InstructionSimplify.cpp revision 4f0dfbb454ea8110459e2d1ee5f92e74cb3e8a5c
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/DataLayout.h" 35using namespace llvm; 36using namespace llvm::PatternMatch; 37 38enum { RecursionLimit = 3 }; 39 40STATISTIC(NumExpand, "Number of expansions"); 41STATISTIC(NumFactor , "Number of factorizations"); 42STATISTIC(NumReassoc, "Number of reassociations"); 43 44struct Query { 45 const DataLayout *TD; 46 const TargetLibraryInfo *TLI; 47 const DominatorTree *DT; 48 49 Query(const DataLayout *td, const TargetLibraryInfo *tli, 50 const DominatorTree *dt) : TD(td), TLI(tli), DT(dt) {} 51}; 52 53static Value *SimplifyAndInst(Value *, Value *, const Query &, unsigned); 54static Value *SimplifyBinOp(unsigned, Value *, Value *, const Query &, 55 unsigned); 56static Value *SimplifyCmpInst(unsigned, Value *, Value *, const Query &, 57 unsigned); 58static Value *SimplifyOrInst(Value *, Value *, const Query &, unsigned); 59static Value *SimplifyXorInst(Value *, Value *, const Query &, unsigned); 60static 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. 64static 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. 72static 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"? 79static 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? 93static 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. 128static 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. 189static 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. 259static 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. 358static 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. 430static 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. 512static 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. 555static 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. 592static 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 653Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 654 const DataLayout *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. 667static bool accumulateGEPOffset(const DataLayout &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. 699static Constant *stripAndComputeConstantOffsets(const DataLayout &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. 734static Constant *computePointerDifference(const DataLayout &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. 757static 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 882Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 883 const DataLayout *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. 891static 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 954Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const DataLayout *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. 962static 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. 1034static 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 1042Value *llvm::SimplifySDivInst(Value *Op0, Value *Op1, const DataLayout *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. 1050static 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 1058Value *llvm::SimplifyUDivInst(Value *Op0, Value *Op1, const DataLayout *TD, 1059 const TargetLibraryInfo *TLI, 1060 const DominatorTree *DT) { 1061 return ::SimplifyUDivInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1062} 1063 1064static 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 1077Value *llvm::SimplifyFDivInst(Value *Op0, Value *Op1, const DataLayout *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. 1085static 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. 1139static 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 1147Value *llvm::SimplifySRemInst(Value *Op0, Value *Op1, const DataLayout *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. 1155static 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 1163Value *llvm::SimplifyURemInst(Value *Op0, Value *Op1, const DataLayout *TD, 1164 const TargetLibraryInfo *TLI, 1165 const DominatorTree *DT) { 1166 return ::SimplifyURemInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1167} 1168 1169static 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 1182Value *llvm::SimplifyFRemInst(Value *Op0, Value *Op1, const DataLayout *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. 1190static 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. 1234static 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 1250Value *llvm::SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 1251 const DataLayout *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. 1259static 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 1277Value *llvm::SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact, 1278 const DataLayout *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. 1287static 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 1309Value *llvm::SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact, 1310 const DataLayout *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. 1319static 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 1410Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const DataLayout *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. 1418static 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 1504Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const DataLayout *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. 1512static 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 1564Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const DataLayout *TD, 1565 const TargetLibraryInfo *TLI, 1566 const DominatorTree *DT) { 1567 return ::SimplifyXorInst(Op0, Op1, Query (TD, TLI, DT), RecursionLimit); 1568} 1569 1570static 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. 1577static 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 1594static Constant *computePointerICmp(const DataLayout &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. 1636static 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 or they belong to 1723 // different functions. The latter happens during inlining. 1724 if (Instruction *LHSInst = dyn_cast<Instruction>(LHSPtr)) 1725 if (Argument *RHSArg = dyn_cast<Argument>(RHSPtr)) 1726 if (LHSInst->getParent()->getParent() == RHSArg->getParent() && 1727 Pred == CmpInst::ICMP_EQ) 1728 return ConstantInt::get(ITy, false); 1729 } 1730 1731 // Assume that the constant null is on the right. 1732 if (llvm::isKnownNonNull(LHSPtr) && isa<ConstantPointerNull>(RHSPtr)) { 1733 if (Pred == CmpInst::ICMP_EQ) 1734 return ConstantInt::get(ITy, false); 1735 else if (Pred == CmpInst::ICMP_NE) 1736 return ConstantInt::get(ITy, true); 1737 } 1738 } else if (Argument *LHSArg = dyn_cast<Argument>(LHSPtr)) { 1739 RHSPtr = RHSPtr->stripInBoundsOffsets(); 1740 // An alloca can't be equal to an argument unless they come from separate 1741 // functions via inlining. 