Enable libmvec support for AArch64

This patch enables libmvec on AArch64. The proposed change is mainly
implementing build infrastructure to add the new routines to ABI,
tests and benchmarks. I have demonstrated how this all fits together
by adding implementations for vector cos, in both single and double
precision, targeting both Advanced SIMD and SVE.

The implementations of the routines themselves are just loops over the
scalar routine from libm for now, as we are more concerned with
getting the plumbing right at this point. We plan to contribute vector
routines from the Arm Optimized Routines repo that are compliant with
requirements described in the libmvec wiki.

Building libmvec requires minimum GCC 10 for SVE ACLE. To avoid raising
the minimum GCC by such a big jump, we allow users to disable libmvec
if their compiler is too old.

Note that at this point users have to manually call the vector math
functions. This seems to be acceptable to some downstream users.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/INSTALL b/INSTALL
index b406a11268..91262cfe00 100644
--- a/INSTALL
+++ b/INSTALL
@@ -493,6 +493,9 @@ build the GNU C Library:
      For s390x architecture builds, GCC 7.1 or higher is needed (See gcc
      Bug 98269).
 
+     For AArch64 architecture builds with mathvec enabled, GCC 10 or
+     higher is needed due to dependency on arm_sve.h.
+
      For multi-arch support it is recommended to use a GCC which has
      been built with support for GNU indirect functions.  This ensures
      that correct debugging information is generated for functions