEP->isInBounds() || !accumulateGEPOffset(TD, GEP, Offset)) 714 break; 715 V = GEP->getPointerOperand(); 716 } else if (Operator::getOpcode(V) == Instruction::BitCast) { 717 V = cast<Operator>(V)->getOperand(0); 718 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) { 719 if (GA->mayBeOverridden()) 720 break; 721 V = GA->getAliasee(); 722 } else { 723 break; 724 } 725 assert(V->getType()->isPointerTy() && "Unexpected operand type!"); 726 } while (Visited.insert(V)); 727 728 Type *IntPtrTy = TD.getIntPtrType(V->getContext()); 729 return ConstantInt::get(IntPtrTy, Offset); 730 } 731 732 /// \brief Compute the constant difference between two pointer values. 733 /// If the difference is not a constant, returns zero. 734 static Constant *computePointerDifference(const TargetData &TD, 735 Value *LHS, Value *RHS) { 736 Constant *LHSOffset = stripAndComputeConstantOffsets(TD, LHS); 737 if (!LHSOffset) 738 return 0; 739 Constant *RHSOffset = stripAndComputeConstantOffsets(TD, RHS); 740 if (!RHSOffset) 741 return 0; 742 743 // If LHS and RHS are not related via constant offsets to the same base 744 // value, there is nothing we can do here. 745 if (LHS != RHS) 746 return 0; 747 748 // Otherwise, the difference of LHS - RHS can be computed as: 749 // LHS - RHS 750 // = (LHSOffset + Base) - (RHSOffset + Base) 751 // = LHSOffset - RHSOffset 752 return ConstantExpr::getSub(LHSOffset, RHSOffset); 753 } 754 755 /// SimplifySubInst - Given operands for a Sub, see if we can 756 /// fold the result. If not, this returns null. 757 static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 758 const Query &Q, unsigned MaxRecurse) { 759 if (Constant *CLHS = dyn_cast<Constant>(Op0)) 760 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 761 Constant *Ops[] = { CLHS, CRHS }; 762 return ConstantFoldInstOperands(Instruction::Sub, CLHS->getType(), 763 Ops, Q.TD, Q.TLI); 764 } 765 766 // X - undef -> undef 767 // undef - X -> undef 768 if (match(Op0, m_Undef()) || match(Op1, m_Undef())) 769 return UndefValue::get(Op0->getType()); 770 771 // X - 0 -> X 772 if (match(Op1, m_Zero())) 773 return Op0; 774 775 // X - X -> 0 776 if (Op0 == Op1) 777 return Constant::getNullValue(Op0->getType()); 778 779 // (X*2) - X -> X 780 // (X<<1) - X -> X 781 Value *X = 0; 782 if (match(Op0, m_Mul(m_Specific(Op1), m_ConstantInt<2>())) || 783 match(Op0, m_Shl(m_Specific(Op1), m_One()))) 784 return Op1; 785 786 // (X + Y) - Z -> X + (Y - Z) or Y + (X - Z) if everything simplifies. 787 // For example, (X + Y) - Y -> X; (Y + X) - Y -> X 788 Value *Y = 0, *Z = Op1; 789 if (MaxRecurse && match(Op0, m_Add(m_Value(X), m_Value(Y)))) { // (X + Y) - Z 790 // See if "V === Y - Z" simplifies. 791 if (Value *V = SimplifyBinOp(Instruction::Sub, Y, Z, Q, MaxRecurse-1)) 792 // It does! Now see if "X + V" simplifies. 793 if (Value *W = SimplifyBinOp(Instruction::Add, X, V, Q, MaxRecurse-1)) { 794 // It does, we successfully reassociated! 795 ++NumReassoc; 796 return W; 797 } 798 // See if "V === X - Z" simplifies. 799 if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, Q, MaxRecurse-1)) 800 // It does! Now see if "Y + V" simplifies. 801 if (Value *W = SimplifyBinOp(Instruction::Add, Y, V, Q, MaxRecurse-1)) { 802 // It does, we successfully reassociated! 803 ++NumReassoc; 804 return W; 805 } 806 } 807 808 // X - (Y + Z) -> (X - Y) - Z or (X - Z) - Y if everything simplifies. 809 // For example, X - (X + 1) -> -1 810 X = Op0; 811 if (MaxRecurse && match(Op1, m_Add(m_Value(Y), m_Value(Z)))) { // X - (Y + Z) 812 // See if "V === X - Y" simplifies. 813 if (Value *V = SimplifyBinOp(Instruction::Sub, X, Y, Q, MaxRecurse-1)) 814 // It does! Now see if "V - Z" simplifies. 815 if (Value *W = SimplifyBinOp(Instruction::Sub, V, Z, Q, MaxRecurse-1)) { 816 // It does, we successfully reassociated! 817 ++NumReassoc; 818 return W; 819 } 820 // See if "V === X - Z" simplifies. 821 if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, Q, MaxRecurse-1)) 822 // It does! Now see if "V - Y" simplifies. 823 if (Value *W = SimplifyBinOp(Instruction::Sub, V, Y, Q, MaxRecurse-1)) { 824 // It does, we successfully reassociated! 825 ++NumReassoc; 826 return W; 827 } 828 } 829 830 // Z - (X - Y) -> (Z - X) + Y if everything simplifies. 831 // For example, X - (X - Y) -> Y. 832 Z = Op0; 833 if (MaxRecurse && match(Op1, m_Sub(m_Value(X), m_Value(Y)))) // Z - (X - Y) 834 // See if "V === Z - X" simplifies. 835 if (Value *V = SimplifyBinOp(Instruction::Sub, Z, X, Q, MaxRecurse-1)) 836 // It does! Now see if "V + Y" simplifies. 837 if (Value *W = SimplifyBinOp(Instruction::Add, V, Y, Q, MaxRecurse-1)) { 838 // It does, we successfully reassociated! 839 ++NumReassoc; 840 return W; 841 } 842 843 // trunc(X) - trunc(Y) -> trunc(X - Y) if everything simplifies. 844 if (MaxRecurse && match(Op0, m_Trunc(m_Value(X))) && 845 match(Op1, m_Trunc(m_Value(Y)))) 846 if (X->getType() == Y->getType()) 847 // See if "V === X - Y" simplifies. 848 if (Value *V = SimplifyBinOp(Instruction::Sub, X, Y, Q, MaxRecurse-1)) 849 // It does! Now see if "trunc V" simplifies. 850 if (Value *W = SimplifyTruncInst(V, Op0->getType(), Q, MaxRecurse-1)) 851 // It does, return the simplified "trunc V". 852 return W; 853 854 // Variations on GEP(base, I, ...) - GEP(base, i, ...) -> GEP(null, I-i, ...). 855 if (Q.TD && match(Op0, m_PtrToInt(m_Value(X))) && 856 match(Op1, m_PtrToInt(m_Value(Y)))) 857 if (Constant *Result = computePointerDifference(*Q.TD, X, Y)) 858 return ConstantExpr::getIntegerCast(Result, Op0->getType(), true); 859 860 // Mul distributes over Sub. Try some generic simplifications based on this. 861 if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul, 862 Q, MaxRecurse)) 863 return V; 864 865 // i1 sub -> xor. 866 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 867 if (Value *V = SimplifyXorInst(Op0, Op1, Q, MaxRecurse-1)) 868 return V; 869 870 // Threading Sub over selects and phi nodes is pointless, so don't bother. 871 // Threading over the select in "A - select(cond, B, C)" means evaluating 872 // "A-B" and "A-C" and seeing if they are equal; but they are equal if and 873 // only if B and C are equal. If B and C are equal then (since we assume 874 // that operands have already been simplified) "select(cond, B, C)" should 875 // have been simplified to the common value of B and C already. Analysing 876 // "A-B" and "A-C" thus gains nothing, but costs compile time. Similarly 877 // for threading over phi nodes. 878 879 return 0; 880 } 881 882 Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 883 const TargetData *TD, const TargetLibraryInfo *TLI, 884 const DominatorTree *DT) { 885 return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, Query (TD, TLI, DT), 886 RecursionLimit); 887 } 888 889 /// SimplifyMulInst - Given operands for a Mul, see if we can 890 /// fold the result. If not, this returns null. 891 static Value *SimplifyMulInst(Value *Op0, Value *Op1, const Query &Q, 892 unsigned MaxRecurse) { 893 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 894 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 895 Constant *Ops[] = { CLHS, CRHS }; 896 return ConstantFoldInstOperands(Instruction::Mul, CLHS->getType(), 897 Ops, Q.TD, Q.TLI); 898 } 899 900 // Canonicalize the constant to the RHS. 901 std::swap(Op0, Op1); 902 } 903 904 // X * undef -> 0 905 if (match(Op1, m_Undef())) 906 return Constant::getNullValue(Op0->getType()); 907 908 // X * 0 -> 0 909 if (match(Op1, m_Zero())) 910 return Op1; 911 912 // X * 1 -> X 913 if (match(Op1, m_One())) 914 return Op0; 915 916 // (X / Y) * Y -> X if the division is exact. 917 Value *X = 0; 918 if (match(Op0, m_Exact(m_IDiv(m_Value(X), m_Specific(Op1)))) || // (X / Y) * Y 919 match(Op1, m_Exact(m_IDiv(m_Value(X), m_Specific(Op0))))) // Y * (X / Y) 920 return X; 921 922 // i1 mul -> and. 923 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 924 if (Value *V = SimplifyAndInst(Op0, Op1, Q, MaxRecurse-1)) 925 return V; 926 927 // Try some generic simplifications for associative operations. 928 if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, Q, 929 MaxRecurse)) 930 return V; 931 932 // Mul distributes over Add. Try some generic simplifications based on this. 933 if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add, 934 Q, MaxRecurse)) 935 return V; 936 937 // If the operation is with the result of a select instruction, check whether 938 // operating on either branch of the select always yields the same value. 939 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 940 if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, Q, 941 MaxRecurse)) 942 return V; 943 944 // If the operation is with the result of a phi instruction, check whether 945 // operating on all incoming values of the phi always yields the same value. 946 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 947 if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, Q, 948 MaxRecurse)) 949 return V; 950 951 return 0; 952 } 953 954 Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD, 955 const TargetLibraryInfo *TLI, 956 const DominatorTree *DT) { 957 return ::SimplifyMulInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 958 } 959 960 /// SimplifyDiv - Given operands for an SDiv or UDiv, see if we can 961 /// fold the result. If not, this returns null. 962 static Value *SimplifyDiv(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1, 963 const Query &Q, unsigned MaxRecurse) { 964 if (Constant *C0 = dyn_cast<Constant>(Op0)) { 965 if (Constant *C1 = dyn_cast<Constant>(Op1)) { 966 Constant *Ops[] = { C0, C1 }; 967 return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, Q.TD, Q.TLI); 968 } 969 } 970 971 bool isSigned = Opcode == Instruction::SDiv; 972 973 // X / undef -> undef 974 if (match(Op1, m_Undef())) 975 return Op1; 976 977 // undef / X -> 0 978 if (match(Op0, m_Undef())) 979 return Constant::getNullValue(Op0->getType()); 980 981 // 0 / X -> 0, we don't need to preserve faults! 982 if (match(Op0, m_Zero())) 983 return Op0; 984 985 // X / 1 -> X 986 if (match(Op1, m_One())) 987 return Op0; 988 989 if (Op0->getType()->isIntegerTy(1)) 990 // It can't be division by zero, hence it must be division by one. 991 return Op0; 992 993 // X / X -> 1 994 if (Op0 == Op1) 995 return ConstantInt::get(Op0->getType(), 1); 996 997 // (X * Y) / Y -> X if the multiplication does not overflow. 