InstructionSimplify.cpp revision b2f3c383ec62b959ee27d0a5fb890894c4e49e86
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/ADT/Statistic.h" 22#include "llvm/Analysis/InstructionSimplify.h" 23#include "llvm/Analysis/ConstantFolding.h" 24#include "llvm/Analysis/Dominators.h" 25#include "llvm/Support/PatternMatch.h" 26#include "llvm/Support/ValueHandle.h" 27#include "llvm/Target/TargetData.h" 28using namespace llvm; 29using namespace llvm::PatternMatch; 30 31#define RecursionLimit 3 32 33STATISTIC(NumExpand, "Number of expansions"); 34STATISTIC(NumFactor , "Number of factorizations"); 35STATISTIC(NumReassoc, "Number of reassociations"); 36 37static Value *SimplifyAndInst(Value *, Value *, const TargetData *, 38 const DominatorTree *, unsigned); 39static Value *SimplifyBinOp(unsigned, Value *, Value *, const TargetData *, 40 const DominatorTree *, unsigned); 41static Value *SimplifyCmpInst(unsigned, Value *, Value *, const TargetData *, 42 const DominatorTree *, unsigned); 43static Value *SimplifyOrInst(Value *, Value *, const TargetData *, 44 const DominatorTree *, unsigned); 45static Value *SimplifyXorInst(Value *, Value *, const TargetData *, 46 const DominatorTree *, unsigned); 47 48/// ValueDominatesPHI - Does the given value dominate the specified phi node? 49static bool ValueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) { 50 Instruction *I = dyn_cast<Instruction>(V); 51 if (!I) 52 // Arguments and constants dominate all instructions. 53 return true; 54 55 // If we have a DominatorTree then do a precise test. 56 if (DT) 57 return DT->dominates(I, P); 58 59 // Otherwise, if the instruction is in the entry block, and is not an invoke, 60 // then it obviously dominates all phi nodes. 61 if (I->getParent() == &I->getParent()->getParent()->getEntryBlock() && 62 !isa<InvokeInst>(I)) 63 return true; 64 65 return false; 66} 67 68/// ExpandBinOp - Simplify "A op (B op' C)" by distributing op over op', turning 69/// it into "(A op B) op' (A op C)". Here "op" is given by Opcode and "op'" is 70/// given by OpcodeToExpand, while "A" corresponds to LHS and "B op' C" to RHS. 71/// Also performs the transform "(A op' B) op C" -> "(A op C) op' (B op C)". 72/// Returns the simplified value, or null if no simplification was performed. 73static Value *ExpandBinOp(unsigned Opcode, Value *LHS, Value *RHS, 74 unsigned OpcToExpand, const TargetData *TD, 75 const DominatorTree *DT, unsigned MaxRecurse) { 76 Instruction::BinaryOps OpcodeToExpand = (Instruction::BinaryOps)OpcToExpand; 77 // Recursion is always used, so bail out at once if we already hit the limit. 78 if (!MaxRecurse--) 79 return 0; 80 81 // Check whether the expression has the form "(A op' B) op C". 82 if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS)) 83 if (Op0->getOpcode() == OpcodeToExpand) { 84 // It does! Try turning it into "(A op C) op' (B op C)". 85 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; 86 // Do "A op C" and "B op C" both simplify? 87 if (Value *L = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse)) 88 if (Value *R = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) { 89 // They do! Return "L op' R" if it simplifies or is already available. 90 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. 91 if ((L == A && R == B) || (Instruction::isCommutative(OpcodeToExpand) 92 && L == B && R == A)) { 93 ++NumExpand; 94 return LHS; 95 } 96 // Otherwise return "L op' R" if it simplifies. 97 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT, 98 MaxRecurse)) { 99 ++NumExpand; 100 return V; 101 } 102 } 103 } 104 105 // Check whether the expression has the form "A op (B op' C)". 106 if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS)) 107 if (Op1->getOpcode() == OpcodeToExpand) { 108 // It does! Try turning it into "(A op B) op' (A op C)". 109 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); 110 // Do "A op B" and "A op C" both simplify? 111 if (Value *L = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse)) 112 if (Value *R = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse)) { 113 // They do! Return "L op' R" if it simplifies or is already available. 114 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. 115 if ((L == B && R == C) || (Instruction::isCommutative(OpcodeToExpand) 116 && L == C && R == B)) { 117 ++NumExpand; 118 return RHS; 119 } 120 // Otherwise return "L op' R" if it simplifies. 121 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT, 122 MaxRecurse)) { 123 ++NumExpand; 124 return V; 125 } 126 } 127 } 128 129 return 0; 130} 131 132/// FactorizeBinOp - Simplify "LHS Opcode RHS" by factorizing out a common term 133/// using the operation OpCodeToExtract. For example, when Opcode is Add and 134/// OpCodeToExtract is Mul then this tries to turn "(A*B)+(A*C)" into "A*(B+C)". 135/// Returns the simplified value, or null if no simplification was performed. 136static Value *FactorizeBinOp(unsigned Opcode, Value *LHS, Value *RHS, 137 unsigned OpcToExtract, const TargetData *TD, 138 const DominatorTree *DT, unsigned MaxRecurse) { 139 Instruction::BinaryOps OpcodeToExtract = (Instruction::BinaryOps)OpcToExtract; 140 // Recursion is always used, so bail out at once if we already hit the limit. 141 if (!MaxRecurse--) 142 return 0; 143 144 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 145 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 146 147 if (!Op0 || Op0->getOpcode() != OpcodeToExtract || 148 !Op1 || Op1->getOpcode() != OpcodeToExtract) 149 return 0; 150 151 // The expression has the form "(A op' B) op (C op' D)". 152 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1); 153 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1); 154 155 // Use left distributivity, i.e. "X op' (Y op Z) = (X op' Y) op (X op' Z)". 156 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the 157 // commutative case, "(A op' B) op (C op' A)"? 158 if (A == C || (Instruction::isCommutative(OpcodeToExtract) && A == D)) { 159 Value *DD = A == C ? D : C; 160 // Form "A op' (B op DD)" if it simplifies completely. 161 // Does "B op DD" simplify? 162 if (Value *V = SimplifyBinOp(Opcode, B, DD, TD, DT, MaxRecurse)) { 163 // It does! Return "A op' V" if it simplifies or is already available. 164 // If V equals B then "A op' V" is just the LHS. If V equals DD then 165 // "A op' V" is just the RHS. 166 if (V == B || V == DD) { 167 ++NumFactor; 168 return V == B ? LHS : RHS; 169 } 170 // Otherwise return "A op' V" if it simplifies. 171 if (Value *W = SimplifyBinOp(OpcodeToExtract, A, V, TD, DT, MaxRecurse)) { 172 ++NumFactor; 173 return W; 174 } 175 } 176 } 177 178 // Use right distributivity, i.e. "(X op Y) op' Z = (X op' Z) op (Y op' Z)". 179 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the 180 // commutative case, "(A op' B) op (B op' D)"? 181 if (B == D || (Instruction::isCommutative(OpcodeToExtract) && B == C)) { 182 Value *CC = B == D ? C : D; 183 // Form "(A op CC) op' B" if it simplifies completely.. 184 // Does "A op CC" simplify? 185 if (Value *V = SimplifyBinOp(Opcode, A, CC, TD, DT, MaxRecurse)) { 186 // It does! Return "V op' B" if it simplifies or is already available. 187 // If V equals A then "V op' B" is just the LHS. If V equals CC then 188 // "V op' B" is just the RHS. 189 if (V == A || V == CC) { 190 ++NumFactor; 191 return V == A ? LHS : RHS; 192 } 193 // Otherwise return "V op' B" if it simplifies. 