ConstantFold.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f
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// pieces that don't need DataLayout, and the pieces that do. This is to avoid 16// a dependence in IR on Target. 17// 18//===----------------------------------------------------------------------===// 19 20#include "ConstantFold.h" 21#include "llvm/ADT/SmallVector.h" 22#include "llvm/IR/Constants.h" 23#include "llvm/IR/DerivedTypes.h" 24#include "llvm/IR/Function.h" 25#include "llvm/IR/GetElementPtrTypeIterator.h" 26#include "llvm/IR/GlobalAlias.h" 27#include "llvm/IR/GlobalVariable.h" 28#include "llvm/IR/Instructions.h" 29#include "llvm/IR/Operator.h" 30#include "llvm/Support/Compiler.h" 31#include "llvm/Support/ErrorHandling.h" 32#include "llvm/Support/ManagedStatic.h" 33#include "llvm/Support/MathExtras.h" 34#include <limits> 35using namespace llvm; 36 37//===----------------------------------------------------------------------===// 38// ConstantFold*Instruction Implementations 39//===----------------------------------------------------------------------===// 40 41/// BitCastConstantVector - Convert the specified vector Constant node to the 42/// specified vector type. At this point, we know that the elements of the 43/// input vector constant are all simple integer or FP values. 44static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) { 45 46 if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy); 47 if (CV->isNullValue()) return Constant::getNullValue(DstTy); 48 49 // If this cast changes element count then we can't handle it here: 50 // doing so requires endianness information. This should be handled by 51 // Analysis/ConstantFolding.cpp 52 unsigned NumElts = DstTy->getNumElements(); 53 if (NumElts != CV->getType()->getVectorNumElements()) 54 return nullptr; 55 56 Type *DstEltTy = DstTy->getElementType(); 57 58 SmallVector<Constant*, 16> Result; 59 Type *Ty = IntegerType::get(CV->getContext(), 32); 60 for (unsigned i = 0; i != NumElts; ++i) { 61 Constant *C = 62 ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i)); 63 C = ConstantExpr::getBitCast(C, DstEltTy); 64 Result.push_back(C); 65 } 66 67 return ConstantVector::get(Result); 68} 69 70/// This function determines which opcode to use to fold two constant cast 71/// expressions together. It uses CastInst::isEliminableCastPair to determine 72/// the opcode. Consequently its just a wrapper around that function. 73/// @brief Determine if it is valid to fold a cast of a cast 74static unsigned 75foldConstantCastPair( 76 unsigned opc, ///< opcode of the second cast constant expression 77 ConstantExpr *Op, ///< the first cast constant expression 78 Type *DstTy ///< destination type of the first cast 79) { 80 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); 81 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); 82 assert(CastInst::isCast(opc) && "Invalid cast opcode"); 83 84 // The the types and opcodes for the two Cast constant expressions 85 Type *SrcTy = Op->getOperand(0)->getType(); 86 Type *MidTy = Op->getType(); 87 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); 88 Instruction::CastOps secondOp = Instruction::CastOps(opc); 89 90 // Assume that pointers are never more than 64 bits wide, and only use this 91 // for the middle type. Otherwise we could end up folding away illegal 92 // bitcasts between address spaces with different sizes. 93 IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext()); 94 95 // Let CastInst::isEliminableCastPair do the heavy lifting. 96 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, 97 nullptr, FakeIntPtrTy, nullptr); 98} 99 100static Constant *FoldBitCast(Constant *V, Type *DestTy) { 101 Type *SrcTy = V->getType(); 102 if (SrcTy == DestTy) 103 return V; // no-op cast 104 105 // Check to see if we are casting a pointer to an aggregate to a pointer to 106 // the first element. If so, return the appropriate GEP instruction. 107 if (PointerType *PTy = dyn_cast<PointerType>(V->getType())) 108 if (PointerType *DPTy = dyn_cast<PointerType>(DestTy)) 109 if (PTy->getAddressSpace() == DPTy->getAddressSpace() 110 && DPTy->getElementType()->isSized()) { 111 SmallVector<Value*, 8> IdxList; 112 Value *Zero = 113 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); 114 IdxList.push_back(Zero); 115 Type *ElTy = PTy->getElementType(); 116 while (ElTy != DPTy->getElementType()) { 117 if (StructType *STy = dyn_cast<StructType>(ElTy)) { 118 if (STy->getNumElements() == 0) break; 119 ElTy = STy->getElementType(0); 120 IdxList.push_back(Zero); 121 } else if (SequentialType *STy = 122 dyn_cast<SequentialType>(ElTy)) { 123 if (ElTy->isPointerTy()) break; // Can't index into pointers! 124 ElTy = STy->getElementType(); 125 IdxList.push_back(Zero); 126 } else { 127 break; 128 } 129 } 130 131 if (ElTy == DPTy->getElementType()) 132 // This GEP is inbounds because all indices are zero. 133 return ConstantExpr::getInBoundsGetElementPtr(V, IdxList); 134 } 135 136 // Handle casts from one vector constant to another. We know that the src 137 // and dest type have the same size (otherwise its an illegal cast). 138 if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { 139 if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { 140 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && 141 "Not cast between same sized vectors!"); 142 SrcTy = nullptr; 143 // First, check for null. Undef is already handled. 144 if (isa<ConstantAggregateZero>(V)) 145 return Constant::getNullValue(DestTy); 146 147 // Handle ConstantVector and ConstantAggregateVector. 148 return BitCastConstantVector(V, DestPTy); 149 } 150 151 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts 152 // This allows for other simplifications (although some of them 153 // can only be handled by Analysis/ConstantFolding.cpp). 154 if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) 155 return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy); 156 } 157 158 // Finally, implement bitcast folding now. The code below doesn't handle 159 // bitcast right. 160 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 161 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 162 163 // Handle integral constant input. 164 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 165 if (DestTy->isIntegerTy()) 166 // Integral -> Integral. This is a no-op because the bit widths must 167 // be the same. Consequently, we just fold to V. 168 return V; 169 170 if (DestTy->isFloatingPointTy()) 171 return ConstantFP::get(DestTy->getContext(), 172 APFloat(DestTy->getFltSemantics(), 173 CI->getValue())); 174 175 // Otherwise, can't fold this (vector?) 176 return nullptr; 177 } 178 179 // Handle ConstantFP input: FP -> Integral. 180 if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) 181 return ConstantInt::get(FP->getContext(), 182 FP->getValueAPF().bitcastToAPInt()); 183 184 return nullptr; 185} 186 187 188/// ExtractConstantBytes - V is an integer constant which only has a subset of 189/// its bytes used. The bytes used are indicated by ByteStart (which is the 190/// first byte used, counting from the least significant byte) and ByteSize, 191/// which is the number of bytes used. 192/// 193/// This function analyzes the specified constant to see if the specified byte 194/// range can be returned as a simplified constant. If so, the constant is 195/// returned, otherwise null is returned. 196/// 197static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart, 198 unsigned ByteSize) { 199 assert(C->getType()->isIntegerTy() && 200 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 && 201 "Non-byte sized integer input"); 202 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8; 203 assert(ByteSize && "Must be accessing some piece"); 204 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input"); 205 assert(ByteSize != CSize && "Should not extract everything"); 206 207 // Constant Integers are simple. 208 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 209 APInt V = CI->getValue(); 210 if (ByteStart) 211 V = V.lshr(ByteStart*8); 212 V = V.trunc(ByteSize*8); 213 return ConstantInt::get(CI->getContext(), V); 214 } 215 216 // In the input is a constant expr, we might be able to recursively simplify. 217 // If not, we definitely can't do anything. 218 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 219 if (!CE) return nullptr; 220 221 switch (CE->getOpcode()) { 222 default: return nullptr; 223 case Instruction::Or: { 224 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); 225 if (!RHS) 226 return nullptr; 227 228 // X | -1 -> -1. 229 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) 230 if (RHSC->isAllOnesValue()) 231 return RHSC; 232 233 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); 234 if (!LHS) 235 return nullptr; 236 return ConstantExpr::getOr(LHS, RHS); 237 } 238 case Instruction::And: { 239 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); 240 if (!RHS) 241 return nullptr; 242 243 // X & 0 -> 0. 244 if (RHS->isNullValue()) 245 return RHS; 246 247 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); 248 if (!LHS) 249 return nullptr; 250 return ConstantExpr::getAnd(LHS, RHS); 251 } 252 case Instruction::LShr: { 253 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); 254 if (!Amt) 255 return nullptr; 256 unsigned ShAmt = Amt->getZExtValue(); 257 // Cannot analyze non-byte shifts. 258 if ((ShAmt & 7) != 0) 259 return nullptr; 260 ShAmt >>= 3; 261 262 // If the extract is known to be all zeros, return zero. 263 if (ByteStart >= CSize-ShAmt) 264 return Constant::getNullValue(IntegerType::get(CE->getContext(), 265 ByteSize*8)); 266 // If the extract is known to be fully in the input, extract it. 267 if (ByteStart+ByteSize+ShAmt <= CSize) 268 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize); 269 270 // TODO: Handle the 'partially zero' case. 271 return nullptr; 272 } 273 274 case Instruction::Shl: { 275 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); 276 if (!Amt) 277 return nullptr; 278 unsigned ShAmt = Amt->getZExtValue(); 279 // Cannot analyze non-byte shifts. 