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> 35 using 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. 44 static 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 74 static unsigned 75 foldConstantCastPair( 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 } 99 100 static 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 /// 197 static 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 /// 337 static 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 /// 394 static 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 /// 460 static 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 } 509 510 Constant *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 // Do not fold addrspacecast (gep 0, .., 0). It might make the 534 // addrspacecast uncanonicalized. 535 opc != Instruction::AddrSpaceCast) { 536 // If all of the indexes in the GEP are null values, there is no pointer 537 // adjustment going on. We might as well cast the source pointer. 538 bool isAllNull = true; 539 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 540 if (!CE->getOperand(i)->isNullValue()) { 541 isAllNull = false; 542 break; 543 } 544 if (isAllNull) 545 // This is casting one pointer type to another, always BitCast 546 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 547 } 548 } 549 550 // If the cast operand is a constant vector, perform the cast by 551 // operating on each element. In the cast of bitcasts, the element 552 // count may be mismatched; don't attempt to handle that here. 553 if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) && 554 DestTy->isVectorTy() && 555 DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) { 556 SmallVector<Constant*, 16> res; 557 VectorType *DestVecTy = cast<VectorType>(DestTy); 558 Type *DstEltTy = DestVecTy->getElementType(); 559 Type *Ty = IntegerType::get(V->getContext(), 32); 560 for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) { 561 Constant *C = 562 ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); 563 res.push_back(ConstantExpr::getCast(opc, C, DstEltTy)); 564 } 565 return ConstantVector::get(res); 566 } 567 568 // We actually have to do a cast now. Perform the cast according to the 569 // opcode specified. 570 switch (opc) { 571 default: 572 llvm_unreachable("Failed to cast constant expression"); 573 case Instruction::FPTrunc: 574 case Instruction::FPExt: 575 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 576 bool ignored; 577 APFloat Val = FPC->getValueAPF(); 578 Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf : 579 DestTy->isFloatTy() ? APFloat::IEEEsingle : 580 DestTy->isDoubleTy() ? APFloat::IEEEdouble : 581 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended : 582 DestTy->isFP128Ty() ? APFloat::IEEEquad : 583 DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble : 584 APFloat::Bogus, 585 APFloat::rmNearestTiesToEven, &ignored); 586 return ConstantFP::get(V->getContext(), Val); 587 } 588 return nullptr; // Can't fold. 589 case Instruction::FPToUI: 590 case Instruction::FPToSI: 591 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 592 const APFloat &V = FPC->getValueAPF(); 593 bool ignored; 594 uint64_t x[2]; 595 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 596 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 597 APFloat::rmTowardZero, &ignored); 598 APInt Val(DestBitWidth, x); 599 return ConstantInt::get(FPC->getContext(), Val); 600 } 601 return nullptr; // Can't fold. 602 case Instruction::IntToPtr: //always treated as unsigned 603 if (V->isNullValue()) // Is it an integral null value? 604 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 605 return nullptr; // Other pointer types cannot be casted 606 case Instruction::PtrToInt: // always treated as unsigned 607 // Is it a null pointer value? 608 if (V->isNullValue()) 609 return ConstantInt::get(DestTy, 0); 610 // If this is a sizeof-like expression, pull out multiplications by 611 // known factors to expose them to subsequent folding. If it's an 612 // alignof-like expression, factor out known factors. 613 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 614 if (CE->getOpcode() == Instruction::GetElementPtr && 615 CE->getOperand(0)->isNullValue()) { 616 Type *Ty = 617 cast<PointerType>(CE->getOperand(0)->getType())->getElementType(); 618 if (CE->getNumOperands() == 2) { 619 // Handle a sizeof-like expression. 620 Constant *Idx = CE->getOperand(1); 621 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne(); 622 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { 623 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, 624 DestTy, false), 625 Idx, DestTy); 626 return ConstantExpr::getMul(C, Idx); 627 } 628 } else if (CE->getNumOperands() == 3 && 629 CE->getOperand(1)->isNullValue()) { 630 // Handle an alignof-like expression. 631 if (StructType *STy = dyn_cast<StructType>(Ty)) 632 if (!STy->isPacked()) { 633 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2)); 634 if (CI->isOne() && 635 STy->getNumElements() == 2 && 636 STy->getElementType(0)->isIntegerTy(1)) { 637 return getFoldedAlignOf(STy->getElementType(1), DestTy, false); 638 } 639 } 640 // Handle an offsetof-like expression. 641 if (Ty->isStructTy() || Ty->isArrayTy()) { 642 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), 643 DestTy, false)) 644 return C; 645 } 646 } 647 } 648 // Other pointer types cannot be casted 649 return nullptr; 650 case Instruction::UIToFP: 651 case Instruction::SIToFP: 652 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 653 APInt api = CI->getValue(); 654 APFloat apf(DestTy->getFltSemantics(), 655 APInt::getNullValue(DestTy->getPrimitiveSizeInBits())); 656 (void)apf.convertFromAPInt(api, 657 opc==Instruction::SIToFP, 658 APFloat::rmNearestTiesToEven); 659 return ConstantFP::get(V->getContext(), apf); 660 } 661 return nullptr; 662 case Instruction::ZExt: 663 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 664 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 665 return ConstantInt::get(V->getContext(), 666 CI->getValue().zext(BitWidth)); 667 } 668 return nullptr; 669 case Instruction::SExt: 670 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 671 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 672 return ConstantInt::get(V->getContext(), 673 CI->getValue().sext(BitWidth)); 674 } 675 return nullptr; 676 case Instruction::Trunc: { 677 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 678 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 679 return ConstantInt::get(V->getContext(), 680 CI->getValue().trunc(DestBitWidth)); 681 } 682 683 // The input must be a constantexpr. See if we can simplify this based on 684 // the bytes we are demanding. Only do this if the source and dest are an 685 // even multiple of a byte. 686 if ((DestBitWidth & 7) == 0 && 687 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0) 688 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8)) 689 return Res; 690 691 return nullptr; 692 } 693 case Instruction::BitCast: 694 return FoldBitCast(V, DestTy); 695 case Instruction::AddrSpaceCast: 696 return nullptr; 697 } 698 } 699 700 Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, 701 Constant *V1, Constant *V2) { 702 // Check for i1 and vector true/false conditions. 703 if (Cond->isNullValue()) return V2; 704 if (Cond->isAllOnesValue()) return V1; 705 706 // If the condition is a vector constant, fold the result elementwise. 