998 Value *X = 0, *Y = 0; 999 if (match(Op0, m_Mul(m_Value(X), m_Value(Y))) && (X == Op1 || Y == Op1)) { 1000 if (Y != Op1) std::swap(X, Y); // Ensure expression is (X * Y) / Y, Y = Op1 1001 OverflowingBinaryOperator *Mul = cast<OverflowingBinaryOperator>(Op0); 1002 // If the Mul knows it does not overflow, then we are good to go. 1003 if ((isSigned && Mul->hasNoSignedWrap()) || 1004 (!isSigned && Mul->hasNoUnsignedWrap())) 1005 return X; 1006 // If X has the form X = A / Y then X * Y cannot overflow. 1007 if (BinaryOperator *Div = dyn_cast<BinaryOperator>(X)) 1008 if (Div->getOpcode() == Opcode && Div->getOperand(1) == Y) 1009 return X; 1010 } 1011 1012 // (X rem Y) / Y -> 0 1013 if ((isSigned && match(Op0, m_SRem(m_Value(), m_Specific(Op1)))) || 1014 (!isSigned && match(Op0, m_URem(m_Value(), m_Specific(Op1))))) 1015 return Constant::getNullValue(Op0->getType()); 1016 1017 // If the operation is with the result of a select instruction, check whether 1018 // operating on either branch of the select always yields the same value. 1019 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 1020 if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, Q, MaxRecurse)) 1021 return V; 1022 1023 // If the operation is with the result of a phi instruction, check whether 1024 // operating on all incoming values of the phi always yields the same value. 1025 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 1026 if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, Q, MaxRecurse)) 1027 return V; 1028 1029 return 0; 1030 } 1031 1032 /// SimplifySDivInst - Given operands for an SDiv, see if we can 1033 /// fold the result. If not, this returns null. 1034 static Value *SimplifySDivInst(Value *Op0, Value *Op1, const Query &Q, 1035 unsigned MaxRecurse) { 1036 if (Value *V = SimplifyDiv(Instruction::SDiv, Op0, Op1, Q, MaxRecurse)) 1037 return V; 1038 1039 return 0; 1040 } 1041 1042 Value *llvm::SimplifySDivInst(Value *Op0, Value *Op1, const TargetData *TD, 1043 const TargetLibraryInfo *TLI, 1044 const DominatorTree *DT) { 1045 return ::SimplifySDivInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1046 } 1047 1048 /// SimplifyUDivInst - Given operands for a UDiv, see if we can 1049 /// fold the result. If not, this returns null. 1050 static Value *SimplifyUDivInst(Value *Op0, Value *Op1, const Query &Q, 1051 unsigned MaxRecurse) { 1052 if (Value *V = SimplifyDiv(Instruction::UDiv, Op0, Op1, Q, MaxRecurse)) 1053 return V; 1054 1055 return 0; 1056 } 1057 1058 Value *llvm::SimplifyUDivInst(Value *Op0, Value *Op1, const TargetData *TD, 1059 const TargetLibraryInfo *TLI, 1060 const DominatorTree *DT) { 1061 return ::SimplifyUDivInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1062 } 1063 1064 static Value *SimplifyFDivInst(Value *Op0, Value *Op1, const Query &Q, 1065 unsigned) { 1066 // undef / X -> undef (the undef could be a snan). 1067 if (match(Op0, m_Undef())) 1068 return Op0; 1069 1070 // X / undef -> undef 1071 if (match(Op1, m_Undef())) 1072 return Op1; 1073 1074 return 0; 1075 } 1076 1077 Value *llvm::SimplifyFDivInst(Value *Op0, Value *Op1, const TargetData *TD, 1078 const TargetLibraryInfo *TLI, 1079 const DominatorTree *DT) { 1080 return ::SimplifyFDivInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1081 } 1082 1083 /// SimplifyRem - Given operands for an SRem or URem, see if we can 1084 /// fold the result. If not, this returns null. 1085 static Value *SimplifyRem(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1, 1086 const Query &Q, unsigned MaxRecurse) { 1087 if (Constant *C0 = dyn_cast<Constant>(Op0)) { 1088 if (Constant *C1 = dyn_cast<Constant>(Op1)) { 1089 Constant *Ops[] = { C0, C1 }; 1090 return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, Q.TD, Q.TLI); 1091 } 1092 } 1093 1094 // X % undef -> undef 1095 if (match(Op1, m_Undef())) 1096 return Op1; 1097 1098 // undef % X -> 0 1099 if (match(Op0, m_Undef())) 1100 return Constant::getNullValue(Op0->getType()); 1101 1102 // 0 % X -> 0, we don't need to preserve faults! 1103 if (match(Op0, m_Zero())) 1104 return Op0; 1105 1106 // X % 0 -> undef, we don't need to preserve faults! 1107 if (match(Op1, m_Zero())) 1108 return UndefValue::get(Op0->getType()); 1109 1110 // X % 1 -> 0 1111 if (match(Op1, m_One())) 1112 return Constant::getNullValue(Op0->getType()); 1113 1114 if (Op0->getType()->isIntegerTy(1)) 1115 // It can't be remainder by zero, hence it must be remainder by one. 1116 return Constant::getNullValue(Op0->getType()); 1117 1118 // X % X -> 0 1119 if (Op0 == Op1) 1120 return Constant::getNullValue(Op0->getType()); 1121 1122 // If the operation is with the result of a select instruction, check whether 1123 // operating on either branch of the select always yields the same value. 1124 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 1125 if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, Q, MaxRecurse)) 1126 return V; 1127 1128 // If the operation is with the result of a phi instruction, check whether 1129 // operating on all incoming values of the phi always yields the same value. 1130 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 1131 if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, Q, MaxRecurse)) 1132 return V; 1133 1134 return 0; 1135 } 1136 1137 /// SimplifySRemInst - Given operands for an SRem, see if we can 1138 /// fold the result. If not, this returns null. 1139 static Value *SimplifySRemInst(Value *Op0, Value *Op1, const Query &Q, 1140 unsigned MaxRecurse) { 1141 if (Value *V = SimplifyRem(Instruction::SRem, Op0, Op1, Q, MaxRecurse)) 1142 return V; 1143 1144 return 0; 1145 } 1146 1147 Value *llvm::SimplifySRemInst(Value *Op0, Value *Op1, const TargetData *TD, 1148 const TargetLibraryInfo *TLI, 1149 const DominatorTree *DT) { 1150 return ::SimplifySRemInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1151 } 1152 1153 /// SimplifyURemInst - Given operands for a URem, see if we can 1154 /// fold the result. If not, this returns null. 1155 static Value *SimplifyURemInst(Value *Op0, Value *Op1, const Query &Q, 1156 unsigned MaxRecurse) { 1157 if (Value *V = SimplifyRem(Instruction::URem, Op0, Op1, Q, MaxRecurse)) 1158 return V; 1159 1160 return 0; 1161 } 1162 1163 Value *llvm::SimplifyURemInst(Value *Op0, Value *Op1, const TargetData *TD, 1164 const TargetLibraryInfo *TLI, 1165 const DominatorTree *DT) { 1166 return ::SimplifyURemInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1167 } 1168 1169 static Value *SimplifyFRemInst(Value *Op0, Value *Op1, const Query &, 1170 unsigned) { 1171 // undef % X -> undef (the undef could be a snan). 1172 if (match(Op0, m_Undef())) 1173 return Op0; 1174 1175 // X % undef -> undef 1176 if (match(Op1, m_Undef())) 1177 return Op1; 1178 1179 return 0; 1180 } 1181 1182 Value *llvm::SimplifyFRemInst(Value *Op0, Value *Op1, const TargetData *TD, 1183 const TargetLibraryInfo *TLI, 1184 const DominatorTree *DT) { 1185 return ::SimplifyFRemInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1186 } 1187 1188 /// SimplifyShift - Given operands for an Shl, LShr or AShr, see if we can 1189 /// fold the result. If not, this returns null. 1190 static Value *SimplifyShift(unsigned Opcode, Value *Op0, Value *Op1, 1191 const Query &Q, unsigned MaxRecurse) { 1192 if (Constant *C0 = dyn_cast<Constant>(Op0)) { 1193 if (Constant *C1 = dyn_cast<Constant>(Op1)) { 1194 Constant *Ops[] = { C0, C1 }; 1195 return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, Q.TD, Q.TLI); 1196 } 1197 } 1198 1199 // 0 shift by X -> 0 1200 if (match(Op0, m_Zero())) 1201 return Op0; 1202 1203 // X shift by 0 -> X 1204 if (match(Op1, m_Zero())) 1205 return Op0; 1206 1207 // X shift by undef -> undef because it may shift by the bitwidth. 1208 if (match(Op1, m_Undef())) 1209 return Op1; 1210 1211 // Shifting by the bitwidth or more is undefined. 1212 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) 1213 if (CI->getValue().getLimitedValue() >= 1214 Op0->getType()->getScalarSizeInBits()) 1215 return UndefValue::get(Op0->getType()); 1216 1217 // If the operation is with the result of a select instruction, check whether 1218 // operating on either branch of the select always yields the same value. 1219 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 1220 if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, Q, MaxRecurse)) 1221 return V; 1222 1223 // If the operation is with the result of a phi instruction, check whether 1224 // operating on all incoming values of the phi always yields the same value. 1225 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 1226 if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, Q, MaxRecurse)) 1227 return V; 1228 1229 return 0; 1230 } 1231 1232 /// SimplifyShlInst - Given operands for an Shl, see if we can 1233 /// fold the result. If not, this returns null. 1234 static Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 1235 const Query &Q, unsigned MaxRecurse) { 1236 if (Value *V = SimplifyShift(Instruction::Shl, Op0, Op1, Q, MaxRecurse)) 1237 return V; 1238 1239 // undef << X -> 0 1240 if (match(Op0, m_Undef())) 1241 return Constant::getNullValue(Op0->getType()); 1242 1243 // (X >> A) << A -> X 1244 Value *X; 1245 if (match(Op0, m_Exact(m_Shr(m_Value(X), m_Specific(Op1))))) 1246 return X; 1247 return 0; 1248 } 1249 1250 Value *llvm::SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 1251 const TargetData *TD, const TargetLibraryInfo *TLI, 1252 const DominatorTree *DT) { 1253 return ::SimplifyShlInst(Op0, Op1, isNSW, isNUW, Query (TD, TLI, DT), 1254 RecursionLimit); 1255 } 1256 1257 /// SimplifyLShrInst - Given operands for an LShr, see if we can 1258 /// fold the result. If not, this returns null. 1259 static Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact, 1260 const Query &Q, unsigned MaxRecurse) { 1261 if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, Q, MaxRecurse)) 1262 return V; 1263 1264 // undef >>l X -> 0 1265 if (match(Op0, m_Undef())) 1266 return Constant::getNullValue(Op0->getType()); 1267 1268 // (X << A) >> A -> X 1269 Value *X; 1270 if (match(Op0, m_Shl(m_Value(X), m_Specific(Op1))) && 1271 cast<OverflowingBinaryOperator>(Op0)->hasNoUnsignedWrap()) 1272 return X; 1273 1274 return 0; 1275 } 1276 1277 Value *llvm::SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact, 1278 const TargetData *TD, 1279 const TargetLibraryInfo *TLI, 1280 const DominatorTree *DT) { 