ConstantFold.cpp revision 041e2eb51721bcfecee5d9c9fc409ff185526e47
1//===- ConstantFold.cpp - LLVM constant folder ----------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements folding of constants for LLVM. This implements the 11// (internal) ConstantFold.h interface, which is used by the 12// ConstantExpr::get* methods to automatically fold constants when possible. 13// 14// The current constant folding implementation is implemented in two pieces: the 15// template-based folder for simple primitive constants like ConstantInt, and 16// the special case hackery that we use to symbolically evaluate expressions 17// that use ConstantExprs. 18// 19//===----------------------------------------------------------------------===// 20 21#include "ConstantFold.h" 22#include "llvm/Constants.h" 23#include "llvm/Instructions.h" 24#include "llvm/DerivedTypes.h" 25#include "llvm/Function.h" 26#include "llvm/GlobalAlias.h" 27#include "llvm/ADT/SmallVector.h" 28#include "llvm/Support/Compiler.h" 29#include "llvm/Support/GetElementPtrTypeIterator.h" 30#include "llvm/Support/ManagedStatic.h" 31#include "llvm/Support/MathExtras.h" 32#include <limits> 33using namespace llvm; 34 35//===----------------------------------------------------------------------===// 36// ConstantFold*Instruction Implementations 37//===----------------------------------------------------------------------===// 38 39/// BitCastConstantVector - Convert the specified ConstantVector node to the 40/// specified vector type. At this point, we know that the elements of the 41/// input vector constant are all simple integer or FP values. 42static Constant *BitCastConstantVector(ConstantVector *CV, 43 const VectorType *DstTy) { 44 // If this cast changes element count then we can't handle it here: 45 // doing so requires endianness information. This should be handled by 46 // Analysis/ConstantFolding.cpp 47 unsigned NumElts = DstTy->getNumElements(); 48 if (NumElts != CV->getNumOperands()) 49 return 0; 50 51 // Check to verify that all elements of the input are simple. 52 for (unsigned i = 0; i != NumElts; ++i) { 53 if (!isa<ConstantInt>(CV->getOperand(i)) && 54 !isa<ConstantFP>(CV->getOperand(i))) 55 return 0; 56 } 57 58 // Bitcast each element now. 59 std::vector<Constant*> Result; 60 const Type *DstEltTy = DstTy->getElementType(); 61 for (unsigned i = 0; i != NumElts; ++i) 62 Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy)); 63 return ConstantVector::get(Result); 64} 65 66/// This function determines which opcode to use to fold two constant cast 67/// expressions together. It uses CastInst::isEliminableCastPair to determine 68/// the opcode. Consequently its just a wrapper around that function. 69/// @brief Determine if it is valid to fold a cast of a cast 70static unsigned 71foldConstantCastPair( 72 unsigned opc, ///< opcode of the second cast constant expression 73 const ConstantExpr*Op, ///< the first cast constant expression 74 const Type *DstTy ///< desintation type of the first cast 75) { 76 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); 77 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); 78 assert(CastInst::isCast(opc) && "Invalid cast opcode"); 79 80 // The the types and opcodes for the two Cast constant expressions 81 const Type *SrcTy = Op->getOperand(0)->getType(); 82 const Type *MidTy = Op->getType(); 83 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); 84 Instruction::CastOps secondOp = Instruction::CastOps(opc); 85 86 // Let CastInst::isEliminableCastPair do the heavy lifting. 87 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, 88 Type::Int64Ty); 89} 90 91static Constant *FoldBitCast(Constant *V, const Type *DestTy) { 92 const Type *SrcTy = V->getType(); 93 if (SrcTy == DestTy) 94 return V; // no-op cast 95 96 // Check to see if we are casting a pointer to an aggregate to a pointer to 97 // the first element. If so, return the appropriate GEP instruction. 98 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) 99 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) 100 if (PTy->getAddressSpace() == DPTy->getAddressSpace()) { 101 SmallVector<Value*, 8> IdxList; 102 IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); 103 const Type *ElTy = PTy->getElementType(); 104 while (ElTy != DPTy->getElementType()) { 105 if (const StructType *STy = dyn_cast<StructType>(ElTy)) { 106 if (STy->getNumElements() == 0) break; 107 ElTy = STy->getElementType(0); 108 IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); 109 } else if (const SequentialType *STy = 110 dyn_cast<SequentialType>(ElTy)) { 111 if (isa<PointerType>(ElTy)) break; // Can't index into pointers! 112 ElTy = STy->getElementType(); 113 IdxList.push_back(IdxList[0]); 114 } else { 115 break; 116 } 117 } 118 119 if (ElTy == DPTy->getElementType()) 120 return ConstantExpr::getGetElementPtr(V, &IdxList[0], IdxList.size()); 121 } 122 123 // Handle casts from one vector constant to another. We know that the src 124 // and dest type have the same size (otherwise its an illegal cast). 125 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { 126 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { 127 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && 128 "Not cast between same sized vectors!"); 129 // First, check for null. Undef is already handled. 130 if (isa<ConstantAggregateZero>(V)) 131 return Constant::getNullValue(DestTy); 132 133 if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) 134 return BitCastConstantVector(CV, DestPTy); 135 } 136 } 137 138 // Finally, implement bitcast folding now. The code below doesn't handle 139 // bitcast right. 140 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 141 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 142 143 // Handle integral constant input. 144 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 145 if (DestTy->isInteger()) 146 // Integral -> Integral. This is a no-op because the bit widths must 147 // be the same. Consequently, we just fold to V. 148 return V; 149 150 if (DestTy->isFloatingPoint()) { 151 assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) && 152 "Unknown FP type!"); 153 return ConstantFP::get(APFloat(CI->getValue())); 154 } 155 // Otherwise, can't fold this (vector?) 156 return 0; 157 } 158 159 // Handle ConstantFP input. 160 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) { 161 // FP -> Integral. 162 if (DestTy == Type::Int32Ty) { 163 return ConstantInt::get(FP->getValueAPF().convertToAPInt()); 164 } else { 165 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!"); 166 return ConstantInt::get(FP->getValueAPF().convertToAPInt()); 167 } 168 } 169 return 0; 170} 171 172 173Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V, 174 const Type *DestTy) { 175 if (isa<UndefValue>(V)) { 176 // zext(undef) = 0, because the top bits will be zero. 177 // sext(undef) = 0, because the top bits will all be the same. 178 // [us]itofp(undef) = 0, because the result value is bounded. 179 if (opc == Instruction::ZExt || opc == Instruction::SExt || 180 opc == Instruction::UIToFP || opc == Instruction::SIToFP) 181 return Constant::getNullValue(DestTy); 182 return UndefValue::get(DestTy); 183 } 184 // No compile-time operations on this type yet. 185 if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty) 186 return 0; 187 188 // If the cast operand is a constant expression, there's a few things we can 189 // do to try to simplify it. 190 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 191 if (CE->isCast()) { 192 // Try hard to fold cast of cast because they are often eliminable. 