280 if ((ShAmt & 7) != 0) 281 return nullptr; 282 ShAmt >>= 3; 283 284 // If the extract is known to be all zeros, return zero. 285 if (ByteStart+ByteSize <= ShAmt) 286 return Constant::getNullValue(IntegerType::get(CE->getContext(), 287 ByteSize*8)); 288 // If the extract is known to be fully in the input, extract it. 289 if (ByteStart >= ShAmt) 290 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize); 291 292 // TODO: Handle the 'partially zero' case. 293 return nullptr; 294 } 295 296 case Instruction::ZExt: { 297 unsigned SrcBitSize = 298 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth(); 299 300 // If extracting something that is completely zero, return 0. 301 if (ByteStart*8 >= SrcBitSize) 302 return Constant::getNullValue(IntegerType::get(CE->getContext(), 303 ByteSize*8)); 304 305 // If exactly extracting the input, return it. 306 if (ByteStart == 0 && ByteSize*8 == SrcBitSize) 307 return CE->getOperand(0); 308 309 // If extracting something completely in the input, if if the input is a 310 // multiple of 8 bits, recurse. 311 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize) 312 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize); 313 314 // Otherwise, if extracting a subset of the input, which is not multiple of 315 // 8 bits, do a shift and trunc to get the bits. 316 if ((ByteStart+ByteSize)*8 < SrcBitSize) { 317 assert((SrcBitSize&7) && "Shouldn't get byte sized case here"); 318 Constant *Res = CE->getOperand(0); 319 if (ByteStart) 320 Res = ConstantExpr::getLShr(Res, 321 ConstantInt::get(Res->getType(), ByteStart*8)); 322 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(), 323 ByteSize*8)); 324 } 325 326 // TODO: Handle the 'partially zero' case. 327 return nullptr; 328 } 329 } 330} 331 332/// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof 333/// on Ty, with any known factors factored out. If Folded is false, 334/// return null if no factoring was possible, to avoid endlessly 335/// bouncing an unfoldable expression back into the top-level folder. 336/// 337static Constant *getFoldedSizeOf(Type *Ty, Type *DestTy, 338 bool Folded) { 339 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 340 Constant *N = ConstantInt::get(DestTy, ATy->getNumElements()); 341 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); 342 return ConstantExpr::getNUWMul(E, N); 343 } 344 345 if (StructType *STy = dyn_cast<StructType>(Ty)) 346 if (!STy->isPacked()) { 347 unsigned NumElems = STy->getNumElements(); 348 // An empty struct has size zero. 349 if (NumElems == 0) 350 return ConstantExpr::getNullValue(DestTy); 351 // Check for a struct with all members having the same size. 352 Constant *MemberSize = 353 getFoldedSizeOf(STy->getElementType(0), DestTy, true); 354 bool AllSame = true; 355 for (unsigned i = 1; i != NumElems; ++i) 356 if (MemberSize != 357 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { 358 AllSame = false; 359 break; 360 } 361 if (AllSame) { 362 Constant *N = ConstantInt::get(DestTy, NumElems); 363 return ConstantExpr::getNUWMul(MemberSize, N); 364 } 365 } 366 367 // Pointer size doesn't depend on the pointee type, so canonicalize them 368 // to an arbitrary pointee. 369 if (PointerType *PTy = dyn_cast<PointerType>(Ty)) 370 if (!PTy->getElementType()->isIntegerTy(1)) 371 return 372 getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), 373 PTy->getAddressSpace()), 374 DestTy, true); 375 376 // If there's no interesting folding happening, bail so that we don't create 377 // a constant that looks like it needs folding but really doesn't. 378 if (!Folded) 379 return nullptr; 380 381 // Base case: Get a regular sizeof expression. 382 Constant *C = ConstantExpr::getSizeOf(Ty); 383 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 384 DestTy, false), 385 C, DestTy); 386 return C; 387} 388 389/// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof 390/// on Ty, with any known factors factored out. If Folded is false, 391/// return null if no factoring was possible, to avoid endlessly 392/// bouncing an unfoldable expression back into the top-level folder. 393/// 394static Constant *getFoldedAlignOf(Type *Ty, Type *DestTy, 395 bool Folded) { 396 // The alignment of an array is equal to the alignment of the 397 // array element. Note that this is not always true for vectors. 398 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 399 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType()); 400 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 401 DestTy, 402 false), 403 C, DestTy); 404 return C; 405 } 406 407 if (StructType *STy = dyn_cast<StructType>(Ty)) { 408 // Packed structs always have an alignment of 1. 409 if (STy->isPacked()) 410 return ConstantInt::get(DestTy, 1); 411 412 // Otherwise, struct alignment is the maximum alignment of any member. 413 // Without target data, we can't compare much, but we can check to see 414 // if all the members have the same alignment. 415 unsigned NumElems = STy->getNumElements(); 416 // An empty struct has minimal alignment. 417 if (NumElems == 0) 418 return ConstantInt::get(DestTy, 1); 419 // Check for a struct with all members having the same alignment. 420 Constant *MemberAlign = 421 getFoldedAlignOf(STy->getElementType(0), DestTy, true); 422 bool AllSame = true; 423 for (unsigned i = 1; i != NumElems; ++i) 424 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) { 425 AllSame = false; 426 break; 427 } 428 if (AllSame) 429 return MemberAlign; 430 } 431 432 // Pointer alignment doesn't depend on the pointee type, so canonicalize them 433 // to an arbitrary pointee. 434 if (PointerType *PTy = dyn_cast<PointerType>(Ty)) 435 if (!PTy->getElementType()->isIntegerTy(1)) 436 return 437 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(), 438 1), 439 PTy->getAddressSpace()), 440 DestTy, true); 441 442 // If there's no interesting folding happening, bail so that we don't create 443 // a constant that looks like it needs folding but really doesn't. 444 if (!Folded) 445 return nullptr; 446 447 // Base case: Get a regular alignof expression. 448 Constant *C = ConstantExpr::getAlignOf(Ty); 449 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 450 DestTy, false), 451 C, DestTy); 452 return C; 453} 454 455/// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof 456/// on Ty and FieldNo, with any known factors factored out. If Folded is false, 457/// return null if no factoring was possible, to avoid endlessly 458/// bouncing an unfoldable expression back into the top-level folder. 459/// 460static Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo, 461 Type *DestTy, 462 bool Folded) { 463 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 464 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, 465 DestTy, false), 466 FieldNo, DestTy); 467 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); 468 return ConstantExpr::getNUWMul(E, N); 469 } 470 471 if (StructType *STy = dyn_cast<StructType>(Ty)) 472 if (!STy->isPacked()) { 473 unsigned NumElems = STy->getNumElements(); 474 // An empty struct has no members. 475 if (NumElems == 0) 476 return nullptr; 477 // Check for a struct with all members having the same size. 478 Constant *MemberSize = 479 getFoldedSizeOf(STy->getElementType(0), DestTy, true); 480 bool AllSame = true; 481 for (unsigned i = 1; i != NumElems; ++i) 482 if (MemberSize != 483 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { 484 AllSame = false; 485 break; 486 } 487 if (AllSame) { 488 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, 489 false, 490 DestTy, 491 false), 492 FieldNo, DestTy); 493 return ConstantExpr::getNUWMul(MemberSize, N); 494 } 495 } 496 497 // If there's no interesting folding happening, bail so that we don't create 498 // a constant that looks like it needs folding but really doesn't. 499 if (!Folded) 500 return nullptr; 501 502 // Base case: Get a regular offsetof expression. 503 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo); 504 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 505 DestTy, false), 506 C, DestTy); 507 return C; 508} 509 510Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, 511 Type *DestTy) { 512 if (isa<UndefValue>(V)) { 513 // zext(undef) = 0, because the top bits will be zero. 514 // sext(undef) = 0, because the top bits will all be the same. 515 // [us]itofp(undef) = 0, because the result value is bounded. 516 if (opc == Instruction::ZExt || opc == Instruction::SExt || 517 opc == Instruction::UIToFP || opc == Instruction::SIToFP) 518 return Constant::getNullValue(DestTy); 519 return UndefValue::get(DestTy); 520 } 521 522 if (V->isNullValue() && !DestTy->isX86_MMXTy()) 523 return Constant::getNullValue(DestTy); 524 525 // If the cast operand is a constant expression, there's a few things we can 526 // do to try to simplify it. 527 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 528 if (CE->isCast()) { 529 // Try hard to fold cast of cast because they are often eliminable. 530 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 531 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 532 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 533 // If all of the indexes in the GEP are null values, there is no pointer 534 // adjustment going on. We might as well cast the source pointer. 535 bool isAllNull = true; 536 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 537 if (!CE->getOperand(i)->isNullValue()) { 538 isAllNull = false; 539 break; 540 } 541 if (isAllNull) 542 // This is casting one pointer type to another, always BitCast 543 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 544 } 545 } 546 547 // If the cast operand is a constant vector, perform the cast by 548 // operating on each element. In the cast of bitcasts, the element 549 // count may be mismatched; don't attempt to handle that here. 550 if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) && 551 DestTy->isVectorTy() && 552 DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) { 553 SmallVector<Constant*, 16> res; 554 VectorType *DestVecTy = cast<VectorType>(DestTy); 555 Type *DstEltTy = DestVecTy->getElementType(); 556 Type *Ty = IntegerType::get(V->getContext(), 32); 557 for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) { 558 Constant *C = 559 ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); 560 res.push_back(ConstantExpr::getCast(opc, C, DstEltTy)); 561 } 562 return ConstantVector::get(res); 563 } 564 565 // We actually have to do a cast now. Perform the cast according to the 566 // opcode specified. 