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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_MANAGED_STATIC_H
#define LLVM_SUPPORT_MANAGED_STATIC_H
#include "llvm/System/Atomic.h"
namespace llvm {
/// object_deleter - Helper method for ManagedStatic.
///
template<class C>
void object_deleter(void *Ptr) {
delete (C*)Ptr;
}
/// ManagedStaticBase - Common base class for ManagedStatic instances.
class ManagedStaticBase {
protected:
mutable sys::cas_flag InitFlag;
// This should only be used as a static variable, which guarantees that this
// will be zero initialized.
mutable void *Ptr;
mutable void (*DeleterFn)(void*);
mutable const ManagedStaticBase *Next;
void RegisterManagedStatic(void *ObjPtr, void (*deleter)(void*)) const;
public:
/// isConstructed - Return true if this object has not been created yet.
bool isConstructed() const { return Ptr != 0; }
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*() {
sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
if (OldFlag == 0) {
LazyInit();
sys::MemoryFence();
InitFlag = 2;
} else if (OldFlag == 1)
while (OldFlag == 1) ;
return *static_cast<C*>(Ptr);
}
C *operator->() {
sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
if (OldFlag == 0) {
LazyInit();
sys::MemoryFence();
InitFlag = 2;
} else if (OldFlag == 1)
while (OldFlag == 1) ;
return static_cast<C*>(Ptr);
}
const C &operator*() const {
sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
if (OldFlag == 0) {
LazyInit();
sys::MemoryFence();
InitFlag = 2;
} else if (OldFlag == 1)
while (InitFlag == 1) ;
return *static_cast<C*>(Ptr);
}
const C *operator->() const {
sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
if (OldFlag == 0) {
LazyInit();
sys::MemoryFence();
InitFlag = 2;
} else if (OldFlag == 1)
while (OldFlag == 1) ;
return static_cast<C*>(Ptr);
}
public:
void LazyInit() const {
RegisterManagedStatic(new C(), object_deleter<C>);
}
};
template<void (*CleanupFn)(void*)>
class ManagedCleanup : public ManagedStaticBase {
public:
void Register() { RegisterManagedStatic(0, CleanupFn); }
};
/// 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() {}
~llvm_shutdown_obj() { llvm_shutdown(); }
};
}
#endif
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