This is xnu-8019. See this file in:
Directory listing for xnu-8019//osfmk/x86_64
Makefile
WKdmCompress_new.s
WKdmData_new.s
WKdmDecompress_new.s
bcopy.s
boot_pt.c
bzero.s
copyio.c
counter.c
cswitch.s
dwarf_unwind.h
idt64.s
idt_table.h
kpc_x86.c
locore.s
loose_ends.c
lowglobals.h
lowmem_vectors.c
lz4_decode_x86_64.s
machine_kpc.h
machine_remote_time.c
machine_remote_time.h
machine_routines_asm.s
mcount.s
monotonic.h
monotonic_x86_64.c
pal_routines_asm.s
pmap.c
pmap_pcid.c
start.s