//===-- 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_IR_CONSTANT_H #define LLVM_IR_CONSTANT_H #include "llvm/IR/User.h" namespace llvm { class APInt; template<typename T> class SmallVectorImpl; /// 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 &) LLVM_DELETED_FUNCTION; Constant(const Constant &) LLVM_DELETED_FUNCTION; virtual void anchor(); protected: Constant(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps) : User(ty, vty, Ops, NumOps) {} void destroyConstantImpl(); public: /// isNullValue - Return true if this is the value that would be returned by /// getNullValue. bool isNullValue() const; /// isAllOnesValue - Return true if this is the value that would be returned by /// getAllOnesValue. bool isAllOnesValue() const; /// isNegativeZeroValue - Return true if the value is what would be returned /// by getZeroValueForNegation. bool isNegativeZeroValue() const; /// Return true if the value is negative zero or null value. bool isZeroValue() const; /// 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; /// isThreadDependent - Return true if the value can vary between threads. bool isThreadDependent() const; /// isConstantUsed - Return true if the constant has users other than constant /// exprs and other dangling things. bool isConstantUsed() const; enum PossibleRelocationsTy { NoRelocation = 0, LocalRelocation = 1, GlobalRelocations = 2 }; /// getRelocationInfo - This method classifies the entry according to /// whether or not it may generate a relocation entry. This must be /// conservative, so if it might codegen to a relocatable entry, it should say /// so. The return values are: /// /// NoRelocation: This constant pool entry is guaranteed to never have a /// relocation applied to it (because it holds a simple constant like /// '4'). /// LocalRelocation: This entry has relocations, but the entries are /// guaranteed to be resolvable by the static linker, so the dynamic /// linker will never see them. /// GlobalRelocations: This entry may have arbitrary relocations. /// /// FIXME: This really should not be in VMCore. PossibleRelocationsTy getRelocationInfo() const; /// getAggregateElement - For aggregates (struct/array/vector) return the /// constant that corresponds to the specified element if possible, or null if /// not. This can return null if the element index is a ConstantExpr, or if /// 'this' is a constant expr. Constant *getAggregateElement(unsigned Elt) const; Constant *getAggregateElement(Constant *Elt) const; /// getSplatValue - If this is a splat vector constant, meaning that all of /// the elements have the same value, return that value. Otherwise return 0. Constant *getSplatValue() const; /// If C is a constant integer then return its value, otherwise C must be a /// vector of constant integers, all equal, and the common value is returned. const APInt &getUniqueInteger() 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() { llvm_unreachable("Not reached!"); } //// Methods for support type inquiry through isa, cast, and dyn_cast: 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!"); llvm_unreachable("Constants that do not have operands cannot be using " "'From'!"); } static Constant *getNullValue(Type* Ty); /// @returns the value for an integer or vector of integer constant of the /// given type that has all its bits set to true. /// @brief Get the all ones value static Constant *getAllOnesValue(Type* Ty); /// getIntegerValue - Return the value for an integer or pointer constant, /// or a vector thereof, with the given scalar value. static Constant *getIntegerValue(Type* Ty, const APInt &V); /// removeDeadConstantUsers - If there are any dead constant users dangling /// off of this constant, remove them. This method is useful for clients /// that want to check to see if a global is unused, but don't want to deal /// with potentially dead constants hanging off of the globals. void removeDeadConstantUsers() const; }; } // End llvm namespace #endif