RFR: 8332826: Make hashCode methods in ArraysSupport friendlier [v2]

[Pavel Rappo]

On Wed, 29 May 2024 03:21:27 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Pavel Rappo has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix incorrect utf16 hashCode adaptation
>
> src/java.base/share/classes/jdk/internal/util/ArraysSupport.java line 320:
> 
>> 318:      * @return the calculated hash value
>> 319:      */
>> 320:     public static int hashCode(Object[] a, int fromIndex, int length, int initialValue) {
> 
> Is the object variant necessary here? The object version is hard for JIT to profile as it's quite polymorphic compared to other arrays, and the initial value is always 1.

This is a cleanup/refactoring PR, so none of this is necessary. My motivation for the `Object[]` variant was to provide reusable functionality for methods like these:

 - https://github.com/openjdk/jdk/blob/0ef03f122866f010ebf50683097e9b92e41cdaad/src/java.base/share/classes/java/util/concurrent/CopyOnWriteArrayList.java#L1076-L1083
 - https://github.com/openjdk/jdk/blob/0ef03f122866f010ebf50683097e9b92e41cdaad/src/java.base/share/classes/java/util/ArrayList.java#L669-L680

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PR Review Comment: https://git.openjdk.org/jdk/pull/19414#discussion_r1618644177