InstructionSimplify.cpp revision 448a6d3cc23f2a249778bb341ae26589568efdf8
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" 31using namespace llvm; 32using namespace llvm::PatternMatch; 33 34enum { RecursionLimit = 3 }; 35 36STATISTIC(NumExpand, "Number of expansions"); 37STATISTIC(NumFactor , "Number of factorizations"); 38STATISTIC(NumReassoc, "Number of reassociations"); 39 40static Value *SimplifyAndInst(Value *, Value *, const TargetData *, 41 const DominatorTree *, unsigned); 42static Value *SimplifyBinOp(unsigned, Value *, Value *, const TargetData *, 43 const DominatorTree *, unsigned); 44static Value *SimplifyCmpInst(unsigned, Value *, Value *, const TargetData *, 45 const DominatorTree *, unsigned); 46static Value *SimplifyOrInst(Value *, Value *, const TargetData *, 47 const DominatorTree *, unsigned); 48static Value *SimplifyXorInst(Value *, Value *, const TargetData *, 49 const DominatorTree *, unsigned); 50 51/// ValueDominatesPHI - Does the given value dominate the specified phi node? 52static 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. 76static 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. 139static 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. 209static 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. 310static 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. 384static 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. 440static 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. 484static 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. 522static 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, 2, 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 584Value *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. 591static 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, 2, 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 705Value *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. 712static 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, 2, 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 778Value *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. 785static 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, 2, 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. 858static 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 866Value *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. 873static 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 881Value *llvm::SimplifyUDivInst(Value *Op0, Value *Op1, const TargetData *TD, 882 const DominatorTree *DT) { 883 return ::SimplifyUDivInst(Op0, Op1, TD, DT, RecursionLimit); 884} 885 886static 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 899Value *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. 906static 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, 2, 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. 961static 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 969Value *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. 976static 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 984Value *llvm::SimplifyURemInst(Value *Op0, Value *Op1, const TargetData *TD, 985 const DominatorTree *DT) { 986 return ::SimplifyURemInst(Op0, Op1, TD, DT, RecursionLimit); 987} 988 989static 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 1002Value *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. 1009static 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, 2, 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. 1054static 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 1072Value *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. 1079static 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 1098Value *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. 1105static 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 1128Value *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. 1135static 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, 2, 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 1217Value *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. 1224static 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, 2, 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 1311Value *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. 1318static 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, 2, 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 1370Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD, 1371 const DominatorTree *DT) { 1372 return ::SimplifyXorInst(Op0, Op1, TD, DT, RecursionLimit); 1373} 1374 1375static const Type *GetCompareTy(Value *Op) { 1376 return CmpInst::makeCmpResultType(Op->getType()); 1377} 1378 1379/// SimplifyICmpInst - Given operands for an ICmpInst, see if we can 1380/// fold the result. If not, this returns null. 1381static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1382 const TargetData *TD, const DominatorTree *DT, 1383 unsigned MaxRecurse) { 1384 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 1385 assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!"); 1386 1387 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 1388 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 1389 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); 1390 1391 // If we have a constant, make sure it is on the RHS. 1392 std::swap(LHS, RHS); 1393 Pred = CmpInst::getSwappedPredicate(Pred); 1394 } 1395 1396 const Type *ITy = GetCompareTy(LHS); // The return type. 1397 const Type *OpTy = LHS->getType(); // The operand type. 1398 1399 // icmp X, X -> true/false 1400 // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false 1401 // because X could be 0. 