//===-- llvm/Constant.h - Constant class definition -------------*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file contains the declaration of the Constant class. // //===----------------------------------------------------------------------===// #ifndef LLVM_CONSTANT_H #define LLVM_CONSTANT_H #include "llvm/User.h" namespace llvm { template<typename T> class SmallVectorImpl; /// If object contains references to other objects, then relocations are /// usually required for emission of such object (especially in PIC mode). One /// usually distinguishes local and global relocations. Local relocations are /// made wrt objects in the same module and these objects have local (internal /// or private) linkage. Global relocations are made wrt externally visible /// objects. In most cases local relocations can be resolved via so-called /// 'pre-link' technique. namespace Reloc { const unsigned None = 0; const unsigned Local = 1 << 0; ///< Local relocations are required const unsigned Global = 1 << 1; ///< Global relocations are required const unsigned LocalOrGlobal = Local | Global; } /// This is an important base class in LLVM. It provides the common facilities /// of all constant values in an LLVM program. A constant is a value that is /// immutable at runtime. Functions are constants because their address is /// immutable. Same with global variables. /// /// All constants share the capabilities provided in this class. All constants /// can have a null value. They can have an operand list. Constants can be /// simple (integer and floating point values), complex (arrays and structures), /// or expression based (computations yielding a constant value composed of /// only certain operators and other constant values). /// /// Note that Constants are immutable (once created they never change) /// and are fully shared by structural equivalence. This means that two /// structurally equivalent constants will always have the same address. /// Constants are created on demand as needed and never deleted: thus clients /// don't have to worry about the lifetime of the objects. /// @brief LLVM Constant Representation class Constant : public User { void operator=(const Constant &); // Do not implement Constant(const Constant &); // Do not implement protected: Constant(const Type *ty, ValueTy vty, Use *Ops, unsigned NumOps) : User(ty, vty, Ops, NumOps) {} void destroyConstantImpl(); public: /// Static constructor to get a '0' constant of arbitrary type... /// static Constant *getNullValue(const Type *Ty); /// Static constructor to get a '-1' constant. This supports integers and /// vectors. /// static Constant *getAllOnesValue(const Type *Ty); /// isNullValue - Return true if this is the value that would be returned by /// getNullValue. virtual bool isNullValue() const = 0; /// canTrap - Return true if evaluation of this constant could trap. This is /// true for things like constant expressions that could divide by zero. bool canTrap() const; /// ContainsRelocations - Return true if the constant value contains /// relocations which cannot be resolved at compile time. Note that answer is /// not exclusive: there can be possibility that relocations of other kind are /// required as well. bool ContainsRelocations(unsigned Kind = Reloc::LocalOrGlobal) const; // Specialize get/setOperand for Constants as their operands are always // constants as well. Constant *getOperand(unsigned i) { return static_cast<Constant*>(User::getOperand(i)); } const Constant *getOperand(unsigned i) const { return static_cast<const Constant*>(User::getOperand(i)); } void setOperand(unsigned i, Constant *C) { User::setOperand(i, C); } /// getVectorElements - This method, which is only valid on constant of vector /// type, returns the elements of the vector in the specified smallvector. /// This handles breaking down a vector undef into undef elements, etc. For /// constant exprs and other cases we can't handle, we return an empty vector. void getVectorElements(SmallVectorImpl<Constant*> &Elts) const; /// destroyConstant - Called if some element of this constant is no longer /// valid. At this point only other constants may be on the use_list for this /// constant. Any constants on our Use list must also be destroy'd. The /// implementation must be sure to remove the constant from the list of /// available cached constants. Implementations should call /// destroyConstantImpl as the last thing they do, to destroy all users and /// delete this. virtual void destroyConstant() { assert(0 && "Not reached!"); } //// Methods for support type inquiry through isa, cast, and dyn_cast: static inline bool classof(const Constant *) { return true; } static inline bool classof(const GlobalValue *) { return true; } static inline bool classof(const Value *V) { return V->getValueID() >= ConstantFirstVal && V->getValueID() <= ConstantLastVal; } /// replaceUsesOfWithOnConstant - This method is a special form of /// User::replaceUsesOfWith (which does not work on constants) that does work /// on constants. Basically this method goes through the trouble of building /// a new constant that is equivalent to the current one, with all uses of /// From replaced with uses of To. After this construction is completed, all /// of the users of 'this' are replaced to use the new constant, and then /// 'this' is deleted. In general, you should not call this method, instead, /// use Value::replaceAllUsesWith, which automatically dispatches to this /// method as needed. /// virtual void replaceUsesOfWithOnConstant(Value *, Value *, Use *) { // Provide a default implementation for constants (like integers) that // cannot use any other values. This cannot be called at runtime, but needs // to be here to avoid link errors. assert(getNumOperands() == 0 && "replaceUsesOfWithOnConstant must be " "implemented for all constants that have operands!"); assert(0 && "Constants that do not have operands cannot be using 'From'!"); } }; } // End llvm namespace #endif