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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202939 91177308-0d34-0410-b5e6-96231b3b80d8
209 lines
8.2 KiB
C++
209 lines
8.2 KiB
C++
//===-- llvm/GlobalVariable.h - GlobalVariable class ------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains the declaration of the GlobalVariable class, which
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// represents a single global variable (or constant) in the VM.
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//
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// Global variables are constant pointers that refer to hunks of space that are
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// allocated by either the VM, or by the linker in a static compiler. A global
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// variable may have an initial value, which is copied into the executables .data
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// area. Global Constants are required to have initializers.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_IR_GLOBALVARIABLE_H
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#define LLVM_IR_GLOBALVARIABLE_H
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#include "llvm/ADT/Twine.h"
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#include "llvm/ADT/ilist_node.h"
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#include "llvm/IR/GlobalValue.h"
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#include "llvm/IR/OperandTraits.h"
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namespace llvm {
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class Module;
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class Constant;
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template<typename ValueSubClass, typename ItemParentClass>
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class SymbolTableListTraits;
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class GlobalVariable : public GlobalValue, public ilist_node<GlobalVariable> {
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friend class SymbolTableListTraits<GlobalVariable, Module>;
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void *operator new(size_t, unsigned) LLVM_DELETED_FUNCTION;
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void operator=(const GlobalVariable &) LLVM_DELETED_FUNCTION;
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GlobalVariable(const GlobalVariable &) LLVM_DELETED_FUNCTION;
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void setParent(Module *parent);
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bool isConstantGlobal : 1; // Is this a global constant?
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unsigned threadLocalMode : 3; // Is this symbol "Thread Local",
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// if so, what is the desired
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// model?
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bool isExternallyInitializedConstant : 1; // Is this a global whose value
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// can change from its initial
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// value before global
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// initializers are run?
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public:
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// allocate space for exactly one operand
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void *operator new(size_t s) {
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return User::operator new(s, 1);
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}
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enum ThreadLocalMode {
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NotThreadLocal = 0,
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GeneralDynamicTLSModel,
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LocalDynamicTLSModel,
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InitialExecTLSModel,
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LocalExecTLSModel
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};
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/// GlobalVariable ctor - If a parent module is specified, the global is
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/// automatically inserted into the end of the specified modules global list.
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GlobalVariable(Type *Ty, bool isConstant, LinkageTypes Linkage,
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Constant *Initializer = 0, const Twine &Name = "",
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ThreadLocalMode = NotThreadLocal, unsigned AddressSpace = 0,
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bool isExternallyInitialized = false);
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/// GlobalVariable ctor - This creates a global and inserts it before the
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/// specified other global.
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GlobalVariable(Module &M, Type *Ty, bool isConstant,
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LinkageTypes Linkage, Constant *Initializer,
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const Twine &Name = "", GlobalVariable *InsertBefore = 0,
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ThreadLocalMode = NotThreadLocal, unsigned AddressSpace = 0,
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bool isExternallyInitialized = false);
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~GlobalVariable() {
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NumOperands = 1; // FIXME: needed by operator delete
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}
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/// Provide fast operand accessors
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DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
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/// Definitions have initializers, declarations don't.
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///
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inline bool hasInitializer() const { return !isDeclaration(); }
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/// hasDefinitiveInitializer - Whether the global variable has an initializer,
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/// and any other instances of the global (this can happen due to weak
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/// linkage) are guaranteed to have the same initializer.
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///
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/// Note that if you want to transform a global, you must use
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/// hasUniqueInitializer() instead, because of the *_odr linkage type.
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///
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/// Example:
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///
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/// @a = global SomeType* null - Initializer is both definitive and unique.
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///
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/// @b = global weak SomeType* null - Initializer is neither definitive nor
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/// unique.
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///
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/// @c = global weak_odr SomeType* null - Initializer is definitive, but not
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/// unique.
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inline bool hasDefinitiveInitializer() const {
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return hasInitializer() &&
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// The initializer of a global variable with weak linkage may change at
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// link time.
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!mayBeOverridden() &&
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// The initializer of a global variable with the externally_initialized
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// marker may change at runtime before C++ initializers are evaluated.
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!isExternallyInitialized();
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}
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/// hasUniqueInitializer - Whether the global variable has an initializer, and
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/// any changes made to the initializer will turn up in the final executable.
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inline bool hasUniqueInitializer() const {
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return hasInitializer() &&
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// It's not safe to modify initializers of global variables with weak
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// linkage, because the linker might choose to discard the initializer and
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// use the initializer from another instance of the global variable
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// instead. It is wrong to modify the initializer of a global variable
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// with *_odr linkage because then different instances of the global may
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// have different initializers, breaking the One Definition Rule.
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!isWeakForLinker() &&
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// It is not safe to modify initializers of global variables with the
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// external_initializer marker since the value may be changed at runtime
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// before C++ initializers are evaluated.
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!isExternallyInitialized();
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}
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/// getInitializer - Return the initializer for this global variable. It is
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/// illegal to call this method if the global is external, because we cannot
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/// tell what the value is initialized to!
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///
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inline const Constant *getInitializer() const {
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assert(hasInitializer() && "GV doesn't have initializer!");
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return static_cast<Constant*>(Op<0>().get());
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}
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inline Constant *getInitializer() {
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assert(hasInitializer() && "GV doesn't have initializer!");
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return static_cast<Constant*>(Op<0>().get());
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}
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/// setInitializer - Sets the initializer for this global variable, removing
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/// any existing initializer if InitVal==NULL. If this GV has type T*, the
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/// initializer must have type T.
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void setInitializer(Constant *InitVal);
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/// If the value is a global constant, its value is immutable throughout the
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/// runtime execution of the program. Assigning a value into the constant
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/// leads to undefined behavior.
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///
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bool isConstant() const { return isConstantGlobal; }
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void setConstant(bool Val) { isConstantGlobal = Val; }
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/// If the value is "Thread Local", its value isn't shared by the threads.
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bool isThreadLocal() const { return threadLocalMode != NotThreadLocal; }
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void setThreadLocal(bool Val) {
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threadLocalMode = Val ? GeneralDynamicTLSModel : NotThreadLocal;
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}
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void setThreadLocalMode(ThreadLocalMode Val) { threadLocalMode = Val; }
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ThreadLocalMode getThreadLocalMode() const {
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return static_cast<ThreadLocalMode>(threadLocalMode);
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}
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bool isExternallyInitialized() const {
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return isExternallyInitializedConstant;
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}
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void setExternallyInitialized(bool Val) {
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isExternallyInitializedConstant = Val;
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}
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/// copyAttributesFrom - copy all additional attributes (those not needed to
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/// create a GlobalVariable) from the GlobalVariable Src to this one.
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void copyAttributesFrom(const GlobalValue *Src) override;
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/// removeFromParent - This method unlinks 'this' from the containing module,
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/// but does not delete it.
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///
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void removeFromParent() override;
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/// eraseFromParent - This method unlinks 'this' from the containing module
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/// and deletes it.
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///
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void eraseFromParent() override;
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/// Override Constant's implementation of this method so we can
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/// replace constant initializers.
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void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U) override;
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// Methods for support type inquiry through isa, cast, and dyn_cast:
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static inline bool classof(const Value *V) {
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return V->getValueID() == Value::GlobalVariableVal;
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}
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};
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template <>
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struct OperandTraits<GlobalVariable> :
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public OptionalOperandTraits<GlobalVariable> {
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};
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DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value)
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} // End llvm namespace
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#endif
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