ConstantFold.cpp revision 0e488b3d1c9293bbf2d64d0ecc4d6339f9100351
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 TargetData, and the pieces that do. This is to avoid 16// a dependence in VMCore on Target. 17// 18//===----------------------------------------------------------------------===// 19 20#include "ConstantFold.h" 21#include "llvm/Constants.h" 22#include "llvm/Instructions.h" 23#include "llvm/DerivedTypes.h" 24#include "llvm/Function.h" 25#include "llvm/GlobalAlias.h" 26#include "llvm/GlobalVariable.h" 27#include "llvm/ADT/SmallVector.h" 28#include "llvm/Support/Compiler.h" 29#include "llvm/Support/ErrorHandling.h" 30#include "llvm/Support/GetElementPtrTypeIterator.h" 31#include "llvm/Support/ManagedStatic.h" 32#include "llvm/Support/MathExtras.h" 33#include <limits> 34using namespace llvm; 35 36//===----------------------------------------------------------------------===// 37// ConstantFold*Instruction Implementations 38//===----------------------------------------------------------------------===// 39 40/// BitCastConstantVector - Convert the specified ConstantVector node to the 41/// specified vector type. At this point, we know that the elements of the 42/// input vector constant are all simple integer or FP values. 43static Constant *BitCastConstantVector(ConstantVector *CV, 44 const VectorType *DstTy) { 45 // If this cast changes element count then we can't handle it here: 46 // doing so requires endianness information. This should be handled by 47 // Analysis/ConstantFolding.cpp 48 unsigned NumElts = DstTy->getNumElements(); 49 if (NumElts != CV->getNumOperands()) 50 return 0; 51 52 // Check to verify that all elements of the input are simple. 53 for (unsigned i = 0; i != NumElts; ++i) { 54 if (!isa<ConstantInt>(CV->getOperand(i)) && 55 !isa<ConstantFP>(CV->getOperand(i))) 56 return 0; 57 } 58 59 // Bitcast each element now. 60 std::vector<Constant*> Result; 61 const Type *DstEltTy = DstTy->getElementType(); 62 for (unsigned i = 0; i != NumElts; ++i) 63 Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i), 64 DstEltTy)); 65 return ConstantVector::get(Result); 66} 67 68/// This function determines which opcode to use to fold two constant cast 69/// expressions together. It uses CastInst::isEliminableCastPair to determine 70/// the opcode. Consequently its just a wrapper around that function. 71/// @brief Determine if it is valid to fold a cast of a cast 72static unsigned 73foldConstantCastPair( 74 unsigned opc, ///< opcode of the second cast constant expression 75 ConstantExpr *Op, ///< the first cast constant expression 76 const Type *DstTy ///< desintation type of the first cast 77) { 78 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); 79 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); 80 assert(CastInst::isCast(opc) && "Invalid cast opcode"); 81 82 // The the types and opcodes for the two Cast constant expressions 83 const Type *SrcTy = Op->getOperand(0)->getType(); 84 const Type *MidTy = Op->getType(); 85 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); 86 Instruction::CastOps secondOp = Instruction::CastOps(opc); 87 88 // Let CastInst::isEliminableCastPair do the heavy lifting. 89 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, 90 Type::getInt64Ty(DstTy->getContext())); 91} 92 93static Constant *FoldBitCast(Constant *V, const Type *DestTy) { 94 const Type *SrcTy = V->getType(); 95 if (SrcTy == DestTy) 96 return V; // no-op cast 97 98 // Check to see if we are casting a pointer to an aggregate to a pointer to 99 // the first element. If so, return the appropriate GEP instruction. 100 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) 101 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) 102 if (PTy->getAddressSpace() == DPTy->getAddressSpace()) { 103 SmallVector<Value*, 8> IdxList; 104 Value *Zero = 105 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); 106 IdxList.push_back(Zero); 107 const Type *ElTy = PTy->getElementType(); 108 while (ElTy != DPTy->getElementType()) { 109 if (const StructType *STy = dyn_cast<StructType>(ElTy)) { 110 if (STy->getNumElements() == 0) break; 111 ElTy = STy->getElementType(0); 112 IdxList.push_back(Zero); 113 } else if (const SequentialType *STy = 114 dyn_cast<SequentialType>(ElTy)) { 115 if (ElTy->isPointerTy()) break; // Can't index into pointers! 116 ElTy = STy->getElementType(); 117 IdxList.push_back(Zero); 118 } else { 119 break; 120 } 121 } 122 123 if (ElTy == DPTy->getElementType()) 124 // This GEP is inbounds because all indices are zero. 125 return ConstantExpr::getInBoundsGetElementPtr(V, &IdxList[0], 126 IdxList.size()); 127 } 128 129 // Handle casts from one vector constant to another. We know that the src 130 // and dest type have the same size (otherwise its an illegal cast). 131 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { 132 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { 133 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && 134 "Not cast between same sized vectors!"); 135 SrcTy = NULL; 136 // First, check for null. Undef is already handled. 137 if (isa<ConstantAggregateZero>(V)) 138 return Constant::getNullValue(DestTy); 139 140 if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) 141 return BitCastConstantVector(CV, DestPTy); 142 } 143 144 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts 145 // This allows for other simplifications (although some of them 146 // can only be handled by Analysis/ConstantFolding.cpp). 147 if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) 148 return ConstantExpr::getBitCast(ConstantVector::get(&V, 1), DestPTy); 149 } 150 151 // Finally, implement bitcast folding now. The code below doesn't handle 152 // bitcast right. 153 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 154 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 155 156 // Handle integral constant input. 157 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 158 if (DestTy->isIntegerTy()) 159 // Integral -> Integral. This is a no-op because the bit widths must 160 // be the same. Consequently, we just fold to V. 161 return V; 162 163 if (DestTy->isFloatingPointTy()) 164 return ConstantFP::get(DestTy->getContext(), 165 APFloat(CI->getValue(), 166 !DestTy->isPPC_FP128Ty())); 167 168 // Otherwise, can't fold this (vector?) 169 return 0; 170 } 171 172 // Handle ConstantFP input: FP -> Integral. 173 if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) 174 return ConstantInt::get(FP->getContext(), 175 FP->getValueAPF().bitcastToAPInt()); 176 177 return 0; 178} 179 180 181/// ExtractConstantBytes - V is an integer constant which only has a subset of 182/// its bytes used. The bytes used are indicated by ByteStart (which is the 183/// first byte used, counting from the least significant byte) and ByteSize, 184/// which is the number of bytes used. 185/// 186/// This function analyzes the specified constant to see if the specified byte 187/// range can be returned as a simplified constant. If so, the constant is 188/// returned, otherwise null is returned. 189/// 190static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart, 191 unsigned ByteSize) { 192 assert(C->getType()->isIntegerTy() && 193 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 && 194 "Non-byte sized integer input"); 195 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8; 196 assert(ByteSize && "Must be accessing some piece"); 197 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input"); 198 assert(ByteSize != CSize && "Should not extract everything"); 199 200 // Constant Integers are simple. 201 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 202 APInt V = CI->getValue(); 203 if (ByteStart) 204 V = V.lshr(ByteStart*8); 205 V.trunc(ByteSize*8); 206 return ConstantInt::get(CI->getContext(), V); 207 } 208 209 // In the input is a constant expr, we might be able to recursively simplify. 210 // If not, we definitely can't do anything. 211 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 212 if (CE == 0) return 0; 213 214 switch (CE->getOpcode()) { 215 default: return 0; 216 case Instruction::Or: { 217 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); 218 if (RHS == 0) 219 return 0; 220 221 // X | -1 -> -1. 222 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) 223 if (RHSC->isAllOnesValue()) 224 return RHSC; 225 226 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); 227 if (LHS == 0) 228 return 0; 229 return ConstantExpr::getOr(LHS, RHS); 230 } 231 case Instruction::And: { 232 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); 233 if (RHS == 0) 234 return 0; 235 236 // X & 0 -> 0. 237 if (RHS->isNullValue()) 238 return RHS; 239 240 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); 241 if (LHS == 0) 242 return 0; 243 return ConstantExpr::getAnd(LHS, RHS); 244 } 245 case Instruction::LShr: { 246 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); 247 if (Amt == 0) 248 return 0; 249 unsigned ShAmt = Amt->getZExtValue(); 250 // Cannot analyze non-byte shifts. 251 if ((ShAmt & 7) != 0) 252 return 0; 253 ShAmt >>= 3; 254 255 // If the extract is known to be all zeros, return zero. 256 if (ByteStart >= CSize-ShAmt) 257 return Constant::getNullValue(IntegerType::get(CE->getContext(), 258 ByteSize*8)); 259 // If the extract is known to be fully in the input, extract it. 260 if (ByteStart+ByteSize+ShAmt <= CSize) 261 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize); 262 263 // TODO: Handle the 'partially zero' case. 264 return 0; 265 } 266 267 case Instruction::Shl: { 268 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); 269 if (Amt == 0) 270 return 0; 271 unsigned ShAmt = Amt->getZExtValue(); 272 // Cannot analyze non-byte shifts. 273 if ((ShAmt & 7) != 0) 274 return 0; 275 ShAmt >>= 3; 276 277 // If the extract is known to be all zeros, return zero. 278 if (ByteStart+ByteSize <= ShAmt) 279 return Constant::getNullValue(IntegerType::get(CE->getContext(), 280 ByteSize*8)); 281 // If the extract is known to be fully in the input, extract it. 282 if (ByteStart >= ShAmt) 283 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize); 284 285 // TODO: Handle the 'partially zero' case. 286 return 0; 287 } 288 289 case Instruction::ZExt: { 290 unsigned SrcBitSize = 291 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth(); 292 293 // If extracting something that is completely zero, return 0. 294 if (ByteStart*8 >= SrcBitSize) 295 return Constant::getNullValue(IntegerType::get(CE->getContext(), 296 ByteSize*8)); 297 298 // If exactly extracting the input, return it. 299 if (ByteStart == 0 && ByteSize*8 == SrcBitSize) 300 return CE->getOperand(0); 301 302 // If extracting something completely in the input, if if the input is a 303 // multiple of 8 bits, recurse. 