| //===- ConstantFolding.cpp - LLVM constant folder -------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements folding of constants for LLVM. This implements the |
| // (internal) ConstantFolding.h interface, which is used by the |
| // ConstantExpr::get* methods to automatically fold constants when possible. |
| // |
| // The current constant folding implementation is implemented in two pieces: the |
| // template-based folder for simple primitive constants like ConstantInt, and |
| // the special case hackery that we use to symbolically evaluate expressions |
| // that use ConstantExprs. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "ConstantFolding.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Function.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include <limits> |
| #include <cmath> |
| using namespace llvm; |
| |
| namespace { |
| struct ConstRules { |
| ConstRules() {} |
| virtual ~ConstRules() {} |
| |
| // Binary Operators... |
| virtual Constant *add(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *sub(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *mul(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *div(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *rem(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *op_and(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *op_or (const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *op_xor(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *shl(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *shr(const Constant *V1, const Constant *V2) const = 0; |
| virtual Constant *lessthan(const Constant *V1, const Constant *V2) const =0; |
| virtual Constant *equalto(const Constant *V1, const Constant *V2) const = 0; |
| |
| // Casting operators. |
| virtual Constant *castToBool (const Constant *V) const = 0; |
| virtual Constant *castToSByte (const Constant *V) const = 0; |
| virtual Constant *castToUByte (const Constant *V) const = 0; |
| virtual Constant *castToShort (const Constant *V) const = 0; |
| virtual Constant *castToUShort(const Constant *V) const = 0; |
| virtual Constant *castToInt (const Constant *V) const = 0; |
| virtual Constant *castToUInt (const Constant *V) const = 0; |
| virtual Constant *castToLong (const Constant *V) const = 0; |
| virtual Constant *castToULong (const Constant *V) const = 0; |
| virtual Constant *castToFloat (const Constant *V) const = 0; |
| virtual Constant *castToDouble(const Constant *V) const = 0; |
| virtual Constant *castToPointer(const Constant *V, |
| const PointerType *Ty) const = 0; |
| |
| // ConstRules::get - Return an instance of ConstRules for the specified |
| // constant operands. |
| // |
| static ConstRules &get(const Constant *V1, const Constant *V2); |
| private: |
| ConstRules(const ConstRules &); // Do not implement |
| ConstRules &operator=(const ConstRules &); // Do not implement |
| }; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // TemplateRules Class |
| //===----------------------------------------------------------------------===// |
| // |
| // TemplateRules - Implement a subclass of ConstRules that provides all |
| // operations as noops. All other rules classes inherit from this class so |
| // that if functionality is needed in the future, it can simply be added here |
| // and to ConstRules without changing anything else... |
| // |
| // This class also provides subclasses with typesafe implementations of methods |
| // so that don't have to do type casting. |
| // |
| template<class ArgType, class SubClassName> |
| class TemplateRules : public ConstRules { |
| |
| |
| //===--------------------------------------------------------------------===// |
| // Redirecting functions that cast to the appropriate types |
| //===--------------------------------------------------------------------===// |
| |
| virtual Constant *add(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Add((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *sub(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Sub((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *mul(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Mul((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *div(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Div((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *rem(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Rem((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *op_and(const Constant *V1, const Constant *V2) const { |
| return SubClassName::And((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *op_or(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Or((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *op_xor(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Xor((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *shl(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Shl((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *shr(const Constant *V1, const Constant *V2) const { |
| return SubClassName::Shr((const ArgType *)V1, (const ArgType *)V2); |
| } |
| |
| virtual Constant *lessthan(const Constant *V1, const Constant *V2) const { |
| return SubClassName::LessThan((const ArgType *)V1, (const ArgType *)V2); |
| } |
| virtual Constant *equalto(const Constant *V1, const Constant *V2) const { |
| return SubClassName::EqualTo((const ArgType *)V1, (const ArgType *)V2); |
| } |
| |
| // Casting operators. ick |
| virtual Constant *castToBool(const Constant *V) const { |
| return SubClassName::CastToBool((const ArgType*)V); |
| } |
| virtual Constant *castToSByte(const Constant *V) const { |
| return SubClassName::CastToSByte((const ArgType*)V); |
| } |
| virtual Constant *castToUByte(const Constant *V) const { |
| return SubClassName::CastToUByte((const ArgType*)V); |
| } |
