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/SmallPtrSet.h" 21 #include "llvm/ADT/SmallVector.h" 22 #include "llvm/ADT/StringMap.h" 23 #include "llvm/Analysis/ValueTracking.h" 24 #include "llvm/Config/config.h" 25 #include "llvm/IR/Constants.h" 26 #include "llvm/IR/DataLayout.h" 27 #include "llvm/IR/DerivedTypes.h" 28 #include "llvm/IR/Function.h" 29 #include "llvm/IR/GetElementPtrTypeIterator.h" 30 #include "llvm/IR/GlobalVariable.h" 31 #include "llvm/IR/Instructions.h" 32 #include "llvm/IR/Intrinsics.h" 33 #include "llvm/IR/Operator.h" 34 #include "llvm/Support/ErrorHandling.h" 35 #include "llvm/Support/MathExtras.h" 36 #include "llvm/Target/TargetLibraryInfo.h" 37 #include <cerrno> 38 #include <cmath> 39 40 #ifdef HAVE_FENV_H 41 #include <fenv.h> 42 #endif 43 44 using namespace llvm; 45 46 //===----------------------------------------------------------------------===// 47 // Constant Folding internal helper functions 48 //===----------------------------------------------------------------------===// 49 50 /// Constant fold bitcast, symbolically evaluating it with DataLayout. 51 /// This always returns a non-null constant, but it may be a 52 /// ConstantExpr if unfoldable. 53 static Constant *FoldBitCast(Constant *C, Type *DestTy, 54 const DataLayout &TD) { 55 // Catch the obvious splat cases. 56 if (C->isNullValue() && !DestTy->isX86_MMXTy()) 57 return Constant::getNullValue(DestTy); 58 if (C->isAllOnesValue() && !DestTy->isX86_MMXTy() && 59 !DestTy->isPtrOrPtrVectorTy()) // Don't get ones for ptr types! 60 return Constant::getAllOnesValue(DestTy); 61 62 // Handle a vector->integer cast. 63 if (IntegerType *IT = dyn_cast<IntegerType>(DestTy)) { 64 VectorType *VTy = dyn_cast<VectorType>(C->getType()); 65 if (!VTy) 66 return ConstantExpr::getBitCast(C, DestTy); 67 68 unsigned NumSrcElts = VTy->getNumElements(); 69 Type *SrcEltTy = VTy->getElementType(); 70 71 // If the vector is a vector of floating point, convert it to vector of int 72 // to simplify things. 73 if (SrcEltTy->isFloatingPointTy()) { 74 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); 75 Type *SrcIVTy = 76 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElts); 77 // Ask IR to do the conversion now that #elts line up. 78 C = ConstantExpr::getBitCast(C, SrcIVTy); 79 } 80 81 ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(C); 82 if (!CDV) 83 return ConstantExpr::getBitCast(C, DestTy); 84 85 // Now that we know that the input value is a vector of integers, just shift 86 // and insert them into our result. 87 unsigned BitShift = TD.getTypeAllocSizeInBits(SrcEltTy); 88 APInt Result(IT->getBitWidth(), 0); 89 for (unsigned i = 0; i != NumSrcElts; ++i) { 90 Result <<= BitShift; 91 if (TD.isLittleEndian()) 92 Result |= CDV->getElementAsInteger(NumSrcElts-i-1); 93 else 94 Result |= CDV->getElementAsInteger(i); 95 } 96 97 return ConstantInt::get(IT, Result); 98 } 99 100 // The code below only handles casts to vectors currently. 101 VectorType *DestVTy = dyn_cast<VectorType>(DestTy); 102 if (!DestVTy) 103 return ConstantExpr::getBitCast(C, DestTy); 104 105 // If this is a scalar -> vector cast, convert the input into a <1 x scalar> 106 // vector so the code below can handle it uniformly. 107 if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) { 108 Constant *Ops = C; // don't take the address of C! 109 return FoldBitCast(ConstantVector::get(Ops), DestTy, TD); 110 } 111 112 // If this is a bitcast from constant vector -> vector, fold it. 113 if (!isa<ConstantDataVector>(C) && !isa<ConstantVector>(C)) 114 return ConstantExpr::getBitCast(C, DestTy); 115 116 // If the element types match, IR can fold it. 117 unsigned NumDstElt = DestVTy->getNumElements(); 118 unsigned NumSrcElt = C->getType()->getVectorNumElements(); 119 if (NumDstElt == NumSrcElt) 120 return ConstantExpr::getBitCast(C, DestTy); 121 122 Type *SrcEltTy = C->getType()->getVectorElementType(); 123 Type *DstEltTy = DestVTy->getElementType(); 124 125 // Otherwise, we're changing the number of elements in a vector, which 126 // requires endianness information to do the right thing. For example, 127 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 128 // folds to (little endian): 129 // <4 x i32> <i32 0, i32 0, i32 1, i32 0> 130 // and to (big endian): 131 // <4 x i32> <i32 0, i32 0, i32 0, i32 1> 132 133 // First thing is first. We only want to think about integer here, so if 134 // we have something in FP form, recast it as integer. 135 if (DstEltTy->isFloatingPointTy()) { 136 // Fold to an vector of integers with same size as our FP type. 137 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits(); 138 Type *DestIVTy = 139 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt); 140 // Recursively handle this integer conversion, if possible. 141 C = FoldBitCast(C, DestIVTy, TD); 142 143 // Finally, IR can handle this now that #elts line up. 144 return ConstantExpr::getBitCast(C, DestTy); 145 } 146 147 // Okay, we know the destination is integer, if the input is FP, convert 148 // it to integer first. 149 if (SrcEltTy->isFloatingPointTy()) { 150 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); 151 Type *SrcIVTy = 152 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt); 153 // Ask IR to do the conversion now that #elts line up. 154 C = ConstantExpr::getBitCast(C, SrcIVTy); 155 // If IR wasn't able to fold it, bail out. 156 if (!isa<ConstantVector>(C) && // FIXME: Remove ConstantVector. 157 !isa<ConstantDataVector>(C)) 158 return C; 159 } 160 161 // Now we know that the input and output vectors are both integer vectors 162 // of the same size, and that their #elements is not the same. Do the 163 // conversion here, which depends on whether the input or output has 164 // more elements. 165 bool isLittleEndian = TD.isLittleEndian(); 166 167 SmallVector<Constant*, 32> Result; 168 if (NumDstElt < NumSrcElt) { 169 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>) 170 Constant *Zero = Constant::getNullValue(DstEltTy); 171 unsigned Ratio = NumSrcElt/NumDstElt; 172 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits(); 173 unsigned SrcElt = 0; 174 for (unsigned i = 0; i != NumDstElt; ++i) { 175 // Build each element of the result. 176 Constant *Elt = Zero; 177 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1); 178 for (unsigned j = 0; j != Ratio; ++j) { 179 Constant *Src =dyn_cast<ConstantInt>(C->getAggregateElement(SrcElt++)); 180 if (!Src) // Reject constantexpr elements. 181 return ConstantExpr::getBitCast(C, DestTy); 182 183 // Zero extend the element to the right size. 184 Src = ConstantExpr::getZExt(Src, Elt->getType()); 185 186 // Shift it to the right place, depending on endianness. 187 Src = ConstantExpr::getShl(Src, 188 ConstantInt::get(Src->getType(), ShiftAmt)); 189 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize; 190 191 // Mix it in. 192 Elt = ConstantExpr::getOr(Elt, Src); 193 } 194 Result.push_back(Elt); 195 } 196 return ConstantVector::get(Result); 197 } 198 199 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 200 unsigned Ratio = NumDstElt/NumSrcElt; 201 unsigned DstBitSize = TD.getTypeSizeInBits(DstEltTy); 202 203 // Loop over each source value, expanding into multiple results. 204 for (unsigned i = 0; i != NumSrcElt; ++i) { 205 Constant *Src = dyn_cast<ConstantInt>(C->getAggregateElement(i)); 206 if (!Src) // Reject constantexpr elements. 207 return ConstantExpr::getBitCast(C, DestTy); 208 209 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1); 210 for (unsigned j = 0; j != Ratio; ++j) { 211 // Shift the piece of the value into the right place, depending on 212 // endianness. 213 Constant *Elt = ConstantExpr::getLShr(Src, 214 ConstantInt::get(Src->getType(), ShiftAmt)); 215 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize; 216 217 // Truncate the element to an integer with the same pointer size and 218 // convert the element back to a pointer using a inttoptr. 219 if (DstEltTy->isPointerTy()) { 220 IntegerType *DstIntTy = Type::getIntNTy(C->getContext(), DstBitSize); 221 Constant *CE = ConstantExpr::getTrunc(Elt, DstIntTy); 222 Result.push_back(ConstantExpr::getIntToPtr(CE, DstEltTy)); 223 continue; 224 } 225 226 // Truncate and remember this piece. 