ConstantFold.cpp revision ed6af24e146a5d358115123f0d2be694c1fa3a84
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 SrcTy = NULL; 130 // First, check for null. Undef is already handled. 131 if (isa<ConstantAggregateZero>(V)) 132 return Constant::getNullValue(DestTy); 133 134 if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) 135 return BitCastConstantVector(CV, DestPTy); 136 } 137 138 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts 139 // This allows for other simplifications (although some of them 140 // can only be handled by Analysis/ConstantFolding.cpp). 141 if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) 142 return ConstantExpr::getBitCast(ConstantVector::get(&V, 1), DestPTy); 143 } 144 145 // Finally, implement bitcast folding now. The code below doesn't handle 146 // bitcast right. 147 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 148 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 149 150 // Handle integral constant input. 151 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 152 if (DestTy->isInteger()) 153 // Integral -> Integral. This is a no-op because the bit widths must 154 // be the same. Consequently, we just fold to V. 155 return V; 156 157 if (DestTy->isFloatingPoint()) { 158 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) && 159 "Unknown FP type!"); 160 return ConstantFP::get(APFloat(CI->getValue())); 161 } 162 // Otherwise, can't fold this (vector?) 163 return 0; 164 } 165 166 // Handle ConstantFP input. 167 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) { 168 // FP -> Integral. 169 if (DestTy == Type::Int32Ty) { 170 return ConstantInt::get(FP->getValueAPF().bitcastToAPInt()); 171 } else { 172 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!"); 173 return ConstantInt::get(FP->getValueAPF().bitcastToAPInt()); 174 } 175 } 176 return 0; 177} 178 179 180Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V, 181 const Type *DestTy) { 182 if (isa<UndefValue>(V)) { 183 // zext(undef) = 0, because the top bits will be zero. 184 // sext(undef) = 0, because the top bits will all be the same. 185 // [us]itofp(undef) = 0, because the result value is bounded. 186 if (opc == Instruction::ZExt || opc == Instruction::SExt || 187 opc == Instruction::UIToFP || opc == Instruction::SIToFP) 188 return Constant::getNullValue(DestTy); 189 return UndefValue::get(DestTy); 190 } 191 // No compile-time operations on this type yet. 192 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty) 193 return 0; 194 195 // If the cast operand is a constant expression, there's a few things we can 196 // do to try to simplify it. 197 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 198 if (CE->isCast()) { 199 // Try hard to fold cast of cast because they are often eliminable. 200 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 201 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 202 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 203 // If all of the indexes in the GEP are null values, there is no pointer 204 // adjustment going on. We might as well cast the source pointer. 205 bool isAllNull = true; 206 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 207 if (!CE->getOperand(i)->isNullValue()) { 208 isAllNull = false; 209 break; 210 } 211 if (isAllNull) 212 // This is casting one pointer type to another, always BitCast 213 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 214 } 215 } 216 217 // We actually have to do a cast now. Perform the cast according to the 218 // opcode specified. 219 switch (opc) { 220 case Instruction::FPTrunc: 221 case Instruction::FPExt: 222 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 223 bool ignored; 224 APFloat Val = FPC->getValueAPF(); 225 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle : 226 DestTy == Type::DoubleTy ? APFloat::IEEEdouble : 227 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended : 228 DestTy == Type::FP128Ty ? APFloat::IEEEquad : 229 APFloat::Bogus, 230 APFloat::rmNearestTiesToEven, &ignored); 231 return ConstantFP::get(Val); 232 } 233 return 0; // Can't fold. 234 case Instruction::FPToUI: 235 case Instruction::FPToSI: 236 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 237 const APFloat &V = FPC->getValueAPF(); 238 bool ignored; 239 uint64_t x[2]; 240 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 241 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 242 APFloat::rmTowardZero, &ignored); 243 APInt Val(DestBitWidth, 2, x); 244 return ConstantInt::get(Val); 245 } 246 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) { 247 std::vector<Constant*> res; 248 const VectorType *DestVecTy = cast<VectorType>(DestTy); 249 const Type *DstEltTy = DestVecTy->getElementType(); 250 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 251 res.push_back(ConstantExpr::getCast(opc, CV->getOperand(i), DstEltTy)); 252 return ConstantVector::get(DestVecTy, res); 253 } 254 return 0; // Can't fold. 255 case Instruction::IntToPtr: //always treated as unsigned 256 if (V->isNullValue()) // Is it an integral null value? 257 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 258 return 0; // Other pointer types cannot be casted 259 case Instruction::PtrToInt: // always treated as unsigned 260 if (V->isNullValue()) // is it a null pointer value? 261 return ConstantInt::get(DestTy, 0); 262 return 0; // Other pointer types cannot be casted 263 case Instruction::UIToFP: 264 case Instruction::SIToFP: 265 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 266 APInt api = CI->getValue(); 267 const uint64_t zero[] = {0, 0}; 268 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(), 269 2, zero)); 270 (void)apf.convertFromAPInt(api, 271 opc==Instruction::SIToFP, 272 APFloat::rmNearestTiesToEven); 273 return ConstantFP::get(apf); 274 } 275 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) { 276 std::vector<Constant*> res; 277 const VectorType *DestVecTy = cast<VectorType>(DestTy); 278 const Type *DstEltTy = DestVecTy->getElementType(); 279 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 280 res.push_back(ConstantExpr::getCast(opc, CV->getOperand(i), DstEltTy)); 281 return ConstantVector::get(DestVecTy, res); 282 } 283 return 0; 284 case Instruction::ZExt: 285 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 286 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 287 APInt Result(CI->getValue()); 288 Result.zext(BitWidth); 289 return ConstantInt::get(Result); 290 } 291 return 0; 292 case Instruction::SExt: 293 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 294 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 295 APInt Result(CI->getValue()); 296 Result.sext(BitWidth); 297 return ConstantInt::get(Result); 298 } 299 return 0; 300 case Instruction::Trunc: 301 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 302 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 303 APInt Result(CI->getValue()); 304 Result.trunc(BitWidth); 305 return ConstantInt::get(Result); 306 } 307 return 0; 308 case Instruction::BitCast: 309 return FoldBitCast(const_cast<Constant*>(V), DestTy); 310 default: 311 assert(!"Invalid CE CastInst opcode"); 312 break; 313 } 314 315 assert(0 && "Failed to cast constant expression"); 316 return 0; 317} 318 319Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, 320 const Constant *V1, 321 const Constant *V2) { 322 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) 323 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2); 324 325 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); 326 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); 327 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); 328 if (V1 == V2) return const_cast<Constant*>(V1); 329 return 0; 330} 331 332Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, 333 const Constant *Idx) { 334 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 335 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType()); 336 if (Val->isNullValue()) // ee(zero, x) -> zero 337 return Constant::getNullValue( 338 cast<VectorType>(Val->getType())->getElementType()); 339 340 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 341 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 342 return CVal->getOperand(CIdx->getZExtValue()); 343 } else if (isa<UndefValue>(Idx)) { 344 // ee({w,x,y,z}, undef) -> w (an arbitrary value). 