RFR: 8370077: C2: make Compile::_major_progress a boolean [v2]

[Marc Chevalier]

On Tue, 21 Oct 2025 17:29:38 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> I don't think it's the right place for this kind of comment. It's quite hidden, far from where it's actually useful to know we need to set or check that. I'd say it should rather be on `PhaseIdealLoop` for instance, or `PhaseIdealLoop::optimize`, something like that, as a part of a more global overview of how things work.
>
> There should just be some documentation around the `major_progress` family of field/methods. Or at least link from there to where the documentation resides ;)

Probably, but that is out of the scope of this issue. Moreover, I don't know enough of loop optimization to write a helpful and correct comment. It feels like it should just be another RFE done by someone who can do it. The change I'm doing here doesn't actually need to understand how the whole thing works.

Also
> If we ever set the flag, we don't continue with more loop-opts, but spin back to IGVN, clean the graph, and maybe come back to a new loop-opts round.

I don't think it's true. I have the same kind of intuition, but in details, I don't think it holds. We can unroll after peeling (which sets major progress) in the same loop optimization round.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27912#discussion_r2450730268