rtl.h (emit): Add an optional boolean parameter to control whether barriers are emitted.

rtl.h (emit): Add an optional boolean parameter to control whether barriers are emitted.

gcc/
	* rtl.h (emit): Add an optional boolean parameter to control
	whether barriers are emitted.
	* emit-rtl.c (emit): Likewise.
	* gensupport.c (get_emit_function): Return null rather than "emit".
	* genemit.c (gen_emit_seq): Handle the null return value.
	Don't emit barriers after the final instruction in the sequence.
	* gentarget-def.c (main): Don't emit barriers after the instruction.

From-SVN: r225000