RFR: 8329538: Accelerate P256 on x86_64 using Montgomery intrinsic [v2]

[Volodymyr Paprotski]

On Tue, 16 Apr 2024 02:26:57 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Per-above, this is a switch statement (`UNLIKELY`) fallback. I can still add alignment and loop rotation, but being a fallback figured its more important to keep it small&readable...
>
> It's all part of intrinsic, no harm in polishing it.

Done (normalized loop/backedge). There was actually a problem in the loop counter.. (`i-=1` instead of `i-=16`). Can't include a test since classes are sealed, but verified manually.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/18583#discussion_r1578172873