[Libre-soc-isa] [Bug 968] document shift-and-add instruction

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Mon Oct 31 22:58:49 GMT 2022


--- Comment #8 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Andrey Miroshnikov from comment #7)
> (In reply to Luke Kenneth Casson Leighton from comment #1)
> > andrey do you also want to have a go at creating ls004 for this one?
> (In reply to Luke Kenneth Casson Leighton from comment #6)
> > any examples that need to go in ls004 RFC, links in wiki markdown
> > are there, cross-referencing.  a lot of small details.
> Added initial draft for ls004, containing what I know:
> https://libre-soc.org/openpower/sv/rfc/ls004/

the word descriptioj makes no sense at all

    `shift` is determined by the 2-bit bitfield `sm`+1.
    The minimum shift as 1, maximum 4.
    The result is shifted (RB) + (RA), and is stored in register RT.

these are not "instructions", noone could follow them step by step.
try reading them, and following them.  do you know, looking at
nothing else, what will happen?

now try this:

   wben sm is zero, the contents of register RB are multiplied by two,
   added to the contents of register RA, and the result stored in RT.

this is obvious instructions which can be followed, yes?

shadduw is "unsigned word" btw

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