345 return CVal->getOperand(0); 346 } 347 } 348 return 0; 349} 350 351Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, 352 const Constant *Elt, 353 const Constant *Idx) { 354 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 355 if (!CIdx) return 0; 356 APInt idxVal = CIdx->getValue(); 357 if (isa<UndefValue>(Val)) { 358 // Insertion of scalar constant into vector undef 359 // Optimize away insertion of undef 360 if (isa<UndefValue>(Elt)) 361 return const_cast<Constant*>(Val); 362 // Otherwise break the aggregate undef into multiple undefs and do 363 // the insertion 364 unsigned numOps = 365 cast<VectorType>(Val->getType())->getNumElements(); 366 std::vector<Constant*> Ops; 367 Ops.reserve(numOps); 368 for (unsigned i = 0; i < numOps; ++i) { 369 const Constant *Op = 370 (idxVal == i) ? Elt : UndefValue::get(Elt->getType()); 371 Ops.push_back(const_cast<Constant*>(Op)); 372 } 373 return ConstantVector::get(Ops); 374 } 375 if (isa<ConstantAggregateZero>(Val)) { 376 // Insertion of scalar constant into vector aggregate zero 377 // Optimize away insertion of zero 378 if (Elt->isNullValue()) 379 return const_cast<Constant*>(Val); 380 // Otherwise break the aggregate zero into multiple zeros and do 381 // the insertion 382 unsigned numOps = 383 cast<VectorType>(Val->getType())->getNumElements(); 384 std::vector<Constant*> Ops; 385 Ops.reserve(numOps); 386 for (unsigned i = 0; i < numOps; ++i) { 387 const Constant *Op = 388 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType()); 389 Ops.push_back(const_cast<Constant*>(Op)); 390 } 391 return ConstantVector::get(Ops); 392 } 393 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 394 // Insertion of scalar constant into vector constant 395 std::vector<Constant*> Ops; 396 Ops.reserve(CVal->getNumOperands()); 397 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { 398 const Constant *Op = 399 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i)); 400 Ops.push_back(const_cast<Constant*>(Op)); 401 } 402 return ConstantVector::get(Ops); 403 } 404 405 return 0; 406} 407 408/// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef 409/// return the specified element value. Otherwise return null. 410static Constant *GetVectorElement(const Constant *C, unsigned EltNo) { 411 if (const ConstantVector *CV = dyn_cast<ConstantVector>(C)) 412 return CV->getOperand(EltNo); 413 414 const Type *EltTy = cast<VectorType>(C->getType())->getElementType(); 415 if (isa<ConstantAggregateZero>(C)) 416 return Constant::getNullValue(EltTy); 417 if (isa<UndefValue>(C)) 418 return UndefValue::get(EltTy); 419 return 0; 420} 421 422Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, 423 const Constant *V2, 424 const Constant *Mask) { 425 // Undefined shuffle mask -> undefined value. 426 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType()); 427 428 unsigned MaskNumElts = cast<VectorType>(Mask->getType())->getNumElements(); 429 unsigned SrcNumElts = cast<VectorType>(V1->getType())->getNumElements(); 430 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType(); 431 432 // Loop over the shuffle mask, evaluating each element. 433 SmallVector<Constant*, 32> Result; 434 for (unsigned i = 0; i != MaskNumElts; ++i) { 435 Constant *InElt = GetVectorElement(Mask, i); 436 if (InElt == 0) return 0; 437 438 if (isa<UndefValue>(InElt)) 439 InElt = UndefValue::get(EltTy); 440 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) { 441 unsigned Elt = CI->getZExtValue(); 442 if (Elt >= SrcNumElts*2) 443 InElt = UndefValue::get(EltTy); 444 else if (Elt >= SrcNumElts) 445 InElt = GetVectorElement(V2, Elt - SrcNumElts); 446 else 447 InElt = GetVectorElement(V1, Elt); 448 if (InElt == 0) return 0; 449 } else { 450 // Unknown value. 451 return 0; 452 } 453 Result.push_back(InElt); 454 } 455 456 return ConstantVector::get(&Result[0], Result.size()); 457} 458 459Constant *llvm::ConstantFoldExtractValueInstruction(const Constant *Agg, 460 const unsigned *Idxs, 461 unsigned NumIdx) { 462 // Base case: no indices, so return the entire value. 463 if (NumIdx == 0) 464 return const_cast<Constant *>(Agg); 465 466 if (isa<UndefValue>(Agg)) // ev(undef, x) -> undef 467 return UndefValue::get(ExtractValueInst::getIndexedType(Agg->getType(), 468 Idxs, 469 Idxs + NumIdx)); 470 471 if (isa<ConstantAggregateZero>(Agg)) // ev(0, x) -> 0 472 return 473 Constant::getNullValue(ExtractValueInst::getIndexedType(Agg->getType(), 474 Idxs, 475 Idxs + NumIdx)); 476 477 // Otherwise recurse. 478 return ConstantFoldExtractValueInstruction(Agg->getOperand(*Idxs), 479 Idxs+1, NumIdx-1); 480} 481 482Constant *llvm::ConstantFoldInsertValueInstruction(const Constant *Agg, 483 const Constant *Val, 484 const unsigned *Idxs, 485 unsigned NumIdx) { 486 // Base case: no indices, so replace the entire value. 487 if (NumIdx == 0) 488 return const_cast<Constant *>(Val); 489 490 if (isa<UndefValue>(Agg)) { 491 // Insertion of constant into aggregate undef 492 // Optimize away insertion of undef 493 if (isa<UndefValue>(Val)) 494 return const_cast<Constant*>(Agg); 495 // Otherwise break the aggregate undef into multiple undefs and do 496 // the insertion 497 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 498 unsigned numOps; 499 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 500 numOps = AR->getNumElements(); 501 else 502 numOps = cast<StructType>(AggTy)->getNumElements(); 503 std::vector<Constant*> Ops(numOps); 504 for (unsigned i = 0; i < numOps; ++i) { 505 const Type *MemberTy = AggTy->getTypeAtIndex(i); 506 const Constant *Op = 507 (*Idxs == i) ? 508 ConstantFoldInsertValueInstruction(UndefValue::get(MemberTy), 509 Val, Idxs+1, NumIdx-1) : 510 UndefValue::get(MemberTy); 511 Ops[i] = const_cast<Constant*>(Op); 512 } 513 if (isa<StructType>(AggTy)) 514 return ConstantStruct::get(Ops); 515 else 516 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 517 } 518 if (isa<ConstantAggregateZero>(Agg)) { 519 // Insertion of constant into aggregate zero 520 // Optimize away insertion of zero 521 if (Val->isNullValue()) 522 return const_cast<Constant*>(Agg); 523 // Otherwise break the aggregate zero into multiple zeros and do 524 // the insertion 525 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 526 unsigned numOps; 527 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 528 numOps = AR->getNumElements(); 529 else 530 numOps = cast<StructType>(AggTy)->getNumElements(); 531 std::vector<Constant*> Ops(numOps); 532 for (unsigned i = 0; i < numOps; ++i) { 533 const Type *MemberTy = AggTy->getTypeAtIndex(i); 534 const Constant *Op = 535 (*Idxs == i) ? 