193 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 194 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 195 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 196 // If all of the indexes in the GEP are null values, there is no pointer 197 // adjustment going on. We might as well cast the source pointer. 198 bool isAllNull = true; 199 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 200 if (!CE->getOperand(i)->isNullValue()) { 201 isAllNull = false; 202 break; 203 } 204 if (isAllNull) 205 // This is casting one pointer type to another, always BitCast 206 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 207 } 208 } 209 210 // We actually have to do a cast now. Perform the cast according to the 211 // opcode specified. 212 switch (opc) { 213 case Instruction::FPTrunc: 214 case Instruction::FPExt: 215 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 216 APFloat Val = FPC->getValueAPF(); 217 Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle : 218 DestTy == Type::DoubleTy ? APFloat::IEEEdouble : 219 DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended : 220 DestTy == Type::FP128Ty ? APFloat::IEEEquad : 221 APFloat::Bogus, 222 APFloat::rmNearestTiesToEven); 223 return ConstantFP::get(Val); 224 } 225 return 0; // Can't fold. 226 case Instruction::FPToUI: 227 case Instruction::FPToSI: 228 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 229 const APFloat &V = FPC->getValueAPF(); 230 uint64_t x[2]; 231 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 232 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 233 APFloat::rmTowardZero); 234 APInt Val(DestBitWidth, 2, x); 235 return ConstantInt::get(Val); 236 } 237 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) { 238 std::vector<Constant*> res; 239 const VectorType *DestVecTy = cast<VectorType>(DestTy); 240 const Type *DstEltTy = DestVecTy->getElementType(); 241 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 242 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i), 243 DstEltTy)); 244 return ConstantVector::get(DestVecTy, res); 245 } 246 return 0; // Can't fold. 247 case Instruction::IntToPtr: //always treated as unsigned 248 if (V->isNullValue()) // Is it an integral null value? 249 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 250 return 0; // Other pointer types cannot be casted 251 case Instruction::PtrToInt: // always treated as unsigned 252 if (V->isNullValue()) // is it a null pointer value? 253 return ConstantInt::get(DestTy, 0); 254 return 0; // Other pointer types cannot be casted 255 case Instruction::UIToFP: 256 case Instruction::SIToFP: 257 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 258 APInt api = CI->getValue(); 259 const uint64_t zero[] = {0, 0}; 260 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(), 261 2, zero)); 262 (void)apf.convertFromAPInt(api, 263 opc==Instruction::SIToFP, 264 APFloat::rmNearestTiesToEven); 265 return ConstantFP::get(apf); 266 } 267 if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) { 268 std::vector<Constant*> res; 269 const VectorType *DestVecTy = cast<VectorType>(DestTy); 270 const Type *DstEltTy = DestVecTy->getElementType(); 271 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 272 res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i), 273 DstEltTy)); 274 return ConstantVector::get(DestVecTy, res); 275 } 276 return 0; 277 case Instruction::ZExt: 278 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 279 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 280 APInt Result(CI->getValue()); 281 Result.zext(BitWidth); 282 return ConstantInt::get(Result); 283 } 284 return 0; 285 case Instruction::SExt: 286 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 287 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 288 APInt Result(CI->getValue()); 289 Result.sext(BitWidth); 290 return ConstantInt::get(Result); 291 } 292 return 0; 293 case Instruction::Trunc: 294 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 295 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 296 APInt Result(CI->getValue()); 297 Result.trunc(BitWidth); 298 return ConstantInt::get(Result); 299 } 300 return 0; 301 case Instruction::BitCast: 302 return FoldBitCast(const_cast<Constant*>(V), DestTy); 303 default: 304 assert(!"Invalid CE CastInst opcode"); 305 break; 306 } 307 308 assert(0 && "Failed to cast constant expression"); 309 return 0; 310} 311 312Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, 313 const Constant *V1, 314 const Constant *V2) { 315 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) 316 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2); 317 318 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); 319 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); 320 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); 321 if (V1 == V2) return const_cast<Constant*>(V1); 322 return 0; 323} 324 325Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, 326 const Constant *Idx) { 327 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 328 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType()); 329 if (Val->isNullValue()) // ee(zero, x) -> zero 330 return Constant::getNullValue( 331 cast<VectorType>(Val->getType())->getElementType()); 332 333 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 334 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 335 return CVal->getOperand(CIdx->getZExtValue()); 336 } else if (isa<UndefValue>(Idx)) { 337 // ee({w,x,y,z}, undef) -> w (an arbitrary value). 338 return CVal->getOperand(0); 339 } 340 } 341 return 0; 342} 343 344Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, 345 const Constant *Elt, 346 const Constant *Idx) { 347 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 348 if (!CIdx) return 0; 349 APInt idxVal = CIdx->getValue(); 350 if (isa<UndefValue>(Val)) { 351 // Insertion of scalar constant into vector undef 352 // Optimize away insertion of undef 353 if (isa<UndefValue>(Elt)) 354 return const_cast<Constant*>(Val); 355 // Otherwise break the aggregate undef into multiple undefs and do 356 // the insertion 357 unsigned numOps = 358 cast<VectorType>(Val->getType())->getNumElements(); 359 std::vector<Constant*> Ops; 360 Ops.reserve(numOps); 361 for (unsigned i = 0; i < numOps; ++i) { 362 const Constant *Op = 363 (idxVal == i) ? Elt : UndefValue::get(Elt->getType()); 364 Ops.push_back(const_cast<Constant*>(Op)); 365 } 366 return ConstantVector::get(Ops); 367 } 368 if (isa<ConstantAggregateZero>(Val)) { 369 // Insertion of scalar constant into vector aggregate zero 370 // Optimize away insertion of zero 371 if (Elt->isNullValue()) 372 return const_cast<Constant*>(Val); 373 // Otherwise break the aggregate zero into multiple zeros and do 374 // the insertion 375 unsigned numOps = 376 cast<VectorType>(Val->getType())->getNumElements(); 377 std::vector<Constant*> Ops; 378 Ops.reserve(numOps); 379 for (unsigned i = 0; i < numOps; ++i) { 380 const Constant *Op = 381 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType()); 382 Ops.push_back(const_cast<Constant*>(Op)); 383 } 384 return ConstantVector::get(Ops); 385 } 386 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 387 // Insertion of scalar constant into vector constant 388 std::vector<Constant*> Ops; 389 Ops.reserve(CVal->getNumOperands()); 390 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { 391 const Constant *Op = 392 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i)); 393 Ops.push_back(const_cast<Constant*>(Op)); 394 } 395 return ConstantVector::get(Ops); 396 } 397 return 0; 398} 399 400/// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef 401/// return the specified element value. Otherwise return null. 402static Constant *GetVectorElement(const Constant *C, unsigned EltNo) { 403 if (const ConstantVector *CV = dyn_cast<ConstantVector>(C)) 404 return CV->getOperand(EltNo); 405 406 const Type *EltTy = cast<VectorType>(C->getType())->getElementType(); 407 if (isa<ConstantAggregateZero>(C)) 408 return Constant::getNullValue(EltTy); 409 if (isa<UndefValue>(C)) 410 return UndefValue::get(EltTy); 411 return 0; 412} 413 414Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, 415 const Constant *V2, 416 const Constant *Mask) { 417 // Undefined shuffle mask -> undefined value. 