RFR: 8333893: Optimization for StringBuilder append boolean & null [v20]

[Shaojin Wen]

On Fri, 18 Oct 2024 21:56:53 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> After PR https://github.com/openjdk/jdk/pull/16245, C2 optimizes stores into primitive arrays by combining values ​​into larger stores.
>> 
>> This PR rewrites the code of appendNull and append(boolean) methods so that these two methods can be optimized by C2.
>
> Shaojin Wen has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 26 additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'origin/optim_str_builder_append_202406' into optim_str_builder_append_202406
>  - fix build error
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - Merge remote-tracking branch 'origin/optim_str_builder_append_202406' into optim_str_builder_append_202406
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - revert test
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - Merge remote-tracking branch 'upstream/master' into optim_str_builder_append_202406
>  - ... and 16 more: https://git.openjdk.org/jdk/compare/2cc7136e...457735c9

After PR 19970, the performance has been significantly improved. Below are the performance numbers for AMD CPU (x64)

## Script

git remote add wenshao git at github.com:wenshao/jdk.git
git fetch wenshao

# pr 19626
git clone 58dae7888eceb1c61243f658b67c208e6c30f7f2
make test TEST="micro:java.lang.StringBuilders.appendWithNull8Latin1"

# pr 19626 + 19970
git clone 457735c920aad822557e68e75ba1e76811c855a4
make test TEST="micro:java.lang.StringBuilders.appendWithNull8Latin1"


## performance numbers


-Benchmark                             Mode  Cnt  Score   Error  Units (pr 19626)
-StringBuilders.appendWithNull8Latin1  avgt   15  8.316 ± 0.512  ns/op

+Benchmark                             Mode  Cnt  Score   Error  Units (pr 19626 + 19970)
+StringBuilders.appendWithNull8Latin1  avgt   15  5.891 ± 0.043  ns/op

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

PR Comment: https://git.openjdk.org/jdk/pull/19626#issuecomment-2423368506