1 //===-- ConstantFolding.cpp - Fold instructions into constants ------------===// 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 defines routines for folding instructions into constants. 11 // 12 // Also, to supplement the basic IR ConstantExpr simplifications, 13 // this file defines some additional folding routines that can make use of 14 // DataLayout information. These functions cannot go in IR due to library 15 // dependency issues. 16 // 17 //===----------------------------------------------------------------------===// 18 19 #include "llvm/Analysis/ConstantFolding.h" 20 #include "llvm/ADT/SmallVector.h" 21 #include "llvm/ADT/StringMap.h" 22 #include "llvm/Analysis/ValueTracking.h" 23 #include "llvm/IR/Constants.h" 24 #include "llvm/IR/DataLayout.h" 25 #include "llvm/IR/DerivedTypes.h" 26 #include "llvm/IR/Function.h" 27 #include "llvm/IR/GlobalVariable.h" 28 #include "llvm/IR/Instructions.h" 29 #include "llvm/IR/Intrinsics.h" 30 #include "llvm/IR/Operator.h" 31 #include "llvm/Support/ErrorHandling.h" 32 #include "llvm/Support/FEnv.h" 33 #include "llvm/Support/GetElementPtrTypeIterator.h" 34 #include "llvm/Support/MathExtras.h" 35 #include "llvm/Target/TargetLibraryInfo.h" 36 #include <cerrno> 37 #include <cmath> 38 using namespace llvm; 39 40 //===----------------------------------------------------------------------===// 41 // Constant Folding internal helper functions 42 //===----------------------------------------------------------------------===// 43 44 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with 45 /// DataLayout. This always returns a non-null constant, but it may be a 46 /// ConstantExpr if unfoldable. 47 static Constant *FoldBitCast(Constant *C, Type *DestTy, 48 const DataLayout &TD) { 49 // Catch the obvious splat cases. 50 if (C->isNullValue() && !DestTy->isX86_MMXTy()) 51 return Constant::getNullValue(DestTy); 52 if (C->isAllOnesValue() && !DestTy->isX86_MMXTy()) 53 return Constant::getAllOnesValue(DestTy); 54 55 // Handle a vector->integer cast. 56 if (IntegerType *IT = dyn_cast<IntegerType>(DestTy)) { 57 VectorType *VTy = dyn_cast<VectorType>(C->getType()); 58 if (VTy == 0) 59 return ConstantExpr::getBitCast(C, DestTy); 60 61 unsigned NumSrcElts = VTy->getNumElements(); 62 Type *SrcEltTy = VTy->getElementType(); 63 64 // If the vector is a vector of floating point, convert it to vector of int 65 // to simplify things. 66 if (SrcEltTy->isFloatingPointTy()) { 67 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); 68 Type *SrcIVTy = 69 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElts); 70 // Ask IR to do the conversion now that #elts line up. 71 C = ConstantExpr::getBitCast(C, SrcIVTy); 72 } 73 74 ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(C); 75 if (CDV == 0) 76 return ConstantExpr::getBitCast(C, DestTy); 77 78 // Now that we know that the input value is a vector of integers, just shift 79 // and insert them into our result. 80 unsigned BitShift = TD.getTypeAllocSizeInBits(SrcEltTy); 81 APInt Result(IT->getBitWidth(), 0); 82 for (unsigned i = 0; i != NumSrcElts; ++i) { 83 Result <<= BitShift; 84 if (TD.isLittleEndian()) 85 Result |= CDV->getElementAsInteger(NumSrcElts-i-1); 86 else 87 Result |= CDV->getElementAsInteger(i); 88 } 89 90 return ConstantInt::get(IT, Result); 91 } 92 93 // The code below only handles casts to vectors currently. 94 VectorType *DestVTy = dyn_cast<VectorType>(DestTy); 95 if (DestVTy == 0) 96 return ConstantExpr::getBitCast(C, DestTy); 97 98 // If this is a scalar -> vector cast, convert the input into a <1 x scalar> 99 // vector so the code below can handle it uniformly. 100 if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) { 101 Constant *Ops = C; // don't take the address of C! 102 return FoldBitCast(ConstantVector::get(Ops), DestTy, TD); 103 } 104 105 // If this is a bitcast from constant vector -> vector, fold it. 106 if (!isa<ConstantDataVector>(C) && !isa<ConstantVector>(C)) 107 return ConstantExpr::getBitCast(C, DestTy); 108 109 // If the element types match, IR can fold it. 110 unsigned NumDstElt = DestVTy->getNumElements(); 111 unsigned NumSrcElt = C->getType()->getVectorNumElements(); 112 if (NumDstElt == NumSrcElt) 113 return ConstantExpr::getBitCast(C, DestTy); 114 115 Type *SrcEltTy = C->getType()->getVectorElementType(); 116 Type *DstEltTy = DestVTy->getElementType(); 117 118 // Otherwise, we're changing the number of elements in a vector, which 119 // requires endianness information to do the right thing. For example, 120 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 121 // folds to (little endian): 122 // <4 x i32> <i32 0, i32 0, i32 1, i32 0> 123 // and to (big endian): 124 // <4 x i32> <i32 0, i32 0, i32 0, i32 1> 125 126 // First thing is first. We only want to think about integer here, so if 127 // we have something in FP form, recast it as integer. 128 if (DstEltTy->isFloatingPointTy()) { 129 // Fold to an vector of integers with same size as our FP type. 130 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits(); 131 Type *DestIVTy = 132 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt); 133 // Recursively handle this integer conversion, if possible. 134 C = FoldBitCast(C, DestIVTy, TD); 135 136 // Finally, IR can handle this now that #elts line up. 137 return ConstantExpr::getBitCast(C, DestTy); 138 } 139 140 // Okay, we know the destination is integer, if the input is FP, convert 141 // it to integer first. 142 if (SrcEltTy->isFloatingPointTy()) { 143 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); 144 Type *SrcIVTy = 145 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt); 146 // Ask IR to do the conversion now that #elts line up. 147 C = ConstantExpr::getBitCast(C, SrcIVTy); 148 // If IR wasn't able to fold it, bail out. 149 if (!isa<ConstantVector>(C) && // FIXME: Remove ConstantVector. 150 !isa<ConstantDataVector>(C)) 151 return C; 152 } 153 154 // Now we know that the input and output vectors are both integer vectors 155 // of the same size, and that their #elements is not the same. Do the 156 // conversion here, which depends on whether the input or output has 157 // more elements. 158 bool isLittleEndian = TD.isLittleEndian(); 159 160 SmallVector<Constant*, 32> Result; 161 if (NumDstElt < NumSrcElt) { 162 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>) 163 Constant *Zero = Constant::getNullValue(DstEltTy); 164 unsigned Ratio = NumSrcElt/NumDstElt; 165 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits(); 166 unsigned SrcElt = 0; 167 for (unsigned i = 0; i != NumDstElt; ++i) { 168 // Build each element of the result. 169 Constant *Elt = Zero; 170 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1); 171 for (unsigned j = 0; j != Ratio; ++j) { 172 Constant *Src =dyn_cast<ConstantInt>(C->getAggregateElement(SrcElt++)); 173 if (!Src) // Reject constantexpr elements. 174 return ConstantExpr::getBitCast(C, DestTy); 175 176 // Zero extend the element to the right size. 177 Src = ConstantExpr::getZExt(Src, Elt->getType()); 178 179 // Shift it to the right place, depending on endianness. 180 Src = ConstantExpr::getShl(Src, 181 ConstantInt::get(Src->getType(), ShiftAmt)); 182 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize; 183 184 // Mix it in. 185 Elt = ConstantExpr::getOr(Elt, Src); 186 } 187 Result.push_back(Elt); 188 } 189 return ConstantVector::get(Result); 190 } 191 192 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 193 unsigned Ratio = NumDstElt/NumSrcElt; 194 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits(); 195 196 // Loop over each source value, expanding into multiple results. 