gcc/testsuite/gcc.c-torture/execute/ieee/unsafe-fp-assoc-1.c

extern void abort();

typedef union {
       struct {
  unsigned int hi;
  unsigned int lo;
 } i;
       double d;
} hexdouble;

static const double twoTo52 = 0x1.0p+52;

void func ( double x )
{
      hexdouble argument;
      register double y, z;
      unsigned int xHead;
      argument.d = x;
      xHead = argument.i.hi & 0x7fffffff;
      if (__builtin_expect(!!(xHead < 0x43300000u), 1))
       {
                  y = ( x - twoTo52 ) + twoTo52;
                  if ( y != x )
		    abort();
                  z = x - 0.5;			
                  y = ( z - twoTo52 ) + twoTo52;
                  if ( y == (( x - twoTo52 ) + twoTo52) )
		    abort();
       }
     return;
}

int main()
{
	if (sizeof (double) == 4)
		return 0;
	func((double)1.00);
	return 0;
}