227 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy)); 228 } 229 } 230 231 return ConstantVector::get(Result); 232 } 233 234 235 /// If this constant is a constant offset from a global, return the global and 236 /// the constant. Because of constantexprs, this function is recursive. 237 static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, 238 APInt &Offset, const DataLayout &TD) { 239 // Trivial case, constant is the global. 240 if ((GV = dyn_cast<GlobalValue>(C))) { 241 unsigned BitWidth = TD.getPointerTypeSizeInBits(GV->getType()); 242 Offset = APInt(BitWidth, 0); 243 return true; 244 } 245 246 // Otherwise, if this isn't a constant expr, bail out. 247 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 248 if (!CE) return false; 249 250 // Look through ptr->int and ptr->ptr casts. 251 if (CE->getOpcode() == Instruction::PtrToInt || 252 CE->getOpcode() == Instruction::BitCast || 253 CE->getOpcode() == Instruction::AddrSpaceCast) 254 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD); 255 256 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5) 257 GEPOperator *GEP = dyn_cast<GEPOperator>(CE); 258 if (!GEP) 259 return false; 260 261 unsigned BitWidth = TD.getPointerTypeSizeInBits(GEP->getType()); 262 APInt TmpOffset(BitWidth, 0); 263 264 // If the base isn't a global+constant, we aren't either. 265 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, TmpOffset, TD)) 266 return false; 267 268 // Otherwise, add any offset that our operands provide. 269 if (!GEP->accumulateConstantOffset(TD, TmpOffset)) 270 return false; 271 272 Offset = TmpOffset; 273 return true; 274 } 275 276 /// Recursive helper to read bits out of global. C is the constant being copied 277 /// out of. ByteOffset is an offset into C. CurPtr is the pointer to copy 278 /// results into and BytesLeft is the number of bytes left in 279 /// the CurPtr buffer. TD is the target data. 280 static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset, 281 unsigned char *CurPtr, unsigned BytesLeft, 282 const DataLayout &TD) { 283 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) && 284 "Out of range access"); 285 286 // If this element is zero or undefined, we can just return since *CurPtr is 287 // zero initialized. 288 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C)) 289 return true; 290 291 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 292 if (CI->getBitWidth() > 64 || 293 (CI->getBitWidth() & 7) != 0) 294 return false; 295 296 uint64_t Val = CI->getZExtValue(); 297 unsigned IntBytes = unsigned(CI->getBitWidth()/8); 298 299 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) { 300 int n = ByteOffset; 301 if (!TD.isLittleEndian()) 302 n = IntBytes - n - 1; 303 CurPtr[i] = (unsigned char)(Val >> (n * 8)); 304 ++ByteOffset; 305 } 306 return true; 307 } 308 309 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) { 310 if (CFP->getType()->isDoubleTy()) { 311 C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD); 312 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 313 } 314 if (CFP->getType()->isFloatTy()){ 315 C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD); 316 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 317 } 318 if (CFP->getType()->isHalfTy()){ 319 C = FoldBitCast(C, Type::getInt16Ty(C->getContext()), TD); 320 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 321 } 322 return false; 323 } 324 325 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 326 const StructLayout *SL = TD.getStructLayout(CS->getType()); 327 unsigned Index = SL->getElementContainingOffset(ByteOffset); 328 uint64_t CurEltOffset = SL->getElementOffset(Index); 329 ByteOffset -= CurEltOffset; 330 331 while (1) { 332 // If the element access is to the element itself and not to tail padding, 333 // read the bytes from the element. 334 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType()); 335 336 if (ByteOffset < EltSize && 337 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr, 338 BytesLeft, TD)) 339 return false; 340 341 ++Index; 342 343 // Check to see if we read from the last struct element, if so we're done. 344 if (Index == CS->getType()->getNumElements()) 345 return true; 346 347 // If we read all of the bytes we needed from this element we're done. 348 uint64_t NextEltOffset = SL->getElementOffset(Index); 349 350 if (BytesLeft <= NextEltOffset - CurEltOffset - ByteOffset) 351 return true; 352 353 // Move to the next element of the struct. 354 CurPtr += NextEltOffset - CurEltOffset - ByteOffset; 355 BytesLeft -= NextEltOffset - CurEltOffset - ByteOffset; 356 ByteOffset = 0; 357 CurEltOffset = NextEltOffset; 358 } 359 // not reached. 360 } 361 362 if (isa<ConstantArray>(C) || isa<ConstantVector>(C) || 363 isa<ConstantDataSequential>(C)) { 364 Type *EltTy = C->getType()->getSequentialElementType(); 365 uint64_t EltSize = TD.getTypeAllocSize(EltTy); 366 uint64_t Index = ByteOffset / EltSize; 367 uint64_t Offset = ByteOffset - Index * EltSize; 368 uint64_t NumElts; 369 if (ArrayType *AT = dyn_cast<ArrayType>(C->getType())) 370 NumElts = AT->getNumElements(); 371 else 372 NumElts = C->getType()->getVectorNumElements(); 373 374 for (; Index != NumElts; ++Index) { 375 if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr, 376 BytesLeft, TD)) 377 return false; 378 379 uint64_t BytesWritten = EltSize - Offset; 380 assert(BytesWritten <= EltSize && "Not indexing into this element?"); 381 if (BytesWritten >= BytesLeft) 382 return true; 383 384 Offset = 0; 385 BytesLeft -= BytesWritten; 386 CurPtr += BytesWritten; 387 } 388 return true; 389 } 390 391 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 392 if (CE->getOpcode() == Instruction::IntToPtr && 393 CE->getOperand(0)->getType() == TD.getIntPtrType(CE->getType())) { 394 return ReadDataFromGlobal(CE->getOperand(0), ByteOffset, CurPtr, 395 BytesLeft, TD); 396 } 397 } 398 399 // Otherwise, unknown initializer type. 400 return false; 401 } 402 403 static Constant *FoldReinterpretLoadFromConstPtr(Constant *C, 404 const DataLayout &TD) { 405 PointerType *PTy = cast<PointerType>(C->getType()); 406 Type *LoadTy = PTy->getElementType(); 407 IntegerType *IntType = dyn_cast<IntegerType>(LoadTy); 408 409 // If this isn't an integer load we can't fold it directly. 410 if (!IntType) { 411 unsigned AS = PTy->getAddressSpace(); 412 413 // If this is a float/double load, we can try folding it as an int32/64 load 414 // and then bitcast the result. This can be useful for union cases. Note 415 // that address spaces don't matter here since we're not going to result in 416 // an actual new load. 417 Type *MapTy; 418 if (LoadTy->isHalfTy()) 419 MapTy = Type::getInt16PtrTy(C->getContext(), AS); 420 else if (LoadTy->isFloatTy()) 421 MapTy = Type::getInt32PtrTy(C->getContext(), AS); 422 else if (LoadTy->isDoubleTy()) 423 MapTy = Type::getInt64PtrTy(C->getContext(), AS); 424 else if (LoadTy->isVectorTy()) { 425 MapTy = PointerType::getIntNPtrTy(C->getContext(), 426 TD.getTypeAllocSizeInBits(LoadTy), 427 AS); 428 } else 429 return nullptr; 430 431 C = FoldBitCast(C, MapTy, TD); 432 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD)) 433 return FoldBitCast(Res, LoadTy, TD); 434 return nullptr; 435 } 436 437 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8; 438 if (BytesLoaded > 32 || BytesLoaded == 0) 439 return nullptr; 440 441 GlobalValue *GVal; 442 APInt Offset; 443 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD)) 444 return nullptr; 445 446 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal); 447 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() || 448 !GV->getInitializer()->getType()->isSized()) 449 return nullptr; 450 451 // If we're loading off the beginning of the global, some bytes may be valid, 452 // but we don't try to handle this. 453 if (Offset.isNegative()) 454 return nullptr; 455 456 // If we're not accessing anything in this constant, the result is undefined. 