ConstantFolding.cpp revision 01b97dd01eec1197d79fceb7229f5ec233994de3
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->isFloatingPoint()) { 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->isFloatingPoint()) { 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 (isa<VectorType>(LoadTy)) { 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(IntType->getBitWidth(), 0); 402 for (unsigned i = 0; 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->getOperand(0), 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/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP 521/// constant expression, do so. 522static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps, 523 const Type *ResultTy, 524 const TargetData *TD) { 525 Constant *Ptr = Ops[0]; 526 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized()) 527 return 0; 528 529 unsigned BitWidth = 530 TD->getTypeSizeInBits(TD->getIntPtrType(Ptr->getContext())); 531 APInt BasePtr(BitWidth, 0); 532 bool BaseIsInt = true; 533 if (!Ptr->isNullValue()) { 534 // If this is a inttoptr from a constant int, we can fold this as the base, 535 // otherwise we can't. 536 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 537 if (CE->getOpcode() == Instruction::IntToPtr) 538 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) { 539 BasePtr = Base->getValue(); 540 BasePtr.zextOrTrunc(BitWidth); 541 } 542 543 if (BasePtr == 0) 544 BaseIsInt = false; 545 } 546 547 // If this is a constant expr gep that is effectively computing an 548 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' 549 for (unsigned i = 1; i != NumOps; ++i) 550 if (!isa<ConstantInt>(Ops[i])) 551 return 0; 552 553 APInt Offset = APInt(BitWidth, 554 TD->getIndexedOffset(Ptr->getType(), 555 (Value**)Ops+1, NumOps-1)); 556 // If the base value for this address is a literal integer value, fold the 557 // getelementptr to the resulting integer value casted to the pointer type. 558 if (BaseIsInt) { 559 Constant *C = ConstantInt::get(Ptr->getContext(), Offset+BasePtr); 560 return ConstantExpr::getIntToPtr(C, ResultTy); 561 } 562 563 // Otherwise form a regular getelementptr. Recompute the indices so that 564 // we eliminate over-indexing of the notional static type array bounds. 565 // This makes it easy to determine if the getelementptr is "inbounds". 566 // Also, this helps GlobalOpt do SROA on GlobalVariables. 567 const Type *Ty = Ptr->getType(); 568 SmallVector<Constant*, 32> NewIdxs; 569 do { 570 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) { 571 // The only pointer indexing we'll do is on the first index of the GEP. 572 if (isa<PointerType>(ATy) && !NewIdxs.empty()) 573 break; 574 // Determine which element of the array the offset points into. 575 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); 576 if (ElemSize == 0) 577 return 0; 578 APInt NewIdx = Offset.udiv(ElemSize); 579 Offset -= NewIdx * ElemSize; 580 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Ty->getContext()), 581 NewIdx)); 582 Ty = ATy->getElementType(); 583 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) { 584 // Determine which field of the struct the offset points into. The 585 // getZExtValue is at least as safe as the StructLayout API because we 586 // know the offset is within the struct at this point. 587 const StructLayout &SL = *TD->getStructLayout(STy); 588 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); 589 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 590 ElIdx)); 591 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); 592 Ty = STy->getTypeAtIndex(ElIdx); 593 } else { 594 // We've reached some non-indexable type. 595 break; 596 } 597 } while (Ty != cast<PointerType>(ResultTy)->getElementType()); 598 599 // If we haven't used up the entire offset by descending the static 600 // type, then the offset is pointing into the middle of an indivisible 601 // member, so we can't simplify it. 602 if (Offset != 0) 603 return 0; 604 605 // Create a GEP. 606 Constant *C = 607 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size()); 608 assert(cast<PointerType>(C->getType())->getElementType() == Ty && 609 "Computed GetElementPtr has unexpected type!"); 610 611 // If we ended up indexing a member with a type that doesn't match 612 // the type of what the original indices indexed, add