1402 if (LHS == RHS || isa<UndefValue>(RHS)) 1403 return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred)); 1404 1405 // Special case logic when the operands have i1 type. 1406 if (OpTy->isIntegerTy(1) || (OpTy->isVectorTy() && 1407 cast<VectorType>(OpTy)->getElementType()->isIntegerTy(1))) { 1408 switch (Pred) { 1409 default: break; 1410 case ICmpInst::ICMP_EQ: 1411 // X == 1 -> X 1412 if (match(RHS, m_One())) 1413 return LHS; 1414 break; 1415 case ICmpInst::ICMP_NE: 1416 // X != 0 -> X 1417 if (match(RHS, m_Zero())) 1418 return LHS; 1419 break; 1420 case ICmpInst::ICMP_UGT: 1421 // X >u 0 -> X 1422 if (match(RHS, m_Zero())) 1423 return LHS; 1424 break; 1425 case ICmpInst::ICMP_UGE: 1426 // X >=u 1 -> X 1427 if (match(RHS, m_One())) 1428 return LHS; 1429 break; 1430 case ICmpInst::ICMP_SLT: 1431 // X <s 0 -> X 1432 if (match(RHS, m_Zero())) 1433 return LHS; 1434 break; 1435 case ICmpInst::ICMP_SLE: 1436 // X <=s -1 -> X 1437 if (match(RHS, m_One())) 1438 return LHS; 1439 break; 1440 } 1441 } 1442 1443 // icmp <alloca*>, <global/alloca*/null> - Different stack variables have 1444 // different addresses, and what's more the address of a stack variable is 1445 // never null or equal to the address of a global. Note that generalizing 1446 // to the case where LHS is a global variable address or null is pointless, 1447 // since if both LHS and RHS are constants then we already constant folded 1448 // the compare, and if only one of them is then we moved it to RHS already. 1449 if (isa<AllocaInst>(LHS) && (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) || 1450 isa<ConstantPointerNull>(RHS))) 1451 // We already know that LHS != RHS. 1452 return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred)); 1453 1454 // If we are comparing with zero then try hard since this is a common case. 1455 if (match(RHS, m_Zero())) { 1456 bool LHSKnownNonNegative, LHSKnownNegative; 1457 switch (Pred) { 1458 default: 1459 assert(false && "Unknown ICmp predicate!"); 1460 case ICmpInst::ICMP_ULT: 1461 // getNullValue also works for vectors, unlike getFalse. 1462 return Constant::getNullValue(ITy); 1463 case ICmpInst::ICMP_UGE: 1464 // getAllOnesValue also works for vectors, unlike getTrue. 1465 return ConstantInt::getAllOnesValue(ITy); 1466 case ICmpInst::ICMP_EQ: 1467 case ICmpInst::ICMP_ULE: 1468 if (isKnownNonZero(LHS, TD)) 1469 return Constant::getNullValue(ITy); 1470 break; 1471 case ICmpInst::ICMP_NE: 1472 case ICmpInst::ICMP_UGT: 1473 if (isKnownNonZero(LHS, TD)) 1474 return ConstantInt::getAllOnesValue(ITy); 1475 break; 1476 case ICmpInst::ICMP_SLT: 1477 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, TD); 1478 if (LHSKnownNegative) 1479 return ConstantInt::getAllOnesValue(ITy); 1480 if (LHSKnownNonNegative) 1481 return Constant::getNullValue(ITy); 1482 break; 1483 case ICmpInst::ICMP_SLE: 1484 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, TD); 1485 if (LHSKnownNegative) 1486 return ConstantInt::getAllOnesValue(ITy); 1487 if (LHSKnownNonNegative && isKnownNonZero(LHS, TD)) 1488 return Constant::getNullValue(ITy); 1489 break; 1490 case ICmpInst::ICMP_SGE: 1491 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, TD); 1492 if (LHSKnownNegative) 1493 return Constant::getNullValue(ITy); 1494 if (LHSKnownNonNegative) 1495 return ConstantInt::getAllOnesValue(ITy); 1496 break; 1497 case ICmpInst::ICMP_SGT: 1498 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, TD); 1499 if (LHSKnownNegative) 1500 return Constant::getNullValue(ITy); 1501 if (LHSKnownNonNegative && isKnownNonZero(LHS, TD)) 1502 return ConstantInt::getAllOnesValue(ITy); 1503 break; 1504 } 1505 } 1506 1507 // See if we are doing a comparison with a constant integer. 1508 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1509 // Rule out tautological comparisons (eg., ult 0 or uge 0). 1510 ConstantRange RHS_CR = ICmpInst::makeConstantRange(Pred, CI->getValue()); 1511 if (RHS_CR.isEmptySet()) 1512 return ConstantInt::getFalse(CI->getContext()); 1513 if (RHS_CR.isFullSet()) 1514 return ConstantInt::getTrue(CI->getContext()); 1515 1516 // Many binary operators with constant RHS have easy to compute constant 1517 // range. Use them to check whether the comparison is a tautology. 1518 uint32_t Width = CI->getBitWidth(); 1519 APInt Lower = APInt(Width, 0); 1520 APInt Upper = APInt(Width, 0); 1521 ConstantInt *CI2; 1522 if (match(LHS, m_URem(m_Value(), m_ConstantInt(CI2)))) { 1523 // 'urem x, CI2' produces [0, CI2). 