ConstantFold.cpp revision 7f6aa2b162e5daaf7b9ccf05d749597d3d7cf460
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 return ConstantFP::get(APFloat(CI->getValue(), 159 DestTy != Type::PPC_FP128Ty)); 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 return ConstantInt::get(FP->getValueAPF().bitcastToAPInt()); 169 170 return 0; 171} 172 173 174Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V, 175 const Type *DestTy) { 176 if (isa<UndefValue>(V)) { 177 // zext(undef) = 0, because the top bits will be zero. 178 // sext(undef) = 0, because the top bits will all be the same. 179 // [us]itofp(undef) = 0, because the result value is bounded. 180 if (opc == Instruction::ZExt || opc == Instruction::SExt || 181 opc == Instruction::UIToFP || opc == Instruction::SIToFP) 182 return Constant::getNullValue(DestTy); 183 return UndefValue::get(DestTy); 184 } 185 // No compile-time operations on this type yet. 186 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty) 187 return 0; 188 189 // If the cast operand is a constant expression, there's a few things we can 190 // do to try to simplify it. 191 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 192 if (CE->isCast()) { 193 // Try hard to fold cast of cast because they are often eliminable. 194 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 195 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 196 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 197 // If all of the indexes in the GEP are null values, there is no pointer 198 // adjustment going on. We might as well cast the source pointer. 199 bool isAllNull = true; 200 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 201 if (!CE->getOperand(i)->isNullValue()) { 202 isAllNull = false; 203 break; 204 } 205 if (isAllNull) 206 // This is casting one pointer type to another, always BitCast 207 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 208 } 209 } 210 211 // If the cast operand is a constant vector, perform the cast by 212 // operating on each element. In the cast of bitcasts, the element 213 // count may be mismatched; don't attempt to handle that here. 214 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) 215 if (isa<VectorType>(DestTy) && 216 cast<VectorType>(DestTy)->getNumElements() == 217 CV->getType()->getNumElements()) { 218 std::vector<Constant*> res; 219 const VectorType *DestVecTy = cast<VectorType>(DestTy); 220 const Type *DstEltTy = DestVecTy->getElementType(); 221 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 222 res.push_back(ConstantExpr::getCast(opc, 223 CV->getOperand(i), DstEltTy)); 224 return ConstantVector::get(DestVecTy, res); 225 } 226 227 // We actually have to do a cast now. Perform the cast according to the 228 // opcode specified. 229 switch (opc) { 230 case Instruction::FPTrunc: 231 case Instruction::FPExt: 232 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 233 bool ignored; 234 APFloat Val = FPC->getValueAPF(); 235 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle : 236 DestTy == Type::DoubleTy ? APFloat::IEEEdouble : 237 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended : 238 DestTy == Type::FP128Ty ? APFloat::IEEEquad : 239 APFloat::Bogus, 240 APFloat::rmNearestTiesToEven, &ignored); 241 return ConstantFP::get(Val); 242 } 243 return 0; // Can't fold. 244 case Instruction::FPToUI: 245 case Instruction::FPToSI: 246 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 247 const APFloat &V = FPC->getValueAPF(); 248 bool ignored; 249 uint64_t x[2]; 250 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 251 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 252 APFloat::rmTowardZero, &ignored); 253 APInt Val(DestBitWidth, 2, x); 254 return ConstantInt::get(Val); 255 } 256 return 0; // Can't fold. 257 case Instruction::IntToPtr: //always treated as unsigned 258 if (V->isNullValue()) // Is it an integral null value? 259 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 260 return 0; // Other pointer types cannot be casted 261 case Instruction::PtrToInt: // always treated as unsigned 262 if (V->isNullValue()) // is it a null pointer value? 263 return ConstantInt::get(DestTy, 0); 264 return 0; // Other pointer types cannot be casted 265 case Instruction::UIToFP: 266 case Instruction::SIToFP: 267 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 268 APInt api = CI->getValue(); 269 const uint64_t zero[] = {0, 0}; 270 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(), 271 2, zero)); 272 (void)apf.convertFromAPInt(api, 273 opc==Instruction::SIToFP, 274 APFloat::rmNearestTiesToEven); 275 return ConstantFP::get(apf); 276 } 277 return 0; 278 case Instruction::ZExt: 279 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 280 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 281 APInt Result(CI->getValue()); 282 Result.zext(BitWidth); 283 return ConstantInt::get(Result); 284 } 285 return 0; 286 case Instruction::SExt: 287 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 288 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 289 APInt Result(CI->getValue()); 290 Result.sext(BitWidth); 291 return ConstantInt::get(Result); 292 } 293 return 0; 294 case Instruction::Trunc: 295 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 296 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 297 APInt Result(CI->getValue()); 298 Result.trunc(BitWidth); 299 return ConstantInt::get(Result); 300 } 301 return 0; 302 case Instruction::BitCast: 303 return FoldBitCast(const_cast<Constant*>(V), DestTy); 304 default: 305 assert(!"Invalid CE CastInst opcode"); 306 break; 307 } 308 309 assert(0 && "Failed to cast constant expression"); 310 return 0; 311} 312 313Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, 314 const Constant *V1, 315 const Constant *V2) { 316 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) 317 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2); 318 319 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); 320 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); 321 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); 322 if (V1 == V2) return const_cast<Constant*>(V1); 323 return 0; 324} 325 326Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, 327 const Constant *Idx) { 328 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 329 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType()); 330 if (Val->isNullValue()) // ee(zero, x) -> zero 331 return Constant::getNullValue( 332 cast<VectorType>(Val->getType())->getElementType()); 333 334 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 335 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 336 return CVal->getOperand(CIdx->getZExtValue()); 337 } else if (isa<UndefValue>(Idx)) { 338 // ee({w,x,y,z}, undef) -> w (an arbitrary value). 