ConstantFolding.cpp revision b80a2a686fe76496d71397f8bdda394d5718ab01
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 VMCore ConstantExpr simplifications, 13// this file defines some additional folding routines that can make use of 14// TargetData information. These functions cannot go in VMCore due to library 15// dependency issues. 16// 17//===----------------------------------------------------------------------===// 18 19#include "llvm/Analysis/ConstantFolding.h" 20#include "llvm/Constants.h" 21#include "llvm/DerivedTypes.h" 22#include "llvm/Function.h" 23#include "llvm/GlobalVariable.h" 24#include "llvm/Instructions.h" 25#include "llvm/Intrinsics.h" 26#include "llvm/Analysis/ValueTracking.h" 27#include "llvm/Target/TargetData.h" 28#include "llvm/ADT/SmallVector.h" 29#include "llvm/ADT/StringMap.h" 30#include "llvm/Support/ErrorHandling.h" 31#include "llvm/Support/GetElementPtrTypeIterator.h" 32#include "llvm/Support/MathExtras.h" 33#include <cerrno> 34#include <cmath> 35using namespace llvm; 36 37//===----------------------------------------------------------------------===// 38// Constant Folding internal helper functions 39//===----------------------------------------------------------------------===// 40 41/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with 42/// TargetData. This always returns a non-null constant, but it may be a 43/// ConstantExpr if unfoldable. 44static Constant *FoldBitCast(Constant *C, const Type *DestTy, 45 const TargetData &TD) { 46 47 // This only handles casts to vectors currently. 48 const VectorType *DestVTy = dyn_cast<VectorType>(DestTy); 49 if (DestVTy == 0) 50 return ConstantExpr::getBitCast(C, DestTy); 51 52 // If this is a scalar -> vector cast, convert the input into a <1 x scalar> 53 // vector so the code below can handle it uniformly. 54 if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) { 55 Constant *Ops = C; // don't take the address of C! 56 return FoldBitCast(ConstantVector::get(&Ops, 1), DestTy, TD); 57 } 58 59 // If this is a bitcast from constant vector -> vector, fold it. 60 ConstantVector *CV = dyn_cast<ConstantVector>(C); 61 if (CV == 0) 62 return ConstantExpr::getBitCast(C, DestTy); 63 64 // If the element types match, VMCore can fold it. 65 unsigned NumDstElt = DestVTy->getNumElements(); 66 unsigned NumSrcElt = CV->getNumOperands(); 67 if (NumDstElt == NumSrcElt) 68 return ConstantExpr::getBitCast(C, DestTy); 69 70 const Type *SrcEltTy = CV->getType()->getElementType(); 71 const Type *DstEltTy = DestVTy->getElementType(); 72 73 // Otherwise, we're changing the number of elements in a vector, which 74 // requires endianness information to do the right thing. For example, 75 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 76 // folds to (little endian): 77 // <4 x i32> <i32 0, i32 0, i32 1, i32 0> 78 // and to (big endian): 79 // <4 x i32> <i32 0, i32 0, i32 0, i32 1> 80 81 // First thing is first. We only want to think about integer here, so if 82 // we have something in FP form, recast it as integer. 83 if (DstEltTy->isFloatingPointTy()) { 84 // Fold to an vector of integers with same size as our FP type. 85 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits(); 86 const Type *DestIVTy = 87 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt); 88 // Recursively handle this integer conversion, if possible. 89 C = FoldBitCast(C, DestIVTy, TD); 90 if (!C) return ConstantExpr::getBitCast(C, DestTy); 91 92 // Finally, VMCore can handle this now that #elts line up. 93 return ConstantExpr::getBitCast(C, DestTy); 94 } 95 96 // Okay, we know the destination is integer, if the input is FP, convert 97 // it to integer first. 98 if (SrcEltTy->isFloatingPointTy()) { 99 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); 100 const Type *SrcIVTy = 101 VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt); 102 // Ask VMCore to do the conversion now that #elts line up. 103 C = ConstantExpr::getBitCast(C, SrcIVTy); 104 CV = dyn_cast<ConstantVector>(C); 105 if (!CV) // If VMCore wasn't able to fold it, bail out. 106 return C; 107 } 108 109 // Now we know that the input and output vectors are both integer vectors 110 // of the same size, and that their #elements is not the same. Do the 111 // conversion here, which depends on whether the input or output has 112 // more elements. 113 bool isLittleEndian = TD.isLittleEndian(); 114 115 SmallVector<Constant*, 32> Result; 116 if (NumDstElt < NumSrcElt) { 117 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>) 118 Constant *Zero = Constant::getNullValue(DstEltTy); 119 unsigned Ratio = NumSrcElt/NumDstElt; 120 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits(); 121 unsigned SrcElt = 0; 122 for (unsigned i = 0; i != NumDstElt; ++i) { 123 // Build each element of the result. 124 Constant *Elt = Zero; 125 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1); 126 for (unsigned j = 0; j != Ratio; ++j) { 127 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++)); 128 if (!Src) // Reject constantexpr elements. 129 return ConstantExpr::getBitCast(C, DestTy); 130 131 // Zero extend the element to the right size. 132 Src = ConstantExpr::getZExt(Src, Elt->getType()); 133 134 // Shift it to the right place, depending on endianness. 135 Src = ConstantExpr::getShl(Src, 136 ConstantInt::get(Src->getType(), ShiftAmt)); 137 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize; 138 139 // Mix it in. 140 Elt = ConstantExpr::getOr(Elt, Src); 141 } 142 Result.push_back(Elt); 143 } 144 } else { 145 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 146 unsigned Ratio = NumDstElt/NumSrcElt; 147 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits(); 148 149 // Loop over each source value, expanding into multiple results. 