//===- 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/Compiler.h" #include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Support/ManagedStatic.h" #include "llvm/Support/MathExtras.h" #include #include using namespace llvm; namespace { struct VISIBILITY_HIDDEN 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 *udiv(const Constant *V1, const Constant *V2) const = 0; virtual Constant *sdiv(const Constant *V1, const Constant *V2) const = 0; virtual Constant *fdiv(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. // namespace { template class VISIBILITY_HIDDEN 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 *udiv(const Constant *V1, const Constant *V2) const { return SubClassName::UDiv((const ArgType *)V1, (const ArgType *)V2); } virtual Constant *sdiv(const Constant *V1, const Constant *V2) const { return SubClassName::SDiv((const ArgType *)V1, (const ArgType *)V2); } virtual Constant *fdiv(const Constant *V1, const Constant *V2) const { return SubClassName::FDiv((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 *SDiv(const ArgType *V1, const ArgType *V2) { return 0; } static Constant *UDiv(const ArgType *V1, const ArgType *V2) { return 0; } static Constant *FDiv(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() {} }; } // end anonymous namespace //===----------------------------------------------------------------------===// // EmptyRules Class //===----------------------------------------------------------------------===// // // EmptyRules provides a concrete base class of ConstRules that does nothing // namespace { struct VISIBILITY_HIDDEN EmptyRules : public TemplateRules { static Constant *EqualTo(const Constant *V1, const Constant *V2) { if (V1 == V2) return ConstantBool::getTrue(); return 0; } }; } // end anonymous namespace //===----------------------------------------------------------------------===// // BoolRules Class //===----------------------------------------------------------------------===// // // BoolRules provides a concrete base class of ConstRules for the 'bool' type. // namespace { struct VISIBILITY_HIDDEN BoolRules : public TemplateRules { 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 , ConstantInt, signed char) DEF_CAST(UByte , ConstantInt, unsigned char) DEF_CAST(Short , ConstantInt, signed short) DEF_CAST(UShort, ConstantInt, unsigned short) DEF_CAST(Int , ConstantInt, signed int) DEF_CAST(UInt , ConstantInt, unsigned int) DEF_CAST(Long , ConstantInt, int64_t) DEF_CAST(ULong , ConstantInt, uint64_t) DEF_CAST(Float , ConstantFP , float) DEF_CAST(Double, ConstantFP , double) #undef DEF_CAST }; } // end anonymous namespace //===----------------------------------------------------------------------===// // NullPointerRules Class //===----------------------------------------------------------------------===// // // NullPointerRules provides a concrete base class of ConstRules for null // pointers. // namespace { struct VISIBILITY_HIDDEN NullPointerRules : public TemplateRules { static Constant *EqualTo(const Constant *V1, const Constant *V2) { return ConstantBool::getTrue(); // Null pointers are always equal } static Constant *CastToBool(const Constant *V) { return ConstantBool::getFalse(); } static Constant *CastToSByte (const Constant *V) { return ConstantInt::get(Type::SByteTy, 0); } static Constant *CastToUByte (const Constant *V) { return ConstantInt::get(Type::UByteTy, 0); } static Constant *CastToShort (const Constant *V) { return ConstantInt::get(Type::ShortTy, 0); } static Constant *CastToUShort(const Constant *V) { return ConstantInt::get(Type::UShortTy, 0); } static Constant *CastToInt (const Constant *V) { return ConstantInt::get(Type::IntTy, 0); } static Constant *CastToUInt (const Constant *V) { return ConstantInt::get(Type::UIntTy, 0); } static Constant *CastToLong (const Constant *V) { return ConstantInt::get(Type::LongTy, 0); } static Constant *CastToULong (const Constant *V) { return ConstantInt::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); } }; } // end anonymous namespace //===----------------------------------------------------------------------===// // ConstantPackedRules Class //===----------------------------------------------------------------------===// /// DoVectorOp - Given two packed constants and a function pointer, apply the /// function pointer to each element pair, producing a new ConstantPacked /// constant. static Constant *EvalVectorOp(const ConstantPacked *V1, const ConstantPacked *V2, Constant *(*FP)(Constant*, Constant*)) { std::vector Res; for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i) Res.push_back(FP(const_cast(V1->getOperand(i)), const_cast(V2->getOperand(i)))); return ConstantPacked::get(Res); } /// PackedTypeRules provides a concrete base class of ConstRules for /// ConstantPacked operands. /// namespace { struct VISIBILITY_HIDDEN ConstantPackedRules : public TemplateRules { static Constant *Add(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getAdd); } static Constant *Sub(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getSub); } static Constant *Mul(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getMul); } static Constant *UDiv(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getUDiv); } static Constant *SDiv(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getSDiv); } static Constant *FDiv(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getFDiv); } static Constant *Rem(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getRem); } static Constant *And(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getAnd); } static Constant *Or (const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getOr); } static Constant *Xor(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getXor); } static Constant *Shl(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getShl); } static Constant *Shr(const ConstantPacked *V1, const ConstantPacked *V2) { return EvalVectorOp(V1, V2, ConstantExpr::getShr); } static Constant *LessThan(const ConstantPacked *V1, const ConstantPacked *V2){ return 0; } static Constant *EqualTo(const ConstantPacked *V1, const ConstantPacked *V2) { for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i) { Constant *C = ConstantExpr::getSetEQ(const_cast(V1->getOperand(i)), const_cast(V2->getOperand(i))); if (ConstantBool *CB = dyn_cast(C)) return CB; } // Otherwise, could not decide from any element pairs. return 0; } }; } // end anonymous namespace //===----------------------------------------------------------------------===// // GeneralPackedRules Class //===----------------------------------------------------------------------===// /// GeneralPackedRules provides a concrete base class of ConstRules for /// PackedType operands, where both operands are not ConstantPacked. The usual /// cause for this is that one operand is a ConstantAggregateZero. /// namespace { struct VISIBILITY_HIDDEN GeneralPackedRules : public TemplateRules { }; } // end anonymous namespace //===----------------------------------------------------------------------===// // DirectIntRules Class //===----------------------------------------------------------------------===// // // DirectIntRules provides implementations of functions that are valid on // integer types, but not all types in general. // namespace { template struct VISIBILITY_HIDDEN DirectIntRules : public TemplateRules > { static Constant *Add(const ConstantInt *V1, const ConstantInt *V2) { BuiltinType R = (BuiltinType)V1->getZExtValue() + (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } static Constant *Sub(const ConstantInt *V1, const ConstantInt *V2) { BuiltinType R = (BuiltinType)V1->getZExtValue() - (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } static Constant *Mul(const ConstantInt *V1, const ConstantInt *V2) { BuiltinType R = (BuiltinType)V1->getZExtValue() * (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } static Constant *LessThan(const ConstantInt *V1, const ConstantInt *V2) { bool R = (BuiltinType)V1->getZExtValue() < (BuiltinType)V2->getZExtValue(); return ConstantBool::get(R); } static Constant *EqualTo(const ConstantInt *V1, const ConstantInt *V2) { bool R = (BuiltinType)V1->getZExtValue() == (BuiltinType)V2->getZExtValue(); return ConstantBool::get(R); } static Constant *CastToPointer(const ConstantInt *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 