[vectorIntrinsics] RFR: 8283709: Add x86 back-end implementation for bit BIT_COUNT operation [v7]

[Sandhya Viswanathan]

On Fri, 8 Apr 2022 19:14:40 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> src/hotspot/cpu/x86/x86.ad line 8673:
>> 
>>> 8671:     BasicType bt = Matcher::vector_element_basic_type(this, $src);
>>> 8672:     __ evmovdquq($dst$$XMMRegister, $src$$XMMRegister, vlen_enc);
>>> 8673:     __ vector_popcount_integral_evex(bt, $dst$$XMMRegister, $src$$XMMRegister, $mask$$KRegister, true, vlen_enc);
>> 
>> No auto vectorizer path here where the result in int vector for long vector.
>
> Yes, because this is predicated operation pattern and auto-vectorizer does not support predicate operation inferencing.

The post loop work on the mainline would support the masked instructions generation.

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PR: https://git.openjdk.java.net/panama-vector/pull/185