[Bug ld/21677] ld 2.27 has unexplained 10x performance improvement in some cases

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=21677

--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to H.J. Lu from comment #3)
> (In reply to Doug from comment #1)
> > Some additional detail:
> > 
> > This behaviour appears only while linking executables with 
> > 
> > gcc -Wl,--gc-sections
> > 
> > against .a archives that contain object code compiled with 
> > 
> > gcc -ffunction-sections -fdata-sections
> 
> Did you see the improvement on ALL targets or just x86 targets?
> This commit:
> 
> commit d968975277ba280372002800c6c25bb1b29f496e
> Author: H.J. Lu <address@hidden>
> Date:   Wed Apr 20 05:26:37 2016 -0700
> 
>     Check ELF relocs after opening all input files
>     
>     Delaying checking ELF relocations until opening all input files so
>     that symbol information is final when relocations are checked.  This
>     is only enabled for x86 targets.
>     
> improved --gc-sections performance, but only on x86.

Also this patch:

commit fbf05aa70d7a6ad3dd92ca718faa4bb383b975ee
Author: H.J. Lu <address@hidden>
Date:   Wed Apr 20 17:06:58 2016 -0700

    Move ELF relocation check after lang_gc_sections

    Move ELF relocation check after lang_gc_sections so that all the
    reference counting code for plt and got relocs can be removed.  This
    only affects ELF targets which check relocations after opening all
    input file.

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