[Libre-soc-dev] [RFC] SVP64 on branch instructions

Luke Kenneth Casson Leighton lkcl at lkcl.net
Tue Aug 10 12:48:43 BST 2021

hm, i'm starting to implement the SVP64 Branch in ISACaller and ran immediately
into an issue.  unlike CTR decrementing, combining SVSTEP capability into Branch
is actually very complicated: a lot of gates, a lot of state.

question: when preparing the *next* SVSTATE (the next src/dest step), do you
use the CR bit to test from the *CURRENT* src/dest step, or the NEXT src/dest

what happens when REMAP is involved? how many gates in the chain are
there before you can even determine if the branch should go ahead?

CTR you can just subtract one.

much as i would like an svstep mode in sv.bc, it's too CISC.  annoying.


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