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 SME2 intrinsics. The patch can be
applied to 453c30e9e633f5b1e9bebed950592e3e51645a94.
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.