567 switch (opc) { 568 default: 569 llvm_unreachable("Failed to cast constant expression"); 570 case Instruction::FPTrunc: 571 case Instruction::FPExt: 572 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 573 bool ignored; 574 APFloat Val = FPC->getValueAPF(); 575 Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf : 576 DestTy->isFloatTy() ? APFloat::IEEEsingle : 577 DestTy->isDoubleTy() ? APFloat::IEEEdouble : 578 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended : 579 DestTy->isFP128Ty() ? APFloat::IEEEquad : 580 DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble : 581 APFloat::Bogus, 582 APFloat::rmNearestTiesToEven, &ignored); 583 return ConstantFP::get(V->getContext(), Val); 584 } 585 return nullptr; // Can't fold. 586 case Instruction::FPToUI: 587 case Instruction::FPToSI: 588 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 589 const APFloat &V = FPC->getValueAPF(); 590 bool ignored; 591 uint64_t x[2]; 592 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 593 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 594 APFloat::rmTowardZero, &ignored); 595 APInt Val(DestBitWidth, x); 596 return ConstantInt::get(FPC->getContext(), Val); 597 } 598 return nullptr; // Can't fold. 599 case Instruction::IntToPtr: //always treated as unsigned 600 if (V->isNullValue()) // Is it an integral null value? 601 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 602 return nullptr; // Other pointer types cannot be casted 603 case Instruction::PtrToInt: // always treated as unsigned 604 // Is it a null pointer value? 605 if (V->isNullValue()) 606 return ConstantInt::get(DestTy, 0); 607 // If this is a sizeof-like expression, pull out multiplications by 608 // known factors to expose them to subsequent folding. If it's an 609 // alignof-like expression, factor out known factors. 610 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 611 if (CE->getOpcode() == Instruction::GetElementPtr && 612 CE->getOperand(0)->isNullValue()) { 613 Type *Ty = 614 cast<PointerType>(CE->getOperand(0)->getType())->getElementType(); 615 if (CE->getNumOperands() == 2) { 616 // Handle a sizeof-like expression. 617 Constant *Idx = CE->getOperand(1); 618 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne(); 619 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { 620 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, 621 DestTy, false), 622 Idx, DestTy); 623 return ConstantExpr::getMul(C, Idx); 624 } 625 } else if (CE->getNumOperands() == 3 && 626 CE->getOperand(1)->isNullValue()) { 627 // Handle an alignof-like expression. 628 if (StructType *STy = dyn_cast<StructType>(Ty)) 629 if (!STy->isPacked()) { 630 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2)); 631 if (CI->isOne() && 632 STy->getNumElements() == 2 && 633 STy->getElementType(0)->isIntegerTy(1)) { 634 return getFoldedAlignOf(STy->getElementType(1), DestTy, false); 635 } 636 } 637 // Handle an offsetof-like expression. 638 if (Ty->isStructTy() || Ty->isArrayTy()) { 639 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), 640 DestTy, false)) 641 return C; 642 } 643 } 644 } 645 // Other pointer types cannot be casted 646 return nullptr; 647 case Instruction::UIToFP: 648 case Instruction::SIToFP: 649 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 650 APInt api = CI->getValue(); 651 APFloat apf(DestTy->getFltSemantics(), 652 APInt::getNullValue(DestTy->getPrimitiveSizeInBits())); 653 (void)apf.convertFromAPInt(api, 654 opc==Instruction::SIToFP, 655 APFloat::rmNearestTiesToEven); 656 return ConstantFP::get(V->getContext(), apf); 657 } 658 return nullptr; 659 case Instruction::ZExt: 660 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 661 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 662 return ConstantInt::get(V->getContext(), 663 CI->getValue().zext(BitWidth)); 664 } 665 return nullptr; 666 case Instruction::SExt: 667 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 668 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 669 return ConstantInt::get(V->getContext(), 670 CI->getValue().sext(BitWidth)); 671 } 672 return nullptr; 673 case Instruction::Trunc: { 674 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 675 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 676 return ConstantInt::get(V->getContext(), 677 CI->getValue().trunc(DestBitWidth)); 678 } 679 680 // The input must be a constantexpr. See if we can simplify this based on 681 // the bytes we are demanding. Only do this if the source and dest are an 682 // even multiple of a byte. 683 if ((DestBitWidth & 7) == 0 && 684 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0) 685 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8)) 686 return Res; 687 688 return nullptr; 689 } 690 case Instruction::BitCast: 691 return FoldBitCast(V, DestTy); 692 case Instruction::AddrSpaceCast: 693 return nullptr; 694 } 695} 696 697Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, 698 Constant *V1, Constant *V2) { 699 // Check for i1 and vector true/false conditions. 700 if (Cond->isNullValue()) return V2; 701 if (Cond->isAllOnesValue()) return V1; 702 703 // If the condition is a vector constant, fold the result elementwise. 704 if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) { 705 SmallVector<Constant*, 16> Result; 706 Type *Ty = IntegerType::get(CondV->getContext(), 32); 707 for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){ 708 Constant *V; 709 Constant *V1Element = ConstantExpr::getExtractElement(V1, 710 ConstantInt::get(Ty, i)); 711 Constant *V2Element = ConstantExpr::getExtractElement(V2, 712 ConstantInt::get(Ty, i)); 713 Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i)); 714 if (V1Element == V2Element) { 715 V = V1Element; 716 } else if (isa<UndefValue>(Cond)) { 717 V = isa<UndefValue>(V1Element) ? V1Element : V2Element; 718 } else { 719 if (!isa<ConstantInt>(Cond)) break; 720 V = Cond->isNullValue() ? V2Element : V1Element; 721 } 722 Result.push_back(V); 723 } 724 725 // If we were able to build the vector, return it. 726 if (Result.size() == V1->getType()->getVectorNumElements()) 727 return ConstantVector::get(Result); 728 } 729 730 if (isa<UndefValue>(Cond)) { 731 if (isa<UndefValue>(V1)) return V1; 732 return V2; 733 } 734 if (isa<UndefValue>(V1)) return V2; 735 if (isa<UndefValue>(V2)) return V1; 736 if (V1 == V2) return V1; 737 738 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) { 739 if (TrueVal->getOpcode() == Instruction::Select) 740 if (TrueVal->getOperand(0) == Cond) 741 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2); 742 } 743 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) { 744 if (FalseVal->getOpcode() == Instruction::Select) 745 if (FalseVal->getOperand(0) == Cond) 746 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2)); 747 } 748 749 return nullptr; 750} 751 752Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, 753 Constant *Idx) { 754 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 755 return UndefValue::get(Val->getType()->getVectorElementType()); 756 if (Val->isNullValue()) // ee(zero, x) -> zero 757 return Constant::getNullValue(Val->getType()->getVectorElementType()); 758 // ee({w,x,y,z}, undef) -> undef 759 if (isa<UndefValue>(Idx)) 760 return UndefValue::get(Val->getType()->getVectorElementType()); 761 762 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 763 uint64_t Index = CIdx->getZExtValue(); 764 // ee({w,x,y,z}, wrong_value) -> undef 765 if (Index >= Val->getType()->getVectorNumElements()) 766 return UndefValue::get(Val->getType()->getVectorElementType()); 767 return Val->getAggregateElement(Index); 768 } 769 return nullptr; 770} 771 772Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, 773 Constant *Elt, 774 Constant *Idx) { 775 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 776 if (!CIdx) return nullptr; 777 const APInt &IdxVal = CIdx->getValue(); 778 779 SmallVector<Constant*, 16> Result; 780 Type *Ty = IntegerType::get(Val->getContext(), 32); 781 for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){ 782 if (i == IdxVal) { 783 Result.push_back(Elt); 784 continue; 785 } 786 787 Constant *C = 788 ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i)); 789 Result.push_back(C); 790 } 791 792 return ConstantVector::get(Result); 793} 794 795Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, 796 Constant *V2, 797 Constant *Mask) { 798 unsigned MaskNumElts = Mask->getType()->getVectorNumElements(); 799 Type *EltTy = V1->getType()->getVectorElementType(); 800 801 // Undefined shuffle mask -> undefined value. 802 if (isa<UndefValue>(Mask)) 803 return UndefValue::get(VectorType::get(EltTy, MaskNumElts)); 804 805 // Don't break the bitcode reader hack. 806 if (isa<ConstantExpr>(Mask)) return nullptr; 807 808 unsigned SrcNumElts = V1->getType()->getVectorNumElements(); 809 810 // Loop over the shuffle mask, evaluating each element. 811 SmallVector<Constant*, 32> Result; 812 for (unsigned i = 0; i != MaskNumElts; ++i) { 813 int Elt = ShuffleVectorInst::getMaskValue(Mask, i); 814 if (Elt == -1) { 815 Result.push_back(UndefValue::get(EltTy)); 816 continue; 817 } 818 Constant *InElt; 819 if (unsigned(Elt) >= SrcNumElts*2) 820 InElt = UndefValue::get(EltTy); 821 else if (unsigned(Elt) >= SrcNumElts) { 822 Type *Ty = IntegerType::get(V2->getContext(), 32); 823 InElt = 824 ConstantExpr::getExtractElement(V2, 825 ConstantInt::get(Ty, Elt - SrcNumElts)); 826 } else { 827 Type *Ty = IntegerType::get(V1->getContext(), 32); 828 InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt)); 829 } 830 Result.push_back(InElt); 831 } 832 833 return ConstantVector::get(Result); 834} 835 836Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, 837 ArrayRef<unsigned> Idxs) { 838 // Base case: no indices, so return the entire value. 839 if (Idxs.empty()) 840 return Agg; 841 842 if (Constant *C = Agg->getAggregateElement(Idxs[0])) 843 return ConstantFoldExtractValueInstruction(C, Idxs.slice(1)); 844 845 return nullptr; 846} 847 848Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, 849 Constant *Val, 850 ArrayRef<unsigned> Idxs) { 851 // Base case: no indices, so replace the entire value. 