194 if (Value *W = SimplifyBinOp(OpcodeToExtract, V, B, TD, DT, MaxRecurse)) { 195 ++NumFactor; 196 return W; 197 } 198 } 199 } 200 201 return 0; 202} 203 204/// SimplifyAssociativeBinOp - Generic simplifications for associative binary 205/// operations. Returns the simpler value, or null if none was found. 206static Value *SimplifyAssociativeBinOp(unsigned Opc, Value *LHS, Value *RHS, 207 const TargetData *TD, 208 const DominatorTree *DT, 209 unsigned MaxRecurse) { 210 Instruction::BinaryOps Opcode = (Instruction::BinaryOps)Opc; 211 assert(Instruction::isAssociative(Opcode) && "Not an associative operation!"); 212 213 // Recursion is always used, so bail out at once if we already hit the limit. 214 if (!MaxRecurse--) 215 return 0; 216 217 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 218 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 219 220 // Transform: "(A op B) op C" ==> "A op (B op C)" if it simplifies completely. 221 if (Op0 && Op0->getOpcode() == Opcode) { 222 Value *A = Op0->getOperand(0); 223 Value *B = Op0->getOperand(1); 224 Value *C = RHS; 225 226 // Does "B op C" simplify? 227 if (Value *V = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) { 228 // It does! Return "A op V" if it simplifies or is already available. 229 // If V equals B then "A op V" is just the LHS. 230 if (V == B) return LHS; 231 // Otherwise return "A op V" if it simplifies. 232 if (Value *W = SimplifyBinOp(Opcode, A, V, TD, DT, MaxRecurse)) { 233 ++NumReassoc; 234 return W; 235 } 236 } 237 } 238 239 // Transform: "A op (B op C)" ==> "(A op B) op C" if it simplifies completely. 240 if (Op1 && Op1->getOpcode() == Opcode) { 241 Value *A = LHS; 242 Value *B = Op1->getOperand(0); 243 Value *C = Op1->getOperand(1); 244 245 // Does "A op B" simplify? 246 if (Value *V = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse)) { 247 // It does! Return "V op C" if it simplifies or is already available. 248 // If V equals B then "V op C" is just the RHS. 249 if (V == B) return RHS; 250 // Otherwise return "V op C" if it simplifies. 251 if (Value *W = SimplifyBinOp(Opcode, V, C, TD, DT, MaxRecurse)) { 252 ++NumReassoc; 253 return W; 254 } 255 } 256 } 257 258 // The remaining transforms require commutativity as well as associativity. 259 if (!Instruction::isCommutative(Opcode)) 260 return 0; 261 262 // Transform: "(A op B) op C" ==> "(C op A) op B" if it simplifies completely. 263 if (Op0 && Op0->getOpcode() == Opcode) { 264 Value *A = Op0->getOperand(0); 265 Value *B = Op0->getOperand(1); 266 Value *C = RHS; 267 268 // Does "C op A" simplify? 269 if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) { 270 // It does! Return "V op B" if it simplifies or is already available. 271 // If V equals A then "V op B" is just the LHS. 272 if (V == A) return LHS; 273 // Otherwise return "V op B" if it simplifies. 274 if (Value *W = SimplifyBinOp(Opcode, V, B, TD, DT, MaxRecurse)) { 275 ++NumReassoc; 276 return W; 277 } 278 } 279 } 280 281 // Transform: "A op (B op C)" ==> "B op (C op A)" if it simplifies completely. 282 if (Op1 && Op1->getOpcode() == Opcode) { 283 Value *A = LHS; 284 Value *B = Op1->getOperand(0); 285 Value *C = Op1->getOperand(1); 286 287 // Does "C op A" simplify? 288 if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) { 289 // It does! Return "B op V" if it simplifies or is already available. 290 // If V equals C then "B op V" is just the RHS. 291 if (V == C) return RHS; 292 // Otherwise return "B op V" if it simplifies. 293 if (Value *W = SimplifyBinOp(Opcode, B, V, TD, DT, MaxRecurse)) { 294 ++NumReassoc; 295 return W; 296 } 297 } 298 } 299 300 return 0; 301} 302 303/// ThreadBinOpOverSelect - In the case of a binary operation with a select 304/// instruction as an operand, try to simplify the binop by seeing whether 305/// evaluating it on both branches of the select results in the same value. 306/// Returns the common value if so, otherwise returns null. 307static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS, 308 const TargetData *TD, 309 const DominatorTree *DT, 310 unsigned MaxRecurse) { 311 // Recursion is always used, so bail out at once if we already hit the limit. 312 if (!MaxRecurse--) 313 return 0; 314 315 SelectInst *SI; 316 if (isa<SelectInst>(LHS)) { 317 SI = cast<SelectInst>(LHS); 318 } else { 319 assert(isa<SelectInst>(RHS) && "No select instruction operand!"); 320 SI = cast<SelectInst>(RHS); 321 } 322 323 // Evaluate the BinOp on the true and false branches of the select. 324 Value *TV; 325 Value *FV; 326 if (SI == LHS) { 327 TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, TD, DT, MaxRecurse); 328 FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, TD, DT, MaxRecurse); 329 } else { 330 TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), TD, DT, MaxRecurse); 331 FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), TD, DT, MaxRecurse); 332 } 333 334 // If they simplified to the same value, then return the common value. 335 // If they both failed to simplify then return null. 336 if (TV == FV) 337 return TV; 338 339 // If one branch simplified to undef, return the other one. 340 if (TV && isa<UndefValue>(TV)) 341 return FV; 342 if (FV && isa<UndefValue>(FV)) 343 return TV; 344 345 // If applying the operation did not change the true and false select values, 346 // then the result of the binop is the select itself. 347 if (TV == SI->getTrueValue() && FV == SI->getFalseValue()) 348 return SI; 349 350 // If one branch simplified and the other did not, and the simplified 351 // value is equal to the unsimplified one, return the simplified value. 352 // For example, select (cond, X, X & Z) & Z -> X & Z. 353 if ((FV && !TV) || (TV && !FV)) { 354 // Check that the simplified value has the form "X op Y" where "op" is the 355 // same as the original operation. 356 Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV); 357 if (Simplified && Simplified->getOpcode() == Opcode) { 358 // The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS". 359 // We already know that "op" is the same as for the simplified value. See 360 // if the operands match too. If so, return the simplified value. 361 Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue(); 362 Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS; 363 Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch; 364 if (Simplified->getOperand(0) == UnsimplifiedLHS && 365 Simplified->getOperand(1) == UnsimplifiedRHS) 366 return Simplified; 367 if (Simplified->isCommutative() && 368 Simplified->getOperand(1) == UnsimplifiedLHS && 369 Simplified->getOperand(0) == UnsimplifiedRHS) 370 return Simplified; 371 } 372 } 373 374 return 0; 375} 376 377/// ThreadCmpOverSelect - In the case of a comparison with a select instruction, 378/// try to simplify the comparison by seeing whether both branches of the select 379/// result in the same value. Returns the common value if so, otherwise returns 380/// null. 381static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS, 382 Value *RHS, const TargetData *TD, 383 const DominatorTree *DT, 384 unsigned MaxRecurse) { 385 // Recursion is always used, so bail out at once if we already hit the limit. 386 if (!MaxRecurse--) 387 return 0; 388 389 // Make sure the select is on the LHS. 390 if (!isa<SelectInst>(LHS)) { 391 std::swap(LHS, RHS); 392 Pred = CmpInst::getSwappedPredicate(Pred); 393 } 394 assert(isa<SelectInst>(LHS) && "Not comparing with a select instruction!"); 395 SelectInst *SI = cast<SelectInst>(LHS); 396 397 // Now that we have "cmp select(cond, TV, FV), RHS", analyse it. 398 // Does "cmp TV, RHS" simplify? 