On Mon, 10 Aug 2026 08:55:10 GMT, Volkan Yazici <[email protected]> wrote:
>> Liam Miller-Cushon has updated the pull request incrementally with two
>> additional commits since the last revision:
>>
>> - Add OutOfMemoryError checks for UTF-16 encodedLength fast paths
>> - Copyright years
>
> src/java.base/share/classes/java/lang/String.java line 1655:
>
>> 1653: }
>> 1654: sp++;
>> 1655: }
>
> Does this pre-scan bring any measurable benefits?
>
> Have you considered collapsing the two loops and retaining the fast checks?
> Consider the following:
>
> for (int sp = off, sl = off + len; sp < sl;) {
> char c = StringUTF16.getChar(val, sp++);
> if (c < Character.MIN_HIGH_SURROGATE) {
> continue;
> }
> if (c > Character.MAX_LOW_SURROGATE) {
> continue;
> }
> if (sp == sl || !Character.isLowSurrogate(StringUTF16.getChar(val,
> sp))) {
> return true;
> }
> sp++;
> }
> return false;
My recollection from the similar pre-scan in `encodedLengthUTF8_UTF16` is that
C2 was able to optimize the simpler loop better and it made a measurable
difference, the same pattern is used in `encodeUTF8_UTF16`. I haven't
re-measured for this loop though.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/32268#discussion_r3749911871
