ConstantFold.cpp revision 868510328fc0b25ca97f2fba466a77c2c4e29c45
1//===- ConstantFold.cpp - LLVM constant folder ----------------------------===// 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 folding of constants for LLVM. This implements the 11// (internal) ConstantFold.h interface, which is used by the 12// ConstantExpr::get* methods to automatically fold constants when possible. 13// 14// The current constant folding implementation is implemented in two pieces: the 15// template-based folder for simple primitive constants like ConstantInt, and 16// the special case hackery that we use to symbolically evaluate expressions 17// that use ConstantExprs. 18// 19//===----------------------------------------------------------------------===// 20 21#include "ConstantFold.h" 22#include "llvm/Constants.h" 23#include "llvm/Instructions.h" 24#include "llvm/DerivedTypes.h" 25#include "llvm/Function.h" 26#include "llvm/GlobalAlias.h" 27#include "llvm/ADT/SmallVector.h" 28#include "llvm/Support/Compiler.h" 29#include "llvm/Support/GetElementPtrTypeIterator.h" 30#include "llvm/Support/ManagedStatic.h" 31#include "llvm/Support/MathExtras.h" 32#include <limits> 33using namespace llvm; 34 35//===----------------------------------------------------------------------===// 36// ConstantFold*Instruction Implementations 37//===----------------------------------------------------------------------===// 38 39/// BitCastConstantVector - Convert the specified ConstantVector node to the 40/// specified vector type. At this point, we know that the elements of the 41/// input vector constant are all simple integer or FP values. 42static Constant *BitCastConstantVector(ConstantVector *CV, 43 const VectorType *DstTy) { 44 // If this cast changes element count then we can't handle it here: 45 // doing so requires endianness information. This should be handled by 46 // Analysis/ConstantFolding.cpp 47 unsigned NumElts = DstTy->getNumElements(); 48 if (NumElts != CV->getNumOperands()) 49 return 0; 50 51 // Check to verify that all elements of the input are simple. 52 for (unsigned i = 0; i != NumElts; ++i) { 53 if (!isa<ConstantInt>(CV->getOperand(i)) && 54 !isa<ConstantFP>(CV->getOperand(i))) 55 return 0; 56 } 57 58 // Bitcast each element now. 59 std::vector<Constant*> Result; 60 const Type *DstEltTy = DstTy->getElementType(); 61 for (unsigned i = 0; i != NumElts; ++i) 62 Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy)); 63 return ConstantVector::get(Result); 64} 65 66/// This function determines which opcode to use to fold two constant cast 67/// expressions together. It uses CastInst::isEliminableCastPair to determine 68/// the opcode. Consequently its just a wrapper around that function. 69/// @brief Determine if it is valid to fold a cast of a cast 70static unsigned 71foldConstantCastPair( 72 unsigned opc, ///< opcode of the second cast constant expression 73 const ConstantExpr*Op, ///< the first cast constant expression 74 const Type *DstTy ///< desintation type of the first cast 75) { 76 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); 77 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); 78 assert(CastInst::isCast(opc) && "Invalid cast opcode"); 79 80 // The the types and opcodes for the two Cast constant expressions 81 const Type *SrcTy = Op->getOperand(0)->getType(); 82 const Type *MidTy = Op->getType(); 83 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); 84 Instruction::CastOps secondOp = Instruction::CastOps(opc); 85 86 // Let CastInst::isEliminableCastPair do the heavy lifting. 87 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, 88 Type::Int64Ty); 89} 90 91static Constant *FoldBitCast(Constant *V, const Type *DestTy) { 92 const Type *SrcTy = V->getType(); 93 if (SrcTy == DestTy) 94 return V; // no-op cast 95 96 // Check to see if we are casting a pointer to an aggregate to a pointer to 97 // the first element. If so, return the appropriate GEP instruction. 98 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) 99 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) 100 if (PTy->getAddressSpace() == DPTy->getAddressSpace()) { 101 SmallVector<Value*, 8> IdxList; 102 IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); 103 const Type *ElTy = PTy->getElementType(); 104 while (ElTy != DPTy->getElementType()) { 105 if (const StructType *STy = dyn_cast<StructType>(ElTy)) { 106 if (STy->getNumElements() == 0) break; 107 ElTy = STy->getElementType(0); 108 IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); 109 } else if (const SequentialType *STy = 110 dyn_cast<SequentialType>(ElTy)) { 111 if (isa<PointerType>(ElTy)) break; // Can't index into pointers! 112 ElTy = STy->getElementType(); 113 IdxList.push_back(IdxList[0]); 114 } else { 115 break; 116 } 117 } 118 119 if (ElTy == DPTy->getElementType()) 120 return ConstantExpr::getGetElementPtr(V, &IdxList[0], IdxList.size()); 121 } 122 123 // Handle casts from one vector constant to another. We know that the src 124 // and dest type have the same size (otherwise its an illegal cast). 125 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { 126 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { 127 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && 128 "Not cast between same sized vectors!"); 129 // First, check for null. Undef is already handled. 130 if (isa<ConstantAggregateZero>(V)) 131 return Constant::getNullValue(DestTy); 132 133 if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) 134 return BitCastConstantVector(CV, DestPTy); 135 } 136 137 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts 138 // This allows for other simplifications (although some of them 139 // can only be handled by Analysis/ConstantFolding.cpp). 140 if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) 141 return ConstantExpr::getBitCast(ConstantVector::get(&V, 1), DestPTy); 142 } 143 144 // Finally, implement bitcast folding now. The code below doesn't handle 145 // bitcast right. 146 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 147 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 148 149 // Handle integral constant input. 150 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 151 if (DestTy->isInteger()) 152 // Integral -> Integral. This is a no-op because the bit widths must 153 // be the same. Consequently, we just fold to V. 154 return V; 155 156 if (DestTy->isFloatingPoint()) { 157 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) && 158 "Unknown FP type!"); 159 return ConstantFP::get(APFloat(CI->getValue())); 160 } 161 // Otherwise, can't fold this (vector?) 162 return 0; 163 } 164 165 // Handle ConstantFP input. 166 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) { 167 // FP -> Integral. 168 if (DestTy == Type::Int32Ty) { 169 return ConstantInt::get(FP->getValueAPF().bitcastToAPInt()); 170 } else { 171 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!"); 172 return ConstantInt::get(FP->getValueAPF().bitcastToAPInt()); 173 } 174 } 175 return 0; 176} 177 178 179Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V, 180 const Type *DestTy) { 181 if (isa<UndefValue>(V)) { 182 // zext(undef) = 0, because the top bits will be zero. 183 // sext(undef) = 0, because the top bits will all be the same. 184 // [us]itofp(undef) = 0, because the result value is bounded. 185 if (opc == Instruction::ZExt || opc == Instruction::SExt || 186 opc == Instruction::UIToFP || opc == Instruction::SIToFP) 187 return Constant::getNullValue(DestTy); 188 return UndefValue::get(DestTy); 189 } 190 // No compile-time operations on this type yet. 191 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty) 192 return 0; 193 194 // If the cast operand is a constant expression, there's a few things we can 195 // do to try to simplify it. 196 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 197 if (CE->isCast()) { 198 // Try hard to fold cast of cast because they are often eliminable. 