1742 if (AllocaInst *RHSInst = dyn_cast<AllocaInst>(RHSPtr)) { 1743 if (LHSArg->getParent() == RHSInst->getParent()->getParent()) { 1744 if (Pred == CmpInst::ICMP_EQ) 1745 return ConstantInt::get(ITy, false); 1746 else if (Pred == CmpInst::ICMP_NE) 1747 return ConstantInt::get(ITy, true); 1748 } 1749 } 1750 } 1751 1752 // If we are comparing with zero then try hard since this is a common case. 1753 if (match(RHS, m_Zero())) { 1754 bool LHSKnownNonNegative, LHSKnownNegative; 1755 switch (Pred) { 1756 default: llvm_unreachable("Unknown ICmp predicate!"); 1757 case ICmpInst::ICMP_ULT: 1758 return getFalse(ITy); 1759 case ICmpInst::ICMP_UGE: 1760 return getTrue(ITy); 1761 case ICmpInst::ICMP_EQ: 1762 case ICmpInst::ICMP_ULE: 1763 if (isKnownNonZero(LHS, Q.TD)) 1764 return getFalse(ITy); 1765 break; 1766 case ICmpInst::ICMP_NE: 1767 case ICmpInst::ICMP_UGT: 1768 if (isKnownNonZero(LHS, Q.TD)) 1769 return getTrue(ITy); 1770 break; 1771 case ICmpInst::ICMP_SLT: 1772 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.TD); 1773 if (LHSKnownNegative) 1774 return getTrue(ITy); 1775 if (LHSKnownNonNegative) 1776 return getFalse(ITy); 1777 break; 1778 case ICmpInst::ICMP_SLE: 1779 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.TD); 1780 if (LHSKnownNegative) 1781 return getTrue(ITy); 1782 if (LHSKnownNonNegative && isKnownNonZero(LHS, Q.TD)) 1783 return getFalse(ITy); 1784 break; 1785 case ICmpInst::ICMP_SGE: 1786 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.TD); 1787 if (LHSKnownNegative) 1788 return getFalse(ITy); 1789 if (LHSKnownNonNegative) 1790 return getTrue(ITy); 1791 break; 1792 case ICmpInst::ICMP_SGT: 1793 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.TD); 1794 if (LHSKnownNegative) 1795 return getFalse(ITy); 1796 if (LHSKnownNonNegative && isKnownNonZero(LHS, Q.TD)) 1797 return getTrue(ITy); 1798 break; 1799 } 1800 } 1801 1802 // See if we are doing a comparison with a constant integer. 1803 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1804 // Rule out tautological comparisons (eg., ult 0 or uge 0). 1805 ConstantRange RHS_CR = ICmpInst::makeConstantRange(Pred, CI->getValue()); 1806 if (RHS_CR.isEmptySet()) 1807 return ConstantInt::getFalse(CI->getContext()); 1808 if (RHS_CR.isFullSet()) 1809 return ConstantInt::getTrue(CI->getContext()); 1810 1811 // Many binary operators with constant RHS have easy to compute constant 1812 // range. Use them to check whether the comparison is a tautology. 1813 uint32_t Width = CI->getBitWidth(); 1814 APInt Lower = APInt(Width, 0); 1815 APInt Upper = APInt(Width, 0); 1816 ConstantInt *CI2; 1817 if (match(LHS, m_URem(m_Value(), m_ConstantInt(CI2)))) { 1818 // 'urem x, CI2' produces [0, CI2). 1819 Upper = CI2->getValue(); 1820 } else if (match(LHS, m_SRem(m_Value(), m_ConstantInt(CI2)))) { 1821 // 'srem x, CI2' produces (-|CI2|, |CI2|). 1822 Upper = CI2->getValue().abs(); 1823 Lower = (-Upper) + 1; 1824 } else if (match(LHS, m_UDiv(m_ConstantInt(CI2), m_Value()))) { 1825 // 'udiv CI2, x' produces [0, CI2]. 1826 Upper = CI2->getValue() + 1; 1827 } else if (match(LHS, m_UDiv(m_Value(), m_ConstantInt(CI2)))) { 1828 // 'udiv x, CI2' produces [0, UINT_MAX / CI2]. 1829 APInt NegOne = APInt::getAllOnesValue(Width); 1830 if (!CI2->isZero()) 1831 Upper = NegOne.udiv(CI2->getValue()) + 1; 1832 } else if (match(LHS, m_SDiv(m_Value(), m_ConstantInt(CI2)))) { 1833 // 'sdiv x, CI2' produces [INT_MIN / CI2, INT_MAX / CI2]. 1834 APInt IntMin = APInt::getSignedMinValue(Width); 1835 APInt IntMax = APInt::getSignedMaxValue(Width); 1836 APInt Val = CI2->getValue().abs(); 1837 if (!Val.isMinValue()) { 1838 Lower = IntMin.sdiv(Val); 1839 Upper = IntMax.sdiv(Val) + 1; 1840 } 1841 } else if (match(LHS, m_LShr(m_Value(), m_ConstantInt(CI2)))) { 1842 // 'lshr x, CI2' produces [0, UINT_MAX >> CI2]. 1843 APInt NegOne = APInt::getAllOnesValue(Width); 1844 if (CI2->getValue().ult(Width)) 1845 Upper = NegOne.lshr(CI2->getValue()) + 1; 1846 } else if (match(LHS, m_AShr(m_Value(), m_ConstantInt(CI2)))) { 1847 // 'ashr x, CI2' produces [INT_MIN >> CI2, INT_MAX >> CI2]. 1848 APInt IntMin = APInt::getSignedMinValue(Width); 1849 APInt IntMax = APInt::getSignedMaxValue(Width); 1850 if (CI2->getValue().ult(Width)) { 1851 Lower = IntMin.ashr(CI2->getValue()); 1852 Upper = IntMax.ashr(CI2->getValue()) + 1; 1853 } 1854 } else if (match(LHS, m_Or(m_Value(), m_ConstantInt(CI2)))) { 1855 // 'or x, CI2' produces [CI2, UINT_MAX]. 1856 Lower = CI2->getValue(); 1857 } else if (match(LHS, m_And(m_Value(), m_ConstantInt(CI2)))) { 1858 // 'and x, CI2' produces [0, CI2]. 1859 Upper = CI2->getValue() + 1; 1860 } 1861 if (Lower != Upper) { 1862 ConstantRange LHS_CR = ConstantRange(Lower, Upper); 1863 if (RHS_CR.contains(LHS_CR)) 1864 return ConstantInt::getTrue(RHS->getContext()); 1865 if (RHS_CR.inverse().contains(LHS_CR)) 1866 return ConstantInt::getFalse(RHS->getContext()); 1867 } 1868 } 1869 1870 // Compare of cast, for example (zext X) != 0 -> X != 0 1871 if (isa<CastInst>(LHS) && (isa<Constant>(RHS) || isa<CastInst>(RHS))) { 1872 Instruction *LI = cast<CastInst>(LHS); 1873 Value *SrcOp = LI->getOperand(0); 1874 Type *SrcTy = SrcOp->getType(); 1875 Type *DstTy = LI->getType(); 1876 1877 // Turn icmp (ptrtoint x), (ptrtoint/constant) into a compare of the input 1878 // if the integer type is the same size as the pointer type. 1879 if (MaxRecurse && Q.TD && isa<PtrToIntInst>(LI) && 1880 Q.TD->getPointerSizeInBits() == DstTy->getPrimitiveSizeInBits()) { 1881 if (Constant *RHSC = dyn_cast<Constant>(RHS)) { 1882 // Transfer the cast to the constant. 1883 if (Value *V = SimplifyICmpInst(Pred, SrcOp, 1884 ConstantExpr::getIntToPtr(RHSC, SrcTy), 1885 Q, MaxRecurse-1)) 1886 return V; 1887 } else if (PtrToIntInst *RI = dyn_cast<PtrToIntInst>(RHS)) { 1888 if (RI->getOperand(0)->getType() == SrcTy) 1889 // Compare without the cast. 1890 if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), 1891 Q, MaxRecurse-1)) 1892 return V; 1893 } 1894 } 1895 1896 if (isa<ZExtInst>(LHS)) { 1897 // Turn icmp (zext X), (zext Y) into a compare of X and Y if they have the 1898 // same type. 1899 if (ZExtInst *RI = dyn_cast<ZExtInst>(RHS)) { 1900 if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) 1901 // Compare X and Y. Note that signed predicates become unsigned. 1902 if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), 1903 SrcOp, RI->getOperand(0), Q, 1904 MaxRecurse-1)) 1905 return V; 1906 } 1907 // Turn icmp (zext X), Cst into a compare of X and Cst if Cst is extended 1908 // too. If not, then try to deduce the result of the comparison. 