[Bug ld/19739] New: ld.bfd performance regression

[address@hidden]

https://sourceware.org/bugzilla/show_bug.cgi?id=19739

            Bug ID: 19739
           Summary: ld.bfd performance regression
           Product: binutils
           Version: 2.26
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: address@hidden
  Target Milestone: ---

ld.bfd -r on mips

When compiling object files with dwarf debug info the link time goes up
significantly. I suspect this is due to the large amount of sections.

I needed to reduce the amount of object files used in the example below because
otherwise it would just never stop.


Binutils 2.23.2, not very fast, but acceptable.

Samples: 8K of event 'cycles', Event count (approx.): 5959804941
 64.81%  ld-new  ld-new             [.] _bfd_elf_make_section_from_shdr
 11.45%  ld-new  [kernel.kallsyms]  [k] 0xffffffff8103ba6a
  2.51%  ld-new  ld-new             [.] walk_wild_section_general
  1.62%  ld-new  libc-2.12.so       [.] __gconv_transform_utf8_internal




Binutils 2.26

Samples: 214K of event 'cycles', Event count (approx.): 161542081964
 68.51%  ld-new  ld-new             [.] bfd_get_next_section_by_name
 14.44%  ld-new  libc-2.12.so       [.] __strcmp_sse42
 10.75%  ld-new  ld-new             [.] gldelf32btsmip_place_orphan
  2.40%  ld-new  ld-new             [.] _bfd_elf_make_section_from_shdr
  1.67%  ld-new  [kernel.kallsyms]  [k] 0xffffffff8103ba6a



       │      for (sh = (struct section_hash_entry *) sh->root.next;
  0.00 │      test   %rbx,%rbx
       │    ↓ je     50
       │           sh != NULL;
       │           sh = (struct section_hash_entry *) sh->root.next)
       │        if (sh->root.hash == hash
  0.78 │28:   cmp    %rbp,0x10(%rbx)
  1.38 │    ↑ jne    20
       │           && strcmp (sh->root.string, name) == 0)
 85.90 │      mov    0x8(%rbx),%rdi
  5.69 │      mov    %r13,%rsi
  0.01 │    → callq  address@hidden
       │      hash = sh->root.hash;
       │      name = sec->name;


Is this sufficient information ?

Thanks

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