RFR: 8350864: C2: verify structural invariants of the Ideal graph [v5]

[Marc Chevalier]

On Mon, 8 Sep 2025 16:55:38 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Marc Chevalier has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   One more ResourceMark
>
> src/hotspot/share/opto/graphInvariants.cpp line 528:
> 
>> 526:     if (!center->is_CountedLoop() && !center->is_LongCountedLoop()) {
>> 527:       return CheckResult::NOT_APPLICABLE;
>> 528:     }
> 
> Actually: why not applie that to `OuterStripMinedLoop` as well? Or any `BaseCountedLoop`? Are there more than these 3 cases? If there are ever more, they should probably also adhere to this backedge pattern, we'll just need an extension. But it would be nice to trip over something here if we ever do extend.

I'm going to push back on that. I rather want this one to be about counted loops, which have more structure that is HEAVILY relied on, that I haven't all enumerated, but that can be done.

One can make another check for the few things that hold for other flavors.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/26362#discussion_r2333891737