339 return CVal->getOperand(0); 340 } 341 } 342 return 0; 343} 344 345Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, 346 const Constant *Elt, 347 const Constant *Idx) { 348 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 349 if (!CIdx) return 0; 350 APInt idxVal = CIdx->getValue(); 351 if (isa<UndefValue>(Val)) { 352 // Insertion of scalar constant into vector undef 353 // Optimize away insertion of undef 354 if (isa<UndefValue>(Elt)) 355 return const_cast<Constant*>(Val); 356 // Otherwise break the aggregate undef into multiple undefs and do 357 // the insertion 358 unsigned numOps = 359 cast<VectorType>(Val->getType())->getNumElements(); 360 std::vector<Constant*> Ops; 361 Ops.reserve(numOps); 362 for (unsigned i = 0; i < numOps; ++i) { 363 const Constant *Op = 364 (idxVal == i) ? Elt : UndefValue::get(Elt->getType()); 365 Ops.push_back(const_cast<Constant*>(Op)); 366 } 367 return ConstantVector::get(Ops); 368 } 369 if (isa<ConstantAggregateZero>(Val)) { 370 // Insertion of scalar constant into vector aggregate zero 371 // Optimize away insertion of zero 372 if (Elt->isNullValue()) 373 return const_cast<Constant*>(Val); 374 // Otherwise break the aggregate zero into multiple zeros and do 375 // the insertion 376 unsigned numOps = 377 cast<VectorType>(Val->getType())->getNumElements(); 378 std::vector<Constant*> Ops; 379 Ops.reserve(numOps); 380 for (unsigned i = 0; i < numOps; ++i) { 381 const Constant *Op = 382 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType()); 383 Ops.push_back(const_cast<Constant*>(Op)); 384 } 385 return ConstantVector::get(Ops); 386 } 387 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 388 // Insertion of scalar constant into vector constant 389 std::vector<Constant*> Ops; 390 Ops.reserve(CVal->getNumOperands()); 391 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { 392 const Constant *Op = 393 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i)); 394 Ops.push_back(const_cast<Constant*>(Op)); 395 } 396 return ConstantVector::get(Ops); 397 } 398 399 return 0; 400} 401 402/// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef 403/// return the specified element value. Otherwise return null. 404static Constant *GetVectorElement(const Constant *C, unsigned EltNo) { 405 if (const ConstantVector *CV = dyn_cast<ConstantVector>(C)) 406 return CV->getOperand(EltNo); 407 408 const Type *EltTy = cast<VectorType>(C->getType())->getElementType(); 409 if (isa<ConstantAggregateZero>(C)) 410 return Constant::getNullValue(EltTy); 411 if (isa<UndefValue>(C)) 412 return UndefValue::get(EltTy); 413 return 0; 414} 415 416Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, 417 const Constant *V2, 418 const Constant *Mask) { 419 // Undefined shuffle mask -> undefined value. 420 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType()); 421 422 unsigned MaskNumElts = cast<VectorType>(Mask->getType())->getNumElements(); 423 unsigned SrcNumElts = cast<VectorType>(V1->getType())->getNumElements(); 424 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType(); 425 426 // Loop over the shuffle mask, evaluating each element. 427 SmallVector<Constant*, 32> Result; 428 for (unsigned i = 0; i != MaskNumElts; ++i) { 429 Constant *InElt = GetVectorElement(Mask, i); 430 if (InElt == 0) return 0; 431 432 if (isa<UndefValue>(InElt)) 433 InElt = UndefValue::get(EltTy); 434 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) { 435 unsigned Elt = CI->getZExtValue(); 436 if (Elt >= SrcNumElts*2) 437 InElt = UndefValue::get(EltTy); 438 else if (Elt >= SrcNumElts) 439 InElt = GetVectorElement(V2, Elt - SrcNumElts); 440 else 441 InElt = GetVectorElement(V1, Elt); 442 if (InElt == 0) return 0; 443 } else { 444 // Unknown value. 445 return 0; 446 } 447 Result.push_back(InElt); 448 } 449 450 return ConstantVector::get(&Result[0], Result.size()); 451} 452 453Constant *llvm::ConstantFoldExtractValueInstruction(const Constant *Agg, 454 const unsigned *Idxs, 455 unsigned NumIdx) { 456 // Base case: no indices, so return the entire value. 457 if (NumIdx == 0) 458 return const_cast<Constant *>(Agg); 459 460 if (isa<UndefValue>(Agg)) // ev(undef, x) -> undef 461 return UndefValue::get(ExtractValueInst::getIndexedType(Agg->getType(), 462 Idxs, 463 Idxs + NumIdx)); 464 465 if (isa<ConstantAggregateZero>(Agg)) // ev(0, x) -> 0 466 return 467 Constant::getNullValue(ExtractValueInst::getIndexedType(Agg->getType(), 468 Idxs, 469 Idxs + NumIdx)); 470 471 // Otherwise recurse. 472 return ConstantFoldExtractValueInstruction(Agg->getOperand(*Idxs), 473 Idxs+1, NumIdx-1); 474} 475 476Constant *llvm::ConstantFoldInsertValueInstruction(const Constant *Agg, 477 const Constant *Val, 478 const unsigned *Idxs, 479 unsigned NumIdx) { 480 // Base case: no indices, so replace the entire value. 481 if (NumIdx == 0) 482 return const_cast<Constant *>(Val); 483 484 if (isa<UndefValue>(Agg)) { 485 // Insertion of constant into aggregate undef 486 // Optimize away insertion of undef 487 if (isa<UndefValue>(Val)) 488 return const_cast<Constant*>(Agg); 489 // Otherwise break the aggregate undef into multiple undefs and do 490 // the insertion 491 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 492 unsigned numOps; 493 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 494 numOps = AR->getNumElements(); 495 else 496 numOps = cast<StructType>(AggTy)->getNumElements(); 497 std::vector<Constant*> Ops(numOps); 498 for (unsigned i = 0; i < numOps; ++i) { 499 const Type *MemberTy = AggTy->getTypeAtIndex(i); 500 const Constant *Op = 501 (*Idxs == i) ? 502 ConstantFoldInsertValueInstruction(UndefValue::get(MemberTy), 503 Val, Idxs+1, NumIdx-1) : 504 UndefValue::get(MemberTy); 505 Ops[i] = const_cast<Constant*>(Op); 506 } 507 if (isa<StructType>(AggTy)) 508 return ConstantStruct::get(Ops); 509 else 510 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 511 } 512 if (isa<ConstantAggregateZero>(Agg)) { 513 // Insertion of constant into aggregate zero 514 // Optimize away insertion of zero 515 if (Val->isNullValue()) 516 return const_cast<Constant*>(Agg); 517 // Otherwise break the aggregate zero into multiple zeros and do 518 // the insertion 519 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 520 unsigned numOps; 521 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 522 numOps = AR->getNumElements(); 523 else 524 numOps = cast<StructType>(AggTy)->getNumElements(); 525 std::vector<Constant*> Ops(numOps); 526 for (unsigned i = 0; i < numOps; ++i) { 527 const Type *MemberTy = AggTy->getTypeAtIndex(i); 528 const Constant *Op = 529 (*Idxs == i) ? 530 ConstantFoldInsertValueInstruction(Constant::getNullValue(MemberTy), 531 Val, Idxs+1, NumIdx-1) : 532 Constant::getNullValue(MemberTy); 533 Ops[i] = const_cast<Constant*>(Op); 534 } 535 if (isa<StructType>(AggTy)) 536 return ConstantStruct::get(Ops); 537 else 538 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 539 } 540 if (isa<ConstantStruct>(Agg) || isa<ConstantArray>(Agg)) { 541 // Insertion of constant into aggregate constant 542 std::vector<Constant*> Ops(Agg->getNumOperands()); 543 for (unsigned i = 0; i < Agg->getNumOperands(); ++i) { 544 const Constant *Op = 545 (*Idxs == i) ? 