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

[Emanuel Peter]

On Wed, 22 Oct 2025 21:56:26 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Marc Chevalier has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Adapt the comment
>
> It doesn't look safe to me to change the restore_major_progress() behavior in build_and_optimize().  It certainly looks possible to call set_major_progress() in the do_max_unroll case (lines 5146 - 5163) at least.

Given @dean-long and @vnkozlov 's answers, I would suggest something like this:

If major progress is set:
  Marks that the loop tree information (get_ctrl, idom, get_loop, etc) could be invalid, and we need to rebuild the loop tree.
  It also indicates that we have made progress, and so it is likely that we can make even more progress in a next round of loop optimizations.
If major progress is not set:
  Loop tree information is valid.
  If major progress is not set at the end of a loop opts phase, then we can stop loop opts, because we do not expect any further progress if we did more loop ops phases.

Suggestions for improvements?

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PR Comment: https://git.openjdk.org/jdk/pull/27912#issuecomment-3435159446