ConstantFolding.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f
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/IR/Constants.h" 25#include "llvm/IR/DataLayout.h" 26#include "llvm/IR/DerivedTypes.h" 27#include "llvm/IR/Function.h" 28#include "llvm/IR/GetElementPtrTypeIterator.h" 29#include "llvm/IR/GlobalVariable.h" 30#include "llvm/IR/Instructions.h" 31#include "llvm/IR/Intrinsics.h" 32#include "llvm/IR/Operator.h" 33#include "llvm/Support/ErrorHandling.h" 34#include "llvm/Support/FEnv.h" 35#include "llvm/Support/MathExtras.h" 36#include "llvm/Target/TargetLibraryInfo.h" 37#include <cerrno> 38#include <cmath> 39using namespace llvm; 40 41//===----------------------------------------------------------------------===// 42// Constant Folding internal helper functions 43//===----------------------------------------------------------------------===// 44 45/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with 46/// DataLayout. This always returns a non-null constant, but it may be a 47/// ConstantExpr if unfoldable. 48static Constant *FoldBitCast(Constant *C, Type *DestTy, 49 const DataLayout &TD) { 50 // Catch the obvious splat cases. 51 if (C->isNullValue() && !DestTy->isX86_MMXTy()) 52 return Constant::getNullValue(DestTy); 53 if (C->isAllOnesValue() && !DestTy->isX86_MMXTy()) 54 return Constant::getAllOnesValue(DestTy); 55 56 // Handle a vector->integer cast. 57 if (IntegerType *IT = dyn_cast<IntegerType>(DestTy)) { 58 VectorType *VTy = dyn_cast<VectorType>(C->getType()); 59 if (!VTy) 60 return ConstantExpr::getBitCast(C, DestTy); 61 62 unsigned NumSrcElts = VTy->getNumElements(); 63 Type *SrcEltTy = VTy->getElementType(); 64 65 // If the vector is a vector of floating point, convert it to vector of int 66 // to simplify things. 67 if (SrcEltTy->isFloatingPointTy()) { 68 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); 69 Type *SrcIVTy = 70 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElts); 71 // Ask IR to do the conversion now that #elts line up. 72 C = ConstantExpr::getBitCast(C, SrcIVTy); 73 } 74 75 ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(C); 76 if (!CDV) 77 return ConstantExpr::getBitCast(C, DestTy); 78 79 // Now that we know that the input value is a vector of integers, just shift 80 // and insert them into our result. 81 unsigned BitShift = TD.getTypeAllocSizeInBits(SrcEltTy); 82 APInt Result(IT->getBitWidth(), 0); 83 for (unsigned i = 0; i != NumSrcElts; ++i) { 84 Result <<= BitShift; 85 if (TD.isLittleEndian()) 86 Result |= CDV->getElementAsInteger(NumSrcElts-i-1); 87 else 88 Result |= CDV->getElementAsInteger(i); 89 } 90 91 return ConstantInt::get(IT, Result); 92 } 93 94 // The code below only handles casts to vectors currently. 95 VectorType *DestVTy = dyn_cast<VectorType>(DestTy); 96 if (!DestVTy) 97 return ConstantExpr::getBitCast(C, DestTy); 98 99 // If this is a scalar -> vector cast, convert the input into a <1 x scalar> 100 // vector so the code below can handle it uniformly. 101 if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) { 102 Constant *Ops = C; // don't take the address of C! 103 return FoldBitCast(ConstantVector::get(Ops), DestTy, TD); 104 } 105 106 // If this is a bitcast from constant vector -> vector, fold it. 107 if (!isa<ConstantDataVector>(C) && !isa<ConstantVector>(C)) 108 return ConstantExpr::getBitCast(C, DestTy); 109 110 // If the element types match, IR can fold it. 111 unsigned NumDstElt = DestVTy->getNumElements(); 112 unsigned NumSrcElt = C->getType()->getVectorNumElements(); 113 if (NumDstElt == NumSrcElt) 114 return ConstantExpr::getBitCast(C, DestTy); 115 116 Type *SrcEltTy = C->getType()->getVectorElementType(); 117 Type *DstEltTy = DestVTy->getElementType(); 118 119 // Otherwise, we're changing the number of elements in a vector, which 120 // requires endianness information to do the right thing. For example, 121 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 122 // folds to (little endian): 123 // <4 x i32> <i32 0, i32 0, i32 1, i32 0> 124 // and to (big endian): 125 // <4 x i32> <i32 0, i32 0, i32 0, i32 1> 126 127 // First thing is first. We only want to think about integer here, so if 128 // we have something in FP form, recast it as integer. 129 if (DstEltTy->isFloatingPointTy()) { 130 // Fold to an vector of integers with same size as our FP type. 131 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits(); 132 Type *DestIVTy = 133 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt); 134 // Recursively handle this integer conversion, if possible. 135 C = FoldBitCast(C, DestIVTy, TD); 136 137 // Finally, IR can handle this now that #elts line up. 138 return ConstantExpr::getBitCast(C, DestTy); 139 } 140 141 // Okay, we know the destination is integer, if the input is FP, convert 142 // it to integer first. 143 if (SrcEltTy->isFloatingPointTy()) { 144 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); 145 Type *SrcIVTy = 146 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt); 147 // Ask IR to do the conversion now that #elts line up. 148 C = ConstantExpr::getBitCast(C, SrcIVTy); 149 // If IR wasn't able to fold it, bail out. 150 if (!isa<ConstantVector>(C) && // FIXME: Remove ConstantVector. 151 !isa<ConstantDataVector>(C)) 152 return C; 153 } 154 155 // Now we know that the input and output vectors are both integer vectors 156 // of the same size, and that their #elements is not the same. Do the 157 // conversion here, which depends on whether the input or output has 158 // more elements. 159 bool isLittleEndian = TD.isLittleEndian(); 160 161 SmallVector<Constant*, 32> Result; 162 if (NumDstElt < NumSrcElt) { 163 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>) 164 Constant *Zero = Constant::getNullValue(DstEltTy); 165 unsigned Ratio = NumSrcElt/NumDstElt; 166 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits(); 167 unsigned SrcElt = 0; 168 for (unsigned i = 0; i != NumDstElt; ++i) { 169 // Build each element of the result. 170 Constant *Elt = Zero; 171 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1); 172 for (unsigned j = 0; j != Ratio; ++j) { 173 Constant *Src =dyn_cast<ConstantInt>(C->getAggregateElement(SrcElt++)); 174 if (!Src) // Reject constantexpr elements. 175 return ConstantExpr::getBitCast(C, DestTy); 176 177 // Zero extend the element to the right size. 178 Src = ConstantExpr::getZExt(Src, Elt->getType()); 179 180 // Shift it to the right place, depending on endianness. 181 Src = ConstantExpr::getShl(Src, 182 ConstantInt::get(Src->getType(), ShiftAmt)); 183 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize; 184 185 // Mix it in. 186 Elt = ConstantExpr::getOr(Elt, Src); 187 } 188 Result.push_back(Elt); 189 } 190 return ConstantVector::get(Result); 191 } 192 193 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 194 unsigned Ratio = NumDstElt/NumSrcElt; 195 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits(); 196 197 // Loop over each source value, expanding into multiple results. 198 for (unsigned i = 0; i != NumSrcElt; ++i) { 199 Constant *Src = dyn_cast<ConstantInt>(C->getAggregateElement(i)); 200 if (!Src) // Reject constantexpr elements. 201 return ConstantExpr::getBitCast(C, DestTy); 202 203 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1); 204 for (unsigned j = 0; j != Ratio; ++j) { 205 // Shift the piece of the value into the right place, depending on 206 // endianness. 207 Constant *Elt = ConstantExpr::getLShr(Src, 208 ConstantInt::get(Src->getType(), ShiftAmt)); 209 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize; 210 211 // Truncate and remember this piece. 212 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy)); 213 } 214 } 215 216 return ConstantVector::get(Result); 217} 218 219 220/// IsConstantOffsetFromGlobal - If this constant is actually a constant offset 221/// from a global, return the global and the constant. Because of 222/// constantexprs, this function is recursive. 