RFR: 8332268: C2: Add missing optimizations for UDivI/L and UModI/L and unify the shared logic with the signed nodes [v21]

[Christian Hagedorn]

On Tue, 10 Dec 2024 15:00:21 GMT, theoweidmannoracle <duke at openjdk.org> wrote:

>> This PR introduces
>> - several new optimizations to unsigned division and modulo
>>    - x % 1, x % x, x % 2^k
>>    - x / 1, x / x, x / 2^k 
>>    - does not implement the Granlund and Montgomery algorithm, which has been implemented for signed modulo division in the past. It is unclear if a lot is to be gained by implementing this.
>> - tests to test existing optimizations for signed division and modulo 
>>    - does not test the Granlund and Montgomery algorithm directly
>
> theoweidmannoracle has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Merge branch 'unsigned-div-opts' of https://github.com/theoweidmannoracle/jdk into unsigned-div-opts
>  - Rename variables

Marked as reviewed by chagedorn (Reviewer).

src/hotspot/share/opto/divnode.cpp line 1200:

> 1198:     Unsigned au = static_cast<Unsigned>(type_dividend->get_con());
> 1199:     Unsigned bu = static_cast<Unsigned>(type_divisor->get_con());
> 1200:     return TypeClass::make(static_cast<Signed>(au % bu));

Thanks for the updates, one last nit:
Suggestion:

    Unsigned dividend = static_cast<Unsigned>(type_dividend->get_con());
    Unsigned divisor = static_cast<Unsigned>(type_divisor->get_con());
    return TypeClass::make(static_cast<Signed>(dividend % divisor));

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PR Review: https://git.openjdk.org/jdk/pull/22061#pullrequestreview-2492679451
PR Review Comment: https://git.openjdk.org/jdk/pull/22061#discussion_r1878299973