1281 return ::SimplifyLShrInst(Op0, Op1, isExact, Query (TD, TLI, DT), 1282 RecursionLimit); 1283 } 1284 1285 /// SimplifyAShrInst - Given operands for an AShr, see if we can 1286 /// fold the result. If not, this returns null. 1287 static Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact, 1288 const Query &Q, unsigned MaxRecurse) { 1289 if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, Q, MaxRecurse)) 1290 return V; 1291 1292 // all ones >>a X -> all ones 1293 if (match(Op0, m_AllOnes())) 1294 return Op0; 1295 1296 // undef >>a X -> all ones 1297 if (match(Op0, m_Undef())) 1298 return Constant::getAllOnesValue(Op0->getType()); 1299 1300 // (X << A) >> A -> X 1301 Value *X; 1302 if (match(Op0, m_Shl(m_Value(X), m_Specific(Op1))) && 1303 cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap()) 1304 return X; 1305 1306 return 0; 1307 } 1308 1309 Value *llvm::SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact, 1310 const TargetData *TD, 1311 const TargetLibraryInfo *TLI, 1312 const DominatorTree *DT) { 1313 return ::SimplifyAShrInst(Op0, Op1, isExact, Query (TD, TLI, DT), 1314 RecursionLimit); 1315 } 1316 1317 /// SimplifyAndInst - Given operands for an And, see if we can 1318 /// fold the result. If not, this returns null. 1319 static Value *SimplifyAndInst(Value *Op0, Value *Op1, const Query &Q, 1320 unsigned MaxRecurse) { 1321 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 1322 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 1323 Constant *Ops[] = { CLHS, CRHS }; 1324 return ConstantFoldInstOperands(Instruction::And, CLHS->getType(), 1325 Ops, Q.TD, Q.TLI); 1326 } 1327 1328 // Canonicalize the constant to the RHS. 1329 std::swap(Op0, Op1); 1330 } 1331 1332 // X & undef -> 0 1333 if (match(Op1, m_Undef())) 1334 return Constant::getNullValue(Op0->getType()); 1335 1336 // X & X = X 1337 if (Op0 == Op1) 1338 return Op0; 1339 1340 // X & 0 = 0 1341 if (match(Op1, m_Zero())) 1342 return Op1; 1343 1344 // X & -1 = X 1345 if (match(Op1, m_AllOnes())) 1346 return Op0; 1347 1348 // A & ~A = ~A & A = 0 1349 if (match(Op0, m_Not(m_Specific(Op1))) || 1350 match(Op1, m_Not(m_Specific(Op0)))) 1351 return Constant::getNullValue(Op0->getType()); 1352 1353 // (A | ?) & A = A 1354 Value *A = 0, *B = 0; 1355 if (match(Op0, m_Or(m_Value(A), m_Value(B))) && 1356 (A == Op1 || B == Op1)) 1357 return Op1; 1358 1359 // A & (A | ?) = A 1360 if (match(Op1, m_Or(m_Value(A), m_Value(B))) && 1361 (A == Op0 || B == Op0)) 1362 return Op0; 1363 1364 // A & (-A) = A if A is a power of two or zero. 1365 if (match(Op0, m_Neg(m_Specific(Op1))) || 1366 match(Op1, m_Neg(m_Specific(Op0)))) { 1367 if (isPowerOfTwo(Op0, Q.TD, /*OrZero*/true)) 1368 return Op0; 1369 if (isPowerOfTwo(Op1, Q.TD, /*OrZero*/true)) 1370 return Op1; 1371 } 1372 1373 // Try some generic simplifications for associative operations. 1374 if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, Q, 1375 MaxRecurse)) 1376 return V; 1377 1378 // And distributes over Or. Try some generic simplifications based on this. 1379 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or, 1380 Q, MaxRecurse)) 1381 return V; 1382 1383 // And distributes over Xor. Try some generic simplifications based on this. 1384 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor, 1385 Q, MaxRecurse)) 1386 return V; 1387 1388 // Or distributes over And. Try some generic simplifications based on this. 1389 if (Value *V = FactorizeBinOp(Instruction::And, Op0, Op1, Instruction::Or, 1390 Q, MaxRecurse)) 1391 return V; 1392 1393 // If the operation is with the result of a select instruction, check whether 1394 // operating on either branch of the select always yields the same value. 1395 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 1396 if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, Q, 1397 MaxRecurse)) 1398 return V; 1399 1400 // If the operation is with the result of a phi instruction, check whether 1401 // operating on all incoming values of the phi always yields the same value. 1402 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 1403 if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, Q, 1404 MaxRecurse)) 1405 return V; 1406 1407 return 0; 1408 } 1409 1410 Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD, 1411 const TargetLibraryInfo *TLI, 1412 const DominatorTree *DT) { 1413 return ::SimplifyAndInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1414 } 1415 1416 /// SimplifyOrInst - Given operands for an Or, see if we can 1417 /// fold the result. If not, this returns null. 1418 static Value *SimplifyOrInst(Value *Op0, Value *Op1, const Query &Q, 1419 unsigned MaxRecurse) { 1420 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 1421 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 1422 Constant *Ops[] = { CLHS, CRHS }; 1423 return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(), 1424 Ops, Q.TD, Q.TLI); 1425 } 1426 1427 // Canonicalize the constant to the RHS. 1428 std::swap(Op0, Op1); 1429 } 1430 1431 // X | undef -> -1 1432 if (match(Op1, m_Undef())) 1433 return Constant::getAllOnesValue(Op0->getType()); 1434 1435 // X | X = X 1436 if (Op0 == Op1) 1437 return Op0; 1438 1439 // X | 0 = X 1440 if (match(Op1, m_Zero())) 1441 return Op0; 1442 1443 // X | -1 = -1 1444 if (match(Op1, m_AllOnes())) 1445 return Op1; 1446 1447 // A | ~A = ~A | A = -1 1448 if (match(Op0, m_Not(m_Specific(Op1))) || 1449 match(Op1, m_Not(m_Specific(Op0)))) 1450 return Constant::getAllOnesValue(Op0->getType()); 1451 1452 // (A & ?) | A = A 1453 Value *A = 0, *B = 0; 1454 if (match(Op0, m_And(m_Value(A), m_Value(B))) && 1455 (A == Op1 || B == Op1)) 1456 return Op1; 1457 1458 // A | (A & ?) = A 1459 if (match(Op1, m_And(m_Value(A), m_Value(B))) && 1460 (A == Op0 || B == Op0)) 1461 return Op0; 1462 1463 // ~(A & ?) | A = -1 1464 if (match(Op0, m_Not(m_And(m_Value(A), m_Value(B)))) && 1465 (A == Op1 || B == Op1)) 1466 return Constant::getAllOnesValue(Op1->getType()); 1467 1468 // A | ~(A & ?) = -1 1469 if (match(Op1, m_Not(m_And(m_Value(A), m_Value(B)))) && 1470 (A == Op0 || B == Op0)) 1471 return Constant::getAllOnesValue(Op0->getType()); 1472 1473 // Try some generic simplifications for associative operations. 1474 if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, Q, 1475 MaxRecurse)) 1476 return V; 1477 1478 // Or distributes over And. Try some generic simplifications based on this. 1479 if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And, Q, 1480 MaxRecurse)) 1481 return V; 1482 1483 // And distributes over Or. Try some generic simplifications based on this. 1484 if (Value *V = FactorizeBinOp(Instruction::Or, Op0, Op1, Instruction::And, 1485 Q, MaxRecurse)) 1486 return V; 1487 1488 // If the operation is with the result of a select instruction, check whether 1489 // operating on either branch of the select always yields the same value. 1490 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 1491 if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, Q, 1492 MaxRecurse)) 1493 return V; 1494 1495 // If the operation is with the result of a phi instruction, check whether 1496 // operating on all incoming values of the phi always yields the same value. 1497 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 1498 if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, Q, MaxRecurse)) 1499 return V; 1500 1501 return 0; 1502 } 1503 1504 Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD, 1505 const TargetLibraryInfo *TLI, 1506 const DominatorTree *DT) { 1507 return ::SimplifyOrInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1508 } 1509 1510 /// SimplifyXorInst - Given operands for a Xor, see if we can 1511 /// fold the result. If not, this returns null. 1512 static Value *SimplifyXorInst(Value *Op0, Value *Op1, const Query &Q, 1513 unsigned MaxRecurse) { 1514 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 1515 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 1516 Constant *Ops[] = { CLHS, CRHS }; 1517 return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(), 1518 Ops, Q.TD, Q.TLI); 1519 } 1520 1521 // Canonicalize the constant to the RHS. 1522 std::swap(Op0, Op1); 1523 } 1524 1525 // A ^ undef -> undef 1526 if (match(Op1, m_Undef())) 1527 return Op1; 1528 1529 // A ^ 0 = A 1530 if (match(Op1, m_Zero())) 1531 return Op0; 1532 1533 // A ^ A = 0 1534 if (Op0 == Op1) 1535 return Constant::getNullValue(Op0->getType()); 1536 1537 // A ^ ~A = ~A ^ A = -1 1538 if (match(Op0, m_Not(m_Specific(Op1))) || 1539 match(Op1, m_Not(m_Specific(Op0)))) 1540 return Constant::getAllOnesValue(Op0->getType()); 1541 1542 // Try some generic simplifications for associative operations. 1543 if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, Q, 1544 MaxRecurse)) 1545 return V; 1546 1547 // And distributes over Xor. Try some generic simplifications based on this. 1548 if (Value *V = FactorizeBinOp(Instruction::Xor, Op0, Op1, Instruction::And, 1549 Q, MaxRecurse)) 1550 return V; 1551 1552 // Threading Xor over selects and phi nodes is pointless, so don't bother. 1553 // Threading over the select in "A ^ select(cond, B, C)" means evaluating 1554 // "A^B" and "A^C" and seeing if they are equal; but they are equal if and 1555 // only if B and C are equal. If B and C are equal then (since we assume 1556 // that operands have already been simplified) "select(cond, B, C)" should 1557 // have been simplified to the common value of B and C already. Analysing 1558 // "A^B" and "A^C" thus gains nothing, but costs compile time. Similarly 1559 // for threading over phi nodes. 1560 1561 return 0; 1562 } 1563 1564 Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD, 1565 const TargetLibraryInfo *TLI, 1566 const DominatorTree *DT) { 1567 return ::SimplifyXorInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1568 } 1569 1570 static Type *GetCompareTy(Value *Op) { 1571 return CmpInst::makeCmpResultType(Op->getType()); 1572 } 1573 1574 /// ExtractEquivalentCondition - Rummage around inside V looking for something 1575 /// equivalent to the comparison "LHS Pred RHS". Return such a value if found, 1576 /// otherwise return null. Helper function for analyzing max/min idioms. 