RFR: 8282365: Optimize divideUnsigned and remainderUnsigned for constants [v4]

[Quan Anh Mai]

On Tue, 27 Sep 2022 20:54:22 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> src/hotspot/share/opto/divnode.cpp line 1142:
>> 
>>> 1140:   }
>>> 1141: 
>>> 1142:   // Divisor very large, constant 2**31 can be transform to a shift
>> 
>> @vnkozlov Oh the transformation is here
>
> It only works for cases with narrowed type. Which is not common case unless Java user's code check for that.

May you expand on this, please? How can I know that a divisor is negative without using its type information? Thanks.

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PR: https://git.openjdk.org/jdk/pull/9947