[Bug c++/33611] New: Optimizations generate incorrect code

["macracan at yahoo dot com" <gcc-bugzilla at gcc dot gnu dot org>]

The following snipped when compiled with -O0 generates a program that quickly
finishes (correct behavior). But when compiled with any optimizations (-O1, -O2
or -O3) generates a program that never finishes. Variations on the code, (such
as the comment line) geneate valid program with either level of optimization.
Checked in 4.1.1 too (i386) and the bug is there too. Checked in 4.1.2 on
x86_64 and the bug is NOT there.

-- star of file aa.cpp
struct A
{
  unsigned int e;
};
A a = {1};
double f[] = {0.0461109, 0.285433};
int main(void)
{
  for (bool bEncore = true; bEncore; )
  {
    bEncore = false;
    double p = 0.422244 * f[a.e];
//    double p = 0.422244 * f[1];
    if (f[0] < p)
    {
      f[0] = p;
      bEncore = true;
    }
  }
  return 0;
}
-- end of file aa.cpp

g++ -O3 aa.cpp
./a.out           --> goes into infinite loop


-- 
           Summary: Optimizations generate incorrect code
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: macracan at yahoo dot com
 GCC build triplet: GNU/linux i386/i686
  GCC host triplet: GNU/linux i386/i686
GCC target triplet: GNU/linux i386/i686


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