1577 static Value *ExtractEquivalentCondition(Value *V, CmpInst::Predicate Pred, 1578 Value *LHS, Value *RHS) { 1579 SelectInst *SI = dyn_cast<SelectInst>(V); 1580 if (!SI) 1581 return 0; 1582 CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition()); 1583 if (!Cmp) 1584 return 0; 1585 Value *CmpLHS = Cmp->getOperand(0), *CmpRHS = Cmp->getOperand(1); 1586 if (Pred == Cmp->getPredicate() && LHS == CmpLHS && RHS == CmpRHS) 1587 return Cmp; 1588 if (Pred == CmpInst::getSwappedPredicate(Cmp->getPredicate()) && 1589 LHS == CmpRHS && RHS == CmpLHS) 1590 return Cmp; 1591 return 0; 1592 } 1593 1594 static Constant *computePointerICmp(const TargetData &TD, 1595 CmpInst::Predicate Pred, 1596 Value *LHS, Value *RHS) { 1597 // We can only fold certain predicates on pointer comparisons. 1598 switch (Pred) { 1599 default: 1600 return 0; 1601 1602 // Equality comaprisons are easy to fold. 1603 case CmpInst::ICMP_EQ: 1604 case CmpInst::ICMP_NE: 1605 break; 1606 1607 // We can only handle unsigned relational comparisons because 'inbounds' on 1608 // a GEP only protects against unsigned wrapping. 1609 case CmpInst::ICMP_UGT: 1610 case CmpInst::ICMP_UGE: 1611 case CmpInst::ICMP_ULT: 1612 case CmpInst::ICMP_ULE: 1613 // However, we have to switch them to their signed variants to handle 1614 // negative indices from the base pointer. 1615 Pred = ICmpInst::getSignedPredicate(Pred); 1616 break; 1617 } 1618 1619 Constant *LHSOffset = stripAndComputeConstantOffsets(TD, LHS); 1620 if (!LHSOffset) 1621 return 0; 1622 Constant *RHSOffset = stripAndComputeConstantOffsets(TD, RHS); 1623 if (!RHSOffset) 1624 return 0; 1625 1626 // If LHS and RHS are not related via constant offsets to the same base 1627 // value, there is nothing we can do here. 1628 if (LHS != RHS) 1629 return 0; 1630 1631 return ConstantExpr::getICmp(Pred, LHSOffset, RHSOffset); 1632 } 1633 1634 /// SimplifyICmpInst - Given operands for an ICmpInst, see if we can 1635 /// fold the result. If not, this returns null. 1636 static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1637 const Query &Q, unsigned MaxRecurse) { 1638 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 1639 assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!"); 1640 1641 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 1642 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 1643 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, Q.TD, Q.TLI); 1644 1645 // If we have a constant, make sure it is on the RHS. 1646 std::swap(LHS, RHS); 1647 Pred = CmpInst::getSwappedPredicate(Pred); 1648 } 1649 1650 Type *ITy = GetCompareTy(LHS); // The return type. 1651 Type *OpTy = LHS->getType(); // The operand type. 1652 1653 // icmp X, X -> true/false 1654 // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false 1655 // because X could be 0. 1656 if (LHS == RHS || isa<UndefValue>(RHS)) 1657 return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred)); 1658 1659 // Special case logic when the operands have i1 type. 1660 if (OpTy->getScalarType()->isIntegerTy(1)) { 1661 switch (Pred) { 1662 default: break; 1663 case ICmpInst::ICMP_EQ: 1664 // X == 1 -> X 1665 if (match(RHS, m_One())) 1666 return LHS; 1667 break; 1668 case ICmpInst::ICMP_NE: 1669 // X != 0 -> X 1670 if (match(RHS, m_Zero())) 1671 return LHS; 1672 break; 1673 case ICmpInst::ICMP_UGT: 1674 // X >u 0 -> X 1675 if (match(RHS, m_Zero())) 1676 return LHS; 1677 break; 1678 case ICmpInst::ICMP_UGE: 1679 // X >=u 1 -> X 1680 if (match(RHS, m_One())) 1681 return LHS; 1682 break; 1683 case ICmpInst::ICMP_SLT: 1684 // X <s 0 -> X 1685 if (match(RHS, m_Zero())) 1686 return LHS; 1687 break; 1688 case ICmpInst::ICMP_SLE: 1689 // X <=s -1 -> X 1690 if (match(RHS, m_One())) 1691 return LHS; 1692 break; 1693 } 1694 } 1695 1696 // icmp <object*>, <object*/null> - Different identified objects have 1697 // different addresses (unless null), and what's more the address of an 1698 // identified local is never equal to another argument (again, barring null). 1699 // Note that generalizing to the case where LHS is a global variable address 1700 // or null is pointless, since if both LHS and RHS are constants then we 1701 // already constant folded the compare, and if only one of them is then we 1702 // moved it to RHS already. 1703 Value *LHSPtr = LHS->stripPointerCasts(); 1704 Value *RHSPtr = RHS->stripPointerCasts(); 1705 if (LHSPtr == RHSPtr) 1706 return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred)); 1707 1708 // Be more aggressive about stripping pointer adjustments when checking a 1709 // comparison of an alloca address to another object. We can rip off all 1710 // inbounds GEP operations, even if they are variable. 1711 LHSPtr = LHSPtr->stripInBoundsOffsets(); 1712 if (llvm::isIdentifiedObject(LHSPtr)) { 1713 RHSPtr = RHSPtr->stripInBoundsOffsets(); 1714 if (llvm::isKnownNonNull(LHSPtr) || llvm::isKnownNonNull(RHSPtr)) { 1715 // If both sides are different identified objects, they aren't equal 1716 // unless they're null. 1717 if (LHSPtr != RHSPtr && llvm::isIdentifiedObject(RHSPtr) && 1718 Pred == CmpInst::ICMP_EQ) 1719 return ConstantInt::get(ITy, false); 1720 1721 // A local identified object (alloca or noalias call) can't equal any 1722 // incoming argument, unless they're both null. 1723 if (isa<Instruction>(LHSPtr) && isa<Argument>(RHSPtr) && 1724 Pred == CmpInst::ICMP_EQ) 1725 return ConstantInt::get(ITy, false); 1726 } 1727 1728 // Assume that the constant null is on the right. 1729 if (llvm::isKnownNonNull(LHSPtr) && isa<ConstantPointerNull>(RHSPtr)) { 1730 if (Pred == CmpInst::ICMP_EQ) 1731 return ConstantInt::get(ITy, false); 1732 else if (Pred == CmpInst::ICMP_NE) 1733 return ConstantInt::get(ITy, true); 1734 } 1735 } else if (isa<Argument>(LHSPtr)) { 1736 RHSPtr = RHSPtr->stripInBoundsOffsets(); 1737 // An alloca can't be equal to an argument. 1738 if (isa<AllocaInst>(RHSPtr)) { 1739 if (Pred == CmpInst::ICMP_EQ) 1740 return ConstantInt::get(ITy, false); 1741 else if (Pred == CmpInst::ICMP_NE) 1742 return ConstantInt::get(ITy, true); 1743 } 1744 } 1745 1746 // If we are comparing with zero then try hard since this is a common case. 1747 if (match(RHS, m_Zero())) { 1748 bool LHSKnownNonNegative, LHSKnownNegative; 1749 switch (Pred) { 1750 default: llvm_unreachable("Unknown ICmp predicate!"); 1751 case ICmpInst::ICMP_ULT: 1752 return getFalse(ITy); 1753 case ICmpInst::ICMP_UGE: 1754 return getTrue(ITy); 1755 case ICmpInst::ICMP_EQ: 1756 case ICmpInst::ICMP_ULE: 1757 if (isKnownNonZero(LHS, Q.TD)) 1758 return getFalse(ITy); 1759 break; 1760 case ICmpInst::ICMP_NE: 1761 case ICmpInst::ICMP_UGT: 1762 if (isKnownNonZero(LHS, Q.TD)) 1763 return getTrue(ITy); 1764 break; 1765 case ICmpInst::ICMP_SLT: 1766 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.TD); 1767 if (LHSKnownNegative) 1768 return getTrue(ITy); 1769 if (LHSKnownNonNegative) 1770 return getFalse(ITy); 1771 break; 1772 case ICmpInst::ICMP_SLE: 1773 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.TD); 1774 if (LHSKnownNegative) 1775 return getTrue(ITy); 1776 if (LHSKnownNonNegative && isKnownNonZero(LHS, Q.TD)) 1777 return getFalse(ITy); 1778 break; 1779 case ICmpInst::ICMP_SGE: 1780 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.TD); 1781 if (LHSKnownNegative) 1782 return getFalse(ITy); 1783 if (LHSKnownNonNegative) 1784 return getTrue(ITy); 1785 break; 1786 case ICmpInst::ICMP_SGT: 1787 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.TD); 1788 if (LHSKnownNegative) 1789 return getFalse(ITy); 1790 if (LHSKnownNonNegative && isKnownNonZero(LHS, Q.TD)) 1791 return getTrue(ITy); 1792 break; 1793 } 1794 } 1795 1796 // See if we are doing a comparison with a constant integer. 1797 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1798 // Rule out tautological comparisons (eg., ult 0 or uge 0). 1799 ConstantRange RHS_CR = ICmpInst::makeConstantRange(Pred, CI->getValue()); 1800 if (RHS_CR.isEmptySet()) 1801 return ConstantInt::getFalse(CI->getContext()); 1802 if (RHS_CR.isFullSet()) 1803 return ConstantInt::getTrue(CI->getContext()); 1804 1805 // Many binary operators with constant RHS have easy to compute constant 1806 // range. Use them to check whether the comparison is a tautology. 1807 uint32_t Width = CI->getBitWidth(); 1808 APInt Lower = APInt(Width, 0); 1809 APInt Upper = APInt(Width, 0); 1810 ConstantInt *CI2; 1811 if (match(LHS, m_URem(m_Value(), m_ConstantInt(CI2)))) { 1812 // 'urem x, CI2' produces [0, CI2). 1813 Upper = CI2->getValue(); 1814 } else if (match(LHS, m_SRem(m_Value(), m_ConstantInt(CI2)))) { 1815 // 'srem x, CI2' produces (-|CI2|, |CI2|). 1816 Upper = CI2->getValue().abs(); 1817 Lower = (-Upper) + 1; 1818 } else if (match(LHS, m_UDiv(m_ConstantInt(CI2), m_Value()))) { 1819 // 'udiv CI2, x' produces [0, CI2]. 1820 Upper = CI2->getValue() + 1; 1821 } else if (match(LHS, m_UDiv(m_Value(), m_ConstantInt(CI2)))) { 1822 // 'udiv x, CI2' produces [0, UINT_MAX / CI2]. 1823 APInt NegOne = APInt::getAllOnesValue(Width); 1824 if (!CI2->isZero()) 1825 Upper = NegOne.udiv(CI2->getValue()) + 1; 1826 } else if (match(LHS, m_SDiv(m_Value(), m_ConstantInt(CI2)))) { 1827 // 'sdiv x, CI2' produces [INT_MIN / CI2, INT_MAX / CI2]. 1828 APInt IntMin = APInt::getSignedMinValue(Width); 1829 APInt IntMax = APInt::getSignedMaxValue(Width); 1830 APInt Val = CI2->getValue().abs(); 1831 if (!Val.isMinValue()) { 1832 Lower = IntMin.sdiv(Val); 1833 Upper = IntMax.sdiv(Val) + 1; 1834 } 1835 } else if (match(LHS, m_LShr(m_Value(), m_ConstantInt(CI2)))) { 1836 // 'lshr x, CI2' produces [0, UINT_MAX >> CI2]. 1837 APInt NegOne = APInt::getAllOnesValue(Width); 1838 if (CI2->getValue().ult(Width)) 1839 Upper = NegOne.lshr(CI2->getValue()) + 1; 1840 } else if (match(LHS, m_AShr(m_Value(), m_ConstantInt(CI2)))) { 1841 // 'ashr x, CI2' produces [INT_MIN >> CI2, INT_MAX >> CI2]. 1842 APInt IntMin = APInt::getSignedMinValue(Width); 1843 APInt IntMax = APInt::getSignedMaxValue(Width); 1844 if (CI2->getValue().ult(Width)) { 1845 Lower = IntMin.ashr(CI2->getValue()); 1846 Upper = IntMax.ashr(CI2->getValue()) + 1; 1847 } 1848 } else if (match(LHS, m_Or(m_Value(), m_ConstantInt(CI2)))) { 1849 // 'or x, CI2' produces [CI2, UINT_MAX]. 1850 Lower = CI2->getValue(); 1851 } else if (match(LHS, m_And(m_Value(), m_ConstantInt(CI2)))) { 1852 // 'and x, CI2' produces [0, CI2]. 