[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]

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: unassig...@gcc.gnu.org

        ReportedBy: ja...@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.