[PATCH][RFC]Speed up bfd_dwarf2_find_line.

[Nick Clifton]

Hi Doug,

> 2007-07-17  Doug Kwan  <dougkwan@google.com>
> 
>     Speed up bfd_dwarf2_find_line.
>     * dwarf2.c (struct dwarf2_debug): Add new fields to support function
>     and variable info hash tables. Add last_comp_unit, info_hash_count,
>     funcinfo_hash_table, varinfo_hash_table, hash_units_head.
>     (struct comp_unit): Add prev_unit, cached.
>     (struct info_list_node, struct info_hash_entry,
>     struct info_hash_table): New.
>     (info_hash_table_newfunc, create_info_hash_table,
>     insert_info_hash_table, lookup_info_hash_table): New functions
>     implementing function and variable info hash tables.
>     (scan_unit_for_symbols): Add checks to make sure hash tables are
>     consistent with compilation units.
>     (comp_unit_maybe_decode_line_info): New function.
>     (comp_unit_find_line): Use comp_unit_maybe_decode_line_info.
>     (reverse_funcinfo_list, reverse_varinfo_list, comp_unit_hash_info,
>     info_hash_lookup_funcinfo, info_hash_lookup_varinfo,
>     stash_maybe_update_info_hash_table, stash_verify_info_hash_table,
>     stash_maybe_enable_info_hash_tables, stash_find_line_fast): New
>     functions. Make use of info hash tables to speed up
>     bfd_dwarf2_find_line.
>     (find_line): Use hash table for faster lookup if it is turned on.
>     Also add code to maintain bi-directional link in comp units.

Approved and applied.

Cheers
   Nick