1524 Upper = CI2->getValue(); 1525 } else if (match(LHS, m_SRem(m_Value(), m_ConstantInt(CI2)))) { 1526 // 'srem x, CI2' produces (-|CI2|, |CI2|). 1527 Upper = CI2->getValue().abs(); 1528 Lower = (-Upper) + 1; 1529 } else if (match(LHS, m_UDiv(m_Value(), m_ConstantInt(CI2)))) { 1530 // 'udiv x, CI2' produces [0, UINT_MAX / CI2]. 1531 APInt NegOne = APInt::getAllOnesValue(Width); 1532 if (!CI2->isZero()) 1533 Upper = NegOne.udiv(CI2->getValue()) + 1; 1534 } else if (match(LHS, m_SDiv(m_Value(), m_ConstantInt(CI2)))) { 1535 // 'sdiv x, CI2' produces [INT_MIN / CI2, INT_MAX / CI2]. 1536 APInt IntMin = APInt::getSignedMinValue(Width); 1537 APInt IntMax = APInt::getSignedMaxValue(Width); 1538 APInt Val = CI2->getValue().abs(); 1539 if (!Val.isMinValue()) { 1540 Lower = IntMin.sdiv(Val); 1541 Upper = IntMax.sdiv(Val) + 1; 1542 } 1543 } else if (match(LHS, m_LShr(m_Value(), m_ConstantInt(CI2)))) { 1544 // 'lshr x, CI2' produces [0, UINT_MAX >> CI2]. 1545 APInt NegOne = APInt::getAllOnesValue(Width); 1546 if (CI2->getValue().ult(Width)) 1547 Upper = NegOne.lshr(CI2->getValue()) + 1; 1548 } else if (match(LHS, m_AShr(m_Value(), m_ConstantInt(CI2)))) { 1549 // 'ashr x, CI2' produces [INT_MIN >> CI2, INT_MAX >> CI2]. 1550 APInt IntMin = APInt::getSignedMinValue(Width); 1551 APInt IntMax = APInt::getSignedMaxValue(Width); 1552 if (CI2->getValue().ult(Width)) { 1553 Lower = IntMin.ashr(CI2->getValue()); 1554 Upper = IntMax.ashr(CI2->getValue()) + 1; 1555 } 1556 } else if (match(LHS, m_Or(m_Value(), m_ConstantInt(CI2)))) { 1557 // 'or x, CI2' produces [CI2, UINT_MAX]. 1558 Lower = CI2->getValue(); 1559 } else if (match(LHS, m_And(m_Value(), m_ConstantInt(CI2)))) { 1560 // 'and x, CI2' produces [0, CI2]. 1561 Upper = CI2->getValue() + 1; 1562 } 1563 if (Lower != Upper) { 1564 ConstantRange LHS_CR = ConstantRange(Lower, Upper); 1565 if (RHS_CR.contains(LHS_CR)) 1566 return ConstantInt::getTrue(RHS->getContext()); 1567 if (RHS_CR.inverse().contains(LHS_CR)) 1568 return ConstantInt::getFalse(RHS->getContext()); 1569 } 1570 } 1571 1572 // Compare of cast, for example (zext X) != 0 -> X != 0 1573 if (isa<CastInst>(LHS) && (isa<Constant>(RHS) || isa<CastInst>(RHS))) { 1574 Instruction *LI = cast<CastInst>(LHS); 1575 Value *SrcOp = LI->getOperand(0); 1576 const Type *SrcTy = SrcOp->getType(); 1577 const Type *DstTy = LI->getType(); 1578 1579 // Turn icmp (ptrtoint x), (ptrtoint/constant) into a compare of the input 1580 // if the integer type is the same size as the pointer type. 1581 if (MaxRecurse && TD && isa<PtrToIntInst>(LI) && 1582 TD->getPointerSizeInBits() == DstTy->getPrimitiveSizeInBits()) { 1583 if (Constant *RHSC = dyn_cast<Constant>(RHS)) { 1584 // Transfer the cast to the constant. 1585 if (Value *V = SimplifyICmpInst(Pred, SrcOp, 1586 ConstantExpr::getIntToPtr(RHSC, SrcTy), 1587 TD, DT, MaxRecurse-1)) 1588 return V; 1589 } else if (PtrToIntInst *RI = dyn_cast<PtrToIntInst>(RHS)) { 1590 if (RI->getOperand(0)->getType() == SrcTy) 1591 // Compare without the cast. 1592 if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), 1593 TD, DT, MaxRecurse-1)) 1594 return V; 1595 } 1596 } 1597 1598 if (isa<ZExtInst>(LHS)) { 1599 // Turn icmp (zext X), (zext Y) into a compare of X and Y if they have the 1600 // same type. 1601 if (ZExtInst *RI = dyn_cast<ZExtInst>(RHS)) { 1602 if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) 1603 // Compare X and Y. Note that signed predicates become unsigned. 1604 if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), 1605 SrcOp, RI->getOperand(0), TD, DT, 1606 MaxRecurse-1)) 1607 return V; 1608 } 1609 // Turn icmp (zext X), Cst into a compare of X and Cst if Cst is extended 1610 // too. If not, then try to deduce the result of the comparison. 1611 else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1612 // Compute the constant that would happen if we truncated to SrcTy then 1613 // reextended to DstTy. 1614 Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); 1615 Constant *RExt = ConstantExpr::getCast(CastInst::ZExt, Trunc, DstTy); 1616 1617 // If the re-extended constant didn't change then this is effectively 1618 // also a case of comparing two zero-extended values. 1619 if (RExt == CI && MaxRecurse) 1620 if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), 1621 SrcOp, Trunc, TD, DT, MaxRecurse-1)) 1622 return V; 1623 1624 // Otherwise the upper bits of LHS are zero while RHS has a non-zero bit 1625 // there. Use this to work out the result of the comparison. 1626 if (RExt != CI) { 1627 switch (Pred) { 1628 default: 1629 assert(false && "Unknown ICmp predicate!"); 1630 // LHS <u RHS. 1631 case ICmpInst::ICMP_EQ: 1632 case ICmpInst::ICMP_UGT: 1633 case ICmpInst::ICMP_UGE: 1634 return ConstantInt::getFalse(CI->getContext()); 1635 1636 case ICmpInst::ICMP_NE: 1637 case ICmpInst::ICMP_ULT: 1638 case ICmpInst::ICMP_ULE: 1639 return ConstantInt::getTrue(CI->getContext()); 1640 1641 // LHS is non-negative. If RHS is negative then LHS >s LHS. If RHS 1642 // is non-negative then LHS <s RHS. 1643 case ICmpInst::ICMP_SGT: 1644 case ICmpInst::ICMP_SGE: 1645 return CI->getValue().isNegative() ? 