ConstantFolding.cpp revision 8f73deaa8732a556046bf4ac6207be55972e3b74
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 Ops.push_back(cast<Constant>(*i)); 676 677 if (CE->isCompare()) 678 return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1], 679 TD); 680 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), 681 Ops.data(), Ops.size(), TD); 682} 683 684/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 685/// specified opcode and operands. If successful, the constant result is 686/// returned, if not, null is returned. Note that this function can fail when 687/// attempting to fold instructions like loads and stores, which have no 688/// constant expression form. 689/// 690Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy, 691 Constant* const* Ops, unsigned NumOps, 692 const TargetData *TD) { 693 // Handle easy binops first. 694 if (Instruction::isBinaryOp(Opcode)) { 695 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) 696 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD)) 697 return C; 698 699 return ConstantExpr::get(Opcode, Ops[0], Ops[1]); 700 } 701 702 switch (Opcode) { 703 default: return 0; 704 case Instruction::Call: 705 if (Function *F = dyn_cast<Function>(Ops[0])) 706 if (canConstantFoldCallTo(F)) 707 return ConstantFoldCall(F, Ops+1, NumOps-1); 708 return 0; 709 case Instruction::ICmp: 710 case Instruction::FCmp: 711 llvm_unreachable("This function is invalid for compares: no predicate specified"); 712 case Instruction::PtrToInt: 713 // If the input is a inttoptr, eliminate the pair. This requires knowing 714 // the width of a pointer, so it can't be done in ConstantExpr::getCast. 715 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 716 if (TD && CE->getOpcode() == Instruction::IntToPtr) { 717 Constant *Input = CE->getOperand(0); 718 unsigned InWidth = Input->getType()->getScalarSizeInBits(); 719 if (TD->getPointerSizeInBits() < InWidth) { 720 Constant *Mask = 721 ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth, 722 TD->getPointerSizeInBits())); 723 Input = ConstantExpr::getAnd(Input, Mask); 724 } 725 // Do a zext or trunc to get to the dest size. 726 return ConstantExpr::getIntegerCast(Input, DestTy, false); 727 } 728 } 729 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 730 case Instruction::IntToPtr: 731 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if 732 // the int size is >= the ptr size. This requires knowing the width of a 733 // pointer, so it can't be done in ConstantExpr::getCast. 734 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 735 if (TD && 736 TD->getPointerSizeInBits() <= 737 CE->getType()->getScalarSizeInBits()) { 738 if (CE->getOpcode() == Instruction::PtrToInt) 739 return FoldBitCast(CE->getOperand(0), DestTy, *TD); 740 741 // If there's a constant offset added to the integer value before 742 // it is casted back to a pointer, see if the expression can be 743 // converted into a GEP. 744 if (CE->getOpcode() == Instruction::Add) 745 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0))) 746 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1))) 747 if (R->getOpcode() == Instruction::PtrToInt) 748 if (GlobalVariable *GV = 749 dyn_cast<GlobalVariable>(R->getOperand(0))) { 750 const PointerType *GVTy = cast<PointerType>(GV->getType()); 751 if (const ArrayType *AT = 752 dyn_cast<ArrayType>(GVTy->getElementType())) { 753 const Type *ElTy = AT->getElementType(); 754 uint64_t AllocSize = TD->getTypeAllocSize(ElTy); 755 APInt PSA(L->getValue().getBitWidth(), AllocSize); 756 if (ElTy == cast<PointerType>(DestTy)->getElementType() && 757 L->getValue().urem(PSA) == 0) { 758 APInt ElemIdx = L->getValue().udiv(PSA); 759 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(), 760 AT->getNumElements()))) { 761 Constant *Index[] = { 762 Constant::getNullValue(CE->getType()), 763 ConstantInt::get(ElTy->getContext(), ElemIdx) 764 }; 765 return 766 ConstantExpr::getGetElementPtr(GV, &Index[0], 2); 767 } 768 } 769 } 770 } 771 } 772 } 773 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 774 case Instruction::Trunc: 775 case Instruction::ZExt: 776 case Instruction::SExt: 777 case Instruction::FPTrunc: 778 case Instruction::FPExt: 779 case Instruction::UIToFP: 780 case Instruction::SIToFP: 781 case Instruction::FPToUI: 782 case Instruction::FPToSI: 783 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 784 case Instruction::BitCast: 785 if (TD) 786 return FoldBitCast(Ops[0], DestTy, *TD); 787 return ConstantExpr::getBitCast(Ops[0], DestTy); 788 case Instruction::Select: 789 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); 790 case Instruction::ExtractElement: 791 return ConstantExpr::getExtractElement(Ops[0], Ops[1]); 792 case Instruction::InsertElement: 793 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); 794 case Instruction::ShuffleVector: 795 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); 796 case Instruction::GetElementPtr: 797 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD)) 798 return C; 799 800 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1); 801 } 802} 803 804/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 805/// instruction (icmp/fcmp) with the specified operands. If it fails, it 806/// returns a constant expression of the specified operands. 