[Bug c/115374] fmod() in x86_64 -O3 not using return value from the glibc's implementation if x87 FPU fprem returns NaN

[ubizjak at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115374

--- Comment #8 from Uroš Bizjak <ubizjak at gmail dot com> ---
When compiling the following testcase:

--cut here--
#include <math.h>

double
__attribute__((noinline))
do_fmod (double x, double y)
{
  return fmod(x, y);
}
--cut here--

one can find in _.265t.optimized:

__attribute__((noinline))
double do_fmod (double x, double y)
{
  double _5;

  <bb 2> [local count: 1073741824]:
  _5 = .FMOD (x_2(D), y_3(D));
  if (_5 == _5)
    goto <bb 4>; [99.95%]
  else
    goto <bb 3>; [0.05%]

  <bb 3> [local count: 536864]:
  fmod (x_2(D), y_3(D));

  <bb 4> [local count: 1073741824]:
  return _5;

}