Re: [RFC][PATCH][X86_64] Eliminate PLT stubs for specified external functions via -fno-plt=

[Sriraman Tallam <tmsriram at google dot com>]

On Thu, May 28, 2015 at 12:05 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, May 28, 2015 at 11:50 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>> On Thu, May 28, 2015 at 11:42 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Thu, May 28, 2015 at 11:34 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>>>> I have attached a patch that adds the new attribute "noplt".  Please review.
>>>>
>>>> * config/i386/i386.c (avoid_plt_to_call): New function.
>>>> (ix86_output_call_insn): Generate indirect call for functions
>>>> marked with "noplt" attribute.
>>>> (attribute_spec ix86_attribute_): Define new attribute "noplt".
>>>> * doc/extend.texi: Document new attribute "noplt".
>>>> * gcc.target/i386/noplt-1.c: New testcase.
>>>> * gcc.target/i386/noplt-2.c: New testcase.
>>>>
>>>
>>> 2 comments:
>>>
>>> 1. Don't remove "%!" prefix before call/jmp.  It is needed for MPX.
>>> 2. Don't you need to check
>>>
>>>       && !TARGET_MACHO
>>>       && !TARGET_SEH
>>>       && !TARGET_PECOFF
>>>
>>> since it only works for ELF.
>>
>> Ok, I will make this change. OTOH, is it just better to piggy-back on
>> existing -fno-plt change by Alex in calls.c
>> and do this:
>>
>> Index: calls.c
>> ===================================================================
>> --- calls.c (revision 223720)
>> +++ calls.c (working copy)
>> @@ -226,9 +226,11 @@ prepare_call_address (tree fndecl_or_type, rtx fun
>>         && targetm.small_register_classes_for_mode_p (FUNCTION_MODE))
>>        ? force_not_mem (memory_address (FUNCTION_MODE, funexp))
>>        : memory_address (FUNCTION_MODE, funexp));
>> -  else if (flag_pic && !flag_plt && fndecl_or_type
>> +  else if (fndecl_or_type
>>     && TREE_CODE (fndecl_or_type) == FUNCTION_DECL
>> -   && !targetm.binds_local_p (fndecl_or_type))
>> +   && !targetm.binds_local_p (fndecl_or_type)
>> +   && ((flag_pic && !flag_plt)
>> +       || (lookup_attribute ("noplt", DECL_ATTRIBUTES(fndecl_or_type)))))
>>      {
>>        funexp = force_reg (Pmode, funexp);
>>      }
>>
>
> Does it work on non-PIC calls?

You are right, it doesnt work.  I have attached the patch with the
changes you mentioned.

Thanks
Sri

>
> --
> H.J.

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