RFR: 8282664: Unroll by hand StringUTF16 and StringLatin1 polynomial hash loops [v13]

[Claes Redestad]

On Sat, 12 Nov 2022 01:06:27 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Missing & 0xff in StringLatin1::hashCode
>
> src/hotspot/cpu/x86/x86_64.ad line 12073:
> 
>> 12071:                          legRegD tmp_vec13, rRegI tmp1, rRegI tmp2, rRegI tmp3, rFlagsReg cr)
>> 12072: %{
>> 12073:   predicate(UseAVX >= 2 && ((VectorizedHashCodeNode*)n)->mode() == VectorizedHashCodeNode::LATIN1);
> 
> If you represent `VectorizedHashCodeNode::mode()` as an input, it would allow to abstract over supported modes and come up with a single AD instruction. Take a look at `VectorMaskCmp` for an example (not a perfect one though since it has both _predicate member and constant input which is redundant).

Thanks for the pointer, I'll check it out!

-------------

PR: https://git.openjdk.org/jdk/pull/10847