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8257594: C2 compiled checkcast of non-null object triggers endless de…
…optimization/recompilation cycle

Reviewed-by: roland, vlivanov
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TobiHartmann committed Dec 3, 2020
1 parent e4497c9 commit 129c37700ff1ab6f2b9540422f93689970b5e9a0
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Showing 4 changed files with 133 additions and 2 deletions.
@@ -3311,7 +3311,13 @@ Node* GraphKit::gen_checkcast(Node *obj, Node* superklass,
case Compile::SSC_always_false:
// It needs a null check because a null will *pass* the cast check.
// A non-null value will always produce an exception.
return null_assert(obj);
if (!objtp->maybe_null()) {
builtin_throw(Deoptimization::Reason_class_check, makecon(TypeKlassPtr::make(objtp->klass())));
return top();
} else if (!too_many_traps_or_recompiles(Deoptimization::Reason_null_assert)) {
return null_assert(obj);
}
break; // Fall through to full check
}
}
}
@@ -83,6 +83,9 @@ void Parse::array_store(BasicType bt) {
if (stopped()) return; // guaranteed null or range check
if (bt == T_OBJECT) {
array_store_check();
if (stopped()) {
return;
}
}
Node* val; // Oop to store
if (big_val) {
@@ -89,7 +89,10 @@ void Parse::do_checkcast() {
return;
}

Node *res = gen_checkcast(obj, makecon(TypeKlassPtr::make(klass)) );
Node* res = gen_checkcast(obj, makecon(TypeKlassPtr::make(klass)));
if (stopped()) {
return;
}

// Pop from stack AFTER gen_checkcast because it can uncommon trap and
// the debug info has to be correct.
@@ -0,0 +1,119 @@
/*
* Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/

/*
* @test
* @bug 8257594
* @summary Test that failing checkcast does not trigger repeated recompilation until cutoff is hit.
* @requires vm.compiler2.enabled
* @modules java.base/jdk.internal.misc
* @library /test/lib
* @build sun.hotspot.WhiteBox
* @run driver ClassFileInstaller sun.hotspot.WhiteBox
* @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
* -Xbatch -XX:CompileCommand=dontinline,compiler.uncommontrap.TestNullAssertAtCheckCast::test*
* -XX:CompileCommand=inline,compiler.uncommontrap.TestNullAssertAtCheckCast::cast
* -XX:CompileCommand=inline,compiler.uncommontrap.TestNullAssertAtCheckCast::store
* compiler.uncommontrap.TestNullAssertAtCheckCast
*/

package compiler.uncommontrap;

import sun.hotspot.WhiteBox;

import java.lang.reflect.Method;

public class TestNullAssertAtCheckCast {
private static final WhiteBox WB = WhiteBox.getWhiteBox();
private static final int COMP_LEVEL_FULL_OPTIMIZATION = 4;

static Long cast(Object val) {
return (Long)val;
}

static void test1() {
try {
// Always fails
cast(new Integer(42));
} catch (ClassCastException cce) {
// Ignored
}
}

static void test2(Integer val) {
try {
// Always fails
cast(val);
} catch (ClassCastException cce) {
// Ignored
}
}

static void store(Object[] array, Object val) {
array[0] = val;
}

static void test3() {
try {
// Always fails
store(new Long[1], new Integer(42));
} catch (ArrayStoreException cce) {
// Ignored
}
}

static void test4(Integer val) {
try {
// Always fails
store(new Long[1], val);
} catch (ArrayStoreException cce) {
// Ignored
}
}

public static void main(String[] args) throws Exception {
for (int i = 0; i < 1_000_000; ++i) {
test1();
test2((i % 2 == 0) ? null : 42);
test3();
test4((i % 2 == 0) ? null : 42);
}
Method method = TestNullAssertAtCheckCast.class.getDeclaredMethod("test1");
if (!WB.isMethodCompilable(method, COMP_LEVEL_FULL_OPTIMIZATION, false)) {
throw new RuntimeException("TestNullAssertAtCheckCast::test1 not compilable");
}
method = TestNullAssertAtCheckCast.class.getDeclaredMethod("test2", Integer.class);
if (!WB.isMethodCompilable(method, COMP_LEVEL_FULL_OPTIMIZATION, false)) {
throw new RuntimeException("TestNullAssertAtCheckCast::test2 not compilable");
}
method = TestNullAssertAtCheckCast.class.getDeclaredMethod("test3");
if (!WB.isMethodCompilable(method, COMP_LEVEL_FULL_OPTIMIZATION, false)) {
throw new RuntimeException("TestNullAssertAtCheckCast::test3 not compilable");
}
method = TestNullAssertAtCheckCast.class.getDeclaredMethod("test4", Integer.class);
if (!WB.isMethodCompilable(method, COMP_LEVEL_FULL_OPTIMIZATION, false)) {
throw new RuntimeException("TestNullAssertAtCheckCast::test4 not compilable");
}
}
}

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