ConstantFolding.cpp revision b36f2f729d30b0e535ebaac9119ee65f4214ea1d
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/GlobalVariable.h" 29#include "llvm/IR/Instructions.h" 30#include "llvm/IR/Intrinsics.h" 31#include "llvm/IR/Operator.h" 32#include "llvm/Support/ErrorHandling.h" 33#include "llvm/Support/FEnv.h" 34#include "llvm/Support/GetElementPtrTypeIterator.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 == 0) 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 == 0) 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 == 0) 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 Offset.clearAllBits(); 228 return true; 229 } 230 231 // Otherwise, if this isn't a constant expr, bail out. 232 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 233 if (!CE) return false; 234 235 // Look through ptr->int and ptr->ptr casts. 236 if (CE->getOpcode() == Instruction::PtrToInt || 237 CE->getOpcode() == Instruction::BitCast) 238 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD); 239 240 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5) 241 if (GEPOperator *GEP = dyn_cast<GEPOperator>(CE)) { 242 // If the base isn't a global+constant, we aren't either. 243 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD)) 244 return false; 245 246 // Otherwise, add any offset that our operands provide. 247 return GEP->accumulateConstantOffset(TD, Offset); 248 } 249 250 return false; 251} 252 253/// ReadDataFromGlobal - Recursive helper to read bits out of global. C is the 254/// constant being copied out of. ByteOffset is an offset into C. CurPtr is the 255/// pointer to copy results into and BytesLeft is the number of bytes left in 256/// the CurPtr buffer. TD is the target data. 257static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset, 258 unsigned char *CurPtr, unsigned BytesLeft, 259 const DataLayout &TD) { 260 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) && 261 "Out of range access"); 262 263 // If this element is zero or undefined, we can just return since *CurPtr is 264 // zero initialized. 265 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C)) 266 return true; 267 268 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 269 if (CI->getBitWidth() > 64 || 270 (CI->getBitWidth() & 7) != 0) 271 return false; 272 273 uint64_t Val = CI->getZExtValue(); 274 unsigned IntBytes = unsigned(CI->getBitWidth()/8); 275 276 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) { 277 int n = ByteOffset; 278 if (!TD.isLittleEndian()) 279 n = IntBytes - n - 1; 280 CurPtr[i] = (unsigned char)(Val >> (n * 8)); 281 ++ByteOffset; 282 } 283 return true; 284 } 285 286 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) { 287 if (CFP->getType()->isDoubleTy()) { 288 C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD); 289 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 290 } 291 if (CFP->getType()->isFloatTy()){ 292 C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD); 293 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 294 } 295 if (CFP->getType()->isHalfTy()){ 296 C = FoldBitCast(C, Type::getInt16Ty(C->getContext()), TD); 297 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 298 } 299 return false; 300 } 301 302 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 303 const StructLayout *SL = TD.getStructLayout(CS->getType()); 304 unsigned Index = SL->getElementContainingOffset(ByteOffset); 305 uint64_t CurEltOffset = SL->getElementOffset(Index); 306 ByteOffset -= CurEltOffset; 307 308 while (1) { 309 // If the element access is to the element itself and not to tail padding, 310 // read the bytes from the element. 311 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType()); 312 313 if (ByteOffset < EltSize && 314 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr, 315 BytesLeft, TD)) 316 return false; 317 318 ++Index; 319 320 // Check to see if we read from the last struct element, if so we're done. 321 if (Index == CS->getType()->getNumElements()) 322 return true; 323 324 // If we read all of the bytes we needed from this element we're done. 325 uint64_t NextEltOffset = SL->getElementOffset(Index); 326 327 if (BytesLeft <= NextEltOffset-CurEltOffset-ByteOffset) 328 return true; 329 330 // Move to the next element of the struct. 331 CurPtr += NextEltOffset-CurEltOffset-ByteOffset; 332 BytesLeft -= NextEltOffset-CurEltOffset-ByteOffset; 333 ByteOffset = 0; 334 CurEltOffset = NextEltOffset; 335 } 336 // not reached. 337 } 338 339 if (isa<ConstantArray>(C) || isa<ConstantVector>(C) || 340 isa<ConstantDataSequential>(C)) { 341 Type *EltTy = cast<SequentialType>(C->getType())->getElementType(); 342 uint64_t EltSize = TD.getTypeAllocSize(EltTy); 343 uint64_t Index = ByteOffset / EltSize; 344 uint64_t Offset = ByteOffset - Index * EltSize; 345 uint64_t NumElts; 346 if (ArrayType *AT = dyn_cast<ArrayType>(C->getType())) 347 NumElts = AT->getNumElements(); 348 else 349 NumElts = cast<VectorType>(C->getType())->getNumElements(); 350 351 for (; Index != NumElts; ++Index) { 352 if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr, 353 BytesLeft, TD)) 354 return false; 355 356 uint64_t BytesWritten = EltSize - Offset; 357 assert(BytesWritten <= EltSize && "Not indexing into this element?"); 358 if (BytesWritten >= BytesLeft) 359 return true; 360 361 Offset = 0; 362 BytesLeft -= BytesWritten; 363 CurPtr += BytesWritten; 364 } 365 return true; 366 } 367 368 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 369 if (CE->getOpcode() == Instruction::IntToPtr && 370 CE->getOperand(0)->getType() == TD.getIntPtrType(CE->getContext())) { 371 return ReadDataFromGlobal(CE->getOperand(0), ByteOffset, CurPtr, 372 BytesLeft, TD); 373 } 374 } 375 376 // Otherwise, unknown initializer type. 377 return false; 378} 379 380static Constant *FoldReinterpretLoadFromConstPtr(Constant *C, 381 const DataLayout &TD) { 382 Type *LoadTy = cast<PointerType>(C->getType())->getElementType(); 383 IntegerType *IntType = dyn_cast<IntegerType>(LoadTy); 384 385 // If this isn't an integer load we can't fold it directly. 