1646 ConstantInt::getTrue(CI->getContext()) : 1647 ConstantInt::getFalse(CI->getContext()); 1648 1649 case ICmpInst::ICMP_SLT: 1650 case ICmpInst::ICMP_SLE: 1651 return CI->getValue().isNegative() ? 1652 ConstantInt::getFalse(CI->getContext()) : 1653 ConstantInt::getTrue(CI->getContext()); 1654 } 1655 } 1656 } 1657 } 1658 1659 if (isa<SExtInst>(LHS)) { 1660 // Turn icmp (sext X), (sext Y) into a compare of X and Y if they have the 1661 // same type. 1662 if (SExtInst *RI = dyn_cast<SExtInst>(RHS)) { 1663 if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) 1664 // Compare X and Y. Note that the predicate does not change. 1665 if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), 1666 TD, DT, MaxRecurse-1)) 1667 return V; 1668 } 1669 // Turn icmp (sext X), Cst into a compare of X and Cst if Cst is extended 1670 // too. If not, then try to deduce the result of the comparison. 1671 else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1672 // Compute the constant that would happen if we truncated to SrcTy then 1673 // reextended to DstTy. 1674 Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); 1675 Constant *RExt = ConstantExpr::getCast(CastInst::SExt, Trunc, DstTy); 1676 1677 // If the re-extended constant didn't change then this is effectively 1678 // also a case of comparing two sign-extended values. 1679 if (RExt == CI && MaxRecurse) 1680 if (Value *V = SimplifyICmpInst(Pred, SrcOp, Trunc, TD, DT, 1681 MaxRecurse-1)) 1682 return V; 1683 1684 // Otherwise the upper bits of LHS are all equal, while RHS has varying 1685 // bits there. Use this to work out the result of the comparison. 1686 if (RExt != CI) { 1687 switch (Pred) { 1688 default: 1689 assert(false && "Unknown ICmp predicate!"); 1690 case ICmpInst::ICMP_EQ: 1691 return ConstantInt::getFalse(CI->getContext()); 1692 case ICmpInst::ICMP_NE: 1693 return ConstantInt::getTrue(CI->getContext()); 1694 1695 // If RHS is non-negative then LHS <s RHS. If RHS is negative then 1696 // LHS >s RHS. 1697 case ICmpInst::ICMP_SGT: 1698 case ICmpInst::ICMP_SGE: 1699 return CI->getValue().isNegative() ? 1700 ConstantInt::getTrue(CI->getContext()) : 1701 ConstantInt::getFalse(CI->getContext()); 1702 case ICmpInst::ICMP_SLT: 1703 case ICmpInst::ICMP_SLE: 1704 return CI->getValue().isNegative() ? 1705 ConstantInt::getFalse(CI->getContext()) : 1706 ConstantInt::getTrue(CI->getContext()); 1707 1708 // If LHS is non-negative then LHS <u RHS. If LHS is negative then 1709 // LHS >u RHS. 1710 case ICmpInst::ICMP_UGT: 1711 case ICmpInst::ICMP_UGE: 1712 // Comparison is true iff the LHS <s 0. 1713 if (MaxRecurse) 1714 if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SLT, SrcOp, 1715 Constant::getNullValue(SrcTy), 1716 TD, DT, MaxRecurse-1)) 1717 return V; 1718 break; 1719 case ICmpInst::ICMP_ULT: 1720 case ICmpInst::ICMP_ULE: 1721 // Comparison is true iff the LHS >=s 0. 1722 if (MaxRecurse) 1723 if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SGE, SrcOp, 1724 Constant::getNullValue(SrcTy), 1725 TD, DT, MaxRecurse-1)) 1726 return V; 1727 break; 1728 } 1729 } 1730 } 1731 } 1732 } 1733 1734 // Special logic for binary operators. 1735 BinaryOperator *LBO = dyn_cast<BinaryOperator>(LHS); 1736 BinaryOperator *RBO = dyn_cast<BinaryOperator>(RHS); 1737 if (MaxRecurse && (LBO || RBO)) { 1738 // Analyze the case when either LHS or RHS is an add instruction. 1739 Value *A = 0, *B = 0, *C = 0, *D = 0; 1740 // LHS = A + B (or A and B are null); RHS = C + D (or C and D are null). 1741 bool NoLHSWrapProblem = false, NoRHSWrapProblem = false; 1742 if (LBO && LBO->getOpcode() == Instruction::Add) { 1743 A = LBO->getOperand(0); B = LBO->getOperand(1); 1744 NoLHSWrapProblem = ICmpInst::isEquality(Pred) || 1745 (CmpInst::isUnsigned(Pred) && LBO->hasNoUnsignedWrap()) || 1746 (CmpInst::isSigned(Pred) && LBO->hasNoSignedWrap()); 1747 } 1748 if (RBO && RBO->getOpcode() == Instruction::Add) { 1749 C = RBO->getOperand(0); D = RBO->getOperand(1); 1750 NoRHSWrapProblem = ICmpInst::isEquality(Pred) || 1751 (CmpInst::isUnsigned(Pred) && RBO->hasNoUnsignedWrap()) || 1752 (CmpInst::isSigned(Pred) && RBO->hasNoSignedWrap()); 1753 } 1754 1755 // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow. 1756 if ((A == RHS || B == RHS) && NoLHSWrapProblem) 1757 if (Value *V = SimplifyICmpInst(Pred, A == RHS ? B : A, 1758 Constant::getNullValue(RHS->getType()), 1759 TD, DT, MaxRecurse-1)) 1760 return V; 1761 1762 // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow. 1763 if ((C == LHS || D == LHS) && NoRHSWrapProblem) 1764 if (Value *V = SimplifyICmpInst(Pred, 1765 Constant::getNullValue(LHS->getType()), 1766 C == LHS ? D : C, TD, DT, MaxRecurse-1)) 1767 return V; 1768 1769 // icmp (X+Y), (X+Z) -> icmp Y,Z for equalities or if there is no overflow. 1770 if (A && C && (A == C || A == D || B == C || B == D) && 1771 NoLHSWrapProblem && NoRHSWrapProblem) { 1772 // Determine Y and Z in the form icmp (X+Y), (X+Z). 