852 if (Idxs.empty()) 853 return Val; 854 855 unsigned NumElts; 856 if (StructType *ST = dyn_cast<StructType>(Agg->getType())) 857 NumElts = ST->getNumElements(); 858 else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) 859 NumElts = AT->getNumElements(); 860 else 861 NumElts = Agg->getType()->getVectorNumElements(); 862 863 SmallVector<Constant*, 32> Result; 864 for (unsigned i = 0; i != NumElts; ++i) { 865 Constant *C = Agg->getAggregateElement(i); 866 if (!C) return nullptr; 867 868 if (Idxs[0] == i) 869 C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1)); 870 871 Result.push_back(C); 872 } 873 874 if (StructType *ST = dyn_cast<StructType>(Agg->getType())) 875 return ConstantStruct::get(ST, Result); 876 if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) 877 return ConstantArray::get(AT, Result); 878 return ConstantVector::get(Result); 879} 880 881 882Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 883 Constant *C1, Constant *C2) { 884 // Handle UndefValue up front. 885 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 886 switch (Opcode) { 887 case Instruction::Xor: 888 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 889 // Handle undef ^ undef -> 0 special case. This is a common 890 // idiom (misuse). 891 return Constant::getNullValue(C1->getType()); 892 // Fallthrough 893 case Instruction::Add: 894 case Instruction::Sub: 895 return UndefValue::get(C1->getType()); 896 case Instruction::And: 897 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef 898 return C1; 899 return Constant::getNullValue(C1->getType()); // undef & X -> 0 900 case Instruction::Mul: { 901 ConstantInt *CI; 902 // X * undef -> undef if X is odd or undef 903 if (((CI = dyn_cast<ConstantInt>(C1)) && CI->getValue()[0]) || 904 ((CI = dyn_cast<ConstantInt>(C2)) && CI->getValue()[0]) || 905 (isa<UndefValue>(C1) && isa<UndefValue>(C2))) 906 return UndefValue::get(C1->getType()); 907 908 // X * undef -> 0 otherwise 909 return Constant::getNullValue(C1->getType()); 910 } 911 case Instruction::UDiv: 912 case Instruction::SDiv: 913 // undef / 1 -> undef 914 if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv) 915 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) 916 if (CI2->isOne()) 917 return C1; 918 // FALL THROUGH 919 case Instruction::URem: 920 case Instruction::SRem: 921 if (!isa<UndefValue>(C2)) // undef / X -> 0 922 return Constant::getNullValue(C1->getType()); 923 return C2; // X / undef -> undef 924 case Instruction::Or: // X | undef -> -1 925 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef 926 return C1; 927 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 928 case Instruction::LShr: 929 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 930 return C1; // undef lshr undef -> undef 931 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 932 // undef lshr X -> 0 933 case Instruction::AShr: 934 if (!isa<UndefValue>(C2)) // undef ashr X --> all ones 935 return Constant::getAllOnesValue(C1->getType()); 936 else if (isa<UndefValue>(C1)) 937 return C1; // undef ashr undef -> undef 938 else 939 return C1; // X ashr undef --> X 940 case Instruction::Shl: 941 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 942 return C1; // undef shl undef -> undef 943 // undef << X -> 0 or X << undef -> 0 944 return Constant::getNullValue(C1->getType()); 945 } 946 } 947 948 // Handle simplifications when the RHS is a constant int. 949 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 950 switch (Opcode) { 951 case Instruction::Add: 952 if (CI2->equalsInt(0)) return C1; // X + 0 == X 953 break; 954 case Instruction::Sub: 955 if (CI2->equalsInt(0)) return C1; // X - 0 == X 956 break; 957 case Instruction::Mul: 958 if (CI2->equalsInt(0)) return C2; // X * 0 == 0 959 if (CI2->equalsInt(1)) 960 return C1; // X * 1 == X 961 break; 962 case Instruction::UDiv: 963 case Instruction::SDiv: 964 if (CI2->equalsInt(1)) 965 return C1; // X / 1 == X 966 if (CI2->equalsInt(0)) 967 return UndefValue::get(CI2->getType()); // X / 0 == undef 968 break; 969 case Instruction::URem: 970 case Instruction::SRem: 971 if (CI2->equalsInt(1)) 972 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 973 if (CI2->equalsInt(0)) 974 return UndefValue::get(CI2->getType()); // X % 0 == undef 975 break; 976 case Instruction::And: 977 if (CI2->isZero()) return C2; // X & 0 == 0 978 if (CI2->isAllOnesValue()) 979 return C1; // X & -1 == X 980 981 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 982 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 983 if (CE1->getOpcode() == Instruction::ZExt) { 984 unsigned DstWidth = CI2->getType()->getBitWidth(); 985 unsigned SrcWidth = 986 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 987 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 988 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 989 return C1; 990 } 991 992 // If and'ing the address of a global with a constant, fold it. 993 if (CE1->getOpcode() == Instruction::PtrToInt && 994 isa<GlobalValue>(CE1->getOperand(0))) { 995 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 996 997 // Functions are at least 4-byte aligned. 998 unsigned GVAlign = GV->getAlignment(); 999 if (isa<Function>(GV)) 1000 GVAlign = std::max(GVAlign, 4U); 1001 1002 if (GVAlign > 1) { 1003 unsigned DstWidth = CI2->getType()->getBitWidth(); 1004 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 1005 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 1006 1007 // If checking bits we know are clear, return zero. 1008 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 1009 return Constant::getNullValue(CI2->getType()); 1010 } 1011 } 1012 } 1013 break; 1014 case Instruction::Or: 1015 if (CI2->equalsInt(0)) return C1; // X | 0 == X 1016 if (CI2->isAllOnesValue()) 1017 return C2; // X | -1 == -1 1018 break; 1019 case Instruction::Xor: 1020 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X 1021 1022 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1023 switch (CE1->getOpcode()) { 1024 default: break; 1025 case Instruction::ICmp: 1026 case Instruction::FCmp: 1027 // cmp pred ^ true -> cmp !pred 1028 assert(CI2->equalsInt(1)); 1029 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate(); 1030 pred = CmpInst::getInversePredicate(pred); 1031 return ConstantExpr::getCompare(pred, CE1->getOperand(0), 1032 CE1->getOperand(1)); 1033 } 1034 } 1035 break; 1036 case Instruction::AShr: 1037 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 1038 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 1039 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 1040 return ConstantExpr::getLShr(C1, C2); 1041 break; 1042 } 1043 } else if (isa<ConstantInt>(C1)) { 1044 // If C1 is a ConstantInt and C2 is not, swap the operands. 1045 if (Instruction::isCommutative(Opcode)) 1046 return ConstantExpr::get(Opcode, C2, C1); 1047 } 1048 1049 // At this point we know neither constant is an UndefValue. 1050 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 1051 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 1052 const APInt &C1V = CI1->getValue(); 1053 const APInt &C2V = CI2->getValue(); 1054 switch (Opcode) { 1055 default: 1056 break; 1057 case Instruction::Add: 1058 return ConstantInt::get(CI1->getContext(), C1V + C2V); 1059 case Instruction::Sub: 1060 return ConstantInt::get(CI1->getContext(), C1V - C2V); 1061 case Instruction::Mul: 1062 return ConstantInt::get(CI1->getContext(), C1V * C2V); 1063 case Instruction::UDiv: 1064 assert(!CI2->isNullValue() && "Div by zero handled above"); 1065 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); 1066 case Instruction::SDiv: 1067 assert(!CI2->isNullValue() && "Div by zero handled above"); 1068 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1069 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef 1070 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); 1071 case Instruction::URem: 1072 assert(!CI2->isNullValue() && "Div by zero handled above"); 1073 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); 1074 case Instruction::SRem: 1075 assert(!CI2->isNullValue() && "Div by zero handled above"); 1076 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1077 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef 1078 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); 1079 case Instruction::And: 1080 return ConstantInt::get(CI1->getContext(), C1V & C2V); 1081 case Instruction::Or: 1082 return ConstantInt::get(CI1->getContext(), C1V | C2V); 1083 case Instruction::Xor: 1084 return ConstantInt::get(CI1->getContext(), C1V ^ C2V); 1085 case Instruction::Shl: { 1086 uint32_t shiftAmt = C2V.getZExtValue(); 1087 if (shiftAmt < C1V.getBitWidth()) 1088 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt)); 1089 else 1090 return UndefValue::get(C1->getType()); // too big shift is undef 1091 } 1092 case Instruction::LShr: { 1093 uint32_t shiftAmt = C2V.getZExtValue(); 1094 if (shiftAmt < C1V.getBitWidth()) 1095 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt)); 1096 else 1097 return UndefValue::get(C1->getType()); // too big shift is undef 1098 } 1099 case Instruction::AShr: { 1100 uint32_t shiftAmt = C2V.getZExtValue(); 1101 if (shiftAmt < C1V.getBitWidth()) 1102 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt)); 1103 else 1104 return UndefValue::get(C1->getType()); // too big shift is undef 1105 } 1106 } 1107 } 1108 1109 switch (Opcode) { 1110 case Instruction::SDiv: 1111 case Instruction::UDiv: 1112 case Instruction::URem: 1113 case Instruction::SRem: 1114 case Instruction::LShr: 1115 case Instruction::AShr: 1116 case Instruction::Shl: 1117 if (CI1->equalsInt(0)) return C1; 1118 break; 1119 default: 1120 break; 1121 } 1122 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 1123 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 1124 APFloat C1V = CFP1->getValueAPF(); 1125 APFloat C2V = CFP2->getValueAPF(); 1126 APFloat C3V = C1V; // copy for modification 1127 switch (Opcode) { 1128 default: 1129 break; 1130 case Instruction::FAdd: 1131 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 1132 return ConstantFP::get(C1->getContext(), C3V); 1133 case Instruction::FSub: 1134 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 1135 return ConstantFP::get(C1->getContext(), C3V); 1136 case Instruction::FMul: 1137 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 1138 return ConstantFP::get(C1->getContext(), C3V); 1139 case Instruction::FDiv: 1140 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 1141 return ConstantFP::get(C1->getContext(), C3V); 1142 case Instruction::FRem: 1143 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 1144 return ConstantFP::get(C1->getContext(), C3V); 1145 } 1146 } 1147 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 1148 // Perform elementwise folding. 