[Libre-soc-isa] [Bug 1089] feedback on OPF SVP64 RFC for "managment" instructions: ls008

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Thu Nov 30 23:19:13 GMT 2023


https://bugs.libre-soc.org/show_bug.cgi?id=1089

--- Comment #3 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Dmitry Selyutin from comment #2)
> Luke, could you, please, clarify, what's assumed here with "remove _RT and
> _RA"? From the page I saw this:
> 
> Notation, Section 1.3.2
> When destination register operands (RT, RS) are prefixed by a single
> underscore (_RT, _RS) the variable also contains the contents of the
> instruction field. This avoids confusion in pseudocode when a destination
> register is assigned (RT <- x) but earlier it was the operand bits that were
> checked (if RT = 0).
> 
> I assume that we need to discard the underscore from pseudocode variables,
> is it correct?

yes. basically (RA) is for accessing the *contents of the regfile* for register
RA, where "RA" is just "the register number".

however if you want to *assign* to register RA in Power ISA section 1.3
notation you do "RA <- xyz" which obviously does NOT chnge the 5 bits
in the binary instruction.

this confused the hell out of me so i added _RA notation. unnecessarily.
has to go.

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