//===-- ConstantFolding.cpp - Fold instructions into constants ------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file defines routines for folding instructions into constants. // // Also, to supplement the basic IR ConstantExpr simplifications, // this file defines some additional folding routines that can make use of // DataLayout information. These functions cannot go in IR due to library // dependency issues. // //===----------------------------------------------------------------------===// #include "llvm/Analysis/ConstantFolding.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/StringMap.h" #include "llvm/Analysis/TargetLibraryInfo.h" #include "llvm/Analysis/ValueTracking.h" #include "llvm/Config/config.h" #include "llvm/IR/Constants.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/DerivedTypes.h" #include "llvm/IR/Function.h" #include "llvm/IR/GetElementPtrTypeIterator.h" #include "llvm/IR/GlobalVariable.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/Intrinsics.h" #include "llvm/IR/Operator.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/MathExtras.h" #include #include #ifdef HAVE_FENV_H #include #endif using namespace llvm; //===----------------------------------------------------------------------===// // Constant Folding internal helper functions //===----------------------------------------------------------------------===// /// Constant fold bitcast, symbolically evaluating it with DataLayout. /// This always returns a non-null constant, but it may be a /// ConstantExpr if unfoldable. static Constant *FoldBitCast(Constant *C, Type *DestTy, const DataLayout &TD) { // Catch the obvious splat cases. if (C->isNullValue() && !DestTy->isX86_MMXTy()) return Constant::getNullValue(DestTy); if (C->isAllOnesValue() && !DestTy->isX86_MMXTy() && !DestTy->isPtrOrPtrVectorTy()) // Don't get ones for ptr types! return Constant::getAllOnesValue(DestTy); // Handle a vector->integer cast. if (IntegerType *IT = dyn_cast(DestTy)) { VectorType *VTy = dyn_cast(C->getType()); if (!VTy) return ConstantExpr::getBitCast(C, DestTy); unsigned NumSrcElts = VTy->getNumElements(); Type *SrcEltTy = VTy->getElementType(); // If the vector is a vector of floating point, convert it to vector of int // to simplify things. if (SrcEltTy->isFloatingPointTy()) { unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); Type *SrcIVTy = VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElts); // Ask IR to do the conversion now that #elts line up. C = ConstantExpr::getBitCast(C, SrcIVTy); } ConstantDataVector *CDV = dyn_cast(C); if (!CDV) return ConstantExpr::getBitCast(C, DestTy); // Now that we know that the input value is a vector of integers, just shift // and insert them into our result. unsigned BitShift = TD.getTypeAllocSizeInBits(SrcEltTy); APInt Result(IT->getBitWidth(), 0); for (unsigned i = 0; i != NumSrcElts; ++i) { Result <<= BitShift; if (TD.isLittleEndian()) Result |= CDV->getElementAsInteger(NumSrcElts-i-1); else Result |= CDV->getElementAsInteger(i); } return ConstantInt::get(IT, Result); } // The code below only handles casts to vectors currently. VectorType *DestVTy = dyn_cast(DestTy); if (!DestVTy) return ConstantExpr::getBitCast(C, DestTy); // If this is a scalar -> vector cast, convert the input into a <1 x scalar> // vector so the code below can handle it uniformly. if (isa(C) || isa(C)) { Constant *Ops = C; // don't take the address of C! return FoldBitCast(ConstantVector::get(Ops), DestTy, TD); } // If this is a bitcast from constant vector -> vector, fold it. if (!isa(C) && !isa(C)) return ConstantExpr::getBitCast(C, DestTy); // If the element types match, IR can fold it. unsigned NumDstElt = DestVTy->getNumElements(); unsigned NumSrcElt = C->getType()->getVectorNumElements(); if (NumDstElt == NumSrcElt) return ConstantExpr::getBitCast(C, DestTy); Type *SrcEltTy = C->getType()->getVectorElementType(); Type *DstEltTy = DestVTy->getElementType(); // Otherwise, we're changing the number of elements in a vector, which // requires endianness information to do the right thing. For example, // bitcast (<2 x i64> to <4 x i32>) // folds to (little endian): // <4 x i32> // and to (big endian): // <4 x i32> // First thing is first. We only want to think about integer here, so if // we have something in FP form, recast it as integer. if (DstEltTy->isFloatingPointTy()) { // Fold to an vector of integers with same size as our FP type. unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits(); Type *DestIVTy = VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt); // Recursively handle this integer conversion, if possible. C = FoldBitCast(C, DestIVTy, TD); // Finally, IR can handle this now that #elts line up. return ConstantExpr::getBitCast(C, DestTy); } // Okay, we know the destination is integer, if the input is FP, convert // it to integer first. if (SrcEltTy->isFloatingPointTy()) { unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); Type *SrcIVTy = VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt); // Ask IR to do the conversion now that #elts line up. C = ConstantExpr::getBitCast(C, SrcIVTy); // If IR wasn't able to fold it, bail out. if (!isa(C) && // FIXME: Remove ConstantVector. !isa(C)) return C; } // Now we know that the input and output vectors are both integer vectors // of the same size, and that their #elements is not the same. Do the // conversion here, which depends on whether the input or output has // more elements. bool isLittleEndian = TD.isLittleEndian(); SmallVector Result; if (NumDstElt < NumSrcElt) { // Handle: bitcast (<4 x i32> to <2 x i64>) Constant *Zero = Constant::getNullValue(DstEltTy); unsigned Ratio = NumSrcElt/NumDstElt; unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits(); unsigned SrcElt = 0; for (unsigned i = 0; i != NumDstElt; ++i) { // Build each element of the result. Constant *Elt = Zero; unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1); for (unsigned j = 0; j != Ratio; ++j) { Constant *Src =dyn_cast(C->getAggregateElement(SrcElt++)); if (!Src) // Reject constantexpr elements. return ConstantExpr::getBitCast(C, DestTy); // Zero extend the element to the right size. Src = ConstantExpr::getZExt(Src, Elt->getType()); // Shift it to the right place, depending on endianness. Src = ConstantExpr::getShl(Src, ConstantInt::get(Src->getType(), ShiftAmt)); ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize; // Mix it in. Elt = ConstantExpr::getOr(Elt, Src); } Result.push_back(Elt); } return ConstantVector::get(Result); } // Handle: bitcast (<2 x i64> to <4 x i32>) unsigned Ratio = NumDstElt/NumSrcElt; unsigned DstBitSize = TD.getTypeSizeInBits(DstEltTy); // Loop over each source value, expanding into multiple results. for (unsigned i = 0; i != NumSrcElt; ++i) { Constant *Src = dyn_cast(C->getAggregateElement(i)); if (!Src) // Reject constantexpr elements. return ConstantExpr::getBitCast(C, DestTy); unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1); for (unsigned j = 0; j != Ratio; ++j) { // Shift the piece of the value into the right place, depending on // endianness. Constant *Elt = ConstantExpr::getLShr(Src, ConstantInt::get(Src->getType(), ShiftAmt)); ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize; // Truncate the element to an integer with the same pointer size and // convert the element back to a pointer using a inttoptr. if (DstEltTy->isPointerTy()) { IntegerType *DstIntTy = Type::getIntNTy(C->getContext(), DstBitSize); Constant *CE = ConstantExpr::getTrunc(Elt, DstIntTy); Result.push_back(ConstantExpr::getIntToPtr(CE, DstEltTy)); continue; } // Truncate and remember this piece. Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy)); } } return ConstantVector::get(Result); } /// If this constant is a constant offset from a global, return the global and /// the constant. Because of constantexprs, this function is recursive. static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, APInt &Offset, const DataLayout &TD) { // Trivial case, constant is the global. if ((GV = dyn_cast(C))) { unsigned BitWidth = TD.getPointerTypeSizeInBits(GV->getType()); Offset = APInt(BitWidth, 0); return true; } // Otherwise, if this isn't a constant expr, bail out. ConstantExpr *CE = dyn_cast(C); if (!CE) return false; // Look through ptr->int and ptr->ptr casts. if (CE->getOpcode() == Instruction::PtrToInt || CE->getOpcode() == Instruction::BitCast || CE->getOpcode() == Instruction::AddrSpaceCast) return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD); // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5) GEPOperator *GEP = dyn_cast(CE); if (!GEP) return false; unsigned BitWidth = TD.getPointerTypeSizeInBits(GEP->getType()); APInt TmpOffset(BitWidth, 0); // If the base isn't a global+constant, we aren't either. if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, TmpOffset, TD)) return false; // Otherwise, add any offset that our operands provide. if (!GEP->accumulateConstantOffset(TD, TmpOffset)) return false; Offset = TmpOffset; return true; } /// Recursive helper to read bits out of global. C is the constant being copied /// out of. ByteOffset is an offset into C. CurPtr is the pointer to copy /// results into and BytesLeft is the number of bytes left in /// the CurPtr buffer. TD is the target data. static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset, unsigned char *CurPtr, unsigned BytesLeft, const DataLayout &TD) { assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) && "Out of range access"); // If this element is zero or undefined, we can just return since *CurPtr is // zero initialized. if (isa(C) || isa(C)) return true; if (ConstantInt *CI = dyn_cast(C)) { if (CI->getBitWidth() > 64 || (CI->getBitWidth() & 7) != 0) return false; uint64_t Val = CI->getZExtValue(); unsigned IntBytes = unsigned(CI->getBitWidth()/8); for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) { int n = ByteOffset; if (!TD.isLittleEndian()) n = IntBytes - n - 1; CurPtr[i] = (unsigned char)(Val >> (n * 8)); ++ByteOffset; } return true; } if (ConstantFP *CFP = dyn_cast(C)) { if (CFP->getType()->isDoubleTy()) { C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD); return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); } if (CFP->getType()->isFloatTy()){ C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD); return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); } if (CFP->getType()->isHalfTy()){ C = FoldBitCast(C, Type::getInt16Ty(C->getContext()), TD); return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD); } return false; } if (ConstantStruct *CS = dyn_cast(C)) { const StructLayout *SL = TD.getStructLayout(CS->getType()); unsigned Index = SL->getElementContainingOffset(ByteOffset); uint64_t CurEltOffset = SL->getElementOffset(Index); ByteOffset -= CurEltOffset; while (1) { // If the element access is to the element itself and not to tail padding, // read the bytes from the element. uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType()); if (ByteOffset < EltSize && !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr, BytesLeft, TD)) return false; ++Index; // Check to see if we read from the last struct element, if so we're done. if (Index == CS->getType()->getNumElements()) return true; // If we read all of the bytes we needed from this element we're done. uint64_t NextEltOffset = SL->getElementOffset(Index); if (BytesLeft <= NextEltOffset - CurEltOffset - ByteOffset) return true; // Move to the next element of the struct. CurPtr += NextEltOffset - CurEltOffset - ByteOffset; BytesLeft -= NextEltOffset - CurEltOffset - ByteOffset; ByteOffset = 0; CurEltOffset = NextEltOffset; } // not reached. } if (isa(C) || isa(C) || isa(C)) { Type *EltTy = C->getType()->getSequentialElementType(); uint64_t EltSize = TD.getTypeAllocSize(EltTy); uint64_t Index = ByteOffset / EltSize; uint64_t Offset = ByteOffset - Index * EltSize; uint64_t NumElts; if (ArrayType *AT = dyn_cast(C->getType())) NumElts = AT->getNumElements(); else NumElts = C->getType()->getVectorNumElements(); for (; Index != NumElts; ++Index) { if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr, BytesLeft, TD)) return false; uint64_t BytesWritten = EltSize - Offset; assert(BytesWritten <= EltSize && "Not indexing into this element?"); if (BytesWritten >= BytesLeft) return true; Offset = 0; BytesLeft -= BytesWritten; CurPtr += BytesWritten; } return true; } if (ConstantExpr *CE = dyn_cast(C)) { if (CE->getOpcode() == Instruction::IntToPtr && CE->getOperand(0)->getType() == TD.getIntPtrType(CE->getType())) { return ReadDataFromGlobal(CE->getOperand(0), ByteOffset, CurPtr, BytesLeft, TD); } } // Otherwise, unknown initializer type. return false; } static Constant *FoldReinterpretLoadFromConstPtr(Constant *C, const DataLayout &TD) { PointerType *PTy = cast(C->getType()); Type *LoadTy = PTy->getElementType(); IntegerType *IntType = dyn_cast(LoadTy); // If this isn't an integer load we can't fold it directly. if (!IntType) { unsigned AS = PTy->getAddressSpace(); // If this is a float/double load, we can try folding it as an int32/64 load // and then bitcast the result. This can be useful for union cases. Note // that address spaces don't matter here since we're not going to result in // an actual new load. Type *MapTy; if (LoadTy->isHalfTy()) MapTy = Type::getInt16PtrTy(C->getContext(), AS); else if (LoadTy->isFloatTy()) MapTy = Type::getInt32PtrTy(C->getContext(), AS); else if (LoadTy->isDoubleTy()) MapTy = Type::getInt64PtrTy(C->getContext(), AS); else if (LoadTy->isVectorTy()) { MapTy = PointerType::getIntNPtrTy(C->getContext(), TD.getTypeAllocSizeInBits(LoadTy), AS); } else return nullptr; C = FoldBitCast(C, MapTy, TD); if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD)) return FoldBitCast(Res, LoadTy, TD); return nullptr; } unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8; if (BytesLoaded > 32 || BytesLoaded == 0) return nullptr; GlobalValue *GVal; APInt Offset; if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD)) return nullptr; GlobalVariable *GV = dyn_cast(GVal); if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() || !GV->getInitializer()->getType()->isSized()) return nullptr; // If we're loading off the beginning of the global, some bytes may be valid, // but we don't try to handle this. if (Offset.isNegative()) return nullptr; // If we're not accessing anything in this constant, the result is undefined. if (Offset.getZExtValue() >= TD.getTypeAllocSize(GV->getInitializer()->getType())) return UndefValue::get(IntType); unsigned char RawBytes[32] = {0}; if (!ReadDataFromGlobal(GV->getInitializer(), Offset.getZExtValue(), RawBytes, BytesLoaded, TD)) return nullptr; APInt ResultVal = APInt(IntType->getBitWidth(), 0); if (TD.isLittleEndian()) { ResultVal = RawBytes[BytesLoaded - 1]; for (unsigned i = 1; i != BytesLoaded; ++i) { ResultVal <<= 8; ResultVal |= RawBytes[BytesLoaded - 1 - i]; } } else { ResultVal = RawBytes[0]; for (unsigned i = 1; i != BytesLoaded; ++i) { ResultVal <<= 8; ResultVal |= RawBytes[i]; } } return ConstantInt::get(IntType->getContext(), ResultVal); } static Constant *ConstantFoldLoadThroughBitcast(ConstantExpr *CE, const DataLayout *DL) { if (!DL) return nullptr; auto *DestPtrTy = dyn_cast(CE->getType()); if (!DestPtrTy) return nullptr; Type *DestTy = DestPtrTy->getElementType(); Constant *C = ConstantFoldLoadFromConstPtr(CE->getOperand(0), DL); if (!C) return nullptr; do { Type *SrcTy = C->getType(); // If the type sizes are the same and a cast is legal, just directly // cast the constant. if (DL->getTypeSizeInBits(DestTy) == DL->getTypeSizeInBits(SrcTy)) { Instruction::CastOps Cast = Instruction::BitCast; // If we are going from a pointer to int or vice versa, we spell the cast // differently. if (SrcTy->isIntegerTy() && DestTy->isPointerTy()) Cast = Instruction::IntToPtr; else if (SrcTy->isPointerTy() && DestTy->isIntegerTy()) Cast = Instruction::PtrToInt; if (CastInst::castIsValid(Cast, C, DestTy)) return ConstantExpr::getCast(Cast, C, DestTy); } // If this isn't an aggregate type, there is nothing we can do to drill down // and find a bitcastable constant. if (!SrcTy->isAggregateType()) return nullptr; // We're simulating a load through a pointer that was bitcast to point to // a different type, so we can try to walk down through the initial // elements of an aggregate to see if some part of th e aggregate is // castable to implement the "load" semantic model. C = C->getAggregateElement(0u); } while (C); return nullptr; } /// Return the value that a load from C would produce if it is constant and /// determinable. If this is not determinable, return null. Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, const DataLayout *TD) { // First, try the easy cases: if (GlobalVariable *GV = dyn_cast(C)) if (GV->isConstant() && GV->hasDefinitiveInitializer()) return GV->getInitializer(); // If the loaded value isn't a constant expr, we can't handle it. ConstantExpr *CE = dyn_cast(C); if (!CE) return nullptr; if (CE->getOpcode() == Instruction::GetElementPtr) { if (GlobalVariable *GV = dyn_cast(CE->getOperand(0))) { if (GV->isConstant() && GV->hasDefinitiveInitializer()) { if (Constant *V = ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) return V; } } } if (CE->getOpcode() == Instruction::BitCast) if (Constant *LoadedC = ConstantFoldLoadThroughBitcast(CE, TD)) return LoadedC; // Instead of loading constant c string, use corresponding integer value // directly if string length is small enough. StringRef Str; if (TD && getConstantStringInfo(CE, Str) && !Str.empty()) { unsigned StrLen = Str.size(); Type *Ty = cast(CE->getType())->getElementType(); unsigned NumBits = Ty->getPrimitiveSizeInBits(); // Replace load with immediate integer if the result is an integer or fp // value. if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 && (isa(Ty) || Ty->isFloatingPointTy())) { APInt StrVal(NumBits, 0); APInt SingleChar(NumBits, 0); if (TD->isLittleEndian()) { for (signed i = StrLen-1; i >= 0; i--) { SingleChar = (uint64_t) Str[i] & UCHAR_MAX; StrVal = (StrVal << 8) | SingleChar; } } else { for (unsigned i = 0; i < StrLen; i++) { SingleChar = (uint64_t) Str[i] & UCHAR_MAX; StrVal = (StrVal << 8) | SingleChar; } // Append NULL at the end. SingleChar = 0; StrVal = (StrVal << 8) | SingleChar; } Constant *Res = ConstantInt::get(CE->getContext(), StrVal); if (Ty->isFloatingPointTy()) Res = ConstantExpr::getBitCast(Res, Ty); return Res; } } // If this load comes from anywhere in a constant global, and if the global // is all undef or zero, we know what it loads. if (GlobalVariable *GV = dyn_cast(GetUnderlyingObject(CE, TD))) { if (GV->isConstant() && GV->hasDefinitiveInitializer()) { Type *ResTy = cast(C->getType())->getElementType(); if (GV->getInitializer()->isNullValue()) return Constant::getNullValue(ResTy); if (isa(GV->getInitializer())) return UndefValue::get(ResTy); } } // Try hard to fold loads from bitcasted strange and non-type-safe things. if (TD) return FoldReinterpretLoadFromConstPtr(CE, *TD); return nullptr; } static Constant *ConstantFoldLoadInst(const LoadInst *LI, const DataLayout *TD){ if (LI->isVolatile()) return nullptr; if (Constant *C = dyn_cast(LI->getOperand(0))) return ConstantFoldLoadFromConstPtr(C, TD); return nullptr; } /// One of Op0/Op1 is a constant expression. /// Attempt to symbolically evaluate the result of a binary operator merging /// these together. If target data info is available, it is provided as DL, /// otherwise DL is null. static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, Constant *Op1, const DataLayout *DL){ // SROA // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl. // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute // bits. if (Opc == Instruction::And && DL) { unsigned BitWidth = DL->getTypeSizeInBits(Op0->getType()->getScalarType()); APInt KnownZero0(BitWidth, 0), KnownOne0(BitWidth, 0); APInt KnownZero1(BitWidth, 0), KnownOne1(BitWidth, 0); computeKnownBits(Op0, KnownZero0, KnownOne0, DL); computeKnownBits(Op1, KnownZero1, KnownOne1, DL); if ((KnownOne1 | KnownZero0).isAllOnesValue()) { // All the bits of Op0 that the 'and' could be masking are already zero. return Op0; } if ((KnownOne0 | KnownZero1).isAllOnesValue()) { // All the bits of Op1 that the 'and' could be masking are already zero. return Op1; } APInt KnownZero = KnownZero0 | KnownZero1; APInt KnownOne = KnownOne0 & KnownOne1; if ((KnownZero | KnownOne).isAllOnesValue()) { return ConstantInt::get(Op0->getType(), KnownOne); } } // If the constant expr is something like &A[123] - &A[4].f, fold this into a // constant. This happens frequently when iterating over a global array. if (Opc == Instruction::Sub && DL) { GlobalValue *GV1, *GV2; APInt Offs1, Offs2; if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *DL)) if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *DL) && GV1 == GV2) { unsigned OpSize = DL->getTypeSizeInBits(Op0->getType()); // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow. // PtrToInt may change the bitwidth so we have convert to the right size // first. return ConstantInt::get(Op0->getType(), Offs1.zextOrTrunc(OpSize) - Offs2.zextOrTrunc(OpSize)); } } return nullptr; } /// If array indices are not pointer-sized integers, explicitly cast them so /// that they aren't implicitly casted by the getelementptr. static Constant *CastGEPIndices(ArrayRef Ops, Type *ResultTy, const DataLayout *TD, const TargetLibraryInfo *TLI) { if (!TD) return nullptr; Type *IntPtrTy = TD->getIntPtrType(ResultTy); bool Any = false; SmallVector NewIdxs; for (unsigned i = 1, e = Ops.size(); i != e; ++i) { if ((i == 1 || !isa(GetElementPtrInst::getIndexedType( Ops[0]->getType(), Ops.slice(1, i - 1)))) && Ops[i]->getType() != IntPtrTy) { Any = true; NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i], true, IntPtrTy, true), Ops[i], IntPtrTy)); } else NewIdxs.push_back(Ops[i]); } if (!Any) return nullptr; Constant *C = ConstantExpr::getGetElementPtr(Ops[0], NewIdxs); if (ConstantExpr *CE = dyn_cast(C)) { if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI)) C = Folded; } return C; } /// Strip the pointer casts, but preserve the address space information. static Constant* StripPtrCastKeepAS(Constant* Ptr) { assert(Ptr->getType()->isPointerTy() && "Not a pointer type"); PointerType *OldPtrTy = cast(Ptr->getType()); Ptr = Ptr->stripPointerCasts(); PointerType *NewPtrTy = cast(Ptr->getType()); // Preserve the address space number of the pointer. if (NewPtrTy->getAddressSpace() != OldPtrTy->getAddressSpace()) { NewPtrTy = NewPtrTy->getElementType()->getPointerTo( OldPtrTy->getAddressSpace()); Ptr = ConstantExpr::getPointerCast(Ptr, NewPtrTy); } return Ptr; } /// If we can symbolically evaluate the GEP constant expression, do so. static Constant *SymbolicallyEvaluateGEP(ArrayRef Ops, Type *ResultTy, const DataLayout *TD, const TargetLibraryInfo *TLI) { Constant *Ptr = Ops[0]; if (!TD || !Ptr->getType()->getPointerElementType()->isSized() || !Ptr->getType()->isPointerTy()) return nullptr; Type *IntPtrTy = TD->getIntPtrType(Ptr->getType()); Type *ResultElementTy = ResultTy->getPointerElementType(); // If this is a constant expr gep that is effectively computing an // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' for (unsigned i = 1, e = Ops.size(); i != e; ++i) if (!isa(Ops[i])) { // If this is "gep i8* Ptr, (sub 0, V)", fold this as: // "inttoptr (sub (ptrtoint Ptr), V)" if (Ops.size() == 2 && ResultElementTy->isIntegerTy(8)) { ConstantExpr *CE = dyn_cast(Ops[1]); assert((!CE || CE->getType() == IntPtrTy) && "CastGEPIndices didn't canonicalize index types!"); if (CE && CE->getOpcode() == Instruction::Sub && CE->getOperand(0)->isNullValue()) { Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType()); Res = ConstantExpr::getSub(Res, CE->getOperand(1)); Res = ConstantExpr::getIntToPtr(Res, ResultTy); if (ConstantExpr *ResCE = dyn_cast(Res)) Res = ConstantFoldConstantExpression(ResCE, TD, TLI); return Res; } } return nullptr; } unsigned BitWidth = TD->getTypeSizeInBits(IntPtrTy); APInt Offset = APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(), makeArrayRef((Value *const*) Ops.data() + 1, Ops.size() - 1))); Ptr = StripPtrCastKeepAS(Ptr); // If this is a GEP of a GEP, fold it all into a single GEP. while (GEPOperator *GEP = dyn_cast(Ptr)) { SmallVector NestedOps(GEP->op_begin() + 1, GEP->op_end()); // Do not try the incorporate the sub-GEP if some index is not a number. bool AllConstantInt = true; for (unsigned i = 0, e = NestedOps.size(); i != e; ++i) if (!isa(NestedOps[i])) { AllConstantInt = false; break; } if (!AllConstantInt) break; Ptr = cast(GEP->getOperand(0)); Offset += APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(), NestedOps)); Ptr = StripPtrCastKeepAS(Ptr); } // If the base value for this address is a literal integer value, fold the // getelementptr to the resulting integer value casted to the pointer type. APInt BasePtr(BitWidth, 0); if (ConstantExpr *CE = dyn_cast(Ptr)) { if (CE->getOpcode() == Instruction::IntToPtr) { if (ConstantInt *Base = dyn_cast(CE->getOperand(0))) BasePtr = Base->getValue().zextOrTrunc(BitWidth); } } if (Ptr->isNullValue() || BasePtr != 0) { Constant *C = ConstantInt::get(Ptr->getContext(), Offset + BasePtr); return ConstantExpr::getIntToPtr(C, ResultTy); } // Otherwise form a regular getelementptr. Recompute the indices so that // we eliminate over-indexing of the notional static type array bounds. // This makes it easy to determine if the getelementptr is "inbounds". // Also, this helps GlobalOpt do SROA on GlobalVariables. Type *Ty = Ptr->getType(); assert(Ty->isPointerTy() && "Forming regular GEP of non-pointer type"); SmallVector NewIdxs; do { if (SequentialType *ATy = dyn_cast(Ty)) { if (ATy->isPointerTy()) { // The only pointer indexing we'll do is on the first index of the GEP. if (!NewIdxs.empty()) break; // Only handle pointers to sized types, not pointers to functions. if (!ATy->getElementType()->isSized()) return nullptr; } // Determine which element of the array the offset points into. APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); if (ElemSize == 0) // The element size is 0. This may be [0 x Ty]*, so just use a zero // index for this level and proceed to the next level to see if it can // accommodate the offset. NewIdxs.push_back(ConstantInt::get(IntPtrTy, 0)); else { // The element size is non-zero divide the offset by the element // size (rounding down), to compute the index at this level. APInt NewIdx = Offset.udiv(ElemSize); Offset -= NewIdx * ElemSize; NewIdxs.push_back(ConstantInt::get(IntPtrTy, NewIdx)); } Ty = ATy->getElementType(); } else if (StructType *STy = dyn_cast(Ty)) { // If we end up with an offset that isn't valid for this struct type, we // can't re-form this GEP in a regular form, so bail out. The pointer // operand likely went through casts that are necessary to make the GEP // sensible. const StructLayout &SL = *TD->getStructLayout(STy); if (Offset.uge(SL.getSizeInBytes())) break; // Determine which field of the struct the offset points into. The // getZExtValue is fine as we've already ensured that the offset is // within the range representable by the StructLayout API. unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), ElIdx)); Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); Ty = STy->getTypeAtIndex(ElIdx); } else { // We've reached some non-indexable type. break; } } while (Ty != ResultElementTy); // If we haven't used up the entire offset by descending the static // type, then the offset is pointing into the middle of an indivisible // member, so we can't simplify it. if (Offset != 0) return nullptr; // Create a GEP. Constant *C = ConstantExpr::getGetElementPtr(Ptr, NewIdxs); assert(C->getType()->getPointerElementType() == Ty && "Computed GetElementPtr has unexpected type!"); // If we ended up indexing a member with a type that doesn't match // the type of what the original indices indexed, add a cast. if (Ty != ResultElementTy) C = FoldBitCast(C, ResultTy, *TD); return C; } //===----------------------------------------------------------------------===// // Constant