199 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 200 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 201 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 202 // If all of the indexes in the GEP are null values, there is no pointer 203 // adjustment going on. We might as well cast the source pointer. 204 bool isAllNull = true; 205 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 206 if (!CE->getOperand(i)->isNullValue()) { 207 isAllNull = false; 208 break; 209 } 210 if (isAllNull) 211 // This is casting one pointer type to another, always BitCast 212 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 213 } 214 } 215 216 // We actually have to do a cast now. Perform the cast according to the 217 // opcode specified. 218 switch (opc) { 219 case Instruction::FPTrunc: 220 case Instruction::FPExt: 221 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 222 bool ignored; 223 APFloat Val = FPC->getValueAPF(); 224 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle : 225 DestTy == Type::DoubleTy ? APFloat::IEEEdouble : 226 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended : 227 DestTy == Type::FP128Ty ? APFloat::IEEEquad : 228 APFloat::Bogus, 229 APFloat::rmNearestTiesToEven, &ignored); 230 return ConstantFP::get(Val); 231 } 232 return 0; // Can't fold. 233 case Instruction::FPToUI: 234 case Instruction::FPToSI: 235 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 236 const APFloat &V = FPC->getValueAPF(); 237 bool ignored; 238 uint64_t x[2]; 239 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 240 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 241 APFloat::rmTowardZero, &ignored); 242 APInt Val(DestBitWidth, 2, x); 243 return ConstantInt::get(Val); 244 } 245 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) { 246 std::vector<Constant*> res; 247 const VectorType *DestVecTy = cast<VectorType>(DestTy); 248 const Type *DstEltTy = DestVecTy->getElementType(); 249 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 250 res.push_back(ConstantExpr::getCast(opc, CV->getOperand(i), DstEltTy)); 251 return ConstantVector::get(DestVecTy, res); 252 } 253 return 0; // Can't fold. 254 case Instruction::IntToPtr: //always treated as unsigned 255 if (V->isNullValue()) // Is it an integral null value? 256 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 257 return 0; // Other pointer types cannot be casted 258 case Instruction::PtrToInt: // always treated as unsigned 259 if (V->isNullValue()) // is it a null pointer value? 260 return ConstantInt::get(DestTy, 0); 261 return 0; // Other pointer types cannot be casted 262 case Instruction::UIToFP: 263 case Instruction::SIToFP: 264 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 265 APInt api = CI->getValue(); 266 const uint64_t zero[] = {0, 0}; 267 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(), 268 2, zero)); 269 (void)apf.convertFromAPInt(api, 270 opc==Instruction::SIToFP, 271 APFloat::rmNearestTiesToEven); 272 return ConstantFP::get(apf); 273 } 274 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) { 275 std::vector<Constant*> res; 276 const VectorType *DestVecTy = cast<VectorType>(DestTy); 277 const Type *DstEltTy = DestVecTy->getElementType(); 278 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 279 res.push_back(ConstantExpr::getCast(opc, CV->getOperand(i), DstEltTy)); 280 return ConstantVector::get(DestVecTy, res); 281 } 282 return 0; 283 case Instruction::ZExt: 284 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 285 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 286 APInt Result(CI->getValue()); 287 Result.zext(BitWidth); 288 return ConstantInt::get(Result); 289 } 290 return 0; 291 case Instruction::SExt: 292 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 293 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 294 APInt Result(CI->getValue()); 295 Result.sext(BitWidth); 296 return ConstantInt::get(Result); 297 } 298 return 0; 299 case Instruction::Trunc: 300 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 301 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 302 APInt Result(CI->getValue()); 303 Result.trunc(BitWidth); 304 return ConstantInt::get(Result); 305 } 306 return 0; 307 case Instruction::BitCast: 308 return FoldBitCast(const_cast<Constant*>(V), DestTy); 309 default: 310 assert(!"Invalid CE CastInst opcode"); 311 break; 312 } 313 314 assert(0 && "Failed to cast constant expression"); 315 return 0; 316} 317 318Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, 319 const Constant *V1, 320 const Constant *V2) { 321 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) 322 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2); 323 324 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); 325 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); 326 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); 327 if (V1 == V2) return const_cast<Constant*>(V1); 328 return 0; 329} 330 331Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, 332 const Constant *Idx) { 333 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 334 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType()); 335 if (Val->isNullValue()) // ee(zero, x) -> zero 336 return Constant::getNullValue( 337 cast<VectorType>(Val->getType())->getElementType()); 338 339 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 340 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 341 return CVal->getOperand(CIdx->getZExtValue()); 342 } else if (isa<UndefValue>(Idx)) { 343 // ee({w,x,y,z}, undef) -> w (an arbitrary value). 344 return CVal->getOperand(0); 345 } 346 } 347 return 0; 348} 349 350Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, 351 const Constant *Elt, 352 const Constant *Idx) { 353 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 354 if (!CIdx) return 0; 355 APInt idxVal = CIdx->getValue(); 356 if (isa<UndefValue>(Val)) { 357 // Insertion of scalar constant into vector undef 358 // Optimize away insertion of undef 359 if (isa<UndefValue>(Elt)) 360 return const_cast<Constant*>(Val); 361 // Otherwise break the aggregate undef into multiple undefs and do 362 // the insertion 363 unsigned numOps = 364 cast<VectorType>(Val->getType())->getNumElements(); 365 std::vector<Constant*> Ops; 366 Ops.reserve(numOps); 367 for (unsigned i = 0; i < numOps; ++i) { 368 const Constant *Op = 369 (idxVal == i) ? Elt : UndefValue::get(Elt->getType()); 370 Ops.push_back(const_cast<Constant*>(Op)); 371 } 372 return ConstantVector::get(Ops); 373 } 374 if (isa<ConstantAggregateZero>(Val)) { 375 // Insertion of scalar constant into vector aggregate zero 376 // Optimize away insertion of zero 377 if (Elt->isNullValue()) 378 return const_cast<Constant*>(Val); 379 // Otherwise break the aggregate zero into multiple zeros and do 380 // the insertion 381 unsigned numOps = 382 cast<VectorType>(Val->getType())->getNumElements(); 383 std::vector<Constant*> Ops; 384 Ops.reserve(numOps); 385 for (unsigned i = 0; i < numOps; ++i) { 386 const Constant *Op = 387 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType()); 388 Ops.push_back(const_cast<Constant*>(Op)); 389 } 390 return ConstantVector::get(Ops); 391 } 392 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 393 // Insertion of scalar constant into vector constant 394 std::vector<Constant*> Ops; 395 Ops.reserve(CVal->getNumOperands()); 396 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { 397 const Constant *Op = 398 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i)); 399 Ops.push_back(const_cast<Constant*>(Op)); 400 } 401 return ConstantVector::get(Ops); 402 } 403 404 return 0; 405} 406 407/// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef 408/// return the specified element value. Otherwise return null. 409static Constant *GetVectorElement(const Constant *C, unsigned EltNo) { 410 if (const ConstantVector *CV = dyn_cast<ConstantVector>(C)) 411 return CV->getOperand(EltNo); 412 413 const Type *EltTy = cast<VectorType>(C->getType())->getElementType(); 414 if (isa<ConstantAggregateZero>(C)) 415 return Constant::getNullValue(EltTy); 416 if (isa<UndefValue>(C)) 417 return UndefValue::get(EltTy); 418 return 0; 419} 420 421Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, 422 const Constant *V2, 423 const Constant *Mask) { 424 // Undefined shuffle mask -> undefined value. 