150 for (unsigned i = 0; i != NumSrcElt; ++i) { 151 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i)); 152 if (!Src) // Reject constantexpr elements. 153 return ConstantExpr::getBitCast(C, DestTy); 154 155 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1); 156 for (unsigned j = 0; j != Ratio; ++j) { 157 // Shift the piece of the value into the right place, depending on 158 // endianness. 159 Constant *Elt = ConstantExpr::getLShr(Src, 160 ConstantInt::get(Src->getType(), ShiftAmt)); 161 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize; 162 163 // Truncate and remember this piece. 164 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy)); 165 } 166 } 167 } 168 169 return ConstantVector::get(Result.data(), Result.size()); 170} 171 172 173/// IsConstantOffsetFromGlobal - If this constant is actually a constant offset 174/// from a global, return the global and the constant. Because of 175/// constantexprs, this function is recursive. 176static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, 177 int64_t &Offset, const TargetData &TD) { 178 // Trivial case, constant is the global. 179 if ((GV = dyn_cast<GlobalValue>(C))) { 180 Offset = 0; 181 return true; 182 } 183 184 // Otherwise, if this isn't a constant expr, bail out. 185 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 186 if (!CE) return false; 187 188 // Look through ptr->int and ptr->ptr casts. 189 if (CE->getOpcode() == Instruction::PtrToInt || 190 CE->getOpcode() == Instruction::BitCast) 191 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD); 192 193 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5) 194 if (CE->getOpcode() == Instruction::GetElementPtr) { 195 // Cannot compute this if the element type of the pointer is missing size 196 // info. 197 if (!cast<PointerType>(CE->getOperand(0)->getType()) 198 ->getElementType()->isSized()) 199 return false; 200 201 // If the base isn't a global+constant, we aren't either. 202 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD)) 203 return false; 204 205 // Otherwise, add any offset that our operands provide. 206 gep_type_iterator GTI = gep_type_begin(CE); 207 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end(); 208 i != e; ++i, ++GTI) { 209 ConstantInt *CI = dyn_cast<ConstantInt>(*i); 210 if (!CI) return false; // Index isn't a simple constant? 211 if (CI->getZExtValue() == 0) continue; // Not adding anything. 212 213 if (const StructType *ST = dyn_cast<StructType>(*GTI)) { 214 // N = N + Offset 215 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue()); 216 } else { 217 const SequentialType *SQT = cast<SequentialType>(*GTI); 218 Offset += TD.getTypeAllocSize(SQT->getElementType())*CI->getSExtValue(); 219 } 220 } 221 return true; 222 } 223 224 return false; 225} 226 227/// ReadDataFromGlobal - Recursive helper to read bits out of global. C is the 228/// constant being copied out of. ByteOffset is an offset into C. CurPtr is the 229/// pointer to copy results into and BytesLeft is the number of bytes left in 230/// the CurPtr buffer. TD is the target data. 231static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset, 232 unsigned char *CurPtr, unsigned BytesLeft, 233 const TargetData &TD) { 234 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) && 235 "Out of range access"); 236 237 // If this element is zero or undefined, we can just return since *CurPtr is 238 // zero initialized. 239 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C)) 240 return true; 241 242 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 243 if (CI->getBitWidth() > 64 || 244 (CI->getBitWidth() & 7) != 0) 245 return false; 246 247 uint64_t Val = CI->getZExtValue(); 248 unsigned IntBytes = unsigned(CI->getBitWidth()/8); 249 250 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) { 251 CurPtr[i] = (unsigned char)(Val >> (ByteOffset * 8)); 252 ++ByteOffset; 253 } 254 return true; 255 } 256 257 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) { 258 if (CFP->getType()->isDoubleTy()) { 259 C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD); 260 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 261 } 262 if (CFP->getType()->isFloatTy()){ 263 C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD); 264 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 265 } 266 return false; 267 } 268 269 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 270 const StructLayout *SL = TD.getStructLayout(CS->getType()); 271 unsigned Index = SL->getElementContainingOffset(ByteOffset); 272 uint64_t CurEltOffset = SL->getElementOffset(Index); 273 ByteOffset -= CurEltOffset; 274 275 while (1) { 276 // If the element access is to the element itself and not to tail padding, 277 // read the bytes from the element. 278 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType()); 279 280 if (ByteOffset < EltSize && 281 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr, 282 BytesLeft, TD)) 283 return false; 284 285 ++Index; 286 287 // Check to see if we read from the last struct element, if so we're done. 288 if (Index == CS->getType()->getNumElements()) 289 return true; 290 291 // If we read all of the bytes we needed from this element we're done. 292 uint64_t NextEltOffset = SL->getElementOffset(Index); 293 294 if (BytesLeft <= NextEltOffset-CurEltOffset-ByteOffset) 295 return true; 296 297 // Move to the next element of the struct. 298 CurPtr += NextEltOffset-CurEltOffset-ByteOffset; 299 BytesLeft -= NextEltOffset-CurEltOffset-ByteOffset; 300 ByteOffset = 0; 301 CurEltOffset = NextEltOffset; 302 } 303 // not reached. 