197 for (unsigned i = 0; i != NumSrcElt; ++i) { 198 Constant *Src = dyn_cast<ConstantInt>(C->getAggregateElement(i)); 199 if (!Src) // Reject constantexpr elements. 200 return ConstantExpr::getBitCast(C, DestTy); 201 202 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1); 203 for (unsigned j = 0; j != Ratio; ++j) { 204 // Shift the piece of the value into the right place, depending on 205 // endianness. 206 Constant *Elt = ConstantExpr::getLShr(Src, 207 ConstantInt::get(Src->getType(), ShiftAmt)); 208 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize; 209 210 // Truncate and remember this piece. 211 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy)); 212 } 213 } 214 215 return ConstantVector::get(Result); 216 } 217 218 219 /// IsConstantOffsetFromGlobal - If this constant is actually a constant offset 220 /// from a global, return the global and the constant. Because of 221 /// constantexprs, this function is recursive. 222 static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, 223 APInt &Offset, const DataLayout &TD) { 224 // Trivial case, constant is the global. 225 if ((GV = dyn_cast<GlobalValue>(C))) { 226 Offset.clearAllBits(); 227 return true; 228 } 229 230 // Otherwise, if this isn't a constant expr, bail out. 231 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 232 if (!CE) return false; 233 234 // Look through ptr->int and ptr->ptr casts. 235 if (CE->getOpcode() == Instruction::PtrToInt || 236 CE->getOpcode() == Instruction::BitCast) 237 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD); 238 239 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5) 240 if (GEPOperator *GEP = dyn_cast<GEPOperator>(CE)) { 241 // If the base isn't a global+constant, we aren't either. 242 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD)) 243 return false; 244 245 // Otherwise, add any offset that our operands provide. 246 return GEP->accumulateConstantOffset(TD, Offset); 247 } 248 249 return false; 250 } 251 252 /// ReadDataFromGlobal - Recursive helper to read bits out of global. C is the 253 /// constant being copied out of. ByteOffset is an offset into C. CurPtr is the 254 /// pointer to copy results into and BytesLeft is the number of bytes left in 255 /// the CurPtr buffer. TD is the target data. 256 static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset, 257 unsigned char *CurPtr, unsigned BytesLeft, 258 const DataLayout &TD) { 259 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) && 260 "Out of range access"); 261 262 // If this element is zero or undefined, we can just return since *CurPtr is 263 // zero initialized. 264 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C)) 265 return true; 266 267 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 268 if (CI->getBitWidth() > 64 || 269 (CI->getBitWidth() & 7) != 0) 270 return false; 271 272 uint64_t Val = CI->getZExtValue(); 273 unsigned IntBytes = unsigned(CI->getBitWidth()/8); 274 275 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) { 276 int n = ByteOffset; 277 if (!TD.isLittleEndian()) 278 n = IntBytes - n - 1; 279 CurPtr[i] = (unsigned char)(Val >> (n * 8)); 280 ++ByteOffset; 281 } 282 return true; 283 } 284 285 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) { 286 if (CFP->getType()->isDoubleTy()) { 287 C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD); 288 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 289 } 290 if (CFP->getType()->isFloatTy()){ 291 C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD); 292 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 293 } 294 if (CFP->getType()->isHalfTy()){ 295 C = FoldBitCast(C, Type::getInt16Ty(C->getContext()), TD); 296 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 297 } 298 return false; 299 } 300 301 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 302 const StructLayout *SL = TD.getStructLayout(CS->getType()); 303 unsigned Index = SL->getElementContainingOffset(ByteOffset); 304 uint64_t CurEltOffset = SL->getElementOffset(Index); 305 ByteOffset -= CurEltOffset; 306 307 while (1) { 308 // If the element access is to the element itself and not to tail padding, 309 // read the bytes from the element. 310 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType()); 311 312 if (ByteOffset < EltSize && 313 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr, 314 BytesLeft, TD)) 315 return false; 316 317 ++Index; 318 319 // Check to see if we read from the last struct element, if so we're done. 320 if (Index == CS->getType()->getNumElements()) 321 return true; 322 323 // If we read all of the bytes we needed from this element we're done. 324 uint64_t NextEltOffset = SL->getElementOffset(Index); 325 326 if (BytesLeft <= NextEltOffset-CurEltOffset-ByteOffset) 327 return true; 328 329 // Move to the next element of the struct. 330 CurPtr += NextEltOffset-CurEltOffset-ByteOffset; 331 BytesLeft -= NextEltOffset-CurEltOffset-ByteOffset; 332 ByteOffset = 0; 333 CurEltOffset = NextEltOffset; 334 } 335 // not reached. 336 } 337 338 if (isa<ConstantArray>(C) || isa<ConstantVector>(C) || 339 isa<ConstantDataSequential>(C)) { 340 Type *EltTy = cast<SequentialType>(C->getType())->getElementType(); 341 uint64_t EltSize = TD.getTypeAllocSize(EltTy); 342 uint64_t Index = ByteOffset / EltSize; 343 uint64_t Offset = ByteOffset - Index * EltSize; 344 uint64_t NumElts; 345 if (ArrayType *AT = dyn_cast<ArrayType>(C->getType())) 346 NumElts = AT->getNumElements(); 347 else 348 NumElts = cast<VectorType>(C->getType())->getNumElements(); 349 350 for (; Index != NumElts; ++Index) { 351 if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr, 352 BytesLeft, TD)) 353 return false; 354 355 uint64_t BytesWritten = EltSize - Offset; 356 assert(BytesWritten <= EltSize && "Not indexing into this element?"); 357 if (BytesWritten >= BytesLeft) 358 return true; 359 360 Offset = 0; 361 BytesLeft -= BytesWritten; 362 CurPtr += BytesWritten; 363 } 364 return true; 365 } 366 367 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 368 if (CE->getOpcode() == Instruction::IntToPtr && 369 CE->getOperand(0)->getType() == TD.getIntPtrType(CE->getContext())) 370 return ReadDataFromGlobal(CE->getOperand(0), ByteOffset, CurPtr, 371 BytesLeft, TD); 372 } 373 374 // Otherwise, unknown initializer type. 375 return false; 376 } 377 378 static Constant *FoldReinterpretLoadFromConstPtr(Constant *C, 379 const DataLayout &TD) { 380 Type *LoadTy = cast<PointerType>(C->getType())->getElementType(); 381 IntegerType *IntType = dyn_cast<IntegerType>(LoadTy); 382 383 // If this isn't an integer load we can't fold it directly. 