ConstantFolding.cpp revision c7b1382e351249774be63bd73839e8a0671635e1
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/LLVMContext.h" 27#include "llvm/Analysis/ValueTracking.h" 28#include "llvm/Target/TargetData.h" 29#include "llvm/ADT/SmallVector.h" 30#include "llvm/ADT/StringMap.h" 31#include "llvm/Support/ErrorHandling.h" 32#include "llvm/Support/GetElementPtrTypeIterator.h" 33#include "llvm/Support/MathExtras.h" 34#include <cerrno> 35#include <cmath> 36using namespace llvm; 37 38//===----------------------------------------------------------------------===// 39// Constant Folding internal helper functions 40//===----------------------------------------------------------------------===// 41 42/// IsConstantOffsetFromGlobal - If this constant is actually a constant offset 43/// from a global, return the global and the constant. Because of 44/// constantexprs, this function is recursive. 45static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, 46 int64_t &Offset, const TargetData &TD) { 47 // Trivial case, constant is the global. 48 if ((GV = dyn_cast<GlobalValue>(C))) { 49 Offset = 0; 50 return true; 51 } 52 53 // Otherwise, if this isn't a constant expr, bail out. 54 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 55 if (!CE) return false; 56 57 // Look through ptr->int and ptr->ptr casts. 58 if (CE->getOpcode() == Instruction::PtrToInt || 59 CE->getOpcode() == Instruction::BitCast) 60 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD); 61 62 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5) 63 if (CE->getOpcode() == Instruction::GetElementPtr) { 64 // Cannot compute this if the element type of the pointer is missing size 65 // info. 66 if (!cast<PointerType>(CE->getOperand(0)->getType()) 67 ->getElementType()->isSized()) 68 return false; 69 70 // If the base isn't a global+constant, we aren't either. 71 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD)) 72 return false; 73 74 // Otherwise, add any offset that our operands provide. 75 gep_type_iterator GTI = gep_type_begin(CE); 76 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end(); 77 i != e; ++i, ++GTI) { 78 ConstantInt *CI = dyn_cast<ConstantInt>(*i); 79 if (!CI) return false; // Index isn't a simple constant? 80 if (CI->getZExtValue() == 0) continue; // Not adding anything. 81 82 if (const StructType *ST = dyn_cast<StructType>(*GTI)) { 83 // N = N + Offset 84 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue()); 85 } else { 86 const SequentialType *SQT = cast<SequentialType>(*GTI); 87 Offset += TD.getTypeAllocSize(SQT->getElementType())*CI->getSExtValue(); 88 } 89 } 90 return true; 91 } 92 93 return false; 94} 95 96/// ReadDataFromGlobal - Recursive helper to read bits out of global. C is the 97/// constant being copied out of. ByteOffset is an offset into C. CurPtr is the 98/// pointer to copy results into and BytesLeft is the number of bytes left in 99/// the CurPtr buffer. TD is the target data. 100static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset, 101 unsigned char *CurPtr, unsigned BytesLeft, 102 const TargetData &TD) { 103 assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) && 104 "Out of range access"); 105 106 // If this element is zero or undefined, we can just return since *CurPtr is 107 // zero initialized. 108 if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C)) 109 return true; 110 111 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 112 if (CI->getBitWidth() > 64 || 113 (CI->getBitWidth() & 7) != 0) 114 return false; 115 116 uint64_t Val = CI->getZExtValue(); 117 unsigned IntBytes = unsigned(CI->getBitWidth()/8); 118 119 for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) { 120 CurPtr[i] = (unsigned char)(Val >> (ByteOffset * 8)); 121 ++ByteOffset; 122 } 123 return true; 124 } 125 126 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) { 127 if (CFP->getType()->isDoubleTy()) { 128 C = ConstantExpr::getBitCast(C, Type::getInt64Ty(C->getContext())); 129 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 130 } 131 if (CFP->getType()->isFloatTy()){ 132 C = ConstantExpr::getBitCast(C, Type::getInt32Ty(C->getContext())); 133 return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); 134 } 135 return false; 136 } 137 138 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 139 const StructLayout *SL = TD.getStructLayout(CS->getType()); 140 unsigned Index = SL->getElementContainingOffset(ByteOffset); 141 uint64_t CurEltOffset = SL->getElementOffset(Index); 142 ByteOffset -= CurEltOffset; 143 144 while (1) { 145 // If the element access is to the element itself and not to tail padding, 146 // read the bytes from the element. 147 uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType()); 148 149 if (ByteOffset < EltSize && 150 !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr, 151 BytesLeft, TD)) 152 return false; 153 154 ++Index; 155 156 // Check to see if we read from the last struct element, if so we're done. 157 if (Index == CS->getType()->getNumElements()) 158 return true; 159 160 // If we read all of the bytes we needed from this element we're done. 161 uint64_t NextEltOffset = SL->getElementOffset(Index); 162 163 if (BytesLeft <= NextEltOffset-CurEltOffset-ByteOffset) 164 return true; 165 166 // Move to the next element of the struct. 167 CurPtr += NextEltOffset-CurEltOffset-ByteOffset; 168 BytesLeft -= NextEltOffset-CurEltOffset-ByteOffset; 169 ByteOffset = 0; 170 CurEltOffset = NextEltOffset; 171 } 172 // not reached. 