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


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?

-- 
H.J.


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