807/// 808Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, 809 Constant *Ops0, Constant *Ops1, 810 const TargetData *TD) { 811 // fold: icmp (inttoptr x), null -> icmp x, 0 812 // fold: icmp (ptrtoint x), 0 -> icmp x, null 813 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y 814 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y 815 // 816 // ConstantExpr::getCompare cannot do this, because it doesn't have TD 817 // around to know if bit truncation is happening. 818 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) { 819 if (TD && Ops1->isNullValue()) { 820 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 821 if (CE0->getOpcode() == Instruction::IntToPtr) { 822 // Convert the integer value to the right size to ensure we get the 823 // proper extension or truncation. 824 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), 825 IntPtrTy, false); 826 Constant *Null = Constant::getNullValue(C->getType()); 827 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD); 828 } 829 830 // Only do this transformation if the int is intptrty in size, otherwise 831 // there is a truncation or extension that we aren't modeling. 832 if (CE0->getOpcode() == Instruction::PtrToInt && 833 CE0->getType() == IntPtrTy) { 834 Constant *C = CE0->getOperand(0); 835 Constant *Null = Constant::getNullValue(C->getType()); 836 return ConstantFoldCompareInstOperands(Predicate, C, Null, TD); 837 } 838 } 839 840 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) { 841 if (TD && CE0->getOpcode() == CE1->getOpcode()) { 842 const Type *IntPtrTy = TD->getIntPtrType(CE0->getContext()); 843 844 if (CE0->getOpcode() == Instruction::IntToPtr) { 845 // Convert the integer value to the right size to ensure we get the 846 // proper extension or truncation. 847 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), 848 IntPtrTy, false); 849 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), 850 IntPtrTy, false); 851 return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD); 852 } 853 854 // Only do this transformation if the int is intptrty in size, otherwise 855 // there is a truncation or extension that we aren't modeling. 856 if ((CE0->getOpcode() == Instruction::PtrToInt && 857 CE0->getType() == IntPtrTy && 858 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) 859 return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), 860 CE1->getOperand(0), TD); 861 } 862 } 863 } 864 865 return ConstantExpr::getCompare(Predicate, Ops0, Ops1); 866} 867 868 869/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 870/// getelementptr constantexpr, return the constant value being addressed by the 871/// constant expression, or null if something is funny and we can't decide. 872Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, 873 ConstantExpr *CE) { 874 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType())) 875 return 0; // Do not allow stepping over the value! 876 877 // Loop over all of the operands, tracking down which value we are 878 // addressing... 879 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 880 for (++I; I != E; ++I) 881 if (const StructType *STy = dyn_cast<StructType>(*I)) { 882 ConstantInt *CU = cast<ConstantInt>(I.getOperand()); 883 assert(CU->getZExtValue() < STy->getNumElements() && 884 "Struct index out of range!"); 885 unsigned El = (unsigned)CU->getZExtValue(); 886 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 887 C = CS->getOperand(El); 888 } else if (isa<ConstantAggregateZero>(C)) { 889 C = Constant::getNullValue(STy->getElementType(El)); 890 } else if (isa<UndefValue>(C)) { 891 C = UndefValue::get(STy->getElementType(El)); 892 } else { 893 return 0; 894 } 895 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) { 896 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) { 897 if (CI->getZExtValue() >= ATy->getNumElements()) 898 return 0; 899 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) 900 C = CA->getOperand(CI->getZExtValue()); 901 else if (isa<ConstantAggregateZero>(C)) 902 C = Constant::getNullValue(ATy->getElementType()); 903 else if (isa<UndefValue>(C)) 904 C = UndefValue::get(ATy->getElementType()); 905 else 906 return 0; 