| virtual Constant *castToShort(const Constant *V) const { |
| return SubClassName::CastToShort((const ArgType*)V); |
| } |
| virtual Constant *castToUShort(const Constant *V) const { |
| return SubClassName::CastToUShort((const ArgType*)V); |
| } |
| virtual Constant *castToInt(const Constant *V) const { |
| return SubClassName::CastToInt((const ArgType*)V); |
| } |
| virtual Constant *castToUInt(const Constant *V) const { |
| return SubClassName::CastToUInt((const ArgType*)V); |
| } |
| virtual Constant *castToLong(const Constant *V) const { |
| return SubClassName::CastToLong((const ArgType*)V); |
| } |
| virtual Constant *castToULong(const Constant *V) const { |
| return SubClassName::CastToULong((const ArgType*)V); |
| } |
| virtual Constant *castToFloat(const Constant *V) const { |
| return SubClassName::CastToFloat((const ArgType*)V); |
| } |
| virtual Constant *castToDouble(const Constant *V) const { |
| return SubClassName::CastToDouble((const ArgType*)V); |
| } |
| virtual Constant *castToPointer(const Constant *V, |
| const PointerType *Ty) const { |
| return SubClassName::CastToPointer((const ArgType*)V, Ty); |
| } |
| |
| //===--------------------------------------------------------------------===// |
| // Default "noop" implementations |
| //===--------------------------------------------------------------------===// |
| |
| static Constant *Add(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *Sub(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *Mul(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *Div(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *Rem(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *And(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *Or (const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *Xor(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *Shl(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *Shr(const ArgType *V1, const ArgType *V2) { return 0; } |
| static Constant *LessThan(const ArgType *V1, const ArgType *V2) { |
| return 0; |
| } |
| static Constant *EqualTo(const ArgType *V1, const ArgType *V2) { |
| return 0; |
| } |
| |
| // Casting operators. ick |
| static Constant *CastToBool (const Constant *V) { return 0; } |
| static Constant *CastToSByte (const Constant *V) { return 0; } |
| static Constant *CastToUByte (const Constant *V) { return 0; } |
| static Constant *CastToShort (const Constant *V) { return 0; } |
| static Constant *CastToUShort(const Constant *V) { return 0; } |
| static Constant *CastToInt (const Constant *V) { return 0; } |
| static Constant *CastToUInt (const Constant *V) { return 0; } |
| static Constant *CastToLong (const Constant *V) { return 0; } |
| static Constant *CastToULong (const Constant *V) { return 0; } |
| static Constant *CastToFloat (const Constant *V) { return 0; } |
| static Constant *CastToDouble(const Constant *V) { return 0; } |
| static Constant *CastToPointer(const Constant *, |
| const PointerType *) {return 0;} |
| |
| public: |
| virtual ~TemplateRules() {} |
| }; |
| |
| |
| |
| //===----------------------------------------------------------------------===// |
| // EmptyRules Class |
| //===----------------------------------------------------------------------===// |
| // |
| // EmptyRules provides a concrete base class of ConstRules that does nothing |
| // |
| struct EmptyRules : public TemplateRules<Constant, EmptyRules> { |
| static Constant *EqualTo(const Constant *V1, const Constant *V2) { |
| if (V1 == V2) return ConstantBool::True; |
| return 0; |
| } |
| }; |
| |
| |
| |
| //===----------------------------------------------------------------------===// |
| // BoolRules Class |
| //===----------------------------------------------------------------------===// |
| // |
| // BoolRules provides a concrete base class of ConstRules for the 'bool' type. |
| // |
| struct BoolRules : public TemplateRules<ConstantBool, BoolRules> { |
| |
| static Constant *LessThan(const ConstantBool *V1, const ConstantBool *V2){ |
| return ConstantBool::get(V1->getValue() < V2->getValue()); |
| } |
| |
| static Constant *EqualTo(const Constant *V1, const Constant *V2) { |
| return ConstantBool::get(V1 == V2); |
| } |
| |
| static Constant *And(const ConstantBool *V1, const ConstantBool *V2) { |
| return ConstantBool::get(V1->getValue() & V2->getValue()); |
| } |
| |
| static Constant *Or(const ConstantBool *V1, const ConstantBool *V2) { |
| return ConstantBool::get(V1->getValue() | V2->getValue()); |
| } |
| |
| static Constant *Xor(const ConstantBool *V1, const ConstantBool *V2) { |
| return ConstantBool::get(V1->getValue() ^ V2->getValue()); |
| } |
| |
| // Casting operators. ick |
| #define DEF_CAST(TYPE, CLASS, CTYPE) \ |
| static Constant *CastTo##TYPE (const ConstantBool *V) { \ |
| return CLASS::get(Type::TYPE##Ty, (CTYPE)(bool)V->getValue()); \ |
| } |
| |
| DEF_CAST(Bool , ConstantBool, bool) |
| DEF_CAST(SByte , ConstantSInt, signed char) |
| DEF_CAST(UByte , ConstantUInt, unsigned char) |
| DEF_CAST(Short , ConstantSInt, signed short) |
| DEF_CAST(UShort, ConstantUInt, unsigned short) |
| DEF_CAST(Int , ConstantSInt, signed int) |
| DEF_CAST(UInt , ConstantUInt, unsigned int) |
| DEF_CAST(Long , ConstantSInt, int64_t) |
| DEF_CAST(ULong , ConstantUInt, uint64_t) |
| DEF_CAST(Float , ConstantFP , float) |
| DEF_CAST(Double, ConstantFP , double) |
| #undef DEF_CAST |
| }; |
| |
| |
| //===----------------------------------------------------------------------===// |
| // NullPointerRules Class |
| //===----------------------------------------------------------------------===// |
| // |
| // NullPointerRules provides a concrete base class of ConstRules for null |
| // pointers. |
| // |
| struct NullPointerRules : public TemplateRules<ConstantPointerNull, |
| NullPointerRules> { |