425 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType()); 426 427 unsigned NumElts = cast<VectorType>(V1->getType())->getNumElements(); 428 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType(); 429 430 // Loop over the shuffle mask, evaluating each element. 431 SmallVector<Constant*, 32> Result; 432 for (unsigned i = 0; i != NumElts; ++i) { 433 Constant *InElt = GetVectorElement(Mask, i); 434 if (InElt == 0) return 0; 435 436 if (isa<UndefValue>(InElt)) 437 InElt = UndefValue::get(EltTy); 438 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) { 439 unsigned Elt = CI->getZExtValue(); 440 if (Elt >= NumElts*2) 441 InElt = UndefValue::get(EltTy); 442 else if (Elt >= NumElts) 443 InElt = GetVectorElement(V2, Elt-NumElts); 444 else 445 InElt = GetVectorElement(V1, Elt); 446 if (InElt == 0) return 0; 447 } else { 448 // Unknown value. 449 return 0; 450 } 451 Result.push_back(InElt); 452 } 453 454 return ConstantVector::get(&Result[0], Result.size()); 455} 456 457Constant *llvm::ConstantFoldExtractValueInstruction(const Constant *Agg, 458 const unsigned *Idxs, 459 unsigned NumIdx) { 460 // Base case: no indices, so return the entire value. 461 if (NumIdx == 0) 462 return const_cast<Constant *>(Agg); 463 464 if (isa<UndefValue>(Agg)) // ev(undef, x) -> undef 465 return UndefValue::get(ExtractValueInst::getIndexedType(Agg->getType(), 466 Idxs, 467 Idxs + NumIdx)); 468 469 if (isa<ConstantAggregateZero>(Agg)) // ev(0, x) -> 0 470 return 471 Constant::getNullValue(ExtractValueInst::getIndexedType(Agg->getType(), 472 Idxs, 473 Idxs + NumIdx)); 474 475 // Otherwise recurse. 476 return ConstantFoldExtractValueInstruction(Agg->getOperand(*Idxs), 477 Idxs+1, NumIdx-1); 478} 479 480Constant *llvm::ConstantFoldInsertValueInstruction(const Constant *Agg, 481 const Constant *Val, 482 const unsigned *Idxs, 483 unsigned NumIdx) { 484 // Base case: no indices, so replace the entire value. 485 if (NumIdx == 0) 486 return const_cast<Constant *>(Val); 487 488 if (isa<UndefValue>(Agg)) { 489 // Insertion of constant into aggregate undef 490 // Optimize away insertion of undef 491 if (isa<UndefValue>(Val)) 492 return const_cast<Constant*>(Agg); 493 // Otherwise break the aggregate undef into multiple undefs and do 494 // the insertion 495 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 496 unsigned numOps; 497 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 498 numOps = AR->getNumElements(); 499 else 500 numOps = cast<StructType>(AggTy)->getNumElements(); 501 std::vector<Constant*> Ops(numOps); 502 for (unsigned i = 0; i < numOps; ++i) { 503 const Type *MemberTy = AggTy->getTypeAtIndex(i); 504 const Constant *Op = 505 (*Idxs == i) ? 506 ConstantFoldInsertValueInstruction(UndefValue::get(MemberTy), 507 Val, Idxs+1, NumIdx-1) : 508 UndefValue::get(MemberTy); 509 Ops[i] = const_cast<Constant*>(Op); 510 } 511 if (isa<StructType>(AggTy)) 512 return ConstantStruct::get(Ops); 513 else 514 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 515 } 516 if (isa<ConstantAggregateZero>(Agg)) { 517 // Insertion of constant into aggregate zero 518 // Optimize away insertion of zero 519 if (Val->isNullValue()) 520 return const_cast<Constant*>(Agg); 521 // Otherwise break the aggregate zero into multiple zeros and do 522 // the insertion 523 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 524 unsigned numOps; 525 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 526 numOps = AR->getNumElements(); 527 else 528 numOps = cast<StructType>(AggTy)->getNumElements(); 529 std::vector<Constant*> Ops(numOps); 530 for (unsigned i = 0; i < numOps; ++i) { 531 const Type *MemberTy = AggTy->getTypeAtIndex(i); 532 const Constant *Op = 533 (*Idxs == i) ? 534 ConstantFoldInsertValueInstruction(Constant::getNullValue(MemberTy), 535 Val, Idxs+1, NumIdx-1) : 536 Constant::getNullValue(MemberTy); 537 Ops[i] = const_cast<Constant*>(Op); 538 } 539 if (isa<StructType>(AggTy)) 540 return ConstantStruct::get(Ops); 541 else 542 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 543 } 544 if (isa<ConstantStruct>(Agg) || isa<ConstantArray>(Agg)) { 545 // Insertion of constant into aggregate constant 546 std::vector<Constant*> Ops(Agg->getNumOperands()); 547 for (unsigned i = 0; i < Agg->getNumOperands(); ++i) { 548 const Constant *Op = 549 (*Idxs == i) ? 550 ConstantFoldInsertValueInstruction(Agg->getOperand(i), 551 Val, Idxs+1, NumIdx-1) : 552 Agg->getOperand(i); 553 Ops[i] = const_cast<Constant*>(Op); 554 } 555 Constant *C; 556 if (isa<StructType>(Agg->getType())) 557 C = ConstantStruct::get(Ops); 558 else 559 C = ConstantArray::get(cast<ArrayType>(Agg->getType()), Ops); 560 return C; 561 } 562 563 return 0; 564} 565 566/// EvalVectorOp - Given two vector constants and a function pointer, apply the 567/// function pointer to each element pair, producing a new ConstantVector 568/// constant. Either or both of V1 and V2 may be NULL, meaning a 569/// ConstantAggregateZero operand. 570static Constant *EvalVectorOp(const ConstantVector *V1, 571 const ConstantVector *V2, 572 const VectorType *VTy, 573 Constant *(*FP)(Constant*, Constant*)) { 574 std::vector<Constant*> Res; 575 const Type *EltTy = VTy->getElementType(); 576 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 577 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy); 578 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy); 579 Res.push_back(FP(const_cast<Constant*>(C1), 580 const_cast<Constant*>(C2))); 581 } 582 return ConstantVector::get(Res); 583} 584 585Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 586 const Constant *C1, 587 const Constant *C2) { 588 // No compile-time operations on this type yet. 589 if (C1->getType() == Type::PPC_FP128Ty) 590 return 0; 591 592 // Handle UndefValue up front 593 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 594 switch (Opcode) { 595 case Instruction::Xor: 596 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 597 // Handle undef ^ undef -> 0 special case. This is a common 598 // idiom (misuse). 599 return Constant::getNullValue(C1->getType()); 600 // Fallthrough 601 case Instruction::Add: 602 case Instruction::Sub: 603 return UndefValue::get(C1->getType()); 604 case Instruction::Mul: 605 case Instruction::And: 606 return Constant::getNullValue(C1->getType()); 607 case Instruction::UDiv: 608 case Instruction::SDiv: 609 case Instruction::FDiv: 610 case Instruction::URem: 611 case Instruction::SRem: 612 case Instruction::FRem: 613 if (!isa<UndefValue>(C2)) // undef / X -> 0 614 return Constant::getNullValue(C1->getType()); 615 return const_cast<Constant*>(C2); // X / undef -> undef 616 case Instruction::Or: // X | undef -> -1 617 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType())) 618 return ConstantVector::getAllOnesValue(PTy); 619 return ConstantInt::getAllOnesValue(C1->getType()); 620 case Instruction::LShr: 621 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 622 return const_cast<Constant*>(C1); // undef lshr undef -> undef 623 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 624 // undef lshr X -> 0 625 case Instruction::AShr: 626 if (!isa<UndefValue>(C2)) 627 return const_cast<Constant*>(C1); // undef ashr X --> undef 628 else if (isa<UndefValue>(C1)) 629 return const_cast<Constant*>(C1); // undef ashr undef -> undef 630 else 631 return const_cast<Constant*>(C1); // X ashr undef --> X 632 case Instruction::Shl: 633 // undef << X -> 0 or X << undef -> 0 634 return Constant::getNullValue(C1->getType()); 635 } 636 } 637 638 // Handle simplifications of the RHS when a constant int. 639 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 640 switch (Opcode) { 641 case Instruction::Add: 642 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X + 0 == X 643 break; 644 case Instruction::Sub: 645 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X - 0 == X 646 break; 647 case Instruction::Mul: 648 if (CI2->equalsInt(0)) return