[Bug fortran/44156] dot_product / matmul and signed zeros

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

------- Comment #1 from kargl at gcc dot gnu dot org  2010-05-16 16:19 -------
The generated code is fine.  The F2003 standard states on page 38.

   The real type includes a zero value. Processors that distinguish between
   positive and negative zeros shall treat them as equivalent
   (1)   in all relational operations,
   (2)   as actual arguments to intrinsic procedures other than those
         for which it is explicitly specified that negative zero is
         distinguished, and

MATMAL and DOT_PRODUCT are not in the list that (2) applies to.

Remove wrong-code keyword.
Change Severity to enhancement, because might try to argue that this 
is a Quality of Implementation issue.  I'll leave it to Thomas to 
decide whether to close as WONTFIX.

PS:  DOT_PRODUCT is in-lined. -ftree-dump-original shows

      val.2 = 0.0;
      {
        integer(kind=4) S.3;

        S.3 = 1;
        while (1)
          {
            if (S.3 > 1) goto L.1;
            val.2 = a[S.3 + -1] * b[S.3 + -1] + val.2;
            S.3 = S.3 + 1;
          }
        L.1:;
      }
      D.1505 = val.2;

Even if a[S.3 + -1] * b[S.3 + -1] = -0.  The accumulation of the
sum -0 + 0 in the above will result in 0 (without the sign).


-- 

kargl at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|minor                       |enhancement
           Keywords|wrong-code                  |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44156