223static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, 224 APInt &Offset, const DataLayout &TD) { 225 // Trivial case, constant is the global. 226 if ((GV = dyn_cast<GlobalValue>(C))) { 227 unsigned BitWidth = TD.getPointerTypeSizeInBits(GV->getType()); 228 Offset = APInt(BitWidth, 0); 229 return true; 230 } 231 232 // Otherwise, if this isn't a constant expr, bail out. 233 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 234 if (!CE) return false; 235 236 // Look through ptr->int and ptr->ptr casts. 237 if (CE->getOpcode() == Instruction::PtrToInt || 238 CE->getOpcode() == Instruction::BitCast) 239 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD); 240 241 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5) 242 GEPOperator *GEP = dyn_cast<GEPOperator>(CE); 243 if (!GEP) 244 return false; 245 246 unsigned BitWidth = TD.getPointerTypeSizeInBits(GEP->getType()); 247 APInt TmpOffset(BitWidth, 0); 248 249 // If the base isn't a global+constant, we aren't either. 250 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, TmpOffset, TD)) 251 return false; 252 253 // Otherwise, add any offset that our operands provide. 254 if (!GEP->accumulateConstantOffset(TD, TmpOffset)) 255 return false; 256 257 Offset = TmpOffset; 258 return true; 259} 260 261/// ReadDataFromGlobal - Recursive helper to read bits out of global. C is the 262/// constant being copied out of. ByteOffset is an offset into C. CurPtr is the 263/// pointer to copy results into and BytesLeft is the number of bytes left in 264/// the CurPtr buffer. TD is the target data. 265static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset, 266 unsigned char *CurPtr, unsigned BytesLeft, 267 const DataLayout &TD) { 268 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) && 269 "Out of range access"); 270 271 // If this element is zero or undefined, we can just return since *CurPtr is 272 // zero initialized. 273 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C)) 274 return true; 275 276 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 277 if (CI->getBitWidth() > 64 || 278 (CI->getBitWidth() & 7) != 0) 279 return false; 280 281 uint64_t Val = CI->getZExtValue(); 282 unsigned IntBytes = unsigned(CI->getBitWidth()/8); 283 284 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) { 285 int n = ByteOffset; 286 if (!TD.isLittleEndian()) 287 n = IntBytes - n - 1; 288 CurPtr[i] = (unsigned char)(Val >> (n * 8)); 289 ++ByteOffset; 290 } 291 return true; 292 } 293 294 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) { 295 if (CFP->getType()->isDoubleTy()) { 296 C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD); 297 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 298 } 299 if (CFP->getType()->isFloatTy()){ 300 C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD); 301 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 302 } 303 if (CFP->getType()->isHalfTy()){ 304 C = FoldBitCast(C, Type::getInt16Ty(C->getContext()), TD); 305 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 306 } 307 return false; 308 } 309 310 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 311 const StructLayout *SL = TD.getStructLayout(CS->getType()); 312 unsigned Index = SL->getElementContainingOffset(ByteOffset); 313 uint64_t CurEltOffset = SL->getElementOffset(Index); 314 ByteOffset -= CurEltOffset; 315 316 while (1) { 317 // If the element access is to the element itself and not to tail padding, 318 // read the bytes from the element. 319 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType()); 320 321 if (ByteOffset < EltSize && 322 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr, 323 BytesLeft, TD)) 324 return false; 325 326 ++Index; 327 328 // Check to see if we read from the last struct element, if so we're done. 329 if (Index == CS->getType()->getNumElements()) 330 return true; 331 332 // If we read all of the bytes we needed from this element we're done. 333 uint64_t NextEltOffset = SL->getElementOffset(Index); 334 335 if (BytesLeft <= NextEltOffset - CurEltOffset - ByteOffset) 336 return true; 337 338 // Move to the next element of the struct. 339 CurPtr += NextEltOffset - CurEltOffset - ByteOffset; 340 BytesLeft -= NextEltOffset - CurEltOffset - ByteOffset; 341 ByteOffset = 0; 342 CurEltOffset = NextEltOffset; 343 } 344 // not reached. 345 } 346 347 if (isa<ConstantArray>(C) || isa<ConstantVector>(C) || 348 isa<ConstantDataSequential>(C)) { 349 Type *EltTy = C->getType()->getSequentialElementType(); 350 uint64_t EltSize = TD.getTypeAllocSize(EltTy); 351 uint64_t Index = ByteOffset / EltSize; 352 uint64_t Offset = ByteOffset - Index * EltSize; 353 uint64_t NumElts; 354 if (ArrayType *AT = dyn_cast<ArrayType>(C->getType())) 355 NumElts = AT->getNumElements(); 356 else 357 NumElts = C->getType()->getVectorNumElements(); 358 359 for (; Index != NumElts; ++Index) { 360 if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr, 361 BytesLeft, TD)) 362 return false; 363 364 uint64_t BytesWritten = EltSize - Offset; 365 assert(BytesWritten <= EltSize && "Not indexing into this element?"); 366 if (BytesWritten >= BytesLeft) 367 return true; 368 369 Offset = 0; 370 BytesLeft -= BytesWritten; 371 CurPtr += BytesWritten; 372 } 373 return true; 374 } 375 376 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 377 if (CE->getOpcode() == Instruction::IntToPtr && 378 CE->getOperand(0)->getType() == TD.getIntPtrType(CE->getType())) { 379 return ReadDataFromGlobal(CE->getOperand(0), ByteOffset, CurPtr, 380 BytesLeft, TD); 381 } 382 } 383 384 // Otherwise, unknown initializer type. 385 return false; 386} 387 388static Constant *FoldReinterpretLoadFromConstPtr(Constant *C, 389 const DataLayout &TD) { 390 PointerType *PTy = cast<PointerType>(C->getType()); 391 Type *LoadTy = PTy->getElementType(); 392 IntegerType *IntType = dyn_cast<IntegerType>(LoadTy); 393 394 // If this isn't an integer load we can't fold it directly. 395 if (!IntType) { 396 unsigned AS = PTy->getAddressSpace(); 397 398 // If this is a float/double load, we can try folding it as an int32/64 load 399 // and then bitcast the result. This can be useful for union cases. Note 400 // that address spaces don't matter here since we're not going to result in 401 // an actual new load. 402 Type *MapTy; 403 if (LoadTy->isHalfTy()) 404 MapTy = Type::getInt16PtrTy(C->getContext(), AS); 405 else if (LoadTy->isFloatTy()) 406 MapTy = Type::getInt32PtrTy(C->getContext(), AS); 407 else if (LoadTy->isDoubleTy()) 408 MapTy = Type::getInt64PtrTy(C->getContext(), AS); 409 else if (LoadTy->isVectorTy()) { 410 MapTy = PointerType::getIntNPtrTy(C->getContext(), 411 TD.getTypeAllocSizeInBits(LoadTy), 412 AS); 413 } else 414 return nullptr; 415 416 C = FoldBitCast(C, MapTy, TD); 417 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD)) 418 return FoldBitCast(Res, LoadTy, TD); 419 return nullptr; 420 } 421 422 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8; 423 if (BytesLoaded > 32 || BytesLoaded == 0) 424 return nullptr; 425 426 GlobalValue *GVal; 427 APInt Offset; 428 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD)) 429 return nullptr; 430 431 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal); 432 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() || 433 !GV->getInitializer()->getType()->isSized()) 434 return nullptr; 435 436 // If we're loading off the beginning of the global, some bytes may be valid, 437 // but we don't try to handle this. 438 if (Offset.isNegative()) 439 return nullptr; 440 441 // If we're not accessing anything in this constant, the result is undefined. 