Re: [Sbcl-devel] Modular functions for PPC

[Alexey D. <ade...@co...>]

Hello,

Christophe Rhodes <cs...@ca...> writes:

> Hence new derive-type
> optimizers, which required factoring things so that I could apply
> combinations of auxiliary functions rather than writing 8
> almost-identical pieces of code :-)

Good! It will be very useful, if some day we will be asked to derive
types of *-MOD32.

> Alexey, does this look right so far?

Yes. You can also strip several lines from definitions of
32BIT-LOGICAL-* and BIGNUM-LOGNOT. Ideally, their definitions may be
shared between backends.

>  I confess that I _still_ don't
> understand what a "good" modular function is, so I've ignored that
> bit.

Neither do I, as you can see from the name "good" :-). The idea is
that for some functions (now AND and IOR) the general variant with the
ub32 VOP works good enough. The only difference is in a situation,
when 32-bit result is produced from bignum or negative source. But I'd
prefer to see such code before thinking how to optimize it properly.

-- 
Regards,
Alexey Dejneka

"Alas, the spheres of truth are less transparent than those of
illusion." -- L.E.J. Brouwer