1773 Value *Y = (A == C || A == D) ? B : A; 1774 Value *Z = (C == A || C == B) ? D : C; 1775 if (Value *V = SimplifyICmpInst(Pred, Y, Z, TD, DT, MaxRecurse-1)) 1776 return V; 1777 } 1778 } 1779 1780 if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) { 1781 bool KnownNonNegative, KnownNegative; 1782 switch (Pred) { 1783 default: 1784 break; 1785 case ICmpInst::ICMP_SGT: 1786 case ICmpInst::ICMP_SGE: 1787 ComputeSignBit(LHS, KnownNonNegative, KnownNegative, TD); 1788 if (!KnownNonNegative) 1789 break; 1790 // fall-through 1791 case ICmpInst::ICMP_EQ: 1792 case ICmpInst::ICMP_UGT: 1793 case ICmpInst::ICMP_UGE: 1794 // getNullValue also works for vectors, unlike getFalse. 1795 return Constant::getNullValue(ITy); 1796 case ICmpInst::ICMP_SLT: 1797 case ICmpInst::ICMP_SLE: 1798 ComputeSignBit(LHS, KnownNonNegative, KnownNegative, TD); 1799 if (!KnownNonNegative) 1800 break; 1801 // fall-through 1802 case ICmpInst::ICMP_NE: 1803 case ICmpInst::ICMP_ULT: 1804 case ICmpInst::ICMP_ULE: 1805 // getAllOnesValue also works for vectors, unlike getTrue. 1806 return Constant::getAllOnesValue(ITy); 1807 } 1808 } 1809 if (RBO && match(RBO, m_URem(m_Value(), m_Specific(LHS)))) { 1810 bool KnownNonNegative, KnownNegative; 1811 switch (Pred) { 1812 default: 1813 break; 1814 case ICmpInst::ICMP_SGT: 1815 case ICmpInst::ICMP_SGE: 1816 ComputeSignBit(RHS, KnownNonNegative, KnownNegative, TD); 1817 if (!KnownNonNegative) 1818 break; 1819 // fall-through 1820 case ICmpInst::ICMP_NE: 1821 case ICmpInst::ICMP_UGT: 1822 case ICmpInst::ICMP_UGE: 1823 // getAllOnesValue also works for vectors, unlike getTrue. 1824 return Constant::getAllOnesValue(ITy); 1825 case ICmpInst::ICMP_SLT: 1826 case ICmpInst::ICMP_SLE: 1827 ComputeSignBit(RHS, KnownNonNegative, KnownNegative, TD); 1828 if (!KnownNonNegative) 1829 break; 1830 // fall-through 1831 case ICmpInst::ICMP_EQ: 1832 case ICmpInst::ICMP_ULT: 1833 case ICmpInst::ICMP_ULE: 1834 // getNullValue also works for vectors, unlike getFalse. 1835 return Constant::getNullValue(ITy); 1836 } 1837 } 1838 1839 if (MaxRecurse && LBO && RBO && LBO->getOpcode() == RBO->getOpcode() && 1840 LBO->getOperand(1) == RBO->getOperand(1)) { 1841 switch (LBO->getOpcode()) { 1842 default: break; 1843 case Instruction::UDiv: 1844 case Instruction::LShr: 1845 if (ICmpInst::isSigned(Pred)) 1846 break; 1847 // fall-through 1848 case Instruction::SDiv: 1849 case Instruction::AShr: 1850 if (!LBO->isExact() && !RBO->isExact()) 1851 break; 1852 if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0), 1853 RBO->getOperand(0), TD, DT, MaxRecurse-1)) 1854 return V; 1855 break; 1856 case Instruction::Shl: { 1857 bool NUW = LBO->hasNoUnsignedWrap() && LBO->hasNoUnsignedWrap(); 1858 bool NSW = LBO->hasNoSignedWrap() && RBO->hasNoSignedWrap(); 1859 if (!NUW && !NSW) 1860 break; 1861 if (!NSW && ICmpInst::isSigned(Pred)) 1862 break; 1863 if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0), 1864 RBO->getOperand(0), TD, DT, MaxRecurse-1)) 1865 return V; 1866 break; 1867 } 1868 } 1869 } 1870 1871 // If the comparison is with the result of a select instruction, check whether 1872 // comparing with either branch of the select always yields the same value. 1873 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 1874 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1875 return V; 1876 1877 // If the comparison is with the result of a phi instruction, check whether 1878 // doing the compare with each incoming phi value yields a common result. 1879 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 1880 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1881 return V; 1882 1883 return 0; 1884} 1885 1886Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1887 const TargetData *TD, const DominatorTree *DT) { 1888 return ::SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 1889} 1890 1891/// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can 1892/// fold the result. If not, this returns null. 1893static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1894 const TargetData *TD, const DominatorTree *DT, 1895 unsigned MaxRecurse) { 1896 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 1897 assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!"); 1898 1899 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 1900 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 1901 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); 1902 1903 // If we have a constant, make sure it is on the RHS. 1904 std::swap(LHS, RHS); 1905 Pred = CmpInst::getSwappedPredicate(Pred); 1906 } 1907 1908 // Fold trivial predicates. 1909 if (Pred == FCmpInst::FCMP_FALSE) 1910 return ConstantInt::get(GetCompareTy(LHS), 0); 1911 if (Pred == FCmpInst::FCMP_TRUE) 1912 return ConstantInt::get(GetCompareTy(LHS), 1); 1913 1914 if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef 1915 return UndefValue::get(GetCompareTy(LHS)); 1916 1917 // fcmp x,x -> true/false. Not all compares are foldable. 