[Libre-soc-isa] [Bug 937] instructions for bigint shift and prefix-code encode

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Fri Oct 28 08:47:07 BST 2022


--- Comment #23 from Jacob Lifshay <programmerjake at gmail.com> ---
for bigint shift, (as well as other useful stuff that needs dynamic shifting),
we will want the equivalent of RVV's vslideup/vslidedown -- they shift a vector
by a variable number of whole elements (dsld/dsrd handles shifts within

Technically, they can be done by using svindex, but that wastes a bunch of
extra registers, takes extra time to set up the indices' values and is likely
to be quite slow.

Additional instructions for shifts by constant amounts aren't needed since we
can use svstate.offset combined with adjusting register numbers in the

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