On Wed, 15 Mar 2023 11:26:21 GMT, Eirik Bjorsnos <d...@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
Nice one!
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) {`
-------------
Marked as reviewed by redestad (Reviewer).
PR: https://git.openjdk.org/jdk/pull/13040