a cast. 613 if (Ty != cast<PointerType>(ResultTy)->getElementType()) 614 C = FoldBitCast(C, ResultTy, *TD); 615 616 return C; 617} 618 619 620 621//===----------------------------------------------------------------------===// 622// Constant Folding public APIs 623//===----------------------------------------------------------------------===// 624 625 626/// ConstantFoldInstruction - Attempt to constant fold the specified 627/// instruction. If successful, the constant result is returned, if not, null 628/// is returned. Note that this function can only fail when attempting to fold 629/// instructions like loads and stores, which have no constant expression form. 630/// 631Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) { 632 if (PHINode *PN = dyn_cast<PHINode>(I)) { 633 if (PN->getNumIncomingValues() == 0) 634 return UndefValue::get(PN->getType()); 635 636 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0)); 637 if (Result == 0) return 0; 638 639 // Handle PHI nodes specially here... 640 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) 641 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN) 642 return 0; // Not all the same incoming constants... 643 644 // If we reach here, all incoming values are the same constant. 645 return Result; 646 } 647 648 // Scan the operand list, checking to see if they are all constants, if so, 649 // hand off to ConstantFoldInstOperands. 650 SmallVector<Constant*, 8> Ops; 651 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) 652 if (Constant *Op = dyn_cast<Constant>(*i)) 653 Ops.push_back(Op); 654 else 655 return 0; // All operands not constant! 656 657 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 658 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], 659 TD); 660 661 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 662 return ConstantFoldLoadInst(LI, TD); 663 664 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), 665 Ops.data(), Ops.size(), TD); 666} 667 668/// ConstantFoldConstantExpression - Attempt to fold the constant expression 669/// using the specified TargetData. If successful, the constant result is 670/// result is returned, if not, null is returned. 671Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE, 672 const TargetData *TD) { 673 SmallVector<Constant*, 8> Ops; 674 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) { 675 Constant *NewC = cast<Constant>(*i); 676 // Recursively fold the ConstantExpr's operands. 677 if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC)) 678 NewC = ConstantFoldConstantExpression(NewCE, TD); 679 Ops.push_back(NewC); 680 } 681 682 if (CE->isCompare()) 683 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1], 684 TD); 685 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), 686 Ops.data(), Ops.size(), TD); 687} 688 689/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 690/// specified opcode and operands. If successful, the constant result is 691/// returned, if not, null is returned. Note that this function can fail when 692/// attempting to fold instructions like loads and stores, which have no 693/// constant expression form. 694/// 695/// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc 696/// information, due to only being passed an opcode and operands. Constant 697/// folding using this function strips this information. 698/// 699Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy, 700 Constant* const* Ops, unsigned NumOps, 701 const TargetData *TD) { 702 // Handle easy binops first. 703 if (Instruction::isBinaryOp(Opcode)) { 704 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) 705 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD)) 706 return C; 707 708 return ConstantExpr::get(Opcode, Ops[0], Ops[1]); 709 } 710 711 switch (Opcode) { 712 default: return 0; 713 case Instruction::Call: 714 if (Function *F = dyn_cast<Function>(Ops[0])) 715 if (canConstantFoldCallTo(F)) 716 return ConstantFoldCall(F, Ops+1, NumOps-1); 717 return 0; 718 case Instruction::ICmp: 719 case Instruction::FCmp: 720 llvm_unreachable("This function is invalid for compares: no predicate specified"); 721 case Instruction::PtrToInt: 722 // If the input is a inttoptr, eliminate the pair. This requires knowing 723 // the width of a pointer, so it can't be done in ConstantExpr::getCast. 