546 ConstantFoldInsertValueInstruction(Agg->getOperand(i), 547 Val, Idxs+1, NumIdx-1) : 548 Agg->getOperand(i); 549 Ops[i] = const_cast<Constant*>(Op); 550 } 551 Constant *C; 552 if (isa<StructType>(Agg->getType())) 553 C = ConstantStruct::get(Ops); 554 else 555 C = ConstantArray::get(cast<ArrayType>(Agg->getType()), Ops); 556 return C; 557 } 558 559 return 0; 560} 561 562/// EvalVectorOp - Given two vector constants and a function pointer, apply the 563/// function pointer to each element pair, producing a new ConstantVector 564/// constant. Either or both of V1 and V2 may be NULL, meaning a 565/// ConstantAggregateZero operand. 566static Constant *EvalVectorOp(const ConstantVector *V1, 567 const ConstantVector *V2, 568 const VectorType *VTy, 569 Constant *(*FP)(Constant*, Constant*)) { 570 std::vector<Constant*> Res; 571 const Type *EltTy = VTy->getElementType(); 572 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 573 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy); 574 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy); 575 Res.push_back(FP(const_cast<Constant*>(C1), 576 const_cast<Constant*>(C2))); 577 } 578 return ConstantVector::get(Res); 579} 580 581Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 582 const Constant *C1, 583 const Constant *C2) { 584 // No compile-time operations on this type yet. 585 if (C1->getType() == Type::PPC_FP128Ty) 586 return 0; 587 588 // Handle UndefValue up front 589 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 590 switch (Opcode) { 591 case Instruction::Xor: 592 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 593 // Handle undef ^ undef -> 0 special case. This is a common 594 // idiom (misuse). 595 return Constant::getNullValue(C1->getType()); 596 // Fallthrough 597 case Instruction::Add: 598 case Instruction::Sub: 599 return UndefValue::get(C1->getType()); 600 case Instruction::Mul: 601 case Instruction::And: 602 return Constant::getNullValue(C1->getType()); 603 case Instruction::UDiv: 604 case Instruction::SDiv: 605 case Instruction::URem: 606 case Instruction::SRem: 607 if (!isa<UndefValue>(C2)) // undef / X -> 0 608 return Constant::getNullValue(C1->getType()); 609 return const_cast<Constant*>(C2); // X / undef -> undef 610 case Instruction::Or: // X | undef -> -1 611 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType())) 612 return ConstantVector::getAllOnesValue(PTy); 613 return ConstantInt::getAllOnesValue(C1->getType()); 614 case Instruction::LShr: 615 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 616 return const_cast<Constant*>(C1); // undef lshr undef -> undef 617 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 618 // undef lshr X -> 0 619 case Instruction::AShr: 620 if (!isa<UndefValue>(C2)) 621 return const_cast<Constant*>(C1); // undef ashr X --> undef 622 else if (isa<UndefValue>(C1)) 623 return const_cast<Constant*>(C1); // undef ashr undef -> undef 624 else 625 return const_cast<Constant*>(C1); // X ashr undef --> X 626 case Instruction::Shl: 627 // undef << X -> 0 or X << undef -> 0 628 return Constant::getNullValue(C1->getType()); 629 } 630 } 631 632 // Handle simplifications when the RHS is a constant int. 633 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 634 switch (Opcode) { 635 case Instruction::Add: 636 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X + 0 == X 637 break; 638 case Instruction::Sub: 639 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X - 0 == X 640 break; 641 case Instruction::Mul: 642 if (CI2->equalsInt(0)) return const_cast<Constant*>(C2); // X * 0 == 0 643 if (CI2->equalsInt(1)) 644 return const_cast<Constant*>(C1); // X * 1 == X 645 break; 646 case Instruction::UDiv: 647 case Instruction::SDiv: 648 if (CI2->equalsInt(1)) 649 return const_cast<Constant*>(C1); // X / 1 == X 650 if (CI2->equalsInt(0)) 651 return UndefValue::get(CI2->getType()); // X / 0 == undef 652 break; 653 case Instruction::URem: 654 case Instruction::SRem: 655 if (CI2->equalsInt(1)) 656 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 657 if (CI2->equalsInt(0)) 658 return UndefValue::get(CI2->getType()); // X % 0 == undef 659 break; 660 case Instruction::And: 661 if (CI2->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0 662 if (CI2->isAllOnesValue()) 663 return const_cast<Constant*>(C1); // X & -1 == X 664 665 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 666 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 667 if (CE1->getOpcode() == Instruction::ZExt) { 668 unsigned DstWidth = CI2->getType()->getBitWidth(); 669 unsigned SrcWidth = 670 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 671 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 672 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 673 return const_cast<Constant*>(C1); 674 } 675 676 // If and'ing the address of a global with a constant, fold it. 677 if (CE1->getOpcode() == Instruction::PtrToInt && 678 isa<GlobalValue>(CE1->getOperand(0))) { 679 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 680 681 // Functions are at least 4-byte aligned. 682 unsigned GVAlign = GV->getAlignment(); 683 if (isa<Function>(GV)) 684 GVAlign = std::max(GVAlign, 4U); 685 686 if (GVAlign > 1) { 687 unsigned DstWidth = CI2->getType()->getBitWidth(); 688 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 689 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 690 691 // If checking bits we know are clear, return zero. 692 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 693 return Constant::getNullValue(CI2->getType()); 694 } 695 } 696 } 697 break; 698 case Instruction::Or: 699 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X | 0 == X 700 if (CI2->isAllOnesValue()) 701 return const_cast<Constant*>(C2); // X | -1 == -1 702 break; 703 case Instruction::Xor: 704 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X ^ 0 == X 705 break; 706 case Instruction::AShr: 707 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 708 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 709 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 710 return ConstantExpr::getLShr(const_cast<Constant*>(C1), 711 const_cast<Constant*>(C2)); 712 break; 713 } 714 } 715 716 // At this point we know neither constant is an UndefValue. 717 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 718 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 719 using namespace APIntOps; 720 const APInt &C1V = CI1->getValue(); 721 const APInt &C2V = CI2->getValue(); 722 switch (Opcode) { 723 default: 724 break; 725 case Instruction::Add: 726 return ConstantInt::get(C1V + C2V); 727 case Instruction::Sub: 728 return ConstantInt::get(C1V - C2V); 729 case Instruction::Mul: 730 return ConstantInt::get(C1V * C2V); 731 case Instruction::UDiv: 732 assert(!CI2->isNullValue() && "Div by zero handled above"); 733 return ConstantInt::get(C1V.udiv(C2V)); 734 case Instruction::SDiv: 735 assert(!CI2->isNullValue() && "Div by zero handled above"); 736 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 737 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef 738 return ConstantInt::get(C1V.sdiv(C2V)); 739 case Instruction::URem: 740 assert(!CI2->isNullValue() && "Div by zero handled above"); 741 return ConstantInt::get(C1V.urem(C2V)); 742 case Instruction::SRem: 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.srem(C2V)); 747 case Instruction::And: 748 return ConstantInt::get(C1V & C2V); 749 case Instruction::Or: 