304 } 305 306 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) { 307 uint64_t EltSize = TD.getTypeAllocSize(CA->getType()->getElementType()); 308 uint64_t Index = ByteOffset / EltSize; 309 uint64_t Offset = ByteOffset - Index * EltSize; 310 for (; Index != CA->getType()->getNumElements(); ++Index) { 311 if (!ReadDataFromGlobal(CA->getOperand(Index), Offset, CurPtr, 312 BytesLeft, TD)) 313 return false; 314 if (EltSize >= BytesLeft) 315 return true; 316 317 Offset = 0; 318 BytesLeft -= EltSize; 319 CurPtr += EltSize; 320 } 321 return true; 322 } 323 324 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) { 325 uint64_t EltSize = TD.getTypeAllocSize(CV->getType()->getElementType()); 326 uint64_t Index = ByteOffset / EltSize; 327 uint64_t Offset = ByteOffset - Index * EltSize; 328 for (; Index != CV->getType()->getNumElements(); ++Index) { 329 if (!ReadDataFromGlobal(CV->getOperand(Index), Offset, CurPtr, 330 BytesLeft, TD)) 331 return false; 332 if (EltSize >= BytesLeft) 333 return true; 334 335 Offset = 0; 336 BytesLeft -= EltSize; 337 CurPtr += EltSize; 338 } 339 return true; 340 } 341 342 // Otherwise, unknown initializer type. 343 return false; 344} 345 346static Constant *FoldReinterpretLoadFromConstPtr(Constant *C, 347 const TargetData &TD) { 348 const Type *LoadTy = cast<PointerType>(C->getType())->getElementType(); 349 const IntegerType *IntType = dyn_cast<IntegerType>(LoadTy); 350 351 // If this isn't an integer load we can't fold it directly. 352 if (!IntType) { 353 // If this is a float/double load, we can try folding it as an int32/64 load 354 // and then bitcast the result. This can be useful for union cases. Note 355 // that address spaces don't matter here since we're not going to result in 356 // an actual new load. 357 const Type *MapTy; 358 if (LoadTy->isFloatTy()) 359 MapTy = Type::getInt32PtrTy(C->getContext()); 360 else if (LoadTy->isDoubleTy()) 361 MapTy = Type::getInt64PtrTy(C->getContext()); 362 else if (LoadTy->isVectorTy()) { 363 MapTy = IntegerType::get(C->getContext(), 364 TD.getTypeAllocSizeInBits(LoadTy)); 365 MapTy = PointerType::getUnqual(MapTy); 366 } else 367 return 0; 368 369 C = FoldBitCast(C, MapTy, TD); 370 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD)) 371 return FoldBitCast(Res, LoadTy, TD); 372 return 0; 373 } 374 375 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8; 376 if (BytesLoaded > 32 || BytesLoaded == 0) return 0; 377 378 GlobalValue *GVal; 379 int64_t Offset; 380 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD)) 381 return 0; 382 383 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal); 384 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() || 385 !GV->getInitializer()->getType()->isSized()) 386 return 0; 387 388 // If we're loading off the beginning of the global, some bytes may be valid, 389 // but we don't try to handle this. 390 if (Offset < 0) return 0; 391 392 // If we're not accessing anything in this constant, the result is undefined. 393 if (uint64_t(Offset) >= TD.getTypeAllocSize(GV->getInitializer()->getType())) 394 return UndefValue::get(IntType); 395 396 unsigned char RawBytes[32] = {0}; 397 if (!ReadDataFromGlobal(GV->getInitializer(), Offset, RawBytes, 398 BytesLoaded, TD)) 399 return 0; 400 401 APInt ResultVal = APInt(IntType->getBitWidth(), RawBytes[BytesLoaded-1]); 402 for (unsigned i = 1; i != BytesLoaded; ++i) { 403 ResultVal <<= 8; 404 ResultVal |= APInt(IntType->getBitWidth(), RawBytes[BytesLoaded-1-i]); 405 } 406 407 return ConstantInt::get(IntType->getContext(), ResultVal); 408} 409 410/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 411/// produce if it is constant and determinable. If this is not determinable, 412/// return null. 413Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, 414 const TargetData *TD) { 415 // First, try the easy cases: 416 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 417 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 418 return GV->getInitializer(); 419 420 // If the loaded value isn't a constant expr, we can't handle it. 421 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 422 if (!CE) return 0; 423 424 if (CE->getOpcode() == Instruction::GetElementPtr) { 425 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) 426 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 427 if (Constant *V = 428 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) 429 return V; 430 } 431 432 // Instead of loading constant c string, use corresponding integer value 433 // directly if string length is small enough. 434 std::string Str; 435 if (TD && GetConstantStringInfo(CE, Str) && !Str.empty()) { 436 unsigned StrLen = Str.length(); 437 const Type *Ty = cast<PointerType>(CE->getType())->getElementType(); 438 unsigned NumBits = Ty->getPrimitiveSizeInBits(); 439 // Replace LI with immediate integer store. 440 if ((NumBits >> 3) == StrLen + 1) { 441 APInt StrVal(NumBits, 0); 442 APInt SingleChar(NumBits, 0); 443 if (TD->isLittleEndian()) { 444 for (signed i = StrLen-1; i >= 0; i--) { 445 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 446 StrVal = (StrVal << 8) | SingleChar; 447 } 448 } else { 449 for (unsigned i = 0; i < StrLen; i++) { 450 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 451 StrVal = (StrVal << 8) | SingleChar; 452 } 453 // Append NULL at the end. 454 SingleChar = 0; 455 StrVal = (StrVal << 8) | SingleChar; 456 } 457 return ConstantInt::get(CE->getContext(), StrVal); 458 } 459 } 460 461 // If this load comes from anywhere in a constant global, and if the global 462 // is all undef or zero, we know what it loads. 