418 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType()); 419 420 unsigned NumElts = cast<VectorType>(V1->getType())->getNumElements(); 421 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType(); 422 423 // Loop over the shuffle mask, evaluating each element. 424 SmallVector<Constant*, 32> Result; 425 for (unsigned i = 0; i != NumElts; ++i) { 426 Constant *InElt = GetVectorElement(Mask, i); 427 if (InElt == 0) return 0; 428 429 if (isa<UndefValue>(InElt)) 430 InElt = UndefValue::get(EltTy); 431 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) { 432 unsigned Elt = CI->getZExtValue(); 433 if (Elt >= NumElts*2) 434 InElt = UndefValue::get(EltTy); 435 else if (Elt >= NumElts) 436 InElt = GetVectorElement(V2, Elt-NumElts); 437 else 438 InElt = GetVectorElement(V1, Elt); 439 if (InElt == 0) return 0; 440 } else { 441 // Unknown value. 442 return 0; 443 } 444 Result.push_back(InElt); 445 } 446 447 return ConstantVector::get(&Result[0], Result.size()); 448} 449 450Constant *llvm::ConstantFoldExtractValue(const Constant *Agg, 451 Constant* const *Idxs, 452 unsigned NumIdx) { 453 // FIXME: implement some constant folds 454 return 0; 455} 456 457Constant *llvm::ConstantFoldInsertValue(const Constant *Agg, 458 const Constant *Val, 459 Constant* const *Idxs, 460 unsigned NumIdx) { 461 // FIXME: implement some constant folds 462 return 0; 463} 464 465/// EvalVectorOp - Given two vector constants and a function pointer, apply the 466/// function pointer to each element pair, producing a new ConstantVector 467/// constant. Either or both of V1 and V2 may be NULL, meaning a 468/// ConstantAggregateZero operand. 469static Constant *EvalVectorOp(const ConstantVector *V1, 470 const ConstantVector *V2, 471 const VectorType *VTy, 472 Constant *(*FP)(Constant*, Constant*)) { 473 std::vector<Constant*> Res; 474 const Type *EltTy = VTy->getElementType(); 475 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 476 const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy); 477 const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy); 478 Res.push_back(FP(const_cast<Constant*>(C1), 479 const_cast<Constant*>(C2))); 480 } 481 return ConstantVector::get(Res); 482} 483 484Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 485 const Constant *C1, 486 const Constant *C2) { 487 // No compile-time operations on this type yet. 488 if (C1->getType() == Type::PPC_FP128Ty) 489 return 0; 490 491 // Handle UndefValue up front 492 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 493 switch (Opcode) { 494 case Instruction::Xor: 495 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 496 // Handle undef ^ undef -> 0 special case. This is a common 497 // idiom (misuse). 498 return Constant::getNullValue(C1->getType()); 499 // Fallthrough 500 case Instruction::Add: 501 case Instruction::Sub: 502 return UndefValue::get(C1->getType()); 503 case Instruction::Mul: 504 case Instruction::And: 505 return Constant::getNullValue(C1->getType()); 506 case Instruction::UDiv: 507 case Instruction::SDiv: 508 case Instruction::FDiv: 509 case Instruction::URem: 510 case Instruction::SRem: 511 case Instruction::FRem: 512 if (!isa<UndefValue>(C2)) // undef / X -> 0 513 return Constant::getNullValue(C1->getType()); 514 return const_cast<Constant*>(C2); // X / undef -> undef 515 case Instruction::Or: // X | undef -> -1 516 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType())) 517 return ConstantVector::getAllOnesValue(PTy); 518 return ConstantInt::getAllOnesValue(C1->getType()); 519 case Instruction::LShr: 520 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 521 return const_cast<Constant*>(C1); // undef lshr undef -> undef 522 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 523 // undef lshr X -> 0 524 case Instruction::AShr: 525 if (!isa<UndefValue>(C2)) 526 return const_cast<Constant*>(C1); // undef ashr X --> undef 527 else if (isa<UndefValue>(C1)) 528 return const_cast<Constant*>(C1); // undef ashr undef -> undef 529 else 530 return const_cast<Constant*>(C1); // X ashr undef --> X 531 case Instruction::Shl: 532 // undef << X -> 0 or X << undef -> 0 533 return Constant::getNullValue(C1->getType()); 534 } 535 } 536 537 // Handle simplifications of the RHS when a constant int. 538 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 539 switch (Opcode) { 540 case Instruction::Add: 541 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X + 0 == X 542 break; 543 case Instruction::Sub: 544 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X - 0 == X 545 break; 546 case Instruction::Mul: 547 if (CI2->equalsInt(0)) return const_cast<Constant*>(C2); // X * 0 == 0 548 if (CI2->equalsInt(1)) 549 return const_cast<Constant*>(C1); // X * 1 == X 550 break; 551 case Instruction::UDiv: 552 case Instruction::SDiv: 553 if (CI2->equalsInt(1)) 554 return const_cast<Constant*>(C1); // X / 1 == X 555 break; 556 case Instruction::URem: 557 case Instruction::SRem: 558 if (CI2->equalsInt(1)) 559 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 560 break; 561 case Instruction::And: 562 if (CI2->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0 563 if (CI2->isAllOnesValue()) 564 return const_cast<Constant*>(C1); // X & -1 == X 565 566 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 567 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 568 if (CE1->getOpcode() == Instruction::ZExt) { 569 unsigned DstWidth = CI2->getType()->getBitWidth(); 570 unsigned SrcWidth = 571 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 572 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 573 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 574 return const_cast<Constant*>(C1); 575 } 576 577 // If and'ing the address of a global with a constant, fold it. 578 if (CE1->getOpcode() == Instruction::PtrToInt && 579 isa<GlobalValue>(CE1->getOperand(0))) { 580 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 581 582 // Functions are at least 4-byte aligned. 