LLVM API Documentation
00001 //===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file is a common base class of all globally definable objects. As such, 00011 // it is subclassed by GlobalVariable and by Function. This is used because you 00012 // can do certain things with these global objects that you can't do to anything 00013 // else. For example, use the address of one as a constant. 00014 // 00015 //===----------------------------------------------------------------------===// 00016 00017 #ifndef LLVM_GLOBALVALUE_H 00018 #define LLVM_GLOBALVALUE_H 00019 00020 #include "llvm/Constant.h" 00021 00022 namespace llvm { 00023 00024 class PointerType; 00025 class Module; 00026 00027 class GlobalValue : public Constant { 00028 GlobalValue(const GlobalValue &); // do not implement 00029 public: 00030 enum LinkageTypes { 00031 ExternalLinkage, /// Externally visible function 00032 LinkOnceLinkage, /// Keep one copy of named function when linking (inline) 00033 WeakLinkage, /// Keep one copy of named function when linking (weak) 00034 AppendingLinkage, /// Special purpose, only applies to global arrays 00035 InternalLinkage, /// Rename collisions when linking (static functions) 00036 GhostLinkage /// Stand-in functions for streaming fns from BC files 00037 }; 00038 protected: 00039 GlobalValue(const Type *Ty, ValueTy vty, Use *Ops, unsigned NumOps, 00040 LinkageTypes linkage, const std::string &name = "") 00041 : Constant(Ty, vty, Ops, NumOps, name), 00042 Parent(0), Linkage(linkage), Alignment(0) { } 00043 00044 Module *Parent; 00045 LinkageTypes Linkage; // The linkage of this global 00046 unsigned Alignment; // Alignment of this symbol, must be power of two 00047 std::string Section; // Section to emit this into, empty mean default 00048 public: 00049 ~GlobalValue() { 00050 removeDeadConstantUsers(); // remove any dead constants using this. 00051 } 00052 00053 unsigned getAlignment() const { return Alignment; } 00054 void setAlignment(unsigned Align) { 00055 assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!"); 00056 Alignment = Align; 00057 } 00058 00059 bool hasSection() const { return !Section.empty(); } 00060 const std::string &getSection() const { return Section; } 00061 void setSection(const std::string &S) { Section = S; } 00062 00063 /// If the usage is empty (except transitively dead constants), then this 00064 /// global value can can be safely deleted since the destructor will 00065 /// delete the dead constants as well. 00066 /// @brief Determine if the usage of this global value is empty except 00067 /// for transitively dead constants. 00068 bool use_empty_except_constants(); 00069 00070 /// getType - Global values are always pointers. 00071 inline const PointerType *getType() const { 00072 return reinterpret_cast<const PointerType*>(User::getType()); 00073 } 00074 00075 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; } 00076 bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; } 00077 bool hasWeakLinkage() const { return Linkage == WeakLinkage; } 00078 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; } 00079 bool hasInternalLinkage() const { return Linkage == InternalLinkage; } 00080 void setLinkage(LinkageTypes LT) { Linkage = LT; } 00081 LinkageTypes getLinkage() const { return Linkage; } 00082 00083 /// hasNotBeenReadFromBytecode - If a module provider is being used to lazily 00084 /// stream in functions from disk, this method can be used to check to see if 00085 /// the function has been read in yet or not. Unless you are working on the 00086 /// JIT or something else that streams stuff in lazily, you don't need to 00087 /// worry about this. 00088 bool hasNotBeenReadFromBytecode() const { return Linkage == GhostLinkage; } 00089 00090 /// Override from Constant class. No GlobalValue's are null values so this 00091 /// always returns false. 00092 virtual bool isNullValue() const { return false; } 00093 00094 /// Override from Constant class. 00095 virtual void destroyConstant(); 00096 00097 /// isExternal - Return true if the primary definition of this global value is 00098 /// outside of the current translation unit... 00099 virtual bool isExternal() const = 0; 00100 00101 /// getParent - Get the module that this global value is contained inside 00102 /// of... 00103 inline Module *getParent() { return Parent; } 00104 inline const Module *getParent() const { return Parent; } 00105 00106 /// removeDeadConstantUsers - If there are any dead constant users dangling 00107 /// off of this global value, remove them. This method is useful for clients 00108 /// that want to check to see if a global is unused, but don't want to deal 00109 /// with potentially dead constants hanging off of the globals. 00110 /// 00111 /// This method tries to make the global dead. If it detects a user that 00112 /// would prevent it from becoming completely dead, it gives up early, 00113 /// potentially leaving some dead constant users around. 00114 void removeDeadConstantUsers(); 00115 00116 // Methods for support type inquiry through isa, cast, and dyn_cast: 00117 static inline bool classof(const GlobalValue *) { return true; } 00118 static inline bool classof(const Value *V) { 00119 return V->getValueType() == Value::FunctionVal || 00120 V->getValueType() == Value::GlobalVariableVal; 00121 } 00122 }; 00123 00124 } // End llvm namespace 00125 00126 #endif