707 if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) { 708 SmallVector<Constant*, 16> Result; 709 Type *Ty = IntegerType::get(CondV->getContext(), 32); 710 for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){ 711 Constant *V; 712 Constant *V1Element = ConstantExpr::getExtractElement(V1, 713 ConstantInt::get(Ty, i)); 714 Constant *V2Element = ConstantExpr::getExtractElement(V2, 715 ConstantInt::get(Ty, i)); 716 Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i)); 717 if (V1Element == V2Element) { 718 V = V1Element; 719 } else if (isa<UndefValue>(Cond)) { 720 V = isa<UndefValue>(V1Element) ? V1Element : V2Element; 721 } else { 722 if (!isa<ConstantInt>(Cond)) break; 723 V = Cond->isNullValue() ? V2Element : V1Element; 724 } 725 Result.push_back(V); 726 } 727 728 // If we were able to build the vector, return it. 729 if (Result.size() == V1->getType()->getVectorNumElements()) 730 return ConstantVector::get(Result); 731 } 732 733 if (isa<UndefValue>(Cond)) { 734 if (isa<UndefValue>(V1)) return V1; 735 return V2; 736 } 737 if (isa<UndefValue>(V1)) return V2; 738 if (isa<UndefValue>(V2)) return V1; 739 if (V1 == V2) return V1; 740 741 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) { 742 if (TrueVal->getOpcode() == Instruction::Select) 743 if (TrueVal->getOperand(0) == Cond) 744 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2); 745 } 746 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) { 747 if (FalseVal->getOpcode() == Instruction::Select) 748 if (FalseVal->getOperand(0) == Cond) 749 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2)); 750 } 751 752 return nullptr; 753 } 754 755 Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, 756 Constant *Idx) { 757 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 758 return UndefValue::get(Val->getType()->getVectorElementType()); 759 if (Val->isNullValue()) // ee(zero, x) -> zero 760 return Constant::getNullValue(Val->getType()->getVectorElementType()); 761 // ee({w,x,y,z}, undef) -> undef 762 if (isa<UndefValue>(Idx)) 763 return UndefValue::get(Val->getType()->getVectorElementType()); 764 765 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 766 uint64_t Index = CIdx->getZExtValue(); 767 // ee({w,x,y,z}, wrong_value) -> undef 768 if (Index >= Val->getType()->getVectorNumElements()) 769 return UndefValue::get(Val->getType()->getVectorElementType()); 770 return Val->getAggregateElement(Index); 771 } 772 return nullptr; 773 } 774 775 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, 776 Constant *Elt, 777 Constant *Idx) { 778 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 779 if (!CIdx) return nullptr; 780 const APInt &IdxVal = CIdx->getValue(); 781 782 SmallVector<Constant*, 16> Result; 783 Type *Ty = IntegerType::get(Val->getContext(), 32); 784 for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){ 785 if (i == IdxVal) { 786 Result.push_back(Elt); 787 continue; 788 } 789 790 Constant *C = 791 ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i)); 792 Result.push_back(C); 793 } 794 795 return ConstantVector::get(Result); 796 } 797 798 Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, 799 Constant *V2, 800 Constant *Mask) { 801 unsigned MaskNumElts = Mask->getType()->getVectorNumElements(); 802 Type *EltTy = V1->getType()->getVectorElementType(); 803 804 // Undefined shuffle mask -> undefined value. 805 if (isa<UndefValue>(Mask)) 806 return UndefValue::get(VectorType::get(EltTy, MaskNumElts)); 807 808 // Don't break the bitcode reader hack. 809 if (isa<ConstantExpr>(Mask)) return nullptr; 810 811 unsigned SrcNumElts = V1->getType()->getVectorNumElements(); 812 813 // Loop over the shuffle mask, evaluating each element. 814 SmallVector<Constant*, 32> Result; 815 for (unsigned i = 0; i != MaskNumElts; ++i) { 816 int Elt = ShuffleVectorInst::getMaskValue(Mask, i); 817 if (Elt == -1) { 818 Result.push_back(UndefValue::get(EltTy)); 819 continue; 820 } 821 Constant *InElt; 822 if (unsigned(Elt) >= SrcNumElts*2) 823 InElt = UndefValue::get(EltTy); 824 else if (unsigned(Elt) >= SrcNumElts) { 825 Type *Ty = IntegerType::get(V2->getContext(), 32); 826 InElt = 827 ConstantExpr::getExtractElement(V2, 828 ConstantInt::get(Ty, Elt - SrcNumElts)); 829 } else { 830 Type *Ty = IntegerType::get(V1->getContext(), 32); 831 InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt)); 832 } 833 Result.push_back(InElt); 834 } 835 836 return ConstantVector::get(Result); 837 } 838 839 Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, 840 ArrayRef<unsigned> Idxs) { 841 // Base case: no indices, so return the entire value. 842 if (Idxs.empty()) 843 return Agg; 844 845 if (Constant *C = Agg->getAggregateElement(Idxs[0])) 846 return ConstantFoldExtractValueInstruction(C, Idxs.slice(1)); 847 848 return nullptr; 849 } 850 851 Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, 852 Constant *Val, 853 ArrayRef<unsigned> Idxs) { 854 // Base case: no indices, so replace the entire value. 855 if (Idxs.empty()) 856 return Val; 857 858 unsigned NumElts; 859 if (StructType *ST = dyn_cast<StructType>(Agg->getType())) 860 NumElts = ST->getNumElements(); 861 else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) 862 NumElts = AT->getNumElements(); 863 else 864 NumElts = Agg->getType()->getVectorNumElements(); 865 866 SmallVector<Constant*, 32> Result; 867 for (unsigned i = 0; i != NumElts; ++i) { 868 Constant *C = Agg->getAggregateElement(i); 869 if (!C) return nullptr; 870 871 if (Idxs[0] == i) 872 C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1)); 873 874 Result.push_back(C); 875 } 876 877 if (StructType *ST = dyn_cast<StructType>(Agg->getType())) 878 return ConstantStruct::get(ST, Result); 879 if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) 880 return ConstantArray::get(AT, Result); 881 return ConstantVector::get(Result); 882 } 883 884 885 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 886 Constant *C1, Constant *C2) { 887 // Handle UndefValue up front. 888 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 889 switch (Opcode) { 890 case Instruction::Xor: 891 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 892 // Handle undef ^ undef -> 0 special case. This is a common 893 // idiom (misuse). 894 return Constant::getNullValue(C1->getType()); 895 // Fallthrough 896 case Instruction::Add: 897 case Instruction::Sub: 898 return UndefValue::get(C1->getType()); 899 case Instruction::And: 900 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef 901 return C1; 902 return Constant::getNullValue(C1->getType()); // undef & X -> 0 903 case Instruction::Mul: { 904 ConstantInt *CI; 905 // X * undef -> undef if X is odd or undef 906 if (((CI = dyn_cast<ConstantInt>(C1)) && CI->getValue()[0]) || 907 ((CI = dyn_cast<ConstantInt>(C2)) && CI->getValue()[0]) || 908 (isa<UndefValue>(C1) && isa<UndefValue>(C2))) 909 return UndefValue::get(C1->getType()); 910 911 // X * undef -> 0 otherwise 912 return Constant::getNullValue(C1->getType()); 913 } 914 case Instruction::UDiv: 915 case Instruction::SDiv: 916 // undef / 1 -> undef 917 if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv) 918 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) 919 if (CI2->isOne()) 920 return C1; 921 // FALL THROUGH 922 case Instruction::URem: 923 case Instruction::SRem: 924 if (!isa<UndefValue>(C2)) // undef / X -> 0 925 return Constant::getNullValue(C1->getType()); 926 return C2; // X / undef -> undef 927 case Instruction::Or: // X | undef -> -1 928 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef 929 return C1; 930 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 931 case Instruction::LShr: 932 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 933 return C1; // undef lshr undef -> undef 934 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 935 // undef lshr X -> 0 936 case Instruction::AShr: 937 if (!isa<UndefValue>(C2)) // undef ashr X --> all ones 938 return Constant::getAllOnesValue(C1->getType()); 939 else if (isa<UndefValue>(C1)) 940 return C1; // undef ashr undef -> undef 941 else 942 return C1; // X ashr undef --> X 943 case Instruction::Shl: 944 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 945 return C1; // undef shl undef -> undef 946 // undef << X -> 0 or X << undef -> 0 947 return Constant::getNullValue(C1->getType()); 948 } 949 } 950 951 // Handle simplifications when the RHS is a constant int. 952 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 953 switch (Opcode) { 954 case Instruction::Add: 955 if (CI2->equalsInt(0)) return C1; // X + 0 == X 956 break; 957 case