[vectorIntrinsics] RFR: 8283413: Add C2 mid-end and x86 back-end implementation for bit REVERSE operation [v2]

[Xiaohong Gong]

On Tue, 22 Mar 2022 01:20:25 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> src/hotspot/share/opto/compile.cpp line 3425:
>> 
>>> 3423:     }
>>> 3424:     break;
>>> 3425:   }
>> 
>> The mid-end part looks good to me.  Thanks! BTW, may I ask why you add this transformation here while not in the `ReverseVNode::Idea()` ? Thanks so much！
>
> Blend IR node is created in a subsequent step after ReverseV node creation and are not visible to during eager identity transformation of ReverseV;   Final graph reshaping gives us opportunity to perform point transformation on graph patterns which cannot be easily handled through gvn based transformations.

I see. Thanks for your explanation!

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PR: https://git.openjdk.java.net/panama-vector/pull/182