442 if (Offset.getZExtValue() >= 443 TD.getTypeAllocSize(GV->getInitializer()->getType())) 444 return UndefValue::get(IntType); 445 446 unsigned char RawBytes[32] = {0}; 447 if (!ReadDataFromGlobal(GV->getInitializer(), Offset.getZExtValue(), RawBytes, 448 BytesLoaded, TD)) 449 return nullptr; 450 451 APInt ResultVal = APInt(IntType->getBitWidth(), 0); 452 if (TD.isLittleEndian()) { 453 ResultVal = RawBytes[BytesLoaded - 1]; 454 for (unsigned i = 1; i != BytesLoaded; ++i) { 455 ResultVal <<= 8; 456 ResultVal |= RawBytes[BytesLoaded - 1 - i]; 457 } 458 } else { 459 ResultVal = RawBytes[0]; 460 for (unsigned i = 1; i != BytesLoaded; ++i) { 461 ResultVal <<= 8; 462 ResultVal |= RawBytes[i]; 463 } 464 } 465 466 return ConstantInt::get(IntType->getContext(), ResultVal); 467} 468 469static Constant *ConstantFoldLoadThroughBitcast(ConstantExpr *CE, 470 const DataLayout *DL) { 471 if (!DL) 472 return nullptr; 473 auto *DestPtrTy = dyn_cast<PointerType>(CE->getType()); 474 if (!DestPtrTy) 475 return nullptr; 476 Type *DestTy = DestPtrTy->getElementType(); 477 478 Constant *C = ConstantFoldLoadFromConstPtr(CE->getOperand(0), DL); 479 if (!C) 480 return nullptr; 481 482 do { 483 Type *SrcTy = C->getType(); 484 485 // If the type sizes are the same and a cast is legal, just directly 486 // cast the constant. 487 if (DL->getTypeSizeInBits(DestTy) == DL->getTypeSizeInBits(SrcTy)) { 488 Instruction::CastOps Cast = Instruction::BitCast; 489 // If we are going from a pointer to int or vice versa, we spell the cast 490 // differently. 491 if (SrcTy->isIntegerTy() && DestTy->isPointerTy()) 492 Cast = Instruction::IntToPtr; 493 else if (SrcTy->isPointerTy() && DestTy->isIntegerTy()) 494 Cast = Instruction::PtrToInt; 495 496 if (CastInst::castIsValid(Cast, C, DestTy)) 497 return ConstantExpr::getCast(Cast, C, DestTy); 498 } 499 500 // If this isn't an aggregate type, there is nothing we can do to drill down 501 // and find a bitcastable constant. 502 if (!SrcTy->isAggregateType()) 503 return nullptr; 504 505 // We're simulating a load through a pointer that was bitcast to point to 506 // a different type, so we can try to walk down through the initial 507 // elements of an aggregate to see if some part of th e aggregate is 508 // castable to implement the "load" semantic model. 509 C = C->getAggregateElement(0u); 510 } while (C); 511 512 return nullptr; 513} 514 515/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 516/// produce if it is constant and determinable. If this is not determinable, 517/// return null. 518Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, 519 const DataLayout *TD) { 520 // First, try the easy cases: 521 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 522 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 523 return GV->getInitializer(); 524 525 // If the loaded value isn't a constant expr, we can't handle it. 526 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 527 if (!CE) 528 return nullptr; 529 530 if (CE->getOpcode() == Instruction::GetElementPtr) { 531 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) { 532 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 533 if (Constant *V = 534 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) 535 return V; 536 } 537 } 538 } 539 540 if (CE->getOpcode() == Instruction::BitCast) 541 if (Constant *LoadedC = ConstantFoldLoadThroughBitcast(CE, TD)) 542 return LoadedC; 543 544 // Instead of loading constant c string, use corresponding integer value 545 // directly if string length is small enough. 546 StringRef Str; 547 if (TD && getConstantStringInfo(CE, Str) && !Str.empty()) { 548 unsigned StrLen = Str.size(); 549 Type *Ty = cast<PointerType>(CE->getType())->getElementType(); 550 unsigned NumBits = Ty->getPrimitiveSizeInBits(); 551 // Replace load with immediate integer if the result is an integer or fp 552 // value. 553 if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 && 554 (isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) { 555 APInt StrVal(NumBits, 0); 556 APInt SingleChar(NumBits, 0); 557 if (TD->isLittleEndian()) { 558 for (signed i = StrLen-1; i >= 0; i--) { 559 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 560 StrVal = (StrVal << 8) | SingleChar; 561 } 562 } else { 563 for (unsigned i = 0; i < StrLen; i++) { 564 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 565 StrVal = (StrVal << 8) | SingleChar; 566 } 567 // Append NULL at the end. 568 SingleChar = 0; 569 StrVal = (StrVal << 8) | SingleChar; 570 } 571 572 Constant *Res = ConstantInt::get(CE->getContext(), StrVal); 573 if (Ty->isFloatingPointTy()) 574 Res = ConstantExpr::getBitCast(Res, Ty); 575 return Res; 576 } 577 } 578 579 // If this load comes from anywhere in a constant global, and if the global 580 // is all undef or zero, we know what it loads. 581 if (GlobalVariable *GV = 582 dyn_cast<GlobalVariable>(GetUnderlyingObject(CE, TD))) { 583 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 584 Type *ResTy = cast<PointerType>(C->getType())->getElementType(); 585 if (GV->getInitializer()->isNullValue()) 586 return Constant::getNullValue(ResTy); 587 if (isa<UndefValue>(GV->getInitializer())) 588 return UndefValue::get(ResTy); 589 } 590 } 591 592 // Try hard to fold loads from bitcasted strange and non-type-safe things. 593 if (TD) 594 return FoldReinterpretLoadFromConstPtr(CE, *TD); 595 return nullptr; 596} 597 598static Constant *ConstantFoldLoadInst(const LoadInst *LI, const DataLayout *TD){ 599 if (LI->isVolatile()) return nullptr; 600 601 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0))) 602 return ConstantFoldLoadFromConstPtr(C, TD); 603 604 return nullptr; 605} 606 607/// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression. 608/// Attempt to symbolically evaluate the result of a binary operator merging 609/// these together. If target data info is available, it is provided as DL, 610/// otherwise DL is null. 611static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, 612 Constant *Op1, const DataLayout *DL){ 613 // SROA 614 615 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl. 616 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute 617 // bits. 618 619 620 if (Opc == Instruction::And && DL) { 621 unsigned BitWidth = DL->getTypeSizeInBits(Op0->getType()->getScalarType()); 622 APInt KnownZero0(BitWidth, 0), KnownOne0(BitWidth, 0); 623 APInt KnownZero1(BitWidth, 0), KnownOne1(BitWidth, 0); 624 computeKnownBits(Op0, KnownZero0, KnownOne0, DL); 625 computeKnownBits(Op1, KnownZero1, KnownOne1, DL); 626 if ((KnownOne1 | KnownZero0).isAllOnesValue()) { 627 // All the bits of Op0 that the 'and' could be masking are already zero. 628 return Op0; 629 } 630 if ((KnownOne0 | KnownZero1).isAllOnesValue()) { 631 // All the bits of Op1 that the 'and' could be masking are already zero. 632 return Op1; 633 } 634 635 APInt KnownZero = KnownZero0 | KnownZero1; 636 APInt KnownOne = KnownOne0 & KnownOne1; 637 if ((KnownZero | KnownOne).isAllOnesValue()) { 638 return ConstantInt::get(Op0->getType(), KnownOne); 639 } 640 } 641 642 // If the constant expr is something like &A[123] - &A[4].f, fold this into a 643 // constant. This happens frequently when iterating over a global array. 644 if (Opc == Instruction::Sub && DL) { 645 GlobalValue *GV1, *GV2; 646 APInt Offs1, Offs2; 647 648 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *DL)) 649 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *DL) && 650 GV1 == GV2) { 651 unsigned OpSize = DL->getTypeSizeInBits(Op0->getType()); 652 653 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow. 654 // PtrToInt may change the bitwidth so we have convert to the right size 655 // first. 656 return ConstantInt::get(Op0->getType(), Offs1.zextOrTrunc(OpSize) - 657 Offs2.zextOrTrunc(OpSize)); 658 } 659 } 660 661 return nullptr; 662} 663 664/// CastGEPIndices - If array indices are not pointer-sized integers, 665/// explicitly cast them so that they aren't implicitly casted by the 666/// getelementptr. 