304 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize) 305 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize); 306 307 // Otherwise, if extracting a subset of the input, which is not multiple of 308 // 8 bits, do a shift and trunc to get the bits. 309 if ((ByteStart+ByteSize)*8 < SrcBitSize) { 310 assert((SrcBitSize&7) && "Shouldn't get byte sized case here"); 311 Constant *Res = CE->getOperand(0); 312 if (ByteStart) 313 Res = ConstantExpr::getLShr(Res, 314 ConstantInt::get(Res->getType(), ByteStart*8)); 315 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(), 316 ByteSize*8)); 317 } 318 319 // TODO: Handle the 'partially zero' case. 320 return 0; 321 } 322 } 323} 324 325/// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof 326/// on Ty, with any known factors factored out. If Folded is false, 327/// return null if no factoring was possible, to avoid endlessly 328/// bouncing an unfoldable expression back into the top-level folder. 329/// 330static Constant *getFoldedSizeOf(const Type *Ty, const Type *DestTy, 331 bool Folded) { 332 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 333 Constant *N = ConstantInt::get(DestTy, ATy->getNumElements()); 334 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); 335 return ConstantExpr::getNUWMul(E, N); 336 } 337 if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) { 338 Constant *N = ConstantInt::get(DestTy, VTy->getNumElements()); 339 Constant *E = getFoldedSizeOf(VTy->getElementType(), DestTy, true); 340 return ConstantExpr::getNUWMul(E, N); 341 } 342 if (const StructType *STy = dyn_cast<StructType>(Ty)) 343 if (!STy->isPacked()) { 344 unsigned NumElems = STy->getNumElements(); 345 // An empty struct has size zero. 346 if (NumElems == 0) 347 return ConstantExpr::getNullValue(DestTy); 348 // Check for a struct with all members having the same size. 349 Constant *MemberSize = 350 getFoldedSizeOf(STy->getElementType(0), DestTy, true); 351 bool AllSame = true; 352 for (unsigned i = 1; i != NumElems; ++i) 353 if (MemberSize != 354 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { 355 AllSame = false; 356 break; 357 } 358 if (AllSame) { 359 Constant *N = ConstantInt::get(DestTy, NumElems); 360 return ConstantExpr::getNUWMul(MemberSize, N); 361 } 362 } 363 364 // Pointer size doesn't depend on the pointee type, so canonicalize them 365 // to an arbitrary pointee. 366 if (const PointerType *PTy = dyn_cast<PointerType>(Ty)) 367 if (!PTy->getElementType()->isIntegerTy(1)) 368 return 369 getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), 370 PTy->getAddressSpace()), 371 DestTy, true); 372 373 // If there's no interesting folding happening, bail so that we don't create 374 // a constant that looks like it needs folding but really doesn't. 375 if (!Folded) 376 return 0; 377 378 // Base case: Get a regular sizeof expression. 379 Constant *C = ConstantExpr::getSizeOf(Ty); 380 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 381 DestTy, false), 382 C, DestTy); 383 return C; 384} 385 386/// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof 387/// on Ty, with any known factors factored out. If Folded is false, 388/// return null if no factoring was possible, to avoid endlessly 389/// bouncing an unfoldable expression back into the top-level folder. 390/// 391static Constant *getFoldedAlignOf(const Type *Ty, const Type *DestTy, 392 bool Folded) { 393 // The alignment of an array is equal to the alignment of the 394 // array element. Note that this is not always true for vectors. 395 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 396 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType()); 397 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 398 DestTy, 399 false), 400 C, DestTy); 401 return C; 402 } 403 404 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 405 // Packed structs always have an alignment of 1. 406 if (STy->isPacked()) 407 return ConstantInt::get(DestTy, 1); 408 409 // Otherwise, struct alignment is the maximum alignment of any member. 410 // Without target data, we can't compare much, but we can check to see 411 // if all the members have the same alignment. 412 unsigned NumElems = STy->getNumElements(); 413 // An empty struct has minimal alignment. 414 if (NumElems == 0) 415 return ConstantInt::get(DestTy, 1); 416 // Check for a struct with all members having the same alignment. 417 Constant *MemberAlign = 418 getFoldedAlignOf(STy->getElementType(0), DestTy, true); 419 bool AllSame = true; 420 for (unsigned i = 1; i != NumElems; ++i) 421 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) { 422 AllSame = false; 423 break; 424 } 425 if (AllSame) 426 return MemberAlign; 427 } 428 429 // Pointer alignment doesn't depend on the pointee type, so canonicalize them 430 // to an arbitrary pointee. 431 if (const PointerType *PTy = dyn_cast<PointerType>(Ty)) 432 if (!PTy->getElementType()->isIntegerTy(1)) 433 return 434 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(), 435 1), 436 PTy->getAddressSpace()), 437 DestTy, true); 438 439 // If there's no interesting folding happening, bail so that we don't create 440 // a constant that looks like it needs folding but really doesn't. 441 if (!Folded) 442 return 0; 443 444 // Base case: Get a regular alignof expression. 445 Constant *C = ConstantExpr::getAlignOf(Ty); 446 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 447 DestTy, false), 448 C, DestTy); 449 return C; 450} 451 452/// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof 453/// on Ty and FieldNo, with any known factors factored out. If Folded is false, 454/// return null if no factoring was possible, to avoid endlessly 455/// bouncing an unfoldable expression back into the top-level folder. 456/// 457static Constant *getFoldedOffsetOf(const Type *Ty, Constant *FieldNo, 458 const Type *DestTy, 459 bool Folded) { 460 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 461 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, 462 DestTy, false), 463 FieldNo, DestTy); 464 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); 465 return ConstantExpr::getNUWMul(E, N); 466 } 467 if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) { 468 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, 469 DestTy, false), 470 FieldNo, DestTy); 471 Constant *E = getFoldedSizeOf(VTy->getElementType(), DestTy, true); 472 return ConstantExpr::getNUWMul(E, N); 473 } 474 if (const StructType *STy = dyn_cast<StructType>(Ty)) 475 if (!STy->isPacked()) { 476 unsigned NumElems = STy->getNumElements(); 477 // An empty struct has no members. 478 if (NumElems == 0) 479 return 0; 480 // Check for a struct with all members having the same size. 481 Constant *MemberSize = 482 getFoldedSizeOf(STy->getElementType(0), DestTy, true); 483 bool AllSame = true; 484 for (unsigned i = 1; i != NumElems; ++i) 485 if (MemberSize != 486 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { 487 AllSame = false; 488 break; 489 } 490 if (AllSame) { 491 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, 492 false, 493 DestTy, 494 false), 495 FieldNo, DestTy); 496 return ConstantExpr::getNUWMul(MemberSize, N); 497 } 498 } 499 500 // If there's no interesting folding happening, bail so that we don't create 501 // a constant that looks like it needs folding but really doesn't. 502 if (!Folded) 503 return 0; 504 505 // Base case: Get a regular offsetof expression. 506 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo); 507 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 508 DestTy, false), 509 C, DestTy); 510 return C; 511} 512 513Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, 514 const Type *DestTy) { 515 if (isa<UndefValue>(V)) { 516 // zext(undef) = 0, because the top bits will be zero. 517 // sext(undef) = 0, because the top bits will all be the same. 518 // [us]itofp(undef) = 0, because the result value is bounded. 519 if (opc == Instruction::ZExt || opc == Instruction::SExt || 520 opc == Instruction::UIToFP || opc == Instruction::SIToFP) 521 return Constant::getNullValue(DestTy); 522 return UndefValue::get(DestTy); 523 } 524 // No compile-time operations on this type yet. 525 if (V->getType()->isPPC_FP128Ty() || DestTy->isPPC_FP128Ty()) 526 return 0; 527 528 // If the cast operand is a constant expression, there's a few things we can 529 // do to try to simplify it. 530 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 531 if (CE->isCast()) { 532 // Try hard to fold cast of cast because they are often eliminable. 533 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 534 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 535 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 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 (ConstantVector *CV = dyn_cast<ConstantVector>(V)) 554 if (DestTy->isVectorTy() && 555 cast<VectorType>(DestTy)->getNumElements() == 556 CV->getType()->getNumElements()) { 557 std::vector<Constant*> res; 558 const VectorType *DestVecTy = cast<VectorType>(DestTy); 559 const Type *DstEltTy = DestVecTy->getElementType(); 560 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 561 res.push_back(ConstantExpr::getCast(opc, 562 CV->getOperand(i), DstEltTy)); 563 return ConstantVector::get(DestVecTy, res); 564 } 565 566 // We actually have to do a cast now. Perform the cast according to the 567 // opcode specified. 568 switch (opc) { 569 default: 570 llvm_unreachable("Failed to cast constant expression"); 571 case Instruction::FPTrunc: 572 case Instruction::FPExt: 573 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 574 bool ignored; 575 APFloat Val = FPC->getValueAPF(); 576 Val.convert(DestTy->isFloatTy() ? APFloat::IEEEsingle : 577 DestTy->isDoubleTy() ? APFloat::IEEEdouble : 578 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended : 579 DestTy->isFP128Ty() ? APFloat::IEEEquad : 580 APFloat::Bogus, 581 APFloat::rmNearestTiesToEven, &ignored); 582 return ConstantFP::get(V->getContext(), Val); 583 } 584 return 0; // Can't fold. 585 case Instruction::FPToUI: 586 case Instruction::FPToSI: 587 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 588 const APFloat &V = FPC->getValueAPF(); 589 bool ignored; 590 uint64_t x[2]; 591 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 592 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 593 APFloat::rmTowardZero, &ignored); 594 APInt Val(DestBitWidth, 2, x); 595 return ConstantInt::get(FPC->getContext(), Val); 596 } 597 return 0; // Can't fold. 598 case Instruction::IntToPtr: //always treated as unsigned 599 if (V->isNullValue()) // Is it an integral null value? 