386 if (!IntType) { 387 // If this is a float/double load, we can try folding it as an int32/64 load 388 // and then bitcast the result. This can be useful for union cases. Note 389 // that address spaces don't matter here since we're not going to result in 390 // an actual new load. 391 Type *MapTy; 392 if (LoadTy->isHalfTy()) 393 MapTy = Type::getInt16PtrTy(C->getContext()); 394 else if (LoadTy->isFloatTy()) 395 MapTy = Type::getInt32PtrTy(C->getContext()); 396 else if (LoadTy->isDoubleTy()) 397 MapTy = Type::getInt64PtrTy(C->getContext()); 398 else if (LoadTy->isVectorTy()) { 399 MapTy = IntegerType::get(C->getContext(), 400 TD.getTypeAllocSizeInBits(LoadTy)); 401 MapTy = PointerType::getUnqual(MapTy); 402 } else 403 return 0; 404 405 C = FoldBitCast(C, MapTy, TD); 406 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD)) 407 return FoldBitCast(Res, LoadTy, TD); 408 return 0; 409 } 410 411 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8; 412 if (BytesLoaded > 32 || BytesLoaded == 0) return 0; 413 414 GlobalValue *GVal; 415 APInt Offset(TD.getPointerSizeInBits(), 0); 416 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD)) 417 return 0; 418 419 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal); 420 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() || 421 !GV->getInitializer()->getType()->isSized()) 422 return 0; 423 424 // If we're loading off the beginning of the global, some bytes may be valid, 425 // but we don't try to handle this. 426 if (Offset.isNegative()) return 0; 427 428 // If we're not accessing anything in this constant, the result is undefined. 429 if (Offset.getZExtValue() >= 430 TD.getTypeAllocSize(GV->getInitializer()->getType())) 431 return UndefValue::get(IntType); 432 433 unsigned char RawBytes[32] = {0}; 434 if (!ReadDataFromGlobal(GV->getInitializer(), Offset.getZExtValue(), RawBytes, 435 BytesLoaded, TD)) 436 return 0; 437 438 APInt ResultVal = APInt(IntType->getBitWidth(), 0); 439 if (TD.isLittleEndian()) { 440 ResultVal = RawBytes[BytesLoaded - 1]; 441 for (unsigned i = 1; i != BytesLoaded; ++i) { 442 ResultVal <<= 8; 443 ResultVal |= RawBytes[BytesLoaded - 1 - i]; 444 } 445 } else { 446 ResultVal = RawBytes[0]; 447 for (unsigned i = 1; i != BytesLoaded; ++i) { 448 ResultVal <<= 8; 449 ResultVal |= RawBytes[i]; 450 } 451 } 452 453 return ConstantInt::get(IntType->getContext(), ResultVal); 454} 455 456/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 457/// produce if it is constant and determinable. If this is not determinable, 458/// return null. 459Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, 460 const DataLayout *TD) { 461 // First, try the easy cases: 462 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 463 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 464 return GV->getInitializer(); 465 466 // If the loaded value isn't a constant expr, we can't handle it. 467 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 468 if (!CE) 469 return 0; 470 471 if (CE->getOpcode() == Instruction::GetElementPtr) { 472 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) { 473 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 474 if (Constant *V = 475 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) 476 return V; 477 } 478 } 479 } 480 481 // Instead of loading constant c string, use corresponding integer value 482 // directly if string length is small enough. 483 StringRef Str; 484 if (TD && getConstantStringInfo(CE, Str) && !Str.empty()) { 485 unsigned StrLen = Str.size(); 486 Type *Ty = cast<PointerType>(CE->getType())->getElementType(); 487 unsigned NumBits = Ty->getPrimitiveSizeInBits(); 488 // Replace load with immediate integer if the result is an integer or fp 489 // value. 490 if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 && 491 (isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) { 492 APInt StrVal(NumBits, 0); 493 APInt SingleChar(NumBits, 0); 494 if (TD->isLittleEndian()) { 495 for (signed i = StrLen-1; i >= 0; i--) { 496 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 497 StrVal = (StrVal << 8) | SingleChar; 498 } 499 } else { 500 for (unsigned i = 0; i < StrLen; i++) { 501 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 502 StrVal = (StrVal << 8) | SingleChar; 503 } 504 // Append NULL at the end. 505 SingleChar = 0; 506 StrVal = (StrVal << 8) | SingleChar; 507 } 508 509 Constant *Res = ConstantInt::get(CE->getContext(), StrVal); 510 if (Ty->isFloatingPointTy()) 511 Res = ConstantExpr::getBitCast(Res, Ty); 512 return Res; 513 } 514 } 515 516 // If this load comes from anywhere in a constant global, and if the global 517 // is all undef or zero, we know what it loads. 518 if (GlobalVariable *GV = 519 dyn_cast<GlobalVariable>(GetUnderlyingObject(CE, TD))) { 520 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 521 Type *ResTy = cast<PointerType>(C->getType())->getElementType(); 522 if (GV->getInitializer()->isNullValue()) 523 return Constant::getNullValue(ResTy); 524 if (isa<UndefValue>(GV->getInitializer())) 525 return UndefValue::get(ResTy); 526 } 527 } 528 529 // Try hard to fold loads from bitcasted strange and non-type-safe things. 530 if (TD) 531 return FoldReinterpretLoadFromConstPtr(CE, *TD); 532 return 0; 533} 534 535static Constant *ConstantFoldLoadInst(const LoadInst *LI, const DataLayout *TD){ 536 if (LI->isVolatile()) return 0; 537 538 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0))) 539 return ConstantFoldLoadFromConstPtr(C, TD); 540 541 return 0; 542} 543 544/// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression. 545/// Attempt to symbolically evaluate the result of a binary operator merging 546/// these together. If target data info is available, it is provided as DL, 547/// otherwise DL is null. 548static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, 549 Constant *Op1, const DataLayout *DL){ 550 // SROA 551 552 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl. 553 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute 554 // bits. 555 556 557 if (Opc == Instruction::And && DL) { 558 unsigned BitWidth = DL->getTypeSizeInBits(Op0->getType()->getScalarType()); 559 APInt KnownZero0(BitWidth, 0), KnownOne0(BitWidth, 0); 560 APInt KnownZero1(BitWidth, 0), KnownOne1(BitWidth, 0); 561 ComputeMaskedBits(Op0, KnownZero0, KnownOne0, DL); 562 ComputeMaskedBits(Op1, KnownZero1, KnownOne1, DL); 563 if ((KnownOne1 | KnownZero0).isAllOnesValue()) { 564 // All the bits of Op0 that the 'and' could be masking are already zero. 565 return Op0; 566 } 567 if ((KnownOne0 | KnownZero1).isAllOnesValue()) { 568 // All the bits of Op1 that the 'and' could be masking are already zero. 569 return Op1; 570 } 571 572 APInt KnownZero = KnownZero0 | KnownZero1; 573 APInt KnownOne = KnownOne0 & KnownOne1; 574 if ((KnownZero | KnownOne).isAllOnesValue()) { 575 return ConstantInt::get(Op0->getType(), KnownOne); 576 } 577 } 578 579 // If the constant expr is something like &A[123] - &A[4].f, fold this into a 580 // constant. This happens frequently when iterating over a global array. 