ConstantFold.cpp revision a0c138429e101f573d43740322245c1d5b8b04a0
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/Operator.h" 28#include "llvm/ADT/SmallVector.h" 29#include "llvm/Support/Compiler.h" 30#include "llvm/Support/ErrorHandling.h" 31#include "llvm/Support/GetElementPtrTypeIterator.h" 32#include "llvm/Support/ManagedStatic.h" 33#include "llvm/Support/MathExtras.h" 34#include <limits> 35using namespace llvm; 36 37//===----------------------------------------------------------------------===// 38// ConstantFold*Instruction Implementations 39//===----------------------------------------------------------------------===// 40 41/// BitCastConstantVector - Convert the specified ConstantVector node to the 42/// specified vector type. At this point, we know that the elements of the 43/// input vector constant are all simple integer or FP values. 44static Constant *BitCastConstantVector(ConstantVector *CV, 45 const VectorType *DstTy) { 46 47 if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy); 48 if (CV->isNullValue()) return Constant::getNullValue(DstTy); 49 50 // If this cast changes element count then we can't handle it here: 51 // doing so requires endianness information. This should be handled by 52 // Analysis/ConstantFolding.cpp 53 unsigned NumElts = DstTy->getNumElements(); 54 if (NumElts != CV->getNumOperands()) 55 return 0; 56 57 // Check to verify that all elements of the input are simple. 58 for (unsigned i = 0; i != NumElts; ++i) { 59 if (!isa<ConstantInt>(CV->getOperand(i)) && 60 !isa<ConstantFP>(CV->getOperand(i))) 61 return 0; 62 } 63 64 // Bitcast each element now. 65 std::vector<Constant*> Result; 66 const Type *DstEltTy = DstTy->getElementType(); 67 for (unsigned i = 0; i != NumElts; ++i) 68 Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i), 69 DstEltTy)); 70 return ConstantVector::get(Result); 71} 72 73/// This function determines which opcode to use to fold two constant cast 74/// expressions together. It uses CastInst::isEliminableCastPair to determine 75/// the opcode. Consequently its just a wrapper around that function. 76/// @brief Determine if it is valid to fold a cast of a cast 77static unsigned 78foldConstantCastPair( 79 unsigned opc, ///< opcode of the second cast constant expression 80 ConstantExpr *Op, ///< the first cast constant expression 81 const Type *DstTy ///< desintation type of the first cast 82) { 83 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); 84 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); 85 assert(CastInst::isCast(opc) && "Invalid cast opcode"); 86 87 // The the types and opcodes for the two Cast constant expressions 88 const Type *SrcTy = Op->getOperand(0)->getType(); 89 const Type *MidTy = Op->getType(); 90 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); 91 Instruction::CastOps secondOp = Instruction::CastOps(opc); 92 93 // Let CastInst::isEliminableCastPair do the heavy lifting. 94 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, 95 Type::getInt64Ty(DstTy->getContext())); 96} 97 98static Constant *FoldBitCast(Constant *V, const Type *DestTy) { 99 const Type *SrcTy = V->getType(); 100 if (SrcTy == DestTy) 101 return V; // no-op cast 102 103 // Check to see if we are casting a pointer to an aggregate to a pointer to 104 // the first element. If so, return the appropriate GEP instruction. 105 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) 106 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) 107 if (PTy->getAddressSpace() == DPTy->getAddressSpace()) { 108 SmallVector<Value*, 8> IdxList; 109 Value *Zero = 110 Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); 111 IdxList.push_back(Zero); 112 const Type *ElTy = PTy->getElementType(); 113 while (ElTy != DPTy->getElementType()) { 114 if (const StructType *STy = dyn_cast<StructType>(ElTy)) { 115 if (STy->getNumElements() == 0) break; 116 ElTy = STy->getElementType(0); 117 IdxList.push_back(Zero); 118 } else if (const SequentialType *STy = 119 dyn_cast<SequentialType>(ElTy)) { 120 if (ElTy->isPointerTy()) break; // Can't index into pointers! 121 ElTy = STy->getElementType(); 122 IdxList.push_back(Zero); 123 } else { 124 break; 125 } 126 } 127 128 if (ElTy == DPTy->getElementType()) 129 // This GEP is inbounds because all indices are zero. 130 return ConstantExpr::getInBoundsGetElementPtr(V, &IdxList[0], 131 IdxList.size()); 132 } 133 134 // Handle casts from one vector constant to another. We know that the src 135 // and dest type have the same size (otherwise its an illegal cast). 136 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { 137 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { 138 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && 139 "Not cast between same sized vectors!"); 140 SrcTy = NULL; 141 // First, check for null. Undef is already handled. 142 if (isa<ConstantAggregateZero>(V)) 143 return Constant::getNullValue(DestTy); 144 145 if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) 146 return BitCastConstantVector(CV, DestPTy); 147 } 148 149 // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts 150 // This allows for other simplifications (although some of them 151 // can only be handled by Analysis/ConstantFolding.cpp). 152 if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) 153 return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy); 154 } 155 156 // Finally, implement bitcast folding now. The code below doesn't handle 157 // bitcast right. 158 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 159 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 160 161 // Handle integral constant input. 162 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 163 if (DestTy->isIntegerTy()) 164 // Integral -> Integral. This is a no-op because the bit widths must 165 // be the same. Consequently, we just fold to V. 166 return V; 167 168 if (DestTy->isFloatingPointTy()) 169 return ConstantFP::get(DestTy->getContext(), 170 APFloat(CI->getValue(), 171 !DestTy->isPPC_FP128Ty())); 172 173 // Otherwise, can't fold this (vector?) 174 return 0; 175 } 176 177 // Handle ConstantFP input: FP -> Integral. 178 if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) 179 return ConstantInt::get(FP->getContext(), 180 FP->getValueAPF().bitcastToAPInt()); 181 182 return 0; 183} 184 185 186/// ExtractConstantBytes - V is an integer constant which only has a subset of 187/// its bytes used. The bytes used are indicated by ByteStart (which is the 188/// first byte used, counting from the least significant byte) and ByteSize, 189/// which is the number of bytes used. 190/// 191/// This function analyzes the specified constant to see if the specified byte 192/// range can be returned as a simplified constant. If so, the constant is 193/// returned, otherwise null is returned. 194/// 195static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart, 196 unsigned ByteSize) { 197 assert(C->getType()->isIntegerTy() && 198 (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 && 199 "Non-byte sized integer input"); 200 unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8; 201 assert(ByteSize && "Must be accessing some piece"); 202 assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input"); 203 assert(ByteSize != CSize && "Should not extract everything"); 204 205 // Constant Integers are simple. 206 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 207 APInt V = CI->getValue(); 208 if (ByteStart) 209 V = V.lshr(ByteStart*8); 210 V = V.trunc(ByteSize*8); 211 return ConstantInt::get(CI->getContext(), V); 212 } 213 214 // In the input is a constant expr, we might be able to recursively simplify. 215 // If not, we definitely can't do anything. 216 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 217 if (CE == 0) return 0; 218 219 switch (CE->getOpcode()) { 220 default: return 0; 221 case Instruction::Or: { 222 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); 223 if (RHS == 0) 224 return 0; 225 226 // X | -1 -> -1. 227 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) 228 if (RHSC->isAllOnesValue()) 229 return RHSC; 230 231 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); 232 if (LHS == 0) 233 return 0; 234 return ConstantExpr::getOr(LHS, RHS); 235 } 236 case Instruction::And: { 237 Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); 238 if (RHS == 0) 239 return 0; 240 241 // X & 0 -> 0. 242 if (RHS->isNullValue()) 243 return RHS; 244 245 Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); 246 if (LHS == 0) 247 return 0; 248 return ConstantExpr::getAnd(LHS, RHS); 249 } 250 case Instruction::LShr: { 251 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); 252 if (Amt == 0) 253 return 0; 254 unsigned ShAmt = Amt->getZExtValue(); 255 // Cannot analyze non-byte shifts. 256 if ((ShAmt & 7) != 0) 257 return 0; 258 ShAmt >>= 3; 259 260 // If the extract is known to be all zeros, return zero. 261 if (ByteStart >= CSize-ShAmt) 262 return Constant::getNullValue(IntegerType::get(CE->getContext(), 263 ByteSize*8)); 264 // If the extract is known to be fully in the input, extract it. 265 if (ByteStart+ByteSize+ShAmt <= CSize) 266 return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize); 267 268 // TODO: Handle the 'partially zero' case. 269 return 0; 270 } 271 272 case Instruction::Shl: { 273 ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); 274 if (Amt == 0) 275 return 0; 276 unsigned ShAmt = Amt->getZExtValue(); 277 // Cannot analyze non-byte shifts. 278 if ((ShAmt & 7) != 0) 279 return 0; 280 ShAmt >>= 3; 281 282 // If the extract is known to be all zeros, return zero. 283 if (ByteStart+ByteSize <= ShAmt) 284 return Constant::getNullValue(IntegerType::get(CE->getContext(), 285 ByteSize*8)); 286 // If the extract is known to be fully in the input, extract it. 287 if (ByteStart >= ShAmt) 288 return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize); 289 290 // TODO: Handle the 'partially zero' case. 291 return 0; 292 } 293 294 case Instruction::ZExt: { 295 unsigned SrcBitSize = 296 cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth(); 297 298 // If extracting something that is completely zero, return 0. 299 if (ByteStart*8 >= SrcBitSize) 300 return Constant::getNullValue(IntegerType::get(CE->getContext(), 301 ByteSize*8)); 302 303 // If exactly extracting the input, return it. 304 if (ByteStart == 0 && ByteSize*8 == SrcBitSize) 305 return CE->getOperand(0); 306 307 // If extracting something completely in the input, if if the input is a 308 // multiple of 8 bits, recurse. 