463 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getUnderlyingObject())){ 464 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 465 const Type *ResTy = cast<PointerType>(C->getType())->getElementType(); 466 if (GV->getInitializer()->isNullValue()) 467 return Constant::getNullValue(ResTy); 468 if (isa<UndefValue>(GV->getInitializer())) 469 return UndefValue::get(ResTy); 470 } 471 } 472 473 // Try hard to fold loads from bitcasted strange and non-type-safe things. We 474 // currently don't do any of this for big endian systems. It can be 475 // generalized in the future if someone is interested. 476 if (TD && TD->isLittleEndian()) 477 return FoldReinterpretLoadFromConstPtr(CE, *TD); 478 return 0; 479} 480 481static Constant *ConstantFoldLoadInst(const LoadInst *LI, const TargetData *TD){ 482 if (LI->isVolatile()) return 0; 483 484 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0))) 485 return ConstantFoldLoadFromConstPtr(C, TD); 486 487 return 0; 488} 489 490/// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression. 491/// Attempt to symbolically evaluate the result of a binary operator merging 492/// these together. If target data info is available, it is provided as TD, 493/// otherwise TD is null. 494static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, 495 Constant *Op1, const TargetData *TD){ 496 // SROA 497 498 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl. 499 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute 500 // bits. 501 502 503 // If the constant expr is something like &A[123] - &A[4].f, fold this into a 504 // constant. This happens frequently when iterating over a global array. 505 if (Opc == Instruction::Sub && TD) { 506 GlobalValue *GV1, *GV2; 507 int64_t Offs1, Offs2; 508 509 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD)) 510 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) && 511 GV1 == GV2) { 512 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow. 513 return ConstantInt::get(Op0->getType(), Offs1-Offs2); 514 } 515 } 516 517 return 0; 518} 519 520/// CastGEPIndices - If array indices are not pointer-sized integers, 521/// explicitly cast them so that they aren't implicitly casted by the 522/// getelementptr. 523static Constant *CastGEPIndices(Constant *const *Ops, unsigned NumOps, 524 const Type *ResultTy, 525 const TargetData *TD) { 526 if (!TD) return 0; 527 const Type *IntPtrTy = TD->getIntPtrType(ResultTy->getContext()); 528 529 bool Any = false; 530 SmallVector<Constant*, 32> NewIdxs; 531 for (unsigned i = 1; i != NumOps; ++i) { 532 if ((i == 1 || 533 !isa<StructType>(GetElementPtrInst::getIndexedType(Ops[0]->getType(), 534 reinterpret_cast<Value *const *>(Ops+1), 535 i-1))) && 536 Ops[i]->getType() != IntPtrTy) { 537 Any = true; 538 NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i], 539 true, 540 IntPtrTy, 541 true), 542 Ops[i], IntPtrTy)); 543 } else 544 NewIdxs.push_back(Ops[i]); 545 } 546 if (!Any) return 0; 547 548 Constant *C = 549 ConstantExpr::getGetElementPtr(Ops[0], &NewIdxs[0], NewIdxs.size()); 550 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 551 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD)) 552 C = Folded; 553 return C; 554} 555 556/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP 557/// constant expression, do so. 558static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps, 559 const Type *ResultTy, 560 const TargetData *TD) { 561 Constant *Ptr = Ops[0]; 562 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized()) 563 return 0; 564 565 unsigned BitWidth = 566 TD->getTypeSizeInBits(TD->getIntPtrType(Ptr->getContext())); 567 APInt BasePtr(BitWidth, 0); 568 bool BaseIsInt = true; 569 if (!Ptr->isNullValue()) { 570 // If this is a inttoptr from a constant int, we can fold this as the base, 571 // otherwise we can't. 572 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 573 if (CE->getOpcode() == Instruction::IntToPtr) 574 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) { 575 BasePtr = Base->getValue(); 576 BasePtr.zextOrTrunc(BitWidth); 577 } 578 579 if (BasePtr == 0) 580 BaseIsInt = false; 581 } 582 583 // If this is a constant expr gep that is effectively computing an 584 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' 585 for (unsigned i = 1; i != NumOps; ++i) 586 if (!isa<ConstantInt>(Ops[i])) 587 return 0; 588 589 APInt Offset = APInt(BitWidth, 590 TD->getIndexedOffset(Ptr->getType(), 591 (Value**)Ops+1, NumOps-1)); 592 // If the base value for this address is a literal integer value, fold the 593 // getelementptr to the resulting integer value casted to the pointer type. 594 if (BaseIsInt) { 595 Constant *C = ConstantInt::get(Ptr->getContext(), Offset+BasePtr); 596 return ConstantExpr::getIntToPtr(C, ResultTy); 597 } 598 599 // Otherwise form a regular getelementptr. Recompute the indices so that 600 // we eliminate over-indexing of the notional static type array bounds. 601 // This makes it easy to determine if the getelementptr is "inbounds". 602 // Also, this helps GlobalOpt do SROA on GlobalVariables. 603 Ptr = cast<Constant>(Ptr->stripPointerCasts()); 604 const Type *Ty = Ptr->getType(); 605 SmallVector<Constant*, 32> NewIdxs; 606 do { 607 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) { 608 if (ATy->isPointerTy()) { 609 // The only pointer indexing we'll do is on the first index of the GEP. 610 if (!NewIdxs.empty()) 611 break; 612 613 // Only handle pointers to sized types, not pointers to functions. 