Instruction::Sub: 958 if (CI2->equalsInt(0)) return C1; // X - 0 == X 959 break; 960 case Instruction::Mul: 961 if (CI2->equalsInt(0)) return C2; // X * 0 == 0 962 if (CI2->equalsInt(1)) 963 return C1; // X * 1 == X 964 break; 965 case Instruction::UDiv: 966 case Instruction::SDiv: 967 if (CI2->equalsInt(1)) 968 return C1; // X / 1 == X 969 if (CI2->equalsInt(0)) 970 return UndefValue::get(CI2->getType()); // X / 0 == undef 971 break; 972 case Instruction::URem: 973 case Instruction::SRem: 974 if (CI2->equalsInt(1)) 975 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 976 if (CI2->equalsInt(0)) 977 return UndefValue::get(CI2->getType()); // X % 0 == undef 978 break; 979 case Instruction::And: 980 if (CI2->isZero()) return C2; // X & 0 == 0 981 if (CI2->isAllOnesValue()) 982 return C1; // X & -1 == X 983 984 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 985 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 986 if (CE1->getOpcode() == Instruction::ZExt) { 987 unsigned DstWidth = CI2->getType()->getBitWidth(); 988 unsigned SrcWidth = 989 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 990 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 991 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 992 return C1; 993 } 994 995 // If and'ing the address of a global with a constant, fold it. 996 if (CE1->getOpcode() == Instruction::PtrToInt && 997 isa<GlobalValue>(CE1->getOperand(0))) { 998 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 999 1000 // Functions are at least 4-byte aligned. 1001 unsigned GVAlign = GV->getAlignment(); 1002 if (isa<Function>(GV)) 1003 GVAlign = std::max(GVAlign, 4U); 1004 1005 if (GVAlign > 1) { 1006 unsigned DstWidth = CI2->getType()->getBitWidth(); 1007 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 1008 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 1009 1010 // If checking bits we know are clear, return zero. 1011 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 1012 return Constant::getNullValue(CI2->getType()); 1013 } 1014 } 1015 } 1016 break; 1017 case Instruction::Or: 1018 if (CI2->equalsInt(0)) return C1; // X | 0 == X 1019 if (CI2->isAllOnesValue()) 1020 return C2; // X | -1 == -1 1021 break; 1022 case Instruction::Xor: 1023 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X 1024 1025 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1026 switch (CE1->getOpcode()) { 1027 default: break; 1028 case Instruction::ICmp: 1029 case Instruction::FCmp: 1030 // cmp pred ^ true -> cmp !pred 1031 assert(CI2->equalsInt(1)); 1032 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate(); 1033 pred = CmpInst::getInversePredicate(pred); 1034 return ConstantExpr::getCompare(pred, CE1->getOperand(0), 1035 CE1->getOperand(1)); 1036 } 1037 } 1038 break; 1039 case Instruction::AShr: 1040 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 1041 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 1042 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 1043 return ConstantExpr::getLShr(C1, C2); 1044 break; 1045 } 1046 } else if (isa<ConstantInt>(C1)) { 1047 // If C1 is a ConstantInt and C2 is not, swap the operands. 1048 if (Instruction::isCommutative(Opcode)) 1049 return ConstantExpr::get(Opcode, C2, C1); 1050 } 1051 1052 // At this point we know neither constant is an UndefValue. 1053 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 1054 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 1055 const APInt &C1V = CI1->getValue(); 1056 const APInt &C2V = CI2->getValue(); 1057 switch (Opcode) { 1058 default: 1059 break; 1060 case Instruction::Add: 1061 return ConstantInt::get(CI1->getContext(), C1V + C2V); 1062 case Instruction::Sub: 1063 return ConstantInt::get(CI1->getContext(), C1V - C2V); 1064 case Instruction::Mul: 1065 return ConstantInt::get(CI1->getContext(), C1V * C2V); 1066 case Instruction::UDiv: 1067 assert(!CI2->isNullValue() && "Div by zero handled above"); 1068 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); 1069 case Instruction::SDiv: 1070 assert(!CI2->isNullValue() && "Div by zero handled above"); 1071 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1072 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef 1073 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); 1074 case Instruction::URem: 1075 assert(!CI2->isNullValue() && "Div by zero handled above"); 1076 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); 1077 case Instruction::SRem: 1078 assert(!CI2->isNullValue() && "Div by zero handled above"); 1079 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1080 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef 1081 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); 1082 case Instruction::And: 1083 return ConstantInt::get(CI1->getContext(), C1V & C2V); 1084 case Instruction::Or: 1085 return ConstantInt::get(CI1->getContext(), C1V | C2V); 1086 case Instruction::Xor: 1087 return ConstantInt::get(CI1->getContext(), C1V ^ C2V); 1088 case Instruction::Shl: { 1089 uint32_t shiftAmt = C2V.getZExtValue(); 1090 if (shiftAmt < C1V.getBitWidth()) 1091 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt)); 1092 else 1093 return UndefValue::get(C1->getType()); // too big shift is undef 1094 } 1095 case Instruction::LShr: { 1096 uint32_t shiftAmt = C2V.getZExtValue(); 1097 if (shiftAmt < C1V.getBitWidth()) 1098 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt)); 1099 else 1100 return UndefValue::get(C1->getType()); // too big shift is undef 1101 } 1102 case Instruction::AShr: { 1103 uint32_t shiftAmt = C2V.getZExtValue(); 1104 if (shiftAmt < C1V.getBitWidth()) 1105 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt)); 1106 else 1107 return UndefValue::get(C1->getType()); // too big shift is undef 1108 } 1109 } 1110 } 1111 1112 switch (Opcode) { 1113 case Instruction::SDiv: 1114 case Instruction::UDiv: 1115 case Instruction::URem: 1116 case Instruction::SRem: 1117 case Instruction::LShr: 1118 case Instruction::AShr: 1119 case Instruction::Shl: 1120 if (CI1->equalsInt(0)) return C1; 1121 break; 1122 default: 1123 break; 1124 } 1125 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 1126 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 1127 APFloat C1V = CFP1->getValueAPF(); 1128 APFloat C2V = CFP2->getValueAPF(); 1129 APFloat C3V = C1V; // copy for modification 1130 switch (Opcode) { 1131 default: 1132 break; 1133 case Instruction::FAdd: 1134 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 1135 return ConstantFP::get(C1->getContext(), C3V); 1136 case Instruction::FSub: 1137 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 1138 return ConstantFP::get(C1->getContext(), C3V); 1139 case Instruction::FMul: 1140 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 1141 return ConstantFP::get(C1->getContext(), C3V); 1142 case Instruction::FDiv: 1143 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 1144 return ConstantFP::get(C1->getContext(), C3V); 1145 case Instruction::FRem: 1146 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 1147 return ConstantFP::get(C1->getContext(), C3V); 1148 } 1149 } 1150 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 1151 // Perform elementwise folding. 1152 SmallVector<Constant*, 16> Result; 1153 Type *Ty = IntegerType::get(VTy->getContext(), 32); 1154 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1155 Constant *LHS = 1156 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); 1157 Constant *RHS = 1158 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); 1159 1160 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS)); 1161 } 1162 1163 return ConstantVector::get(Result); 1164 } 1165 1166 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1167 // There are many possible foldings we could do here. We should probably 1168 // at least fold add of a pointer with an integer into the appropriate 1169 // getelementptr. This will improve alias analysis a bit. 1170 1171 // Given ((a + b) + c), if (b + c) folds to something interesting, return 1172 // (a + (b + c)). 