583 unsigned GVAlign = GV->getAlignment(); 584 if (isa<Function>(GV)) 585 GVAlign = std::max(GVAlign, 4U); 586 587 if (GVAlign > 1) { 588 unsigned DstWidth = CI2->getType()->getBitWidth(); 589 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 590 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 591 592 // If checking bits we know are clear, return zero. 593 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 594 return Constant::getNullValue(CI2->getType()); 595 } 596 } 597 } 598 break; 599 case Instruction::Or: 600 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X | 0 == X 601 if (CI2->isAllOnesValue()) 602 return const_cast<Constant*>(C2); // X | -1 == -1 603 break; 604 case Instruction::Xor: 605 if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X ^ 0 == X 606 break; 607 case Instruction::AShr: 608 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 609 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 610 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 611 return ConstantExpr::getLShr(const_cast<Constant*>(C1), 612 const_cast<Constant*>(C2)); 613 break; 614 } 615 } 616 617 // At this point we know neither constant is an UndefValue. 618 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 619 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 620 using namespace APIntOps; 621 const APInt &C1V = CI1->getValue(); 622 const APInt &C2V = CI2->getValue(); 623 switch (Opcode) { 624 default: 625 break; 626 case Instruction::Add: 627 return ConstantInt::get(C1V + C2V); 628 case Instruction::Sub: 629 return ConstantInt::get(C1V - C2V); 630 case Instruction::Mul: 631 return ConstantInt::get(C1V * C2V); 632 case Instruction::UDiv: 633 if (CI2->isNullValue()) 634 return 0; // X / 0 -> can't fold 635 return ConstantInt::get(C1V.udiv(C2V)); 636 case Instruction::SDiv: 637 if (CI2->isNullValue()) 638 return 0; // X / 0 -> can't fold 639 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 640 return 0; // MIN_INT / -1 -> overflow 641 return ConstantInt::get(C1V.sdiv(C2V)); 642 case Instruction::URem: 643 if (C2->isNullValue()) 644 return 0; // X / 0 -> can't fold 645 return ConstantInt::get(C1V.urem(C2V)); 646 case Instruction::SRem: 647 if (CI2->isNullValue()) 648 return 0; // X % 0 -> can't fold 649 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 650 return 0; // MIN_INT % -1 -> overflow 651 return ConstantInt::get(C1V.srem(C2V)); 652 case Instruction::And: 653 return ConstantInt::get(C1V & C2V); 654 case Instruction::Or: 655 return ConstantInt::get(C1V | C2V); 656 case Instruction::Xor: 657 return ConstantInt::get(C1V ^ C2V); 658 case Instruction::Shl: { 659 uint32_t shiftAmt = C2V.getZExtValue(); 660 if (shiftAmt < C1V.getBitWidth()) 661 return ConstantInt::get(C1V.shl(shiftAmt)); 662 else 663 return UndefValue::get(C1->getType()); // too big shift is undef 664 } 665 case Instruction::LShr: { 666 uint32_t shiftAmt = C2V.getZExtValue(); 667 if (shiftAmt < C1V.getBitWidth()) 668 return ConstantInt::get(C1V.lshr(shiftAmt)); 669 else 670 return UndefValue::get(C1->getType()); // too big shift is undef 671 } 672 case Instruction::AShr: { 673 uint32_t shiftAmt = C2V.getZExtValue(); 674 if (shiftAmt < C1V.getBitWidth()) 675 return ConstantInt::get(C1V.ashr(shiftAmt)); 676 else 677 return UndefValue::get(C1->getType()); // too big shift is undef 678 } 679 } 680 } 681 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 682 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 683 APFloat C1V = CFP1->getValueAPF(); 684 APFloat C2V = CFP2->getValueAPF(); 685 APFloat C3V = C1V; // copy for modification 686 switch (Opcode) { 687 default: 688 break; 689 case Instruction::Add: 690 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 691 return ConstantFP::get(C3V); 692 case Instruction::Sub: 693 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 694 return ConstantFP::get(C3V); 695 case Instruction::Mul: 696 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 697 return ConstantFP::get(C3V); 698 case Instruction::FDiv: 699 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 700 return ConstantFP::get(C3V); 701 case Instruction::FRem: 702 if (C2V.isZero()) { 703 // IEEE 754, Section 7.1, #5 704 if (CFP1->getType() == Type::DoubleTy) 705 return ConstantFP::get(APFloat(std::numeric_limits<double>:: 706 quiet_NaN())); 707 if (CFP1->getType() == Type::FloatTy) 708 return ConstantFP::get(APFloat(std::numeric_limits<float>:: 709 quiet_NaN())); 710 break; 711 } 712 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 713 return ConstantFP::get(C3V); 714 } 715 } 716 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 717 const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1); 718 const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2); 719 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) && 720 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) { 721 switch (Opcode) { 722 default: 723 break; 724 case Instruction::Add: 725 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd); 726 case Instruction::Sub: 727 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub); 728 case Instruction::Mul: 729 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul); 730 case Instruction::UDiv: 731 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv); 732 case Instruction::SDiv: 733 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv); 734 case Instruction::FDiv: 735 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv); 736 case Instruction::URem: 737 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem); 738 case Instruction::SRem: 739 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem); 740 case Instruction::FRem: 741 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem); 742 case Instruction::And: 743 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd); 744 case Instruction::Or: 745 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr); 746 case Instruction::Xor: 747 return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor); 748 } 749 } 750 } 751 752 if (isa<ConstantExpr>(C1)) { 753 // There are many possible foldings we could do here. We should probably 754 // at least fold add of a pointer with an integer into the appropriate 755 // getelementptr. This will improve alias analysis a bit. 756 } else if (isa<ConstantExpr>(C2)) { 757 // If C2 is a constant expr and C1 isn't, flop them around and fold the 758 // other way if possible. 759 switch (Opcode) { 760 case Instruction::Add: 761 case Instruction::Mul: 762 case Instruction::And: 763 case Instruction::Or: 764 case Instruction::Xor: 765 // No change of opcode required. 766 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 767 768 case Instruction::Shl: 769 case Instruction::LShr: 770 case Instruction::AShr: 771 case Instruction::Sub: 772 case Instruction::SDiv: 773 case Instruction::UDiv: 774 case Instruction::FDiv: 775 case Instruction::URem: 776 case Instruction::SRem: 777 case Instruction::FRem: 778 default: // These instructions cannot be flopped around. 779 break; 780 } 781 } 782 783 // We don't know how to fold this. 784 return 0; 785} 786 787/// isZeroSizedType - This type is zero sized if its an array or structure of 788/// zero sized types. The only leaf zero sized type is an empty structure. 789static bool isMaybeZeroSizedType(const Type *Ty) { 790 if (isa<OpaqueType>(Ty)) return true; // Can't say. 791 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 792 793 // If all of elements have zero size, this does too. 794 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 795 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 796 return true; 797 798 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 799 return isMaybeZeroSizedType(ATy->getElementType()); 800 } 801 return false; 802} 803 804/// IdxCompare - Compare the two constants as though they were getelementptr 805/// indices. This allows coersion of the types to be the same thing. 