384 if (!IntType) { 385 // If this is a float/double load, we can try folding it as an int32/64 load 386 // and then bitcast the result. This can be useful for union cases. Note 387 // that address spaces don't matter here since we're not going to result in 388 // an actual new load. 389 Type *MapTy; 390 if (LoadTy->isHalfTy()) 391 MapTy = Type::getInt16PtrTy(C->getContext()); 392 else if (LoadTy->isFloatTy()) 393 MapTy = Type::getInt32PtrTy(C->getContext()); 394 else if (LoadTy->isDoubleTy()) 395 MapTy = Type::getInt64PtrTy(C->getContext()); 396 else if (LoadTy->isVectorTy()) { 397 MapTy = IntegerType::get(C->getContext(), 398 TD.getTypeAllocSizeInBits(LoadTy)); 399 MapTy = PointerType::getUnqual(MapTy); 400 } else 401 return 0; 402 403 C = FoldBitCast(C, MapTy, TD); 404 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD)) 405 return FoldBitCast(Res, LoadTy, TD); 406 return 0; 407 } 408 409 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8; 410 if (BytesLoaded > 32 || BytesLoaded == 0) return 0; 411 412 GlobalValue *GVal; 413 APInt Offset(TD.getPointerSizeInBits(), 0); 414 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD)) 415 return 0; 416 417 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal); 418 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() || 419 !GV->getInitializer()->getType()->isSized()) 420 return 0; 421 422 // If we're loading off the beginning of the global, some bytes may be valid, 423 // but we don't try to handle this. 424 if (Offset.isNegative()) return 0; 425 426 // If we're not accessing anything in this constant, the result is undefined. 427 if (Offset.getZExtValue() >= 428 TD.getTypeAllocSize(GV->getInitializer()->getType())) 429 return UndefValue::get(IntType); 430 431 unsigned char RawBytes[32] = {0}; 432 if (!ReadDataFromGlobal(GV->getInitializer(), Offset.getZExtValue(), RawBytes, 433 BytesLoaded, TD)) 434 return 0; 435 436 APInt ResultVal = APInt(IntType->getBitWidth(), 0); 437 if (TD.isLittleEndian()) { 438 ResultVal = RawBytes[BytesLoaded - 1]; 439 for (unsigned i = 1; i != BytesLoaded; ++i) { 440 ResultVal <<= 8; 441 ResultVal |= RawBytes[BytesLoaded-1-i]; 442 } 443 } else { 444 ResultVal = RawBytes[0]; 445 for (unsigned i = 1; i != BytesLoaded; ++i) { 446 ResultVal <<= 8; 447 ResultVal |= RawBytes[i]; 448 } 449 } 450 451 return ConstantInt::get(IntType->getContext(), ResultVal); 452 } 453 454 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 455 /// produce if it is constant and determinable. If this is not determinable, 456 /// return null. 457 Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, 458 const DataLayout *TD) { 459 // First, try the easy cases: 460 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 461 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 462 return GV->getInitializer(); 463 464 // If the loaded value isn't a constant expr, we can't handle it. 465 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 466 if (!CE) return 0; 467 468 if (CE->getOpcode() == Instruction::GetElementPtr) { 469 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) 470 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 471 if (Constant *V = 472 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) 473 return V; 474 } 475 476 // Instead of loading constant c string, use corresponding integer value 477 // directly if string length is small enough. 478 StringRef Str; 479 if (TD && getConstantStringInfo(CE, Str) && !Str.empty()) { 480 unsigned StrLen = Str.size(); 481 Type *Ty = cast<PointerType>(CE->getType())->getElementType(); 482 unsigned NumBits = Ty->getPrimitiveSizeInBits(); 483 // Replace load with immediate integer if the result is an integer or fp 484 // value. 485 if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 && 486 (isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) { 487 APInt StrVal(NumBits, 0); 488 APInt SingleChar(NumBits, 0); 489 if (TD->isLittleEndian()) { 490 for (signed i = StrLen-1; i >= 0; i--) { 491 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 492 StrVal = (StrVal << 8) | SingleChar; 493 } 494 } else { 495 for (unsigned i = 0; i < StrLen; i++) { 496 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 497 StrVal = (StrVal << 8) | SingleChar; 498 } 499 // Append NULL at the end. 500 SingleChar = 0; 501 StrVal = (StrVal << 8) | SingleChar; 502 } 503 504 Constant *Res = ConstantInt::get(CE->getContext(), StrVal); 505 if (Ty->isFloatingPointTy()) 506 Res = ConstantExpr::getBitCast(Res, Ty); 507 return Res; 508 } 509 } 510 511 // If this load comes from anywhere in a constant global, and if the global 512 // is all undef or zero, we know what it loads. 513 if (GlobalVariable *GV = 514 dyn_cast<GlobalVariable>(GetUnderlyingObject(CE, TD))) { 515 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 516 Type *ResTy = cast<PointerType>(C->getType())->getElementType(); 517 if (GV->getInitializer()->isNullValue()) 518 return Constant::getNullValue(ResTy); 519 if (isa<UndefValue>(GV->getInitializer())) 520 return UndefValue::get(ResTy); 521 } 522 } 523 524 // Try hard to fold loads from bitcasted strange and non-type-safe things. 525 if (TD) 526 return FoldReinterpretLoadFromConstPtr(CE, *TD); 527 return 0; 528 } 529 530 static Constant *ConstantFoldLoadInst(const LoadInst *LI, const DataLayout *TD){ 531 if (LI->isVolatile()) return 0; 532 533 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0))) 534 return ConstantFoldLoadFromConstPtr(C, TD); 535 536 return 0; 537 } 538 539 /// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression. 540 /// Attempt to symbolically evaluate the result of a binary operator merging 541 /// these together. If target data info is available, it is provided as DL, 542 /// otherwise DL is null. 543 static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, 544 Constant *Op1, const DataLayout *DL){ 545 // SROA 546 547 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl. 548 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute 549 // bits. 550 551 552 if (Opc == Instruction::And && DL) { 553 unsigned BitWidth = DL->getTypeSizeInBits(Op0->getType()); 554 APInt KnownZero0(BitWidth, 0), KnownOne0(BitWidth, 0); 555 APInt KnownZero1(BitWidth, 0), KnownOne1(BitWidth, 0); 556 ComputeMaskedBits(Op0, KnownZero0, KnownOne0, DL); 557 ComputeMaskedBits(Op1, KnownZero1, KnownOne1, DL); 558 if ((KnownOne1 | KnownZero0).isAllOnesValue()) { 559 // All the bits of Op0 that the 'and' could be masking are already zero. 560 return Op0; 561 } 562 if ((KnownOne0 | KnownZero1).isAllOnesValue()) { 563 // All the bits of Op1 that the 'and' could be masking are already zero. 564 return Op1; 565 } 566 567 APInt KnownZero = KnownZero0 | KnownZero1; 568 APInt KnownOne = KnownOne0 & KnownOne1; 569 if ((KnownZero | KnownOne).isAllOnesValue()) { 570 return ConstantInt::get(Op0->getType(), KnownOne); 571 } 572 } 573 574 // If the constant expr is something like &A[123] - &A[4].f, fold this into a 575 // constant. This happens frequently when iterating over a global array. 576 if (Opc == Instruction::Sub && DL) { 577 GlobalValue *GV1, *GV2; 578 unsigned PtrSize = DL->getPointerSizeInBits(); 579 unsigned OpSize = DL->getTypeSizeInBits(Op0->getType()); 580 APInt Offs1(PtrSize, 0), Offs2(PtrSize, 0); 581 582 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *DL)) 583 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *DL) && 584 GV1 == GV2) { 585 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow. 586 // PtrToInt may change the bitwidth so we have convert to the right size 587 // first. 588 return ConstantInt::get(Op0->getType(), Offs1.zextOrTrunc(OpSize) - 589 Offs2.zextOrTrunc(OpSize)); 590 } 591 } 592 593 return 0; 594 } 595 596 /// CastGEPIndices - If array indices are not pointer-sized integers, 597 /// explicitly cast them so that they aren't implicitly casted by the 598 /// getelementptr. 