RFR: 8303401: Add a Vector API equalsIgnoreCase micro benchmark [v3]

[Paul Sandoz]

On Tue, 28 Feb 2023 23:08:29 GMT, Eirik Bjorsnos <duke at openjdk.org> wrote:

>> This PR suggests we add a vectorized equalsIgnoreCase benchmark to the set of benchmarks in `org.openjdk.bench.jdk.incubator.vector`. This benchmark serves as an example of how vectorization can be useful also in the area of text processing. It takes advantage of the fact that ASCII and Latin-1 were designed to optimize case-twiddling operations.
>> 
>> The code came about during the work on #12632, where vectorization was deemed out of scope.
>> 
>> Benchmark results:
>> 
>> 
>> Benchmark                             (size)  Mode  Cnt     Score   Error  Units
>> EqualsIgnoreCaseBenchmark.scalar          16  avgt   15    20.671 ± 0.718  ns/op
>> EqualsIgnoreCaseBenchmark.scalar          32  avgt   15    46.155 ± 3.258  ns/op
>> EqualsIgnoreCaseBenchmark.scalar          64  avgt   15    68.248 ± 1.767  ns/op
>> EqualsIgnoreCaseBenchmark.scalar         128  avgt   15   148.948 ± 0.890  ns/op
>> EqualsIgnoreCaseBenchmark.scalar        1024  avgt   15  1090.708 ± 7.540  ns/op
>> EqualsIgnoreCaseBenchmark.vectorized      16  avgt   15    21.872 ± 0.232  ns/op
>> EqualsIgnoreCaseBenchmark.vectorized      32  avgt   15    11.378 ± 0.097  ns/op
>> EqualsIgnoreCaseBenchmark.vectorized      64  avgt   15    13.703 ± 0.135  ns/op
>> EqualsIgnoreCaseBenchmark.vectorized     128  avgt   15    21.632 ± 0.735  ns/op
>> EqualsIgnoreCaseBenchmark.vectorized    1024  avgt   15   105.509 ± 7.493  ns/op
>
> Eirik Bjorsnos has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Uppercase Thorn is 0xDE
>  - Update 'a' to 'A' and 'z' to 'Z' in comments

test/micro/org/openjdk/bench/jdk/incubator/vector/EqualsIgnoreCaseBenchmark.java line 67:

> 65:     public void scalar(Blackhole blackhole) {
> 66:         blackhole.consume(scalarEqualsIgnoreCase(a, b, len));
> 67:     }

If you like there is no need to explicitly use a black hole, instead declare the benchmark method to return `boolean` and return the result of the call. JMH will do the right thing. I find that a little more concise and easier to read.

-------------

PR: https://git.openjdk.org/jdk/pull/12790