1853 Upper = CI2->getValue() + 1; 1854 } 1855 if (Lower != Upper) { 1856 ConstantRange LHS_CR = ConstantRange(Lower, Upper); 1857 if (RHS_CR.contains(LHS_CR)) 1858 return ConstantInt::getTrue(RHS->getContext()); 1859 if (RHS_CR.inverse().contains(LHS_CR)) 1860 return ConstantInt::getFalse(RHS->getContext()); 1861 } 1862 } 1863 1864 // Compare of cast, for example (zext X) != 0 -> X != 0 1865 if (isa<CastInst>(LHS) && (isa<Constant>(RHS) || isa<CastInst>(RHS))) { 1866 Instruction *LI = cast<CastInst>(LHS); 1867 Value *SrcOp = LI->getOperand(0); 1868 Type *SrcTy = SrcOp->getType(); 1869 Type *DstTy = LI->getType(); 1870 1871 // Turn icmp (ptrtoint x), (ptrtoint/constant) into a compare of the input 1872 // if the integer type is the same size as the pointer type. 1873 if (MaxRecurse && Q.TD && isa<PtrToIntInst>(LI) && 1874 Q.TD->getPointerSizeInBits() == DstTy->getPrimitiveSizeInBits()) { 1875 if (Constant *RHSC = dyn_cast<Constant>(RHS)) { 1876 // Transfer the cast to the constant. 1877 if (Value *V = SimplifyICmpInst(Pred, SrcOp, 1878 ConstantExpr::getIntToPtr(RHSC, SrcTy), 1879 Q, MaxRecurse-1)) 1880 return V; 1881 } else if (PtrToIntInst *RI = dyn_cast<PtrToIntInst>(RHS)) { 1882 if (RI->getOperand(0)->getType() == SrcTy) 1883 // Compare without the cast. 1884 if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), 1885 Q, MaxRecurse-1)) 1886 return V; 1887 } 1888 } 1889 1890 if (isa<ZExtInst>(LHS)) { 1891 // Turn icmp (zext X), (zext Y) into a compare of X and Y if they have the 1892 // same type. 1893 if (ZExtInst *RI = dyn_cast<ZExtInst>(RHS)) { 1894 if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) 1895 // Compare X and Y. Note that signed predicates become unsigned. 1896 if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), 1897 SrcOp, RI->getOperand(0), Q, 1898 MaxRecurse-1)) 1899 return V; 1900 } 1901 // Turn icmp (zext X), Cst into a compare of X and Cst if Cst is extended 1902 // too. If not, then try to deduce the result of the comparison. 1903 else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1904 // Compute the constant that would happen if we truncated to SrcTy then 1905 // reextended to DstTy. 1906 Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); 1907 Constant *RExt = ConstantExpr::getCast(CastInst::ZExt, Trunc, DstTy); 1908 1909 // If the re-extended constant didn't change then this is effectively 1910 // also a case of comparing two zero-extended values. 1911 if (RExt == CI && MaxRecurse) 1912 if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), 1913 SrcOp, Trunc, Q, MaxRecurse-1)) 1914 return V; 1915 1916 // Otherwise the upper bits of LHS are zero while RHS has a non-zero bit 1917 // there. Use this to work out the result of the comparison. 1918 if (RExt != CI) { 1919 switch (Pred) { 1920 default: llvm_unreachable("Unknown ICmp predicate!"); 1921 // LHS <u RHS. 1922 case ICmpInst::ICMP_EQ: 1923 case ICmpInst::ICMP_UGT: 1924 case ICmpInst::ICMP_UGE: 1925 return ConstantInt::getFalse(CI->getContext()); 1926 1927 case ICmpInst::ICMP_NE: 1928 case ICmpInst::ICMP_ULT: 1929 case ICmpInst::ICMP_ULE: 1930 return ConstantInt::getTrue(CI->getContext()); 1931 1932 // LHS is non-negative. If RHS is negative then LHS >s LHS. If RHS 1933 // is non-negative then LHS <s RHS. 1934 case ICmpInst::ICMP_SGT: 1935 case ICmpInst::ICMP_SGE: 1936 return CI->getValue().isNegative() ? 1937 ConstantInt::getTrue(CI->getContext()) : 1938 ConstantInt::getFalse(CI->getContext()); 1939 1940 case ICmpInst::ICMP_SLT: 1941 case ICmpInst::ICMP_SLE: 1942 return CI->getValue().isNegative() ? 1943 ConstantInt::getFalse(CI->getContext()) : 1944 ConstantInt::getTrue(CI->getContext()); 1945 } 1946 } 1947 } 1948 } 1949 1950 if (isa<SExtInst>(LHS)) { 1951 // Turn icmp (sext X), (sext Y) into a compare of X and Y if they have the 1952 // same type. 1953 if (SExtInst *RI = dyn_cast<SExtInst>(RHS)) { 1954 if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) 1955 // Compare X and Y. Note that the predicate does not change. 1956 if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), 1957 Q, MaxRecurse-1)) 1958 return V; 1959 } 1960 // Turn icmp (sext X), Cst into a compare of X and Cst if Cst is extended 1961 // too. If not, then try to deduce the result of the comparison. 1962 else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1963 // Compute the constant that would happen if we truncated to SrcTy then 1964 // reextended to DstTy. 1965 Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); 1966 Constant *RExt = ConstantExpr::getCast(CastInst::SExt, Trunc, DstTy); 1967 1968 // If the re-extended constant didn't change then this is effectively 1969 // also a case of comparing two sign-extended values. 1970 if (RExt == CI && MaxRecurse) 1971 if (Value *V = SimplifyICmpInst(Pred, SrcOp, Trunc, Q, MaxRecurse-1)) 1972 return V; 1973 1974 // Otherwise the upper bits of LHS are all equal, while RHS has varying 1975 // bits there. Use this to work out the result of the comparison. 1976 if (RExt != CI) { 1977 switch (Pred) { 1978 default: llvm_unreachable("Unknown ICmp predicate!"); 1979 case ICmpInst::ICMP_EQ: 1980 return ConstantInt::getFalse(CI->getContext()); 1981 case ICmpInst::ICMP_NE: 1982 return ConstantInt::getTrue(CI->getContext()); 1983 1984 // If RHS is non-negative then LHS <s RHS. If RHS is negative then 1985 // LHS >s RHS. 1986 case ICmpInst::ICMP_SGT: 1987 case ICmpInst::ICMP_SGE: 1988 return CI->getValue().isNegative() ? 1989 ConstantInt::getTrue(CI->getContext()) : 1990 ConstantInt::getFalse(CI->getContext()); 1991 case ICmpInst::ICMP_SLT: 1992 case ICmpInst::ICMP_SLE: 1993 return CI->getValue().isNegative() ? 1994 ConstantInt::getFalse(CI->getContext()) : 1995 ConstantInt::getTrue(CI->getContext()); 1996 1997 // If LHS is non-negative then LHS <u RHS. If LHS is negative then 1998 // LHS >u RHS. 1999 case ICmpInst::ICMP_UGT: 2000 case ICmpInst::ICMP_UGE: 2001 // Comparison is true iff the LHS <s 0. 2002 if (MaxRecurse) 2003 if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SLT, SrcOp, 2004 Constant::getNullValue(SrcTy), 2005 Q, MaxRecurse-1)) 2006 return V; 2007 break; 2008 case ICmpInst::ICMP_ULT: 2009 case ICmpInst::ICMP_ULE: 2010 // Comparison is true iff the LHS >=s 0. 2011 if (MaxRecurse) 2012 if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SGE, SrcOp, 2013 Constant::getNullValue(SrcTy), 2014 Q, MaxRecurse-1)) 2015 return V; 2016 break; 2017 } 2018 } 2019 } 2020 } 2021 } 2022 2023 // Special logic for binary operators. 2024 BinaryOperator *LBO = dyn_cast<BinaryOperator>(LHS); 2025 BinaryOperator *RBO = dyn_cast<BinaryOperator>(RHS); 2026 if (MaxRecurse && (LBO || RBO)) { 2027 // Analyze the case when either LHS or RHS is an add instruction. 2028 Value *A = 0, *B = 0, *C = 0, *D = 0; 2029 // LHS = A + B (or A and B are null); RHS = C + D (or C and D are null). 2030 bool NoLHSWrapProblem = false, NoRHSWrapProblem = false; 2031 if (LBO && LBO->getOpcode() == Instruction::Add) { 2032 A = LBO->getOperand(0); B = LBO->getOperand(1); 2033 NoLHSWrapProblem = ICmpInst::isEquality(Pred) || 2034 (CmpInst::isUnsigned(Pred) && LBO->hasNoUnsignedWrap()) || 2035 (CmpInst::isSigned(Pred) && LBO->hasNoSignedWrap()); 2036 } 2037 if (RBO && RBO->getOpcode() == Instruction::Add) { 2038 C = RBO->getOperand(0); D = RBO->getOperand(1); 2039 NoRHSWrapProblem = ICmpInst::isEquality(Pred) || 2040 (CmpInst::isUnsigned(Pred) && RBO->hasNoUnsignedWrap()) || 2041 (CmpInst::isSigned(Pred) && RBO->hasNoSignedWrap()); 2042 } 2043 2044 // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow. 2045 if ((A == RHS || B == RHS) && NoLHSWrapProblem) 2046 if (Value *V = SimplifyICmpInst(Pred, A == RHS ? B : A, 2047 Constant::getNullValue(RHS->getType()), 2048 Q, MaxRecurse-1)) 2049 return V; 2050 2051 // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow. 2052 if ((C == LHS || D == LHS) && NoRHSWrapProblem) 2053 if (Value *V = SimplifyICmpInst(Pred, 2054 Constant::getNullValue(LHS->getType()), 2055 C == LHS ? D : C, Q, MaxRecurse-1)) 2056 return V; 2057 2058 // icmp (X+Y), (X+Z) -> icmp Y,Z for equalities or if there is no overflow. 2059 if (A && C && (A == C || A == D || B == C || B == D) && 2060 NoLHSWrapProblem && NoRHSWrapProblem) { 2061 // Determine Y and Z in the form icmp (X+Y), (X+Z). 2062 Value *Y = (A == C || A == D) ? B : A; 2063 Value *Z = (C == A || C == B) ? D : C; 2064 if (Value *V = SimplifyICmpInst(Pred, Y, Z, Q, MaxRecurse-1)) 2065 return V; 2066 } 2067 } 2068 2069 if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) { 2070 bool KnownNonNegative, KnownNegative; 2071 switch (Pred) { 2072 default: 2073 break; 2074 case ICmpInst::ICMP_SGT: 2075 case ICmpInst::ICMP_SGE: 2076 ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.TD); 2077 if (!KnownNonNegative) 2078 break; 2079 // fall-through 2080 case ICmpInst::ICMP_EQ: 2081 case ICmpInst::ICMP_UGT: 2082 case ICmpInst::ICMP_UGE: 2083 return getFalse(ITy); 2084 case ICmpInst::ICMP_SLT: 2085 case ICmpInst::ICMP_SLE: 2086 ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.TD); 2087 if (!KnownNonNegative) 2088 break; 2089 // fall-through 2090 case ICmpInst::ICMP_NE: 2091 case ICmpInst::ICMP_ULT: 2092 case ICmpInst::ICMP_ULE: 2093 return getTrue(ITy); 2094 } 2095 } 2096 if (RBO && match(RBO, m_URem(m_Value(), m_Specific(LHS)))) { 2097 bool KnownNonNegative, KnownNegative; 2098 switch (Pred) { 2099 default: 2100 break; 2101 case ICmpInst::ICMP_SGT: 2102 case ICmpInst::ICMP_SGE: 2103 ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.TD); 2104 if (!KnownNonNegative) 2105 break; 2106 // fall-through 2107 case ICmpInst::ICMP_NE: 2108 case ICmpInst::ICMP_UGT: 2109 case ICmpInst::ICMP_UGE: 2110 return getTrue(ITy); 2111 case ICmpInst::ICMP_SLT: 2112 case ICmpInst::ICMP_SLE: 2113 ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.TD); 2114 if (!KnownNonNegative) 2115 break; 2116 // fall-through 2117 case ICmpInst::ICMP_EQ: 2118 case ICmpInst::ICMP_ULT: 2119 case ICmpInst::ICMP_ULE: 2120 return getFalse(ITy); 2121 } 2122 } 2123 2124 // x udiv y <=u x. 2125 if (LBO && match(LBO, m_UDiv(m_Specific(RHS), m_Value()))) { 2126 // icmp pred (X /u Y), X 2127 if (Pred == ICmpInst::ICMP_UGT) 2128 return getFalse(ITy); 2129 if (Pred == ICmpInst::ICMP_ULE) 2130 return getTrue(ITy); 2131 } 2132 2133 if (MaxRecurse && LBO && RBO && LBO->getOpcode() == RBO->getOpcode() && 2134 LBO->getOperand(1) == RBO->getOperand(1)) { 2135 switch (LBO->getOpcode()) { 2136 default: break; 2137 case Instruction::UDiv: 2138 case Instruction::LShr: 2139 if (ICmpInst::isSigned(Pred)) 2140 break; 2141 // fall-through 2142 case Instruction::SDiv: 2143 case Instruction::AShr: 2144 if (!LBO->isExact() || !RBO->isExact()) 2145 break; 2146 if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0), 2147 RBO->getOperand(0), Q, MaxRecurse-1)) 2148 return V; 2149 break; 2150 case Instruction::Shl: { 2151 bool NUW = LBO->hasNoUnsignedWrap() && RBO->hasNoUnsignedWrap(); 2152 bool NSW = LBO->hasNoSignedWrap() && RBO->hasNoSignedWrap(); 2153 if (!NUW && !NSW) 2154 break; 2155 if (!NSW && ICmpInst::isSigned(Pred)) 2156 break; 2157 if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0), 2158 RBO->getOperand(0), Q, MaxRecurse-1)) 2159 return V; 2160 break; 2161 } 2162 } 2163 } 2164 2165 // Simplify comparisons involving max/min. 2166 Value *A, *B; 2167 CmpInst::Predicate P = CmpInst::BAD_ICMP_PREDICATE; 2168 CmpInst::Predicate EqP; // Chosen so that "A == max/min(A,B)" iff "A EqP B". 