/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import java.lang.reflect.Field;
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import java.util.concurrent.atomic.AtomicBoolean;
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import sun.misc.Unsafe;
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/**
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* Checker test on the 1.8 unsafe operations. Note, this is by no means an
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* exhaustive unit test for these CAS (compare-and-swap) and fence operations.
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* Instead, this test ensures the methods are recognized as intrinsic and behave
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* as expected.
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*/
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public class Main {
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private static final Unsafe unsafe = getUnsafe();
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private static Thread[] sThreads = new Thread[10];
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//
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// Fields accessed by setters and adders, and by memory fence tests.
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//
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public int i = 0;
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public long l = 0;
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public Object o = null;
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public int x_value;
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public int y_value;
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public volatile boolean running;
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//
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// Setters.
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//
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/// CHECK-START: int Main.set32(java.lang.Object, long, int) builder (after)
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/// CHECK-DAG: <<Result:i\d+>> InvokeVirtual intrinsic:UnsafeGetAndSetInt
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/// CHECK-DAG: Return [<<Result>>]
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private static int set32(Object o, long offset, int newValue) {
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return unsafe.getAndSetInt(o, offset, newValue);
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}
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/// CHECK-START: long Main.set64(java.lang.Object, long, long) builder (after)
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/// CHECK-DAG: <<Result:j\d+>> InvokeVirtual intrinsic:UnsafeGetAndSetLong
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/// CHECK-DAG: Return [<<Result>>]
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private static long set64(Object o, long offset, long newValue) {
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return unsafe.getAndSetLong(o, offset, newValue);
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}
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/// CHECK-START: java.lang.Object Main.setObj(java.lang.Object, long, java.lang.Object) builder (after)
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/// CHECK-DAG: <<Result:l\d+>> InvokeVirtual intrinsic:UnsafeGetAndSetObject
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/// CHECK-DAG: Return [<<Result>>]
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private static Object setObj(Object o, long offset, Object newValue) {
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return unsafe.getAndSetObject(o, offset, newValue);
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}
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//
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// Adders.
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//
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/// CHECK-START: int Main.add32(java.lang.Object, long, int) builder (after)
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/// CHECK-DAG: <<Result:i\d+>> InvokeVirtual intrinsic:UnsafeGetAndAddInt
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/// CHECK-DAG: Return [<<Result>>]
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private static int add32(Object o, long offset, int delta) {
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return unsafe.getAndAddInt(o, offset, delta);
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}
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/// CHECK-START: long Main.add64(java.lang.Object, long, long) builder (after)
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/// CHECK-DAG: <<Result:j\d+>> InvokeVirtual intrinsic:UnsafeGetAndAddLong
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/// CHECK-DAG: Return [<<Result>>]
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private static long add64(Object o, long offset, long delta) {
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return unsafe.getAndAddLong(o, offset, delta);
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}
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//
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// Fences (native).
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//
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/// CHECK-START: void Main.load() builder (after)
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/// CHECK-DAG: InvokeVirtual intrinsic:UnsafeLoadFence
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//
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/// CHECK-START: void Main.load() instruction_simplifier (after)
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/// CHECK-NOT: InvokeVirtual intrinsic:UnsafeLoadFence
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//
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/// CHECK-START: void Main.load() instruction_simplifier (after)
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/// CHECK-DAG: MemoryBarrier kind:LoadAny
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private static void load() {
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unsafe.loadFence();
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}
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/// CHECK-START: void Main.store() builder (after)
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/// CHECK-DAG: InvokeVirtual intrinsic:UnsafeStoreFence
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//
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/// CHECK-START: void Main.store() instruction_simplifier (after)
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/// CHECK-NOT: InvokeVirtual intrinsic:UnsafeStoreFence
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//
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/// CHECK-START: void Main.store() instruction_simplifier (after)
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/// CHECK-DAG: MemoryBarrier kind:AnyStore
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private static void store() {
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unsafe.storeFence();
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}
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/// CHECK-START: void Main.full() builder (after)
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/// CHECK-DAG: InvokeVirtual intrinsic:UnsafeFullFence
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//
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/// CHECK-START: void Main.full() instruction_simplifier (after)
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/// CHECK-NOT: InvokeVirtual intrinsic:UnsafeFullFence
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//
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/// CHECK-START: void Main.full() instruction_simplifier (after)
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/// CHECK-DAG: MemoryBarrier kind:AnyAny
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private static void full() {
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unsafe.fullFence();
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}
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//
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// Thread fork/join.
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//
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private static void fork(Runnable r) {
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for (int i = 0; i < 10; i++) {
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sThreads[i] = new Thread(r);
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}
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// Start the threads only after the full array has been written with new threads,
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// because one test relies on the contents of this array to be consistent.
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for (int i = 0; i < 10; i++) {
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sThreads[i].start();
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}
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}
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private static void join() {
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try {
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for (int i = 0; i < 10; i++) {
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sThreads[i].join();
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}
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} catch (InterruptedException e) {
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throw new Error("Failed join: " + e);
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}
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}
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//
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// Driver.
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//
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public static void main(String[] args) {
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System.out.println("starting");
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final Main m = new Main();
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// Get the offsets.
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final long intOffset, longOffset, objOffset;
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try {
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Field intField = Main.class.getDeclaredField("i");
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Field longField = Main.class.getDeclaredField("l");
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Field objField = Main.class.getDeclaredField("o");
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intOffset = unsafe.objectFieldOffset(intField);
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longOffset = unsafe.objectFieldOffset(longField);
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objOffset = unsafe.objectFieldOffset(objField);
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} catch (NoSuchFieldException e) {
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throw new Error("No offset: " + e);
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}
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// Some sanity on setters and adders within same thread.
