| //===-- 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 VMCore ConstantExpr simplifications, |
| // this file defines some additional folding routines that can make use of |
| // TargetData information. These functions cannot go in VMCore due to library |
| // dependency issues. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Function.h" |
| #include "llvm/GlobalVariable.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Intrinsics.h" |
| #include "llvm/LLVMContext.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/StringMap.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/MathExtras.h" |
| #include <cerrno> |
| #include <cmath> |
| using namespace llvm; |
| |
| //===----------------------------------------------------------------------===// |
| // Constant Folding internal helper functions |
| //===----------------------------------------------------------------------===// |
| |
| /// IsConstantOffsetFromGlobal - If this constant is actually 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, |
| int64_t &Offset, const TargetData &TD) { |
| // Trivial case, constant is the global. |
| if ((GV = dyn_cast<GlobalValue>(C))) { |
| Offset = 0; |
| return true; |
| } |
| |
| // Otherwise, if this isn't a constant expr, bail out. |
| ConstantExpr *CE = dyn_cast<ConstantExpr>(C); |
| if (!CE) return false; |
| |
| // Look through ptr->int and ptr->ptr casts. |
| if (CE->getOpcode() == Instruction::PtrToInt || |
| CE->getOpcode() == Instruction::BitCast) |
| return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD); |
| |
| // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5) |
| if (CE->getOpcode() == Instruction::GetElementPtr) { |
| // Cannot compute this if the element type of the pointer is missing size |
| // info. |
| if (!cast<PointerType>(CE->getOperand(0)->getType()) |
| ->getElementType()->isSized()) |
| return false; |
| |
| // If the base isn't a global+constant, we aren't either. |
| if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD)) |
| return false; |
| |
| // Otherwise, add any offset that our operands provide. |
| gep_type_iterator GTI = gep_type_begin(CE); |
| for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end(); |
| i != e; ++i, ++GTI) { |
| ConstantInt *CI = dyn_cast<ConstantInt>(*i); |
| if (!CI) return false; // Index isn't a simple constant? |
| if (CI->getZExtValue() == 0) continue; // Not adding anything. |
| |
| if (const StructType *ST = dyn_cast<StructType>(*GTI)) { |
| // N = N + Offset |
| Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue()); |
| } else { |
| const SequentialType *SQT = cast<SequentialType>(*GTI); |
| Offset += TD.getTypeAllocSize(SQT->getElementType())*CI->getSExtValue(); |
| } |
| } |
| return true; |
| } |
| |
| return false; |
| } |
| |
| |
| /// SymbolicallyEvaluateBinop - 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 TD, |
| /// otherwise TD is null. |
| static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, |
| Constant *Op1, const TargetData *TD, |
| LLVMContext &Context){ |
| // 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 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 && TD) { |
| GlobalValue *GV1, *GV2; |
| int64_t Offs1, Offs2; |
| |
| if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD)) |
| if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) && |
| GV1 == GV2) { |
| // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow. |
| return ConstantInt::get(Op0->getType(), Offs1-Offs2); |
| } |
| } |
| |
| return 0; |
| } |
| |
| /// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP |
| /// constant expression, do so. |
| static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps, |
| const Type *ResultTy, |
| LLVMContext &Context, |
| const TargetData *TD) { |
| Constant *Ptr = Ops[0]; |
| if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized()) |
| return 0; |
| |
| unsigned BitWidth = TD->getTypeSizeInBits(TD->getIntPtrType(Context)); |
| APInt BasePtr(BitWidth, 0); |
| bool BaseIsInt = true; |
| if (!Ptr->isNullValue()) { |
| // If this is a inttoptr from a constant int, we can fold this as the base, |
| // otherwise we can't. |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) |
| if (CE->getOpcode() == Instruction::IntToPtr) |
