re PR debug/43478 (Missing DW_AT_location for a variable)

re PR debug/43478 (Missing DW_AT_location for a variable)

	PR debug/43478
	* df-problems.c (struct dead_debug_use, struct dead_debug): New.
	(dead_debug_init, dead_debug_finish): New functions.
	(dead_debug_add, dead_debug_insert_before): Likewise.
	(df_note_bb_compute): Initialize a dead_debug object, add dead
	debug uses to it, insert debug bind insns before death insns,
	reset debug insns that refer to pending uses at the end.
	* rtl.h (make_debug_expr_from_rtl): New prototype.
	* varasm.c (make_debug_expr_from_rtl): New function.

Co-Authored-By: Jakub Jelinek <jakub@redhat.com>
From-SVN: r159063