750 return ConstantInt::get(C1V | C2V); 751 case Instruction::Xor: 752 return ConstantInt::get(C1V ^ C2V); 753 case Instruction::Shl: { 754 uint32_t shiftAmt = C2V.getZExtValue(); 755 if (shiftAmt < C1V.getBitWidth()) 756 return ConstantInt::get(C1V.shl(shiftAmt)); 757 else 758 return UndefValue::get(C1->getType()); // too big shift is undef 759 } 760 case Instruction::LShr: { 761 uint32_t shiftAmt = C2V.getZExtValue(); 762 if (shiftAmt < C1V.getBitWidth()) 763 return ConstantInt::get(C1V.lshr(shiftAmt)); 764 else 765 return UndefValue::get(C1->getType()); // too big shift is undef 766 } 767 case Instruction::AShr: { 768 uint32_t shiftAmt = C2V.getZExtValue(); 769 if (shiftAmt < C1V.getBitWidth()) 770 return ConstantInt::get(C1V.ashr(shiftAmt)); 771 else 772 return UndefValue::get(C1->getType()); // too big shift is undef 773 } 774 } 775 } 776 777 switch (Opcode) { 778 case Instruction::SDiv: 779 case Instruction::UDiv: 780 case Instruction::URem: 781 case Instruction::SRem: 782 case Instruction::LShr: 783 case Instruction::AShr: 784 case Instruction::Shl: 785 if (CI1->equalsInt(0)) return const_cast<Constant*>(C1); 786 break; 787 default: 788 break; 789 } 790 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 791 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 792 APFloat C1V = CFP1->getValueAPF(); 793 APFloat C2V = CFP2->getValueAPF(); 794 APFloat C3V = C1V; // copy for modification 795 switch (Opcode) { 796 default: 797 break; 798 case Instruction::FAdd: 799 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 800 return ConstantFP::get(C3V); 801 case Instruction::FSub: 802 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 803 return ConstantFP::get(C3V); 804 case Instruction::FMul: 805 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 806 return ConstantFP::get(C3V); 807 case Instruction::FDiv: 808 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 809 return ConstantFP::get(C3V); 810 case Instruction::FRem: 811 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 812 return ConstantFP::get(C3V); 813 } 814 } 815 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 816 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1); 817 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2); 818 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) && 819 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) { 820 switch (Opcode) { 821 default: 822 break; 823 case Instruction::Add: 824 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd); 825 case Instruction::FAdd: 826 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFAdd); 827 case Instruction::Sub: 828 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub); 829 case Instruction::FSub: 830 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFSub); 831 case Instruction::Mul: 832 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul); 833 case Instruction::FMul: 834 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFMul); 835 case Instruction::UDiv: 836 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv); 837 case Instruction::SDiv: 838 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv); 839 case Instruction::FDiv: 840 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv); 841 case Instruction::URem: 842 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem); 843 case Instruction::SRem: 844 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem); 845 case Instruction::FRem: 846 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem); 847 case Instruction::And: 848 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd); 849 case Instruction::Or: 850 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr); 851 case Instruction::Xor: 852 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor); 853 case Instruction::LShr: 854 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getLShr); 855 case Instruction::AShr: 856 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAShr); 857 case Instruction::Shl: 858 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getShl); 859 } 860 } 861 } 862 863 if (isa<ConstantExpr>(C1)) { 864 // There are many possible foldings we could do here. We should probably 865 // at least fold add of a pointer with an integer into the appropriate 866 // getelementptr. This will improve alias analysis a bit. 867 } else if (isa<ConstantExpr>(C2)) { 868 // If C2 is a constant expr and C1 isn't, flop them around and fold the 869 // other way if possible. 870 switch (Opcode) { 871 case Instruction::Add: 872 case Instruction::FAdd: 873 case Instruction::Mul: 874 case Instruction::FMul: 875 case Instruction::And: 876 case Instruction::Or: 877 case Instruction::Xor: 878 // No change of opcode required. 879 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 880 881 case Instruction::Shl: 882 case Instruction::LShr: 883 case Instruction::AShr: 884 case Instruction::Sub: 885 case Instruction::FSub: 886 case Instruction::SDiv: 887 case Instruction::UDiv: 888 case Instruction::FDiv: 889 case Instruction::URem: 890 case Instruction::SRem: 891 case Instruction::FRem: 892 default: // These instructions cannot be flopped around. 893 break; 894 } 895 } 896 897 // We don't know how to fold this. 898 return 0; 899} 900 901/// isZeroSizedType - This type is zero sized if its an array or structure of 902/// zero sized types. The only leaf zero sized type is an empty structure. 903static bool isMaybeZeroSizedType(const Type *Ty) { 904 if (isa<OpaqueType>(Ty)) return true; // Can't say. 905 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 906 907 // If all of elements have zero size, this does too. 908 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 909 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 910 return true; 911 912 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 913 return isMaybeZeroSizedType(ATy->getElementType()); 914 } 915 return false; 916} 917 918/// IdxCompare - Compare the two constants as though they were getelementptr 919/// indices. This allows coersion of the types to be the same thing. 920/// 921/// If the two constants are the "same" (after coersion), return 0. If the 922/// first is less than the second, return -1, if the second is less than the 923/// first, return 1. If the constants are not integral, return -2. 924/// 925static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 926 if (C1 == C2) return 0; 927 928 // Ok, we found a different index. If they are not ConstantInt, we can't do 929 // anything with them. 930 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 931 return -2; // don't know! 932 933 // Ok, we have two differing integer indices. Sign extend them to be the same 934 // type. Long is always big enough, so we use it. 935 if (C1->getType() != Type::Int64Ty) 936 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); 937 938 if (C2->getType() != Type::Int64Ty) 939 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); 940 941 if (C1 == C2) return 0; // They are equal 942 943 // If the type being indexed over is really just a zero sized type, there is 944 // no pointer difference being made here. 945 if (isMaybeZeroSizedType(ElTy)) 946 return -2; // dunno. 