PR rtl-optimization/42889
	* df.h (df_set_bb_dirty_nonlr): New prototype.
	* df-core.c (df_set_bb_dirty_nonlr): New function.
	* df-scan.c (df_insn_rescan): Call it instead of
	df_set_bb_dirty for DEBUG_INSNs.

	* gcc.dg/pr42889.c: New test.

From-SVN: r156344