| if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) { |
| BasePtr = Base->getValue(); |
| BasePtr.zextOrTrunc(BitWidth); |
| } |
| |
| if (BasePtr == 0) |
| BaseIsInt = false; |
| } |
| |
| // 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; i != NumOps; ++i) |
| if (!isa<ConstantInt>(Ops[i])) |
| return 0; |
| |
| APInt Offset = APInt(BitWidth, |
| TD->getIndexedOffset(Ptr->getType(), |
| (Value**)Ops+1, NumOps-1)); |
| // 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. |
| if (BaseIsInt) { |
| Constant *C = ConstantInt::get(Context, 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. |
| const Type *Ty = Ptr->getType(); |
| SmallVector<Constant*, 32> NewIdxs; |
| do { |
| if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) { |
| // The only pointer indexing we'll do is on the first index of the GEP. |
| if (isa<PointerType>(ATy) && !NewIdxs.empty()) |
| break; |
| // Determine which element of the array the offset points into. |
| APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType())); |
| if (ElemSize == 0) |
| return 0; |
| APInt NewIdx = Offset.udiv(ElemSize); |
| Offset -= NewIdx * ElemSize; |
| NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Context), NewIdx)); |
| Ty = ATy->getElementType(); |
| } else if (const StructType *STy = dyn_cast<StructType>(Ty)) { |
| // Determine which field of the struct the offset points into. The |
| // getZExtValue is at least as safe as the StructLayout API because we |
| // know the offset is within the struct at this point. |
| const StructLayout &SL = *TD->getStructLayout(STy); |
| unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue()); |
| NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Context), ElIdx)); |
| Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx)); |
| Ty = STy->getTypeAtIndex(ElIdx); |
| } else { |
| // We've reached some non-indexable type. |
| break; |
| } |
| } while (Ty != cast<PointerType>(ResultTy)->getElementType()); |
| |
| // 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 0; |
| |
| // Create a GEP. |
| Constant *C = |
| ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size()); |
| assert(cast<PointerType>(C->getType())->getElementType() == 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 != cast<PointerType>(ResultTy)->getElementType()) |
| C = ConstantExpr::getBitCast(C, ResultTy); |
| |
| return C; |
| } |
| |
| /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with |
| /// targetdata. Return 0 if unfoldable. |
| static Constant *FoldBitCast(Constant *C, const Type *DestTy, |
| const TargetData &TD, LLVMContext &Context) { |
| // If this is a bitcast from constant vector -> vector, fold it. |
| if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) { |
| if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) { |
| // If the element types match, VMCore can fold it. |
| unsigned NumDstElt = DestVTy->getNumElements(); |
| unsigned NumSrcElt = CV->getNumOperands(); |
| if (NumDstElt == NumSrcElt) |
| return 0; |
| |
| const Type *SrcEltTy = CV->getType()->getElementType(); |
| const 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> <i64 0, i64 1> to <4 x i32>) |
| // folds to (little endian): |
| // <4 x i32> <i32 0, i32 0, i32 1, i32 0> |
| // and to (big endian): |
| // <4 x i32> <i32 0, i32 0, i32 0, i32 1> |
| |
| // 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->isFloatingPoint()) { |
| // Fold to an vector of integers with same size as our FP type. |
| unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits(); |
| const Type *DestIVTy = VectorType::get( |
| IntegerType::get(Context, FPWidth), NumDstElt); |
| // Recursively handle this integer conversion, if possible. |
| C = FoldBitCast(C, DestIVTy, TD, Context); |
| if (!C) return 0; |
| |
| // Finally, VMCore 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->isFloatingPoint()) { |
| unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits(); |
| const Type *SrcIVTy = VectorType::get( |
| IntegerType::get(Context, FPWidth), NumSrcElt); |
| // Ask VMCore to do the conversion now that #elts line up. |
| C = ConstantExpr::getBitCast(C, SrcIVTy); |
| CV = dyn_cast<ConstantVector>(C); |
| if (!CV) return 0; // If VMCore wasn't able to fold it, bail out. |
