RFR: 8355177: Speed up StringBuilder::append(char[]) via Unsafe::copyMemory [v8]

[Shaojin Wen]

On Tue, 22 Jul 2025 04:03:20 GMT, Chen Liang <liach at openjdk.org> wrote:

> I just noticed there is `LibraryCallKit::inline_string_getCharsU` that is for byte -> char conversion. I wonder if we can slightly update it for char -> byte conversion.

If the performance is the same, the current proposal to use Unsafe should be more maintainable, and the maintainer only needs to know Java. If intrinsics are used, the maintainer needs to know C++, Java, and intrinsic mechanisms.

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PR Comment: https://git.openjdk.org/jdk/pull/24773#issuecomment-3112974656