1149 SmallVector<Constant*, 16> Result; 1150 Type *Ty = IntegerType::get(VTy->getContext(), 32); 1151 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1152 Constant *LHS = 1153 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); 1154 Constant *RHS = 1155 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); 1156 1157 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS)); 1158 } 1159 1160 return ConstantVector::get(Result); 1161 } 1162 1163 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1164 // There are many possible foldings we could do here. We should probably 1165 // at least fold add of a pointer with an integer into the appropriate 1166 // getelementptr. This will improve alias analysis a bit. 1167 1168 // Given ((a + b) + c), if (b + c) folds to something interesting, return 1169 // (a + (b + c)). 1170 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) { 1171 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2); 1172 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode) 1173 return ConstantExpr::get(Opcode, CE1->getOperand(0), T); 1174 } 1175 } else if (isa<ConstantExpr>(C2)) { 1176 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1177 // other way if possible. 1178 if (Instruction::isCommutative(Opcode)) 1179 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 1180 } 1181 1182 // i1 can be simplified in many cases. 1183 if (C1->getType()->isIntegerTy(1)) { 1184 switch (Opcode) { 1185 case Instruction::Add: 1186 case Instruction::Sub: 1187 return ConstantExpr::getXor(C1, C2); 1188 case Instruction::Mul: 1189 return ConstantExpr::getAnd(C1, C2); 1190 case Instruction::Shl: 1191 case Instruction::LShr: 1192 case Instruction::AShr: 1193 // We can assume that C2 == 0. If it were one the result would be 1194 // undefined because the shift value is as large as the bitwidth. 1195 return C1; 1196 case Instruction::SDiv: 1197 case Instruction::UDiv: 1198 // We can assume that C2 == 1. If it were zero the result would be 1199 // undefined through division by zero. 1200 return C1; 1201 case Instruction::URem: 1202 case Instruction::SRem: 1203 // We can assume that C2 == 1. If it were zero the result would be 1204 // undefined through division by zero. 1205 return ConstantInt::getFalse(C1->getContext()); 1206 default: 1207 break; 1208 } 1209 } 1210 1211 // We don't know how to fold this. 1212 return nullptr; 1213} 1214 1215/// isZeroSizedType - This type is zero sized if its an array or structure of 1216/// zero sized types. The only leaf zero sized type is an empty structure. 1217static bool isMaybeZeroSizedType(Type *Ty) { 1218 if (StructType *STy = dyn_cast<StructType>(Ty)) { 1219 if (STy->isOpaque()) return true; // Can't say. 1220 1221 // If all of elements have zero size, this does too. 1222 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1223 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 1224 return true; 1225 1226 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1227 return isMaybeZeroSizedType(ATy->getElementType()); 1228 } 1229 return false; 1230} 1231 1232/// IdxCompare - Compare the two constants as though they were getelementptr 1233/// indices. This allows coersion of the types to be the same thing. 1234/// 1235/// If the two constants are the "same" (after coersion), return 0. If the 1236/// first is less than the second, return -1, if the second is less than the 1237/// first, return 1. If the constants are not integral, return -2. 1238/// 1239static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) { 1240 if (C1 == C2) return 0; 1241 1242 // Ok, we found a different index. If they are not ConstantInt, we can't do 1243 // anything with them. 1244 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 1245 return -2; // don't know! 1246 1247 // Ok, we have two differing integer indices. Sign extend them to be the same 1248 // type. Long is always big enough, so we use it. 1249 if (!C1->getType()->isIntegerTy(64)) 1250 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext())); 1251 1252 if (!C2->getType()->isIntegerTy(64)) 1253 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext())); 1254 1255 if (C1 == C2) return 0; // They are equal 1256 1257 // If the type being indexed over is really just a zero sized type, there is 1258 // no pointer difference being made here. 1259 if (isMaybeZeroSizedType(ElTy)) 1260 return -2; // dunno. 1261 1262 // If they are really different, now that they are the same type, then we 1263 // found a difference! 1264 if (cast<ConstantInt>(C1)->getSExtValue() < 1265 cast<ConstantInt>(C2)->getSExtValue()) 1266 return -1; 1267 else 1268 return 1; 1269} 1270 1271/// evaluateFCmpRelation - This function determines if there is anything we can 1272/// decide about the two constants provided. This doesn't need to handle simple 1273/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 1274/// If we can determine that the two constants have a particular relation to 1275/// each other, we should return the corresponding FCmpInst predicate, 1276/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 1277/// ConstantFoldCompareInstruction. 1278/// 1279/// To simplify this code we canonicalize the relation so that the first 1280/// operand is always the most "complex" of the two. We consider ConstantFP 1281/// to be the simplest, and ConstantExprs to be the most complex. 1282static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) { 1283 assert(V1->getType() == V2->getType() && 1284 "Cannot compare values of different types!"); 1285 1286 // Handle degenerate case quickly 1287 if (V1 == V2) return FCmpInst::FCMP_OEQ; 1288 1289 if (!isa<ConstantExpr>(V1)) { 1290 if (!isa<ConstantExpr>(V2)) { 1291 // We distilled thisUse the standard constant folder for a few cases 1292 ConstantInt *R = nullptr; 1293 R = dyn_cast<ConstantInt>( 1294 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); 1295 if (R && !R->isZero()) 1296 return FCmpInst::FCMP_OEQ; 1297 R = dyn_cast<ConstantInt>( 1298 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); 1299 if (R && !R->isZero()) 1300 return FCmpInst::FCMP_OLT; 1301 R = dyn_cast<ConstantInt>( 1302 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2)); 1303 if (R && !R->isZero()) 1304 return FCmpInst::FCMP_OGT; 1305 1306 // Nothing more we can do 1307 return FCmpInst::BAD_FCMP_PREDICATE; 1308 } 1309 1310 // If the first operand is simple and second is ConstantExpr, swap operands. 1311 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 1312 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 1313 return FCmpInst::getSwappedPredicate(SwappedRelation); 1314 } else { 1315 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1316 // constantexpr or a simple constant. 1317 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1318 switch (CE1->getOpcode()) { 1319 case Instruction::FPTrunc: 1320 case Instruction::FPExt: 1321 case Instruction::UIToFP: 1322 case Instruction::SIToFP: 1323 // We might be able to do something with these but we don't right now. 1324 break; 1325 default: 1326 break; 1327 } 1328 } 1329 // There are MANY other foldings that we could perform here. They will 1330 // probably be added on demand, as they seem needed. 1331 return FCmpInst::BAD_FCMP_PREDICATE; 1332} 1333 1334/// evaluateICmpRelation - This function determines if there is anything we can 1335/// decide about the two constants provided. This doesn't need to handle simple 1336/// things like integer comparisons, but should instead handle ConstantExprs 1337/// and GlobalValues. If we can determine that the two constants have a 1338/// particular relation to each other, we should return the corresponding ICmp 1339/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 1340/// 1341/// To simplify this code we canonicalize the relation so that the first 1342/// operand is always the most "complex" of the two. We consider simple 1343/// constants (like ConstantInt) to be the simplest, followed by 1344/// GlobalValues, followed by ConstantExpr's (the most complex). 1345/// 1346static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, 1347 bool isSigned) { 1348 assert(V1->getType() == V2->getType() && 1349 "Cannot compare different types of values!"); 1350 if (V1 == V2) return ICmpInst::ICMP_EQ; 1351 1352 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) && 1353 !isa<BlockAddress>(V1)) { 1354 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) && 1355 !isa<BlockAddress>(V2)) { 1356 // We distilled this down to a simple case, use the standard constant 1357 // folder. 1358 ConstantInt *R = nullptr; 1359 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 1360 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1361 if (R && !R->isZero()) 1362 return pred; 1363 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1364 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1365 if (R && !R->isZero()) 1366 return pred; 1367 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1368 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1369 if (R && !R->isZero()) 1370 return pred; 1371 1372 // If we couldn't figure it out, bail. 1373 return ICmpInst::BAD_ICMP_PREDICATE; 1374 } 1375 1376 // If the first operand is simple, swap operands. 