600 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 601 return 0; // Other pointer types cannot be casted 602 case Instruction::PtrToInt: // always treated as unsigned 603 // Is it a null pointer value? 604 if (V->isNullValue()) 605 return ConstantInt::get(DestTy, 0); 606 // If this is a sizeof-like expression, pull out multiplications by 607 // known factors to expose them to subsequent folding. If it's an 608 // alignof-like expression, factor out known factors. 609 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 610 if (CE->getOpcode() == Instruction::GetElementPtr && 611 CE->getOperand(0)->isNullValue()) { 612 const Type *Ty = 613 cast<PointerType>(CE->getOperand(0)->getType())->getElementType(); 614 if (CE->getNumOperands() == 2) { 615 // Handle a sizeof-like expression. 616 Constant *Idx = CE->getOperand(1); 617 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne(); 618 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { 619 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, 620 DestTy, false), 621 Idx, DestTy); 622 return ConstantExpr::getMul(C, Idx); 623 } 624 } else if (CE->getNumOperands() == 3 && 625 CE->getOperand(1)->isNullValue()) { 626 // Handle an alignof-like expression. 627 if (const StructType *STy = dyn_cast<StructType>(Ty)) 628 if (!STy->isPacked()) { 629 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2)); 630 if (CI->isOne() && 631 STy->getNumElements() == 2 && 632 STy->getElementType(0)->isIntegerTy(1)) { 633 return getFoldedAlignOf(STy->getElementType(1), DestTy, false); 634 } 635 } 636 // Handle an offsetof-like expression. 637 if (Ty->isStructTy() || Ty->isArrayTy() || Ty->isVectorTy()){ 638 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), 639 DestTy, false)) 640 return C; 641 } 642 } 643 } 644 // Other pointer types cannot be casted 645 return 0; 646 case Instruction::UIToFP: 647 case Instruction::SIToFP: 648 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 649 APInt api = CI->getValue(); 650 const uint64_t zero[] = {0, 0}; 651 APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(), 652 2, zero)); 653 (void)apf.convertFromAPInt(api, 654 opc==Instruction::SIToFP, 655 APFloat::rmNearestTiesToEven); 656 return ConstantFP::get(V->getContext(), apf); 657 } 658 return 0; 659 case Instruction::ZExt: 660 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 661 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 662 APInt Result(CI->getValue()); 663 Result.zext(BitWidth); 664 return ConstantInt::get(V->getContext(), Result); 665 } 666 return 0; 667 case Instruction::SExt: 668 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 669 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 670 APInt Result(CI->getValue()); 671 Result.sext(BitWidth); 672 return ConstantInt::get(V->getContext(), Result); 673 } 674 return 0; 675 case Instruction::Trunc: { 676 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 677 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 678 APInt Result(CI->getValue()); 679 Result.trunc(DestBitWidth); 680 return ConstantInt::get(V->getContext(), Result); 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 0; 692 } 693 case Instruction::BitCast: 694 return FoldBitCast(V, DestTy); 695 } 696} 697 698Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, 699 Constant *V1, Constant *V2) { 700 if (ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) 701 return CB->getZExtValue() ? V1 : V2; 702 703 if (isa<UndefValue>(V1)) return V2; 704 if (isa<UndefValue>(V2)) return V1; 705 if (isa<UndefValue>(Cond)) return V1; 706 if (V1 == V2) return V1; 707 return 0; 708} 709 710Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, 711 Constant *Idx) { 712 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 713 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType()); 714 if (Val->isNullValue()) // ee(zero, x) -> zero 715 return Constant::getNullValue( 716 cast<VectorType>(Val->getType())->getElementType()); 717 718 if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 719 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 720 return CVal->getOperand(CIdx->getZExtValue()); 721 } else if (isa<UndefValue>(Idx)) { 722 // ee({w,x,y,z}, undef) -> w (an arbitrary value). 723 return CVal->getOperand(0); 724 } 725 } 726 return 0; 727} 728 729Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, 730 Constant *Elt, 731 Constant *Idx) { 732 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 733 if (!CIdx) return 0; 734 APInt idxVal = CIdx->getValue(); 735 if (isa<UndefValue>(Val)) { 736 // Insertion of scalar constant into vector undef 737 // Optimize away insertion of undef 738 if (isa<UndefValue>(Elt)) 739 return Val; 740 // Otherwise break the aggregate undef into multiple undefs and do 741 // the insertion 742 unsigned numOps = 743 cast<VectorType>(Val->getType())->getNumElements(); 744 std::vector<Constant*> Ops; 745 Ops.reserve(numOps); 746 for (unsigned i = 0; i < numOps; ++i) { 747 Constant *Op = 748 (idxVal == i) ? Elt : UndefValue::get(Elt->getType()); 749 Ops.push_back(Op); 750 } 751 return ConstantVector::get(Ops); 752 } 753 if (isa<ConstantAggregateZero>(Val)) { 754 // Insertion of scalar constant into vector aggregate zero 755 // Optimize away insertion of zero 756 if (Elt->isNullValue()) 757 return Val; 758 // Otherwise break the aggregate zero into multiple zeros and do 759 // the insertion 760 unsigned numOps = 761 cast<VectorType>(Val->getType())->getNumElements(); 762 std::vector<Constant*> Ops; 763 Ops.reserve(numOps); 764 for (unsigned i = 0; i < numOps; ++i) { 765 Constant *Op = 766 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType()); 767 Ops.push_back(Op); 768 } 769 return ConstantVector::get(Ops); 770 } 771 if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 772 // Insertion of scalar constant into vector constant 773 std::vector<Constant*> Ops; 774 Ops.reserve(CVal->getNumOperands()); 775 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { 776 Constant *Op = 777 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i)); 778 Ops.push_back(Op); 779 } 780 return ConstantVector::get(Ops); 781 } 782 783 return 0; 784} 785 786/// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef 787/// return the specified element value. Otherwise return null. 788static Constant *GetVectorElement(Constant *C, unsigned EltNo) { 789 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) 790 return CV->getOperand(EltNo); 791 792 const Type *EltTy = cast<VectorType>(C->getType())->getElementType(); 793 if (isa<ConstantAggregateZero>(C)) 794 return Constant::getNullValue(EltTy); 795 if (isa<UndefValue>(C)) 796 return UndefValue::get(EltTy); 797 return 0; 798} 799 800Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, 801 Constant *V2, 802 Constant *Mask) { 803 // Undefined shuffle mask -> undefined value. 804 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType()); 805 806 unsigned MaskNumElts = cast<VectorType>(Mask->getType())->getNumElements(); 807 unsigned SrcNumElts = cast<VectorType>(V1->getType())->getNumElements(); 808 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType(); 809 810 // Loop over the shuffle mask, evaluating each element. 811 SmallVector<Constant*, 32> Result; 812 for (unsigned i = 0; i != MaskNumElts; ++i) { 813 Constant *InElt = GetVectorElement(Mask, i); 814 if (InElt == 0) return 0; 815 816 if (isa<UndefValue>(InElt)) 817 InElt = UndefValue::get(EltTy); 818 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) { 819 unsigned Elt = CI->getZExtValue(); 820 if (Elt >= SrcNumElts*2) 821 InElt = UndefValue::get(EltTy); 822 else if (Elt >= SrcNumElts) 823 InElt = GetVectorElement(V2, Elt - SrcNumElts); 824 else 825 InElt = GetVectorElement(V1, Elt); 826 if (InElt == 0) return 0; 827 } else { 828 // Unknown value. 829 return 0; 830 } 831 Result.push_back(InElt); 832 } 833 834 return ConstantVector::get(&Result[0], Result.size()); 835} 836 837Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, 838 const unsigned *Idxs, 839 unsigned NumIdx) { 840 // Base case: no indices, so return the entire value. 841 if (NumIdx == 0) 842 return Agg; 843 844 if (isa<UndefValue>(Agg)) // ev(undef, x) -> undef 845 return UndefValue::get(ExtractValueInst::getIndexedType(Agg->getType(), 846 Idxs, 847 Idxs + NumIdx)); 848 849 if (isa<ConstantAggregateZero>(Agg)) // ev(0, x) -> 0 850 return 851 Constant::getNullValue(ExtractValueInst::getIndexedType(Agg->getType(), 852 Idxs, 853 Idxs + NumIdx)); 854 855 // Otherwise recurse. 856 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) 857 return ConstantFoldExtractValueInstruction(CS->getOperand(*Idxs), 858 Idxs+1, NumIdx-1); 859 860 if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) 861 return ConstantFoldExtractValueInstruction(CA->getOperand(*Idxs), 862 Idxs+1, NumIdx-1); 863 ConstantVector *CV = cast<ConstantVector>(Agg); 864 return ConstantFoldExtractValueInstruction(CV->getOperand(*Idxs), 865 Idxs+1, NumIdx-1); 866} 867 868Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, 869 Constant *Val, 870 const unsigned *Idxs, 871 unsigned NumIdx) { 872 // Base case: no indices, so replace the entire value. 873 if (NumIdx == 0) 874 return Val; 875 876 if (isa<UndefValue>(Agg)) { 877 // Insertion of constant into aggregate undef 878 // Optimize away insertion of undef. 879 if (isa<UndefValue>(Val)) 880 return Agg; 881 882 // Otherwise break the aggregate undef into multiple undefs and do 883 // the insertion. 884 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 885 unsigned numOps; 886 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 887 numOps = AR->getNumElements(); 888 else if (AggTy->isUnionTy()) 889 numOps = 1; 890 else 891 numOps = cast<StructType>(AggTy)->getNumElements(); 892 893 std::vector<Constant*> Ops(numOps); 894 for (unsigned i = 0; i < numOps; ++i) { 895 const Type *MemberTy = AggTy->getTypeAtIndex(i); 896 Constant *Op = 897 (*Idxs == i) ? 898 ConstantFoldInsertValueInstruction(UndefValue::get(MemberTy), 899 Val, Idxs+1, NumIdx-1) : 900 UndefValue::get(MemberTy); 901 Ops[i] = Op; 902 } 903 904 if (const StructType* ST = dyn_cast<StructType>(AggTy)) 905 return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked()); 906 if (const UnionType* UT = dyn_cast<UnionType>(AggTy)) { 907 assert(Ops.size() == 1 && "Union can only contain a single value!"); 908 return ConstantUnion::get(UT, Ops[0]); 909 } 910 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 911 } 912 913 if (isa<ConstantAggregateZero>(Agg)) { 914 // Insertion of constant into aggregate zero 915 // Optimize away insertion of zero. 916 if (Val->isNullValue()) 917 return Agg; 918 919 // Otherwise break the aggregate zero into multiple zeros and do 920 // the insertion. 