581 if (Opc == Instruction::Sub && DL) { 582 GlobalValue *GV1, *GV2; 583 unsigned PtrSize = DL->getPointerSizeInBits(); 584 unsigned OpSize = DL->getTypeSizeInBits(Op0->getType()); 585 APInt Offs1(PtrSize, 0), Offs2(PtrSize, 0); 586 587 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *DL)) 588 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *DL) && 589 GV1 == GV2) { 590 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow. 591 // PtrToInt may change the bitwidth so we have convert to the right size 592 // first. 593 return ConstantInt::get(Op0->getType(), Offs1.zextOrTrunc(OpSize) - 594 Offs2.zextOrTrunc(OpSize)); 595 } 596 } 597 598 return 0; 599} 600 601/// CastGEPIndices - If array indices are not pointer-sized integers, 602/// explicitly cast them so that they aren't implicitly casted by the 603/// getelementptr. 604static Constant *CastGEPIndices(ArrayRef<Constant *> Ops, 605 Type *ResultTy, const DataLayout *TD, 606 const TargetLibraryInfo *TLI) { 607 if (!TD) return 0; 608 Type *IntPtrTy = TD->getIntPtrType(ResultTy->getContext()); 609 610 bool Any = false; 611 SmallVector<Constant*, 32> NewIdxs; 612 for (unsigned i = 1, e = Ops.size(); i != e; ++i) { 613 if ((i == 1 || 614 !isa<StructType>(GetElementPtrInst::getIndexedType( 615 Ops[0]->getType(), 616 Ops.slice(1, i - 1)))) && 617 Ops[i]->getType() != IntPtrTy) { 618 Any = true; 619 NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i], 620 true, 621 IntPtrTy, 622 true), 623 Ops[i], IntPtrTy)); 624 } else 625 NewIdxs.push_back(Ops[i]); 626 } 627 628 if (!Any) 629 return 0; 630 631 Constant *C = ConstantExpr::getGetElementPtr(Ops[0], NewIdxs); 632 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 633 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI)) 634 C = Folded; 635 } 636 637 return C; 638} 639 640/// Strip the pointer casts, but preserve the address space information. 641static Constant* StripPtrCastKeepAS(Constant* Ptr) { 642 assert(Ptr->getType()->isPointerTy() && "Not a pointer type"); 643 PointerType *OldPtrTy = cast<PointerType>(Ptr->getType()); 644 Ptr = cast<Constant>(Ptr->stripPointerCasts()); 645 PointerType *NewPtrTy = cast<PointerType>(Ptr->getType()); 646 647 // Preserve the address space number of the pointer. 648 if (NewPtrTy->getAddressSpace() != OldPtrTy->getAddressSpace()) { 649 NewPtrTy = NewPtrTy->getElementType()->getPointerTo( 650 OldPtrTy->getAddressSpace()); 651 Ptr = ConstantExpr::getBitCast(Ptr, NewPtrTy); 652 } 653 return Ptr; 654} 655 656/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP 657/// constant expression, do so. 658static Constant *SymbolicallyEvaluateGEP(ArrayRef<Constant *> Ops, 659 Type *ResultTy, const DataLayout *TD, 660 const TargetLibraryInfo *TLI) { 661 Constant *Ptr = Ops[0]; 662 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized() || 663 !Ptr->getType()->isPointerTy()) 664 return 0; 665 666 Type *IntPtrTy = TD->getIntPtrType(Ptr->getContext()); 667 668 // If this is a constant expr gep that is effectively computing an 669 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' 670 for (unsigned i = 1, e = Ops.size(); i != e; ++i) 671 if (!isa<ConstantInt>(Ops[i])) { 672 673 // If this is "gep i8* Ptr, (sub 0, V)", fold this as: 674 // "inttoptr (sub (ptrtoint Ptr), V)" 675 if (Ops.size() == 2 && 676 cast<PointerType>(ResultTy)->getElementType()->isIntegerTy(8)) { 677 ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[1]); 678 assert((CE == 0 || CE->getType() == IntPtrTy) && 679 "CastGEPIndices didn't canonicalize index types!"); 680 if (CE && CE->getOpcode() == Instruction::Sub && 681 CE->getOperand(0)->isNullValue()) { 682 Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType()); 683 Res = ConstantExpr::getSub(Res, CE->getOperand(1)); 684 Res = ConstantExpr::getIntToPtr(Res, ResultTy); 685 if (ConstantExpr *ResCE = dyn_cast<ConstantExpr>(Res)) 686 Res = ConstantFoldConstantExpression(ResCE, TD, TLI); 687 return Res; 688 } 689 } 690 return 0; 691 } 692 693 unsigned BitWidth = TD->getTypeSizeInBits(IntPtrTy); 694 APInt Offset = 695 APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(), 696 makeArrayRef((Value *const*) 697 Ops.data() + 1, 698 Ops.size() - 1))); 699 Ptr = StripPtrCastKeepAS(Ptr); 700 701 // If this is a GEP of a GEP, fold it all into a single GEP. 702 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) { 703 SmallVector<Value *, 4> NestedOps(GEP->op_begin() + 1, GEP->op_end()); 704 705 // Do not try the incorporate the sub-GEP if some index is not a number. 706 bool AllConstantInt = true; 707 for (unsigned i = 0, e = NestedOps.size(); i != e; ++i) 708 if (!isa<ConstantInt>(NestedOps[i])) { 709 AllConstantInt = false; 710 break; 711 } 712 if (!AllConstantInt) 713 break; 714 715 Ptr = cast<Constant>(GEP->getOperand(0)); 716 Offset += APInt(BitWidth, 717 TD->getIndexedOffset(Ptr->getType(), NestedOps)); 718 Ptr = StripPtrCastKeepAS(Ptr); 719 } 720 721 // If the base value for this address is a literal integer value, fold the 722 // getelementptr to the resulting integer value casted to the pointer type. 723 APInt BasePtr(BitWidth, 0); 724 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) { 725 if (CE->getOpcode() == Instruction::IntToPtr) { 726 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) 727 BasePtr = Base->getValue().zextOrTrunc(BitWidth); 728 } 729 } 730 731 if (Ptr->isNullValue() || BasePtr != 0) { 732 Constant *C = ConstantInt::get(Ptr->getContext(), Offset + BasePtr); 733 return ConstantExpr::getIntToPtr(C, ResultTy); 734 } 735 736 // Otherwise form a regular getelementptr. Recompute the indices so that 737 // we eliminate over-indexing of the notional static type array bounds. 738 // This makes it easy to determine if the getelementptr is "inbounds". 739 // Also, this helps GlobalOpt do SROA on GlobalVariables. 740 Type *Ty = Ptr->getType(); 741 assert(Ty->isPointerTy() && "Forming regular GEP of non-pointer type"); 742 SmallVector<Constant*, 32> NewIdxs; 743 do { 744 if (SequentialType *ATy = dyn_cast<SequentialType>(Ty)) { 745 if (ATy->isPointerTy()) { 746 // The only pointer indexing we'll do is on the first index of the GEP. 747 if (!NewIdxs.empty()) 748 break; 749 750 // Only handle pointers to sized types, not pointers to functions. 