667static Constant *CastGEPIndices(ArrayRef<Constant *> Ops, 668 Type *ResultTy, const DataLayout *TD, 669 const TargetLibraryInfo *TLI) { 670 if (!TD) 671 return nullptr; 672 673 Type *IntPtrTy = TD->getIntPtrType(ResultTy); 674 675 bool Any = false; 676 SmallVector<Constant*, 32> NewIdxs; 677 for (unsigned i = 1, e = Ops.size(); i != e; ++i) { 678 if ((i == 1 || 679 !isa<StructType>(GetElementPtrInst::getIndexedType( 680 Ops[0]->getType(), 681 Ops.slice(1, i - 1)))) && 682 Ops[i]->getType() != IntPtrTy) { 683 Any = true; 684 NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i], 685 true, 686 IntPtrTy, 687 true), 688 Ops[i], IntPtrTy)); 689 } else 690 NewIdxs.push_back(Ops[i]); 691 } 692 693 if (!Any) 694 return nullptr; 695 696 Constant *C = ConstantExpr::getGetElementPtr(Ops[0], NewIdxs); 697 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 698 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI)) 699 C = Folded; 700 } 701 702 return C; 703} 704 705/// Strip the pointer casts, but preserve the address space information. 706static Constant* StripPtrCastKeepAS(Constant* Ptr) { 707 assert(Ptr->getType()->isPointerTy() && "Not a pointer type"); 708 PointerType *OldPtrTy = cast<PointerType>(Ptr->getType()); 709 Ptr = cast<Constant>(Ptr->stripPointerCasts()); 710 PointerType *NewPtrTy = cast<PointerType>(Ptr->getType()); 711 712 // Preserve the address space number of the pointer. 713 if (NewPtrTy->getAddressSpace() != OldPtrTy->getAddressSpace()) { 714 NewPtrTy = NewPtrTy->getElementType()->getPointerTo( 715 OldPtrTy->getAddressSpace()); 716 Ptr = ConstantExpr::getPointerCast(Ptr, NewPtrTy); 717 } 718 return Ptr; 719} 720 721/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP 722/// constant expression, do so. 723static Constant *SymbolicallyEvaluateGEP(ArrayRef<Constant *> Ops, 724 Type *ResultTy, const DataLayout *TD, 725 const TargetLibraryInfo *TLI) { 726 Constant *Ptr = Ops[0]; 727 if (!TD || !Ptr->getType()->getPointerElementType()->isSized() || 728 !Ptr->getType()->isPointerTy()) 729 return nullptr; 730 731 Type *IntPtrTy = TD->getIntPtrType(Ptr->getType()); 732 Type *ResultElementTy = ResultTy->getPointerElementType(); 733 734 // If this is a constant expr gep that is effectively computing an 735 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' 736 for (unsigned i = 1, e = Ops.size(); i != e; ++i) 737 if (!isa<ConstantInt>(Ops[i])) { 738 739 // If this is "gep i8* Ptr, (sub 0, V)", fold this as: 740 // "inttoptr (sub (ptrtoint Ptr), V)" 741 if (Ops.size() == 2 && ResultElementTy->isIntegerTy(8)) { 742 ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[1]); 743 assert((!CE || CE->getType() == IntPtrTy) && 744 "CastGEPIndices didn't canonicalize index types!"); 745 if (CE && CE->getOpcode() == Instruction::Sub && 746 CE->getOperand(0)->isNullValue()) { 747 Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType()); 748 Res = ConstantExpr::getSub(Res, CE->getOperand(1)); 749 Res = ConstantExpr::getIntToPtr(Res, ResultTy); 750 if (ConstantExpr *ResCE = dyn_cast<ConstantExpr>(Res)) 751 Res = ConstantFoldConstantExpression(ResCE, TD, TLI); 752 return Res; 753 } 754 } 755 return nullptr; 756 } 757 758 unsigned BitWidth = TD->getTypeSizeInBits(IntPtrTy); 759 APInt Offset = 760 APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(), 761 makeArrayRef((Value *const*) 762 Ops.data() + 1, 763 Ops.size() - 1))); 764 Ptr = StripPtrCastKeepAS(Ptr); 765 766 // If this is a GEP of a GEP, fold it all into a single GEP. 767 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) { 768 SmallVector<Value *, 4> NestedOps(GEP->op_begin() + 1, GEP->op_end()); 769 770 // Do not try the incorporate the sub-GEP if some index is not a number. 771 bool AllConstantInt = true; 772 for (unsigned i = 0, e = NestedOps.size(); i != e; ++i) 773 if (!isa<ConstantInt>(NestedOps[i])) { 774 AllConstantInt = false; 775 break; 776 } 777 if (!AllConstantInt) 778 break; 779 780 Ptr = cast<Constant>(GEP->getOperand(0)); 781 Offset += APInt(BitWidth, 782 TD->getIndexedOffset(Ptr->getType(), NestedOps)); 783 Ptr = StripPtrCastKeepAS(Ptr); 784 } 785 786 // If the base value for this address is a literal integer value, fold the 787 // getelementptr to the resulting integer value casted to the pointer type. 788 APInt BasePtr(BitWidth, 0); 789 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) { 790 if (CE->getOpcode() == Instruction::IntToPtr) { 791 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) 792 BasePtr = Base->getValue().zextOrTrunc(BitWidth); 793 } 794 } 795 796 if (Ptr->isNullValue() || BasePtr != 0) { 797 Constant *C = ConstantInt::get(Ptr->getContext(), Offset + BasePtr); 798 return ConstantExpr::getIntToPtr(C, ResultTy); 799 } 800 801 // Otherwise form a regular getelementptr. Recompute the indices so that 802 // we eliminate over-indexing of the notional static type array bounds. 803 // This makes it easy to determine if the getelementptr is "inbounds". 804 // Also, this helps GlobalOpt do SROA on GlobalVariables. 805 Type *Ty = Ptr->getType(); 806 assert(Ty->isPointerTy() && "Forming regular GEP of non-pointer type"); 807 SmallVector<Constant *, 32> NewIdxs; 808 809 do { 810 if (SequentialType *ATy = dyn_cast<SequentialType>(Ty)) { 811 if (ATy->isPointerTy()) { 812 // The only pointer indexing we'll do is on the first index of the GEP. 813 if (!NewIdxs.empty()) 814 break; 815 816 // Only handle pointers to sized types, not pointers to functions. 817 if (!ATy->getElementType()->isSized()) 818 return nullptr; 819 } 820 821 // Determine which element of the array the offset points into. 822 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); 823 if (ElemSize == 0) 824 // The element size is 0. This may be [0 x Ty]*, so just use a zero 825 // index for this level and proceed to the next level to see if it can 826 // accommodate the offset. 827 NewIdxs.push_back(ConstantInt::get(IntPtrTy, 0)); 828 else { 829 // The element size is non-zero divide the offset by the element 830 // size (rounding down), to compute the index at this level. 831 APInt NewIdx = Offset.udiv(ElemSize); 832 Offset -= NewIdx * ElemSize; 833 NewIdxs.push_back(ConstantInt::get(IntPtrTy, NewIdx)); 834 } 835 Ty = ATy->getElementType(); 836 } else if (StructType *STy = dyn_cast<StructType>(Ty)) { 837 // If we end up with an offset that isn't valid for this struct type, we 838 // can't re-form this GEP in a regular form, so bail out. The pointer 839 // operand likely went through casts that are necessary to make the GEP 840 // sensible. 841 const StructLayout &SL = *TD->getStructLayout(STy); 842 if (Offset.uge(SL.getSizeInBytes())) 843 break; 844 845 // Determine which field of the struct the offset points into. The 846 // getZExtValue is fine as we've already ensured that the offset is 847 // within the range representable by the StructLayout API. 848 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); 849 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 850 ElIdx)); 851 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); 852 Ty = STy->getTypeAtIndex(ElIdx); 853 } else { 854 // We've reached some non-indexable type. 855 break; 856 } 857 } while (Ty != ResultElementTy); 858 859 // If we haven't used up the entire offset by descending the static 860 // type, then the offset is pointing into the middle of an indivisible 861 // member, so we can't simplify it. 862 if (Offset != 0) 863 return nullptr; 864 865 // Create a GEP. 866 Constant *C = ConstantExpr::getGetElementPtr(Ptr, NewIdxs); 867 assert(C->getType()->getPointerElementType() == Ty && 868 "Computed GetElementPtr has unexpected type!"); 869 870 // If we ended up indexing a member with a type that doesn't match 871 // the type of what the original indices indexed, add a cast. 872 if (Ty != ResultElementTy) 873 C = FoldBitCast(C, ResultTy, *TD); 874 875 return C; 876} 877 878 879 880//===----------------------------------------------------------------------===// 881// Constant Folding public APIs 882//===----------------------------------------------------------------------===// 883 884/// ConstantFoldInstruction - Try to constant fold the specified instruction. 