ConstantInt *V) { \ return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getZExtValue()); \ } DEF_CAST(Bool , ConstantBool, bool) DEF_CAST(SByte , ConstantInt, signed char) DEF_CAST(UByte , ConstantInt, unsigned char) DEF_CAST(Short , ConstantInt, signed short) DEF_CAST(UShort, ConstantInt, unsigned short) DEF_CAST(Int , ConstantInt, signed int) DEF_CAST(UInt , ConstantInt, unsigned int) DEF_CAST(Long , ConstantInt, int64_t) DEF_CAST(ULong , ConstantInt, uint64_t) DEF_CAST(Float , ConstantFP , float) DEF_CAST(Double, ConstantFP , double) #undef DEF_CAST static Constant *UDiv(const ConstantInt *V1, const ConstantInt *V2) { if (V2->isNullValue()) return 0; BuiltinType R = (BuiltinType)(V1->getZExtValue() / V2->getZExtValue()); return ConstantInt::get(*Ty, R); } static Constant *SDiv(const ConstantInt *V1, const ConstantInt *V2) { if (V2->isNullValue()) return 0; if (V2->isAllOnesValue() && // MIN_INT / -1 (BuiltinType)V1->getSExtValue() == -(BuiltinType)V1->getSExtValue()) return 0; BuiltinType R = (BuiltinType)(V1->getSExtValue() / V2->getSExtValue()); return ConstantInt::get(*Ty, R); } static Constant *Rem(const ConstantInt *V1, const ConstantInt *V2) { if (V2->isNullValue()) return 0; // X / 0 if (V2->isAllOnesValue() && // MIN_INT / -1 (BuiltinType)V1->getZExtValue() == -(BuiltinType)V1->getZExtValue()) return 0; BuiltinType R = (BuiltinType)V1->getZExtValue() % (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } static Constant *And(const ConstantInt *V1, const ConstantInt *V2) { BuiltinType R = (BuiltinType)V1->getZExtValue() & (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } static Constant *Or(const ConstantInt *V1, const ConstantInt *V2) { BuiltinType R = (BuiltinType)V1->getZExtValue() | (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } static Constant *Xor(const ConstantInt *V1, const ConstantInt *V2) { BuiltinType R = (BuiltinType)V1->getZExtValue() ^ (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } static Constant *Shl(const ConstantInt *V1, const ConstantInt *V2) { BuiltinType R = (BuiltinType)V1->getZExtValue() << (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } static Constant *Shr(const ConstantInt *V1, const ConstantInt *V2) { BuiltinType R = (BuiltinType)V1->getZExtValue() >> (BuiltinType)V2->getZExtValue(); return ConstantInt::get(*Ty, R); } }; } // end anonymous namespace //===----------------------------------------------------------------------===// // DirectFPRules Class //===----------------------------------------------------------------------===// // /// DirectFPRules provides implementations of functions that are valid on /// floating point types, but not all types in general. /// namespace { template struct VISIBILITY_HIDDEN DirectFPRules : public TemplateRules > { static Constant *Add(const ConstantFP *V1, const ConstantFP *V2) { BuiltinType R = (BuiltinType)V1->getValue() + (BuiltinType)V2->getValue(); return ConstantFP::get(*Ty, R); } static Constant *Sub(const ConstantFP *V1, const ConstantFP *V2) { BuiltinType R = (BuiltinType)V1->getValue() - (BuiltinType)V2->getValue(); return ConstantFP::get(*Ty, R); } static Constant *Mul(const ConstantFP *V1, const ConstantFP *V2) { BuiltinType R = (BuiltinType)V1->getValue() * (BuiltinType)V2->getValue(); return ConstantFP::get(*Ty, R); } static Constant *LessThan(const ConstantFP *V1, const ConstantFP *V2) { bool R = (BuiltinType)V1->getValue() < (BuiltinType)V2->getValue(); return ConstantBool::get(R); } static Constant *EqualTo(const ConstantFP *V1, const ConstantFP *V2) { bool R = (BuiltinType)V1->getValue() == (BuiltinType)V2->getValue(); return ConstantBool::get(R); } static Constant *CastToPointer(const ConstantFP *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 ConstantFP *V) { \ return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getValue()); \ } DEF_CAST(Bool , ConstantBool, bool) DEF_CAST(SByte , ConstantInt, signed char) DEF_CAST(UByte , ConstantInt, unsigned char) DEF_CAST(Short , ConstantInt, signed short) DEF_CAST(UShort, ConstantInt, unsigned short) DEF_CAST(Int , ConstantInt, signed int) DEF_CAST(UInt , ConstantInt, unsigned int) DEF_CAST(Long , ConstantInt, int64_t) DEF_CAST(ULong , ConstantInt, uint64_t) DEF_CAST(Float , ConstantFP , float) DEF_CAST(Double, ConstantFP , double) #undef DEF_CAST static Constant *Rem(const ConstantFP *V1, const ConstantFP *V2) { if (V2->isNullValue()) return 0; BuiltinType Result = std::fmod((BuiltinType)V1->getValue(), (BuiltinType)V2->getValue()); return ConstantFP::get(*Ty, Result); } static Constant *FDiv(const ConstantFP *V1, const ConstantFP *V2) { BuiltinType inf = std::numeric_limits::infinity(); if (V2->isExactlyValue(0.0)) return ConstantFP::get(*Ty, inf); if (V2->isExactlyValue(-0.0)) return ConstantFP::get(*Ty, -inf); BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue(); return ConstantFP::get(*Ty, R); } }; } // end anonymous namespace static ManagedStatic EmptyR; static ManagedStatic BoolR; static ManagedStatic NullPointerR; static ManagedStatic ConstantPackedR; static ManagedStatic GeneralPackedR; static ManagedStatic > SByteR; static ManagedStatic > UByteR; static ManagedStatic > ShortR; static ManagedStatic > UShortR; static ManagedStatic > IntR; static ManagedStatic > UIntR; static ManagedStatic > LongR; static ManagedStatic > ULongR; static ManagedStatic > FloatR; static ManagedStatic > DoubleR; /// 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) { if (isa(V1) || isa(V2) || isa(V1) || isa(V2) || isa(V1) || isa(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; case Type::PackedTyID: if (isa(V1) && isa(V2)) return *ConstantPackedR; return *GeneralPackedR; // Constant folding rules for ConstantAggregateZero. } } //===----------------------------------------------------------------------===// // 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 } /// CastConstantPacked - Convert the specified ConstantPacked node to the /// specified packed type. At this point, we know that the elements of the /// input packed constant are all simple integer or FP values. static Constant *CastConstantPacked(ConstantPacked *CP, const PackedType *DstTy) { unsigned SrcNumElts = CP->getType()->getNumElements(); unsigned DstNumElts = DstTy->getNumElements(); const Type *SrcEltTy = CP->getType()->getElementType(); const Type *DstEltTy = DstTy->getElementType(); // If both vectors have the same number of elements (thus, the elements // are the same size), perform the conversion now. if (SrcNumElts == DstNumElts) { std::vector Result; // If the src and dest elements are both integers, just cast each one // which will do the appropriate bit-convert. if (SrcEltTy->isIntegral() && DstEltTy->isIntegral()) { for (unsigned i = 0; i != SrcNumElts; ++i) Result.push_back(ConstantExpr::getCast(CP->getOperand(i), DstEltTy)); return ConstantPacked::get(Result); } if (SrcEltTy->isIntegral()) { // Otherwise, this is an int-to-fp cast. assert(DstEltTy->isFloatingPoint()); if (DstEltTy->getTypeID() == Type::DoubleTyID) { for (unsigned i = 0; i != SrcNumElts; ++i) { double V = BitsToDouble(cast(CP->getOperand(i))->getZExtValue()); Result.push_back(ConstantFP::get(Type::DoubleTy, V)); } return ConstantPacked::get(Result); } assert(DstEltTy == Type::FloatTy && "Unknown fp type!"); for (unsigned i = 0; i != SrcNumElts; ++i) { float V = BitsToFloat(cast(CP->getOperand(i))->getZExtValue()); Result.push_back(ConstantFP::get(Type::FloatTy, V)); } return ConstantPacked::get(Result); } // Otherwise, this is an fp-to-int cast. assert(SrcEltTy->isFloatingPoint() && DstEltTy->isIntegral()); if (SrcEltTy->getTypeID() == Type::DoubleTyID) { for (unsigned i = 0; i != SrcNumElts; ++i) { uint64_t V = DoubleToBits(cast(CP->getOperand(i))->getValue()); Constant *C = ConstantInt::get(Type::ULongTy, V); Result.push_back(ConstantExpr::getCast(C, DstEltTy)); } return ConstantPacked::get(Result); } assert(SrcEltTy->getTypeID() == Type::FloatTyID); for (unsigned i = 0; i != SrcNumElts; ++i) { uint32_t V = FloatToBits(cast(CP->getOperand(i))->getValue()); Constant *C = ConstantInt::get(Type::UIntTy, V); Result.push_back(ConstantExpr::getCast(C, DstEltTy)); } return ConstantPacked::get(Result); } // Otherwise, this is a cast that changes element count and size. Handle // casts which shrink the elements here. // FIXME: We need to