[2/5] s390: Fix missing .size directives.

It seems at some point the .size hook was hijacked to emit some
machine-specific directives, and the actual .size directive was
forgotten.  This caused problems for split-stack support, since
linker couldn't scan the function body for non-split-stack calls.

gcc/ChangeLog:

	* config/s390/s390.c (s390_asm_declare_function_size): Add code
	to actually emit the .size directive.
---
 gcc/ChangeLog          | 5 +++++
 gcc/config/s390/s390.c | 4 +++-
 2 files changed, 8 insertions(+), 1 deletion(-)

On 01/02/2016 08:16 PM, Marcin Kościelnicki wrote:
> It seems at some point the .size hook was hijacked to emit some
> machine-specific directives, and the actual .size directive was
> forgotten.  This caused problems for split-stack support, since
> linker couldn't scan the function body for non-split-stack calls.
> 
> gcc/ChangeLog:
> 
> 	* config/s390/s390.c (s390_asm_declare_function_size): Add code
> 	to actually emit the .size directive.

...

>  s390_asm_declare_function_size (FILE *asm_out_file,
> -				const char *fnname ATTRIBUTE_UNUSED, tree decl)
> +				const char *fnname, tree decl)
>  {
> +  if (!flag_inhibit_size_directive)
> +    ASM_OUTPUT_MEASURED_SIZE (asm_out_file, fnname);
>    if (DECL_FUNCTION_SPECIFIC_TARGET (decl) == NULL)
>      return;
>    fprintf (asm_out_file, "\t.machine pop\n");

It would be good to use the original ASM_DECLARE_FUNCTION_SIZE macro from config/elfos.h here.  This
probably would require to change its name in s390.h first and then use it from
s390_asm_declare_function_size. Not really beautiful but at least changes to the original macro
would not require adjusting our backend.

-Andreas-

On Wed, Jan 20, 2016 at 02:16:23PM +0100, Andreas Krebbel wrote:
> On 01/02/2016 08:16 PM, Marcin Kościelnicki wrote:
> >  s390_asm_declare_function_size (FILE *asm_out_file,
> > -				const char *fnname ATTRIBUTE_UNUSED, tree decl)
> > +				const char *fnname, tree decl)
> >  {
> > +  if (!flag_inhibit_size_directive)
> > +    ASM_OUTPUT_MEASURED_SIZE (asm_out_file, fnname);
> >    if (DECL_FUNCTION_SPECIFIC_TARGET (decl) == NULL)
> >      return;
> >    fprintf (asm_out_file, "\t.machine pop\n");
> 
> It would be good to use the original ASM_DECLARE_FUNCTION_SIZE macro from config/elfos.h here.  This
> probably would require to change its name in s390.h first and then use it from
> s390_asm_declare_function_size. Not really beautiful but at least changes to the original macro
> would not require adjusting our backend.

Maybe it's better not to invent yet another solution to deal with
this and just do it like proposed in the patch.  So if the default
implementation is ever changed, the same search pattern will find
all identical copies of the code.

Ciao

Dominik ^_^  ^_^

On 01/20/2016 02:16 PM, Andreas Krebbel wrote:
> On 01/02/2016 08:16 PM, Marcin Kościelnicki wrote:
>> It seems at some point the .size hook was hijacked to emit some
>> machine-specific directives, and the actual .size directive was
>> forgotten.  This caused problems for split-stack support, since
>> linker couldn't scan the function body for non-split-stack calls.
>>
>> gcc/ChangeLog:
>>
>> 	* config/s390/s390.c (s390_asm_declare_function_size): Add code
>> 	to actually emit the .size directive.
> 
> ...
> 
>>  s390_asm_declare_function_size (FILE *asm_out_file,
>> -				const char *fnname ATTRIBUTE_UNUSED, tree decl)
>> +				const char *fnname, tree decl)
>>  {
>> +  if (!flag_inhibit_size_directive)
>> +    ASM_OUTPUT_MEASURED_SIZE (asm_out_file, fnname);
>>    if (DECL_FUNCTION_SPECIFIC_TARGET (decl) == NULL)
>>      return;
>>    fprintf (asm_out_file, "\t.machine pop\n");
> 
> It would be good to use the original ASM_DECLARE_FUNCTION_SIZE macro from config/elfos.h here.  This
> probably would require to change its name in s390.h first and then use it from
> s390_asm_declare_function_size. Not really beautiful but at least changes to the original macro
> would not require adjusting our backend.

I've looked into how the other archs are doing this and didn't find anything better than just
including the code from the original macro. The real fix probably would be to turn this into a
target hook instead.

I've committed the patch now since it fixes a real problem not only with split-stack.

Thanks!

-Andreas-