On Wed, 29 May 2024 15:20:15 GMT, Chen Liang <li...@openjdk.org> wrote:
>> This was something that I tried and I observed a performance regression on >> the ARM platform that I was testing. From my understanding, `@Stable` tells >> the compiler to trust the contents of this field which is only given when >> the field holder is a known constant. This is generally true for cases like >> `Enums` but not usually for `Method`. >> >> >> Benchmark Mode Cnt Score Error Units >> # Intel Skylake >> MethodHashCode.benchmarkHashCode avgt 5 1.113 ± 1.146 ns/op >> # Arm Neoverse N1 >> MethodHashCode.benchmarkHashCode avgt 5 3.204 ± 0.001 ns/op > > Interesting, don't know about hotspot internals so I can't diagnose the exact > cause of this regression. In order to be eligible for constant folding, the benchmark must declare the `Method hashCodeMethod;` as `static final`. It is hard for me to understand why a `@Stable` annotation should have a detrimental performance impact on an instance field. Can we see a benchmark on Arm Neoverse N1 with the field declared `@Stable` compared to not declared `@Stable`? Also, if the field is `static final`, how would it look like? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/19433#discussion_r1627803876
