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114 lines
4.7 KiB
C++
114 lines
4.7 KiB
C++
//===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a common base class of all globally definable objects. As such,
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// it is subclassed by GlobalVariable and by Function. This is used because you
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// can do certain things with these global objects that you can't do to anything
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// else. For example, use the address of one as a constant.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_GLOBALVALUE_H
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#define LLVM_GLOBALVALUE_H
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#include "llvm/Constant.h"
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namespace llvm {
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class PointerType;
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class Module;
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class GlobalValue : public Constant {
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GlobalValue(const GlobalValue &); // do not implement
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public:
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enum LinkageTypes {
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ExternalLinkage, // Externally visible function
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LinkOnceLinkage, // Keep one copy of named function when linking (inline)
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WeakLinkage, // Keep one copy of named function when linking (weak)
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AppendingLinkage, // Special purpose, only applies to global arrays
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InternalLinkage, // Rename collisions when linking (static functions)
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GhostLinkage // Stand-in functions for streaming fns from BC files
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};
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protected:
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GlobalValue(const Type *Ty, ValueTy vty, Use *Ops, unsigned NumOps,
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LinkageTypes linkage, const std::string &name = "")
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: Constant(Ty, vty, Ops, NumOps, name), Linkage(linkage), Parent(0) { }
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LinkageTypes Linkage; // The linkage of this global
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Module *Parent;
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public:
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~GlobalValue() {
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removeDeadConstantUsers(); // remove any dead constants using this.
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}
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/// If the usage is empty (except transitively dead constants), then this
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/// global value can can be safely deleted since the destructor will
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/// delete the dead constants as well.
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/// @brief Determine if the usage of this global value is empty except
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/// for transitively dead constants.
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bool use_empty_except_constants();
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/// getType - Global values are always pointers.
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inline const PointerType *getType() const {
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return reinterpret_cast<const PointerType*>(User::getType());
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}
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bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
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bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; }
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bool hasWeakLinkage() const { return Linkage == WeakLinkage; }
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bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
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bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
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void setLinkage(LinkageTypes LT) { Linkage = LT; }
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LinkageTypes getLinkage() const { return Linkage; }
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/// hasNotBeenReadFromBytecode - If a module provider is being used to lazily
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/// stream in functions from disk, this method can be used to check to see if
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/// the function has been read in yet or not. Unless you are working on the
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/// JIT or something else that streams stuff in lazily, you don't need to
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/// worry about this.
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bool hasNotBeenReadFromBytecode() const { return Linkage == GhostLinkage; }
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/// Override from Constant class. No GlobalValue's are null values so this
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/// always returns false.
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virtual bool isNullValue() const { return false; }
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/// Override from Constant class.
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virtual void destroyConstant();
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/// isExternal - Return true if the primary definition of this global value is
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/// outside of the current translation unit...
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virtual bool isExternal() const = 0;
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/// getParent - Get the module that this global value is contained inside
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/// of...
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inline Module *getParent() { return Parent; }
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inline const Module *getParent() const { return Parent; }
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/// removeDeadConstantUsers - If there are any dead constant users dangling
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/// off of this global value, remove them. This method is useful for clients
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/// that want to check to see if a global is unused, but don't want to deal
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/// with potentially dead constants hanging off of the globals.
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///
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/// This method tries to make the global dead. If it detects a user that
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/// would prevent it from becoming completely dead, it gives up early,
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/// potentially leaving some dead constant users around.
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void removeDeadConstantUsers();
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// Methods for support type inquiry through isa, cast, and dyn_cast:
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static inline bool classof(const GlobalValue *T) { return true; }
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static inline bool classof(const Value *V) {
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return V->getValueType() == Value::FunctionVal ||
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V->getValueType() == Value::GlobalVariableVal;
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}
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};
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} // End llvm namespace
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#endif
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