https://lists.libre-soc.org/pipermail/libre-soc-dev/2022-April/004701.html
marking as blocking bug #776 since this is part of NLnet.2021.02A.052.CryptoRouter and that seemed like an appropriate bug so this doesn't get lost. budget TBD.
this was when i was looking at Intel's mulx instruction app note from 2012. the alternative idea i had was to create an "add-using-cr-fields" instruction which would create overflow in a CR field but also use CRfs as carry-in and carry-out. TBdiscussed