InstructionSimplify.cpp revision 1cd05bb605e3c3eee9197d3f10b628c60d0cc07a
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 OpcodeToExpand, const TargetData *TD, 75 const DominatorTree *DT, unsigned MaxRecurse) { 76 // Recursion is always used, so bail out at once if we already hit the limit. 77 if (!MaxRecurse--) 78 return 0; 79 80 // Check whether the expression has the form "(A op' B) op C". 81 if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS)) 82 if (Op0->getOpcode() == OpcodeToExpand) { 83 // It does! Try turning it into "(A op C) op' (B op C)". 84 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; 85 // Do "A op C" and "B op C" both simplify? 86 if (Value *L = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse)) 87 if (Value *R = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) { 88 // They do! Return "L op' R" if it simplifies or is already available. 89 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. 90 if ((L == A && R == B) || (Instruction::isCommutative(OpcodeToExpand) 91 && L == B && R == A)) { 92 ++NumExpand; 93 return LHS; 94 } 95 // Otherwise return "L op' R" if it simplifies. 96 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT, 97 MaxRecurse)) { 98 ++NumExpand; 99 return V; 100 } 101 } 102 } 103 104 // Check whether the expression has the form "A op (B op' C)". 105 if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS)) 106 if (Op1->getOpcode() == OpcodeToExpand) { 107 // It does! Try turning it into "(A op B) op' (A op C)". 108 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); 109 // Do "A op B" and "A op C" both simplify? 110 if (Value *L = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse)) 111 if (Value *R = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse)) { 112 // They do! Return "L op' R" if it simplifies or is already available. 113 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. 114 if ((L == B && R == C) || (Instruction::isCommutative(OpcodeToExpand) 115 && L == C && R == B)) { 116 ++NumExpand; 117 return RHS; 118 } 119 // Otherwise return "L op' R" if it simplifies. 120 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT, 121 MaxRecurse)) { 122 ++NumExpand; 123 return V; 124 } 125 } 126 } 127 128 return 0; 129} 130 131/// FactorizeBinOp - Simplify "LHS Opcode RHS" by factorizing out a common term 132/// using the operation OpCodeToExtract. For example, when Opcode is Add and 133/// OpCodeToExtract is Mul then this tries to turn "(A*B)+(A*C)" into "A*(B+C)". 134/// Returns the simplified value, or null if no simplification was performed. 135static Value *FactorizeBinOp(unsigned Opcode, Value *LHS, Value *RHS, 136 unsigned OpcodeToExtract, const TargetData *TD, 137 const DominatorTree *DT, unsigned MaxRecurse) { 138 // Recursion is always used, so bail out at once if we already hit the limit. 139 if (!MaxRecurse--) 140 return 0; 141 142 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 143 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 144 145 if (!Op0 || Op0->getOpcode() != OpcodeToExtract || 146 !Op1 || Op1->getOpcode() != OpcodeToExtract) 147 return 0; 148 149 // The expression has the form "(A op' B) op (C op' D)". 150 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1); 151 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1); 152 153 // Use left distributivity, i.e. "X op' (Y op Z) = (X op' Y) op (X op' Z)". 154 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the 155 // commutative case, "(A op' B) op (C op' A)"? 156 if (A == C || (Instruction::isCommutative(OpcodeToExtract) && A == D)) { 157 Value *DD = A == C ? D : C; 158 // Form "A op' (B op DD)" if it simplifies completely. 159 // Does "B op DD" simplify? 160 if (Value *V = SimplifyBinOp(Opcode, B, DD, TD, DT, MaxRecurse)) { 161 // It does! Return "A op' V" if it simplifies or is already available. 162 // If V equals B then "A op' V" is just the LHS. If V equals DD then 163 // "A op' V" is just the RHS. 164 if (V == B || V == DD) { 165 ++NumFactor; 166 return V == B ? LHS : RHS; 167 } 168 // Otherwise return "A op' V" if it simplifies. 169 if (Value *W = SimplifyBinOp(OpcodeToExtract, A, V, TD, DT, MaxRecurse)) { 170 ++NumFactor; 171 return W; 172 } 173 } 174 } 175 176 // Use right distributivity, i.e. "(X op Y) op' Z = (X op' Z) op (Y op' Z)". 177 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the 178 // commutative case, "(A op' B) op (B op' D)"? 179 if (B == D || (Instruction::isCommutative(OpcodeToExtract) && B == C)) { 180 Value *CC = B == D ? C : D; 181 // Form "(A op CC) op' B" if it simplifies completely.. 182 // Does "A op CC" simplify? 183 if (Value *V = SimplifyBinOp(Opcode, A, CC, TD, DT, MaxRecurse)) { 184 // It does! Return "V op' B" if it simplifies or is already available. 185 // If V equals A then "V op' B" is just the LHS. If V equals CC then 186 // "V op' B" is just the RHS. 187 if (V == A || V == CC) { 188 ++NumFactor; 189 return V == A ? LHS : RHS; 190 } 191 // Otherwise return "V op' B" if it simplifies. 192 if (Value *W = SimplifyBinOp(OpcodeToExtract, V, B, TD, DT, MaxRecurse)) { 193 ++NumFactor; 194 return W; 195 } 196 } 197 } 198 199 return 0; 200} 201 202/// SimplifyAssociativeBinOp - Generic simplifications for associative binary 203/// operations. Returns the simpler value, or null if none was found. 204static Value *SimplifyAssociativeBinOp(unsigned Opcode, Value *LHS, Value *RHS, 205 const TargetData *TD, 206 const DominatorTree *DT, 207 unsigned MaxRecurse) { 208 assert(Instruction::isAssociative(Opcode) && "Not an associative operation!"); 209 210 // Recursion is always used, so bail out at once if we already hit the limit. 211 if (!MaxRecurse--) 212 return 0; 213 214 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); 215 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); 216 217 // Transform: "(A op B) op C" ==> "A op (B op C)" if it simplifies completely. 218 if (Op0 && Op0->getOpcode() == Opcode) { 219 Value *A = Op0->getOperand(0); 220 Value *B = Op0->getOperand(1); 221 Value *C = RHS; 222 223 // Does "B op C" simplify? 