Re: [GOLD] override get_comdat_behavior

[Ian Lance Taylor <iant at google dot com>]

On Wed, Oct 17, 2012 at 8:02 AM, Alan Modra <amodra@gmail.com> wrote:
> Powerpc use of .got2 section in -fPIC code can lead to "relocation
> refers to discarded section" warnings in testcases like gcc's
> g++.old-deja/g++.other/comdat5.C when comdat group sections for a
> function are dropped but not the function's .got2 entries.  This type
> of problem shows up in other sections shared between functions on
> powerpc64, eg. .opd and .toc.  Fixed by suppressing the warning the
> same way bfd ld does.  OK to apply?
>
>         * target-reloc.h (relocate_section): Call get_comdat_behavior
>         from class Relocate.
>         * arm.cc (Relocate::get_comdat_behavior): New.
>         * i386.cc (Relocate::get_comdat_behavior): New.
>         * sparc.cc (Relocate::get_comdat_behavior): New.
>         * tilegx.cc (Relocate::get_comdat_behavior): New.
>         * x86_64.cc (Relocate::get_comdat_behavior): New.
>         * powerpc.cc (Relocate::get_comdat_behavior): New.
>         (Target_powerpc::relocate_section): Don't zap opd relocs.


You can implement this without requiring every target to have a
trivial get_comdat_behavior method.  Add a new template parameter to
relocate_section in target-reloc.h.  Give it a default value.

template<..., typename Relocate_omdat_behaviour = Default_comdat_behavior>
inline void
Relocate_section(...)

Add a local variable
  Relocate_comdat_behavior comdat_behavior;

Change the calls to get_comdat_behavior() to call comdat_behavior.get().

Change the function get_comdat_behavior to

class Default_comdat_behavior
{
 public:
  Comdat_behavior
  get(const char *name)
  {
    // Same implementation.
  }
};

At this point all the target should work with the old behavior.  Now
change the call to relocate_section in powerpc.cc to pass
Powerpc_comdat_behavior as the last template argument.  Write that
class with a get method that does what you want.

All untested, obviously.

Ian