599 static Constant *CastGEPIndices(ArrayRef<Constant *> Ops, 600 Type *ResultTy, const DataLayout *TD, 601 const TargetLibraryInfo *TLI) { 602 if (!TD) return 0; 603 Type *IntPtrTy = TD->getIntPtrType(ResultTy->getContext()); 604 605 bool Any = false; 606 SmallVector<Constant*, 32> NewIdxs; 607 for (unsigned i = 1, e = Ops.size(); i != e; ++i) { 608 if ((i == 1 || 609 !isa<StructType>(GetElementPtrInst::getIndexedType(Ops[0]->getType(), 610 Ops.slice(1, i-1)))) && 611 Ops[i]->getType() != IntPtrTy) { 612 Any = true; 613 NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i], 614 true, 615 IntPtrTy, 616 true), 617 Ops[i], IntPtrTy)); 618 } else 619 NewIdxs.push_back(Ops[i]); 620 } 621 if (!Any) return 0; 622 623 Constant *C = 624 ConstantExpr::getGetElementPtr(Ops[0], NewIdxs); 625 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 626 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI)) 627 C = Folded; 628 return C; 629 } 630 631 /// Strip the pointer casts, but preserve the address space information. 632 static Constant* StripPtrCastKeepAS(Constant* Ptr) { 633 assert(Ptr->getType()->isPointerTy() && "Not a pointer type"); 634 PointerType *OldPtrTy = cast<PointerType>(Ptr->getType()); 635 Ptr = cast<Constant>(Ptr->stripPointerCasts()); 636 PointerType *NewPtrTy = cast<PointerType>(Ptr->getType()); 637 638 // Preserve the address space number of the pointer. 639 if (NewPtrTy->getAddressSpace() != OldPtrTy->getAddressSpace()) { 640 NewPtrTy = NewPtrTy->getElementType()->getPointerTo( 641 OldPtrTy->getAddressSpace()); 642 Ptr = ConstantExpr::getBitCast(Ptr, NewPtrTy); 643 } 644 return Ptr; 645 } 646 647 /// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP 648 /// constant expression, do so. 649 static Constant *SymbolicallyEvaluateGEP(ArrayRef<Constant *> Ops, 650 Type *ResultTy, const DataLayout *TD, 651 const TargetLibraryInfo *TLI) { 652 Constant *Ptr = Ops[0]; 653 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized() || 654 !Ptr->getType()->isPointerTy()) 655 return 0; 656 657 Type *IntPtrTy = TD->getIntPtrType(Ptr->getContext()); 658 659 // If this is a constant expr gep that is effectively computing an 660 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' 661 for (unsigned i = 1, e = Ops.size(); i != e; ++i) 662 if (!isa<ConstantInt>(Ops[i])) { 663 664 // If this is "gep i8* Ptr, (sub 0, V)", fold this as: 665 // "inttoptr (sub (ptrtoint Ptr), V)" 666 if (Ops.size() == 2 && 667 cast<PointerType>(ResultTy)->getElementType()->isIntegerTy(8)) { 668 ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[1]); 669 assert((CE == 0 || CE->getType() == IntPtrTy) && 670 "CastGEPIndices didn't canonicalize index types!"); 671 if (CE && CE->getOpcode() == Instruction::Sub && 672 CE->getOperand(0)->isNullValue()) { 673 Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType()); 674 Res = ConstantExpr::getSub(Res, CE->getOperand(1)); 675 Res = ConstantExpr::getIntToPtr(Res, ResultTy); 676 if (ConstantExpr *ResCE = dyn_cast<ConstantExpr>(Res)) 677 Res = ConstantFoldConstantExpression(ResCE, TD, TLI); 678 return Res; 679 } 680 } 681 return 0; 682 } 683 684 unsigned BitWidth = TD->getTypeSizeInBits(IntPtrTy); 685 APInt Offset = 686 APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(), 687 makeArrayRef((Value *const*) 688 Ops.data() + 1, 689 Ops.size() - 1))); 690 Ptr = StripPtrCastKeepAS(Ptr); 691 692 // If this is a GEP of a GEP, fold it all into a single GEP. 693 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) { 694 SmallVector<Value *, 4> NestedOps(GEP->op_begin()+1, GEP->op_end()); 695 696 // Do not try the incorporate the sub-GEP if some index is not a number. 697 bool AllConstantInt = true; 698 for (unsigned i = 0, e = NestedOps.size(); i != e; ++i) 699 if (!isa<ConstantInt>(NestedOps[i])) { 700 AllConstantInt = false; 701 break; 702 } 703 if (!AllConstantInt) 704 break; 705 706 Ptr = cast<Constant>(GEP->getOperand(0)); 707 Offset += APInt(BitWidth, 708 TD->getIndexedOffset(Ptr->getType(), NestedOps)); 709 Ptr = StripPtrCastKeepAS(Ptr); 710 } 711 712 // If the base value for this address is a literal integer value, fold the 713 // getelementptr to the resulting integer value casted to the pointer type. 714 APInt BasePtr(BitWidth, 0); 715 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 716 if (CE->getOpcode() == Instruction::IntToPtr) 717 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) 718 BasePtr = Base->getValue().zextOrTrunc(BitWidth); 719 if (Ptr->isNullValue() || BasePtr != 0) { 720 Constant *C = ConstantInt::get(Ptr->getContext(), Offset+BasePtr); 721 return ConstantExpr::getIntToPtr(C, ResultTy); 722 } 723 724 // Otherwise form a regular getelementptr. Recompute the indices so that 725 // we eliminate over-indexing of the notional static type array bounds. 726 // This makes it easy to determine if the getelementptr is "inbounds". 727 // Also, this helps GlobalOpt do SROA on GlobalVariables. 728 Type *Ty = Ptr->getType(); 729 assert(Ty->isPointerTy() && "Forming regular GEP of non-pointer type"); 730 SmallVector<Constant*, 32> NewIdxs; 731 do { 732 if (SequentialType *ATy = dyn_cast<SequentialType>(Ty)) { 733 if (ATy->isPointerTy()) { 734 // The only pointer indexing we'll do is on the first index of the GEP. 735 if (!NewIdxs.empty()) 736 break; 737 738 // Only handle pointers to sized types, not pointers to functions. 739 if (!ATy->getElementType()->isSized()) 740 return 0; 741 } 742 743 // Determine which element of the array the offset points into. 744 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); 745 IntegerType *IntPtrTy = TD->getIntPtrType(Ty->getContext()); 746 if (ElemSize == 0) 747 // The element size is 0. This may be [0 x Ty]*, so just use a zero 748 // index for this level and proceed to the next level to see if it can 749 // accommodate the offset. 750 NewIdxs.push_back(ConstantInt::get(IntPtrTy, 0)); 751 else { 752 // The element size is non-zero divide the offset by the element 753 // size (rounding down), to compute the index at this level. 754 APInt NewIdx = Offset.udiv(ElemSize); 755 Offset -= NewIdx * ElemSize; 756 NewIdxs.push_back(ConstantInt::get(IntPtrTy, NewIdx)); 757 } 758 Ty = ATy->getElementType(); 759 } else if (StructType *STy = dyn_cast<StructType>(Ty)) { 760 // If we end up with an offset that isn't valid for this struct type, we 761 // can't re-form this GEP in a regular form, so bail out. The pointer 762 // operand likely went through casts that are necessary to make the GEP 763 // sensible. 