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Re: [PATCH x86_64] Optimize access to globals in "-fpie -pie" builds with copy relocations
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Uros Bizjak <ubizjak at gmail dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Sriraman Tallam <tmsriram at google dot com>, Jakub Jelinek <jakub at redhat dot com>
- Date: Wed, 3 Dec 2014 05:47:32 -0800
- Subject: Re: [PATCH x86_64] Optimize access to globals in "-fpie -pie" builds with copy relocations
- Authentication-results: sourceware.org; auth=none
- References: <CAFULd4aMopCHZHTWa3V=6-CwVLq1grorwRqT7yCaOfpLWYZibw at mail dot gmail dot com> <CAMe9rOok=sUB=OVdFNt369gkpNWxVgzQKjeDVQT96SrSNRS=Vw at mail dot gmail dot com> <CAFULd4Z=WaenYMr=Ke1QLQAq4bVQpkOD_Wt3nW4w9F71fuaPAw at mail dot gmail dot com>
On Tue, Dec 2, 2014 at 12:01 PM, Uros Bizjak <ubizjak@gmail.com> wrote:
> On Tue, Dec 2, 2014 at 8:40 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Tue, Dec 2, 2014 at 11:19 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
>>> Hello!
>>>
>>>> Ping.
>>>>> Ping.
>>>>>> Ping.
>>>>>>> Ping.
>>>
>>> It would probably help reviewers if you pointed to actual path
>>> submission [1], which unfortunately contains the explanation in the
>>> patch itself [2], which further explains that this functionality is
>>> currently only supported with gold, patched with [3].
>>>
>>> [1] https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00645.html
>>> [2] https://gcc.gnu.org/ml/gcc-patches/2014-09/txt2CHtu81P1O.txt
>>> [3] https://sourceware.org/ml/binutils/2014-05/msg00092.html
>>>
>>> After a bit of the above detective work, I think that new gcc option
>>> is not necessary. The configure should detect if new functionality is
>>> supported in the linker, and auto-configure gcc to use it when
>>> appropriate.
>>
>> I think GCC option is needed since one can use -fuse-ld= to
>> change linker.
>
> IMO, nobody will use this highly special x86_64-only option. It would
> be best for gnu-ld to reach feature parity with gold as far as this
> functionality is concerned. In this case, the optimization would be
> auto-configured, and would fire automatically, without any user
> intervention.
>
Let's do it. I implemented the same feature in bfd linker on both
master and 2.25 branch.
--
H.J.