Add GCC support for -gfission option. Debug info is partitioned

Add GCC support for -gfission option.  Debug info is partitioned
into skeleton sections that will remain in the .o file, and "dwo"
sections that will be moved to a .dwo file.  After compilation,
the gcc driver calls objcopy twice: once to extract the "dwo"
sections into the .dwo file, and a second time to remove the
sections from the .o file.

For google/gcc-4_6 branch. (To be submitted for trunk soon.)

Tested: bootstrap,core,mantle,crust

2012-03-09  Sterling Augustine  <saugustine@google.com>
	    Cary Coutant  <ccoutant@google.com>

	* gcc.c (ASM_FINAL_SPEC): For -gfission, call objcopy.
	(static_spec_functions): Add replace-extension.
	(replace_extension_spec_func): New function.
	* dwarf2out.c (debug_skeleton_info_section)
	(debug_skeleton_abbrev_section, debug_ref_section, debug_addr_section)
	(debug_skeleton_line_section, debug_str_offsets_section): New
	variables.
	(struct indirect_string_node): Add index field.
	(DEBUG_DWO_INFO_SECTION, DEBUG_DWO_ABBREV_SECTION, DEBUG_REF_SECTION)
	(DEBUG_ADDR_SECTION, DEBUG_DWO_LINE_SECTION)
	(DEBUG_NORM_STR_OFFSETS_SECTION, DEBUG_DWO_STR_OFFSETS_SECTION)
	(DEBUG_STR_OFFSETS_SECTION, DEBUG_DWO_STR_SECTION)
	(DEBUG_NORM_STR_SECTION): New debug section macros.
	(DEBUG_STR_SECTION): Change definition for -gfission.
	(DEBUG_STR_SECTION_FLAGS): Don't set SECTION_MERGE for -gfission.
	(DEBUG_SKELETON_LINE_SECTION_LABEL, DEBUG_SKELETON_INFO_SECTION_LABEL)
	(DEBUG_SKELETON_ABBREV_SECTION_LABEL, DEBUG_REF_SECTION_LABEL)
	(DEBUG_ADDR_SECTION_LABEL): New section label macros.
	(SKELETON_COMP_DIE_ABBREV, SKELETON_TYPE_DIE_ABBREV): New macros.
	(debug_skeleton_info_section_label, debug_skeleton_abbrev_section_label)
	(debug_ref_section_label, debug_addr_section_label)
	(debug_skeleton_line_section_label): New section label variables.
	(dwarf_attr_name): Add new attribute names.
	(dwarf_form_name): Add new form names.
	(AT_index): New function.
	(set_AT_index): New function.
	(index_string_table): New variable.
	(AT_string_form): Use DW_FORM_GNU_str_index for -gfission.
	(add_addr_table_entry): New function.
	(add_AT_addr): Record index for indirect references with -gfission.
	(add_AT_lbl_id): Likewise.
	(add_ref_table_entry): New function.
	(add_AT_range_list): Use indirect reference for -gfission.
	(break_out_comdat_types): Don't add DW_AT_GNU_pubnames/pubtypes
	attributes here.
	(size_of_die): Account for indirect forms with -gfission.
	(value_format): Use indirect forms for -gfission.
	(output_die_abbrevs): New function.
	(output_abbrev_section): Refactor code into output_die_abbrevs.
	(output_range_list_offset): New function.
	(output_loc_list_offset): New function.
	(output_attr_index_or_value): New function.
	(output_die): Call output_attr_index_or_value to output possibly
	indirect forms.  Output indirect strings for -gfission.
	(add_AT_pubnames): New function.
	(add_top_level_skeleton_die_attrs): New function.
	(skeleton_type_unit): New variable.
	(output_skeleton_debug_sections): New function.
	(output_comdat_type_unit): Write to .debug_types.dwo for -gfission.
	(output_pubnames): Add assembly label to beginning of section; use
	label for skeleton info section with -gfission.
	(output_aranges): Use label for skeleton info section with -gfission.
	(output_line_info ): Add prologue_only parameter.
	(dwarf2out_init): Create new sections for -gfission.
	(output_index_strings): New function.
	(output_ref_table): New function.
	(output_addr_table): New function.
	(index_location_lists): New function.
	(dwarf2out_finish): For -gfission, write skeleton debug sections,
	write pubnames tables unconditionally, and write indirect sections.
	* opts.c (common_handle_option): Add OPT_gfission.
	* common.opt: Add -gfission option.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/google@185269 138bc75d-0d04-0410-961f-82ee72b054a4