const_cast<Constant*>(C2); // X * 0 == 0 649 if (CI2->equalsInt(1)) 650 return const_cast<Constant*>(C1); // X * 1 == X 651 break; 652 case Instruction::UDiv: 653 case Instruction::SDiv: 654 if (CI2->equalsInt(1)) 655 return const_cast<Constant*>(C1); // X / 1 == X 656 break; 657 case Instruction::URem: 658 case Instruction::SRem: 659 if (CI2->equalsInt(1)) 660 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 661 break; 662 case Instruction::And: 663 if (CI2->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0 664 if (CI2->isAllOnesValue()) 665 return const_cast<Constant*>(C1); // X & -1 == X 666 667 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 668 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 669 if (CE1->getOpcode() == Instruction::ZExt) { 670 unsigned DstWidth = CI2->getType()->getBitWidth(); 671 unsigned SrcWidth = 672 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 673 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 674 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 675 return const_cast<Constant*>(C1); 676 } 677 678 // If and'ing the address of a global with a constant, fold it. 679 if (CE1->getOpcode() == Instruction::PtrToInt && 680 isa<GlobalValue>(CE1->getOperand(0))) { 681 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 682 683 // Functions are at least 4-byte aligned. 684 unsigned GVAlign = GV->getAlignment(); 685 if (isa<Function>(GV)) 686 GVAlign = std::max(GVAlign, 4U); 687 688 if (GVAlign > 1) { 689 unsigned DstWidth = CI2->getType()->getBitWidth(); 690 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 691 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 692 693 // If checking bits we know are clear, return zero. 694 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 695 return Constant::getNullValue(CI2->getType()); 696 } 697 } 698 } 699 break; 700 case Instruction::Or: 701 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X | 0 == X 702 if (CI2->isAllOnesValue()) 703 return const_cast<Constant*>(C2); // X | -1 == -1 704 break; 705 case Instruction::Xor: 706 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X ^ 0 == X 707 break; 708 case Instruction::AShr: 709 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 710 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 711 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 712 return ConstantExpr::getLShr(const_cast<Constant*>(C1), 713 const_cast<Constant*>(C2)); 714 break; 715 } 716 } 717 718 // At this point we know neither constant is an UndefValue. 719 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 720 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 721 using namespace APIntOps; 722 const APInt &C1V = CI1->getValue(); 723 const APInt &C2V = CI2->getValue(); 724 switch (Opcode) { 725 default: 726 break; 727 case Instruction::Add: 728 return ConstantInt::get(C1V + C2V); 729 case Instruction::Sub: 730 return ConstantInt::get(C1V - C2V); 731 case Instruction::Mul: 732 return ConstantInt::get(C1V * C2V); 733 case Instruction::UDiv: 734 if (CI2->isNullValue()) 735 return 0; // X / 0 -> can't fold 736 return ConstantInt::get(C1V.udiv(C2V)); 737 case Instruction::SDiv: 738 if (CI2->isNullValue()) 739 return 0; // X / 0 -> can't fold 740 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 741 return 0; // MIN_INT / -1 -> overflow 742 return ConstantInt::get(C1V.sdiv(C2V)); 743 case Instruction::URem: 744 if (C2->isNullValue()) 745 return 0; // X / 0 -> can't fold 746 return ConstantInt::get(C1V.urem(C2V)); 747 case Instruction::SRem: 748 if (CI2->isNullValue()) 749 return 0; // X % 0 -> can't fold 750 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 751 return 0; // MIN_INT % -1 -> overflow 752 return ConstantInt::get(C1V.srem(C2V)); 753 case Instruction::And: 754 return ConstantInt::get(C1V & C2V); 755 case Instruction::Or: 756 return ConstantInt::get(C1V | C2V); 757 case Instruction::Xor: 758 return ConstantInt::get(C1V ^ C2V); 759 case Instruction::Shl: { 760 uint32_t shiftAmt = C2V.getZExtValue(); 761 if (shiftAmt < C1V.getBitWidth()) 762 return ConstantInt::get(C1V.shl(shiftAmt)); 763 else 764 return UndefValue::get(C1->getType()); // too big shift is undef 765 } 766 case Instruction::LShr: { 767 uint32_t shiftAmt = C2V.getZExtValue(); 768 if (shiftAmt < C1V.getBitWidth()) 769 return ConstantInt::get(C1V.lshr(shiftAmt)); 770 else 771 return UndefValue::get(C1->getType()); // too big shift is undef 772 } 773 case Instruction::AShr: { 774 uint32_t shiftAmt = C2V.getZExtValue(); 775 if (shiftAmt < C1V.getBitWidth()) 776 return ConstantInt::get(C1V.ashr(shiftAmt)); 777 else 778 return UndefValue::get(C1->getType()); // too big shift is undef 779 } 780 } 781 } 782 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 783 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 784 APFloat C1V = CFP1->getValueAPF(); 785 APFloat C2V = CFP2->getValueAPF(); 786 APFloat C3V = C1V; // copy for modification 787 switch (Opcode) { 788 default: 789 break; 790 case Instruction::Add: 791 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 792 return ConstantFP::get(C3V); 793 case Instruction::Sub: 794 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 795 return ConstantFP::get(C3V); 796 case Instruction::Mul: 797 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 798 return ConstantFP::get(C3V); 799 case Instruction::FDiv: 800 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 801 return ConstantFP::get(C3V); 802 case Instruction::FRem: 803 if (C2V.isZero()) { 804 // IEEE 754, Section 7.1, #5 805 if (CFP1->getType() == Type::DoubleTy) 806 return ConstantFP::get(APFloat(std::numeric_limits<double>:: 807 quiet_NaN())); 808 if (CFP1->getType() == Type::FloatTy) 809 return ConstantFP::get(APFloat(std::numeric_limits<float>:: 810 quiet_NaN())); 811 break; 812 } 813 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 814 return ConstantFP::get(C3V); 815 } 816 } 817 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 818 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1); 819 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2); 820 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) && 821 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) { 822 switch (Opcode) { 823 default: 824 break; 825 case Instruction::Add: 826 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd); 827 case Instruction::Sub: 828 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub); 829 case Instruction::Mul: 830 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul); 831 case Instruction::UDiv: 832 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv); 833 case Instruction::SDiv: 834 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv); 835 case Instruction::FDiv: 836 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv); 837 case Instruction::URem: 838 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem); 839 case Instruction::SRem: 840 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem); 841 case Instruction::FRem: 842 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem); 843 case Instruction::And: 844 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd); 845 case Instruction::Or: 846 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr); 847 case Instruction::Xor: 848 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor); 849 } 850 } 851 } 852 853 if (isa<ConstantExpr>(C1)) { 854 // There are many possible foldings we could do here. We should probably 855 // at least fold add of a pointer with an integer into the appropriate 856 // getelementptr. This will improve alias analysis a bit. 857 } else if (isa<ConstantExpr>(C2)) { 858 // If C2 is a constant expr and C1 isn't, flop them around and fold the 859 // other way if possible. 860 switch (Opcode) { 861 case Instruction::Add: 862 case Instruction::Mul: 863 case Instruction::And: 864 case Instruction::Or: 865 case Instruction::Xor: 866 // No change of opcode required. 