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

[Sandhya Viswanathan]

On Fri, 8 Apr 2022 19:14:33 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> src/hotspot/cpu/x86/x86.ad line 8700:
>> 
>>> 8698:   format %{ "vector_popcount_long  $dst, $src\t! using $xtmp1, $xtmp2, $xtmp3, and $rtmp as TEMP" %}
>>> 8699:   ins_encode %{
>>> 8700:     assert(UsePopCountInstruction, "not enabled");
>> 
>> The assert needs to be removed on this path. Do you know why the testing didn't catch this?
>
> Same a above, it should be OK to keep this as is since its already used in match_rule_supported method.

But this is !VM_Version::supports_avx512_vpopcntdq() so UsePopCountInstruction should have been false.

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