| static Constant *EqualTo(const Constant *V1, const Constant *V2) { |
| return ConstantBool::True; // Null pointers are always equal |
| } |
| static Constant *CastToBool(const Constant *V) { |
| return ConstantBool::False; |
| } |
| static Constant *CastToSByte (const Constant *V) { |
| return ConstantSInt::get(Type::SByteTy, 0); |
| } |
| static Constant *CastToUByte (const Constant *V) { |
| return ConstantUInt::get(Type::UByteTy, 0); |
| } |
| static Constant *CastToShort (const Constant *V) { |
| return ConstantSInt::get(Type::ShortTy, 0); |
| } |
| static Constant *CastToUShort(const Constant *V) { |
| return ConstantUInt::get(Type::UShortTy, 0); |
| } |
| static Constant *CastToInt (const Constant *V) { |
| return ConstantSInt::get(Type::IntTy, 0); |
| } |
| static Constant *CastToUInt (const Constant *V) { |
| return ConstantUInt::get(Type::UIntTy, 0); |
| } |
| static Constant *CastToLong (const Constant *V) { |
| return ConstantSInt::get(Type::LongTy, 0); |
| } |
| static Constant *CastToULong (const Constant *V) { |
| return ConstantUInt::get(Type::ULongTy, 0); |
| } |
| static Constant *CastToFloat (const Constant *V) { |
| return ConstantFP::get(Type::FloatTy, 0); |
| } |
| static Constant *CastToDouble(const Constant *V) { |
| return ConstantFP::get(Type::DoubleTy, 0); |
| } |
| |
| static Constant *CastToPointer(const ConstantPointerNull *V, |
| const PointerType *PTy) { |
| return ConstantPointerNull::get(PTy); |
| } |
| }; |
| |
| |
| //===----------------------------------------------------------------------===// |
| // DirectRules Class |
| //===----------------------------------------------------------------------===// |
| // |
| // DirectRules provides a concrete base classes of ConstRules for a variety of |
| // different types. This allows the C++ compiler to automatically generate our |
| // constant handling operations in a typesafe and accurate manner. |
| // |
| template<class ConstantClass, class BuiltinType, Type **Ty, class SuperClass> |
| struct DirectRules : public TemplateRules<ConstantClass, SuperClass> { |
| static Constant *Add(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType R = (BuiltinType)V1->getValue() + (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| |
| static Constant *Sub(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType R = (BuiltinType)V1->getValue() - (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| |
| static Constant *Mul(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType R = (BuiltinType)V1->getValue() * (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| |
| static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) { |
| if (V2->isNullValue()) return 0; |
| BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| |
| static Constant *LessThan(const ConstantClass *V1, const ConstantClass *V2) { |
| bool R = (BuiltinType)V1->getValue() < (BuiltinType)V2->getValue(); |
| return ConstantBool::get(R); |
| } |
| |
| static Constant *EqualTo(const ConstantClass *V1, const ConstantClass *V2) { |
| bool R = (BuiltinType)V1->getValue() == (BuiltinType)V2->getValue(); |
| return ConstantBool::get(R); |
| } |
| |
| static Constant *CastToPointer(const ConstantClass *V, |
| const PointerType *PTy) { |
| if (V->isNullValue()) // Is it a FP or Integral null value? |
| return ConstantPointerNull::get(PTy); |
| return 0; // Can't const prop other types of pointers |
| } |
| |
| // Casting operators. ick |
| #define DEF_CAST(TYPE, CLASS, CTYPE) \ |
| static Constant *CastTo##TYPE (const ConstantClass *V) { \ |
| return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getValue()); \ |
| } |
| |
| DEF_CAST(Bool , ConstantBool, bool) |
| DEF_CAST(SByte , ConstantSInt, signed char) |
| DEF_CAST(UByte , ConstantUInt, unsigned char) |
| DEF_CAST(Short , ConstantSInt, signed short) |
| DEF_CAST(UShort, ConstantUInt, unsigned short) |
| DEF_CAST(Int , ConstantSInt, signed int) |
| DEF_CAST(UInt , ConstantUInt, unsigned int) |
| DEF_CAST(Long , ConstantSInt, int64_t) |
| DEF_CAST(ULong , ConstantUInt, uint64_t) |
| DEF_CAST(Float , ConstantFP , float) |
| DEF_CAST(Double, ConstantFP , double) |
| #undef DEF_CAST |
| }; |
| |
| |
| //===----------------------------------------------------------------------===// |
| // DirectIntRules Class |
| //===----------------------------------------------------------------------===// |
| // |
| // DirectIntRules provides implementations of functions that are valid on |
| // integer types, but not all types in general. |
| // |
| template <class ConstantClass, class BuiltinType, Type **Ty> |
| struct DirectIntRules |
| : public DirectRules<ConstantClass, BuiltinType, Ty, |
| DirectIntRules<ConstantClass, BuiltinType, Ty> > { |
| |
| static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) { |
| if (V2->isNullValue()) return 0; |
| if (V2->isAllOnesValue() && // MIN_INT / -1 |
| (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue()) |
| return 0; |
| BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| |
| static Constant *Rem(const ConstantClass *V1, |
| const ConstantClass *V2) { |
| if (V2->isNullValue()) return 0; // X / 0 |
| if (V2->isAllOnesValue() && // MIN_INT / -1 |
| (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue()) |
| return 0; |
| BuiltinType R = (BuiltinType)V1->getValue() % (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| |
| static Constant *And(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType R = (BuiltinType)V1->getValue() & (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| static Constant *Or(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType R = (BuiltinType)V1->getValue() | (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| static Constant *Xor(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType R = (BuiltinType)V1->getValue() ^ (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| |
