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

[Ludovic Henry]

On Wed, 16 Nov 2022 18:18:55 GMT, Claes Redestad <redestad 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
>
> I'm getting pulled into other tasks and would request for this to be either accepted as-is, rejected or picked up by someone else to rewrite it to something that can be accepted.
> 
> Obviously I'm biased towards acceptance: While imperfect, it provides improved testing - both functional and performance-wise - and establishes a significantly improved benchmark for more future-proof solutions to beat. There are many ways to iteratively improve upon this solution, some of which would even simplify the implementation. But in the face of upcoming changes that might allow C2 to optimize these kinds of loops without intrinsic support I am not sure spending more time on perfecting the current patch is worth our while.
> 
> Rejecting it might be the reasonable thing to do, too, especially if the C2 loop optimizations @iwanowww points out might be coming around sooner rather than later. Even if that's not coming soon, the PR at hand adds a chunk of complexity for the compiler team to maintain.

@cl4es @iwanowww is that change still good to go forward? What else would you like to see for it to be merged? Thanks!

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