_extra_flags_ = -fno-builtin -m64
-#We #undef __x86_64__ for kernelspace, not for userspace where
-#it's needed for headers to work!
-ARCH_KERNEL_DEFINES = -U__$(SUBARCH)__
KBUILD_CFLAGS += $(_extra_flags_)
-CHECKFLAGS += -m64
+CHECKFLAGS += -m64 -D__x86_64__
KBUILD_AFLAGS += -m64
LDFLAGS += -m elf_x86_64
KBUILD_CPPFLAGS += -m64
LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
LINK-y += -m64
+
+# Do unit-at-a-time unconditionally on x86_64, following the host
+KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)