907 } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) { 908 if (CI->getZExtValue() >= VTy->getNumElements()) 909 return 0; 910 if (ConstantVector *CP = dyn_cast<ConstantVector>(C)) 911 C = CP->getOperand(CI->getZExtValue()); 912 else if (isa<ConstantAggregateZero>(C)) 913 C = Constant::getNullValue(VTy->getElementType()); 914 else if (isa<UndefValue>(C)) 915 C = UndefValue::get(VTy->getElementType()); 916 else 917 return 0; 918 } else { 919 return 0; 920 } 921 } else { 922 return 0; 923 } 924 return C; 925} 926 927 928//===----------------------------------------------------------------------===// 929// Constant Folding for Calls 930// 931 932/// canConstantFoldCallTo - Return true if its even possible to fold a call to 933/// the specified function. 934bool 935llvm::canConstantFoldCallTo(const Function *F) { 936 switch (F->getIntrinsicID()) { 937 case Intrinsic::sqrt: 938 case Intrinsic::powi: 939 case Intrinsic::bswap: 940 case Intrinsic::ctpop: 941 case Intrinsic::ctlz: 942 case Intrinsic::cttz: 943 case Intrinsic::uadd_with_overflow: 944 case Intrinsic::usub_with_overflow: 945 case Intrinsic::sadd_with_overflow: 946 case Intrinsic::ssub_with_overflow: 947 return true; 948 default: 949 return false; 950 case 0: break; 951 } 952 953 if (!F->hasName()) return false; 954 StringRef Name = F->getName(); 955 956 // In these cases, the check of the length is required. We don't want to 957 // return true for a name like "cos\0blah" which strcmp would return equal to 958 // "cos", but has length 8. 959 switch (Name[0]) { 960 default: return false; 961 case 'a': 962 return Name == "acos" || Name == "asin" || 963 Name == "atan" || Name == "atan2"; 964 case 'c': 965 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; 966 case 'e': 967 return Name == "exp"; 968 case 'f': 969 return Name == "fabs" || Name == "fmod" || Name == "floor"; 970 case 'l': 971 return Name == "log" || Name == "log10"; 972 case 'p': 973 return Name == "pow"; 974 case 's': 975 return Name == "sin" || Name == "sinh" || Name == "sqrt" || 976 Name == "sinf" || Name == "sqrtf"; 977 case 't': 978 return Name == "tan" || Name == "tanh"; 979 } 980} 981 982static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 983 const Type *Ty) { 984 errno = 0; 985 V = NativeFP(V); 986 if (errno != 0) { 987 errno = 0; 988 return 0; 989 } 990 991 if (Ty->isFloatTy()) 992 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 993 if (Ty->isDoubleTy()) 994 return ConstantFP::get(Ty->getContext(), APFloat(V)); 995 llvm_unreachable("Can only constant fold float/double"); 996 return 0; // dummy return to suppress warning 997} 998 999static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), 1000 double V, double W, const Type *Ty) { 1001 errno = 0; 1002 V = NativeFP(V, W); 1003 if (errno != 0) { 1004 errno = 0; 1005 return 0; 1006 } 1007 1008 if (Ty->isFloatTy()) 1009 return ConstantFP::get(Ty->getContext(), APFloat((float)V)); 1010 if (Ty->isDoubleTy()) 1011 return ConstantFP::get(Ty->getContext(), APFloat(V)); 1012 llvm_unreachable("Can only constant fold float/double"); 1013 return 0; // dummy return to suppress warning 1014} 1015 1016/// ConstantFoldCall - Attempt to constant fold a call to the specified function 1017/// with the specified arguments, returning null if unsuccessful. 1018Constant * 1019llvm::ConstantFoldCall(Function *F, 1020 Constant *const *Operands, unsigned NumOperands) { 1021 if (!F->hasName()) return 0; 1022 StringRef Name = F->getName(); 1023 1024 const Type *Ty = F->getReturnType(); 1025 if (NumOperands == 1) { 1026 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { 1027 if (!Ty->isFloatTy() && !Ty->isDoubleTy()) 1028 return 0; 1029 /// Currently APFloat versions of these functions do not exist, so we use 1030 /// the host native double versions. Float versions are not called 1031 /// directly but for all these it is true (float)(f((double)arg)) == 1032 /// f(arg). Long double not supported yet. 1033 double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() : 1034 Op->getValueAPF().convertToDouble(); 1035 switch (Name[0]) { 1036 case 'a': 1037 if (Name == "acos") 1038 return ConstantFoldFP(acos, V, Ty); 1039 else if (Name == "asin") 1040 return ConstantFoldFP(asin, V, Ty); 1041 else if (Name == "atan") 1042 return ConstantFoldFP(atan, V, Ty); 1043 break; 1044 case 'c': 1045 if (Name == "ceil") 1046 return ConstantFoldFP(ceil, V, Ty); 1047 else if (Name == "cos") 1048 return ConstantFoldFP(cos, V, Ty); 1049 else if (Name == "cosh") 1050 return ConstantFoldFP(cosh, V, Ty); 1051 else if (Name == "cosf") 1052 return ConstantFoldFP(cos, V, Ty); 1053 break; 1054 case 'e': 1055 if (Name == "exp") 1056 return ConstantFoldFP(exp, V, Ty); 1057 break; 1058 case 'f': 