| static Constant *Shl(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType R = (BuiltinType)V1->getValue() << (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| |
| static Constant *Shr(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType R = (BuiltinType)V1->getValue() >> (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| }; |
| |
| |
| //===----------------------------------------------------------------------===// |
| // DirectFPRules Class |
| //===----------------------------------------------------------------------===// |
| // |
| /// DirectFPRules provides implementations of functions that are valid on |
| /// floating point types, but not all types in general. |
| /// |
| template <class ConstantClass, class BuiltinType, Type **Ty> |
| struct DirectFPRules |
| : public DirectRules<ConstantClass, BuiltinType, Ty, |
| DirectFPRules<ConstantClass, BuiltinType, Ty> > { |
| static Constant *Rem(const ConstantClass *V1, const ConstantClass *V2) { |
| if (V2->isNullValue()) return 0; |
| BuiltinType Result = std::fmod((BuiltinType)V1->getValue(), |
| (BuiltinType)V2->getValue()); |
| return ConstantClass::get(*Ty, Result); |
| } |
| static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) { |
| BuiltinType inf = std::numeric_limits<BuiltinType>::infinity(); |
| if (V2->isExactlyValue(0.0)) return ConstantClass::get(*Ty, inf); |
| if (V2->isExactlyValue(-0.0)) return ConstantClass::get(*Ty, -inf); |
| BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); |
| return ConstantClass::get(*Ty, R); |
| } |
| }; |
| |
| |
| /// ConstRules::get - This method returns the constant rules implementation that |
| /// implements the semantics of the two specified constants. |
| ConstRules &ConstRules::get(const Constant *V1, const Constant *V2) { |
| static EmptyRules EmptyR; |
| static BoolRules BoolR; |
| static NullPointerRules NullPointerR; |
| static DirectIntRules<ConstantSInt, signed char , &Type::SByteTy> SByteR; |
| static DirectIntRules<ConstantUInt, unsigned char , &Type::UByteTy> UByteR; |
| static DirectIntRules<ConstantSInt, signed short, &Type::ShortTy> ShortR; |
| static DirectIntRules<ConstantUInt, unsigned short, &Type::UShortTy> UShortR; |
| static DirectIntRules<ConstantSInt, signed int , &Type::IntTy> IntR; |
| static DirectIntRules<ConstantUInt, unsigned int , &Type::UIntTy> UIntR; |
| static DirectIntRules<ConstantSInt, int64_t , &Type::LongTy> LongR; |
| static DirectIntRules<ConstantUInt, uint64_t , &Type::ULongTy> ULongR; |
| static DirectFPRules <ConstantFP , float , &Type::FloatTy> FloatR; |
| static DirectFPRules <ConstantFP , double , &Type::DoubleTy> DoubleR; |
| |
| if (isa<ConstantExpr>(V1) || isa<ConstantExpr>(V2) || |
| isa<GlobalValue>(V1) || isa<GlobalValue>(V2) || |
| isa<UndefValue>(V1) || isa<UndefValue>(V2)) |
| return EmptyR; |
| |
| switch (V1->getType()->getTypeID()) { |
| default: assert(0 && "Unknown value type for constant folding!"); |
| case Type::BoolTyID: return BoolR; |
| case Type::PointerTyID: return NullPointerR; |
| case Type::SByteTyID: return SByteR; |
| case Type::UByteTyID: return UByteR; |
| case Type::ShortTyID: return ShortR; |
| case Type::UShortTyID: return UShortR; |
| case Type::IntTyID: return IntR; |
| case Type::UIntTyID: return UIntR; |
| case Type::LongTyID: return LongR; |
| case Type::ULongTyID: return ULongR; |
| case Type::FloatTyID: return FloatR; |
| case Type::DoubleTyID: return DoubleR; |
| } |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // ConstantFold*Instruction Implementations |
| //===----------------------------------------------------------------------===// |
| // |
| // These methods contain the special case hackery required to symbolically |
| // evaluate some constant expression cases, and use the ConstantRules class to |
| // evaluate normal constants. |
| // |
| static unsigned getSize(const Type *Ty) { |
| unsigned S = Ty->getPrimitiveSize(); |
| return S ? S : 8; // Treat pointers at 8 bytes |
| } |
| |
| Constant *llvm::ConstantFoldCastInstruction(const Constant *V, |
| const Type *DestTy) { |
| if (V->getType() == DestTy) return (Constant*)V; |
| |
| // Cast of a global address to boolean is always true. |
| if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) { |
| if (DestTy == Type::BoolTy) |
| // FIXME: When we support 'external weak' references, we have to prevent |
| // this transformation from happening. This code will need to be updated |
| // to ignore external weak symbols when we support it. |
| return ConstantBool::True; |
| } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { |
| if (CE->getOpcode() == Instruction::Cast) { |
| Constant *Op = const_cast<Constant*>(CE->getOperand(0)); |
| // Try to not produce a cast of a cast, which is almost always redundant. |
| if (!Op->getType()->isFloatingPoint() && |
| !CE->getType()->isFloatingPoint() && |
| !DestTy->isFloatingPoint()) { |
| unsigned S1 = getSize(Op->getType()), S2 = getSize(CE->getType()); |
| unsigned S3 = getSize(DestTy); |
| if (Op->getType() == DestTy && S3 >= S2) |
| return Op; |
| if (S1 >= S2 && S2 >= S3) |
| return ConstantExpr::getCast(Op, DestTy); |
| if (S1 <= S2 && S2 >= S3 && S1 <= S3) |
| return ConstantExpr::getCast(Op, DestTy); |
| } |
| } else if (CE->getOpcode() == Instruction::GetElementPtr) { |
| // If all of the indexes in the GEP are null values, there is no pointer |
| // adjustment going on. We might as well cast the source pointer. |
| bool isAllNull = true; |
| for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) |
| if (!CE->getOperand(i)->isNullValue()) { |
| isAllNull = false; |
| break; |
| } |
| if (isAllNull) |
| return ConstantExpr::getCast(CE->getOperand(0), DestTy); |
| } |
| } else if (isa<UndefValue>(V)) { |