| } |
| |
| // 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<Constant*, 32> Result; |
| if (NumDstElt < NumSrcElt) { |
| // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> 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<ConstantInt>(CV->getOperand(SrcElt++)); |
| if (!Src) return 0; // Reject constantexpr elements. |
| |
| // 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); |
| } |
| } else { |
| // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) |
| unsigned Ratio = NumDstElt/NumSrcElt; |
| unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits(); |
| |
| // Loop over each source value, expanding into multiple results. |
| for (unsigned i = 0; i != NumSrcElt; ++i) { |
| Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i)); |
| if (!Src) return 0; // Reject constantexpr elements. |
| |
| 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 and remember this piece. |
| Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy)); |
| } |
| } |
| } |
| |
| return ConstantVector::get(Result.data(), Result.size()); |
| } |
| } |
| |
| return 0; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Constant Folding public APIs |
| //===----------------------------------------------------------------------===// |
| |
| |
| /// ConstantFoldInstruction - Attempt to constant fold the specified |
| /// instruction. If successful, the constant result is returned, if not, null |
| /// is returned. Note that 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, LLVMContext &Context, |
| const TargetData *TD) { |
| if (PHINode *PN = dyn_cast<PHINode>(I)) { |
| if (PN->getNumIncomingValues() == 0) |
| return UndefValue::get(PN->getType()); |
| |
| Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0)); |
| if (Result == 0) return 0; |
| |
| // Handle PHI nodes specially here... |
| for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) |
| if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN) |
| return 0; // Not all the same incoming constants... |
| |
| // If we reach here, all incoming values are the same constant. |
| return Result; |
| } |
| |
| // Scan the operand list, checking to see if they are all constants, if so, |
| // hand off to ConstantFoldInstOperands. |
| SmallVector<Constant*, 8> Ops; |
| for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) |
| if (Constant *Op = dyn_cast<Constant>(*i)) |
| Ops.push_back(Op); |
| else |
| return 0; // All operands not constant! |
| |
| if (const CmpInst *CI = dyn_cast<CmpInst>(I)) |
| return ConstantFoldCompareInstOperands(CI->getPredicate(), |
| Ops.data(), Ops.size(), |
| Context, TD); |
| |
| return ConstantFoldInstOperands(I->getOpcode(), I->getType(), |
| Ops.data(), Ops.size(), Context, TD); |
| } |
| |
| /// ConstantFoldConstantExpression - Attempt to fold the constant expression |
| /// using the specified TargetData. If successful, the constant result is |
| /// result is returned, if not, null is returned. |
| Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE, |
| LLVMContext &Context, |
| const TargetData *TD) { |
| SmallVector<Constant*, 8> Ops; |
| for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i) |
| Ops.push_back(cast<Constant>(*i)); |
| |
| if (CE->isCompare()) |
| return ConstantFoldCompareInstOperands(CE->getPredicate(), |
| Ops.data(), Ops.size(), |
| Context, TD); |
| return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), |
| Ops.data(), Ops.size(), Context, TD); |
| } |
| |
| /// ConstantFoldInstOperands - 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. |
| /// |
| Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy, |
| Constant* const* Ops, unsigned NumOps, |
| LLVMContext &Context, |
| const TargetData *TD) { |
| // Handle easy binops first. |
| if (Instruction::isBinaryOp(Opcode)) { |
| if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) |
| if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD, |
| Context)) |
| return C; |
| |
| return ConstantExpr::get(Opcode, Ops[0], Ops[1]); |
| } |
| |
| switch (Opcode) { |
| default: return 0; |
| case Instruction::Call: |
| if (Function *F = dyn_cast<Function>(Ops[0])) |
| if (canConstantFoldCallTo(F)) |
| return ConstantFoldCall(F, Ops+1, NumOps-1); |
| return 0; |
