i386: Disable check_consistency for GCC 5 and above [BZ #25788]

  check_consistency should be disabled for GCC 5 and above since there is
no fixed PIC register in GCC 5 and above.  Check __GNUC_PREREQ (5,0)
instead OPTIMIZE_FOR_GCC_5 since OPTIMIZE_FOR_GCC_5 is false with
-fno-omit-frame-pointer.
---
 sysdeps/unix/sysv/linux/i386/sysdep.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
  

On 06/04/2020 10:24, H.J. Lu via Libc-alpha wrote:
> check_consistency should be disabled for GCC 5 and above since there is
> no fixed PIC register in GCC 5 and above.  Check __GNUC_PREREQ (5,0)
> instead OPTIMIZE_FOR_GCC_5 since OPTIMIZE_FOR_GCC_5 is false with
> -fno-omit-frame-pointer.
> ---
>  sysdeps/unix/sysv/linux/i386/sysdep.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/i386/sysdep.h b/sysdeps/unix/sysv/linux/i386/sysdep.h
> index 5e3888060b..6671afe65e 100644
> --- a/sysdeps/unix/sysv/linux/i386/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/i386/sysdep.h
> @@ -580,8 +580,9 @@ struct libc_do_syscall_args
>  # define EXTRAVAR_5
>  #endif
>  
> -/* Consistency check for position-independent code.  */
> -#if defined __PIC__ && !defined OPTIMIZE_FOR_GCC_5
> +/* Consistency check for position-independent code.  Disabled for GCC 5
> +   and above since there is no fixed PIC register in GCC 5 and above.  */
> +#if defined __PIC__ && !__GNUC_PREREQ (5,0)
>  # define check_consistency()						      \
>    ({ int __res;								      \
>       __asm__ __volatile__						      \
> 

I think we can just remove the check_consistency altogether, since 
we already required GCC 6.2 or later to build gcc (4dcbbc3b28a).
  

On Mon, Apr 6, 2020 at 6:31 AM Adhemerval Zanella via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
>
>
> On 06/04/2020 10:24, H.J. Lu via Libc-alpha wrote:
> > check_consistency should be disabled for GCC 5 and above since there is
> > no fixed PIC register in GCC 5 and above.  Check __GNUC_PREREQ (5,0)
> > instead OPTIMIZE_FOR_GCC_5 since OPTIMIZE_FOR_GCC_5 is false with
> > -fno-omit-frame-pointer.
> > ---
> >  sysdeps/unix/sysv/linux/i386/sysdep.h | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/sysdeps/unix/sysv/linux/i386/sysdep.h b/sysdeps/unix/sysv/linux/i386/sysdep.h
> > index 5e3888060b..6671afe65e 100644
> > --- a/sysdeps/unix/sysv/linux/i386/sysdep.h
> > +++ b/sysdeps/unix/sysv/linux/i386/sysdep.h
> > @@ -580,8 +580,9 @@ struct libc_do_syscall_args
> >  # define EXTRAVAR_5
> >  #endif
> >
> > -/* Consistency check for position-independent code.  */
> > -#if defined __PIC__ && !defined OPTIMIZE_FOR_GCC_5
> > +/* Consistency check for position-independent code.  Disabled for GCC 5
> > +   and above since there is no fixed PIC register in GCC 5 and above.  */
> > +#if defined __PIC__ && !__GNUC_PREREQ (5,0)
> >  # define check_consistency()                                               \
> >    ({ int __res;                                                                    \
> >       __asm__ __volatile__                                                  \
> >
>
> I think we can just remove the check_consistency altogether, since
> we already required GCC 6.2 or later to build gcc (4dcbbc3b28a).

This affects all branches.  I prefer this so that it can be backported.  Support
for GCC older than GCC 5 should be removed as a separate patch.
  

On 06/04/2020 10:35, H.J. Lu wrote:
> On Mon, Apr 6, 2020 at 6:31 AM Adhemerval Zanella via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
>>
>>
>>
>> On 06/04/2020 10:24, H.J. Lu via Libc-alpha wrote:
>>> check_consistency should be disabled for GCC 5 and above since there is
>>> no fixed PIC register in GCC 5 and above.  Check __GNUC_PREREQ (5,0)
>>> instead OPTIMIZE_FOR_GCC_5 since OPTIMIZE_FOR_GCC_5 is false with
>>> -fno-omit-frame-pointer.
>>> ---
>>>  sysdeps/unix/sysv/linux/i386/sysdep.h | 5 +++--
>>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/sysdeps/unix/sysv/linux/i386/sysdep.h b/sysdeps/unix/sysv/linux/i386/sysdep.h
>>> index 5e3888060b..6671afe65e 100644
>>> --- a/sysdeps/unix/sysv/linux/i386/sysdep.h
>>> +++ b/sysdeps/unix/sysv/linux/i386/sysdep.h
>>> @@ -580,8 +580,9 @@ struct libc_do_syscall_args
>>>  # define EXTRAVAR_5
>>>  #endif
>>>
>>> -/* Consistency check for position-independent code.  */
>>> -#if defined __PIC__ && !defined OPTIMIZE_FOR_GCC_5
>>> +/* Consistency check for position-independent code.  Disabled for GCC 5
>>> +   and above since there is no fixed PIC register in GCC 5 and above.  */
>>> +#if defined __PIC__ && !__GNUC_PREREQ (5,0)
>>>  # define check_consistency()                                               \
>>>    ({ int __res;                                                                    \
>>>       __asm__ __volatile__                                                  \
>>>
>>
>> I think we can just remove the check_consistency altogether, since
>> we already required GCC 6.2 or later to build gcc (4dcbbc3b28a).
> 
> This affects all branches.  I prefer this so that it can be backported.  Support
> for GCC older than GCC 5 should be removed as a separate patch.

Fair enough, LGTM then.