Summary:
This patch adds the following intrinsics for creating two-tuple,
three-tuple and four-tuple scalable vectors:
* llvm.aarch64.sve.tuple.create2
* llvm.aarch64.sve.tuple.create3
* llvm.aarch64.sve.tuple.create4
As well as:
* llvm.aarch64.sve.tuple.get
* llvm.aarch64.sve.tuple.set
For extracting and inserting scalable vectors from vector tuples. These
intrinsics are intended to be used by the ACLE functions svcreate<n>,
svget and svset.
This patch also includes calling convention support for passing and
returning tuples of scalable vectors to/from functions.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D75674
