THIS IS A PROOF OF CONCEPT, PLEASE DO NOT REVIEW
We're sharing this patch for people who want to try out the full C/C++ ->
asm flow for the SME (and some of the SME2) intrinsics. The patch can be
applied to b50392342be27efdc01d877ba0c357485dc7e918.
Some parts are being upstreamed independently from this proof of concept.
Some changes in this patch may have already diverged from the patches that
are in flight on Phabricator (this is mostly true for the SME2 assembler).