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Differential D133714 Diff 459512 llvm/unittests/ADT/LazyAtomicPointerTest.cpp

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llvm/unittests/ADT/LazyAtomicPointerTest.cpp

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				//===- LazyAtomicPointerTest.cpp ------------------------------------------===//
				//
				// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
				// See https://llvm.org/LICENSE.txt for license information.
				// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
				//
				//===----------------------------------------------------------------------===//

				#include "llvm/ADT/LazyAtomicPointer.h"
				#include "llvm/Support/ThreadPool.h"
				#include "gtest/gtest.h"

				using namespace llvm;

				namespace {

				TEST(LazyAtomicPointer, loadOrGenerate) {
				int Value = 0;
				LazyAtomicPointer<int> Ptr;
				ThreadPool Threads;
				for (unsigned I = 0; I < 4; ++I)
				Threads.async([&]() {
				Ptr.loadOrGenerate([&]() {
				// Make sure this is only called once.
				static std::atomic<bool> Once(false);
				bool Current = false;
				EXPECT_TRUE(Once.compare_exchange_strong(Current, true));
				return &Value;
				});
				});

				Threads.wait();

				EXPECT_EQ(Ptr.load(), &Value);
				}

				TEST(LazyAtomicPointer, BusyState) {
				int Value = 0;
				LazyAtomicPointer<int> Ptr;
				ThreadPool Threads;

				std::mutex BusyStart, BusyEnd;
				BusyStart.lock();
				BusyEnd.lock();
				Threads.async([&]() {
				Ptr.loadOrGenerate([&]() {
				BusyStart.unlock();
				while (!BusyEnd.try_lock()) {
				// wait till the lock is unlocked.
				}
				return &Value;
				});
				});

				// Wait for busy state.
				std::lock_guard<std::mutex> BusyLockG(BusyStart);
				int *ExistingValue = nullptr;
				// Busy state will not exchange the value.
				EXPECT_FALSE(Ptr.compare_exchange_weak(ExistingValue, nullptr));
				// Busy state return nullptr on load/compare_exchange_weak.
				EXPECT_EQ(ExistingValue, nullptr);
				EXPECT_EQ(Ptr.load(), nullptr);

				// End busy state.
				BusyEnd.unlock();
				Threads.wait();
				EXPECT_EQ(Ptr.load(), &Value);
				}

				} // namespace