1 //===-- llvm/Constant.h - Constant class definition -------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the declaration of the Constant class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_IR_CONSTANT_H
15 #define LLVM_IR_CONSTANT_H
17 #include "llvm/IR/User.h"
18 #include "llvm/IR/Value.h"
19 #include "llvm/Support/Casting.h"
25 /// This is an important base class in LLVM. It provides the common facilities
26 /// of all constant values in an LLVM program. A constant is a value that is
27 /// immutable at runtime. Functions are constants because their address is
28 /// immutable. Same with global variables.
30 /// All constants share the capabilities provided in this class. All constants
31 /// can have a null value. They can have an operand list. Constants can be
32 /// simple (integer and floating point values), complex (arrays and structures),
33 /// or expression based (computations yielding a constant value composed of
34 /// only certain operators and other constant values).
36 /// Note that Constants are immutable (once created they never change)
37 /// and are fully shared by structural equivalence. This means that two
38 /// structurally equivalent constants will always have the same address.
39 /// Constants are created on demand as needed and never deleted: thus clients
40 /// don't have to worry about the lifetime of the objects.
41 /// LLVM Constant Representation
42 class Constant : public User {
44 Constant(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
45 : User(ty, vty, Ops, NumOps) {}
48 void operator=(const Constant &) = delete;
49 Constant(const Constant &) = delete;
51 /// Return true if this is the value that would be returned by getNullValue.
52 bool isNullValue() const;
54 /// Returns true if the value is one.
55 bool isOneValue() const;
57 /// Return true if this is the value that would be returned by
59 bool isAllOnesValue() const;
61 /// Return true if the value is what would be returned by
62 /// getZeroValueForNegation.
63 bool isNegativeZeroValue() const;
65 /// Return true if the value is negative zero or null value.
66 bool isZeroValue() const;
68 /// Return true if the value is not the smallest signed value.
69 bool isNotMinSignedValue() const;
71 /// Return true if the value is the smallest signed value.
72 bool isMinSignedValue() const;
74 /// Return true if this is a finite and non-zero floating-point scalar
75 /// constant or a vector constant with all finite and non-zero elements.
76 bool isFiniteNonZeroFP() const;
78 /// Return true if this is a normal (as opposed to denormal) floating-point
79 /// scalar constant or a vector constant with all normal elements.
80 bool isNormalFP() const;
82 /// Return true if this scalar has an exact multiplicative inverse or this
83 /// vector has an exact multiplicative inverse for each element in the vector.
84 bool hasExactInverseFP() const;
86 /// Return true if this is a floating-point NaN constant or a vector
87 /// floating-point constant with all NaN elements.
90 /// Return true if this is a vector constant that includes any undefined
92 bool containsUndefElement() const;
94 /// Return true if evaluation of this constant could trap. This is true for
95 /// things like constant expressions that could divide by zero.
98 /// Return true if the value can vary between threads.
99 bool isThreadDependent() const;
101 /// Return true if the value is dependent on a dllimport variable.
102 bool isDLLImportDependent() const;
104 /// Return true if the constant has users other than constant expressions and
105 /// other dangling things.
106 bool isConstantUsed() const;
108 /// This method classifies the entry according to whether or not it may
109 /// generate a relocation entry. This must be conservative, so if it might
110 /// codegen to a relocatable entry, it should say so.
112 /// FIXME: This really should not be in IR.
113 bool needsRelocation() const;
115 /// For aggregates (struct/array/vector) return the constant that corresponds
116 /// to the specified element if possible, or null if not. This can return null
117 /// if the element index is a ConstantExpr, or if 'this' is a constant expr.
118 Constant *getAggregateElement(unsigned Elt) const;
119 Constant *getAggregateElement(Constant *Elt) const;
121 /// If this is a splat vector constant, meaning that all of the elements have
122 /// the same value, return that value. Otherwise return 0.
123 Constant *getSplatValue() const;
125 /// If C is a constant integer then return its value, otherwise C must be a
126 /// vector of constant integers, all equal, and the common value is returned.
127 const APInt &getUniqueInteger() const;
129 /// Called if some element of this constant is no longer valid.
130 /// At this point only other constants may be on the use_list for this
131 /// constant. Any constants on our Use list must also be destroy'd. The
132 /// implementation must be sure to remove the constant from the list of
133 /// available cached constants. Implementations should implement
134 /// destroyConstantImpl to remove constants from any pools/maps they are
136 void destroyConstant();
138 //// Methods for support type inquiry through isa, cast, and dyn_cast:
139 static bool classof(const Value *V) {
140 static_assert(ConstantFirstVal == 0, "V->getValueID() >= ConstantFirstVal always succeeds");
141 return V->getValueID() <= ConstantLastVal;
144 /// This method is a special form of User::replaceUsesOfWith
145 /// (which does not work on constants) that does work
146 /// on constants. Basically this method goes through the trouble of building
147 /// a new constant that is equivalent to the current one, with all uses of
148 /// From replaced with uses of To. After this construction is completed, all
149 /// of the users of 'this' are replaced to use the new constant, and then
150 /// 'this' is deleted. In general, you should not call this method, instead,
151 /// use Value::replaceAllUsesWith, which automatically dispatches to this
152 /// method as needed.
154 void handleOperandChange(Value *, Value *);
156 static Constant *getNullValue(Type* Ty);
158 /// @returns the value for an integer or vector of integer constant of the
159 /// given type that has all its bits set to true.
160 /// Get the all ones value
161 static Constant *getAllOnesValue(Type* Ty);
163 /// Return the value for an integer or pointer constant, or a vector thereof,
164 /// with the given scalar value.
165 static Constant *getIntegerValue(Type *Ty, const APInt &V);
167 /// If there are any dead constant users dangling off of this constant, remove
168 /// them. This method is useful for clients that want to check to see if a
169 /// global is unused, but don't want to deal with potentially dead constants
170 /// hanging off of the globals.
171 void removeDeadConstantUsers() const;
173 const Constant *stripPointerCasts() const {
174 return cast<Constant>(Value::stripPointerCasts());
177 Constant *stripPointerCasts() {
178 return const_cast<Constant*>(
179 static_cast<const Constant *>(this)->stripPointerCasts());
183 } // end namespace llvm
185 #endif // LLVM_IR_CONSTANT_H