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
31 ExternalLinkage, /// Externally visible function
32 LinkOnceLinkage, /// Keep one copy of named function when linking (inline)
33 WeakLinkage, /// Keep one copy of named function when linking (weak)
34 AppendingLinkage, /// Special purpose, only applies to global arrays
35 InternalLinkage, /// Rename collisions when linking (static functions)
36 DLLImportLinkage, /// Function to be imported from DLL
37 DLLExportLinkage, /// Function to be accessible from DLL
38 ExternalWeakLinkage, /// TBD: ExternalWeak linkage description
39 GhostLinkage /// Stand-in functions for streaming fns from BC files
42 GlobalValue(const Type *Ty, ValueTy vty, Use *Ops, unsigned NumOps,
43 LinkageTypes linkage, const std::string &name = "")
44 : Constant(Ty, vty, Ops, NumOps, name),
45 Parent(0), Linkage(linkage), Alignment(0) { }
48 LinkageTypes Linkage; // The linkage of this global
49 unsigned Alignment; // Alignment of this symbol, must be power of two
50 std::string Section; // Section to emit this into, empty mean default
53 removeDeadConstantUsers(); // remove any dead constants using this.
56 unsigned getAlignment() const { return Alignment; }
57 void setAlignment(unsigned Align) {
58 assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
62 bool hasSection() const { return !Section.empty(); }
63 const std::string &getSection() const { return Section; }
64 void setSection(const std::string &S) { Section = S; }
66 /// If the usage is empty (except transitively dead constants), then this
67 /// global value can can be safely deleted since the destructor will
68 /// delete the dead constants as well.
69 /// @brief Determine if the usage of this global value is empty except
70 /// for transitively dead constants.
71 bool use_empty_except_constants();
73 /// getType - Global values are always pointers.
74 inline const PointerType *getType() const {
75 return reinterpret_cast<const PointerType*>(User::getType());
78 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
79 bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; }
80 bool hasWeakLinkage() const { return Linkage == WeakLinkage; }
81 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
82 bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
83 bool hasDLLImportLinkage() const { return Linkage == DLLImportLinkage; }
84 bool hasDLLExportLinkage() const { return Linkage == DLLExportLinkage; }
85 bool hasExternalWeakLinkage() const { return Linkage == ExternalWeakLinkage; }
86 void setLinkage(LinkageTypes LT) { Linkage = LT; }
87 LinkageTypes getLinkage() const { return Linkage; }
89 /// hasNotBeenReadFromBytecode - If a module provider is being used to lazily
90 /// stream in functions from disk, this method can be used to check to see if
91 /// the function has been read in yet or not. Unless you are working on the
92 /// JIT or something else that streams stuff in lazily, you don't need to
94 bool hasNotBeenReadFromBytecode() const { return Linkage == GhostLinkage; }
96 /// Override from Constant class. No GlobalValue's are null values so this
97 /// always returns false.
98 virtual bool isNullValue() const { return false; }
100 /// Override from Constant class.
101 virtual void destroyConstant();
103 /// isExternal - Return true if the primary definition of this global value is
104 /// outside of the current translation unit...
105 virtual bool isExternal() const = 0;
107 /// getParent - Get the module that this global value is contained inside
109 inline Module *getParent() { return Parent; }
110 inline const Module *getParent() const { return Parent; }
112 /// removeDeadConstantUsers - If there are any dead constant users dangling
113 /// off of this global value, remove them. This method is useful for clients
114 /// that want to check to see if a global is unused, but don't want to deal
115 /// with potentially dead constants hanging off of the globals.
117 /// This method tries to make the global dead. If it detects a user that
118 /// would prevent it from becoming completely dead, it gives up early,
119 /// potentially leaving some dead constant users around.
120 void removeDeadConstantUsers();
122 // Methods for support type inquiry through isa, cast, and dyn_cast:
123 static inline bool classof(const GlobalValue *) { return true; }
124 static inline bool classof(const Value *V) {
125 return V->getValueType() == Value::FunctionVal ||
126 V->getValueType() == Value::GlobalVariableVal;
130 } // End llvm namespace