On Thu, May 28, 2015 at 2:27 PM, Sriraman Tallam <tmsri...@google.com> wrote:
> On Thu, May 28, 2015 at 2:01 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>> On Thu, May 28, 2015 at 1:54 PM, Sriraman Tallam <tmsri...@google.com> wrote:
>>> On Thu, May 28, 2015 at 12:05 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>>>> On Thu, May 28, 2015 at 11:50 AM, Sriraman Tallam <tmsri...@google.com>
>>>> wrote:
>>>>> On Thu, May 28, 2015 at 11:42 AM, H.J. Lu <hjl.to...@gmail.com> wrote:
>>>>>> On Thu, May 28, 2015 at 11:34 AM, Sriraman Tallam <tmsri...@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.
>>>
>>
>> Since direct_p is true, do wee need
>>
>> + if (GET_CODE (call_op) != SYMBOL_REF
>> + || SYMBOL_REF_LOCAL_P (call_op))
>> + return false;
>
> We do need it right because for this case below, I do not want an
> indirect call:
>
> __attribute__((noplt))
> int foo() {
> return 0;
> }
>
> int main()
> {
> return foo();
> }
>
> Assuming foo is not inlined, if I remove the lines you mentioned, I
> will get an indirect call which is unnecessary.
>
I meant the "GET_CODE (call_op) != SYMBOL_REF" part isn't
needed.
--
H.J.
