This is xnu-8019. See this file in:
Directory listing for xnu-8019//bsd/dev/arm64
conf.c
cpu_copy_in_cksum.s
cpu_in_cksum.s
cpu_memcmp_mask.s
disassembler.c
dtrace_isa.c
dtrace_subr_arm.c
fasttrap_isa.c
fbt_arm.c
sdt_arm.c
sysctl.c