On Thu, 16 Jul 2026 04:23:01 GMT, Kuai Wei <[email protected]> wrote:
>> I recently noticed a behavioral discrepancy in
>> jdk.internal.util.ArraysSupport.vectorizedMismatch between the Java
>> implementation and the platform intrinsic implementations.
>>
>> Current behavior
>>
>> The Java implementation may leave a tail of elements unchecked, returning
>> the bitwise complement of the number of remaining elements (i.e.,
>> ~remaining).
>> The x86_64 intrinsic, by contrast, compares all elements and simply returns
>> -1 when no mismatch is found.
>>
>> Proposed change
>>
>> This PR refines the Java implementation so that it always compares all
>> elements and returns -1 when no mismatch is found, matching the x86_64
>> intrinsic behavior.
>>
>> A regression test is included at
>> `test/hotspot/jtreg/compiler/intrinsics/VectorizedMismatchReturnDiffTest.java`
>> which demonstrates the original behavioral difference.
>>
>> ## Test
>> - [x] tier1 test suites on linux x86_64
>> - [x] tier1 test suites on linux aarch64
>>
>> ---------
>> - [x] I confirm that I make this contribution in accordance with the
>> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai).
>
> Kuai Wei has updated the pull request incrementally with two additional
> commits since the last revision:
>
> - Fix indent
> - Recovery comments
src/java.base/share/classes/jdk/internal/util/ArraysSupport.java line 115:
> 113: * in the two arrays. Otherwise, if a mismatch is not found the
> bitwise
> 114: * compliment of the number of remaining pairs of elements to be
> checked in
> 115: * the tail of the two arrays.
Suggestion:
* in the two arrays. Otherwise, no mismatch is found over the range,
* this method returns -1.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/31802#discussion_r3592623721
