1 //===-- llvm/Constant.h - Constant class definition -------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the declaration of the Constant class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CONSTANT_H
15 #define LLVM_CONSTANT_H
17 #include "llvm/User.h"
21 /// This is an important base class in LLVM. It provides the common facilities
22 /// of all constant values in an LLVM program. A constant is a value that is
23 /// immutable at runtime. Functions are constants because their address is
24 /// immutable. Same with global variables.
26 /// All constants share the capabilities provided in this class. All constants
27 /// can have a null value. They can have an operand list. Constants can be
28 /// simple (integer and floating point values), complex (arrays and structures),
29 /// or expression based (computations yielding a constant value composed of
30 /// only certain operators and other constant values).
32 /// Note that Constants are immutable (once created they never change)
33 /// and are fully shared by structural equivalence. This means that two
34 /// structurally equivalent constants will always have the same address.
35 /// Constant's are created on demand as needed and never deleted: thus clients
36 /// don't have to worry about the lifetime of the objects.
37 /// @brief LLVM Constant Representation
38 class Constant : public User {
39 void operator=(const Constant &); // Do not implement
40 Constant(const Constant &); // Do not implement
42 Constant(const Type *Ty, ValueTy vty, Use *Ops, unsigned NumOps,
43 const std::string& Name = "")
44 : User(Ty, vty, Ops, NumOps, Name) {}
46 void destroyConstantImpl();
48 /// Static constructor to get a '0' constant of arbitrary type...
50 static Constant *getNullValue(const Type *Ty);
52 /// isNullValue - Return true if this is the value that would be returned by
54 virtual bool isNullValue() const = 0;
56 virtual void print(std::ostream &O) const;
57 void print(std::ostream *O) const { if (O) print(*O); }
59 /// canTrap - Return true if evaluation of this constant could trap. This is
60 /// true for things like constant expressions that could divide by zero.
63 // Specialize get/setOperand for Constant's as their operands are always
65 Constant *getOperand(unsigned i) {
66 return static_cast<Constant*>(User::getOperand(i));
68 const Constant *getOperand(unsigned i) const {
69 return static_cast<const Constant*>(User::getOperand(i));
71 void setOperand(unsigned i, Constant *C) {
72 User::setOperand(i, C);
75 /// destroyConstant - Called if some element of this constant is no longer
76 /// valid. At this point only other constants may be on the use_list for this
77 /// constant. Any constants on our Use list must also be destroy'd. The
78 /// implementation must be sure to remove the constant from the list of
79 /// available cached constants. Implementations should call
80 /// destroyConstantImpl as the last thing they do, to destroy all users and
82 virtual void destroyConstant() { assert(0 && "Not reached!"); }
84 //// Methods for support type inquiry through isa, cast, and dyn_cast:
85 static inline bool classof(const Constant *) { return true; }
86 static inline bool classof(const GlobalValue *) { return true; }
87 static inline bool classof(const Value *V) {
88 return V->getValueType() >= ConstantFirstVal &&
89 V->getValueType() <= ConstantLastVal;
92 /// replaceUsesOfWithOnConstant - This method is a special form of
93 /// User::replaceUsesOfWith (which does not work on constants) that does work
94 /// on constants. Basically this method goes through the trouble of building
95 /// a new constant that is equivalent to the current one, with all uses of
96 /// From replaced with uses of To. After this construction is completed, all
97 /// of the users of 'this' are replaced to use the new constant, and then
98 /// 'this' is deleted. In general, you should not call this method, instead,
99 /// use Value::replaceAllUsesWith, which automatically dispatches to this
100 /// method as needed.
102 virtual void replaceUsesOfWithOnConstant(Value *, Value *, Use *) {
103 // Provide a default implementation for constants (like integers) that
104 // cannot use any other values. This cannot be called at runtime, but needs
105 // to be here to avoid link errors.
106 assert(getNumOperands() == 0 && "replaceUsesOfWithOnConstant must be "
107 "implemented for all constants that have operands!");
108 assert(0 && "Constants that do not have operands cannot be using 'From'!");
111 /// getStringValue - Turn an LLVM constant pointer that eventually points to a
112 /// global into a string value. Return an empty string if we can't do it.
113 /// Parameter Chop determines if the result is chopped at the first null
116 std::string getStringValue(bool Chop = true, unsigned Offset = 0);
119 } // End llvm namespace