724 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 725 if (TD && CE->getOpcode() == Instruction::IntToPtr) { 726 Constant *Input = CE->getOperand(0); 727 unsigned InWidth = Input->getType()->getScalarSizeInBits(); 728 if (TD->getPointerSizeInBits() < InWidth) { 729 Constant *Mask = 730 ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth, 731 TD->getPointerSizeInBits())); 732 Input = ConstantExpr::getAnd(Input, Mask); 733 } 734 // Do a zext or trunc to get to the dest size. 735 return ConstantExpr::getIntegerCast(Input, DestTy, false); 736 } 737 } 738 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 739 case Instruction::IntToPtr: 740 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if 741 // the int size is >= the ptr size. This requires knowing the width of a 742 // pointer, so it can't be done in ConstantExpr::getCast. 743 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 744 if (TD && 745 TD->getPointerSizeInBits() <= 746 CE->getType()->getScalarSizeInBits()) { 747 if (CE->getOpcode() == Instruction::PtrToInt) 748 return FoldBitCast(CE->getOperand(0), DestTy, *TD); 749 750 // If there's a constant offset added to the integer value before 751 // it is casted back to a pointer, see if the expression can be 752 // converted into a GEP. 753 if (CE->getOpcode() == Instruction::Add) 754 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0))) 755 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1))) 756 if (R->getOpcode() == Instruction::PtrToInt) 757 if (GlobalVariable *GV = 758 dyn_cast<GlobalVariable>(R->getOperand(0))) { 759 const PointerType *GVTy = cast<PointerType>(GV->getType()); 760 if (const ArrayType *AT = 761 dyn_cast<ArrayType>(GVTy->getElementType())) { 762 const Type *ElTy = AT->getElementType(); 763 uint64_t AllocSize = TD->getTypeAllocSize(ElTy); 764 APInt PSA(L->getValue().getBitWidth(), AllocSize); 765 if (ElTy == cast<PointerType>(DestTy)->getElementType() && 766 L->getValue().urem(PSA) == 0) { 767 APInt ElemIdx = L->getValue().udiv(PSA); 768 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(), 769 AT->getNumElements()))) { 770 Constant *Index[] = { 771 Constant::getNullValue(CE->getType()), 772 ConstantInt::get(ElTy->getContext(), ElemIdx) 773 }; 774 return 775 ConstantExpr::getGetElementPtr(GV, &Index[0], 2); 776 } 777 } 778 } 779 } 780 } 781 } 782 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 783 case Instruction::Trunc: 784 case Instruction::ZExt: 785 case Instruction::SExt: 786 case Instruction::FPTrunc: 787 case Instruction::FPExt: 788 case Instruction::UIToFP: 789 case Instruction::SIToFP: 790 case Instruction::FPToUI: 791 case Instruction::FPToSI: 792 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 793 case Instruction::BitCast: 794 if (TD) 795 return FoldBitCast(Ops[0], DestTy, *TD); 796 return ConstantExpr::getBitCast(Ops[0], DestTy); 797 case Instruction::Select: 798 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); 799 case Instruction::ExtractElement: 800 return ConstantExpr::getExtractElement(Ops[0], Ops[1]); 801 case Instruction::InsertElement: 802 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); 803 case Instruction::ShuffleVector: 804 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); 805 case Instruction::GetElementPtr: 806 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD)) 807 return C; 808 809 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1); 810 } 811} 812 813/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 814/// instruction (icmp/fcmp) with the specified operands. If it fails, it 815/// returns a constant expression of the specified operands. 816/// 817Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, 818 Constant *Ops0, Constant *Ops1, 819 const TargetData *TD) { 820 // fold: icmp (inttoptr x), null -> icmp x, 0 821 // fold: icmp (ptrtoint x), 0 -> icmp x, null 822 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y 823 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y 824 // 825 // ConstantExpr::getCompare cannot do this, because it doesn't have TD 826 // around to know if bit truncation is happening. 827 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) { 828 if (TD && Ops1->isNullValue()) { 829 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 830 if (CE0->getOpcode() == Instruction::IntToPtr) { 831 // Convert the integer value to the right size to ensure we get the 832 // proper extension or truncation. 