224 if (Value *V = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) { 225 // It does! Return "A op V" if it simplifies or is already available. 226 // If V equals B then "A op V" is just the LHS. 227 if (V == B) return LHS; 228 // Otherwise return "A op V" if it simplifies. 229 if (Value *W = SimplifyBinOp(Opcode, A, V, TD, DT, MaxRecurse)) { 230 ++NumReassoc; 231 return W; 232 } 233 } 234 } 235 236 // Transform: "A op (B op C)" ==> "(A op B) op C" if it simplifies completely. 237 if (Op1 && Op1->getOpcode() == Opcode) { 238 Value *A = LHS; 239 Value *B = Op1->getOperand(0); 240 Value *C = Op1->getOperand(1); 241 242 // Does "A op B" simplify? 243 if (Value *V = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse)) { 244 // It does! Return "V op C" if it simplifies or is already available. 245 // If V equals B then "V op C" is just the RHS. 246 if (V == B) return RHS; 247 // Otherwise return "V op C" if it simplifies. 248 if (Value *W = SimplifyBinOp(Opcode, V, C, TD, DT, MaxRecurse)) { 249 ++NumReassoc; 250 return W; 251 } 252 } 253 } 254 255 // The remaining transforms require commutativity as well as associativity. 256 if (!Instruction::isCommutative(Opcode)) 257 return 0; 258 259 // Transform: "(A op B) op C" ==> "(C op A) op B" if it simplifies completely. 260 if (Op0 && Op0->getOpcode() == Opcode) { 261 Value *A = Op0->getOperand(0); 262 Value *B = Op0->getOperand(1); 263 Value *C = RHS; 264 265 // Does "C op A" simplify? 266 if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) { 267 // It does! Return "V op B" if it simplifies or is already available. 268 // If V equals A then "V op B" is just the LHS. 269 if (V == A) return LHS; 270 // Otherwise return "V op B" if it simplifies. 271 if (Value *W = SimplifyBinOp(Opcode, V, B, TD, DT, MaxRecurse)) { 272 ++NumReassoc; 273 return W; 274 } 275 } 276 } 277 278 // Transform: "A op (B op C)" ==> "B op (C op A)" if it simplifies completely. 279 if (Op1 && Op1->getOpcode() == Opcode) { 280 Value *A = LHS; 281 Value *B = Op1->getOperand(0); 282 Value *C = Op1->getOperand(1); 283 284 // Does "C op A" simplify? 285 if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) { 286 // It does! Return "B op V" if it simplifies or is already available. 287 // If V equals C then "B op V" is just the RHS. 288 if (V == C) return RHS; 289 // Otherwise return "B op V" if it simplifies. 290 if (Value *W = SimplifyBinOp(Opcode, B, V, TD, DT, MaxRecurse)) { 291 ++NumReassoc; 292 return W; 293 } 294 } 295 } 296 297 return 0; 298} 299 300/// ThreadBinOpOverSelect - In the case of a binary operation with a select 301/// instruction as an operand, try to simplify the binop by seeing whether 302/// evaluating it on both branches of the select results in the same value. 303/// Returns the common value if so, otherwise returns null. 304static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS, 305 const TargetData *TD, 306 const DominatorTree *DT, 307 unsigned MaxRecurse) { 308 // Recursion is always used, so bail out at once if we already hit the limit. 309 if (!MaxRecurse--) 310 return 0; 311 312 SelectInst *SI; 313 if (isa<SelectInst>(LHS)) { 314 SI = cast<SelectInst>(LHS); 315 } else { 316 assert(isa<SelectInst>(RHS) && "No select instruction operand!"); 317 SI = cast<SelectInst>(RHS); 318 } 319 320 // Evaluate the BinOp on the true and false branches of the select. 321 Value *TV; 322 Value *FV; 323 if (SI == LHS) { 324 TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, TD, DT, MaxRecurse); 325 FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, TD, DT, MaxRecurse); 326 } else { 327 TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), TD, DT, MaxRecurse); 328 FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), TD, DT, MaxRecurse); 329 } 330 331 // If they simplified to the same value, then return the common value. 332 // If they both failed to simplify then return null. 333 if (TV == FV) 334 return TV; 335 336 // If one branch simplified to undef, return the other one. 337 if (TV && isa<UndefValue>(TV)) 338 return FV; 339 if (FV && isa<UndefValue>(FV)) 340 return TV; 341 342 // If applying the operation did not change the true and false select values, 343 // then the result of the binop is the select itself. 344 if (TV == SI->getTrueValue() && FV == SI->getFalseValue()) 345 return SI; 346 347 // If one branch simplified and the other did not, and the simplified 348 // value is equal to the unsimplified one, return the simplified value. 349 // For example, select (cond, X, X & Z) & Z -> X & Z. 350 if ((FV && !TV) || (TV && !FV)) { 351 // Check that the simplified value has the form "X op Y" where "op" is the 352 // same as the original operation. 353 Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV); 354 if (Simplified && Simplified->getOpcode() == Opcode) { 355 // The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS". 356 // We already know that "op" is the same as for the simplified value. See 357 // if the operands match too. If so, return the simplified value. 358 Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue(); 359 Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS; 360 Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch; 361 if (Simplified->getOperand(0) == UnsimplifiedLHS && 362 Simplified->getOperand(1) == UnsimplifiedRHS) 363 return Simplified; 364 if (Simplified->isCommutative() && 365 Simplified->getOperand(1) == UnsimplifiedLHS && 366 Simplified->getOperand(0) == UnsimplifiedRHS) 367 return Simplified; 368 } 369 } 370 371 return 0; 372} 373 374/// ThreadCmpOverSelect - In the case of a comparison with a select instruction, 375/// try to simplify the comparison by seeing whether both branches of the select 376/// result in the same value. Returns the common value if so, otherwise returns 377/// null. 378static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS, 379 Value *RHS, const TargetData *TD, 380 const DominatorTree *DT, 381 unsigned MaxRecurse) { 382 // Recursion is always used, so bail out at once if we already hit the limit. 