173 } 174 175 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) { 176 uint64_t EltSize = TD.getTypeAllocSize(CA->getType()->getElementType()); 177 uint64_t Index = ByteOffset / EltSize; 178 uint64_t Offset = ByteOffset - Index * EltSize; 179 for (; Index != CA->getType()->getNumElements(); ++Index) { 180 if (!ReadDataFromGlobal(CA->getOperand(Index), Offset, CurPtr, 181 BytesLeft, TD)) 182 return false; 183 if (EltSize >= BytesLeft) 184 return true; 185 186 Offset = 0; 187 BytesLeft -= EltSize; 188 CurPtr += EltSize; 189 } 190 return true; 191 } 192 193 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) { 194 uint64_t EltSize = TD.getTypeAllocSize(CV->getType()->getElementType()); 195 uint64_t Index = ByteOffset / EltSize; 196 uint64_t Offset = ByteOffset - Index * EltSize; 197 for (; Index != CV->getType()->getNumElements(); ++Index) { 198 if (!ReadDataFromGlobal(CV->getOperand(Index), Offset, CurPtr, 199 BytesLeft, TD)) 200 return false; 201 if (EltSize >= BytesLeft) 202 return true; 203 204 Offset = 0; 205 BytesLeft -= EltSize; 206 CurPtr += EltSize; 207 } 208 return true; 209 } 210 211 // Otherwise, unknown initializer type. 212 return false; 213} 214 215static Constant *FoldReinterpretLoadFromConstPtr(Constant *C, 216 const TargetData &TD) { 217 const Type *LoadTy = cast<PointerType>(C->getType())->getElementType(); 218 const IntegerType *IntType = dyn_cast<IntegerType>(LoadTy); 219 220 // If this isn't an integer load we can't fold it directly. 221 if (!IntType) { 222 // If this is a float/double load, we can try folding it as an int32/64 load 223 // and then bitcast the result. This can be useful for union cases. Note 224 // that address spaces don't matter here since we're not going to result in 225 // an actual new load. 226 const Type *MapTy; 227 if (LoadTy->isFloatTy()) 228 MapTy = Type::getInt32PtrTy(C->getContext()); 229 else if (LoadTy->isDoubleTy()) 230 MapTy = Type::getInt64PtrTy(C->getContext()); 231 else if (isa<VectorType>(LoadTy)) { 232 MapTy = IntegerType::get(C->getContext(), 233 TD.getTypeAllocSizeInBits(LoadTy)); 234 MapTy = PointerType::getUnqual(MapTy); 235 } else 236 return 0; 237 238 C = ConstantExpr::getBitCast(C, MapTy); 239 if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD)) 240 return ConstantExpr::getBitCast(Res, LoadTy); 241 return 0; 242 } 243 244 unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8; 245 if (BytesLoaded > 32 || BytesLoaded == 0) return 0; 246 247 GlobalValue *GVal; 248 int64_t Offset; 249 if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD)) 250 return 0; 251 252 GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal); 253 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() || 254 !GV->getInitializer()->getType()->isSized()) 255 return 0; 256 257 // If we're loading off the beginning of the global, some bytes may be valid, 258 // but we don't try to handle this. 259 if (Offset < 0) return 0; 260 261 // If we're not accessing anything in this constant, the result is undefined. 262 if (uint64_t(Offset) >= TD.getTypeAllocSize(GV->getInitializer()->getType())) 263 return UndefValue::get(IntType); 264 265 unsigned char RawBytes[32] = {0}; 266 if (!ReadDataFromGlobal(GV->getInitializer(), Offset, RawBytes, 267 BytesLoaded, TD)) 268 return 0; 269 270 APInt ResultVal(IntType->getBitWidth(), 0); 271 for (unsigned i = 0; i != BytesLoaded; ++i) { 272 ResultVal <<= 8; 273 ResultVal |= APInt(IntType->getBitWidth(), RawBytes[BytesLoaded-1-i]); 274 } 275 276 return ConstantInt::get(IntType->getContext(), ResultVal); 277} 278 279/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 280/// produce if it is constant and determinable. If this is not determinable, 281/// return null. 282Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, 283 const TargetData *TD) { 284 // First, try the easy cases: 285 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 286 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 287 return GV->getInitializer(); 288 289 // If the loaded value isn't a constant expr, we can't handle it. 290 ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 291 if (!CE) return 0; 292 293 if (CE->getOpcode() == Instruction::GetElementPtr) { 294 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) 295 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 296 if (Constant *V = 297 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) 298 return V; 299 } 300 301 // Instead of loading constant c string, use corresponding integer value 302 // directly if string length is small enough. 303 std::string Str; 304 if (TD && GetConstantStringInfo(CE->getOperand(0), Str) && !Str.empty()) { 305 unsigned StrLen = Str.length(); 306 const Type *Ty = cast<PointerType>(CE->getType())->getElementType(); 307 unsigned NumBits = Ty->getPrimitiveSizeInBits(); 308 // Replace LI with immediate integer store. 309 if ((NumBits >> 3) == StrLen + 1) { 310 APInt StrVal(NumBits, 0); 311 APInt SingleChar(NumBits, 0); 312 if (TD->isLittleEndian()) { 313 for (signed i = StrLen-1; i >= 0; i--) { 314 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 315 StrVal = (StrVal << 8) | SingleChar; 316 } 317 } else { 318 for (unsigned i = 0; i < StrLen; i++) { 319 SingleChar = (uint64_t) Str[i] & UCHAR_MAX; 320 StrVal = (StrVal << 8) | SingleChar; 321 } 322 // Append NULL at the end. 323 SingleChar = 0; 324 StrVal = (StrVal << 8) | SingleChar; 325 } 326 return ConstantInt::get(CE->getContext(), StrVal); 327 } 328 } 329 330 // If this load comes from anywhere in a constant global, and if the global 331 // is all undef or zero, we know what it loads. 