RFR: 8355177: Speed up StringBuilder::append(char[]) via UTF16::compress & Unsafe::copyMemory

[Chen Liang]

On Mon, 21 Apr 2025 07:00:36 GMT, Shaojin Wen <swen at openjdk.org> wrote:

> In BufferedReader.readLine and other similar scenarios, we need to use StringBuilder.append(char[]) to build the string.
> 
> For these scenarios, we can use the intrinsic method StringUTF16.compress and Unsafe.copyMemory instead of the character copy of the char-by-char loop to improve the speed.

This might be helpful combined with #21730.

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PR Comment: https://git.openjdk.org/jdk/pull/24773#issuecomment-2818748083