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//===-- llvm/Support/ManagedStatic.h - Static Global wrapper ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the ManagedStatic class and the llvm_shutdown() function.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_MANAGEDSTATIC_H
#define LLVM_SUPPORT_MANAGEDSTATIC_H
#include "llvm/Support/Compiler.h"
#include <atomic>
#include <cstddef>
namespace llvm {
/// object_creator - Helper method for ManagedStatic.
template<class C>
LLVM_LIBRARY_VISIBILITY void* object_creator() {
return new C();
}
/// object_deleter - Helper method for ManagedStatic.
///
template <typename T> struct LLVM_LIBRARY_VISIBILITY object_deleter {
static void call(void *Ptr) { delete (T *)Ptr; }
};
template <typename T, size_t N>
struct LLVM_LIBRARY_VISIBILITY object_deleter<T[N]> {
static void call(void *Ptr) { delete[](T *)Ptr; }
};
/// ManagedStaticBase - Common base class for ManagedStatic instances.
class ManagedStaticBase {
protected:
// This should only be used as a static variable, which guarantees that this
// will be zero initialized.
mutable std::atomic<void *> Ptr;
mutable void (*DeleterFn)(void*);
mutable const ManagedStaticBase *Next;
void RegisterManagedStatic(void *(*creator)(), void (*deleter)(void*)) const;
public:
/// isConstructed - Return true if this object has not been created yet.
bool isConstructed() const { return Ptr != nullptr; }
void destroy() const;
};
/// ManagedStatic - This transparently changes the behavior of global statics to
/// be lazily constructed on demand (good for reducing startup times of dynamic
/// libraries that link in LLVM components) and for making destruction be
/// explicit through the llvm_shutdown() function call.
///
template<class C>
class ManagedStatic : public ManagedStaticBase {
public:
// Accessors.
C &operator*() {
void *Tmp = Ptr.load(std::memory_order_acquire);
if (!Tmp)
RegisterManagedStatic(object_creator<C>, object_deleter<C>::call);
return *static_cast<C *>(Ptr.load(std::memory_order_relaxed));
}
C *operator->() { return &**this; }
const C &operator*() const {
void *Tmp = Ptr.load(std::memory_order_acquire);
if (!Tmp)
RegisterManagedStatic(object_creator<C>, object_deleter<C>::call);
return *static_cast<C *>(Ptr.load(std::memory_order_relaxed));
}
const C *operator->() const { return &**this; }
};
/// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
void llvm_shutdown();
/// llvm_shutdown_obj - This is a simple helper class that calls
/// llvm_shutdown() when it is destroyed.
struct llvm_shutdown_obj {
llvm_shutdown_obj() = default;
~llvm_shutdown_obj() { llvm_shutdown(); }
};
} // end namespace llvm
#endif // LLVM_SUPPORT_MANAGEDSTATIC_H