457 if (Offset.getZExtValue() >= 458 TD.getTypeAllocSize(GV->getInitializer()->getType())) 459 return UndefValue::get(IntType); 460 461 unsigned char RawBytes[32] = {0}; 462 if (!ReadDataFromGlobal(GV->getInitializer(), Offset.getZExtValue(), RawBytes, 463 BytesLoaded, TD)) 464 return nullptr; 465 466 APInt ResultVal = APInt(IntType->getBitWidth(), 0); 467 if (TD.isLittleEndian()) { 468 ResultVal = RawBytes[BytesLoaded - 1]; 469 for (unsigned i = 1; i != BytesLoaded; ++i) { 470 ResultVal <<= 8; 471 ResultVal |= RawBytes[BytesLoaded - 1 - i]; 472 } 473 } else { 474 ResultVal = RawBytes[0]; 475 for (unsigned i = 1; i != BytesLoaded; ++i) { 476 ResultVal <<= 8; 477 ResultVal |= RawBytes[i]; 478 } 479 } 480 481 return ConstantInt::get(IntType->getContext(), ResultVal); 482 } 483 484 static Constant *ConstantFoldLoadThroughBitcast(ConstantExpr *CE, 485 const DataLayout *DL) { 486 if (!DL) 487 return nullptr; 488 auto *DestPtrTy = dyn_cast<PointerType>(CE->getType()); 489 if (!DestPtrTy) 490 return nullptr; 491 Type *DestTy = DestPtrTy->getElementType(); 492 493 Constant *C = ConstantFoldLoadFromConstPtr(CE->getOperand(0), DL); 494 if (!C) 495 return nullptr; 496 497 do { 498 Type *SrcTy = C->getType(); 499 500 // If the type sizes are the same and a cast is legal, just directly 501 // cast the constant. 502 if (DL->getTypeSizeInBits(DestTy) == DL->getTypeSizeInBits(SrcTy)) { 503 Instruction::CastOps Cast = Instruction::BitCast; 504 // If we are going from a pointer to int or vice versa, we spell the cast 505 // differently. 506 if (SrcTy->isIntegerTy() && DestTy->isPointerTy()) 507 Cast = Instruction::IntToPtr; 508 else if (SrcTy->isPointerTy() && DestTy->isIntegerTy()) 509 Cast = Instruction::PtrToInt; 510 511 if (CastInst::castIsValid(Cast, C, DestTy)) 512 return ConstantExpr::getCast(Cast, C, DestTy); 513 } 514 515 // If this isn't an aggregate type, there is nothing we can do to drill down 516 // and find a bitcastable constant. 517 if (!SrcTy->isAggregateType()) 518 return nullptr; 519 520 // We're simulating a load through a pointer that was bitcast to point to 521 // a different type, so we can try to walk down through the initial 522 // elements of an aggregate to see if some part of th e aggregate is 523 // castable to implement the "load" semantic model. 524 C = C->getAggregateElement(0u); 525 } while (C); 526 527 return nullptr; 528 } 529 530 /// Return the value that a load from C would produce if it is constant and 531 /// determinable. If this is not determinable, return null. 532 Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, 533 const DataLayout *TD) { 534 // First, try the easy cases: 535 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 536 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 537 return GV->getInitializer(); 538 539 // If the loaded value isn't a constant expr, we can't handle it. 540 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 541 if (!CE) 542 return nullptr; 543 544 if (CE->getOpcode() == Instruction::GetElementPtr) { 545 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) { 546 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 547 if (Constant *V = 548 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) 549 return V; 550 } 551 } 552 } 553 554 if (CE->getOpcode() == Instruction::BitCast) 555 if (Constant *LoadedC = ConstantFoldLoadThroughBitcast(CE, TD)) 556 return LoadedC; 557 558 // Instead of loading constant c string, use corresponding integer value 559 // directly if string length is small enough. 560 StringRef Str; 561 if (TD && getConstantStringInfo(CE, Str) && !Str.empty()) { 562 unsigned StrLen = Str.size(); 563 Type *Ty = cast<PointerType>(CE->getType())->getElementType(); 564 unsigned NumBits = Ty->getPrimitiveSizeInBits(); 565 // Replace load with immediate integer if the result is an integer or fp 566 // value. 567 if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 && 568 (isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) { 569 APInt StrVal(NumBits, 0); 570 APInt SingleChar(NumBits, 0); 571 if (TD->isLittleEndian()) { 572 for (signed i = StrLen-1; i >= 0; i--) { 573 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 574 StrVal = (StrVal << 8) | SingleChar; 575 } 576 } else { 577 for (unsigned i = 0; i < StrLen; i++) { 578 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 579 StrVal = (StrVal << 8) | SingleChar; 580 } 581 // Append NULL at the end. 582 SingleChar = 0; 583 StrVal = (StrVal << 8) | SingleChar; 584 } 585 586 Constant *Res = ConstantInt::get(CE->getContext(), StrVal); 587 if (Ty->isFloatingPointTy()) 588 Res = ConstantExpr::getBitCast(Res, Ty); 589 return Res; 590 } 591 } 592 593 // If this load comes from anywhere in a constant global, and if the global 594 // is all undef or zero, we know what it loads. 595 if (GlobalVariable *GV = 596 dyn_cast<GlobalVariable>(GetUnderlyingObject(CE, TD))) { 597 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 598 Type *ResTy = cast<PointerType>(C->getType())->getElementType(); 599 if (GV->getInitializer()->isNullValue()) 600 return Constant::getNullValue(ResTy); 601 if (isa<UndefValue>(GV->getInitializer())) 602 return UndefValue::get(ResTy); 603 } 604 } 605 606 // Try hard to fold loads from bitcasted strange and non-type-safe things. 607 if (TD) 608 return FoldReinterpretLoadFromConstPtr(CE, *TD); 609 return nullptr; 610 } 611 612 static Constant *ConstantFoldLoadInst(const LoadInst *LI, const DataLayout *TD){ 613 if (LI->isVolatile()) return nullptr; 614 615 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0))) 616 return ConstantFoldLoadFromConstPtr(C, TD); 617 618 return nullptr; 619 } 620 621 /// One of Op0/Op1 is a constant expression. 622 /// Attempt to symbolically evaluate the result of a binary operator merging 623 /// these together. If target data info is available, it is provided as DL, 624 /// otherwise DL is null. 625 static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, 626 Constant *Op1, const DataLayout *DL){ 627 // SROA 628 629 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl. 630 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute 631 // bits. 632 633 634 if (Opc == Instruction::And && DL) { 635 unsigned BitWidth = DL->getTypeSizeInBits(Op0->getType()->getScalarType()); 636 APInt KnownZero0(BitWidth, 0), KnownOne0(BitWidth, 0); 637 APInt KnownZero1(BitWidth, 0), KnownOne1(BitWidth, 0); 638 computeKnownBits(Op0, KnownZero0, KnownOne0, DL); 639 computeKnownBits(Op1, KnownZero1, KnownOne1, DL); 640 if ((KnownOne1 | KnownZero0).isAllOnesValue()) { 641 // All the bits of Op0 that the 'and' could be masking are already zero. 642 return Op0; 643 } 644 if ((KnownOne0 | KnownZero1).isAllOnesValue()) { 645 // All the bits of Op1 that the 'and' could be masking are already zero. 646 return Op1; 647 } 648 649 APInt KnownZero = KnownZero0 | KnownZero1; 650 APInt KnownOne = KnownOne0 & KnownOne1; 651 if ((KnownZero | KnownOne).isAllOnesValue()) { 652 return ConstantInt::get(Op0->getType(), KnownOne); 653 } 654 } 655 656 // If the constant expr is something like &A[123] - &A[4].f, fold this into a 657 // constant. This happens frequently when iterating over a global array. 658 if (Opc == Instruction::Sub && DL) { 659 GlobalValue *GV1, *GV2; 660 APInt Offs1, Offs2; 661 662 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *DL)) 663 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *DL) && 664 GV1 == GV2) { 665 unsigned OpSize = DL->getTypeSizeInBits(Op0->getType()); 666 667 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow. 668 // PtrToInt may change the bitwidth so we have convert to the right size 669 // first. 670 return ConstantInt::get(Op0->getType(), Offs1.zextOrTrunc(OpSize) - 671 Offs2.zextOrTrunc(OpSize)); 672 } 673 } 674 675 return nullptr; 676 } 677 678 /// If array indices are not pointer-sized integers, explicitly cast them so 679 /// that they aren't implicitly casted by the getelementptr. 