RFR: 8268229: Aarch64: Use Neon in intrinsics for String.equals [v3]

[Nick Gasson]

On Mon, 5 Jul 2021 06:38:00 GMT, Wang Huang <whuang at openjdk.org> wrote:

>> * Why we unroll the loop ?
>> *  It is found that these codes degrades performance 
>>  ```
>>     br(LE, B16);
>>     subs(cnt1, cnt1, wordSize);
>>     br(LE, B24);
>>     subs(cnt1, cnt1, wordSize);
>> 
>>  We unroll the loop to remove these comparsion.
>
> * Why we unroll the loop ?
> *  It is found that these codes degrades performance 
>  ```
>     br(LE, B16);
>     subs(cnt1, cnt1, wordSize);
>     br(LE, B24);
>     subs(cnt1, cnt1, wordSize);
> 
>  We unroll the loop to remove these comparsion.

But we need to balance performance against code size, given that this is expanded frequently.

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PR: https://git.openjdk.java.net/jdk/pull/4423