921 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 922 unsigned numOps; 923 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 924 numOps = AR->getNumElements(); 925 else 926 numOps = cast<StructType>(AggTy)->getNumElements(); 927 928 std::vector<Constant*> Ops(numOps); 929 for (unsigned i = 0; i < numOps; ++i) { 930 const Type *MemberTy = AggTy->getTypeAtIndex(i); 931 Constant *Op = 932 (*Idxs == i) ? 933 ConstantFoldInsertValueInstruction(Constant::getNullValue(MemberTy), 934 Val, Idxs+1, NumIdx-1) : 935 Constant::getNullValue(MemberTy); 936 Ops[i] = Op; 937 } 938 939 if (const StructType *ST = dyn_cast<StructType>(AggTy)) 940 return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked()); 941 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 942 } 943 944 if (isa<ConstantStruct>(Agg) || isa<ConstantArray>(Agg)) { 945 // Insertion of constant into aggregate constant. 946 std::vector<Constant*> Ops(Agg->getNumOperands()); 947 for (unsigned i = 0; i < Agg->getNumOperands(); ++i) { 948 Constant *Op = cast<Constant>(Agg->getOperand(i)); 949 if (*Idxs == i) 950 Op = ConstantFoldInsertValueInstruction(Op, Val, Idxs+1, NumIdx-1); 951 Ops[i] = Op; 952 } 953 954 if (const StructType* ST = dyn_cast<StructType>(Agg->getType())) 955 return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked()); 956 return ConstantArray::get(cast<ArrayType>(Agg->getType()), Ops); 957 } 958 959 return 0; 960} 961 962 963Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 964 Constant *C1, Constant *C2) { 965 // No compile-time operations on this type yet. 966 if (C1->getType()->isPPC_FP128Ty()) 967 return 0; 968 969 // Handle UndefValue up front. 970 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 971 switch (Opcode) { 972 case Instruction::Xor: 973 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 974 // Handle undef ^ undef -> 0 special case. This is a common 975 // idiom (misuse). 976 return Constant::getNullValue(C1->getType()); 977 // Fallthrough 978 case Instruction::Add: 979 case Instruction::Sub: 980 return UndefValue::get(C1->getType()); 981 case Instruction::Mul: 982 case Instruction::And: 983 return Constant::getNullValue(C1->getType()); 984 case Instruction::UDiv: 985 case Instruction::SDiv: 986 case Instruction::URem: 987 case Instruction::SRem: 988 if (!isa<UndefValue>(C2)) // undef / X -> 0 989 return Constant::getNullValue(C1->getType()); 990 return C2; // X / undef -> undef 991 case Instruction::Or: // X | undef -> -1 992 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType())) 993 return Constant::getAllOnesValue(PTy); 994 return Constant::getAllOnesValue(C1->getType()); 995 case Instruction::LShr: 996 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 997 return C1; // undef lshr undef -> undef 998 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 999 // undef lshr X -> 0 1000 case Instruction::AShr: 1001 if (!isa<UndefValue>(C2)) 1002 return C1; // undef ashr X --> undef 1003 else if (isa<UndefValue>(C1)) 1004 return C1; // undef ashr undef -> undef 1005 else 1006 return C1; // X ashr undef --> X 1007 case Instruction::Shl: 1008 // undef << X -> 0 or X << undef -> 0 1009 return Constant::getNullValue(C1->getType()); 1010 } 1011 } 1012 1013 // Handle simplifications when the RHS is a constant int. 1014 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 1015 switch (Opcode) { 1016 case Instruction::Add: 1017 if (CI2->equalsInt(0)) return C1; // X + 0 == X 1018 break; 1019 case Instruction::Sub: 1020 if (CI2->equalsInt(0)) return C1; // X - 0 == X 1021 break; 1022 case Instruction::Mul: 1023 if (CI2->equalsInt(0)) return C2; // X * 0 == 0 1024 if (CI2->equalsInt(1)) 1025 return C1; // X * 1 == X 1026 break; 1027 case Instruction::UDiv: 1028 case Instruction::SDiv: 1029 if (CI2->equalsInt(1)) 1030 return C1; // X / 1 == X 1031 if (CI2->equalsInt(0)) 1032 return UndefValue::get(CI2->getType()); // X / 0 == undef 1033 break; 1034 case Instruction::URem: 1035 case Instruction::SRem: 1036 if (CI2->equalsInt(1)) 1037 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 1038 if (CI2->equalsInt(0)) 1039 return UndefValue::get(CI2->getType()); // X % 0 == undef 1040 break; 1041 case Instruction::And: 1042 if (CI2->isZero()) return C2; // X & 0 == 0 1043 if (CI2->isAllOnesValue()) 1044 return C1; // X & -1 == X 1045 1046 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1047 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 1048 if (CE1->getOpcode() == Instruction::ZExt) { 1049 unsigned DstWidth = CI2->getType()->getBitWidth(); 1050 unsigned SrcWidth = 1051 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 1052 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 1053 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 1054 return C1; 1055 } 1056 1057 // If and'ing the address of a global with a constant, fold it. 1058 if (CE1->getOpcode() == Instruction::PtrToInt && 1059 isa<GlobalValue>(CE1->getOperand(0))) { 1060 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 1061 1062 // Functions are at least 4-byte aligned. 1063 unsigned GVAlign = GV->getAlignment(); 1064 if (isa<Function>(GV)) 1065 GVAlign = std::max(GVAlign, 4U); 1066 1067 if (GVAlign > 1) { 1068 unsigned DstWidth = CI2->getType()->getBitWidth(); 1069 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 1070 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 1071 1072 // If checking bits we know are clear, return zero. 1073 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 1074 return Constant::getNullValue(CI2->getType()); 1075 } 1076 } 1077 } 1078 break; 1079 case Instruction::Or: 1080 if (CI2->equalsInt(0)) return C1; // X | 0 == X 1081 if (CI2->isAllOnesValue()) 1082 return C2; // X | -1 == -1 1083 break; 1084 case Instruction::Xor: 1085 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X 1086 1087 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1088 switch (CE1->getOpcode()) { 1089 default: break; 1090 case Instruction::ICmp: 1091 case Instruction::FCmp: 1092 // cmp pred ^ true -> cmp !pred 1093 assert(CI2->equalsInt(1)); 1094 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate(); 1095 pred = CmpInst::getInversePredicate(pred); 1096 return ConstantExpr::getCompare(pred, CE1->getOperand(0), 1097 CE1->getOperand(1)); 1098 } 1099 } 1100 break; 1101 case Instruction::AShr: 1102 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 1103 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 1104 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 1105 return ConstantExpr::getLShr(C1, C2); 1106 break; 1107 } 1108 } else if (isa<ConstantInt>(C1)) { 1109 // If C1 is a ConstantInt and C2 is not, swap the operands. 1110 if (Instruction::isCommutative(Opcode)) 1111 return ConstantExpr::get(Opcode, C2, C1); 1112 } 1113 1114 // At this point we know neither constant is an UndefValue. 1115 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 1116 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 1117 using namespace APIntOps; 1118 const APInt &C1V = CI1->getValue(); 1119 const APInt &C2V = CI2->getValue(); 1120 switch (Opcode) { 1121 default: 1122 break; 1123 case Instruction::Add: 1124 return ConstantInt::get(CI1->getContext(), C1V + C2V); 1125 case Instruction::Sub: 1126 return ConstantInt::get(CI1->getContext(), C1V - C2V); 1127 case Instruction::Mul: 1128 return ConstantInt::get(CI1->getContext(), C1V * C2V); 1129 case Instruction::UDiv: 1130 assert(!CI2->isNullValue() && "Div by zero handled above"); 1131 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); 1132 case Instruction::SDiv: 1133 assert(!CI2->isNullValue() && "Div by zero handled above"); 1134 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1135 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef 1136 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); 1137 case Instruction::URem: 1138 assert(!CI2->isNullValue() && "Div by zero handled above"); 1139 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); 1140 case Instruction::SRem: 1141 assert(!CI2->isNullValue() && "Div by zero handled above"); 1142 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1143 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef 1144 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); 1145 case Instruction::And: 1146 return ConstantInt::get(CI1->getContext(), C1V & C2V); 1147 case Instruction::Or: 1148 return ConstantInt::get(CI1->getContext(), C1V | C2V); 1149 case Instruction::Xor: 1150 return ConstantInt::get(CI1->getContext(), C1V ^ C2V); 1151 case Instruction::Shl: { 1152 uint32_t shiftAmt = C2V.getZExtValue(); 1153 if (shiftAmt < C1V.getBitWidth()) 1154 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt)); 1155 else 1156 return UndefValue::get(C1->getType()); // too big shift is undef 1157 } 1158 case Instruction::LShr: { 1159 uint32_t shiftAmt = C2V.getZExtValue(); 1160 if (shiftAmt < C1V.getBitWidth()) 1161 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt)); 1162 else 1163 return UndefValue::get(C1->getType()); // too big shift is undef 1164 } 1165 case Instruction::AShr: { 1166 uint32_t shiftAmt = C2V.getZExtValue(); 1167 if (shiftAmt < C1V.getBitWidth()) 1168 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt)); 1169 else 1170 return UndefValue::get(C1->getType()); // too big shift is undef 1171 } 1172 } 1173 } 1174 1175 switch (Opcode) { 1176 case Instruction::SDiv: 1177 case Instruction::UDiv: 1178 case Instruction::URem: 1179 case Instruction::SRem: 1180 case Instruction::LShr: 1181 case Instruction::AShr: 1182 case Instruction::Shl: 1183 if (CI1->equalsInt(0)) return C1; 1184 break; 1185 default: 1186 break; 1187 } 1188 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 1189 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 1190 APFloat C1V = CFP1->getValueAPF(); 1191 APFloat C2V = CFP2->getValueAPF(); 1192 APFloat C3V = C1V; // copy for modification 1193 switch (Opcode) { 1194 default: 1195 break; 1196 case Instruction::FAdd: 1197 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 1198 return ConstantFP::get(C1->getContext(), C3V); 1199 case Instruction::FSub: 1200 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 1201 return ConstantFP::get(C1->getContext(), C3V); 1202 case Instruction::FMul: 1203 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 1204 return ConstantFP::get(C1->getContext(), C3V); 1205 case Instruction::FDiv: 1206 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 1207 return ConstantFP::get(C1->getContext(), C3V); 1208 case Instruction::FRem: 1209 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 1210 return ConstantFP::get(C1->getContext(), C3V); 1211 } 1212 } 1213 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 1214 ConstantVector *CP1 = dyn_cast<ConstantVector>(C1); 1215 ConstantVector *CP2 = dyn_cast<ConstantVector>(C2); 