309 if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize) 310 return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize); 311 312 // Otherwise, if extracting a subset of the input, which is not multiple of 313 // 8 bits, do a shift and trunc to get the bits. 314 if ((ByteStart+ByteSize)*8 < SrcBitSize) { 315 assert((SrcBitSize&7) && "Shouldn't get byte sized case here"); 316 Constant *Res = CE->getOperand(0); 317 if (ByteStart) 318 Res = ConstantExpr::getLShr(Res, 319 ConstantInt::get(Res->getType(), ByteStart*8)); 320 return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(), 321 ByteSize*8)); 322 } 323 324 // TODO: Handle the 'partially zero' case. 325 return 0; 326 } 327 } 328} 329 330/// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof 331/// on Ty, with any known factors factored out. If Folded is false, 332/// return null if no factoring was possible, to avoid endlessly 333/// bouncing an unfoldable expression back into the top-level folder. 334/// 335static Constant *getFoldedSizeOf(const Type *Ty, const Type *DestTy, 336 bool Folded) { 337 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 338 Constant *N = ConstantInt::get(DestTy, ATy->getNumElements()); 339 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); 340 return ConstantExpr::getNUWMul(E, N); 341 } 342 343 if (const StructType *STy = dyn_cast<StructType>(Ty)) 344 if (!STy->isPacked()) { 345 unsigned NumElems = STy->getNumElements(); 346 // An empty struct has size zero. 347 if (NumElems == 0) 348 return ConstantExpr::getNullValue(DestTy); 349 // Check for a struct with all members having the same size. 350 Constant *MemberSize = 351 getFoldedSizeOf(STy->getElementType(0), DestTy, true); 352 bool AllSame = true; 353 for (unsigned i = 1; i != NumElems; ++i) 354 if (MemberSize != 355 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { 356 AllSame = false; 357 break; 358 } 359 if (AllSame) { 360 Constant *N = ConstantInt::get(DestTy, NumElems); 361 return ConstantExpr::getNUWMul(MemberSize, N); 362 } 363 } 364 365 // Pointer size doesn't depend on the pointee type, so canonicalize them 366 // to an arbitrary pointee. 367 if (const PointerType *PTy = dyn_cast<PointerType>(Ty)) 368 if (!PTy->getElementType()->isIntegerTy(1)) 369 return 370 getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), 371 PTy->getAddressSpace()), 372 DestTy, true); 373 374 // If there's no interesting folding happening, bail so that we don't create 375 // a constant that looks like it needs folding but really doesn't. 376 if (!Folded) 377 return 0; 378 379 // Base case: Get a regular sizeof expression. 380 Constant *C = ConstantExpr::getSizeOf(Ty); 381 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 382 DestTy, false), 383 C, DestTy); 384 return C; 385} 386 387/// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof 388/// on Ty, with any known factors factored out. If Folded is false, 389/// return null if no factoring was possible, to avoid endlessly 390/// bouncing an unfoldable expression back into the top-level folder. 391/// 392static Constant *getFoldedAlignOf(const Type *Ty, const Type *DestTy, 393 bool Folded) { 394 // The alignment of an array is equal to the alignment of the 395 // array element. Note that this is not always true for vectors. 396 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 397 Constant *C = ConstantExpr::getAlignOf(ATy->getElementType()); 398 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 399 DestTy, 400 false), 401 C, DestTy); 402 return C; 403 } 404 405 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 406 // Packed structs always have an alignment of 1. 407 if (STy->isPacked()) 408 return ConstantInt::get(DestTy, 1); 409 410 // Otherwise, struct alignment is the maximum alignment of any member. 411 // Without target data, we can't compare much, but we can check to see 412 // if all the members have the same alignment. 413 unsigned NumElems = STy->getNumElements(); 414 // An empty struct has minimal alignment. 415 if (NumElems == 0) 416 return ConstantInt::get(DestTy, 1); 417 // Check for a struct with all members having the same alignment. 418 Constant *MemberAlign = 419 getFoldedAlignOf(STy->getElementType(0), DestTy, true); 420 bool AllSame = true; 421 for (unsigned i = 1; i != NumElems; ++i) 422 if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) { 423 AllSame = false; 424 break; 425 } 426 if (AllSame) 427 return MemberAlign; 428 } 429 430 // Pointer alignment doesn't depend on the pointee type, so canonicalize them 431 // to an arbitrary pointee. 432 if (const PointerType *PTy = dyn_cast<PointerType>(Ty)) 433 if (!PTy->getElementType()->isIntegerTy(1)) 434 return 435 getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(), 436 1), 437 PTy->getAddressSpace()), 438 DestTy, true); 439 440 // If there's no interesting folding happening, bail so that we don't create 441 // a constant that looks like it needs folding but really doesn't. 442 if (!Folded) 443 return 0; 444 445 // Base case: Get a regular alignof expression. 446 Constant *C = ConstantExpr::getAlignOf(Ty); 447 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 448 DestTy, false), 449 C, DestTy); 450 return C; 451} 452 453/// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof 454/// on Ty and FieldNo, with any known factors factored out. If Folded is false, 455/// return null if no factoring was possible, to avoid endlessly 456/// bouncing an unfoldable expression back into the top-level folder. 457/// 458static Constant *getFoldedOffsetOf(const Type *Ty, Constant *FieldNo, 459 const Type *DestTy, 460 bool Folded) { 461 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 462 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, 463 DestTy, false), 464 FieldNo, DestTy); 465 Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); 466 return ConstantExpr::getNUWMul(E, N); 467 } 468 469 if (const StructType *STy = dyn_cast<StructType>(Ty)) 470 if (!STy->isPacked()) { 471 unsigned NumElems = STy->getNumElements(); 472 // An empty struct has no members. 473 if (NumElems == 0) 474 return 0; 475 // Check for a struct with all members having the same size. 476 Constant *MemberSize = 477 getFoldedSizeOf(STy->getElementType(0), DestTy, true); 478 bool AllSame = true; 479 for (unsigned i = 1; i != NumElems; ++i) 480 if (MemberSize != 481 getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { 482 AllSame = false; 483 break; 484 } 485 if (AllSame) { 486 Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, 487 false, 488 DestTy, 489 false), 490 FieldNo, DestTy); 491 return ConstantExpr::getNUWMul(MemberSize, N); 492 } 493 } 494 495 // If there's no interesting folding happening, bail so that we don't create 496 // a constant that looks like it needs folding but really doesn't. 497 if (!Folded) 498 return 0; 499 500 // Base case: Get a regular offsetof expression. 501 Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo); 502 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 503 DestTy, false), 504 C, DestTy); 505 return C; 506} 507 508Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, 509 const Type *DestTy) { 510 if (isa<UndefValue>(V)) { 511 // zext(undef) = 0, because the top bits will be zero. 512 // sext(undef) = 0, because the top bits will all be the same. 513 // [us]itofp(undef) = 0, because the result value is bounded. 514 if (opc == Instruction::ZExt || opc == Instruction::SExt || 515 opc == Instruction::UIToFP || opc == Instruction::SIToFP) 516 return Constant::getNullValue(DestTy); 517 return UndefValue::get(DestTy); 518 } 519 520 // No compile-time operations on this type yet. 521 if (V->getType()->isPPC_FP128Ty() || DestTy->isPPC_FP128Ty()) 522 return 0; 523 524 if (V->isNullValue() && !DestTy->isX86_MMXTy()) 525 return Constant::getNullValue(DestTy); 526 527 // If the cast operand is a constant expression, there's a few things we can 528 // do to try to simplify it. 529 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 530 if (CE->isCast()) { 531 // Try hard to fold cast of cast because they are often eliminable. 532 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 533 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 534 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 535 // If all of the indexes in the GEP are null values, there is no pointer 536 // adjustment going on. We might as well cast the source pointer. 537 bool isAllNull = true; 538 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 539 if (!CE->getOperand(i)->isNullValue()) { 540 isAllNull = false; 541 break; 542 } 543 if (isAllNull) 544 // This is casting one pointer type to another, always BitCast 545 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 546 } 547 } 548 549 // If the cast operand is a constant vector, perform the cast by 550 // operating on each element. In the cast of bitcasts, the element 551 // count may be mismatched; don't attempt to handle that here. 552 if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) 553 if (DestTy->isVectorTy() && 554 cast<VectorType>(DestTy)->getNumElements() == 555 CV->getType()->getNumElements()) { 556 std::vector<Constant*> res; 557 const VectorType *DestVecTy = cast<VectorType>(DestTy); 558 const Type *DstEltTy = DestVecTy->getElementType(); 559 for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) 560 res.push_back(ConstantExpr::getCast(opc, 561 CV->getOperand(i), DstEltTy)); 562 return ConstantVector::get(res); 563 } 564 565 // We actually have to do a cast now. Perform the cast according to the 566 // opcode specified. 567 switch (opc) { 568 default: 569 llvm_unreachable("Failed to cast constant expression"); 570 case Instruction::FPTrunc: 571 case Instruction::FPExt: 572 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 573 bool ignored; 574 APFloat Val = FPC->getValueAPF(); 575 Val.convert(DestTy->isFloatTy() ? APFloat::IEEEsingle : 576 DestTy->isDoubleTy() ? APFloat::IEEEdouble : 577 DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended : 578 DestTy->isFP128Ty() ? APFloat::IEEEquad : 579 APFloat::Bogus, 580 APFloat::rmNearestTiesToEven, &ignored); 581 return ConstantFP::get(V->getContext(), Val); 582 } 583 return 0; // Can't fold. 584 case Instruction::FPToUI: 585 case Instruction::FPToSI: 586 if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 587 const APFloat &V = FPC->getValueAPF(); 588 bool ignored; 589 uint64_t x[2]; 590 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 591 (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 592 APFloat::rmTowardZero, &ignored); 593 APInt Val(DestBitWidth, 2, x); 594 return ConstantInt::get(FPC->getContext(), Val); 595 } 596 return 0; // Can't fold. 597 case Instruction::IntToPtr: //always treated as unsigned 598 if (V->isNullValue()) // Is it an integral null value? 599 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 600 return 0; // Other pointer types cannot be casted 601 case Instruction::PtrToInt: // always treated as unsigned 602 // Is it a null pointer value? 603 if (V->isNullValue()) 604 return ConstantInt::get(DestTy, 0); 605 // If this is a sizeof-like expression, pull out multiplications by 606 // known factors to expose them to subsequent folding. If it's an 607 // alignof-like expression, factor out known factors. 