Re-commit after adding "-aarch64-neon-syntax=generic" to fix the failure on OS X.
This patch was firstly committed in r239514, then reverted in r239544 because of a syntax incompatible failure on OS X.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239711 91177308-0d34-0410-b5e6-96231b3b80d8