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, LinkageTypes linkage, 00040 const std::string &name = "") 00041 : Constant(Ty, vty, name), Linkage(linkage), Parent(0) { } 00042 00043 LinkageTypes Linkage; // The linkage of this global 00044 Module *Parent; 00045 public: 00046 ~GlobalValue() { 00047 removeDeadConstantUsers(); // remove any dead constants using this. 00048 } 00049 00050 /// If the usage is empty (except transitively dead constants), then this 00051 /// global value can can be safely deleted since the destructor will 00052 /// delete the dead constants as well. 00053 /// @brief Determine if the usage of this global value is empty except 00054 /// for transitively dead constants. 00055 bool use_empty_except_constants(); 00056 00057 /// getType - Global values are always pointers. 00058 inline const PointerType *getType() const { 00059 return reinterpret_cast<const PointerType*>(User::getType()); 00060 } 00061 00062 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; } 00063 bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; } 00064 bool hasWeakLinkage() const { return Linkage == WeakLinkage; } 00065 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; } 00066 bool hasInternalLinkage() const { return Linkage == InternalLinkage; } 00067 void setLinkage(LinkageTypes LT) { Linkage = LT; } 00068 LinkageTypes getLinkage() const { return Linkage; } 00069 00070 /// hasNotBeenReadFromBytecode - If a module provider is being used to lazily 00071 /// stream in functions from disk, this method can be used to check to see if 00072 /// the function has been read in yet or not. Unless you are working on the 00073 /// JIT or something else that streams stuff in lazily, you don't need to 00074 /// worry about this. 00075 bool hasNotBeenReadFromBytecode() const { return Linkage == GhostLinkage; } 00076 00077 /// Override from Constant class. No GlobalValue's are null values so this 00078 /// always returns false. 00079 virtual bool isNullValue() const { return false; } 00080 00081 /// Override from Constant class. 00082 virtual void destroyConstant(); 00083 00084 /// isExternal - Return true if the primary definition of this global value is 00085 /// outside of the current translation unit... 00086 virtual bool isExternal() const = 0; 00087 00088 /// getParent - Get the module that this global value is contained inside 00089 /// of... 00090 inline Module *getParent() { return Parent; } 00091 inline const Module *getParent() const { return Parent; } 00092 00093 /// removeDeadConstantUsers - If there are any dead constant users dangling 00094 /// off of this global value, remove them. This method is useful for clients 00095 /// that want to check to see if a global is unused, but don't want to deal 00096 /// with potentially dead constants hanging off of the globals. 00097 /// 00098 /// This method tries to make the global dead. If it detects a user that 00099 /// would prevent it from becoming completely dead, it gives up early, 00100 /// potentially leaving some dead constant users around. 00101 void removeDeadConstantUsers(); 00102 00103 // Methods for support type inquiry through isa, cast, and dyn_cast: 00104 static inline bool classof(const GlobalValue *T) { return true; } 00105 static inline bool classof(const Value *V) { 00106 return V->getValueType() == Value::FunctionVal || 00107 V->getValueType() == Value::GlobalVariableVal; 00108 } 00109 }; 00110 00111 } // End llvm namespace 00112 00113 #endif