1909 else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1910 // Compute the constant that would happen if we truncated to SrcTy then 1911 // reextended to DstTy. 1912 Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); 1913 Constant *RExt = ConstantExpr::getCast(CastInst::ZExt, Trunc, DstTy); 1914 1915 // If the re-extended constant didn't change then this is effectively 1916 // also a case of comparing two zero-extended values. 1917 if (RExt == CI && MaxRecurse) 1918 if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), 1919 SrcOp, Trunc, Q, MaxRecurse-1)) 1920 return V; 1921 1922 // Otherwise the upper bits of LHS are zero while RHS has a non-zero bit 1923 // there. Use this to work out the result of the comparison. 1924 if (RExt != CI) { 1925 switch (Pred) { 1926 default: llvm_unreachable("Unknown ICmp predicate!"); 1927 // LHS <u RHS. 1928 case ICmpInst::ICMP_EQ: 1929 case ICmpInst::ICMP_UGT: 1930 case ICmpInst::ICMP_UGE: 1931 return ConstantInt::getFalse(CI->getContext()); 1932 1933 case ICmpInst::ICMP_NE: 1934 case ICmpInst::ICMP_ULT: 1935 case ICmpInst::ICMP_ULE: 1936 return ConstantInt::getTrue(CI->getContext()); 1937 1938 // LHS is non-negative. If RHS is negative then LHS >s LHS. If RHS 1939 // is non-negative then LHS <s RHS. 1940 case ICmpInst::ICMP_SGT: 1941 case ICmpInst::ICMP_SGE: 1942 return CI->getValue().isNegative() ? 1943 ConstantInt::getTrue(CI->getContext()) : 1944 ConstantInt::getFalse(CI->getContext()); 1945 1946 case ICmpInst::ICMP_SLT: 1947 case ICmpInst::ICMP_SLE: 1948 return CI->getValue().isNegative() ? 1949 ConstantInt::getFalse(CI->getContext()) : 1950 ConstantInt::getTrue(CI->getContext()); 1951 } 1952 } 1953 } 1954 } 1955 1956 if (isa<SExtInst>(LHS)) { 1957 // Turn icmp (sext X), (sext Y) into a compare of X and Y if they have the 1958 // same type. 1959 if (SExtInst *RI = dyn_cast<SExtInst>(RHS)) { 1960 if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) 1961 // Compare X and Y. Note that the predicate does not change. 1962 if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), 1963 Q, MaxRecurse-1)) 1964 return V; 1965 } 1966 // Turn icmp (sext X), Cst into a compare of X and Cst if Cst is extended 1967 // too. If not, then try to deduce the result of the comparison. 1968 else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1969 // Compute the constant that would happen if we truncated to SrcTy then 1970 // reextended to DstTy. 1971 Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); 1972 Constant *RExt = ConstantExpr::getCast(CastInst::SExt, Trunc, DstTy); 1973 1974 // If the re-extended constant didn't change then this is effectively 1975 // also a case of comparing two sign-extended values. 1976 if (RExt == CI && MaxRecurse) 1977 if (Value *V = SimplifyICmpInst(Pred, SrcOp, Trunc, Q, MaxRecurse-1)) 1978 return V; 1979 1980 // Otherwise the upper bits of LHS are all equal, while RHS has varying 1981 // bits there. Use this to work out the result of the comparison. 1982 if (RExt != CI) { 1983 switch (Pred) { 1984 default: llvm_unreachable("Unknown ICmp predicate!"); 1985 case ICmpInst::ICMP_EQ: 1986 return ConstantInt::getFalse(CI->getContext()); 1987 case ICmpInst::ICMP_NE: 1988 return ConstantInt::getTrue(CI->getContext()); 1989 1990 // If RHS is non-negative then LHS <s RHS. If RHS is negative then 1991 // LHS >s RHS. 1992 case ICmpInst::ICMP_SGT: 1993 case ICmpInst::ICMP_SGE: 1994 return CI->getValue().isNegative() ? 1995 ConstantInt::getTrue(CI->getContext()) : 1996 ConstantInt::getFalse(CI->getContext()); 1997 case ICmpInst::ICMP_SLT: 1998 case ICmpInst::ICMP_SLE: 1999 return CI->getValue().isNegative() ? 2000 ConstantInt::getFalse(CI->getContext()) : 2001 ConstantInt::getTrue(CI->getContext()); 2002 2003 // If LHS is non-negative then LHS <u RHS. If LHS is negative then 2004 // LHS >u RHS. 2005 case ICmpInst::ICMP_UGT: 2006 case ICmpInst::ICMP_UGE: 2007 // Comparison is true iff the LHS <s 0. 2008 if (MaxRecurse) 2009 if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SLT, SrcOp, 2010 Constant::getNullValue(SrcTy), 2011 Q, MaxRecurse-1)) 2012 return V; 2013 break; 2014 case ICmpInst::ICMP_ULT: 2015 case ICmpInst::ICMP_ULE: 2016 // Comparison is true iff the LHS >=s 0. 2017 if (MaxRecurse) 2018 if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SGE, SrcOp, 2019 Constant::getNullValue(SrcTy), 2020 Q, MaxRecurse-1)) 2021 return V; 2022 break; 2023 } 2024 } 2025 } 2026 } 2027 } 2028 2029 // Special logic for binary operators. 2030 BinaryOperator *LBO = dyn_cast<BinaryOperator>(LHS); 2031 BinaryOperator *RBO = dyn_cast<BinaryOperator>(RHS); 2032 if (MaxRecurse && (LBO || RBO)) { 2033 // Analyze the case when either LHS or RHS is an add instruction. 2034 Value *A = 0, *B = 0, *C = 0, *D = 0; 2035 // LHS = A + B (or A and B are null); RHS = C + D (or C and D are null). 2036 bool NoLHSWrapProblem = false, NoRHSWrapProblem = false; 2037 if (LBO && LBO->getOpcode() == Instruction::Add) { 2038 A = LBO->getOperand(0); B = LBO->getOperand(1); 2039 NoLHSWrapProblem = ICmpInst::isEquality(Pred) || 2040 (CmpInst::isUnsigned(Pred) && LBO->hasNoUnsignedWrap()) || 2041 (CmpInst::isSigned(Pred) && LBO->hasNoSignedWrap()); 2042 } 2043 if (RBO && RBO->getOpcode() == Instruction::Add) { 2044 C = RBO->getOperand(0); D = RBO->getOperand(1); 2045 NoRHSWrapProblem = ICmpInst::isEquality(Pred) || 2046 (CmpInst::isUnsigned(Pred) && RBO->hasNoUnsignedWrap()) || 2047 (CmpInst::isSigned(Pred) && RBO->hasNoSignedWrap()); 2048 } 2049 2050 // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow. 2051 if ((A == RHS || B == RHS) && NoLHSWrapProblem) 2052 if (Value *V = SimplifyICmpInst(Pred, A == RHS ? B : A, 2053 Constant::getNullValue(RHS->getType()), 2054 Q, MaxRecurse-1)) 2055 return V; 2056 2057 // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow. 2058 if ((C == LHS || D == LHS) && NoRHSWrapProblem) 2059 if (Value *V = SimplifyICmpInst(Pred, 2060 Constant::getNullValue(LHS->getType()), 2061 C == LHS ? D : C, Q, MaxRecurse-1)) 2062 return V; 2063 2064 // icmp (X+Y), (X+Z) -> icmp Y,Z for equalities or if there is no overflow. 2065 if (A && C && (A == C || A == D || B == C || B == D) && 2066 NoLHSWrapProblem && NoRHSWrapProblem) { 2067 // Determine Y and Z in the form icmp (X+Y), (X+Z). 