RFR: 8256438: AArch64: Implement match rules with ROR shift register value

[Andrew Haley]

On 29/01/2021 10:11, Andrew Haley wrote:
> On 1/29/21 8:35 AM, Eric Liu wrote:
>> I benchmarked on 7 platforms with jmh test[1], most of them were hard to see any performance changes. On one platform the performance become bad, and seems a little unstable.

Your benchmark did not work for me. It did not generate the correct
instructions.

Please try with this or similar:

    @Benchmark
    public void xorRotateRight(MyState s, Blackhole blackhole) {
        int x = s.xi;
        int y = s.yi;
        for (int i = 0; i < COUNT; i++) {
            y = x ^ ((y >>> 5) | (y << -5));
            x = y ^ ((x >>> 5) | (x << -5));
        }
        blackhole.consume(x);
    }

I get:

Benchmark                             Mode  Cnt     Score    Error  Units
Rotation.xorRotateRight   (before)    avgt    3  6142.575 ± 15.940  ns/op
Rotation.xorRotateRight   (after)     avgt    3  4081.587 ± 33.904  ns/op

Please integrate the corrected benchmark into your patch.

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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