RFR: 8303466: C2: failed: malformed control flow. Limit type made precise with MaxL/MinL [v4]

[Vladimir Kozlov]

On Mon, 17 Apr 2023 14:21:51 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> But I think I can do the same with just collapsing `SubL -> MaxL -> SubL -> MaxL` to `SubL -> MaxL`. That may be cleaner.

I prefer this if you can do it. So you have sequence (after folding `Conv` nodes) 

MaxL(SubL(MaxL(SubL(limit, stride), min_int), stride*2), min_int);


Yes, I think it can be collapsed to:

MaxL(SubL(limit, stride*3), min_int);


If in any point of chain `limit` become `min_int` it will stay `min_int`  (even if `stride` is `max_int`) because you use Long arithmetic and we have "small" limit on unrolling (16?).
If it does not hit min_int the result it similar to SubL(SubL((limit, stride), stride*2).
So you just need to correctly collect `stride*N` values.

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PR Comment: https://git.openjdk.org/jdk/pull/13269#issuecomment-1511996427