2068 Value *Y, *Z; 2069 if (A == C) { 2070 // C + B == C + D -> B == D 2071 Y = B; 2072 Z = D; 2073 } else if (A == D) { 2074 // D + B == C + D -> B == C 2075 Y = B; 2076 Z = C; 2077 } else if (B == C) { 2078 // A + C == C + D -> A == D 2079 Y = A; 2080 Z = D; 2081 } else { 2082 assert(B == D); 2083 // A + D == C + D -> A == C 2084 Y = A; 2085 Z = C; 2086 } 2087 if (Value *V = SimplifyICmpInst(Pred, Y, Z, Q, MaxRecurse-1)) 2088 return V; 2089 } 2090 } 2091 2092 if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) { 2093 bool KnownNonNegative, KnownNegative; 2094 switch (Pred) { 2095 default: 2096 break; 2097 case ICmpInst::ICMP_SGT: 2098 case ICmpInst::ICMP_SGE: 2099 ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.TD); 2100 if (!KnownNonNegative) 2101 break; 2102 // fall-through 2103 case ICmpInst::ICMP_EQ: 2104 case ICmpInst::ICMP_UGT: 2105 case ICmpInst::ICMP_UGE: 2106 return getFalse(ITy); 2107 case ICmpInst::ICMP_SLT: 2108 case ICmpInst::ICMP_SLE: 2109 ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.TD); 2110 if (!KnownNonNegative) 2111 break; 2112 // fall-through 2113 case ICmpInst::ICMP_NE: 2114 case ICmpInst::ICMP_ULT: 2115 case ICmpInst::ICMP_ULE: 2116 return getTrue(ITy); 2117 } 2118 } 2119 if (RBO && match(RBO, m_URem(m_Value(), m_Specific(LHS)))) { 2120 bool KnownNonNegative, KnownNegative; 2121 switch (Pred) { 2122 default: 2123 break; 2124 case ICmpInst::ICMP_SGT: 2125 case ICmpInst::ICMP_SGE: 2126 ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.TD); 2127 if (!KnownNonNegative) 2128 break; 2129 // fall-through 2130 case ICmpInst::ICMP_NE: 2131 case ICmpInst::ICMP_UGT: 2132 case ICmpInst::ICMP_UGE: 2133 return getTrue(ITy); 2134 case ICmpInst::ICMP_SLT: 2135 case ICmpInst::ICMP_SLE: 2136 ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.TD); 2137 if (!KnownNonNegative) 2138 break; 2139 // fall-through 2140 case ICmpInst::ICMP_EQ: 2141 case ICmpInst::ICMP_ULT: 2142 case ICmpInst::ICMP_ULE: 2143 return getFalse(ITy); 2144 } 2145 } 2146 2147 // x udiv y <=u x. 2148 if (LBO && match(LBO, m_UDiv(m_Specific(RHS), m_Value()))) { 2149 // icmp pred (X /u Y), X 2150 if (Pred == ICmpInst::ICMP_UGT) 2151 return getFalse(ITy); 2152 if (Pred == ICmpInst::ICMP_ULE) 2153 return getTrue(ITy); 2154 } 2155 2156 if (MaxRecurse && LBO && RBO && LBO->getOpcode() == RBO->getOpcode() && 2157 LBO->getOperand(1) == RBO->getOperand(1)) { 2158 switch (LBO->getOpcode()) { 2159 default: break; 2160 case Instruction::UDiv: 2161 case Instruction::LShr: 2162 if (ICmpInst::isSigned(Pred)) 2163 break; 2164 // fall-through 2165 case Instruction::SDiv: 2166 case Instruction::AShr: 2167 if (!LBO->isExact() || !RBO->isExact()) 2168 break; 2169 if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0), 2170 RBO->getOperand(0), Q, MaxRecurse-1)) 2171 return V; 2172 break; 2173 case Instruction::Shl: { 2174 bool NUW = LBO->hasNoUnsignedWrap() && RBO->hasNoUnsignedWrap(); 2175 bool NSW = LBO->hasNoSignedWrap() && RBO->hasNoSignedWrap(); 2176 if (!NUW && !NSW) 2177 break; 2178 if (!NSW && ICmpInst::isSigned(Pred)) 2179 break; 2180 if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0), 2181 RBO->getOperand(0), Q, MaxRecurse-1)) 2182 return V; 2183 break; 2184 } 2185 } 2186 } 2187 2188 // Simplify comparisons involving max/min. 2189 Value *A, *B; 2190 CmpInst::Predicate P = CmpInst::BAD_ICMP_PREDICATE; 2191 CmpInst::Predicate EqP; // Chosen so that "A == max/min(A,B)" iff "A EqP B". 2192 2193 // Signed variants on "max(a,b)>=a -> true". 2194 if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) { 2195 if (A != RHS) std::swap(A, B); // smax(A, B) pred A. 2196 EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B". 2197 // We analyze this as smax(A, B) pred A. 2198 P = Pred; 2199 } else if (match(RHS, m_SMax(m_Value(A), m_Value(B))) && 2200 (A == LHS || B == LHS)) { 2201 if (A != LHS) std::swap(A, B); // A pred smax(A, B). 2202 EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B". 2203 // We analyze this as smax(A, B) swapped-pred A. 2204 P = CmpInst::getSwappedPredicate(Pred); 2205 } else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) && 2206 (A == RHS || B == RHS)) { 2207 if (A != RHS) std::swap(A, B); // smin(A, B) pred A. 2208 EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B". 2209 // We analyze this as smax(-A, -B) swapped-pred -A. 2210 // Note that we do not need to actually form -A or -B thanks to EqP. 2211 P = CmpInst::getSwappedPredicate(Pred); 2212 } else if (match(RHS, m_SMin(m_Value(A), m_Value(B))) && 2213 (A == LHS || B == LHS)) { 2214 if (A != LHS) std::swap(A, B); // A pred smin(A, B). 2215 EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B". 2216 // We analyze this as smax(-A, -B) pred -A. 2217 // Note that we do not need to actually form -A or -B thanks to EqP. 2218 P = Pred; 2219 } 2220 if (P != CmpInst::BAD_ICMP_PREDICATE) { 2221 // Cases correspond to "max(A, B) p A". 2222 switch (P) { 2223 default: 2224 break; 2225 case CmpInst::ICMP_EQ: 2226 case CmpInst::ICMP_SLE: 2227 // Equivalent to "A EqP B". This may be the same as the condition tested 2228 // in the max/min; if so, we can just return that. 2229 if (Value *V = ExtractEquivalentCondition(LHS, EqP, A, B)) 2230 return V; 2231 if (Value *V = ExtractEquivalentCondition(RHS, EqP, A, B)) 2232 return V; 2233 // Otherwise, see if "A EqP B" simplifies. 2234 if (MaxRecurse) 2235 if (Value *V = SimplifyICmpInst(EqP, A, B, Q, MaxRecurse-1)) 2236 return V; 2237 break; 2238 case CmpInst::ICMP_NE: 2239 case CmpInst::ICMP_SGT: { 2240 CmpInst::Predicate InvEqP = CmpInst::getInversePredicate(EqP); 2241 // Equivalent to "A InvEqP B". This may be the same as the condition 2242 // tested in the max/min; if so, we can just return that. 2243 if (Value *V = ExtractEquivalentCondition(LHS, InvEqP, A, B)) 2244 return V; 2245 if (Value *V = ExtractEquivalentCondition(RHS, InvEqP, A, B)) 2246 return V; 2247 // Otherwise, see if "A InvEqP B" simplifies. 2248 if (MaxRecurse) 2249 if (Value *V = SimplifyICmpInst(InvEqP, A, B, Q, MaxRecurse-1)) 2250 return V; 2251 break; 2252 } 2253 case CmpInst::ICMP_SGE: 2254 // Always true. 2255 return getTrue(ITy); 2256 case CmpInst::ICMP_SLT: 2257 // Always false. 2258 return getFalse(ITy); 2259 } 2260 } 2261 2262 // Unsigned variants on "max(a,b)>=a -> true". 2263 P = CmpInst::BAD_ICMP_PREDICATE; 2264 if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) { 2265 if (A != RHS) std::swap(A, B); // umax(A, B) pred A. 2266 EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B". 2267 // We analyze this as umax(A, B) pred A. 2268 P = Pred; 2269 } else if (match(RHS, m_UMax(m_Value(A), m_Value(B))) && 2270 (A == LHS || B == LHS)) { 2271 if (A != LHS) std::swap(A, B); // A pred umax(A, B). 2272 EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B". 2273 // We analyze this as umax(A, B) swapped-pred A. 2274 P = CmpInst::getSwappedPredicate(Pred); 2275 } else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) && 2276 (A == RHS || B == RHS)) { 2277 if (A != RHS) std::swap(A, B); // umin(A, B) pred A. 2278 EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B". 