r220270 - in /branches/google/gcc-4_9/gcc: comm...

[ccoutant@gcc.gnu.org]

Author: ccoutant
Date: Fri Jan 30 00:50:32 2015
New Revision: 220270

URL: https://gcc.gnu.org/viewcvs?rev=220270&root=gcc&view=rev
Log:
Add -ftwo-level-line-tables and -gline-tables-only options.

With -ftwo-level-line-tables, GCC will generate two-level line tables,
which adds inline call information to the line tables, obviating the
need to keep bulky debug info around for the purposes of generating
stack traces.

The -gline-tables-only option suppresses all other debug info except
the single DW_AT_compilation_unit DIE that points to the line table
for that compilation unit, and any .debug_ranges entries needed for
that DIE.

Two-level line tables are being proposed for the DWARF version 6
standard, and are described here:

  http://dwarfstd.org/ShowIssue.php?issue=140906.1

  http://wiki.dwarfstd.org/index.php?title=TwoLevelLineTables

In order to generate two-level line tables, GCC requires support
from the assembler, in the form of new .subprog and .lloc pseudo-ops.

This patch is for the google/gcc-4_9 branch. I plan to propose it
for trunk after we gain more experience with it.

2015-01-23  Cary Coutant  <ccoutant@google.com>

gcc/
	* common.opt (-ftwo-level-line-tables): New option.
        (-gline-tables-only): New option.
	* dwarf2out.c (struct dw_line_info_table_struct): Add subprog_num
        and context fields.
	(dwarf2out_abstract_function): Check for line tables only.
	(dwarf2out_decl): Likewise.
	(block_stack): New variable.
	(dwarf2out_begin_block): For two-level line tables, keep a stack of
	current blocks.
	(dwarf2out_end_block): Likewise.
	(dwarf2out_var_location): Check for line tables only.
	(new_line_info_table): Initialize subprog_num and context fields.
	(struct subprog_entry): New type.
	(struct subprog_hasher): New type.
	(subprog_hasher::hash): New function.
	(subprog_hasher::equal): New function.
	(subprog_table): New variable.
	(last_subprog_num): New variable.
	(add_subprog_entry): New function.
	(struct block_entry): New type.
	(struct block_hasher): New type.
	(block_hasher::hash): New function.
	(block_hasher::equal): New function.
	(block_table): New variable.
	(struct logical_entry): New type.
	(struct logical_hasher): New type.
	(logical_hasher::hash): New function.
	(logical_hasher::equal): New function.
	(logical_table): New variable.
	(last_logical_num): New variable.
	(scan_blocks_for_inlined_calls): New function.
	(dwarf2out_begin_function): For two-level line tables, build map
	of blocks to inlined call stacks.
	(out_subprog_directive): New function.
	(out_logical_entry): New function.
	(dwarf2out_source_line): Add support for two-level line tables.
	(dwarf2out_init): Create subprog_table, block_table, and logical_table.
	(dwarf2out_finish): When -gline-tables-only is set, always output
	the compilation_unit DIE; don't output aranges table.
	* final.c (final_start_function): Move call to number blocks...
	(rest_of_handle_final): ... to here.
	* opts.c (common_handle_option): Add -gline-tables-only.
	(set_debug_level): Clear debug_line_tables_only flag.

Modified:
    branches/google/gcc-4_9/gcc/common.opt
    branches/google/gcc-4_9/gcc/dwarf2out.c
    branches/google/gcc-4_9/gcc/final.c
    branches/google/gcc-4_9/gcc/opts.c