RFR: 8347645: C2: XOR bounded value handling blocks constant folding [v4]

[Johannes Graham]

On Thu, 23 Jan 2025 19:01:34 GMT, Johannes Graham <duke at openjdk.org> wrote:

>> If one arg was (lo=0,hi=1) and the other was 0 though, it might be a problem. Depends where x ^ 0 gets simplified.
>> *edit* Your alternative version below avoids this concern.
>
> *edit2* Actually, the alternative version has an issue if either of the lo values is 0

How about this?
    ``juint max = round_up_power_of_2<juint>( (r0->_hi | r1->_hi) +1) - 1;``

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PR Review Comment: https://git.openjdk.org/jdk/pull/23089#discussion_r1927554356