know endianness to do this! return 0; } 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(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::getTrue(); } else if (const ConstantExpr *CE = dyn_cast(V)) { if (CE->getOpcode() == Instruction::Cast) { Constant *Op = const_cast(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(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(V->getType())) if (const PointerType *DPTy = dyn_cast(DestTy)) { std::vector IdxList; IdxList.push_back(Constant::getNullValue(Type::IntTy)); const Type *ElTy = PTy->getElementType(); while (ElTy != DPTy->getElementType()) { if (const StructType *STy = dyn_cast(ElTy)) { if (STy->getNumElements() == 0) break; ElTy = STy->getElementType(0); IdxList.push_back(Constant::getNullValue(Type::UIntTy)); } else if (const SequentialType *STy = dyn_cast(ElTy)) { if (isa(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(V),IdxList); } // Handle casts from one packed constant to another. We know that the src and // dest type have the same size. if (const PackedType *DestPTy = dyn_cast(DestTy)) { if (const PackedType *SrcTy = dyn_cast(V->getType())) { assert(DestPTy->getElementType()->getPrimitiveSizeInBits() * DestPTy->getNumElements() == SrcTy->getElementType()->getPrimitiveSizeInBits() * SrcTy->getNumElements() && "Not cast between same sized vectors!"); if (isa(V)) return Constant::getNullValue(DestTy); if (isa(V)) return UndefValue::get(DestTy); if (const ConstantPacked *CP = dyn_cast(V)) { // This is a cast from a ConstantPacked of one type to a ConstantPacked // of another type. Check to see if all elements of the input are // simple. bool AllSimpleConstants = true; for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i) { if (!isa(CP->getOperand(i)) && !isa(CP->getOperand(i))) { AllSimpleConstants = false; break; } } // If all of the elements are simple constants, we can fold this. if (AllSimpleConstants) return CastConstantPacked(const_cast(CP), DestPTy); } } } 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(DestTy)); default: return 0; } } Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, const Constant *V1, const Constant *V2) { if (const ConstantBool *CB = dyn_cast(Cond)) return const_cast(CB->getValue() ? V1 : V2); if (isa(V1)) return const_cast(V2); if (isa(V2)) return const_cast(V1); if (isa(Cond)) return const_cast(V1); if (V1 == V2) return const_cast(V1); return 0; } Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, const Constant *Idx) { if (isa(Val)) // ee(undef, x) -> undef return UndefValue::get(cast(Val->getType())->getElementType()); if (Val->isNullValue()) // ee(zero, x) -> zero return Constant::getNullValue( cast(Val->getType())->getElementType()); if (const ConstantPacked *CVal = dyn_cast(Val)) { if (const ConstantInt *CIdx = dyn_cast(Idx)) { return const_cast(CVal->getOperand(CIdx->getZExtValue())); } else if (isa(Idx)) { // ee({w,x,y,z}, undef) -> w (an arbitrary value). return const_cast(CVal->getOperand(0)); } } return 0; } Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, const Constant *Elt, const Constant *Idx) { const ConstantInt *CIdx = dyn_cast(Idx); if (!CIdx) return 0; uint64_t idxVal = CIdx->getZExtValue(); if (const UndefValue *UVal = dyn_cast(Val)) { // Insertion of scalar constant into packed undef // Optimize away insertion of undef if (isa(Elt)) return const_cast(Val); // Otherwise break the aggregate undef into multiple undefs and do // the insertion unsigned numOps = cast(Val->getType())->getNumElements(); std::vector Ops; Ops.reserve(numOps); for (unsigned i = 0; i < numOps; ++i) { const Constant *Op = (i == idxVal) ? Elt : UndefValue::get(Elt->getType()); Ops.push_back(const_cast(Op)); } return ConstantPacked::get(Ops); } if (const ConstantAggregateZero *CVal = dyn_cast(Val)) { // Insertion of scalar constant into packed aggregate zero // Optimize away insertion of zero if (Elt->isNullValue()) return const_cast(Val); // Otherwise break the aggregate zero into multiple zeros and do // the insertion unsigned numOps = cast(Val->getType())->getNumElements(); std::vector Ops; Ops.reserve(numOps); for (unsigned i = 0; i < numOps; ++i) { const Constant *Op = (i == idxVal) ? Elt : Constant::getNullValue(Elt->getType()); Ops.push_back(const_cast(Op)); } return ConstantPacked::get(Ops); } if (const ConstantPacked *CVal = dyn_cast(Val)) { // Insertion of scalar constant into packed constant std::vector Ops; Ops.reserve(CVal->getNumOperands()); for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { const Constant *Op = (i == idxVal) ? Elt : cast(CVal->getOperand(i)); Ops.push_back(const_cast(Op)); } return ConstantPacked::get(Ops); } return 0; } Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, const Constant *V2, const Constant *Mask) { // TODO: 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(Ty)) return true; // Can't say. if (const StructType *STy = dyn_cast(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(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(C1) || !isa(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(C1)->getSExtValue() < cast(C2)->getSExtValue()) 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(Constant *V1, Constant *V2) { assert(V1->getType() == V2->getType() && "Cannot compare different types of values!"); if (V1 == V2) return Instruction::SetEQ; if (!isa(V1) && !isa(V1)) { if (!isa(V2) && !isa(V2)) { // We distilled this down to a simple case, use the standard constant // folder. ConstantBool *R = dyn_cast(ConstantExpr::getSetEQ(V1, V2)); if (R && R->getValue()) return Instruction::SetEQ; R = dyn_cast(ConstantExpr::getSetLT(V1, V2)); if (R && R->getValue()) return Instruction::SetLT; R = dyn_cast(ConstantExpr::getSetGT(V1, V2)); if (R && R->getValue()) return Instruction::SetGT; // If we couldn't figure it out, bail. return Instruction::BinaryOpsEnd; } // If the first operand is simple, swap operands. Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1); if (SwappedRelation != Instruction::BinaryOpsEnd) return SetCondInst::getSwappedCondition(SwappedRelation); } else if (const GlobalValue *CPR1 = dyn_cast(V1)) { if (isa(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(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(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. ConstantExpr *CE1 = cast(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() && (isa(CE1->getType()) || CE1->getType()->isIntegral())) return evaluateRelation(CE1Op0, Constant::getNullValue(CE1Op0->getType())); // If the dest type is a pointer type, and the RHS is a constantexpr cast // from the same type as the src of the LHS, evaluate the inputs. This is // important for things like "seteq (cast 4 to int*), (cast 5 to int*)", // which happens a lot in compilers with tagged integers. if (ConstantExpr *CE2 = dyn_cast(V2)) if (isa(CE1->getType()) && CE2->getOpcode() == Instruction::Cast && CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && CE1->getOperand(0)->getType()->isIntegral()) { return evaluateRelation(CE1->getOperand(0), CE2->getOperand(0)); } 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(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(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(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(V2)) { if (isa(CE1Op0)) { // FIXME: This is not true with external weak references. return Instruction::SetLT; } else if (const GlobalValue *CPR1 = dyn_cast(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(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(CE1Op0) && isa(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(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(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::UDiv: C = ConstRules::get(V1, V2).udiv(V1, V2); break; case Instruction::SDiv: C = ConstRules::get(V1, V2).sdiv(V1, V2); break; case Instruction::FDiv: C = ConstRules::get(V1, V2).fdiv(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::getNot(C); break; case Instruction::SetLE: // V1 <= V2 === !(V2 < V1) C = ConstRules::get(V1, V2).lessthan(V2, V1); if (C) return ConstantExpr::getNot(C); break; case Instruction::SetGE: // V1 >= V2 === !