Adds mappings between scalable MVT types and IR Types,
along with string printing. Fixes an issue reported by Jeroen.
Depends on https://reviews.llvm.org/D32530
Part of the initial SVE codegen series, rfc will be posted soon.
I can't find where these are defined, but given that the IR type is <scalable v4f32> should these names reflect that? "nx" is nice and short but may be confusing in that the mapping from "scalable" to "nx" isn't necessarily obvious.
As MC layer support for SVE started landing quite a while ago, the backend types too landed back then with names matching the then-current proposal for the IR types (<n x 4 x ...>). I agree it would be nice to have the backend type names match, but that's a bunch of churn, so it shouldn't be coupled to this patch and should wait until the IR type system changes are committed in case their name changes again.