885/// If successful, the constant result is returned, if not, null is returned. 886/// Note that this fails if not all of the operands are constant. Otherwise, 887/// this function can only fail when attempting to fold instructions like loads 888/// and stores, which have no constant expression form. 889Constant *llvm::ConstantFoldInstruction(Instruction *I, 890 const DataLayout *TD, 891 const TargetLibraryInfo *TLI) { 892 // Handle PHI nodes quickly here... 893 if (PHINode *PN = dyn_cast<PHINode>(I)) { 894 Constant *CommonValue = nullptr; 895 896 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 897 Value *Incoming = PN->getIncomingValue(i); 898 // If the incoming value is undef then skip it. Note that while we could 899 // skip the value if it is equal to the phi node itself we choose not to 900 // because that would break the rule that constant folding only applies if 901 // all operands are constants. 902 if (isa<UndefValue>(Incoming)) 903 continue; 904 // If the incoming value is not a constant, then give up. 905 Constant *C = dyn_cast<Constant>(Incoming); 906 if (!C) 907 return nullptr; 908 // Fold the PHI's operands. 909 if (ConstantExpr *NewC = dyn_cast<ConstantExpr>(C)) 910 C = ConstantFoldConstantExpression(NewC, TD, TLI); 911 // If the incoming value is a different constant to 912 // the one we saw previously, then give up. 913 if (CommonValue && C != CommonValue) 914 return nullptr; 915 CommonValue = C; 916 } 917 918 919 // If we reach here, all incoming values are the same constant or undef. 920 return CommonValue ? CommonValue : UndefValue::get(PN->getType()); 921 } 922 923 // Scan the operand list, checking to see if they are all constants, if so, 924 // hand off to ConstantFoldInstOperands. 925 SmallVector<Constant*, 8> Ops; 926 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) { 927 Constant *Op = dyn_cast<Constant>(*i); 928 if (!Op) 929 return nullptr; // All operands not constant! 930 931 // Fold the Instruction's operands. 932 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(Op)) 933 Op = ConstantFoldConstantExpression(NewCE, TD, TLI); 934 935 Ops.push_back(Op); 936 } 937 938 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 939 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], 940 TD, TLI); 941 942 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 943 return ConstantFoldLoadInst(LI, TD); 944 945 if (InsertValueInst *IVI = dyn_cast<InsertValueInst>(I)) { 946 return ConstantExpr::getInsertValue( 947 cast<Constant>(IVI->getAggregateOperand()), 948 cast<Constant>(IVI->getInsertedValueOperand()), 949 IVI->getIndices()); 950 } 951 952 if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I)) { 953 return ConstantExpr::getExtractValue( 954 cast<Constant>(EVI->getAggregateOperand()), 955 EVI->getIndices()); 956 } 957 958 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops, TD, TLI); 959} 960 961static Constant * 962ConstantFoldConstantExpressionImpl(const ConstantExpr *CE, const DataLayout *TD, 963 const TargetLibraryInfo *TLI, 964 SmallPtrSet<ConstantExpr *, 4> &FoldedOps) { 965 SmallVector<Constant *, 8> Ops; 966 for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; 967 ++i) { 968 Constant *NewC = cast<Constant>(*i); 969 // Recursively fold the ConstantExpr's operands. If we have already folded 970 // a ConstantExpr, we don't have to process it again. 971 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC)) { 972 if (FoldedOps.insert(NewCE)) 973 NewC = ConstantFoldConstantExpressionImpl(NewCE, TD, TLI, FoldedOps); 974 } 975 Ops.push_back(NewC); 976 } 977 978 if (CE->isCompare()) 979 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1], 980 TD, TLI); 981 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), Ops, TD, TLI); 982} 983 984/// ConstantFoldConstantExpression - Attempt to fold the constant expression 985/// using the specified DataLayout. If successful, the constant result is 986/// result is returned, if not, null is returned. 987Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE, 988 const DataLayout *TD, 989 const TargetLibraryInfo *TLI) { 990 SmallPtrSet<ConstantExpr *, 4> FoldedOps; 991 return ConstantFoldConstantExpressionImpl(CE, TD, TLI, FoldedOps); 992} 993 994/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 995/// specified opcode and operands. If successful, the constant result is 996/// returned, if not, null is returned. Note that this function can fail when 997/// attempting to fold instructions like loads and stores, which have no 998/// constant expression form. 999/// 1000/// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc 1001/// information, due to only being passed an opcode and operands. Constant 1002/// folding using this function strips this information. 1003/// 1004Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, 1005 ArrayRef<Constant *> Ops, 1006 const DataLayout *TD, 1007 const TargetLibraryInfo *TLI) { 1008 // Handle easy binops first. 1009 if (Instruction::isBinaryOp(Opcode)) { 1010 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) { 1011 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD)) 1012 return C; 1013 } 1014 1015 return ConstantExpr::get(Opcode, Ops[0], Ops[1]); 1016 } 1017 1018 switch (Opcode) { 1019 default: return nullptr; 1020 case Instruction::ICmp: 1021 case Instruction::FCmp: llvm_unreachable("Invalid for compares"); 1022 case Instruction::Call: 1023 if (Function *F = dyn_cast<Function>(Ops.back())) 1024 if (canConstantFoldCallTo(F)) 1025 return ConstantFoldCall(F, Ops.slice(0, Ops.size() - 1), TLI); 1026 return nullptr; 1027 case Instruction::PtrToInt: 1028 // If the input is a inttoptr, eliminate the pair. This requires knowing 1029 // the width of a pointer, so it can't be done in ConstantExpr::getCast. 1030 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 1031 if (TD && CE->getOpcode() == Instruction::IntToPtr) { 1032 Constant *Input = CE->getOperand(0); 1033 unsigned InWidth = Input->getType()->getScalarSizeInBits(); 1034 unsigned PtrWidth = TD->getPointerTypeSizeInBits(CE->getType()); 1035 if (PtrWidth < InWidth) { 1036 Constant *Mask = 1037 ConstantInt::get(CE->getContext(), 1038 APInt::getLowBitsSet(InWidth, PtrWidth)); 1039 Input = ConstantExpr::getAnd(Input, Mask); 1040 } 1041 // Do a zext or trunc to get to the dest size. 1042 return ConstantExpr::getIntegerCast(Input, DestTy, false); 1043 } 1044 } 1045 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 1046 case Instruction::IntToPtr: 1047 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if 1048 // the int size is >= the ptr size and the address spaces are the same. 1049 // This requires knowing the width of a pointer, so it can't be done in 1050 // ConstantExpr::getCast. 1051 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 1052 if (TD && CE->getOpcode() == Instruction::PtrToInt) { 1053 Constant *SrcPtr = CE->getOperand(0); 1054 unsigned SrcPtrSize = TD->getPointerTypeSizeInBits(SrcPtr->getType()); 1055 unsigned MidIntSize = CE->getType()->getScalarSizeInBits(); 1056 1057 if (MidIntSize >= SrcPtrSize) { 1058 unsigned SrcAS = SrcPtr->getType()->getPointerAddressSpace(); 1059 if (SrcAS == DestTy->getPointerAddressSpace()) 1060 return FoldBitCast(CE->getOperand(0), DestTy, *TD); 1061 } 1062 } 1063 } 1064 1065 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 1066 case Instruction::Trunc: 1067 case Instruction::ZExt: 1068 case Instruction::SExt: 1069 case Instruction::FPTrunc: 1070 case Instruction::FPExt: 1071 case Instruction::UIToFP: 1072 case Instruction::SIToFP: 1073 case Instruction::FPToUI: 1074 case Instruction::FPToSI: 1075 case Instruction::AddrSpaceCast: 1076 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 1077 case Instruction::BitCast: 1078 if (TD) 1079 return FoldBitCast(Ops[0], DestTy, *TD); 1080 return ConstantExpr::getBitCast(Ops[0], DestTy); 1081 case Instruction::Select: 1082 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); 1083 case Instruction::ExtractElement: 1084 return ConstantExpr::getExtractElement(Ops[0], Ops[1]); 1085 case Instruction::InsertElement: 1086 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); 1087 case Instruction::ShuffleVector: 1088 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); 1089 case Instruction::GetElementPtr: 1090 if (Constant *C = CastGEPIndices(Ops, DestTy, TD, TLI)) 1091 return C; 1092 if (Constant *C = SymbolicallyEvaluateGEP(Ops, DestTy, TD, TLI)) 1093 return C; 1094 1095 return ConstantExpr::getGetElementPtr(Ops[0], Ops.slice(1)); 1096 } 1097} 1098 1099/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 1100/// instruction (icmp/fcmp) with the specified operands. If it fails, it 1101/// returns a constant expression of the specified operands. 