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8389341: [lworld] C2 Class.isAssignableFrom intrinsic returns false for identical array Class arguments

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Reviewed-by: chagedorn, mchevalier
This commit is contained in:
Tobias Hartmann 2026-08-03 06:54:09 +00:00
parent 775ecc3b63
commit d5da754c6e
2 changed files with 70 additions and 0 deletions
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12
src/hotspot/share/opto/library_call.cpp
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@ -4691,6 +4691,7 @@ bool LibraryCallKit::inline_native_subtype_check() {
// {P,P} & superc!=subc => false
_prim_same_path, // {P,P} & superc==subc => true
_prim_1_path, // {N,P} => false
_ref_same_path, // {N,N} & superk==subk => true
_ref_subtype_path, // {N,N} & subtype check wins => true
_both_ref_path, // {N,N} & subtype check loses => false
PATH_LIMIT
@ -4738,6 +4739,16 @@ bool LibraryCallKit::inline_native_subtype_check() {
// now we have two reference types, in klasses[0..1]
Node* subk = klasses[1]; // the argument to isAssignableFrom
Node* superk = klasses[0]; // the receiver
// gen_subtype_check() refines exact array superklasses for comparison with
// (refined) klasses loaded from the header. Since both operands here are unrefined
// klasses, handle equality first. Unequal types then use the regular hierarchy check.
Node* cmp = _gvn.transform(new CmpPNode(subk, superk));
Node* bol = _gvn.transform(new BoolNode(cmp, BoolTest::eq));
IfNode* iff = create_and_xform_if(control(), bol, PROB_STATIC_FREQUENT, COUNT_UNKNOWN);
region->set_req(_ref_same_path, _gvn.transform(new IfTrueNode(iff)));
set_control(_gvn.transform(new IfFalseNode(iff)));
region->set_req(_both_ref_path, gen_subtype_check(subk, superk));
region->set_req(_ref_subtype_path, control());
}
@ -4762,6 +4773,7 @@ bool LibraryCallKit::inline_native_subtype_check() {
// these are the only paths that produce 'true':
phi->set_req(_prim_same_path, intcon(1));
phi->set_req(_ref_same_path, intcon(1));
phi->set_req(_ref_subtype_path, intcon(1));
// pull together the cases:

58
test/hotspot/jtreg/compiler/valhalla/inlinetypes/TestIsAssignableFrom.java Normal file
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@ -0,0 +1,58 @@
/*
* Copyright (c) 2026, 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 8389341
* @summary Test that Class.isAssignableFrom returns true for two identical arguments.
* @library /test/lib
* @run main ${test.main.class}
* @run main/othervm -Xcomp -XX:-TieredCompilation
* -XX:CompileCommand=compileonly,${test.main.class}::test*
* -XX:CompileCommand=delayinline,${test.main.class}::helperDelayed
* ${test.main.class}
*/
package compiler.valhalla.inlinetypes;
import jdk.test.lib.Asserts;
public final class TestIsAssignableFrom {
static boolean test(Class<?> c) {
return TestIsAssignableFrom[].class.isAssignableFrom(c);
}
static Class<?> helperDelayed() {
return TestIsAssignableFrom[].class;
}
static boolean testLate(Class<?> c) {
return helperDelayed().isAssignableFrom(c);
}
public static void main(String[] args) {
Asserts.assertEQ(test(TestIsAssignableFrom[].class), true);
Asserts.assertEQ(testLate(TestIsAssignableFrom[].class), true);
}
}