332 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getUnderlyingObject())){ 333 if (GV->isConstant() && GV->hasDefinitiveInitializer()) { 334 const Type *ResTy = cast<PointerType>(C->getType())->getElementType(); 335 if (GV->getInitializer()->isNullValue()) 336 return Constant::getNullValue(ResTy); 337 if (isa<UndefValue>(GV->getInitializer())) 338 return UndefValue::get(ResTy); 339 } 340 } 341 342 // Try hard to fold loads from bitcasted strange and non-type-safe things. We 343 // currently don't do any of this for big endian systems. It can be 344 // generalized in the future if someone is interested. 345 if (TD && TD->isLittleEndian()) 346 return FoldReinterpretLoadFromConstPtr(CE, *TD); 347 return 0; 348} 349 350static Constant *ConstantFoldLoadInst(const LoadInst *LI, const TargetData *TD){ 351 if (LI->isVolatile()) return 0; 352 353 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0))) 354 return ConstantFoldLoadFromConstPtr(C, TD); 355 356 return 0; 357} 358 359/// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression. 360/// Attempt to symbolically evaluate the result of a binary operator merging 361/// these together. If target data info is available, it is provided as TD, 362/// otherwise TD is null. 363static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, 364 Constant *Op1, const TargetData *TD, 365 LLVMContext &Context){ 366 // SROA 367 368 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl. 369 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute 370 // bits. 371 372 373 // If the constant expr is something like &A[123] - &A[4].f, fold this into a 374 // constant. This happens frequently when iterating over a global array. 375 if (Opc == Instruction::Sub && TD) { 376 GlobalValue *GV1, *GV2; 377 int64_t Offs1, Offs2; 378 379 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD)) 380 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) && 381 GV1 == GV2) { 382 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow. 383 return ConstantInt::get(Op0->getType(), Offs1-Offs2); 384 } 385 } 386 387 return 0; 388} 389 390/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP 391/// constant expression, do so. 392static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps, 393 const Type *ResultTy, 394 LLVMContext &Context, 395 const TargetData *TD) { 396 Constant *Ptr = Ops[0]; 397 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized()) 398 return 0; 399 400 unsigned BitWidth = TD->getTypeSizeInBits(TD->getIntPtrType(Context)); 401 APInt BasePtr(BitWidth, 0); 402 bool BaseIsInt = true; 403 if (!Ptr->isNullValue()) { 404 // If this is a inttoptr from a constant int, we can fold this as the base, 405 // otherwise we can't. 406 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 407 if (CE->getOpcode() == Instruction::IntToPtr) 408 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) { 409 BasePtr = Base->getValue(); 410 BasePtr.zextOrTrunc(BitWidth); 411 } 412 413 if (BasePtr == 0) 414 BaseIsInt = false; 415 } 416 417 // If this is a constant expr gep that is effectively computing an 418 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' 419 for (unsigned i = 1; i != NumOps; ++i) 420 if (!isa<ConstantInt>(Ops[i])) 421 return 0; 422 423 APInt Offset = APInt(BitWidth, 424 TD->getIndexedOffset(Ptr->getType(), 425 (Value**)Ops+1, NumOps-1)); 426 // If the base value for this address is a literal integer value, fold the 427 // getelementptr to the resulting integer value casted to the pointer type. 428 if (BaseIsInt) { 429 Constant *C = ConstantInt::get(Context, Offset+BasePtr); 430 return ConstantExpr::getIntToPtr(C, ResultTy); 431 } 432 433 // Otherwise form a regular getelementptr. Recompute the indices so that 434 // we eliminate over-indexing of the notional static type array bounds. 435 // This makes it easy to determine if the getelementptr is "inbounds". 436 // Also, this helps GlobalOpt do SROA on GlobalVariables. 437 const Type *Ty = Ptr->getType(); 438 SmallVector<Constant*, 32> NewIdxs; 439 do { 440 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) { 441 // The only pointer indexing we'll do is on the first index of the GEP. 442 if (isa<PointerType>(ATy) && !NewIdxs.empty()) 443 break; 444 // Determine which element of the array the offset points into. 445 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); 446 if (ElemSize == 0) 447 return 0; 448 APInt NewIdx = Offset.udiv(ElemSize); 449 Offset -= NewIdx * ElemSize; 450 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Context), NewIdx)); 451 Ty = ATy->getElementType(); 452 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) { 453 // Determine which field of the struct the offset points into. The 454 // getZExtValue is at least as safe as the StructLayout API because we 455 // know the offset is within the struct at this point. 