1059 if (Name == "fabs") 1060 return ConstantFoldFP(fabs, V, Ty); 1061 else if (Name == "floor") 1062 return ConstantFoldFP(floor, V, Ty); 1063 break; 1064 case 'l': 1065 if (Name == "log" && V > 0) 1066 return ConstantFoldFP(log, V, Ty); 1067 else if (Name == "log10" && V > 0) 1068 return ConstantFoldFP(log10, V, Ty); 1069 else if (Name == "llvm.sqrt.f32" || 1070 Name == "llvm.sqrt.f64") { 1071 if (V >= -0.0) 1072 return ConstantFoldFP(sqrt, V, Ty); 1073 else // Undefined 1074 return Constant::getNullValue(Ty); 1075 } 1076 break; 1077 case 's': 1078 if (Name == "sin") 1079 return ConstantFoldFP(sin, V, Ty); 1080 else if (Name == "sinh") 1081 return ConstantFoldFP(sinh, V, Ty); 1082 else if (Name == "sqrt" && V >= 0) 1083 return ConstantFoldFP(sqrt, V, Ty); 1084 else if (Name == "sqrtf" && V >= 0) 1085 return ConstantFoldFP(sqrt, V, Ty); 1086 else if (Name == "sinf") 1087 return ConstantFoldFP(sin, V, Ty); 1088 break; 1089 case 't': 1090 if (Name == "tan") 1091 return ConstantFoldFP(tan, V, Ty); 1092 else if (Name == "tanh") 1093 return ConstantFoldFP(tanh, V, Ty); 1094 break; 1095 default: 1096 break; 1097 } 1098 return 0; 1099 } 1100 1101 1102 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { 1103 if (Name.startswith("llvm.bswap")) 1104 return ConstantInt::get(F->getContext(), Op->getValue().byteSwap()); 1105 else if (Name.startswith("llvm.ctpop")) 1106 return ConstantInt::get(Ty, Op->getValue().countPopulation()); 1107 else if (Name.startswith("llvm.cttz")) 1108 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros()); 1109 else if (Name.startswith("llvm.ctlz")) 1110 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros()); 1111 return 0; 1112 } 1113 1114 return 0; 1115 } 1116 1117 if (NumOperands == 2) { 1118 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1119 if (!Ty->isFloatTy() && !Ty->isDoubleTy()) 1120 return 0; 1121 double Op1V = Ty->isFloatTy() ? 1122 (double)Op1->getValueAPF().convertToFloat() : 1123 Op1->getValueAPF().convertToDouble(); 1124 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1125 if (Op2->getType() != Op1->getType()) 1126 return 0; 1127 1128 double Op2V = Ty->isFloatTy() ? 1129 (double)Op2->getValueAPF().convertToFloat(): 1130 Op2->getValueAPF().convertToDouble(); 1131 1132 if (Name == "pow") 1133 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); 1134 if (Name == "fmod") 1135 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty); 1136 if (Name == "atan2") 1137 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty); 1138 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { 1139 if (Name == "llvm.powi.f32") 1140 return ConstantFP::get(F->getContext(), 1141 APFloat((float)std::pow((float)Op1V, 1142 (int)Op2C->getZExtValue()))); 1143 if (Name == "llvm.powi.f64") 1144 return ConstantFP::get(F->getContext(), 1145 APFloat((double)std::pow((double)Op1V, 1146 (int)Op2C->getZExtValue()))); 1147 } 1148 return 0; 1149 } 1150 1151 1152 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) { 1153 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) { 1154 switch (F->getIntrinsicID()) { 1155 default: break; 1156 case Intrinsic::uadd_with_overflow: { 1157 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result. 1158 Constant *Ops[] = { 1159 Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow. 1160 }; 1161 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1162 } 1163 case Intrinsic::usub_with_overflow: { 1164 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result. 1165 Constant *Ops[] = { 1166 Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow. 1167 }; 1168 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1169 } 1170 case Intrinsic::sadd_with_overflow: { 1171 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result. 1172 Constant *Overflow = ConstantExpr::getSelect( 1173 ConstantExpr::getICmp(CmpInst::ICMP_SGT, 1174 ConstantInt::get(Op1->getType(), 0), Op1), 1175 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2), 1176 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow. 1177 1178 Constant *Ops[] = { Res, Overflow }; 1179 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1180 } 1181 case Intrinsic::ssub_with_overflow: { 1182 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result. 1183 Constant *Overflow = ConstantExpr::getSelect( 1184 ConstantExpr::getICmp(CmpInst::ICMP_SGT, 1185 ConstantInt::get(Op2->getType(), 0), Op2), 1186 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1), 1187 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow. 1188 1189 Constant *Ops[] = { Res, Overflow }; 1190 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1191 } 1192 } 1193 } 1194 1195 return 0; 1196 } 1197 return 0; 1198 } 1199 return 0; 1200} 1201 1202