[Libre-soc-isa] [Bug 1056] questions and feedback (v2) on OPF RFC ls010

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=1056

--- Comment #13 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
i started on an illustrative page, which gives some idea as to
what addi would be turned into (if done in a naive but "at-the-trenches"
way).  bear in mind that *200* of these modifications would be needed (!!!)

   https://libre-soc.org/openpower/sv/ls010/hypothetical_addi/

the absolute most important thing - not really emphasised enough before - is
that the operands MUST NOT change (bits, meaning)

it is ABSOLUTELY PROHIBITED to have this, just because {PO14} is {PO9}
prefixed:

    sv.addi RT,RA,SI,R

aside from anything, where on earth would you get the contents of the "R"
field from? there's certainly no room in the *PO9-Prefix* bits.

i did actually try this once (redefinition of the Suffix operands based
on Prefixing).  it was awful.  six months later i was still unwinding
the damage done.

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