614 if (!ATy->getElementType()->isSized()) 615 return 0; 616 } 617 618 // Determine which element of the array the offset points into. 619 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); 620 if (ElemSize == 0) 621 return 0; 622 APInt NewIdx = Offset.udiv(ElemSize); 623 Offset -= NewIdx * ElemSize; 624 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Ty->getContext()), 625 NewIdx)); 626 Ty = ATy->getElementType(); 627 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) { 628 // Determine which field of the struct the offset points into. The 629 // getZExtValue is at least as safe as the StructLayout API because we 630 // know the offset is within the struct at this point. 631 const StructLayout &SL = *TD->getStructLayout(STy); 632 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); 633 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 634 ElIdx)); 635 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); 636 Ty = STy->getTypeAtIndex(ElIdx); 637 } else { 638 // We've reached some non-indexable type. 639 break; 640 } 641 } while (Ty != cast<PointerType>(ResultTy)->getElementType()); 642 643 // If we haven't used up the entire offset by descending the static 644 // type, then the offset is pointing into the middle of an indivisible 645 // member, so we can't simplify it. 646 if (Offset != 0) 647 return 0; 648 649 // Create a GEP. 650 Constant *C = 651 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size()); 652 assert(cast<PointerType>(C->getType())->getElementType() == Ty && 653 "Computed GetElementPtr has unexpected type!"); 654 655 // If we ended up indexing a member with a type that doesn't match 656 // the type of what the original indices indexed, add a cast. 657 if (Ty != cast<PointerType>(ResultTy)->getElementType()) 658 C = FoldBitCast(C, ResultTy, *TD); 659 660 return C; 661} 662 663 664 665//===----------------------------------------------------------------------===// 666// Constant Folding public APIs 667//===----------------------------------------------------------------------===// 668 669 670/// ConstantFoldInstruction - Attempt to constant fold the specified 671/// instruction. If successful, the constant result is returned, if not, null 672/// is returned. Note that this function can only fail when attempting to fold 673/// instructions like loads and stores, which have no constant expression form. 674/// 675Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) { 676 if (PHINode *PN = dyn_cast<PHINode>(I)) { 677 if (PN->getNumIncomingValues() == 0) 678 return UndefValue::get(PN->getType()); 679 680 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0)); 681 if (Result == 0) return 0; 682 683 // Handle PHI nodes specially here... 684 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) 685 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN) 686 return 0; // Not all the same incoming constants... 687 688 // If we reach here, all incoming values are the same constant. 689 return Result; 690 } 691 692 // Scan the operand list, checking to see if they are all constants, if so, 693 // hand off to ConstantFoldInstOperands. 694 SmallVector<Constant*, 8> Ops; 695 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) 696 if (Constant *Op = dyn_cast<Constant>(*i)) 697 Ops.push_back(Op); 698 else 699 return 0; // All operands not constant! 700 701 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 702 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], 703 TD); 704 705 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 706 return ConstantFoldLoadInst(LI, TD); 707 708 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), 709 Ops.data(), Ops.size(), TD); 710} 711 712/// ConstantFoldConstantExpression - Attempt to fold the constant expression 713/// using the specified TargetData. If successful, the constant result is 714/// result is returned, if not, null is returned. 715Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE, 716 const TargetData *TD) { 717 SmallVector<Constant*, 8> Ops; 718 for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) { 719 Constant *NewC = cast<Constant>(*i); 720 // Recursively fold the ConstantExpr's operands. 721 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC)) 722 NewC = ConstantFoldConstantExpression(NewCE, TD); 723 Ops.push_back(NewC); 724 } 725 726 if (CE->isCompare()) 727 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1], 728 TD); 729 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), 730 Ops.data(), Ops.size(), TD); 731} 732 733/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 734/// specified opcode and operands. If successful, the constant result is 735/// returned, if not, null is returned. Note that this function can fail when 736/// attempting to fold instructions like loads and stores, which have no 737/// constant expression form. 738/// 739/// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc 740/// information, due to only being passed an opcode and operands. Constant 741/// folding using this function strips this information. 742/// 743Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy, 744 Constant* const* Ops, unsigned NumOps, 745 const TargetData *TD) { 746 // Handle easy binops first. 747 if (Instruction::isBinaryOp(Opcode)) { 748 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) 749 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD)) 750 return C; 751 752 return ConstantExpr::get(Opcode, Ops[0], Ops[1]); 753 } 754 755 switch (Opcode) { 756 default: return 0; 757 case Instruction::ICmp: 758 case Instruction::FCmp: assert(0 && "Invalid for compares"); 759 case Instruction::Call: 760 if (Function *F = dyn_cast<Function>(Ops[0])) 761 if (canConstantFoldCallTo(F)) 762 return ConstantFoldCall(F, Ops+1, NumOps-1); 763 return 0; 764 case Instruction::PtrToInt: 765 // If the input is a inttoptr, eliminate the pair. This requires knowing 766 // the width of a pointer, so it can't be done in ConstantExpr::getCast. 