2279 // We analyze this as umax(-A, -B) swapped-pred -A. 2280 // Note that we do not need to actually form -A or -B thanks to EqP. 2281 P = CmpInst::getSwappedPredicate(Pred); 2282 } else if (match(RHS, m_UMin(m_Value(A), m_Value(B))) && 2283 (A == LHS || B == LHS)) { 2284 if (A != LHS) std::swap(A, B); // A pred umin(A, B). 2285 EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B". 2286 // We analyze this as umax(-A, -B) pred -A. 2287 // Note that we do not need to actually form -A or -B thanks to EqP. 2288 P = Pred; 2289 } 2290 if (P != CmpInst::BAD_ICMP_PREDICATE) { 2291 // Cases correspond to "max(A, B) p A". 2292 switch (P) { 2293 default: 2294 break; 2295 case CmpInst::ICMP_EQ: 2296 case CmpInst::ICMP_ULE: 2297 // Equivalent to "A EqP B". This may be the same as the condition tested 2298 // in the max/min; if so, we can just return that. 2299 if (Value *V = ExtractEquivalentCondition(LHS, EqP, A, B)) 2300 return V; 2301 if (Value *V = ExtractEquivalentCondition(RHS, EqP, A, B)) 2302 return V; 2303 // Otherwise, see if "A EqP B" simplifies. 2304 if (MaxRecurse) 2305 if (Value *V = SimplifyICmpInst(EqP, A, B, Q, MaxRecurse-1)) 2306 return V; 2307 break; 2308 case CmpInst::ICMP_NE: 2309 case CmpInst::ICMP_UGT: { 2310 CmpInst::Predicate InvEqP = CmpInst::getInversePredicate(EqP); 2311 // Equivalent to "A InvEqP B". This may be the same as the condition 2312 // tested in the max/min; if so, we can just return that. 2313 if (Value *V = ExtractEquivalentCondition(LHS, InvEqP, A, B)) 2314 return V; 2315 if (Value *V = ExtractEquivalentCondition(RHS, InvEqP, A, B)) 2316 return V; 2317 // Otherwise, see if "A InvEqP B" simplifies. 2318 if (MaxRecurse) 2319 if (Value *V = SimplifyICmpInst(InvEqP, A, B, Q, MaxRecurse-1)) 2320 return V; 2321 break; 2322 } 2323 case CmpInst::ICMP_UGE: 2324 // Always true. 2325 return getTrue(ITy); 2326 case CmpInst::ICMP_ULT: 2327 // Always false. 2328 return getFalse(ITy); 2329 } 2330 } 2331 2332 // Variants on "max(x,y) >= min(x,z)". 2333 Value *C, *D; 2334 if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && 2335 match(RHS, m_SMin(m_Value(C), m_Value(D))) && 2336 (A == C || A == D || B == C || B == D)) { 2337 // max(x, ?) pred min(x, ?). 2338 if (Pred == CmpInst::ICMP_SGE) 2339 // Always true. 2340 return getTrue(ITy); 2341 if (Pred == CmpInst::ICMP_SLT) 2342 // Always false. 2343 return getFalse(ITy); 2344 } else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) && 2345 match(RHS, m_SMax(m_Value(C), m_Value(D))) && 2346 (A == C || A == D || B == C || B == D)) { 2347 // min(x, ?) pred max(x, ?). 2348 if (Pred == CmpInst::ICMP_SLE) 2349 // Always true. 2350 return getTrue(ITy); 2351 if (Pred == CmpInst::ICMP_SGT) 2352 // Always false. 2353 return getFalse(ITy); 2354 } else if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && 2355 match(RHS, m_UMin(m_Value(C), m_Value(D))) && 2356 (A == C || A == D || B == C || B == D)) { 2357 // max(x, ?) pred min(x, ?). 2358 if (Pred == CmpInst::ICMP_UGE) 2359 // Always true. 2360 return getTrue(ITy); 2361 if (Pred == CmpInst::ICMP_ULT) 2362 // Always false. 2363 return getFalse(ITy); 2364 } else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) && 2365 match(RHS, m_UMax(m_Value(C), m_Value(D))) && 2366 (A == C || A == D || B == C || B == D)) { 2367 // min(x, ?) pred max(x, ?). 2368 if (Pred == CmpInst::ICMP_ULE) 2369 // Always true. 2370 return getTrue(ITy); 2371 if (Pred == CmpInst::ICMP_UGT) 2372 // Always false. 2373 return getFalse(ITy); 2374 } 2375 2376 // Simplify comparisons of related pointers using a powerful, recursive 2377 // GEP-walk when we have target data available.. 2378 if (Q.TD && LHS->getType()->isPointerTy() && RHS->getType()->isPointerTy()) 2379 if (Constant *C = computePointerICmp(*Q.TD, Pred, LHS, RHS)) 2380 return C; 2381 2382 if (GetElementPtrInst *GLHS = dyn_cast<GetElementPtrInst>(LHS)) { 2383 if (GEPOperator *GRHS = dyn_cast<GEPOperator>(RHS)) { 2384 if (GLHS->getPointerOperand() == GRHS->getPointerOperand() && 2385 GLHS->hasAllConstantIndices() && GRHS->hasAllConstantIndices() && 2386 (ICmpInst::isEquality(Pred) || 2387 (GLHS->isInBounds() && GRHS->isInBounds() && 2388 Pred == ICmpInst::getSignedPredicate(Pred)))) { 2389 // The bases are equal and the indices are constant. Build a constant 2390 // expression GEP with the same indices and a null base pointer to see 2391 // what constant folding can make out of it. 2392 Constant *Null = Constant::getNullValue(GLHS->getPointerOperandType()); 2393 SmallVector<Value *, 4> IndicesLHS(GLHS->idx_begin(), GLHS->idx_end()); 2394 Constant *NewLHS = ConstantExpr::getGetElementPtr(Null, IndicesLHS); 2395 2396 SmallVector<Value *, 4> IndicesRHS(GRHS->idx_begin(), GRHS->idx_end()); 2397 Constant *NewRHS = ConstantExpr::getGetElementPtr(Null, IndicesRHS); 2398 return ConstantExpr::getICmp(Pred, NewLHS, NewRHS); 2399 } 2400 } 2401 } 2402 2403 // If the comparison is with the result of a select instruction, check whether 2404 // comparing with either branch of the select always yields the same value. 2405 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 2406 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, Q, MaxRecurse)) 2407 return V; 2408 2409 // If the comparison is with the result of a phi instruction, check whether 2410 // doing the compare with each incoming phi value yields a common result. 2411 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 2412 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, Q, MaxRecurse)) 2413 return V; 2414 2415 return 0; 2416} 2417 2418Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2419 const DataLayout *TD, 2420 const TargetLibraryInfo *TLI, 2421 const DominatorTree *DT) { 2422 return ::SimplifyICmpInst(Predicate, LHS, RHS, Query (TD, TLI, DT), 2423 RecursionLimit); 2424} 2425 2426/// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can 2427/// fold the result. If not, this returns null. 2428static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2429 const Query &Q, unsigned MaxRecurse) { 2430 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 2431 assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!"); 2432 2433 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 2434 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 2435 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, Q.TD, Q.TLI); 2436 2437 // If we have a constant, make sure it is on the RHS. 2438 std::swap(LHS, RHS); 2439 Pred = CmpInst::getSwappedPredicate(Pred); 2440 } 2441 2442 // Fold trivial predicates. 