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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
97 lines
3.0 KiB
C++
97 lines
3.0 KiB
C++
//===-- llvm/Support/ManagedStatic.h - Static Global wrapper ----*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the ManagedStatic class and the llvm_shutdown() function.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_MANAGEDSTATIC_H
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#define LLVM_SUPPORT_MANAGEDSTATIC_H
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#include <atomic>
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#include <cstddef>
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namespace llvm {
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/// object_creator - Helper method for ManagedStatic.
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template <class C> struct object_creator {
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static void *call() { return new C(); }
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};
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/// object_deleter - Helper method for ManagedStatic.
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///
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template <typename T> struct object_deleter {
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static void call(void *Ptr) { delete (T *)Ptr; }
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};
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template <typename T, size_t N> struct object_deleter<T[N]> {
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static void call(void *Ptr) { delete[](T *)Ptr; }
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};
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/// ManagedStaticBase - Common base class for ManagedStatic instances.
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class ManagedStaticBase {
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protected:
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// This should only be used as a static variable, which guarantees that this
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// will be zero initialized.
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mutable std::atomic<void *> Ptr;
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mutable void (*DeleterFn)(void*);
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mutable const ManagedStaticBase *Next;
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void RegisterManagedStatic(void *(*creator)(), void (*deleter)(void*)) const;
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public:
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/// isConstructed - Return true if this object has not been created yet.
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bool isConstructed() const { return Ptr != nullptr; }
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void destroy() const;
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};
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/// ManagedStatic - This transparently changes the behavior of global statics to
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/// be lazily constructed on demand (good for reducing startup times of dynamic
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/// libraries that link in LLVM components) and for making destruction be
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/// explicit through the llvm_shutdown() function call.
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///
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template <class C, class Creator = object_creator<C>,
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class Deleter = object_deleter<C>>
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class ManagedStatic : public ManagedStaticBase {
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public:
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// Accessors.
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C &operator*() {
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void *Tmp = Ptr.load(std::memory_order_acquire);
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if (!Tmp)
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RegisterManagedStatic(Creator::call, Deleter::call);
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return *static_cast<C *>(Ptr.load(std::memory_order_relaxed));
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}
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C *operator->() { return &**this; }
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const C &operator*() const {
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void *Tmp = Ptr.load(std::memory_order_acquire);
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if (!Tmp)
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RegisterManagedStatic(Creator::call, Deleter::call);
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return *static_cast<C *>(Ptr.load(std::memory_order_relaxed));
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}
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const C *operator->() const { return &**this; }
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};
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/// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
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void llvm_shutdown();
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/// llvm_shutdown_obj - This is a simple helper class that calls
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/// llvm_shutdown() when it is destroyed.
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struct llvm_shutdown_obj {
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llvm_shutdown_obj() = default;
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~llvm_shutdown_obj() { llvm_shutdown(); }
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};
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} // end namespace llvm
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#endif // LLVM_SUPPORT_MANAGEDSTATIC_H
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