536 ConstantFoldInsertValueInstruction(Constant::getNullValue(MemberTy), 537 Val, Idxs+1, NumIdx-1) : 538 Constant::getNullValue(MemberTy); 539 Ops[i] = const_cast<Constant*>(Op); 540 } 541 if (isa<StructType>(AggTy)) 542 return ConstantStruct::get(Ops); 543 else 544 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 545 } 546 if (isa<ConstantStruct>(Agg) || isa<ConstantArray>(Agg)) { 547 // Insertion of constant into aggregate constant 548 std::vector<Constant*> Ops(Agg->getNumOperands()); 549 for (unsigned i = 0; i < Agg->getNumOperands(); ++i) { 550 const Constant *Op = 551 (*Idxs == i) ? 552 ConstantFoldInsertValueInstruction(Agg->getOperand(i), 553 Val, Idxs+1, NumIdx-1) : 554 Agg->getOperand(i); 555 Ops[i] = const_cast<Constant*>(Op); 556 } 557 Constant *C; 558 if (isa<StructType>(Agg->getType())) 559 C = ConstantStruct::get(Ops); 560 else 561 C = ConstantArray::get(cast<ArrayType>(Agg->getType()), Ops); 562 return C; 563 } 564 565 return 0; 566} 567 568/// EvalVectorOp - Given two vector constants and a function pointer, apply the 569/// function pointer to each element pair, producing a new ConstantVector 570/// constant. Either or both of V1 and V2 may be NULL, meaning a 571/// ConstantAggregateZero operand. 572static Constant *EvalVectorOp(const ConstantVector *V1, 573 const ConstantVector *V2, 574 const VectorType *VTy, 575 Constant *(*FP)(Constant*, Constant*)) { 576 std::vector<Constant*> Res; 577 const Type *EltTy = VTy->getElementType(); 578 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 579 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy); 580 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy); 581 Res.push_back(FP(const_cast<Constant*>(C1), 582 const_cast<Constant*>(C2))); 583 } 584 return ConstantVector::get(Res); 585} 586 587Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 588 const Constant *C1, 589 const Constant *C2) { 590 // No compile-time operations on this type yet. 591 if (C1->getType() == Type::PPC_FP128Ty) 592 return 0; 593 594 // Handle UndefValue up front 595 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 596 switch (Opcode) { 597 case Instruction::Xor: 598 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 599 // Handle undef ^ undef -> 0 special case. This is a common 600 // idiom (misuse). 601 return Constant::getNullValue(C1->getType()); 602 // Fallthrough 603 case Instruction::Add: 604 case Instruction::Sub: 605 return UndefValue::get(C1->getType()); 606 case Instruction::Mul: 607 case Instruction::And: 608 return Constant::getNullValue(C1->getType()); 609 case Instruction::UDiv: 610 case Instruction::SDiv: 611 case Instruction::FDiv: 612 case Instruction::URem: 613 case Instruction::SRem: 614 case Instruction::FRem: 615 if (!isa<UndefValue>(C2)) // undef / X -> 0 616 return Constant::getNullValue(C1->getType()); 617 return const_cast<Constant*>(C2); // X / undef -> undef 618 case Instruction::Or: // X | undef -> -1 619 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType())) 620 return ConstantVector::getAllOnesValue(PTy); 621 return ConstantInt::getAllOnesValue(C1->getType()); 622 case Instruction::LShr: 623 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 624 return const_cast<Constant*>(C1); // undef lshr undef -> undef 625 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 626 // undef lshr X -> 0 627 case Instruction::AShr: 628 if (!isa<UndefValue>(C2)) 629 return const_cast<Constant*>(C1); // undef ashr X --> undef 630 else if (isa<UndefValue>(C1)) 631 return const_cast<Constant*>(C1); // undef ashr undef -> undef 632 else 633 return const_cast<Constant*>(C1); // X ashr undef --> X 634 case Instruction::Shl: 635 // undef << X -> 0 or X << undef -> 0 636 return Constant::getNullValue(C1->getType()); 637 } 638 } 639 640 // Handle simplifications of the RHS when a constant int. 641 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 642 switch (Opcode) { 643 case Instruction::Add: 644 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X + 0 == X 645 break; 646 case Instruction::Sub: 647 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X - 0 == X 648 break; 649 case Instruction::Mul: 650 if (CI2->equalsInt(0)) return const_cast<Constant*>(C2); // X * 0 == 0 651 if (CI2->equalsInt(1)) 652 return const_cast<Constant*>(C1); // X * 1 == X 653 break; 654 case Instruction::UDiv: 655 case Instruction::SDiv: 656 if (CI2->equalsInt(1)) 657 return const_cast<Constant*>(C1); // X / 1 == X 658 if (CI2->equalsInt(0)) 659 return UndefValue::get(CI2->getType()); // X / 0 == undef 660 break; 661 case Instruction::URem: 662 case Instruction::SRem: 663 if (CI2->equalsInt(1)) 664 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 665 if (CI2->equalsInt(0)) 666 return UndefValue::get(CI2->getType()); // X % 0 == undef 667 break; 668 case Instruction::And: 669 if (CI2->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0 670 if (CI2->isAllOnesValue()) 671 return const_cast<Constant*>(C1); // X & -1 == X 672 673 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 674 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 675 if (CE1->getOpcode() == Instruction::ZExt) { 676 unsigned DstWidth = CI2->getType()->getBitWidth(); 677 unsigned SrcWidth = 678 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 679 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 680 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 681 return const_cast<Constant*>(C1); 682 } 683 684 // If and'ing the address of a global with a constant, fold it. 685 if (CE1->getOpcode() == Instruction::PtrToInt && 686 isa<GlobalValue>(CE1->getOperand(0))) { 687 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 688 689 // Functions are at least 4-byte aligned. 690 unsigned GVAlign = GV->getAlignment(); 691 if (isa<Function>(GV)) 692 GVAlign = std::max(GVAlign, 4U); 693 694 if (GVAlign > 1) { 695 unsigned DstWidth = CI2->getType()->getBitWidth(); 696 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 697 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 698 699 // If checking bits we know are clear, return zero. 700 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 701 return Constant::getNullValue(CI2->getType()); 702 } 703 } 704 } 705 break; 706 case Instruction::Or: 707 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X | 0 == X 708 if (CI2->isAllOnesValue()) 709 return const_cast<Constant*>(C2); // X | -1 == -1 710 break; 711 case Instruction::Xor: 712 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X ^ 0 == X 713 break; 714 case Instruction::AShr: 715 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 716 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 717 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 718 return ConstantExpr::getLShr(const_cast<Constant*>(C1), 719 const_cast<Constant*>(C2)); 720 break; 721 } 722 } 723 724 // At this point we know neither constant is an UndefValue. 