1173 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) { 1174 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2); 1175 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode) 1176 return ConstantExpr::get(Opcode, CE1->getOperand(0), T); 1177 } 1178 } else if (isa<ConstantExpr>(C2)) { 1179 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1180 // other way if possible. 1181 if (Instruction::isCommutative(Opcode)) 1182 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 1183 } 1184 1185 // i1 can be simplified in many cases. 1186 if (C1->getType()->isIntegerTy(1)) { 1187 switch (Opcode) { 1188 case Instruction::Add: 1189 case Instruction::Sub: 1190 return ConstantExpr::getXor(C1, C2); 1191 case Instruction::Mul: 1192 return ConstantExpr::getAnd(C1, C2); 1193 case Instruction::Shl: 1194 case Instruction::LShr: 1195 case Instruction::AShr: 1196 // We can assume that C2 == 0. If it were one the result would be 1197 // undefined because the shift value is as large as the bitwidth. 1198 return C1; 1199 case Instruction::SDiv: 1200 case Instruction::UDiv: 1201 // We can assume that C2 == 1. If it were zero the result would be 1202 // undefined through division by zero. 1203 return C1; 1204 case Instruction::URem: 1205 case Instruction::SRem: 1206 // We can assume that C2 == 1. If it were zero the result would be 1207 // undefined through division by zero. 1208 return ConstantInt::getFalse(C1->getContext()); 1209 default: 1210 break; 1211 } 1212 } 1213 1214 // We don't know how to fold this. 1215 return nullptr; 1216 } 1217 1218 /// isZeroSizedType - This type is zero sized if its an array or structure of 1219 /// zero sized types. The only leaf zero sized type is an empty structure. 1220 static bool isMaybeZeroSizedType(Type *Ty) { 1221 if (StructType *STy = dyn_cast<StructType>(Ty)) { 1222 if (STy->isOpaque()) return true; // Can't say. 1223 1224 // If all of elements have zero size, this does too. 1225 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1226 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 1227 return true; 1228 1229 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1230 return isMaybeZeroSizedType(ATy->getElementType()); 1231 } 1232 return false; 1233 } 1234 1235 /// IdxCompare - Compare the two constants as though they were getelementptr 1236 /// indices. This allows coersion of the types to be the same thing. 1237 /// 1238 /// If the two constants are the "same" (after coersion), return 0. If the 1239 /// first is less than the second, return -1, if the second is less than the 1240 /// first, return 1. If the constants are not integral, return -2. 1241 /// 1242 static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) { 1243 if (C1 == C2) return 0; 1244 1245 // Ok, we found a different index. If they are not ConstantInt, we can't do 1246 // anything with them. 1247 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 1248 return -2; // don't know! 1249 1250 // Ok, we have two differing integer indices. Sign extend them to be the same 1251 // type. Long is always big enough, so we use it. 1252 if (!C1->getType()->isIntegerTy(64)) 1253 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext())); 1254 1255 if (!C2->getType()->isIntegerTy(64)) 1256 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext())); 1257 1258 if (C1 == C2) return 0; // They are equal 1259 1260 // If the type being indexed over is really just a zero sized type, there is 1261 // no pointer difference being made here. 1262 if (isMaybeZeroSizedType(ElTy)) 1263 return -2; // dunno. 1264 1265 // If they are really different, now that they are the same type, then we 1266 // found a difference! 1267 if (cast<ConstantInt>(C1)->getSExtValue() < 1268 cast<ConstantInt>(C2)->getSExtValue()) 1269 return -1; 1270 else 1271 return 1; 1272 } 1273 1274 /// evaluateFCmpRelation - This function determines if there is anything we can 1275 /// decide about the two constants provided. This doesn't need to handle simple 1276 /// things like ConstantFP comparisons, but should instead handle ConstantExprs. 1277 /// If we can determine that the two constants have a particular relation to 1278 /// each other, we should return the corresponding FCmpInst predicate, 1279 /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 1280 /// ConstantFoldCompareInstruction. 1281 /// 1282 /// To simplify this code we canonicalize the relation so that the first 1283 /// operand is always the most "complex" of the two. We consider ConstantFP 1284 /// to be the simplest, and ConstantExprs to be the most complex. 1285 static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) { 1286 assert(V1->getType() == V2->getType() && 1287 "Cannot compare values of different types!"); 1288 1289 // Handle degenerate case quickly 1290 if (V1 == V2) return FCmpInst::FCMP_OEQ; 1291 1292 if (!isa<ConstantExpr>(V1)) { 1293 if (!isa<ConstantExpr>(V2)) { 1294 // We distilled thisUse the standard constant folder for a few cases 1295 ConstantInt *R = nullptr; 1296 R = dyn_cast<ConstantInt>( 1297 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); 1298 if (R && !R->isZero()) 1299 return FCmpInst::FCMP_OEQ; 1300 R = dyn_cast<ConstantInt>( 1301 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); 1302 if (R && !R->isZero()) 1303 return FCmpInst::FCMP_OLT; 1304 R = dyn_cast<ConstantInt>( 1305 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2)); 1306 if (R && !R->isZero()) 1307 return FCmpInst::FCMP_OGT; 1308 1309 // Nothing more we can do 1310 return FCmpInst::BAD_FCMP_PREDICATE; 1311 } 1312 1313 // If the first operand is simple and second is ConstantExpr, swap operands. 1314 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 1315 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 1316 return FCmpInst::getSwappedPredicate(SwappedRelation); 1317 } else { 1318 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1319 // constantexpr or a simple constant. 1320 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1321 switch (CE1->getOpcode()) { 1322 case Instruction::FPTrunc: 1323 case Instruction::FPExt: 1324 case Instruction::UIToFP: 1325 case Instruction::SIToFP: 1326 // We might be able to do something with these but we don't right now. 1327 break; 1328 default: 1329 break; 1330 } 1331 } 1332 // There are MANY other foldings that we could perform here. They will 1333 // probably be added on demand, as they seem needed. 1334 return FCmpInst::BAD_FCMP_PREDICATE; 1335 } 1336 1337 static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1, 1338 const GlobalValue *GV2) { 1339 // Don't try to decide equality of aliases. 1340 if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2)) 1341 if (!GV1->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) 1342 return ICmpInst::ICMP_NE; 1343 return ICmpInst::BAD_ICMP_PREDICATE; 1344 } 1345 1346 /// evaluateICmpRelation - This function determines if there is anything we can 1347 /// decide about the two constants provided. This doesn't need to handle simple 1348 /// things like integer comparisons, but should instead handle ConstantExprs 1349 /// and GlobalValues. If we can determine that the two constants have a 1350 /// particular relation to each other, we should return the corresponding ICmp 1351 /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 1352 /// 1353 /// To simplify this code we canonicalize the relation so that the first 1354 /// operand is always the most "complex" of the two. We consider simple 1355 /// constants (like ConstantInt) to be the simplest, followed by 1356 /// GlobalValues, followed by ConstantExpr's (the most complex). 1357 /// 1358 static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, 1359 bool isSigned) { 1360 assert(V1->getType() == V2->getType() && 1361 "Cannot compare different types of values!"); 1362 if (V1 == V2) return ICmpInst::ICMP_EQ; 1363 1364 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) && 1365 !isa<BlockAddress>(V1)) { 1366 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) && 1367 !isa<BlockAddress>(V2)) { 1368 // We distilled this down to a simple case, use the standard constant 1369 // folder. 