235 lines
7.9 KiB
Java
235 lines
7.9 KiB
Java
/*
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* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package compiler.gcbarriers;
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import compiler.lib.ir_framework.*;
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import java.lang.invoke.VarHandle;
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import java.lang.invoke.MethodHandles;
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import java.lang.ref.Reference;
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import java.lang.ref.ReferenceQueue;
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import java.lang.ref.SoftReference;
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import java.lang.ref.WeakReference;
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import jdk.test.lib.Asserts;
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/**
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* @test
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* @summary Test that implicit null checks are generated as expected for
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different GC memory accesses.
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* @library /test/lib /
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* @run driver compiler.gcbarriers.TestImplicitNullChecks
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*/
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public class TestImplicitNullChecks {
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static class Outer {
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Object f;
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}
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static class OuterWithVolatileField {
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volatile Object f;
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}
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static final VarHandle fVarHandle;
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static {
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MethodHandles.Lookup l = MethodHandles.lookup();
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try {
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fVarHandle = l.findVarHandle(Outer.class, "f", Object.class);
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} catch (Exception e) {
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throw new Error(e);
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}
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}
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public static void main(String[] args) {
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TestFramework.runWithFlags("-XX:CompileCommand=inline,java.lang.ref.*::*",
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"-XX:-TieredCompilation");
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}
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@Test
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// On AIX, implicit null checks are limited because the zero page is
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// readable (but not writable). See os::zero_page_read_protected().
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@IR(applyIfPlatform = {"aix", "false"},
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applyIfOr = {"UseZGC", "true", "UseG1GC", "true"},
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counts = {IRNode.NULL_CHECK, "1"},
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phase = CompilePhase.FINAL_CODE)
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static Object testLoad(Outer o) {
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return o.f;
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}
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@Test
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// On aarch64, volatile loads always use indirect memory operands, which
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// leads to a pattern that cannot be exploited by the current C2 analysis.
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// On PPC64, volatile loads are preceded by membar_volatile instructions,
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// which also inhibits the current C2 analysis.
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@IR(applyIfPlatformAnd = {"aarch64", "false", "ppc", "false"},
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applyIfOr = {"UseZGC", "true", "UseG1GC", "true"},
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counts = {IRNode.NULL_CHECK, "1"},
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phase = CompilePhase.FINAL_CODE)
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static Object testLoadVolatile(OuterWithVolatileField o) {
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return o.f;
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}
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@Run(test = {"testLoad",
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"testLoadVolatile"},
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mode = RunMode.STANDALONE)
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static void runLoadTests() {
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{
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Outer o = new Outer();
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// Trigger compilation with implicit null check.
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for (int i = 0; i < 10_000; i++) {
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testLoad(o);
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}
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// Trigger null pointer exception.
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o = null;
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boolean nullPointerException = false;
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try {
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testLoad(o);
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} catch (NullPointerException e) { nullPointerException = true; }
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Asserts.assertTrue(nullPointerException);
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}
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{
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OuterWithVolatileField o = new OuterWithVolatileField();
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// Trigger compilation with implicit null check.
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for (int i = 0; i < 10_000; i++) {
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testLoadVolatile(o);
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}
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// Trigger null pointer exception.
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o = null;
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boolean nullPointerException = false;
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try {
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testLoadVolatile(o);
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} catch (NullPointerException e) { nullPointerException = true; }
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Asserts.assertTrue(nullPointerException);
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}
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}
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@Test
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// G1 and ZGC stores cannot be currently used to implement implicit null
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// checks, because they expand into multiple memory access instructions that
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// are not necessarily located at the initial instruction start address.
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@IR(applyIfOr = {"UseZGC", "true", "UseG1GC", "true"},
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failOn = IRNode.NULL_CHECK,
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phase = CompilePhase.FINAL_CODE)
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static void testStore(Outer o, Object o1) {
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o.f = o1;
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}
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@Run(test = {"testStore"})
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static void runStoreTests() {
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{
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Outer o = new Outer();
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Object o1 = new Object();
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testStore(o, o1);
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}
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}
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@Test
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// G1 and ZGC compare-and-exchange operations cannot be currently used to
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// implement implicit null checks, because they expand into multiple memory
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// access instructions that are not necessarily located at the initial
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// instruction start address. The same holds for testCompareAndSwap and
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// testGetAndSet below.
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@IR(applyIfOr = {"UseZGC", "true", "UseG1GC", "true"},
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failOn = IRNode.NULL_CHECK,
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phase = CompilePhase.FINAL_CODE)
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static Object testCompareAndExchange(Outer o, Object oldVal, Object newVal) {
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return fVarHandle.compareAndExchange(o, oldVal, newVal);
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}
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@Test
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@IR(applyIfOr = {"UseZGC", "true", "UseG1GC", "true"},
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failOn = IRNode.NULL_CHECK,
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phase = CompilePhase.FINAL_CODE)
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static boolean testCompareAndSwap(Outer o, Object oldVal, Object newVal) {
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return fVarHandle.compareAndSet(o, oldVal, newVal);
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}
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@Test
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@IR(applyIfOr = {"UseZGC", "true", "UseG1GC", "true"},
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failOn = IRNode.NULL_CHECK,
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phase = CompilePhase.FINAL_CODE)
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static Object testGetAndSet(Outer o, Object newVal) {
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return fVarHandle.getAndSet(o, newVal);
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}
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@Run(test = {"testCompareAndExchange",
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"testCompareAndSwap",
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"testGetAndSet"})
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static void runAtomicTests() {
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{
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Outer o = new Outer();
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Object oldVal = new Object();
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Object newVal = new Object();
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testCompareAndExchange(o, oldVal, newVal);
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}
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{
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Outer o = new Outer();
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Object oldVal = new Object();
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Object newVal = new Object();
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testCompareAndSwap(o, oldVal, newVal);
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}
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{
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Outer o = new Outer();
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Object oldVal = new Object();
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Object newVal = new Object();
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testGetAndSet(o, newVal);
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}
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}
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@Test
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// G1 reference loads use indirect memory operands, which leads to a pattern
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// that cannot be exploited by the current C2 analysis. The same holds for
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// testLoadWeakReference.
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@IR(applyIf = {"UseZGC", "true"},
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counts = {IRNode.NULL_CHECK, "1"},
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phase = CompilePhase.FINAL_CODE)
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static Object testLoadSoftReference(SoftReference<Object> ref) {
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return ref.get();
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}
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@Test
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@IR(applyIf = {"UseZGC", "true"},
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counts = {IRNode.NULL_CHECK, "1"},
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phase = CompilePhase.FINAL_CODE)
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static Object testLoadWeakReference(WeakReference<Object> ref) {
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return ref.get();
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}
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@Run(test = {"testLoadSoftReference",
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"testLoadWeakReference"})
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static void runReferenceTests() {
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{
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Object o1 = new Object();
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SoftReference<Object> sref = new SoftReference<Object>(o1);
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Object o2 = testLoadSoftReference(sref);
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}
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{
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Object o1 = new Object();
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WeakReference<Object> wref = new WeakReference<Object>(o1);
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Object o2 = testLoadWeakReference(wref);
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}
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}
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}
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