383 if (!MaxRecurse--) 384 return 0; 385 386 // Make sure the select is on the LHS. 387 if (!isa<SelectInst>(LHS)) { 388 std::swap(LHS, RHS); 389 Pred = CmpInst::getSwappedPredicate(Pred); 390 } 391 assert(isa<SelectInst>(LHS) && "Not comparing with a select instruction!"); 392 SelectInst *SI = cast<SelectInst>(LHS); 393 394 // Now that we have "cmp select(cond, TV, FV), RHS", analyse it. 395 // Does "cmp TV, RHS" simplify? 396 if (Value *TCmp = SimplifyCmpInst(Pred, SI->getTrueValue(), RHS, TD, DT, 397 MaxRecurse)) 398 // It does! Does "cmp FV, RHS" simplify? 399 if (Value *FCmp = SimplifyCmpInst(Pred, SI->getFalseValue(), RHS, TD, DT, 400 MaxRecurse)) 401 // It does! If they simplified to the same value, then use it as the 402 // result of the original comparison. 403 if (TCmp == FCmp) 404 return TCmp; 405 return 0; 406} 407 408/// ThreadBinOpOverPHI - In the case of a binary operation with an operand that 409/// is a PHI instruction, try to simplify the binop by seeing whether evaluating 410/// it on the incoming phi values yields the same result for every value. If so 411/// returns the common value, otherwise returns null. 412static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS, 413 const TargetData *TD, const DominatorTree *DT, 414 unsigned MaxRecurse) { 415 // Recursion is always used, so bail out at once if we already hit the limit. 416 if (!MaxRecurse--) 417 return 0; 418 419 PHINode *PI; 420 if (isa<PHINode>(LHS)) { 421 PI = cast<PHINode>(LHS); 422 // Bail out if RHS and the phi may be mutually interdependent due to a loop. 423 if (!ValueDominatesPHI(RHS, PI, DT)) 424 return 0; 425 } else { 426 assert(isa<PHINode>(RHS) && "No PHI instruction operand!"); 427 PI = cast<PHINode>(RHS); 428 // Bail out if LHS and the phi may be mutually interdependent due to a loop. 429 if (!ValueDominatesPHI(LHS, PI, DT)) 430 return 0; 431 } 432 433 // Evaluate the BinOp on the incoming phi values. 434 Value *CommonValue = 0; 435 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) { 436 Value *Incoming = PI->getIncomingValue(i); 437 // If the incoming value is the phi node itself, it can safely be skipped. 438 if (Incoming == PI) continue; 439 Value *V = PI == LHS ? 440 SimplifyBinOp(Opcode, Incoming, RHS, TD, DT, MaxRecurse) : 441 SimplifyBinOp(Opcode, LHS, Incoming, TD, DT, MaxRecurse); 442 // If the operation failed to simplify, or simplified to a different value 443 // to previously, then give up. 444 if (!V || (CommonValue && V != CommonValue)) 445 return 0; 446 CommonValue = V; 447 } 448 449 return CommonValue; 450} 451 452/// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try 453/// try to simplify the comparison by seeing whether comparing with all of the 454/// incoming phi values yields the same result every time. If so returns the 455/// common result, otherwise returns null. 456static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS, 457 const TargetData *TD, const DominatorTree *DT, 458 unsigned MaxRecurse) { 459 // Recursion is always used, so bail out at once if we already hit the limit. 460 if (!MaxRecurse--) 461 return 0; 462 463 // Make sure the phi is on the LHS. 464 if (!isa<PHINode>(LHS)) { 465 std::swap(LHS, RHS); 466 Pred = CmpInst::getSwappedPredicate(Pred); 467 } 468 assert(isa<PHINode>(LHS) && "Not comparing with a phi instruction!"); 469 PHINode *PI = cast<PHINode>(LHS); 470 471 // Bail out if RHS and the phi may be mutually interdependent due to a loop. 472 if (!ValueDominatesPHI(RHS, PI, DT)) 473 return 0; 474 475 // Evaluate the BinOp on the incoming phi values. 476 Value *CommonValue = 0; 477 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) { 478 Value *Incoming = PI->getIncomingValue(i); 479 // If the incoming value is the phi node itself, it can safely be skipped. 480 if (Incoming == PI) continue; 481 Value *V = SimplifyCmpInst(Pred, Incoming, RHS, TD, DT, MaxRecurse); 482 // If the operation failed to simplify, or simplified to a different value 483 // to previously, then give up. 484 if (!V || (CommonValue && V != CommonValue)) 485 return 0; 486 CommonValue = V; 487 } 488 489 return CommonValue; 490} 491 492/// SimplifyAddInst - Given operands for an Add, see if we can 493/// fold the result. If not, this returns null. 494static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 495 const TargetData *TD, const DominatorTree *DT, 496 unsigned MaxRecurse) { 497 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 498 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 499 Constant *Ops[] = { CLHS, CRHS }; 500 return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(), 501 Ops, 2, TD); 502 } 503 504 // Canonicalize the constant to the RHS. 505 std::swap(Op0, Op1); 506 } 507 508 // X + undef -> undef 509 if (isa<UndefValue>(Op1)) 510 return Op1; 511 512 // X + 0 -> X 513 if (match(Op1, m_Zero())) 514 return Op0; 515 516 // X + (Y - X) -> Y 517 // (Y - X) + X -> Y 518 // Eg: X + -X -> 0 519 Value *Y = 0; 520 if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) || 521 match(Op0, m_Sub(m_Value(Y), m_Specific(Op1)))) 522 return Y; 523 524 // X + ~X -> -1 since ~X = -X-1 525 if (match(Op0, m_Not(m_Specific(Op1))) || 526 match(Op1, m_Not(m_Specific(Op0)))) 527 return Constant::getAllOnesValue(Op0->getType()); 528 529 /// i1 add -> xor. 530 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 531 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1)) 532 return V; 533 534 // Try some generic simplifications for associative operations. 535 if (Value *V = SimplifyAssociativeBinOp(Instruction::Add, Op0, Op1, TD, DT, 536 MaxRecurse)) 537 return V; 538 539 // Mul distributes over Add. Try some generic simplifications based on this. 540 if (Value *V = FactorizeBinOp(Instruction::Add, Op0, Op1, Instruction::Mul, 541 TD, DT, MaxRecurse)) 542 return V; 543 544 // Threading Add over selects and phi nodes is pointless, so don't bother. 