[Libre-soc-bugs] [Bug 776] Documentation of designs, code, processes, and other relevant things as needed

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=776

--- Comment #4 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Konstantinos Margaritis (markos) from comment #3)
> (In reply to Jacob Lifshay from comment #2)
> > unfortunately, because a long-multiply needs 2 kinds of insns
> > (carrying-wide-madd and carrying-add), you can't easily do that as a REMAP
> > schedule. Additionally, it is substantially faster to use Karatsuba
> > multiplication once you get inputs more than a few hundred bits wide (and
> > other more complex algorithms for wider multiplies).
> 
> I would pick the simplest and fastest to implement long-multiply method for
> this one, speed is not a requirement. We can always optimize later.

yes, except that the stuff that's going into the PowerISA spec. needs to
actually be as fast as we can make it since it's for forever, not just for the
crypto-router.

imho doing REMAP for just O(n^2) multiply is fine (except for the complexity
due to multiple different insns), since Karatsuba multiplication can just run
those insns a bunch of times.

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