867 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 868 869 case Instruction::Shl: 870 case Instruction::LShr: 871 case Instruction::AShr: 872 case Instruction::Sub: 873 case Instruction::SDiv: 874 case Instruction::UDiv: 875 case Instruction::FDiv: 876 case Instruction::URem: 877 case Instruction::SRem: 878 case Instruction::FRem: 879 default: // These instructions cannot be flopped around. 880 break; 881 } 882 } 883 884 // We don't know how to fold this. 885 return 0; 886} 887 888/// isZeroSizedType - This type is zero sized if its an array or structure of 889/// zero sized types. The only leaf zero sized type is an empty structure. 890static bool isMaybeZeroSizedType(const Type *Ty) { 891 if (isa<OpaqueType>(Ty)) return true; // Can't say. 892 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 893 894 // If all of elements have zero size, this does too. 895 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 896 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 897 return true; 898 899 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 900 return isMaybeZeroSizedType(ATy->getElementType()); 901 } 902 return false; 903} 904 905/// IdxCompare - Compare the two constants as though they were getelementptr 906/// indices. This allows coersion of the types to be the same thing. 907/// 908/// If the two constants are the "same" (after coersion), return 0. If the 909/// first is less than the second, return -1, if the second is less than the 910/// first, return 1. If the constants are not integral, return -2. 911/// 912static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 913 if (C1 == C2) return 0; 914 915 // Ok, we found a different index. If they are not ConstantInt, we can't do 916 // anything with them. 917 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 918 return -2; // don't know! 919 920 // Ok, we have two differing integer indices. Sign extend them to be the same 921 // type. Long is always big enough, so we use it. 922 if (C1->getType() != Type::Int64Ty) 923 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); 924 925 if (C2->getType() != Type::Int64Ty) 926 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); 927 928 if (C1 == C2) return 0; // They are equal 929 930 // If the type being indexed over is really just a zero sized type, there is 931 // no pointer difference being made here. 932 if (isMaybeZeroSizedType(ElTy)) 933 return -2; // dunno. 934 935 // If they are really different, now that they are the same type, then we 936 // found a difference! 937 if (cast<ConstantInt>(C1)->getSExtValue() < 938 cast<ConstantInt>(C2)->getSExtValue()) 939 return -1; 940 else 941 return 1; 942} 943 944/// evaluateFCmpRelation - This function determines if there is anything we can 945/// decide about the two constants provided. This doesn't need to handle simple 946/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 947/// If we can determine that the two constants have a particular relation to 948/// each other, we should return the corresponding FCmpInst predicate, 949/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 950/// ConstantFoldCompareInstruction. 951/// 952/// To simplify this code we canonicalize the relation so that the first 953/// operand is always the most "complex" of the two. We consider ConstantFP 954/// to be the simplest, and ConstantExprs to be the most complex. 955static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, 956 const Constant *V2) { 957 assert(V1->getType() == V2->getType() && 958 "Cannot compare values of different types!"); 959 960 // No compile-time operations on this type yet. 961 if (V1->getType() == Type::PPC_FP128Ty) 962 return FCmpInst::BAD_FCMP_PREDICATE; 963 964 // Handle degenerate case quickly 965 if (V1 == V2) return FCmpInst::FCMP_OEQ; 966 967 if (!isa<ConstantExpr>(V1)) { 968 if (!isa<ConstantExpr>(V2)) { 969 // We distilled thisUse the standard constant folder for a few cases 970 ConstantInt *R = 0; 971 Constant *C1 = const_cast<Constant*>(V1); 972 Constant *C2 = const_cast<Constant*>(V2); 973 R = dyn_cast<ConstantInt>( 974 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); 975 if (R && !R->isZero()) 976 return FCmpInst::FCMP_OEQ; 977 R = dyn_cast<ConstantInt>( 978 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); 979 if (R && !R->isZero()) 980 return FCmpInst::FCMP_OLT; 981 R = dyn_cast<ConstantInt>( 982 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); 983 if (R && !R->isZero()) 984 return FCmpInst::FCMP_OGT; 985 986 // Nothing more we can do 987 return FCmpInst::BAD_FCMP_PREDICATE; 988 } 989 990 // If the first operand is simple and second is ConstantExpr, swap operands. 991 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 992 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 993 return FCmpInst::getSwappedPredicate(SwappedRelation); 994 } else { 995 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 996 // constantexpr or a simple constant. 997 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 998 switch (CE1->getOpcode()) { 999 case Instruction::FPTrunc: 1000 case Instruction::FPExt: 1001 case Instruction::UIToFP: 1002 case Instruction::SIToFP: 1003 // We might be able to do something with these but we don't right now. 1004 break; 1005 default: 1006 break; 1007 } 1008 } 1009 // There are MANY other foldings that we could perform here. They will 1010 // probably be added on demand, as they seem needed. 1011 return FCmpInst::BAD_FCMP_PREDICATE; 1012} 1013 1014/// evaluateICmpRelation - This function determines if there is anything we can 1015/// decide about the two constants provided. This doesn't need to handle simple 1016/// things like integer comparisons, but should instead handle ConstantExprs 1017/// and GlobalValues. If we can determine that the two constants have a 1018/// particular relation to each other, we should return the corresponding ICmp 1019/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 1020/// 1021/// To simplify this code we canonicalize the relation so that the first 1022/// operand is always the most "complex" of the two. We consider simple 1023/// constants (like ConstantInt) to be the simplest, followed by 1024/// GlobalValues, followed by ConstantExpr's (the most complex). 1025/// 1026static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, 1027 const Constant *V2, 1028 bool isSigned) { 1029 assert(V1->getType() == V2->getType() && 1030 "Cannot compare different types of values!"); 1031 if (V1 == V2) return ICmpInst::ICMP_EQ; 1032 1033 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 1034 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { 1035 // We distilled this down to a simple case, use the standard constant 1036 // folder. 1037 ConstantInt *R = 0; 1038 Constant *C1 = const_cast<Constant*>(V1); 1039 Constant *C2 = const_cast<Constant*>(V2); 1040 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 1041 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1042 if (R && !R->isZero()) 1043 return pred; 1044 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1045 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1046 if (R && !R->isZero()) 1047 return pred; 1048 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1049 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1050 if (R && !R->isZero()) 1051 return pred; 1052 1053 // If we couldn't figure it out, bail. 1054 return ICmpInst::BAD_ICMP_PREDICATE; 1055 } 1056 1057 // If the first operand is simple, swap operands. 1058 ICmpInst::Predicate SwappedRelation = 1059 evaluateICmpRelation(V2, V1, isSigned); 1060 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1061 return ICmpInst::getSwappedPredicate(SwappedRelation); 1062 1063 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { 1064 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1065 ICmpInst::Predicate SwappedRelation = 1066 evaluateICmpRelation(V2, V1, isSigned); 1067 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1068 return ICmpInst::getSwappedPredicate(SwappedRelation); 1069 else 1070 return ICmpInst::BAD_ICMP_PREDICATE; 1071 } 1072 1073 // Now we know that the RHS is a GlobalValue or simple constant, 1074 // which (since the types must match) means that it's a ConstantPointerNull. 