456 const StructLayout &SL = *TD->getStructLayout(STy); 457 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); 458 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Context), ElIdx)); 459 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); 460 Ty = STy->getTypeAtIndex(ElIdx); 461 } else { 462 // We've reached some non-indexable type. 463 break; 464 } 465 } while (Ty != cast<PointerType>(ResultTy)->getElementType()); 466 467 // If we haven't used up the entire offset by descending the static 468 // type, then the offset is pointing into the middle of an indivisible 469 // member, so we can't simplify it. 470 if (Offset != 0) 471 return 0; 472 473 // Create a GEP. 474 Constant *C = 475 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size()); 476 assert(cast<PointerType>(C->getType())->getElementType() == Ty && 477 "Computed GetElementPtr has unexpected type!"); 478 479 // If we ended up indexing a member with a type that doesn't match 480 // the type of what the original indices indexed, add a cast. 481 if (Ty != cast<PointerType>(ResultTy)->getElementType()) 482 C = ConstantExpr::getBitCast(C, ResultTy); 483 484 return C; 485} 486 487/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with 488/// targetdata. Return 0 if unfoldable. 489static Constant *FoldBitCast(Constant *C, const Type *DestTy, 490 const TargetData &TD, LLVMContext &Context) { 491 // If this is a bitcast from constant vector -> vector, fold it. 492 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) { 493 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) { 494 // If the element types match, VMCore can fold it. 495 unsigned NumDstElt = DestVTy->getNumElements(); 496 unsigned NumSrcElt = CV->getNumOperands(); 497 if (NumDstElt == NumSrcElt) 498 return 0; 499 500 const Type *SrcEltTy = CV->getType()->getElementType(); 501 const Type *DstEltTy = DestVTy->getElementType(); 502 503 // Otherwise, we're changing the number of elements in a vector, which 504 // requires endianness information to do the right thing. For example, 505 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 506 // folds to (little endian): 507 // <4 x i32> <i32 0, i32 0, i32 1, i32 0> 508 // and to (big endian): 509 // <4 x i32> <i32 0, i32 0, i32 0, i32 1> 510 511 // First thing is first. We only want to think about integer here, so if 512 // we have something in FP form, recast it as integer. 513 if (DstEltTy->isFloatingPoint()) { 514 // Fold to an vector of integers with same size as our FP type. 515 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits(); 516 const Type *DestIVTy = VectorType::get( 517 IntegerType::get(Context, FPWidth), NumDstElt); 518 // Recursively handle this integer conversion, if possible. 519 C = FoldBitCast(C, DestIVTy, TD, Context); 520 if (!C) return 0; 521 522 // Finally, VMCore can handle this now that #elts line up. 523 return ConstantExpr::getBitCast(C, DestTy); 524 } 525 526 // Okay, we know the destination is integer, if the input is FP, convert 527 // it to integer first. 528 if (SrcEltTy->isFloatingPoint()) { 529 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); 530 const Type *SrcIVTy = VectorType::get( 531 IntegerType::get(Context, FPWidth), NumSrcElt); 532 // Ask VMCore to do the conversion now that #elts line up. 533 C = ConstantExpr::getBitCast(C, SrcIVTy); 534 CV = dyn_cast<ConstantVector>(C); 535 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out. 536 } 537 538 // Now we know that the input and output vectors are both integer vectors 539 // of the same size, and that their #elements is not the same. Do the 540 // conversion here, which depends on whether the input or output has 541 // more elements. 542 bool isLittleEndian = TD.isLittleEndian(); 543 544 SmallVector<Constant*, 32> Result; 545 if (NumDstElt < NumSrcElt) { 546 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>) 547 Constant *Zero = Constant::getNullValue(DstEltTy); 548 unsigned Ratio = NumSrcElt/NumDstElt; 549 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits(); 550 unsigned SrcElt = 0; 551 for (unsigned i = 0; i != NumDstElt; ++i) { 552 // Build each element of the result. 553 Constant *Elt = Zero; 554 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1); 555 for (unsigned j = 0; j != Ratio; ++j) { 556 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++)); 557 if (!Src) return 0; // Reject constantexpr elements. 558 559 // Zero extend the element to the right size. 560 Src = ConstantExpr::getZExt(Src, Elt->getType()); 561 562 // Shift it to the right place, depending on endianness. 563 Src = ConstantExpr::getShl(Src, 564 ConstantInt::get(Src->getType(), ShiftAmt)); 565 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize; 566 567 // Mix it in. 568 Elt = ConstantExpr::getOr(Elt, Src); 569 } 570 Result.push_back(Elt); 571 } 572 } else { 573 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) 574 unsigned Ratio = NumDstElt/NumSrcElt; 575 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits(); 576 577 // Loop over each source value, expanding into multiple results. 578 for (unsigned i = 0; i != NumSrcElt; ++i) { 579 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i)); 580 if (!Src) return 0; // Reject constantexpr elements. 581 582 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1); 583 for (unsigned j = 0; j != Ratio; ++j) { 584 // Shift the piece of the value into the right place, depending on 585 // endianness. 586 Constant *Elt = ConstantExpr::getLShr(Src, 587 ConstantInt::get(Src->getType(), ShiftAmt)); 588 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize; 589 590 // Truncate and remember this piece. 