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Optimize the performance of the group_setup function. 

When processing a section that is a member of a group, the group
that contains it is looked up using a linear search. The resulting
O(n^2) complexity causes significant performance issues when
dealing with object files with very many groups.

By remembering the index of the last found group and restarting
the next search from that index, the search instead becomes O(n)
in common cases.

	* elf.c (setup_group): Optimize search for group by remembering
	last found group and restarting search at that index.
	* elf-bfd.h (struct elf_obj_tdata): Add group_search_offset field.
This commit is contained in:
Jens Widell 2018-01-12 13:16:17 +00:00 committed by Nick Clifton
parent b5b6200652
commit 564e11c9a9
3 changed files with 18 additions and 3 deletions
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6
bfd/ChangeLog
View File

@ -1,3 +1,9 @@
2018-01-12 Jens Widell <jl@opera.com>
* elf.c (setup_group): Optimize search for group by remembering
last found group and restarting search at that index.
* elf-bfd.h (struct elf_obj_tdata): Add group_search_offset field.
2018-01-12 Gunther Nikl <gnikl@users.sourceforge.net>
* aoutx.h (aout_link_check_ar_symbols): Remove default and handle

4
bfd/elf-bfd.h
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@ -1909,6 +1909,10 @@ struct elf_obj_tdata
Elf_Internal_Shdr **group_sect_ptr;
int num_group;
/* Index into group_sect_ptr, updated by setup_group when finding a
section's group. Used to optimize subsequent group searches. */
unsigned int group_search_offset;
unsigned int symtab_section, dynsymtab_section;
unsigned int dynversym_section, dynverdef_section, dynverref_section;

11
bfd/elf.c
View File

@ -737,10 +737,14 @@ setup_group (bfd *abfd, Elf_Internal_Shdr *hdr, asection *newsect)
if (num_group != (unsigned) -1)
{
unsigned int i;
unsigned int search_offset = elf_tdata (abfd)->group_search_offset;
unsigned int j;
for (i = 0; i < num_group; i++)
for (j = 0; j < num_group; j++)
{
/* Begin search from previous found group. */
unsigned i = (j + search_offset) % num_group;
Elf_Internal_Shdr *shdr = elf_tdata (abfd)->group_sect_ptr[i];
Elf_Internal_Group *idx;
bfd_size_type n_elt;
@ -803,7 +807,8 @@ setup_group (bfd *abfd, Elf_Internal_Shdr *hdr, asection *newsect)
if (shdr->bfd_section != NULL)
elf_next_in_group (shdr->bfd_section) = newsect;
i = num_group - 1;
elf_tdata (abfd)->group_search_offset = i;
j = num_group - 1;
break;
}
}