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Re: [PATCH x86_64] Optimize access to globals in "-fpie -pie" builds with copy relocations


On February 5, 2015 12:29:40 AM GMT+01:00, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>On Wed, Feb 4, 2015 at 3:10 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Wed, Feb 4, 2015 at 2:47 PM, Bernhard Reutner-Fischer
>> <rep.dot.nop@gmail.com> wrote:
>>> On February 4, 2015 11:37:01 PM GMT+01:00, "H.J. Lu"
><hjl.tools@gmail.com> wrote:
>>>>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.
>>>
>>> Yea and i think this is still wrong and known as
>>> http://gcc.gnu.org/PR32219
>>>
>>
>
>I am testing this patch.

I cannot test it ATM, sorry.

Please make sure to add the test case from the PR32219, comment13  https://gcc.gnu.org/bugzilla/attachment.cgi?id=27716&action=diff#gcc-4_7-branch/gcc/testsuite/gcc.dg/visibility-21.c_sec1

The PR33219 should be marked as 4.8, 4.9, 5.0 regression, too.

Thanks for taking care of this one!



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