1370 ConstantInt *R = nullptr; 1371 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 1372 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1373 if (R && !R->isZero()) 1374 return pred; 1375 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1376 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1377 if (R && !R->isZero()) 1378 return pred; 1379 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1380 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1381 if (R && !R->isZero()) 1382 return pred; 1383 1384 // If we couldn't figure it out, bail. 1385 return ICmpInst::BAD_ICMP_PREDICATE; 1386 } 1387 1388 // If the first operand is simple, swap operands. 1389 ICmpInst::Predicate SwappedRelation = 1390 evaluateICmpRelation(V2, V1, isSigned); 1391 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1392 return ICmpInst::getSwappedPredicate(SwappedRelation); 1393 1394 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) { 1395 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1396 ICmpInst::Predicate SwappedRelation = 1397 evaluateICmpRelation(V2, V1, isSigned); 1398 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1399 return ICmpInst::getSwappedPredicate(SwappedRelation); 1400 return ICmpInst::BAD_ICMP_PREDICATE; 1401 } 1402 1403 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1404 // constant (which, since the types must match, means that it's a 1405 // ConstantPointerNull). 1406 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1407 return areGlobalsPotentiallyEqual(GV, GV2); 1408 } else if (isa<BlockAddress>(V2)) { 1409 return ICmpInst::ICMP_NE; // Globals never equal labels. 1410 } else { 1411 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 1412 // GlobalVals can never be null unless they have external weak linkage. 1413 // We don't try to evaluate aliases here. 1414 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV)) 1415 return ICmpInst::ICMP_NE; 1416 } 1417 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) { 1418 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1419 ICmpInst::Predicate SwappedRelation = 1420 evaluateICmpRelation(V2, V1, isSigned); 1421 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1422 return ICmpInst::getSwappedPredicate(SwappedRelation); 1423 return ICmpInst::BAD_ICMP_PREDICATE; 1424 } 1425 1426 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1427 // constant (which, since the types must match, means that it is a 1428 // ConstantPointerNull). 1429 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) { 1430 // Block address in another function can't equal this one, but block 1431 // addresses in the current function might be the same if blocks are 1432 // empty. 1433 if (BA2->getFunction() != BA->getFunction()) 1434 return ICmpInst::ICMP_NE; 1435 } else { 1436 // Block addresses aren't null, don't equal the address of globals. 1437 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) && 1438 "Canonicalization guarantee!"); 1439 return ICmpInst::ICMP_NE; 1440 } 1441 } else { 1442 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1443 // constantexpr, a global, block address, or a simple constant. 1444 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1445 Constant *CE1Op0 = CE1->getOperand(0); 1446 1447 switch (CE1->getOpcode()) { 1448 case Instruction::Trunc: 1449 case Instruction::FPTrunc: 1450 case Instruction::FPExt: 1451 case Instruction::FPToUI: 1452 case Instruction::FPToSI: 1453 break; // We can't evaluate floating point casts or truncations. 1454 1455 case Instruction::UIToFP: 1456 case Instruction::SIToFP: 1457 case Instruction::BitCast: 1458 case Instruction::ZExt: 1459 case Instruction::SExt: 1460 // If the cast is not actually changing bits, and the second operand is a 1461 // null pointer, do the comparison with the pre-casted value. 1462 if (V2->isNullValue() && 1463 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) { 1464 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1465 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1466 return evaluateICmpRelation(CE1Op0, 1467 Constant::getNullValue(CE1Op0->getType()), 1468 isSigned); 1469 } 1470 break; 1471 1472 case Instruction::GetElementPtr: { 1473 GEPOperator *CE1GEP = cast<GEPOperator>(CE1); 1474 // Ok, since this is a getelementptr, we know that the constant has a 1475 // pointer type. Check the various cases. 1476 if (isa<ConstantPointerNull>(V2)) { 1477 // If we are comparing a GEP to a null pointer, check to see if the base 1478 // of the GEP equals the null pointer. 1479 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1480 if (GV->hasExternalWeakLinkage()) 1481 // Weak linkage GVals could be zero or not. We're comparing that 1482 // to null pointer so its greater-or-equal 1483 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1484 else 1485 // If its not weak linkage, the GVal must have a non-zero address 1486 // so the result is greater-than 1487 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1488 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1489 // If we are indexing from a null pointer, check to see if we have any 1490 // non-zero indices. 1491 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1492 if (!CE1->getOperand(i)->isNullValue()) 1493 // Offsetting from null, must not be equal. 1494 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1495 // Only zero indexes from null, must still be zero. 1496 return ICmpInst::ICMP_EQ; 1497 } 1498 // Otherwise, we can't really say if the first operand is null or not. 1499 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1500 if (isa<ConstantPointerNull>(CE1Op0)) { 1501 if (GV2->hasExternalWeakLinkage()) 1502 // Weak linkage GVals could be zero or not. We're comparing it to 1503 // a null pointer, so its less-or-equal 1504 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1505 else 1506 // If its not weak linkage, the GVal must have a non-zero address 1507 // so the result is less-than 1508 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1509 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1510 if (GV == GV2) { 1511 // If this is a getelementptr of the same global, then it must be 1512 // different. Because the types must match, the getelementptr could 1513 // only have at most one index, and because we fold getelementptr's 1514 // with a single zero index, it must be nonzero. 1515 assert(CE1->getNumOperands() == 2 && 1516 !CE1->getOperand(1)->isNullValue() && 1517 "Surprising getelementptr!"); 1518 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1519 } else { 1520 if (CE1GEP->hasAllZeroIndices()) 1521 return areGlobalsPotentiallyEqual(GV, GV2); 1522 return ICmpInst::BAD_ICMP_PREDICATE; 1523 } 1524 } 1525 } else { 1526 ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1527 Constant *CE2Op0 = CE2->getOperand(0); 1528 1529 // There are MANY other foldings that we could perform here. They will 1530 // probably be added on demand, as they seem needed. 1531 switch (CE2->getOpcode()) { 1532 default: break; 1533 case Instruction::GetElementPtr: 1534 // By far the most common case to handle is when the base pointers are 1535 // obviously to the same global. 1536 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1537 // Don't know relative ordering, but check for inequality. 1538 if (CE1Op0 != CE2Op0) { 1539 GEPOperator *CE2GEP = cast<GEPOperator>(CE2); 1540 if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices()) 1541 return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0), 1542 cast<GlobalValue>(CE2Op0)); 1543 return ICmpInst::BAD_ICMP_PREDICATE; 1544 } 1545 // Ok, we know that both getelementptr instructions are based on the 1546 // same global. From this, we can precisely determine the relative 1547 // ordering of the resultant pointers. 