RFR: 8288294: [vector] Add Identity/Ideal transformations for vector logic operations

[Vladimir Kozlov]

On Thu, 30 Jun 2022 02:48:50 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> src/hotspot/share/opto/vectornode.cpp line 1869:
>> 
>>> 1867:   // (XorV src src)      => (Replicate zero)
>>> 1868:   // (XorVMask src src)  => (MaskAll zero)
>>> 1869:   //
>> 
>> Do we really need this? Is `Replicate` asm instruction faster than `XorV`? I understand it may help reduce registers pressure.
>
> Thanks for looking at this patch! I think the main benefit is "(Replicate zero)" is loop invariant which could be hoist outside of the loop.

okay

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PR: https://git.openjdk.org/jdk/pull/9211