399 if (Value *TCmp = SimplifyCmpInst(Pred, SI->getTrueValue(), RHS, TD, DT, 400 MaxRecurse)) 401 // It does! Does "cmp FV, RHS" simplify? 402 if (Value *FCmp = SimplifyCmpInst(Pred, SI->getFalseValue(), RHS, TD, DT, 403 MaxRecurse)) 404 // It does! If they simplified to the same value, then use it as the 405 // result of the original comparison. 406 if (TCmp == FCmp) 407 return TCmp; 408 return 0; 409} 410 411/// ThreadBinOpOverPHI - In the case of a binary operation with an operand that 412/// is a PHI instruction, try to simplify the binop by seeing whether evaluating 413/// it on the incoming phi values yields the same result for every value. If so 414/// returns the common value, otherwise returns null. 415static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS, 416 const TargetData *TD, const DominatorTree *DT, 417 unsigned MaxRecurse) { 418 // Recursion is always used, so bail out at once if we already hit the limit. 419 if (!MaxRecurse--) 420 return 0; 421 422 PHINode *PI; 423 if (isa<PHINode>(LHS)) { 424 PI = cast<PHINode>(LHS); 425 // Bail out if RHS and the phi may be mutually interdependent due to a loop. 426 if (!ValueDominatesPHI(RHS, PI, DT)) 427 return 0; 428 } else { 429 assert(isa<PHINode>(RHS) && "No PHI instruction operand!"); 430 PI = cast<PHINode>(RHS); 431 // Bail out if LHS and the phi may be mutually interdependent due to a loop. 432 if (!ValueDominatesPHI(LHS, PI, DT)) 433 return 0; 434 } 435 436 // Evaluate the BinOp on the incoming phi values. 437 Value *CommonValue = 0; 438 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) { 439 Value *Incoming = PI->getIncomingValue(i); 440 // If the incoming value is the phi node itself, it can safely be skipped. 441 if (Incoming == PI) continue; 442 Value *V = PI == LHS ? 443 SimplifyBinOp(Opcode, Incoming, RHS, TD, DT, MaxRecurse) : 444 SimplifyBinOp(Opcode, LHS, Incoming, TD, DT, MaxRecurse); 445 // If the operation failed to simplify, or simplified to a different value 446 // to previously, then give up. 447 if (!V || (CommonValue && V != CommonValue)) 448 return 0; 449 CommonValue = V; 450 } 451 452 return CommonValue; 453} 454 455/// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try 456/// try to simplify the comparison by seeing whether comparing with all of the 457/// incoming phi values yields the same result every time. If so returns the 458/// common result, otherwise returns null. 459static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS, 460 const TargetData *TD, const DominatorTree *DT, 461 unsigned MaxRecurse) { 462 // Recursion is always used, so bail out at once if we already hit the limit. 463 if (!MaxRecurse--) 464 return 0; 465 466 // Make sure the phi is on the LHS. 467 if (!isa<PHINode>(LHS)) { 468 std::swap(LHS, RHS); 469 Pred = CmpInst::getSwappedPredicate(Pred); 470 } 471 assert(isa<PHINode>(LHS) && "Not comparing with a phi instruction!"); 472 PHINode *PI = cast<PHINode>(LHS); 473 474 // Bail out if RHS and the phi may be mutually interdependent due to a loop. 475 if (!ValueDominatesPHI(RHS, PI, DT)) 476 return 0; 477 478 // Evaluate the BinOp on the incoming phi values. 479 Value *CommonValue = 0; 480 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) { 481 Value *Incoming = PI->getIncomingValue(i); 482 // If the incoming value is the phi node itself, it can safely be skipped. 483 if (Incoming == PI) continue; 484 Value *V = SimplifyCmpInst(Pred, Incoming, RHS, TD, DT, MaxRecurse); 485 // If the operation failed to simplify, or simplified to a different value 486 // to previously, then give up. 487 if (!V || (CommonValue && V != CommonValue)) 488 return 0; 489 CommonValue = V; 490 } 491 492 return CommonValue; 493} 494 495/// SimplifyAddInst - Given operands for an Add, see if we can 496/// fold the result. If not, this returns null. 497static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 498 const TargetData *TD, const DominatorTree *DT, 499 unsigned MaxRecurse) { 500 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 501 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 502 Constant *Ops[] = { CLHS, CRHS }; 503 return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(), 504 Ops, 2, TD); 505 } 506 507 // Canonicalize the constant to the RHS. 508 std::swap(Op0, Op1); 509 } 510 511 // X + undef -> undef 512 if (isa<UndefValue>(Op1)) 513 return Op1; 514 515 // X + 0 -> X 516 if (match(Op1, m_Zero())) 517 return Op0; 518 519 // X + (Y - X) -> Y 520 // (Y - X) + X -> Y 521 // Eg: X + -X -> 0 522 Value *Y = 0; 523 if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) || 524 match(Op0, m_Sub(m_Value(Y), m_Specific(Op1)))) 525 return Y; 526 527 // X + ~X -> -1 since ~X = -X-1 528 if (match(Op0, m_Not(m_Specific(Op1))) || 529 match(Op1, m_Not(m_Specific(Op0)))) 530 return Constant::getAllOnesValue(Op0->getType()); 531 532 /// i1 add -> xor. 533 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 534 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1)) 535 return V; 536 537 // Try some generic simplifications for associative operations. 538 if (Value *V = SimplifyAssociativeBinOp(Instruction::Add, Op0, Op1, TD, DT, 539 MaxRecurse)) 540 return V; 541 542 // Mul distributes over Add. Try some generic simplifications based on this. 543 if (Value *V = FactorizeBinOp(Instruction::Add, Op0, Op1, Instruction::Mul, 544 TD, DT, MaxRecurse)) 545 return V; 546 547 // Threading Add over selects and phi nodes is pointless, so don't bother. 548 // Threading over the select in "A + select(cond, B, C)" means evaluating 549 // "A+B" and "A+C" and seeing if they are equal; but they are equal if and 550 // only if B and C are equal. If B and C are equal then (since we assume 551 // that operands have already been simplified) "select(cond, B, C)" should 552 // have been simplified to the common value of B and C already. Analysing 553 // "A+B" and "A+C" thus gains nothing, but costs compile time. Similarly 554 // for threading over phi nodes. 555 556 return 0; 557} 558 559Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 560 const TargetData *TD, const DominatorTree *DT) { 561 return ::SimplifyAddInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit); 562} 563 564/// SimplifySubInst - Given operands for a Sub, see if we can 565/// fold the result. If not, this returns null. 566static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 567 const TargetData *TD, const DominatorTree *DT, 568 unsigned MaxRecurse) { 569 if (Constant *CLHS = dyn_cast<Constant>(Op0)) 570 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 571 Constant *Ops[] = { CLHS, CRHS }; 572 return ConstantFoldInstOperands(Instruction::Sub, CLHS->getType(), 573 Ops, 2, TD); 574 } 575 576 // X - undef -> undef 577 // undef - X -> undef 578 if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1)) 579 return UndefValue::get(Op0->getType()); 580 581 // X - 0 -> X 582 if (match(Op1, m_Zero())) 583 return Op0; 584 585 // X - X -> 0 586 if (Op0 == Op1) 587 return Constant::getNullValue(Op0->getType()); 588 589 // (X*2) - X -> X 590 // (X<<1) - X -> X 591 Value *X = 0; 592 if (match(Op0, m_Mul(m_Specific(Op1), m_ConstantInt<2>())) || 593 match(Op0, m_Shl(m_Specific(Op1), m_One()))) 594 return Op1; 595 596 // (X + Y) - Z -> X + (Y - Z) or Y + (X - Z) if everything simplifies. 