608 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 609 if (CE->getOpcode() == Instruction::GetElementPtr && 610 CE->getOperand(0)->isNullValue()) { 611 const Type *Ty = 612 cast<PointerType>(CE->getOperand(0)->getType())->getElementType(); 613 if (CE->getNumOperands() == 2) { 614 // Handle a sizeof-like expression. 615 Constant *Idx = CE->getOperand(1); 616 bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne(); 617 if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { 618 Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, 619 DestTy, false), 620 Idx, DestTy); 621 return ConstantExpr::getMul(C, Idx); 622 } 623 } else if (CE->getNumOperands() == 3 && 624 CE->getOperand(1)->isNullValue()) { 625 // Handle an alignof-like expression. 626 if (const StructType *STy = dyn_cast<StructType>(Ty)) 627 if (!STy->isPacked()) { 628 ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2)); 629 if (CI->isOne() && 630 STy->getNumElements() == 2 && 631 STy->getElementType(0)->isIntegerTy(1)) { 632 return getFoldedAlignOf(STy->getElementType(1), DestTy, false); 633 } 634 } 635 // Handle an offsetof-like expression. 636 if (Ty->isStructTy() || Ty->isArrayTy()) { 637 if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), 638 DestTy, false)) 639 return C; 640 } 641 } 642 } 643 // Other pointer types cannot be casted 644 return 0; 645 case Instruction::UIToFP: 646 case Instruction::SIToFP: 647 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 648 APInt api = CI->getValue(); 649 APFloat apf(APInt::getNullValue(DestTy->getPrimitiveSizeInBits()), true); 650 (void)apf.convertFromAPInt(api, 651 opc==Instruction::SIToFP, 652 APFloat::rmNearestTiesToEven); 653 return ConstantFP::get(V->getContext(), apf); 654 } 655 return 0; 656 case Instruction::ZExt: 657 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 658 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 659 return ConstantInt::get(V->getContext(), 660 CI->getValue().zext(BitWidth)); 661 } 662 return 0; 663 case Instruction::SExt: 664 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 665 uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 666 return ConstantInt::get(V->getContext(), 667 CI->getValue().sext(BitWidth)); 668 } 669 return 0; 670 case Instruction::Trunc: { 671 uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 672 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 673 return ConstantInt::get(V->getContext(), 674 CI->getValue().trunc(DestBitWidth)); 675 } 676 677 // The input must be a constantexpr. See if we can simplify this based on 678 // the bytes we are demanding. Only do this if the source and dest are an 679 // even multiple of a byte. 680 if ((DestBitWidth & 7) == 0 && 681 (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0) 682 if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8)) 683 return Res; 684 685 return 0; 686 } 687 case Instruction::BitCast: 688 return FoldBitCast(V, DestTy); 689 } 690} 691 692Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, 693 Constant *V1, Constant *V2) { 694 if (ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) 695 return CB->getZExtValue() ? V1 : V2; 696 697 // Check for zero aggregate and ConstantVector of zeros 698 if (Cond->isNullValue()) return V2; 699 700 if (ConstantVector* CondV = dyn_cast<ConstantVector>(Cond)) { 701 702 if (CondV->isAllOnesValue()) return V1; 703 704 const VectorType *VTy = cast<VectorType>(V1->getType()); 705 ConstantVector *CP1 = dyn_cast<ConstantVector>(V1); 706 ConstantVector *CP2 = dyn_cast<ConstantVector>(V2); 707 708 if ((CP1 || isa<ConstantAggregateZero>(V1)) && 709 (CP2 || isa<ConstantAggregateZero>(V2))) { 710 711 // Find the element type of the returned vector 712 const Type *EltTy = VTy->getElementType(); 713 unsigned NumElem = VTy->getNumElements(); 714 std::vector<Constant*> Res(NumElem); 715 716 bool Valid = true; 717 for (unsigned i = 0; i < NumElem; ++i) { 718 ConstantInt* c = dyn_cast<ConstantInt>(CondV->getOperand(i)); 719 if (!c) { 720 Valid = false; 721 break; 722 } 723 Constant *C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 724 Constant *C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 725 Res[i] = c->getZExtValue() ? C1 : C2; 726 } 727 // If we were able to build the vector, return it 728 if (Valid) return ConstantVector::get(Res); 729 } 730 } 731 732 733 if (isa<UndefValue>(V1)) return V2; 734 if (isa<UndefValue>(V2)) return V1; 735 if (isa<UndefValue>(Cond)) return V1; 736 if (V1 == V2) return V1; 737 738 if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) { 739 if (TrueVal->getOpcode() == Instruction::Select) 740 if (TrueVal->getOperand(0) == Cond) 741 return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2); 742 } 743 if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) { 744 if (FalseVal->getOpcode() == Instruction::Select) 745 if (FalseVal->getOperand(0) == Cond) 746 return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2)); 747 } 748 749 return 0; 750} 751 752Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, 753 Constant *Idx) { 754 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 755 return UndefValue::get(cast<VectorType>(Val->getType())->getElementType()); 756 if (Val->isNullValue()) // ee(zero, x) -> zero 757 return Constant::getNullValue( 758 cast<VectorType>(Val->getType())->getElementType()); 759 760 if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 761 if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 762 return CVal->getOperand(CIdx->getZExtValue()); 763 } else if (isa<UndefValue>(Idx)) { 764 // ee({w,x,y,z}, undef) -> w (an arbitrary value). 765 return CVal->getOperand(0); 766 } 767 } 768 return 0; 769} 770 771Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, 772 Constant *Elt, 773 Constant *Idx) { 774 ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 775 if (!CIdx) return 0; 776 APInt idxVal = CIdx->getValue(); 777 if (isa<UndefValue>(Val)) { 778 // Insertion of scalar constant into vector undef 779 // Optimize away insertion of undef 780 if (isa<UndefValue>(Elt)) 781 return Val; 782 // Otherwise break the aggregate undef into multiple undefs and do 783 // the insertion 784 unsigned numOps = 785 cast<VectorType>(Val->getType())->getNumElements(); 786 std::vector<Constant*> Ops; 787 Ops.reserve(numOps); 788 for (unsigned i = 0; i < numOps; ++i) { 789 Constant *Op = 790 (idxVal == i) ? Elt : UndefValue::get(Elt->getType()); 791 Ops.push_back(Op); 792 } 793 return ConstantVector::get(Ops); 794 } 795 if (isa<ConstantAggregateZero>(Val)) { 796 // Insertion of scalar constant into vector aggregate zero 797 // Optimize away insertion of zero 798 if (Elt->isNullValue()) 799 return Val; 800 // Otherwise break the aggregate zero into multiple zeros and do 801 // the insertion 802 unsigned numOps = 803 cast<VectorType>(Val->getType())->getNumElements(); 804 std::vector<Constant*> Ops; 805 Ops.reserve(numOps); 806 for (unsigned i = 0; i < numOps; ++i) { 807 Constant *Op = 808 (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType()); 809 Ops.push_back(Op); 810 } 811 return ConstantVector::get(Ops); 812 } 813 if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { 814 // Insertion of scalar constant into vector constant 815 std::vector<Constant*> Ops; 816 Ops.reserve(CVal->getNumOperands()); 817 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { 818 Constant *Op = 819 (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i)); 820 Ops.push_back(Op); 821 } 822 return ConstantVector::get(Ops); 823 } 824 825 return 0; 826} 827 828/// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef 829/// return the specified element value. Otherwise return null. 830static Constant *GetVectorElement(Constant *C, unsigned EltNo) { 831 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) 832 return CV->getOperand(EltNo); 833 834 const Type *EltTy = cast<VectorType>(C->getType())->getElementType(); 835 if (isa<ConstantAggregateZero>(C)) 836 return Constant::getNullValue(EltTy); 837 if (isa<UndefValue>(C)) 838 return UndefValue::get(EltTy); 839 return 0; 840} 841 842Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, 843 Constant *V2, 844 Constant *Mask) { 845 // Undefined shuffle mask -> undefined value. 846 if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType()); 847 848 unsigned MaskNumElts = cast<VectorType>(Mask->getType())->getNumElements(); 849 unsigned SrcNumElts = cast<VectorType>(V1->getType())->getNumElements(); 850 const Type *EltTy = cast<VectorType>(V1->getType())->getElementType(); 851 852 // Loop over the shuffle mask, evaluating each element. 853 SmallVector<Constant*, 32> Result; 854 for (unsigned i = 0; i != MaskNumElts; ++i) { 855 Constant *InElt = GetVectorElement(Mask, i); 856 if (InElt == 0) return 0; 857 858 if (isa<UndefValue>(InElt)) 859 InElt = UndefValue::get(EltTy); 860 else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) { 861 unsigned Elt = CI->getZExtValue(); 862 if (Elt >= SrcNumElts*2) 863 InElt = UndefValue::get(EltTy); 864 else if (Elt >= SrcNumElts) 865 InElt = GetVectorElement(V2, Elt - SrcNumElts); 866 else 867 InElt = GetVectorElement(V1, Elt); 868 if (InElt == 0) return 0; 869 } else { 870 // Unknown value. 871 return 0; 872 } 873 Result.push_back(InElt); 874 } 875 876 return ConstantVector::get(Result); 877} 878 879Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, 880 const unsigned *Idxs, 881 unsigned NumIdx) { 882 // Base case: no indices, so return the entire value. 883 if (NumIdx == 0) 884 return Agg; 885 886 if (isa<UndefValue>(Agg)) // ev(undef, x) -> undef 887 return UndefValue::get(ExtractValueInst::getIndexedType(Agg->getType(), 888 Idxs, 889 Idxs + NumIdx)); 890 891 if (isa<ConstantAggregateZero>(Agg)) // ev(0, x) -> 0 892 return 893 Constant::getNullValue(ExtractValueInst::getIndexedType(Agg->getType(), 894 Idxs, 895 Idxs + NumIdx)); 896 897 // Otherwise recurse. 898 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) 899 return ConstantFoldExtractValueInstruction(CS->getOperand(*Idxs), 900 Idxs+1, NumIdx-1); 901 902 if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) 903 return ConstantFoldExtractValueInstruction(CA->getOperand(*Idxs), 904 Idxs+1, NumIdx-1); 905 ConstantVector *CV = cast<ConstantVector>(Agg); 906 return ConstantFoldExtractValueInstruction(CV->getOperand(*Idxs), 907 Idxs+1, NumIdx-1); 908} 909 910Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, 911 Constant *Val, 912 const unsigned *Idxs, 913 unsigned NumIdx) { 914 // Base case: no indices, so replace the entire value. 915 if (NumIdx == 0) 916 return Val; 917 918 if (isa<UndefValue>(Agg)) { 919 // Insertion of constant into aggregate undef 920 // Optimize away insertion of undef. 921 if (isa<UndefValue>(Val)) 922 return Agg; 923 924 // Otherwise break the aggregate undef into multiple undefs and do 925 // the insertion. 926 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 927 unsigned numOps; 928 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 929 numOps = AR->getNumElements(); 930 else 931 numOps = cast<StructType>(AggTy)->getNumElements(); 932 933 std::vector<Constant*> Ops(numOps); 934 for (unsigned i = 0; i < numOps; ++i) { 935 const Type *MemberTy = AggTy->getTypeAtIndex(i); 936 Constant *Op = 937 (*Idxs == i) ? 