[ARM,MVE] Add the `vsbciq` intrinsics.

Authored by simon_tatham on Mar 3 2020, 9:37 AM.


[ARM,MVE] Add the vsbciq intrinsics.

These are exactly parallel to the existing vadciq intrinsics, which
we implemented last year as part of the original MVE intrinsics
framework setup.

Just like VADC/VADCI, the MVE VSBC/VSBCI instructions deliver two
outputs, both of which the intrinsic exposes: a modified vector
register and a carry flag. So they have to be instruction-selected in
C++ rather than Tablegen. However, in this case, that's trivial: the
same C++ isel routine we already have for VADC works unchanged, and
all we have to do is to pass it a different instruction id.

Reviewers: MarkMurrayARM, dmgreen, miyuki, ostannard

Reviewed By: miyuki

Subscribers: kristof.beyls, hiraditya, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D75444