[Libre-soc-isa] [Bug 960] OPF ISA External RFC ls003 - maddedu and divmod2du

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=960

--- Comment #19 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
  75 # [DRAFT] Double-width Shift Left Doubleword
  76 
  77 VA2-Form
  78 
  80 * dsld.   RT,RA,RB,RC  (Rc=1)
  81 

damn damn damn these are also 4-in 3-out which will be such a high cost
in the Dependency Hazard Management that it will be impractical to
implement.  Rc=1 has to be eliminated.

this is what independent parallel (RS=RT+MAXVL) result production helps solve:
the result-pairs may be analysed (cmpi) and a third instruction (sv.or) used
to merge the partial results together.

a similar trick will have to be found for the other operations (using sv.subfe)

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