RFR: 8350896: Integer/Long.compress gets wrong type from CompressBitsNode::Value [v15]

[Vladimir Kozlov]

On Wed, 16 Jul 2025 10:43:34 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Hi All,
>> 
>> This bugfix patch fixes incorrect value computation for Integer/Long. compress APIs.
>> 
>> Problems occur with a constant input and variable mask where the input's value is equal to the lower bound of the mask value., In this case, an erroneous value range estimation results in a constant value. Existing value routine first attempts to constant fold the compression operation if both input and compression mask are constant values; otherwise, it attempts to constrain the value range of result based on the upper and lower bounds of mask type.
>> 
>> New IR test covers the issue reported in the bug report along with a case for value range based logic pruning.
>> 
>> Kindly review and share your feedback.
>> 
>> Best Regards,
>> Jatin
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Refine lower bound computation

I am not sure about JDK 25 approval for these changes.

Can you do simple fix for JDK 25 as @merykitty suggested: "I suggest removing all the logic and simply returning the bottom type" ?  Will it be the same complexity? Will it affect performance (and how much)?

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PR Comment: https://git.openjdk.org/jdk/pull/23947#issuecomment-3098578332