RFR: 8293116: Incremental JDK build could be sped up [v3]

[Jan Lahoda]

On Tue, 6 Sep 2022 14:33:10 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>>> The `Depend` plugin will do a full build if a non-Java file is present in the list, which I hope should lead to a more reliable recompilation for some complex changes among the sources.
>> 
>> Ah, I had missed that and that's clever! That also means there is a reason to generate MODFILES in the actual compile recipe instead of the separate rule as I suggested earlier. For this to be "safe" we need `$$?` to really contain all the updated prereqs, otherwise we may miss compiling everything when something external actually should make us do just that.
>
> ... and also that we *must* include the vardeps file, since any change there should trigger a complete rebuild.
> 
> The logic here seems correct, but apparently somewhat hard to fully understand correctly. Maybe a few lines of comments summarizing the important points raised here would be a good thing?

> ... and also that we _must_ include the vardeps file, since any change there should trigger a complete rebuild.
> 
> The logic here seems correct, but apparently somewhat hard to fully understand correctly. Maybe a few lines of comments summarizing the important points raised here would be a good thing?

How about:
https://github.com/openjdk/jdk/pull/10104/commits/6c1a83b28ee72a99bf24e7f66c96d1294ad485dd

Thanks,
    Jan

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PR: https://git.openjdk.org/jdk/pull/10104