597 // For example, (X + Y) - Y -> X; (Y + X) - Y -> X 598 Value *Y = 0, *Z = Op1; 599 if (MaxRecurse && match(Op0, m_Add(m_Value(X), m_Value(Y)))) { // (X + Y) - Z 600 // See if "V === Y - Z" simplifies. 601 if (Value *V = SimplifyBinOp(Instruction::Sub, Y, Z, TD, DT, MaxRecurse-1)) 602 // It does! Now see if "X + V" simplifies. 603 if (Value *W = SimplifyBinOp(Instruction::Add, X, V, TD, DT, 604 MaxRecurse-1)) { 605 // It does, we successfully reassociated! 606 ++NumReassoc; 607 return W; 608 } 609 // See if "V === X - Z" simplifies. 610 if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, TD, DT, MaxRecurse-1)) 611 // It does! Now see if "Y + V" simplifies. 612 if (Value *W = SimplifyBinOp(Instruction::Add, Y, V, TD, DT, 613 MaxRecurse-1)) { 614 // It does, we successfully reassociated! 615 ++NumReassoc; 616 return W; 617 } 618 } 619 620 // X - (Y + Z) -> (X - Y) - Z or (X - Z) - Y if everything simplifies. 621 // For example, X - (X + 1) -> -1 622 X = Op0; 623 if (MaxRecurse && match(Op1, m_Add(m_Value(Y), m_Value(Z)))) { // X - (Y + Z) 624 // See if "V === X - Y" simplifies. 625 if (Value *V = SimplifyBinOp(Instruction::Sub, X, Y, TD, DT, MaxRecurse-1)) 626 // It does! Now see if "V - Z" simplifies. 627 if (Value *W = SimplifyBinOp(Instruction::Sub, V, Z, TD, DT, 628 MaxRecurse-1)) { 629 // It does, we successfully reassociated! 630 ++NumReassoc; 631 return W; 632 } 633 // See if "V === X - Z" simplifies. 634 if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, TD, DT, MaxRecurse-1)) 635 // It does! Now see if "V - Y" simplifies. 636 if (Value *W = SimplifyBinOp(Instruction::Sub, V, Y, TD, DT, 637 MaxRecurse-1)) { 638 // It does, we successfully reassociated! 639 ++NumReassoc; 640 return W; 641 } 642 } 643 644 // Z - (X - Y) -> (Z - X) + Y if everything simplifies. 645 // For example, X - (X - Y) -> Y. 646 Z = Op0; 647 if (MaxRecurse && match(Op1, m_Sub(m_Value(X), m_Value(Y)))) // Z - (X - Y) 648 // See if "V === Z - X" simplifies. 649 if (Value *V = SimplifyBinOp(Instruction::Sub, Z, X, TD, DT, MaxRecurse-1)) 650 // It does! Now see if "V + Y" simplifies. 651 if (Value *W = SimplifyBinOp(Instruction::Add, V, Y, TD, DT, 652 MaxRecurse-1)) { 653 // It does, we successfully reassociated! 654 ++NumReassoc; 655 return W; 656 } 657 658 // Mul distributes over Sub. Try some generic simplifications based on this. 659 if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul, 660 TD, DT, MaxRecurse)) 661 return V; 662 663 // i1 sub -> xor. 664 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 665 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1)) 666 return V; 667 668 // Threading Sub over selects and phi nodes is pointless, so don't bother. 669 // Threading over the select in "A - select(cond, B, C)" means evaluating 670 // "A-B" and "A-C" and seeing if they are equal; but they are equal if and 671 // only if B and C are equal. If B and C are equal then (since we assume 672 // that operands have already been simplified) "select(cond, B, C)" should 673 // have been simplified to the common value of B and C already. Analysing 674 // "A-B" and "A-C" thus gains nothing, but costs compile time. Similarly 675 // for threading over phi nodes. 676 677 return 0; 678} 679 680Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 681 const TargetData *TD, const DominatorTree *DT) { 682 return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit); 683} 684 685/// SimplifyMulInst - Given operands for a Mul, see if we can 686/// fold the result. If not, this returns null. 687static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD, 688 const DominatorTree *DT, unsigned MaxRecurse) { 689 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 690 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 691 Constant *Ops[] = { CLHS, CRHS }; 692 return ConstantFoldInstOperands(Instruction::Mul, CLHS->getType(), 693 Ops, 2, TD); 694 } 695 696 // Canonicalize the constant to the RHS. 697 std::swap(Op0, Op1); 698 } 699 700 // X * undef -> 0 701 if (isa<UndefValue>(Op1)) 702 return Constant::getNullValue(Op0->getType()); 703 704 // X * 0 -> 0 705 if (match(Op1, m_Zero())) 706 return Op1; 707 708 // X * 1 -> X 709 if (match(Op1, m_One())) 710 return Op0; 711 712 /// i1 mul -> and. 713 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 714 if (Value *V = SimplifyAndInst(Op0, Op1, TD, DT, MaxRecurse-1)) 715 return V; 716 717 // Try some generic simplifications for associative operations. 718 if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, TD, DT, 719 MaxRecurse)) 720 return V; 721 722 // Mul distributes over Add. Try some generic simplifications based on this. 723 if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add, 724 TD, DT, MaxRecurse)) 725 return V; 726 727 // If the operation is with the result of a select instruction, check whether 728 // operating on either branch of the select always yields the same value. 729 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 730 if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, TD, DT, 731 MaxRecurse)) 732 return V; 733 734 // If the operation is with the result of a phi instruction, check whether 735 // operating on all incoming values of the phi always yields the same value. 736 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 737 if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, TD, DT, 738 MaxRecurse)) 739 return V; 740 741 return 0; 742} 743 744Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD, 745 const DominatorTree *DT) { 746 return ::SimplifyMulInst(Op0, Op1, TD, DT, RecursionLimit); 747} 748 749/// SimplifyShift - Given operands for an Shl, LShr or AShr, see if we can 750/// fold the result. If not, this returns null. 751static Value *SimplifyShift(unsigned Opcode, Value *Op0, Value *Op1, 752 const TargetData *TD, const DominatorTree *DT, 753 unsigned MaxRecurse) { 754 if (Constant *C0 = dyn_cast<Constant>(Op0)) { 755 if (Constant *C1 = dyn_cast<Constant>(Op1)) { 756 Constant *Ops[] = { C0, C1 }; 757 return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, 2, TD); 758 } 759 } 760 761 // 0 shift by X -> 0 762 if (match(Op0, m_Zero())) 763 return Op0; 764 765 // X shift by 0 -> X 766 if (match(Op1, m_Zero())) 767 return Op0; 768 769 // X shift by undef -> undef because it may shift by the bitwidth. 770 if (isa<UndefValue>(Op1)) 771 return Op1; 772 773 // Shifting by the bitwidth or more is undefined. 774 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) 775 if (CI->getValue().getLimitedValue() >= 776 Op0->getType()->getScalarSizeInBits()) 777 return UndefValue::get(Op0->getType()); 778 779 // If the operation is with the result of a select instruction, check whether 780 // operating on either branch of the select always yields the same value. 781 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 782 if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, TD, DT, MaxRecurse)) 783 return V; 784 785 // If the operation is with the result of a phi instruction, check whether 786 // operating on all incoming values of the phi always yields the same value. 