This is xnu-8019. See this file in:
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#BEGIN	Machine dependent Makefile fragment for x86_64
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CWARNFLAGS = $(CWARNFLAGS_STD) -Wno-atomic-implicit-seq-cst

# Files that must go in the __HIB segment:
UNCONFIGURED_HIB_FILES=					\
           WKdmDecompress_new.o         \
           WKdmData_new.o               \
           hibernate_restore.o          \
           bcopy.o			\
           bzero.o

HIB_FILES=$(filter $(UNCONFIGURED_HIB_FILES),$(OBJS))

# Unconfigured __HIB files must be Mach-O for "setsegname"
WKdmDecompress_new.o_CFLAGS_ADD += -fno-stack-protector -fno-stack-check $(CFLAGS_NOLTO_FLAG)
WKdmData_new.o_CFLAGS_ADD += -fno-stack-protector -fno-stack-check $(CFLAGS_NOLTO_FLAG)
hibernate_restore.o_CFLAGS_ADD += -fno-stack-protector -fno-stack-check $(CFLAGS_NOLTO_FLAG)
bcopy.o_CFLAGS_ADD += -fno-stack-protector -fno-stack-check $(CFLAGS_NOLTO_FLAG)
bzero.o_CFLAGS_ADD += -fno-stack-protector -fno-stack-check $(CFLAGS_NOLTO_FLAG)
fp_simd.o_SFLAGS_ADD += -mavx512f

# To appear at the beginning of the __HIB segment, emit
# as Mach-O so that the linker can enforce symbol order
boot_pt.o_CFLAGS_ADD += $(CFLAGS_NOLTO_FLAG)

# fast path lock C leaf functions must be built without stack frames
locks_i386_opt.o_CFLAGS_ADD += -momit-leaf-frame-pointer -O2

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#END	Machine dependent Makefile fragment for x86_64
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