1216 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) && 1217 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) { 1218 std::vector<Constant*> Res; 1219 const Type* EltTy = VTy->getElementType(); 1220 Constant *C1 = 0; 1221 Constant *C2 = 0; 1222 switch (Opcode) { 1223 default: 1224 break; 1225 case Instruction::Add: 1226 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1227 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1228 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1229 Res.push_back(ConstantExpr::getAdd(C1, C2)); 1230 } 1231 return ConstantVector::get(Res); 1232 case Instruction::FAdd: 1233 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1234 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1235 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1236 Res.push_back(ConstantExpr::getFAdd(C1, C2)); 1237 } 1238 return ConstantVector::get(Res); 1239 case Instruction::Sub: 1240 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1241 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1242 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1243 Res.push_back(ConstantExpr::getSub(C1, C2)); 1244 } 1245 return ConstantVector::get(Res); 1246 case Instruction::FSub: 1247 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1248 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1249 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1250 Res.push_back(ConstantExpr::getFSub(C1, C2)); 1251 } 1252 return ConstantVector::get(Res); 1253 case Instruction::Mul: 1254 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1255 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1256 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1257 Res.push_back(ConstantExpr::getMul(C1, C2)); 1258 } 1259 return ConstantVector::get(Res); 1260 case Instruction::FMul: 1261 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1262 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1263 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1264 Res.push_back(ConstantExpr::getFMul(C1, C2)); 1265 } 1266 return ConstantVector::get(Res); 1267 case Instruction::UDiv: 1268 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1269 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1270 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1271 Res.push_back(ConstantExpr::getUDiv(C1, C2)); 1272 } 1273 return ConstantVector::get(Res); 1274 case Instruction::SDiv: 1275 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1276 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1277 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1278 Res.push_back(ConstantExpr::getSDiv(C1, C2)); 1279 } 1280 return ConstantVector::get(Res); 1281 case Instruction::FDiv: 1282 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1283 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1284 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1285 Res.push_back(ConstantExpr::getFDiv(C1, C2)); 1286 } 1287 return ConstantVector::get(Res); 1288 case Instruction::URem: 1289 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1290 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1291 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1292 Res.push_back(ConstantExpr::getURem(C1, C2)); 1293 } 1294 return ConstantVector::get(Res); 1295 case Instruction::SRem: 1296 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1297 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1298 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1299 Res.push_back(ConstantExpr::getSRem(C1, C2)); 1300 } 1301 return ConstantVector::get(Res); 1302 case Instruction::FRem: 1303 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1304 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1305 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1306 Res.push_back(ConstantExpr::getFRem(C1, C2)); 1307 } 1308 return ConstantVector::get(Res); 1309 case Instruction::And: 1310 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1311 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1312 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1313 Res.push_back(ConstantExpr::getAnd(C1, C2)); 1314 } 1315 return ConstantVector::get(Res); 1316 case Instruction::Or: 1317 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1318 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1319 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1320 Res.push_back(ConstantExpr::getOr(C1, C2)); 1321 } 1322 return ConstantVector::get(Res); 1323 case Instruction::Xor: 1324 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1325 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1326 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1327 Res.push_back(ConstantExpr::getXor(C1, C2)); 1328 } 1329 return ConstantVector::get(Res); 1330 case Instruction::LShr: 1331 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1332 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1333 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1334 Res.push_back(ConstantExpr::getLShr(C1, C2)); 1335 } 1336 return ConstantVector::get(Res); 1337 case Instruction::AShr: 1338 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1339 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1340 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1341 Res.push_back(ConstantExpr::getAShr(C1, C2)); 1342 } 1343 return ConstantVector::get(Res); 1344 case Instruction::Shl: 1345 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1346 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1347 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1348 Res.push_back(ConstantExpr::getShl(C1, C2)); 1349 } 1350 return ConstantVector::get(Res); 1351 } 1352 } 1353 } 1354 1355 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1356 // There are many possible foldings we could do here. We should probably 1357 // at least fold add of a pointer with an integer into the appropriate 1358 // getelementptr. This will improve alias analysis a bit. 1359 1360 // Given ((a + b) + c), if (b + c) folds to something interesting, return 1361 // (a + (b + c)). 1362 if (Instruction::isAssociative(Opcode, C1->getType()) && 1363 CE1->getOpcode() == Opcode) { 1364 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2); 1365 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode) 1366 return ConstantExpr::get(Opcode, CE1->getOperand(0), T); 1367 } 1368 } else if (isa<ConstantExpr>(C2)) { 1369 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1370 // other way if possible. 1371 if (Instruction::isCommutative(Opcode)) 1372 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 1373 } 1374 1375 // i1 can be simplified in many cases. 1376 if (C1->getType()->isIntegerTy(1)) { 1377 switch (Opcode) { 1378 case Instruction::Add: 1379 case Instruction::Sub: 1380 return ConstantExpr::getXor(C1, C2); 1381 case Instruction::Mul: 1382 return ConstantExpr::getAnd(C1, C2); 1383 case Instruction::Shl: 1384 case Instruction::LShr: 1385 case Instruction::AShr: 1386 // We can assume that C2 == 0. If it were one the result would be 1387 // undefined because the shift value is as large as the bitwidth. 1388 return C1; 1389 case Instruction::SDiv: 1390 case Instruction::UDiv: 1391 // We can assume that C2 == 1. If it were zero the result would be 1392 // undefined through division by zero. 1393 return C1; 1394 case Instruction::URem: 1395 case Instruction::SRem: 1396 // We can assume that C2 == 1. If it were zero the result would be 1397 // undefined through division by zero. 1398 return ConstantInt::getFalse(C1->getContext()); 1399 default: 1400 break; 1401 } 1402 } 1403 1404 // We don't know how to fold this. 1405 return 0; 1406} 1407 1408/// isZeroSizedType - This type is zero sized if its an array or structure of 1409/// zero sized types. The only leaf zero sized type is an empty structure. 1410static bool isMaybeZeroSizedType(const Type *Ty) { 1411 if (Ty->isOpaqueTy()) return true; // Can't say. 1412 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 1413 1414 // If all of elements have zero size, this does too. 1415 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1416 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 1417 return true; 1418 1419 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1420 return isMaybeZeroSizedType(ATy->getElementType()); 1421 } 1422 return false; 1423} 1424 1425/// IdxCompare - Compare the two constants as though they were getelementptr 1426/// indices. This allows coersion of the types to be the same thing. 1427/// 1428/// If the two constants are the "same" (after coersion), return 0. If the 1429/// first is less than the second, return -1, if the second is less than the 1430/// first, return 1. If the constants are not integral, return -2. 1431/// 1432static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 1433 if (C1 == C2) return 0; 1434 1435 // Ok, we found a different index. If they are not ConstantInt, we can't do 1436 // anything with them. 1437 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 1438 return -2; // don't know! 1439 1440 // Ok, we have two differing integer indices. Sign extend them to be the same 1441 // type. Long is always big enough, so we use it. 1442 if (!C1->getType()->isIntegerTy(64)) 1443 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext())); 1444 1445 if (!C2->getType()->isIntegerTy(64)) 1446 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext())); 1447 1448 if (C1 == C2) return 0; // They are equal 1449 1450 // If the type being indexed over is really just a zero sized type, there is 1451 // no pointer difference being made here. 1452 if (isMaybeZeroSizedType(ElTy)) 1453 return -2; // dunno. 1454 1455 // If they are really different, now that they are the same type, then we 1456 // found a difference! 1457 if (cast<ConstantInt>(C1)->getSExtValue() < 1458 cast<ConstantInt>(C2)->getSExtValue()) 1459 return -1; 1460 else 1461 return 1; 1462} 1463 1464/// evaluateFCmpRelation - This function determines if there is anything we can 1465/// decide about the two constants provided. This doesn't need to handle simple 1466/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 1467/// If we can determine that the two constants have a particular relation to 1468/// each other, we should return the corresponding FCmpInst predicate, 1469/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 1470/// ConstantFoldCompareInstruction. 1471/// 1472/// To simplify this code we canonicalize the relation so that the first 1473/// operand is always the most "complex" of the two. We consider ConstantFP 1474/// to be the simplest, and ConstantExprs to be the most complex. 