RFR: 8317795: Add an ImmutableBitSetPredicate variant for bitsets <= 128 elements

[Chen Liang]

On Sun, 8 Oct 2023 21:02:25 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> Alternative to #16082
> 
> Name                             (unchanged) Cnt  Base   Error   Test   Error  Unit  Change
> URLEncodeDecode.testEncodeLatin1           0  15 2,066 ± 0,104  1,899 ± 0,007 ms/op   1,09x (p = 0,000*)
> URLEncodeDecode.testEncodeLatin1          75  15 0,934 ± 0,017  0,811 ± 0,014 ms/op   1,15x (p = 0,000*)
> URLEncodeDecode.testEncodeLatin1         100  15 0,433 ± 0,060  0,389 ± 0,007 ms/op   1,11x (p = 0,008*)
>   * = significant
>   ```

src/java.base/share/classes/jdk/internal/util/ImmutableBitSetPredicate.java line 94:

> 92:         private SmallImmutableBitSetPredicate(BitSet original) {
> 93:             // If this class is made public, we need to do
> 94:             // a defensive array copy as certain BitSet implementations

Outdated comments about defensive copy here, as we already copy the longs by value

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PR Review Comment: https://git.openjdk.org/jdk/pull/16094#discussion_r1349837796