751 if (!ATy->getElementType()->isSized()) 752 return 0; 753 } 754 755 // Determine which element of the array the offset points into. 756 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); 757 IntegerType *IntPtrTy = TD->getIntPtrType(Ty->getContext()); 758 if (ElemSize == 0) 759 // The element size is 0. This may be [0 x Ty]*, so just use a zero 760 // index for this level and proceed to the next level to see if it can 761 // accommodate the offset. 762 NewIdxs.push_back(ConstantInt::get(IntPtrTy, 0)); 763 else { 764 // The element size is non-zero divide the offset by the element 765 // size (rounding down), to compute the index at this level. 766 APInt NewIdx = Offset.udiv(ElemSize); 767 Offset -= NewIdx * ElemSize; 768 NewIdxs.push_back(ConstantInt::get(IntPtrTy, NewIdx)); 769 } 770 Ty = ATy->getElementType(); 771 } else if (StructType *STy = dyn_cast<StructType>(Ty)) { 772 // If we end up with an offset that isn't valid for this struct type, we 773 // can't re-form this GEP in a regular form, so bail out. The pointer 774 // operand likely went through casts that are necessary to make the GEP 775 // sensible. 776 const StructLayout &SL = *TD->getStructLayout(STy); 777 if (Offset.uge(SL.getSizeInBytes())) 778 break; 779 780 // Determine which field of the struct the offset points into. The 781 // getZExtValue is fine as we've already ensured that the offset is 782 // within the range representable by the StructLayout API. 783 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); 784 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 785 ElIdx)); 786 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); 787 Ty = STy->getTypeAtIndex(ElIdx); 788 } else { 789 // We've reached some non-indexable type. 790 break; 791 } 792 } while (Ty != cast<PointerType>(ResultTy)->getElementType()); 793 794 // If we haven't used up the entire offset by descending the static 795 // type, then the offset is pointing into the middle of an indivisible 796 // member, so we can't simplify it. 797 if (Offset != 0) 798 return 0; 799 800 // Create a GEP. 801 Constant *C = ConstantExpr::getGetElementPtr(Ptr, NewIdxs); 802 assert(cast<PointerType>(C->getType())->getElementType() == Ty && 803 "Computed GetElementPtr has unexpected type!"); 804 805 // If we ended up indexing a member with a type that doesn't match 806 // the type of what the original indices indexed, add a cast. 807 if (Ty != cast<PointerType>(ResultTy)->getElementType()) 808 C = FoldBitCast(C, ResultTy, *TD); 809 810 return C; 811} 812 813 814 815//===----------------------------------------------------------------------===// 816// Constant Folding public APIs 817//===----------------------------------------------------------------------===// 818 819/// ConstantFoldInstruction - Try to constant fold the specified instruction. 820/// If successful, the constant result is returned, if not, null is returned. 821/// Note that this fails if not all of the operands are constant. Otherwise, 822/// this function can only fail when attempting to fold instructions like loads 823/// and stores, which have no constant expression form. 824Constant *llvm::ConstantFoldInstruction(Instruction *I, 825 const DataLayout *TD, 826 const TargetLibraryInfo *TLI) { 827 // Handle PHI nodes quickly here... 828 if (PHINode *PN = dyn_cast<PHINode>(I)) { 829 Constant *CommonValue = 0; 830 831 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 832 Value *Incoming = PN->getIncomingValue(i); 833 // If the incoming value is undef then skip it. Note that while we could 834 // skip the value if it is equal to the phi node itself we choose not to 835 // because that would break the rule that constant folding only applies if 836 // all operands are constants. 837 if (isa<UndefValue>(Incoming)) 838 continue; 839 // If the incoming value is not a constant, then give up. 840 Constant *C = dyn_cast<Constant>(Incoming); 841 if (!C) 842 return 0; 843 // Fold the PHI's operands. 844 if (ConstantExpr *NewC = dyn_cast<ConstantExpr>(C)) 845 C = ConstantFoldConstantExpression(NewC, TD, TLI); 846 // If the incoming value is a different constant to 847 // the one we saw previously, then give up. 848 if (CommonValue && C != CommonValue) 849 return 0; 850 CommonValue = C; 851 } 852 853 854 // If we reach here, all incoming values are the same constant or undef. 855 return CommonValue ? CommonValue : UndefValue::get(PN->getType()); 856 } 857 858 // Scan the operand list, checking to see if they are all constants, if so, 859 // hand off to ConstantFoldInstOperands. 860 SmallVector<Constant*, 8> Ops; 861 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) { 862 Constant *Op = dyn_cast<Constant>(*i); 863 if (!Op) 864 return 0; // All operands not constant! 865 866 // Fold the Instruction's operands. 867 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(Op)) 868 Op = ConstantFoldConstantExpression(NewCE, TD, TLI); 869 870 Ops.push_back(Op); 871 } 872 873 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 874 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], 875 TD, TLI); 876 877 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 878 return ConstantFoldLoadInst(LI, TD); 879 880 if (InsertValueInst *IVI = dyn_cast<InsertValueInst>(I)) { 881 return ConstantExpr::getInsertValue( 882 cast<Constant>(IVI->getAggregateOperand()), 883 cast<Constant>(IVI->getInsertedValueOperand()), 884 IVI->getIndices()); 885 } 886 887 if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I)) { 888 return ConstantExpr::getExtractValue( 889 cast<Constant>(EVI->getAggregateOperand()), 890 EVI->getIndices()); 891 } 892 893 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops, TD, TLI); 894} 895 896static Constant * 897ConstantFoldConstantExpressionImpl(const ConstantExpr *CE, const DataLayout *TD, 898 const TargetLibraryInfo *TLI, 899 SmallPtrSet<ConstantExpr *, 4> &FoldedOps) { 900 SmallVector<Constant *, 8> Ops; 901 for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; 902 ++i) { 903 Constant *NewC = cast<Constant>(*i); 904 // Recursively fold the ConstantExpr's operands. If we have already folded 905 // a ConstantExpr, we don't have to process it again. 