RFR: 8328702: C2: Crash during parsing because sub type check is not folded

[Christian Hagedorn]

On Wed, 27 Mar 2024 16:05:12 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> Thanks Roland for your review!
>> 
>>> > When running with -XX:+ExpandSubTypeCheckAtParseTime
>>> 
>>> Do we want to retire `ExpandSubTypeCheckAtParseTime`? Is there any reason to keep it?
>> 
>> I'm not sure about how much benefit it gives us. A quick JBS search for "ExpandSubTypeCheckAtParseTime" revealed a few issues - but would need to double check how many of them really only triggered with that flag and were real bugs. So, apart from having it as a stress option, I don't see a real benefit for it - but that might be a good enough reason to keep it for now.
>> 
>> What do you think?
>
>> I'm not sure about how much benefit it gives us. A quick JBS search for "ExpandSubTypeCheckAtParseTime" revealed a few issues - but would need to double check how many of them really only triggered with that flag and were real bugs. So, apart from having it as a stress option, I don't see a real benefit for it - but that might be a good enough reason to keep it for now.
>> 
>> What do you think?
> 
> It also has a maintenance cost (you had to make a code change for it in this PR and I also remember having to take `ExpandSubTypeCheckAtParseTime` into consideration at some point). I would vote for removing it unless it's known to have some value.

Thanks @rwestrel and @vnkozlov for your reviews!

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PR Comment: https://git.openjdk.org/jdk/pull/18512#issuecomment-2034362752