Daniel Andersson
e7fb1c8516
Using volatile on a word size location will generate a single move instruction without order guarantees and is supported on all compilers. Replace FetchAndAdd with FetchAndDecrement, since the latter is sufficient and eaiser to implement portably (in particular on some Windows setups). BUG=https://github.com/dart-lang/sdk/issues/24049 R=iposva@google.com Review URL: https://codereview.chromium.org//1287853005 .
64 lines
1.9 KiB
C++
64 lines
1.9 KiB
C++
// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef VM_ATOMIC_H_
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#define VM_ATOMIC_H_
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#include "platform/globals.h"
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#include "vm/allocation.h"
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#include "vm/simulator.h"
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namespace dart {
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class AtomicOperations : public AllStatic {
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public:
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// Atomically fetch the value at p and increment the value at p.
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// Returns the original value at p.
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//
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// NOTE: Not to be used for any atomic operations involving memory locations
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// that are accessed by generated code
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static uintptr_t FetchAndIncrement(uintptr_t* p);
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// Atomically fetch the value at p and decrement the value at p.
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// Returns the original value at p.
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//
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// NOTE: Not to be used for any atomic operations involving memory locations
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// that are accessed by generated code
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static uintptr_t FetchAndDecrement(uintptr_t* p);
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// Atomically compare *ptr to old_value, and if equal, store new_value.
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// Returns the original value at ptr.
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//
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// NOTE: OK to use with memory locations that are accessed by generated code
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static uword CompareAndSwapWord(uword* ptr, uword old_value, uword new_value);
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// Performs a load of a word from 'ptr', but without any guarantees about
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// memory order (i.e., no load barriers/fences).
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static uword LoadRelaxed(uword* ptr) {
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return *static_cast<volatile uword*>(ptr);
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}
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};
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} // namespace dart
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// We need to use the simulator to ensure that atomic operations are observed
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// both in C++ and in generated code if the simulator is active.
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#include "vm/atomic_simulator.h"
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#if defined(TARGET_OS_ANDROID)
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#include "vm/atomic_android.h"
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#elif defined(TARGET_OS_LINUX)
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#include "vm/atomic_linux.h"
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#elif defined(TARGET_OS_MACOS)
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#include "vm/atomic_macos.h"
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#elif defined(TARGET_OS_WINDOWS)
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#include "vm/atomic_win.h"
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#else
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#error Unknown target os.
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#endif
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#endif // VM_ATOMIC_H_
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