938 ConstantFoldInsertValueInstruction(UndefValue::get(MemberTy), 939 Val, Idxs+1, NumIdx-1) : 940 UndefValue::get(MemberTy); 941 Ops[i] = Op; 942 } 943 944 if (const StructType* ST = dyn_cast<StructType>(AggTy)) 945 return ConstantStruct::get(ST, Ops); 946 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 947 } 948 949 if (isa<ConstantAggregateZero>(Agg)) { 950 // Insertion of constant into aggregate zero 951 // Optimize away insertion of zero. 952 if (Val->isNullValue()) 953 return Agg; 954 955 // Otherwise break the aggregate zero into multiple zeros and do 956 // the insertion. 957 const CompositeType *AggTy = cast<CompositeType>(Agg->getType()); 958 unsigned numOps; 959 if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy)) 960 numOps = AR->getNumElements(); 961 else 962 numOps = cast<StructType>(AggTy)->getNumElements(); 963 964 std::vector<Constant*> Ops(numOps); 965 for (unsigned i = 0; i < numOps; ++i) { 966 const Type *MemberTy = AggTy->getTypeAtIndex(i); 967 Constant *Op = 968 (*Idxs == i) ? 969 ConstantFoldInsertValueInstruction(Constant::getNullValue(MemberTy), 970 Val, Idxs+1, NumIdx-1) : 971 Constant::getNullValue(MemberTy); 972 Ops[i] = Op; 973 } 974 975 if (const StructType *ST = dyn_cast<StructType>(AggTy)) 976 return ConstantStruct::get(ST, Ops); 977 return ConstantArray::get(cast<ArrayType>(AggTy), Ops); 978 } 979 980 if (isa<ConstantStruct>(Agg) || isa<ConstantArray>(Agg)) { 981 // Insertion of constant into aggregate constant. 982 std::vector<Constant*> Ops(Agg->getNumOperands()); 983 for (unsigned i = 0; i < Agg->getNumOperands(); ++i) { 984 Constant *Op = cast<Constant>(Agg->getOperand(i)); 985 if (*Idxs == i) 986 Op = ConstantFoldInsertValueInstruction(Op, Val, Idxs+1, NumIdx-1); 987 Ops[i] = Op; 988 } 989 990 if (const StructType* ST = dyn_cast<StructType>(Agg->getType())) 991 return ConstantStruct::get(ST, Ops); 992 return ConstantArray::get(cast<ArrayType>(Agg->getType()), Ops); 993 } 994 995 return 0; 996} 997 998 999Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 1000 Constant *C1, Constant *C2) { 1001 // No compile-time operations on this type yet. 1002 if (C1->getType()->isPPC_FP128Ty()) 1003 return 0; 1004 1005 // Handle UndefValue up front. 1006 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 1007 switch (Opcode) { 1008 case Instruction::Xor: 1009 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 1010 // Handle undef ^ undef -> 0 special case. This is a common 1011 // idiom (misuse). 1012 return Constant::getNullValue(C1->getType()); 1013 // Fallthrough 1014 case Instruction::Add: 1015 case Instruction::Sub: 1016 return UndefValue::get(C1->getType()); 1017 case Instruction::Mul: 1018 case Instruction::And: 1019 return Constant::getNullValue(C1->getType()); 1020 case Instruction::UDiv: 1021 case Instruction::SDiv: 1022 case Instruction::URem: 1023 case Instruction::SRem: 1024 if (!isa<UndefValue>(C2)) // undef / X -> 0 1025 return Constant::getNullValue(C1->getType()); 1026 return C2; // X / undef -> undef 1027 case Instruction::Or: // X | undef -> -1 1028 if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType())) 1029 return Constant::getAllOnesValue(PTy); 1030 return Constant::getAllOnesValue(C1->getType()); 1031 case Instruction::LShr: 1032 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 1033 return C1; // undef lshr undef -> undef 1034 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 1035 // undef lshr X -> 0 1036 case Instruction::AShr: 1037 if (!isa<UndefValue>(C2)) // undef ashr X --> all ones 1038 return Constant::getAllOnesValue(C1->getType()); 1039 else if (isa<UndefValue>(C1)) 1040 return C1; // undef ashr undef -> undef 1041 else 1042 return C1; // X ashr undef --> X 1043 case Instruction::Shl: 1044 // undef << X -> 0 or X << undef -> 0 1045 return Constant::getNullValue(C1->getType()); 1046 } 1047 } 1048 1049 // Handle simplifications when the RHS is a constant int. 1050 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 1051 switch (Opcode) { 1052 case Instruction::Add: 1053 if (CI2->equalsInt(0)) return C1; // X + 0 == X 1054 break; 1055 case Instruction::Sub: 1056 if (CI2->equalsInt(0)) return C1; // X - 0 == X 1057 break; 1058 case Instruction::Mul: 1059 if (CI2->equalsInt(0)) return C2; // X * 0 == 0 1060 if (CI2->equalsInt(1)) 1061 return C1; // X * 1 == X 1062 break; 1063 case Instruction::UDiv: 1064 case Instruction::SDiv: 1065 if (CI2->equalsInt(1)) 1066 return C1; // X / 1 == X 1067 if (CI2->equalsInt(0)) 1068 return UndefValue::get(CI2->getType()); // X / 0 == undef 1069 break; 1070 case Instruction::URem: 1071 case Instruction::SRem: 1072 if (CI2->equalsInt(1)) 1073 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 1074 if (CI2->equalsInt(0)) 1075 return UndefValue::get(CI2->getType()); // X % 0 == undef 1076 break; 1077 case Instruction::And: 1078 if (CI2->isZero()) return C2; // X & 0 == 0 1079 if (CI2->isAllOnesValue()) 1080 return C1; // X & -1 == X 1081 1082 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1083 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 1084 if (CE1->getOpcode() == Instruction::ZExt) { 1085 unsigned DstWidth = CI2->getType()->getBitWidth(); 1086 unsigned SrcWidth = 1087 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 1088 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 1089 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 1090 return C1; 1091 } 1092 1093 // If and'ing the address of a global with a constant, fold it. 1094 if (CE1->getOpcode() == Instruction::PtrToInt && 1095 isa<GlobalValue>(CE1->getOperand(0))) { 1096 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 1097 1098 // Functions are at least 4-byte aligned. 1099 unsigned GVAlign = GV->getAlignment(); 1100 if (isa<Function>(GV)) 1101 GVAlign = std::max(GVAlign, 4U); 1102 1103 if (GVAlign > 1) { 1104 unsigned DstWidth = CI2->getType()->getBitWidth(); 1105 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 1106 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 1107 1108 // If checking bits we know are clear, return zero. 1109 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 1110 return Constant::getNullValue(CI2->getType()); 1111 } 1112 } 1113 } 1114 break; 1115 case Instruction::Or: 1116 if (CI2->equalsInt(0)) return C1; // X | 0 == X 1117 if (CI2->isAllOnesValue()) 1118 return C2; // X | -1 == -1 1119 break; 1120 case Instruction::Xor: 1121 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X 1122 1123 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1124 switch (CE1->getOpcode()) { 1125 default: break; 1126 case Instruction::ICmp: 1127 case Instruction::FCmp: 1128 // cmp pred ^ true -> cmp !pred 1129 assert(CI2->equalsInt(1)); 1130 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate(); 1131 pred = CmpInst::getInversePredicate(pred); 1132 return ConstantExpr::getCompare(pred, CE1->getOperand(0), 1133 CE1->getOperand(1)); 1134 } 1135 } 1136 break; 1137 case Instruction::AShr: 1138 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 1139 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 1140 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 1141 return ConstantExpr::getLShr(C1, C2); 1142 break; 1143 } 1144 } else if (isa<ConstantInt>(C1)) { 1145 // If C1 is a ConstantInt and C2 is not, swap the operands. 1146 if (Instruction::isCommutative(Opcode)) 1147 return ConstantExpr::get(Opcode, C2, C1); 1148 } 1149 1150 // At this point we know neither constant is an UndefValue. 1151 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 1152 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 1153 using namespace APIntOps; 1154 const APInt &C1V = CI1->getValue(); 1155 const APInt &C2V = CI2->getValue(); 1156 switch (Opcode) { 1157 default: 1158 break; 1159 case Instruction::Add: 1160 return ConstantInt::get(CI1->getContext(), C1V + C2V); 1161 case Instruction::Sub: 1162 return ConstantInt::get(CI1->getContext(), C1V - C2V); 1163 case Instruction::Mul: 1164 return ConstantInt::get(CI1->getContext(), C1V * C2V); 1165 case Instruction::UDiv: 1166 assert(!CI2->isNullValue() && "Div by zero handled above"); 1167 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); 1168 case Instruction::SDiv: 1169 assert(!CI2->isNullValue() && "Div by zero handled above"); 1170 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1171 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef 1172 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); 1173 case Instruction::URem: 1174 assert(!CI2->isNullValue() && "Div by zero handled above"); 1175 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); 1176 case Instruction::SRem: 1177 assert(!CI2->isNullValue() && "Div by zero handled above"); 1178 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1179 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef 1180 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); 1181 case Instruction::And: 1182 return ConstantInt::get(CI1->getContext(), C1V & C2V); 1183 case Instruction::Or: 1184 return ConstantInt::get(CI1->getContext(), C1V | C2V); 1185 case Instruction::Xor: 1186 return ConstantInt::get(CI1->getContext(), C1V ^ C2V); 1187 case Instruction::Shl: { 1188 uint32_t shiftAmt = C2V.getZExtValue(); 1189 if (shiftAmt < C1V.getBitWidth()) 1190 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt)); 1191 else 1192 return UndefValue::get(C1->getType()); // too big shift is undef 1193 } 1194 case Instruction::LShr: { 1195 uint32_t shiftAmt = C2V.getZExtValue(); 1196 if (shiftAmt < C1V.getBitWidth()) 1197 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt)); 1198 else 1199 return UndefValue::get(C1->getType()); // too big shift is undef 1200 } 1201 case Instruction::AShr: { 1202 uint32_t shiftAmt = C2V.getZExtValue(); 1203 if (shiftAmt < C1V.getBitWidth()) 1204 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt)); 1205 else 1206 return UndefValue::get(C1->getType()); // too big shift is undef 1207 } 1208 } 1209 } 1210 1211 switch (Opcode) { 1212 case Instruction::SDiv: 1213 case Instruction::UDiv: 1214 case Instruction::URem: 1215 case Instruction::SRem: 1216 case Instruction::LShr: 1217 case Instruction::AShr: 1218 case Instruction::Shl: 1219 if (CI1->equalsInt(0)) return C1; 1220 break; 1221 default: 1222 break; 1223 } 1224 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 1225 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 1226 APFloat C1V = CFP1->getValueAPF(); 1227 APFloat C2V = CFP2->getValueAPF(); 1228 APFloat C3V = C1V; // copy for modification 1229 switch (Opcode) { 1230 default: 1231 break; 1232 case Instruction::FAdd: 1233 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 1234 return ConstantFP::get(C1->getContext(), C3V); 1235 case Instruction::FSub: 1236 