1475static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) { 1476 assert(V1->getType() == V2->getType() && 1477 "Cannot compare values of different types!"); 1478 1479 // No compile-time operations on this type yet. 1480 if (V1->getType()->isPPC_FP128Ty()) 1481 return FCmpInst::BAD_FCMP_PREDICATE; 1482 1483 // Handle degenerate case quickly 1484 if (V1 == V2) return FCmpInst::FCMP_OEQ; 1485 1486 if (!isa<ConstantExpr>(V1)) { 1487 if (!isa<ConstantExpr>(V2)) { 1488 // We distilled thisUse the standard constant folder for a few cases 1489 ConstantInt *R = 0; 1490 R = dyn_cast<ConstantInt>( 1491 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); 1492 if (R && !R->isZero()) 1493 return FCmpInst::FCMP_OEQ; 1494 R = dyn_cast<ConstantInt>( 1495 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); 1496 if (R && !R->isZero()) 1497 return FCmpInst::FCMP_OLT; 1498 R = dyn_cast<ConstantInt>( 1499 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2)); 1500 if (R && !R->isZero()) 1501 return FCmpInst::FCMP_OGT; 1502 1503 // Nothing more we can do 1504 return FCmpInst::BAD_FCMP_PREDICATE; 1505 } 1506 1507 // If the first operand is simple and second is ConstantExpr, swap operands. 1508 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 1509 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 1510 return FCmpInst::getSwappedPredicate(SwappedRelation); 1511 } else { 1512 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1513 // constantexpr or a simple constant. 1514 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1515 switch (CE1->getOpcode()) { 1516 case Instruction::FPTrunc: 1517 case Instruction::FPExt: 1518 case Instruction::UIToFP: 1519 case Instruction::SIToFP: 1520 // We might be able to do something with these but we don't right now. 1521 break; 1522 default: 1523 break; 1524 } 1525 } 1526 // There are MANY other foldings that we could perform here. They will 1527 // probably be added on demand, as they seem needed. 1528 return FCmpInst::BAD_FCMP_PREDICATE; 1529} 1530 1531/// evaluateICmpRelation - This function determines if there is anything we can 1532/// decide about the two constants provided. This doesn't need to handle simple 1533/// things like integer comparisons, but should instead handle ConstantExprs 1534/// and GlobalValues. If we can determine that the two constants have a 1535/// particular relation to each other, we should return the corresponding ICmp 1536/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 1537/// 1538/// To simplify this code we canonicalize the relation so that the first 1539/// operand is always the most "complex" of the two. We consider simple 1540/// constants (like ConstantInt) to be the simplest, followed by 1541/// GlobalValues, followed by ConstantExpr's (the most complex). 1542/// 1543static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, 1544 bool isSigned) { 1545 assert(V1->getType() == V2->getType() && 1546 "Cannot compare different types of values!"); 1547 if (V1 == V2) return ICmpInst::ICMP_EQ; 1548 1549 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) && 1550 !isa<BlockAddress>(V1)) { 1551 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) && 1552 !isa<BlockAddress>(V2)) { 1553 // We distilled this down to a simple case, use the standard constant 1554 // folder. 1555 ConstantInt *R = 0; 1556 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 1557 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1558 if (R && !R->isZero()) 1559 return pred; 1560 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1561 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1562 if (R && !R->isZero()) 1563 return pred; 1564 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1565 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1566 if (R && !R->isZero()) 1567 return pred; 1568 1569 // If we couldn't figure it out, bail. 1570 return ICmpInst::BAD_ICMP_PREDICATE; 1571 } 1572 1573 // If the first operand is simple, swap operands. 1574 ICmpInst::Predicate SwappedRelation = 1575 evaluateICmpRelation(V2, V1, isSigned); 1576 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1577 return ICmpInst::getSwappedPredicate(SwappedRelation); 1578 1579 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) { 1580 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1581 ICmpInst::Predicate SwappedRelation = 1582 evaluateICmpRelation(V2, V1, isSigned); 1583 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1584 return ICmpInst::getSwappedPredicate(SwappedRelation); 1585 return ICmpInst::BAD_ICMP_PREDICATE; 1586 } 1587 1588 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1589 // constant (which, since the types must match, means that it's a 1590 // ConstantPointerNull). 1591 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1592 // Don't try to decide equality of aliases. 1593 if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2)) 1594 if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) 1595 return ICmpInst::ICMP_NE; 1596 } else if (isa<BlockAddress>(V2)) { 1597 return ICmpInst::ICMP_NE; // Globals never equal labels. 1598 } else { 1599 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 1600 // GlobalVals can never be null unless they have external weak linkage. 1601 // We don't try to evaluate aliases here. 1602 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV)) 1603 return ICmpInst::ICMP_NE; 1604 } 1605 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) { 1606 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1607 ICmpInst::Predicate SwappedRelation = 1608 evaluateICmpRelation(V2, V1, isSigned); 1609 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1610 return ICmpInst::getSwappedPredicate(SwappedRelation); 1611 return ICmpInst::BAD_ICMP_PREDICATE; 1612 } 1613 1614 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1615 // constant (which, since the types must match, means that it is a 1616 // ConstantPointerNull). 1617 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) { 1618 // Block address in another function can't equal this one, but block 1619 // addresses in the current function might be the same if blocks are 1620 // empty. 1621 if (BA2->getFunction() != BA->getFunction()) 1622 return ICmpInst::ICMP_NE; 1623 } else { 1624 // Block addresses aren't null, don't equal the address of globals. 1625 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) && 1626 "Canonicalization guarantee!"); 1627 return ICmpInst::ICMP_NE; 1628 } 1629 } else { 1630 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1631 // constantexpr, a global, block address, or a simple constant. 1632 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1633 Constant *CE1Op0 = CE1->getOperand(0); 1634 1635 switch (CE1->getOpcode()) { 1636 case Instruction::Trunc: 1637 case Instruction::FPTrunc: 1638 case Instruction::FPExt: 1639 case Instruction::FPToUI: 1640 case Instruction::FPToSI: 1641 break; // We can't evaluate floating point casts or truncations. 1642 1643 case Instruction::UIToFP: 1644 case Instruction::SIToFP: 1645 case Instruction::BitCast: 1646 case Instruction::ZExt: 1647 case Instruction::SExt: 1648 // If the cast is not actually changing bits, and the second operand is a 1649 // null pointer, do the comparison with the pre-casted value. 1650 if (V2->isNullValue() && 1651 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) { 1652 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1653 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1654 return evaluateICmpRelation(CE1Op0, 1655 Constant::getNullValue(CE1Op0->getType()), 1656 isSigned); 1657 } 1658 break; 1659 1660 case Instruction::GetElementPtr: 1661 // Ok, since this is a getelementptr, we know that the constant has a 1662 // pointer type. Check the various cases. 1663 if (isa<ConstantPointerNull>(V2)) { 1664 // If we are comparing a GEP to a null pointer, check to see if the base 1665 // of the GEP equals the null pointer. 1666 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1667 if (GV->hasExternalWeakLinkage()) 1668 // Weak linkage GVals could be zero or not. We're comparing that 1669 // to null pointer so its greater-or-equal 1670 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1671 else 1672 // If its not weak linkage, the GVal must have a non-zero address 1673 // so the result is greater-than 1674 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1675 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1676 // If we are indexing from a null pointer, check to see if we have any 1677 // non-zero indices. 1678 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1679 if (!CE1->getOperand(i)->isNullValue()) 1680 // Offsetting from null, must not be equal. 1681 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1682 // Only zero indexes from null, must still be zero. 1683 return ICmpInst::ICMP_EQ; 1684 } 1685 // Otherwise, we can't really say if the first operand is null or not. 1686 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1687 if (isa<ConstantPointerNull>(CE1Op0)) { 1688 if (GV2->hasExternalWeakLinkage()) 1689 // Weak linkage GVals could be zero or not. We're comparing it to 1690 // a null pointer, so its less-or-equal 1691 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1692 else 1693 // If its not weak linkage, the GVal must have a non-zero address 1694 // so the result is less-than 1695 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1696 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1697 if (GV == GV2) { 1698 // If this is a getelementptr of the same global, then it must be 1699 // different. Because the types must match, the getelementptr could 1700 // only have at most one index, and because we fold getelementptr's 1701 // with a single zero index, it must be nonzero. 1702 assert(CE1->getNumOperands() == 2 && 1703 !CE1->getOperand(1)->isNullValue() && 1704 "Suprising getelementptr!"); 1705 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1706 } else { 1707 // If they are different globals, we don't know what the value is, 1708 // but they can't be equal. 1709 return ICmpInst::ICMP_NE; 1710 } 1711 } 1712 } else { 1713 ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1714 Constant *CE2Op0 = CE2->getOperand(0); 1715 1716 // There are MANY other foldings that we could perform here. They will 1717 // probably be added on demand, as they seem needed. 1718 switch (CE2->getOpcode()) { 1719 default: break; 1720 case Instruction::GetElementPtr: 1721 // By far the most common case to handle is when the base pointers are 1722 // obviously to the same or different globals. 1723 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1724 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 1725 return ICmpInst::ICMP_NE; 1726 // Ok, we know that both getelementptr instructions are based on the 1727 // same global. From this, we can precisely determine the relative 1728 // ordering of the resultant pointers. 