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set32(m, intOffset, 3);
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expectEqual32(3, m.i);
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set64(m, longOffset, 7L);
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expectEqual64(7L, m.l);
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setObj(m, objOffset, m);
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expectEqualObj(m, m.o);
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add32(m, intOffset, 11);
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expectEqual32(14, m.i);
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add64(m, longOffset, 13L);
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expectEqual64(20L, m.l);
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// Some sanity on setters within different threads.
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fork(new Runnable() {
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public void run() {
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for (int i = 0; i < 10; i++)
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set32(m, intOffset, i);
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}
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});
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join();
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expectEqual32(9, m.i); // one thread's last value wins
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fork(new Runnable() {
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public void run() {
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for (int i = 0; i < 10; i++)
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set64(m, longOffset, (long) (100 + i));
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}
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});
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join();
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expectEqual64(109L, m.l); // one thread's last value wins
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fork(new Runnable() {
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public void run() {
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for (int i = 0; i < 10; i++)
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setObj(m, objOffset, sThreads[i]);
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}
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});
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join();
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expectEqualObj(sThreads[9], m.o); // one thread's last value wins
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// Some sanity on adders within different threads.
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fork(new Runnable() {
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public void run() {
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for (int i = 0; i < 10; i++)
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add32(m, intOffset, i + 1);
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}
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});
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join();
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expectEqual32(559, m.i); // all values accounted for
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fork(new Runnable() {
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public void run() {
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for (int i = 0; i < 10; i++)
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add64(m, longOffset, (long) (i + 1));
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}
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});
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join();
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expectEqual64(659L, m.l); // all values accounted for
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// Some sanity on fences within same thread. Note that memory fences within one
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// thread make little sense, but the sanity check ensures nothing bad happens.
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m.i = -1;
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m.l = -2L;
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m.o = null;
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load();
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store();
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full();
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expectEqual32(-1, m.i);
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expectEqual64(-2L, m.l);
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expectEqualObj(null, m.o);
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// Some sanity on full fence within different threads. We write the non-volatile m.l after
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// the fork(), which means there is no happens-before relation in the Java memory model
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// with respect to the read in the threads. This relation is enforced by the memory fences
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// and the weak-set() -> get() guard. Note that the guard semantics used here are actually
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// too strong and already enforce total memory visibility, but this test illustrates what
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// should still happen if Java had a true relaxed memory guard.
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final AtomicBoolean guard1 = new AtomicBoolean();
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m.l = 0L;
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fork(new Runnable() {
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public void run() {
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while (!guard1.get()); // busy-waiting
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full();
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expectEqual64(-123456789L, m.l);
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}
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});
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m.l = -123456789L;
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full();
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while (!guard1.weakCompareAndSet(false, true)); // relaxed memory order
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join();
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// Some sanity on release/acquire fences within different threads. We write the non-volatile
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// m.l after the fork(), which means there is no happens-before relation in the Java memory
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// model with respect to the read in the threads. This relation is enforced by the memory fences
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// and the weak-set() -> get() guard. Note that the guard semantics used here are actually
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// too strong and already enforce total memory visibility, but this test illustrates what
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// should still happen if Java had a true relaxed memory guard.
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final AtomicBoolean guard2 = new AtomicBoolean();
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m.l = 0L;
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fork(new Runnable() {
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public void run() {
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while (!guard2.get()); // busy-waiting
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load();
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expectEqual64(-987654321L, m.l);
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}
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});
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m.l = -987654321L;
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store();
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while (!guard2.weakCompareAndSet(false, true)); // relaxed memory order
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join();
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// Some sanity on release/acquire fences within different threads using a test suggested by
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// Hans Boehm. Even this test remains with the realm of sanity only, since having the threads
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// read the same value consistently would be a valid outcome.
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m.x_value = -1;
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m.y_value = -1;
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m.running = true;
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fork(new Runnable() {
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public void run() {
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while (m.running) {
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for (int few_times = 0; few_times < 1000; few_times++) {
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// Read y first, then load fence, then read x.
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// They should appear in order, if seen at all.
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int local_y = m.y_value;
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load();
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int local_x = m.x_value;
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expectLessThanOrEqual32(local_y, local_x);
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}
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}
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}
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});
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for (int many_times = 0; many_times < 100000; many_times++) {
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m.x_value = many_times;
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store();
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m.y_value = many_times;
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}
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m.running = false;
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join();
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// All done!
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System.out.println("passed");
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}
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// Use reflection to implement "Unsafe.getUnsafe()";
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private static Unsafe getUnsafe() {
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try {
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Class<?> unsafeClass = Unsafe.class;
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Field f = unsafeClass.getDeclaredField("theUnsafe");
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f.setAccessible(true);
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return (Unsafe) f.get(null);
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} catch (Exception e) {
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throw new Error("Cannot get Unsafe instance");
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}
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}
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private static void expectEqual32(int expected, int result) {
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if (expected != result) {
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throw new Error("Expected: " + expected + ", found: " + result);
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}
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}
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private static void expectLessThanOrEqual32(int val1, int val2) {
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if (val1 > val2) {
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throw new Error("Expected: " + val1 + " <= " + val2);
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}
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}
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private static void expectEqual64(long expected, long result) {
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if (expected != result) {
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throw new Error("Expected: " + expected + ", found: " + result);
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}
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}
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private static void expectEqualObj(Object expected, Object result) {
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if (expected != result) {
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throw new Error("Expected: " + expected + ", found: " + result);
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}
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}
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}
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