1075 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 1076 // Don't try to decide equality of aliases. 1077 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2)) 1078 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) 1079 return ICmpInst::ICMP_NE; 1080 } else { 1081 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 1082 // GlobalVals can never be null. Don't try to evaluate aliases. 1083 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1)) 1084 return ICmpInst::ICMP_NE; 1085 } 1086 } else { 1087 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1088 // constantexpr, a CPR, or a simple constant. 1089 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1090 const Constant *CE1Op0 = CE1->getOperand(0); 1091 1092 switch (CE1->getOpcode()) { 1093 case Instruction::Trunc: 1094 case Instruction::FPTrunc: 1095 case Instruction::FPExt: 1096 case Instruction::FPToUI: 1097 case Instruction::FPToSI: 1098 break; // We can't evaluate floating point casts or truncations. 1099 1100 case Instruction::UIToFP: 1101 case Instruction::SIToFP: 1102 case Instruction::BitCast: 1103 case Instruction::ZExt: 1104 case Instruction::SExt: 1105 // If the cast is not actually changing bits, and the second operand is a 1106 // null pointer, do the comparison with the pre-casted value. 1107 if (V2->isNullValue() && 1108 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) { 1109 bool sgnd = isSigned; 1110 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1111 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1112 return evaluateICmpRelation(CE1Op0, 1113 Constant::getNullValue(CE1Op0->getType()), 1114 sgnd); 1115 } 1116 1117 // If the dest type is a pointer type, and the RHS is a constantexpr cast 1118 // from the same type as the src of the LHS, evaluate the inputs. This is 1119 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", 1120 // which happens a lot in compilers with tagged integers. 1121 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) 1122 if (CE2->isCast() && isa<PointerType>(CE1->getType()) && 1123 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && 1124 CE1->getOperand(0)->getType()->isInteger()) { 1125 bool sgnd = isSigned; 1126 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1127 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1128 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), 1129 sgnd); 1130 } 1131 break; 1132 1133 case Instruction::GetElementPtr: 1134 // Ok, since this is a getelementptr, we know that the constant has a 1135 // pointer type. Check the various cases. 1136 if (isa<ConstantPointerNull>(V2)) { 1137 // If we are comparing a GEP to a null pointer, check to see if the base 1138 // of the GEP equals the null pointer. 1139 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1140 if (GV->hasExternalWeakLinkage()) 1141 // Weak linkage GVals could be zero or not. We're comparing that 1142 // to null pointer so its greater-or-equal 1143 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1144 else 1145 // If its not weak linkage, the GVal must have a non-zero address 1146 // so the result is greater-than 1147 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1148 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1149 // If we are indexing from a null pointer, check to see if we have any 1150 // non-zero indices. 1151 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1152 if (!CE1->getOperand(i)->isNullValue()) 1153 // Offsetting from null, must not be equal. 1154 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1155 // Only zero indexes from null, must still be zero. 1156 return ICmpInst::ICMP_EQ; 1157 } 1158 // Otherwise, we can't really say if the first operand is null or not. 1159 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 1160 if (isa<ConstantPointerNull>(CE1Op0)) { 1161 if (CPR2->hasExternalWeakLinkage()) 1162 // Weak linkage GVals could be zero or not. We're comparing it to 1163 // a null pointer, so its less-or-equal 1164 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1165 else 1166 // If its not weak linkage, the GVal must have a non-zero address 1167 // so the result is less-than 1168 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1169 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 1170 if (CPR1 == CPR2) { 1171 // If this is a getelementptr of the same global, then it must be 1172 // different. Because the types must match, the getelementptr could 1173 // only have at most one index, and because we fold getelementptr's 1174 // with a single zero index, it must be nonzero. 1175 assert(CE1->getNumOperands() == 2 && 1176 !CE1->getOperand(1)->isNullValue() && 1177 "Suprising getelementptr!"); 1178 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1179 } else { 1180 // If they are different globals, we don't know what the value is, 1181 // but they can't be equal. 1182 return ICmpInst::ICMP_NE; 1183 } 1184 } 1185 } else { 1186 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1187 const Constant *CE2Op0 = CE2->getOperand(0); 1188 1189 // There are MANY other foldings that we could perform here. They will 1190 // probably be added on demand, as they seem needed. 1191 switch (CE2->getOpcode()) { 1192 default: break; 1193 case Instruction::GetElementPtr: 1194 // By far the most common case to handle is when the base pointers are 1195 // obviously to the same or different globals. 1196 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1197 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 1198 return ICmpInst::ICMP_NE; 1199 // Ok, we know that both getelementptr instructions are based on the 1200 // same global. From this, we can precisely determine the relative 1201 // ordering of the resultant pointers. 1202 unsigned i = 1; 1203 1204 // Compare all of the operands the GEP's have in common. 1205 gep_type_iterator GTI = gep_type_begin(CE1); 1206 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1207 ++i, ++GTI) 1208 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), 1209 GTI.getIndexedType())) { 1210 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1211 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1212 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1213 } 1214 1215 // Ok, we ran out of things they have in common. If any leftovers 1216 // are non-zero then we have a difference, otherwise we are equal. 1217 for (; i < CE1->getNumOperands(); ++i) 1218 if (!CE1->getOperand(i)->isNullValue()) { 1219 if (isa<ConstantInt>(CE1->getOperand(i))) 1220 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1221 else 1222 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1223 } 1224 1225 for (; i < CE2->getNumOperands(); ++i) 1226 if (!CE2->getOperand(i)->isNullValue()) { 1227 if (isa<ConstantInt>(CE2->getOperand(i))) 1228 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1229 else 1230 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1231 } 1232 return ICmpInst::ICMP_EQ; 1233 } 1234 } 1235 } 1236 default: 1237 break; 1238 } 1239 } 1240 1241 return ICmpInst::BAD_ICMP_PREDICATE; 1242} 1243 1244Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1245 const Constant *C1, 1246 const Constant *C2) { 1247 // Fold FCMP_FALSE/FCMP_TRUE unconditionally. 