RFR: 8331724: Refactor j.l.constant implementation to internal package [v9]

[Claes Redestad]

On Tue, 14 May 2024 20:20:59 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add microbenchmark for ClassDesc methods + a few optimizations
>
> src/java.base/share/classes/java/lang/constant/ClassDesc.java line 226:
> 
>> 224:         for (int i = 0; i < rank; i++) {
>> 225:             sb.append('[');
>> 226:         }
> 
> Would `sb.repeat("[", rank);` be better here?
> 
> Also for parity with `arrayType()` I recommend moving this building code to after the void check.

Oh, that's new (in 21). I was comparing against `append("[".repeat(rank))` which had a cost here. `sb.repeat('[', rank)` is in the same ballpark and simpler. Fixing.


Benchmark                                       Mode  Cnt     Score     Error   Units
ClassDescMethods.arrayType2                     avgt   15    31,568 ±   2,108   ns/op
ClassDescMethods.arrayType2:gc.alloc.rate       avgt   15  7758,056 ± 474,378  MB/sec
ClassDescMethods.arrayType2:gc.alloc.rate.norm  avgt   15   256,000 ±   0,001    B/op


I'll align the code to construct `newDesc` before the void check in both methods.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19105#discussion_r1601088246