[Bug tree-optimization/39233] New: [4.4 Regression] ivopts + vrp miscompilation

[jakub at gcc dot gnu dot org]

extern void abort (void);

__attribute__((noinline)) void
foo (void *p)
{
  long l = (long) p;
  if (l < 0 || l > 6)
    abort ();
}

int
main ()
{
  int i;
  for (i = 6; i >= 0; i--)
    foo ((void *) (long) i);
  return 0;
}

is miscompiled (into endless loop).  First ivopts decides to use a pointer IV,
going from (void *) 6 down, with (void *) ivtmp.51 != (void *) -1 as loop
condition, then VRP comes in and as pointers can never wrap around, optimizes
the loop condition into 1.


-- 
           Summary: [4.4 Regression] ivopts + vrp miscompilation
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jakub at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39233