[Bug middle-end/33611] [4.1/4.2/4.3 regression] Optimizations generate incorrect code

[bangerth at dealii dot org]

------- Comment #3 from bangerth at dealii dot org  2007-10-01 17:16 -------
For once a real floating point bug. In this code
    double p = 0.422244 * f[a.e];
    if (f[0] < p)

with a.e=1, f[1]=0.285433, we should calculate p=0.285433. Since
f[0]=0.0461109, we shouldn't enter the if-clause, but we do when
optimization is on. Since the numbers aren't even close, this isn't
due to excess precision or any other floating point instability but
a real bug.

Funny enough, this was already broken in 2.95, 3.2.3 and 3.3.6 but then
worked in 3.4.6 and 4.0.x only to be broken again in 4.1.2.

W.


-- 

bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at dealii dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |wrong-code
      Known to fail|                            |2.95 3.2.3 3.3.6 4.1.2
      Known to work|                            |3.4.6 4.0.4
   Last reconfirmed|0000-00-00 00:00:00         |2007-10-01 17:16:44
               date|                            |
            Summary|Optimizations generate      |[4.1/4.2/4.3 regression]
                   |incorrect code              |Optimizations generate
                   |                            |incorrect code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33611