On Wed, 15 Mar 2023 11:58:14 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> By avoiding a bit shift operation for the latin1 fast-path test, we can
>> speed up the `java.lang.CharacterData.of` method by ~25% for latin1 code
>> points.
>>
>> The latin1 test is currently implemented as `ch >>> 8 == 0`. We can replace
>> this with `ch >= 0 && ch <= 0xFF` for a noticable performance gain
>> (especially for Latin1 code points):
>>
>> This method is called frequently by various property-determining methods in
>> `java.lang.Character` like `isLowerCase`, `isDigit` etc, so one should
>> expect improvements for all these methods.
>>
>> Performance is tested using the `Characters.isDigit` benchmark using the
>> digits '0' (decimal 48, in CharacterDataLatin1) and '\u0660' (decimal 1632,
>> in CharacterData00):
>>
>> Baseline:
>>
>>
>> Benchmark (codePoint) Mode Cnt Score Error Units
>> Characters.isDigit 48 avgt 15 0.870 ± 0.011 ns/op
>> Characters.isDigit 1632 avgt 15 2.168 ± 0.017 ns/op
>>
>> PR:
>>
>>
>> Benchmark (codePoint) Mode Cnt Score Error Units
>> Characters.isDigit 48 avgt 15 0.654 ± 0.007 ns/op
>> Characters.isDigit 1632 avgt 15 2.032 ± 0.019 ns/op
>
> src/java.base/share/classes/java/lang/CharacterData.java line 72:
>
>> 70:
>> 71: static final CharacterData of(int ch) {
>> 72: if (ch >= 0 && ch <= 0xFF) { // fast-path
>
> Maybereducing to a single branch with a mask op helps further? Or maybe the
> JIT already effectively does that:
>
> `if (ch && 0xFFFFFF00 == 0) {`
Btw, I think we can do the same for `StringLatin1.canEncode()`
-------------
PR: https://git.openjdk.org/jdk/pull/13040
