RFR: 8311207: Optimization for j.u.UUID.toString [v6]

[温绍锦]

> [PR 14578 ](https://github.com/openjdk/jdk/pull/14578) still has unresolved discussions, continue to make improvements.
> 
> # Benchmark Result
> 
> 
> sh make/devkit/createJMHBundle.sh
> bash configure --with-jmh=build/jmh/jars
> make test TEST="micro:java.util.UUIDBench.toString"
> 
> 
> ## 1. [aliyun_ecs_c8i.xlarge](https://help.aliyun.com/document_detail/25378.html#c8i)
> * cpu : intel xeon sapphire rapids (x64)
> 
> ``` diff
> -Benchmark           (size)   Mode  Cnt   Score   Error   Units (baseline)
> -UUIDBench.toString   20000  thrpt   15  62.019 ± 0.622  ops/us
> 
> +Benchmark           (size)   Mode  Cnt   Score   Error   Units
> +UUIDBench.toString   20000  thrpt   15  82.998 ± 0.739  ops/us (+33.82%)
> 
> 
> ## 2. [aliyun_ecs_c8a.xlarge](https://help.aliyun.com/document_detail/25378.html#c8a)
> * cpu : amd epc genoa (x64)
> 
> ``` diff
> -Benchmark           (size)   Mode  Cnt   Score   Error   Units (baseline)
> -UUIDBench.toString   20000  thrpt   15  88.668 ± 0.672  ops/us
> 
> +Benchmark           (size)   Mode  Cnt   Score   Error   Units
> +UUIDBench.toString   20000  thrpt   15  89.229 ± 0.271  ops/us (+0.63%)
> 
> 
> 
> ## 3. [aliyun_ecs_c8y.xlarge](https://help.aliyun.com/document_detail/25378.html#c8y)
> * cpu : aliyun yitian 710 (aarch64)
> ``` diff
> -Benchmark           (size)   Mode  Cnt   Score   Error   Units (baseline)
> -UUIDBench.toString   20000  thrpt   15  49.382 ± 2.160  ops/us
> 
> +Benchmark           (size)   Mode  Cnt   Score   Error   Units
> +UUIDBench.toString   20000  thrpt   15  49.636 ± 1.974  ops/us (+0.51%)
> 
> 
> ## 4. MacBookPro M1 Pro
> ``` diff
> -Benchmark           (size)   Mode  Cnt    Score   Error   Units (baseline)
> -UUIDBench.toString   20000  thrpt   15  103.543 ± 0.963  ops/us
> 
> +Benchmark           (size)   Mode  Cnt    Score   Error   Units
> +UUIDBench.toString   20000  thrpt   15  110.976 ± 0.685  ops/us (+7.17%)
> 
> 
> ## 5. Orange Pi 5 Plus
> 
> ``` diff
> -Benchmark           (size)   Mode  Cnt   Score   Error   Units (baseline)
> -UUIDBench.toString   20000  thrpt   15  33.532 ± 0.396  ops/us
> 
> +Benchmark           (size)   Mode  Cnt   Score   Error   Units (PR)
> +UUIDBench.toString   20000  thrpt   15  33.054 ± 0.190  ops/us (-4.42%)

温绍锦 has updated the pull request incrementally with one additional commit since the last revision:

  code style

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14745/files
  - new: https://git.openjdk.org/jdk/pull/14745/files/6abf3148..e5274ddc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14745&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14745&range=04-05

  Stats: 15 lines in 1 file changed: 2 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/14745.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14745/head:pull/14745

PR: https://git.openjdk.org/jdk/pull/14745