680 static Constant *CastGEPIndices(ArrayRef<Constant *> Ops, 681 Type *ResultTy, const DataLayout *TD, 682 const TargetLibraryInfo *TLI) { 683 if (!TD) 684 return nullptr; 685 686 Type *IntPtrTy = TD->getIntPtrType(ResultTy); 687 688 bool Any = false; 689 SmallVector<Constant*, 32> NewIdxs; 690 for (unsigned i = 1, e = Ops.size(); i != e; ++i) { 691 if ((i == 1 || 692 !isa<StructType>(GetElementPtrInst::getIndexedType( 693 Ops[0]->getType(), 694 Ops.slice(1, i - 1)))) && 695 Ops[i]->getType() != IntPtrTy) { 696 Any = true; 697 NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i], 698 true, 699 IntPtrTy, 700 true), 701 Ops[i], IntPtrTy)); 702 } else 703 NewIdxs.push_back(Ops[i]); 704 } 705 706 if (!Any) 707 return nullptr; 708 709 Constant *C = ConstantExpr::getGetElementPtr(Ops[0], NewIdxs); 710 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 711 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI)) 712 C = Folded; 713 } 714 715 return C; 716 } 717 718 /// Strip the pointer casts, but preserve the address space information. 719 static Constant* StripPtrCastKeepAS(Constant* Ptr) { 720 assert(Ptr->getType()->isPointerTy() && "Not a pointer type"); 721 PointerType *OldPtrTy = cast<PointerType>(Ptr->getType()); 722 Ptr = Ptr->stripPointerCasts(); 723 PointerType *NewPtrTy = cast<PointerType>(Ptr->getType()); 724 725 // Preserve the address space number of the pointer. 726 if (NewPtrTy->getAddressSpace() != OldPtrTy->getAddressSpace()) { 727 NewPtrTy = NewPtrTy->getElementType()->getPointerTo( 728 OldPtrTy->getAddressSpace()); 729 Ptr = ConstantExpr::getPointerCast(Ptr, NewPtrTy); 730 } 731 return Ptr; 732 } 733 734 /// If we can symbolically evaluate the GEP constant expression, do so. 735 static Constant *SymbolicallyEvaluateGEP(ArrayRef<Constant *> Ops, 736 Type *ResultTy, const DataLayout *TD, 737 const TargetLibraryInfo *TLI) { 738 Constant *Ptr = Ops[0]; 739 if (!TD || !Ptr->getType()->getPointerElementType()->isSized() || 740 !Ptr->getType()->isPointerTy()) 741 return nullptr; 742 743 Type *IntPtrTy = TD->getIntPtrType(Ptr->getType()); 744 Type *ResultElementTy = ResultTy->getPointerElementType(); 745 746 // If this is a constant expr gep that is effectively computing an 747 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' 748 for (unsigned i = 1, e = Ops.size(); i != e; ++i) 749 if (!isa<ConstantInt>(Ops[i])) { 750 751 // If this is "gep i8* Ptr, (sub 0, V)", fold this as: 752 // "inttoptr (sub (ptrtoint Ptr), V)" 753 if (Ops.size() == 2 && ResultElementTy->isIntegerTy(8)) { 754 ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[1]); 755 assert((!CE || CE->getType() == IntPtrTy) && 756 "CastGEPIndices didn't canonicalize index types!"); 757 if (CE && CE->getOpcode() == Instruction::Sub && 758 CE->getOperand(0)->isNullValue()) { 759 Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType()); 760 Res = ConstantExpr::getSub(Res, CE->getOperand(1)); 761 Res = ConstantExpr::getIntToPtr(Res, ResultTy); 762 if (ConstantExpr *ResCE = dyn_cast<ConstantExpr>(Res)) 763 Res = ConstantFoldConstantExpression(ResCE, TD, TLI); 764 return Res; 765 } 766 } 767 return nullptr; 768 } 769 770 unsigned BitWidth = TD->getTypeSizeInBits(IntPtrTy); 771 APInt Offset = 772 APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(), 773 makeArrayRef((Value *const*) 774 Ops.data() + 1, 775 Ops.size() - 1))); 776 Ptr = StripPtrCastKeepAS(Ptr); 777 778 // If this is a GEP of a GEP, fold it all into a single GEP. 779 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) { 780 SmallVector<Value *, 4> NestedOps(GEP->op_begin() + 1, GEP->op_end()); 781 782 // Do not try the incorporate the sub-GEP if some index is not a number. 783 bool AllConstantInt = true; 784 for (unsigned i = 0, e = NestedOps.size(); i != e; ++i) 785 if (!isa<ConstantInt>(NestedOps[i])) { 786 AllConstantInt = false; 787 break; 788 } 789 if (!AllConstantInt) 790 break; 791 792 Ptr = cast<Constant>(GEP->getOperand(0)); 793 Offset += APInt(BitWidth, 794 TD->getIndexedOffset(Ptr->getType(), NestedOps)); 795 Ptr = StripPtrCastKeepAS(Ptr); 796 } 797 798 // If the base value for this address is a literal integer value, fold the 799 // getelementptr to the resulting integer value casted to the pointer type. 800 APInt BasePtr(BitWidth, 0); 801 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) { 802 if (CE->getOpcode() == Instruction::IntToPtr) { 803 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) 804 BasePtr = Base->getValue().zextOrTrunc(BitWidth); 805 } 806 } 807 808 if (Ptr->isNullValue() || BasePtr != 0) { 809 Constant *C = ConstantInt::get(Ptr->getContext(), Offset + BasePtr); 810 return ConstantExpr::getIntToPtr(C, ResultTy); 811 } 812 813 // Otherwise form a regular getelementptr. Recompute the indices so that 814 // we eliminate over-indexing of the notional static type array bounds. 815 // This makes it easy to determine if the getelementptr is "inbounds". 816 // Also, this helps GlobalOpt do SROA on GlobalVariables. 817 Type *Ty = Ptr->getType(); 818 assert(Ty->isPointerTy() && "Forming regular GEP of non-pointer type"); 819 SmallVector<Constant *, 32> NewIdxs; 820 821 do { 822 if (SequentialType *ATy = dyn_cast<SequentialType>(Ty)) { 823 if (ATy->isPointerTy()) { 824 // The only pointer indexing we'll do is on the first index of the GEP. 825 if (!NewIdxs.empty()) 826 break; 827 828 // Only handle pointers to sized types, not pointers to functions. 829 if (!ATy->getElementType()->isSized()) 830 return nullptr; 831 } 832 833 // Determine which element of the array the offset points into. 834 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); 835 if (ElemSize == 0) 836 // The element size is 0. This may be [0 x Ty]*, so just use a zero 837 // index for this level and proceed to the next level to see if it can 838 // accommodate the offset. 839 NewIdxs.push_back(ConstantInt::get(IntPtrTy, 0)); 840 else { 841 // The element size is non-zero divide the offset by the element 842 // size (rounding down), to compute the index at this level. 843 APInt NewIdx = Offset.udiv(ElemSize); 844 Offset -= NewIdx * ElemSize; 845 NewIdxs.push_back(ConstantInt::get(IntPtrTy, NewIdx)); 846 } 847 Ty = ATy->getElementType(); 848 } else if (StructType *STy = dyn_cast<StructType>(Ty)) { 849 // If we end up with an offset that isn't valid for this struct type, we 850 // can't re-form this GEP in a regular form, so bail out. The pointer 851 // operand likely went through casts that are necessary to make the GEP 852 // sensible. 853 const StructLayout &SL = *TD->getStructLayout(STy); 854 if (Offset.uge(SL.getSizeInBytes())) 855 break; 856 857 // Determine which field of the struct the offset points into. The 858 // getZExtValue is fine as we've already ensured that the offset is 859 // within the range representable by the StructLayout API. 860 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); 861 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 862 ElIdx)); 863 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); 864 Ty = STy->getTypeAtIndex(ElIdx); 865 } else { 866 // We've reached some non-indexable type. 867 break; 868 } 869 } while (Ty != ResultElementTy); 870 871 // If we haven't used up the entire offset by descending the static 872 // type, then the offset is pointing into the middle of an indivisible 873 // member, so we can't simplify it. 874 if (Offset != 0) 875 return nullptr; 876 877 // Create a GEP. 878 Constant *C = ConstantExpr::getGetElementPtr(Ptr, NewIdxs); 879 assert(C->getType()->getPointerElementType() == Ty && 880 "Computed GetElementPtr has unexpected type!"); 881 882 // If we ended up indexing a member with a type that doesn't match 883 // the type of what the original indices indexed, add a cast. 884 if (Ty != ResultElementTy) 885 C = FoldBitCast(C, ResultTy, *TD); 886 887 return C; 888 } 889 890 891 892 //===----------------------------------------------------------------------===// 893 // Constant Folding public APIs 894 //===----------------------------------------------------------------------===// 895 896 /// Try to constant fold the specified instruction. 897 /// If successful, the constant result is returned, if not, null is returned. 