947 948 // If they are really different, now that they are the same type, then we 949 // found a difference! 950 if (cast<ConstantInt>(C1)->getSExtValue() < 951 cast<ConstantInt>(C2)->getSExtValue()) 952 return -1; 953 else 954 return 1; 955} 956 957/// evaluateFCmpRelation - This function determines if there is anything we can 958/// decide about the two constants provided. This doesn't need to handle simple 959/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 960/// If we can determine that the two constants have a particular relation to 961/// each other, we should return the corresponding FCmpInst predicate, 962/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 963/// ConstantFoldCompareInstruction. 964/// 965/// To simplify this code we canonicalize the relation so that the first 966/// operand is always the most "complex" of the two. We consider ConstantFP 967/// to be the simplest, and ConstantExprs to be the most complex. 968static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, 969 const Constant *V2) { 970 assert(V1->getType() == V2->getType() && 971 "Cannot compare values of different types!"); 972 973 // No compile-time operations on this type yet. 974 if (V1->getType() == Type::PPC_FP128Ty) 975 return FCmpInst::BAD_FCMP_PREDICATE; 976 977 // Handle degenerate case quickly 978 if (V1 == V2) return FCmpInst::FCMP_OEQ; 979 980 if (!isa<ConstantExpr>(V1)) { 981 if (!isa<ConstantExpr>(V2)) { 982 // We distilled thisUse the standard constant folder for a few cases 983 ConstantInt *R = 0; 984 Constant *C1 = const_cast<Constant*>(V1); 985 Constant *C2 = const_cast<Constant*>(V2); 986 R = dyn_cast<ConstantInt>( 987 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); 988 if (R && !R->isZero()) 989 return FCmpInst::FCMP_OEQ; 990 R = dyn_cast<ConstantInt>( 991 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); 992 if (R && !R->isZero()) 993 return FCmpInst::FCMP_OLT; 994 R = dyn_cast<ConstantInt>( 995 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); 996 if (R && !R->isZero()) 997 return FCmpInst::FCMP_OGT; 998 999 // Nothing more we can do 1000 return FCmpInst::BAD_FCMP_PREDICATE; 1001 } 1002 1003 // If the first operand is simple and second is ConstantExpr, swap operands. 1004 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 1005 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 1006 return FCmpInst::getSwappedPredicate(SwappedRelation); 1007 } else { 1008 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1009 // constantexpr or a simple constant. 1010 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1011 switch (CE1->getOpcode()) { 1012 case Instruction::FPTrunc: 1013 case Instruction::FPExt: 1014 case Instruction::UIToFP: 1015 case Instruction::SIToFP: 1016 // We might be able to do something with these but we don't right now. 1017 break; 1018 default: 1019 break; 1020 } 1021 } 1022 // There are MANY other foldings that we could perform here. They will 1023 // probably be added on demand, as they seem needed. 1024 return FCmpInst::BAD_FCMP_PREDICATE; 1025} 1026 1027/// evaluateICmpRelation - This function determines if there is anything we can 1028/// decide about the two constants provided. This doesn't need to handle simple 1029/// things like integer comparisons, but should instead handle ConstantExprs 1030/// and GlobalValues. If we can determine that the two constants have a 1031/// particular relation to each other, we should return the corresponding ICmp 1032/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 1033/// 1034/// To simplify this code we canonicalize the relation so that the first 1035/// operand is always the most "complex" of the two. We consider simple 1036/// constants (like ConstantInt) to be the simplest, followed by 1037/// GlobalValues, followed by ConstantExpr's (the most complex). 1038/// 1039static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, 1040 const Constant *V2, 1041 bool isSigned) { 1042 assert(V1->getType() == V2->getType() && 1043 "Cannot compare different types of values!"); 1044 if (V1 == V2) return ICmpInst::ICMP_EQ; 1045 1046 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 1047 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { 1048 // We distilled this down to a simple case, use the standard constant 1049 // folder. 1050 ConstantInt *R = 0; 1051 Constant *C1 = const_cast<Constant*>(V1); 1052 Constant *C2 = const_cast<Constant*>(V2); 1053 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 1054 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1055 if (R && !R->isZero()) 1056 return pred; 1057 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1058 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1059 if (R && !R->isZero()) 1060 return pred; 1061 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1062 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 1063 if (R && !R->isZero()) 1064 return pred; 1065 1066 // If we couldn't figure it out, bail. 1067 return ICmpInst::BAD_ICMP_PREDICATE; 1068 } 1069 1070 // If the first operand is simple, swap operands. 1071 ICmpInst::Predicate SwappedRelation = 1072 evaluateICmpRelation(V2, V1, isSigned); 1073 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1074 return ICmpInst::getSwappedPredicate(SwappedRelation); 1075 1076 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { 1077 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1078 ICmpInst::Predicate SwappedRelation = 1079 evaluateICmpRelation(V2, V1, isSigned); 1080 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1081 return ICmpInst::getSwappedPredicate(SwappedRelation); 1082 else 1083 return ICmpInst::BAD_ICMP_PREDICATE; 1084 } 1085 1086 // Now we know that the RHS is a GlobalValue or simple constant, 1087 // which (since the types must match) means that it's a ConstantPointerNull. 1088 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 1089 // Don't try to decide equality of aliases. 1090 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2)) 1091 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) 1092 return ICmpInst::ICMP_NE; 1093 } else { 1094 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 1095 // GlobalVals can never be null. Don't try to evaluate aliases. 1096 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1)) 1097 return ICmpInst::ICMP_NE; 1098 } 1099 } else { 1100 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1101 // constantexpr, a CPR, or a simple constant. 1102 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1103 const Constant *CE1Op0 = CE1->getOperand(0); 1104 1105 switch (CE1->getOpcode()) { 1106 case Instruction::Trunc: 1107 case Instruction::FPTrunc: 1108 case Instruction::FPExt: 1109 case Instruction::FPToUI: 1110 case Instruction::FPToSI: 1111 break; // We can't evaluate floating point casts or truncations. 1112 1113 case Instruction::UIToFP: 1114 case Instruction::SIToFP: 1115 case Instruction::BitCast: 1116 case Instruction::ZExt: 1117 case Instruction::SExt: 1118 // If the cast is not actually changing bits, and the second operand is a 1119 // null pointer, do the comparison with the pre-casted value. 