806/// 807/// If the two constants are the "same" (after coersion), return 0. If the 808/// first is less than the second, return -1, if the second is less than the 809/// first, return 1. If the constants are not integral, return -2. 810/// 811static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 812 if (C1 == C2) return 0; 813 814 // Ok, we found a different index. If they are not ConstantInt, we can't do 815 // anything with them. 816 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 817 return -2; // don't know! 818 819 // Ok, we have two differing integer indices. Sign extend them to be the same 820 // type. Long is always big enough, so we use it. 821 if (C1->getType() != Type::Int64Ty) 822 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); 823 824 if (C2->getType() != Type::Int64Ty) 825 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); 826 827 if (C1 == C2) return 0; // They are equal 828 829 // If the type being indexed over is really just a zero sized type, there is 830 // no pointer difference being made here. 831 if (isMaybeZeroSizedType(ElTy)) 832 return -2; // dunno. 833 834 // If they are really different, now that they are the same type, then we 835 // found a difference! 836 if (cast<ConstantInt>(C1)->getSExtValue() < 837 cast<ConstantInt>(C2)->getSExtValue()) 838 return -1; 839 else 840 return 1; 841} 842 843/// evaluateFCmpRelation - This function determines if there is anything we can 844/// decide about the two constants provided. This doesn't need to handle simple 845/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 846/// If we can determine that the two constants have a particular relation to 847/// each other, we should return the corresponding FCmpInst predicate, 848/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 849/// ConstantFoldCompareInstruction. 850/// 851/// To simplify this code we canonicalize the relation so that the first 852/// operand is always the most "complex" of the two. We consider ConstantFP 853/// to be the simplest, and ConstantExprs to be the most complex. 854static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, 855 const Constant *V2) { 856 assert(V1->getType() == V2->getType() && 857 "Cannot compare values of different types!"); 858 859 // No compile-time operations on this type yet. 860 if (V1->getType() == Type::PPC_FP128Ty) 861 return FCmpInst::BAD_FCMP_PREDICATE; 862 863 // Handle degenerate case quickly 864 if (V1 == V2) return FCmpInst::FCMP_OEQ; 865 866 if (!isa<ConstantExpr>(V1)) { 867 if (!isa<ConstantExpr>(V2)) { 868 // We distilled thisUse the standard constant folder for a few cases 869 ConstantInt *R = 0; 870 Constant *C1 = const_cast<Constant*>(V1); 871 Constant *C2 = const_cast<Constant*>(V2); 872 R = dyn_cast<ConstantInt>( 873 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); 874 if (R && !R->isZero()) 875 return FCmpInst::FCMP_OEQ; 876 R = dyn_cast<ConstantInt>( 877 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); 878 if (R && !R->isZero()) 879 return FCmpInst::FCMP_OLT; 880 R = dyn_cast<ConstantInt>( 881 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); 882 if (R && !R->isZero()) 883 return FCmpInst::FCMP_OGT; 884 885 // Nothing more we can do 886 return FCmpInst::BAD_FCMP_PREDICATE; 887 } 888 889 // If the first operand is simple and second is ConstantExpr, swap operands. 890 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 891 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 892 return FCmpInst::getSwappedPredicate(SwappedRelation); 893 } else { 894 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 895 // constantexpr or a simple constant. 896 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 897 switch (CE1->getOpcode()) { 898 case Instruction::FPTrunc: 899 case Instruction::FPExt: 900 case Instruction::UIToFP: 901 case Instruction::SIToFP: 902 // We might be able to do something with these but we don't right now. 903 break; 904 default: 905 break; 906 } 907 } 908 // There are MANY other foldings that we could perform here. They will 909 // probably be added on demand, as they seem needed. 910 return FCmpInst::BAD_FCMP_PREDICATE; 911} 912 913/// evaluateICmpRelation - This function determines if there is anything we can 914/// decide about the two constants provided. This doesn't need to handle simple 915/// things like integer comparisons, but should instead handle ConstantExprs 916/// and GlobalValues. If we can determine that the two constants have a 917/// particular relation to each other, we should return the corresponding ICmp 918/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 919/// 920/// To simplify this code we canonicalize the relation so that the first 921/// operand is always the most "complex" of the two. We consider simple 922/// constants (like ConstantInt) to be the simplest, followed by 923/// GlobalValues, followed by ConstantExpr's (the most complex). 924/// 925static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, 926 const Constant *V2, 927 bool isSigned) { 928 assert(V1->getType() == V2->getType() && 929 "Cannot compare different types of values!"); 930 if (V1 == V2) return ICmpInst::ICMP_EQ; 931 932 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 933 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { 934 // We distilled this down to a simple case, use the standard constant 935 // folder. 936 ConstantInt *R = 0; 937 Constant *C1 = const_cast<Constant*>(V1); 938 Constant *C2 = const_cast<Constant*>(V2); 939 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 940 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 941 if (R && !R->isZero()) 942 return pred; 943 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 944 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 945 if (R && !R->isZero()) 946 return pred; 947 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 948 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 949 if (R && !R->isZero()) 950 return pred; 951 952 // If we couldn't figure it out, bail. 953 return ICmpInst::BAD_ICMP_PREDICATE; 954 } 955 956 // If the first operand is simple, swap operands. 957 ICmpInst::Predicate SwappedRelation = 958 evaluateICmpRelation(V2, V1, isSigned); 959 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 960 return ICmpInst::getSwappedPredicate(SwappedRelation); 961 962 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { 963 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 964 ICmpInst::Predicate SwappedRelation = 965 evaluateICmpRelation(V2, V1, isSigned); 966 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 967 return ICmpInst::getSwappedPredicate(SwappedRelation); 968 else 969 return ICmpInst::BAD_ICMP_PREDICATE; 970 } 971 972 // Now we know that the RHS is a GlobalValue or simple constant, 973 // which (since the types must match) means that it's a ConstantPointerNull. 974 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 975 // Don't try to decide equality of aliases. 976 if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2)) 977 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) 978 return ICmpInst::ICMP_NE; 979 } else { 980 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 981 // GlobalVals can never be null. Don't try to evaluate aliases. 