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 1237 return ConstantFP::get(C1->getContext(), C3V); 1238 case Instruction::FMul: 1239 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 1240 return ConstantFP::get(C1->getContext(), C3V); 1241 case Instruction::FDiv: 1242 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 1243 return ConstantFP::get(C1->getContext(), C3V); 1244 case Instruction::FRem: 1245 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 1246 return ConstantFP::get(C1->getContext(), C3V); 1247 } 1248 } 1249 } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 1250 ConstantVector *CP1 = dyn_cast<ConstantVector>(C1); 1251 ConstantVector *CP2 = dyn_cast<ConstantVector>(C2); 1252 if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) && 1253 (CP2 != NULL || isa<ConstantAggregateZero>(C2))) { 1254 std::vector<Constant*> Res; 1255 const Type* EltTy = VTy->getElementType(); 1256 Constant *C1 = 0; 1257 Constant *C2 = 0; 1258 switch (Opcode) { 1259 default: 1260 break; 1261 case Instruction::Add: 1262 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1263 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1264 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1265 Res.push_back(ConstantExpr::getAdd(C1, C2)); 1266 } 1267 return ConstantVector::get(Res); 1268 case Instruction::FAdd: 1269 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1270 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1271 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1272 Res.push_back(ConstantExpr::getFAdd(C1, C2)); 1273 } 1274 return ConstantVector::get(Res); 1275 case Instruction::Sub: 1276 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1277 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1278 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1279 Res.push_back(ConstantExpr::getSub(C1, C2)); 1280 } 1281 return ConstantVector::get(Res); 1282 case Instruction::FSub: 1283 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1284 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1285 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1286 Res.push_back(ConstantExpr::getFSub(C1, C2)); 1287 } 1288 return ConstantVector::get(Res); 1289 case Instruction::Mul: 1290 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1291 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1292 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1293 Res.push_back(ConstantExpr::getMul(C1, C2)); 1294 } 1295 return ConstantVector::get(Res); 1296 case Instruction::FMul: 1297 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1298 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1299 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1300 Res.push_back(ConstantExpr::getFMul(C1, C2)); 1301 } 1302 return ConstantVector::get(Res); 1303 case Instruction::UDiv: 1304 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1305 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1306 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1307 Res.push_back(ConstantExpr::getUDiv(C1, C2)); 1308 } 1309 return ConstantVector::get(Res); 1310 case Instruction::SDiv: 1311 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1312 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1313 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1314 Res.push_back(ConstantExpr::getSDiv(C1, C2)); 1315 } 1316 return ConstantVector::get(Res); 1317 case Instruction::FDiv: 1318 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1319 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1320 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1321 Res.push_back(ConstantExpr::getFDiv(C1, C2)); 1322 } 1323 return ConstantVector::get(Res); 1324 case Instruction::URem: 1325 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1326 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1327 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1328 Res.push_back(ConstantExpr::getURem(C1, C2)); 1329 } 1330 return ConstantVector::get(Res); 1331 case Instruction::SRem: 1332 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1333 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1334 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1335 Res.push_back(ConstantExpr::getSRem(C1, C2)); 1336 } 1337 return ConstantVector::get(Res); 1338 case Instruction::FRem: 1339 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1340 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1341 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1342 Res.push_back(ConstantExpr::getFRem(C1, C2)); 1343 } 1344 return ConstantVector::get(Res); 1345 case Instruction::And: 1346 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1347 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1348 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1349 Res.push_back(ConstantExpr::getAnd(C1, C2)); 1350 } 1351 return ConstantVector::get(Res); 1352 case Instruction::Or: 1353 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1354 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1355 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1356 Res.push_back(ConstantExpr::getOr(C1, C2)); 1357 } 1358 return ConstantVector::get(Res); 1359 case Instruction::Xor: 1360 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1361 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1362 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1363 Res.push_back(ConstantExpr::getXor(C1, C2)); 1364 } 1365 return ConstantVector::get(Res); 1366 case Instruction::LShr: 1367 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1368 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1369 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1370 Res.push_back(ConstantExpr::getLShr(C1, C2)); 1371 } 1372 return ConstantVector::get(Res); 1373 case Instruction::AShr: 1374 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1375 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1376 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1377 Res.push_back(ConstantExpr::getAShr(C1, C2)); 1378 } 1379 return ConstantVector::get(Res); 1380 case Instruction::Shl: 1381 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1382 C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); 1383 C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); 1384 Res.push_back(ConstantExpr::getShl(C1, C2)); 1385 } 1386 return ConstantVector::get(Res); 1387 } 1388 } 1389 } 1390 1391 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1392 // There are many possible foldings we could do here. We should probably 1393 // at least fold add of a pointer with an integer into the appropriate 1394 // getelementptr. This will improve alias analysis a bit. 1395 1396 // Given ((a + b) + c), if (b + c) folds to something interesting, return 1397 // (a + (b + c)). 1398 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) { 1399 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2); 1400 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode) 1401 return ConstantExpr::get(Opcode, CE1->getOperand(0), T); 1402 } 1403 } else if (isa<ConstantExpr>(C2)) { 1404 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1405 // other way if possible. 1406 if (Instruction::isCommutative(Opcode)) 1407 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 1408 } 1409 1410 // i1 can be simplified in many cases. 1411 if (C1->getType()->isIntegerTy(1)) { 1412 switch (Opcode) { 1413 case Instruction::Add: 1414 case Instruction::Sub: 1415 return ConstantExpr::getXor(C1, C2); 1416 case Instruction::Mul: 1417 return ConstantExpr::getAnd(C1, C2); 1418 case Instruction::Shl: 1419 case Instruction::LShr: 1420 case Instruction::AShr: 1421 // We can assume that C2 == 0. If it were one the result would be 1422 // undefined because the shift value is as large as the bitwidth. 1423 return C1; 1424 case Instruction::SDiv: 1425 case Instruction::UDiv: 1426 // We can assume that C2 == 1. If it were zero the result would be 1427 // undefined through division by zero. 1428 return C1; 1429 case Instruction::URem: 1430 case Instruction::SRem: 1431 // We can assume that C2 == 1. If it were zero the result would be 1432 // undefined through division by zero. 1433 return ConstantInt::getFalse(C1->getContext()); 1434 default: 1435 break; 1436 } 1437 } 1438 1439 // We don't know how to fold this. 1440 return 0; 1441} 1442 1443/// isZeroSizedType - This type is zero sized if its an array or structure of 1444/// zero sized types. The only leaf zero sized type is an empty structure. 1445static bool isMaybeZeroSizedType(const Type *Ty) { 1446 if (Ty->isOpaqueTy()) return true; // Can't say. 1447 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 1448 1449 // If all of elements have zero size, this does too. 1450 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1451 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 1452 return true; 1453 1454 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1455 return isMaybeZeroSizedType(ATy->getElementType()); 1456 } 1457 return false; 1458} 1459 1460/// IdxCompare - Compare the two constants as though they were getelementptr 1461/// indices. This allows coersion of the types to be the same thing. 1462/// 1463/// If the two constants are the "same" (after coersion), return 0. If the 1464/// first is less than the second, return -1, if the second is less than the 1465/// first, return 1. If the constants are not integral, return -2. 1466/// 1467static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 1468 if (C1 == C2) return 0; 1469 1470 // Ok, we found a different index. If they are not ConstantInt, we can't do 1471 // anything with them. 1472 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 1473 return -2; // don't know! 1474 1475 // Ok, we have two differing integer indices. Sign extend them to be the same 1476 // type. Long is always big enough, so we use it. 1477 if (!C1->getType()->isIntegerTy(64)) 1478 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext())); 1479 1480 if (!C2->getType()->isIntegerTy(64)) 1481 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext())); 1482 1483 if (C1 == C2) return 0; // They are equal 1484 1485 // If the type being indexed over is really just a zero sized type, there is 1486 // no pointer difference being made here. 1487 if (isMaybeZeroSizedType(ElTy)) 1488 return -2; // dunno. 1489 1490 // If they are really different, now that they are the same type, then we 1491 // found a difference! 1492 if (cast<ConstantInt>(C1)->getSExtValue() < 1493 cast<ConstantInt>(C2)->getSExtValue()) 1494 return -1; 1495 else 1496 return 1; 1497} 1498 1499/// evaluateFCmpRelation - This function determines if there is anything we can 1500/// decide about the two constants provided. This doesn't need to handle simple 1501/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 1502/// If we can determine that the two constants have a particular relation to 1503/// each other, we should return the corresponding FCmpInst predicate, 1504/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 1505/// ConstantFoldCompareInstruction. 