725 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 726 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 727 using namespace APIntOps; 728 const APInt &C1V = CI1->getValue(); 729 const APInt &C2V = CI2->getValue(); 730 switch (Opcode) { 731 default: 732 break; 733 case Instruction::Add: 734 return ConstantInt::get(C1V + C2V); 735 case Instruction::Sub: 736 return ConstantInt::get(C1V - C2V); 737 case Instruction::Mul: 738 return ConstantInt::get(C1V * C2V); 739 case Instruction::UDiv: 740 assert(!CI2->isNullValue() && "Div by zero handled above"); 741 return ConstantInt::get(C1V.udiv(C2V)); 742 case Instruction::SDiv: 743 assert(!CI2->isNullValue() && "Div by zero handled above"); 744 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 745 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef 746 return ConstantInt::get(C1V.sdiv(C2V)); 747 case Instruction::URem: 748 assert(!CI2->isNullValue() && "Div by zero handled above"); 749 return ConstantInt::get(C1V.urem(C2V)); 750 case Instruction::SRem: 751 assert(!CI2->isNullValue() && "Div by zero handled above"); 752 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 753 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef 754 return ConstantInt::get(C1V.srem(C2V)); 755 case Instruction::And: 756 return ConstantInt::get(C1V & C2V); 757 case Instruction::Or: 758 return ConstantInt::get(C1V | C2V); 759 case Instruction::Xor: 760 return ConstantInt::get(C1V ^ C2V); 761 case Instruction::Shl: { 762 uint32_t shiftAmt = C2V.getZExtValue(); 763 if (shiftAmt < C1V.getBitWidth()) 764 return ConstantInt::get(C1V.shl(shiftAmt)); 765 else 766 return UndefValue::get(C1->getType()); // too big shift is undef 767 } 768 case Instruction::LShr: { 769 uint32_t shiftAmt = C2V.getZExtValue(); 770 if (shiftAmt < C1V.getBitWidth()) 771 return ConstantInt::get(C1V.lshr(shiftAmt)); 772 else 773 return UndefValue::get(C1->getType()); // too big shift is undef 774 } 775 case Instruction::AShr: { 776 uint32_t shiftAmt = C2V.getZExtValue(); 777 if (shiftAmt < C1V.getBitWidth()) 778 return ConstantInt::get(C1V.ashr(shiftAmt)); 779 else 780 return UndefValue::get(C1->getType()); // too big shift is undef 781 } 782 } 783 } 784 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 785 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 786 APFloat C1V = CFP1->getValueAPF(); 787 APFloat C2V = CFP2->getValueAPF(); 788 APFloat C3V = C1V; // copy for modification 789 switch (Opcode) { 790 default: 791 break; 792 case Instruction::Add: 793 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 794 return ConstantFP::get(C3V); 795 case Instruction::Sub: 796 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 797 return ConstantFP::get(C3V); 798 case Instruction::Mul: 799 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 800 return ConstantFP::get(C3V); 801 case Instruction::FDiv: 802 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 803 return ConstantFP::get(C3V); 804 case Instruction::FRem: 805 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 806 return ConstantFP::get(C3V); 807 } 808 } 809 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 810 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1); 811 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2); 812 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) && 813 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) { 814 switch (Opcode) { 815 default: 816 break; 817 case Instruction::Add: 818 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd); 819 case Instruction::Sub: 820 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub); 821 case Instruction::Mul: 822 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul); 823 case Instruction::UDiv: 824 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv); 825 case Instruction::SDiv: 826 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv); 827 case Instruction::FDiv: 828 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv); 829 case Instruction::URem: 830 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem); 831 case Instruction::SRem: 832 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem); 833 case Instruction::FRem: 834 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem); 835 case Instruction::And: 836 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd); 837 case Instruction::Or: 838 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr); 839 case Instruction::Xor: 840 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor); 841 } 842 } 843 } 844 845 if (isa<ConstantExpr>(C1)) { 846 // There are many possible foldings we could do here. We should probably 847 // at least fold add of a pointer with an integer into the appropriate 848 // getelementptr. This will improve alias analysis a bit. 849 } else if (isa<ConstantExpr>(C2)) { 850 // If C2 is a constant expr and C1 isn't, flop them around and fold the 851 // other way if possible. 852 switch (Opcode) { 853 case Instruction::Add: 854 case Instruction::Mul: 855 case Instruction::And: 856 case Instruction::Or: 857 case Instruction::Xor: 858 // No change of opcode required. 859 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 860 861 case Instruction::Shl: 862 case Instruction::LShr: 863 case Instruction::AShr: 864 case Instruction::Sub: 865 case Instruction::SDiv: 866 case Instruction::UDiv: 867 case Instruction::FDiv: 868 case Instruction::URem: 869 case Instruction::SRem: 870 case Instruction::FRem: 871 default: // These instructions cannot be flopped around. 872 break; 873 } 874 } 875 876 // We don't know how to fold this. 877 return 0; 878} 879 880/// isZeroSizedType - This type is zero sized if its an array or structure of 881/// zero sized types. The only leaf zero sized type is an empty structure. 882static bool isMaybeZeroSizedType(const Type *Ty) { 883 if (isa<OpaqueType>(Ty)) return true; // Can't say. 884 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 885 886 // If all of elements have zero size, this does too. 887 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 888 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 889 return true; 890 891 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 892 return isMaybeZeroSizedType(ATy->getElementType()); 893 } 894 return false; 895} 896 897/// IdxCompare - Compare the two constants as though they were getelementptr 898/// indices. This allows coersion of the types to be the same thing. 899/// 900/// If the two constants are the "same" (after coersion), return 0. If the 901/// first is less than the second, return -1, if the second is less than the 902/// first, return 1. If the constants are not integral, return -2. 903/// 904static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 905 if (C1 == C2) return 0; 906 907 // Ok, we found a different index. If they are not ConstantInt, we can't do 908 // anything with them. 909 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 910 return -2; // don't know! 911 912 // Ok, we have two differing integer indices. Sign extend them to be the same 913 // type. Long is always big enough, so we use it. 914 if (C1->getType() != Type::Int64Ty) 915 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); 916 917 if (C2->getType() != Type::Int64Ty) 918 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); 919 920 if (C1 == C2) return 0; // They are equal 921 922 // If the type being indexed over is really just a zero sized type, there is 923 // no pointer difference being made here. 924 if (isMaybeZeroSizedType(ElTy)) 925 return -2; // dunno. 926 927 // If they are really different, now that they are the same type, then we 928 // found a difference! 