787 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 788 if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, TD, DT, MaxRecurse)) 789 return V; 790 791 return 0; 792} 793 794/// SimplifyShlInst - Given operands for an Shl, see if we can 795/// fold the result. If not, this returns null. 796static Value *SimplifyShlInst(Value *Op0, Value *Op1, const TargetData *TD, 797 const DominatorTree *DT, unsigned MaxRecurse) { 798 if (Value *V = SimplifyShift(Instruction::Shl, Op0, Op1, TD, DT, MaxRecurse)) 799 return V; 800 801 // undef << X -> 0 802 if (isa<UndefValue>(Op0)) 803 return Constant::getNullValue(Op0->getType()); 804 805 return 0; 806} 807 808Value *llvm::SimplifyShlInst(Value *Op0, Value *Op1, const TargetData *TD, 809 const DominatorTree *DT) { 810 return ::SimplifyShlInst(Op0, Op1, TD, DT, RecursionLimit); 811} 812 813/// SimplifyLShrInst - Given operands for an LShr, see if we can 814/// fold the result. If not, this returns null. 815static Value *SimplifyLShrInst(Value *Op0, Value *Op1, const TargetData *TD, 816 const DominatorTree *DT, unsigned MaxRecurse) { 817 if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, TD, DT, MaxRecurse)) 818 return V; 819 820 // undef >>l X -> 0 821 if (isa<UndefValue>(Op0)) 822 return Constant::getNullValue(Op0->getType()); 823 824 return 0; 825} 826 827Value *llvm::SimplifyLShrInst(Value *Op0, Value *Op1, const TargetData *TD, 828 const DominatorTree *DT) { 829 return ::SimplifyLShrInst(Op0, Op1, TD, DT, RecursionLimit); 830} 831 832/// SimplifyAShrInst - Given operands for an AShr, see if we can 833/// fold the result. If not, this returns null. 834static Value *SimplifyAShrInst(Value *Op0, Value *Op1, const TargetData *TD, 835 const DominatorTree *DT, unsigned MaxRecurse) { 836 if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, TD, DT, MaxRecurse)) 837 return V; 838 839 // all ones >>a X -> all ones 840 if (match(Op0, m_AllOnes())) 841 return Op0; 842 843 // undef >>a X -> all ones 844 if (isa<UndefValue>(Op0)) 845 return Constant::getAllOnesValue(Op0->getType()); 846 847 return 0; 848} 849 850Value *llvm::SimplifyAShrInst(Value *Op0, Value *Op1, const TargetData *TD, 851 const DominatorTree *DT) { 852 return ::SimplifyAShrInst(Op0, Op1, TD, DT, RecursionLimit); 853} 854 855/// SimplifyAndInst - Given operands for an And, see if we can 856/// fold the result. If not, this returns null. 857static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD, 858 const DominatorTree *DT, unsigned MaxRecurse) { 859 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 860 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 861 Constant *Ops[] = { CLHS, CRHS }; 862 return ConstantFoldInstOperands(Instruction::And, CLHS->getType(), 863 Ops, 2, TD); 864 } 865 866 // Canonicalize the constant to the RHS. 867 std::swap(Op0, Op1); 868 } 869 870 // X & undef -> 0 871 if (isa<UndefValue>(Op1)) 872 return Constant::getNullValue(Op0->getType()); 873 874 // X & X = X 875 if (Op0 == Op1) 876 return Op0; 877 878 // X & 0 = 0 879 if (match(Op1, m_Zero())) 880 return Op1; 881 882 // X & -1 = X 883 if (match(Op1, m_AllOnes())) 884 return Op0; 885 886 // A & ~A = ~A & A = 0 887 Value *A = 0, *B = 0; 888 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) || 889 (match(Op1, m_Not(m_Value(A))) && A == Op0)) 890 return Constant::getNullValue(Op0->getType()); 891 892 // (A | ?) & A = A 893 if (match(Op0, m_Or(m_Value(A), m_Value(B))) && 894 (A == Op1 || B == Op1)) 895 return Op1; 896 897 // A & (A | ?) = A 898 if (match(Op1, m_Or(m_Value(A), m_Value(B))) && 899 (A == Op0 || B == Op0)) 900 return Op0; 901 902 // Try some generic simplifications for associative operations. 903 if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, TD, DT, 904 MaxRecurse)) 905 return V; 906 907 // And distributes over Or. Try some generic simplifications based on this. 908 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or, 909 TD, DT, MaxRecurse)) 910 return V; 911 912 // And distributes over Xor. Try some generic simplifications based on this. 913 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor, 914 TD, DT, MaxRecurse)) 915 return V; 916 917 // Or distributes over And. Try some generic simplifications based on this. 918 if (Value *V = FactorizeBinOp(Instruction::And, Op0, Op1, Instruction::Or, 919 TD, DT, MaxRecurse)) 920 return V; 921 922 // If the operation is with the result of a select instruction, check whether 923 // operating on either branch of the select always yields the same value. 924 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 925 if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, DT, 926 MaxRecurse)) 927 return V; 928 929 // If the operation is with the result of a phi instruction, check whether 930 // operating on all incoming values of the phi always yields the same value. 931 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 932 if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, DT, 933 MaxRecurse)) 934 return V; 935 936 return 0; 937} 938 939Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD, 940 const DominatorTree *DT) { 941 return ::SimplifyAndInst(Op0, Op1, TD, DT, RecursionLimit); 942} 943 944/// SimplifyOrInst - Given operands for an Or, see if we can 945/// fold the result. If not, this returns null. 946static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD, 947 const DominatorTree *DT, unsigned MaxRecurse) { 948 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 949 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 950 Constant *Ops[] = { CLHS, CRHS }; 951 return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(), 952 Ops, 2, TD); 953 } 954 955 // Canonicalize the constant to the RHS. 956 std::swap(Op0, Op1); 957 } 958 959 // X | undef -> -1 960 if (isa<UndefValue>(Op1)) 961 return Constant::getAllOnesValue(Op0->getType()); 962 963 // X | X = X 964 if (Op0 == Op1) 965 return Op0; 966 967 // X | 0 = X 968 if (match(Op1, m_Zero())) 969 return Op0; 970 971 // X | -1 = -1 972 if (match(Op1, m_AllOnes())) 973 return Op1; 974 975 // A | ~A = ~A | A = -1 976 Value *A = 0, *B = 0; 977 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) || 978 (match(Op1, m_Not(m_Value(A))) && A == Op0)) 979 return Constant::getAllOnesValue(Op0->getType()); 980 981 // (A & ?) | A = A 982 if (match(Op0, m_And(m_Value(A), m_Value(B))) && 983 (A == Op1 || B == Op1)) 984 return Op1; 985 986 // A | (A & ?) = A 987 if (match(Op1, m_And(m_Value(A), m_Value(B))) && 988 (A == Op0 || B == Op0)) 989 return Op0; 990 991 // Try some generic simplifications for associative operations. 992 if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, TD, DT, 993 MaxRecurse)) 994 return V; 995 996 // Or distributes over And. Try some generic simplifications based on this. 997 if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And, 998 TD, DT, MaxRecurse)) 999 return V; 1000 1001 // And distributes over Or. Try some generic simplifications based on this. 1002 if (Value *V = FactorizeBinOp(Instruction::Or, Op0, Op1, Instruction::And, 1003 TD, DT, MaxRecurse)) 1004 return V; 1005 1006 // If the operation is with the result of a select instruction, check whether 1007 // operating on either branch of the select always yields the same value. 1008 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 1009 if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, DT, 1010 MaxRecurse)) 1011 return V; 1012 1013 // If the operation is with the result of a phi instruction, check whether 1014 // operating on all incoming values of the phi always yields the same value. 