1506/// 1507/// To simplify this code we canonicalize the relation so that the first 1508/// operand is always the most "complex" of the two. We consider ConstantFP 1509/// to be the simplest, and ConstantExprs to be the most complex. 1510static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) { 1511 assert(V1->getType() == V2->getType() && 1512 "Cannot compare values of different types!"); 1513 1514 // No compile-time operations on this type yet. 1515 if (V1->getType()->isPPC_FP128Ty()) 1516 return FCmpInst::BAD_FCMP_PREDICATE; 1517 1518 // Handle degenerate case quickly 1519 if (V1 == V2) return FCmpInst::FCMP_OEQ; 1520 1521 if (!isa<ConstantExpr>(V1)) { 1522 if (!isa<ConstantExpr>(V2)) { 1523 // We distilled thisUse the standard constant folder for a few cases 1524 ConstantInt *R = 0; 1525 R = dyn_cast<ConstantInt>( 1526 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); 1527 if (R && !R->isZero()) 1528 return FCmpInst::FCMP_OEQ; 1529 R = dyn_cast<ConstantInt>( 1530 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); 1531 if (R && !R->isZero()) 1532 return FCmpInst::FCMP_OLT; 1533 R = dyn_cast<ConstantInt>( 1534 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2)); 1535 if (R && !R->isZero()) 1536 return FCmpInst::FCMP_OGT; 1537 1538 // Nothing more we can do 1539 return FCmpInst::BAD_FCMP_PREDICATE; 1540 } 1541 1542 // If the first operand is simple and second is ConstantExpr, swap operands. 1543 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 1544 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 1545 return FCmpInst::getSwappedPredicate(SwappedRelation); 1546 } else { 1547 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1548 // constantexpr or a simple constant. 1549 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1550 switch (CE1->getOpcode()) { 1551 case Instruction::FPTrunc: 1552 case Instruction::FPExt: 1553 case Instruction::UIToFP: 1554 case Instruction::SIToFP: 1555 // We might be able to do something with these but we don't right now. 1556 break; 1557 default: 1558 break; 1559 } 1560 } 1561 // There are MANY other foldings that we could perform here. They will 1562 // probably be added on demand, as they seem needed. 1563 return FCmpInst::BAD_FCMP_PREDICATE; 1564} 1565 1566/// evaluateICmpRelation - This function determines if there is anything we can 1567/// decide about the two constants provided. This doesn't need to handle simple 1568/// things like integer comparisons, but should instead handle ConstantExprs 1569/// and GlobalValues. If we can determine that the two constants have a 1570/// particular relation to each other, we should return the corresponding ICmp 1571/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 1572/// 1573/// To simplify this code we canonicalize the relation so that the first 1574/// operand is always the most "complex" of the two. We consider simple 1575/// constants (like ConstantInt) to be the simplest, followed by 1576/// GlobalValues, followed by ConstantExpr's (the most complex). 1577/// 1578static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, 1579 bool isSigned) { 1580 assert(V1->getType() == V2->getType() && 1581 "Cannot compare different types of values!"); 1582 if (V1 == V2) return ICmpInst::ICMP_EQ; 1583 1584 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) && 1585 !isa<BlockAddress>(V1)) { 1586 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) && 1587 !isa<BlockAddress>(V2)) { 1588 // We distilled this down to a simple case, use the standard constant 1589 // folder. 1590 ConstantInt *R = 0; 1591 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 1592 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1593 if (R && !R->isZero()) 1594 return pred; 1595 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1596 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1597 if (R && !R->isZero()) 1598 return pred; 1599 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1600 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1601 if (R && !R->isZero()) 1602 return pred; 1603 1604 // If we couldn't figure it out, bail. 1605 return ICmpInst::BAD_ICMP_PREDICATE; 1606 } 1607 1608 // If the first operand is simple, swap operands. 1609 ICmpInst::Predicate SwappedRelation = 1610 evaluateICmpRelation(V2, V1, isSigned); 1611 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1612 return ICmpInst::getSwappedPredicate(SwappedRelation); 1613 1614 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) { 1615 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1616 ICmpInst::Predicate SwappedRelation = 1617 evaluateICmpRelation(V2, V1, isSigned); 1618 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1619 return ICmpInst::getSwappedPredicate(SwappedRelation); 1620 return ICmpInst::BAD_ICMP_PREDICATE; 1621 } 1622 1623 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1624 // constant (which, since the types must match, means that it's a 1625 // ConstantPointerNull). 1626 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1627 // Don't try to decide equality of aliases. 1628 if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2)) 1629 if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) 1630 return ICmpInst::ICMP_NE; 1631 } else if (isa<BlockAddress>(V2)) { 1632 return ICmpInst::ICMP_NE; // Globals never equal labels. 1633 } else { 1634 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 1635 // GlobalVals can never be null unless they have external weak linkage. 1636 // We don't try to evaluate aliases here. 1637 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV)) 1638 return ICmpInst::ICMP_NE; 1639 } 1640 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) { 1641 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1642 ICmpInst::Predicate SwappedRelation = 1643 evaluateICmpRelation(V2, V1, isSigned); 1644 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1645 return ICmpInst::getSwappedPredicate(SwappedRelation); 1646 return ICmpInst::BAD_ICMP_PREDICATE; 1647 } 1648 1649 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1650 // constant (which, since the types must match, means that it is a 1651 // ConstantPointerNull). 1652 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) { 1653 // Block address in another function can't equal this one, but block 1654 // addresses in the current function might be the same if blocks are 1655 // empty. 1656 if (BA2->getFunction() != BA->getFunction()) 1657 return ICmpInst::ICMP_NE; 1658 } else { 1659 // Block addresses aren't null, don't equal the address of globals. 1660 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) && 1661 "Canonicalization guarantee!"); 1662 return ICmpInst::ICMP_NE; 1663 } 1664 } else { 1665 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1666 // constantexpr, a global, block address, or a simple constant. 1667 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1668 Constant *CE1Op0 = CE1->getOperand(0); 1669 1670 switch (CE1->getOpcode()) { 1671 case Instruction::Trunc: 1672 case Instruction::FPTrunc: 1673 case Instruction::FPExt: 1674 case Instruction::FPToUI: 1675 case Instruction::FPToSI: 1676 break; // We can't evaluate floating point casts or truncations. 1677 1678 case Instruction::UIToFP: 1679 case Instruction::SIToFP: 1680 case Instruction::BitCast: 1681 case Instruction::ZExt: 1682 case Instruction::SExt: 1683 // If the cast is not actually changing bits, and the second operand is a 1684 // null pointer, do the comparison with the pre-casted value. 1685 if (V2->isNullValue() && 1686 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) { 1687 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1688 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1689 return evaluateICmpRelation(CE1Op0, 1690 Constant::getNullValue(CE1Op0->getType()), 1691 isSigned); 1692 } 1693 break; 1694 1695 case Instruction::GetElementPtr: 1696 // Ok, since this is a getelementptr, we know that the constant has a 1697 // pointer type. Check the various cases. 1698 if (isa<ConstantPointerNull>(V2)) { 1699 // If we are comparing a GEP to a null pointer, check to see if the base 1700 // of the GEP equals the null pointer. 1701 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1702 if (GV->hasExternalWeakLinkage()) 1703 // Weak linkage GVals could be zero or not. We're comparing that 1704 // to null pointer so its greater-or-equal 1705 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1706 else 1707 // If its not weak linkage, the GVal must have a non-zero address 1708 // so the result is greater-than 1709 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1710 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1711 // If we are indexing from a null pointer, check to see if we have any 1712 // non-zero indices. 1713 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1714 if (!CE1->getOperand(i)->isNullValue()) 1715 // Offsetting from null, must not be equal. 1716 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1717 // Only zero indexes from null, must still be zero. 1718 return ICmpInst::ICMP_EQ; 1719 } 1720 // Otherwise, we can't really say if the first operand is null or not. 1721 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1722 if (isa<ConstantPointerNull>(CE1Op0)) { 1723 if (GV2->hasExternalWeakLinkage()) 1724 // Weak linkage GVals could be zero or not. We're comparing it to 1725 // a null pointer, so its less-or-equal 1726 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1727 else 1728 // If its not weak linkage, the GVal must have a non-zero address 1729 // so the result is less-than 1730 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1731 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1732 if (GV == GV2) { 1733 // If this is a getelementptr of the same global, then it must be 1734 // different. Because the types must match, the getelementptr could 1735 // only have at most one index, and because we fold getelementptr's 1736 // with a single zero index, it must be nonzero. 1737 assert(CE1->getNumOperands() == 2 && 1738 !CE1->getOperand(1)->isNullValue() && 1739 "Surprising getelementptr!"); 1740 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1741 } else { 1742 // If they are different globals, we don't know what the value is, 1743 // but they can't be equal. 1744 return ICmpInst::ICMP_NE; 1745 } 1746 } 1747 } else { 1748 ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1749 Constant *CE2Op0 = CE2->getOperand(0); 1750 1751 // There are MANY other foldings that we could perform here. They will 1752 // probably be added on demand, as they seem needed. 1753 switch (CE2->getOpcode()) { 1754 default: break; 1755 case Instruction::GetElementPtr: 1756 // By far the most common case to handle is when the base pointers are 1757 // obviously to the same or different globals. 