2443 if (Pred == FCmpInst::FCMP_FALSE) 2444 return ConstantInt::get(GetCompareTy(LHS), 0); 2445 if (Pred == FCmpInst::FCMP_TRUE) 2446 return ConstantInt::get(GetCompareTy(LHS), 1); 2447 2448 if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef 2449 return UndefValue::get(GetCompareTy(LHS)); 2450 2451 // fcmp x,x -> true/false. Not all compares are foldable. 2452 if (LHS == RHS) { 2453 if (CmpInst::isTrueWhenEqual(Pred)) 2454 return ConstantInt::get(GetCompareTy(LHS), 1); 2455 if (CmpInst::isFalseWhenEqual(Pred)) 2456 return ConstantInt::get(GetCompareTy(LHS), 0); 2457 } 2458 2459 // Handle fcmp with constant RHS 2460 if (Constant *RHSC = dyn_cast<Constant>(RHS)) { 2461 // If the constant is a nan, see if we can fold the comparison based on it. 2462 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) { 2463 if (CFP->getValueAPF().isNaN()) { 2464 if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo" 2465 return ConstantInt::getFalse(CFP->getContext()); 2466 assert(FCmpInst::isUnordered(Pred) && 2467 "Comparison must be either ordered or unordered!"); 2468 // True if unordered. 2469 return ConstantInt::getTrue(CFP->getContext()); 2470 } 2471 // Check whether the constant is an infinity. 2472 if (CFP->getValueAPF().isInfinity()) { 2473 if (CFP->getValueAPF().isNegative()) { 2474 switch (Pred) { 2475 case FCmpInst::FCMP_OLT: 2476 // No value is ordered and less than negative infinity. 2477 return ConstantInt::getFalse(CFP->getContext()); 2478 case FCmpInst::FCMP_UGE: 2479 // All values are unordered with or at least negative infinity. 2480 return ConstantInt::getTrue(CFP->getContext()); 2481 default: 2482 break; 2483 } 2484 } else { 2485 switch (Pred) { 2486 case FCmpInst::FCMP_OGT: 2487 // No value is ordered and greater than infinity. 2488 return ConstantInt::getFalse(CFP->getContext()); 2489 case FCmpInst::FCMP_ULE: 2490 // All values are unordered with and at most infinity. 2491 return ConstantInt::getTrue(CFP->getContext()); 2492 default: 2493 break; 2494 } 2495 } 2496 } 2497 } 2498 } 2499 2500 // If the comparison is with the result of a select instruction, check whether 2501 // comparing with either branch of the select always yields the same value. 2502 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 2503 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, Q, MaxRecurse)) 2504 return V; 2505 2506 // If the comparison is with the result of a phi instruction, check whether 2507 // doing the compare with each incoming phi value yields a common result. 2508 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 2509 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, Q, MaxRecurse)) 2510 return V; 2511 2512 return 0; 2513} 2514 2515Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2516 const DataLayout *TD, 2517 const TargetLibraryInfo *TLI, 2518 const DominatorTree *DT) { 2519 return ::SimplifyFCmpInst(Predicate, LHS, RHS, Query (TD, TLI, DT), 2520 RecursionLimit); 2521} 2522 2523/// SimplifySelectInst - Given operands for a SelectInst, see if we can fold 2524/// the result. If not, this returns null. 2525static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal, 2526 Value *FalseVal, const Query &Q, 2527 unsigned MaxRecurse) { 2528 // select true, X, Y -> X 2529 // select false, X, Y -> Y 2530 if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal)) 2531 return CB->getZExtValue() ? TrueVal : FalseVal; 2532 2533 // select C, X, X -> X 2534 if (TrueVal == FalseVal) 2535 return TrueVal; 2536 2537 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y 2538 if (isa<Constant>(TrueVal)) 2539 return TrueVal; 2540 return FalseVal; 2541 } 2542 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X 2543 return FalseVal; 2544 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X 2545 return TrueVal; 2546 2547 return 0; 2548} 2549 2550Value *llvm::SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, 2551 const DataLayout *TD, 2552 const TargetLibraryInfo *TLI, 2553 const DominatorTree *DT) { 2554 return ::SimplifySelectInst(Cond, TrueVal, FalseVal, Query (TD, TLI, DT), 2555 RecursionLimit); 2556} 2557 2558/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can 2559/// fold the result. If not, this returns null. 2560static Value *SimplifyGEPInst(ArrayRef<Value *> Ops, const Query &Q, unsigned) { 2561 // The type of the GEP pointer operand. 2562 PointerType *PtrTy = dyn_cast<PointerType>(Ops[0]->getType()); 2563 // The GEP pointer operand is not a pointer, it's a vector of pointers. 2564 if (!PtrTy) 2565 return 0; 2566 2567 // getelementptr P -> P. 2568 if (Ops.size() == 1) 2569 return Ops[0]; 2570 2571 if (isa<UndefValue>(Ops[0])) { 2572 // Compute the (pointer) type returned by the GEP instruction. 2573 Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, Ops.slice(1)); 2574 Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace()); 2575 return UndefValue::get(GEPTy); 2576 } 2577 2578 if (Ops.size() == 2) { 2579 // getelementptr P, 0 -> P. 2580 if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1])) 2581 if (C->isZero()) 2582 return Ops[0]; 2583 // getelementptr P, N -> P if P points to a type of zero size. 2584 if (Q.TD) { 2585 Type *Ty = PtrTy->getElementType(); 2586 if (Ty->isSized() && Q.TD->getTypeAllocSize(Ty) == 0) 2587 return Ops[0]; 2588 } 2589 } 2590 2591 // Check to see if this is constant foldable. 2592 for (unsigned i = 0, e = Ops.size(); i != e; ++i) 2593 if (!isa<Constant>(Ops[i])) 2594 return 0; 2595 2596 return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]), Ops.slice(1)); 2597} 2598 2599Value *llvm::SimplifyGEPInst(ArrayRef<Value *> Ops, const DataLayout *TD, 2600 const TargetLibraryInfo *TLI, 2601 const DominatorTree *DT) { 2602 return ::SimplifyGEPInst(Ops, Query (TD, TLI, DT), RecursionLimit); 2603} 2604 2605/// SimplifyInsertValueInst - Given operands for an InsertValueInst, see if we 2606/// can fold the result. If not, this returns null. 2607static Value *SimplifyInsertValueInst(Value *Agg, Value *Val, 2608 ArrayRef<unsigned> Idxs, const Query &Q, 2609 unsigned) { 2610 if (Constant *CAgg = dyn_cast<Constant>(Agg)) 2611 if (Constant *CVal = dyn_cast<Constant>(Val)) 2612 return ConstantFoldInsertValueInstruction(CAgg, CVal, Idxs); 2613 2614 // insertvalue x, undef, n -> x 2615 if (match(Val, m_Undef())) 2616 return Agg; 2617 2618 // insertvalue x, (extractvalue y, n), n 2619 if (ExtractValueInst *EV = dyn_cast<ExtractValueInst>(Val)) 2620 if (EV->getAggregateOperand()->getType() == Agg->getType() && 2621 EV->getIndices() == Idxs) { 2622 // insertvalue undef, (extractvalue y, n), n -> y 2623 if (match(Agg, m_Undef())) 2624 return EV->getAggregateOperand(); 2625 2626 // insertvalue y, (extractvalue y, n), n -> y 2627 if (Agg == EV->getAggregateOperand()) 2628 return Agg; 2629 } 2630 2631 return 0; 2632} 2633 2634Value *llvm::SimplifyInsertValueInst(Value *Agg, Value *Val, 2635 ArrayRef<unsigned> Idxs, 2636 const DataLayout *TD, 2637 const TargetLibraryInfo *TLI, 2638 const DominatorTree *DT) { 2639 return ::SimplifyInsertValueInst(Agg, Val, Idxs, Query (TD, TLI, DT), 2640 RecursionLimit); 2641} 2642 2643/// SimplifyPHINode - See if we can fold the given phi. If not, returns null. 2644static Value *SimplifyPHINode(PHINode *PN, const Query &Q) { 2645 // If all of the PHI's incoming values are the same then replace the PHI node 2646 // with the common value. 