RFR: 8315999: Improve Date toString performance [v9]

[温绍锦]

On Tue, 12 Sep 2023 23:08:25 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> 温绍锦 has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   merge from master
>
> src/java.base/share/classes/jdk/internal/util/DecimalDigits.java line 77:
> 
>> 75: 
>> 76:     static {
>> 77:         int[] digits_k = new int[1000];
> 
> I'm very skeptical that adding a 1000 element lookup table for  is worthwhile. That's a lookup table that'd span many cache lines, with plenty of cache misses. And even _if_ it is to be considered it should be split out and considered in isolation from this PR.
> 
> What does the 2, 1 or 0 value you put in the lowest byte signify?

DIGITS_K has been removed

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PR Review Comment: https://git.openjdk.org/jdk/pull/15658#discussion_r1323808508