One of the defining features of the SVE ACLE types is that they
are "sizeless"; see the SVE ACLE spec:
or the email message:
for a fuller definition of what that means.
This patch adds two associated type queries:
- isSizelessBuiltinType asks specifically about types that are built into clang. It is effectively an enum range check.
- isSizelessType instead tests for any type that has the "sizeless" type property. At the moment it only returns true for the built-in types, but it seems better not to hard-code that assumption throughout the codebase. (E.g. we could in principle support some form of user-defined sizeless types in future. Even if that seems unlikely and never actually happens, the possibility at least exists.)