[PATCH 3/4] Use libc_fe* macros in ldbl-128/e_expl.c.

[Adhemerval Zanella]

On 25/03/2020 12:00, Adhemerval Zanella wrote:
> 
> 
> On 25/03/2020 07:13, Stefan Liebler via Libc-alpha wrote:
>> Unfortunately, this patch is responsible for testfails on x86_64:
>>
>> math/test-float128-exp.out:
>> Failure: exp (-0x1p-10000): Exception "Underflow" set
>> Failure: exp (-0x2p-16384): Exception "Underflow" set
>> ...
>>
>> math/test-float128-cexp.out:
>> Failure: Real part of: cexp (0x2p-16384 - 0x4p-1076 i): Exception "Underflow" set
>> Failure: Real part of: cexp (0x2p-16384 - 0x8p-152 i): Exception "Underflow" set
> 
> The sysdeps/x86/fpu/fenv_private.h states:
> 
> 296 #ifdef __x86_64__
> 297 /* The SSE rounding mode is used by soft-fp (libgcc and glibc) on
> 298    x86_64, so that must be set for float128 computations.  */
> 299 # define SET_RESTORE_ROUNDF128(RM) \
> 300   SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetround_sse, libc_feresetround_sse)
> 
> So 
> 
>>> diff --git a/sysdeps/ieee754/ldbl-128/e_expl.c b/sysdeps/ieee754/ldbl-128/e_expl.c
>>> index 37c1538c08..104ace1690 100644
>>> --- a/sysdeps/ieee754/ldbl-128/e_expl.c
>>> +++ b/sysdeps/ieee754/ldbl-128/e_expl.c
>>> @@ -66,6 +66,7 @@
>>>   #include <inttypes.h>
>>>   #include <math-barriers.h>
>>>   #include <math_private.h>
>>> +#include <fenv_private.h>
>>>   #include <math-underflow.h>
>>>   #include <stdlib.h>
>>>   #include "t_expl.h"
>>> @@ -146,9 +147,10 @@ __ieee754_expl (_Float128 x)
>>>         union ieee854_long_double ex2_u, scale_u;
>>>         fenv_t oldenv;
>>>   -      feholdexcept (&oldenv);
>>>   #ifdef FE_TONEAREST
>>> -      fesetround (FE_TONEAREST);
>>> +      libc_feholdexcept_setroundl (&oldenv, FE_TONEAREST);
> 
> Should be libc_feholdexcept_setroundf128.

But it does not see to help here, so I don't know what is failing as well.

> 
>>> +#else
>>> +      libc_feholdexceptl (&oldenv);
> 
> And here libc_fesetenvf128.
> 
>>>   #endif
>>>           /* Calculate n.  */
>>> @@ -198,7 +200,7 @@ __ieee754_expl (_Float128 x)
>>>         math_force_eval (x22);
>>>           /* Return result.  */
>>> -      fesetenv (&oldenv);
>>> +      libc_fesetenvl (&oldenv);
>>>           result = x22 * ex2_u.d + ex2_u.d;
> 
> It might require extend the libc_*f128 macros to other architectures
> (not sure).
>