906 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC)) { 907 if (FoldedOps.insert(NewCE)) 908 NewC = ConstantFoldConstantExpressionImpl(NewCE, TD, TLI, FoldedOps); 909 } 910 Ops.push_back(NewC); 911 } 912 913 if (CE->isCompare()) 914 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1], 915 TD, TLI); 916 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), Ops, TD, TLI); 917} 918 919/// ConstantFoldConstantExpression - Attempt to fold the constant expression 920/// using the specified DataLayout. If successful, the constant result is 921/// result is returned, if not, null is returned. 922Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE, 923 const DataLayout *TD, 924 const TargetLibraryInfo *TLI) { 925 SmallPtrSet<ConstantExpr *, 4> FoldedOps; 926 return ConstantFoldConstantExpressionImpl(CE, TD, TLI, FoldedOps); 927} 928 929/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 930/// specified opcode and operands. If successful, the constant result is 931/// returned, if not, null is returned. Note that this function can fail when 932/// attempting to fold instructions like loads and stores, which have no 933/// constant expression form. 934/// 935/// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc 936/// information, due to only being passed an opcode and operands. Constant 937/// folding using this function strips this information. 938/// 939Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, 940 ArrayRef<Constant *> Ops, 941 const DataLayout *TD, 942 const TargetLibraryInfo *TLI) { 943 // Handle easy binops first. 944 if (Instruction::isBinaryOp(Opcode)) { 945 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) { 946 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD)) 947 return C; 948 } 949 950 return ConstantExpr::get(Opcode, Ops[0], Ops[1]); 951 } 952 953 switch (Opcode) { 954 default: return 0; 955 case Instruction::ICmp: 956 case Instruction::FCmp: llvm_unreachable("Invalid for compares"); 957 case Instruction::Call: 958 if (Function *F = dyn_cast<Function>(Ops.back())) 959 if (canConstantFoldCallTo(F)) 960 return ConstantFoldCall(F, Ops.slice(0, Ops.size() - 1), TLI); 961 return 0; 962 case Instruction::PtrToInt: 963 // If the input is a inttoptr, eliminate the pair. This requires knowing 964 // the width of a pointer, so it can't be done in ConstantExpr::getCast. 965 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 966 if (TD && CE->getOpcode() == Instruction::IntToPtr) { 967 Constant *Input = CE->getOperand(0); 968 unsigned InWidth = Input->getType()->getScalarSizeInBits(); 969 if (TD->getPointerSizeInBits() < InWidth) { 970 Constant *Mask = 971 ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth, 972 TD->getPointerSizeInBits())); 973 Input = ConstantExpr::getAnd(Input, Mask); 974 } 975 // Do a zext or trunc to get to the dest size. 976 return ConstantExpr::getIntegerCast(Input, DestTy, false); 977 } 978 } 979 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 980 case Instruction::IntToPtr: 981 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if 982 // the int size is >= the ptr size. This requires knowing the width of a 983 // pointer, so it can't be done in ConstantExpr::getCast. 984 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) 985 if (TD && 986 TD->getPointerSizeInBits() <= CE->getType()->getScalarSizeInBits() && 987 CE->getOpcode() == Instruction::PtrToInt) 988 return FoldBitCast(CE->getOperand(0), DestTy, *TD); 989 990 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 991 case Instruction::Trunc: 992 case Instruction::ZExt: 993 case Instruction::SExt: 994 case Instruction::FPTrunc: 995 case Instruction::FPExt: 996 case Instruction::UIToFP: 997 case Instruction::SIToFP: 998 case Instruction::FPToUI: 999 case Instruction::FPToSI: 1000 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 1001 case Instruction::BitCast: 1002 if (TD) 1003 return FoldBitCast(Ops[0], DestTy, *TD); 1004 return ConstantExpr::getBitCast(Ops[0], DestTy); 1005 case Instruction::Select: 1006 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); 1007 case Instruction::ExtractElement: 1008 return ConstantExpr::getExtractElement(Ops[0], Ops[1]); 1009 case Instruction::InsertElement: 1010 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); 1011 case Instruction::ShuffleVector: 1012 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); 1013 case Instruction::GetElementPtr: 1014 if (Constant *C = CastGEPIndices(Ops, DestTy, TD, TLI)) 1015 return C; 1016 if (Constant *C = SymbolicallyEvaluateGEP(Ops, DestTy, TD, TLI)) 1017 return C; 1018 1019 return ConstantExpr::getGetElementPtr(Ops[0], Ops.slice(1)); 1020 } 1021} 1022 1023/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 1024/// instruction (icmp/fcmp) with the specified operands. If it fails, it 1025/// returns a constant expression of the specified operands. 1026/// 1027Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, 1028 Constant *Ops0, Constant *Ops1, 1029 const DataLayout *TD, 1030 const TargetLibraryInfo *TLI) { 1031 // fold: icmp (inttoptr x), null -> icmp x, 0 1032 // fold: icmp (ptrtoint x), 0 -> icmp x, null 1033 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y 1034 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y 1035 // 1036 // ConstantExpr::getCompare cannot do this, because it doesn't have TD 1037 // around to know if bit truncation is happening. 1038 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) { 1039 if (TD && Ops1->isNullValue()) { 1040 Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 1041 if (CE0->getOpcode() == Instruction::IntToPtr) { 1042 // Convert the integer value to the right size to ensure we get the 1043 // proper extension or truncation. 1044 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), 1045 IntPtrTy, false); 1046 Constant *Null = Constant::getNullValue(C->getType()); 1047 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); 1048 } 1049 1050 // Only do this transformation if the int is intptrty in size, otherwise 1051 // there is a truncation or extension that we aren't modeling. 1052 if (CE0->getOpcode() == Instruction::PtrToInt && 1053 CE0->getType() == IntPtrTy) { 1054 Constant *C = CE0->getOperand(0); 1055 Constant *Null = Constant::getNullValue(C->getType()); 1056 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); 1057 } 1058 } 1059 1060 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) { 1061 if (TD && CE0->getOpcode() == CE1->getOpcode()) { 1062 Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 1063 1064 if (CE0->getOpcode() == Instruction::IntToPtr) { 1065 // Convert the integer value to the right size to ensure we get the 1066 // proper extension or truncation. 