764 const StructLayout &SL = *TD->getStructLayout(STy); 765 if (Offset.uge(SL.getSizeInBytes())) 766 break; 767 768 // Determine which field of the struct the offset points into. The 769 // getZExtValue is fine as we've already ensured that the offset is 770 // within the range representable by the StructLayout API. 771 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); 772 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 773 ElIdx)); 774 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); 775 Ty = STy->getTypeAtIndex(ElIdx); 776 } else { 777 // We've reached some non-indexable type. 778 break; 779 } 780 } while (Ty != cast<PointerType>(ResultTy)->getElementType()); 781 782 // If we haven't used up the entire offset by descending the static 783 // type, then the offset is pointing into the middle of an indivisible 784 // member, so we can't simplify it. 785 if (Offset != 0) 786 return 0; 787 788 // Create a GEP. 789 Constant *C = 790 ConstantExpr::getGetElementPtr(Ptr, NewIdxs); 791 assert(cast<PointerType>(C->getType())->getElementType() == Ty && 792 "Computed GetElementPtr has unexpected type!"); 793 794 // If we ended up indexing a member with a type that doesn't match 795 // the type of what the original indices indexed, add a cast. 796 if (Ty != cast<PointerType>(ResultTy)->getElementType()) 797 C = FoldBitCast(C, ResultTy, *TD); 798 799 return C; 800 } 801 802 803 804 //===----------------------------------------------------------------------===// 805 // Constant Folding public APIs 806 //===----------------------------------------------------------------------===// 807 808 /// ConstantFoldInstruction - Try to constant fold the specified instruction. 809 /// If successful, the constant result is returned, if not, null is returned. 810 /// Note that this fails if not all of the operands are constant. Otherwise, 811 /// this function can only fail when attempting to fold instructions like loads 812 /// and stores, which have no constant expression form. 813 Constant *llvm::ConstantFoldInstruction(Instruction *I, 814 const DataLayout *TD, 815 const TargetLibraryInfo *TLI) { 816 // Handle PHI nodes quickly here... 817 if (PHINode *PN = dyn_cast<PHINode>(I)) { 818 Constant *CommonValue = 0; 819 820 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 821 Value *Incoming = PN->getIncomingValue(i); 822 // If the incoming value is undef then skip it. Note that while we could 823 // skip the value if it is equal to the phi node itself we choose not to 824 // because that would break the rule that constant folding only applies if 825 // all operands are constants. 826 if (isa<UndefValue>(Incoming)) 827 continue; 828 // If the incoming value is not a constant, then give up. 829 Constant *C = dyn_cast<Constant>(Incoming); 830 if (!C) 831 return 0; 832 // Fold the PHI's operands. 833 if (ConstantExpr *NewC = dyn_cast<ConstantExpr>(C)) 834 C = ConstantFoldConstantExpression(NewC, TD, TLI); 835 // If the incoming value is a different constant to 836 // the one we saw previously, then give up. 837 if (CommonValue && C != CommonValue) 838 return 0; 839 CommonValue = C; 840 } 841 842 843 // If we reach here, all incoming values are the same constant or undef. 844 return CommonValue ? CommonValue : UndefValue::get(PN->getType()); 845 } 846 847 // Scan the operand list, checking to see if they are all constants, if so, 848 // hand off to ConstantFoldInstOperands. 849 SmallVector<Constant*, 8> Ops; 850 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) { 851 Constant *Op = dyn_cast<Constant>(*i); 852 if (!Op) 853 return 0; // All operands not constant! 854 855 // Fold the Instruction's operands. 856 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(Op)) 857 Op = ConstantFoldConstantExpression(NewCE, TD, TLI); 858 859 Ops.push_back(Op); 860 } 861 862 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 863 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], 864 TD, TLI); 865 866 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 867 return ConstantFoldLoadInst(LI, TD); 868 869 if (InsertValueInst *IVI = dyn_cast<InsertValueInst>(I)) 870 return ConstantExpr::getInsertValue( 871 cast<Constant>(IVI->getAggregateOperand()), 872 cast<Constant>(IVI->getInsertedValueOperand()), 873 IVI->getIndices()); 874 875 if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I)) 876 return ConstantExpr::getExtractValue( 877 cast<Constant>(EVI->getAggregateOperand()), 878 EVI->getIndices()); 879 880 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops, TD, TLI); 881 } 882 883 /// ConstantFoldConstantExpression - Attempt to fold the constant expression 884 /// using the specified DataLayout. If successful, the constant result is 885 /// result is returned, if not, null is returned. 886 Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE, 887 const DataLayout *TD, 888 const TargetLibraryInfo *TLI) { 889 SmallVector<Constant*, 8> Ops; 890 for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); 891 i != e; ++i) { 892 Constant *NewC = cast<Constant>(*i); 893 // Recursively fold the ConstantExpr's operands. 894 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC)) 895 NewC = ConstantFoldConstantExpression(NewCE, TD, TLI); 896 Ops.push_back(NewC); 897 } 898 899 if (CE->isCompare()) 900 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1], 901 TD, TLI); 902 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), Ops, TD, TLI); 903 } 904 905 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 906 /// specified opcode and operands. If successful, the constant result is 907 /// returned, if not, null is returned. Note that this function can fail when 908 /// attempting to fold instructions like loads and stores, which have no 909 /// constant expression form. 910 /// 911 /// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc 912 /// information, due to only being passed an opcode and operands. Constant 913 /// folding using this function strips this information. 914 /// 915 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, 916 ArrayRef<Constant *> Ops, 917 const DataLayout *TD, 918 const TargetLibraryInfo *TLI) { 919 // Handle easy binops first. 920 if (Instruction::isBinaryOp(Opcode)) { 921 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) 922 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD)) 923 return C; 924 925 return ConstantExpr::get(Opcode, Ops[0], Ops[1]); 926 } 927 928 switch (Opcode) { 929 default: return 0; 930 case Instruction::ICmp: 931 case Instruction::FCmp: llvm_unreachable("Invalid for compares"); 932 case Instruction::Call: 933 if (Function *F = dyn_cast<Function>(Ops.back())) 934 if (canConstantFoldCallTo(F)) 935 return ConstantFoldCall(F, Ops.slice(0, Ops.size() - 1), TLI); 936 return 0; 937 case Instruction::PtrToInt: 938 // If the input is a inttoptr, eliminate the pair. This requires knowing 939 // the width of a pointer, so it can't be done in ConstantExpr::getCast. 940 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 941 if (TD && CE->getOpcode() == Instruction::IntToPtr) { 942 Constant *Input = CE->getOperand(0); 943 unsigned InWidth = Input->getType()->getScalarSizeInBits(); 944 if (TD->getPointerSizeInBits() < InWidth) { 945 Constant *Mask = 946 ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth, 947 TD->getPointerSizeInBits())); 948 Input = ConstantExpr::getAnd(Input, Mask); 949 } 950 // Do a zext or trunc to get to the dest size. 951 return ConstantExpr::getIntegerCast(Input, DestTy, false); 952 } 953 } 954 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 955 case Instruction::IntToPtr: 956 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if 957 // the int size is >= the ptr size. This requires knowing the width of a 958 // pointer, so it can't be done in ConstantExpr::getCast. 