1729 unsigned i = 1; 1730 1731 // The logic below assumes that the result of the comparison 1732 // can be determined by finding the first index that differs. 1733 // This doesn't work if there is over-indexing in any 1734 // subsequent indices, so check for that case first. 1735 if (!CE1->isGEPWithNoNotionalOverIndexing() || 1736 !CE2->isGEPWithNoNotionalOverIndexing()) 1737 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1738 1739 // Compare all of the operands the GEP's have in common. 1740 gep_type_iterator GTI = gep_type_begin(CE1); 1741 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1742 ++i, ++GTI) 1743 switch (IdxCompare(CE1->getOperand(i), 1744 CE2->getOperand(i), GTI.getIndexedType())) { 1745 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1746 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1747 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1748 } 1749 1750 // Ok, we ran out of things they have in common. If any leftovers 1751 // are non-zero then we have a difference, otherwise we are equal. 1752 for (; i < CE1->getNumOperands(); ++i) 1753 if (!CE1->getOperand(i)->isNullValue()) { 1754 if (isa<ConstantInt>(CE1->getOperand(i))) 1755 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1756 else 1757 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1758 } 1759 1760 for (; i < CE2->getNumOperands(); ++i) 1761 if (!CE2->getOperand(i)->isNullValue()) { 1762 if (isa<ConstantInt>(CE2->getOperand(i))) 1763 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1764 else 1765 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1766 } 1767 return ICmpInst::ICMP_EQ; 1768 } 1769 } 1770 } 1771 default: 1772 break; 1773 } 1774 } 1775 1776 return ICmpInst::BAD_ICMP_PREDICATE; 1777} 1778 1779Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1780 Constant *C1, Constant *C2) { 1781 const Type *ResultTy; 1782 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1783 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), 1784 VT->getNumElements()); 1785 else 1786 ResultTy = Type::getInt1Ty(C1->getContext()); 1787 1788 // Fold FCMP_FALSE/FCMP_TRUE unconditionally. 1789 if (pred == FCmpInst::FCMP_FALSE) 1790 return Constant::getNullValue(ResultTy); 1791 1792 if (pred == FCmpInst::FCMP_TRUE) 1793 return Constant::getAllOnesValue(ResultTy); 1794 1795 // Handle some degenerate cases first 1796 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) 1797 return UndefValue::get(ResultTy); 1798 1799 // No compile-time operations on this type yet. 1800 if (C1->getType()->isPPC_FP128Ty()) 1801 return 0; 1802 1803 // icmp eq/ne(null,GV) -> false/true 1804 if (C1->isNullValue()) { 1805 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1806 // Don't try to evaluate aliases. External weak GV can be null. 1807 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1808 if (pred == ICmpInst::ICMP_EQ) 1809 return ConstantInt::getFalse(C1->getContext()); 1810 else if (pred == ICmpInst::ICMP_NE) 1811 return ConstantInt::getTrue(C1->getContext()); 1812 } 1813 // icmp eq/ne(GV,null) -> false/true 1814 } else if (C2->isNullValue()) { 1815 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1816 // Don't try to evaluate aliases. External weak GV can be null. 1817 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1818 if (pred == ICmpInst::ICMP_EQ) 1819 return ConstantInt::getFalse(C1->getContext()); 1820 else if (pred == ICmpInst::ICMP_NE) 1821 return ConstantInt::getTrue(C1->getContext()); 1822 } 1823 } 1824 1825 // If the comparison is a comparison between two i1's, simplify it. 1826 if (C1->getType()->isIntegerTy(1)) { 1827 switch(pred) { 1828 case ICmpInst::ICMP_EQ: 1829 if (isa<ConstantInt>(C2)) 1830 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2)); 1831 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2); 1832 case ICmpInst::ICMP_NE: 1833 return ConstantExpr::getXor(C1, C2); 1834 default: 1835 break; 1836 } 1837 } 1838 1839 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1840 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1841 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1842 switch (pred) { 1843 default: llvm_unreachable("Invalid ICmp Predicate"); return 0; 1844 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); 1845 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); 1846 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); 1847 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); 1848 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); 1849 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); 1850 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); 1851 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); 1852 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); 1853 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); 1854 } 1855 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1856 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1857 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1858 APFloat::cmpResult R = C1V.compare(C2V); 1859 switch (pred) { 1860 default: llvm_unreachable("Invalid FCmp Predicate"); return 0; 1861 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); 1862 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); 1863 case FCmpInst::FCMP_UNO: 1864 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); 1865 case FCmpInst::FCMP_ORD: 1866 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); 1867 case FCmpInst::FCMP_UEQ: 1868 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1869 R==APFloat::cmpEqual); 1870 case FCmpInst::FCMP_OEQ: 1871 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); 1872 case FCmpInst::FCMP_UNE: 1873 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); 1874 case FCmpInst::FCMP_ONE: 1875 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1876 R==APFloat::cmpGreaterThan); 1877 case FCmpInst::FCMP_ULT: 1878 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1879 R==APFloat::cmpLessThan); 1880 case FCmpInst::FCMP_OLT: 1881 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); 1882 case FCmpInst::FCMP_UGT: 1883 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1884 R==APFloat::cmpGreaterThan); 1885 case FCmpInst::FCMP_OGT: 1886 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); 1887 case FCmpInst::FCMP_ULE: 1888 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); 1889 case FCmpInst::FCMP_OLE: 1890 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1891 R==APFloat::cmpEqual); 1892 case FCmpInst::FCMP_UGE: 1893 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); 1894 case FCmpInst::FCMP_OGE: 1895 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || 1896 R==APFloat::cmpEqual); 1897 } 1898 } else if (C1->getType()->isVectorTy()) { 1899 SmallVector<Constant*, 16> C1Elts, C2Elts; 1900 C1->getVectorElements(C1Elts); 1901 C2->getVectorElements(C2Elts); 1902 if (C1Elts.empty() || C2Elts.empty()) 1903 return 0; 1904 1905 // If we can constant fold the comparison of each element, constant fold 1906 // the whole vector comparison. 1907 SmallVector<Constant*, 4> ResElts; 1908 for (unsigned i = 0, e = C1Elts.size(); i != e; ++i) { 1909 // Compare the elements, producing an i1 result or constant expr. 1910 ResElts.push_back(ConstantExpr::getCompare(pred, C1Elts[i], C2Elts[i])); 1911 } 1912 return ConstantVector::get(&ResElts[0], ResElts.size()); 1913 } 1914 1915 if (C1->getType()->isFloatingPointTy()) { 1916 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1917 switch (evaluateFCmpRelation(C1, C2)) { 1918 default: llvm_unreachable("Unknown relation!"); 1919 case FCmpInst::FCMP_UNO: 1920 case FCmpInst::FCMP_ORD: 1921 case FCmpInst::FCMP_UEQ: 1922 case FCmpInst::FCMP_UNE: 1923 case FCmpInst::FCMP_ULT: 1924 case FCmpInst::FCMP_UGT: 1925 case FCmpInst::FCMP_ULE: 1926 case FCmpInst::FCMP_UGE: 1927 case FCmpInst::FCMP_TRUE: 1928 case FCmpInst::FCMP_FALSE: 1929 case FCmpInst::BAD_FCMP_PREDICATE: 1930 break; // Couldn't determine anything about these constants. 1931 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1932 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1933 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1934 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1935 break; 1936 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1937 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1938 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1939 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1940 break; 1941 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1942 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1943 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1944 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1945 break; 1946 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1947 // We can only partially decide this relation. 1948 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1949 Result = 0; 1950 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1951 Result = 1; 1952 break; 1953 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1954 // We can only partially decide this relation. 1955 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1956 Result = 0; 1957 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1958 Result = 1; 1959 break; 1960 case ICmpInst::ICMP_NE: // We know that C1 != C2 1961 // We can only partially decide this relation. 1962 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1963 Result = 0; 1964 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1965 Result = 1; 1966 break; 1967 } 1968 1969 // If we evaluated the result, return it now. 1970 if (Result != -1) 1971 return ConstantInt::get(ResultTy, Result); 1972 1973 } else { 1974 // Evaluate the relation between the two constants, per the predicate. 1975 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1976 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1977 default: llvm_unreachable("Unknown relational!"); 1978 case ICmpInst::BAD_ICMP_PREDICATE: 1979 break; // Couldn't determine anything about these constants. 1980 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1981 // If we know the constants are equal, we can decide the result of this 1982 // computation precisely. 