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8330699: Obsolete -XX:+UseEmptySlotsInSupers

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Reviewed-by: shade, fparain, dholmes
This commit is contained in:
Coleen Phillimore 2024-06-20 19:03:50 +00:00
parent 187710e1c1
commit 4b4a483b6f
4 changed files with 3 additions and 100 deletions
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18
src/hotspot/share/classfile/fieldLayoutBuilder.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2020, 2024, 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
@ -137,7 +137,7 @@ void FieldLayout::initialize_instance_layout(const InstanceKlass* super_klass) {
} else {
bool has_fields = reconstruct_layout(super_klass);
fill_holes(super_klass);
if ((UseEmptySlotsInSupers && !super_klass->has_contended_annotations()) || !has_fields) {
if (!super_klass->has_contended_annotations() || !has_fields) {
_start = _blocks; // start allocating fields from the first empty block
} else {
_start = _last; // append fields at the end of the reconstructed layout
@ -364,20 +364,6 @@ void FieldLayout::fill_holes(const InstanceKlass* super_klass) {
b = p;
}
if (!UseEmptySlotsInSupers) {
// Add an empty slots to align fields of the subclass on a heapOopSize boundary
// in order to emulate the behavior of the previous algorithm
int align = (b->offset() + b->size()) % heapOopSize;
if (align != 0) {
int sz = heapOopSize - align;
LayoutRawBlock* p = new LayoutRawBlock(LayoutRawBlock::EMPTY, sz);
p->set_offset(b->offset() + b->size());
b->set_next_block(p);
p->set_prev_block(b);
b = p;
}
}
LayoutRawBlock* last = new LayoutRawBlock(LayoutRawBlock::EMPTY, INT_MAX);
last->set_offset(b->offset() + b->size());
assert(last->offset() > 0, "Sanity check");

2
src/hotspot/share/runtime/arguments.cpp
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@ -505,7 +505,6 @@ static SpecialFlag const special_jvm_flags[] = {
{ "DontYieldALot", JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
{ "PreserveAllAnnotations", JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
{ "UseNotificationThread", JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
{ "UseEmptySlotsInSupers", JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
// --- Deprecated alias flags (see also aliased_jvm_flags) - sorted by obsolete_in then expired_in:
{ "CreateMinidumpOnCrash", JDK_Version::jdk(9), JDK_Version::undefined(), JDK_Version::undefined() },
@ -513,6 +512,7 @@ static SpecialFlag const special_jvm_flags[] = {
{ "MetaspaceReclaimPolicy", JDK_Version::undefined(), JDK_Version::jdk(21), JDK_Version::undefined() },
{ "UseEmptySlotsInSupers", JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
{ "OldSize", JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
#if defined(X86)
{ "UseRTMLocking", JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },

4
src/hotspot/share/runtime/globals.hpp
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@ -1948,10 +1948,6 @@ const int ObjectAlignmentInBytes = 8;
product(bool, UseFastUnorderedTimeStamps, false, EXPERIMENTAL, \
"Use platform unstable time where supported for timestamps only") \
\
product(bool, UseEmptySlotsInSupers, true, \
"(Deprecated) Allow allocating fields in empty slots of " \
"super-classes") \
\
product(bool, DeoptimizeNMethodBarriersALot, false, DIAGNOSTIC, \
"Make nmethod barriers deoptimise a lot.") \
\

79
test/hotspot/jtreg/runtime/FieldLayout/OldLayoutCheck.java
View File

@ -1,79 +0,0 @@
/*
* 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 8239014
* @summary -XX:-UseEmptySlotsInSupers sometime fails to reproduce the layout of the old code
* @library /test/lib
* @modules java.base/jdk.internal.misc
* java.management
* @requires vm.bits == "64" & vm.opt.final.UseCompressedOops == true & vm.gc != "Z"
* @run main/othervm -XX:+UseCompressedClassPointers -XX:-UseEmptySlotsInSupers OldLayoutCheck
*/
/*
* @test
* @requires vm.bits == "32"
* @library /test/lib
* @modules java.base/jdk.internal.misc
* java.management
* @run main/othervm -XX:-UseEmptySlotsInSupers OldLayoutCheck
*/
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.Comparator;
import jdk.internal.misc.Unsafe;
import jdk.test.lib.Asserts;
import jdk.test.lib.Platform;
public class OldLayoutCheck {
static class LIClass {
public long l;
public int i;
}
// 32-bit VMs: @0: 8 byte header, @8: long field, @16: int field
// 64-bit VMs: @0: 12 byte header, @12: int field, @16: long field
static final long INT_OFFSET = Platform.is64bit() ? 12L : 16L;
static final long LONG_OFFSET = Platform.is64bit() ? 16L : 8L;
static public void main(String[] args) {
Unsafe unsafe = Unsafe.getUnsafe();
Class c = LIClass.class;
Field[] fields = c.getFields();
for (int i = 0; i < fields.length; i++) {
long offset = unsafe.objectFieldOffset(fields[i]);
if (fields[i].getType() == int.class) {
Asserts.assertEquals(offset, INT_OFFSET, "Misplaced int field");
} else if (fields[i].getType() == long.class) {
Asserts.assertEquals(offset, LONG_OFFSET, "Misplaced long field");
} else {
Asserts.fail("Unexpected field type");
}
}
}
}