Clang changed to representing tuples of scalable vectors as
structs rather than as wide vectors (that is, scalable vector types
where the `N` part of the `<vscale x N x ty>` type was multiplied by
the number of vectors). rustc mirrored this in the initial implementation
of scalable vectors.
Earlier versions of our patches used the wide vector representation and
our intrinsic patches used the legacy
`llvm.aarch64.sve.tuple.{create,get,set}{2,3,4}` intrinsics for creating
these tuples/getting/setting the vectors, which were only supported
due to LLVM's `AutoUpgrade` pass converting these intrinsics into
`llvm.vector.insert`. `AutoUpgrade` only supports these legacy intrinsics
with the wide vector representation.
With the current struct representation, Clang has special handling in
codegen for generating `insertvalue`/`extractvalue` instructions for
these operations, which must be replicated by rustc's codegen for our
intrinsics to use. This patch implements new intrinsics in
`core::intrinsics::scalable` (mirroring the structure of
`core::intrinsics::simd`) which rustc lowers to the appropriate
`insertvalue`/`extractvalue` instructions.
David Wood
4fbcb031de