898 /// Note that this fails if not all of the operands are constant. Otherwise, 899 /// this function can only fail when attempting to fold instructions like loads 900 /// and stores, which have no constant expression form. 901 Constant *llvm::ConstantFoldInstruction(Instruction *I, 902 const DataLayout *TD, 903 const TargetLibraryInfo *TLI) { 904 // Handle PHI nodes quickly here... 905 if (PHINode *PN = dyn_cast<PHINode>(I)) { 906 Constant *CommonValue = nullptr; 907 908 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 909 Value *Incoming = PN->getIncomingValue(i); 910 // If the incoming value is undef then skip it. Note that while we could 911 // skip the value if it is equal to the phi node itself we choose not to 912 // because that would break the rule that constant folding only applies if 913 // all operands are constants. 914 if (isa<UndefValue>(Incoming)) 915 continue; 916 // If the incoming value is not a constant, then give up. 917 Constant *C = dyn_cast<Constant>(Incoming); 918 if (!C) 919 return nullptr; 920 // Fold the PHI's operands. 921 if (ConstantExpr *NewC = dyn_cast<ConstantExpr>(C)) 922 C = ConstantFoldConstantExpression(NewC, TD, TLI); 923 // If the incoming value is a different constant to 924 // the one we saw previously, then give up. 925 if (CommonValue && C != CommonValue) 926 return nullptr; 927 CommonValue = C; 928 } 929 930 931 // If we reach here, all incoming values are the same constant or undef. 932 return CommonValue ? CommonValue : UndefValue::get(PN->getType()); 933 } 934 935 // Scan the operand list, checking to see if they are all constants, if so, 936 // hand off to ConstantFoldInstOperands. 937 SmallVector<Constant*, 8> Ops; 938 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) { 939 Constant *Op = dyn_cast<Constant>(*i); 940 if (!Op) 941 return nullptr; // All operands not constant! 942 943 // Fold the Instruction's operands. 944 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(Op)) 945 Op = ConstantFoldConstantExpression(NewCE, TD, TLI); 946 947 Ops.push_back(Op); 948 } 949 950 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 951 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], 952 TD, TLI); 953 954 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 955 return ConstantFoldLoadInst(LI, TD); 956 957 if (InsertValueInst *IVI = dyn_cast<InsertValueInst>(I)) { 958 return ConstantExpr::getInsertValue( 959 cast<Constant>(IVI->getAggregateOperand()), 960 cast<Constant>(IVI->getInsertedValueOperand()), 961 IVI->getIndices()); 962 } 963 964 if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I)) { 965 return ConstantExpr::getExtractValue( 966 cast<Constant>(EVI->getAggregateOperand()), 967 EVI->getIndices()); 968 } 969 970 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops, TD, TLI); 971 } 972 973 static Constant * 974 ConstantFoldConstantExpressionImpl(const ConstantExpr *CE, const DataLayout *TD, 975 const TargetLibraryInfo *TLI, 976 SmallPtrSetImpl<ConstantExpr *> &FoldedOps) { 977 SmallVector<Constant *, 8> Ops; 978 for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; 979 ++i) { 980 Constant *NewC = cast<Constant>(*i); 981 // Recursively fold the ConstantExpr's operands. If we have already folded 982 // a ConstantExpr, we don't have to process it again. 983 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC)) { 984 if (FoldedOps.insert(NewCE).second) 985 NewC = ConstantFoldConstantExpressionImpl(NewCE, TD, TLI, FoldedOps); 986 } 987 Ops.push_back(NewC); 988 } 989 990 if (CE->isCompare()) 991 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1], 992 TD, TLI); 993 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), Ops, TD, TLI); 994 } 995 996 /// Attempt to fold the constant expression 997 /// using the specified DataLayout. If successful, the constant result is 998 /// result is returned, if not, null is returned. 999 Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE, 1000 const DataLayout *TD, 1001 const TargetLibraryInfo *TLI) { 1002 SmallPtrSet<ConstantExpr *, 4> FoldedOps; 1003 return ConstantFoldConstantExpressionImpl(CE, TD, TLI, FoldedOps); 1004 } 1005 1006 /// Attempt to constant fold an instruction with the 1007 /// specified opcode and operands. If successful, the constant result is 1008 /// returned, if not, null is returned. Note that this function can fail when 1009 /// attempting to fold instructions like loads and stores, which have no 1010 /// constant expression form. 1011 /// 1012 /// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc 1013 /// information, due to only being passed an opcode and operands. Constant 1014 /// folding using this function strips this information. 1015 /// 1016 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, 1017 ArrayRef<Constant *> Ops, 1018 const DataLayout *TD, 1019 const TargetLibraryInfo *TLI) { 1020 // Handle easy binops first. 1021 if (Instruction::isBinaryOp(Opcode)) { 1022 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) { 1023 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD)) 1024 return C; 1025 } 1026 1027 return ConstantExpr::get(Opcode, Ops[0], Ops[1]); 1028 } 1029 1030 switch (Opcode) { 1031 default: return nullptr; 1032 case Instruction::ICmp: 1033 case Instruction::FCmp: llvm_unreachable("Invalid for compares"); 1034 case Instruction::Call: 1035 if (Function *F = dyn_cast<Function>(Ops.back())) 1036 if (canConstantFoldCallTo(F)) 1037 return ConstantFoldCall(F, Ops.slice(0, Ops.size() - 1), TLI); 1038 return nullptr; 1039 case Instruction::PtrToInt: 1040 // If the input is a inttoptr, eliminate the pair. This requires knowing 1041 // the width of a pointer, so it can't be done in ConstantExpr::getCast. 1042 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 1043 if (TD && CE->getOpcode() == Instruction::IntToPtr) { 1044 Constant *Input = CE->getOperand(0); 1045 unsigned InWidth = Input->getType()->getScalarSizeInBits(); 1046 unsigned PtrWidth = TD->getPointerTypeSizeInBits(CE->getType()); 1047 if (PtrWidth < InWidth) { 1048 Constant *Mask = 1049 ConstantInt::get(CE->getContext(), 1050 APInt::getLowBitsSet(InWidth, PtrWidth)); 1051 Input = ConstantExpr::getAnd(Input, Mask); 1052 } 1053 // Do a zext or trunc to get to the dest size. 1054 return ConstantExpr::getIntegerCast(Input, DestTy, false); 1055 } 1056 } 1057 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 1058 case Instruction::IntToPtr: 1059 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if 1060 // the int size is >= the ptr size and the address spaces are the same. 1061 // This requires knowing the width of a pointer, so it can't be done in 1062 // ConstantExpr::getCast. 1063 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 1064 if (TD && CE->getOpcode() == Instruction::PtrToInt) { 1065 Constant *SrcPtr = CE->getOperand(0); 1066 unsigned SrcPtrSize = TD->getPointerTypeSizeInBits(SrcPtr->getType()); 1067 unsigned MidIntSize = CE->getType()->getScalarSizeInBits(); 1068 1069 if (MidIntSize >= SrcPtrSize) { 1070 unsigned SrcAS = SrcPtr->getType()->getPointerAddressSpace(); 1071 if (SrcAS == DestTy->getPointerAddressSpace()) 1072 return FoldBitCast(CE->getOperand(0), DestTy, *TD); 1073 } 1074 } 1075 } 1076 1077 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 1078 case Instruction::Trunc: 1079 case Instruction::ZExt: 1080 case Instruction::SExt: 1081 case Instruction::FPTrunc: 1082 case Instruction::FPExt: 1083 case Instruction::UIToFP: 1084 case Instruction::SIToFP: 1085 case Instruction::FPToUI: 1086 case Instruction::FPToSI: 1087 case Instruction::AddrSpaceCast: 1088 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 1089 case Instruction::BitCast: 1090 if (TD) 1091 return FoldBitCast(Ops[0], DestTy, *TD); 1092 return ConstantExpr::getBitCast(Ops[0], DestTy); 1093 case Instruction::Select: 1094 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); 1095 case Instruction::ExtractElement: 1096 return ConstantExpr::getExtractElement(Ops[0], Ops[1]); 1097 case Instruction::InsertElement: 1098 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); 1099 case Instruction::ShuffleVector: 1100 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); 1101 case Instruction::GetElementPtr: 1102 if (Constant *C = CastGEPIndices(Ops, DestTy, TD, TLI)) 1103 return C; 1104 if (Constant *C = SymbolicallyEvaluateGEP(Ops, DestTy, TD, TLI)) 1105 return C; 1106 1107 return ConstantExpr::getGetElementPtr(Ops[0], Ops.slice(1)); 1108 } 1109 } 1110 1111 /// Attempt to constant fold a compare 1112 /// instruction (icmp/fcmp) with the specified operands. If it fails, it 1113 /// returns a constant expression of the specified operands. 