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Re: [PATCH] PR gold/17640
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Cary Coutant <ccoutant at google dot com>
- Cc: Ilya Tocar <tocarip dot intel at gmail dot com>, Binutils <binutils at sourceware dot org>
- Date: Fri, 13 Mar 2015 10:23:38 -0700
- 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> <20150313112631 dot GA72598 at msticlxl7 dot ims dot intel dot com> <CAMe9rOqs=QROJZexdXKebsKrLrNat4mg=vgzuUrUpH1skpdTTQ at mail dot gmail dot com> <CAHACq4q761ontKOo3cr46hbo5dgi7A892GMB8rBBYuYwgY8ZKA at mail dot gmail dot com>
On Fri, Mar 13, 2015 at 9:44 AM, Cary Coutant <ccoutant@google.com> wrote:
>> addq _DYNAMIC@GOTPCREL(%rip), %rax
>> ...
>> addl _DYNAMIC@GOT(%ecx), %eax
>> ...
>> Both requires preserve _DYNAMIC GOT entry.
>
> Well, yes, these aren't mov instructions, and we won't optimize them
> because of that. That's the point of this test:
>
> + if (view[reloc.get_r_offset() - 2] == 0x8b)
> + break;
>
> You still haven't explained why we need to look for the symbol
> "_DYNAMIC" and treat it as a special case.
>
This isn't the optimal code. Compiler may generate
movl %eax, %edx
movl _DYNAMIC@GOT(%ecx), %eax
addl %edx, %eax
instead of
addl _DYNAMIC@GOT(%ecx), %eax
I just want to be on the safe side.
--
H.J.