1248 if (pred == FCmpInst::FCMP_FALSE) { 1249 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1250 return Constant::getNullValue(VectorType::getInteger(VT)); 1251 else 1252 return ConstantInt::getFalse(); 1253 } 1254 1255 if (pred == FCmpInst::FCMP_TRUE) { 1256 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1257 return Constant::getAllOnesValue(VectorType::getInteger(VT)); 1258 else 1259 return ConstantInt::getTrue(); 1260 } 1261 1262 // Handle some degenerate cases first 1263 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 1264 // vicmp/vfcmp -> [vector] undef 1265 if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) 1266 return UndefValue::get(VectorType::getInteger(VTy)); 1267 1268 // icmp/fcmp -> i1 undef 1269 return UndefValue::get(Type::Int1Ty); 1270 } 1271 1272 // No compile-time operations on this type yet. 1273 if (C1->getType() == Type::PPC_FP128Ty) 1274 return 0; 1275 1276 // icmp eq/ne(null,GV) -> false/true 1277 if (C1->isNullValue()) { 1278 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1279 // Don't try to evaluate aliases. External weak GV can be null. 1280 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1281 if (pred == ICmpInst::ICMP_EQ) 1282 return ConstantInt::getFalse(); 1283 else if (pred == ICmpInst::ICMP_NE) 1284 return ConstantInt::getTrue(); 1285 } 1286 // icmp eq/ne(GV,null) -> false/true 1287 } else if (C2->isNullValue()) { 1288 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1289 // Don't try to evaluate aliases. External weak GV can be null. 1290 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1291 if (pred == ICmpInst::ICMP_EQ) 1292 return ConstantInt::getFalse(); 1293 else if (pred == ICmpInst::ICMP_NE) 1294 return ConstantInt::getTrue(); 1295 } 1296 } 1297 1298 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1299 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1300 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1301 switch (pred) { 1302 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1303 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); 1304 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); 1305 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2)); 1306 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2)); 1307 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2)); 1308 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2)); 1309 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2)); 1310 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2)); 1311 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2)); 1312 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2)); 1313 } 1314 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1315 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1316 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1317 APFloat::cmpResult R = C1V.compare(C2V); 1318 switch (pred) { 1319 default: assert(0 && "Invalid FCmp Predicate"); return 0; 1320 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); 1321 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); 1322 case FCmpInst::FCMP_UNO: 1323 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered); 1324 case FCmpInst::FCMP_ORD: 1325 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered); 1326 case FCmpInst::FCMP_UEQ: 1327 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1328 R==APFloat::cmpEqual); 1329 case FCmpInst::FCMP_OEQ: 1330 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual); 1331 case FCmpInst::FCMP_UNE: 1332 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual); 1333 case FCmpInst::FCMP_ONE: 1334 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || 1335 R==APFloat::cmpGreaterThan); 1336 case FCmpInst::FCMP_ULT: 1337 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1338 R==APFloat::cmpLessThan); 1339 case FCmpInst::FCMP_OLT: 1340 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan); 1341 case FCmpInst::FCMP_UGT: 1342 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1343 R==APFloat::cmpGreaterThan); 1344 case FCmpInst::FCMP_OGT: 1345 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan); 1346 case FCmpInst::FCMP_ULE: 1347 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan); 1348 case FCmpInst::FCMP_OLE: 1349 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || 1350 R==APFloat::cmpEqual); 1351 case FCmpInst::FCMP_UGE: 1352 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan); 1353 case FCmpInst::FCMP_OGE: 1354 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan || 1355 R==APFloat::cmpEqual); 1356 } 1357 } else if (isa<VectorType>(C1->getType())) { 1358 SmallVector<Constant*, 16> C1Elts, C2Elts; 1359 C1->getVectorElements(C1Elts); 1360 C2->getVectorElements(C2Elts); 1361 1362 // If we can constant fold the comparison of each element, constant fold 1363 // the whole vector comparison. 1364 SmallVector<Constant*, 4> ResElts; 1365 const Type *InEltTy = C1Elts[0]->getType(); 1366 bool isFP = InEltTy->isFloatingPoint(); 1367 const Type *ResEltTy = InEltTy; 1368 if (isFP) 1369 ResEltTy = IntegerType::get(InEltTy->getPrimitiveSizeInBits()); 1370 1371 for (unsigned i = 0, e = C1Elts.size(); i != e; ++i) { 1372 // Compare the elements, producing an i1 result or constant expr. 1373 Constant *C; 1374 if (isFP) 1375 C = ConstantExpr::getFCmp(pred, C1Elts[i], C2Elts[i]); 1376 else 1377 C = ConstantExpr::getICmp(pred, C1Elts[i], C2Elts[i]); 1378 1379 // If it is a bool or undef result, convert to the dest type. 1380 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 1381 if (CI->isZero()) 1382 ResElts.push_back(Constant::getNullValue(ResEltTy)); 1383 else 1384 ResElts.push_back(Constant::getAllOnesValue(ResEltTy)); 1385 } else if (isa<UndefValue>(C)) { 1386 ResElts.push_back(UndefValue::get(ResEltTy)); 1387 } else { 1388 break; 1389 } 1390 } 1391 1392 if (ResElts.size() == C1Elts.size()) 1393 return ConstantVector::get(&ResElts[0], ResElts.size()); 1394 } 1395 1396 if (C1->getType()->isFloatingPoint()) { 1397 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1398 switch (evaluateFCmpRelation(C1, C2)) { 1399 default: assert(0 && "Unknown relation!"); 1400 case FCmpInst::FCMP_UNO: 1401 case FCmpInst::FCMP_ORD: 1402 case FCmpInst::FCMP_UEQ: 1403 case FCmpInst::FCMP_UNE: 1404 case FCmpInst::FCMP_ULT: 1405 case FCmpInst::FCMP_UGT: 1406 case FCmpInst::FCMP_ULE: 1407 case FCmpInst::FCMP_UGE: 1408 case FCmpInst::FCMP_TRUE: 1409 case FCmpInst::FCMP_FALSE: 1410 case FCmpInst::BAD_FCMP_PREDICATE: 1411 break; // Couldn't determine anything about these constants. 1412 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1413 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1414 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1415 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1416 break; 1417 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1418 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1419 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1420 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1421 break; 1422 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1423 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1424 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1425 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1426 break; 1427 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1428 // We can only partially decide this relation. 1429 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1430 Result = 0; 1431 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1432 Result = 1; 1433 break; 1434 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1435 // We can only partially decide this relation. 1436 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1437 Result = 0; 1438 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1439 Result = 1; 1440 break; 1441 case ICmpInst::ICMP_NE: // We know that C1 != C2 1442 // We can only partially decide this relation. 1443 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1444 Result = 0; 1445 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1446 Result = 1; 1447 break; 1448 } 1449 1450 // If we evaluated the result, return it now. 1451 if (Result != -1) { 1452 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) { 1453 if (Result == 0) 1454 return Constant::getNullValue(VectorType::getInteger(VT)); 1455 else 1456 return Constant::getAllOnesValue(VectorType::getInteger(VT)); 1457 } 1458 return ConstantInt::get(Type::Int1Ty, Result); 1459 } 1460 1461 } else { 1462 // Evaluate the relation between the two constants, per the predicate. 1463 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1464 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1465 default: assert(0 && "Unknown relational!"); 1466 case ICmpInst::BAD_ICMP_PREDICATE: 1467 break; // Couldn't determine anything about these constants. 