Folding public APIs //===----------------------------------------------------------------------===// /// Try to constant fold the specified instruction. /// If successful, the constant result is returned, if not, null is returned. /// Note that this fails if not all of the operands are constant. Otherwise, /// this function can only fail when attempting to fold instructions like loads /// and stores, which have no constant expression form. Constant *llvm::ConstantFoldInstruction(Instruction *I, const DataLayout *TD, const TargetLibraryInfo *TLI) { // Handle PHI nodes quickly here... if (PHINode *PN = dyn_cast(I)) { Constant *CommonValue = nullptr; for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { Value *Incoming = PN->getIncomingValue(i); // If the incoming value is undef then skip it. Note that while we could // skip the value if it is equal to the phi node itself we choose not to // because that would break the rule that constant folding only applies if // all operands are constants. if (isa(Incoming)) continue; // If the incoming value is not a constant, then give up. Constant *C = dyn_cast(Incoming); if (!C) return nullptr; // Fold the PHI's operands. if (ConstantExpr *NewC = dyn_cast(C)) C = ConstantFoldConstantExpression(NewC, TD, TLI); // If the incoming value is a different constant to // the one we saw previously, then give up. if (CommonValue && C != CommonValue) return nullptr; CommonValue = C; } // If we reach here, all incoming values are the same constant or undef. return CommonValue ? CommonValue : UndefValue::get(PN->getType()); } // Scan the operand list, checking to see if they are all constants, if so, // hand off to ConstantFoldInstOperands. SmallVector Ops; for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) { Constant *Op = dyn_cast(*i); if (!Op) return nullptr; // All operands not constant! // Fold the Instruction's operands. if (ConstantExpr *NewCE = dyn_cast(Op)) Op = ConstantFoldConstantExpression(NewCE, TD, TLI); Ops.push_back(Op); } if (const CmpInst *CI = dyn_cast(I)) return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], TD, TLI); if (const LoadInst *LI = dyn_cast(I)) return ConstantFoldLoadInst(LI, TD); if (InsertValueInst *IVI = dyn_cast(I)) { return ConstantExpr::getInsertValue( cast(IVI->getAggregateOperand()), cast(IVI->getInsertedValueOperand()), IVI->getIndices()); } if (ExtractValueInst *EVI = dyn_cast(I)) { return ConstantExpr::getExtractValue( cast(EVI->getAggregateOperand()), EVI->getIndices()); } return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops, TD, TLI); } static Constant * ConstantFoldConstantExpressionImpl(const ConstantExpr *CE, const DataLayout *TD, const TargetLibraryInfo *TLI, SmallPtrSetImpl &FoldedOps) { SmallVector Ops; for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) { Constant *NewC = cast(*i); // Recursively fold the ConstantExpr's operands. If we have already folded // a ConstantExpr, we don't have to process it again. if (ConstantExpr *NewCE = dyn_cast(NewC)) { if (FoldedOps.insert(NewCE).second) NewC = ConstantFoldConstantExpressionImpl(NewCE, TD, TLI, FoldedOps); } Ops.push_back(NewC); } if (CE->isCompare()) return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1], TD, TLI); return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), Ops, TD, TLI); } /// Attempt to fold the constant expression /// using the specified DataLayout. If successful, the constant result is /// result is returned, if not, null is returned. Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE, const DataLayout *TD, const TargetLibraryInfo *TLI) { SmallPtrSet FoldedOps; return ConstantFoldConstantExpressionImpl(CE, TD, TLI, FoldedOps); } /// Attempt to constant fold an instruction with the /// specified opcode and operands. If successful, the constant result is /// returned, if not, null is returned. Note that this function can fail when /// attempting to fold instructions like loads and stores, which have no /// constant expression form. /// /// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc /// information, due to only being passed an opcode and operands. Constant /// folding using this function strips this information. /// Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, ArrayRef Ops, const DataLayout *TD, const TargetLibraryInfo *TLI) { // Handle easy binops first. if (Instruction::isBinaryOp(Opcode)) { if (isa(Ops[0]) || isa(Ops[1])) { if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD)) return C; } return ConstantExpr::get(Opcode, Ops[0], Ops[1]); } switch (Opcode) { default: return nullptr; case Instruction::ICmp: case Instruction::FCmp: llvm_unreachable("Invalid for compares"); case Instruction::Call: if (Function *F = dyn_cast(Ops.back())) if (canConstantFoldCallTo(F)) return ConstantFoldCall(F, Ops.slice(0, Ops.size() - 1), TLI); return nullptr; case Instruction::PtrToInt: // If the input is a inttoptr, eliminate the pair. This requires knowing // the width of a pointer, so it can't be done in ConstantExpr::getCast. if (ConstantExpr *CE = dyn_cast(Ops[0])) { if (TD && CE->getOpcode() == Instruction::IntToPtr) { Constant *Input = CE->getOperand(0); unsigned InWidth = Input->getType()->getScalarSizeInBits(); unsigned PtrWidth = TD->getPointerTypeSizeInBits(CE->getType()); if (PtrWidth < InWidth) { Constant *Mask = ConstantInt::get(CE->getContext(), APInt::getLowBitsSet(InWidth, PtrWidth)); Input = ConstantExpr::getAnd(Input, Mask); } // Do a zext or trunc to get to the dest size. return ConstantExpr::getIntegerCast(Input, DestTy, false); } } return ConstantExpr::getCast(Opcode, Ops[0], DestTy); case Instruction::IntToPtr: // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if // the int size is >= the ptr size and the address spaces are the same. // This requires knowing the width of a pointer, so it can't be done in // ConstantExpr::getCast. if (ConstantExpr *CE = dyn_cast(Ops[0])) { if (TD && CE->getOpcode() == Instruction::PtrToInt) { Constant *SrcPtr = CE->getOperand(0); unsigned SrcPtrSize = TD->getPointerTypeSizeInBits(SrcPtr->getType()); unsigned MidIntSize = CE->getType()->getScalarSizeInBits(); if (MidIntSize >= SrcPtrSize) { unsigned SrcAS = SrcPtr->getType()->getPointerAddressSpace(); if (SrcAS == DestTy->getPointerAddressSpace()) return FoldBitCast(CE->getOperand(0), DestTy, *TD); } } } return ConstantExpr::getCast(Opcode, Ops[0], DestTy); case Instruction::Trunc: case Instruction::ZExt: case Instruction::SExt: case Instruction::FPTrunc: case Instruction::FPExt: case Instruction::UIToFP: case Instruction::SIToFP: case Instruction::FPToUI: case Instruction::FPToSI: case Instruction::AddrSpaceCast: return ConstantExpr::getCast(Opcode, Ops[0], DestTy); case Instruction::BitCast: if (TD) return FoldBitCast(Ops[0], DestTy, *TD); return ConstantExpr::getBitCast(Ops[0], DestTy); case Instruction::Select: return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]); case Instruction::ExtractElement: return ConstantExpr::getExtractElement(Ops[0], Ops[1]); case Instruction::InsertElement: return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]); case Instruction::ShuffleVector: return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]); case Instruction::GetElementPtr: if (Constant *C = CastGEPIndices(Ops, DestTy, TD, TLI)) return C; if (Constant *C = SymbolicallyEvaluateGEP(Ops, DestTy, TD, TLI)) return C; return ConstantExpr::getGetElementPtr(Ops[0], Ops.slice(1)); } } /// Attempt to constant fold a compare /// instruction (icmp/fcmp) with the specified operands. If it fails, it /// returns a constant expression of the specified operands. Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate, Constant *Ops0, Constant *Ops1, const DataLayout *TD, const TargetLibraryInfo *TLI) { // fold: icmp (inttoptr x), null -> icmp x, 0 // fold: icmp (ptrtoint x), 0 -> icmp x, null // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y // // ConstantExpr::getCompare cannot do this, because it doesn't have TD // around to know if bit truncation is happening. if (ConstantExpr *CE0 = dyn_cast(Ops0)) { if (TD && Ops1->isNullValue()) { if (CE0->getOpcode() == Instruction::IntToPtr) { Type *IntPtrTy = TD->getIntPtrType(CE0->getType()); // Convert the integer value to the right size to ensure we get the // proper extension or truncation. Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0), IntPtrTy, false); Constant *Null = Constant::getNullValue(C->getType()); return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); } // Only do this transformation if the int is intptrty in size, otherwise // there is a truncation or extension that we aren't modeling. if (CE0->getOpcode() == Instruction::PtrToInt) { Type *IntPtrTy = TD->getIntPtrType(CE0->getOperand(0)->getType()); if (CE0->getType() == IntPtrTy) { Constant *C = CE0->getOperand(0); Constant *Null = Constant::getNullValue(C->getType()); return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI); } } } if (ConstantExpr *CE1 = dyn_cast(Ops1)) { if (TD && CE0->getOpcode() == CE1->getOpcode()) { if (CE0->getOpcode() == Instruction::IntToPtr) { Type *IntPtrTy = TD->getIntPtrType(CE0->getType()); // Convert the integer value to the right size to ensure we get the // proper extension or truncation. Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0), IntPtrTy, false); Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0), IntPtrTy, false); return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD, TLI); } // Only do this transformation if the int is intptrty in size, otherwise // there is a truncation or extension that we aren't modeling. if (CE0->getOpcode() == Instruction::PtrToInt) { Type *IntPtrTy = TD->getIntPtrType(CE0->getOperand(0)->getType()); if (CE0->getType() == IntPtrTy && CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()) { return ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), CE1->getOperand(0), TD, TLI); } } } } // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0) // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0) if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) && CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) { Constant *LHS = ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1, TD, TLI); Constant *RHS = ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1, TD, TLI); unsigned OpC = Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or; Constant *Ops[] = { LHS, RHS }; return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, TD, TLI); } } return ConstantExpr::getCompare(Predicate, Ops0, Ops1); } /// Given a constant and a getelementptr constantexpr, return the constant value /// being addressed by the constant expression, or null if something is funny /// and we can't decide. Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE) { if (!CE->getOperand(1)->isNullValue()) return nullptr; // Do not allow stepping over the value! // Loop over all of the operands, tracking down which value we are // addressing. for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i) { C = C->getAggregateElement(CE->getOperand(i)); if (!C) return nullptr; } return C; } /// Given a constant and getelementptr indices (with an *implied* zero pointer /// index that is not in the list), return the constant value being addressed by /// a virtual load, or null if something is funny and we can't decide. Constant *llvm::ConstantFoldLoadThroughGEPIndices(Constant *C, ArrayRef Indices) { // Loop over all of the operands, tracking down which value we are // addressing. for (unsigned i = 0, e = Indices.size(); i != e; ++i) { C = C->getAggregateElement(Indices[i]); if (!C) return nullptr; } return C; } //===----------------------------------------------------------------------===// // Constant Folding for Calls // /// Return true if it's even possible to fold a call to the specified function. bool llvm::canConstantFoldCallTo(const Function *F) { switch (F->getIntrinsicID()) { case Intrinsic::fabs: case Intrinsic::minnum: case Intrinsic::maxnum: case Intrinsic::log: case Intrinsic::log2: case Intrinsic::log10: case Intrinsic::exp: case Intrinsic::exp2: case Intrinsic::floor: case Intrinsic::ceil: case Intrinsic::sqrt: case Intrinsic::pow: case Intrinsic::powi: case Intrinsic::bswap: case Intrinsic::ctpop: case Intrinsic::ctlz: case Intrinsic::cttz: case Intrinsic::fma: case Intrinsic::fmuladd: case Intrinsic::copysign: case Intrinsic::round: case Intrinsic::sadd_with_overflow: case Intrinsic::uadd_with_overflow: case Intrinsic::ssub_with_overflow: case Intrinsic::usub_with_overflow: case Intrinsic::smul_with_overflow: case Intrinsic::umul_with_overflow: case Intrinsic::convert_from_fp16: case Intrinsic::convert_to_fp16: case Intrinsic::x86_sse_cvtss2si: case Intrinsic::x86_sse_cvtss2si64: case Intrinsic::x86_sse_cvttss2si: case Intrinsic::x86_sse_cvttss2si64: case Intrinsic::x86_sse2_cvtsd2si: case Intrinsic::x86_sse2_cvtsd2si64: case Intrinsic::x86_sse2_cvttsd2si: case Intrinsic::x86_sse2_cvttsd2si64: return true; default: return false; case 0: break; } if (!F->hasName()) return false; StringRef Name = F->getName(); // In these cases, the check of the length is required. We don't want to // return true for a name like "cos\0blah" which strcmp would return equal to // "cos", but has length 8. switch (Name[0]) { default: return false; case 'a': return Name == "acos" || Name == "asin" || Name == "atan" || Name =="atan2"; case 'c': return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh"; case 'e': return Name == "exp" || Name == "exp2"; case 'f': return Name == "fabs" || Name == "fmod" || Name == "floor"; case 'l': return Name == "log" || Name == "log10"; case 'p': return Name == "pow"; case 's': return Name == "sin" || Name == "sinh" || Name == "sqrt" || Name == "sinf" || Name == "sqrtf"; case 't': return Name == "tan" || Name == "tanh"; } } static Constant *GetConstantFoldFPValue(double V, Type *Ty) { if (Ty->isHalfTy()) { APFloat APF(V); bool unused; APF.