Re: New signaling NaN causes 12 testsuite failures

[Steve Kargl <sgk@troutmask.apl.washington.edu>]

On Tue, Jan 25, 2022 at 09:05:55AM +0100, FX wrote:
> Hi Steve,
> 
> > New signaling NaN causes 12 testsuite failures
> 
> Thanks for alerting me.
> 
> > Line 42 of signal_1.f90 looks wrong unless the
> > line is testing conversion on assignment.  Should
> > y be x?
> 
> Indeed. Fixed: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=c0a4a658097c56fa03d04b8d15c3ea02961d62a4
> 

Thanks.

> > Got the following in testsuite/gfortran/gfortran.log
> > 
> > NaN 7FFFA000000000000000
> > NaN 7FFFC000000000000000
> > NaN 7FFFA000000000000000
> > 
> > and with "stop 300" commented out everything passes.  Now to
> > chase down hex representations for sNaN and qNaN.  Suspect
> > ieee_class() is broken.
> 
> How does the long double formation look like on x86_64-unknown-freebsd?

Ugh.  I'm afraid that this might be a mess.

> That test passes on x86_64 for linux and darwin, so I’m wondering
> what’s different about freebsd…
> 
> Can you tell me whether the C front-end defines __LDBL_IS_IEC_60559__?
> What is the value of __LDBL_DIG__? __DBL_DIG__?
> __FLOAT_WORD_ORDER == __BIG_ENDIAN or __LITTLE_ENDIAN?
> 

% cat a.c
#include <stdio.h>
int
main(void)
{
#ifdef __LDBL_IS_IEC_60559__
   printf("__LDBL_IS_IEC_60559__?  yes\n");
#else
   printf("__LDBL_IS_IEC_60559__?  no\n");
#endif
   return 0;
};

% gcc11 -o z a.c && ./z            <-- initial bootstrap compiler
__LDBL_IS_IEC_60559__?  yes
% cc -o z a.c && ./z               <-- clang/llvm FreeBSD system compiler
__LDBL_IS_IEC_60559__?  no
% ~/work/x/bin/gcc -o z a.c && ./z <-- gcc build from origin/master
__LDBL_IS_IEC_60559__?  yes

There might be some strange interaction between FreeBSD native
toolchain binaries and the binaries I build duringi bootstrap.

The LDBL info from /usr/include/x86/float is

#define LDBL_MANT_DIG   64
#define LDBL_EPSILON    1.0842021724855044340E-19L
#define LDBL_DIG        18
#define LDBL_MIN_EXP    (-16381)
#define LDBL_MIN        3.3621031431120935063E-4932L
#define LDBL_MIN_10_EXP (-4931)
#define LDBL_MAX_EXP    16384
#define LDBL_MAX        1.1897314953572317650E+4932L
#define LDBL_MAX_10_EXP 4932
#if __ISO_C_VISIBLE >= 2011
#define LDBL_TRUE_MIN   3.6451995318824746025E-4951L
#define LDBL_DECIMAL_DIG 21
#define LDBL_HAS_SUBNORM 1
#endif /* __ISO_C_VISIBLE >= 2011 */

which is what I expect.  How this maps to the __LDBL_DIG__
info, I do not know.

% grep -R __LDBL_DIG__ /usr/include
/usr/include/c++/v1/limits:    static _LIBCPP_CONSTEXPR const int  digits10 = __LDBL_DIG__;

%  grep -R __FLOAT_WORD_ORDER /usr/include

Returns no hits, but I see

% grep -R __BIG_ENDIAN /usr/include
/usr/include/c++/v1/__config:#ifdef __BIG_ENDIAN__
/usr/include/c++/v1/__config:#  if __BIG_ENDIAN__
/usr/include/c++/v1/__config:#  endif  // __BIG_ENDIAN__
/usr/include/c++/v1/__config:#endif // __BIG_ENDIAN__
/usr/include/c++/v1/__config:#  elif __BYTE_ORDER == __BIG_ENDIAN
/usr/include/c++/v1/__config:#  else  // __BYTE_ORDER == __BIG_ENDIAN

So, maybe __BYTE_ORDER instead of  __FLOAT_WORD_ORDER?

-- 
Steve