2169 2170 // Signed variants on "max(a,b)>=a -> true". 2171 if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) { 2172 if (A != RHS) std::swap(A, B); // smax(A, B) pred A. 2173 EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B". 2174 // We analyze this as smax(A, B) pred A. 2175 P = Pred; 2176 } else if (match(RHS, m_SMax(m_Value(A), m_Value(B))) && 2177 (A == LHS || B == LHS)) { 2178 if (A != LHS) std::swap(A, B); // A pred smax(A, B). 2179 EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B". 2180 // We analyze this as smax(A, B) swapped-pred A. 2181 P = CmpInst::getSwappedPredicate(Pred); 2182 } else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) && 2183 (A == RHS || B == RHS)) { 2184 if (A != RHS) std::swap(A, B); // smin(A, B) pred A. 2185 EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B". 2186 // We analyze this as smax(-A, -B) swapped-pred -A. 2187 // Note that we do not need to actually form -A or -B thanks to EqP. 2188 P = CmpInst::getSwappedPredicate(Pred); 2189 } else if (match(RHS, m_SMin(m_Value(A), m_Value(B))) && 2190 (A == LHS || B == LHS)) { 2191 if (A != LHS) std::swap(A, B); // A pred smin(A, B). 2192 EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B". 2193 // We analyze this as smax(-A, -B) pred -A. 2194 // Note that we do not need to actually form -A or -B thanks to EqP. 2195 P = Pred; 2196 } 2197 if (P != CmpInst::BAD_ICMP_PREDICATE) { 2198 // Cases correspond to "max(A, B) p A". 2199 switch (P) { 2200 default: 2201 break; 2202 case CmpInst::ICMP_EQ: 2203 case CmpInst::ICMP_SLE: 2204 // Equivalent to "A EqP B". This may be the same as the condition tested 2205 // in the max/min; if so, we can just return that. 2206 if (Value *V = ExtractEquivalentCondition(LHS, EqP, A, B)) 2207 return V; 2208 if (Value *V = ExtractEquivalentCondition(RHS, EqP, A, B)) 2209 return V; 2210 // Otherwise, see if "A EqP B" simplifies. 2211 if (MaxRecurse) 2212 if (Value *V = SimplifyICmpInst(EqP, A, B, Q, MaxRecurse-1)) 2213 return V; 2214 break; 2215 case CmpInst::ICMP_NE: 2216 case CmpInst::ICMP_SGT: { 2217 CmpInst::Predicate InvEqP = CmpInst::getInversePredicate(EqP); 2218 // Equivalent to "A InvEqP B". This may be the same as the condition 2219 // tested in the max/min; if so, we can just return that. 2220 if (Value *V = ExtractEquivalentCondition(LHS, InvEqP, A, B)) 2221 return V; 2222 if (Value *V = ExtractEquivalentCondition(RHS, InvEqP, A, B)) 2223 return V; 2224 // Otherwise, see if "A InvEqP B" simplifies. 2225 if (MaxRecurse) 2226 if (Value *V = SimplifyICmpInst(InvEqP, A, B, Q, MaxRecurse-1)) 2227 return V; 2228 break; 2229 } 2230 case CmpInst::ICMP_SGE: 2231 // Always true. 2232 return getTrue(ITy); 2233 case CmpInst::ICMP_SLT: 2234 // Always false. 2235 return getFalse(ITy); 2236 } 2237 } 2238 2239 // Unsigned variants on "max(a,b)>=a -> true". 2240 P = CmpInst::BAD_ICMP_PREDICATE; 2241 if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) { 2242 if (A != RHS) std::swap(A, B); // umax(A, B) pred A. 2243 EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B". 2244 // We analyze this as umax(A, B) pred A. 2245 P = Pred; 2246 } else if (match(RHS, m_UMax(m_Value(A), m_Value(B))) && 2247 (A == LHS || B == LHS)) { 2248 if (A != LHS) std::swap(A, B); // A pred umax(A, B). 2249 EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B". 2250 // We analyze this as umax(A, B) swapped-pred A. 2251 P = CmpInst::getSwappedPredicate(Pred); 2252 } else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) && 2253 (A == RHS || B == RHS)) { 2254 if (A != RHS) std::swap(A, B); // umin(A, B) pred A. 2255 EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B". 2256 // We analyze this as umax(-A, -B) swapped-pred -A. 2257 // Note that we do not need to actually form -A or -B thanks to EqP. 2258 P = CmpInst::getSwappedPredicate(Pred); 2259 } else if (match(RHS, m_UMin(m_Value(A), m_Value(B))) && 2260 (A == LHS || B == LHS)) { 2261 if (A != LHS) std::swap(A, B); // A pred umin(A, B). 2262 EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B". 2263 // We analyze this as umax(-A, -B) pred -A. 2264 // Note that we do not need to actually form -A or -B thanks to EqP. 2265 P = Pred; 2266 } 2267 if (P != CmpInst::BAD_ICMP_PREDICATE) { 2268 // Cases correspond to "max(A, B) p A". 2269 switch (P) { 2270 default: 2271 break; 2272 case CmpInst::ICMP_EQ: 2273 case CmpInst::ICMP_ULE: 2274 // Equivalent to "A EqP B". This may be the same as the condition tested 2275 // in the max/min; if so, we can just return that. 2276 if (Value *V = ExtractEquivalentCondition(LHS, EqP, A, B)) 2277 return V; 2278 if (Value *V = ExtractEquivalentCondition(RHS, EqP, A, B)) 2279 return V; 2280 // Otherwise, see if "A EqP B" simplifies. 2281 if (MaxRecurse) 2282 if (Value *V = SimplifyICmpInst(EqP, A, B, Q, MaxRecurse-1)) 2283 return V; 2284 break; 2285 case CmpInst::ICMP_NE: 2286 case CmpInst::ICMP_UGT: { 2287 CmpInst::Predicate InvEqP = CmpInst::getInversePredicate(EqP); 2288 // Equivalent to "A InvEqP B". This may be the same as the condition 2289 // tested in the max/min; if so, we can just return that. 2290 if (Value *V = ExtractEquivalentCondition(LHS, InvEqP, A, B)) 2291 return V; 2292 if (Value *V = ExtractEquivalentCondition(RHS, InvEqP, A, B)) 2293 return V; 2294 // Otherwise, see if "A InvEqP B" simplifies. 2295 if (MaxRecurse) 2296 if (Value *V = SimplifyICmpInst(InvEqP, A, B, Q, MaxRecurse-1)) 2297 return V; 2298 break; 2299 } 2300 case CmpInst::ICMP_UGE: 2301 // Always true. 2302 return getTrue(ITy); 2303 case CmpInst::ICMP_ULT: 2304 // Always false. 2305 return getFalse(ITy); 2306 } 2307 } 2308 2309 // Variants on "max(x,y) >= min(x,z)". 2310 Value *C, *D; 2311 if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && 2312 match(RHS, m_SMin(m_Value(C), m_Value(D))) && 2313 (A == C || A == D || B == C || B == D)) { 2314 // max(x, ?) pred min(x, ?). 2315 if (Pred == CmpInst::ICMP_SGE) 2316 // Always true. 2317 return getTrue(ITy); 2318 if (Pred == CmpInst::ICMP_SLT) 2319 // Always false. 2320 return getFalse(ITy); 2321 } else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) && 2322 match(RHS, m_SMax(m_Value(C), m_Value(D))) && 2323 (A == C || A == D || B == C || B == D)) { 2324 // min(x, ?) pred max(x, ?). 2325 if (Pred == CmpInst::ICMP_SLE) 2326 // Always true. 2327 return getTrue(ITy); 2328 if (Pred == CmpInst::ICMP_SGT) 2329 // Always false. 2330 return getFalse(ITy); 2331 } else if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && 2332 match(RHS, m_UMin(m_Value(C), m_Value(D))) && 2333 (A == C || A == D || B == C || B == D)) { 2334 // max(x, ?) pred min(x, ?). 2335 if (Pred == CmpInst::ICMP_UGE) 2336 // Always true. 2337 return getTrue(ITy); 2338 if (Pred == CmpInst::ICMP_ULT) 2339 // Always false. 2340 return getFalse(ITy); 2341 } else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) && 2342 match(RHS, m_UMax(m_Value(C), m_Value(D))) && 2343 (A == C || A == D || B == C || B == D)) { 2344 // min(x, ?) pred max(x, ?). 2345 if (Pred == CmpInst::ICMP_ULE) 2346 // Always true. 2347 return getTrue(ITy); 2348 if (Pred == CmpInst::ICMP_UGT) 2349 // Always false. 2350 return getFalse(ITy); 2351 } 2352 2353 // Simplify comparisons of related pointers using a powerful, recursive 2354 // GEP-walk when we have target data available.. 2355 if (Q.TD && LHS->getType()->isPointerTy() && RHS->getType()->isPointerTy()) 2356 if (Constant *C = computePointerICmp(*Q.TD, Pred, LHS, RHS)) 2357 return C; 2358 2359 if (GetElementPtrInst *GLHS = dyn_cast<GetElementPtrInst>(LHS)) { 2360 if (GEPOperator *GRHS = dyn_cast<GEPOperator>(RHS)) { 2361 if (GLHS->getPointerOperand() == GRHS->getPointerOperand() && 2362 GLHS->hasAllConstantIndices() && GRHS->hasAllConstantIndices() && 2363 (ICmpInst::isEquality(Pred) || 2364 (GLHS->isInBounds() && GRHS->isInBounds() && 2365 Pred == ICmpInst::getSignedPredicate(Pred)))) { 2366 // The bases are equal and the indices are constant. Build a constant 2367 // expression GEP with the same indices and a null base pointer to see 2368 // what constant folding can make out of it. 2369 Constant *Null = Constant::getNullValue(GLHS->getPointerOperandType()); 2370 SmallVector<Value *, 4> IndicesLHS(GLHS->idx_begin(), GLHS->idx_end()); 2371 Constant *NewLHS = ConstantExpr::getGetElementPtr(Null, IndicesLHS); 2372 2373 SmallVector<Value *, 4> IndicesRHS(GRHS->idx_begin(), GRHS->idx_end()); 2374 Constant *NewRHS = ConstantExpr::getGetElementPtr(Null, IndicesRHS); 2375 return ConstantExpr::getICmp(Pred, NewLHS, NewRHS); 2376 } 2377 } 2378 } 2379 2380 // If the comparison is with the result of a select instruction, check whether 2381 // comparing with either branch of the select always yields the same value. 2382 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 2383 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, Q, MaxRecurse)) 2384 return V; 2385 2386 // If the comparison is with the result of a phi instruction, check whether 2387 // doing the compare with each incoming phi value yields a common result. 