591 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy)); 592 } 593 } 594 } 595 596 return ConstantVector::get(Result.data(), Result.size()); 597 } 598 } 599 600 return 0; 601} 602 603 604//===----------------------------------------------------------------------===// 605// Constant Folding public APIs 606//===----------------------------------------------------------------------===// 607 608 609/// ConstantFoldInstruction - Attempt to constant fold the specified 610/// instruction. If successful, the constant result is returned, if not, null 611/// is returned. Note that this function can only fail when attempting to fold 612/// instructions like loads and stores, which have no constant expression form. 613/// 614Constant *llvm::ConstantFoldInstruction(Instruction *I, LLVMContext &Context, 615 const TargetData *TD) { 616 if (PHINode *PN = dyn_cast<PHINode>(I)) { 617 if (PN->getNumIncomingValues() == 0) 618 return UndefValue::get(PN->getType()); 619 620 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0)); 621 if (Result == 0) return 0; 622 623 // Handle PHI nodes specially here... 624 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) 625 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN) 626 return 0; // Not all the same incoming constants... 627 628 // If we reach here, all incoming values are the same constant. 629 return Result; 630 } 631 632 // Scan the operand list, checking to see if they are all constants, if so, 633 // hand off to ConstantFoldInstOperands. 634 SmallVector<Constant*, 8> Ops; 635 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) 636 if (Constant *Op = dyn_cast<Constant>(*i)) 637 Ops.push_back(Op); 638 else 639 return 0; // All operands not constant! 640 641 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 642 return ConstantFoldCompareInstOperands(CI->getPredicate(), 643 Ops.data(), Ops.size(), 644 Context, TD); 645 646 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 647 return ConstantFoldLoadInst(LI, TD); 648 649 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), 650 Ops.data(), Ops.size(), Context, TD); 651} 652 653/// ConstantFoldConstantExpression - Attempt to fold the constant expression 654/// using the specified TargetData. If successful, the constant result is 655/// result is returned, if not, null is returned. 656Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE, 657 LLVMContext &Context, 658 const TargetData *TD) { 659 SmallVector<Constant*, 8> Ops; 660 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) 661 Ops.push_back(cast<Constant>(*i)); 662 663 if (CE->isCompare()) 664 return ConstantFoldCompareInstOperands(CE->getPredicate(), 665 Ops.data(), Ops.size(), 666 Context, TD); 667 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), 668 Ops.data(), Ops.size(), Context, TD); 669} 670 671/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 672/// specified opcode and operands. If successful, the constant result is 673/// returned, if not, null is returned. Note that this function can fail when 674/// attempting to fold instructions like loads and stores, which have no 675/// constant expression form. 676/// 677Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy, 678 Constant* const* Ops, unsigned NumOps, 679 LLVMContext &Context, 680 const TargetData *TD) { 681 // Handle easy binops first. 682 if (Instruction::isBinaryOp(Opcode)) { 683 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) 684 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD, 685 Context)) 686 return C; 687 688 return ConstantExpr::get(Opcode, Ops[0], Ops[1]); 689 } 690 691 switch (Opcode) { 692 default: return 0; 693 case Instruction::Call: 694 if (Function *F = dyn_cast<Function>(Ops[0])) 695 if (canConstantFoldCallTo(F)) 696 return ConstantFoldCall(F, Ops+1, NumOps-1); 697 return 0; 698 case Instruction::ICmp: 699 case Instruction::FCmp: 700 llvm_unreachable("This function is invalid for compares: no predicate specified"); 701 case Instruction::PtrToInt: 702 // If the input is a inttoptr, eliminate the pair. This requires knowing 703 // the width of a pointer, so it can't be done in ConstantExpr::getCast. 704 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 705 if (TD && CE->getOpcode() == Instruction::IntToPtr) { 706 Constant *Input = CE->getOperand(0); 707 unsigned InWidth = Input->getType()->getScalarSizeInBits(); 708 if (TD->getPointerSizeInBits() < InWidth) { 709 Constant *Mask = 710 ConstantInt::get(Context, APInt::getLowBitsSet(InWidth, 711 TD->getPointerSizeInBits())); 712 Input = ConstantExpr::getAnd(Input, Mask); 713 } 714 // Do a zext or trunc to get to the dest size. 715 return ConstantExpr::getIntegerCast(Input, DestTy, false); 716 } 717 } 718 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 719 case Instruction::IntToPtr: 720 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if 721 // the int size is >= the ptr size. This requires knowing the width of a 722 // pointer, so it can't be done in ConstantExpr::getCast. 