929 if (cast<ConstantInt>(C1)->getSExtValue() < 930 cast<ConstantInt>(C2)->getSExtValue()) 931 return -1; 932 else 933 return 1; 934} 935 936/// evaluateFCmpRelation - This function determines if there is anything we can 937/// decide about the two constants provided. This doesn't need to handle simple 938/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 939/// If we can determine that the two constants have a particular relation to 940/// each other, we should return the corresponding FCmpInst predicate, 941/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 942/// ConstantFoldCompareInstruction. 943/// 944/// To simplify this code we canonicalize the relation so that the first 945/// operand is always the most "complex" of the two. We consider ConstantFP 946/// to be the simplest, and ConstantExprs to be the most complex. 947static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, 948 const Constant *V2) { 949 assert(V1->getType() == V2->getType() && 950 "Cannot compare values of different types!"); 951 952 // No compile-time operations on this type yet. 953 if (V1->getType() == Type::PPC_FP128Ty) 954 return FCmpInst::BAD_FCMP_PREDICATE; 955 956 // Handle degenerate case quickly 957 if (V1 == V2) return FCmpInst::FCMP_OEQ; 958 959 if (!isa<ConstantExpr>(V1)) { 960 if (!isa<ConstantExpr>(V2)) { 961 // We distilled thisUse the standard constant folder for a few cases 962 ConstantInt *R = 0; 963 Constant *C1 = const_cast<Constant*>(V1); 964 Constant *C2 = const_cast<Constant*>(V2); 965 R = dyn_cast<ConstantInt>( 966 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); 967 if (R && !R->isZero()) 968 return FCmpInst::FCMP_OEQ; 969 R = dyn_cast<ConstantInt>( 970 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); 971 if (R && !R->isZero()) 972 return FCmpInst::FCMP_OLT; 973 R = dyn_cast<ConstantInt>( 974 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); 975 if (R && !R->isZero()) 976 return FCmpInst::FCMP_OGT; 977 978 // Nothing more we can do 979 return FCmpInst::BAD_FCMP_PREDICATE; 980 } 981 982 // If the first operand is simple and second is ConstantExpr, swap operands. 983 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 984 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 985 return FCmpInst::getSwappedPredicate(SwappedRelation); 986 } else { 987 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 988 // constantexpr or a simple constant. 989 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 990 switch (CE1->getOpcode()) { 991 case Instruction::FPTrunc: 992 case Instruction::FPExt: 993 case Instruction::UIToFP: 994 case Instruction::SIToFP: 995 // We might be able to do something with these but we don't right now. 996 break; 997 default: 998 break; 999 } 1000 } 1001 // There are MANY other foldings that we could perform here. They will 1002 // probably be added on demand, as they seem needed. 1003 return FCmpInst::BAD_FCMP_PREDICATE; 1004} 1005 1006/// evaluateICmpRelation - This function determines if there is anything we can 1007/// decide about the two constants provided. This doesn't need to handle simple 1008/// things like integer comparisons, but should instead handle ConstantExprs 1009/// and GlobalValues. If we can determine that the two constants have a 1010/// particular relation to each other, we should return the corresponding ICmp 1011/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 1012/// 1013/// To simplify this code we canonicalize the relation so that the first 1014/// operand is always the most "complex" of the two. We consider simple 1015/// constants (like ConstantInt) to be the simplest, followed by 1016/// GlobalValues, followed by ConstantExpr's (the most complex). 1017/// 1018static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, 1019 const Constant *V2, 1020 bool isSigned) { 1021 assert(V1->getType() == V2->getType() && 1022 "Cannot compare different types of values!"); 1023 if (V1 == V2) return ICmpInst::ICMP_EQ; 1024 1025 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 1026 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { 1027 // We distilled this down to a simple case, use the standard constant 1028 // folder. 1029 ConstantInt *R = 0; 1030 Constant *C1 = const_cast<Constant*>(V1); 1031 Constant *C2 = const_cast<Constant*>(V2); 1032 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 1033 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1034 if (R && !R->isZero()) 1035 return pred; 1036 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1037 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1038 if (R && !R->isZero()) 1039 return pred; 1040 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1041 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1042 if (R && !R->isZero()) 1043 return pred; 1044 1045 // If we couldn't figure it out, bail. 1046 return ICmpInst::BAD_ICMP_PREDICATE; 1047 } 1048 1049 // If the first operand is simple, swap operands. 1050 ICmpInst::Predicate SwappedRelation = 1051 evaluateICmpRelation(V2, V1, isSigned); 1052 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1053 return ICmpInst::getSwappedPredicate(SwappedRelation); 1054 1055 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { 1056 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1057 ICmpInst::Predicate SwappedRelation = 1058 evaluateICmpRelation(V2, V1, isSigned); 1059 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1060 return ICmpInst::getSwappedPredicate(SwappedRelation); 1061 else 1062 return ICmpInst::BAD_ICMP_PREDICATE; 1063 } 1064 1065 // Now we know that the RHS is a GlobalValue or simple constant, 1066 // which (since the types must match) means that it's a ConstantPointerNull. 1067 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 1068 // Don't try to decide equality of aliases. 1069 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2)) 1070 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) 1071 return ICmpInst::ICMP_NE; 1072 } else { 1073 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 1074 // GlobalVals can never be null. Don't try to evaluate aliases. 1075 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1)) 1076 return ICmpInst::ICMP_NE; 1077 } 1078 } else { 1079 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1080 // constantexpr, a CPR, or a simple constant. 1081 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1082 const Constant *CE1Op0 = CE1->getOperand(0); 1083 1084 switch (CE1->getOpcode()) { 1085 case Instruction::Trunc: 1086 case Instruction::FPTrunc: 1087 case Instruction::FPExt: 1088 case Instruction::FPToUI: 1089 case Instruction::FPToSI: 1090 break; // We can't evaluate floating point casts or truncations. 1091 1092 case Instruction::UIToFP: 1093 case Instruction::SIToFP: 1094 case Instruction::BitCast: 1095 case Instruction::ZExt: 1096 case Instruction::SExt: 1097 // If the cast is not actually changing bits, and the second operand is a 1098 // null pointer, do the comparison with the pre-casted value. 1099 if (V2->isNullValue() && 1100 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) { 1101 bool sgnd = isSigned; 1102 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1103 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1104 return evaluateICmpRelation(CE1Op0, 1105 Constant::getNullValue(CE1Op0->getType()), 1106 sgnd); 1107 } 1108 1109 // If the dest type is a pointer type, and the RHS is a constantexpr cast 1110 // from the same type as the src of the LHS, evaluate the inputs. This is 1111 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", 1112 // which happens a lot in compilers with tagged integers. 