545 // Threading over the select in "A + select(cond, B, C)" means evaluating 546 // "A+B" and "A+C" and seeing if they are equal; but they are equal if and 547 // only if B and C are equal. If B and C are equal then (since we assume 548 // that operands have already been simplified) "select(cond, B, C)" should 549 // have been simplified to the common value of B and C already. Analysing 550 // "A+B" and "A+C" thus gains nothing, but costs compile time. Similarly 551 // for threading over phi nodes. 552 553 return 0; 554} 555 556Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 557 const TargetData *TD, const DominatorTree *DT) { 558 return ::SimplifyAddInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit); 559} 560 561/// SimplifySubInst - Given operands for a Sub, see if we can 562/// fold the result. If not, this returns null. 563static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 564 const TargetData *TD, const DominatorTree *DT, 565 unsigned MaxRecurse) { 566 if (Constant *CLHS = dyn_cast<Constant>(Op0)) 567 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 568 Constant *Ops[] = { CLHS, CRHS }; 569 return ConstantFoldInstOperands(Instruction::Sub, CLHS->getType(), 570 Ops, 2, TD); 571 } 572 573 // X - undef -> undef 574 // undef - X -> undef 575 if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1)) 576 return UndefValue::get(Op0->getType()); 577 578 // X - 0 -> X 579 if (match(Op1, m_Zero())) 580 return Op0; 581 582 // X - X -> 0 583 if (Op0 == Op1) 584 return Constant::getNullValue(Op0->getType()); 585 586 // (X + Y) - Y -> X 587 // (Y + X) - Y -> X 588 Value *X = 0; 589 if (match(Op0, m_Add(m_Value(X), m_Specific(Op1))) || 590 match(Op0, m_Add(m_Specific(Op1), m_Value(X)))) 591 return X; 592 593 /// i1 sub -> xor. 594 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 595 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1)) 596 return V; 597 598 // Mul distributes over Sub. Try some generic simplifications based on this. 599 if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul, 600 TD, DT, MaxRecurse)) 601 return V; 602 603 // Threading Sub over selects and phi nodes is pointless, so don't bother. 604 // Threading over the select in "A - select(cond, B, C)" means evaluating 605 // "A-B" and "A-C" and seeing if they are equal; but they are equal if and 606 // only if B and C are equal. If B and C are equal then (since we assume 607 // that operands have already been simplified) "select(cond, B, C)" should 608 // have been simplified to the common value of B and C already. Analysing 609 // "A-B" and "A-C" thus gains nothing, but costs compile time. Similarly 610 // for threading over phi nodes. 611 612 return 0; 613} 614 615Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 616 const TargetData *TD, const DominatorTree *DT) { 617 return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit); 618} 619 620/// SimplifyMulInst - Given operands for a Mul, see if we can 621/// fold the result. If not, this returns null. 622static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD, 623 const DominatorTree *DT, unsigned MaxRecurse) { 624 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 625 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 626 Constant *Ops[] = { CLHS, CRHS }; 627 return ConstantFoldInstOperands(Instruction::Mul, CLHS->getType(), 628 Ops, 2, TD); 629 } 630 631 // Canonicalize the constant to the RHS. 632 std::swap(Op0, Op1); 633 } 634 635 // X * undef -> 0 636 if (isa<UndefValue>(Op1)) 637 return Constant::getNullValue(Op0->getType()); 638 639 // X * 0 -> 0 640 if (match(Op1, m_Zero())) 641 return Op1; 642 643 // X * 1 -> X 644 if (match(Op1, m_One())) 645 return Op0; 646 647 /// i1 mul -> and. 648 if (MaxRecurse && Op0->getType()->isIntegerTy(1)) 649 if (Value *V = SimplifyAndInst(Op0, Op1, TD, DT, MaxRecurse-1)) 650 return V; 651 652 // Try some generic simplifications for associative operations. 653 if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, TD, DT, 654 MaxRecurse)) 655 return V; 656 657 // Mul distributes over Add. Try some generic simplifications based on this. 658 if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add, 659 TD, DT, MaxRecurse)) 660 return V; 661 662 // If the operation is with the result of a select instruction, check whether 663 // operating on either branch of the select always yields the same value. 664 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 665 if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, TD, DT, 666 MaxRecurse)) 667 return V; 668 669 // If the operation is with the result of a phi instruction, check whether 670 // operating on all incoming values of the phi always yields the same value. 671 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 672 if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, TD, DT, 673 MaxRecurse)) 674 return V; 675 676 return 0; 677} 678 679Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD, 680 const DominatorTree *DT) { 681 return ::SimplifyMulInst(Op0, Op1, TD, DT, RecursionLimit); 682} 683 684/// SimplifyAndInst - Given operands for an And, see if we can 685/// fold the result. If not, this returns null. 686static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD, 687 const DominatorTree *DT, unsigned MaxRecurse) { 688 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 689 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 690 Constant *Ops[] = { CLHS, CRHS }; 691 return ConstantFoldInstOperands(Instruction::And, CLHS->getType(), 692 Ops, 2, TD); 693 } 694 695 // Canonicalize the constant to the RHS. 696 std::swap(Op0, Op1); 697 } 698 699 // X & undef -> 0 700 if (isa<UndefValue>(Op1)) 701 return Constant::getNullValue(Op0->getType()); 702 703 // X & X = X 704 if (Op0 == Op1) 705 return Op0; 706 707 // X & 0 = 0 708 if (match(Op1, m_Zero())) 709 return Op1; 710 711 // X & -1 = X 712 if (match(Op1, m_AllOnes())) 713 return Op0; 714 715 // A & ~A = ~A & A = 0 716 Value *A = 0, *B = 0; 717 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) || 718 (match(Op1, m_Not(m_Value(A))) && A == Op0)) 719 return Constant::getNullValue(Op0->getType()); 720 721 // (A | ?) & A = A 722 if (match(Op0, m_Or(m_Value(A), m_Value(B))) && 723 (A == Op1 || B == Op1)) 724 return Op1; 725 726 // A & (A | ?) = A 727 if (match(Op1, m_Or(m_Value(A), m_Value(B))) && 728 (A == Op0 || B == Op0)) 729 return Op0; 730 731 // Try some generic simplifications for associative operations. 