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &unused); return ConstantFP::get(Ty->getContext(), APF); } if (Ty->isFloatTy()) return ConstantFP::get(Ty->getContext(), APFloat((float)V)); if (Ty->isDoubleTy()) return ConstantFP::get(Ty->getContext(), APFloat(V)); llvm_unreachable("Can only constant fold half/float/double"); } namespace { /// Clear the floating-point exception state. static inline void llvm_fenv_clearexcept() { #if defined(HAVE_FENV_H) && HAVE_DECL_FE_ALL_EXCEPT feclearexcept(FE_ALL_EXCEPT); #endif errno = 0; } /// Test if a floating-point exception was raised. static inline bool llvm_fenv_testexcept() { int errno_val = errno; if (errno_val == ERANGE || errno_val == EDOM) return true; #if defined(HAVE_FENV_H) && HAVE_DECL_FE_ALL_EXCEPT && HAVE_DECL_FE_INEXACT if (fetestexcept(FE_ALL_EXCEPT & ~FE_INEXACT)) return true; #endif return false; } } // End namespace static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, Type *Ty) { llvm_fenv_clearexcept(); V = NativeFP(V); if (llvm_fenv_testexcept()) { llvm_fenv_clearexcept(); return nullptr; } return GetConstantFoldFPValue(V, Ty); } static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), double V, double W, Type *Ty) { llvm_fenv_clearexcept(); V = NativeFP(V, W); if (llvm_fenv_testexcept()) { llvm_fenv_clearexcept(); return nullptr; } return GetConstantFoldFPValue(V, Ty); } /// Attempt to fold an SSE floating point to integer conversion of a constant /// floating point. If roundTowardZero is false, the default IEEE rounding is /// used (toward nearest, ties to even). This matches the behavior of the /// non-truncating SSE instructions in the default rounding mode. The desired /// integer type Ty is used to select how many bits are available for the /// result. Returns null if the conversion cannot be performed, otherwise /// returns the Constant value resulting from the conversion. static Constant *ConstantFoldConvertToInt(const APFloat &Val, bool roundTowardZero, Type *Ty) { // All of these conversion intrinsics form an integer of at most 64bits. unsigned ResultWidth = Ty->getIntegerBitWidth(); assert(ResultWidth <= 64 && "Can only constant fold conversions to 64 and 32 bit ints"); uint64_t UIntVal; bool isExact = false; APFloat::roundingMode mode = roundTowardZero? APFloat::rmTowardZero : APFloat::rmNearestTiesToEven; APFloat::opStatus status = Val.convertToInteger(&UIntVal, ResultWidth, /*isSigned=*/true, mode, &isExact); if (status != APFloat::opOK && status != APFloat::opInexact) return nullptr; return ConstantInt::get(Ty, UIntVal, /*isSigned=*/true); } static double getValueAsDouble(ConstantFP *Op) { Type *Ty = Op->getType(); if (Ty->isFloatTy()) return Op->getValueAPF().convertToFloat(); if (Ty->isDoubleTy()) return Op->getValueAPF().convertToDouble(); bool unused; APFloat APF = Op->getValueAPF(); APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused); return APF.convertToDouble(); } static Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty, ArrayRef Operands, const TargetLibraryInfo *TLI) { if (Operands.size() == 1) { if (ConstantFP *Op = dyn_cast(Operands[0])) { if (IntrinsicID == Intrinsic::convert_to_fp16) { APFloat Val(Op->getValueAPF()); bool lost = false; Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost); return ConstantInt::get(Ty->getContext(), Val.bitcastToAPInt()); } if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) return nullptr; if (IntrinsicID == Intrinsic::round) { APFloat V = Op->getValueAPF(); V.roundToIntegral(APFloat::rmNearestTiesToAway); return ConstantFP::get(Ty->getContext(), V); } /// We only fold functions with finite arguments. Folding NaN and inf is /// likely to be aborted with an exception anyway, and some host libms /// have known errors raising exceptions. if (Op->getValueAPF().isNaN() || Op->getValueAPF().isInfinity()) return nullptr; /// Currently APFloat versions of these functions do not exist, so we use /// the host native double versions. Float versions are not called /// directly but for all these it is true (float)(f((double)arg)) == /// f(arg). Long double not supported yet. double V = getValueAsDouble(Op); switch (IntrinsicID) { default: break; case Intrinsic::fabs: return ConstantFoldFP(fabs, V, Ty); #if HAVE_LOG2 case Intrinsic::log2: return ConstantFoldFP(log2, V, Ty); #endif #if HAVE_LOG case Intrinsic::log: return ConstantFoldFP(log, V, Ty); #endif #if HAVE_LOG10 case Intrinsic::log10: return ConstantFoldFP(log10, V, Ty); #endif #if HAVE_EXP case Intrinsic::exp: return ConstantFoldFP(exp, V, Ty); #endif #if HAVE_EXP2 case Intrinsic::exp2: return ConstantFoldFP(exp2, V, Ty); #endif case Intrinsic::floor: return ConstantFoldFP(floor, V, Ty); case Intrinsic::ceil: return ConstantFoldFP(ceil, V, Ty); } if (!TLI) return nullptr; switch (Name[0]) { case 'a': if (Name == "acos" && TLI->has(LibFunc::acos)) return ConstantFoldFP(acos, V, Ty); else if (Name == "asin" && TLI->has(LibFunc::asin)) return ConstantFoldFP(asin, V, Ty); else if (Name == "atan" && TLI->has(LibFunc::atan)) return ConstantFoldFP(atan, V, Ty); break; case 'c': if (Name == "ceil" && TLI->has(LibFunc::ceil)) return ConstantFoldFP(ceil, V, Ty); else if (Name == "cos" && TLI->has(LibFunc::cos)) return ConstantFoldFP(cos, V, Ty); else if (Name == "cosh" && TLI->has(LibFunc::cosh)) return ConstantFoldFP(cosh, V, Ty); else if (Name == "cosf" && TLI->has(LibFunc::cosf)) return ConstantFoldFP(cos, V, Ty); break; case 'e': if (Name == "exp" && TLI->has(LibFunc::exp)) return ConstantFoldFP(exp, V, Ty); if (Name == "exp2" && TLI->has(LibFunc::exp2)) { // Constant fold exp2(x) as pow(2,x) in case the host doesn't have a // C99 library. return ConstantFoldBinaryFP(pow, 2.0, V, Ty); } break; case 'f': if (Name == "fabs" && TLI->has(LibFunc::fabs)) return ConstantFoldFP(fabs, V, Ty); else if (Name == "floor" && TLI->has(LibFunc::floor)) return ConstantFoldFP(floor, V, Ty); break; case 'l': if (Name == "log" && V > 0 && TLI->has(LibFunc::log)) return ConstantFoldFP(log, V, Ty); else if (Name == "log10" && V > 0 && TLI->has(LibFunc::log10)) return ConstantFoldFP(log10, V, Ty); else if (IntrinsicID == Intrinsic::sqrt && (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy())) { if (V >= -0.0) return ConstantFoldFP(sqrt, V, Ty); else { // Unlike the sqrt definitions in C/C++, POSIX, and IEEE-754 - which // all guarantee or favor returning NaN - the square root of a // negative number is not defined for the LLVM sqrt intrinsic. // This is because the intrinsic should only be emitted in place of // libm's sqrt function when using "no-nans-fp-math". return UndefValue::get(Ty); } } break; case 's': if (Name == "sin" && TLI->has(LibFunc::sin)) return ConstantFoldFP(sin, V, Ty); else if (Name == "sinh" && TLI->has(LibFunc::sinh)) return ConstantFoldFP(sinh, V, Ty); else if (Name == "sqrt" && V >= 0 && TLI->has(LibFunc::sqrt)) return ConstantFoldFP(sqrt, V, Ty); else if (Name == "sqrtf" && V >= 0 && TLI->has(LibFunc::sqrtf)) return ConstantFoldFP(sqrt, V, Ty); else if (Name == "sinf" && TLI->has(LibFunc::sinf)) return ConstantFoldFP(sin, V, Ty); break; case 't': if (Name == "tan" && TLI->has(LibFunc::tan)) return ConstantFoldFP(tan, V, Ty); else if (Name == "tanh" && TLI->has(LibFunc::tanh)) return ConstantFoldFP(tanh, V, Ty); break; default: break; } return nullptr; } if (ConstantInt *Op = dyn_cast(Operands[0])) { switch (IntrinsicID) { case Intrinsic::bswap: return ConstantInt::get(Ty->getContext(), Op->getValue().byteSwap()); case Intrinsic::ctpop: return ConstantInt::get(Ty, Op->getValue().countPopulation()); case Intrinsic::convert_from_fp16: { APFloat Val(APFloat::IEEEhalf, Op->getValue()); bool lost = false; APFloat::opStatus status = Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost); // Conversion is always precise. (void)status; assert(status == APFloat::opOK && !lost && "Precision lost during fp16 constfolding"); return ConstantFP::get(Ty->getContext(), Val); } default: return nullptr; } } // Support ConstantVector in case we have an Undef in the top. if (isa(Operands[0]) || isa(Operands[0])) { Constant *Op = cast(Operands[0]); switch (IntrinsicID) { default: break; case Intrinsic::x86_sse_cvtss2si: case Intrinsic::x86_sse_cvtss2si64: case Intrinsic::x86_sse2_cvtsd2si: case Intrinsic::x86_sse2_cvtsd2si64: if (ConstantFP *FPOp = dyn_cast_or_null(Op->getAggregateElement(0U))) return ConstantFoldConvertToInt(FPOp->getValueAPF(), /*roundTowardZero=*/false, Ty); case Intrinsic::x86_sse_cvttss2si: case Intrinsic::x86_sse_cvttss2si64: case Intrinsic::x86_sse2_cvttsd2si: case Intrinsic::x86_sse2_cvttsd2si64: if (ConstantFP *FPOp = dyn_cast_or_null(Op->getAggregateElement(0U))) return ConstantFoldConvertToInt(FPOp->getValueAPF(), /*roundTowardZero=*/true, Ty); } } if (isa(Operands[0])) { if (IntrinsicID == Intrinsic::bswap) return Operands[0]; return nullptr; } return nullptr; } if (Operands.size() == 2) { if (ConstantFP *Op1 = dyn_cast(Operands[0])) { if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy()) return nullptr; double Op1V = getValueAsDouble(Op1); if (ConstantFP *Op2 = dyn_cast(Operands[1])) { if (Op2->getType() != Op1->getType()) return nullptr; double Op2V = getValueAsDouble(Op2); if (IntrinsicID == Intrinsic::pow) { return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); } if (IntrinsicID == Intrinsic::copysign) { APFloat V1 = Op1->getValueAPF(); APFloat V2 = Op2->getValueAPF(); V1.copySign(V2); return ConstantFP::get(Ty->getContext(), V1); } if (IntrinsicID == Intrinsic::minnum) { const APFloat &C1 = Op1->getValueAPF(); const APFloat &C2 = Op2->getValueAPF(); return ConstantFP::get(Ty->getContext(), minnum(C1, C2)); } if (IntrinsicID == Intrinsic::maxnum) { const APFloat &C1 = Op1->getValueAPF(); const APFloat &C2 = Op2->getValueAPF(); return ConstantFP::get(Ty->getContext(), maxnum(C1, C2)); } if (!TLI) return nullptr; if (Name == "pow" && TLI->has(LibFunc::pow)) return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty); if (Name == "fmod" && TLI->has(LibFunc::fmod)) return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty); if (Name == "atan2" && TLI->has(LibFunc::atan2)) return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty); } else if (ConstantInt *Op2C = dyn_cast(Operands[1])) { if (IntrinsicID == Intrinsic::powi && Ty->isHalfTy()) return ConstantFP::get(Ty->getContext(), APFloat((float)std::pow((float)Op1V, (int)Op2C->getZExtValue()))); if (IntrinsicID == Intrinsic::powi && Ty->isFloatTy()) return ConstantFP::get(Ty->getContext(), APFloat((float)std::pow((float)Op1V, (int)Op2C->getZExtValue()))); if (IntrinsicID == Intrinsic::powi && Ty->isDoubleTy()) return ConstantFP::get(Ty->getContext(), APFloat((double)std::pow((double)Op1V, (int)Op2C->getZExtValue()))); } return nullptr; } if (ConstantInt *Op1 = dyn_cast(Operands[0])) { if (ConstantInt *Op2 = dyn_cast(Operands[1])) { switch (IntrinsicID) { default: break; case Intrinsic::sadd_with_overflow: case Intrinsic::uadd_with_overflow: case Intrinsic::ssub_with_overflow: case Intrinsic::usub_with_overflow: case Intrinsic::smul_with_overflow: case Intrinsic::umul_with_overflow: { APInt Res; bool Overflow; switch (IntrinsicID) { default: llvm_unreachable("Invalid case"); case Intrinsic::sadd_with_overflow: Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow); break; case Intrinsic::uadd_with_overflow: Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow); break; case Intrinsic::ssub_with_overflow: Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow); break; case Intrinsic::usub_with_overflow: Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow); break; case Intrinsic::smul_with_overflow: Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow); break; case Intrinsic::umul_with_overflow: Res = Op1->getValue().umul_ov(Op2->getValue(), Overflow); break; } Constant *Ops[] = { ConstantInt::get(Ty->getContext(), Res), ConstantInt::get(Type::getInt1Ty(Ty->getContext()), Overflow) }; return ConstantStruct::get(cast(Ty), Ops); } case Intrinsic::cttz: if (Op2->isOne() && Op1->isZero()) // cttz(0, 1) is undef. return UndefValue::get(Ty); return ConstantInt::get(Ty, Op1->getValue().countTrailingZeros()); case Intrinsic::ctlz: if (Op2->isOne() && Op1->isZero()) // ctlz(0, 1) is undef. return UndefValue::get(Ty); return ConstantInt::get(Ty, Op1->getValue().countLeadingZeros()); } } return nullptr; } return nullptr; } if (Operands.size() != 3) return nullptr; if (const ConstantFP *Op1 = dyn_cast(Operands[0])) { if (const ConstantFP *Op2 = dyn_cast(Operands[1])) { if (const ConstantFP *Op3 = dyn_cast(Operands[2])) { switch (IntrinsicID) { default: break; case Intrinsic::fma: case Intrinsic::fmuladd: { APFloat V = Op1->getValueAPF(); APFloat::opStatus s = V.fusedMultiplyAdd(Op2->getValueAPF(), Op3->getValueAPF(), APFloat::rmNearestTiesToEven); if (s != APFloat::opInvalidOp) return ConstantFP::get(Ty->getContext(), V); return nullptr; } } } } } return nullptr; } static Constant *ConstantFoldVectorCall(StringRef Name, unsigned IntrinsicID, VectorType *VTy, ArrayRef Operands, const TargetLibraryInfo *TLI) { SmallVector Result(VTy->getNumElements()); SmallVector Lane(Operands.size()); Type *Ty = VTy->getElementType(); for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) { // Gather a column of constants. for (unsigned J = 0, JE = Operands.size(); J != JE; ++J) { Constant *Agg = Operands[J]->getAggregateElement(I); if (!Agg) return nullptr; Lane[J] = Agg; } // Use the regular scalar folding to simplify this column. Constant *Folded = ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI); if (!Folded) return nullptr; Result[I] = Folded; } return ConstantVector::get(Result); } /// Attempt to constant fold a call to the specified function /// with the specified arguments, returning null if unsuccessful. Constant * llvm::ConstantFoldCall(Function *F, ArrayRef Operands, const TargetLibraryInfo *TLI) { if (!F->hasName()) return nullptr; StringRef Name = F->getName(); Type *Ty = F->getReturnType(); if (VectorType *VTy = dyn_cast(Ty)) return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands, TLI); return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI); }