1468 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1469 // If we know the constants are equal, we can decide the result of this 1470 // computation precisely. 1471 Result = (pred == ICmpInst::ICMP_EQ || 1472 pred == ICmpInst::ICMP_ULE || 1473 pred == ICmpInst::ICMP_SLE || 1474 pred == ICmpInst::ICMP_UGE || 1475 pred == ICmpInst::ICMP_SGE); 1476 break; 1477 case ICmpInst::ICMP_ULT: 1478 // If we know that C1 < C2, we can decide the result of this computation 1479 // precisely. 1480 Result = (pred == ICmpInst::ICMP_ULT || 1481 pred == ICmpInst::ICMP_NE || 1482 pred == ICmpInst::ICMP_ULE); 1483 break; 1484 case ICmpInst::ICMP_SLT: 1485 // If we know that C1 < C2, we can decide the result of this computation 1486 // precisely. 1487 Result = (pred == ICmpInst::ICMP_SLT || 1488 pred == ICmpInst::ICMP_NE || 1489 pred == ICmpInst::ICMP_SLE); 1490 break; 1491 case ICmpInst::ICMP_UGT: 1492 // If we know that C1 > C2, we can decide the result of this computation 1493 // precisely. 1494 Result = (pred == ICmpInst::ICMP_UGT || 1495 pred == ICmpInst::ICMP_NE || 1496 pred == ICmpInst::ICMP_UGE); 1497 break; 1498 case ICmpInst::ICMP_SGT: 1499 // If we know that C1 > C2, we can decide the result of this computation 1500 // precisely. 1501 Result = (pred == ICmpInst::ICMP_SGT || 1502 pred == ICmpInst::ICMP_NE || 1503 pred == ICmpInst::ICMP_SGE); 1504 break; 1505 case ICmpInst::ICMP_ULE: 1506 // If we know that C1 <= C2, we can only partially decide this relation. 1507 if (pred == ICmpInst::ICMP_UGT) Result = 0; 1508 if (pred == ICmpInst::ICMP_ULT) Result = 1; 1509 break; 1510 case ICmpInst::ICMP_SLE: 1511 // If we know that C1 <= C2, we can only partially decide this relation. 1512 if (pred == ICmpInst::ICMP_SGT) Result = 0; 1513 if (pred == ICmpInst::ICMP_SLT) Result = 1; 1514 break; 1515 1516 case ICmpInst::ICMP_UGE: 1517 // If we know that C1 >= C2, we can only partially decide this relation. 1518 if (pred == ICmpInst::ICMP_ULT) Result = 0; 1519 if (pred == ICmpInst::ICMP_UGT) Result = 1; 1520 break; 1521 case ICmpInst::ICMP_SGE: 1522 // If we know that C1 >= C2, we can only partially decide this relation. 1523 if (pred == ICmpInst::ICMP_SLT) Result = 0; 1524 if (pred == ICmpInst::ICMP_SGT) Result = 1; 1525 break; 1526 1527 case ICmpInst::ICMP_NE: 1528 // If we know that C1 != C2, we can only partially decide this relation. 1529 if (pred == ICmpInst::ICMP_EQ) Result = 0; 1530 if (pred == ICmpInst::ICMP_NE) Result = 1; 1531 break; 1532 } 1533 1534 // If we evaluated the result, return it now. 1535 if (Result != -1) { 1536 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) { 1537 if (Result == 0) 1538 return Constant::getNullValue(VT); 1539 else 1540 return Constant::getAllOnesValue(VT); 1541 } 1542 return ConstantInt::get(Type::Int1Ty, Result); 1543 } 1544 1545 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) { 1546 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1547 // other way if possible. 1548 switch (pred) { 1549 case ICmpInst::ICMP_EQ: 1550 case ICmpInst::ICMP_NE: 1551 // No change of predicate required. 1552 return ConstantFoldCompareInstruction(pred, C2, C1); 1553 1554 case ICmpInst::ICMP_ULT: 1555 case ICmpInst::ICMP_SLT: 1556 case ICmpInst::ICMP_UGT: 1557 case ICmpInst::ICMP_SGT: 1558 case ICmpInst::ICMP_ULE: 1559 case ICmpInst::ICMP_SLE: 1560 case ICmpInst::ICMP_UGE: 1561 case ICmpInst::ICMP_SGE: 1562 // Change the predicate as necessary to swap the operands. 1563 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1564 return ConstantFoldCompareInstruction(pred, C2, C1); 1565 1566 default: // These predicates cannot be flopped around. 1567 break; 1568 } 1569 } 1570 } 1571 return 0; 1572} 1573 1574Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 1575 Constant* const *Idxs, 1576 unsigned NumIdx) { 1577 if (NumIdx == 0 || 1578 (NumIdx == 1 && Idxs[0]->isNullValue())) 1579 return const_cast<Constant*>(C); 1580 1581 if (isa<UndefValue>(C)) { 1582 const PointerType *Ptr = cast<PointerType>(C->getType()); 1583 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 1584 (Value **)Idxs, 1585 (Value **)Idxs+NumIdx); 1586 assert(Ty != 0 && "Invalid indices for GEP!"); 1587 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 1588 } 1589 1590 Constant *Idx0 = Idxs[0]; 1591 if (C->isNullValue()) { 1592 bool isNull = true; 1593 for (unsigned i = 0, e = NumIdx; i != e; ++i) 1594 if (!Idxs[i]->isNullValue()) { 1595 isNull = false; 1596 break; 1597 } 1598 if (isNull) { 1599 const PointerType *Ptr = cast<PointerType>(C->getType()); 1600 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 1601 (Value**)Idxs, 1602 (Value**)Idxs+NumIdx); 1603 assert(Ty != 0 && "Invalid indices for GEP!"); 1604 return 1605 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace())); 1606 } 1607 } 1608 1609 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 1610 // Combine Indices - If the source pointer to this getelementptr instruction 1611 // is a getelementptr instruction, combine the indices of the two 1612 // getelementptr instructions into a single instruction. 1613 // 1614 if (CE->getOpcode() == Instruction::GetElementPtr) { 1615 const Type *LastTy = 0; 1616 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1617 I != E; ++I) 1618 LastTy = *I; 1619 1620 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 1621 SmallVector<Value*, 16> NewIndices; 1622 NewIndices.reserve(NumIdx + CE->getNumOperands()); 1623 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 1624 NewIndices.push_back(CE->getOperand(i)); 1625 1626 // Add the last index of the source with the first index of the new GEP. 1627 // Make sure to handle the case when they are actually different types. 1628 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 1629 // Otherwise it must be an array. 1630 if (!Idx0->isNullValue()) { 1631 const Type *IdxTy = Combined->getType(); 1632 if (IdxTy != Idx0->getType()) { 1633 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); 1634 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, 1635 Type::Int64Ty); 1636 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 1637 } else { 1638 Combined = 1639 ConstantExpr::get(Instruction::Add, Idx0, Combined); 1640 } 1641 } 1642 1643 NewIndices.push_back(Combined); 1644 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); 1645 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], 1646 NewIndices.size()); 1647 } 1648 } 1649 1650 // Implement folding of: 1651 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 1652 // long 0, long 0) 1653 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 1654 // 1655 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) { 1656 if (const PointerType *SPT = 1657 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 1658 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 1659 if (const ArrayType *CAT = 1660 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 1661 if (CAT->getElementType() == SAT->getElementType()) 1662 return ConstantExpr::getGetElementPtr( 1663 (Constant*)CE->getOperand(0), Idxs, NumIdx); 1664 } 1665 1666 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1) 1667 // Into: inttoptr (i64 0 to i8*) 1668 // This happens with pointers to member functions in C++. 1669 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 && 1670 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) && 1671 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) { 1672 Constant *Base = CE->getOperand(0); 1673 Constant *Offset = Idxs[0]; 1674 1675 // Convert the smaller integer to the larger type. 1676 if (Offset->getType()->getPrimitiveSizeInBits() < 1677 Base->getType()->getPrimitiveSizeInBits()) 1678 Offset = ConstantExpr::getSExt(Offset, Base->getType()); 1679 else if (Base->getType()->getPrimitiveSizeInBits() < 1680 Offset->getType()->getPrimitiveSizeInBits()) 1681 Base = ConstantExpr::getZExt(Base, Base->getType()); 1682 1683 Base = ConstantExpr::getAdd(Base, Offset); 1684 return ConstantExpr::getIntToPtr(Base, CE->getType()); 1685 } 1686 } 1687 return 0; 1688} 1689 1690