1377 ICmpInst::Predicate SwappedRelation = 1378 evaluateICmpRelation(V2, V1, isSigned); 1379 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1380 return ICmpInst::getSwappedPredicate(SwappedRelation); 1381 1382 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) { 1383 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1384 ICmpInst::Predicate SwappedRelation = 1385 evaluateICmpRelation(V2, V1, isSigned); 1386 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1387 return ICmpInst::getSwappedPredicate(SwappedRelation); 1388 return ICmpInst::BAD_ICMP_PREDICATE; 1389 } 1390 1391 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1392 // constant (which, since the types must match, means that it's a 1393 // ConstantPointerNull). 1394 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1395 // Don't try to decide equality of aliases. 1396 if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2)) 1397 if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) 1398 return ICmpInst::ICMP_NE; 1399 } else if (isa<BlockAddress>(V2)) { 1400 return ICmpInst::ICMP_NE; // Globals never equal labels. 1401 } else { 1402 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 1403 // GlobalVals can never be null unless they have external weak linkage. 1404 // We don't try to evaluate aliases here. 1405 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV)) 1406 return ICmpInst::ICMP_NE; 1407 } 1408 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) { 1409 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1410 ICmpInst::Predicate SwappedRelation = 1411 evaluateICmpRelation(V2, V1, isSigned); 1412 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1413 return ICmpInst::getSwappedPredicate(SwappedRelation); 1414 return ICmpInst::BAD_ICMP_PREDICATE; 1415 } 1416 1417 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1418 // constant (which, since the types must match, means that it is a 1419 // ConstantPointerNull). 1420 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) { 1421 // Block address in another function can't equal this one, but block 1422 // addresses in the current function might be the same if blocks are 1423 // empty. 1424 if (BA2->getFunction() != BA->getFunction()) 1425 return ICmpInst::ICMP_NE; 1426 } else { 1427 // Block addresses aren't null, don't equal the address of globals. 1428 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) && 1429 "Canonicalization guarantee!"); 1430 return ICmpInst::ICMP_NE; 1431 } 1432 } else { 1433 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1434 // constantexpr, a global, block address, or a simple constant. 1435 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1436 Constant *CE1Op0 = CE1->getOperand(0); 1437 1438 switch (CE1->getOpcode()) { 1439 case Instruction::Trunc: 1440 case Instruction::FPTrunc: 1441 case Instruction::FPExt: 1442 case Instruction::FPToUI: 1443 case Instruction::FPToSI: 1444 break; // We can't evaluate floating point casts or truncations. 1445 1446 case Instruction::UIToFP: 1447 case Instruction::SIToFP: 1448 case Instruction::BitCast: 1449 case Instruction::ZExt: 1450 case Instruction::SExt: 1451 // If the cast is not actually changing bits, and the second operand is a 1452 // null pointer, do the comparison with the pre-casted value. 1453 if (V2->isNullValue() && 1454 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) { 1455 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1456 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1457 return evaluateICmpRelation(CE1Op0, 1458 Constant::getNullValue(CE1Op0->getType()), 1459 isSigned); 1460 } 1461 break; 1462 1463 case Instruction::GetElementPtr: 1464 // Ok, since this is a getelementptr, we know that the constant has a 1465 // pointer type. Check the various cases. 1466 if (isa<ConstantPointerNull>(V2)) { 1467 // If we are comparing a GEP to a null pointer, check to see if the base 1468 // of the GEP equals the null pointer. 1469 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1470 if (GV->hasExternalWeakLinkage()) 1471 // Weak linkage GVals could be zero or not. We're comparing that 1472 // to null pointer so its greater-or-equal 1473 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1474 else 1475 // If its not weak linkage, the GVal must have a non-zero address 1476 // so the result is greater-than 1477 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1478 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1479 // If we are indexing from a null pointer, check to see if we have any 1480 // non-zero indices. 1481 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1482 if (!CE1->getOperand(i)->isNullValue()) 1483 // Offsetting from null, must not be equal. 1484 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1485 // Only zero indexes from null, must still be zero. 1486 return ICmpInst::ICMP_EQ; 1487 } 1488 // Otherwise, we can't really say if the first operand is null or not. 1489 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1490 if (isa<ConstantPointerNull>(CE1Op0)) { 1491 if (GV2->hasExternalWeakLinkage()) 1492 // Weak linkage GVals could be zero or not. We're comparing it to 1493 // a null pointer, so its less-or-equal 1494 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1495 else 1496 // If its not weak linkage, the GVal must have a non-zero address 1497 // so the result is less-than 1498 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1499 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1500 if (GV == GV2) { 1501 // If this is a getelementptr of the same global, then it must be 1502 // different. Because the types must match, the getelementptr could 1503 // only have at most one index, and because we fold getelementptr's 1504 // with a single zero index, it must be nonzero. 1505 assert(CE1->getNumOperands() == 2 && 1506 !CE1->getOperand(1)->isNullValue() && 1507 "Surprising getelementptr!"); 1508 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1509 } else { 1510 // If they are different globals, we don't know what the value is. 1511 return ICmpInst::BAD_ICMP_PREDICATE; 1512 } 1513 } 1514 } else { 1515 ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1516 Constant *CE2Op0 = CE2->getOperand(0); 1517 1518 // There are MANY other foldings that we could perform here. They will 1519 // probably be added on demand, as they seem needed. 1520 switch (CE2->getOpcode()) { 1521 default: break; 1522 case Instruction::GetElementPtr: 1523 // By far the most common case to handle is when the base pointers are 1524 // obviously to the same global. 1525 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1526 if (CE1Op0 != CE2Op0) // Don't know relative ordering. 1527 return ICmpInst::BAD_ICMP_PREDICATE; 1528 // Ok, we know that both getelementptr instructions are based on the 1529 // same global. From this, we can precisely determine the relative 1530 // ordering of the resultant pointers. 1531 unsigned i = 1; 1532 1533 // The logic below assumes that the result of the comparison 1534 // can be determined by finding the first index that differs. 1535 // This doesn't work if there is over-indexing in any 1536 // subsequent indices, so check for that case first. 1537 if (!CE1->isGEPWithNoNotionalOverIndexing() || 1538 !CE2->isGEPWithNoNotionalOverIndexing()) 1539 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1540 1541 // Compare all of the operands the GEP's have in common. 1542 gep_type_iterator GTI = gep_type_begin(CE1); 1543 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1544 ++i, ++GTI) 1545 switch (IdxCompare(CE1->getOperand(i), 1546 CE2->getOperand(i), GTI.getIndexedType())) { 1547 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1548 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1549 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1550 } 1551 1552 // Ok, we ran out of things they have in common. If any leftovers 1553 // are non-zero then we have a difference, otherwise we are equal. 1554 for (; i < CE1->getNumOperands(); ++i) 1555 if (!CE1->getOperand(i)->isNullValue()) { 1556 if (isa<ConstantInt>(CE1->getOperand(i))) 1557 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1558 else 1559 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1560 } 1561 1562 for (; i < CE2->getNumOperands(); ++i) 1563 if (!CE2->getOperand(i)->isNullValue()) { 1564 if (isa<ConstantInt>(CE2->getOperand(i))) 1565 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1566 else 1567 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1568 } 1569 return ICmpInst::ICMP_EQ; 1570 } 1571 } 1572 } 1573 default: 1574 break; 1575 } 1576 } 1577 1578 return ICmpInst::BAD_ICMP_PREDICATE; 1579} 1580 1581Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1582 Constant *C1, Constant *C2) { 1583 Type *ResultTy; 1584 if (VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1585 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), 1586 VT->getNumElements()); 1587 else 1588 ResultTy = Type::getInt1Ty(C1->getContext()); 1589 1590 // Fold FCMP_FALSE/FCMP_TRUE unconditionally. 1591 if (pred == FCmpInst::FCMP_FALSE) 1592 return Constant::getNullValue(ResultTy); 1593 1594 if (pred == FCmpInst::FCMP_TRUE) 1595 return Constant::getAllOnesValue(ResultTy); 1596 1597 // Handle some degenerate cases first 1598 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 1599 // For EQ and NE, we can always pick a value for the undef to make the 1600 // predicate pass or fail, so we can return undef. 1601 // Also, if both operands are undef, we can return undef. 1602 if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) || 1603 (isa<UndefValue>(C1) && isa<UndefValue>(C2))) 1604 return UndefValue::get(ResultTy); 1605 // Otherwise, pick the same value as the non-undef operand, and fold 1606 // it to true or false. 