723 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { 724 if (TD && 725 TD->getPointerSizeInBits() <= 726 CE->getType()->getScalarSizeInBits()) { 727 if (CE->getOpcode() == Instruction::PtrToInt) { 728 Constant *Input = CE->getOperand(0); 729 Constant *C = FoldBitCast(Input, DestTy, *TD, Context); 730 return C ? C : ConstantExpr::getBitCast(Input, DestTy); 731 } 732 // If there's a constant offset added to the integer value before 733 // it is casted back to a pointer, see if the expression can be 734 // converted into a GEP. 735 if (CE->getOpcode() == Instruction::Add) 736 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0))) 737 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1))) 738 if (R->getOpcode() == Instruction::PtrToInt) 739 if (GlobalVariable *GV = 740 dyn_cast<GlobalVariable>(R->getOperand(0))) { 741 const PointerType *GVTy = cast<PointerType>(GV->getType()); 742 if (const ArrayType *AT = 743 dyn_cast<ArrayType>(GVTy->getElementType())) { 744 const Type *ElTy = AT->getElementType(); 745 uint64_t AllocSize = TD->getTypeAllocSize(ElTy); 746 APInt PSA(L->getValue().getBitWidth(), AllocSize); 747 if (ElTy == cast<PointerType>(DestTy)->getElementType() && 748 L->getValue().urem(PSA) == 0) { 749 APInt ElemIdx = L->getValue().udiv(PSA); 750 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(), 751 AT->getNumElements()))) { 752 Constant *Index[] = { 753 Constant::getNullValue(CE->getType()), 754 ConstantInt::get(Context, ElemIdx) 755 }; 756 return 757 ConstantExpr::getGetElementPtr(GV, &Index[0], 2); 758 } 759 } 760 } 761 } 762 } 763 } 764 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 765 case Instruction::Trunc: 766 case Instruction::ZExt: 767 case Instruction::SExt: 768 case Instruction::FPTrunc: 769 case Instruction::FPExt: 770 case Instruction::UIToFP: 771 case Instruction::SIToFP: 772 case Instruction::FPToUI: 773 case Instruction::FPToSI: 774 return ConstantExpr::getCast(Opcode, Ops[0], DestTy); 775 case Instruction::BitCast: 776 if (TD) 777 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context)) 778 return C; 779 return ConstantExpr::getBitCast(Ops[0], DestTy); 780 case Instruction::Select: 781 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); 782 case Instruction::ExtractElement: 783 return ConstantExpr::getExtractElement(Ops[0], Ops[1]); 784 case Instruction::InsertElement: 785 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); 786 case Instruction::ShuffleVector: 787 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); 788 case Instruction::GetElementPtr: 789 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD)) 790 return C; 791 792 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1); 793 } 794} 795 796/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 797/// instruction (icmp/fcmp) with the specified operands. If it fails, it 798/// returns a constant expression of the specified operands. 799/// 800Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, 801 Constant*const * Ops, 802 unsigned NumOps, 803 LLVMContext &Context, 804 const TargetData *TD) { 805 // fold: icmp (inttoptr x), null -> icmp x, 0 806 // fold: icmp (ptrtoint x), 0 -> icmp x, null 807 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y 808 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y 809 // 810 // ConstantExpr::getCompare cannot do this, because it doesn't have TD 811 // around to know if bit truncation is happening. 812 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) { 813 if (TD && Ops[1]->isNullValue()) { 814 const Type *IntPtrTy = TD->getIntPtrType(Context); 815 if (CE0->getOpcode() == Instruction::IntToPtr) { 816 // Convert the integer value to the right size to ensure we get the 817 // proper extension or truncation. 818 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), 819 IntPtrTy, false); 820 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) }; 821 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, 822 Context, TD); 823 } 824 825 // Only do this transformation if the int is intptrty in size, otherwise 826 // there is a truncation or extension that we aren't modeling. 827 if (CE0->getOpcode() == Instruction::PtrToInt && 828 CE0->getType() == IntPtrTy) { 829 Constant *C = CE0->getOperand(0); 830 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) }; 831 // FIXME! 832 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, 833 Context, TD); 834 } 835 } 836 837 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) { 838 if (TD && CE0->getOpcode() == CE1->getOpcode()) { 839 const Type *IntPtrTy = TD->getIntPtrType(Context); 840 841 if (CE0->getOpcode() == Instruction::IntToPtr) { 842 // Convert the integer value to the right size to ensure we get the 843 // proper extension or truncation. 844 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), 845 IntPtrTy, false); 846 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), 847 IntPtrTy, false); 848 Constant *NewOps[] = { C0, C1 }; 849 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, 850 Context, TD); 851 } 852 853 // Only do this transformation if the int is intptrty in size, otherwise 854 // there is a truncation or extension that we aren't modeling. 855 if ((CE0->getOpcode() == Instruction::PtrToInt && 856 CE0->getType() == IntPtrTy && 857 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) { 858 Constant *NewOps[] = { 859 CE0->getOperand(0), CE1->getOperand(0) 860 }; 861 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, 862 Context, TD); 863 } 864 } 865 } 866 } 867 return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]); 868} 869 870 871/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 872/// getelementptr constantexpr, return the constant value being addressed by the 873/// constant expression, or null if something is funny and we can't decide. 874Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, 875 ConstantExpr *CE) { 876 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType())) 877 return 0; // Do not allow stepping over the value! 878 879 // Loop over all of the operands, tracking down which value we are 880 // addressing... 