1918 if (LHS == RHS) { 1919 if (CmpInst::isTrueWhenEqual(Pred)) 1920 return ConstantInt::get(GetCompareTy(LHS), 1); 1921 if (CmpInst::isFalseWhenEqual(Pred)) 1922 return ConstantInt::get(GetCompareTy(LHS), 0); 1923 } 1924 1925 // Handle fcmp with constant RHS 1926 if (Constant *RHSC = dyn_cast<Constant>(RHS)) { 1927 // If the constant is a nan, see if we can fold the comparison based on it. 1928 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) { 1929 if (CFP->getValueAPF().isNaN()) { 1930 if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo" 1931 return ConstantInt::getFalse(CFP->getContext()); 1932 assert(FCmpInst::isUnordered(Pred) && 1933 "Comparison must be either ordered or unordered!"); 1934 // True if unordered. 1935 return ConstantInt::getTrue(CFP->getContext()); 1936 } 1937 // Check whether the constant is an infinity. 1938 if (CFP->getValueAPF().isInfinity()) { 1939 if (CFP->getValueAPF().isNegative()) { 1940 switch (Pred) { 1941 case FCmpInst::FCMP_OLT: 1942 // No value is ordered and less than negative infinity. 1943 return ConstantInt::getFalse(CFP->getContext()); 1944 case FCmpInst::FCMP_UGE: 1945 // All values are unordered with or at least negative infinity. 1946 return ConstantInt::getTrue(CFP->getContext()); 1947 default: 1948 break; 1949 } 1950 } else { 1951 switch (Pred) { 1952 case FCmpInst::FCMP_OGT: 1953 // No value is ordered and greater than infinity. 1954 return ConstantInt::getFalse(CFP->getContext()); 1955 case FCmpInst::FCMP_ULE: 1956 // All values are unordered with and at most infinity. 1957 return ConstantInt::getTrue(CFP->getContext()); 1958 default: 1959 break; 1960 } 1961 } 1962 } 1963 } 1964 } 1965 1966 // If the comparison is with the result of a select instruction, check whether 1967 // comparing with either branch of the select always yields the same value. 1968 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 1969 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1970 return V; 1971 1972 // If the comparison is with the result of a phi instruction, check whether 1973 // doing the compare with each incoming phi value yields a common result. 1974 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 1975 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1976 return V; 1977 1978 return 0; 1979} 1980 1981Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1982 const TargetData *TD, const DominatorTree *DT) { 1983 return ::SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 1984} 1985 1986/// SimplifySelectInst - Given operands for a SelectInst, see if we can fold 1987/// the result. If not, this returns null. 1988Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal, 1989 const TargetData *TD, const DominatorTree *) { 1990 // select true, X, Y -> X 1991 // select false, X, Y -> Y 1992 if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal)) 1993 return CB->getZExtValue() ? TrueVal : FalseVal; 1994 1995 // select C, X, X -> X 1996 if (TrueVal == FalseVal) 1997 return TrueVal; 1998 1999 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X 2000 return FalseVal; 2001 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X 2002 return TrueVal; 2003 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y 2004 if (isa<Constant>(TrueVal)) 2005 return TrueVal; 2006 return FalseVal; 2007 } 2008 2009 return 0; 2010} 2011 2012/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can 2013/// fold the result. If not, this returns null. 2014Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps, 2015 const TargetData *TD, const DominatorTree *) { 2016 // The type of the GEP pointer operand. 2017 const PointerType *PtrTy = cast<PointerType>(Ops[0]->getType()); 2018 2019 // getelementptr P -> P. 2020 if (NumOps == 1) 2021 return Ops[0]; 2022 2023 if (isa<UndefValue>(Ops[0])) { 2024 // Compute the (pointer) type returned by the GEP instruction. 2025 const Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, &Ops[1], 2026 NumOps-1); 2027 const Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace()); 2028 return UndefValue::get(GEPTy); 2029 } 2030 2031 if (NumOps == 2) { 2032 // getelementptr P, 0 -> P. 2033 if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1])) 2034 if (C->isZero()) 2035 return Ops[0]; 2036 // getelementptr P, N -> P if P points to a type of zero size. 2037 if (TD) { 2038 const Type *Ty = PtrTy->getElementType(); 2039 if (Ty->isSized() && TD->getTypeAllocSize(Ty) == 0) 2040 return Ops[0]; 2041 } 2042 } 2043 2044 // Check to see if this is constant foldable. 2045 for (unsigned i = 0; i != NumOps; ++i) 2046 if (!isa<Constant>(Ops[i])) 2047 return 0; 2048 2049 return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]), 2050 (Constant *const*)Ops+1, NumOps-1); 2051} 2052 2053/// SimplifyPHINode - See if we can fold the given phi. If not, returns null. 2054static Value *SimplifyPHINode(PHINode *PN, const DominatorTree *DT) { 2055 // If all of the PHI's incoming values are the same then replace the PHI node 2056 // with the common value. 2057 Value *CommonValue = 0; 2058 bool HasUndefInput = false; 2059 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 2060 Value *Incoming = PN->getIncomingValue(i); 2061 // If the incoming value is the phi node itself, it can safely be skipped. 