[Libre-soc-isa] [Bug 933] prefix-code (like huffman code) decode/encode instructions

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Sat Sep 24 09:49:52 BST 2022


https://bugs.libre-soc.org/show_bug.cgi?id=933

--- Comment #30 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Jacob Lifshay from comment #29)

> a prefix-code encode instruction is possibly not as necessary, since it's
> possible to encode in parallel by looking up the symbol's bits and lengths
> in a table, and shifting them into position in parallel and or-ing them all
> together.

mapreduce-mode on a scalar-targetted sv.or would do the job there.
sv.or/mr

some time ago i was looking at a bitmanip instruction to combine the
shift-and-or into one instruction.  bmset group? v. expensive operations,
3-in 1-out, has to be done as an RT-overwrite

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