982 if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1)) 983 return ICmpInst::ICMP_NE; 984 } 985 } else { 986 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 987 // constantexpr, a CPR, or a simple constant. 988 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 989 const Constant *CE1Op0 = CE1->getOperand(0); 990 991 switch (CE1->getOpcode()) { 992 case Instruction::Trunc: 993 case Instruction::FPTrunc: 994 case Instruction::FPExt: 995 case Instruction::FPToUI: 996 case Instruction::FPToSI: 997 break; // We can't evaluate floating point casts or truncations. 998 999 case Instruction::UIToFP: 1000 case Instruction::SIToFP: 1001 case Instruction::BitCast: 1002 case Instruction::ZExt: 1003 case Instruction::SExt: 1004 // If the cast is not actually changing bits, and the second operand is a 1005 // null pointer, do the comparison with the pre-casted value. 1006 if (V2->isNullValue() && 1007 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) { 1008 bool sgnd = isSigned; 1009 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1010 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1011 return evaluateICmpRelation(CE1Op0, 1012 Constant::getNullValue(CE1Op0->getType()), 1013 sgnd); 1014 } 1015 1016 // If the dest type is a pointer type, and the RHS is a constantexpr cast 1017 // from the same type as the src of the LHS, evaluate the inputs. This is 1018 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", 1019 // which happens a lot in compilers with tagged integers. 1020 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) 1021 if (CE2->isCast() && isa<PointerType>(CE1->getType()) && 1022 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && 1023 CE1->getOperand(0)->getType()->isInteger()) { 1024 bool sgnd = isSigned; 1025 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1026 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1027 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), 1028 sgnd); 1029 } 1030 break; 1031 1032 case Instruction::GetElementPtr: 1033 // Ok, since this is a getelementptr, we know that the constant has a 1034 // pointer type. Check the various cases. 1035 if (isa<ConstantPointerNull>(V2)) { 1036 // If we are comparing a GEP to a null pointer, check to see if the base 1037 // of the GEP equals the null pointer. 1038 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1039 if (GV->hasExternalWeakLinkage()) 1040 // Weak linkage GVals could be zero or not. We're comparing that 1041 // to null pointer so its greater-or-equal 1042 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1043 else 1044 // If its not weak linkage, the GVal must have a non-zero address 1045 // so the result is greater-than 1046 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1047 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1048 // If we are indexing from a null pointer, check to see if we have any 1049 // non-zero indices. 1050 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1051 if (!CE1->getOperand(i)->isNullValue()) 1052 // Offsetting from null, must not be equal. 1053 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1054 // Only zero indexes from null, must still be zero. 1055 return ICmpInst::ICMP_EQ; 1056 } 1057 // Otherwise, we can't really say if the first operand is null or not. 1058 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 1059 if (isa<ConstantPointerNull>(CE1Op0)) { 1060 if (CPR2->hasExternalWeakLinkage()) 1061 // Weak linkage GVals could be zero or not. We're comparing it to 1062 // a null pointer, so its less-or-equal 1063 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1064 else 1065 // If its not weak linkage, the GVal must have a non-zero address 1066 // so the result is less-than 1067 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1068 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 1069 if (CPR1 == CPR2) { 1070 // If this is a getelementptr of the same global, then it must be 1071 // different. Because the types must match, the getelementptr could 1072 // only have at most one index, and because we fold getelementptr's 1073 // with a single zero index, it must be nonzero. 1074 assert(CE1->getNumOperands() == 2 && 1075 !CE1->getOperand(1)->isNullValue() && 1076 "Suprising getelementptr!"); 1077 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1078 } else { 1079 // If they are different globals, we don't know what the value is, 1080 // but they can't be equal. 1081 return ICmpInst::ICMP_NE; 1082 } 1083 } 1084 } else { 1085 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1086 const Constant *CE2Op0 = CE2->getOperand(0); 1087 1088 // There are MANY other foldings that we could perform here. They will 1089 // probably be added on demand, as they seem needed. 1090 switch (CE2->getOpcode()) { 1091 default: break; 1092 case Instruction::GetElementPtr: 1093 // By far the most common case to handle is when the base pointers are 1094 // obviously to the same or different globals. 1095 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1096 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 1097 return ICmpInst::ICMP_NE; 1098 // Ok, we know that both getelementptr instructions are based on the 1099 // same global. From this, we can precisely determine the relative 1100 // ordering of the resultant pointers. 1101 unsigned i = 1; 1102 1103 // Compare all of the operands the GEP's have in common. 1104 gep_type_iterator GTI = gep_type_begin(CE1); 1105 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1106 ++i, ++GTI) 1107 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), 1108 GTI.getIndexedType())) { 1109 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1110 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1111 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1112 } 1113 1114 // Ok, we ran out of things they have in common. If any leftovers 1115 // are non-zero then we have a difference, otherwise we are equal. 1116 for (; i < CE1->getNumOperands(); ++i) 1117 if (!CE1->getOperand(i)->isNullValue()) { 1118 if (isa<ConstantInt>(CE1->getOperand(i))) 1119 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1120 else 1121 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1122 } 1123 1124 for (; i < CE2->getNumOperands(); ++i) 1125 if (!CE2->getOperand(i)->isNullValue()) { 1126 if (isa<ConstantInt>(CE2->getOperand(i))) 1127 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1128 else 1129 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1130 } 1131 return ICmpInst::ICMP_EQ; 1132 } 1133 } 1134 } 1135 default: 1136 break; 1137 } 1138 } 1139 1140 return ICmpInst::BAD_ICMP_PREDICATE; 1141} 1142 1143Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1144 const Constant *C1, 1145 const Constant *C2) { 1146 1147 // Handle some degenerate cases first 1148 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) 1149 return UndefValue::get(Type::Int1Ty); 1150 1151 // No compile-time operations on this type yet. 1152 if (C1->getType() == Type::PPC_FP128Ty) 1153 return 0; 1154 1155 // icmp eq/ne(null,GV) -> false/true 1156 if (C1->isNullValue()) { 1157 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1158 // Don't try to evaluate aliases. External weak GV can be null. 1159 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1160 if (pred == ICmpInst::ICMP_EQ) 1161 return ConstantInt::getFalse(); 1162 else if (pred == ICmpInst::ICMP_NE) 1163 return ConstantInt::getTrue(); 1164 } 1165 // icmp eq/ne(GV,null) -> false/true 1166 } else if (C2->isNullValue()) { 1167 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1168 // Don't try to evaluate aliases. External weak GV can be null. 1169 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1170 if (pred == ICmpInst::ICMP_EQ) 1171 return ConstantInt::getFalse(); 1172 else if (pred == ICmpInst::ICMP_NE) 1173 return ConstantInt::getTrue(); 1174 } 1175 } 1176 1177 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1178 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1179 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1180 switch (pred) { 1181 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1182 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); 1183 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); 1184 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2)); 1185 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2)); 1186 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2)); 1187 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2)); 1188 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2)); 1189 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2)); 1190 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2)); 1191 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2)); 1192 } 1193 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1194 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1195 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1196 APFloat::cmpResult R = C1V.compare(C2V); 1197 switch (pred) { 1198 default: assert(0 && "Invalid FCmp Predicate"); return 0; 1199 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); 1200 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); 1201 case FCmpInst::FCMP_UNO: 1202 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered); 1203 case FCmpInst::FCMP_ORD: 1204 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered); 1205 case FCmpInst::FCMP_UEQ: 1206 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1207 R==APFloat::cmpEqual); 1208 case FCmpInst::FCMP_OEQ: 1209 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual); 1210 case FCmpInst::FCMP_UNE: 1211 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual); 1212 case FCmpInst::FCMP_ONE: 1213 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || 1214 R==APFloat::cmpGreaterThan); 1215 case FCmpInst::FCMP_ULT: 1216 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1217 R==APFloat::cmpLessThan); 1218 case FCmpInst::FCMP_OLT: 1219 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan); 1220 case FCmpInst::FCMP_UGT: 1221 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || 1222 R==APFloat::cmpGreaterThan); 1223 case FCmpInst::FCMP_OGT: 1224 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan); 1225 case FCmpInst::FCMP_ULE: 1226 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan); 1227 case FCmpInst::FCMP_OLE: 1228 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || 1229 R==APFloat::cmpEqual); 1230 case FCmpInst::FCMP_UGE: 1231 return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan); 1232 case FCmpInst::FCMP_OGE: 1233 return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan || 1234 R==APFloat::cmpEqual); 1235 } 1236 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) { 1237 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) { 1238 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) { 1239 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { 1240 Constant *C = ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, 1241 CP1->getOperand(i), 1242 CP2->getOperand(i)); 1243 if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) 1244 return CB; 1245 } 1246 // Otherwise, could not decide from any element pairs. 1247 return 0; 1248 } else if (pred == ICmpInst::ICMP_EQ) { 1249 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { 1250 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ, 1251 CP1->getOperand(i), 1252 CP2->getOperand(i)); 1253 if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) 1254 return CB; 1255 } 1256 // Otherwise, could not decide from any element pairs. 1257 return 0; 1258 } 1259 } 1260 } 1261 1262 if (C1->getType()->isFloatingPoint()) { 1263 switch (evaluateFCmpRelation(C1, C2)) { 1264 default: assert(0 && "Unknown relation!"); 1265 case FCmpInst::FCMP_UNO: 1266 case FCmpInst::FCMP_ORD: 1267 case FCmpInst::FCMP_UEQ: 1268 case FCmpInst::FCMP_UNE: 1269 case FCmpInst::FCMP_ULT: 1270 case FCmpInst::FCMP_UGT: 1271 case FCmpInst::FCMP_ULE: 1272 case FCmpInst::FCMP_UGE: 1273 case FCmpInst::FCMP_TRUE: 1274 case FCmpInst::FCMP_FALSE: 1275 case FCmpInst::BAD_FCMP_PREDICATE: 1276 break; // Couldn't determine anything about these constants. 1277 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1278 return ConstantInt::get(Type::Int1Ty, 1279 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1280 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1281 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1282 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1283 return ConstantInt::get(Type::Int1Ty, 1284 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1285 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1286 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1287 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1288 return ConstantInt::get(Type::Int1Ty, 1289 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1290 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1291 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1292 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1293 // We can only partially decide this relation. 1294 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1295 return ConstantInt::getFalse(); 1296 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1297 return ConstantInt::getTrue(); 1298 break; 1299 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1300 // We can only partially decide this relation. 1301 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1302 return ConstantInt::getFalse(); 1303 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1304 return ConstantInt::getTrue(); 1305 break; 1306 case ICmpInst::ICMP_NE: // We know that C1 != C2 1307 // We can only partially decide this relation. 1308 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1309 return ConstantInt::getFalse(); 1310 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1311 return ConstantInt::getTrue(); 1312 break; 1313 } 1314 } else { 1315 // Evaluate the relation between the two constants, per the predicate. 1316 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1317 default: assert(0 && "Unknown relational!"); 1318 case ICmpInst::BAD_ICMP_PREDICATE: 1319 break; // Couldn't determine anything about these constants. 1320 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1321 // If we know the constants are equal, we can decide the result of this 1322 // computation precisely. 1323 return ConstantInt::get(Type::Int1Ty, 1324 pred == ICmpInst::ICMP_EQ || 1325 pred == ICmpInst::ICMP_ULE || 1326 pred == ICmpInst::ICMP_SLE || 1327 pred == ICmpInst::ICMP_UGE || 1328 pred == ICmpInst::ICMP_SGE); 1329 case ICmpInst::ICMP_ULT: 1330 // If we know that C1 < C2, we can decide the result of this computation 1331 // precisely. 