[Bug tree-optimization/37449] [4.4 Regression] calculix gets wrong answer for -O1 -ffast-math

[jakub at gcc dot gnu dot org]

------- Comment #17 from jakub at gcc dot gnu dot org  2008-10-15 09:47 -------
Testcase where only one constant, not two alternative constants, are on the
entry of the threaded bb.

extern int printf (const char *, ...);

void
__attribute__((noinline))
test (double cn, int *neig)
{
  double tt, al[3];

  *neig = 3;

  if (__builtin_fabs(cn) > 1.)
    cn = -1.;

  tt = __builtin_atan2 (__builtin_sqrt (1. - __builtin_pow (cn, 2.)), cn)
       * 3.333333333333333e-1;

  al[0] = __builtin_cos (tt);
  al[1] = __builtin_cos (2.0943951023931944 + tt);
  al[2] = __builtin_cos (4.1887902047863879 + tt);

  if ((__builtin_fabs ( al[0] - al[1]) < 1.e-5)
      || (__builtin_fabs (al[0] - al[2]) < 1.e-5)
      || (__builtin_fabs (al[1] - al[2]) < 1.e-5))
    *neig = 2;
}

int
main ()
{
  int neig;

  test (-1.0, &neig);
  printf ("neig = %d\n", neig);
  if (neig != 2)
    __builtin_abort ();
  test (1.0, &neig);
  printf ("neig = %d\n", neig);
  if (neig != 2)
    __builtin_abort ();
  test (-2.0, &neig);
  printf ("neig = %d\n", neig);
  if (neig != 2)
    __builtin_abort ();
  return 0;  
}

At -O2 -funsafe-math-optimizations, before ccp3 we have:
  D.1262_38 = __builtin_pow (-1.0e+0, 2.0e+0);
  D.1263_40 = 1.0e+0 - D.1262_38;
  D.1264_41 = __builtin_sqrt (D.1263_40);
  D.1265_43 = __builtin_atan2 (D.1264_41, -1.0e+0);
  tt_45 = D.1265_43 *
3.33333333333333314829616256247390992939472198486328125e-1;
  D.1266_46 = __builtin_cos (tt_45);
  D.1267_47 = tt_45 + 2.094395102393194374457152662216685712337493896484375e+0;
  D.1268_48 = __builtin_cos (D.1267_47);
  D.1269_49 = tt_45 + 4.1887902047863878607358856243081390857696533203125e+0;
  D.1270_50 = __builtin_cos (D.1269_49);
and neither ccp3, nor pre is able to optimize it out, only fab optimizes the
first call (pow) and then dom2 handles the rest.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.5.0                       |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37449