881 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 882 for (++I; I != E; ++I) 883 if (const StructType *STy = dyn_cast<StructType>(*I)) { 884 ConstantInt *CU = cast<ConstantInt>(I.getOperand()); 885 assert(CU->getZExtValue() < STy->getNumElements() && 886 "Struct index out of range!"); 887 unsigned El = (unsigned)CU->getZExtValue(); 888 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { 889 C = CS->getOperand(El); 890 } else if (isa<ConstantAggregateZero>(C)) { 891 C = Constant::getNullValue(STy->getElementType(El)); 892 } else if (isa<UndefValue>(C)) { 893 C = UndefValue::get(STy->getElementType(El)); 894 } else { 895 return 0; 896 } 897 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) { 898 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) { 899 if (CI->getZExtValue() >= ATy->getNumElements()) 900 return 0; 901 if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) 902 C = CA->getOperand(CI->getZExtValue()); 903 else if (isa<ConstantAggregateZero>(C)) 904 C = Constant::getNullValue(ATy->getElementType()); 905 else if (isa<UndefValue>(C)) 906 C = UndefValue::get(ATy->getElementType()); 907 else 908 return 0; 909 } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) { 910 if (CI->getZExtValue() >= VTy->getNumElements()) 911 return 0; 912 if (ConstantVector *CP = dyn_cast<ConstantVector>(C)) 913 C = CP->getOperand(CI->getZExtValue()); 914 else if (isa<ConstantAggregateZero>(C)) 915 C = Constant::getNullValue(VTy->getElementType()); 916 else if (isa<UndefValue>(C)) 917 C = UndefValue::get(VTy->getElementType()); 918 else 919 return 0; 920 } else { 921 return 0; 922 } 923 } else { 924 return 0; 925 } 926 return C; 927} 928 929 930//===----------------------------------------------------------------------===// 931// Constant Folding for Calls 932// 933 934/// canConstantFoldCallTo - Return true if its even possible to fold a call to 935/// the specified function. 936bool 937llvm::canConstantFoldCallTo(const Function *F) { 938 switch (F->getIntrinsicID()) { 939 case Intrinsic::sqrt: 940 case Intrinsic::powi: 941 case Intrinsic::bswap: 942 case Intrinsic::ctpop: 943 case Intrinsic::ctlz: 944 case Intrinsic::cttz: 945 case Intrinsic::uadd_with_overflow: 946 case Intrinsic::usub_with_overflow: 947 case Intrinsic::sadd_with_overflow: 948 case Intrinsic::ssub_with_overflow: 949 return true; 950 default: 951 return false; 952 case 0: break; 953 } 954 955 if (!F->hasName()) return false; 956 StringRef Name = F->getName(); 957 958 // In these cases, the check of the length is required. We don't want to 959 // return true for a name like "cos\0blah" which strcmp would return equal to 960 // "cos", but has length 8. 961 switch (Name[0]) { 962 default: return false; 963 case 'a': 964 return Name == "acos" || Name == "asin" || 965 Name == "atan" || Name == "atan2"; 966 case 'c': 967 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; 968 case 'e': 969 return Name == "exp"; 970 case 'f': 971 return Name == "fabs" || Name == "fmod" || Name == "floor"; 972 case 'l': 973 return Name == "log" || Name == "log10"; 974 case 'p': 975 return Name == "pow"; 976 case 's': 977 return Name == "sin" || Name == "sinh" || Name == "sqrt" || 978 Name == "sinf" || Name == "sqrtf"; 979 case 't': 980 return Name == "tan" || Name == "tanh"; 981 } 982} 983 984static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 985 const Type *Ty, LLVMContext &Context) { 986 errno = 0; 987 V = NativeFP(V); 988 if (errno != 0) { 989 errno = 0; 990 return 0; 991 } 992 993 if (Ty->isFloatTy()) 994 return ConstantFP::get(Context, APFloat((float)V)); 995 if (Ty->isDoubleTy()) 996 return ConstantFP::get(Context, APFloat(V)); 997 llvm_unreachable("Can only constant fold float/double"); 998 return 0; // dummy return to suppress warning 999} 1000 1001static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), 1002 double V, double W, 1003 const Type *Ty, 1004 LLVMContext &Context) { 1005 errno = 0; 1006 V = NativeFP(V, W); 1007 if (errno != 0) { 1008 errno = 0; 1009 return 0; 1010 } 1011 1012 if (Ty->isFloatTy()) 1013 return ConstantFP::get(Context, APFloat((float)V)); 1014 if (Ty->isDoubleTy()) 1015 return ConstantFP::get(Context, APFloat(V)); 1016 llvm_unreachable("Can only constant fold float/double"); 1017 return 0; // dummy return to suppress warning 1018} 1019 1020/// ConstantFoldCall - Attempt to constant fold a call to the specified function 1021/// with the specified arguments, returning null if unsuccessful. 1022Constant * 1023llvm::ConstantFoldCall(Function *F, 1024 Constant *const *Operands, unsigned NumOperands) { 1025 if (!F->hasName()) return 0; 1026 LLVMContext &Context = F->getContext(); 1027 StringRef Name = F->getName(); 1028 1029 const Type *Ty = F->getReturnType(); 1030 if (NumOperands == 1) { 1031 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { 1032 if (!Ty->isFloatTy() && !Ty->isDoubleTy()) 1033 return 0; 1034 /// Currently APFloat versions of these functions do not exist, so we use 1035 /// the host native double versions. Float versions are not called 1036 /// directly but for all these it is true (float)(f((double)arg)) == 1037 /// f(arg). Long double not supported yet. 1038 double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() : 1039 Op->getValueAPF().convertToDouble(); 1040 switch (Name[0]) { 1041 case 'a': 1042 if (Name == "acos") 1043 return ConstantFoldFP(acos, V, Ty, Context); 1044 else if (Name == "asin") 1045 return ConstantFoldFP(asin, V, Ty, Context); 1046 else if (Name == "atan") 1047 return ConstantFoldFP(atan, V, Ty, Context); 1048 break; 1049 case 'c': 1050 if (Name == "ceil") 1051 return ConstantFoldFP(ceil, V, Ty, Context); 1052 else if (Name == "cos") 1053 return ConstantFoldFP(cos, V, Ty, Context); 1054 else if (Name == "cosh") 1055 return ConstantFoldFP(cosh, V, Ty, Context); 1056 else if (Name == "cosf") 1057 return ConstantFoldFP(cos, V, Ty, Context); 1058 break; 1059 case 'e': 1060 if (Name == "exp") 1061 return ConstantFoldFP(exp, V, Ty, Context); 1062 break; 1063 case 'f': 1064 if (Name == "fabs") 1065 return ConstantFoldFP(fabs, V, Ty, Context); 1066 else if (Name == "floor") 1067 return ConstantFoldFP(floor, V, Ty, Context); 1068 break; 1069 case 'l': 1070 if (Name == "log" && V > 0) 1071 return ConstantFoldFP(log, V, Ty, Context); 1072 else if (Name == "log10" && V > 0) 1073 return ConstantFoldFP(log10, V, Ty, Context); 1074 else if (Name == "llvm.sqrt.f32" || 1075 Name == "llvm.sqrt.f64") { 1076 if (V >= -0.0) 1077 return ConstantFoldFP(sqrt, V, Ty, Context); 1078 else // Undefined 1079 return Constant::getNullValue(Ty); 1080 } 1081 break; 1082 case 's': 1083 if (Name == "sin") 1084 return ConstantFoldFP(sin, V, Ty, Context); 1085 else if (Name == "sinh") 1086 return ConstantFoldFP(sinh, V, Ty, Context); 1087 else if (Name == "sqrt" && V >= 0) 1088 return ConstantFoldFP(sqrt, V, Ty, Context); 1089 else if (Name == "sqrtf" && V >= 0) 1090 return ConstantFoldFP(sqrt, V, Ty, Context); 1091 else if (Name == "sinf") 1092 return ConstantFoldFP(sin, V, Ty, Context); 1093 break; 1094 case 't': 1095 if (Name == "tan") 1096 return ConstantFoldFP(tan, V, Ty, Context); 1097 else if (Name == "tanh") 1098 return ConstantFoldFP(tanh, V, Ty, Context); 1099 break; 1100 default: 1101 break; 1102 } 1103 return 0; 1104 } 1105 1106 1107 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { 1108 if (Name.startswith("llvm.bswap")) 1109 return ConstantInt::get(Context, Op->getValue().byteSwap()); 1110 else if (Name.startswith("llvm.ctpop")) 1111 return ConstantInt::get(Ty, Op->getValue().countPopulation()); 1112 else if (Name.startswith("llvm.cttz")) 1113 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros()); 1114 else if (Name.startswith("llvm.ctlz")) 1115 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros()); 1116 return 0; 1117 } 1118 1119 return 0; 1120 } 1121 1122 if (NumOperands == 2) { 1123 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { 1124 if (!Ty->isFloatTy() && !Ty->isDoubleTy()) 1125 return 0; 1126 double Op1V = Ty->isFloatTy() ? 1127 (double)Op1->getValueAPF().convertToFloat() : 1128 Op1->getValueAPF().convertToDouble(); 1129 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { 1130 if (Op2->getType() != Op1->getType()) 1131 return 0; 1132 1133 double Op2V = Ty->isFloatTy() ? 1134 (double)Op2->getValueAPF().convertToFloat(): 1135 Op2->getValueAPF().convertToDouble(); 1136 1137 if (Name == "pow") 1138 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty, Context); 1139 if (Name == "fmod") 1140 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty, Context); 1141 if (Name == "atan2") 1142 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty, Context); 1143 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { 1144 if (Name == "llvm.powi.f32") 1145 return ConstantFP::get(Context, APFloat((float)std::pow((float)Op1V, 1146 (int)Op2C->getZExtValue()))); 1147 if (Name == "llvm.powi.f64") 1148 return ConstantFP::get(Context, APFloat((double)std::pow((double)Op1V, 1149 (int)Op2C->getZExtValue()))); 1150 } 1151 return 0; 1152 } 1153 1154 1155 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) { 1156 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) { 1157 switch (F->getIntrinsicID()) { 1158 default: break; 1159 case Intrinsic::uadd_with_overflow: { 1160 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result. 1161 Constant *Ops[] = { 1162 Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow. 1163 }; 1164 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1165 } 1166 case Intrinsic::usub_with_overflow: { 1167 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result. 1168 Constant *Ops[] = { 1169 Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow. 1170 }; 1171 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1172 } 1173 case Intrinsic::sadd_with_overflow: { 1174 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result. 1175 Constant *Overflow = ConstantExpr::getSelect( 1176 ConstantExpr::getICmp(CmpInst::ICMP_SGT, 1177 ConstantInt::get(Op1->getType(), 0), Op1), 1178 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2), 1179 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow. 1180 1181 Constant *Ops[] = { Res, Overflow }; 1182 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1183 } 1184 case Intrinsic::ssub_with_overflow: { 1185 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result. 1186 Constant *Overflow = ConstantExpr::getSelect( 1187 ConstantExpr::getICmp(CmpInst::ICMP_SGT, 1188 ConstantInt::get(Op2->getType(), 0), Op2), 1189 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1), 1190 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow. 1191 1192 Constant *Ops[] = { Res, Overflow }; 1193 return ConstantStruct::get(F->getContext(), Ops, 2, false); 1194 } 1195 } 1196 } 1197 1198 return 0; 1199 } 1200 return 0; 1201 } 1202 return 0; 1203} 1204 1205