(V1 < V2) C = ConstRules::get(V1, V2).lessthan(V1, V2); if (C) return ConstantExpr::getNot(C); break; } // If we successfully folded the expression, return it now. if (C) return C; if (SetCondInst::isComparison(Opcode)) { if (isa(V1) || isa(V2)) return UndefValue::get(Type::BoolTy); switch (evaluateRelation(const_cast(V1), const_cast(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::getFalse(); if (Opcode == Instruction::SetLT) return ConstantBool::getTrue(); break; case Instruction::SetGE: // If we know that V1 >= V2, we can only partially decide this relation. if (Opcode == Instruction::SetLT) return ConstantBool::getFalse(); if (Opcode == Instruction::SetGT) return ConstantBool::getTrue(); break; case Instruction::SetNE: // If we know that V1 != V2, we can only partially decide this relation. if (Opcode == Instruction::SetEQ) return ConstantBool::getFalse(); if (Opcode == Instruction::SetNE) return ConstantBool::getTrue(); break; } } if (isa(V1) || isa(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::UDiv: case Instruction::SDiv: case Instruction::FDiv: case Instruction::Rem: if (!isa(V2)) // undef/X -> 0 return Constant::getNullValue(V1->getType()); return const_cast(V2); // X/undef -> undef case Instruction::Or: // X|undef -> -1 return ConstantInt::getAllOnesValue(V1->getType()); case Instruction::Shr: if (!isa(V2)) { if (V1->getType()->isSigned()) return const_cast(V1); // undef >>s X -> undef // undef >>u X -> 0 } else if (isa(V1)) { return const_cast(V1); // undef >> undef -> undef } else { if (V1->getType()->isSigned()) return const_cast(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(V1)) { if (const ConstantExpr *CE2 = dyn_cast(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(V1); // X + 0 == X break; case Instruction::Sub: if (V2->isNullValue()) return const_cast(V1); // X - 0 == X break; case Instruction::Mul: if (V2->isNullValue()) return const_cast(V2); // X * 0 == 0 if (const ConstantInt *CI = dyn_cast(V2)) if (CI->getZExtValue() == 1) return const_cast(V1); // X * 1 == X break; case Instruction::UDiv: case Instruction::SDiv: if (const ConstantInt *CI = dyn_cast(V2)) if (CI->getZExtValue() == 1) return const_cast(V1); // X / 1 == X break; case Instruction::Rem: if (const ConstantInt *CI = dyn_cast(V2)) if (CI->getZExtValue() == 1) return Constant::getNullValue(CI->getType()); // X % 1 == 0 break; case Instruction::And: if (cast(V2)->isAllOnesValue()) return const_cast(V1); // X & -1 == X if (V2->isNullValue()) return const_cast(V2); // X & 0 == 0 if (CE1->getOpcode() == Instruction::Cast && isa(CE1->getOperand(0))) { GlobalValue *CPR = cast(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(V2)) if (CI->getZExtValue() < 4 && isa(CPR)) return Constant::getNullValue(CI->getType()); } break; case Instruction::Or: if (V2->isNullValue()) return const_cast(V1); // X | 0 == X if (cast(V2)->isAllOnesValue()) return const_cast(V2); // X | -1 == -1 break; case Instruction::Xor: if (V2->isNullValue()) return const_cast(V1); // X ^ 0 == X break; } } } else if (const ConstantExpr *CE2 = dyn_cast(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::SDiv: case Instruction::UDiv: case Instruction::FDiv: case Instruction::Rem: default: // These instructions cannot be flopped around. break; } } return 0; } Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, const std::vector &IdxList) { if (IdxList.size() == 0 || (IdxList.size() == 1 && cast(IdxList[0])->isNullValue())) return const_cast(C); if (isa(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(IdxList[0]); if (C->isNullValue()) { bool isNull = true; for (unsigned i = 0, e = IdxList.size(); i != e; ++i) if (!cast(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(C->getType())->getElementType(); if (uint32_t 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 = ConstantInt::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(const_cast(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(LastTy)) || Idx0->isNullValue()) { std::vector 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(CE->getOperand(0)->getType())) if (const ArrayType *SAT = dyn_cast(SPT->getElementType())) if (const ArrayType *CAT = dyn_cast(cast(C->getType())->getElementType())) if (CAT->getElementType() == SAT->getElementType()) return ConstantExpr::getGetElementPtr( (Constant*)CE->getOperand(0), IdxList); } return 0; }