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