1548 unsigned i = 1; 1549 1550 // The logic below assumes that the result of the comparison 1551 // can be determined by finding the first index that differs. 1552 // This doesn't work if there is over-indexing in any 1553 // subsequent indices, so check for that case first. 1554 if (!CE1->isGEPWithNoNotionalOverIndexing() || 1555 !CE2->isGEPWithNoNotionalOverIndexing()) 1556 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1557 1558 // Compare all of the operands the GEP's have in common. 1559 gep_type_iterator GTI = gep_type_begin(CE1); 1560 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1561 ++i, ++GTI) 1562 switch (IdxCompare(CE1->getOperand(i), 1563 CE2->getOperand(i), GTI.getIndexedType())) { 1564 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1565 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1566 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1567 } 1568 1569 // Ok, we ran out of things they have in common. If any leftovers 1570 // are non-zero then we have a difference, otherwise we are equal. 1571 for (; i < CE1->getNumOperands(); ++i) 1572 if (!CE1->getOperand(i)->isNullValue()) { 1573 if (isa<ConstantInt>(CE1->getOperand(i))) 1574 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1575 else 1576 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1577 } 1578 1579 for (; i < CE2->getNumOperands(); ++i) 1580 if (!CE2->getOperand(i)->isNullValue()) { 1581 if (isa<ConstantInt>(CE2->getOperand(i))) 1582 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1583 else 1584 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1585 } 1586 return ICmpInst::ICMP_EQ; 1587 } 1588 } 1589 } 1590 } 1591 default: 1592 break; 1593 } 1594 } 1595 1596 return ICmpInst::BAD_ICMP_PREDICATE; 1597 } 1598 1599 Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1600 Constant *C1, Constant *C2) { 1601 Type *ResultTy; 1602 if (VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1603 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), 1604 VT->getNumElements()); 1605 else 1606 ResultTy = Type::getInt1Ty(C1->getContext()); 1607 1608 // Fold FCMP_FALSE/FCMP_TRUE unconditionally. 1609 if (pred == FCmpInst::FCMP_FALSE) 1610 return Constant::getNullValue(ResultTy); 1611 1612 if (pred == FCmpInst::FCMP_TRUE) 1613 return Constant::getAllOnesValue(ResultTy); 1614 1615 // Handle some degenerate cases first 1616 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 1617 // For EQ and NE, we can always pick a value for the undef to make the 1618 // predicate pass or fail, so we can return undef. 1619 // Also, if both operands are undef, we can return undef. 1620 if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) || 1621 (isa<UndefValue>(C1) && isa<UndefValue>(C2))) 1622 return UndefValue::get(ResultTy); 1623 // Otherwise, pick the same value as the non-undef operand, and fold 1624 // it to true or false. 1625 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred)); 1626 } 1627 1628 // icmp eq/ne(null,GV) -> false/true 1629 if (C1->isNullValue()) { 1630 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1631 // Don't try to evaluate aliases. External weak GV can be null. 1632 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1633 if (pred == ICmpInst::ICMP_EQ) 1634 return ConstantInt::getFalse(C1->getContext()); 1635 else if (pred == ICmpInst::ICMP_NE) 1636 return ConstantInt::getTrue(C1->getContext()); 1637 } 1638 // icmp eq/ne(GV,null) -> false/true 1639 } else if (C2->isNullValue()) { 1640 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1641 // Don't try to evaluate aliases. External weak GV can be null. 1642 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1643 if (pred == ICmpInst::ICMP_EQ) 1644 return ConstantInt::getFalse(C1->getContext()); 1645 else if (pred == ICmpInst::ICMP_NE) 1646 return ConstantInt::getTrue(C1->getContext()); 1647 } 1648 } 1649 1650 // If the comparison is a comparison between two i1's, simplify it. 1651 if (C1->getType()->isIntegerTy(1)) { 1652 switch(pred) { 1653 case ICmpInst::ICMP_EQ: 1654 if (isa<ConstantInt>(C2)) 1655 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2)); 1656 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2); 1657 case ICmpInst::ICMP_NE: 1658 return ConstantExpr::getXor(C1, C2); 1659 default: 1660 break; 1661 } 1662 } 1663 1664 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1665 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1666 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1667 switch (pred) { 1668 default: llvm_unreachable("Invalid ICmp Predicate"); 1669 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); 1670 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); 1671 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); 1672 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); 1673 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); 1674 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); 1675 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); 1676 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); 1677 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); 1678 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); 1679 } 1680 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1681 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1682 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1683 APFloat::cmpResult R = C1V.compare(C2V); 1684 switch (pred) { 1685 default: llvm_unreachable("Invalid FCmp Predicate"); 1686 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); 1687 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); 1688 case FCmpInst::FCMP_UNO: 1689 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); 1690 case FCmpInst::FCMP_ORD: 1691 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); 1692 case FCmpInst::FCMP_UEQ: 1693 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1694 R==APFloat::cmpEqual); 1695 case FCmpInst::FCMP_OEQ: 1696 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); 1697 case FCmpInst::FCMP_UNE: 1698 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); 1699 case FCmpInst::FCMP_ONE: 1700 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1701 R==APFloat::cmpGreaterThan); 1702 case FCmpInst::FCMP_ULT: 1703 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1704 R==APFloat::cmpLessThan); 1705 case FCmpInst::FCMP_OLT: 1706 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); 1707 case FCmpInst::FCMP_UGT: 1708 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1709 R==APFloat::cmpGreaterThan); 1710 case FCmpInst::FCMP_OGT: 1711 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); 1712 case FCmpInst::FCMP_ULE: 1713 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); 1714 case FCmpInst::FCMP_OLE: 1715 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1716 R==APFloat::cmpEqual); 1717 case FCmpInst::FCMP_UGE: 1718 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); 1719 case FCmpInst::FCMP_OGE: 1720 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || 1721 R==APFloat::cmpEqual); 1722 } 1723 } else if (C1->getType()->isVectorTy()) { 1724 // If we can constant fold the comparison of each element, constant fold 1725 // the whole vector comparison. 1726 SmallVector<Constant*, 4> ResElts; 1727 Type *Ty = IntegerType::get(C1->getContext(), 32); 1728 // Compare the elements, producing an i1 result or constant expr. 1729 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){ 1730 Constant *C1E = 1731 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); 1732 Constant *C2E = 1733 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); 1734 1735 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E)); 1736 } 1737 1738 return ConstantVector::get(ResElts); 1739 } 1740 1741 if (C1->getType()->isFloatingPointTy()) { 1742 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1743 switch (evaluateFCmpRelation(C1, C2)) { 1744 default: llvm_unreachable("Unknown relation!"); 1745 case FCmpInst::FCMP_UNO: 1746 case FCmpInst::FCMP_ORD: 1747 case FCmpInst::FCMP_UEQ: 1748 case FCmpInst::FCMP_UNE: 1749 case FCmpInst::FCMP_ULT: 1750 case FCmpInst::FCMP_UGT: 1751 case FCmpInst::FCMP_ULE: 1752 case FCmpInst::FCMP_UGE: 1753 case FCmpInst::FCMP_TRUE: 1754 case FCmpInst::FCMP_FALSE: 1755 case FCmpInst::BAD_FCMP_PREDICATE: 1756 break; // Couldn't determine anything about these constants. 