732 if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, TD, DT, 733 MaxRecurse)) 734 return V; 735 736 // And distributes over Or. Try some generic simplifications based on this. 737 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or, 738 TD, DT, MaxRecurse)) 739 return V; 740 741 // And distributes over Xor. Try some generic simplifications based on this. 742 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor, 743 TD, DT, MaxRecurse)) 744 return V; 745 746 // Or distributes over And. Try some generic simplifications based on this. 747 if (Value *V = FactorizeBinOp(Instruction::And, Op0, Op1, Instruction::Or, 748 TD, DT, MaxRecurse)) 749 return V; 750 751 // If the operation is with the result of a select instruction, check whether 752 // operating on either branch of the select always yields the same value. 753 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 754 if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, DT, 755 MaxRecurse)) 756 return V; 757 758 // If the operation is with the result of a phi instruction, check whether 759 // operating on all incoming values of the phi always yields the same value. 760 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 761 if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, DT, 762 MaxRecurse)) 763 return V; 764 765 return 0; 766} 767 768Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD, 769 const DominatorTree *DT) { 770 return ::SimplifyAndInst(Op0, Op1, TD, DT, RecursionLimit); 771} 772 773/// SimplifyOrInst - Given operands for an Or, see if we can 774/// fold the result. If not, this returns null. 775static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD, 776 const DominatorTree *DT, unsigned MaxRecurse) { 777 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 778 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 779 Constant *Ops[] = { CLHS, CRHS }; 780 return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(), 781 Ops, 2, TD); 782 } 783 784 // Canonicalize the constant to the RHS. 785 std::swap(Op0, Op1); 786 } 787 788 // X | undef -> -1 789 if (isa<UndefValue>(Op1)) 790 return Constant::getAllOnesValue(Op0->getType()); 791 792 // X | X = X 793 if (Op0 == Op1) 794 return Op0; 795 796 // X | 0 = X 797 if (match(Op1, m_Zero())) 798 return Op0; 799 800 // X | -1 = -1 801 if (match(Op1, m_AllOnes())) 802 return Op1; 803 804 // A | ~A = ~A | A = -1 805 Value *A = 0, *B = 0; 806 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) || 807 (match(Op1, m_Not(m_Value(A))) && A == Op0)) 808 return Constant::getAllOnesValue(Op0->getType()); 809 810 // (A & ?) | A = A 811 if (match(Op0, m_And(m_Value(A), m_Value(B))) && 812 (A == Op1 || B == Op1)) 813 return Op1; 814 815 // A | (A & ?) = A 816 if (match(Op1, m_And(m_Value(A), m_Value(B))) && 817 (A == Op0 || B == Op0)) 818 return Op0; 819 820 // Try some generic simplifications for associative operations. 821 if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, TD, DT, 822 MaxRecurse)) 823 return V; 824 825 // Or distributes over And. Try some generic simplifications based on this. 826 if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And, 827 TD, DT, MaxRecurse)) 828 return V; 829 830 // And distributes over Or. Try some generic simplifications based on this. 831 if (Value *V = FactorizeBinOp(Instruction::Or, Op0, Op1, Instruction::And, 832 TD, DT, MaxRecurse)) 833 return V; 834 835 // If the operation is with the result of a select instruction, check whether 836 // operating on either branch of the select always yields the same value. 837 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)) 838 if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, DT, 839 MaxRecurse)) 840 return V; 841 842 // If the operation is with the result of a phi instruction, check whether 843 // operating on all incoming values of the phi always yields the same value. 844 if (isa<PHINode>(Op0) || isa<PHINode>(Op1)) 845 if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, DT, 846 MaxRecurse)) 847 return V; 848 849 return 0; 850} 851 852Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD, 853 const DominatorTree *DT) { 854 return ::SimplifyOrInst(Op0, Op1, TD, DT, RecursionLimit); 855} 856 857/// SimplifyXorInst - Given operands for a Xor, see if we can 858/// fold the result. If not, this returns null. 859static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD, 860 const DominatorTree *DT, unsigned MaxRecurse) { 861 if (Constant *CLHS = dyn_cast<Constant>(Op0)) { 862 if (Constant *CRHS = dyn_cast<Constant>(Op1)) { 863 Constant *Ops[] = { CLHS, CRHS }; 864 return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(), 865 Ops, 2, TD); 866 } 867 868 // Canonicalize the constant to the RHS. 869 std::swap(Op0, Op1); 870 } 871 872 // A ^ undef -> undef 873 if (isa<UndefValue>(Op1)) 874 return Op1; 875 876 // A ^ 0 = A 877 if (match(Op1, m_Zero())) 878 return Op0; 879 880 // A ^ A = 0 881 if (Op0 == Op1) 882 return Constant::getNullValue(Op0->getType()); 883 884 // A ^ ~A = ~A ^ A = -1 885 Value *A = 0; 886 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) || 887 (match(Op1, m_Not(m_Value(A))) && A == Op0)) 888 return Constant::getAllOnesValue(Op0->getType()); 889 890 // Try some generic simplifications for associative operations. 891 if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, TD, DT, 892 MaxRecurse)) 893 return V; 894 895 // And distributes over Xor. Try some generic simplifications based on this. 896 if (Value *V = FactorizeBinOp(Instruction::Xor, Op0, Op1, Instruction::And, 897 TD, DT, MaxRecurse)) 898 return V; 899 900 // Threading Xor over selects and phi nodes is pointless, so don't bother. 901 // Threading over the select in "A ^ select(cond, B, C)" means evaluating 902 // "A^B" and "A^C" and seeing if they are equal; but they are equal if and 903 // only if B and C are equal. If B and C are equal then (since we assume 904 // that operands have already been simplified) "select(cond, B, C)" should 905 // have been simplified to the common value of B and C already. Analysing 906 // "A^B" and "A^C" thus gains nothing, but costs compile time. Similarly 907 // for threading over phi nodes. 