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Re: PATCH: Store ELF section index for input file
On Sun, Mar 20, 2005 at 04:19:46PM +1030, Alan Modra wrote:
> On Sat, Mar 19, 2005 at 09:57:01AM -0800, H. J. Lu wrote:
> > On Sat, Mar 19, 2005 at 08:14:00PM +1030, Alan Modra wrote:
> > > On Thu, Mar 17, 2005 at 12:58:27PM -0800, H. J. Lu wrote:
> > > > @@ -4823,9 +4830,16 @@ _bfd_elf_section_from_bfd_section (bfd *
> > > > const struct elf_backend_data *bed;
> > > > int index;
> > > >
> > > > - if (elf_section_data (asect) != NULL
> > > > - && elf_section_data (asect)->this_idx != 0)
> > > > - return elf_section_data (asect)->this_idx;
> > > > + if (elf_section_data (asect) != NULL)
> > > > + {
> > > > + index = elf_section_data (asect)->this_idx;
> > > > + if (index != 0)
> > > > + {
> > > > + Elf_Internal_Shdr **i_shdrp = elf_elfsections (abfd);
> > > > + if (!i_shdrp || i_shdrp [index]->bfd_section == asect)
> > > > + return index;
> > > > + }
> > > > + }
> > >
> > > Please explain why this change is necessary.
> > >
> >
> > _bfd_elf_section_from_bfd_section is called on input sections. When
> > there are more than 64K input sections, linear search over a linked
> > list can be very very slow. Since this_idx isn't used for input section
> > and for input section, its bfd section is created from its ELF
> > section index, we can use this_idx to store the ELF section index. The
> > result is the linking time went from
>
> No, I meant why that particular hunk. You first posted a patch without
> it, then just said it was needed, but not why.
>
I don't think it is really needed. I put it there for sanity check. I
think we can remove it.
> > 966.01s user 0.81s system 99% cpu 16:06.87 total
> >
> > to
> >
> > 45.61s user 0.81s system 99% cpu 46.448 total
> >
> > It is 20X speed up. I tested it with Linux kernel, binutils, gcc and
> > glibc on ia32, ia64 and x86_64. There are no regressions.
> >
> > BTW, it only solves the 64K input section problem. The 64K output
> > sections is still very slow. bfd_section has a pointer to its BFD
> > owner. Can we add a pointer to bfd_section, used_by_ld, which will
> > be used by ld for lang_output_section_statement_type?
>
> I think it might be worth investigating a larger change, not creating
> lang_output_section_statemtents for orphans. I'll look at this some
> time when I have a free moment or two.
Great.
H.J.