RFR: 8370077: C2: make Compile::_major_progress a boolean

[Marc Chevalier]

On Tue, 21 Oct 2025 17:32:08 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Simply change `Compile::_major_progress` from `int` to `bool` since we are only checking if it's non-zero.
>> 
>> There is one detail, we used to have
>> 
>> void          restore_major_progress(int progress) { _major_progress += progress; }
>> 
>> 
>> It is used after some verification code (maybe not only?) that may reset the major progress, using the progress saved before the said code.
>> 
>> It has a weird semantics:
>> 
>> Progress before | Progress after verification | Progress after restore
>> ----------------|-----------------------------|-----------------------
>> 0               | 0                           | 0
>> 1               | 0                           | 1
>> 0               | 1                           | 1
>> 1               | 1                           | 2
>> 
>> It is rather a or than a restore, and a proper boolean version of that would be
>> 
>> void restore_major_progress(bool progress) { _major_progress = _major_progress || progress; }
>> 
>> but then, I'd argue the name is confusing. It also doesn't fit so well the idea that we just want to be back to the situation before the verification code. I suspect the unsaid assumption, is that the 3rd line (progress clear before, set by verification) is not possible. Anyway, I've tried with this or-semantics, or with a more natural
>> 
>> void set_major_progress(bool progress) { _major_progress = progress; }
>> 
>> that actually restore what we saved. Both pass (tier1-6 + some internal tests). Thus, I prefered the simpler semantics.
>> 
>> Thanks,
>> Marc
>
> Or you can keep temporary (just for testing this PR and remove it before integration) original logic in debug VM to compare result of `major_progress()`.

@vnkozlov I fear I don't understand what you're suggesting.

I've tried to add in my `set_major_progress(bool)` an assert to check we are not in the 3rd case, the one where the assignment-semantics and the OR-semantics mismatch (that is with `progress` parameter (old progress) unset and current `_major_progress` set). And indeed the assert does not fire in tier1-6+some other internal testing.

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PR Comment: https://git.openjdk.org/jdk/pull/27912#issuecomment-3430850080