767 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 768 if (TD && CE->getOpcode() == Instruction::IntToPtr) { 769 Constant *Input = CE->getOperand(0); 770 unsigned InWidth = Input->getType()->getScalarSizeInBits(); 771 if (TD->getPointerSizeInBits() < InWidth) { 772 Constant *Mask = 773 ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth, 774 TD->getPointerSizeInBits())); 775 Input = ConstantExpr::getAnd(Input, Mask); 776 } 777 // Do a zext or trunc to get to the dest size. 778 return ConstantExpr::getIntegerCast(Input, DestTy, false); 779 } 780 } 781 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 782 case Instruction::IntToPtr: 783 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if 784 // the int size is >= the ptr size. This requires knowing the width of a 785 // pointer, so it can't be done in ConstantExpr::getCast. 786 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) 787 if (TD && 788 TD->getPointerSizeInBits() <= CE->getType()->getScalarSizeInBits() && 789 CE->getOpcode() == Instruction::PtrToInt) 790 return FoldBitCast(CE->getOperand(0), DestTy, *TD); 791 792 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 793 case Instruction::Trunc: 794 case Instruction::ZExt: 795 case Instruction::SExt: 796 case Instruction::FPTrunc: 797 case Instruction::FPExt: 798 case Instruction::UIToFP: 799 case Instruction::SIToFP: 800 case Instruction::FPToUI: 801 case Instruction::FPToSI: 802 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 803 case Instruction::BitCast: 804 if (TD) 805 return FoldBitCast(Ops[0], DestTy, *TD); 806 return ConstantExpr::getBitCast(Ops[0], DestTy); 807 case Instruction::Select: 808 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); 809 case Instruction::ExtractElement: 810 return ConstantExpr::getExtractElement(Ops[0], Ops[1]); 811 case Instruction::InsertElement: 812 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); 813 case Instruction::ShuffleVector: 814 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); 815 case Instruction::GetElementPtr: 816 if (Constant *C = CastGEPIndices(Ops, NumOps, DestTy, TD)) 817 return C; 818 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD)) 819 return C; 820 821 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1); 822 } 823} 824 825/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 826/// instruction (icmp/fcmp) with the specified operands. If it fails, it 827/// returns a constant expression of the specified operands. 828/// 829Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, 830 Constant *Ops0, Constant *Ops1, 831 const TargetData *TD) { 832 // fold: icmp (inttoptr x), null -> icmp x, 0 833 // fold: icmp (ptrtoint x), 0 -> icmp x, null 834 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y 835 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y 836 // 837 // ConstantExpr::getCompare cannot do this, because it doesn't have TD 838 // around to know if bit truncation is happening. 839 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) { 840 if (TD && Ops1->isNullValue()) { 841 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 842 if (CE0->getOpcode() == Instruction::IntToPtr) { 843 // Convert the integer value to the right size to ensure we get the 844 // proper extension or truncation. 845 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), 846 IntPtrTy, false); 847 Constant *Null = Constant::getNullValue(C->getType()); 848 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD); 849 } 850 851 // Only do this transformation if the int is intptrty in size, otherwise 852 // there is a truncation or extension that we aren't modeling. 853 if (CE0->getOpcode() == Instruction::PtrToInt && 854 CE0->getType() == IntPtrTy) { 855 Constant *C = CE0->getOperand(0); 856 Constant *Null = Constant::getNullValue(C->getType()); 857 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD); 858 } 859 } 860 861 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) { 862 if (TD && CE0->getOpcode() == CE1->getOpcode()) { 863 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 864 865 if (CE0->getOpcode() == Instruction::IntToPtr) { 866 // Convert the integer value to the right size to ensure we get the 867 // proper extension or truncation. 868 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), 869 IntPtrTy, false); 870 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), 871 IntPtrTy, false); 872 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD); 873 } 874 875 // Only do this transformation if the int is intptrty in size, otherwise 876 // there is a truncation or extension that we aren't modeling. 877 if ((CE0->getOpcode() == Instruction::PtrToInt && 878 CE0->getType() == IntPtrTy && 879 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) 880 return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), 881 CE1->getOperand(0), TD); 882 } 883 } 884 885 // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0) 886 // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0) 887 if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) && 888 CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) { 889 Constant *LHS = 890 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1,TD); 891 Constant *RHS = 892 ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1,TD); 893 unsigned OpC = 894 Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or; 895 Constant *Ops[] = { LHS, RHS }; 896 return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, 2, TD); 897 } 898 } 899 900 return ConstantExpr::getCompare(Predicate, Ops0, Ops1); 901} 902 903 904/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 905/// getelementptr constantexpr, return the constant value being addressed by the 906/// constant expression, or null if something is funny and we can't decide. 907Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, 908 ConstantExpr *CE) { 909 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType())) 910 return 0; // Do not allow stepping over the value! 911 912 // Loop over all of the operands, tracking down which value we are 913 // addressing... 914 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 915 for (++I; I != E; ++I) 916 if (const StructType *STy = dyn_cast<StructType>(*I)) { 917 ConstantInt *CU = cast<ConstantInt>(I.getOperand()); 918 assert(CU->getZExtValue() < STy->getNumElements() && 919 "Struct index out of range!"); 920 unsigned El = (unsigned)CU->getZExtValue(); 921 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 922 C = CS->getOperand(El); 923 } else if (isa<ConstantAggregateZero>(C)) { 924 C = Constant::getNullValue(STy->getElementType(El)); 925 } else if (isa<UndefValue>(C)) { 926 C = UndefValue::get(STy->getElementType(El)); 927 } else { 928 return 0; 929 } 930 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) { 931 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) { 932 if (CI->getZExtValue() >= ATy->getNumElements()) 933 return 0; 934 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) 935 C = CA->getOperand(CI->getZExtValue()); 936 else if (isa<ConstantAggregateZero>(C)) 937 C = Constant::getNullValue(ATy->getElementType()); 938 else if (isa<UndefValue>(C)) 939 C = UndefValue::get(ATy->getElementType()); 940 else 941 return 0; 942 } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) { 943 if (CI->getZExtValue() >= VTy->getNumElements()) 944 return 0; 945 if (ConstantVector *CP = dyn_cast<ConstantVector>(C)) 946 C = CP->getOperand(CI->getZExtValue()); 947 else if (isa<ConstantAggregateZero>(C)) 948 C = Constant::getNullValue(VTy->getElementType()); 949 else if (isa<UndefValue>(C)) 950 C = UndefValue::get(VTy->getElementType()); 951 else 952 return 0; 953 } else { 954 return 0; 955 } 956 } else { 957 return 0; 958 } 959 return C; 960} 961 962 963//===----------------------------------------------------------------------===// 964// Constant Folding for Calls 965// 966 967/// canConstantFoldCallTo - Return true if its even possible to fold a call to 968/// the specified function. 969bool 970llvm::canConstantFoldCallTo(const Function *F) { 971 switch (F->getIntrinsicID()) { 972 case Intrinsic::sqrt: 973 case Intrinsic::powi: 974 case Intrinsic::bswap: 975 case Intrinsic::ctpop: 976 case Intrinsic::ctlz: 977 case Intrinsic::cttz: 978 case Intrinsic::uadd_with_overflow: 979 case Intrinsic::usub_with_overflow: 980 case Intrinsic::sadd_with_overflow: 981 case Intrinsic::ssub_with_overflow: 982 return true; 983 default: 984 return false; 985 case 0: break; 986 } 987 988 if (!F->hasName()) return false; 989 StringRef Name = F->getName(); 990 991 // In these cases, the check of the length is required. We don't want to 992 // return true for a name like "cos\0blah" which strcmp would return equal to 993 // "cos", but has length 8. 994 switch (Name[0]) { 995 default: return false; 996 case 'a': 997 return Name == "acos" || Name == "asin" || 998 Name == "atan" || Name == "atan2"; 999 case 'c': 1000 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; 1001 case 'e': 1002 return Name == "exp"; 1003 case 'f': 1004 return Name == "fabs" || Name == "fmod" || Name == "floor"; 1005 case 'l': 1006 return Name == "log" || Name == "log10"; 1007 case 'p': 1008 return Name == "pow"; 1009 case 's': 1010 return Name == "sin" || Name == "sinh" || Name == "sqrt" || 1011 Name == "sinf" || Name == "sqrtf"; 1012 case 't': 1013 return Name == "tan" || Name == "tanh"; 1014 } 1015} 1016 1017static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 1018 const Type *Ty) { 1019 errno = 0; 1020 V = NativeFP(V); 1021 if (errno != 0) { 1022 errno = 0; 1023 return 0; 1024 } 1025 1026 if (Ty->isFloatTy()) 1027 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1028 if (Ty->isDoubleTy()) 1029 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1030 llvm_unreachable("Can only constant fold float/double"); 1031 return 0; // dummy return to suppress warning 1032} 1033 1034static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), 1035 double V, double W, const Type *Ty) { 1036 errno = 0; 1037 V = NativeFP(V, W); 1038 if (errno != 0) { 1039 errno = 0; 1040 return 0; 1041 } 1042 1043 if (Ty->isFloatTy()) 1044 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1045 if (Ty->isDoubleTy()) 1046 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1047 llvm_unreachable("Can only constant fold float/double"); 1048 return 0; // dummy return to suppress warning 1049} 1050 1051/// ConstantFoldCall - Attempt to constant fold a call to the specified function 1052/// with the specified arguments, returning null if unsuccessful. 