1332 return ConstantInt::get(Type::Int1Ty, 1333 pred == ICmpInst::ICMP_ULT || 1334 pred == ICmpInst::ICMP_NE || 1335 pred == ICmpInst::ICMP_ULE); 1336 case ICmpInst::ICMP_SLT: 1337 // If we know that C1 < C2, we can decide the result of this computation 1338 // precisely. 1339 return ConstantInt::get(Type::Int1Ty, 1340 pred == ICmpInst::ICMP_SLT || 1341 pred == ICmpInst::ICMP_NE || 1342 pred == ICmpInst::ICMP_SLE); 1343 case ICmpInst::ICMP_UGT: 1344 // If we know that C1 > C2, we can decide the result of this computation 1345 // precisely. 1346 return ConstantInt::get(Type::Int1Ty, 1347 pred == ICmpInst::ICMP_UGT || 1348 pred == ICmpInst::ICMP_NE || 1349 pred == ICmpInst::ICMP_UGE); 1350 case ICmpInst::ICMP_SGT: 1351 // If we know that C1 > C2, we can decide the result of this computation 1352 // precisely. 1353 return ConstantInt::get(Type::Int1Ty, 1354 pred == ICmpInst::ICMP_SGT || 1355 pred == ICmpInst::ICMP_NE || 1356 pred == ICmpInst::ICMP_SGE); 1357 case ICmpInst::ICMP_ULE: 1358 // If we know that C1 <= C2, we can only partially decide this relation. 1359 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse(); 1360 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue(); 1361 break; 1362 case ICmpInst::ICMP_SLE: 1363 // If we know that C1 <= C2, we can only partially decide this relation. 1364 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse(); 1365 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue(); 1366 break; 1367 1368 case ICmpInst::ICMP_UGE: 1369 // If we know that C1 >= C2, we can only partially decide this relation. 1370 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse(); 1371 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue(); 1372 break; 1373 case ICmpInst::ICMP_SGE: 1374 // If we know that C1 >= C2, we can only partially decide this relation. 1375 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse(); 1376 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue(); 1377 break; 1378 1379 case ICmpInst::ICMP_NE: 1380 // If we know that C1 != C2, we can only partially decide this relation. 1381 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(); 1382 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(); 1383 break; 1384 } 1385 1386 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) { 1387 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1388 // other way if possible. 1389 switch (pred) { 1390 case ICmpInst::ICMP_EQ: 1391 case ICmpInst::ICMP_NE: 1392 // No change of predicate required. 1393 return ConstantFoldCompareInstruction(pred, C2, C1); 1394 1395 case ICmpInst::ICMP_ULT: 1396 case ICmpInst::ICMP_SLT: 1397 case ICmpInst::ICMP_UGT: 1398 case ICmpInst::ICMP_SGT: 1399 case ICmpInst::ICMP_ULE: 1400 case ICmpInst::ICMP_SLE: 1401 case ICmpInst::ICMP_UGE: 1402 case ICmpInst::ICMP_SGE: 1403 // Change the predicate as necessary to swap the operands. 1404 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1405 return ConstantFoldCompareInstruction(pred, C2, C1); 1406 1407 default: // These predicates cannot be flopped around. 1408 break; 1409 } 1410 } 1411 } 1412 return 0; 1413} 1414 1415Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 1416 Constant* const *Idxs, 1417 unsigned NumIdx) { 1418 if (NumIdx == 0 || 1419 (NumIdx == 1 && Idxs[0]->isNullValue())) 1420 return const_cast<Constant*>(C); 1421 1422 if (isa<UndefValue>(C)) { 1423 const PointerType *Ptr = cast<PointerType>(C->getType()); 1424 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 1425 (Value **)Idxs, 1426 (Value **)Idxs+NumIdx); 1427 assert(Ty != 0 && "Invalid indices for GEP!"); 1428 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 1429 } 1430 1431 Constant *Idx0 = Idxs[0]; 1432 if (C->isNullValue()) { 1433 bool isNull = true; 1434 for (unsigned i = 0, e = NumIdx; i != e; ++i) 1435 if (!Idxs[i]->isNullValue()) { 1436 isNull = false; 1437 break; 1438 } 1439 if (isNull) { 1440 const PointerType *Ptr = cast<PointerType>(C->getType()); 1441 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 1442 (Value**)Idxs, 1443 (Value**)Idxs+NumIdx); 1444 assert(Ty != 0 && "Invalid indices for GEP!"); 1445 return 1446 ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace())); 1447 } 1448 } 1449 1450 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 1451 // Combine Indices - If the source pointer to this getelementptr instruction 1452 // is a getelementptr instruction, combine the indices of the two 1453 // getelementptr instructions into a single instruction. 1454 // 1455 if (CE->getOpcode() == Instruction::GetElementPtr) { 1456 const Type *LastTy = 0; 1457 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1458 I != E; ++I) 1459 LastTy = *I; 1460 1461 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 1462 SmallVector<Value*, 16> NewIndices; 1463 NewIndices.reserve(NumIdx + CE->getNumOperands()); 1464 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 1465 NewIndices.push_back(CE->getOperand(i)); 1466 1467 // Add the last index of the source with the first index of the new GEP. 1468 // Make sure to handle the case when they are actually different types. 1469 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 1470 // Otherwise it must be an array. 1471 if (!Idx0->isNullValue()) { 1472 const Type *IdxTy = Combined->getType(); 1473 if (IdxTy != Idx0->getType()) { 1474 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); 1475 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, 1476 Type::Int64Ty); 1477 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 1478 } else { 1479 Combined = 1480 ConstantExpr::get(Instruction::Add, Idx0, Combined); 1481 } 1482 } 1483 1484 NewIndices.push_back(Combined); 1485 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); 1486 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], 1487 NewIndices.size()); 1488 } 1489 } 1490 1491 // Implement folding of: 1492 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 1493 // long 0, long 0) 1494 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 1495 // 1496 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) { 1497 if (const PointerType *SPT = 1498 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 1499 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 1500 if (const ArrayType *CAT = 1501 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 1502 if (CAT->getElementType() == SAT->getElementType()) 1503 return ConstantExpr::getGetElementPtr( 1504 (Constant*)CE->getOperand(0), Idxs, NumIdx); 1505 } 1506 1507 // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1) 1508 // Into: inttoptr (i64 0 to i8*) 1509 // This happens with pointers to member functions in C++. 1510 if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 && 1511 isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) && 1512 cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) { 1513 Constant *Base = CE->getOperand(0); 1514 Constant *Offset = Idxs[0]; 1515 1516 // Convert the smaller integer to the larger type. 1517 if (Offset->getType()->getPrimitiveSizeInBits() < 1518 Base->getType()->getPrimitiveSizeInBits()) 1519 Offset = ConstantExpr::getSExt(Offset, Base->getType()); 1520 else if (Base->getType()->getPrimitiveSizeInBits() < 1521 Offset->getType()->getPrimitiveSizeInBits()) 1522 Base = ConstantExpr::getZExt(Base, Base->getType()); 1523 1524 Base = ConstantExpr::getAdd(Base, Offset); 1525 return ConstantExpr::getIntToPtr(Base, CE->getType()); 1526 } 1527 } 1528 return 0; 1529} 1530 1531