RFR: 8333583: Crypto-XDH.generateSecret regression after JDK-8329538 [v3]

[Volodymyr Paprotski]

On Mon, 24 Jun 2024 14:48:43 GMT, Ferenc Rakoczi <duke at openjdk.org> wrote:

>> @ferakocz just tagging you as reminder of (the many) items in your queue :) 
>> Thanks!
>
>> @ferakocz just tagging you as reminder of (the many) items in your queue :) Thanks!
> 
> Sorry, I was out of office last week. I will take a deeper look at the changes tomorrow, but I have a question based on my first look at it: Do you attribute the performance loss of the XDH code path to the mult() function returning an int instead of being void? Do you think that this prevented some optimization in the hotspot compiler?

@ferakocz, now I was out on long weekend...

> Do you attribute the performance loss of the XDH code path to the mult() function returning an int instead of being void? Do you think that this prevented some optimization in the hotspot compiler?

That's exactly it. I 'proved experimentally' that that's the case. Though I haven't identified which exact sequence of optimizations is missing deterministically from compilation logs. That's beyond me yet. Identifying which optimization(s) is missing might be great for long term, but figured since we are closing down commits for this release, I should put something in soonest. This PR essentially 'reverts' the part of my ECC PR to original code. Which in turn should be easiest to review.

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PR Comment: https://git.openjdk.org/jdk/pull/19728#issuecomment-2186847183