| return UndefValue::get(DestTy); |
| } |
| |
| // Check to see if we are casting an pointer to an aggregate to a pointer to |
| // the first element. If so, return the appropriate GEP instruction. |
| if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) |
| if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) { |
| std::vector<Value*> IdxList; |
| IdxList.push_back(Constant::getNullValue(Type::IntTy)); |
| const Type *ElTy = PTy->getElementType(); |
| while (ElTy != DPTy->getElementType()) { |
| if (const StructType *STy = dyn_cast<StructType>(ElTy)) { |
| if (STy->getNumElements() == 0) break; |
| ElTy = STy->getElementType(0); |
| IdxList.push_back(Constant::getNullValue(Type::UIntTy)); |
| } else if (const SequentialType *STy = dyn_cast<SequentialType>(ElTy)) { |
| if (isa<PointerType>(ElTy)) break; // Can't index into pointers! |
| ElTy = STy->getElementType(); |
| IdxList.push_back(IdxList[0]); |
| } else { |
| break; |
| } |
| } |
| |
| if (ElTy == DPTy->getElementType()) |
| return ConstantExpr::getGetElementPtr(const_cast<Constant*>(V),IdxList); |
| } |
| |
| ConstRules &Rules = ConstRules::get(V, V); |
| |
| switch (DestTy->getTypeID()) { |
| case Type::BoolTyID: return Rules.castToBool(V); |
| case Type::UByteTyID: return Rules.castToUByte(V); |
| case Type::SByteTyID: return Rules.castToSByte(V); |
| case Type::UShortTyID: return Rules.castToUShort(V); |
| case Type::ShortTyID: return Rules.castToShort(V); |
| case Type::UIntTyID: return Rules.castToUInt(V); |
| case Type::IntTyID: return Rules.castToInt(V); |
| case Type::ULongTyID: return Rules.castToULong(V); |
| case Type::LongTyID: return Rules.castToLong(V); |
| case Type::FloatTyID: return Rules.castToFloat(V); |
| case Type::DoubleTyID: return Rules.castToDouble(V); |
| case Type::PointerTyID: |
| return Rules.castToPointer(V, cast<PointerType>(DestTy)); |
| default: return 0; |
| } |
| } |
| |
| Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, |
| const Constant *V1, |
| const Constant *V2) { |
| if (Cond == ConstantBool::True) |
| return const_cast<Constant*>(V1); |
| else if (Cond == ConstantBool::False) |
| return const_cast<Constant*>(V2); |
| |
| if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); |
| if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); |
| if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); |
| return 0; |
| } |
| |
| /// isZeroSizedType - This type is zero sized if its an array or structure of |
| /// zero sized types. The only leaf zero sized type is an empty structure. |
| static bool isMaybeZeroSizedType(const Type *Ty) { |
| if (isa<OpaqueType>(Ty)) return true; // Can't say. |
| if (const StructType *STy = dyn_cast<StructType>(Ty)) { |
| |
| // If all of elements have zero size, this does too. |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; |
| return true; |
| |
| } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| return isMaybeZeroSizedType(ATy->getElementType()); |
| } |
| return false; |
| } |
| |
| /// IdxCompare - Compare the two constants as though they were getelementptr |
| /// indices. This allows coersion of the types to be the same thing. |
| /// |
| /// If the two constants are the "same" (after coersion), return 0. If the |
| /// first is less than the second, return -1, if the second is less than the |
| /// first, return 1. If the constants are not integral, return -2. |
| /// |
| static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { |
| if (C1 == C2) return 0; |
| |
| // Ok, we found a different index. Are either of the operands |
| // ConstantExprs? If so, we can't do anything with them. |
| if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) |
| return -2; // don't know! |
| |
| // Ok, we have two differing integer indices. Sign extend them to be the same |
| // type. Long is always big enough, so we use it. |
| C1 = ConstantExpr::getSignExtend(C1, Type::LongTy); |
| C2 = ConstantExpr::getSignExtend(C2, Type::LongTy); |
| if (C1 == C2) return 0; // Are they just differing types? |
| |
| // If the type being indexed over is really just a zero sized type, there is |
| // no pointer difference being made here. |
| if (isMaybeZeroSizedType(ElTy)) |
| return -2; // dunno. |
| |
| // If they are really different, now that they are the same type, then we |
| // found a difference! |
| if (cast<ConstantSInt>(C1)->getValue() < cast<ConstantSInt>(C2)->getValue()) |
| return -1; |
| else |
| return 1; |
| } |
| |
| /// evaluateRelation - This function determines if there is anything we can |
| /// decide about the two constants provided. This doesn't need to handle simple |
| /// things like integer comparisons, but should instead handle ConstantExprs |
| /// and GlobalValuess. If we can determine that the two constants have a |
| /// particular relation to each other, we should return the corresponding SetCC |
| /// code, otherwise return Instruction::BinaryOpsEnd. |
| /// |
| /// To simplify this code we canonicalize the relation so that the first |
| /// operand is always the most "complex" of the two. We consider simple |
| /// constants (like ConstantInt) to be the simplest, followed by |
| /// GlobalValues, followed by ConstantExpr's (the most complex). |
| /// |
| static Instruction::BinaryOps evaluateRelation(const Constant *V1, |
| const Constant *V2) { |
| assert(V1->getType() == V2->getType() && |
| "Cannot compare different types of values!"); |
| if (V1 == V2) return Instruction::SetEQ; |
| |
| if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { |
| // If the first operand is simple, swap operands. |
| assert((isa<GlobalValue>(V2) || isa<ConstantExpr>(V2)) && |
| "Simple cases should have been handled by caller!"); |
| Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1); |
| if (SwappedRelation != Instruction::BinaryOpsEnd) |