1102/// 1103Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, 1104 Constant *Ops0, Constant *Ops1, 1105 const DataLayout *TD, 1106 const TargetLibraryInfo *TLI) { 1107 // fold: icmp (inttoptr x), null -> icmp x, 0 1108 // fold: icmp (ptrtoint x), 0 -> icmp x, null 1109 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y 1110 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y 1111 // 1112 // ConstantExpr::getCompare cannot do this, because it doesn't have TD 1113 // around to know if bit truncation is happening. 1114 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) { 1115 if (TD && Ops1->isNullValue()) { 1116 if (CE0->getOpcode() == Instruction::IntToPtr) { 1117 Type *IntPtrTy = TD->getIntPtrType(CE0->getType()); 1118 // Convert the integer value to the right size to ensure we get the 1119 // proper extension or truncation. 1120 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), 1121 IntPtrTy, false); 1122 Constant *Null = Constant::getNullValue(C->getType()); 1123 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); 1124 } 1125 1126 // Only do this transformation if the int is intptrty in size, otherwise 1127 // there is a truncation or extension that we aren't modeling. 1128 if (CE0->getOpcode() == Instruction::PtrToInt) { 1129 Type *IntPtrTy = TD->getIntPtrType(CE0->getOperand(0)->getType()); 1130 if (CE0->getType() == IntPtrTy) { 1131 Constant *C = CE0->getOperand(0); 1132 Constant *Null = Constant::getNullValue(C->getType()); 1133 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); 1134 } 1135 } 1136 } 1137 1138 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) { 1139 if (TD && CE0->getOpcode() == CE1->getOpcode()) { 1140 if (CE0->getOpcode() == Instruction::IntToPtr) { 1141 Type *IntPtrTy = TD->getIntPtrType(CE0->getType()); 1142 1143 // Convert the integer value to the right size to ensure we get the 1144 // proper extension or truncation. 1145 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), 1146 IntPtrTy, false); 1147 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), 1148 IntPtrTy, false); 1149 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD, TLI); 1150 } 1151 1152 // Only do this transformation if the int is intptrty in size, otherwise 1153 // there is a truncation or extension that we aren't modeling. 1154 if (CE0->getOpcode() == Instruction::PtrToInt) { 1155 Type *IntPtrTy = TD->getIntPtrType(CE0->getOperand(0)->getType()); 1156 if (CE0->getType() == IntPtrTy && 1157 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()) { 1158 return ConstantFoldCompareInstOperands(Predicate, 1159 CE0->getOperand(0), 1160 CE1->getOperand(0), 1161 TD, 1162 TLI); 1163 } 1164 } 1165 } 1166 } 1167 1168 // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0) 1169 // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0) 1170 if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) && 1171 CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) { 1172 Constant *LHS = 1173 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1, 1174 TD, TLI); 1175 Constant *RHS = 1176 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1, 1177 TD, TLI); 1178 unsigned OpC = 1179 Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or; 1180 Constant *Ops[] = { LHS, RHS }; 1181 return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, TD, TLI); 1182 } 1183 } 1184 1185 return ConstantExpr::getCompare(Predicate, Ops0, Ops1); 1186} 1187 1188 1189/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 1190/// getelementptr constantexpr, return the constant value being addressed by the 1191/// constant expression, or null if something is funny and we can't decide. 1192Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, 1193 ConstantExpr *CE) { 1194 if (!CE->getOperand(1)->isNullValue()) 1195 return nullptr; // Do not allow stepping over the value! 1196 1197 // Loop over all of the operands, tracking down which value we are 1198 // addressing. 1199 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i) { 1200 C = C->getAggregateElement(CE->getOperand(i)); 1201 if (!C) 1202 return nullptr; 1203 } 1204 return C; 1205} 1206 1207/// ConstantFoldLoadThroughGEPIndices - Given a constant and getelementptr 1208/// indices (with an *implied* zero pointer index that is not in the list), 1209/// return the constant value being addressed by a virtual load, or null if 1210/// something is funny and we can't decide. 1211Constant *llvm::ConstantFoldLoadThroughGEPIndices(Constant *C, 1212 ArrayRef<Constant*> Indices) { 1213 // Loop over all of the operands, tracking down which value we are 1214 // addressing. 1215 for (unsigned i = 0, e = Indices.size(); i != e; ++i) { 1216 C = C->getAggregateElement(Indices[i]); 1217 if (!C) 1218 return nullptr; 1219 } 1220 return C; 1221} 1222 1223 1224//===----------------------------------------------------------------------===// 1225// Constant Folding for Calls 1226// 1227 1228/// canConstantFoldCallTo - Return true if its even possible to fold a call to 1229/// the specified function. 1230bool llvm::canConstantFoldCallTo(const Function *F) { 1231 switch (F->getIntrinsicID()) { 1232 case Intrinsic::fabs: 1233 case Intrinsic::log: 1234 case Intrinsic::log2: 1235 case Intrinsic::log10: 1236 case Intrinsic::exp: 1237 case Intrinsic::exp2: 1238 case Intrinsic::floor: 1239 case Intrinsic::ceil: 1240 case Intrinsic::sqrt: 1241 case Intrinsic::pow: 1242 case Intrinsic::powi: 1243 case Intrinsic::bswap: 1244 case Intrinsic::ctpop: 1245 case Intrinsic::ctlz: 1246 case Intrinsic::cttz: 1247 case Intrinsic::fma: 1248 case Intrinsic::fmuladd: 1249 case Intrinsic::copysign: 1250 case Intrinsic::round: 1251 case Intrinsic::sadd_with_overflow: 1252 case Intrinsic::uadd_with_overflow: 1253 case Intrinsic::ssub_with_overflow: 1254 case Intrinsic::usub_with_overflow: 1255 case Intrinsic::smul_with_overflow: 1256 case Intrinsic::umul_with_overflow: 1257 case Intrinsic::convert_from_fp16: 1258 case Intrinsic::convert_to_fp16: 1259 case Intrinsic::x86_sse_cvtss2si: 1260 case Intrinsic::x86_sse_cvtss2si64: 1261 case Intrinsic::x86_sse_cvttss2si: 1262 case Intrinsic::x86_sse_cvttss2si64: 1263 case Intrinsic::x86_sse2_cvtsd2si: 1264 case Intrinsic::x86_sse2_cvtsd2si64: 1265 case Intrinsic::x86_sse2_cvttsd2si: 1266 case Intrinsic::x86_sse2_cvttsd2si64: 1267 return true; 1268 default: 1269 return false; 1270 case 0: break; 1271 } 1272 1273 if (!F->hasName()) 1274 return false; 1275 StringRef Name = F->getName(); 1276 1277 // In these cases, the check of the length is required. We don't want to 1278 // return true for a name like "cos\0blah" which strcmp would return equal to 1279 // "cos", but has length 8. 