[Libre-soc-isa] [Bug 1017] ISA WG RFC for binary and ternary bitops

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=1017

--- Comment #26 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Luke Kenneth Casson Leighton from comment #25)
> (In reply to Jacob Lifshay from comment #24)
> 
> > still don't agree with only having a crbinlut instruction that uses a CR as
> > the LUT.

> the instructions remain in.

in that case, please let me insert a note to the isa wg that we considered the
alternative of also/instead having a crbinlog that uses a gpr for the lut but
you overrode my objections, because otherwise i consider intentionally
submitting something with known easily-fixable flaws from my perspective and
intentionally hiding them to be unethical and I can not sign off on that. I am
not trying to say you are unethical, because you honestly believe those to not
be flaws.

> i have explained adequately that those reasons are invalid due to lack of
> knowledge on your part.

I understand you point, however I know that your justification of power usage
is almost certainly incorrect because of nearly all usage of crbinlog requiring
a separate instruction to move the lut from a gpr immediately before
crbinlog...executing a full separate instruction almost certainly requires
substantially more power than having crbinlog read the lut from a GPR directly.

also, there are ease-of-use and code size considerations due to the extra gpr
-> cr move usually being required.

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