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Re: [Committed] XFAIL gfortran.dg/ieee/ieee_9.f90


On Tue, Dec 25, 2018 at 09:51:03AM +0200, Janne Blomqvist wrote:
> On Mon, Dec 24, 2018 at 9:42 PM Steve Kargl <
> sgk@troutmask.apl.washington.edu> wrote:
> 
> > On Mon, Dec 24, 2018 at 09:29:50PM +0200, Janne Blomqvist wrote:
> > > On Mon, Dec 24, 2018 at 8:05 PM Steve Kargl <
> > > sgk@troutmask.apl.washington.edu> wrote:
> > >
> > > > I've added the following patch to a recently committed testcase.
> > > >
> > > > Index: gcc/testsuite/gfortran.dg/ieee/ieee_9.f90
> > > > ===================================================================
> > > > --- gcc/testsuite/gfortran.dg/ieee/ieee_9.f90   (revision 267413)
> > > > +++ gcc/testsuite/gfortran.dg/ieee/ieee_9.f90   (working copy)
> > > > @@ -1,4 +1,4 @@
> > > > -! { dg-do run }
> > > > +! { dg-do run { xfail arm*-*-gnueabi arm*-*-gnueabihf } }
> > > >  program foo
> > > >     use ieee_arithmetic
> > > >     use iso_fortran_env
> > > >
> > >
> > > The problem seems to be that GFortran says the real128 kind value is > 0
> > > (i.e. that the target supports quad precision floating point (with
> > software
> > > emulation, presumably)), but then trying to use it fails.
> > >
> > > Would be nice if somebody who cares about arm-none-linux-gnueabihf could
> > > help figure out the proper resolution instead of papering over it with
> > > XFAIL.
> > >
> > > But I guess XFAIL is good enough until said somebody turns up.
> > >
> >
> > Thanks for chasing down the details.  I have no access to arm*-*-*.
> >
> > It's a shame the real128 is defined, and arm*-*-* doesn't
> > actually use it.  I certainly have no time or interest in
> > fix this.
> >
> 
> I think there are arm systems on the compile farm, but I haven't actually
> checked myself, just going by the error messages Sudi Das reported.
> 
> That being said, having slept over it, I actually think there is a problem
> with the testcase, and not with arm*. So the errors in the testcase occurs
> in code like
> 
> if (real128 > 0) then
>     p = int(ieee_scalb(real(x, real128), int(i, int8)))
>     if (p /= 64) stop 3
> end if
> 
> So if real128 is negative, as it should be if the target doesn't support
> quad precision float, the branch will never be taken, but the frontend will
> still generate code for it (though it will later be optimized away as
> unreachable), and that's where the error occurs. So the testcase would need
> something like
> 
> integer, parameter :: large_real = max (real64, real128)
> ! ...
> if (real128 > 0) then
>     p = int(ieee_scalb(real(x, large_real), int(i, int8)))
>     if (p /= 64) stop 3
> end if
> 
> If you concur, please consider a patch fixing the testcase and removing the
> xfail pre-approved.
> 

Indeed, you are probably correct that gfortran will generate 
intermediate code and then garbage collect it.  This then will
give an error for real(..., real128) in the statement for p. 
If real128 /= 4, 8, 10, or 16.  I'll fix the testcase.

Do you know if we can get gfortran to pre-define macros for cpp?
That is, it would be nice if gfortran would recognize, say,
HAVE_GFC_REAL_10 and HAVE_GFC_REAL_16 if the target supports those
types.  Then the testcase could be copied to ieee_9.F90, and 
modified to 

#ifdef HAVE_REAL_16
    p = int(ieee_scalb(real(x, 16), int(i, int8)))
    if (p /= 64) stop 3
#endif

-- 
Steve


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