- Global vector variables expose the vector ABI through their alignments only
if they are >=16 bytes in size.
- Vectors passed between functions expose the vector ABI only if they are
<=16 bytes in size.
LLVM test suite builds with gcc/clang now give the same gnu attributes emitted.
Reviewed By: Ulrich Weigand
Differential Revision: https://reviews.llvm.org/D141409