| return SetCondInst::getSwappedCondition(SwappedRelation); |
| |
| } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)){ |
| if (isa<ConstantExpr>(V2)) { // Swap as necessary. |
| Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1); |
| if (SwappedRelation != Instruction::BinaryOpsEnd) |
| return SetCondInst::getSwappedCondition(SwappedRelation); |
| else |
| return Instruction::BinaryOpsEnd; |
| } |
| |
| // Now we know that the RHS is a GlobalValue or simple constant, |
| // which (since the types must match) means that it's a ConstantPointerNull. |
| if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { |
| assert(CPR1 != CPR2 && |
| "GVs for the same value exist at different addresses??"); |
| // FIXME: If both globals are external weak, they might both be null! |
| return Instruction::SetNE; |
| } else { |
| assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); |
| // Global can never be null. FIXME: if we implement external weak |
| // linkage, this is not necessarily true! |
| return Instruction::SetNE; |
| } |
| |
| } else { |
| // Ok, the LHS is known to be a constantexpr. The RHS can be any of a |
| // constantexpr, a CPR, or a simple constant. |
| const ConstantExpr *CE1 = cast<ConstantExpr>(V1); |
| Constant *CE1Op0 = CE1->getOperand(0); |
| |
| switch (CE1->getOpcode()) { |
| case Instruction::Cast: |
| // If the cast is not actually changing bits, and the second operand is a |
| // null pointer, do the comparison with the pre-casted value. |
| if (V2->isNullValue() && |
| CE1->getType()->isLosslesslyConvertibleTo(CE1Op0->getType())) |
| return evaluateRelation(CE1Op0, |
| Constant::getNullValue(CE1Op0->getType())); |
| break; |
| |
| case Instruction::GetElementPtr: |
| // Ok, since this is a getelementptr, we know that the constant has a |
| // pointer type. Check the various cases. |
| if (isa<ConstantPointerNull>(V2)) { |
| // If we are comparing a GEP to a null pointer, check to see if the base |
| // of the GEP equals the null pointer. |
| if (isa<GlobalValue>(CE1Op0)) { |
| // FIXME: this is not true when we have external weak references! |
| // No offset can go from a global to a null pointer. |
| return Instruction::SetGT; |
| } else if (isa<ConstantPointerNull>(CE1Op0)) { |
| // If we are indexing from a null pointer, check to see if we have any |
| // non-zero indices. |
| for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) |
| if (!CE1->getOperand(i)->isNullValue()) |
| // Offsetting from null, must not be equal. |
| return Instruction::SetGT; |
| // Only zero indexes from null, must still be zero. |
| return Instruction::SetEQ; |
| } |
| // Otherwise, we can't really say if the first operand is null or not. |
| } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { |
| if (isa<ConstantPointerNull>(CE1Op0)) { |
| // FIXME: This is not true with external weak references. |
| return Instruction::SetLT; |
| } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { |
| if (CPR1 == CPR2) { |
| // If this is a getelementptr of the same global, then it must be |
| // different. Because the types must match, the getelementptr could |
| // only have at most one index, and because we fold getelementptr's |
| // with a single zero index, it must be nonzero. |
| assert(CE1->getNumOperands() == 2 && |
| !CE1->getOperand(1)->isNullValue() && |
| "Suprising getelementptr!"); |
| return Instruction::SetGT; |
| } else { |
| // If they are different globals, we don't know what the value is, |
| // but they can't be equal. |
| return Instruction::SetNE; |
| } |
| } |
| } else { |
| const ConstantExpr *CE2 = cast<ConstantExpr>(V2); |
| const Constant *CE2Op0 = CE2->getOperand(0); |
| |
| // There are MANY other foldings that we could perform here. They will |
| // probably be added on demand, as they seem needed. |
| switch (CE2->getOpcode()) { |
| default: break; |
| case Instruction::GetElementPtr: |
| // By far the most common case to handle is when the base pointers are |
| // obviously to the same or different globals. |
| if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { |
| if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal |
| return Instruction::SetNE; |
| // Ok, we know that both getelementptr instructions are based on the |
| // same global. From this, we can precisely determine the relative |
| // ordering of the resultant pointers. |
| unsigned i = 1; |
| |
| // Compare all of the operands the GEP's have in common. |
| gep_type_iterator GTI = gep_type_begin(CE1); |
| for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); |
| ++i, ++GTI) |
| switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), |
| GTI.getIndexedType())) { |
| case -1: return Instruction::SetLT; |
| case 1: return Instruction::SetGT; |
| case -2: return Instruction::BinaryOpsEnd; |
| } |
| |
| // Ok, we ran out of things they have in common. If any leftovers |
| // are non-zero then we have a difference, otherwise we are equal. |
| for (; i < CE1->getNumOperands(); ++i) |
| if (!CE1->getOperand(i)->isNullValue()) |
| if (isa<ConstantIntegral>(CE1->getOperand(i))) |
| return Instruction::SetGT; |
| else |
| return Instruction::BinaryOpsEnd; // Might be equal. |
| |
| for (; i < CE2->getNumOperands(); ++i) |
| if (!CE2->getOperand(i)->isNullValue()) |
| if (isa<ConstantIntegral>(CE2->getOperand(i))) |
| return Instruction::SetLT; |
| else |
| return Instruction::BinaryOpsEnd; // Might be equal. |
| return Instruction::SetEQ; |
| } |
| } |
| } |
| |
| default: |
| break; |
| } |
| } |
| |
| return Instruction::BinaryOpsEnd; |
| } |
| |
| Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, |
| const Constant *V1, |
| const Constant *V2) { |
| Constant *C = 0; |
| switch (Opcode) { |
| default: break; |
| case Instruction::Add: C = ConstRules::get(V1, V2).add(V1, V2); break; |
