Niels Möller nisse at lysator.liu.se
Wed Jun 30 19:42:59 UTC 2021

nisse at lysator.liu.se (Niels Möller) writes:

> nisse at lysator.liu.se (Niels Möller) writes:
>> You're idea of conditonally adding the invariant d * B2 at the right
>> place is also interesting,
> I've tried it out. Works nicely, but no speedup on my machine. I'm
> attaching another patch. There are then 4 methods:
> method 1: Old loop around udiv_qrnnd_preinv.
> method 2: The clever code from 10 years ago, with the microoptimization
>   I commited the other day.
> method 3: More or less the same as I posted a few days ago.
> method 4: Postpones the update u1 -= u2 d, off the critical recurrency
>   chain. Instead, conditionally adds in the constant B2 (B - d) to the
>   lower u limbs.

I'm tempted to commit this code. I.e., new variants (not enabled) +
tuneup changes. To see which variants are favorites on the various test
machines. Should give some guidance as to what's most promising for
assembly implementation.

What do you think?


Niels Möller. PGP-encrypted email is preferred. Keyid 368C6677.
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