| case Instruction::ICmp: |
| case Instruction::FCmp: |
| llvm_unreachable("This function is invalid for compares: no predicate specified"); |
| 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<ConstantExpr>(Ops[0])) { |
| if (TD && CE->getOpcode() == Instruction::IntToPtr) { |
| Constant *Input = CE->getOperand(0); |
| unsigned InWidth = Input->getType()->getScalarSizeInBits(); |
| if (TD->getPointerSizeInBits() < InWidth) { |
| Constant *Mask = |
| ConstantInt::get(Context, APInt::getLowBitsSet(InWidth, |
| TD->getPointerSizeInBits())); |
| 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. This requires knowing the width of a |
| // pointer, so it can't be done in ConstantExpr::getCast. |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) { |
| if (TD && |
| TD->getPointerSizeInBits() <= |
| CE->getType()->getScalarSizeInBits()) { |
| if (CE->getOpcode() == Instruction::PtrToInt) { |
| Constant *Input = CE->getOperand(0); |
| Constant *C = FoldBitCast(Input, DestTy, *TD, Context); |
| return C ? C : ConstantExpr::getBitCast(Input, DestTy); |
| } |
| // If there's a constant offset added to the integer value before |
| // it is casted back to a pointer, see if the expression can be |
| // converted into a GEP. |
| if (CE->getOpcode() == Instruction::Add) |
| if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0))) |
| if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1))) |
| if (R->getOpcode() == Instruction::PtrToInt) |
| if (GlobalVariable *GV = |
| dyn_cast<GlobalVariable>(R->getOperand(0))) { |
| const PointerType *GVTy = cast<PointerType>(GV->getType()); |
| if (const ArrayType *AT = |
| dyn_cast<ArrayType>(GVTy->getElementType())) { |
| const Type *ElTy = AT->getElementType(); |
| uint64_t AllocSize = TD->getTypeAllocSize(ElTy); |
| APInt PSA(L->getValue().getBitWidth(), AllocSize); |
| if (ElTy == cast<PointerType>(DestTy)->getElementType() && |
| L->getValue().urem(PSA) == 0) { |
| APInt ElemIdx = L->getValue().udiv(PSA); |
| if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(), |
| AT->getNumElements()))) { |
| Constant *Index[] = { |
| Constant::getNullValue(CE->getType()), |
| ConstantInt::get(Context, ElemIdx) |
| }; |
| return |
| ConstantExpr::getGetElementPtr(GV, &Index[0], 2); |
| } |
| } |
| } |
| } |
| } |
| } |
| 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: |
| return ConstantExpr::getCast(Opcode, Ops[0], DestTy); |
| case Instruction::BitCast: |
| if (TD) |
| if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context)) |
| return C; |
| 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 = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD)) |
| return C; |
| |
| return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1); |
| } |
| } |
| |
| /// ConstantFoldCompareInstOperands - 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*const * Ops, |
| unsigned NumOps, |
| LLVMContext &Context, |
| const TargetData *TD) { |
| // 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<ConstantExpr>(Ops[0])) { |
| if (TD && Ops[1]->isNullValue()) { |
| const Type *IntPtrTy = TD->getIntPtrType(Context); |
| if (CE0->getOpcode() == Instruction::IntToPtr) { |
| // 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 *NewOps[] = { C, Constant::getNullValue(C->getType()) }; |
| return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, |
| Context, TD); |
| } |
| |
| // 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 && |
| CE0->getType() == IntPtrTy) { |
| Constant *C = CE0->getOperand(0); |
| Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) }; |
| // FIXME! |
| return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, |
| Context, TD); |
| } |
| } |
| |
| if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) { |
| if (TD && CE0->getOpcode() == CE1->getOpcode()) { |
| const Type *IntPtrTy = TD->getIntPtrType(Context); |
| |
| if (CE0->getOpcode() == Instruction::IntToPtr) { |
| // 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); |
| Constant *NewOps[] = { C0, C1 }; |
| return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, |
| Context, TD); |
| } |
| |
| // 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 && |
| CE0->getType() == IntPtrTy && |
| CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) { |
