cse.c (is_dead_reg): Change argument to const_rtx.

cse.c (is_dead_reg): Change argument to const_rtx.

gcc/
	* cse.c (is_dead_reg): Change argument to const_rtx.
	(dead_debug_insn_data): Delete.
	(is_dead_debug_insn): Expand commentary.  Turn from being a
	for_each_rtx callback to being a function that examines
	each subrtx itself.  Take the fields of dead_debug_insn_data
	as argument.
	(delete_trivially_dead_insns): Update call accordingly.

From-SVN: r214630