1113 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) 1114 if (CE2->isCast() && isa<PointerType>(CE1->getType()) && 1115 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && 1116 CE1->getOperand(0)->getType()->isInteger()) { 1117 bool sgnd = isSigned; 1118 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1119 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1120 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), 1121 sgnd); 1122 } 1123 break; 1124 1125 case Instruction::GetElementPtr: 1126 // Ok, since this is a getelementptr, we know that the constant has a 1127 // pointer type. Check the various cases. 1128 if (isa<ConstantPointerNull>(V2)) { 1129 // If we are comparing a GEP to a null pointer, check to see if the base 1130 // of the GEP equals the null pointer. 1131 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1132 if (GV->hasExternalWeakLinkage()) 1133 // Weak linkage GVals could be zero or not. We're comparing that 1134 // to null pointer so its greater-or-equal 1135 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1136 else 1137 // If its not weak linkage, the GVal must have a non-zero address 1138 // so the result is greater-than 1139 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1140 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1141 // If we are indexing from a null pointer, check to see if we have any 1142 // non-zero indices. 1143 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1144 if (!CE1->getOperand(i)->isNullValue()) 1145 // Offsetting from null, must not be equal. 1146 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1147 // Only zero indexes from null, must still be zero. 1148 return ICmpInst::ICMP_EQ; 1149 } 1150 // Otherwise, we can't really say if the first operand is null or not. 1151 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 1152 if (isa<ConstantPointerNull>(CE1Op0)) { 1153 if (CPR2->hasExternalWeakLinkage()) 1154 // Weak linkage GVals could be zero or not. We're comparing it to 1155 // a null pointer, so its less-or-equal 1156 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1157 else 1158 // If its not weak linkage, the GVal must have a non-zero address 1159 // so the result is less-than 1160 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1161 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 1162 if (CPR1 == CPR2) { 1163 // If this is a getelementptr of the same global, then it must be 1164 // different. Because the types must match, the getelementptr could 1165 // only have at most one index, and because we fold getelementptr's 1166 // with a single zero index, it must be nonzero. 1167 assert(CE1->getNumOperands() == 2 && 1168 !CE1->getOperand(1)->isNullValue() && 1169 "Suprising getelementptr!"); 1170 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1171 } else { 1172 // If they are different globals, we don't know what the value is, 1173 // but they can't be equal. 1174 return ICmpInst::ICMP_NE; 1175 } 1176 } 1177 } else { 1178 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1179 const Constant *CE2Op0 = CE2->getOperand(0); 1180 1181 // There are MANY other foldings that we could perform here. They will 1182 // probably be added on demand, as they seem needed. 1183 switch (CE2->getOpcode()) { 1184 default: break; 1185 case Instruction::GetElementPtr: 1186 // By far the most common case to handle is when the base pointers are 1187 // obviously to the same or different globals. 1188 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1189 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 1190 return ICmpInst::ICMP_NE; 1191 // Ok, we know that both getelementptr instructions are based on the 1192 // same global. From this, we can precisely determine the relative 1193 // ordering of the resultant pointers. 1194 unsigned i = 1; 1195 1196 // Compare all of the operands the GEP's have in common. 1197 gep_type_iterator GTI = gep_type_begin(CE1); 1198 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1199 ++i, ++GTI) 1200 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), 1201 GTI.getIndexedType())) { 1202 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1203 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1204 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1205 } 1206 1207 // Ok, we ran out of things they have in common. If any leftovers 1208 // are non-zero then we have a difference, otherwise we are equal. 1209 for (; i < CE1->getNumOperands(); ++i) 1210 if (!CE1->getOperand(i)->isNullValue()) { 1211 if (isa<ConstantInt>(CE1->getOperand(i))) 1212 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1213 else 1214 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1215 } 1216 1217 for (; i < CE2->getNumOperands(); ++i) 1218 if (!CE2->getOperand(i)->isNullValue()) { 1219 if (isa<ConstantInt>(CE2->getOperand(i))) 1220 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1221 else 1222 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1223 } 1224 return ICmpInst::ICMP_EQ; 1225 } 1226 } 1227 } 1228 default: 1229 break; 1230 } 1231 } 1232 1233 return ICmpInst::BAD_ICMP_PREDICATE; 1234} 1235 1236Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1237 const Constant *C1, 1238 const Constant *C2) { 1239 // Fold FCMP_FALSE/FCMP_TRUE unconditionally. 1240 if (pred == FCmpInst::FCMP_FALSE) { 1241 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1242 return Constant::getNullValue(VectorType::getInteger(VT)); 1243 else 1244 return ConstantInt::getFalse(); 1245 } 1246 1247 if (pred == FCmpInst::FCMP_TRUE) { 1248 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1249 return Constant::getAllOnesValue(VectorType::getInteger(VT)); 1250 else 1251 return ConstantInt::getTrue(); 1252 } 1253 1254 // Handle some degenerate cases first 1255 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 1256 // vicmp/vfcmp -> [vector] undef 1257 if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) 1258 return UndefValue::get(VectorType::getInteger(VTy)); 1259 1260 // icmp/fcmp -> i1 undef 1261 return UndefValue::get(Type::Int1Ty); 1262 } 1263 1264 // No compile-time operations on this type yet. 1265 if (C1->getType() == Type::PPC_FP128Ty) 1266 return 0; 1267 1268 // icmp eq/ne(null,GV) -> false/true 1269 if (C1->isNullValue()) { 1270 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1271 // Don't try to evaluate aliases. External weak GV can be null. 1272 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1273 if (pred == ICmpInst::ICMP_EQ) 1274 return ConstantInt::getFalse(); 1275 else if (pred == ICmpInst::ICMP_NE) 1276 return ConstantInt::getTrue(); 1277 } 1278 // icmp eq/ne(GV,null) -> false/true 1279 } else if (C2->isNullValue()) { 1280 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1281 // Don't try to evaluate aliases. External weak GV can be null. 1282 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1283 if (pred == ICmpInst::ICMP_EQ) 1284 return ConstantInt::getFalse(); 1285 else if (pred == ICmpInst::ICMP_NE) 1286 return ConstantInt::getTrue(); 1287 } 1288 } 1289 1290 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1291 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1292 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1293 switch (pred) { 1294 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1295 