realmode _WAKEUP

Hello all, There is following definition at arch/x86/realmode/rm/Makefile: KBUILD_CFLAGS := $(LINUXINCLUDE) $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \ -I$(srctree)/arch/x86/boot Is it used now? I'm asking because _WAKEUP definition everywhere undefined in the code. Thank you.