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

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Sat Dec 19 17:37:32 GMT 2020


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

--- Comment #58 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to cand from comment #12)
> Commented on the horizontal mapreduce.

i got it.  i gotitigotit.

ok so if it is acceptable to use a destination *vector* for the mapreduce, then
all elements above 0 may be used to compute and store intermediary results.

this gets rid of the huge problem associated with performing large numbers of
non-reentrant iterations, discarding work that was half way completed just
because of an interrupt.

also initially i thought it would be a problem to store sufficient state to
manage this, i realised that in the STATE SPR there are *two* offsets, srcoffs
destoffs, the 2nd normally being used for twin predication.

of course, 2pred can't have mapreduce done on it because it is 1 src 1 dest.

therefore destoffs is free for use.

ta-daaa :)

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