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); 1296 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); 1297 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2)); 1298 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2)); 1299 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2)); 1300 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2)); 1301 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2)); 1302 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2)); 1303 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2)); 1304 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2)); 1305 } 1306 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1307 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1308 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1309 APFloat::cmpResult R = C1V.compare(C2V); 1310 switch (pred) { 1311 default: assert(0 && "Invalid FCmp Predicate"); return 0; 1312 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); 1313 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); 1314 case FCmpInst::FCMP_UNO: 1315 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered); 1316 case FCmpInst::FCMP_ORD: 1317 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered); 1318 case FCmpInst::FCMP_UEQ: 1319 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1320 R==APFloat::cmpEqual); 1321 case FCmpInst::FCMP_OEQ: 1322 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual); 1323 case FCmpInst::FCMP_UNE: 1324 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual); 1325 case FCmpInst::FCMP_ONE: 1326 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || 1327 R==APFloat::cmpGreaterThan); 1328 case FCmpInst::FCMP_ULT: 1329 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1330 R==APFloat::cmpLessThan); 1331 case FCmpInst::FCMP_OLT: 1332 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan); 1333 case FCmpInst::FCMP_UGT: 1334 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1335 R==APFloat::cmpGreaterThan); 1336 case FCmpInst::FCMP_OGT: 1337 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan); 1338 case FCmpInst::FCMP_ULE: 1339 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan); 1340 case FCmpInst::FCMP_OLE: 1341 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || 1342 R==APFloat::cmpEqual); 1343 case FCmpInst::FCMP_UGE: 1344 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan); 1345 case FCmpInst::FCMP_OGE: 1346 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan || 1347 R==APFloat::cmpEqual); 1348 } 1349 } else if (isa<VectorType>(C1->getType())) { 1350 SmallVector<Constant*, 16> C1Elts, C2Elts; 1351 C1->getVectorElements(C1Elts); 1352 C2->getVectorElements(C2Elts); 1353 1354 // If we can constant fold the comparison of each element, constant fold 1355 // the whole vector comparison. 1356 SmallVector<Constant*, 4> ResElts; 1357 const Type *InEltTy = C1Elts[0]->getType(); 1358 bool isFP = InEltTy->isFloatingPoint(); 1359 const Type *ResEltTy = InEltTy; 1360 if (isFP) 1361 ResEltTy = IntegerType::get(InEltTy->getPrimitiveSizeInBits()); 1362 1363 for (unsigned i = 0, e = C1Elts.size(); i != e; ++i) { 1364 // Compare the elements, producing an i1 result or constant expr. 1365 Constant *C; 1366 if (isFP) 1367 C = ConstantExpr::getFCmp(pred, C1Elts[i], C2Elts[i]); 1368 else 1369 C = ConstantExpr::getICmp(pred, C1Elts[i], C2Elts[i]); 1370 1371 // If it is a bool or undef result, convert to the dest type. 1372 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 1373 if (CI->isZero()) 1374 ResElts.push_back(Constant::getNullValue(ResEltTy)); 1375 else 1376 ResElts.push_back(Constant::getAllOnesValue(ResEltTy)); 1377 } else if (isa<UndefValue>(C)) { 1378 ResElts.push_back(UndefValue::get(ResEltTy)); 1379 } else { 1380 break; 1381 } 1382 } 1383 1384 if (ResElts.size() == C1Elts.size()) 1385 return ConstantVector::get(&ResElts[0], ResElts.size()); 1386 } 1387 1388 if (C1->getType()->isFloatingPoint()) { 1389 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1390 switch (evaluateFCmpRelation(C1, C2)) { 1391 default: assert(0 && "Unknown relation!"); 1392 case FCmpInst::FCMP_UNO: 1393 case FCmpInst::FCMP_ORD: 1394 case FCmpInst::FCMP_UEQ: 1395 case FCmpInst::FCMP_UNE: 1396 case FCmpInst::FCMP_ULT: 1397 case FCmpInst::FCMP_UGT: 1398 case FCmpInst::FCMP_ULE: 1399 case FCmpInst::FCMP_UGE: 1400 case FCmpInst::FCMP_TRUE: 1401 case FCmpInst::FCMP_FALSE: 1402 case FCmpInst::BAD_FCMP_PREDICATE: 1403 break; // Couldn't determine anything about these constants. 1404 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1405 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1406 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1407 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1408 break; 1409 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1410 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1411 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1412 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1413 break; 1414 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1415 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1416 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1417 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1418 break; 1419 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1420 // We can only partially decide this relation. 1421 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1422 Result = 0; 1423 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1424 Result = 1; 1425 break; 1426 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1427 // We can only partially decide this relation. 1428 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1429 Result = 0; 1430 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1431 Result = 1; 1432 break; 1433 case ICmpInst::ICMP_NE: // We know that C1 != C2 1434 // We can only partially decide this relation. 1435 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1436 Result = 0; 1437 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1438 Result = 1; 1439 break; 1440 } 1441 1442 // If we evaluated the result, return it now. 1443 if (Result != -1) { 1444 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) { 1445 if (Result == 0) 1446 return Constant::getNullValue(VectorType::getInteger(VT)); 1447 else 1448 return Constant::getAllOnesValue(VectorType::getInteger(VT)); 1449 } 1450 return ConstantInt::get(Type::Int1Ty, Result); 1451 } 1452 1453 } else { 1454 // Evaluate the relation between the two constants, per the predicate. 1455 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1456 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1457 default: assert(0 && "Unknown relational!"); 1458 case ICmpInst::BAD_ICMP_PREDICATE: 1459 break; // Couldn't determine anything about these constants. 1460 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1461 // If we know the constants are equal, we can decide the result of this 1462 // computation precisely. 1463 Result = (pred == ICmpInst::ICMP_EQ || 1464 pred == ICmpInst::ICMP_ULE || 1465 pred == ICmpInst::ICMP_SLE || 1466 pred == ICmpInst::ICMP_UGE || 1467 pred == ICmpInst::ICMP_SGE); 1468 break; 1469 case ICmpInst::ICMP_ULT: 1470 // If we know that C1 < C2, we can decide the result of this computation 1471 // precisely. 