833 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), 834 IntPtrTy, false); 835 Constant *Null = Constant::getNullValue(C->getType()); 836 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD); 837 } 838 839 // Only do this transformation if the int is intptrty in size, otherwise 840 // there is a truncation or extension that we aren't modeling. 841 if (CE0->getOpcode() == Instruction::PtrToInt && 842 CE0->getType() == IntPtrTy) { 843 Constant *C = CE0->getOperand(0); 844 Constant *Null = Constant::getNullValue(C->getType()); 845 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD); 846 } 847 } 848 849 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) { 850 if (TD && CE0->getOpcode() == CE1->getOpcode()) { 851 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 852 853 if (CE0->getOpcode() == Instruction::IntToPtr) { 854 // Convert the integer value to the right size to ensure we get the 855 // proper extension or truncation. 856 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), 857 IntPtrTy, false); 858 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), 859 IntPtrTy, false); 860 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD); 861 } 862 863 // Only do this transformation if the int is intptrty in size, otherwise 864 // there is a truncation or extension that we aren't modeling. 865 if ((CE0->getOpcode() == Instruction::PtrToInt && 866 CE0->getType() == IntPtrTy && 867 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) 868 return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), 869 CE1->getOperand(0), TD); 870 } 871 } 872 } 873 874 return ConstantExpr::getCompare(Predicate, Ops0, Ops1); 875} 876 877 878/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 879/// getelementptr constantexpr, return the constant value being addressed by the 880/// constant expression, or null if something is funny and we can't decide. 881Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, 882 ConstantExpr *CE) { 883 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType())) 884 return 0; // Do not allow stepping over the value! 885 886 // Loop over all of the operands, tracking down which value we are 887 // addressing... 888 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 889 for (++I; I != E; ++I) 890 if (const StructType *STy = dyn_cast<StructType>(*I)) { 891 ConstantInt *CU = cast<ConstantInt>(I.getOperand()); 892 assert(CU->getZExtValue() < STy->getNumElements() && 893 "Struct index out of range!"); 894 unsigned El = (unsigned)CU->getZExtValue(); 895 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 896 C = CS->getOperand(El); 897 } else if (isa<ConstantAggregateZero>(C)) { 898 C = Constant::getNullValue(STy->getElementType(El)); 899 } else if (isa<UndefValue>(C)) { 900 C = UndefValue::get(STy->getElementType(El)); 901 } else { 902 return 0; 903 } 904 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) { 905 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) { 906 if (CI->getZExtValue() >= ATy->getNumElements()) 907 return 0; 908 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) 909 C = CA->getOperand(CI->getZExtValue()); 910 else if (isa<ConstantAggregateZero>(C)) 911 C = Constant::getNullValue(ATy->getElementType()); 912 else if (isa<UndefValue>(C)) 913 C = UndefValue::get(ATy->getElementType()); 914 else 915 return 0; 916 } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) { 917 if (CI->getZExtValue() >= VTy->getNumElements()) 918 return 0; 919 if (ConstantVector *CP = dyn_cast<ConstantVector>(C)) 920 C = CP->getOperand(CI->getZExtValue()); 921 else if (isa<ConstantAggregateZero>(C)) 922 C = Constant::getNullValue(VTy->getElementType()); 923 else if (isa<UndefValue>(C)) 924 C = UndefValue::get(VTy->getElementType()); 925 else 926 return 0; 927 } else { 928 return 0; 929 } 930 } else { 931 return 0; 932 } 933 return C; 934} 935 936 937//===----------------------------------------------------------------------===// 938// Constant Folding for Calls 939// 940 941/// canConstantFoldCallTo - Return true if its even possible to fold a call to 942/// the specified function. 