908 909 return 0; 910} 911 912Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD, 913 const DominatorTree *DT) { 914 return ::SimplifyXorInst(Op0, Op1, TD, DT, RecursionLimit); 915} 916 917static const Type *GetCompareTy(Value *Op) { 918 return CmpInst::makeCmpResultType(Op->getType()); 919} 920 921/// SimplifyICmpInst - Given operands for an ICmpInst, see if we can 922/// fold the result. If not, this returns null. 923static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 924 const TargetData *TD, const DominatorTree *DT, 925 unsigned MaxRecurse) { 926 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 927 assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!"); 928 929 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 930 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 931 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); 932 933 // If we have a constant, make sure it is on the RHS. 934 std::swap(LHS, RHS); 935 Pred = CmpInst::getSwappedPredicate(Pred); 936 } 937 938 // ITy - This is the return type of the compare we're considering. 939 const Type *ITy = GetCompareTy(LHS); 940 941 // icmp X, X -> true/false 942 // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false 943 // because X could be 0. 944 if (LHS == RHS || isa<UndefValue>(RHS)) 945 return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred)); 946 947 // icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value 948 // addresses never equal each other! We already know that Op0 != Op1. 949 if ((isa<GlobalValue>(LHS) || isa<AllocaInst>(LHS) || 950 isa<ConstantPointerNull>(LHS)) && 951 (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) || 952 isa<ConstantPointerNull>(RHS))) 953 return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred)); 954 955 // See if we are doing a comparison with a constant. 956 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 957 // If we have an icmp le or icmp ge instruction, turn it into the 958 // appropriate icmp lt or icmp gt instruction. This allows us to rely on 959 // them being folded in the code below. 960 switch (Pred) { 961 default: break; 962 case ICmpInst::ICMP_ULE: 963 if (CI->isMaxValue(false)) // A <=u MAX -> TRUE 964 return ConstantInt::getTrue(CI->getContext()); 965 break; 966 case ICmpInst::ICMP_SLE: 967 if (CI->isMaxValue(true)) // A <=s MAX -> TRUE 968 return ConstantInt::getTrue(CI->getContext()); 969 break; 970 case ICmpInst::ICMP_UGE: 971 if (CI->isMinValue(false)) // A >=u MIN -> TRUE 972 return ConstantInt::getTrue(CI->getContext()); 973 break; 974 case ICmpInst::ICMP_SGE: 975 if (CI->isMinValue(true)) // A >=s MIN -> TRUE 976 return ConstantInt::getTrue(CI->getContext()); 977 break; 978 } 979 } 980 981 // If the comparison is with the result of a select instruction, check whether 982 // comparing with either branch of the select always yields the same value. 983 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 984 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse)) 985 return V; 986 987 // If the comparison is with the result of a phi instruction, check whether 988 // doing the compare with each incoming phi value yields a common result. 989 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 990 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse)) 991 return V; 992 993 return 0; 994} 995 996Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 997 const TargetData *TD, const DominatorTree *DT) { 998 return ::SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 999} 1000 1001/// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can 1002/// fold the result. If not, this returns null. 1003static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1004 const TargetData *TD, const DominatorTree *DT, 1005 unsigned MaxRecurse) { 1006 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; 1007 assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!"); 1008 1009 if (Constant *CLHS = dyn_cast<Constant>(LHS)) { 1010 if (Constant *CRHS = dyn_cast<Constant>(RHS)) 1011 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); 1012 1013 // If we have a constant, make sure it is on the RHS. 1014 std::swap(LHS, RHS); 1015 Pred = CmpInst::getSwappedPredicate(Pred); 1016 } 1017 1018 // Fold trivial predicates. 1019 if (Pred == FCmpInst::FCMP_FALSE) 1020 return ConstantInt::get(GetCompareTy(LHS), 0); 1021 if (Pred == FCmpInst::FCMP_TRUE) 1022 return ConstantInt::get(GetCompareTy(LHS), 1); 1023 1024 if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef 1025 return UndefValue::get(GetCompareTy(LHS)); 1026 1027 // fcmp x,x -> true/false. Not all compares are foldable. 1028 if (LHS == RHS) { 1029 if (CmpInst::isTrueWhenEqual(Pred)) 1030 return ConstantInt::get(GetCompareTy(LHS), 1); 1031 if (CmpInst::isFalseWhenEqual(Pred)) 1032 return ConstantInt::get(GetCompareTy(LHS), 0); 1033 } 1034 1035 // Handle fcmp with constant RHS 1036 if (Constant *RHSC = dyn_cast<Constant>(RHS)) { 1037 // If the constant is a nan, see if we can fold the comparison based on it. 1038 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) { 1039 if (CFP->getValueAPF().isNaN()) { 1040 if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo" 1041 return ConstantInt::getFalse(CFP->getContext()); 1042 assert(FCmpInst::isUnordered(Pred) && 1043 "Comparison must be either ordered or unordered!"); 1044 // True if unordered. 1045 return ConstantInt::getTrue(CFP->getContext()); 1046 } 1047 // Check whether the constant is an infinity. 1048 if (CFP->getValueAPF().isInfinity()) { 1049 if (CFP->getValueAPF().isNegative()) { 1050 switch (Pred) { 1051 case FCmpInst::FCMP_OLT: 1052 // No value is ordered and less than negative infinity. 1053 return ConstantInt::getFalse(CFP->getContext()); 1054 case FCmpInst::FCMP_UGE: 1055 // All values are unordered with or at least negative infinity. 