1120 if (V2->isNullValue() && 1121 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) { 1122 bool sgnd = isSigned; 1123 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1124 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1125 return evaluateICmpRelation(CE1Op0, 1126 Constant::getNullValue(CE1Op0->getType()), 1127 sgnd); 1128 } 1129 1130 // If the dest type is a pointer type, and the RHS is a constantexpr cast 1131 // from the same type as the src of the LHS, evaluate the inputs. This is 1132 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", 1133 // which happens a lot in compilers with tagged integers. 1134 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) 1135 if (CE2->isCast() && isa<PointerType>(CE1->getType()) && 1136 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && 1137 CE1->getOperand(0)->getType()->isInteger()) { 1138 bool sgnd = isSigned; 1139 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1140 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1141 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), 1142 sgnd); 1143 } 1144 break; 1145 1146 case Instruction::GetElementPtr: 1147 // Ok, since this is a getelementptr, we know that the constant has a 1148 // pointer type. Check the various cases. 1149 if (isa<ConstantPointerNull>(V2)) { 1150 // If we are comparing a GEP to a null pointer, check to see if the base 1151 // of the GEP equals the null pointer. 1152 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1153 if (GV->hasExternalWeakLinkage()) 1154 // Weak linkage GVals could be zero or not. We're comparing that 1155 // to null pointer so its greater-or-equal 1156 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1157 else 1158 // If its not weak linkage, the GVal must have a non-zero address 1159 // so the result is greater-than 1160 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1161 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1162 // If we are indexing from a null pointer, check to see if we have any 1163 // non-zero indices. 1164 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1165 if (!CE1->getOperand(i)->isNullValue()) 1166 // Offsetting from null, must not be equal. 1167 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1168 // Only zero indexes from null, must still be zero. 1169 return ICmpInst::ICMP_EQ; 1170 } 1171 // Otherwise, we can't really say if the first operand is null or not. 1172 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 1173 if (isa<ConstantPointerNull>(CE1Op0)) { 1174 if (CPR2->hasExternalWeakLinkage()) 1175 // Weak linkage GVals could be zero or not. We're comparing it to 1176 // a null pointer, so its less-or-equal 1177 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1178 else 1179 // If its not weak linkage, the GVal must have a non-zero address 1180 // so the result is less-than 1181 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1182 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 1183 if (CPR1 == CPR2) { 1184 // If this is a getelementptr of the same global, then it must be 1185 // different. Because the types must match, the getelementptr could 1186 // only have at most one index, and because we fold getelementptr's 1187 // with a single zero index, it must be nonzero. 1188 assert(CE1->getNumOperands() == 2 && 1189 !CE1->getOperand(1)->isNullValue() && 1190 "Suprising getelementptr!"); 1191 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1192 } else { 1193 // If they are different globals, we don't know what the value is, 1194 // but they can't be equal. 1195 return ICmpInst::ICMP_NE; 1196 } 1197 } 1198 } else { 1199 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1200 const Constant *CE2Op0 = CE2->getOperand(0); 1201 1202 // There are MANY other foldings that we could perform here. They will 1203 // probably be added on demand, as they seem needed. 1204 switch (CE2->getOpcode()) { 1205 default: break; 1206 case Instruction::GetElementPtr: 1207 // By far the most common case to handle is when the base pointers are 1208 // obviously to the same or different globals. 1209 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1210 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 1211 return ICmpInst::ICMP_NE; 1212 // Ok, we know that both getelementptr instructions are based on the 1213 // same global. From this, we can precisely determine the relative 1214 // ordering of the resultant pointers. 1215 unsigned i = 1; 1216 1217 // Compare all of the operands the GEP's have in common. 1218 gep_type_iterator GTI = gep_type_begin(CE1); 1219 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1220 ++i, ++GTI) 1221 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), 1222 GTI.getIndexedType())) { 1223 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1224 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1225 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1226 } 1227 1228 // Ok, we ran out of things they have in common. If any leftovers 1229 // are non-zero then we have a difference, otherwise we are equal. 1230 for (; i < CE1->getNumOperands(); ++i) 1231 if (!CE1->getOperand(i)->isNullValue()) { 1232 if (isa<ConstantInt>(CE1->getOperand(i))) 1233 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1234 else 1235 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1236 } 1237 1238 for (; i < CE2->getNumOperands(); ++i) 1239 if (!CE2->getOperand(i)->isNullValue()) { 1240 if (isa<ConstantInt>(CE2->getOperand(i))) 1241 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1242 else 1243 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1244 } 1245 return ICmpInst::ICMP_EQ; 1246 } 1247 } 1248 } 1249 default: 1250 break; 1251 } 1252 } 1253 1254 return ICmpInst::BAD_ICMP_PREDICATE; 1255} 1256 1257Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1258 const Constant *C1, 1259 const Constant *C2) { 1260 const Type *ResultTy; 1261 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1262 ResultTy = VectorType::get(Type::Int1Ty, VT->getNumElements()); 1263 else 1264 ResultTy = Type::Int1Ty; 1265 1266 // Fold FCMP_FALSE/FCMP_TRUE unconditionally. 