<i18n dev> RFR: 8311188: Simplify and modernize equals and hashCode in java.text

[John R Rose]

On Tue, 4 Jul 2023 01:01:22 GMT, Pavel Rappo <prappo at openjdk.org> wrote:

>> Hmm, I think that issue refers to code that have explicit non-Object parameter types (like `X::equals(Object)boolean` in the issue's sample). This method already have both arguments as `Object`, so I don't think there's any type-specific inlining opportunities.
>
>> Hmm, I think that issue refers to code that have explicit non-Object parameter types (like `X::equals(Object)boolean` in the issue's sample). This method already have both arguments as `Object`, so I don't think there's any type-specific inlining opportunities.
> 
> If that's true, then perhaps those (and some other) locations got that idea wrong:
> * https://github.com/openjdk/jdk/blob/faf1b822d03b726413d77a2b247dfbbf4db7d57e/src/java.base/share/classes/java/util/Collections.java#L5712-L5719
> * https://github.com/openjdk/jdk/blob/faf1b822d03b726413d77a2b247dfbbf4db7d57e/src/java.base/share/classes/java/util/AbstractMap.java#L577-L585
> 
> Maybe @rose00 could clarify that? 
> 
> FWIW, I also note that `HashMap` does not use similar private static methods; it uses `Objects.equals(Object, Object)` and `Objects.hashCode` overloads that take parameters.

I wrote a little case study on `Objects::equals` that talks about how it should optimize, when it does, why it doesn’t, and how (maybe) to fix that.

https://cr.openjdk.org/~jrose/jvm/equals-profile.html
https://cr.openjdk.org/~jrose/jvm/equals-profile.md

This is also attached to the JBS bug.

The work on [JDK-8026251](https://bugs.openjdk.org/browse/JDK-8026251) with the `TypeProfileLevel` switch bring us closer to correctly optimizing `Objects::equals` in more cases.  Sadly, JDK refactoring by itself will not get all the way to where we want to go.  The JVM’s profiling logic needs tweaking.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14752#discussion_r1252383352