Re: [PATCH v3, Fortran] TS 29113 testsuite

[Sandra Loosemore <sandra@codesourcery.com>]

On 9/3/21 3:14 AM, Tobias Burnus wrote:

> If I read https://gcc.gnu.org/onlinedocs/gcc/Floating-Types.html 
> correctly, we should use _Float128 for the following errors
> 
> "The _Float128 type is supported on all systems where __float128 is 
> supported or where long double has the IEEE binary128 format."
> 
> Applies to:
> 
>> For
>> typecodes-array-float128.f90
>> FAIL: gfortran.dg/c-interop/typecodes-array-float128.f90   -O0  (test 
>> for excess errors)
>> Excess errors:
>> /gcc/testsuite/gfortran.dg/c-interop/typecodes-array-float128-c.c:35:32: 
>> error: '__float128' undeclared (first use in this function); did you 
>> mean '_Float128'?
>> typecodes-sanity.f90
>> FAIL: gfortran.dg/c-interop/typecodes-sanity.f90   -O0  (test for 
>> excess errors)
>> Excess errors:
>> /gcc/testsuite/gfortran.dg/c-interop/typecodes-sanity-c.c:41:13: 
>> error: '__float128' undeclared here (not in a function); did you mean 
>> '_Float128'?
>> typecodes-scalar-float128.f90
>> FAIL: gfortran.dg/c-interop/typecodes-scalar-float128.f90   -O0  (test 
>> for excess errors)
>> Excess errors:
>> /gcc/testsuite/gfortran.dg/c-interop/typecodes-scalar-float128-c.c:34:32: 
>> error: '__float128' undeclared (first use in this function); did you 
>> mean '_Float128'?

Just so I'm clear on this, the situation with ARM/AArch64 is that it 
provides _Float128 but not __float128?

The GNU Fortran manual explicitly defines C_FLOAT128 as corresponding to 
__float128, not _Float128 or some other 128-bit floating-point type.

https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gfortran/ISO_005fC_005fBINDING.html#ISO_005fC_005fBINDING

So the situation with ARM/AArch64 is that it provides _Float128 but not 
__float128?

I guess we could change the documentation and all the references in the 
implementation as well as the test cases to tie this kind to _Float128 
instead.  I think that is backward-compatible with all existing uses?

> * * *
>> PR100914.f90
>> FAIL: gfortran.dg/PR100914.f90   -O0  (test for excess errors)
>> Excess errors:
>> /gcc/testsuite/gfortran.dg/PR100914.c:8:10: fatal error: quadmath.h: 
>> No such file or directory

Does ARM/Aarch64 provide _Float128 support without also providing 
libquadmath.h?  I'm trying to understand why it got that particular 
error.  :-S

> 
>   * * *
> 
> On a normal x86-64 system, I get XPASS for:
> 
> gfortran.dg/PR100914.f90
> 
> gfortran.dg/c-interop/typecodes-array-float128.f90
> 
> The ! { dg-do run { xfail { { x86_64*-*-* i?86*-*-* } && longdouble128 } 
> } }
> does not help as it just checks whether 'sizeof(long double)==16',
> which seemingly passes also on x86-64 with 80bit long double.

I don't understand this, either.  I've been testing on an 
i686-pc-linux-gnu build with both -m32 and -m64.  The tests PASS on -m32 
and XFAIL on -m64.  The XFAIL is there because with -m64, sizeof (long 
double) == 16 and it can't be disambiguated from the true 128-bit 
floating point type __float128 which also has size 16, and the other 
patch I committed makes it choose the standard type over the GNU 
extension type.  With -m32, the 80-bit long double type has size 12 
instead so there is no conflict.

-Sandra