943bool 944llvm::canConstantFoldCallTo(const Function *F) { 945 switch (F->getIntrinsicID()) { 946 case Intrinsic::sqrt: 947 case Intrinsic::powi: 948 case Intrinsic::bswap: 949 case Intrinsic::ctpop: 950 case Intrinsic::ctlz: 951 case Intrinsic::cttz: 952 case Intrinsic::uadd_with_overflow: 953 case Intrinsic::usub_with_overflow: 954 case Intrinsic::sadd_with_overflow: 955 case Intrinsic::ssub_with_overflow: 956 return true; 957 default: 958 return false; 959 case 0: break; 960 } 961 962 if (!F->hasName()) return false; 963 StringRef Name = F->getName(); 964 965 // In these cases, the check of the length is required. We don't want to 966 // return true for a name like "cos\0blah" which strcmp would return equal to 967 // "cos", but has length 8. 968 switch (Name[0]) { 969 default: return false; 970 case 'a': 971 return Name == "acos" || Name == "asin" || 972 Name == "atan" || Name == "atan2"; 973 case 'c': 974 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; 975 case 'e': 976 return Name == "exp"; 977 case 'f': 978 return Name == "fabs" || Name == "fmod" || Name == "floor"; 979 case 'l': 980 return Name == "log" || Name == "log10"; 981 case 'p': 982 return Name == "pow"; 983 case 's': 984 return Name == "sin" || Name == "sinh" || Name == "sqrt" || 985 Name == "sinf" || Name == "sqrtf"; 986 case 't': 987 return Name == "tan" || Name == "tanh"; 988 } 989} 990 991static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 992 const Type *Ty) { 993 errno = 0; 994 V = NativeFP(V); 995 if (errno != 0) { 996 errno = 0; 997 return 0; 998 } 999 1000 if (Ty->isFloatTy()) 1001 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1002 if (Ty->isDoubleTy()) 1003 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1004 llvm_unreachable("Can only constant fold float/double"); 1005 return 0; // dummy return to suppress warning 1006} 1007 1008static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), 1009 double V, double W, const Type *Ty) { 1010 errno = 0; 1011 V = NativeFP(V, W); 1012 if (errno != 0) { 1013 errno = 0; 1014 return 0; 1015 } 1016 1017 if (Ty->isFloatTy()) 1018 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1019 if (Ty->isDoubleTy()) 1020 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1021 llvm_unreachable("Can only constant fold float/double"); 1022 return 0; // dummy return to suppress warning 1023} 1024 1025/// ConstantFoldCall - Attempt to constant fold a call to the specified function 1026/// with the specified arguments, returning null if unsuccessful. 1027Constant * 1028llvm::ConstantFoldCall(Function *F, 1029 Constant *const *Operands, unsigned NumOperands) { 1030 if (!F->hasName()) return 0; 1031 StringRef Name = F->getName(); 1032 1033 const Type *Ty = F->getReturnType(); 1034 if (NumOperands == 1) { 1035 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { 1036 if (!Ty->isFloatTy() && !Ty->isDoubleTy()) 1037 return 0; 1038 /// Currently APFloat versions of these functions do not exist, so we use 1039 /// the host native double versions. Float versions are not called 1040 /// directly but for all these it is true (float)(f((double)arg)) == 1041 /// f(arg). Long double not supported yet. 1042 double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() : 1043 Op->getValueAPF().convertToDouble(); 1044 switch (Name[0]) { 1045 case 'a': 1046 if (Name == "acos") 1047 return ConstantFoldFP(acos, V, Ty); 1048 else if (Name == "asin") 1049 return ConstantFoldFP(asin, V, Ty); 1050 else if (Name == "atan") 1051 return ConstantFoldFP(atan, V, Ty); 1052 break; 1053 case 'c': 1054 if (Name == "ceil") 1055 return ConstantFoldFP(ceil, V, Ty); 1056 else if (Name == "cos") 1057 return ConstantFoldFP(cos, V, Ty); 1058 else if (Name == "cosh") 1059 return ConstantFoldFP(cosh, V, Ty); 1060 else if (Name == "cosf") 1061 return ConstantFoldFP(cos, V, Ty); 1062 break; 1063 case 'e': 1064 if (Name == "exp") 1065 return ConstantFoldFP(exp, V, Ty); 1066 break; 1067 case 'f': 1068 if (Name == "fabs") 1069 return ConstantFoldFP(fabs, V, Ty); 1070 else if (Name == "floor") 1071 return ConstantFoldFP(floor, V, Ty); 1072 break; 1073 case 'l': 1074 if (Name == "log" && V > 0) 1075 return ConstantFoldFP(log, V, Ty); 1076 else if (Name == "log10" && V > 0) 1077 return ConstantFoldFP(log10, V, Ty); 1078 else if (Name == "llvm.sqrt.f32" || 1079 Name == "llvm.sqrt.f64") { 1080 if (V >= -0.0) 