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https://github.com/c64scene-ar/llvm-6502.git
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This matches gcc's behavior. It also seems natural given that aliases contain other properties that govern how it is accessed (linkage, visibility, dll storage). Clang still has to be updated to expose this feature to C. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209759 91177308-0d34-0410-b5e6-96231b3b80d8
188 lines
7.4 KiB
C++
188 lines
7.4 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/GlobalObject.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 GlobalObject, 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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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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/// 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 = nullptr, 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 = nullptr,
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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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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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