[libre-riscv-dev] [Bug 173] dynamic partitioned "shift"

[bugzilla-daemon at libre-riscv.org]

http://bugs.libre-riscv.org/show_bug.cgi?id=173

--- Comment #21 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Michael Nolan from comment #17)
> > it does... however i think the Switch statement really has to go.  if
> > you
> > run "proc" "opt" then "show top" on a 64-bit shifter, it's awful.
> > the MUX chain is absolutely dreadful: each "switch" statement gets
> > turned
> > into a "if x == 0b00001 if x == 0b00010 if x == 0b000011"... with the
> > results *chained* between each!

Note that there are specific yosys optimizations for mux trees that greatly
simplify them: muxpack is probably the one you want to try

http://www.clifford.at/yosys/cmd_muxpack.html

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