1056 return ConstantInt::getTrue(CFP->getContext()); 1057 default: 1058 break; 1059 } 1060 } else { 1061 switch (Pred) { 1062 case FCmpInst::FCMP_OGT: 1063 // No value is ordered and greater than infinity. 1064 return ConstantInt::getFalse(CFP->getContext()); 1065 case FCmpInst::FCMP_ULE: 1066 // All values are unordered with and at most infinity. 1067 return ConstantInt::getTrue(CFP->getContext()); 1068 default: 1069 break; 1070 } 1071 } 1072 } 1073 } 1074 } 1075 1076 // If the comparison is with the result of a select instruction, check whether 1077 // comparing with either branch of the select always yields the same value. 1078 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 1079 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1080 return V; 1081 1082 // If the comparison is with the result of a phi instruction, check whether 1083 // doing the compare with each incoming phi value yields a common result. 1084 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 1085 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse)) 1086 return V; 1087 1088 return 0; 1089} 1090 1091Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1092 const TargetData *TD, const DominatorTree *DT) { 1093 return ::SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 1094} 1095 1096/// SimplifySelectInst - Given operands for a SelectInst, see if we can fold 1097/// the result. If not, this returns null. 1098Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal, 1099 const TargetData *TD, const DominatorTree *) { 1100 // select true, X, Y -> X 1101 // select false, X, Y -> Y 1102 if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal)) 1103 return CB->getZExtValue() ? TrueVal : FalseVal; 1104 1105 // select C, X, X -> X 1106 if (TrueVal == FalseVal) 1107 return TrueVal; 1108 1109 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X 1110 return FalseVal; 1111 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X 1112 return TrueVal; 1113 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y 1114 if (isa<Constant>(TrueVal)) 1115 return TrueVal; 1116 return FalseVal; 1117 } 1118 1119 return 0; 1120} 1121 1122/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can 1123/// fold the result. If not, this returns null. 1124Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps, 1125 const TargetData *TD, const DominatorTree *) { 1126 // The type of the GEP pointer operand. 1127 const PointerType *PtrTy = cast<PointerType>(Ops[0]->getType()); 1128 1129 // getelementptr P -> P. 1130 if (NumOps == 1) 1131 return Ops[0]; 1132 1133 if (isa<UndefValue>(Ops[0])) { 1134 // Compute the (pointer) type returned by the GEP instruction. 1135 const Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, &Ops[1], 1136 NumOps-1); 1137 const Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace()); 1138 return UndefValue::get(GEPTy); 1139 } 1140 1141 if (NumOps == 2) { 1142 // getelementptr P, 0 -> P. 1143 if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1])) 1144 if (C->isZero()) 1145 return Ops[0]; 1146 // getelementptr P, N -> P if P points to a type of zero size. 1147 if (TD) { 1148 const Type *Ty = PtrTy->getElementType(); 1149 if (Ty->isSized() && TD->getTypeAllocSize(Ty) == 0) 1150 return Ops[0]; 1151 } 1152 } 1153 1154 // Check to see if this is constant foldable. 1155 for (unsigned i = 0; i != NumOps; ++i) 1156 if (!isa<Constant>(Ops[i])) 1157 return 0; 1158 1159 return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]), 1160 (Constant *const*)Ops+1, NumOps-1); 1161} 1162 1163/// SimplifyPHINode - See if we can fold the given phi. If not, returns null. 1164static Value *SimplifyPHINode(PHINode *PN, const DominatorTree *DT) { 1165 // If all of the PHI's incoming values are the same then replace the PHI node 1166 // with the common value. 1167 Value *CommonValue = 0; 1168 bool HasUndefInput = false; 1169 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1170 Value *Incoming = PN->getIncomingValue(i); 1171 // If the incoming value is the phi node itself, it can safely be skipped. 1172 if (Incoming == PN) continue; 1173 if (isa<UndefValue>(Incoming)) { 1174 // Remember that we saw an undef value, but otherwise ignore them. 1175 HasUndefInput = true; 1176 continue; 1177 } 1178 if (CommonValue && Incoming != CommonValue) 1179 return 0; // Not the same, bail out. 1180 CommonValue = Incoming; 1181 } 1182 1183 // If CommonValue is null then all of the incoming values were either undef or 1184 // equal to the phi node itself. 1185 if (!CommonValue) 1186 return UndefValue::get(PN->getType()); 1187 1188 // If we have a PHI node like phi(X, undef, X), where X is defined by some 1189 // instruction, we cannot return X as the result of the PHI node unless it 1190 // dominates the PHI block. 1191 if (HasUndefInput) 1192 return ValueDominatesPHI(CommonValue, PN, DT) ? CommonValue : 0; 1193 1194 return CommonValue; 1195} 1196 1197 1198//=== Helper functions for higher up the class hierarchy. 1199 1200/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can 1201/// fold the result. If not, this returns null. 1202static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 1203 const TargetData *TD, const DominatorTree *DT, 1204 unsigned MaxRecurse) { 1205 switch (Opcode) { 1206 case Instruction::Add: return SimplifyAddInst(LHS, RHS, /* isNSW */ false, 1207 /* isNUW */ false, TD, DT, 1208 MaxRecurse); 1209 case Instruction::Sub: return SimplifySubInst(LHS, RHS, /* isNSW */ false, 1210 /* isNUW */ false, TD, DT, 1211 MaxRecurse); 1212 case Instruction::Mul: return SimplifyMulInst(LHS, RHS, TD, DT, MaxRecurse); 1213 case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, DT, MaxRecurse); 1214 case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD, DT, MaxRecurse); 1215 case Instruction::Xor: return SimplifyXorInst(LHS, RHS, TD, DT, MaxRecurse); 1216 default: 1217 if (Constant *CLHS = dyn_cast<Constant>(LHS)) 1218 if (Constant *CRHS = dyn_cast<Constant>(RHS)) { 1219 Constant *COps[] = {CLHS, CRHS}; 1220 return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, 2, TD); 1221 } 1222 1223 // If the operation is associative, try some generic simplifications. 