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 GhostLinkage /// Stand-in functions for streaming fns from BC files
39 GlobalValue(const Type *Ty, ValueTy vty, Use *Ops, unsigned NumOps,
40 LinkageTypes linkage, const std::string &name = "")
41 : Constant(Ty, vty, Ops, NumOps, name), Linkage(linkage), Parent(0) { }
43 LinkageTypes Linkage; // The linkage of this global
48 removeDeadConstantUsers(); // remove any dead constants using this.
51 unsigned getAlignment() const { return Alignment; }
52 void setAlignment(unsigned Align) {
53 assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
57 /// If the usage is empty (except transitively dead constants), then this
58 /// global value can can be safely deleted since the destructor will
59 /// delete the dead constants as well.
60 /// @brief Determine if the usage of this global value is empty except
61 /// for transitively dead constants.
62 bool use_empty_except_constants();
64 /// getType - Global values are always pointers.
65 inline const PointerType *getType() const {
66 return reinterpret_cast<const PointerType*>(User::getType());
69 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
70 bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; }
71 bool hasWeakLinkage() const { return Linkage == WeakLinkage; }
72 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
73 bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
74 void setLinkage(LinkageTypes LT) { Linkage = LT; }
75 LinkageTypes getLinkage() const { return Linkage; }
77 /// hasNotBeenReadFromBytecode - If a module provider is being used to lazily
78 /// stream in functions from disk, this method can be used to check to see if
79 /// the function has been read in yet or not. Unless you are working on the
80 /// JIT or something else that streams stuff in lazily, you don't need to
82 bool hasNotBeenReadFromBytecode() const { return Linkage == GhostLinkage; }
84 /// Override from Constant class. No GlobalValue's are null values so this
85 /// always returns false.
86 virtual bool isNullValue() const { return false; }
88 /// Override from Constant class.
89 virtual void destroyConstant();
91 /// isExternal - Return true if the primary definition of this global value is
92 /// outside of the current translation unit...
93 virtual bool isExternal() const = 0;
95 /// getParent - Get the module that this global value is contained inside
97 inline Module *getParent() { return Parent; }
98 inline const Module *getParent() const { return Parent; }
100 /// removeDeadConstantUsers - If there are any dead constant users dangling
101 /// off of this global value, remove them. This method is useful for clients
102 /// that want to check to see if a global is unused, but don't want to deal
103 /// with potentially dead constants hanging off of the globals.
105 /// This method tries to make the global dead. If it detects a user that
106 /// would prevent it from becoming completely dead, it gives up early,
107 /// potentially leaving some dead constant users around.
108 void removeDeadConstantUsers();
110 // Methods for support type inquiry through isa, cast, and dyn_cast:
111 static inline bool classof(const GlobalValue *) { return true; }
112 static inline bool classof(const Value *V) {
113 return V->getValueType() == Value::FunctionVal ||
114 V->getValueType() == Value::GlobalVariableVal;
118 } // End llvm namespace