1114 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, 1115 Constant *Ops0, Constant *Ops1, 1116 const DataLayout *TD, 1117 const TargetLibraryInfo *TLI) { 1118 // fold: icmp (inttoptr x), null -> icmp x, 0 1119 // fold: icmp (ptrtoint x), 0 -> icmp x, null 1120 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y 1121 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y 1122 // 1123 // ConstantExpr::getCompare cannot do this, because it doesn't have TD 1124 // around to know if bit truncation is happening. 1125 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) { 1126 if (TD && Ops1->isNullValue()) { 1127 if (CE0->getOpcode() == Instruction::IntToPtr) { 1128 Type *IntPtrTy = TD->getIntPtrType(CE0->getType()); 1129 // Convert the integer value to the right size to ensure we get the 1130 // proper extension or truncation. 1131 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), 1132 IntPtrTy, false); 1133 Constant *Null = Constant::getNullValue(C->getType()); 1134 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); 1135 } 1136 1137 // Only do this transformation if the int is intptrty in size, otherwise 1138 // there is a truncation or extension that we aren't modeling. 1139 if (CE0->getOpcode() == Instruction::PtrToInt) { 1140 Type *IntPtrTy = TD->getIntPtrType(CE0->getOperand(0)->getType()); 1141 if (CE0->getType() == IntPtrTy) { 1142 Constant *C = CE0->getOperand(0); 1143 Constant *Null = Constant::getNullValue(C->getType()); 1144 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); 1145 } 1146 } 1147 } 1148 1149 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) { 1150 if (TD && CE0->getOpcode() == CE1->getOpcode()) { 1151 if (CE0->getOpcode() == Instruction::IntToPtr) { 1152 Type *IntPtrTy = TD->getIntPtrType(CE0->getType()); 1153 1154 // Convert the integer value to the right size to ensure we get the 1155 // proper extension or truncation. 1156 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), 1157 IntPtrTy, false); 1158 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), 1159 IntPtrTy, false); 1160 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD, TLI); 1161 } 1162 1163 // Only do this transformation if the int is intptrty in size, otherwise 1164 // there is a truncation or extension that we aren't modeling. 1165 if (CE0->getOpcode() == Instruction::PtrToInt) { 1166 Type *IntPtrTy = TD->getIntPtrType(CE0->getOperand(0)->getType()); 1167 if (CE0->getType() == IntPtrTy && 1168 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()) { 1169 return ConstantFoldCompareInstOperands(Predicate, 1170 CE0->getOperand(0), 1171 CE1->getOperand(0), 1172 TD, 1173 TLI); 1174 } 1175 } 1176 } 1177 } 1178 1179 // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0) 1180 // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0) 1181 if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) && 1182 CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) { 1183 Constant *LHS = 1184 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1, 1185 TD, TLI); 1186 Constant *RHS = 1187 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1, 1188 TD, TLI); 1189 unsigned OpC = 1190 Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or; 1191 Constant *Ops[] = { LHS, RHS }; 1192 return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, TD, TLI); 1193 } 1194 } 1195 1196 return ConstantExpr::getCompare(Predicate, Ops0, Ops1); 1197 } 1198 1199 1200 /// Given a constant and a getelementptr constantexpr, return the constant value 1201 /// being addressed by the constant expression, or null if something is funny 1202 /// and we can't decide. 1203 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, 1204 ConstantExpr *CE) { 1205 if (!CE->getOperand(1)->isNullValue()) 1206 return nullptr; // Do not allow stepping over the value! 1207 1208 // Loop over all of the operands, tracking down which value we are 1209 // addressing. 1210 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i) { 1211 C = C->getAggregateElement(CE->getOperand(i)); 1212 if (!C) 1213 return nullptr; 1214 } 1215 return C; 1216 } 1217 1218 /// Given a constant and getelementptr indices (with an *implied* zero pointer 1219 /// index that is not in the list), return the constant value being addressed by 1220 /// a virtual load, or null if something is funny and we can't decide. 1221 Constant *llvm::ConstantFoldLoadThroughGEPIndices(Constant *C, 1222 ArrayRef<Constant*> Indices) { 1223 // Loop over all of the operands, tracking down which value we are 1224 // addressing. 1225 for (unsigned i = 0, e = Indices.size(); i != e; ++i) { 1226 C = C->getAggregateElement(Indices[i]); 1227 if (!C) 1228 return nullptr; 1229 } 1230 return C; 1231 } 1232 1233 1234 //===----------------------------------------------------------------------===// 1235 // Constant Folding for Calls 1236 // 1237 1238 /// Return true if it's even possible to fold a call to the specified function. 1239 bool llvm::canConstantFoldCallTo(const Function *F) { 1240 switch (F->getIntrinsicID()) { 1241 case Intrinsic::fabs: 1242 case Intrinsic::minnum: 1243 case Intrinsic::maxnum: 1244 case Intrinsic::log: 1245 case Intrinsic::log2: 1246 case Intrinsic::log10: 1247 case Intrinsic::exp: 1248 case Intrinsic::exp2: 1249 case Intrinsic::floor: 1250 case Intrinsic::ceil: 1251 case Intrinsic::sqrt: 1252 case Intrinsic::pow: 1253 case Intrinsic::powi: 1254 case Intrinsic::bswap: 1255 case Intrinsic::ctpop: 1256 case Intrinsic::ctlz: 1257 case Intrinsic::cttz: 1258 case Intrinsic::fma: 1259 case Intrinsic::fmuladd: 1260 case Intrinsic::copysign: 1261 case Intrinsic::round: 1262 case Intrinsic::sadd_with_overflow: 1263 case Intrinsic::uadd_with_overflow: 1264 case Intrinsic::ssub_with_overflow: 1265 case Intrinsic::usub_with_overflow: 1266 case Intrinsic::smul_with_overflow: 1267 case Intrinsic::umul_with_overflow: 1268 case Intrinsic::convert_from_fp16: 1269 case Intrinsic::convert_to_fp16: 1270 case Intrinsic::x86_sse_cvtss2si: 1271 case Intrinsic::x86_sse_cvtss2si64: 1272 case Intrinsic::x86_sse_cvttss2si: 1273 case Intrinsic::x86_sse_cvttss2si64: 1274 case Intrinsic::x86_sse2_cvtsd2si: 1275 case Intrinsic::x86_sse2_cvtsd2si64: 1276 case Intrinsic::x86_sse2_cvttsd2si: 1277 case Intrinsic::x86_sse2_cvttsd2si64: 1278 return true; 1279 default: 1280 return false; 1281 case 0: break; 1282 } 1283 1284 if (!F->hasName()) 1285 return false; 1286 StringRef Name = F->getName(); 1287 1288 // In these cases, the check of the length is required. We don't want to 1289 // return true for a name like "cos\0blah" which strcmp would return equal to 1290 // "cos", but has length 8. 1291 switch (Name[0]) { 1292 default: return false; 1293 case 'a': 1294 return Name == "acos" || Name == "asin" || Name == "atan" || Name =="atan2"; 1295 case 'c': 1296 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; 1297 case 'e': 1298 return Name == "exp" || Name == "exp2"; 1299 case 'f': 1300 return Name == "fabs" || Name == "fmod" || Name == "floor"; 1301 case 'l': 1302 return Name == "log" || Name == "log10"; 1303 case 'p': 1304 return Name == "pow"; 1305 case 's': 1306 return Name == "sin" || Name == "sinh" || Name == "sqrt" || 1307 Name == "sinf" || Name == "sqrtf"; 1308 case 't': 1309 return Name == "tan" || Name == "tanh"; 1310 } 1311 } 1312 1313 static Constant *GetConstantFoldFPValue(double V, Type *Ty) { 1314 if (Ty->isHalfTy()) { 1315 APFloat APF(V); 1316 bool unused; 1317 APF.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &unused); 1318 return ConstantFP::get(Ty->getContext(), APF); 1319 } 1320 if (Ty->isFloatTy()) 1321 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1322 if (Ty->isDoubleTy()) 1323 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1324 llvm_unreachable("Can only constant fold half/float/double"); 1325 1326 } 1327 1328 namespace { 1329 /// Clear the floating-point exception state. 