1081 return ConstantFoldFP(sqrt, V, Ty); 1082 else // Undefined 1083 return Constant::getNullValue(Ty); 1084 } 1085 break; 1086 case 's': 1087 if (Name == "sin") 1088 return ConstantFoldFP(sin, V, Ty); 1089 else if (Name == "sinh") 1090 return ConstantFoldFP(sinh, V, Ty); 1091 else if (Name == "sqrt" && V >= 0) 1092 return ConstantFoldFP(sqrt, V, Ty); 1093 else if (Name == "sqrtf" && V >= 0) 1094 return ConstantFoldFP(sqrt, V, Ty); 1095 else if (Name == "sinf") 1096 return ConstantFoldFP(sin, V, Ty); 1097 break; 1098 case 't': 1099 if (Name == "tan") 1100 return ConstantFoldFP(tan, V, Ty); 1101 else if (Name == "tanh") 1102 return ConstantFoldFP(tanh, V, Ty); 1103 break; 1104 default: 1105 break; 1106 } 1107 return 0; 1108 } 1109 1110 1111 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { 1112 if (Name.startswith("llvm.bswap")) 1113 return ConstantInt::get(F->getContext(), Op->getValue().byteSwap()); 1114 else if (Name.startswith("llvm.ctpop")) 1115 return ConstantInt::get(Ty, Op->getValue().countPopulation()); 1116 else if (Name.startswith("llvm.cttz")) 1117 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros()); 1118 else if (Name.startswith("llvm.ctlz")) 1119 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros()); 1120 return 0; 1121 } 1122 1123 return 0; 1124 } 1125 1126 if (NumOperands == 2) { 1127 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1128 if (!Ty->isFloatTy() && !Ty->isDoubleTy()) 1129 return 0; 1130 double Op1V = Ty->isFloatTy() ? 1131 (double)Op1->getValueAPF().convertToFloat() : 1132 Op1->getValueAPF().convertToDouble(); 1133 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1134 if (Op2->getType() != Op1->getType()) 1135 return 0; 1136 1137 double Op2V = Ty->isFloatTy() ? 1138 (double)Op2->getValueAPF().convertToFloat(): 1139 Op2->getValueAPF().convertToDouble(); 1140 1141 if (Name == "pow") 1142 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1143 if (Name == "fmod") 1144 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty); 1145 if (Name == "atan2") 1146 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty); 1147 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { 1148 if (Name == "llvm.powi.f32") 1149 return ConstantFP::get(F->getContext(), 1150 APFloat((float)std::pow((float)Op1V, 1151 (int)Op2C->getZExtValue()))); 1152 if (Name == "llvm.powi.f64") 1153 return ConstantFP::get(F->getContext(), 1154 APFloat((double)std::pow((double)Op1V, 1155 (int)Op2C->getZExtValue()))); 1156 } 1157 return 0; 1158 } 1159 1160 1161 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) { 1162 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) { 1163 switch (F->getIntrinsicID()) { 1164 default: break; 1165 case Intrinsic::uadd_with_overflow: { 1166 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result. 1167 Constant *Ops[] = { 1168 Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow. 1169 }; 1170 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1171 } 1172 case Intrinsic::usub_with_overflow: { 1173 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result. 1174 Constant *Ops[] = { 1175 Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow. 1176 }; 1177 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1178 } 1179 case Intrinsic::sadd_with_overflow: { 1180 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result. 1181 Constant *Overflow = ConstantExpr::getSelect( 1182 ConstantExpr::getICmp(CmpInst::ICMP_SGT, 1183 ConstantInt::get(Op1->getType(), 0), Op1), 1184 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2), 1185 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow. 1186 1187 Constant *Ops[] = { Res, Overflow }; 1188 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1189 } 1190 case Intrinsic::ssub_with_overflow: { 1191 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result. 1192 Constant *Overflow = ConstantExpr::getSelect( 1193 ConstantExpr::getICmp(CmpInst::ICMP_SGT, 1194 ConstantInt::get(Op2->getType(), 0), Op2), 1195 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1), 1196 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow. 1197 1198 Constant *Ops[] = { Res, Overflow }; 1199 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1200 } 1201 } 1202 } 1203 1204 return 0; 1205 } 1206 return 0; 1207 } 1208 return 0; 1209} 1210 1211