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Re: [PATCH] PR gold/17640
- From: Ilya Tocar <tocarip dot intel at gmail dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Cary Coutant <ccoutant at google dot com>, Binutils <binutils at sourceware dot org>
- Date: Fri, 13 Mar 2015 14:26:31 +0300
- Subject: Re: [PATCH] PR gold/17640
- Authentication-results: sourceware.org; auth=none
- References: <CAMe9rOq-uSd64h6eeogR3SywtQipMupN9Ng9-EvPLF+3bp7Exw at mail dot gmail dot com> <20150305104052 dot GA16361 at msticlxl7 dot ims dot intel dot com> <CAMe9rOqRQ+HMS12+hn9Nz0pnb95tUDmbAU2QjK9G1Rc-q=woCA at mail dot gmail dot com> <20150310112745 dot GA104717 at msticlxl7 dot ims dot intel dot com> <CAMe9rOoG6NOVLYxZBJ5KRuS9_47=ptsd=Ft9iA9HfN2Asw0UeQ at mail dot gmail dot com> <20150312143236 dot GA95320 at msticlxl7 dot ims dot intel dot com> <CAMe9rOpn0uGDm1qbwgL-7CiYKjQeSHMHX6WzsnZ6eyfcp2MBAw at mail dot gmail dot com> <20150312145732 dot GB95320 at msticlxl7 dot ims dot intel dot com> <CAHACq4qF26jr8QYR_V55oVewLyHpgD2g7TrxDmgye0_S4pdroQ at mail dot gmail dot com> <CAMe9rOrMMxkR4bnoomCdW2P6TQtExMyMeC1oBHXNE3vXEEawLw at mail dot gmail dot com>
On 12 Mar 16:37, H.J. Lu wrote:
> On Thu, Mar 12, 2015 at 3:08 PM, Cary Coutant <ccoutant@google.com> wrote:
> > + // If we convert this from
> > + // mov foo@GOT(%reg), %reg
> > + // to
> > + // lea foo@GOTOFF(%reg), %reg
> > + // in Relocate::relocate, then there is nothing to do here.
> > + // Avoid converting _DYNAMIC, because its address may be used.
> >
> > I'm sorry, but I still don't understand the rationale for treating
> > _DYNAMIC specially. If you convert all of the references to @GOTOFF,
> > what's the point of having the GOT entry? If the loader is going to
> > use it, how does it find it?
I was trying to mirror behavior of bfd linker.
>
> It is related to
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=14538
>
> With the old x86-64 elf_machine_dynamic, we generate
>
> addq _DYNAMIC@GOTPCREL(%rip), %rdx
>
> We need to keep _DYNAMIC GOT entry.
>
Than why does 32-bit bfd linker also avoids optimizing _DYNAMIC?