959 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) 960 if (TD && 961 TD->getPointerSizeInBits() <= CE->getType()->getScalarSizeInBits() && 962 CE->getOpcode() == Instruction::PtrToInt) 963 return FoldBitCast(CE->getOperand(0), DestTy, *TD); 964 965 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 966 case Instruction::Trunc: 967 case Instruction::ZExt: 968 case Instruction::SExt: 969 case Instruction::FPTrunc: 970 case Instruction::FPExt: 971 case Instruction::UIToFP: 972 case Instruction::SIToFP: 973 case Instruction::FPToUI: 974 case Instruction::FPToSI: 975 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 976 case Instruction::BitCast: 977 if (TD) 978 return FoldBitCast(Ops[0], DestTy, *TD); 979 return ConstantExpr::getBitCast(Ops[0], DestTy); 980 case Instruction::Select: 981 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); 982 case Instruction::ExtractElement: 983 return ConstantExpr::getExtractElement(Ops[0], Ops[1]); 984 case Instruction::InsertElement: 985 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); 986 case Instruction::ShuffleVector: 987 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); 988 case Instruction::GetElementPtr: 989 if (Constant *C = CastGEPIndices(Ops, DestTy, TD, TLI)) 990 return C; 991 if (Constant *C = SymbolicallyEvaluateGEP(Ops, DestTy, TD, TLI)) 992 return C; 993 994 return ConstantExpr::getGetElementPtr(Ops[0], Ops.slice(1)); 995 } 996 } 997 998 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 999 /// instruction (icmp/fcmp) with the specified operands. If it fails, it 1000 /// returns a constant expression of the specified operands. 1001 /// 1002 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, 1003 Constant *Ops0, Constant *Ops1, 1004 const DataLayout *TD, 1005 const TargetLibraryInfo *TLI) { 1006 // fold: icmp (inttoptr x), null -> icmp x, 0 1007 // fold: icmp (ptrtoint x), 0 -> icmp x, null 1008 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y 1009 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y 1010 // 1011 // ConstantExpr::getCompare cannot do this, because it doesn't have TD 1012 // around to know if bit truncation is happening. 1013 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) { 1014 if (TD && Ops1->isNullValue()) { 1015 Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 1016 if (CE0->getOpcode() == Instruction::IntToPtr) { 1017 // Convert the integer value to the right size to ensure we get the 1018 // proper extension or truncation. 1019 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), 1020 IntPtrTy, false); 1021 Constant *Null = Constant::getNullValue(C->getType()); 1022 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); 1023 } 1024 1025 // Only do this transformation if the int is intptrty in size, otherwise 1026 // there is a truncation or extension that we aren't modeling. 1027 if (CE0->getOpcode() == Instruction::PtrToInt && 1028 CE0->getType() == IntPtrTy) { 1029 Constant *C = CE0->getOperand(0); 1030 Constant *Null = Constant::getNullValue(C->getType()); 1031 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); 1032 } 1033 } 1034 1035 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) { 1036 if (TD && CE0->getOpcode() == CE1->getOpcode()) { 1037 Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 1038 1039 if (CE0->getOpcode() == Instruction::IntToPtr) { 1040 // Convert the integer value to the right size to ensure we get the 1041 // proper extension or truncation. 1042 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), 1043 IntPtrTy, false); 1044 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), 1045 IntPtrTy, false); 1046 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD, TLI); 1047 } 1048 1049 // Only do this transformation if the int is intptrty in size, otherwise 1050 // there is a truncation or extension that we aren't modeling. 1051 if ((CE0->getOpcode() == Instruction::PtrToInt && 1052 CE0->getType() == IntPtrTy && 1053 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) 1054 return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), 1055 CE1->getOperand(0), TD, TLI); 1056 } 1057 } 1058 1059 // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0) 1060 // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0) 1061 if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) && 1062 CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) { 1063 Constant *LHS = 1064 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1, 1065 TD, TLI); 1066 Constant *RHS = 1067 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1, 1068 TD, TLI); 1069 unsigned OpC = 1070 Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or; 1071 Constant *Ops[] = { LHS, RHS }; 1072 return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, TD, TLI); 1073 } 1074 } 1075 1076 return ConstantExpr::getCompare(Predicate, Ops0, Ops1); 1077 } 1078 1079 1080 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 1081 /// getelementptr constantexpr, return the constant value being addressed by the 1082 /// constant expression, or null if something is funny and we can't decide. 1083 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, 1084 ConstantExpr *CE) { 1085 if (!CE->getOperand(1)->isNullValue()) 1086 return 0; // Do not allow stepping over the value! 1087 1088 // Loop over all of the operands, tracking down which value we are 1089 // addressing. 1090 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i) { 1091 C = C->getAggregateElement(CE->getOperand(i)); 1092 if (C == 0) return 0; 1093 } 1094 return C; 1095 } 1096 1097 /// ConstantFoldLoadThroughGEPIndices - Given a constant and getelementptr 1098 /// indices (with an *implied* zero pointer index that is not in the list), 1099 /// return the constant value being addressed by a virtual load, or null if 1100 /// something is funny and we can't decide. 1101 Constant *llvm::ConstantFoldLoadThroughGEPIndices(Constant *C, 1102 ArrayRef<Constant*> Indices) { 1103 // Loop over all of the operands, tracking down which value we are 1104 // addressing. 1105 for (unsigned i = 0, e = Indices.size(); i != e; ++i) { 1106 C = C->getAggregateElement(Indices[i]); 1107 if (C == 0) return 0; 1108 } 1109 return C; 1110 } 1111 1112 1113 //===----------------------------------------------------------------------===// 1114 // Constant Folding for Calls 1115 // 1116 1117 /// canConstantFoldCallTo - Return true if its even possible to fold a call to 1118 /// the specified function. 1119 bool 1120 llvm::canConstantFoldCallTo(const Function *F) { 1121 switch (F->getIntrinsicID()) { 1122 case Intrinsic::fabs: 1123 case Intrinsic::log: 1124 case Intrinsic::log2: 1125 case Intrinsic::log10: 1126 case Intrinsic::exp: 1127 case Intrinsic::exp2: 1128 case Intrinsic::floor: 1129 case Intrinsic::sqrt: 1130 case Intrinsic::pow: 1131 case Intrinsic::powi: 1132 case Intrinsic::bswap: 1133 case Intrinsic::ctpop: 1134 case Intrinsic::ctlz: 1135 case Intrinsic::cttz: 1136 case Intrinsic::sadd_with_overflow: 1137 case Intrinsic::uadd_with_overflow: 1138 case Intrinsic::ssub_with_overflow: 1139 case Intrinsic::usub_with_overflow: 1140 case Intrinsic::smul_with_overflow: 1141 case Intrinsic::umul_with_overflow: 1142 case Intrinsic::convert_from_fp16: 1143 case Intrinsic::convert_to_fp16: 1144 case Intrinsic::x86_sse_cvtss2si: 1145 case Intrinsic::x86_sse_cvtss2si64: 1146 case Intrinsic::x86_sse_cvttss2si: 1147 case Intrinsic::x86_sse_cvttss2si64: 1148 case Intrinsic::x86_sse2_cvtsd2si: 1149 case Intrinsic::x86_sse2_cvtsd2si64: 1150 case Intrinsic::x86_sse2_cvttsd2si: 1151 case Intrinsic::x86_sse2_cvttsd2si64: 1152 return true; 1153 default: 1154 return false; 1155 case 0: break; 1156 } 1157 1158 if (!F->hasName()) return false; 1159 StringRef Name = F->getName(); 1160 1161 // In these cases, the check of the length is required. We don't want to 1162 // return true for a name like "cos\0blah" which strcmp would return equal to 1163 // "cos", but has length 8. 