1472 Result = (pred == ICmpInst::ICMP_ULT || 1473 pred == ICmpInst::ICMP_NE || 1474 pred == ICmpInst::ICMP_ULE); 1475 break; 1476 case ICmpInst::ICMP_SLT: 1477 // If we know that C1 < C2, we can decide the result of this computation 1478 // precisely. 1479 Result = (pred == ICmpInst::ICMP_SLT || 1480 pred == ICmpInst::ICMP_NE || 1481 pred == ICmpInst::ICMP_SLE); 1482 break; 1483 case ICmpInst::ICMP_UGT: 1484 // If we know that C1 > C2, we can decide the result of this computation 1485 // precisely. 1486 Result = (pred == ICmpInst::ICMP_UGT || 1487 pred == ICmpInst::ICMP_NE || 1488 pred == ICmpInst::ICMP_UGE); 1489 break; 1490 case ICmpInst::ICMP_SGT: 1491 // If we know that C1 > C2, we can decide the result of this computation 1492 // precisely. 1493 Result = (pred == ICmpInst::ICMP_SGT || 1494 pred == ICmpInst::ICMP_NE || 1495 pred == ICmpInst::ICMP_SGE); 1496 break; 1497 case ICmpInst::ICMP_ULE: 1498 // If we know that C1 <= C2, we can only partially decide this relation. 1499 if (pred == ICmpInst::ICMP_UGT) Result = 0; 1500 if (pred == ICmpInst::ICMP_ULT) Result = 1; 1501 break; 1502 case ICmpInst::ICMP_SLE: 1503 // If we know that C1 <= C2, we can only partially decide this relation. 1504 if (pred == ICmpInst::ICMP_SGT) Result = 0; 1505 if (pred == ICmpInst::ICMP_SLT) Result = 1; 1506 break; 1507 1508 case ICmpInst::ICMP_UGE: 1509 // If we know that C1 >= C2, we can only partially decide this relation. 1510 if (pred == ICmpInst::ICMP_ULT) Result = 0; 1511 if (pred == ICmpInst::ICMP_UGT) Result = 1; 1512 break; 1513 case ICmpInst::ICMP_SGE: 1514 // If we know that C1 >= C2, we can only partially decide this relation. 1515 if (pred == ICmpInst::ICMP_SLT) Result = 0; 1516 if (pred == ICmpInst::ICMP_SGT) Result = 1; 1517 break; 1518 1519 case ICmpInst::ICMP_NE: 1520 // If we know that C1 != C2, we can only partially decide this relation. 1521 if (pred == ICmpInst::ICMP_EQ) Result = 0; 1522 if (pred == ICmpInst::ICMP_NE) Result = 1; 1523 break; 1524 } 1525 1526 // If we evaluated the result, return it now. 1527 if (Result != -1) { 1528 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) { 1529 if (Result == 0) 1530 return Constant::getNullValue(VT); 1531 else 1532 return Constant::getAllOnesValue(VT); 1533 } 1534 return ConstantInt::get(Type::Int1Ty, Result); 1535 } 1536 1537 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) { 1538 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1539 // other way if possible. 1540 switch (pred) { 1541 case ICmpInst::ICMP_EQ: 1542 case ICmpInst::ICMP_NE: 1543 // No change of predicate required. 1544 return ConstantFoldCompareInstruction(pred, C2, C1); 1545 1546 case ICmpInst::ICMP_ULT: 1547 case ICmpInst::ICMP_SLT: 1548 case ICmpInst::ICMP_UGT: 1549 case ICmpInst::ICMP_SGT: 1550 case ICmpInst::ICMP_ULE: 1551 case ICmpInst::ICMP_SLE: 1552 case ICmpInst::ICMP_UGE: 1553 case ICmpInst::ICMP_SGE: 1554 // Change the predicate as necessary to swap the operands. 1555 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1556 return ConstantFoldCompareInstruction(pred, C2, C1); 1557 1558 default: // These predicates cannot be flopped around. 1559 break; 1560 } 1561 } 1562 } 1563 return 0; 1564} 1565 1566Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 1567 Constant* const *Idxs, 1568 unsigned NumIdx) { 1569 if (NumIdx == 0 || 1570 (NumIdx == 1 && Idxs[0]->isNullValue())) 1571 return const_cast<Constant*>(C); 1572 1573 if (isa<UndefValue>(C)) { 1574 const PointerType *Ptr = cast<PointerType>(C->getType()); 1575 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 1576 (Value **)Idxs, 1577 (Value **)Idxs+NumIdx); 1578 assert(Ty != 0 && "Invalid indices for GEP!"); 1579 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 1580 } 1581 1582 Constant *Idx0 = Idxs[0]; 1583 if (C->isNullValue()) { 1584 bool isNull = true; 1585 for (unsigned i = 0, e = NumIdx; i != e; ++i) 1586 if (!Idxs[i]->isNullValue()) { 1587 isNull = false; 1588 break; 1589 } 1590 if (isNull) { 1591 const PointerType *Ptr = cast<PointerType>(C->getType()); 1592 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 1593 (Value**)Idxs, 1594 (Value**)Idxs+NumIdx); 1595 assert(Ty != 0 && "Invalid indices for GEP!"); 1596 return 1597 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace())); 1598 } 1599 } 1600 1601 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 1602 // Combine Indices - If the source pointer to this getelementptr instruction 1603 // is a getelementptr instruction, combine the indices of the two 1604 // getelementptr instructions into a single instruction. 1605 // 1606 if (CE->getOpcode() == Instruction::GetElementPtr) { 1607 const Type *LastTy = 0; 1608 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1609 I != E; ++I) 1610 LastTy = *I; 1611 1612 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 1613 SmallVector<Value*, 16> NewIndices; 1614 NewIndices.reserve(NumIdx + CE->getNumOperands()); 1615 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 1616 NewIndices.push_back(CE->getOperand(i)); 1617 1618 // Add the last index of the source with the first index of the new GEP. 1619 // Make sure to handle the case when they are actually different types. 1620 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 1621 // Otherwise it must be an array. 1622 if (!Idx0->isNullValue()) { 1623 const Type *IdxTy = Combined->getType(); 1624 if (IdxTy != Idx0->getType()) { 1625 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); 1626 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, 1627 Type::Int64Ty); 1628 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 1629 } else { 1630 Combined = 1631 ConstantExpr::get(Instruction::Add, Idx0, Combined); 1632 } 1633 } 1634 1635 NewIndices.push_back(Combined); 1636 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); 1637 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], 1638 NewIndices.size()); 1639 } 1640 } 1641 1642 // Implement folding of: 1643 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 1644 // long 0, long 0) 1645 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 1646 // 1647 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) { 1648 if (const PointerType *SPT = 1649 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 1650 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 1651 if (const ArrayType *CAT = 1652 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 1653 if (CAT->getElementType() == SAT->getElementType()) 1654 return ConstantExpr::getGetElementPtr( 1655 (Constant*)CE->getOperand(0), Idxs, NumIdx); 1656 } 1657 1658 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1) 1659 // Into: inttoptr (i64 0 to i8*) 1660 // This happens with pointers to member functions in C++. 1661 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 && 1662 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) && 1663 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) { 1664 Constant *Base = CE->getOperand(0); 1665 Constant *Offset = Idxs[0]; 1666 1667 // Convert the smaller integer to the larger type. 1668 if (Offset->getType()->getPrimitiveSizeInBits() < 1669 Base->getType()->getPrimitiveSizeInBits()) 1670 Offset = ConstantExpr::getSExt(Offset, Base->getType()); 1671 else if (Base->getType()->getPrimitiveSizeInBits() < 1672 Offset->getType()->getPrimitiveSizeInBits()) 1673 Base = ConstantExpr::getZExt(Base, Base->getType()); 1674 1675 Base = ConstantExpr::getAdd(Base, Offset); 1676 return ConstantExpr::getIntToPtr(Base, CE->getType()); 1677 } 1678 } 1679 return 0; 1680} 1681 1682