[Bug middle-end/49958] New: fold performs invalid association

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49958

           Summary: fold performs invalid association
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: rgue...@gcc.gnu.org


extern void abort (void);
int foo (int i, int j, int o, int m) { return i*o + 1 + j*m > 1; }
int main()
{
  if (foo (- __INT_MAX__ - 1, -1, 1, 1))
    abort ();
  return 0;
}

abort()s with -fstrict-overflow even though there is no overflow
involved in INT_MIN + 1 - 1.  But fold re-associates this to
INT_MIN - 1 + 1 which overflows (it does require the two multiplications
to trigger).