1164 switch (Name[0]) { 1165 default: return false; 1166 case 'a': 1167 return Name == "acos" || Name == "asin" || Name == "atan" || Name =="atan2"; 1168 case 'c': 1169 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; 1170 case 'e': 1171 return Name == "exp" || Name == "exp2"; 1172 case 'f': 1173 return Name == "fabs" || Name == "fmod" || Name == "floor"; 1174 case 'l': 1175 return Name == "log" || Name == "log10"; 1176 case 'p': 1177 return Name == "pow"; 1178 case 's': 1179 return Name == "sin" || Name == "sinh" || Name == "sqrt" || 1180 Name == "sinf" || Name == "sqrtf"; 1181 case 't': 1182 return Name == "tan" || Name == "tanh"; 1183 } 1184 } 1185 1186 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 1187 Type *Ty) { 1188 sys::llvm_fenv_clearexcept(); 1189 V = NativeFP(V); 1190 if (sys::llvm_fenv_testexcept()) { 1191 sys::llvm_fenv_clearexcept(); 1192 return 0; 1193 } 1194 1195 if (Ty->isHalfTy()) { 1196 APFloat APF(V); 1197 bool unused; 1198 APF.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &unused); 1199 return ConstantFP::get(Ty->getContext(), APF); 1200 } 1201 if (Ty->isFloatTy()) 1202 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1203 if (Ty->isDoubleTy()) 1204 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1205 llvm_unreachable("Can only constant fold half/float/double"); 1206 } 1207 1208 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), 1209 double V, double W, Type *Ty) { 1210 sys::llvm_fenv_clearexcept(); 1211 V = NativeFP(V, W); 1212 if (sys::llvm_fenv_testexcept()) { 1213 sys::llvm_fenv_clearexcept(); 1214 return 0; 1215 } 1216 1217 if (Ty->isHalfTy()) { 1218 APFloat APF(V); 1219 bool unused; 1220 APF.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &unused); 1221 return ConstantFP::get(Ty->getContext(), APF); 1222 } 1223 if (Ty->isFloatTy()) 1224 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1225 if (Ty->isDoubleTy()) 1226 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1227 llvm_unreachable("Can only constant fold half/float/double"); 1228 } 1229 1230 /// ConstantFoldConvertToInt - Attempt to an SSE floating point to integer 1231 /// conversion of a constant floating point. If roundTowardZero is false, the 1232 /// default IEEE rounding is used (toward nearest, ties to even). This matches 1233 /// the behavior of the non-truncating SSE instructions in the default rounding 1234 /// mode. The desired integer type Ty is used to select how many bits are 1235 /// available for the result. Returns null if the conversion cannot be 1236 /// performed, otherwise returns the Constant value resulting from the 1237 /// conversion. 1238 static Constant *ConstantFoldConvertToInt(const APFloat &Val, 1239 bool roundTowardZero, Type *Ty) { 1240 // All of these conversion intrinsics form an integer of at most 64bits. 1241 unsigned ResultWidth = cast<IntegerType>(Ty)->getBitWidth(); 1242 assert(ResultWidth <= 64 && 1243 "Can only constant fold conversions to 64 and 32 bit ints"); 1244 1245 uint64_t UIntVal; 1246 bool isExact = false; 1247 APFloat::roundingMode mode = roundTowardZero? APFloat::rmTowardZero 1248 : APFloat::rmNearestTiesToEven; 1249 APFloat::opStatus status = Val.convertToInteger(&UIntVal, ResultWidth, 1250 /*isSigned=*/true, mode, 1251 &isExact); 1252 if (status != APFloat::opOK && status != APFloat::opInexact) 1253 return 0; 1254 return ConstantInt::get(Ty, UIntVal, /*isSigned=*/true); 1255 } 1256 1257 /// ConstantFoldCall - Attempt to constant fold a call to the specified function 1258 /// with the specified arguments, returning null if unsuccessful. 1259 Constant * 1260 llvm::ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands, 1261 const TargetLibraryInfo *TLI) { 1262 if (!F->hasName()) return 0; 1263 StringRef Name = F->getName(); 1264 1265 Type *Ty = F->getReturnType(); 1266 if (Operands.size() == 1) { 1267 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { 1268 if (F->getIntrinsicID() == Intrinsic::convert_to_fp16) { 1269 APFloat Val(Op->getValueAPF()); 1270 1271 bool lost = false; 1272 Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost); 1273 1274 return ConstantInt::get(F->getContext(), Val.bitcastToAPInt()); 1275 } 1276 if (!TLI) 1277 return 0; 1278 1279 if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) 1280 return 0; 1281 1282 /// We only fold functions with finite arguments. Folding NaN and inf is 1283 /// likely to be aborted with an exception anyway, and some host libms 1284 /// have known errors raising exceptions. 1285 if (Op->getValueAPF().isNaN() || Op->getValueAPF().isInfinity()) 1286 return 0; 1287 1288 /// Currently APFloat versions of these functions do not exist, so we use 1289 /// the host native double versions. Float versions are not called 1290 /// directly but for all these it is true (float)(f((double)arg)) == 1291 /// f(arg). Long double not supported yet. 1292 double V; 1293 if (Ty->isFloatTy()) 1294 V = Op->getValueAPF().convertToFloat(); 1295 else if (Ty->isDoubleTy()) 1296 V = Op->getValueAPF().convertToDouble(); 1297 else { 1298 bool unused; 1299 APFloat APF = Op->getValueAPF(); 1300 APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); 1301 V = APF.convertToDouble(); 1302 } 1303 1304 switch (F->getIntrinsicID()) { 1305 default: break; 1306 case Intrinsic::fabs: 1307 return ConstantFoldFP(fabs, V, Ty); 1308 #if HAVE_LOG2 1309 case Intrinsic::log2: 1310 return ConstantFoldFP(log2, V, Ty); 1311 #endif 1312 #if HAVE_LOG 1313 case Intrinsic::log: 1314 return ConstantFoldFP(log, V, Ty); 1315 #endif 1316 #if HAVE_LOG10 1317 case Intrinsic::log10: 1318 return ConstantFoldFP(log10, V, Ty); 1319 #endif 1320 #if HAVE_EXP 1321 case Intrinsic::exp: 1322 return ConstantFoldFP(exp, V, Ty); 1323 #endif 1324 #if HAVE_EXP2 1325 case Intrinsic::exp2: 1326 return ConstantFoldFP(exp2, V, Ty); 1327 #endif 1328 case Intrinsic::floor: 1329 return ConstantFoldFP(floor, V, Ty); 1330 } 1331 1332 switch (Name[0]) { 1333 case 'a': 1334 if (Name == "acos" && TLI->has(LibFunc::acos)) 1335 return ConstantFoldFP(acos, V, Ty); 1336 else if (Name == "asin" && TLI->has(LibFunc::asin)) 1337 return ConstantFoldFP(asin, V, Ty); 1338 else if (Name == "atan" && TLI->has(LibFunc::atan)) 1339 return ConstantFoldFP(atan, V, Ty); 1340 break; 1341 case 'c': 1342 if (Name == "ceil" && TLI->has(LibFunc::ceil)) 1343 return ConstantFoldFP(ceil, V, Ty); 1344 else if (Name == "cos" && TLI->has(LibFunc::cos)) 1345 return ConstantFoldFP(cos, V, Ty); 1346 else if (Name == "cosh" && TLI->has(LibFunc::cosh)) 1347 return ConstantFoldFP(cosh, V, Ty); 1348 else if (Name == "cosf" && TLI->has(LibFunc::cosf)) 1349 return ConstantFoldFP(cos, V, Ty); 1350 break; 1351 case 'e': 1352 if (Name == "exp" && TLI->has(LibFunc::exp)) 1353 return ConstantFoldFP(exp, V, Ty); 1354 1355 if (Name == "exp2" && TLI->has(LibFunc::exp2)) { 1356 // Constant fold exp2(x) as pow(2,x) in case the host doesn't have a 1357 // C99 library. 