| case Instruction::Sub: C = ConstRules::get(V1, V2).sub(V1, V2); break; |
| case Instruction::Mul: C = ConstRules::get(V1, V2).mul(V1, V2); break; |
| case Instruction::Div: C = ConstRules::get(V1, V2).div(V1, V2); break; |
| case Instruction::Rem: C = ConstRules::get(V1, V2).rem(V1, V2); break; |
| case Instruction::And: C = ConstRules::get(V1, V2).op_and(V1, V2); break; |
| case Instruction::Or: C = ConstRules::get(V1, V2).op_or (V1, V2); break; |
| case Instruction::Xor: C = ConstRules::get(V1, V2).op_xor(V1, V2); break; |
| case Instruction::Shl: C = ConstRules::get(V1, V2).shl(V1, V2); break; |
| case Instruction::Shr: C = ConstRules::get(V1, V2).shr(V1, V2); break; |
| case Instruction::SetEQ: C = ConstRules::get(V1, V2).equalto(V1, V2); break; |
| case Instruction::SetLT: C = ConstRules::get(V1, V2).lessthan(V1, V2);break; |
| case Instruction::SetGT: C = ConstRules::get(V1, V2).lessthan(V2, V1);break; |
| case Instruction::SetNE: // V1 != V2 === !(V1 == V2) |
| C = ConstRules::get(V1, V2).equalto(V1, V2); |
| if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True); |
| break; |
| case Instruction::SetLE: // V1 <= V2 === !(V2 < V1) |
| C = ConstRules::get(V1, V2).lessthan(V2, V1); |
| if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True); |
| break; |
| case Instruction::SetGE: // V1 >= V2 === !(V1 < V2) |
| C = ConstRules::get(V1, V2).lessthan(V1, V2); |
| if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True); |
| break; |
| } |
| |
| // If we successfully folded the expression, return it now. |
| if (C) return C; |
| |
| if (SetCondInst::isRelational(Opcode)) { |
| if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) |
| return UndefValue::get(Type::BoolTy); |
| switch (evaluateRelation(V1, V2)) { |
| default: assert(0 && "Unknown relational!"); |
| case Instruction::BinaryOpsEnd: |
| break; // Couldn't determine anything about these constants. |
| case Instruction::SetEQ: // We know the constants are equal! |
| // If we know the constants are equal, we can decide the result of this |
| // computation precisely. |
| return ConstantBool::get(Opcode == Instruction::SetEQ || |
| Opcode == Instruction::SetLE || |
| Opcode == Instruction::SetGE); |
| case Instruction::SetLT: |
| // If we know that V1 < V2, we can decide the result of this computation |
| // precisely. |
| return ConstantBool::get(Opcode == Instruction::SetLT || |
| Opcode == Instruction::SetNE || |
| Opcode == Instruction::SetLE); |
| case Instruction::SetGT: |
| // If we know that V1 > V2, we can decide the result of this computation |
| // precisely. |
| return ConstantBool::get(Opcode == Instruction::SetGT || |
| Opcode == Instruction::SetNE || |
| Opcode == Instruction::SetGE); |
| case Instruction::SetLE: |
| // If we know that V1 <= V2, we can only partially decide this relation. |
| if (Opcode == Instruction::SetGT) return ConstantBool::False; |
| if (Opcode == Instruction::SetLT) return ConstantBool::True; |
| break; |
| |
| case Instruction::SetGE: |
| // If we know that V1 >= V2, we can only partially decide this relation. |
| if (Opcode == Instruction::SetLT) return ConstantBool::False; |
| if (Opcode == Instruction::SetGT) return ConstantBool::True; |
| break; |
| |
| case Instruction::SetNE: |
| // If we know that V1 != V2, we can only partially decide this relation. |
| if (Opcode == Instruction::SetEQ) return ConstantBool::False; |
| if (Opcode == Instruction::SetNE) return ConstantBool::True; |
| break; |
| } |
| } |
| |
| if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) { |
| switch (Opcode) { |
| case Instruction::Add: |
| case Instruction::Sub: |
| case Instruction::Xor: |
| return UndefValue::get(V1->getType()); |
| |
| case Instruction::Mul: |
| case Instruction::And: |
| return Constant::getNullValue(V1->getType()); |
| case Instruction::Div: |
| case Instruction::Rem: |
| if (!isa<UndefValue>(V2)) // undef/X -> 0 |
| return Constant::getNullValue(V1->getType()); |
| return const_cast<Constant*>(V2); // X/undef -> undef |
| case Instruction::Or: // X|undef -> -1 |
| return ConstantInt::getAllOnesValue(V1->getType()); |
| case Instruction::Shr: |
| if (!isa<UndefValue>(V2)) { |
| if (V1->getType()->isSigned()) |
| return const_cast<Constant*>(V1); // undef >>s X -> undef |
| // undef >>u X -> 0 |
| } else if (isa<UndefValue>(V1)) { |
| return const_cast<Constant*>(V1); // undef >> undef -> undef |
| } else { |
| if (V1->getType()->isSigned()) |
| return const_cast<Constant*>(V1); // X >>s undef -> X |
| // X >>u undef -> 0 |
| } |
| return Constant::getNullValue(V1->getType()); |
| |
| case Instruction::Shl: |
| // undef << X -> 0 X << undef -> 0 |
| return Constant::getNullValue(V1->getType()); |
| } |
| } |
| |
| if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(V1)) { |
| if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) { |
| // There are many possible foldings we could do here. We should probably |
| // at least fold add of a pointer with an integer into the appropriate |
| // getelementptr. This will improve alias analysis a bit. |
| |
| |
| |
| |
| } else { |
| // Just implement a couple of simple identities. |
| switch (Opcode) { |
| case Instruction::Add: |
| if (V2->isNullValue()) return const_cast<Constant*>(V1); // X + 0 == X |
| break; |
| case Instruction::Sub: |
| if (V2->isNullValue()) return const_cast<Constant*>(V1); // X - 0 == X |
| break; |
| case Instruction::Mul: |
| if (V2->isNullValue()) return const_cast<Constant*>(V2); // X * 0 == 0 |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) |
| if (CI->getRawValue() == 1) |
| return const_cast<Constant*>(V1); // X * 1 == X |
| break; |
| case Instruction::Div: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) |
| if (CI->getRawValue() == 1) |
| return const_cast<Constant*>(V1); // X / 1 == X |
| break; |
