This is the main CodeGen patch to support the arm64_32 watchOS ABI in LLVM.
FastISel is mostly disabled for now since it would generate incorrect code for
ILP32.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371722 91177308-0d34-0410-b5e6-96231b3b80d8