| Constant *NewOps[] = { |
| CE0->getOperand(0), CE1->getOperand(0) |
| }; |
| return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, |
| Context, TD); |
| } |
| } |
| } |
| } |
| return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]); |
| } |
| |
| |
| /// ConstantFoldLoadThroughGEPConstantExpr - 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, |
| LLVMContext &Context) { |
| if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType())) |
| return 0; // Do not allow stepping over the value! |
| |
| // Loop over all of the operands, tracking down which value we are |
| // addressing... |
| gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); |
| for (++I; I != E; ++I) |
| if (const StructType *STy = dyn_cast<StructType>(*I)) { |
| ConstantInt *CU = cast<ConstantInt>(I.getOperand()); |
| assert(CU->getZExtValue() < STy->getNumElements() && |
| "Struct index out of range!"); |
| unsigned El = (unsigned)CU->getZExtValue(); |
| if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) { |
| C = CS->getOperand(El); |
| } else if (isa<ConstantAggregateZero>(C)) { |
| C = Constant::getNullValue(STy->getElementType(El)); |
| } else if (isa<UndefValue>(C)) { |
| C = UndefValue::get(STy->getElementType(El)); |
| } else { |
| return 0; |
| } |
| } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) { |
| if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) { |
| if (CI->getZExtValue() >= ATy->getNumElements()) |
| return 0; |
| if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) |
| C = CA->getOperand(CI->getZExtValue()); |
| else if (isa<ConstantAggregateZero>(C)) |
| C = Constant::getNullValue(ATy->getElementType()); |
| else if (isa<UndefValue>(C)) |
| C = UndefValue::get(ATy->getElementType()); |
| else |
| return 0; |
| } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) { |
| if (CI->getZExtValue() >= PTy->getNumElements()) |
| return 0; |
| if (ConstantVector *CP = dyn_cast<ConstantVector>(C)) |
| C = CP->getOperand(CI->getZExtValue()); |
| else if (isa<ConstantAggregateZero>(C)) |
| C = Constant::getNullValue(PTy->getElementType()); |
| else if (isa<UndefValue>(C)) |
| C = UndefValue::get(PTy->getElementType()); |
| else |
| return 0; |
| } else { |
| return 0; |
| } |
| } else { |
| return 0; |
| } |
| return C; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Constant Folding for Calls |
| // |
| |
| /// canConstantFoldCallTo - Return true if its even possible to fold a call to |
| /// the specified function. |
| bool |
| llvm::canConstantFoldCallTo(const Function *F) { |
| switch (F->getIntrinsicID()) { |
| case Intrinsic::sqrt: |
| case Intrinsic::powi: |
| case Intrinsic::bswap: |
| case Intrinsic::ctpop: |
| case Intrinsic::ctlz: |
| case Intrinsic::cttz: |
| return true; |
| default: 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"; |
| 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 *ConstantFoldFP(double (*NativeFP)(double), double V, |
| const Type *Ty, LLVMContext &Context) { |
| errno = 0; |
| V = NativeFP(V); |
| if (errno != 0) { |
| errno = 0; |
| return 0; |
| } |
| |
| if (Ty == Type::getFloatTy(Context)) |
| return ConstantFP::get(Context, APFloat((float)V)); |
| if (Ty == Type::getDoubleTy(Context)) |
| return ConstantFP::get(Context, APFloat(V)); |
| llvm_unreachable("Can only constant fold float/double"); |
| return 0; // dummy return to suppress warning |
| } |
| |
| static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), |
| double V, double W, |
| const Type *Ty, |
| LLVMContext &Context) { |
| errno = 0; |
| V = NativeFP(V, W); |
| if (errno != 0) { |
| errno = 0; |
| return 0; |
| } |
| |
| if (Ty == Type::getFloatTy(Context)) |
| return ConstantFP::get(Context, APFloat((float)V)); |
| if (Ty == Type::getDoubleTy(Context)) |
| return ConstantFP::get(Context, APFloat(V)); |
| llvm_unreachable("Can only constant fold float/double"); |
| return 0; // dummy return to suppress warning |
| } |
| |
| /// ConstantFoldCall - Attempt to constant fold a call to the specified function |
| /// with the specified arguments, returning null if unsuccessful. |
| |
| Constant * |
| llvm::ConstantFoldCall(Function *F, |
| Constant* const* Operands, unsigned NumOperands) { |
