LLVM  3.7.0
Constant.h
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1 //===-- llvm/Constant.h - Constant class definition -------------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains the declaration of the Constant class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_IR_CONSTANT_H
15 #define LLVM_IR_CONSTANT_H
16 
17 #include "llvm/IR/User.h"
18 
19 namespace llvm {
20  class APInt;
21 
22  template<typename T> class SmallVectorImpl;
23 
24 /// This is an important base class in LLVM. It provides the common facilities
25 /// of all constant values in an LLVM program. A constant is a value that is
26 /// immutable at runtime. Functions are constants because their address is
27 /// immutable. Same with global variables.
28 ///
29 /// All constants share the capabilities provided in this class. All constants
30 /// can have a null value. They can have an operand list. Constants can be
31 /// simple (integer and floating point values), complex (arrays and structures),
32 /// or expression based (computations yielding a constant value composed of
33 /// only certain operators and other constant values).
34 ///
35 /// Note that Constants are immutable (once created they never change)
36 /// and are fully shared by structural equivalence. This means that two
37 /// structurally equivalent constants will always have the same address.
38 /// Constants are created on demand as needed and never deleted: thus clients
39 /// don't have to worry about the lifetime of the objects.
40 /// @brief LLVM Constant Representation
41 class Constant : public User {
42  void operator=(const Constant &) = delete;
43  Constant(const Constant &) = delete;
44  void anchor() override;
45 
46 protected:
47  Constant(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
48  : User(ty, vty, Ops, NumOps) {}
49 
50 public:
51  /// isNullValue - Return true if this is the value that would be returned by
52  /// getNullValue.
53  bool isNullValue() const;
54 
55  /// \brief Returns true if the value is one.
56  bool isOneValue() const;
57 
58  /// isAllOnesValue - Return true if this is the value that would be returned by
59  /// getAllOnesValue.
60  bool isAllOnesValue() const;
61 
62  /// isNegativeZeroValue - Return true if the value is what would be returned
63  /// by getZeroValueForNegation.
64  bool isNegativeZeroValue() const;
65 
66  /// Return true if the value is negative zero or null value.
67  bool isZeroValue() const;
68 
69  /// \brief Return true if the value is not the smallest signed value.
70  bool isNotMinSignedValue() const;
71 
72  /// \brief Return true if the value is the smallest signed value.
73  bool isMinSignedValue() const;
74 
75  /// canTrap - Return true if evaluation of this constant could trap. This is
76  /// true for things like constant expressions that could divide by zero.
77  bool canTrap() const;
78 
79  /// isThreadDependent - Return true if the value can vary between threads.
80  bool isThreadDependent() const;
81 
82  /// Return true if the value is dependent on a dllimport variable.
83  bool isDLLImportDependent() const;
84 
85  /// isConstantUsed - Return true if the constant has users other than constant
86  /// exprs and other dangling things.
87  bool isConstantUsed() const;
88 
93  };
94 
95  /// getRelocationInfo - This method classifies the entry according to
96  /// whether or not it may generate a relocation entry. This must be
97  /// conservative, so if it might codegen to a relocatable entry, it should say
98  /// so. The return values are:
99  ///
100  /// NoRelocation: This constant pool entry is guaranteed to never have a
101  /// relocation applied to it (because it holds a simple constant like
102  /// '4').
103  /// LocalRelocation: This entry has relocations, but the entries are
104  /// guaranteed to be resolvable by the static linker, so the dynamic
105  /// linker will never see them.
106  /// GlobalRelocations: This entry may have arbitrary relocations.
107  ///
108  /// FIXME: This really should not be in VMCore.
110 
111  /// getAggregateElement - For aggregates (struct/array/vector) return the
112  /// constant that corresponds to the specified element if possible, or null if
113  /// not. This can return null if the element index is a ConstantExpr, or if
114  /// 'this' is a constant expr.
115  Constant *getAggregateElement(unsigned Elt) const;
117 
118  /// getSplatValue - If this is a splat vector constant, meaning that all of
119  /// the elements have the same value, return that value. Otherwise return 0.
120  Constant *getSplatValue() const;
121 
122  /// If C is a constant integer then return its value, otherwise C must be a
123  /// vector of constant integers, all equal, and the common value is returned.
124  const APInt &getUniqueInteger() const;
125 
126  /// Called if some element of this constant is no longer valid.
127  /// At this point only other constants may be on the use_list for this
128  /// constant. Any constants on our Use list must also be destroy'd. The
129  /// implementation must be sure to remove the constant from the list of
130  /// available cached constants. Implementations should implement
131  /// destroyConstantImpl to remove constants from any pools/maps they are
132  /// contained it.
133  void destroyConstant();
134 
135  //// Methods for support type inquiry through isa, cast, and dyn_cast:
136  static inline bool classof(const Value *V) {
137  return V->getValueID() >= ConstantFirstVal &&
138  V->getValueID() <= ConstantLastVal;
139  }
140 
141  /// This method is a special form of User::replaceUsesOfWith
142  /// (which does not work on constants) that does work
143  /// on constants. Basically this method goes through the trouble of building
144  /// a new constant that is equivalent to the current one, with all uses of
145  /// From replaced with uses of To. After this construction is completed, all
146  /// of the users of 'this' are replaced to use the new constant, and then
147  /// 'this' is deleted. In general, you should not call this method, instead,
148  /// use Value::replaceAllUsesWith, which automatically dispatches to this
149  /// method as needed.