2388 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 2389 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, Q, MaxRecurse)) 2390 return V; 2391 2392 return 0; 2393 } 2394 2395 Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2396 const TargetData *TD, 2397 const TargetLibraryInfo *TLI, 2398 const DominatorTree *DT) { 2399 return ::SimplifyICmpInst(Predicate, LHS, RHS, Query (TD, TLI, DT), 2400 RecursionLimit); 2401 } 2402 2403 /// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can 2404 /// fold the result. If not, this returns null. 2405 static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2406 const Query &Q, unsigned MaxRecurse) { 2407 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 2408 assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!"); 2409 2410 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 2411 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 2412 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, Q.TD, Q.TLI); 2413 2414 // If we have a constant, make sure it is on the RHS. 2415 std::swap(LHS, RHS); 2416 Pred = CmpInst::getSwappedPredicate(Pred); 2417 } 2418 2419 // Fold trivial predicates. 2420 if (Pred == FCmpInst::FCMP_FALSE) 2421 return ConstantInt::get(GetCompareTy(LHS), 0); 2422 if (Pred == FCmpInst::FCMP_TRUE) 2423 return ConstantInt::get(GetCompareTy(LHS), 1); 2424 2425 if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef 2426 return UndefValue::get(GetCompareTy(LHS)); 2427 2428 // fcmp x,x -> true/false. Not all compares are foldable. 2429 if (LHS == RHS) { 2430 if (CmpInst::isTrueWhenEqual(Pred)) 2431 return ConstantInt::get(GetCompareTy(LHS), 1); 2432 if (CmpInst::isFalseWhenEqual(Pred)) 2433 return ConstantInt::get(GetCompareTy(LHS), 0); 2434 } 2435 2436 // Handle fcmp with constant RHS 2437 if (Constant *RHSC = dyn_cast<Constant>(RHS)) { 2438 // If the constant is a nan, see if we can fold the comparison based on it. 2439 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) { 2440 if (CFP->getValueAPF().isNaN()) { 2441 if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo" 2442 return ConstantInt::getFalse(CFP->getContext()); 2443 assert(FCmpInst::isUnordered(Pred) && 2444 "Comparison must be either ordered or unordered!"); 2445 // True if unordered. 2446 return ConstantInt::getTrue(CFP->getContext()); 2447 } 2448 // Check whether the constant is an infinity. 2449 if (CFP->getValueAPF().isInfinity()) { 2450 if (CFP->getValueAPF().isNegative()) { 2451 switch (Pred) { 2452 case FCmpInst::FCMP_OLT: 2453 // No value is ordered and less than negative infinity. 2454 return ConstantInt::getFalse(CFP->getContext()); 2455 case FCmpInst::FCMP_UGE: 2456 // All values are unordered with or at least negative infinity. 2457 return ConstantInt::getTrue(CFP->getContext()); 2458 default: 2459 break; 2460 } 2461 } else { 2462 switch (Pred) { 2463 case FCmpInst::FCMP_OGT: 2464 // No value is ordered and greater than infinity. 2465 return ConstantInt::getFalse(CFP->getContext()); 2466 case FCmpInst::FCMP_ULE: 2467 // All values are unordered with and at most infinity. 2468 return ConstantInt::getTrue(CFP->getContext()); 2469 default: 2470 break; 2471 } 2472 } 2473 } 2474 } 2475 } 2476 2477 // If the comparison is with the result of a select instruction, check whether 2478 // comparing with either branch of the select always yields the same value. 2479 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 2480 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, Q, MaxRecurse)) 2481 return V; 2482 2483 // If the comparison is with the result of a phi instruction, check whether 2484 // doing the compare with each incoming phi value yields a common result. 2485 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 2486 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, Q, MaxRecurse)) 2487 return V; 2488 2489 return 0; 2490 } 2491 2492 Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2493 const TargetData *TD, 2494 const TargetLibraryInfo *TLI, 2495 const DominatorTree *DT) { 2496 return ::SimplifyFCmpInst(Predicate, LHS, RHS, Query (TD, TLI, DT), 2497 RecursionLimit); 2498 } 2499 2500 /// SimplifySelectInst - Given operands for a SelectInst, see if we can fold 2501 /// the result. If not, this returns null. 2502 static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal, 2503 Value *FalseVal, const Query &Q, 2504 unsigned MaxRecurse) { 2505 // select true, X, Y -> X 2506 // select false, X, Y -> Y 2507 if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal)) 2508 return CB->getZExtValue() ? TrueVal : FalseVal; 2509 2510 // select C, X, X -> X 2511 if (TrueVal == FalseVal) 2512 return TrueVal; 2513 2514 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y 2515 if (isa<Constant>(TrueVal)) 2516 return TrueVal; 2517 return FalseVal; 2518 } 2519 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X 2520 return FalseVal; 2521 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X 2522 return TrueVal; 2523 2524 return 0; 2525 } 2526 2527 Value *llvm::SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, 2528 const TargetData *TD, 2529 const TargetLibraryInfo *TLI, 2530 const DominatorTree *DT) { 2531 return ::SimplifySelectInst(Cond, TrueVal, FalseVal, Query (TD, TLI, DT), 2532 RecursionLimit); 2533 } 2534 2535 /// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can 2536 /// fold the result. If not, this returns null. 2537 static Value *SimplifyGEPInst(ArrayRef<Value *> Ops, const Query &Q, unsigned) { 2538 // The type of the GEP pointer operand. 2539 PointerType *PtrTy = dyn_cast<PointerType>(Ops[0]->getType()); 2540 // The GEP pointer operand is not a pointer, it's a vector of pointers. 2541 if (!PtrTy) 2542 return 0; 2543 2544 // getelementptr P -> P. 2545 if (Ops.size() == 1) 2546 return Ops[0]; 2547 2548 if (isa<UndefValue>(Ops[0])) { 2549 // Compute the (pointer) type returned by the GEP instruction. 2550 Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, Ops.slice(1)); 2551 Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace()); 2552 return UndefValue::get(GEPTy); 2553 } 2554 2555 if (Ops.size() == 2) { 2556 // getelementptr P, 0 -> P. 2557 if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1])) 2558 if (C->isZero()) 2559 return Ops[0]; 2560 // getelementptr P, N -> P if P points to a type of zero size. 2561 if (Q.TD) { 2562 Type *Ty = PtrTy->getElementType(); 2563 if (Ty->isSized() && Q.TD->getTypeAllocSize(Ty) == 0) 2564 return Ops[0]; 2565 } 2566 } 2567 2568 // Check to see if this is constant foldable. 2569 for (unsigned i = 0, e = Ops.size(); i != e; ++i) 2570 if (!isa<Constant>(Ops[i])) 2571 return 0; 2572 2573 return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]), Ops.slice(1)); 2574 } 2575 2576 Value *llvm::SimplifyGEPInst(ArrayRef<Value *> Ops, const TargetData *TD, 2577 const TargetLibraryInfo *TLI, 2578 const DominatorTree *DT) { 2579 return ::SimplifyGEPInst(Ops, Query (TD, TLI, DT), RecursionLimit); 2580 } 2581 2582 /// SimplifyInsertValueInst - Given operands for an InsertValueInst, see if we 2583 /// can fold the result. If not, this returns null. 2584 static Value *SimplifyInsertValueInst(Value *Agg, Value *Val, 2585 ArrayRef<unsigned> Idxs, const Query &Q, 2586 unsigned) { 2587 if (Constant *CAgg = dyn_cast<Constant>(Agg)) 2588 if (Constant *CVal = dyn_cast<Constant>(Val)) 2589 return ConstantFoldInsertValueInstruction(CAgg, CVal, Idxs); 2590 2591 // insertvalue x, undef, n -> x 2592 if (match(Val, m_Undef())) 2593 return Agg; 2594 2595 // insertvalue x, (extractvalue y, n), n 2596 if (ExtractValueInst *EV = dyn_cast<ExtractValueInst>(Val)) 2597 if (EV->getAggregateOperand()->getType() == Agg->getType() && 2598 EV->getIndices() == Idxs) { 2599 // insertvalue undef, (extractvalue y, n), n -> y 2600 if (match(Agg, m_Undef())) 2601 return EV->getAggregateOperand(); 2602 2603 // insertvalue y, (extractvalue y, n), n -> y 2604 if (Agg == EV->getAggregateOperand()) 2605 return Agg; 2606 } 2607 2608 return 0; 2609 } 2610 2611 Value *llvm::SimplifyInsertValueInst(Value *Agg, Value *Val, 2612 ArrayRef<unsigned> Idxs, 2613 const TargetData *TD, 2614 const TargetLibraryInfo *TLI, 2615 const DominatorTree *DT) { 2616 return ::SimplifyInsertValueInst(Agg, Val, Idxs, Query (TD, TLI, DT), 2617 RecursionLimit); 2618 } 2619 2620 /// SimplifyPHINode - See if we can fold the given phi. If not, returns null. 2621 static Value *SimplifyPHINode(PHINode *PN, const Query &Q) { 2622 // If all of the PHI's incoming values are the same then replace the PHI node 2623 // with the common value. 2624 Value *CommonValue = 0; 2625 bool HasUndefInput = false; 2626 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 2627 Value *Incoming = PN->getIncomingValue(i); 2628 // If the incoming value is the phi node itself, it can safely be skipped. 2629 if (Incoming == PN) continue; 2630 if (isa<UndefValue>(Incoming)) { 2631 // Remember that we saw an undef value, but otherwise ignore them. 2632 HasUndefInput = true; 2633 continue; 2634 } 2635 if (CommonValue && Incoming != CommonValue) 2636 return 0; // Not the same, bail out. 2637 CommonValue = Incoming; 2638 } 2639 2640 // If CommonValue is null then all of the incoming values were either undef or 2641 // equal to the phi node itself. 2642 if (!CommonValue) 2643 return UndefValue::get(PN->getType()); 2644 2645 // If we have a PHI node like phi(X, undef, X), where X is defined by some 2646 // instruction, we cannot return X as the result of the PHI node unless it 2647 // dominates the PHI block. 2648 if (HasUndefInput) 2649 return ValueDominatesPHI(CommonValue, PN, Q.DT) ? CommonValue : 0; 2650 2651 return CommonValue; 2652 } 2653 2654 static Value *SimplifyTruncInst(Value *Op, Type *Ty, const Query &Q, unsigned) { 2655 if (Constant *C = dyn_cast<Constant>(Op)) 2656 return ConstantFoldInstOperands(Instruction::Trunc, Ty, C, Q.TD, Q.TLI); 2657 2658 return 0; 2659 } 2660 2661 Value *llvm::SimplifyTruncInst(Value *Op, Type *Ty, const TargetData *TD, 2662 const TargetLibraryInfo *TLI, 2663 const DominatorTree *DT) { 2664 return ::SimplifyTruncInst(Op, Ty, Query (TD, TLI, DT), RecursionLimit); 2665 } 2666 2667 //=== Helper functions for higher up the class hierarchy. 