RFR: 8261008: Optimize Xor

[Tobias Hartmann]

On Tue, 2 Mar 2021 10:54:53 GMT, Eric Liu <github.com+10482586+theRealELiu at openjdk.org> wrote:

>> `x - x` is already optimized: https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/subnode.cpp#L96
>> `x | x` - here: https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/addnode.cpp#L781
>> 
>> For `x ^ x` Value() method should be used as for SubNode.
>
>> `x - x` is already optimized: https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/subnode.cpp#L96
>> `x | x` - here: https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/addnode.cpp#L781
>> 
>> For `x ^ x` Value() method should be used as for SubNode.
> 
> Thanks for your review. I moved those codes into `Value()` and will update after some tests finished.

I think C2 optimizations could lead to IR shapes containing that pattern even if the Java source code does not. In any case, such simple patterns should be optimized and as Vladimir mentioned, it should be a `::Value` optimization.

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PR: https://git.openjdk.java.net/jdk/pull/2776