1267 if (pred == FCmpInst::FCMP_FALSE) 1268 return Constant::getNullValue(ResultTy); 1269 1270 if (pred == FCmpInst::FCMP_TRUE) 1271 return Constant::getAllOnesValue(ResultTy); 1272 1273 // Handle some degenerate cases first 1274 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) 1275 return UndefValue::get(ResultTy); 1276 1277 // No compile-time operations on this type yet. 1278 if (C1->getType() == Type::PPC_FP128Ty) 1279 return 0; 1280 1281 // icmp eq/ne(null,GV) -> false/true 1282 if (C1->isNullValue()) { 1283 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1284 // Don't try to evaluate aliases. External weak GV can be null. 1285 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1286 if (pred == ICmpInst::ICMP_EQ) 1287 return ConstantInt::getFalse(); 1288 else if (pred == ICmpInst::ICMP_NE) 1289 return ConstantInt::getTrue(); 1290 } 1291 // icmp eq/ne(GV,null) -> false/true 1292 } else if (C2->isNullValue()) { 1293 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1294 // Don't try to evaluate aliases. External weak GV can be null. 1295 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1296 if (pred == ICmpInst::ICMP_EQ) 1297 return ConstantInt::getFalse(); 1298 else if (pred == ICmpInst::ICMP_NE) 1299 return ConstantInt::getTrue(); 1300 } 1301 } 1302 1303 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1304 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1305 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1306 switch (pred) { 1307 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1308 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); 1309 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); 1310 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2)); 1311 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2)); 1312 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2)); 1313 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2)); 1314 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2)); 1315 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2)); 1316 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2)); 1317 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2)); 1318 } 1319 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1320 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1321 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1322 APFloat::cmpResult R = C1V.compare(C2V); 1323 switch (pred) { 1324 default: assert(0 && "Invalid FCmp Predicate"); return 0; 1325 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); 1326 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); 1327 case FCmpInst::FCMP_UNO: 1328 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered); 1329 case FCmpInst::FCMP_ORD: 1330 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered); 1331 case FCmpInst::FCMP_UEQ: 1332 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1333 R==APFloat::cmpEqual); 1334 case FCmpInst::FCMP_OEQ: 1335 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual); 1336 case FCmpInst::FCMP_UNE: 1337 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual); 1338 case FCmpInst::FCMP_ONE: 1339 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || 1340 R==APFloat::cmpGreaterThan); 1341 case FCmpInst::FCMP_ULT: 1342 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1343 R==APFloat::cmpLessThan); 1344 case FCmpInst::FCMP_OLT: 1345 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan); 1346 case FCmpInst::FCMP_UGT: 1347 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1348 R==APFloat::cmpGreaterThan); 1349 case FCmpInst::FCMP_OGT: 1350 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan); 1351 case FCmpInst::FCMP_ULE: 1352 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan); 1353 case FCmpInst::FCMP_OLE: 1354 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || 1355 R==APFloat::cmpEqual); 1356 case FCmpInst::FCMP_UGE: 1357 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan); 1358 case FCmpInst::FCMP_OGE: 1359 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan || 1360 R==APFloat::cmpEqual); 1361 } 1362 } else if (isa<VectorType>(C1->getType())) { 1363 SmallVector<Constant*, 16> C1Elts, C2Elts; 1364 C1->getVectorElements(C1Elts); 1365 C2->getVectorElements(C2Elts); 1366 1367 // If we can constant fold the comparison of each element, constant fold 1368 // the whole vector comparison. 1369 SmallVector<Constant*, 4> ResElts; 1370 for (unsigned i = 0, e = C1Elts.size(); i != e; ++i) { 1371 // Compare the elements, producing an i1 result or constant expr. 1372 ResElts.push_back(ConstantExpr::getCompare(pred, C1Elts[i], C2Elts[i])); 1373 } 1374 return ConstantVector::get(&ResElts[0], ResElts.size()); 1375 } 1376 1377 if (C1->getType()->isFloatingPoint()) { 1378 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1379 switch (evaluateFCmpRelation(C1, C2)) { 1380 default: assert(0 && "Unknown relation!"); 1381 case FCmpInst::FCMP_UNO: 1382 case FCmpInst::FCMP_ORD: 1383 case FCmpInst::FCMP_UEQ: 1384 case FCmpInst::FCMP_UNE: 1385 case FCmpInst::FCMP_ULT: 1386 case FCmpInst::FCMP_UGT: 1387 case FCmpInst::FCMP_ULE: 1388 case FCmpInst::FCMP_UGE: 1389 case FCmpInst::FCMP_TRUE: 1390 case FCmpInst::FCMP_FALSE: 1391 case FCmpInst::BAD_FCMP_PREDICATE: 1392 break; // Couldn't determine anything about these constants. 1393 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1394 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1395 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1396 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1397 break; 1398 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1399 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1400 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1401 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1402 break; 1403 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1404 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1405 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1406 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1407 break; 1408 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1409 // We can only partially decide this relation. 1410 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1411 Result = 0; 1412 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1413 Result = 1; 1414 break; 1415 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1416 // We can only partially decide this relation. 1417 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1418 Result = 0; 1419 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1420 Result = 1; 1421 break; 1422 case ICmpInst::ICMP_NE: // We know that C1 != C2 1423 // We can only partially decide this relation. 1424 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1425 Result = 0; 1426 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1427 Result = 1; 1428 break; 1429 } 1430 1431 // If we evaluated the result, return it now. 1432 if (Result != -1) 1433 return ConstantInt::get(Type::Int1Ty, Result); 1434 1435 } else { 1436 // Evaluate the relation between the two constants, per the predicate. 1437 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1438 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1439 default: assert(0 && "Unknown relational!"); 1440 case ICmpInst::BAD_ICMP_PREDICATE: 1441 break; // Couldn't determine anything about these constants. 1442 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1443 // If we know the constants are equal, we can decide the result of this 1444 // computation precisely. 1445 Result = (pred == ICmpInst::ICMP_EQ || 1446 pred == ICmpInst::ICMP_ULE || 1447 pred == ICmpInst::ICMP_SLE || 1448 pred == ICmpInst::ICMP_UGE || 1449 pred == ICmpInst::ICMP_SGE); 1450 break; 1451 case ICmpInst::ICMP_ULT: 1452 // If we know that C1 < C2, we can decide the result of this computation 1453 // precisely. 1454 Result = (pred == ICmpInst::ICMP_ULT || 1455 pred == ICmpInst::ICMP_NE || 1456 pred == ICmpInst::ICMP_ULE); 1457 break; 1458 case ICmpInst::ICMP_SLT: 1459 // If we know that C1 < C2, we can decide the result of this computation 1460 // precisely. 