RFR: 8335444: Generalize implementation of AndNode mul_ring [v3]

[Quan Anh Mai]

On Fri, 23 Aug 2024 17:52:19 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> This is a great observation! Since bitwise-and can only remove bits, the largest possible value is the smaller of each range's `hi` value so I think it's correct to use the minimum here rather than the maximum. I didn't look into this case too deeply initially since I didn't find any bitwise-and nodes of two negative ranges in my investigation, but I think we should include it since it's a simple enough condition to check.
>
> Another point of view, you can decompose `[lo, hi]` into `[lo, -1] v [0, hi]`. Then `[lo1, hi1] & [lo2, hi2]` can be calculated as:
> 
>     ([lo1, -1] & [lo2, -1]) v ([lo1, -1] & [0, hi2]) v ([0, hi1] & [lo2, -1]) v ([0, hi1] & [0, hi2]) =
>     [lo, -1] v [0, hi2] v [0, h1] v [0, min(hi1, hi2)] =
>     [lo, max(hi1, hi2)]`
> 
> with `lo` being the lower bound you calculated right above.

Just to be clear I think `MAX2` is the correct thing here.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20066#discussion_r1729329256