[Bug tree-optimization/54810] New: VRP doesn't handle comparison of narrowing cast like comparison of BIT_AND_EXPR

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54810

             Bug #: 54810
           Summary: VRP doesn't handle comparison of narrowing cast like
                    comparison of BIT_AND_EXPR
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jakub@gcc.gnu.org


struct S
{
  unsigned long w;
  void (*u) (void *, unsigned int, unsigned int);
};

struct T;
typedef void (*a_t) (struct T *);
typedef void (*b_t) (struct T *);

struct T
{
  a_t a;
  b_t b;
  struct S c;
  int d, e, f;
};

_Bool fn1 (struct T *, unsigned int);
int fn2 (struct T *, unsigned int, void *, unsigned long);
int fn3 (struct T *, unsigned int, unsigned int *);

static _Bool
foo (struct T *x, unsigned int y, unsigned int z)
{
  unsigned int i;
  for (i = 0; i < z; i++)
    if (!fn1 (x, y + i))
      return 0;
  return 1;
}

int
bar (struct T *x, unsigned int y, void *z, unsigned long s)
{
  unsigned long w = x->c.w;
  unsigned long q = s / w;
  unsigned int v;
  int r, i;
  if (s % x->c.w)
    return -22;
  if (y % x->d)
    return -22;
  x->a (x);
  if (foo (x, y, q) || x->f || x->e == 0)
    r = fn2 (x, y, z, s);
  else
    for (i = 0; i < q; i++)
      {
        r = fn3 (x, y + (i * x->d), &v);
        if (r != 0)
          break;

        x->c.u (z + (i * w), v, 0);
      }
  x->b (x);
  return r;
}

reports at -O2 -Wall maybe uninitialized warning.  While generally it is IMHO
an acceptable false positive, especially if foo doesn't get inlined, this
testcase lead to me find out that while we handle
  _7 = _4 & 0xffff;
  if (_7 == 0)
    goto bbX;
by adding ASSERT_EXPRs for _4 (in the _7 != 0 code _4 is known to be non-zero,
in the _7 == 0 code it can e.g. have [0, 0xffff0000] range), we don't handle
  _7 = (unsigned short) _4;
  if (_7 == 0)
    goto bbX;
the same way.