1067 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), 1068 IntPtrTy, false); 1069 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), 1070 IntPtrTy, false); 1071 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD, TLI); 1072 } 1073 1074 // Only do this transformation if the int is intptrty in size, otherwise 1075 // there is a truncation or extension that we aren't modeling. 1076 if ((CE0->getOpcode() == Instruction::PtrToInt && 1077 CE0->getType() == IntPtrTy && 1078 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) 1079 return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), 1080 CE1->getOperand(0), TD, TLI); 1081 } 1082 } 1083 1084 // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0) 1085 // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0) 1086 if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) && 1087 CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) { 1088 Constant *LHS = 1089 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1, 1090 TD, TLI); 1091 Constant *RHS = 1092 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1, 1093 TD, TLI); 1094 unsigned OpC = 1095 Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or; 1096 Constant *Ops[] = { LHS, RHS }; 1097 return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, TD, TLI); 1098 } 1099 } 1100 1101 return ConstantExpr::getCompare(Predicate, Ops0, Ops1); 1102} 1103 1104 1105/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 1106/// getelementptr constantexpr, return the constant value being addressed by the 1107/// constant expression, or null if something is funny and we can't decide. 1108Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, 1109 ConstantExpr *CE) { 1110 if (!CE->getOperand(1)->isNullValue()) 1111 return 0; // Do not allow stepping over the value! 1112 1113 // Loop over all of the operands, tracking down which value we are 1114 // addressing. 1115 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i) { 1116 C = C->getAggregateElement(CE->getOperand(i)); 1117 if (C == 0) 1118 return 0; 1119 } 1120 return C; 1121} 1122 1123/// ConstantFoldLoadThroughGEPIndices - Given a constant and getelementptr 1124/// indices (with an *implied* zero pointer index that is not in the list), 1125/// return the constant value being addressed by a virtual load, or null if 1126/// something is funny and we can't decide. 1127Constant *llvm::ConstantFoldLoadThroughGEPIndices(Constant *C, 1128 ArrayRef<Constant*> Indices) { 1129 // Loop over all of the operands, tracking down which value we are 1130 // addressing. 1131 for (unsigned i = 0, e = Indices.size(); i != e; ++i) { 1132 C = C->getAggregateElement(Indices[i]); 1133 if (C == 0) 1134 return 0; 1135 } 1136 return C; 1137} 1138 1139 1140//===----------------------------------------------------------------------===// 1141// Constant Folding for Calls 1142// 1143 1144/// canConstantFoldCallTo - Return true if its even possible to fold a call to 1145/// the specified function. 1146bool llvm::canConstantFoldCallTo(const Function *F) { 1147 switch (F->getIntrinsicID()) { 1148 case Intrinsic::fabs: 1149 case Intrinsic::log: 1150 case Intrinsic::log2: 1151 case Intrinsic::log10: 1152 case Intrinsic::exp: 1153 case Intrinsic::exp2: 1154 case Intrinsic::floor: 1155 case Intrinsic::sqrt: 1156 case Intrinsic::pow: 1157 case Intrinsic::powi: 1158 case Intrinsic::bswap: 1159 case Intrinsic::ctpop: 1160 case Intrinsic::ctlz: 1161 case Intrinsic::cttz: 1162 case Intrinsic::sadd_with_overflow: 1163 case Intrinsic::uadd_with_overflow: 1164 case Intrinsic::ssub_with_overflow: 1165 case Intrinsic::usub_with_overflow: 1166 case Intrinsic::smul_with_overflow: 1167 case Intrinsic::umul_with_overflow: 1168 case Intrinsic::convert_from_fp16: 1169 case Intrinsic::convert_to_fp16: 1170 case Intrinsic::x86_sse_cvtss2si: 1171 case Intrinsic::x86_sse_cvtss2si64: 1172 case Intrinsic::x86_sse_cvttss2si: 1173 case Intrinsic::x86_sse_cvttss2si64: 1174 case Intrinsic::x86_sse2_cvtsd2si: 1175 case Intrinsic::x86_sse2_cvtsd2si64: 1176 case Intrinsic::x86_sse2_cvttsd2si: 1177 case Intrinsic::x86_sse2_cvttsd2si64: 1178 return true; 1179 default: 1180 return false; 1181 case 0: break; 1182 } 1183 1184 if (!F->hasName()) 1185 return false; 1186 StringRef Name = F->getName(); 1187 1188 // In these cases, the check of the length is required. We don't want to 1189 // return true for a name like "cos\0blah" which strcmp would return equal to 1190 // "cos", but has length 8. 1191 switch (Name[0]) { 1192 default: return false; 1193 case 'a': 1194 return Name == "acos" || Name == "asin" || Name == "atan" || Name =="atan2"; 1195 case 'c': 1196 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; 1197 case 'e': 1198 return Name == "exp" || Name == "exp2"; 1199 case 'f': 1200 return Name == "fabs" || Name == "fmod" || Name == "floor"; 1201 case 'l': 1202 return Name == "log" || Name == "log10"; 1203 case 'p': 1204 return Name == "pow"; 1205 case 's': 1206 return Name == "sin" || Name == "sinh" || Name == "sqrt" || 1207 Name == "sinf" || Name == "sqrtf"; 1208 case 't': 1209 return Name == "tan" || Name == "tanh"; 1210 } 1211} 1212 1213static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 1214 Type *Ty) { 1215 sys::llvm_fenv_clearexcept(); 1216 V = NativeFP(V); 1217 if (sys::llvm_fenv_testexcept()) { 1218 sys::llvm_fenv_clearexcept(); 1219 return 0; 1220 } 1221 1222 if (Ty->isHalfTy()) { 1223 APFloat APF(V); 1224 bool unused; 1225 APF.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &unused); 1226 return ConstantFP::get(Ty->getContext(), APF); 1227 } 1228 if (Ty->isFloatTy()) 1229 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1230 if (Ty->isDoubleTy()) 1231 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1232 llvm_unreachable("Can only constant fold half/float/double"); 1233} 1234 1235static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), 1236 double V, double W, Type *Ty) { 1237 sys::llvm_fenv_clearexcept(); 1238 V = NativeFP(V, W); 1239 if (sys::llvm_fenv_testexcept()) { 1240 sys::llvm_fenv_clearexcept(); 1241 return 0; 1242 } 1243 1244 if (Ty->isHalfTy()) { 1245 APFloat APF(V); 1246 bool unused; 1247 APF.