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Date: Wed, 04 Feb 2015 22:37:00 -0000
Message-ID: <CAMe9rOoGdDBpn12LFyTqdbfhdOxXgw4i9Xmk34fj=K+KzhSoAw@mail.gmail.com>
Subject: Re: [PATCH x86_64] Optimize access to globals in "-fpie -pie" builds with copy relocations
From: "H.J. Lu" <hjl.tools@gmail.com>
To: Sriraman Tallam <tmsriram@google.com>
Cc: Jakub Jelinek <jakub@redhat.com>, Uros Bizjak <ubizjak@gmail.com>, 	"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>, David Li <davidxl@google.com>, 	Cary Coutant <ccoutant@google.com>
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On Wed, Feb 4, 2015 at 1:53 PM, Sriraman Tallam <tmsriram@google.com> wrote:
> On Wed, Feb 4, 2015 at 10:57 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Wed, Feb 4, 2015 at 10:51 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>>> On Wed, Feb 4, 2015 at 10:45 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> On Wed, Feb 4, 2015 at 10:42 AM, Jakub Jelinek <jakub@redhat.com> wrote:
>>>>> On Wed, Feb 04, 2015 at 10:38:48AM -0800, H.J. Lu wrote:
>>>>>> Common symbol should be resolved locally for PIE.
>>>>>
>>>>> binds_local_p yes, binds_to_current_def_p no.
>>>>>
>>>>
>>>> Is SYMBOL_REF_LOCAL_P set to binds_local_p or
>>>> binds_to_current_def_p?
>>>
>>> Looks like binds_local_p:
>>>
>>> varasm.c:
>>> void
>>> default_encode_section_info (tree decl, rtx rtl, int first ATTRIBUTE_UNUSED)
>>> {
>>>   ...
>>>   if (targetm.binds_local_p (decl))
>>>     flags |= SYMBOL_FLAG_LOCAL;
>>>
>>
>> Why is SYMBOL_REF_LOCAL_P false?
>
> In varasm.c, default_binds_local_p_1
>
>
>  /* Default visibility weak data can be overridden by a strong symbol
>      in another module and so are not local.  */
>   else if (DECL_WEAK (exp)
>   && !resolved_locally)
           ^^^^^^^^^^^^^^^^^^^
Why is resolved_locally false? It should be true for common
symbol when compiling for PIE.

>     local_p = false;
>
> For weak definition, it is set to false here.
>

-- 
H.J.