1280 switch (Name[0]) { 1281 default: return false; 1282 case 'a': 1283 return Name == "acos" || Name == "asin" || Name == "atan" || Name =="atan2"; 1284 case 'c': 1285 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; 1286 case 'e': 1287 return Name == "exp" || Name == "exp2"; 1288 case 'f': 1289 return Name == "fabs" || Name == "fmod" || Name == "floor"; 1290 case 'l': 1291 return Name == "log" || Name == "log10"; 1292 case 'p': 1293 return Name == "pow"; 1294 case 's': 1295 return Name == "sin" || Name == "sinh" || Name == "sqrt" || 1296 Name == "sinf" || Name == "sqrtf"; 1297 case 't': 1298 return Name == "tan" || Name == "tanh"; 1299 } 1300} 1301 1302static Constant *GetConstantFoldFPValue(double V, Type *Ty) { 1303 if (Ty->isHalfTy()) { 1304 APFloat APF(V); 1305 bool unused; 1306 APF.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &unused); 1307 return ConstantFP::get(Ty->getContext(), APF); 1308 } 1309 if (Ty->isFloatTy()) 1310 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1311 if (Ty->isDoubleTy()) 1312 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1313 llvm_unreachable("Can only constant fold half/float/double"); 1314 1315} 1316 1317static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 1318 Type *Ty) { 1319 sys::llvm_fenv_clearexcept(); 1320 V = NativeFP(V); 1321 if (sys::llvm_fenv_testexcept()) { 1322 sys::llvm_fenv_clearexcept(); 1323 return nullptr; 1324 } 1325 1326 return GetConstantFoldFPValue(V, Ty); 1327} 1328 1329static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), 1330 double V, double W, Type *Ty) { 1331 sys::llvm_fenv_clearexcept(); 1332 V = NativeFP(V, W); 1333 if (sys::llvm_fenv_testexcept()) { 1334 sys::llvm_fenv_clearexcept(); 1335 return nullptr; 1336 } 1337 1338 return GetConstantFoldFPValue(V, Ty); 1339} 1340 1341/// ConstantFoldConvertToInt - Attempt to an SSE floating point to integer 1342/// conversion of a constant floating point. If roundTowardZero is false, the 1343/// default IEEE rounding is used (toward nearest, ties to even). This matches 1344/// the behavior of the non-truncating SSE instructions in the default rounding 1345/// mode. The desired integer type Ty is used to select how many bits are 1346/// available for the result. Returns null if the conversion cannot be 1347/// performed, otherwise returns the Constant value resulting from the 1348/// conversion. 1349static Constant *ConstantFoldConvertToInt(const APFloat &Val, 1350 bool roundTowardZero, Type *Ty) { 1351 // All of these conversion intrinsics form an integer of at most 64bits. 1352 unsigned ResultWidth = Ty->getIntegerBitWidth(); 1353 assert(ResultWidth <= 64 && 1354 "Can only constant fold conversions to 64 and 32 bit ints"); 1355 1356 uint64_t UIntVal; 1357 bool isExact = false; 1358 APFloat::roundingMode mode = roundTowardZero? APFloat::rmTowardZero 1359 : APFloat::rmNearestTiesToEven; 1360 APFloat::opStatus status = Val.convertToInteger(&UIntVal, ResultWidth, 1361 /*isSigned=*/true, mode, 1362 &isExact); 1363 if (status != APFloat::opOK && status != APFloat::opInexact) 1364 return nullptr; 1365 return ConstantInt::get(Ty, UIntVal, /*isSigned=*/true); 1366} 1367 1368static double getValueAsDouble(ConstantFP *Op) { 1369 Type *Ty = Op->getType(); 1370 1371 if (Ty->isFloatTy()) 1372 return Op->getValueAPF().convertToFloat(); 1373 1374 if (Ty->isDoubleTy()) 1375 return Op->getValueAPF().convertToDouble(); 1376 1377 bool unused; 1378 APFloat APF = Op->getValueAPF(); 1379 APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); 1380 return APF.convertToDouble(); 1381} 1382 1383static Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, 1384 Type *Ty, ArrayRef<Constant *> Operands, 1385 const TargetLibraryInfo *TLI) { 1386 if (Operands.size() == 1) { 1387 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { 1388 if (IntrinsicID == Intrinsic::convert_to_fp16) { 1389 APFloat Val(Op->getValueAPF()); 1390 1391 bool lost = false; 1392 Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost); 1393 1394 return ConstantInt::get(Ty->getContext(), Val.bitcastToAPInt()); 1395 } 1396 1397 if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) 1398 return nullptr; 1399 1400 if (IntrinsicID == Intrinsic::round) { 1401 APFloat V = Op->getValueAPF(); 1402 V.roundToIntegral(APFloat::rmNearestTiesToAway); 1403 return ConstantFP::get(Ty->getContext(), V); 1404 } 1405 1406 /// We only fold functions with finite arguments. Folding NaN and inf is 1407 /// likely to be aborted with an exception anyway, and some host libms 1408 /// have known errors raising exceptions. 1409 if (Op->getValueAPF().isNaN() || Op->getValueAPF().isInfinity()) 1410 return nullptr; 1411 1412 /// Currently APFloat versions of these functions do not exist, so we use 1413 /// the host native double versions. Float versions are not called 1414 /// directly but for all these it is true (float)(f((double)arg)) == 1415 /// f(arg). Long double not supported yet. 1416 double V = getValueAsDouble(Op); 1417 1418 switch (IntrinsicID) { 1419 default: break; 1420 case Intrinsic::fabs: 1421 return ConstantFoldFP(fabs, V, Ty); 1422#if HAVE_LOG2 1423 case Intrinsic::log2: 1424 return ConstantFoldFP(log2, V, Ty); 1425#endif 1426#if HAVE_LOG 1427 case Intrinsic::log: 1428 return ConstantFoldFP(log, V, Ty); 1429#endif 1430#if HAVE_LOG10 1431 case Intrinsic::log10: 1432 return ConstantFoldFP(log10, V, Ty); 1433#endif 1434#if HAVE_EXP 1435 case Intrinsic::exp: 1436 return ConstantFoldFP(exp, V, Ty); 1437#endif 1438#if HAVE_EXP2 1439 case Intrinsic::exp2: 1440 return ConstantFoldFP(exp2, V, Ty); 1441#endif 1442 case Intrinsic::floor: 1443 return ConstantFoldFP(floor, V, Ty); 1444 case Intrinsic::ceil: 1445 return ConstantFoldFP(ceil, V, Ty); 1446 } 1447 1448 if (!TLI) 1449 return nullptr; 1450 1451 switch (Name[0]) { 1452 case 'a': 1453 if (Name == "acos" && TLI->has(LibFunc::acos)) 1454 return ConstantFoldFP(acos, V, Ty); 1455 else if (Name == "asin" && TLI->has(LibFunc::asin)) 1456 return ConstantFoldFP(asin, V, Ty); 1457 else if (Name == "atan" && TLI->has(LibFunc::atan)) 1458 return ConstantFoldFP(atan, V, Ty); 1459 break; 1460 case 'c': 1461 if (Name == "ceil" && TLI->has(LibFunc::ceil)) 1462 return ConstantFoldFP(ceil, V, Ty); 1463 else if (Name == "cos" && TLI->has(LibFunc::cos)) 1464 return ConstantFoldFP(cos, V, Ty); 1465 else if (Name == "cosh" && TLI->has(LibFunc::cosh)) 1466 return ConstantFoldFP(cosh, V, Ty); 1467 else if (Name == "cosf" && TLI->has(LibFunc::cosf)) 1468 return ConstantFoldFP(cos, V, Ty); 1469 break; 1470 case 'e': 1471 if (Name == "exp" && TLI->has(LibFunc::exp)) 1472 return ConstantFoldFP(exp, V, Ty); 1473 1474 if (Name == "exp2" && TLI->has(LibFunc::exp2)) { 1475 // Constant fold exp2(x) as pow(2,x) in case the host doesn't have a 1476 // C99 library. 1477 return ConstantFoldBinaryFP(pow, 2.0, V, Ty); 1478 } 1479 break; 1480 case 'f': 1481 if (Name == "fabs" && TLI->has(LibFunc::fabs)) 1482 return ConstantFoldFP(fabs, V, Ty); 1483 else if (Name == "floor" && TLI->has(LibFunc::floor)) 1484 return ConstantFoldFP(floor, V, Ty); 1485 break; 1486 case 'l': 1487 if (Name == "log" && V > 0 && TLI->has(LibFunc::log)) 1488 return ConstantFoldFP(log, V, Ty); 1489 else if (Name == "log10" && V > 0 && TLI->has(LibFunc::log10)) 1490 return ConstantFoldFP(log10, V, Ty); 1491 else if (IntrinsicID == Intrinsic::sqrt && 1492 (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy())) { 1493 if (V >= -0.0) 1494 return ConstantFoldFP(sqrt, V, Ty); 1495 else // Undefined 1496 return Constant::getNullValue(Ty); 1497 } 1498 break; 1499 case 's': 1500 if (Name == "sin" && TLI->has(LibFunc::sin)) 1501 return ConstantFoldFP(sin, V, Ty); 1502 else if (Name == "sinh" && TLI->has(LibFunc::sinh)) 1503 return ConstantFoldFP(sinh, V, Ty); 1504 else if (Name == "sqrt" && V >= 0 && TLI->has(LibFunc::sqrt)) 1505 return ConstantFoldFP(sqrt, V, Ty); 1506 else if (Name == "sqrtf" && V >= 0 && TLI->has(LibFunc::sqrtf)) 1507 return ConstantFoldFP(sqrt, V, Ty); 1508 else if (Name == "sinf" && TLI->has(LibFunc::sinf)) 1509 return ConstantFoldFP(sin, V, Ty); 1510 break; 1511 case 't': 1512 if (Name == "tan" && TLI->has(LibFunc::tan)) 1513 return ConstantFoldFP(tan, V, Ty); 1514 else if (Name == "tanh" && TLI->has(LibFunc::tanh)) 1515 return ConstantFoldFP(tanh, V, Ty); 1516 break; 1517 default: 1518 break; 1519 } 1520 return nullptr; 1521 } 1522 1523 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { 1524 switch (IntrinsicID) { 1525 case Intrinsic::bswap: 1526 return ConstantInt::get(Ty->getContext(), Op->getValue().byteSwap()); 1527 case Intrinsic::ctpop: 1528 return ConstantInt::get(Ty, Op->getValue().countPopulation()); 1529 case Intrinsic::convert_from_fp16: { 1530 APFloat Val(APFloat::IEEEhalf, Op->getValue()); 1531 1532 bool lost = false; 1533 APFloat::opStatus status = 1534 Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost); 1535 1536 // Conversion is always precise. 