dwarf2out.c (add_dwarf_attr): Check we don't add duplicate attributes.

2017-08-30  Richard Biener  <rguenther@suse.de>

	* dwarf2out.c (add_dwarf_attr): Check we don't add duplicate
	attributes.
	(gen_subprogram_die): Add DW_AT_object_pointer only early.
	(dwarf2out_early_global_decl): Only generate a DIE for the
	abstract origin if it doesn't already exist or is a declaration DIE.
	(resolve_addr): Do not add the linkage name twice when
	generating a stub DIE for the DW_TAG_GNU_call_site target.

	* g++.dg/pr78112-2.C: Do not expect duplicate DW_AT_object_pointer.

From-SVN: r251448