1757 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1758 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1759 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1760 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1761 break; 1762 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1763 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1764 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1765 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1766 break; 1767 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1768 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1769 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1770 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1771 break; 1772 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1773 // We can only partially decide this relation. 1774 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1775 Result = 0; 1776 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1777 Result = 1; 1778 break; 1779 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1780 // We can only partially decide this relation. 1781 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1782 Result = 0; 1783 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1784 Result = 1; 1785 break; 1786 case FCmpInst::FCMP_ONE: // We know that C1 != C2 1787 // We can only partially decide this relation. 1788 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1789 Result = 0; 1790 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1791 Result = 1; 1792 break; 1793 } 1794 1795 // If we evaluated the result, return it now. 1796 if (Result != -1) 1797 return ConstantInt::get(ResultTy, Result); 1798 1799 } else { 1800 // Evaluate the relation between the two constants, per the predicate. 1801 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1802 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1803 default: llvm_unreachable("Unknown relational!"); 1804 case ICmpInst::BAD_ICMP_PREDICATE: 1805 break; // Couldn't determine anything about these constants. 1806 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1807 // If we know the constants are equal, we can decide the result of this 1808 // computation precisely. 1809 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred); 1810 break; 1811 case ICmpInst::ICMP_ULT: 1812 switch (pred) { 1813 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: 1814 Result = 1; break; 1815 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: 1816 Result = 0; break; 1817 } 1818 break; 1819 case ICmpInst::ICMP_SLT: 1820 switch (pred) { 1821 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: 1822 Result = 1; break; 1823 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: 1824 Result = 0; break; 1825 } 1826 break; 1827 case ICmpInst::ICMP_UGT: 1828 switch (pred) { 1829 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: 1830 Result = 1; break; 1831 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: 1832 Result = 0; break; 1833 } 1834 break; 1835 case ICmpInst::ICMP_SGT: 1836 switch (pred) { 1837 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: 1838 Result = 1; break; 1839 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: 1840 Result = 0; break; 1841 } 1842 break; 1843 case ICmpInst::ICMP_ULE: 1844 if (pred == ICmpInst::ICMP_UGT) Result = 0; 1845 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1; 1846 break; 1847 case ICmpInst::ICMP_SLE: 1848 if (pred == ICmpInst::ICMP_SGT) Result = 0; 1849 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1; 1850 break; 1851 case ICmpInst::ICMP_UGE: 1852 if (pred == ICmpInst::ICMP_ULT) Result = 0; 1853 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1; 1854 break; 1855 case ICmpInst::ICMP_SGE: 1856 if (pred == ICmpInst::ICMP_SLT) Result = 0; 1857 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1; 1858 break; 1859 case ICmpInst::ICMP_NE: 1860 if (pred == ICmpInst::ICMP_EQ) Result = 0; 1861 if (pred == ICmpInst::ICMP_NE) Result = 1; 1862 break; 1863 } 1864 1865 // If we evaluated the result, return it now. 1866 if (Result != -1) 1867 return ConstantInt::get(ResultTy, Result); 1868 1869 // If the right hand side is a bitcast, try using its inverse to simplify 1870 // it by moving it to the left hand side. We can't do this if it would turn 1871 // a vector compare into a scalar compare or visa versa. 1872 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) { 1873 Constant *CE2Op0 = CE2->getOperand(0); 1874 if (CE2->getOpcode() == Instruction::BitCast && 1875 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) { 1876 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); 1877 return ConstantExpr::getICmp(pred, Inverse, CE2Op0); 1878 } 1879 } 1880 1881 // If the left hand side is an extension, try eliminating it. 1882 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1883 if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) || 1884 (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){ 1885 Constant *CE1Op0 = CE1->getOperand(0); 1886 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); 1887 if (CE1Inverse == CE1Op0) { 1888 // Check whether we can safely truncate the right hand side. 1889 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType()); 1890 if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse, 1891 C2->getType()) == C2) 1892 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse); 1893 } 1894 } 1895 } 1896 1897 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) || 1898 (C1->isNullValue() && !C2->isNullValue())) { 1899 // If C2 is a constant expr and C1 isn't, flip them around and fold the 1900 // other way if possible. 1901 // Also, if C1 is null and C2 isn't, flip them around. 1902 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1903 return ConstantExpr::getICmp(pred, C2, C1); 1904 } 1905 } 1906 return nullptr; 1907 } 1908 1909 /// isInBoundsIndices - Test whether the given sequence of *normalized* indices 1910 /// is "inbounds". 1911 template<typename IndexTy> 1912 static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) { 1913 // No indices means nothing that could be out of bounds. 1914 if (Idxs.empty()) return true; 1915 1916 // If the first index is zero, it's in bounds. 1917 if (cast<Constant>(Idxs[0])->isNullValue()) return true; 1918 1919 // If the first index is one and all the rest are zero, it's in bounds, 1920 // by the one-past-the-end rule. 1921 if (!cast<ConstantInt>(Idxs[0])->isOne()) 1922 return false; 1923 for (unsigned i = 1, e = Idxs.size(); i != e; ++i) 1924 if (!cast<Constant>(Idxs[i])->isNullValue()) 1925 return false; 1926 return true; 1927 } 1928 1929 /// \brief Test whether a given ConstantInt is in-range for a SequentialType. 1930 static bool isIndexInRangeOfSequentialType(const SequentialType *STy, 1931 const ConstantInt *CI) { 1932 if (const PointerType *PTy = dyn_cast<PointerType>(STy)) 1933 // Only handle pointers to sized types, not pointers to functions. 1934 return PTy->getElementType()->isSized(); 1935 1936 uint64_t NumElements = 0; 1937 // Determine the number of elements in our sequential type. 1938 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy)) 1939 NumElements = ATy->getNumElements(); 1940 else if (const VectorType *VTy = dyn_cast<VectorType>(STy)) 1941 NumElements = VTy->getNumElements(); 1942 1943 assert((isa<ArrayType>(STy) || NumElements > 0) && 1944 "didn't expect non-array type to have zero elements!"); 1945 1946 // We cannot bounds check the index if it doesn't fit in an int64_t. 1947 if (CI->getValue().getActiveBits() > 64) 1948 return false; 1949 1950 // A negative index or an index past the end of our sequential type is 1951 // considered out-of-range. 