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &unused); 1248 return ConstantFP::get(Ty->getContext(), APF); 1249 } 1250 if (Ty->isFloatTy()) 1251 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1252 if (Ty->isDoubleTy()) 1253 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1254 llvm_unreachable("Can only constant fold half/float/double"); 1255} 1256 1257/// ConstantFoldConvertToInt - Attempt to an SSE floating point to integer 1258/// conversion of a constant floating point. If roundTowardZero is false, the 1259/// default IEEE rounding is used (toward nearest, ties to even). This matches 1260/// the behavior of the non-truncating SSE instructions in the default rounding 1261/// mode. The desired integer type Ty is used to select how many bits are 1262/// available for the result. Returns null if the conversion cannot be 1263/// performed, otherwise returns the Constant value resulting from the 1264/// conversion. 1265static Constant *ConstantFoldConvertToInt(const APFloat &Val, 1266 bool roundTowardZero, Type *Ty) { 1267 // All of these conversion intrinsics form an integer of at most 64bits. 1268 unsigned ResultWidth = cast<IntegerType>(Ty)->getBitWidth(); 1269 assert(ResultWidth <= 64 && 1270 "Can only constant fold conversions to 64 and 32 bit ints"); 1271 1272 uint64_t UIntVal; 1273 bool isExact = false; 1274 APFloat::roundingMode mode = roundTowardZero? APFloat::rmTowardZero 1275 : APFloat::rmNearestTiesToEven; 1276 APFloat::opStatus status = Val.convertToInteger(&UIntVal, ResultWidth, 1277 /*isSigned=*/true, mode, 1278 &isExact); 1279 if (status != APFloat::opOK && status != APFloat::opInexact) 1280 return 0; 1281 return ConstantInt::get(Ty, UIntVal, /*isSigned=*/true); 1282} 1283 1284/// ConstantFoldCall - Attempt to constant fold a call to the specified function 1285/// with the specified arguments, returning null if unsuccessful. 1286Constant * 1287llvm::ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands, 1288 const TargetLibraryInfo *TLI) { 1289 if (!F->hasName()) 1290 return 0; 1291 StringRef Name = F->getName(); 1292 1293 Type *Ty = F->getReturnType(); 1294 if (Operands.size() == 1) { 1295 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { 1296 if (F->getIntrinsicID() == Intrinsic::convert_to_fp16) { 1297 APFloat Val(Op->getValueAPF()); 1298 1299 bool lost = false; 1300 Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost); 1301 1302 return ConstantInt::get(F->getContext(), Val.bitcastToAPInt()); 1303 } 1304 if (!TLI) 1305 return 0; 1306 1307 if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) 1308 return 0; 1309 1310 /// We only fold functions with finite arguments. Folding NaN and inf is 1311 /// likely to be aborted with an exception anyway, and some host libms 1312 /// have known errors raising exceptions. 1313 if (Op->getValueAPF().isNaN() || Op->getValueAPF().isInfinity()) 1314 return 0; 1315 1316 /// Currently APFloat versions of these functions do not exist, so we use 1317 /// the host native double versions. Float versions are not called 1318 /// directly but for all these it is true (float)(f((double)arg)) == 1319 /// f(arg). Long double not supported yet. 1320 double V; 1321 if (Ty->isFloatTy()) 1322 V = Op->getValueAPF().convertToFloat(); 1323 else if (Ty->isDoubleTy()) 1324 V = Op->getValueAPF().convertToDouble(); 1325 else { 1326 bool unused; 1327 APFloat APF = Op->getValueAPF(); 1328 APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); 1329 V = APF.convertToDouble(); 1330 } 1331 1332 switch (F->getIntrinsicID()) { 1333 default: break; 1334 case Intrinsic::fabs: 1335 return ConstantFoldFP(fabs, V, Ty); 1336#if HAVE_LOG2 1337 case Intrinsic::log2: 1338 return ConstantFoldFP(log2, V, Ty); 1339#endif 1340#if HAVE_LOG 1341 case Intrinsic::log: 1342 return ConstantFoldFP(log, V, Ty); 1343#endif 1344#if HAVE_LOG10 1345 case Intrinsic::log10: 1346 return ConstantFoldFP(log10, V, Ty); 1347#endif 1348#if HAVE_EXP 1349 case Intrinsic::exp: 1350 return ConstantFoldFP(exp, V, Ty); 1351#endif 1352#if HAVE_EXP2 1353 case Intrinsic::exp2: 1354 return ConstantFoldFP(exp2, V, Ty); 1355#endif 1356 case Intrinsic::floor: 1357 return ConstantFoldFP(floor, V, Ty); 1358 } 1359 1360 switch (Name[0]) { 1361 case 'a': 1362 if (Name == "acos" && TLI->has(LibFunc::acos)) 1363 return ConstantFoldFP(acos, V, Ty); 1364 else if (Name == "asin" && TLI->has(LibFunc::asin)) 1365 return ConstantFoldFP(asin, V, Ty); 1366 else if (Name == "atan" && TLI->has(LibFunc::atan)) 1367 return ConstantFoldFP(atan, V, Ty); 1368 break; 1369 case 'c': 1370 if (Name == "ceil" && TLI->has(LibFunc::ceil)) 1371 return ConstantFoldFP(ceil, V, Ty); 1372 else if (Name == "cos" && TLI->has(LibFunc::cos)) 1373 return ConstantFoldFP(cos, V, Ty); 1374 else if (Name == "cosh" && TLI->has(LibFunc::cosh)) 1375 return ConstantFoldFP(cosh, V, Ty); 1376 else if (Name == "cosf" && TLI->has(LibFunc::cosf)) 1377 return ConstantFoldFP(cos, V, Ty); 1378 break; 1379 case 'e': 1380 if (Name == "exp" && TLI->has(LibFunc::exp)) 1381 return ConstantFoldFP(exp, V, Ty); 1382 1383 if (Name == "exp2" && TLI->has(LibFunc::exp2)) { 1384 // Constant fold exp2(x) as pow(2,x) in case the host doesn't have a 1385 // C99 library. 1386 return ConstantFoldBinaryFP(pow, 2.0, V, Ty); 1387 } 1388 break; 1389 case 'f': 1390 if (Name == "fabs" && TLI->has(LibFunc::fabs)) 1391 return ConstantFoldFP(fabs, V, Ty); 1392 else if (Name == "floor" && TLI->has(LibFunc::floor)) 1393 return ConstantFoldFP(floor, V, Ty); 1394 break; 1395 case 'l': 1396 if (Name == "log" && V > 0 && TLI->has(LibFunc::log)) 1397 return ConstantFoldFP(log, V, Ty); 1398 else if (Name == "log10" && V > 0 && TLI->has(LibFunc::log10)) 1399 return ConstantFoldFP(log10, V, Ty); 1400 else if (F->getIntrinsicID() == Intrinsic::sqrt && 1401 (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy())) { 1402 if (V >= -0.0) 1403 return ConstantFoldFP(sqrt, V, Ty); 1404 else // Undefined 1405 return Constant::getNullValue(Ty); 1406 } 1407 break; 1408 case 's': 1409 if (Name == "sin" && TLI->has(LibFunc::sin)) 1410 return ConstantFoldFP(sin, V, Ty); 1411 else if (Name == "sinh" && TLI->has(LibFunc::sinh)) 1412 return ConstantFoldFP(sinh, V, Ty); 1413 else if (Name == "sqrt" && V >= 0 && TLI->has(LibFunc::sqrt)) 1414 return ConstantFoldFP(sqrt, V, Ty); 1415 else if (Name == "sqrtf" && V >= 0 && TLI->has(LibFunc::sqrtf)) 1416 return ConstantFoldFP(sqrt, V, Ty); 1417 else if (Name == "sinf" && TLI->has(LibFunc::sinf)) 1418 return ConstantFoldFP(sin, V, Ty); 1419 break; 1420 case 't': 1421 if (Name == "tan" && TLI->has(LibFunc::tan)) 1422 return ConstantFoldFP(tan, V, Ty); 1423 else if (Name == "tanh" && TLI->has(LibFunc::tanh)) 1424 return ConstantFoldFP(tanh, V, Ty); 1425 break; 1426 default: 1427 break; 1428 } 1429 return 0; 1430 } 1431 1432 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { 1433 switch (F->getIntrinsicID()) { 1434 case Intrinsic::bswap: 1435 return ConstantInt::get(F->getContext(), Op->getValue().byteSwap()); 1436 case Intrinsic::ctpop: 1437 return ConstantInt::get(Ty, Op->getValue().countPopulation()); 1438 case Intrinsic::convert_from_fp16: { 1439 APFloat Val(APFloat::IEEEhalf, Op->getValue()); 1440 1441 bool lost = false; 1442 APFloat::opStatus status = 1443 Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost); 1444 1445 // Conversion is always precise. 