1358 return ConstantFoldBinaryFP(pow, 2.0, V, Ty); 1359 } 1360 break; 1361 case 'f': 1362 if (Name == "fabs" && TLI->has(LibFunc::fabs)) 1363 return ConstantFoldFP(fabs, V, Ty); 1364 else if (Name == "floor" && TLI->has(LibFunc::floor)) 1365 return ConstantFoldFP(floor, V, Ty); 1366 break; 1367 case 'l': 1368 if (Name == "log" && V > 0 && TLI->has(LibFunc::log)) 1369 return ConstantFoldFP(log, V, Ty); 1370 else if (Name == "log10" && V > 0 && TLI->has(LibFunc::log10)) 1371 return ConstantFoldFP(log10, V, Ty); 1372 else if (F->getIntrinsicID() == Intrinsic::sqrt && 1373 (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy())) { 1374 if (V >= -0.0) 1375 return ConstantFoldFP(sqrt, V, Ty); 1376 else // Undefined 1377 return Constant::getNullValue(Ty); 1378 } 1379 break; 1380 case 's': 1381 if (Name == "sin" && TLI->has(LibFunc::sin)) 1382 return ConstantFoldFP(sin, V, Ty); 1383 else if (Name == "sinh" && TLI->has(LibFunc::sinh)) 1384 return ConstantFoldFP(sinh, V, Ty); 1385 else if (Name == "sqrt" && V >= 0 && TLI->has(LibFunc::sqrt)) 1386 return ConstantFoldFP(sqrt, V, Ty); 1387 else if (Name == "sqrtf" && V >= 0 && TLI->has(LibFunc::sqrtf)) 1388 return ConstantFoldFP(sqrt, V, Ty); 1389 else if (Name == "sinf" && TLI->has(LibFunc::sinf)) 1390 return ConstantFoldFP(sin, V, Ty); 1391 break; 1392 case 't': 1393 if (Name == "tan" && TLI->has(LibFunc::tan)) 1394 return ConstantFoldFP(tan, V, Ty); 1395 else if (Name == "tanh" && TLI->has(LibFunc::tanh)) 1396 return ConstantFoldFP(tanh, V, Ty); 1397 break; 1398 default: 1399 break; 1400 } 1401 return 0; 1402 } 1403 1404 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { 1405 switch (F->getIntrinsicID()) { 1406 case Intrinsic::bswap: 1407 return ConstantInt::get(F->getContext(), Op->getValue().byteSwap()); 1408 case Intrinsic::ctpop: 1409 return ConstantInt::get(Ty, Op->getValue().countPopulation()); 1410 case Intrinsic::convert_from_fp16: { 1411 APFloat Val(APFloat::IEEEhalf, Op->getValue()); 1412 1413 bool lost = false; 1414 APFloat::opStatus status = 1415 Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost); 1416 1417 // Conversion is always precise. 1418 (void)status; 1419 assert(status == APFloat::opOK && !lost && 1420 "Precision lost during fp16 constfolding"); 1421 1422 return ConstantFP::get(F->getContext(), Val); 1423 } 1424 default: 1425 return 0; 1426 } 1427 } 1428 1429 // Support ConstantVector in case we have an Undef in the top. 1430 if (isa<ConstantVector>(Operands[0]) || 1431 isa<ConstantDataVector>(Operands[0])) { 1432 Constant *Op = cast<Constant>(Operands[0]); 1433 switch (F->getIntrinsicID()) { 1434 default: break; 1435 case Intrinsic::x86_sse_cvtss2si: 1436 case Intrinsic::x86_sse_cvtss2si64: 1437 case Intrinsic::x86_sse2_cvtsd2si: 1438 case Intrinsic::x86_sse2_cvtsd2si64: 1439 if (ConstantFP *FPOp = 1440 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U))) 1441 return ConstantFoldConvertToInt(FPOp->getValueAPF(), 1442 /*roundTowardZero=*/false, Ty); 1443 case Intrinsic::x86_sse_cvttss2si: 1444 case Intrinsic::x86_sse_cvttss2si64: 1445 case Intrinsic::x86_sse2_cvttsd2si: 1446 case Intrinsic::x86_sse2_cvttsd2si64: 1447 if (ConstantFP *FPOp = 1448 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U))) 1449 return ConstantFoldConvertToInt(FPOp->getValueAPF(), 1450 /*roundTowardZero=*/true, Ty); 1451 } 1452 } 1453 1454 if (isa<UndefValue>(Operands[0])) { 1455 if (F->getIntrinsicID() == Intrinsic::bswap) 1456 return Operands[0]; 1457 return 0; 1458 } 1459 1460 return 0; 1461 } 1462 1463 if (Operands.size() == 2) { 1464 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1465 if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) 1466 return 0; 1467 double Op1V; 1468 if (Ty->isFloatTy()) 1469 Op1V = Op1->getValueAPF().convertToFloat(); 1470 else if (Ty->isDoubleTy()) 1471 Op1V = Op1->getValueAPF().convertToDouble(); 1472 else { 1473 bool unused; 1474 APFloat APF = Op1->getValueAPF(); 1475 APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); 1476 Op1V = APF.convertToDouble(); 1477 } 1478 1479 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1480 if (Op2->getType() != Op1->getType()) 1481 return 0; 1482 1483 double Op2V; 1484 if (Ty->isFloatTy()) 1485 Op2V = Op2->getValueAPF().convertToFloat(); 1486 else if (Ty->isDoubleTy()) 1487 Op2V = Op2->getValueAPF().convertToDouble(); 1488 else { 1489 bool unused; 1490 APFloat APF = Op2->getValueAPF(); 1491 APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); 1492 Op2V = APF.convertToDouble(); 1493 } 1494 1495 if (F->getIntrinsicID() == Intrinsic::pow) { 1496 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1497 } 1498 if (!TLI) 1499 return 0; 1500 if (Name == "pow" && TLI->has(LibFunc::pow)) 1501 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1502 if (Name == "fmod" && TLI->has(LibFunc::fmod)) 1503 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty); 1504 if (Name == "atan2" && TLI->has(LibFunc::atan2)) 1505 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty); 1506 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { 1507 if (F->getIntrinsicID() == Intrinsic::powi && Ty->isHalfTy()) 1508 return ConstantFP::get(F->getContext(), 1509 APFloat((float)std::pow((float)Op1V, 1510 (int)Op2C->getZExtValue()))); 1511 if (F->getIntrinsicID() == Intrinsic::powi && Ty->isFloatTy()) 1512 return ConstantFP::get(F->getContext(), 1513 APFloat((float)std::pow((float)Op1V, 1514 (int)Op2C->getZExtValue()))); 1515 if (F->getIntrinsicID() == Intrinsic::powi && Ty->isDoubleTy()) 1516 return ConstantFP::get(F->getContext(), 1517 APFloat((double)std::pow((double)Op1V, 1518 (int)Op2C->getZExtValue()))); 1519 } 1520 return 0; 1521 } 1522 1523 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) { 1524 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) { 1525 switch (F->getIntrinsicID()) { 1526 default: break; 1527 case Intrinsic::sadd_with_overflow: 1528 case Intrinsic::uadd_with_overflow: 1529 case Intrinsic::ssub_with_overflow: 1530 case Intrinsic::usub_with_overflow: 1531 case Intrinsic::smul_with_overflow: 1532 case Intrinsic::umul_with_overflow: { 1533 APInt Res; 1534 bool Overflow; 1535 switch (F->getIntrinsicID()) { 1536 default: llvm_unreachable("Invalid case"); 1537 case Intrinsic::sadd_with_overflow: 1538 Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow); 1539 break; 1540 case Intrinsic::uadd_with_overflow: 1541 Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow); 1542 break; 1543 case Intrinsic::ssub_with_overflow: 1544 Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow); 1545 break; 1546 case Intrinsic::usub_with_overflow: 1547 Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow); 1548 break; 1549 case Intrinsic::smul_with_overflow: 1550 Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow); 1551 break; 1552 case Intrinsic::umul_with_overflow: 1553 Res = Op1->getValue().umul_ov(Op2->getValue(), Overflow); 1554 break; 1555 } 1556 Constant *Ops[] = { 1557 ConstantInt::get(F->getContext(), Res), 1558 ConstantInt::get(Type::getInt1Ty(F->getContext()), Overflow) 1559 }; 1560 return ConstantStruct::get(cast<StructType>(F->getReturnType()), Ops); 1561 } 1562 case Intrinsic::cttz: 1563 if (Op2->isOne() && Op1->isZero()) // cttz(0, 1) is undef. 1564 return UndefValue::get(Ty); 1565 return ConstantInt::get(Ty, Op1->getValue().countTrailingZeros()); 1566 case Intrinsic::ctlz: 1567 if (Op2->isOne() && Op1->isZero()) // ctlz(0, 1) is undef. 1568 return UndefValue::get(Ty); 1569 return ConstantInt::get(Ty, Op1->getValue().countLeadingZeros()); 1570 } 1571 } 1572 1573 return 0; 1574 } 1575 return 0; 1576 } 1577 return 0; 1578 } 1579