1330 static inline void llvm_fenv_clearexcept() { 1331 #if defined(HAVE_FENV_H) && HAVE_DECL_FE_ALL_EXCEPT 1332 feclearexcept(FE_ALL_EXCEPT); 1333 #endif 1334 errno = 0; 1335 } 1336 1337 /// Test if a floating-point exception was raised. 1338 static inline bool llvm_fenv_testexcept() { 1339 int errno_val = errno; 1340 if (errno_val == ERANGE || errno_val == EDOM) 1341 return true; 1342 #if defined(HAVE_FENV_H) && HAVE_DECL_FE_ALL_EXCEPT && HAVE_DECL_FE_INEXACT 1343 if (fetestexcept(FE_ALL_EXCEPT & ~FE_INEXACT)) 1344 return true; 1345 #endif 1346 return false; 1347 } 1348 } // End namespace 1349 1350 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 1351 Type *Ty) { 1352 llvm_fenv_clearexcept(); 1353 V = NativeFP(V); 1354 if (llvm_fenv_testexcept()) { 1355 llvm_fenv_clearexcept(); 1356 return nullptr; 1357 } 1358 1359 return GetConstantFoldFPValue(V, Ty); 1360 } 1361 1362 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), 1363 double V, double W, Type *Ty) { 1364 llvm_fenv_clearexcept(); 1365 V = NativeFP(V, W); 1366 if (llvm_fenv_testexcept()) { 1367 llvm_fenv_clearexcept(); 1368 return nullptr; 1369 } 1370 1371 return GetConstantFoldFPValue(V, Ty); 1372 } 1373 1374 /// Attempt to fold an SSE floating point to integer conversion of a constant 1375 /// floating point. If roundTowardZero is false, the default IEEE rounding is 1376 /// used (toward nearest, ties to even). This matches the behavior of the 1377 /// non-truncating SSE instructions in the default rounding mode. The desired 1378 /// integer type Ty is used to select how many bits are available for the 1379 /// result. Returns null if the conversion cannot be performed, otherwise 1380 /// returns the Constant value resulting from the conversion. 1381 static Constant *ConstantFoldConvertToInt(const APFloat &Val, 1382 bool roundTowardZero, Type *Ty) { 1383 // All of these conversion intrinsics form an integer of at most 64bits. 1384 unsigned ResultWidth = Ty->getIntegerBitWidth(); 1385 assert(ResultWidth <= 64 && 1386 "Can only constant fold conversions to 64 and 32 bit ints"); 1387 1388 uint64_t UIntVal; 1389 bool isExact = false; 1390 APFloat::roundingMode mode = roundTowardZero? APFloat::rmTowardZero 1391 : APFloat::rmNearestTiesToEven; 1392 APFloat::opStatus status = Val.convertToInteger(&UIntVal, ResultWidth, 1393 /*isSigned=*/true, mode, 1394 &isExact); 1395 if (status != APFloat::opOK && status != APFloat::opInexact) 1396 return nullptr; 1397 return ConstantInt::get(Ty, UIntVal, /*isSigned=*/true); 1398 } 1399 1400 static double getValueAsDouble(ConstantFP *Op) { 1401 Type *Ty = Op->getType(); 1402 1403 if (Ty->isFloatTy()) 1404 return Op->getValueAPF().convertToFloat(); 1405 1406 if (Ty->isDoubleTy()) 1407 return Op->getValueAPF().convertToDouble(); 1408 1409 bool unused; 1410 APFloat APF = Op->getValueAPF(); 1411 APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); 1412 return APF.convertToDouble(); 1413 } 1414 1415 static Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, 1416 Type *Ty, ArrayRef<Constant *> Operands, 1417 const TargetLibraryInfo *TLI) { 1418 if (Operands.size() == 1) { 1419 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { 1420 if (IntrinsicID == Intrinsic::convert_to_fp16) { 1421 APFloat Val(Op->getValueAPF()); 1422 1423 bool lost = false; 1424 Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost); 1425 1426 return ConstantInt::get(Ty->getContext(), Val.bitcastToAPInt()); 1427 } 1428 1429 if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) 1430 return nullptr; 1431 1432 if (IntrinsicID == Intrinsic::round) { 1433 APFloat V = Op->getValueAPF(); 1434 V.roundToIntegral(APFloat::rmNearestTiesToAway); 1435 return ConstantFP::get(Ty->getContext(), V); 1436 } 1437 1438 /// We only fold functions with finite arguments. Folding NaN and inf is 1439 /// likely to be aborted with an exception anyway, and some host libms 1440 /// have known errors raising exceptions. 1441 if (Op->getValueAPF().isNaN() || Op->getValueAPF().isInfinity()) 1442 return nullptr; 1443 1444 /// Currently APFloat versions of these functions do not exist, so we use 1445 /// the host native double versions. Float versions are not called 1446 /// directly but for all these it is true (float)(f((double)arg)) == 1447 /// f(arg). Long double not supported yet. 1448 double V = getValueAsDouble(Op); 1449 1450 switch (IntrinsicID) { 1451 default: break; 1452 case Intrinsic::fabs: 1453 return ConstantFoldFP(fabs, V, Ty); 1454 #if HAVE_LOG2 1455 case Intrinsic::log2: 1456 return ConstantFoldFP(log2, V, Ty); 1457 #endif 1458 #if HAVE_LOG 1459 case Intrinsic::log: 1460 return ConstantFoldFP(log, V, Ty); 1461 #endif 1462 #if HAVE_LOG10 1463 case Intrinsic::log10: 1464 return ConstantFoldFP(log10, V, Ty); 1465 #endif 1466 #if HAVE_EXP 1467 case Intrinsic::exp: 1468 return ConstantFoldFP(exp, V, Ty); 1469 #endif 1470 #if HAVE_EXP2 1471 case Intrinsic::exp2: 1472 return ConstantFoldFP(exp2, V, Ty); 1473 #endif 1474 case Intrinsic::floor: 1475 return ConstantFoldFP(floor, V, Ty); 1476 case Intrinsic::ceil: 1477 return ConstantFoldFP(ceil, V, Ty); 1478 } 1479 1480 if (!TLI) 1481 return nullptr; 1482 1483 switch (Name[0]) { 1484 case 'a': 1485 if (Name == "acos" && TLI->has(LibFunc::acos)) 1486 return ConstantFoldFP(acos, V, Ty); 1487 else if (Name == "asin" && TLI->has(LibFunc::asin)) 1488 return ConstantFoldFP(asin, V, Ty); 1489 else if (Name == "atan" && TLI->has(LibFunc::atan)) 1490 return ConstantFoldFP(atan, V, Ty); 1491 break; 1492 case 'c': 1493 if (Name == "ceil" && TLI->has(LibFunc::ceil)) 1494 return ConstantFoldFP(ceil, V, Ty); 1495 else if (Name == "cos" && TLI->has(LibFunc::cos)) 1496 return ConstantFoldFP(cos, V, Ty); 1497 else if (Name == "cosh" && TLI->has(LibFunc::cosh)) 1498 return ConstantFoldFP(cosh, V, Ty); 1499 else if (Name == "cosf" && TLI->has(LibFunc::cosf)) 1500 return ConstantFoldFP(cos, V, Ty); 1501 break; 1502 case 'e': 1503 if (Name == "exp" && TLI->has(LibFunc::exp)) 1504 return ConstantFoldFP(exp, V, Ty); 1505 1506 if (Name == "exp2" && TLI->has(LibFunc::exp2)) { 1507 // Constant fold exp2(x) as pow(2,x) in case the host doesn't have a 1508 // C99 library. 1509 return ConstantFoldBinaryFP(pow, 2.0, V, Ty); 1510 } 1511 break; 1512 case 'f': 1513 if (Name == "fabs" && TLI->has(LibFunc::fabs)) 1514 return ConstantFoldFP(fabs, V, Ty); 1515 else if (Name == "floor" && TLI->has(LibFunc::floor)) 1516 return ConstantFoldFP(floor, V, Ty); 1517 break; 1518 case 'l': 1519 if (Name == "log" && V > 0 && TLI->has(LibFunc::log)) 1520 return ConstantFoldFP(log, V, Ty); 1521 else if (Name == "log10" && V > 0 && TLI->has(LibFunc::log10)) 1522 return ConstantFoldFP(log10, V, Ty); 1523 else if (IntrinsicID == Intrinsic::sqrt && 1524 (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy())) { 1525 if (V >= -0.0) 1526 return ConstantFoldFP(sqrt, V, Ty); 1527 else { 1528 // Unlike the sqrt definitions in C/C++, POSIX, and IEEE-754 - which 1529 // all guarantee or favor returning NaN - the square root of a 1530 // negative number is not defined for the LLVM sqrt intrinsic. 1531 // This is because the intrinsic should only be emitted in place of 1532 // libm's sqrt function when using "no-nans-fp-math". 1533 return UndefValue::get(Ty); 1534 } 1535 } 1536 break; 1537 case 's': 1538 if (Name == "sin" && TLI->has(LibFunc::sin)) 1539 return ConstantFoldFP(sin, V, Ty); 1540 else if (Name == "sinh" && TLI->has(LibFunc::sinh)) 1541 return ConstantFoldFP(sinh, V, Ty); 1542 else if (Name == "sqrt" && V >= 0 && TLI->has(LibFunc::sqrt)) 1543 return ConstantFoldFP(sqrt, V, Ty); 1544 else if (Name == "sqrtf" && V >= 0 && TLI->has(LibFunc::sqrtf)) 1545 return ConstantFoldFP(sqrt, V, Ty); 1546 else if (Name == "sinf" && TLI->has(LibFunc::sinf)) 1547 return ConstantFoldFP(sin, V, Ty); 1548 break; 1549 case 't': 1550 if (Name == "tan" && TLI->has(LibFunc::tan)) 1551 return ConstantFoldFP(tan, V, Ty); 1552 else if (Name == "tanh" && TLI->has(LibFunc::tanh)) 1553 return ConstantFoldFP(tanh, V, Ty); 1554 break; 1555 default: 1556 break; 1557 } 1558 return nullptr; 1559 } 1560 1561 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { 1562 switch (IntrinsicID) { 1563 case Intrinsic::bswap: 1564 return ConstantInt::get(Ty->getContext(), Op->getValue().byteSwap()); 1565 case Intrinsic::ctpop: 1566 return ConstantInt::get(Ty, Op->getValue().countPopulation()); 1567 case Intrinsic::convert_from_fp16: { 1568 APFloat Val(APFloat::IEEEhalf, Op->getValue()); 1569 1570 bool lost = false; 1571 APFloat::opStatus status = 1572 Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost); 1573 1574 // Conversion is always precise. 