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

[altrisi]

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/54dfd56d...457735c9

Sure, I already mentioned such program would be incorrect, but one thing is an incorrect result in the StringBuilder and another one is writing outside the bounds of the array into other parts (possibly objects) of the heap, or even outside, causing a VM crash.

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PR Comment: https://git.openjdk.org/jdk/pull/19626#issuecomment-2628991914