[Bug middle-end/38848] Optimizer -O2 doesn't work on linear algebra code on double data type

[rbenedik at fsmat dot htu dot tuwien dot ac dot at]

------- Comment #4 from rbenedik at fsmat dot htu dot tuwien dot ac dot at  
2009-01-15 12:12 -------
I traced the error back to a iteration scheme which is not stable when optmized
with -O2. Sorry this was my fault, so theres no Bug in -O2:

DTYPE FTYPE(SQUARE_ROOT)(DTYPE A)
{
 DTYPE X_N1;
 DTYPE X_N2;

 X_N1=A;

 while(1)
 {
  X_N2 = (DTYPE)(1/2.0) * (X_N1+A/X_N1);
  if(X_N2 == X_N1) break;
  X_N1 = X_N2;
 }

 return X_N2;
}


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38848