1224 if (Instruction::isAssociative(Opcode)) 1225 if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, TD, DT, 1226 MaxRecurse)) 1227 return V; 1228 1229 // If the operation is with the result of a select instruction, check whether 1230 // operating on either branch of the select always yields the same value. 1231 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) 1232 if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, DT, 1233 MaxRecurse)) 1234 return V; 1235 1236 // If the operation is with the result of a phi instruction, check whether 1237 // operating on all incoming values of the phi always yields the same value. 1238 if (isa<PHINode>(LHS) || isa<PHINode>(RHS)) 1239 if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, DT, MaxRecurse)) 1240 return V; 1241 1242 return 0; 1243 } 1244} 1245 1246Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 1247 const TargetData *TD, const DominatorTree *DT) { 1248 return ::SimplifyBinOp(Opcode, LHS, RHS, TD, DT, RecursionLimit); 1249} 1250 1251/// SimplifyCmpInst - Given operands for a CmpInst, see if we can 1252/// fold the result. 1253static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1254 const TargetData *TD, const DominatorTree *DT, 1255 unsigned MaxRecurse) { 1256 if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate)) 1257 return SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse); 1258 return SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse); 1259} 1260 1261Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 1262 const TargetData *TD, const DominatorTree *DT) { 1263 return ::SimplifyCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit); 1264} 1265 1266/// SimplifyInstruction - See if we can compute a simplified version of this 1267/// instruction. If not, this returns null. 1268Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD, 1269 const DominatorTree *DT) { 1270 Value *Result; 1271 1272 switch (I->getOpcode()) { 1273 default: 1274 Result = ConstantFoldInstruction(I, TD); 1275 break; 1276 case Instruction::Add: 1277 Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1), 1278 cast<BinaryOperator>(I)->hasNoSignedWrap(), 1279 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 1280 TD, DT); 1281 break; 1282 case Instruction::Sub: 1283 Result = SimplifySubInst(I->getOperand(0), I->getOperand(1), 1284 cast<BinaryOperator>(I)->hasNoSignedWrap(), 1285 cast<BinaryOperator>(I)->hasNoUnsignedWrap(), 1286 TD, DT); 1287 break; 1288 case Instruction::Mul: 1289 Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, DT); 1290 break; 1291 case Instruction::And: 1292 Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT); 1293 break; 1294 case Instruction::Or: 1295 Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT); 1296 break; 1297 case Instruction::Xor: 1298 Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, DT); 1299 break; 1300 case Instruction::ICmp: 1301 Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(), 1302 I->getOperand(0), I->getOperand(1), TD, DT); 1303 break; 1304 case Instruction::FCmp: 1305 Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(), 1306 I->getOperand(0), I->getOperand(1), TD, DT); 1307 break; 1308 case Instruction::Select: 1309 Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1), 1310 I->getOperand(2), TD, DT); 1311 break; 1312 case Instruction::GetElementPtr: { 1313 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end()); 1314 Result = SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT); 1315 break; 1316 } 1317 case Instruction::PHI: 1318 Result = SimplifyPHINode(cast<PHINode>(I), DT); 1319 break; 1320 } 1321 1322 /// If called on unreachable code, the above logic may report that the 1323 /// instruction simplified to itself. Make life easier for users by 1324 /// detecting that case here, returning a safe value instead. 1325 return Result == I ? UndefValue::get(I->getType()) : Result; 1326} 1327 1328/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then 1329/// delete the From instruction. In addition to a basic RAUW, this does a 1330/// recursive simplification of the newly formed instructions. This catches 1331/// things where one simplification exposes other opportunities. This only 1332/// simplifies and deletes scalar operations, it does not change the CFG. 1333/// 1334void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To, 1335 const TargetData *TD, 1336 const DominatorTree *DT) { 1337 assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!"); 1338 1339 // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that 1340 // we can know if it gets deleted out from under us or replaced in a 1341 // recursive simplification. 1342 WeakVH FromHandle(From); 1343 WeakVH ToHandle(To); 1344 1345 while (!From->use_empty()) { 1346 // Update the instruction to use the new value. 1347 Use &TheUse = From->use_begin().getUse(); 1348 Instruction *User = cast<Instruction>(TheUse.getUser()); 1349 TheUse = To; 1350 1351 // Check to see if the instruction can be folded due to the operand 1352 // replacement. For example changing (or X, Y) into (or X, -1) can replace 1353 // the 'or' with -1. 1354 Value *SimplifiedVal; 1355 { 1356 // Sanity check to make sure 'User' doesn't dangle across 1357 // SimplifyInstruction. 1358 AssertingVH<> UserHandle(User); 1359 1360 SimplifiedVal = SimplifyInstruction(User, TD, DT); 1361 if (SimplifiedVal == 0) continue; 1362 } 1363 1364 // Recursively simplify this user to the new value. 1365 ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, DT); 1366 From = dyn_cast_or_null<Instruction>((Value*)FromHandle); 1367 To = ToHandle; 1368 1369 assert(ToHandle && "To value deleted by recursive simplification?"); 1370 1371 // If the recursive simplification ended up revisiting and deleting 1372 // 'From' then we're done. 1373 if (From == 0) 1374 return; 1375 } 1376 1377 // If 'From' has value handles referring to it, do a real RAUW to update them. 1378 From->replaceAllUsesWith(To); 1379 1380 From->eraseFromParent(); 1381} 1382