[Bug fortran/49010] Result of MOD and MODULO intrinsic has wrong sign

["kargl at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49010

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kargl at gcc dot gnu.org

--- Comment #2 from kargl at gcc dot gnu.org 2011-05-16 20:44:08 UTC ---
This appears to be caused by the use of __builtin_fmod in
trans-intrinsic.c (gfc_conv_intrinsic_mod).  By hacking
the code to disallow the use of the builtin, one uses
the fallback code (which implements the simply code).

program foo
   real a, p, m1, m2
   a = -4.
   p = 2.
   m1 = mod(a, p)
   m2 = a - int(a / p) * p
   print *, m1, m2
end program foo
troutmask:sgk[239] gfc4x -o z t.f90 && ./z
   0.00000000       0.00000000    

Thus, one gets the right answer.  Also, note

#include <stdio.h>
#include <math.h>
int
main(void)
{
  float a, p, m1, m2;
  a = -4.f;
  p = 2.f;
  m1 = fmodf(a, p);
  m2 = a - (int)(a / p) * p;
  printf("%f %f\n", m1, m2);
  return 0;
}
troutmask:sgk[241] cc -o z t.c -lm && ./z
-0.000000 0.000000

which probably means that we either want to not
use the __builtin_fmod() (which is probably some
optimized bit twiddling routine).