1015 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 1016 if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, DT, 1017 MaxRecurse)) 1018 return V; 1019 1020 return 0; 1021} 1022 1023Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD, 1024 const DominatorTree *DT) { 1025 return ::SimplifyOrInst(Op0, Op1, TD, DT, RecursionLimit); 1026} 1027 1028/// SimplifyXorInst - Given operands for a Xor, see if we can 1029/// fold the result. If not, this returns null. 1030static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD, 1031 const DominatorTree *DT, unsigned MaxRecurse) { 1032 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 1033 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 1034 Constant *Ops[] = { CLHS, CRHS }; 1035 return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(), 1036 Ops, 2, TD); 1037 } 1038 1039 // Canonicalize the constant to the RHS. 1040 std::swap(Op0, Op1); 1041 } 1042 1043 // A ^ undef -> undef 1044 if (isa<UndefValue>(Op1)) 1045 return Op1; 1046 1047 // A ^ 0 = A 1048 if (match(Op1, m_Zero())) 1049 return Op0; 1050 1051 // A ^ A = 0 1052 if (Op0 == Op1) 1053 return Constant::getNullValue(Op0->getType()); 1054 1055 // A ^ ~A = ~A ^ A = -1 1056 Value *A = 0; 1057 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) || 1058 (match(Op1, m_Not(m_Value(A))) && A == Op0)) 1059 return Constant::getAllOnesValue(Op0->getType()); 1060 1061 // Try some generic simplifications for associative operations. 1062 if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, TD, DT, 1063 MaxRecurse)) 1064 return V; 1065 1066 // And distributes over Xor. Try some generic simplifications based on this. 1067 if (Value *V = FactorizeBinOp(Instruction::Xor, Op0, Op1, Instruction::And, 1068 TD, DT, MaxRecurse)) 1069 return V; 1070 1071 // Threading Xor over selects and phi nodes is pointless, so don't bother. 1072 // Threading over the select in "A ^ select(cond, B, C)" means evaluating 1073 // "A^B" and "A^C" and seeing if they are equal; but they are equal if and 1074 // only if B and C are equal. If B and C are equal then (since we assume 1075 // that operands have already been simplified) "select(cond, B, C)" should 1076 // have been simplified to the common value of B and C already. Analysing 1077 // "A^B" and "A^C" thus gains nothing, but costs compile time. Similarly 1078 // for threading over phi nodes. 1079 1080 return 0; 1081} 1082 1083Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD, 1084 const DominatorTree *DT) { 1085 return ::SimplifyXorInst(Op0, Op1, TD, DT, RecursionLimit); 1086} 1087 1088static const Type *GetCompareTy(Value *Op) { 1089 return CmpInst::makeCmpResultType(Op->getType()); 1090} 1091 1092/// SimplifyICmpInst - Given operands for an ICmpInst, see if we can 1093/// fold the result. If not, this returns null. 1094static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1095 const TargetData *TD, const DominatorTree *DT, 1096 unsigned MaxRecurse) { 1097 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 1098 assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!"); 1099 1100 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 1101 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 1102 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); 1103 1104 // If we have a constant, make sure it is on the RHS. 1105 std::swap(LHS, RHS); 1106 Pred = CmpInst::getSwappedPredicate(Pred); 1107 } 1108 1109 const Type *ITy = GetCompareTy(LHS); // The return type. 1110 const Type *OpTy = LHS->getType(); // The operand type. 1111 1112 // icmp X, X -> true/false 1113 // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false 1114 // because X could be 0. 1115 if (LHS == RHS || isa<UndefValue>(RHS)) 1116 return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred)); 1117 1118 // Special case logic when the operands have i1 type. 1119 if (OpTy->isIntegerTy(1) || (OpTy->isVectorTy() && 1120 cast<VectorType>(OpTy)->getElementType()->isIntegerTy(1))) { 1121 switch (Pred) { 1122 default: break; 1123 case ICmpInst::ICMP_EQ: 1124 // X == 1 -> X 1125 if (match(RHS, m_One())) 1126 return LHS; 1127 break; 1128 case ICmpInst::ICMP_NE: 1129 // X != 0 -> X 1130 if (match(RHS, m_Zero())) 1131 return LHS; 1132 break; 1133 case ICmpInst::ICMP_UGT: 1134 // X >u 0 -> X 1135 if (match(RHS, m_Zero())) 1136 return LHS; 1137 break; 1138 case ICmpInst::ICMP_UGE: 1139 // X >=u 1 -> X 1140 if (match(RHS, m_One())) 1141 return LHS; 1142 break; 1143 case ICmpInst::ICMP_SLT: 1144 // X <s 0 -> X 1145 if (match(RHS, m_Zero())) 1146 return LHS; 1147 break; 1148 case ICmpInst::ICMP_SLE: 1149 // X <=s -1 -> X 1150 if (match(RHS, m_One())) 1151 return LHS; 1152 break; 1153 } 1154 } 1155 1156 // See if we are doing a comparison with a constant. 1157 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1158 switch (Pred) { 1159 default: break; 1160 case ICmpInst::ICMP_UGT: 1161 if (CI->isMaxValue(false)) // A >u MAX -> FALSE 1162 return ConstantInt::getFalse(CI->getContext()); 1163 break; 1164 case ICmpInst::ICMP_UGE: 1165 if (CI->isMinValue(false)) // A >=u MIN -> TRUE 1166 return ConstantInt::getTrue(CI->getContext()); 1167 break; 1168 case ICmpInst::ICMP_ULT: 1169 if (CI->isMinValue(false)) // A <u MIN -> FALSE 1170 return ConstantInt::getFalse(CI->getContext()); 1171 break; 1172 case ICmpInst::ICMP_ULE: 1173 if (CI->isMaxValue(false)) // A <=u MAX -> TRUE 1174 return ConstantInt::getTrue(CI->getContext()); 1175 break; 1176 case ICmpInst::ICMP_SGT: 1177 if (CI->isMaxValue(true)) // A >s MAX -> FALSE 1178 return ConstantInt::getFalse(CI->getContext()); 1179 break; 1180 case ICmpInst::ICMP_SGE: 1181 if (CI->isMinValue(true)) // A >=s MIN -> TRUE 1182 return ConstantInt::getTrue(CI->getContext()); 1183 break; 1184 case ICmpInst::ICMP_SLT: 1185 if (CI->isMinValue(true)) // A <s MIN -> FALSE 1186 return ConstantInt::getFalse(CI->getContext()); 1187 break; 1188 case ICmpInst::ICMP_SLE: 1189 if (CI->isMaxValue(true)) // A <=s MAX -> TRUE 1190 return ConstantInt::getTrue(CI->getContext()); 1191 break; 1192 } 1193 } 1194 1195 // icmp <alloca*>, <global/alloca*/null> - Different stack variables have 1196 // different addresses, and what's more the address of a stack variable is 1197 // never null or equal to the address of a global. Note that generalizing 1198 // to the case where LHS is a global variable address or null is pointless, 1199 // since if both LHS and RHS are constants then we already constant folded 1200 // the compare, and if only one of them is then we moved it to RHS already. 1201 if (isa<AllocaInst>(LHS) && (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) || 1202 isa<ConstantPointerNull>(RHS))) 1203 // We already know that LHS != LHS. 1204 return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred)); 1205 1206 // If the comparison is with the result of a select instruction, check whether 1207 // comparing with either branch of the select always yields the same value. 1208 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 1209 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1210 return V; 1211 1212 // If the comparison is with the result of a phi instruction, check whether 1213 // doing the compare with each incoming phi value yields a common result. 