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8353266: C2: Wrong execution with Integer.bitCount(int) intrinsic on AArch64

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Reviewed-by: aph, thartmann
This commit is contained in:
Marc Chevalier 2025-06-03 08:06:43 +00:00
parent dbf562c725
commit be923a8b72
2 changed files with 82 additions and 4 deletions
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6
src/hotspot/cpu/aarch64/aarch64.ad
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@ -7761,14 +7761,12 @@ instruct popCountI(iRegINoSp dst, iRegIorL2I src, vRegF tmp) %{
effect(TEMP tmp);
ins_cost(INSN_COST * 13);
format %{ "movw $src, $src\n\t"
"mov $tmp, $src\t# vector (1D)\n\t"
format %{ "fmovs $tmp, $src\t# vector (1S)\n\t"
"cnt $tmp, $tmp\t# vector (8B)\n\t"
"addv $tmp, $tmp\t# vector (8B)\n\t"
"mov $dst, $tmp\t# vector (1D)" %}
ins_encode %{
__ movw($src$$Register, $src$$Register); // ensure top 32 bits 0
__ mov($tmp$$FloatRegister, __ D, 0, $src$$Register);
__ fmovs($tmp$$FloatRegister, $src$$Register);
__ cnt($tmp$$FloatRegister, __ T8B, $tmp$$FloatRegister);
__ addv($tmp$$FloatRegister, __ T8B, $tmp$$FloatRegister);
__ mov($dst$$Register, $tmp$$FloatRegister, __ D, 0);

80
test/hotspot/jtreg/compiler/intrinsics/BitCountIAarch64PreservesArgument.java Normal file
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@ -0,0 +1,80 @@
/*
* Copyright (c) 2025, 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 8353266
* @summary Integer.bitCount modifies input register
* @library /test/lib /
*
* @run main/othervm
* -Xbatch
* -XX:CompileOnly=compiler.intrinsics.BitCountIAarch64PreservesArgument::test
* compiler.intrinsics.BitCountIAarch64PreservesArgument
*/
/**
* @test
* @bug 8353266
* @library /test/lib /
*
* @run main compiler.intrinsics.BitCountIAarch64PreservesArgument
*/
package compiler.intrinsics;
import static compiler.lib.generators.Generators.G;
public class BitCountIAarch64PreservesArgument {
static long lFld;
static long result;
public static void main(String[] args) {
lFld = 0xfedc_ba98_7654_3210L;
for (int i = 0; i < 10_000; i++) {
test();
if (result != 0xfedc_ba98_7654_3210L) {
// Wrongly outputs the cut input 0x7654_3210 == 1985229328
throw new RuntimeException("Wrong result. Expected result = " + lFld + "; Actual result = " + result);
}
}
lFld = G.longs().next();
for (int i = 0; i < 10_000; i++) {
test();
if (result != lFld) {
throw new RuntimeException("Wrong result. Expected result = " + lFld + "; Actual result = " + result);
}
}
}
static void test() {
long x = lFld;
try {
result = Integer.bitCount((int) x); // Cut input: 0x7654_3210 == 1985229328
throw new RuntimeException();
} catch (RuntimeException _) {
}
result = x;
}
}