RFR: 8300543 Compiler Implementation for Pattern Matching for switch [v5]

[Jan Lahoda]

On Fri, 21 Apr 2023 16:49:54 GMT, Vicente Romero <vromero at openjdk.org> wrote:

>> Jan Lahoda has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Adding test.
>>  - Removing redundant continue, as noted on the review.
>
> src/java.base/share/classes/java/lang/runtime/SwitchBootstraps.java line 315:
> 
>> 313:         Object[] labels = resolvedLabels.resolvedLabels;
>> 314: 
>> 315:         // Dumbest possible strategy
> 
> I guess that given that we can't make any assumption about order here, this is the only possible strategy so I guess it makes sense to remove the comment

I certainly hope we can do better. At very least, the current implementation is checking the type of the labels on each pass through the loop. The types of the labels don't change, so checking them again and again is not necessary. In some cases, it might be possible to improve even further, like e.g. in a case where all the labels are enum constants, then we could use a e.g. mapping table.

There's a PR proposed that shows some of that:
https://github.com/openjdk/jdk/pull/9779

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PR Review Comment: https://git.openjdk.org/jdk/pull/13074#discussion_r1175260039