1758 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1759 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 1760 return ICmpInst::ICMP_NE; 1761 // Ok, we know that both getelementptr instructions are based on the 1762 // same global. From this, we can precisely determine the relative 1763 // ordering of the resultant pointers. 1764 unsigned i = 1; 1765 1766 // The logic below assumes that the result of the comparison 1767 // can be determined by finding the first index that differs. 1768 // This doesn't work if there is over-indexing in any 1769 // subsequent indices, so check for that case first. 1770 if (!CE1->isGEPWithNoNotionalOverIndexing() || 1771 !CE2->isGEPWithNoNotionalOverIndexing()) 1772 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1773 1774 // Compare all of the operands the GEP's have in common. 1775 gep_type_iterator GTI = gep_type_begin(CE1); 1776 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1777 ++i, ++GTI) 1778 switch (IdxCompare(CE1->getOperand(i), 1779 CE2->getOperand(i), GTI.getIndexedType())) { 1780 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1781 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1782 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1783 } 1784 1785 // Ok, we ran out of things they have in common. If any leftovers 1786 // are non-zero then we have a difference, otherwise we are equal. 1787 for (; i < CE1->getNumOperands(); ++i) 1788 if (!CE1->getOperand(i)->isNullValue()) { 1789 if (isa<ConstantInt>(CE1->getOperand(i))) 1790 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1791 else 1792 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1793 } 1794 1795 for (; i < CE2->getNumOperands(); ++i) 1796 if (!CE2->getOperand(i)->isNullValue()) { 1797 if (isa<ConstantInt>(CE2->getOperand(i))) 1798 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1799 else 1800 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1801 } 1802 return ICmpInst::ICMP_EQ; 1803 } 1804 } 1805 } 1806 default: 1807 break; 1808 } 1809 } 1810 1811 return ICmpInst::BAD_ICMP_PREDICATE; 1812} 1813 1814Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1815 Constant *C1, Constant *C2) { 1816 const Type *ResultTy; 1817 if (const VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1818 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), 1819 VT->getNumElements()); 1820 else 1821 ResultTy = Type::getInt1Ty(C1->getContext()); 1822 1823 // Fold FCMP_FALSE/FCMP_TRUE unconditionally. 1824 if (pred == FCmpInst::FCMP_FALSE) 1825 return Constant::getNullValue(ResultTy); 1826 1827 if (pred == FCmpInst::FCMP_TRUE) 1828 return Constant::getAllOnesValue(ResultTy); 1829 1830 // Handle some degenerate cases first 1831 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 1832 // For EQ and NE, we can always pick a value for the undef to make the 1833 // predicate pass or fail, so we can return undef. 1834 if (ICmpInst::isEquality(ICmpInst::Predicate(pred))) 1835 return UndefValue::get(ResultTy); 1836 // Otherwise, pick the same value as the non-undef operand, and fold 1837 // it to true or false. 1838 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred)); 1839 } 1840 1841 // No compile-time operations on this type yet. 1842 if (C1->getType()->isPPC_FP128Ty()) 1843 return 0; 1844 1845 // icmp eq/ne(null,GV) -> false/true 1846 if (C1->isNullValue()) { 1847 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1848 // Don't try to evaluate aliases. External weak GV can be null. 1849 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1850 if (pred == ICmpInst::ICMP_EQ) 1851 return ConstantInt::getFalse(C1->getContext()); 1852 else if (pred == ICmpInst::ICMP_NE) 1853 return ConstantInt::getTrue(C1->getContext()); 1854 } 1855 // icmp eq/ne(GV,null) -> false/true 1856 } else if (C2->isNullValue()) { 1857 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1858 // Don't try to evaluate aliases. External weak GV can be null. 1859 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1860 if (pred == ICmpInst::ICMP_EQ) 1861 return ConstantInt::getFalse(C1->getContext()); 1862 else if (pred == ICmpInst::ICMP_NE) 1863 return ConstantInt::getTrue(C1->getContext()); 1864 } 1865 } 1866 1867 // If the comparison is a comparison between two i1's, simplify it. 1868 if (C1->getType()->isIntegerTy(1)) { 1869 switch(pred) { 1870 case ICmpInst::ICMP_EQ: 1871 if (isa<ConstantInt>(C2)) 1872 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2)); 1873 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2); 1874 case ICmpInst::ICMP_NE: 1875 return ConstantExpr::getXor(C1, C2); 1876 default: 1877 break; 1878 } 1879 } 1880 1881 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1882 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1883 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1884 switch (pred) { 1885 default: llvm_unreachable("Invalid ICmp Predicate"); return 0; 1886 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); 1887 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); 1888 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); 1889 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); 1890 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); 1891 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); 1892 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); 1893 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); 1894 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); 1895 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); 1896 } 1897 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1898 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1899 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1900 APFloat::cmpResult R = C1V.compare(C2V); 1901 switch (pred) { 1902 default: llvm_unreachable("Invalid FCmp Predicate"); return 0; 1903 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); 1904 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); 1905 case FCmpInst::FCMP_UNO: 1906 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); 1907 case FCmpInst::FCMP_ORD: 1908 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); 1909 case FCmpInst::FCMP_UEQ: 1910 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1911 R==APFloat::cmpEqual); 1912 case FCmpInst::FCMP_OEQ: 1913 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); 1914 case FCmpInst::FCMP_UNE: 1915 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); 1916 case FCmpInst::FCMP_ONE: 1917 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1918 R==APFloat::cmpGreaterThan); 1919 case FCmpInst::FCMP_ULT: 1920 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1921 R==APFloat::cmpLessThan); 1922 case FCmpInst::FCMP_OLT: 1923 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); 1924 case FCmpInst::FCMP_UGT: 1925 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1926 R==APFloat::cmpGreaterThan); 1927 case FCmpInst::FCMP_OGT: 1928 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); 1929 case FCmpInst::FCMP_ULE: 1930 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); 1931 case FCmpInst::FCMP_OLE: 1932 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1933 R==APFloat::cmpEqual); 1934 case FCmpInst::FCMP_UGE: 1935 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); 1936 case FCmpInst::FCMP_OGE: 1937 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || 1938 R==APFloat::cmpEqual); 1939 } 1940 } else if (C1->getType()->isVectorTy()) { 1941 SmallVector<Constant*, 16> C1Elts, C2Elts; 1942 C1->getVectorElements(C1Elts); 1943 C2->getVectorElements(C2Elts); 1944 if (C1Elts.empty() || C2Elts.empty()) 1945 return 0; 1946 1947 // If we can constant fold the comparison of each element, constant fold 1948 // the whole vector comparison. 1949 SmallVector<Constant*, 4> ResElts; 1950 // Compare the elements, producing an i1 result or constant expr. 1951 for (unsigned i = 0, e = C1Elts.size(); i != e; ++i) 1952 ResElts.push_back(ConstantExpr::getCompare(pred, C1Elts[i], C2Elts[i])); 1953 1954 return ConstantVector::get(ResElts); 1955 } 1956 1957 if (C1->getType()->isFloatingPointTy()) { 1958 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1959 switch (evaluateFCmpRelation(C1, C2)) { 1960 default: llvm_unreachable("Unknown relation!"); 1961 case FCmpInst::FCMP_UNO: 1962 case FCmpInst::FCMP_ORD: 1963 case FCmpInst::FCMP_UEQ: 1964 case FCmpInst::FCMP_UNE: 1965 case FCmpInst::FCMP_ULT: 1966 case FCmpInst::FCMP_UGT: 1967 case FCmpInst::FCMP_ULE: 1968 case FCmpInst::FCMP_UGE: 1969 case FCmpInst::FCMP_TRUE: 1970 case FCmpInst::FCMP_FALSE: 1971 case FCmpInst::BAD_FCMP_PREDICATE: 1972 break; // Couldn't determine anything about these constants. 1973 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1974 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1975 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1976 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1977 break; 1978 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1979 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1980 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1981 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1982 break; 1983 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1984 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1985 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1986 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1987 break; 1988 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1989 // We can only partially decide this relation. 1990 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1991 Result = 0; 1992 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1993 Result = 1; 1994 break; 1995 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1996 // We can only partially decide this relation. 1997 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1998 Result = 0; 1999 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 2000 Result = 1; 2001 break; 2002 case FCmpInst::FCMP_ONE: // We know that C1 != C2 2003 // We can only partially decide this relation. 2004 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 2005 Result = 0; 2006 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 2007 Result = 1; 2008 break; 2009 } 2010 2011 // If we evaluated the result, return it now. 2012 if (Result != -1) 2013 return ConstantInt::get(ResultTy, Result); 2014 2015 } else { 2016 // Evaluate the relation between the two constants, per the predicate. 2017 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 2018 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 2019 default: llvm_unreachable("Unknown relational!"); 2020 case ICmpInst::BAD_ICMP_PREDICATE: 2021 break; // Couldn't determine anything about these constants. 2022 case ICmpInst::ICMP_EQ: // We know the constants are equal! 2023 // If we know the constants are equal, we can decide the result of this 2024 // computation precisely. 