1575 (void)status; 1576 assert(status == APFloat::opOK && !lost && 1577 "Precision lost during fp16 constfolding"); 1578 1579 return ConstantFP::get(Ty->getContext(), Val); 1580 } 1581 default: 1582 return nullptr; 1583 } 1584 } 1585 1586 // Support ConstantVector in case we have an Undef in the top. 1587 if (isa<ConstantVector>(Operands[0]) || 1588 isa<ConstantDataVector>(Operands[0])) { 1589 Constant *Op = cast<Constant>(Operands[0]); 1590 switch (IntrinsicID) { 1591 default: break; 1592 case Intrinsic::x86_sse_cvtss2si: 1593 case Intrinsic::x86_sse_cvtss2si64: 1594 case Intrinsic::x86_sse2_cvtsd2si: 1595 case Intrinsic::x86_sse2_cvtsd2si64: 1596 if (ConstantFP *FPOp = 1597 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U))) 1598 return ConstantFoldConvertToInt(FPOp->getValueAPF(), 1599 /*roundTowardZero=*/false, Ty); 1600 case Intrinsic::x86_sse_cvttss2si: 1601 case Intrinsic::x86_sse_cvttss2si64: 1602 case Intrinsic::x86_sse2_cvttsd2si: 1603 case Intrinsic::x86_sse2_cvttsd2si64: 1604 if (ConstantFP *FPOp = 1605 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U))) 1606 return ConstantFoldConvertToInt(FPOp->getValueAPF(), 1607 /*roundTowardZero=*/true, Ty); 1608 } 1609 } 1610 1611 if (isa<UndefValue>(Operands[0])) { 1612 if (IntrinsicID == Intrinsic::bswap) 1613 return Operands[0]; 1614 return nullptr; 1615 } 1616 1617 return nullptr; 1618 } 1619 1620 if (Operands.size() == 2) { 1621 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1622 if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) 1623 return nullptr; 1624 double Op1V = getValueAsDouble(Op1); 1625 1626 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1627 if (Op2->getType() != Op1->getType()) 1628 return nullptr; 1629 1630 double Op2V = getValueAsDouble(Op2); 1631 if (IntrinsicID == Intrinsic::pow) { 1632 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1633 } 1634 if (IntrinsicID == Intrinsic::copysign) { 1635 APFloat V1 = Op1->getValueAPF(); 1636 APFloat V2 = Op2->getValueAPF(); 1637 V1.copySign(V2); 1638 return ConstantFP::get(Ty->getContext(), V1); 1639 } 1640 1641 if (IntrinsicID == Intrinsic::minnum) { 1642 const APFloat &C1 = Op1->getValueAPF(); 1643 const APFloat &C2 = Op2->getValueAPF(); 1644 return ConstantFP::get(Ty->getContext(), minnum(C1, C2)); 1645 } 1646 1647 if (IntrinsicID == Intrinsic::maxnum) { 1648 const APFloat &C1 = Op1->getValueAPF(); 1649 const APFloat &C2 = Op2->getValueAPF(); 1650 return ConstantFP::get(Ty->getContext(), maxnum(C1, C2)); 1651 } 1652 1653 if (!TLI) 1654 return nullptr; 1655 if (Name == "pow" && TLI->has(LibFunc::pow)) 1656 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1657 if (Name == "fmod" && TLI->has(LibFunc::fmod)) 1658 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty); 1659 if (Name == "atan2" && TLI->has(LibFunc::atan2)) 1660 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty); 1661 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { 1662 if (IntrinsicID == Intrinsic::powi && Ty->isHalfTy()) 1663 return ConstantFP::get(Ty->getContext(), 1664 APFloat((float)std::pow((float)Op1V, 1665 (int)Op2C->getZExtValue()))); 1666 if (IntrinsicID == Intrinsic::powi && Ty->isFloatTy()) 1667 return ConstantFP::get(Ty->getContext(), 1668 APFloat((float)std::pow((float)Op1V, 1669 (int)Op2C->getZExtValue()))); 1670 if (IntrinsicID == Intrinsic::powi && Ty->isDoubleTy()) 1671 return ConstantFP::get(Ty->getContext(), 1672 APFloat((double)std::pow((double)Op1V, 1673 (int)Op2C->getZExtValue()))); 1674 } 1675 return nullptr; 1676 } 1677 1678 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) { 1679 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) { 1680 switch (IntrinsicID) { 1681 default: break; 1682 case Intrinsic::sadd_with_overflow: 1683 case Intrinsic::uadd_with_overflow: 1684 case Intrinsic::ssub_with_overflow: 1685 case Intrinsic::usub_with_overflow: 1686 case Intrinsic::smul_with_overflow: 1687 case Intrinsic::umul_with_overflow: { 1688 APInt Res; 1689 bool Overflow; 1690 switch (IntrinsicID) { 1691 default: llvm_unreachable("Invalid case"); 1692 case Intrinsic::sadd_with_overflow: 1693 Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow); 1694 break; 1695 case Intrinsic::uadd_with_overflow: 1696 Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow); 1697 break; 1698 case Intrinsic::ssub_with_overflow: 1699 Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow); 1700 break; 1701 case Intrinsic::usub_with_overflow: 1702 Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow); 1703 break; 1704 case Intrinsic::smul_with_overflow: 1705 Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow); 1706 break; 1707 case Intrinsic::umul_with_overflow: 1708 Res = Op1->getValue().umul_ov(Op2->getValue(), Overflow); 1709 break; 1710 } 1711 Constant *Ops[] = { 1712 ConstantInt::get(Ty->getContext(), Res), 1713 ConstantInt::get(Type::getInt1Ty(Ty->getContext()), Overflow) 1714 }; 1715 return ConstantStruct::get(cast<StructType>(Ty), Ops); 1716 } 1717 case Intrinsic::cttz: 1718 if (Op2->isOne() && Op1->isZero()) // cttz(0, 1) is undef. 1719 return UndefValue::get(Ty); 1720 return ConstantInt::get(Ty, Op1->getValue().countTrailingZeros()); 1721 case Intrinsic::ctlz: 1722 if (Op2->isOne() && Op1->isZero()) // ctlz(0, 1) is undef. 1723 return UndefValue::get(Ty); 1724 return ConstantInt::get(Ty, Op1->getValue().countLeadingZeros()); 1725 } 1726 } 1727 1728 return nullptr; 1729 } 1730 return nullptr; 1731 } 1732 1733 if (Operands.size() != 3) 1734 return nullptr; 1735 1736 if (const ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1737 if (const ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1738 if (const ConstantFP *Op3 = dyn_cast<ConstantFP>(Operands[2])) { 1739 switch (IntrinsicID) { 1740 default: break; 1741 case Intrinsic::fma: 1742 case Intrinsic::fmuladd: { 1743 APFloat V = Op1->getValueAPF(); 1744 APFloat::opStatus s = V.fusedMultiplyAdd(Op2->getValueAPF(), 1745 Op3->getValueAPF(), 1746 APFloat::rmNearestTiesToEven); 1747 if (s != APFloat::opInvalidOp) 1748 return ConstantFP::get(Ty->getContext(), V); 1749 1750 return nullptr; 1751 } 1752 } 1753 } 1754 } 1755 } 1756 1757 return nullptr; 1758 } 1759 1760 static Constant *ConstantFoldVectorCall(StringRef Name, unsigned IntrinsicID, 1761 VectorType *VTy, 1762 ArrayRef<Constant *> Operands, 1763 const TargetLibraryInfo *TLI) { 1764 SmallVector<Constant *, 4> Result(VTy->getNumElements()); 1765 SmallVector<Constant *, 4> Lane(Operands.size()); 1766 Type *Ty = VTy->getElementType(); 1767 1768 for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) { 1769 // Gather a column of constants. 1770 for (unsigned J = 0, JE = Operands.size(); J != JE; ++J) { 1771 Constant *Agg = Operands[J]->getAggregateElement(I); 1772 if (!Agg) 1773 return nullptr; 1774 1775 Lane[J] = Agg; 1776 } 1777 1778 // Use the regular scalar folding to simplify this column. 1779 Constant *Folded = ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI); 1780 if (!Folded) 1781 return nullptr; 1782 Result[I] = Folded; 1783 } 1784 1785 return ConstantVector::get(Result); 1786 } 1787 1788 /// Attempt to constant fold a call to the specified function 1789 /// with the specified arguments, returning null if unsuccessful. 1790 Constant * 1791 llvm::ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands, 1792 const TargetLibraryInfo *TLI) { 1793 if (!F->hasName()) 1794 return nullptr; 1795 StringRef Name = F->getName(); 1796 1797 Type *Ty = F->getReturnType(); 1798 1799 if (VectorType *VTy = dyn_cast<VectorType>(Ty)) 1800 return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands, TLI); 1801 1802 return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI); 1803 } 1804