| case Instruction::Rem: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) |
| if (CI->getRawValue() == 1) |
| return Constant::getNullValue(CI->getType()); // X % 1 == 0 |
| break; |
| case Instruction::And: |
| if (cast<ConstantIntegral>(V2)->isAllOnesValue()) |
| return const_cast<Constant*>(V1); // X & -1 == X |
| if (V2->isNullValue()) return const_cast<Constant*>(V2); // X & 0 == 0 |
| if (CE1->getOpcode() == Instruction::Cast && |
| isa<GlobalValue>(CE1->getOperand(0))) { |
| GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0)); |
| |
| // Functions are at least 4-byte aligned. If and'ing the address of a |
| // function with a constant < 4, fold it to zero. |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2)) |
| if (CI->getRawValue() < 4 && isa<Function>(CPR)) |
| return Constant::getNullValue(CI->getType()); |
| } |
| break; |
| case Instruction::Or: |
| if (V2->isNullValue()) return const_cast<Constant*>(V1); // X | 0 == X |
| if (cast<ConstantIntegral>(V2)->isAllOnesValue()) |
| return const_cast<Constant*>(V2); // X | -1 == -1 |
| break; |
| case Instruction::Xor: |
| if (V2->isNullValue()) return const_cast<Constant*>(V1); // X ^ 0 == X |
| break; |
| } |
| } |
| |
| } else if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) { |
| // If V2 is a constant expr and V1 isn't, flop them around and fold the |
| // other way if possible. |
| switch (Opcode) { |
| case Instruction::Add: |
| case Instruction::Mul: |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| case Instruction::SetEQ: |
| case Instruction::SetNE: |
| // No change of opcode required. |
| return ConstantFoldBinaryInstruction(Opcode, V2, V1); |
| |
| case Instruction::SetLT: |
| case Instruction::SetGT: |
| case Instruction::SetLE: |
| case Instruction::SetGE: |
| // Change the opcode as necessary to swap the operands. |
| Opcode = SetCondInst::getSwappedCondition((Instruction::BinaryOps)Opcode); |
| return ConstantFoldBinaryInstruction(Opcode, V2, V1); |
| |
| case Instruction::Shl: |
| case Instruction::Shr: |
| case Instruction::Sub: |
| case Instruction::Div: |
| case Instruction::Rem: |
| default: // These instructions cannot be flopped around. |
| break; |
| } |
| } |
| return 0; |
| } |
| |
| Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, |
| const std::vector<Value*> &IdxList) { |
| if (IdxList.size() == 0 || |
| (IdxList.size() == 1 && cast<Constant>(IdxList[0])->isNullValue())) |
| return const_cast<Constant*>(C); |
| |
| if (isa<UndefValue>(C)) { |
| const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList, |
| true); |
| assert(Ty != 0 && "Invalid indices for GEP!"); |
| return UndefValue::get(PointerType::get(Ty)); |
| } |
| |
| Constant *Idx0 = cast<Constant>(IdxList[0]); |
| if (C->isNullValue()) { |
| bool isNull = true; |
| for (unsigned i = 0, e = IdxList.size(); i != e; ++i) |
| if (!cast<Constant>(IdxList[i])->isNullValue()) { |
| isNull = false; |
| break; |
| } |
| if (isNull) { |
| const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList, |
| true); |
| assert(Ty != 0 && "Invalid indices for GEP!"); |
| return ConstantPointerNull::get(PointerType::get(Ty)); |
| } |
| |
| if (IdxList.size() == 1) { |
| const Type *ElTy = cast<PointerType>(C->getType())->getElementType(); |
| if (unsigned ElSize = ElTy->getPrimitiveSize()) { |
| // gep null, C is equal to C*sizeof(nullty). If nullty is a known llvm |
| // type, we can statically fold this. |
| Constant *R = ConstantUInt::get(Type::UIntTy, ElSize); |
| R = ConstantExpr::getCast(R, Idx0->getType()); |
| R = ConstantExpr::getMul(R, Idx0); |
| return ConstantExpr::getCast(R, C->getType()); |
| } |
| } |
| } |
| |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { |
| // Combine Indices - If the source pointer to this getelementptr instruction |
| // is a getelementptr instruction, combine the indices of the two |
| // getelementptr instructions into a single instruction. |
| // |
| if (CE->getOpcode() == Instruction::GetElementPtr) { |
| const Type *LastTy = 0; |
| for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); |
| I != E; ++I) |
| LastTy = *I; |
| |
| if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { |
| std::vector<Value*> NewIndices; |
| NewIndices.reserve(IdxList.size() + CE->getNumOperands()); |
| for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) |
| NewIndices.push_back(CE->getOperand(i)); |
| |
| // Add the last index of the source with the first index of the new GEP. |
| // Make sure to handle the case when they are actually different types. |
| Constant *Combined = CE->getOperand(CE->getNumOperands()-1); |
| // Otherwise it must be an array. |
| if (!Idx0->isNullValue()) { |
| const Type *IdxTy = Combined->getType(); |
| if (IdxTy != Idx0->getType()) IdxTy = Type::LongTy; |
| Combined = |
| ConstantExpr::get(Instruction::Add, |
| ConstantExpr::getCast(Idx0, IdxTy), |
| ConstantExpr::getCast(Combined, IdxTy)); |
| } |
| |
| NewIndices.push_back(Combined); |
| NewIndices.insert(NewIndices.end(), IdxList.begin()+1, IdxList.end()); |
| return ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices); |
| } |
| } |
| |
| // Implement folding of: |
| // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), |
| // long 0, long 0) |
| // To: int* getelementptr ([3 x int]* %X, long 0, long 0) |
| // |
| if (CE->getOpcode() == Instruction::Cast && IdxList.size() > 1 && |
| Idx0->isNullValue()) |
| if (const PointerType *SPT = |
| dyn_cast<PointerType>(CE->getOperand(0)->getType())) |
| if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) |
| if (const ArrayType *CAT = |
| dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) |
| if (CAT->getElementType() == SAT->getElementType()) |
| return ConstantExpr::getGetElementPtr( |
| (Constant*)CE->getOperand(0), IdxList); |
| } |
| return 0; |
| } |
| |