| if (!F->hasName()) return 0; |
| LLVMContext &Context = F->getContext(); |
| StringRef Name = F->getName(); |
| |
| const Type *Ty = F->getReturnType(); |
| if (NumOperands == 1) { |
| if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) { |
| if (Ty!=Type::getFloatTy(F->getContext()) && |
| Ty!=Type::getDoubleTy(Context)) |
| return 0; |
| /// 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 = Ty==Type::getFloatTy(F->getContext()) ? |
| (double)Op->getValueAPF().convertToFloat(): |
| Op->getValueAPF().convertToDouble(); |
| switch (Name[0]) { |
| case 'a': |
| if (Name == "acos") |
| return ConstantFoldFP(acos, V, Ty, Context); |
| else if (Name == "asin") |
| return ConstantFoldFP(asin, V, Ty, Context); |
| else if (Name == "atan") |
| return ConstantFoldFP(atan, V, Ty, Context); |
| break; |
| case 'c': |
| if (Name == "ceil") |
| return ConstantFoldFP(ceil, V, Ty, Context); |
| else if (Name == "cos") |
| return ConstantFoldFP(cos, V, Ty, Context); |
| else if (Name == "cosh") |
| return ConstantFoldFP(cosh, V, Ty, Context); |
| else if (Name == "cosf") |
| return ConstantFoldFP(cos, V, Ty, Context); |
| break; |
| case 'e': |
| if (Name == "exp") |
| return ConstantFoldFP(exp, V, Ty, Context); |
| break; |
| case 'f': |
| if (Name == "fabs") |
| return ConstantFoldFP(fabs, V, Ty, Context); |
| else if (Name == "floor") |
| return ConstantFoldFP(floor, V, Ty, Context); |
| break; |
| case 'l': |
| if (Name == "log" && V > 0) |
| return ConstantFoldFP(log, V, Ty, Context); |
| else if (Name == "log10" && V > 0) |
| return ConstantFoldFP(log10, V, Ty, Context); |
| else if (Name == "llvm.sqrt.f32" || |
| Name == "llvm.sqrt.f64") { |
| if (V >= -0.0) |
| return ConstantFoldFP(sqrt, V, Ty, Context); |
| else // Undefined |
| return Constant::getNullValue(Ty); |
| } |
| break; |
| case 's': |
| if (Name == "sin") |
| return ConstantFoldFP(sin, V, Ty, Context); |
| else if (Name == "sinh") |
| return ConstantFoldFP(sinh, V, Ty, Context); |
| else if (Name == "sqrt" && V >= 0) |
| return ConstantFoldFP(sqrt, V, Ty, Context); |
| else if (Name == "sqrtf" && V >= 0) |
| return ConstantFoldFP(sqrt, V, Ty, Context); |
| else if (Name == "sinf") |
| return ConstantFoldFP(sin, V, Ty, Context); |
| break; |
| case 't': |
| if (Name == "tan") |
| return ConstantFoldFP(tan, V, Ty, Context); |
| else if (Name == "tanh") |
| return ConstantFoldFP(tanh, V, Ty, Context); |
| break; |
| default: |
| break; |
| } |
| } else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) { |
| if (Name.startswith("llvm.bswap")) |
| return ConstantInt::get(Context, Op->getValue().byteSwap()); |
| else if (Name.startswith("llvm.ctpop")) |
| return ConstantInt::get(Ty, Op->getValue().countPopulation()); |
| else if (Name.startswith("llvm.cttz")) |
| return ConstantInt::get(Ty, Op->getValue().countTrailingZeros()); |
| else if (Name.startswith("llvm.ctlz")) |
| return ConstantInt::get(Ty, Op->getValue().countLeadingZeros()); |
| } |
| } else if (NumOperands == 2) { |
| if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) { |
| if (Ty!=Type::getFloatTy(F->getContext()) && |
| Ty!=Type::getDoubleTy(Context)) |
| return 0; |
| double Op1V = Ty==Type::getFloatTy(F->getContext()) ? |
| (double)Op1->getValueAPF().convertToFloat(): |
| Op1->getValueAPF().convertToDouble(); |
| if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) { |
| double Op2V = Ty==Type::getFloatTy(F->getContext()) ? |
| (double)Op2->getValueAPF().convertToFloat(): |
| Op2->getValueAPF().convertToDouble(); |
| |
| if (Name == "pow") { |
| return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty, Context); |
| } else if (Name == "fmod") { |
| return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty, Context); |
| } else if (Name == "atan2") { |
| return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty, Context); |
| } |
| } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) { |
| if (Name == "llvm.powi.f32") { |
| return ConstantFP::get(Context, APFloat((float)std::pow((float)Op1V, |
| (int)Op2C->getZExtValue()))); |
| } else if (Name == "llvm.powi.f64") { |
| return ConstantFP::get(Context, APFloat((double)std::pow((double)Op1V, |
| (int)Op2C->getZExtValue()))); |
| } |
| } |
| } |
| } |
| return 0; |
| } |
| |