1 //===-- llvm/GlobalValue.h - Class to represent a global value --*- 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 is a common base class of all globally definable objects. As such,
11 // it is subclassed by GlobalVariable and by Function. This is used because you
12 // can do certain things with these global objects that you can't do to anything
13 // else. For example, use the address of one as a constant.
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_GLOBALVALUE_H
18 #define LLVM_GLOBALVALUE_H
20 #include "llvm/Constant.h"
27 class GlobalValue : public Constant {
28 GlobalValue(const GlobalValue &); // do not implement
30 /// @brief An enumeration for the kinds of linkage for global values.
32 ExternalLinkage, ///< Externally visible function
33 LinkOnceLinkage, ///< Keep one copy of function when linking (inline)
34 WeakLinkage, ///< Keep one copy of named function when linking (weak)
35 AppendingLinkage, ///< Special purpose, only applies to global arrays
36 InternalLinkage, ///< Rename collisions when linking (static functions)
37 DLLImportLinkage, ///< Function to be imported from DLL
38 DLLExportLinkage, ///< Function to be accessible from DLL
39 ExternalWeakLinkage,///< ExternalWeak linkage description
40 GhostLinkage ///< Stand-in functions for streaming fns from BC files
43 /// @brief An enumeration for the kinds of visibility of global values.
44 enum VisibilityTypes {
45 DefaultVisibility, ///< The GV is visible
46 HiddenVisibility ///< The GV is hidden
50 GlobalValue(const Type *Ty, ValueTy vty, Use *Ops, unsigned NumOps,
51 LinkageTypes linkage, const std::string &name = "")
52 : Constant(Ty, vty, Ops, NumOps, name), Parent(0),
53 Linkage(linkage), Visibility(DefaultVisibility), Alignment(0) { }
56 LinkageTypes Linkage; // The linkage of this global
57 VisibilityTypes Visibility; // The visibility style of this global
58 unsigned Alignment; // Alignment of this symbol, must be power of two
59 std::string Section; // Section to emit this into, empty mean default
62 removeDeadConstantUsers(); // remove any dead constants using this.
65 unsigned getAlignment() const { return Alignment; }
66 void setAlignment(unsigned Align) {
67 assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
71 VisibilityTypes getVisibility() const { return Visibility; }
72 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
73 void setVisibility(VisibilityTypes V) { Visibility = V; }
75 bool hasSection() const { return !Section.empty(); }
76 const std::string &getSection() const { return Section; }
77 void setSection(const std::string &S) { Section = S; }
79 /// If the usage is empty (except transitively dead constants), then this
80 /// global value can can be safely deleted since the destructor will
81 /// delete the dead constants as well.
82 /// @brief Determine if the usage of this global value is empty except
83 /// for transitively dead constants.
84 bool use_empty_except_constants();
86 /// getType - Global values are always pointers.
87 inline const PointerType *getType() const {
88 return reinterpret_cast<const PointerType*>(User::getType());
91 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
92 bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; }
93 bool hasWeakLinkage() const { return Linkage == WeakLinkage; }
94 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
95 bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
96 bool hasDLLImportLinkage() const { return Linkage == DLLImportLinkage; }
97 bool hasDLLExportLinkage() const { return Linkage == DLLExportLinkage; }
98 bool hasExternalWeakLinkage() const { return Linkage == ExternalWeakLinkage; }
99 void setLinkage(LinkageTypes LT) { Linkage = LT; }
100 LinkageTypes getLinkage() const { return Linkage; }
102 /// hasNotBeenReadFromBytecode - If a module provider is being used to lazily
103 /// stream in functions from disk, this method can be used to check to see if
104 /// the function has been read in yet or not. Unless you are working on the
105 /// JIT or something else that streams stuff in lazily, you don't need to
106 /// worry about this.
107 bool hasNotBeenReadFromBytecode() const { return Linkage == GhostLinkage; }
109 /// Override from Constant class. No GlobalValue's are null values so this
110 /// always returns false.
111 virtual bool isNullValue() const { return false; }
113 /// Override from Constant class.
114 virtual void destroyConstant();
116 /// isDeclaration - Return true if the primary definition of this global
117 /// value is outside of the current translation unit...
118 virtual bool isDeclaration() const = 0;
120 /// getParent - Get the module that this global value is contained inside
122 inline Module *getParent() { return Parent; }
123 inline const Module *getParent() const { return Parent; }
125 /// removeDeadConstantUsers - If there are any dead constant users dangling
126 /// off of this global value, remove them. This method is useful for clients
127 /// that want to check to see if a global is unused, but don't want to deal
128 /// with potentially dead constants hanging off of the globals.
130 /// This method tries to make the global dead. If it detects a user that
131 /// would prevent it from becoming completely dead, it gives up early,
132 /// potentially leaving some dead constant users around.
133 void removeDeadConstantUsers();
135 // Methods for support type inquiry through isa, cast, and dyn_cast:
136 static inline bool classof(const GlobalValue *) { return true; }
137 static inline bool classof(const Value *V) {
138 return V->getValueType() == Value::FunctionVal ||
139 V->getValueType() == Value::GlobalVariableVal;
143 } // End llvm namespace