2062 if (Incoming == PN) continue; 2063 if (isa<UndefValue>(Incoming)) { 2064 // Remember that we saw an undef value, but otherwise ignore them. 2065 HasUndefInput = true; 2066 continue; 2067 } 2068 if (CommonValue && Incoming != CommonValue) 2069 return 0; // Not the same, bail out. 2070 CommonValue = Incoming; 2071 } 2072 2073 // If CommonValue is null then all of the incoming values were either undef or 2074 // equal to the phi node itself. 2075 if (!CommonValue) 2076 return UndefValue::get(PN->getType()); 2077 2078 // If we have a PHI node like phi(X, undef, X), where X is defined by some 2079 // instruction, we cannot return X as the result of the PHI node unless it 2080 // dominates the PHI block. 2081 if (HasUndefInput) 2082 return ValueDominatesPHI(CommonValue, PN, DT) ? CommonValue : 0; 2083 2084 return CommonValue; 2085} 2086 2087 2088//=== Helper functions for higher up the class hierarchy. 2089 2090/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can 2091/// fold the result. If not, this returns null. 2092static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 2093 const TargetData *TD, const DominatorTree *DT, 2094 unsigned MaxRecurse) { 2095 switch (Opcode) { 2096 case Instruction::Add: 2097 return SimplifyAddInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2098 TD, DT, MaxRecurse); 2099 case Instruction::Sub: 2100 return SimplifySubInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2101 TD, DT, MaxRecurse); 2102 case Instruction::Mul: return SimplifyMulInst (LHS, RHS, TD, DT, MaxRecurse); 2103 case Instruction::SDiv: return SimplifySDivInst(LHS, RHS, TD, DT, MaxRecurse); 2104 case Instruction::UDiv: return SimplifyUDivInst(LHS, RHS, TD, DT, MaxRecurse); 2105 case Instruction::FDiv: return SimplifyFDivInst(LHS, RHS, TD, DT, MaxRecurse); 2106 case Instruction::SRem: return SimplifySRemInst(LHS, RHS, TD, DT, MaxRecurse); 2107 case Instruction::URem: return SimplifyURemInst(LHS, RHS, TD, DT, MaxRecurse); 2108 case Instruction::FRem: return SimplifyFRemInst(LHS, RHS, TD, DT, MaxRecurse); 2109 case Instruction::Shl: 2110 return SimplifyShlInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, 2111 TD, DT, MaxRecurse); 2112 case Instruction::LShr: 2113 return SimplifyLShrInst(LHS, RHS, /*isExact*/false, TD, DT, MaxRecurse); 2114 case Instruction::AShr: 2115 return SimplifyAShrInst(LHS, RHS, /*isExact*/false, TD, DT, MaxRecurse); 2116 case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, DT, MaxRecurse); 2117 case Instruction::Or: return SimplifyOrInst (LHS, RHS, TD, DT, MaxRecurse); 2118 case Instruction::Xor: return SimplifyXorInst(LHS, RHS, TD, DT, MaxRecurse); 2119 default: 2120 if (Constant *CLHS = dyn_cast<Constant>(LHS)) 2121 if (Constant *CRHS = dyn_cast<Constant>(RHS)) { 2122 Constant *COps[] = {CLHS, CRHS}; 2123 return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, 2, TD); 2124 } 2125 2126 // If the operation is associative, try some generic simplifications. 2127 if (Instruction::isAssociative(Opcode)) 2128 if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, TD, DT, 2129 MaxRecurse)) 2130 return V; 2131 2132 // If the operation is with the result of a select instruction, check whether 2133 // operating on either branch of the select always yields the same value. 2134 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 2135 if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, DT, 2136 MaxRecurse)) 2137 return V; 2138 2139 // If the operation is with the result of a phi instruction, check whether 2140 // operating on all incoming values of the phi always yields the same value. 2141 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 2142 if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, DT, MaxRecurse)) 2143 return V; 2144 2145 return 0; 2146 } 2147} 2148 2149Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 2150 const TargetData *TD, const DominatorTree *DT) { 2151 return ::SimplifyBinOp(Opcode, LHS, RHS, TD, DT, RecursionLimit); 2152} 2153 2154/// SimplifyCmpInst - Given operands for a CmpInst, see if we can 2155/// fold the result. 2156static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2157 const TargetData *TD, const DominatorTree *DT, 2158 unsigned MaxRecurse) { 2159 if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate)) 2160 return SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse); 2161 return SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse); 2162} 2163 2164Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 2165 const TargetData *TD, const DominatorTree *DT) { 2166 return ::SimplifyCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 2167} 2168 2169/// SimplifyInstruction - See if we can compute a simplified version of this 2170/// instruction. If not, this returns null. 2171Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD, 2172 const DominatorTree *DT) { 2173 Value *Result; 2174 2175 switch (I->getOpcode()) { 2176 default: 2177 Result = ConstantFoldInstruction(I, TD); 2178 break; 2179 case Instruction::Add: 2180 Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1), 2181 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2182 