RFR: 8351443: Improve robustness of StringBuilder [v9]

[Chen Liang]

On Sat, 17 May 2025 15:04:21 GMT, Markus KARG <duke at openjdk.org> wrote:

>> Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Removed extraneous "the"
>
> src/java.base/share/classes/java/lang/StringUTF16.java line 1535:
> 
>> 1533:         checkBoundsBeginEnd(i, end, value);
>> 1534:         putChar(value, i, c1);
>> 1535:         putChar(value, i + 1, c2);
> 
> Can someone please shed some light on this change: What is the benefit of `i + constant` over `i++`? 🤔

i++ generates excessive store bytecodes compared to +1, +2, ... and the result bytecode size is larger, which is harmful to jit.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24967#discussion_r2094169027