1537 (void)status; 1538 assert(status == APFloat::opOK && !lost && 1539 "Precision lost during fp16 constfolding"); 1540 1541 return ConstantFP::get(Ty->getContext(), Val); 1542 } 1543 default: 1544 return nullptr; 1545 } 1546 } 1547 1548 // Support ConstantVector in case we have an Undef in the top. 1549 if (isa<ConstantVector>(Operands[0]) || 1550 isa<ConstantDataVector>(Operands[0])) { 1551 Constant *Op = cast<Constant>(Operands[0]); 1552 switch (IntrinsicID) { 1553 default: break; 1554 case Intrinsic::x86_sse_cvtss2si: 1555 case Intrinsic::x86_sse_cvtss2si64: 1556 case Intrinsic::x86_sse2_cvtsd2si: 1557 case Intrinsic::x86_sse2_cvtsd2si64: 1558 if (ConstantFP *FPOp = 1559 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U))) 1560 return ConstantFoldConvertToInt(FPOp->getValueAPF(), 1561 /*roundTowardZero=*/false, Ty); 1562 case Intrinsic::x86_sse_cvttss2si: 1563 case Intrinsic::x86_sse_cvttss2si64: 1564 case Intrinsic::x86_sse2_cvttsd2si: 1565 case Intrinsic::x86_sse2_cvttsd2si64: 1566 if (ConstantFP *FPOp = 1567 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U))) 1568 return ConstantFoldConvertToInt(FPOp->getValueAPF(), 1569 /*roundTowardZero=*/true, Ty); 1570 } 1571 } 1572 1573 if (isa<UndefValue>(Operands[0])) { 1574 if (IntrinsicID == Intrinsic::bswap) 1575 return Operands[0]; 1576 return nullptr; 1577 } 1578 1579 return nullptr; 1580 } 1581 1582 if (Operands.size() == 2) { 1583 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1584 if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) 1585 return nullptr; 1586 double Op1V = getValueAsDouble(Op1); 1587 1588 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1589 if (Op2->getType() != Op1->getType()) 1590 return nullptr; 1591 1592 double Op2V = getValueAsDouble(Op2); 1593 if (IntrinsicID == Intrinsic::pow) { 1594 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1595 } 1596 if (IntrinsicID == Intrinsic::copysign) { 1597 APFloat V1 = Op1->getValueAPF(); 1598 APFloat V2 = Op2->getValueAPF(); 1599 V1.copySign(V2); 1600 return ConstantFP::get(Ty->getContext(), V1); 1601 } 1602 if (!TLI) 1603 return nullptr; 1604 if (Name == "pow" && TLI->has(LibFunc::pow)) 1605 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1606 if (Name == "fmod" && TLI->has(LibFunc::fmod)) 1607 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty); 1608 if (Name == "atan2" && TLI->has(LibFunc::atan2)) 1609 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty); 1610 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { 1611 if (IntrinsicID == Intrinsic::powi && Ty->isHalfTy()) 1612 return ConstantFP::get(Ty->getContext(), 1613 APFloat((float)std::pow((float)Op1V, 1614 (int)Op2C->getZExtValue()))); 1615 if (IntrinsicID == Intrinsic::powi && Ty->isFloatTy()) 1616 return ConstantFP::get(Ty->getContext(), 1617 APFloat((float)std::pow((float)Op1V, 1618 (int)Op2C->getZExtValue()))); 1619 if (IntrinsicID == Intrinsic::powi && Ty->isDoubleTy()) 1620 return ConstantFP::get(Ty->getContext(), 1621 APFloat((double)std::pow((double)Op1V, 1622 (int)Op2C->getZExtValue()))); 1623 } 1624 return nullptr; 1625 } 1626 1627 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) { 1628 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) { 1629 switch (IntrinsicID) { 1630 default: break; 1631 case Intrinsic::sadd_with_overflow: 1632 case Intrinsic::uadd_with_overflow: 1633 case Intrinsic::ssub_with_overflow: 1634 case Intrinsic::usub_with_overflow: 1635 case Intrinsic::smul_with_overflow: 1636 case Intrinsic::umul_with_overflow: { 1637 APInt Res; 1638 bool Overflow; 1639 switch (IntrinsicID) { 1640 default: llvm_unreachable("Invalid case"); 1641 case Intrinsic::sadd_with_overflow: 1642 Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow); 1643 break; 1644 case Intrinsic::uadd_with_overflow: 1645 Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow); 1646 break; 1647 case Intrinsic::ssub_with_overflow: 1648 Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow); 1649 break; 1650 case Intrinsic::usub_with_overflow: 1651 Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow); 1652 break; 1653 case Intrinsic::smul_with_overflow: 1654 Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow); 1655 break; 1656 case Intrinsic::umul_with_overflow: 1657 Res = Op1->getValue().umul_ov(Op2->getValue(), Overflow); 1658 break; 1659 } 1660 Constant *Ops[] = { 1661 ConstantInt::get(Ty->getContext(), Res), 1662 ConstantInt::get(Type::getInt1Ty(Ty->getContext()), Overflow) 1663 }; 1664 return ConstantStruct::get(cast<StructType>(Ty), Ops); 1665 } 1666 case Intrinsic::cttz: 1667 if (Op2->isOne() && Op1->isZero()) // cttz(0, 1) is undef. 1668 return UndefValue::get(Ty); 1669 return ConstantInt::get(Ty, Op1->getValue().countTrailingZeros()); 1670 case Intrinsic::ctlz: 1671 if (Op2->isOne() && Op1->isZero()) // ctlz(0, 1) is undef. 1672 return UndefValue::get(Ty); 1673 return ConstantInt::get(Ty, Op1->getValue().countLeadingZeros()); 1674 } 1675 } 1676 1677 return nullptr; 1678 } 1679 return nullptr; 1680 } 1681 1682 if (Operands.size() != 3) 1683 return nullptr; 1684 1685 if (const ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1686 if (const ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1687 if (const ConstantFP *Op3 = dyn_cast<ConstantFP>(Operands[2])) { 1688 switch (IntrinsicID) { 1689 default: break; 1690 case Intrinsic::fma: 1691 case Intrinsic::fmuladd: { 1692 APFloat V = Op1->getValueAPF(); 1693 APFloat::opStatus s = V.fusedMultiplyAdd(Op2->getValueAPF(), 1694 Op3->getValueAPF(), 1695 APFloat::rmNearestTiesToEven); 1696 if (s != APFloat::opInvalidOp) 1697 return ConstantFP::get(Ty->getContext(), V); 1698 1699 return nullptr; 1700 } 1701 } 1702 } 1703 } 1704 } 1705 1706 return nullptr; 1707} 1708 1709static Constant *ConstantFoldVectorCall(StringRef Name, unsigned IntrinsicID, 1710 VectorType *VTy, 1711 ArrayRef<Constant *> Operands, 1712 const TargetLibraryInfo *TLI) { 1713 SmallVector<Constant *, 4> Result(VTy->getNumElements()); 1714 SmallVector<Constant *, 4> Lane(Operands.size()); 1715 Type *Ty = VTy->getElementType(); 1716 1717 for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) { 1718 // Gather a column of constants. 1719 for (unsigned J = 0, JE = Operands.size(); J != JE; ++J) { 1720 Constant *Agg = Operands[J]->getAggregateElement(I); 1721 if (!Agg) 1722 return nullptr; 1723 1724 Lane[J] = Agg; 1725 } 1726 1727 // Use the regular scalar folding to simplify this column. 1728 Constant *Folded = ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI); 1729 if (!Folded) 1730 return nullptr; 1731 Result[I] = Folded; 1732 } 1733 1734 return ConstantVector::get(Result); 1735} 1736 1737/// ConstantFoldCall - Attempt to constant fold a call to the specified function 1738/// with the specified arguments, returning null if unsuccessful. 1739Constant * 1740llvm::ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands, 1741 const TargetLibraryInfo *TLI) { 1742 if (!F->hasName()) 1743 return nullptr; 1744 StringRef Name = F->getName(); 1745 1746 Type *Ty = F->getReturnType(); 1747 1748 if (VectorType *VTy = dyn_cast<VectorType>(Ty)) 1749 return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands, TLI); 1750 1751 return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI); 1752} 1753