1607 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred)); 1608 } 1609 1610 // icmp eq/ne(null,GV) -> false/true 1611 if (C1->isNullValue()) { 1612 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1613 // Don't try to evaluate aliases. External weak GV can be null. 1614 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1615 if (pred == ICmpInst::ICMP_EQ) 1616 return ConstantInt::getFalse(C1->getContext()); 1617 else if (pred == ICmpInst::ICMP_NE) 1618 return ConstantInt::getTrue(C1->getContext()); 1619 } 1620 // icmp eq/ne(GV,null) -> false/true 1621 } else if (C2->isNullValue()) { 1622 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1623 // Don't try to evaluate aliases. External weak GV can be null. 1624 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1625 if (pred == ICmpInst::ICMP_EQ) 1626 return ConstantInt::getFalse(C1->getContext()); 1627 else if (pred == ICmpInst::ICMP_NE) 1628 return ConstantInt::getTrue(C1->getContext()); 1629 } 1630 } 1631 1632 // If the comparison is a comparison between two i1's, simplify it. 1633 if (C1->getType()->isIntegerTy(1)) { 1634 switch(pred) { 1635 case ICmpInst::ICMP_EQ: 1636 if (isa<ConstantInt>(C2)) 1637 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2)); 1638 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2); 1639 case ICmpInst::ICMP_NE: 1640 return ConstantExpr::getXor(C1, C2); 1641 default: 1642 break; 1643 } 1644 } 1645 1646 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1647 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1648 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1649 switch (pred) { 1650 default: llvm_unreachable("Invalid ICmp Predicate"); 1651 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); 1652 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); 1653 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); 1654 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); 1655 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); 1656 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); 1657 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); 1658 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); 1659 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); 1660 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); 1661 } 1662 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1663 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1664 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1665 APFloat::cmpResult R = C1V.compare(C2V); 1666 switch (pred) { 1667 default: llvm_unreachable("Invalid FCmp Predicate"); 1668 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); 1669 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); 1670 case FCmpInst::FCMP_UNO: 1671 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); 1672 case FCmpInst::FCMP_ORD: 1673 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); 1674 case FCmpInst::FCMP_UEQ: 1675 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1676 R==APFloat::cmpEqual); 1677 case FCmpInst::FCMP_OEQ: 1678 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); 1679 case FCmpInst::FCMP_UNE: 1680 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); 1681 case FCmpInst::FCMP_ONE: 1682 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1683 R==APFloat::cmpGreaterThan); 1684 case FCmpInst::FCMP_ULT: 1685 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1686 R==APFloat::cmpLessThan); 1687 case FCmpInst::FCMP_OLT: 1688 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); 1689 case FCmpInst::FCMP_UGT: 1690 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1691 R==APFloat::cmpGreaterThan); 1692 case FCmpInst::FCMP_OGT: 1693 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); 1694 case FCmpInst::FCMP_ULE: 1695 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); 1696 case FCmpInst::FCMP_OLE: 1697 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1698 R==APFloat::cmpEqual); 1699 case FCmpInst::FCMP_UGE: 1700 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); 1701 case FCmpInst::FCMP_OGE: 1702 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || 1703 R==APFloat::cmpEqual); 1704 } 1705 } else if (C1->getType()->isVectorTy()) { 1706 // If we can constant fold the comparison of each element, constant fold 1707 // the whole vector comparison. 1708 SmallVector<Constant*, 4> ResElts; 1709 Type *Ty = IntegerType::get(C1->getContext(), 32); 1710 // Compare the elements, producing an i1 result or constant expr. 1711 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){ 1712 Constant *C1E = 1713 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); 1714 Constant *C2E = 1715 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); 1716 1717 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E)); 1718 } 1719 1720 return ConstantVector::get(ResElts); 1721 } 1722 1723 if (C1->getType()->isFloatingPointTy()) { 1724 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1725 switch (evaluateFCmpRelation(C1, C2)) { 1726 default: llvm_unreachable("Unknown relation!"); 1727 case FCmpInst::FCMP_UNO: 1728 case FCmpInst::FCMP_ORD: 1729 case FCmpInst::FCMP_UEQ: 1730 case FCmpInst::FCMP_UNE: 1731 case FCmpInst::FCMP_ULT: 1732 case FCmpInst::FCMP_UGT: 1733 case FCmpInst::FCMP_ULE: 1734 case FCmpInst::FCMP_UGE: 1735 case FCmpInst::FCMP_TRUE: 1736 case FCmpInst::FCMP_FALSE: 1737 case FCmpInst::BAD_FCMP_PREDICATE: 1738 break; // Couldn't determine anything about these constants. 1739 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1740 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1741 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1742 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1743 break; 1744 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1745 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1746 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1747 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1748 break; 1749 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1750 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1751 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1752 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1753 break; 1754 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1755 // We can only partially decide this relation. 1756 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1757 Result = 0; 1758 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1759 Result = 1; 1760 break; 1761 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1762 // We can only partially decide this relation. 1763 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1764 Result = 0; 1765 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1766 Result = 1; 1767 break; 1768 case FCmpInst::FCMP_ONE: // We know that C1 != C2 1769 // We can only partially decide this relation. 1770 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1771 Result = 0; 1772 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1773 Result = 1; 1774 break; 1775 } 1776 1777 // If we evaluated the result, return it now. 1778 if (Result != -1) 1779 return ConstantInt::get(ResultTy, Result); 1780 1781 } else { 1782 // Evaluate the relation between the two constants, per the predicate. 1783 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1784 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1785 default: llvm_unreachable("Unknown relational!"); 1786 case ICmpInst::BAD_ICMP_PREDICATE: 1787 break; // Couldn't determine anything about these constants. 1788 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1789 // If we know the constants are equal, we can decide the result of this 1790 // computation precisely. 1791 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred); 1792 break; 1793 case ICmpInst::ICMP_ULT: 1794 switch (pred) { 1795 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: 1796 Result = 1; break; 1797 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: 1798 Result = 0; break; 1799 } 1800 break; 1801 case ICmpInst::ICMP_SLT: 1802 switch (pred) { 1803 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: 1804 Result = 1; break; 1805 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: 1806 Result = 0; break; 1807 } 1808 break; 1809 case ICmpInst::ICMP_UGT: 1810 switch (pred) { 1811 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: 1812 Result = 1; break; 1813 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: 1814 Result = 0; break; 1815 } 1816 break; 1817 case ICmpInst::ICMP_SGT: 1818 switch (pred) { 1819 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: 1820 Result = 1; break; 1821 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: 1822 Result = 0; break; 1823 } 1824 break; 1825 case ICmpInst::ICMP_ULE: 1826 if (pred == ICmpInst::ICMP_UGT) Result = 0; 1827 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1; 1828 break; 1829 case ICmpInst::ICMP_SLE: 1830 if (pred == ICmpInst::ICMP_SGT) Result = 0; 1831 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1; 1832 break; 1833 case ICmpInst::ICMP_UGE: 1834 if (pred == ICmpInst::ICMP_ULT) Result = 0; 1835 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1; 1836 break; 1837 case ICmpInst::ICMP_SGE: 1838 if (pred == ICmpInst::ICMP_SLT) Result = 0; 1839 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1; 1840 break; 1841 case ICmpInst::ICMP_NE: 1842 if (pred == ICmpInst::ICMP_EQ) Result = 0; 1843 if (pred == ICmpInst::ICMP_NE) Result = 1; 1844 break; 1845 } 1846 1847 // If we evaluated the result, return it now. 1848 if (Result != -1) 1849 return ConstantInt::get(ResultTy, Result); 1850 1851 // If the right hand side is a bitcast, try using its inverse to simplify 1852 // it by moving it to the left hand side. We can't do this if it would turn 1853 // a vector compare into a scalar compare or visa versa. 1854 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) { 1855 Constant *CE2Op0 = CE2->getOperand(0); 1856 if (CE2->getOpcode() == Instruction::BitCast && 1857 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) { 1858 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); 1859 return ConstantExpr::getICmp(pred, Inverse, CE2Op0); 1860 } 1861 } 1862 1863 // If the left hand side is an extension, try eliminating it. 1864 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1865 if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) || 1866 (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){ 1867 Constant *CE1Op0 = CE1->getOperand(0); 1868 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); 1869 if (CE1Inverse == CE1Op0) { 1870 // Check whether we can safely truncate the right hand side. 1871 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType()); 1872 if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse, 1873 C2->getType()) == C2) 1874 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse); 1875 } 1876 } 1877 } 1878 1879 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) || 1880 (C1->isNullValue() && !C2->isNullValue())) { 1881 // If C2 is a constant expr and C1 isn't, flip them around and fold the 1882 // other way if possible. 