2025 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred); 2026 break; 2027 case ICmpInst::ICMP_ULT: 2028 switch (pred) { 2029 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: 2030 Result = 1; break; 2031 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: 2032 Result = 0; break; 2033 } 2034 break; 2035 case ICmpInst::ICMP_SLT: 2036 switch (pred) { 2037 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: 2038 Result = 1; break; 2039 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: 2040 Result = 0; break; 2041 } 2042 break; 2043 case ICmpInst::ICMP_UGT: 2044 switch (pred) { 2045 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: 2046 Result = 1; break; 2047 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: 2048 Result = 0; break; 2049 } 2050 break; 2051 case ICmpInst::ICMP_SGT: 2052 switch (pred) { 2053 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: 2054 Result = 1; break; 2055 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: 2056 Result = 0; break; 2057 } 2058 break; 2059 case ICmpInst::ICMP_ULE: 2060 if (pred == ICmpInst::ICMP_UGT) Result = 0; 2061 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1; 2062 break; 2063 case ICmpInst::ICMP_SLE: 2064 if (pred == ICmpInst::ICMP_SGT) Result = 0; 2065 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1; 2066 break; 2067 case ICmpInst::ICMP_UGE: 2068 if (pred == ICmpInst::ICMP_ULT) Result = 0; 2069 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1; 2070 break; 2071 case ICmpInst::ICMP_SGE: 2072 if (pred == ICmpInst::ICMP_SLT) Result = 0; 2073 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1; 2074 break; 2075 case ICmpInst::ICMP_NE: 2076 if (pred == ICmpInst::ICMP_EQ) Result = 0; 2077 if (pred == ICmpInst::ICMP_NE) Result = 1; 2078 break; 2079 } 2080 2081 // If we evaluated the result, return it now. 2082 if (Result != -1) 2083 return ConstantInt::get(ResultTy, Result); 2084 2085 // If the right hand side is a bitcast, try using its inverse to simplify 2086 // it by moving it to the left hand side. We can't do this if it would turn 2087 // a vector compare into a scalar compare or visa versa. 2088 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) { 2089 Constant *CE2Op0 = CE2->getOperand(0); 2090 if (CE2->getOpcode() == Instruction::BitCast && 2091 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) { 2092 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); 2093 return ConstantExpr::getICmp(pred, Inverse, CE2Op0); 2094 } 2095 } 2096 2097 // If the left hand side is an extension, try eliminating it. 2098 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 2099 if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) || 2100 (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){ 2101 Constant *CE1Op0 = CE1->getOperand(0); 2102 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); 2103 if (CE1Inverse == CE1Op0) { 2104 // Check whether we can safely truncate the right hand side. 2105 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType()); 2106 if (ConstantExpr::getZExt(C2Inverse, C2->getType()) == C2) { 2107 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse); 2108 } 2109 } 2110 } 2111 } 2112 2113 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) || 2114 (C1->isNullValue() && !C2->isNullValue())) { 2115 // If C2 is a constant expr and C1 isn't, flip them around and fold the 2116 // other way if possible. 2117 // Also, if C1 is null and C2 isn't, flip them around. 2118 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 2119 return ConstantExpr::getICmp(pred, C2, C1); 2120 } 2121 } 2122 return 0; 2123} 2124 2125/// isInBoundsIndices - Test whether the given sequence of *normalized* indices 2126/// is "inbounds". 2127template<typename IndexTy> 2128static bool isInBoundsIndices(IndexTy const *Idxs, size_t NumIdx) { 2129 // No indices means nothing that could be out of bounds. 2130 if (NumIdx == 0) return true; 2131 2132 // If the first index is zero, it's in bounds. 2133 if (cast<Constant>(Idxs[0])->isNullValue()) return true; 2134 2135 // If the first index is one and all the rest are zero, it's in bounds, 2136 // by the one-past-the-end rule. 2137 if (!cast<ConstantInt>(Idxs[0])->isOne()) 2138 return false; 2139 for (unsigned i = 1, e = NumIdx; i != e; ++i) 2140 if (!cast<Constant>(Idxs[i])->isNullValue()) 2141 return false; 2142 return true; 2143} 2144 2145template<typename IndexTy> 2146static Constant *ConstantFoldGetElementPtrImpl(Constant *C, 2147 bool inBounds, 2148 IndexTy const *Idxs, 2149 unsigned NumIdx) { 2150 Constant *Idx0 = cast<Constant>(Idxs[0]); 2151 if (NumIdx == 0 || 2152 (NumIdx == 1 && Idx0->isNullValue())) 2153 return C; 2154 2155 if (isa<UndefValue>(C)) { 2156 const PointerType *Ptr = cast<PointerType>(C->getType()); 2157 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs, Idxs+NumIdx); 2158 assert(Ty != 0 && "Invalid indices for GEP!"); 2159 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 2160 } 2161 2162 if (C->isNullValue()) { 2163 bool isNull = true; 2164 for (unsigned i = 0, e = NumIdx; i != e; ++i) 2165 if (!cast<Constant>(Idxs[i])->isNullValue()) { 2166 isNull = false; 2167 break; 2168 } 2169 if (isNull) { 2170 const PointerType *Ptr = cast<PointerType>(C->getType()); 2171 const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs, 2172 Idxs+NumIdx); 2173 assert(Ty != 0 && "Invalid indices for GEP!"); 2174 return ConstantPointerNull::get(PointerType::get(Ty, 2175 Ptr->getAddressSpace())); 2176 } 2177 } 2178 2179 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 2180 // Combine Indices - If the source pointer to this getelementptr instruction 2181 // is a getelementptr instruction, combine the indices of the two 2182 // getelementptr instructions into a single instruction. 2183 // 2184 if (CE->getOpcode() == Instruction::GetElementPtr) { 2185 const Type *LastTy = 0; 2186 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 2187 I != E; ++I) 2188 LastTy = *I; 2189 2190 if ((LastTy && LastTy->isArrayTy()) || Idx0->isNullValue()) { 2191 SmallVector<Value*, 16> NewIndices; 2192 NewIndices.reserve(NumIdx + CE->getNumOperands()); 2193 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 2194 NewIndices.push_back(CE->getOperand(i)); 2195 2196 // Add the last index of the source with the first index of the new GEP. 2197 // Make sure to handle the case when they are actually different types. 2198 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 2199 // Otherwise it must be an array. 2200 if (!Idx0->isNullValue()) { 2201 const Type *IdxTy = Combined->getType(); 2202 if (IdxTy != Idx0->getType()) { 2203 const Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext()); 2204 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty); 2205 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty); 2206 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 2207 } else { 2208 Combined = 2209 ConstantExpr::get(Instruction::Add, Idx0, Combined); 2210 } 2211 } 2212 2213 NewIndices.push_back(Combined); 2214 NewIndices.append(Idxs+1, Idxs+NumIdx); 2215 return (inBounds && cast<GEPOperator>(CE)->isInBounds()) ? 2216 ConstantExpr::getInBoundsGetElementPtr(CE->getOperand(0), 2217 &NewIndices[0], 2218 NewIndices.size()) : 2219 ConstantExpr::getGetElementPtr(CE->getOperand(0), 2220 &NewIndices[0], 2221 NewIndices.size()); 2222 } 2223 } 2224 2225 // Implement folding of: 2226 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*), 2227 // i64 0, i64 0) 2228 // To: i32* getelementptr ([3 x i32]* %X, i64 0, i64 0) 2229 // 2230 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) { 2231 if (const PointerType *SPT = 2232 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 2233 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 2234 if (const ArrayType *CAT = 2235 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 2236 if (CAT->getElementType() == SAT->getElementType()) 2237 return inBounds ? 2238 ConstantExpr::getInBoundsGetElementPtr( 2239 (Constant*)CE->getOperand(0), Idxs, NumIdx) : 2240 ConstantExpr::getGetElementPtr( 2241 (Constant*)CE->getOperand(0), Idxs, NumIdx); 2242 } 2243 } 2244 2245 // Check to see if any array indices are not within the corresponding 2246 // notional array bounds. If so, try to determine if they can be factored 2247 // out into preceding dimensions. 2248 bool Unknown = false; 2249 SmallVector<Constant *, 8> NewIdxs; 2250 const Type *Ty = C->getType(); 2251 const Type *Prev = 0; 2252 for (unsigned i = 0; i != NumIdx; 2253 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) { 2254 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) { 2255 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) 2256 if (ATy->getNumElements() <= INT64_MAX && 2257 ATy->getNumElements() != 0 && 2258 CI->getSExtValue() >= (int64_t)ATy->getNumElements()) { 2259 if (isa<SequentialType>(Prev)) { 2260 // It's out of range, but we can factor it into the prior 2261 // dimension. 2262 NewIdxs.resize(NumIdx); 2263 ConstantInt *Factor = ConstantInt::get(CI->getType(), 2264 ATy->getNumElements()); 2265 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor); 2266 2267 Constant *PrevIdx = cast<Constant>(Idxs[i-1]); 2268 Constant *Div = ConstantExpr::getSDiv(CI, Factor); 2269 2270 // Before adding, extend both operands to i64 to avoid 2271 // overflow trouble. 2272 if (!PrevIdx->getType()->isIntegerTy(64)) 2273 PrevIdx = ConstantExpr::getSExt(PrevIdx, 2274 Type::getInt64Ty(Div->getContext())); 2275 if (!Div->getType()->isIntegerTy(64)) 2276 Div = ConstantExpr::getSExt(Div, 2277 Type::getInt64Ty(Div->getContext())); 2278 2279 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div); 2280 } else { 2281 // It's out of range, but the prior dimension is a struct 2282 // so we can't do anything about it. 2283 Unknown = true; 2284 } 2285 } 2286 } else { 2287 // We don't know if it's in range or not. 2288 Unknown = true; 2289 } 2290 } 2291 2292 // If we did any factoring, start over with the adjusted indices. 2293 if (!NewIdxs.empty()) { 2294 for (unsigned i = 0; i != NumIdx; ++i) 2295 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]); 2296 return inBounds ? 2297 ConstantExpr::getInBoundsGetElementPtr(C, NewIdxs.data(), 2298 NewIdxs.size()) : 2299 ConstantExpr::getGetElementPtr(C, NewIdxs.data(), NewIdxs.size()); 2300 } 2301 2302 // If all indices are known integers and normalized, we can do a simple 2303 // check for the "inbounds" property. 2304 if (!Unknown && !inBounds && 2305 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs, NumIdx)) 2306 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs, NumIdx); 2307 2308 return 0; 2309} 2310 2311Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2312 bool inBounds, 2313 Constant* const *Idxs, 2314 unsigned NumIdx) { 2315 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs, NumIdx); 2316} 2317 2318Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2319 bool inBounds, 2320 Value* const *Idxs, 2321 unsigned NumIdx) { 2322 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs, NumIdx); 2323} 2324