1983 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred); 1984 break; 1985 case ICmpInst::ICMP_ULT: 1986 switch (pred) { 1987 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: 1988 Result = 1; break; 1989 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: 1990 Result = 0; break; 1991 } 1992 break; 1993 case ICmpInst::ICMP_SLT: 1994 switch (pred) { 1995 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: 1996 Result = 1; break; 1997 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: 1998 Result = 0; break; 1999 } 2000 break; 2001 case ICmpInst::ICMP_UGT: 2002 switch (pred) { 2003 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: 2004 Result = 1; break; 2005 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: 2006 Result = 0; break; 2007 } 2008 break; 2009 case ICmpInst::ICMP_SGT: 2010 switch (pred) { 2011 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: 2012 Result = 1; break; 2013 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: 2014 Result = 0; break; 2015 } 2016 break; 2017 case ICmpInst::ICMP_ULE: 2018 if (pred == ICmpInst::ICMP_UGT) Result = 0; 2019 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1; 2020 break; 2021 case ICmpInst::ICMP_SLE: 2022 if (pred == ICmpInst::ICMP_SGT) Result = 0; 2023 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1; 2024 break; 2025 case ICmpInst::ICMP_UGE: 2026 if (pred == ICmpInst::ICMP_ULT) Result = 0; 2027 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1; 2028 break; 2029 case ICmpInst::ICMP_SGE: 2030 if (pred == ICmpInst::ICMP_SLT) Result = 0; 2031 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1; 2032 break; 2033 case ICmpInst::ICMP_NE: 2034 if (pred == ICmpInst::ICMP_EQ) Result = 0; 2035 if (pred == ICmpInst::ICMP_NE) Result = 1; 2036 break; 2037 } 2038 2039 // If we evaluated the result, return it now. 2040 if (Result != -1) 2041 return ConstantInt::get(ResultTy, Result); 2042 2043 // If the right hand side is a bitcast, try using its inverse to simplify 2044 // it by moving it to the left hand side. We can't do this if it would turn 2045 // a vector compare into a scalar compare or visa versa. 2046 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) { 2047 Constant *CE2Op0 = CE2->getOperand(0); 2048 if (CE2->getOpcode() == Instruction::BitCast && 2049 CE2->getType()->isVectorTy()==CE2Op0->getType()->isVectorTy()) { 2050 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); 2051 return ConstantExpr::getICmp(pred, Inverse, CE2Op0); 2052 } 2053 } 2054 2055 // If the left hand side is an extension, try eliminating it. 2056 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 2057 if (CE1->getOpcode() == Instruction::SExt || 2058 CE1->getOpcode() == Instruction::ZExt) { 2059 Constant *CE1Op0 = CE1->getOperand(0); 2060 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); 2061 if (CE1Inverse == CE1Op0) { 2062 // Check whether we can safely truncate the right hand side. 2063 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType()); 2064 if (ConstantExpr::getZExt(C2Inverse, C2->getType()) == C2) { 2065 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse); 2066 } 2067 } 2068 } 2069 } 2070 2071 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) || 2072 (C1->isNullValue() && !C2->isNullValue())) { 2073 // If C2 is a constant expr and C1 isn't, flip them around and fold the 2074 // other way if possible. 2075 // Also, if C1 is null and C2 isn't, flip them around. 2076 switch (pred) { 2077 case ICmpInst::ICMP_EQ: 2078 case ICmpInst::ICMP_NE: 2079 // No change of predicate required. 2080 return ConstantExpr::getICmp(pred, C2, C1); 2081 2082 case ICmpInst::ICMP_ULT: 2083 case ICmpInst::ICMP_SLT: 2084 case ICmpInst::ICMP_UGT: 2085 case ICmpInst::ICMP_SGT: 2086 case ICmpInst::ICMP_ULE: 2087 case ICmpInst::ICMP_SLE: 2088 case ICmpInst::ICMP_UGE: 2089 case ICmpInst::ICMP_SGE: 2090 // Change the predicate as necessary to swap the operands. 2091 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 2092 return ConstantExpr::getICmp(pred, C2, C1); 2093 2094 default: // These predicates cannot be flopped around. 2095 break; 2096 } 2097 } 2098 } 2099 return 0; 2100} 2101 2102/// isInBoundsIndices - Test whether the given sequence of *normalized* indices 2103/// is "inbounds". 2104static bool isInBoundsIndices(Constant *const *Idxs, size_t NumIdx) { 2105 // No indices means nothing that could be out of bounds. 2106 if (NumIdx == 0) return true; 2107 2108 // If the first index is zero, it's in bounds. 2109 if (Idxs[0]->isNullValue()) return true; 2110 2111 // If the first index is one and all the rest are zero, it's in bounds, 2112 // by the one-past-the-end rule. 2113 if (!cast<ConstantInt>(Idxs[0])->isOne()) 2114 return false; 2115 for (unsigned i = 1, e = NumIdx; i != e; ++i) 2116 if (!Idxs[i]->isNullValue()) 2117 return false; 2118 return true; 2119} 2120 2121Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2122 bool inBounds, 2123 Constant* const *Idxs, 2124 unsigned NumIdx) { 2125 if (NumIdx == 0 || 2126 (NumIdx == 1 && Idxs[0]->isNullValue())) 2127 return C; 2128 2129 if (isa<UndefValue>(C)) { 2130 const PointerType *Ptr = cast<PointerType>(C->getType()); 2131 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 2132 (Value **)Idxs, 2133 (Value **)Idxs+NumIdx); 2134 assert(Ty != 0 && "Invalid indices for GEP!"); 2135 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 2136 } 2137 2138 Constant *Idx0 = Idxs[0]; 2139 if (C->isNullValue()) { 2140 bool isNull = true; 2141 for (unsigned i = 0, e = NumIdx; i != e; ++i) 2142 if (!Idxs[i]->isNullValue()) { 2143 isNull = false; 2144 break; 2145 } 2146 if (isNull) { 2147 const PointerType *Ptr = cast<PointerType>(C->getType()); 2148 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, 2149 (Value**)Idxs, 2150 (Value**)Idxs+NumIdx); 2151 assert(Ty != 0 && "Invalid indices for GEP!"); 2152 return ConstantPointerNull::get( 2153 PointerType::get(Ty,Ptr->getAddressSpace())); 2154 } 2155 } 2156 2157 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 2158 // Combine Indices - If the source pointer to this getelementptr instruction 2159 // is a getelementptr instruction, combine the indices of the two 2160 // getelementptr instructions into a single instruction. 2161 // 2162 if (CE->getOpcode() == Instruction::GetElementPtr) { 2163 const Type *LastTy = 0; 2164 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 2165 I != E; ++I) 2166 LastTy = *I; 2167 2168 if ((LastTy && LastTy->isArrayTy()) || Idx0->isNullValue()) { 2169 SmallVector<Value*, 16> NewIndices; 2170 NewIndices.reserve(NumIdx + CE->getNumOperands()); 2171 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 2172 NewIndices.push_back(CE->getOperand(i)); 2173 2174 // Add the last index of the source with the first index of the new GEP. 2175 // Make sure to handle the case when they are actually different types. 2176 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 2177 // Otherwise it must be an array. 2178 if (!Idx0->isNullValue()) { 2179 const Type *IdxTy = Combined->getType(); 2180 if (IdxTy != Idx0->getType()) { 2181 const Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext()); 2182 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty); 2183 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty); 2184 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 2185 } else { 2186 Combined = 2187 ConstantExpr::get(Instruction::Add, Idx0, Combined); 2188 } 2189 } 2190 2191 NewIndices.push_back(Combined); 2192 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); 2193 return (inBounds && cast<GEPOperator>(CE)->isInBounds()) ? 2194 ConstantExpr::getInBoundsGetElementPtr(CE->getOperand(0), 2195 &NewIndices[0], 2196 NewIndices.size()) : 2197 ConstantExpr::getGetElementPtr(CE->getOperand(0), 2198 &NewIndices[0], 2199 NewIndices.size()); 2200 } 2201 } 2202 2203 // Implement folding of: 2204 // int* getelementptr ([2 x int]* bitcast ([3 x int]* %X to [2 x int]*), 2205 // long 0, long 0) 2206 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 2207 // 2208 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) { 2209 if (const PointerType *SPT = 2210 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 2211 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 2212 if (const ArrayType *CAT = 2213 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 2214 if (CAT->getElementType() == SAT->getElementType()) 2215 return inBounds ? 2216 ConstantExpr::getInBoundsGetElementPtr( 2217 (Constant*)CE->getOperand(0), Idxs, NumIdx) : 2218 ConstantExpr::getGetElementPtr( 2219 (Constant*)CE->getOperand(0), Idxs, NumIdx); 2220 } 2221 } 2222 2223 // Check to see if any array indices are not within the corresponding 2224 // notional array bounds. If so, try to determine if they can be factored 2225 // out into preceding dimensions. 2226 bool Unknown = false; 2227 SmallVector<Constant *, 8> NewIdxs; 2228 const Type *Ty = C->getType(); 2229 const Type *Prev = 0; 2230 for (unsigned i = 0; i != NumIdx; 2231 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) { 2232 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) { 2233 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) 2234 if (ATy->getNumElements() <= INT64_MAX && 2235 ATy->getNumElements() != 0 && 2236 CI->getSExtValue() >= (int64_t)ATy->getNumElements()) { 2237 if (isa<SequentialType>(Prev)) { 2238 // It's out of range, but we can factor it into the prior 2239 // dimension. 2240 NewIdxs.resize(NumIdx); 2241 ConstantInt *Factor = ConstantInt::get(CI->getType(), 2242 ATy->getNumElements()); 2243 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor); 2244 2245 Constant *PrevIdx = Idxs[i-1]; 2246 Constant *Div = ConstantExpr::getSDiv(CI, Factor); 2247 2248 // Before adding, extend both operands to i64 to avoid 2249 // overflow trouble. 2250 if (!PrevIdx->getType()->isIntegerTy(64)) 2251 PrevIdx = ConstantExpr::getSExt(PrevIdx, 2252 Type::getInt64Ty(Div->getContext())); 2253 if (!Div->getType()->isIntegerTy(64)) 2254 Div = ConstantExpr::getSExt(Div, 2255 Type::getInt64Ty(Div->getContext())); 2256 2257 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div); 2258 } else { 2259 // It's out of range, but the prior dimension is a struct 2260 // so we can't do anything about it. 2261 Unknown = true; 2262 } 2263 } 2264 } else { 2265 // We don't know if it's in range or not. 2266 Unknown = true; 2267 } 2268 } 2269 2270 // If we did any factoring, start over with the adjusted indices. 2271 if (!NewIdxs.empty()) { 2272 for (unsigned i = 0; i != NumIdx; ++i) 2273 if (!NewIdxs[i]) NewIdxs[i] = Idxs[i]; 2274 return inBounds ? 2275 ConstantExpr::getInBoundsGetElementPtr(C, NewIdxs.data(), 2276 NewIdxs.size()) : 2277 ConstantExpr::getGetElementPtr(C, NewIdxs.data(), NewIdxs.size()); 2278 } 2279 2280 // If all indices are known integers and normalized, we can do a simple 2281 // check for the "inbounds" property. 2282 if (!Unknown && !inBounds && 2283 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs, NumIdx)) 2284 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs, NumIdx); 2285 2286 return 0; 2287} 2288