RFR: 8326653: Remove jdk.internal.reflect.UTF8 [v2]

[Alan Bateman]

On Mon, 26 Feb 2024 11:34:18 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> jdk.internal.reflect.UTF8 is used for encoding String to encoded UTF-8 when generating some classes. 
>> 
>> Since JDK 9 we have a fast-path (which avoids creating encoders) for UTF-8-encoding strings which is bootstrapped very early, so it seems safe to rewire this and remove the UTF8 helper class whose stated raison d'être is to avoid bootstrapping issues.
>> 
>> This cleanup also removes a latent bug since the custom encoder isn't able to deal with classfile constants containing surrogate pairs.
>> 
>> For a quick comparison I copied the UTF8 code to the `StringEncode` microbenchmark and set up a benchmark testing the same inputs as `encodeAllMixed`:
>> 
>> 
>> Benchmark                                (charsetName)  Mode  Cnt       Score      Error  Units
>> StringEncode.encodeAllMixed                      UTF-8  avgt   10   12894,551 ±  164,816  ns/op
>> StringEncode.encodeUTF8InternalAllMixed          UTF-8  avgt   10  236614,548 ± 1445,975  ns/op
>> 
>> 
>> I.e. `String.getBytes(UTF_8.instance)` is about 18x faster on mixed inputs. The benchmark is available in 595b464 but as a quick sanity check not intended for integration. 
>> 
>> Testing: tier1-3
>
> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove temporary microbenchmark

Marked as reviewed by alanb (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk/pull/18006#pullrequestreview-1901089641