[Libre-soc-isa] [Bug 817] Big Integer Math (sv.adde, sv.subfe, sv.madded, 128 by 64-bit -> 64-bit div/rem, maybe more...)

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=817

--- Comment #36 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Jacob Lifshay from comment #35)

> well...is 3-in 3-out more expensive than needing an extra compare
> instruction in an important use of divmodqdu?

hell yes. that's 6 FFs inside an entire Dependency Matrix Row.

> i guess we could, instead of writing CR0 or OV, just have it compare like so:
> cmpl n_hi, d
> divmodqdu qhat, d, n_lo, n_hi

much better / sane

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