1883 // Also, if C1 is null and C2 isn't, flip them around. 1884 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1885 return ConstantExpr::getICmp(pred, C2, C1); 1886 } 1887 } 1888 return nullptr; 1889} 1890 1891/// isInBoundsIndices - Test whether the given sequence of *normalized* indices 1892/// is "inbounds". 1893template<typename IndexTy> 1894static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) { 1895 // No indices means nothing that could be out of bounds. 1896 if (Idxs.empty()) return true; 1897 1898 // If the first index is zero, it's in bounds. 1899 if (cast<Constant>(Idxs[0])->isNullValue()) return true; 1900 1901 // If the first index is one and all the rest are zero, it's in bounds, 1902 // by the one-past-the-end rule. 1903 if (!cast<ConstantInt>(Idxs[0])->isOne()) 1904 return false; 1905 for (unsigned i = 1, e = Idxs.size(); i != e; ++i) 1906 if (!cast<Constant>(Idxs[i])->isNullValue()) 1907 return false; 1908 return true; 1909} 1910 1911/// \brief Test whether a given ConstantInt is in-range for a SequentialType. 1912static bool isIndexInRangeOfSequentialType(const SequentialType *STy, 1913 const ConstantInt *CI) { 1914 if (const PointerType *PTy = dyn_cast<PointerType>(STy)) 1915 // Only handle pointers to sized types, not pointers to functions. 1916 return PTy->getElementType()->isSized(); 1917 1918 uint64_t NumElements = 0; 1919 // Determine the number of elements in our sequential type. 1920 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy)) 1921 NumElements = ATy->getNumElements(); 1922 else if (const VectorType *VTy = dyn_cast<VectorType>(STy)) 1923 NumElements = VTy->getNumElements(); 1924 1925 assert((isa<ArrayType>(STy) || NumElements > 0) && 1926 "didn't expect non-array type to have zero elements!"); 1927 1928 // We cannot bounds check the index if it doesn't fit in an int64_t. 1929 if (CI->getValue().getActiveBits() > 64) 1930 return false; 1931 1932 // A negative index or an index past the end of our sequential type is 1933 // considered out-of-range. 1934 int64_t IndexVal = CI->getSExtValue(); 1935 if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements)) 1936 return false; 1937 1938 // Otherwise, it is in-range. 1939 return true; 1940} 1941 1942template<typename IndexTy> 1943static Constant *ConstantFoldGetElementPtrImpl(Constant *C, 1944 bool inBounds, 1945 ArrayRef<IndexTy> Idxs) { 1946 if (Idxs.empty()) return C; 1947 Constant *Idx0 = cast<Constant>(Idxs[0]); 1948 if ((Idxs.size() == 1 && Idx0->isNullValue())) 1949 return C; 1950 1951 if (isa<UndefValue>(C)) { 1952 PointerType *Ptr = cast<PointerType>(C->getType()); 1953 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs); 1954 assert(Ty && "Invalid indices for GEP!"); 1955 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 1956 } 1957 1958 if (C->isNullValue()) { 1959 bool isNull = true; 1960 for (unsigned i = 0, e = Idxs.size(); i != e; ++i) 1961 if (!cast<Constant>(Idxs[i])->isNullValue()) { 1962 isNull = false; 1963 break; 1964 } 1965 if (isNull) { 1966 PointerType *Ptr = cast<PointerType>(C->getType()); 1967 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs); 1968 assert(Ty && "Invalid indices for GEP!"); 1969 return ConstantPointerNull::get(PointerType::get(Ty, 1970 Ptr->getAddressSpace())); 1971 } 1972 } 1973 1974 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 1975 // Combine Indices - If the source pointer to this getelementptr instruction 1976 // is a getelementptr instruction, combine the indices of the two 1977 // getelementptr instructions into a single instruction. 1978 // 1979 if (CE->getOpcode() == Instruction::GetElementPtr) { 1980 Type *LastTy = nullptr; 1981 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1982 I != E; ++I) 1983 LastTy = *I; 1984 1985 // We cannot combine indices if doing so would take us outside of an 1986 // array or vector. Doing otherwise could trick us if we evaluated such a 1987 // GEP as part of a load. 1988 // 1989 // e.g. Consider if the original GEP was: 1990 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, 1991 // i32 0, i32 0, i64 0) 1992 // 1993 // If we then tried to offset it by '8' to get to the third element, 1994 // an i8, we should *not* get: 1995 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, 1996 // i32 0, i32 0, i64 8) 1997 // 1998 // This GEP tries to index array element '8 which runs out-of-bounds. 1999 // Subsequent evaluation would get confused and produce erroneous results. 2000 // 2001 // The following prohibits such a GEP from being formed by checking to see 2002 // if the index is in-range with respect to an array or vector. 2003 bool PerformFold = false; 2004 if (Idx0->isNullValue()) 2005 PerformFold = true; 2006 else if (SequentialType *STy = dyn_cast_or_null<SequentialType>(LastTy)) 2007 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0)) 2008 PerformFold = isIndexInRangeOfSequentialType(STy, CI); 2009 2010 if (PerformFold) { 2011 SmallVector<Value*, 16> NewIndices; 2012 NewIndices.reserve(Idxs.size() + CE->getNumOperands()); 2013 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 2014 NewIndices.push_back(CE->getOperand(i)); 2015 2016 // Add the last index of the source with the first index of the new GEP. 2017 // Make sure to handle the case when they are actually different types. 2018 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 2019 // Otherwise it must be an array. 2020 if (!Idx0->isNullValue()) { 2021 Type *IdxTy = Combined->getType(); 2022 if (IdxTy != Idx0->getType()) { 2023 Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext()); 2024 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty); 2025 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty); 2026 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 2027 } else { 2028 Combined = 2029 ConstantExpr::get(Instruction::Add, Idx0, Combined); 2030 } 2031 } 2032 2033 NewIndices.push_back(Combined); 2034 NewIndices.append(Idxs.begin() + 1, Idxs.end()); 2035 return 2036 ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices, 2037 inBounds && 2038 cast<GEPOperator>(CE)->isInBounds()); 2039 } 2040 } 2041 2042 // Attempt to fold casts to the same type away. For example, folding: 2043 // 2044 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*), 2045 // i64 0, i64 0) 2046 // into: 2047 // 2048 // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0) 2049 // 2050 // Don't fold if the cast is changing address spaces. 2051 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) { 2052 PointerType *SrcPtrTy = 2053 dyn_cast<PointerType>(CE->getOperand(0)->getType()); 2054 PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType()); 2055 if (SrcPtrTy && DstPtrTy) { 2056 ArrayType *SrcArrayTy = 2057 dyn_cast<ArrayType>(SrcPtrTy->getElementType()); 2058 ArrayType *DstArrayTy = 2059 dyn_cast<ArrayType>(DstPtrTy->getElementType()); 2060 if (SrcArrayTy && DstArrayTy 2061 && SrcArrayTy->getElementType() == DstArrayTy->getElementType() 2062 && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace()) 2063 return ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0), 2064 Idxs, inBounds); 2065 } 2066 } 2067 } 2068 2069 // Check to see if any array indices are not within the corresponding 2070 // notional array or vector bounds. If so, try to determine if they can be 2071 // factored out into preceding dimensions. 2072 bool Unknown = false; 2073 SmallVector<Constant *, 8> NewIdxs; 2074 Type *Ty = C->getType(); 2075 Type *Prev = nullptr; 2076 for (unsigned i = 0, e = Idxs.size(); i != e; 2077 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) { 2078 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) { 2079 if (isa<ArrayType>(Ty) || isa<VectorType>(Ty)) 2080 if (CI->getSExtValue() > 0 && 2081 !isIndexInRangeOfSequentialType(cast<SequentialType>(Ty), CI)) { 2082 if (isa<SequentialType>(Prev)) { 2083 // It's out of range, but we can factor it into the prior 2084 // dimension. 2085 NewIdxs.resize(Idxs.size()); 2086 uint64_t NumElements = 0; 2087 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) 2088 NumElements = ATy->getNumElements(); 2089 else 2090 NumElements = cast<VectorType>(Ty)->getNumElements(); 2091 2092 ConstantInt *Factor = ConstantInt::get(CI->getType(), NumElements); 2093 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor); 2094 2095 Constant *PrevIdx = cast<Constant>(Idxs[i-1]); 2096 Constant *Div = ConstantExpr::getSDiv(CI, Factor); 2097 2098 // Before adding, extend both operands to i64 to avoid 2099 // overflow trouble. 2100 if (!PrevIdx->getType()->isIntegerTy(64)) 2101 PrevIdx = ConstantExpr::getSExt(PrevIdx, 2102 Type::getInt64Ty(Div->getContext())); 2103 if (!Div->getType()->isIntegerTy(64)) 2104 Div = ConstantExpr::getSExt(Div, 2105 Type::getInt64Ty(Div->getContext())); 2106 2107 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div); 2108 } else { 2109 // It's out of range, but the prior dimension is a struct 2110 // so we can't do anything about it. 2111 Unknown = true; 2112 } 2113 } 2114 } else { 2115 // We don't know if it's in range or not. 2116 Unknown = true; 2117 } 2118 } 2119 2120 // If we did any factoring, start over with the adjusted indices. 2121 if (!NewIdxs.empty()) { 2122 for (unsigned i = 0, e = Idxs.size(); i != e; ++i) 2123 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]); 2124 return ConstantExpr::getGetElementPtr(C, NewIdxs, inBounds); 2125 } 2126 2127 // If all indices are known integers and normalized, we can do a simple 2128 // check for the "inbounds" property. 2129 if (!Unknown && !inBounds && 2130 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs)) 2131 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs); 2132 2133 return nullptr; 2134} 2135 2136Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2137 bool inBounds, 2138 ArrayRef<Constant *> Idxs) { 2139 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs); 2140} 2141 2142Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2143 bool inBounds, 2144 ArrayRef<Value *> Idxs) { 2145 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs); 2146} 2147