6024e5c395
clang 20.0.0 (based on r547379) from build 12806354. Bug: http://b/379133546 Test: N/A Change-Id: I2eb8938af55d809de674be63cb30cf27e801862b Upstream-Commit: ad834e67b1105d15ef907f6255d4c96e8e733f57
63 lines
2.0 KiB
C++
63 lines
2.0 KiB
C++
//===- ThreadSafeAllocator.h ------------------------------------*- 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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#ifndef LLVM_SUPPORT_THREADSAFEALLOCATOR_H
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#define LLVM_SUPPORT_THREADSAFEALLOCATOR_H
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Support/Allocator.h"
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#include <atomic>
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namespace llvm {
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/// Thread-safe allocator adaptor. Uses a spin lock on the assumption that
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/// contention here is extremely rare.
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///
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/// TODO: Using a spin lock on every allocation can be quite expensive when
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/// contention is high. Since this is mainly used for BumpPtrAllocator and
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/// SpecificBumpPtrAllocator, it'd be better to have a specific thread-safe
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/// BumpPtrAllocator implementation that only use a fair lock when allocating a
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/// new slab but otherwise using atomic and be lock-free.
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template <class AllocatorType> class ThreadSafeAllocator {
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struct LockGuard {
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LockGuard(std::atomic_flag &Flag) : Flag(Flag) {
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if (LLVM_UNLIKELY(Flag.test_and_set(std::memory_order_acquire)))
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while (Flag.test_and_set(std::memory_order_acquire)) {
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}
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}
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~LockGuard() { Flag.clear(std::memory_order_release); }
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std::atomic_flag &Flag;
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};
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public:
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auto Allocate(size_t N) {
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return applyLocked([N](AllocatorType &Alloc) { return Alloc.Allocate(N); });
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}
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auto Allocate(size_t Size, size_t Align) {
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return applyLocked([Size, Align](AllocatorType &Alloc) {
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return Alloc.Allocate(Size, Align);
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});
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}
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template <typename FnT,
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typename T = typename llvm::function_traits<FnT>::result_t>
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T applyLocked(FnT Fn) {
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LockGuard Lock(Flag);
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return Fn(Alloc);
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}
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private:
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AllocatorType Alloc;
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std::atomic_flag Flag = ATOMIC_FLAG_INIT;
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};
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} // namespace llvm
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#endif // LLVM_SUPPORT_THREADSAFEALLOCATOR_H
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