[Libre-soc-bugs] [Bug 230] Video opcode development and discussion

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=230

--- Comment #22 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Cole Poirier from comment #21)

> > thinking that through is an exercise that i have done many times.  all
> > designs involving temporary result storage require far more complexity than
> > i am comfortable with committing to within an already heavily pressured
> > timeframe where we are at least 8 months behind where we should be.
> 
> Would scratch-pad memories be applicable in this instance?

probably depends on the context for which you're thinking scratchpad memories
might be useful.

if they are for a single dedicated purpose, for use by one thread and one
thread only, then they need not be protected by context-switching or anything
at all.

any such scratchpad memory, if considered for use for the explicit purpose of
context-switching (to save for example the above-mentioned "temporary
registers") then its designation actually switches from "scratchpad memory" to
"a type of register file".  which we already said isn't ok to add, because of
the complexity it introduces in its management during context-switching.

the other option is to throw away the entirety of the micro-op up until that
point, and restart it once the context-switch returns.  i dislike these types
of wasteful "solutions".... and, again, they actually have to have resources
dedicated to implementing them.

*whatever* is proposed, there will be an evaluation cost, a design cost, an
implementation cost and a testing cost.

we do not have time for that on something that we have no input yet as to
whether it is 1% used, 10% used or 30% used.

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