150  ///
151  void handleOperandChange(Value *, Value *, Use *);
152 
153  static Constant *getNullValue(Type* Ty);
154 
155  /// @returns the value for an integer or vector of integer constant of the
156  /// given type that has all its bits set to true.
157  /// @brief Get the all ones value
158  static Constant *getAllOnesValue(Type* Ty);
159 
160  /// getIntegerValue - Return the value for an integer or pointer constant,
161  /// or a vector thereof, with the given scalar value.
162  static Constant *getIntegerValue(Type* Ty, const APInt &V);
163 
164  /// removeDeadConstantUsers - If there are any dead constant users dangling
165  /// off of this constant, remove them. This method is useful for clients
166  /// that want to check to see if a global is unused, but don't want to deal
167  /// with potentially dead constants hanging off of the globals.
168  void removeDeadConstantUsers() const;
169 
171  return cast<Constant>(Value::stripPointerCasts());
172  }
173 
174  const Constant *stripPointerCasts() const {
175  return const_cast<Constant*>(this)->stripPointerCasts();
176  }
177 };
178 
179 } // End llvm namespace
180 
181 #endif
Constant * getSplatValue() const
getSplatValue - If this is a splat vector constant, meaning that all of the elements have the same va...
Definition: Constants.cpp:1418
static bool classof(const Value *V)
Definition: Constant.h:136
bool isOneValue() const
Returns true if the value is one.
Definition: Constants.cpp:110
const APInt & getUniqueInteger() const
If C is a constant integer then return its value, otherwise C must be a vector of constant integers...
Definition: Constants.cpp:1443
static Constant * getNullValue(Type *Ty)
Definition: Constants.cpp:178
bool isNegativeZeroValue() const
isNegativeZeroValue - Return true if the value is what would be returned by getZeroValueForNegation.
Definition: Constants.cpp:45
const Constant * stripPointerCasts() const
Definition: Constant.h:174
A Use represents the edge between a Value definition and its users.
Definition: Use.h:69
void handleOperandChange(Value *, Value *, Use *)
This method is a special form of User::replaceUsesOfWith (which does not work on constants) that does...
Definition: Constants.cpp:2840
bool isDLLImportDependent() const
Return true if the value is dependent on a dllimport variable.
Definition: Constants.cpp:392
bool isConstantUsed() const
isConstantUsed - Return true if the constant has users other than constant exprs and other dangling t...
Definition: Constants.cpp:401
Constant(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
Definition: Constant.h:47
bool isNotMinSignedValue() const
Return true if the value is not the smallest signed value.
Definition: Constants.cpp:154
Constant * stripPointerCasts()
Definition: Constant.h:170
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
bool canTrap() const
canTrap - Return true if evaluation of this constant could trap.
Definition: Constants.cpp:354
This is an important base class in LLVM.
Definition: Constant.h:41
bool isZeroValue() const
Return true if the value is negative zero or null value.
Definition: Constants.cpp:66
unsigned getValueID() const
Return an ID for the concrete type of this object.
Definition: Value.h:362
Constant * getAggregateElement(unsigned Elt) const
getAggregateElement - For aggregates (struct/array/vector) return the constant that corresponds to th...
Definition: Constants.cpp:250
static Constant * getAllOnesValue(Type *Ty)
Get the all ones value.
Definition: Constants.cpp:230
static Constant * getIntegerValue(Type *Ty, const APInt &V)
getIntegerValue - Return the value for an integer or pointer constant, or a vector thereof...
Definition: Constants.cpp:213
PossibleRelocationsTy getRelocationInfo() const
getRelocationInfo - This method classifies the entry according to whether or not it may generate a re...
Definition: Constants.cpp:429
Value * stripPointerCasts()
Strip off pointer casts, all-zero GEPs, and aliases.
Definition: Value.cpp:458
bool isNullValue() const
isNullValue - Return true if this is the value that would be returned by getNullValue.
Definition: Constants.cpp:75
ValueTy
Concrete subclass of this.
Definition: Value.h:343
bool isAllOnesValue() const
isAllOnesValue - Return true if this is the value that would be returned by getAllOnesValue.
Definition: Constants.cpp:88
Class for arbitrary precision integers.
Definition: APInt.h:73
void destroyConstant()
Called if some element of this constant is no longer valid.
Definition: Constants.cpp:279
void removeDeadConstantUsers() const
removeDeadConstantUsers - If there are any dead constant users dangling off of this constant...
Definition: Constants.cpp:487
LLVM Value Representation.
Definition: Value.h:69
bool isThreadDependent() const
isThreadDependent - Return true if the value can vary between threads.
Definition: Constants.cpp:385
bool isMinSignedValue() const
Return true if the value is the smallest signed value.
Definition: Constants.cpp:132