1214 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 1215 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1216 return V; 1217 1218 return 0; 1219} 1220 1221Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1222 const TargetData *TD, const DominatorTree *DT) { 1223 return ::SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 1224} 1225 1226/// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can 1227/// fold the result. If not, this returns null. 1228static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1229 const TargetData *TD, const DominatorTree *DT, 1230 unsigned MaxRecurse) { 1231 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 1232 assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!"); 1233 1234 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 1235 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 1236 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); 1237 1238 // If we have a constant, make sure it is on the RHS. 1239 std::swap(LHS, RHS); 1240 Pred = CmpInst::getSwappedPredicate(Pred); 1241 } 1242 1243 // Fold trivial predicates. 1244 if (Pred == FCmpInst::FCMP_FALSE) 1245 return ConstantInt::get(GetCompareTy(LHS), 0); 1246 if (Pred == FCmpInst::FCMP_TRUE) 1247 return ConstantInt::get(GetCompareTy(LHS), 1); 1248 1249 if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef 1250 return UndefValue::get(GetCompareTy(LHS)); 1251 1252 // fcmp x,x -> true/false. Not all compares are foldable. 1253 if (LHS == RHS) { 1254 if (CmpInst::isTrueWhenEqual(Pred)) 1255 return ConstantInt::get(GetCompareTy(LHS), 1); 1256 if (CmpInst::isFalseWhenEqual(Pred)) 1257 return ConstantInt::get(GetCompareTy(LHS), 0); 1258 } 1259 1260 // Handle fcmp with constant RHS 1261 if (Constant *RHSC = dyn_cast<Constant>(RHS)) { 1262 // If the constant is a nan, see if we can fold the comparison based on it. 1263 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) { 1264 if (CFP->getValueAPF().isNaN()) { 1265 if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo" 1266 return ConstantInt::getFalse(CFP->getContext()); 1267 assert(FCmpInst::isUnordered(Pred) && 1268 "Comparison must be either ordered or unordered!"); 1269 // True if unordered. 1270 return ConstantInt::getTrue(CFP->getContext()); 1271 } 1272 // Check whether the constant is an infinity. 1273 if (CFP->getValueAPF().isInfinity()) { 1274 if (CFP->getValueAPF().isNegative()) { 1275 switch (Pred) { 1276 case FCmpInst::FCMP_OLT: 1277 // No value is ordered and less than negative infinity. 1278 return ConstantInt::getFalse(CFP->getContext()); 1279 case FCmpInst::FCMP_UGE: 1280 // All values are unordered with or at least negative infinity. 1281 return ConstantInt::getTrue(CFP->getContext()); 1282 default: 1283 break; 1284 } 1285 } else { 1286 switch (Pred) { 1287 case FCmpInst::FCMP_OGT: 1288 // No value is ordered and greater than infinity. 1289 return ConstantInt::getFalse(CFP->getContext()); 1290 case FCmpInst::FCMP_ULE: 1291 // All values are unordered with and at most infinity. 1292 return ConstantInt::getTrue(CFP->getContext()); 1293 default: 1294 break; 1295 } 1296 } 1297 } 1298 } 1299 } 1300 1301 // If the comparison is with the result of a select instruction, check whether 1302 // comparing with either branch of the select always yields the same value. 1303 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 1304 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1305 return V; 1306 1307 // If the comparison is with the result of a phi instruction, check whether 1308 // doing the compare with each incoming phi value yields a common result. 1309 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 1310 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1311 return V; 1312 1313 return 0; 1314} 1315 1316Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1317 const TargetData *TD, const DominatorTree *DT) { 1318 return ::SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 1319} 1320 1321/// SimplifySelectInst - Given operands for a SelectInst, see if we can fold 1322/// the result. If not, this returns null. 1323Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal, 1324 const TargetData *TD, const DominatorTree *) { 1325 // select true, X, Y -> X 1326 // select false, X, Y -> Y 1327 if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal)) 1328 return CB->getZExtValue() ? TrueVal : FalseVal; 1329 1330 // select C, X, X -> X 1331 if (TrueVal == FalseVal) 1332 return TrueVal; 1333 1334 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X 1335 return FalseVal; 1336 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X 1337 return TrueVal; 1338 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y 1339 if (isa<Constant>(TrueVal)) 1340 return TrueVal; 1341 return FalseVal; 1342 } 1343 1344 return 0; 1345} 1346 1347/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can 1348/// fold the result. If not, this returns null. 1349Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps, 1350 const TargetData *TD, const DominatorTree *) { 1351 // The type of the GEP pointer operand. 1352 const PointerType *PtrTy = cast<PointerType>(Ops[0]->getType()); 1353 1354 // getelementptr P -> P. 1355 if (NumOps == 1) 1356 return Ops[0]; 1357 1358 if (isa<UndefValue>(Ops[0])) { 1359 // Compute the (pointer) type returned by the GEP instruction. 1360 const Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, &Ops[1], 1361 NumOps-1); 1362 const Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace()); 1363 return UndefValue::get(GEPTy); 1364 } 1365 1366 if (NumOps == 2) { 1367 // getelementptr P, 0 -> P. 1368 if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1])) 1369 if (C->isZero()) 1370 return Ops[0]; 1371 // getelementptr P, N -> P if P points to a type of zero size. 1372 if (TD) { 1373 const Type *Ty = PtrTy->getElementType(); 1374 if (Ty->isSized() && TD->getTypeAllocSize(Ty) == 0) 1375 return Ops[0]; 1376 } 1377 } 1378 1379 // Check to see if this is constant foldable. 1380 for (unsigned i = 0; i != NumOps; ++i) 1381 if (!isa<Constant>(Ops[i])) 1382 return 0; 1383 1384 return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]), 1385 (Constant *const*)Ops+1, NumOps-1); 1386} 1387 1388/// SimplifyPHINode - See if we can fold the given phi. If not, returns null. 1389static Value *SimplifyPHINode(PHINode *PN, const DominatorTree *DT) { 1390 // If all of the PHI's incoming values are the same then replace the PHI node 1391 // with the common value. 1392 Value *CommonValue = 0; 1393 bool HasUndefInput = false; 1394 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1395 Value *Incoming = PN->getIncomingValue(i); 1396 // If the incoming value is the phi node itself, it can safely be skipped. 1397 if (Incoming == PN) continue; 1398 if (isa<UndefValue>(Incoming)) { 1399 // Remember that we saw an undef value, but otherwise ignore them. 1400 HasUndefInput = true; 1401 continue; 1402 } 1403 if (CommonValue && Incoming != CommonValue) 1404 return 0; // Not the same, bail out. 1405 CommonValue = Incoming; 1406 } 1407 1408 // If CommonValue is null then all of the incoming values were either undef or 1409 // equal to the phi node itself. 1410 if (!CommonValue) 1411 return UndefValue::get(PN->getType()); 1412 1413 // If we have a PHI node like phi(X, undef, X), where X is defined by some 1414 // instruction, we cannot return X as the result of the PHI node unless it 1415 // dominates the PHI block. 1416 if (HasUndefInput) 1417 return ValueDominatesPHI(CommonValue, PN, DT) ? CommonValue : 0; 1418 1419 return CommonValue; 1420} 1421 1422 1423//=== Helper functions for higher up the class hierarchy. 