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2183 TD, DT); 2184 break; 2185 case Instruction::Sub: 2186 Result = SimplifySubInst(I->getOperand(0), I->getOperand(1), 2187 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2188 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2189 TD, DT); 2190 break; 2191 case Instruction::Mul: 2192 Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, DT); 2193 break; 2194 case Instruction::SDiv: 2195 Result = SimplifySDivInst(I->getOperand(0), I->getOperand(1), TD, DT); 2196 break; 2197 case Instruction::UDiv: 2198 Result = SimplifyUDivInst(I->getOperand(0), I->getOperand(1), TD, DT); 2199 break; 2200 case Instruction::FDiv: 2201 Result = SimplifyFDivInst(I->getOperand(0), I->getOperand(1), TD, DT); 2202 break; 2203 case Instruction::SRem: 2204 Result = SimplifySRemInst(I->getOperand(0), I->getOperand(1), TD, DT); 2205 break; 2206 case Instruction::URem: 2207 Result = SimplifyURemInst(I->getOperand(0), I->getOperand(1), TD, DT); 2208 break; 2209 case Instruction::FRem: 2210 Result = SimplifyFRemInst(I->getOperand(0), I->getOperand(1), TD, DT); 2211 break; 2212 case Instruction::Shl: 2213 Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1), 2214 cast<BinaryOperator>(I)->hasNoSignedWrap(), 2215 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 2216 TD, DT); 2217 break; 2218 case Instruction::LShr: 2219 Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1), 2220 cast<BinaryOperator>(I)->isExact(), 2221 TD, DT); 2222 break; 2223 case Instruction::AShr: 2224 Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1), 2225 cast<BinaryOperator>(I)->isExact(), 2226 TD, DT); 2227 break; 2228 case Instruction::And: 2229 Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT); 2230 break; 2231 case Instruction::Or: 2232 Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT); 2233 break; 2234 case Instruction::Xor: 2235 Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, DT); 2236 break; 2237 case Instruction::ICmp: 2238 Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(), 2239 I->getOperand(0), I->getOperand(1), TD, DT); 2240 break; 2241 case Instruction::FCmp: 2242 Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(), 2243 I->getOperand(0), I->getOperand(1), TD, DT); 2244 break; 2245 case Instruction::Select: 2246 Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1), 2247 I->getOperand(2), TD, DT); 2248 break; 2249 case Instruction::GetElementPtr: { 2250 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end()); 2251 Result = SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT); 2252 break; 2253 } 2254 case Instruction::PHI: 2255 Result = SimplifyPHINode(cast<PHINode>(I), DT); 2256 break; 2257 } 2258 2259 /// If called on unreachable code, the above logic may report that the 2260 /// instruction simplified to itself. Make life easier for users by 2261 /// detecting that case here, returning a safe value instead. 2262 return Result == I ? UndefValue::get(I->getType()) : Result; 2263} 2264 2265/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then 2266/// delete the From instruction. In addition to a basic RAUW, this does a 2267/// recursive simplification of the newly formed instructions. This catches 2268/// things where one simplification exposes other opportunities. This only 2269/// simplifies and deletes scalar operations, it does not change the CFG. 2270/// 2271void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To, 2272 const TargetData *TD, 2273 const DominatorTree *DT) { 2274 assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!"); 2275 2276 // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that 2277 // we can know if it gets deleted out from under us or replaced in a 2278 // recursive simplification. 2279 WeakVH FromHandle(From); 2280 WeakVH ToHandle(To); 2281 2282 while (!From->use_empty()) { 2283 // Update the instruction to use the new value. 2284 Use &TheUse = From->use_begin().getUse(); 2285 Instruction *User = cast<Instruction>(TheUse.getUser()); 2286 TheUse = To; 2287 2288 // Check to see if the instruction can be folded due to the operand 2289 // replacement. For example changing (or X, Y) into (or X, -1) can replace 2290 // the 'or' with -1. 2291 Value *SimplifiedVal; 2292 { 2293 // Sanity check to make sure 'User' doesn't dangle across 2294 // SimplifyInstruction. 2295 AssertingVH<> UserHandle(User); 2296 2297 SimplifiedVal = SimplifyInstruction(User, TD, DT); 2298 if (SimplifiedVal == 0) continue; 2299 } 2300 2301 // Recursively simplify this user to the new value. 2302 ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, DT); 2303 From = dyn_cast_or_null<Instruction>((Value*)FromHandle); 2304 To = ToHandle; 2305 2306 assert(ToHandle && "To value deleted by recursive simplification?"); 2307 2308 // If the recursive simplification ended up revisiting and deleting 2309 // 'From' then we're done. 2310 if (From == 0) 2311 return; 2312 } 2313 2314 // If 'From' has value handles referring to it, do a real RAUW to update them. 2315 From->replaceAllUsesWith(To); 2316 2317 From->eraseFromParent(); 2318} 2319