On Sat, 21 Nov 2020, Toon Moene wrote:
> > 2. libgfortran -- oddly enough for Fortran a piece requires IEEE 754
> > floating-point arithmetic (possibly a porting problem too).
>
> gcc/libgfortran/config.h.in does have:
>
> /* Define to 1 if you have the <ieeefp.h> header file. */
> #undef HAVE_IEEEFP_H
>
> So perhaps it does do the "right thing" if you do not have this header file on
> your VAX operating system.
Well it does not:
In file included from .../libgfortran/generated/maxval_r4.c:26:
.../libgfortran/generated/maxval_r4.c: In function 'maxval_r4':
.../libgfortran/libgfortran.h:292:30: warning: target format does not support
infinity
292 | # define GFC_REAL_4_INFINITY __builtin_inff ()
| ^~~~~~~~~~~~~~
.../libgfortran/generated/maxval_r4.c:149:19:
note: in expansion of macro 'GFC_REAL_4_INFINITY'
149 | result = -GFC_REAL_4_INFINITY;
| ^~~~~~~~~~~~~~~~~~~
.../libgfortran/generated/maxval_r4.c: In function 'mmaxval_r4':
.../libgfortran/libgfortran.h:292:30: warning: target format does not support
infinity
292 | # define GFC_REAL_4_INFINITY __builtin_inff ()
| ^~~~~~~~~~~~~~
.../libgfortran/generated/maxval_r4.c:363:19:
note: in expansion of macro 'GFC_REAL_4_INFINITY'
363 | result = -GFC_REAL_4_INFINITY;
| ^~~~~~~~~~~~~~~~~~~
{standard input}: Assembler messages:
{standard input}:204: Fatal error: Can't relocate expression
make[3]: *** [Makefile:3358: maxval_r4.lo] Error 1
with the offending assembly instruction at 204 being:
movf $0f+QNaN,%r2
and the `QNaN' part of the operand being what GAS complains about (of
course it is a problem too that GCC lets the infinity intrinsics through
with a mere warning and rubbish emitted rather than bailing out right
away, but they are not supposed to be requested in the first place as the
notion of infinity is specific to IEEE 754 FP and the VAX FP format used
here does not support such an FP datum).
The absence of IEEE 754 FP is correctly recognised by the configuration
script:
checking for ieeefp.h... no
[...]
configure: FPU dependent file will be fpu-generic.h
configure: Support for IEEE modules: no
> The Fortran Standard allows an implementation *not* to have IEEE floating
> point support ...
Given how long before IEEE 754 Fortran was invented I would be rather
surprised if it was the other way round, which is why I have suspected, as
I have noted in the piece quoted above, a problem with the VAX/NetBSD port
of libgfortran.
Maciej
