This patch introduces an option to enable the generation of location
views along with location lists.  The exact format depends on the
DWARF version: it can be a separate attribute (DW_AT_GNU_locviews) or
(DW_LLE_view_pair) entries in DWARF5+ loclists.

Line number tables are also affected.  If the assembler is found, at
compiler build time, to support .loc views, we use them and
assembler-computed view labels, otherwise we output compiler-generated
line number programs with conservatively-computed view labels.  In
either case, we output view information next to line number changes
when verbose assembly output is requested.

This patch requires an LVU patch that modifies the exported API of
final_scan_insn.  It also expects the entire SFN patchset to be
installed first, although SFN is not a requirement for LVU.

for  include/ChangeLog

	* dwarf2.def (DW_AT_GNU_locviews): New.
	* dwarf2.h (enum dwarf_location_list_entry_type): Add
	DW_LLE_GNU_view_pair.
	(DW_LLE_view_pair): Define.

for  gcc/ChangeLog

	* common.opt (gvariable-location-views): New.
	(gvariable-location-views=incompat5): New.
	* config.in: Rebuilt.
	* configure: Rebuilt.
	* configure.ac: Test assembler for view support.
	* dwarf2asm.c (dw2_asm_output_symname_uleb128): New.
	* dwarf2asm.h (dw2_asm_output_symname_uleb128): Declare.
	* dwarf2out.c (var_loc_view): New typedef.
	(struct dw_loc_list_struct): Add vl_symbol, vbegin, vend.
	(dwarf2out_locviews_in_attribute): New.
	(dwarf2out_locviews_in_loclist): New.
	(dw_val_equal_p): Compare val_view_list of dw_val_class_view_lists.
	(enum dw_line_info_opcode): Add LI_adv_address.
	(struct dw_line_info_table): Add view.
	(RESET_NEXT_VIEW, RESETTING_VIEW_P): New macros.
	(DWARF2_ASM_VIEW_DEBUG_INFO): Define default.
	(zero_view_p): New variable.
	(ZERO_VIEW_P): New macro.
	(output_asm_line_debug_info): New.
	(struct var_loc_node): Add view.
	(add_AT_view_list, AT_loc_list): New.
	(add_var_loc_to_decl): Add view param.  Test it against last.
	(new_loc_list): Add view params.  Record them.
	(AT_loc_list_ptr): Handle loc and view lists.
	(view_list_to_loc_list_val_node): New.
	(print_dw_val): Handle dw_val_class_view_list.
	(size_of_die): Likewise.
	(value_format): Likewise.
	(loc_list_has_views): New.
	(gen_llsym): Set vl_symbol too.
	(maybe_gen_llsym, skip_loc_list_entry): New.
	(dwarf2out_maybe_output_loclist_view_pair): New.
	(output_loc_list): Output view list or entries too.
	(output_view_list_offset): New.
	(output_die): Handle dw_val_class_view_list.
	(output_dwarf_version): New.
	(output_compilation_unit_header): Use it.
	(output_skeleton_debug_sections): Likewise.
	(output_rnglists, output_line_info): Likewise.
	(output_pubnames, output_aranges): Update version comments.
	(output_one_line_info_table): Output view numbers in asm comments.
	(dw_loc_list): Determine current endview, pass it to new_loc_list.
	Call maybe_gen_llsym.
	(loc_list_from_tree_1): Adjust.
	(add_AT_location_description): Create view list attribute if
	needed, check it's absent otherwise.
	(convert_cfa_to_fb_loc_list): Adjust.
	(maybe_emit_file): Call output_asm_line_debug_info for test.
	(dwarf2out_var_location): Reset views as needed.  Precompute
	add_var_loc_to_decl args.  Call get_attr_min_length only if we have the
	attribute.  Set view.
	(new_line_info_table): Reset next view.
	(set_cur_line_info_table): Call output_asm_line_debug_info for test.
	(dwarf2out_source_line): Likewise.  Output view resets and labels to
	the assembler, or select appropriate line info opcodes.
	(prune_unused_types_walk_attribs): Handle dw_val_class_view_list.
	(optimize_string_length): Catch it.  Adjust.
	(resolve_addr): Copy vl_symbol along with ll_symbol.  Handle
	dw_val_class_view_list, and remove it if no longer needed.
	(hash_loc_list): Hash view numbers.
	(loc_list_hasher::equal): Compare them.
	(optimize_location_lists): Check whether a view list symbol is
	needed, and whether the locview attribute is present, and
	whether they match.  Remove the locview attribute if no longer
	needed.
	(index_location_lists): Call skip_loc_list_entry for test.
	(dwarf2out_finish): Call output_asm_line_debug_info for test.
	Use output_dwarf_version.
	* dwarf2out.h (enum dw_val_class): Add dw_val_class_view_list.
	(struct dw_val_node): Add val_view_list.
	* final.c (SEEN_NEXT_VIEW): New.
	(set_next_view_needed): New.
	(clear_next_view_needed): New.
	(maybe_output_next_view): New.
	(final_start_function): Rename to...
	(final_start_function_1): ... this.  Take pointer to FIRST,
	add SEEN parameter.  Emit param bindings in the initial view.
	(final_start_function): Reintroduce SEEN-less interface.
	(final): Rename to...
	(final_1): ... this.  Take SEEN parameter.  Output final pending
	next view at the end.
	(final): Reintroduce seen-less interface.
	(final_scan_insn): Output pending next view before switching
	sections or ending a block.  Mark the next view as needed when
	outputting variable locations.  Notify debug backend of section
	changes, and of location view changes.
	(rest_of_handle_final): Adjust.
	* toplev.c (process_options): Autodetect value for debug variable
	location views option.  Warn on incompat5 without -gdwarf-5.
	* doc/invoke.texi (gvariable-location-views): New.
	(gvariable-location-views=incompat5): New.
	(gno-variable-location-views): New.

From-SVN: r257510