RFR: 8373613: PEXT/PDEP intrinsics cause performance regression on AMD pre-Zen 3 CPUs

[John Rose]

On 25 Feb 2026, at 3:02, Jasmine Karthikeyan wrote:

> @eme64 It looks like there are compress tests in the `java/lang/Integers.java`/`Longs.java` benchmarks, running them on a Zen 2 device gives me these results:
>
>                                         Baseline                    Patch
> Benchmark          (size)  Mode  Cnt  Score   Error  Units   Score   Error  Units  Improvement
> Integers.compress     500  avgt   15  7.499 ± 0.011  us/op   0.755 ± 0.001  us/op   (9.93x)
> Longs.compress        500  avgt   15  9.011 ± 0.014  us/op   0.851 ± 0.001  us/op   (10.58x)

That’s surprisingly stark.  Score one for RISC machines, because
there surely is superscalar stuff happening in those fast numbers.