2647 Value *CommonValue = 0; 2648 bool HasUndefInput = false; 2649 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 2650 Value *Incoming = PN->getIncomingValue(i); 2651 // If the incoming value is the phi node itself, it can safely be skipped. 2652 if (Incoming == PN) continue; 2653 if (isa<UndefValue>(Incoming)) { 2654 // Remember that we saw an undef value, but otherwise ignore them. 2655 HasUndefInput = true; 2656 continue; 2657 } 2658 if (CommonValue && Incoming != CommonValue) 2659 return 0; // Not the same, bail out. 2660 CommonValue = Incoming; 2661 } 2662 2663 // If CommonValue is null then all of the incoming values were either undef or 2664 // equal to the phi node itself. 2665 if (!CommonValue) 2666 return UndefValue::get(PN->getType()); 2667 2668 // If we have a PHI node like phi(X, undef, X), where X is defined by some 2669 // instruction, we cannot return X as the result of the PHI node unless it 2670 // dominates the PHI block. 2671 if (HasUndefInput) 2672 return ValueDominatesPHI(CommonValue, PN, Q.DT) ? CommonValue : 0; 2673 2674 return CommonValue; 2675} 2676 2677static Value *SimplifyTruncInst(Value *Op, Type *Ty, const Query &Q, unsigned) { 2678 if (Constant *C = dyn_cast<Constant>(Op)) 2679 return ConstantFoldInstOperands(Instruction::Trunc, Ty, C, Q.TD, Q.TLI); 2680 2681 return 0; 2682} 2683 2684Value *llvm::SimplifyTruncInst(Value *Op, Type *Ty, const DataLayout *TD, 2685 const TargetLibraryInfo *TLI, 2686 const DominatorTree *DT) { 2687 return ::SimplifyTruncInst(Op, Ty, Query (TD, TLI, DT), RecursionLimit); 2688} 2689 2690//=== Helper functions for higher up the class hierarchy. 2691 2692/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can 2693/// fold the result. If not, this returns null. 2694static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 2695 const Query &Q, unsigned MaxRecurse) { 2696 switch (Opcode) { 2697 case Instruction::Add: 2698 return SimplifyAddInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2699 Q, MaxRecurse); 2700 case Instruction::Sub: 2701 return SimplifySubInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2702 Q, MaxRecurse); 2703 case Instruction::Mul: return SimplifyMulInst (LHS, RHS, Q, MaxRecurse); 2704 case Instruction::SDiv: return SimplifySDivInst(LHS, RHS, Q, MaxRecurse); 2705 case Instruction::UDiv: return SimplifyUDivInst(LHS, RHS, Q, MaxRecurse); 2706 case Instruction::FDiv: return SimplifyFDivInst(LHS, RHS, Q, MaxRecurse); 2707 case Instruction::SRem: return SimplifySRemInst(LHS, RHS, Q, MaxRecurse); 2708 case Instruction::URem: return SimplifyURemInst(LHS, RHS, Q, MaxRecurse); 2709 case Instruction::FRem: return SimplifyFRemInst(LHS, RHS, Q, MaxRecurse); 2710 case Instruction::Shl: 2711 return SimplifyShlInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2712 Q, MaxRecurse); 2713 case Instruction::LShr: 2714 return SimplifyLShrInst(LHS, RHS, /*isExact*/false, Q, MaxRecurse); 2715 case Instruction::AShr: 2716 return SimplifyAShrInst(LHS, RHS, /*isExact*/false, Q, MaxRecurse); 2717 case Instruction::And: return SimplifyAndInst(LHS, RHS, Q, MaxRecurse); 2718 case Instruction::Or: return SimplifyOrInst (LHS, RHS, Q, MaxRecurse); 2719 case Instruction::Xor: return SimplifyXorInst(LHS, RHS, Q, MaxRecurse); 2720 default: 2721 if (Constant *CLHS = dyn_cast<Constant>(LHS)) 2722 if (Constant *CRHS = dyn_cast<Constant>(RHS)) { 2723 Constant *COps[] = {CLHS, CRHS}; 2724 return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, Q.TD, 2725 Q.TLI); 2726 } 2727 2728 // If the operation is associative, try some generic simplifications. 2729 if (Instruction::isAssociative(Opcode)) 2730 if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, Q, MaxRecurse)) 2731 return V; 2732 2733 // If the operation is with the result of a select instruction check whether 2734 // operating on either branch of the select always yields the same value. 2735 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 2736 if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, Q, MaxRecurse)) 2737 return V; 2738 2739 // If the operation is with the result of a phi instruction, check whether 2740 // operating on all incoming values of the phi always yields the same value. 2741 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 2742 if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, Q, MaxRecurse)) 2743 return V; 2744 2745 return 0; 2746 } 2747} 2748 2749Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 2750 const DataLayout *TD, const TargetLibraryInfo *TLI, 2751 const DominatorTree *DT) { 2752 return ::SimplifyBinOp(Opcode, LHS, RHS, Query (TD, TLI, DT), RecursionLimit); 2753} 2754 2755/// SimplifyCmpInst - Given operands for a CmpInst, see if we can 2756/// fold the result. 2757static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2758 const Query &Q, unsigned MaxRecurse) { 2759 if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate)) 2760 return SimplifyICmpInst(Predicate, LHS, RHS, Q, MaxRecurse); 2761 return SimplifyFCmpInst(Predicate, LHS, RHS, Q, MaxRecurse); 2762} 2763 2764Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2765 const DataLayout *TD, const TargetLibraryInfo *TLI, 2766 const DominatorTree *DT) { 2767 return ::SimplifyCmpInst(Predicate, LHS, RHS, Query (TD, TLI, DT), 2768 RecursionLimit); 2769} 2770 2771static Value *SimplifyCallInst(CallInst *CI, const Query &) { 2772 // call undef -> undef 2773 if (isa<UndefValue>(CI->getCalledValue())) 2774 return UndefValue::get(CI->getType()); 2775 2776 return 0; 2777} 2778 2779/// SimplifyInstruction - See if we can compute a simplified version of this 2780/// instruction. If not, this returns null. 2781Value *llvm::SimplifyInstruction(Instruction *I, const DataLayout *TD, 2782 const TargetLibraryInfo *TLI, 2783 const DominatorTree *DT) { 2784 Value *Result; 2785 2786 switch (I->getOpcode()) { 2787 default: 2788 Result = ConstantFoldInstruction(I, TD, TLI); 2789 break; 2790 case Instruction::Add: 2791 Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1), 2792 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2793 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2794 TD, TLI, DT); 2795 break; 2796 case Instruction::Sub: 2797 Result = SimplifySubInst(I->getOperand(0), I->getOperand(1), 2798 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2799 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2800 TD, TLI, DT); 2801 break; 2802 case Instruction::Mul: 2803 Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2804 break; 2805 case Instruction::SDiv: 2806 Result = SimplifySDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2807 break; 2808 case Instruction::UDiv: 2809 Result = SimplifyUDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2810 break; 2811 case Instruction::FDiv: 2812 Result = SimplifyFDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2813 break; 2814 case Instruction::SRem: 2815 Result = SimplifySRemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2816 break; 2817 case Instruction::URem: 2818 Result = SimplifyURemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2819 break; 2820 case Instruction::FRem: 2821 Result = SimplifyFRemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2822 break; 2823 case Instruction::Shl: 2824 Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1), 2825 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2826 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2827 TD, TLI, DT); 2828 break; 2829 case Instruction::LShr: 2830 Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1), 2831 cast<BinaryOperator>(I)->isExact(), 2832 TD, TLI, DT); 2833 break; 2834 case Instruction::AShr: 2835 Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1), 2836 cast<BinaryOperator>(I)->isExact(), 2837 TD, TLI, DT); 2838 break; 2839 case Instruction::And: 2840 Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2841 break; 2842 case Instruction::Or: 2843 Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2844 break; 2845 case Instruction::Xor: 2846 Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2847 break; 2848 case Instruction::ICmp: 2849 Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(), 2850 I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2851 break; 2852 case Instruction::FCmp: 2853 Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(), 2854 I->getOperand(0), I->getOperand(1), TD, TLI, DT); 2855 break; 2856 case Instruction::Select: 2857 Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1), 2858 I->getOperand(2), TD, TLI, DT); 2859 break; 2860 case Instruction::GetElementPtr: { 2861 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end()); 2862 Result = SimplifyGEPInst(Ops, TD, TLI, DT); 2863 break; 2864 } 2865 case Instruction::InsertValue: { 2866 InsertValueInst *IV = cast<InsertValueInst>(I); 2867 Result = SimplifyInsertValueInst(IV->getAggregateOperand(), 2868 IV->getInsertedValueOperand(), 2869 IV->getIndices(), TD, TLI, DT); 2870 break; 2871 } 2872 case Instruction::PHI: 2873 Result = SimplifyPHINode(cast<PHINode>(I), Query (TD, TLI, DT)); 2874 break; 2875 case Instruction::Call: 2876 Result = SimplifyCallInst(cast<CallInst>(I), Query (TD, TLI, DT)); 2877 break; 2878 case Instruction::Trunc: 2879 Result = SimplifyTruncInst(I->getOperand(0), I->getType(), TD, TLI, DT); 2880 break; 2881 } 2882 2883 /// If called on unreachable code, the above logic may report that the 2884 /// instruction simplified to itself. Make life easier for users by 2885 /// detecting that case here, returning a safe value instead. 2886 return Result == I ? UndefValue::get(I->getType()) : Result; 2887} 2888 2889/// \brief Implementation of recursive simplification through an instructions 2890/// uses. 2891/// 2892/// This is the common implementation of the recursive simplification routines. 2893/// If we have a pre-simplified value in 'SimpleV', that is forcibly used to 2894/// replace the instruction 'I'. Otherwise, we simply add 'I' to the list of 2895/// instructions to process and attempt to simplify it using 2896/// InstructionSimplify. 2897/// 2898/// This routine returns 'true' only when *it* simplifies something. The passed 2899/// in simplified value does not count toward this. 2900static bool replaceAndRecursivelySimplifyImpl(Instruction *I, Value *SimpleV, 2901 const DataLayout *TD, 2902 const TargetLibraryInfo *TLI, 2903 const DominatorTree *DT) { 2904 bool Simplified = false; 2905 SmallSetVector<Instruction *, 8> Worklist; 2906 2907 // If we have an explicit value to collapse to, do that round of the 2908 // simplification loop by hand initially. 2909 if (SimpleV) { 2910 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE; 2911 ++UI) 2912 if (*UI != I) 2913 Worklist.insert(cast<Instruction>(*UI)); 2914 2915 // Replace the instruction with its simplified value. 2916 I->replaceAllUsesWith(SimpleV); 2917 2918 // Gracefully handle edge cases where the instruction is not wired into any 2919 // parent block. 2920 if (I->getParent()) 2921 I->eraseFromParent(); 2922 } else { 2923 Worklist.insert(I); 2924 } 2925 2926 // Note that we must test the size on each iteration, the worklist can grow. 2927 for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) { 2928 I = Worklist[Idx]; 2929 2930 // See if this instruction simplifies. 2931 SimpleV = SimplifyInstruction(I, TD, TLI, DT); 2932 if (!SimpleV) 2933 continue; 2934 2935 Simplified = true; 2936 2937 // Stash away all the uses of the old instruction so we can check them for 2938 // recursive simplifications after a RAUW. This is cheaper than checking all 2939 // uses of To on the recursive step in most cases. 2940 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE; 2941 ++UI) 2942 Worklist.insert(cast<Instruction>(*UI)); 2943 2944 // Replace the instruction with its simplified value. 2945 I->replaceAllUsesWith(SimpleV); 2946 2947 // Gracefully handle edge cases where the instruction is not wired into any 2948 // parent block. 2949 if (I->getParent()) 2950 I->eraseFromParent(); 2951 } 2952 return Simplified; 2953} 2954 2955bool llvm::recursivelySimplifyInstruction(Instruction *I, 2956 const DataLayout *TD, 2957 const TargetLibraryInfo *TLI, 2958 const DominatorTree *DT) { 2959 return replaceAndRecursivelySimplifyImpl(I, 0, TD, TLI, DT); 2960} 2961 2962bool llvm::replaceAndRecursivelySimplify(Instruction *I, Value *SimpleV, 2963 const DataLayout *TD, 2964 const TargetLibraryInfo *TLI, 2965 const DominatorTree *DT) { 2966 assert(I != SimpleV && "replaceAndRecursivelySimplify(X,X) is not valid!"); 2967 assert(SimpleV && "Must provide a simplified value."); 2968 return replaceAndRecursivelySimplifyImpl(I, SimpleV, TD, TLI, DT); 2969} 2970