in this case for CPU_SUBTYPE_ARM64_ALL.
For this cpusubtype it should default to a cyclone CPU
to give proper disassembly without a -mcpu= flag.
rdar://27767188
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294771 91177308-0d34-0410-b5e6-96231b3b80d8