1446 (void)status; 1447 assert(status == APFloat::opOK && !lost && 1448 "Precision lost during fp16 constfolding"); 1449 1450 return ConstantFP::get(F->getContext(), Val); 1451 } 1452 default: 1453 return 0; 1454 } 1455 } 1456 1457 // Support ConstantVector in case we have an Undef in the top. 1458 if (isa<ConstantVector>(Operands[0]) || 1459 isa<ConstantDataVector>(Operands[0])) { 1460 Constant *Op = cast<Constant>(Operands[0]); 1461 switch (F->getIntrinsicID()) { 1462 default: break; 1463 case Intrinsic::x86_sse_cvtss2si: 1464 case Intrinsic::x86_sse_cvtss2si64: 1465 case Intrinsic::x86_sse2_cvtsd2si: 1466 case Intrinsic::x86_sse2_cvtsd2si64: 1467 if (ConstantFP *FPOp = 1468 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U))) 1469 return ConstantFoldConvertToInt(FPOp->getValueAPF(), 1470 /*roundTowardZero=*/false, Ty); 1471 case Intrinsic::x86_sse_cvttss2si: 1472 case Intrinsic::x86_sse_cvttss2si64: 1473 case Intrinsic::x86_sse2_cvttsd2si: 1474 case Intrinsic::x86_sse2_cvttsd2si64: 1475 if (ConstantFP *FPOp = 1476 dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U))) 1477 return ConstantFoldConvertToInt(FPOp->getValueAPF(), 1478 /*roundTowardZero=*/true, Ty); 1479 } 1480 } 1481 1482 if (isa<UndefValue>(Operands[0])) { 1483 if (F->getIntrinsicID() == Intrinsic::bswap) 1484 return Operands[0]; 1485 return 0; 1486 } 1487 1488 return 0; 1489 } 1490 1491 if (Operands.size() == 2) { 1492 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1493 if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) 1494 return 0; 1495 double Op1V; 1496 if (Ty->isFloatTy()) 1497 Op1V = Op1->getValueAPF().convertToFloat(); 1498 else if (Ty->isDoubleTy()) 1499 Op1V = Op1->getValueAPF().convertToDouble(); 1500 else { 1501 bool unused; 1502 APFloat APF = Op1->getValueAPF(); 1503 APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); 1504 Op1V = APF.convertToDouble(); 1505 } 1506 1507 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1508 if (Op2->getType() != Op1->getType()) 1509 return 0; 1510 1511 double Op2V; 1512 if (Ty->isFloatTy()) 1513 Op2V = Op2->getValueAPF().convertToFloat(); 1514 else if (Ty->isDoubleTy()) 1515 Op2V = Op2->getValueAPF().convertToDouble(); 1516 else { 1517 bool unused; 1518 APFloat APF = Op2->getValueAPF(); 1519 APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); 1520 Op2V = APF.convertToDouble(); 1521 } 1522 1523 if (F->getIntrinsicID() == Intrinsic::pow) { 1524 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1525 } 1526 if (!TLI) 1527 return 0; 1528 if (Name == "pow" && TLI->has(LibFunc::pow)) 1529 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1530 if (Name == "fmod" && TLI->has(LibFunc::fmod)) 1531 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty); 1532 if (Name == "atan2" && TLI->has(LibFunc::atan2)) 1533 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty); 1534 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { 1535 if (F->getIntrinsicID() == Intrinsic::powi && Ty->isHalfTy()) 1536 return ConstantFP::get(F->getContext(), 1537 APFloat((float)std::pow((float)Op1V, 1538 (int)Op2C->getZExtValue()))); 1539 if (F->getIntrinsicID() == Intrinsic::powi && Ty->isFloatTy()) 1540 return ConstantFP::get(F->getContext(), 1541 APFloat((float)std::pow((float)Op1V, 1542 (int)Op2C->getZExtValue()))); 1543 if (F->getIntrinsicID() == Intrinsic::powi && Ty->isDoubleTy()) 1544 return ConstantFP::get(F->getContext(), 1545 APFloat((double)std::pow((double)Op1V, 1546 (int)Op2C->getZExtValue()))); 1547 } 1548 return 0; 1549 } 1550 1551 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) { 1552 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) { 1553 switch (F->getIntrinsicID()) { 1554 default: break; 1555 case Intrinsic::sadd_with_overflow: 1556 case Intrinsic::uadd_with_overflow: 1557 case Intrinsic::ssub_with_overflow: 1558 case Intrinsic::usub_with_overflow: 1559 case Intrinsic::smul_with_overflow: 1560 case Intrinsic::umul_with_overflow: { 1561 APInt Res; 1562 bool Overflow; 1563 switch (F->getIntrinsicID()) { 1564 default: llvm_unreachable("Invalid case"); 1565 case Intrinsic::sadd_with_overflow: 1566 Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow); 1567 break; 1568 case Intrinsic::uadd_with_overflow: 1569 Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow); 1570 break; 1571 case Intrinsic::ssub_with_overflow: 1572 Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow); 1573 break; 1574 case Intrinsic::usub_with_overflow: 1575 Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow); 1576 break; 1577 case Intrinsic::smul_with_overflow: 1578 Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow); 1579 break; 1580 case Intrinsic::umul_with_overflow: 1581 Res = Op1->getValue().umul_ov(Op2->getValue(), Overflow); 1582 break; 1583 } 1584 Constant *Ops[] = { 1585 ConstantInt::get(F->getContext(), Res), 1586 ConstantInt::get(Type::getInt1Ty(F->getContext()), Overflow) 1587 }; 1588 return ConstantStruct::get(cast<StructType>(F->getReturnType()), Ops); 1589 } 1590 case Intrinsic::cttz: 1591 if (Op2->isOne() && Op1->isZero()) // cttz(0, 1) is undef. 1592 return UndefValue::get(Ty); 1593 return ConstantInt::get(Ty, Op1->getValue().countTrailingZeros()); 1594 case Intrinsic::ctlz: 1595 if (Op2->isOne() && Op1->isZero()) // ctlz(0, 1) is undef. 1596 return UndefValue::get(Ty); 1597 return ConstantInt::get(Ty, Op1->getValue().countLeadingZeros()); 1598 } 1599 } 1600 1601 return 0; 1602 } 1603 return 0; 1604 } 1605 return 0; 1606} 1607