* cse.c (is_dead_reg): Change into inline function that is not
	called through for_each_rtx.
	(set_live_p): Adjust caller.
	(insn_live_p): Don't reset DEBUG_INSNs here.
	(struct dead_debug_insn_data): New data. 
	(count_stores, is_dead_debug_insn, replace_dead_reg): New functions.
	(delete_trivially_dead_insns): If there is just one setter for the
	dead reg that is referenced by some DEBUG_INSNs, create a DEBUG_EXPR
	and add DEBUG_INSN for it right before the removed setter and
	use the DEBUG_EXPR instead of the dead pseudo.

From-SVN: r165452