1461 Result = (pred == ICmpInst::ICMP_SLT || 1462 pred == ICmpInst::ICMP_NE || 1463 pred == ICmpInst::ICMP_SLE); 1464 break; 1465 case ICmpInst::ICMP_UGT: 1466 // If we know that C1 > C2, we can decide the result of this computation 1467 // precisely. 1468 Result = (pred == ICmpInst::ICMP_UGT || 1469 pred == ICmpInst::ICMP_NE || 1470 pred == ICmpInst::ICMP_UGE); 1471 break; 1472 case ICmpInst::ICMP_SGT: 1473 // If we know that C1 > C2, we can decide the result of this computation 1474 // precisely. 1475 Result = (pred == ICmpInst::ICMP_SGT || 1476 pred == ICmpInst::ICMP_NE || 1477 pred == ICmpInst::ICMP_SGE); 1478 break; 1479 case ICmpInst::ICMP_ULE: 1480 // If we know that C1 <= C2, we can only partially decide this relation. 1481 if (pred == ICmpInst::ICMP_UGT) Result = 0; 1482 if (pred == ICmpInst::ICMP_ULT) Result = 1; 1483 break; 1484 case ICmpInst::ICMP_SLE: 1485 // If we know that C1 <= C2, we can only partially decide this relation. 1486 if (pred == ICmpInst::ICMP_SGT) Result = 0; 1487 if (pred == ICmpInst::ICMP_SLT) Result = 1; 1488 break; 1489 1490 case ICmpInst::ICMP_UGE: 1491 // If we know that C1 >= C2, we can only partially decide this relation. 1492 if (pred == ICmpInst::ICMP_ULT) Result = 0; 1493 if (pred == ICmpInst::ICMP_UGT) Result = 1; 1494 break; 1495 case ICmpInst::ICMP_SGE: 1496 // If we know that C1 >= C2, we can only partially decide this relation. 1497 if (pred == ICmpInst::ICMP_SLT) Result = 0; 1498 if (pred == ICmpInst::ICMP_SGT) Result = 1; 1499 break; 1500 1501 case ICmpInst::ICMP_NE: 1502 // If we know that C1 != C2, we can only partially decide this relation. 1503 if (pred == ICmpInst::ICMP_EQ) Result = 0; 1504 if (pred == ICmpInst::ICMP_NE) Result = 1; 1505 break; 1506 } 1507 1508 // If we evaluated the result, return it now. 1509 if (Result != -1) 1510 return ConstantInt::get(Type::Int1Ty, Result); 1511 1512 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) { 1513 // If C2 is a constant expr and C1 isn't, flip them around and fold the 1514 // other way if possible. 1515 switch (pred) { 1516 case ICmpInst::ICMP_EQ: 1517 case ICmpInst::ICMP_NE: 1518 // No change of predicate required. 1519 return ConstantFoldCompareInstruction(pred, C2, C1); 1520 1521 case ICmpInst::ICMP_ULT: 1522 case ICmpInst::ICMP_SLT: 1523 case ICmpInst::ICMP_UGT: 1524 case ICmpInst::ICMP_SGT: 1525 case ICmpInst::ICMP_ULE: 1526 case ICmpInst::ICMP_SLE: 1527 case ICmpInst::ICMP_UGE: 1528 case ICmpInst::ICMP_SGE: 1529 // Change the predicate as necessary to swap the operands. 1530 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1531 return ConstantFoldCompareInstruction(pred, C2, C1); 1532 1533 default: // These predicates cannot be flopped around. 1534 break; 1535 } 1536 } 1537 } 1538 return 0; 1539 } 1540 1541Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 1542 Constant* const *Idxs, 1543 unsigned NumIdx) { 1544 if (NumIdx == 0 || 1545 (NumIdx == 1 && Idxs[0]->isNullValue())) 1546 return const_cast<Constant*>(C); 1547 1548 if (isa<UndefValue>(C)) { 1549 const PointerType *Ptr = cast<PointerType>(C->getType()); 1550 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 1551 (Value **)Idxs, 1552 (Value **)Idxs+NumIdx); 1553 assert(Ty != 0 && "Invalid indices for GEP!"); 1554 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 1555 } 1556 1557 Constant *Idx0 = Idxs[0]; 1558 if (C->isNullValue()) { 1559 bool isNull = true; 1560 for (unsigned i = 0, e = NumIdx; i != e; ++i) 1561 if (!Idxs[i]->isNullValue()) { 1562 isNull = false; 1563 break; 1564 } 1565 if (isNull) { 1566 const PointerType *Ptr = cast<PointerType>(C->getType()); 1567 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 1568 (Value**)Idxs, 1569 (Value**)Idxs+NumIdx); 1570 assert(Ty != 0 && "Invalid indices for GEP!"); 1571 return 1572 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace())); 1573 } 1574 } 1575 1576 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 1577 // Combine Indices - If the source pointer to this getelementptr instruction 1578 // is a getelementptr instruction, combine the indices of the two 1579 // getelementptr instructions into a single instruction. 1580 // 1581 if (CE->getOpcode() == Instruction::GetElementPtr) { 1582 const Type *LastTy = 0; 1583 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1584 I != E; ++I) 1585 LastTy = *I; 1586 1587 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 1588 SmallVector<Value*, 16> NewIndices; 1589 NewIndices.reserve(NumIdx + CE->getNumOperands()); 1590 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 1591 NewIndices.push_back(CE->getOperand(i)); 1592 1593 // Add the last index of the source with the first index of the new GEP. 1594 // Make sure to handle the case when they are actually different types. 1595 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 1596 // Otherwise it must be an array. 1597 if (!Idx0->isNullValue()) { 1598 const Type *IdxTy = Combined->getType(); 1599 if (IdxTy != Idx0->getType()) { 1600 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); 1601 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, 1602 Type::Int64Ty); 1603 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 1604 } else { 1605 Combined = 1606 ConstantExpr::get(Instruction::Add, Idx0, Combined); 1607 } 1608 } 1609 1610 NewIndices.push_back(Combined); 1611 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); 1612 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], 1613 NewIndices.size()); 1614 } 1615 } 1616 1617 // Implement folding of: 1618 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 1619 // long 0, long 0) 1620 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 1621 // 1622 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) { 1623 if (const PointerType *SPT = 1624 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 1625 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 1626 if (const ArrayType *CAT = 1627 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 1628 if (CAT->getElementType() == SAT->getElementType()) 1629 return ConstantExpr::getGetElementPtr( 1630 (Constant*)CE->getOperand(0), Idxs, NumIdx); 1631 } 1632 1633 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1) 1634 // Into: inttoptr (i64 0 to i8*) 1635 // This happens with pointers to member functions in C++. 1636 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 && 1637 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) && 1638 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) { 1639 Constant *Base = CE->getOperand(0); 1640 Constant *Offset = Idxs[0]; 1641 1642 // Convert the smaller integer to the larger type. 1643 if (Offset->getType()->getPrimitiveSizeInBits() < 1644 Base->getType()->getPrimitiveSizeInBits()) 1645 Offset = ConstantExpr::getSExt(Offset, Base->getType()); 1646 else if (Base->getType()->getPrimitiveSizeInBits() < 1647 Offset->getType()->getPrimitiveSizeInBits()) 1648 Base = ConstantExpr::getZExt(Base, Offset->getType()); 1649 1650 Base = ConstantExpr::getAdd(Base, Offset); 1651 return ConstantExpr::getIntToPtr(Base, CE->getType()); 1652 } 1653 } 1654 return 0; 1655} 1656 1657