1424 1425/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can 1426/// fold the result. If not, this returns null. 1427static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 1428 const TargetData *TD, const DominatorTree *DT, 1429 unsigned MaxRecurse) { 1430 switch (Opcode) { 1431 case Instruction::Add: return SimplifyAddInst(LHS, RHS, /* isNSW */ false, 1432 /* isNUW */ false, TD, DT, 1433 MaxRecurse); 1434 case Instruction::Sub: return SimplifySubInst(LHS, RHS, /* isNSW */ false, 1435 /* isNUW */ false, TD, DT, 1436 MaxRecurse); 1437 case Instruction::Mul: return SimplifyMulInst(LHS, RHS, TD, DT, MaxRecurse); 1438 case Instruction::Shl: return SimplifyShlInst(LHS, RHS, TD, DT, MaxRecurse); 1439 case Instruction::LShr: return SimplifyLShrInst(LHS, RHS, TD, DT, MaxRecurse); 1440 case Instruction::AShr: return SimplifyAShrInst(LHS, RHS, TD, DT, MaxRecurse); 1441 case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, DT, MaxRecurse); 1442 case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD, DT, MaxRecurse); 1443 case Instruction::Xor: return SimplifyXorInst(LHS, RHS, TD, DT, MaxRecurse); 1444 default: 1445 if (Constant *CLHS = dyn_cast<Constant>(LHS)) 1446 if (Constant *CRHS = dyn_cast<Constant>(RHS)) { 1447 Constant *COps[] = {CLHS, CRHS}; 1448 return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, 2, TD); 1449 } 1450 1451 // If the operation is associative, try some generic simplifications. 1452 if (Instruction::isAssociative(Opcode)) 1453 if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, TD, DT, 1454 MaxRecurse)) 1455 return V; 1456 1457 // If the operation is with the result of a select instruction, check whether 1458 // operating on either branch of the select always yields the same value. 1459 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 1460 if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, DT, 1461 MaxRecurse)) 1462 return V; 1463 1464 // If the operation is with the result of a phi instruction, check whether 1465 // operating on all incoming values of the phi always yields the same value. 1466 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 1467 if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, DT, MaxRecurse)) 1468 return V; 1469 1470 return 0; 1471 } 1472} 1473 1474Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 1475 const TargetData *TD, const DominatorTree *DT) { 1476 return ::SimplifyBinOp(Opcode, LHS, RHS, TD, DT, RecursionLimit); 1477} 1478 1479/// SimplifyCmpInst - Given operands for a CmpInst, see if we can 1480/// fold the result. 1481static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1482 const TargetData *TD, const DominatorTree *DT, 1483 unsigned MaxRecurse) { 1484 if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate)) 1485 return SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse); 1486 return SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse); 1487} 1488 1489Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1490 const TargetData *TD, const DominatorTree *DT) { 1491 return ::SimplifyCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 1492} 1493 1494/// SimplifyInstruction - See if we can compute a simplified version of this 1495/// instruction. If not, this returns null. 1496Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD, 1497 const DominatorTree *DT) { 1498 Value *Result; 1499 1500 switch (I->getOpcode()) { 1501 default: 1502 Result = ConstantFoldInstruction(I, TD); 1503 break; 1504 case Instruction::Add: 1505 Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1), 1506 cast<BinaryOperator>(I)->hasNoSignedWrap(), 1507 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 1508 TD, DT); 1509 break; 1510 case Instruction::Sub: 1511 Result = SimplifySubInst(I->getOperand(0), I->getOperand(1), 1512 cast<BinaryOperator>(I)->hasNoSignedWrap(), 1513 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 1514 TD, DT); 1515 break; 1516 case Instruction::Mul: 1517 Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, DT); 1518 break; 1519 case Instruction::Shl: 1520 Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1), TD, DT); 1521 break; 1522 case Instruction::LShr: 1523 Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1), TD, DT); 1524 break; 1525 case Instruction::AShr: 1526 Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1), TD, DT); 1527 break; 1528 case Instruction::And: 1529 Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT); 1530 break; 1531 case Instruction::Or: 1532 Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT); 1533 break; 1534 case Instruction::Xor: 1535 Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, DT); 1536 break; 1537 case Instruction::ICmp: 1538 Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(), 1539 I->getOperand(0), I->getOperand(1), TD, DT); 1540 break; 1541 case Instruction::FCmp: 1542 Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(), 1543 I->getOperand(0), I->getOperand(1), TD, DT); 1544 break; 1545 case Instruction::Select: 1546 Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1), 1547 I->getOperand(2), TD, DT); 1548 break; 1549 case Instruction::GetElementPtr: { 1550 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end()); 1551 Result = SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT); 1552 break; 1553 } 1554 case Instruction::PHI: 1555 Result = SimplifyPHINode(cast<PHINode>(I), DT); 1556 break; 1557 } 1558 1559 /// If called on unreachable code, the above logic may report that the 1560 /// instruction simplified to itself. Make life easier for users by 1561 /// detecting that case here, returning a safe value instead. 1562 return Result == I ? UndefValue::get(I->getType()) : Result; 1563} 1564 1565/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then 1566/// delete the From instruction. In addition to a basic RAUW, this does a 1567/// recursive simplification of the newly formed instructions. This catches 1568/// things where one simplification exposes other opportunities. This only 1569/// simplifies and deletes scalar operations, it does not change the CFG. 1570/// 1571void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To, 1572 const TargetData *TD, 1573 const DominatorTree *DT) { 1574 assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!"); 1575 1576 // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that 1577 // we can know if it gets deleted out from under us or replaced in a 1578 // recursive simplification. 1579 WeakVH FromHandle(From); 1580 WeakVH ToHandle(To); 1581 1582 while (!From->use_empty()) { 1583 // Update the instruction to use the new value. 1584 Use &TheUse = From->use_begin().getUse(); 1585 Instruction *User = cast<Instruction>(TheUse.getUser()); 1586 TheUse = To; 1587 1588 // Check to see if the instruction can be folded due to the operand 1589 // replacement. For example changing (or X, Y) into (or X, -1) can replace 1590 // the 'or' with -1. 1591 Value *SimplifiedVal; 1592 { 1593 // Sanity check to make sure 'User' doesn't dangle across 1594 // SimplifyInstruction. 1595 AssertingVH<> UserHandle(User); 1596 1597 SimplifiedVal = SimplifyInstruction(User, TD, DT); 1598 if (SimplifiedVal == 0) continue; 1599 } 1600 1601 // Recursively simplify this user to the new value. 1602 ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, DT); 1603 From = dyn_cast_or_null<Instruction>((Value*)FromHandle); 1604 To = ToHandle; 1605 1606 assert(ToHandle && "To value deleted by recursive simplification?"); 1607 1608 // If the recursive simplification ended up revisiting and deleting 1609 // 'From' then we're done. 1610 if (From == 0) 1611 return; 1612 } 1613 1614 // If 'From' has value handles referring to it, do a real RAUW to update them. 1615 From->replaceAllUsesWith(To); 1616 1617 From->eraseFromParent(); 1618} 1619