2668 2669 /// SimplifyBinOp - Given operands for a BinaryOperator, see if we can 2670 /// fold the result. If not, this returns null. 2671 static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 2672 const Query &Q, unsigned MaxRecurse) { 2673 switch (Opcode) { 2674 case Instruction::Add: 2675 return SimplifyAddInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2676 Q, MaxRecurse); 2677 case Instruction::Sub: 2678 return SimplifySubInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2679 Q, MaxRecurse); 2680 case Instruction::Mul: return SimplifyMulInst (LHS, RHS, Q, MaxRecurse); 2681 case Instruction::SDiv: return SimplifySDivInst(LHS, RHS, Q, MaxRecurse); 2682 case Instruction::UDiv: return SimplifyUDivInst(LHS, RHS, Q, MaxRecurse); 2683 case Instruction::FDiv: return SimplifyFDivInst(LHS, RHS, Q, MaxRecurse); 2684 case Instruction::SRem: return SimplifySRemInst(LHS, RHS, Q, MaxRecurse); 2685 case Instruction::URem: return SimplifyURemInst(LHS, RHS, Q, MaxRecurse); 2686 case Instruction::FRem: return SimplifyFRemInst(LHS, RHS, Q, MaxRecurse); 2687 case Instruction::Shl: 2688 return SimplifyShlInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2689 Q, MaxRecurse); 2690 case Instruction::LShr: 2691 return SimplifyLShrInst(LHS, RHS, /*isExact*/false, Q, MaxRecurse); 2692 case Instruction::AShr: 2693 return SimplifyAShrInst(LHS, RHS, /*isExact*/false, Q, MaxRecurse); 2694 case Instruction::And: return SimplifyAndInst(LHS, RHS, Q, MaxRecurse); 2695 case Instruction::Or: return SimplifyOrInst (LHS, RHS, Q, MaxRecurse); 2696 case Instruction::Xor: return SimplifyXorInst(LHS, RHS, Q, MaxRecurse); 2697 default: 2698 if (Constant *CLHS = dyn_cast<Constant>(LHS)) 2699 if (Constant *CRHS = dyn_cast<Constant>(RHS)) { 2700 Constant *COps[] = {CLHS, CRHS}; 2701 return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, Q.TD, 2702 Q.TLI); 2703 } 2704 2705 // If the operation is associative, try some generic simplifications. 2706 if (Instruction::isAssociative(Opcode)) 2707 if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, Q, MaxRecurse)) 2708 return V; 2709 2710 // If the operation is with the result of a select instruction check whether 2711 // operating on either branch of the select always yields the same value. 2712 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 2713 if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, Q, MaxRecurse)) 2714 return V; 2715 2716 // If the operation is with the result of a phi instruction, check whether 2717 // operating on all incoming values of the phi always yields the same value. 2718 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 2719 if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, Q, MaxRecurse)) 2720 return V; 2721 2722 return 0; 2723 } 2724 } 2725 2726 Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 2727 const TargetData *TD, const TargetLibraryInfo *TLI, 2728 const DominatorTree *DT) { 2729 return ::SimplifyBinOp(Opcode, LHS, RHS, Query (TD, TLI, DT), RecursionLimit); 2730 } 2731 2732 /// SimplifyCmpInst - Given operands for a CmpInst, see if we can 2733 /// fold the result. 2734 static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2735 const Query &Q, unsigned MaxRecurse) { 2736 if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate)) 2737 return SimplifyICmpInst(Predicate, LHS, RHS, Q, MaxRecurse); 2738 return SimplifyFCmpInst(Predicate, LHS, RHS, Q, MaxRecurse); 2739 } 2740 2741 Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2742 const TargetData *TD, const TargetLibraryInfo *TLI, 2743 const DominatorTree *DT) { 2744 return ::SimplifyCmpInst(Predicate, LHS, RHS, Query (TD, TLI, DT), 2745 RecursionLimit); 2746 } 2747 2748 static Value *SimplifyCallInst(CallInst *CI, const Query &) { 2749 // call undef -> undef 2750 if (isa<UndefValue>(CI->getCalledValue())) 2751 return UndefValue::get(CI->getType()); 2752 2753 return 0; 2754 } 2755 2756 /// SimplifyInstruction - See if we can compute a simplified version of this 2757 /// instruction. If not, this returns null. 2758 Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD, 2759 const TargetLibraryInfo *TLI, 2760 const DominatorTree *DT) { 2761 Value *Result; 2762 2763 switch (I->getOpcode()) { 2764 default: 2765 Result = ConstantFoldInstruction(I, TD, TLI); 2766 break; 2767 case Instruction::Add: 2768 Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1), 2769 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2770 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2771 TD, TLI, DT); 2772 break; 2773 case Instruction::Sub: 2774 Result = SimplifySubInst(I->getOperand(0), I->getOperand(1), 2775 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2776 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2777 TD, TLI, DT); 2778 break; 2779 case Instruction::Mul: 2780 Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2781 break; 2782 case Instruction::SDiv: 2783 Result = SimplifySDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2784 break; 2785 case Instruction::UDiv: 2786 Result = SimplifyUDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2787 break; 2788 case Instruction::FDiv: 2789 Result = SimplifyFDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2790 break; 2791 case Instruction::SRem: 2792 Result = SimplifySRemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2793 break; 2794 case Instruction::URem: 2795 Result = SimplifyURemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2796 break; 2797 case Instruction::FRem: 2798 Result = SimplifyFRemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2799 break; 2800 case Instruction::Shl: 2801 Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1), 2802 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2803 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2804 TD, TLI, DT); 2805 break; 2806 case Instruction::LShr: 2807 Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1), 2808 cast<BinaryOperator>(I)->isExact(), 2809 TD, TLI, DT); 2810 break; 2811 case Instruction::AShr: 2812 Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1), 2813 cast<BinaryOperator>(I)->isExact(), 2814 TD, TLI, DT); 2815 break; 2816 case Instruction::And: 2817 Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2818 break; 2819 case Instruction::Or: 2820 Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2821 break; 2822 case Instruction::Xor: 2823 Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2824 break; 2825 case Instruction::ICmp: 2826 Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(), 2827 I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2828 break; 2829 case Instruction::FCmp: 2830 Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(), 2831 I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2832 break; 2833 case Instruction::Select: 2834 Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1), 2835 I->getOperand(2), TD, TLI, DT); 2836 break; 2837 case Instruction::GetElementPtr: { 2838 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end()); 2839 Result = SimplifyGEPInst(Ops, TD, TLI, DT); 2840 break; 2841 } 2842 case Instruction::InsertValue: { 2843 InsertValueInst *IV = cast<InsertValueInst>(I); 2844 Result = SimplifyInsertValueInst(IV->getAggregateOperand(), 2845 IV->getInsertedValueOperand(), 2846 IV->getIndices(), TD, TLI, DT); 2847 break; 2848 } 2849 case Instruction::PHI: 2850 Result = SimplifyPHINode(cast<PHINode>(I), Query (TD, TLI, DT)); 2851 break; 2852 case Instruction::Call: 2853 Result = SimplifyCallInst(cast<CallInst>(I), Query (TD, TLI, DT)); 2854 break; 2855 case Instruction::Trunc: 2856 Result = SimplifyTruncInst(I->getOperand(0), I->getType(), TD, TLI, DT); 2857 break; 2858 } 2859 2860 /// If called on unreachable code, the above logic may report that the 2861 /// instruction simplified to itself. Make life easier for users by 2862 /// detecting that case here, returning a safe value instead. 2863 return Result == I ? UndefValue::get(I->getType()) : Result; 2864 } 2865 2866 /// \brief Implementation of recursive simplification through an instructions 2867 /// uses. 2868 /// 2869 /// This is the common implementation of the recursive simplification routines. 2870 /// If we have a pre-simplified value in 'SimpleV', that is forcibly used to 2871 /// replace the instruction 'I'. Otherwise, we simply add 'I' to the list of 2872 /// instructions to process and attempt to simplify it using 2873 /// InstructionSimplify. 2874 /// 2875 /// This routine returns 'true' only when *it* simplifies something. The passed 2876 /// in simplified value does not count toward this. 2877 static bool replaceAndRecursivelySimplifyImpl(Instruction *I, Value *SimpleV, 2878 const TargetData *TD, 2879 const TargetLibraryInfo *TLI, 2880 const DominatorTree *DT) { 2881 bool Simplified = false; 2882 SmallSetVector<Instruction *, 8> Worklist; 2883 2884 // If we have an explicit value to collapse to, do that round of the 2885 // simplification loop by hand initially. 2886 if (SimpleV) { 2887 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE; 2888 ++UI) 2889 if (*UI != I) 2890 Worklist.insert(cast<Instruction>(*UI)); 2891 2892 // Replace the instruction with its simplified value. 2893 I->replaceAllUsesWith(SimpleV); 2894 2895 // Gracefully handle edge cases where the instruction is not wired into any 2896 // parent block. 2897 if (I->getParent()) 2898 I->eraseFromParent(); 2899 } else { 2900 Worklist.insert(I); 2901 } 2902 2903 // Note that we must test the size on each iteration, the worklist can grow. 2904 for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) { 2905 I = Worklist[Idx]; 2906 2907 // See if this instruction simplifies. 2908 SimpleV = SimplifyInstruction(I, TD, TLI, DT); 2909 if (!SimpleV) 2910 continue; 2911 2912 Simplified = true; 2913 2914 // Stash away all the uses of the old instruction so we can check them for 2915 // recursive simplifications after a RAUW. This is cheaper than checking all 2916 // uses of To on the recursive step in most cases. 2917 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE; 2918 ++UI) 2919 Worklist.insert(cast<Instruction>(*UI)); 2920 2921 // Replace the instruction with its simplified value. 2922 I->replaceAllUsesWith(SimpleV); 2923 2924 // Gracefully handle edge cases where the instruction is not wired into any 2925 // parent block. 2926 if (I->getParent()) 2927 I->eraseFromParent(); 2928 } 2929 return Simplified; 2930 } 2931 2932 bool llvm::recursivelySimplifyInstruction(Instruction *I, 2933 const TargetData *TD, 2934 const TargetLibraryInfo *TLI, 2935 const DominatorTree *DT) { 2936 return replaceAndRecursivelySimplifyImpl(I, 0, TD, TLI, DT); 2937 } 2938 2939 bool llvm::replaceAndRecursivelySimplify(Instruction *I, Value *SimpleV, 2940 const TargetData *TD, 2941 const TargetLibraryInfo *TLI, 2942 const DominatorTree *DT) { 2943 assert(I != SimpleV && "replaceAndRecursivelySimplify(X,X) is not valid!"); 2944 assert(SimpleV && "Must provide a simplified value."); 2945 return replaceAndRecursivelySimplifyImpl(I, SimpleV, TD, TLI, DT); 2946 } 2947