1952 int64_t IndexVal = CI->getSExtValue(); 1953 if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements)) 1954 return false; 1955 1956 // Otherwise, it is in-range. 1957 return true; 1958 } 1959 1960 template<typename IndexTy> 1961 static Constant *ConstantFoldGetElementPtrImpl(Constant *C, 1962 bool inBounds, 1963 ArrayRef<IndexTy> Idxs) { 1964 if (Idxs.empty()) return C; 1965 Constant *Idx0 = cast<Constant>(Idxs[0]); 1966 if ((Idxs.size() == 1 && Idx0->isNullValue())) 1967 return C; 1968 1969 if (isa<UndefValue>(C)) { 1970 PointerType *Ptr = cast<PointerType>(C->getType()); 1971 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs); 1972 assert(Ty && "Invalid indices for GEP!"); 1973 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 1974 } 1975 1976 if (C->isNullValue()) { 1977 bool isNull = true; 1978 for (unsigned i = 0, e = Idxs.size(); i != e; ++i) 1979 if (!cast<Constant>(Idxs[i])->isNullValue()) { 1980 isNull = false; 1981 break; 1982 } 1983 if (isNull) { 1984 PointerType *Ptr = cast<PointerType>(C->getType()); 1985 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs); 1986 assert(Ty && "Invalid indices for GEP!"); 1987 return ConstantPointerNull::get(PointerType::get(Ty, 1988 Ptr->getAddressSpace())); 1989 } 1990 } 1991 1992 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 1993 // Combine Indices - If the source pointer to this getelementptr instruction 1994 // is a getelementptr instruction, combine the indices of the two 1995 // getelementptr instructions into a single instruction. 1996 // 1997 if (CE->getOpcode() == Instruction::GetElementPtr) { 1998 Type *LastTy = nullptr; 1999 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 2000 I != E; ++I) 2001 LastTy = *I; 2002 2003 // We cannot combine indices if doing so would take us outside of an 2004 // array or vector. Doing otherwise could trick us if we evaluated such a 2005 // GEP as part of a load. 2006 // 2007 // e.g. Consider if the original GEP was: 2008 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, 2009 // i32 0, i32 0, i64 0) 2010 // 2011 // If we then tried to offset it by '8' to get to the third element, 2012 // an i8, we should *not* get: 2013 // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, 2014 // i32 0, i32 0, i64 8) 2015 // 2016 // This GEP tries to index array element '8 which runs out-of-bounds. 2017 // Subsequent evaluation would get confused and produce erroneous results. 2018 // 2019 // The following prohibits such a GEP from being formed by checking to see 2020 // if the index is in-range with respect to an array or vector. 2021 bool PerformFold = false; 2022 if (Idx0->isNullValue()) 2023 PerformFold = true; 2024 else if (SequentialType *STy = dyn_cast_or_null<SequentialType>(LastTy)) 2025 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0)) 2026 PerformFold = isIndexInRangeOfSequentialType(STy, CI); 2027 2028 if (PerformFold) { 2029 SmallVector<Value*, 16> NewIndices; 2030 NewIndices.reserve(Idxs.size() + CE->getNumOperands()); 2031 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 2032 NewIndices.push_back(CE->getOperand(i)); 2033 2034 // Add the last index of the source with the first index of the new GEP. 2035 // Make sure to handle the case when they are actually different types. 2036 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 2037 // Otherwise it must be an array. 2038 if (!Idx0->isNullValue()) { 2039 Type *IdxTy = Combined->getType(); 2040 if (IdxTy != Idx0->getType()) { 2041 Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext()); 2042 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty); 2043 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty); 2044 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 2045 } else { 2046 Combined = 2047 ConstantExpr::get(Instruction::Add, Idx0, Combined); 2048 } 2049 } 2050 2051 NewIndices.push_back(Combined); 2052 NewIndices.append(Idxs.begin() + 1, Idxs.end()); 2053 return 2054 ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices, 2055 inBounds && 2056 cast<GEPOperator>(CE)->isInBounds()); 2057 } 2058 } 2059 2060 // Attempt to fold casts to the same type away. For example, folding: 2061 // 2062 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*), 2063 // i64 0, i64 0) 2064 // into: 2065 // 2066 // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0) 2067 // 2068 // Don't fold if the cast is changing address spaces. 2069 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) { 2070 PointerType *SrcPtrTy = 2071 dyn_cast<PointerType>(CE->getOperand(0)->getType()); 2072 PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType()); 2073 if (SrcPtrTy && DstPtrTy) { 2074 ArrayType *SrcArrayTy = 2075 dyn_cast<ArrayType>(SrcPtrTy->getElementType()); 2076 ArrayType *DstArrayTy = 2077 dyn_cast<ArrayType>(DstPtrTy->getElementType()); 2078 if (SrcArrayTy && DstArrayTy 2079 && SrcArrayTy->getElementType() == DstArrayTy->getElementType() 2080 && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace()) 2081 return ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0), 2082 Idxs, inBounds); 2083 } 2084 } 2085 } 2086 2087 // Check to see if any array indices are not within the corresponding 2088 // notional array or vector bounds. If so, try to determine if they can be 2089 // factored out into preceding dimensions. 2090 bool Unknown = false; 2091 SmallVector<Constant *, 8> NewIdxs; 2092 Type *Ty = C->getType(); 2093 Type *Prev = nullptr; 2094 for (unsigned i = 0, e = Idxs.size(); i != e; 2095 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) { 2096 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) { 2097 if (isa<ArrayType>(Ty) || isa<VectorType>(Ty)) 2098 if (CI->getSExtValue() > 0 && 2099 !isIndexInRangeOfSequentialType(cast<SequentialType>(Ty), CI)) { 2100 if (isa<SequentialType>(Prev)) { 2101 // It's out of range, but we can factor it into the prior 2102 // dimension. 2103 NewIdxs.resize(Idxs.size()); 2104 uint64_t NumElements = 0; 2105 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) 2106 NumElements = ATy->getNumElements(); 2107 else 2108 NumElements = cast<VectorType>(Ty)->getNumElements(); 2109 2110 ConstantInt *Factor = ConstantInt::get(CI->getType(), NumElements); 2111 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor); 2112 2113 Constant *PrevIdx = cast<Constant>(Idxs[i-1]); 2114 Constant *Div = ConstantExpr::getSDiv(CI, Factor); 2115 2116 // Before adding, extend both operands to i64 to avoid 2117 // overflow trouble. 2118 if (!PrevIdx->getType()->isIntegerTy(64)) 2119 PrevIdx = ConstantExpr::getSExt(PrevIdx, 2120 Type::getInt64Ty(Div->getContext())); 2121 if (!Div->getType()->isIntegerTy(64)) 2122 Div = ConstantExpr::getSExt(Div, 2123 Type::getInt64Ty(Div->getContext())); 2124 2125 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div); 2126 } else { 2127 // It's out of range, but the prior dimension is a struct 2128 // so we can't do anything about it. 2129 Unknown = true; 2130 } 2131 } 2132 } else { 2133 // We don't know if it's in range or not. 2134 Unknown = true; 2135 } 2136 } 2137 2138 // If we did any factoring, start over with the adjusted indices. 2139 if (!NewIdxs.empty()) { 2140 for (unsigned i = 0, e = Idxs.size(); i != e; ++i) 2141 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]); 2142 return ConstantExpr::getGetElementPtr(C, NewIdxs, inBounds); 2143 } 2144 2145 // If all indices are known integers and normalized, we can do a simple 2146 // check for the "inbounds" property. 2147 if (!Unknown && !inBounds && 2148 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs)) 2149 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs); 2150 2151 return nullptr; 2152 } 2153 2154 Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2155 bool inBounds, 2156 ArrayRef<Constant *> Idxs) { 2157 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs); 2158 } 2159 2160 Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2161 bool inBounds, 2162 ArrayRef<Value *> Idxs) { 2163 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs); 2164 } 2165