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Re: [RFC][PATCH][X86_64] Eliminate PLT stubs for specified external functions via -fno-plt=
- From: Sriraman Tallam <tmsriram at google dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Pedro Alves <palves at redhat dot com>, Michael Matz <matz at suse dot de>, David Li <davidxl at google dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Jan Hubicka <hubicka at ucw dot cz>, amonakov at ispras dot ru
- Date: Thu, 28 May 2015 11:50:54 -0700
- Subject: Re: [RFC][PATCH][X86_64] Eliminate PLT stubs for specified external functions via -fno-plt=
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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);
}
Thanks
Sri
>
> --
> H.J.