1053Constant * 1054llvm::ConstantFoldCall(Function *F, 1055 Constant *const *Operands, unsigned NumOperands) { 1056 if (!F->hasName()) return 0; 1057 StringRef Name = F->getName(); 1058 1059 const Type *Ty = F->getReturnType(); 1060 if (NumOperands == 1) { 1061 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { 1062 if (!Ty->isFloatTy() && !Ty->isDoubleTy()) 1063 return 0; 1064 /// Currently APFloat versions of these functions do not exist, so we use 1065 /// the host native double versions. Float versions are not called 1066 /// directly but for all these it is true (float)(f((double)arg)) == 1067 /// f(arg). Long double not supported yet. 1068 double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() : 1069 Op->getValueAPF().convertToDouble(); 1070 switch (Name[0]) { 1071 case 'a': 1072 if (Name == "acos") 1073 return ConstantFoldFP(acos, V, Ty); 1074 else if (Name == "asin") 1075 return ConstantFoldFP(asin, V, Ty); 1076 else if (Name == "atan") 1077 return ConstantFoldFP(atan, V, Ty); 1078 break; 1079 case 'c': 1080 if (Name == "ceil") 1081 return ConstantFoldFP(ceil, V, Ty); 1082 else if (Name == "cos") 1083 return ConstantFoldFP(cos, V, Ty); 1084 else if (Name == "cosh") 1085 return ConstantFoldFP(cosh, V, Ty); 1086 else if (Name == "cosf") 1087 return ConstantFoldFP(cos, V, Ty); 1088 break; 1089 case 'e': 1090 if (Name == "exp") 1091 return ConstantFoldFP(exp, V, Ty); 1092 break; 1093 case 'f': 1094 if (Name == "fabs") 1095 return ConstantFoldFP(fabs, V, Ty); 1096 else if (Name == "floor") 1097 return ConstantFoldFP(floor, V, Ty); 1098 break; 1099 case 'l': 1100 if (Name == "log" && V > 0) 1101 return ConstantFoldFP(log, V, Ty); 1102 else if (Name == "log10" && V > 0) 1103 return ConstantFoldFP(log10, V, Ty); 1104 else if (Name == "llvm.sqrt.f32" || 1105 Name == "llvm.sqrt.f64") { 1106 if (V >= -0.0) 1107 return ConstantFoldFP(sqrt, V, Ty); 1108 else // Undefined 1109 return Constant::getNullValue(Ty); 1110 } 1111 break; 1112 case 's': 1113 if (Name == "sin") 1114 return ConstantFoldFP(sin, V, Ty); 1115 else if (Name == "sinh") 1116 return ConstantFoldFP(sinh, V, Ty); 1117 else if (Name == "sqrt" && V >= 0) 1118 return ConstantFoldFP(sqrt, V, Ty); 1119 else if (Name == "sqrtf" && V >= 0) 1120 return ConstantFoldFP(sqrt, V, Ty); 1121 else if (Name == "sinf") 1122 return ConstantFoldFP(sin, V, Ty); 1123 break; 1124 case 't': 1125 if (Name == "tan") 1126 return ConstantFoldFP(tan, V, Ty); 1127 else if (Name == "tanh") 1128 return ConstantFoldFP(tanh, V, Ty); 1129 break; 1130 default: 1131 break; 1132 } 1133 return 0; 1134 } 1135 1136 1137 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { 1138 if (Name.startswith("llvm.bswap")) 1139 return ConstantInt::get(F->getContext(), Op->getValue().byteSwap()); 1140 else if (Name.startswith("llvm.ctpop")) 1141 return ConstantInt::get(Ty, Op->getValue().countPopulation()); 1142 else if (Name.startswith("llvm.cttz")) 1143 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros()); 1144 else if (Name.startswith("llvm.ctlz")) 1145 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros()); 1146 return 0; 1147 } 1148 1149 if (isa<UndefValue>(Operands[0])) { 1150 if (Name.startswith("llvm.bswap")) 1151 return Operands[0]; 1152 return 0; 1153 } 1154 1155 return 0; 1156 } 1157 1158 if (NumOperands == 2) { 1159 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1160 if (!Ty->isFloatTy() && !Ty->isDoubleTy()) 1161 return 0; 1162 double Op1V = Ty->isFloatTy() ? 1163 (double)Op1->getValueAPF().convertToFloat() : 1164 Op1->getValueAPF().convertToDouble(); 1165 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1166 if (Op2->getType() != Op1->getType()) 1167 return 0; 1168 1169 double Op2V = Ty->isFloatTy() ? 1170 (double)Op2->getValueAPF().convertToFloat(): 1171 Op2->getValueAPF().convertToDouble(); 1172 1173 if (Name == "pow") 1174 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1175 if (Name == "fmod") 1176 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty); 1177 if (Name == "atan2") 1178 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty); 1179 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { 1180 if (Name == "llvm.powi.f32") 1181 return ConstantFP::get(F->getContext(), 1182 APFloat((float)std::pow((float)Op1V, 1183 (int)Op2C->getZExtValue()))); 1184 if (Name == "llvm.powi.f64") 1185 return ConstantFP::get(F->getContext(), 1186 APFloat((double)std::pow((double)Op1V, 1187 (int)Op2C->getZExtValue()))); 1188 } 1189 return 0; 1190 } 1191 1192 1193 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) { 1194 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) { 1195 switch (F->getIntrinsicID()) { 1196 default: break; 1197 case Intrinsic::uadd_with_overflow: { 1198 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result. 1199 Constant *Ops[] = { 1200 Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow. 1201 }; 1202 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1203 } 1204 case Intrinsic::usub_with_overflow: { 1205 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result. 1206 Constant *Ops[] = { 1207 Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow. 1208 }; 1209 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1210 } 1211 case Intrinsic::sadd_with_overflow: { 1212 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result. 1213 Constant *Overflow = ConstantExpr::getSelect( 1214 ConstantExpr::getICmp(CmpInst::ICMP_SGT, 1215 ConstantInt::get(Op1->getType(), 0), Op1), 1216 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2), 1217 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow. 1218 1219 Constant *Ops[] = { Res, Overflow }; 1220 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1221 } 1222 case Intrinsic::ssub_with_overflow: { 1223 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result. 1224 Constant *Overflow = ConstantExpr::getSelect( 1225 ConstantExpr::getICmp(CmpInst::ICMP_SGT, 1226 ConstantInt::get(Op2->getType(), 0), Op2), 1227 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1), 1228 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow. 1229 1230 Constant *Ops[] = { Res, Overflow }; 1231 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1232 } 1233 } 1234 } 1235 1236 return 0; 1237 } 1238 return 0; 1239 } 1240 return 0; 1241} 1242 1243