RFR: 8280126: C2: detect and remove dead irreducible loops [v2]

[Vladimir Kozlov]

On Thu, 12 Jan 2023 09:11:55 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> src/hotspot/share/opto/loopnode.cpp line 5058:
>> 
>>> 5056:     }
>>> 5057:   }
>>> 5058:   //if (_verify_only && _verify_me == nullptr) {
>> 
>> Leftover from debugging?
>
> @TobiHartmann already asked about this too.
> The idea is that I will un-comment this later, and only do the verification during `PhaseIdealLoop::verify`.
> In the PR description I wrote:
>>TODO: once we have agreement on the patch, only run verify_regions_in_irreducible_loops during loopopts verification phase. For now I leave it in to improve testing capability, at cost of extra runtime.

okay

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PR: https://git.openjdk.org/jdk/pull/11764