Menguji Kompiler GCC 10 dengan PVS-Studio

Saatnya memeriksa ulang kode kompiler GCC

//  alias.c
....
struct alias_set_hash : int_hash <int, INT_MIN, INT_MIN + 1> {};
struct GTY(()) alias_set_entry {
  alias_set_type alias_set;
  bool has_zero_child;
  bool is_pointer;
  bool has_pointer;
  hash_map<alias_set_hash, int> *children;
};
....

10 cuplikan kode yang mencurigakan

static bool
try_crossjump_to_edge (int mode, edge e1, edge e2,
                       enum replace_direction dir)
{
  ....
  if (FORWARDER_BLOCK_P (s->dest))
    s->dest->count += s->count ();

  if (FORWARDER_BLOCK_P (s2->dest))
    s2->dest->count -= s->count ();
  ....
}

if (FORWARDER_BLOCK_P (s2->dest))
  s2->dest->count -= s2->count ();

tree
vn_reference_lookup_pieces (....)
{
  struct vn_reference_s vr1;
  ....
  vr1.set = set;
  vr1.set = base_set;
  ....
}

vr1.set = set;
vr1.base_set = base_set;

static omp_context *
new_omp_context (gimple *stmt, omp_context *outer_ctx)
{
  omp_context *ctx = XCNEW (omp_context);

  splay_tree_insert (all_contexts, (splay_tree_key) stmt,
         (splay_tree_value) ctx);
  ctx->stmt = stmt;

  if (outer_ctx)
    {
      ctx->outer = outer_ctx;
      ctx->cb = outer_ctx->cb;
      ctx->cb.block = NULL;
      ctx->local_reduction_clauses = NULL;
      ctx->outer_reduction_clauses = ctx->outer_reduction_clauses;  // <=
      ctx->depth = outer_ctx->depth + 1;
    }
  ....
}

#define GET_MODE(RTX)    ((machine_mode) (RTX)->mode)
....
static int
add_equal_note (rtx_insn *insns, rtx target, enum rtx_code code, rtx op0,
                rtx op1, machine_mode op0_mode)
{
  ....
  if (commutative_p
      && GET_MODE (xop0) != xmode0 && GET_MODE (xop1) != xmode1
      && GET_MODE (xop0) == xmode1 && GET_MODE (xop1) == xmode1)
    std::swap (xop0, xop1);
  ....
}

• GET_MODE (xop1)! = Xmode1
• GET_MODE (xop1) == xmode1

&& GET_MODE (xop0) != xmode0 && GET_MODE (xop1) != xmode1
&& GET_MODE (xop0) == xmode1 && GET_MODE (xop1) == xmode0

bool
ipa_polymorphic_call_context::set_by_invariant (tree cst,
                                                tree otr_type,
                                                HOST_WIDE_INT off)
{
  poly_int64 offset2, size, max_size;
  bool reverse;
  tree base;

  invalid = false;
  off = 0;                // <=
  ....
  if (otr_type && !contains_type_p (TREE_TYPE (base), off, otr_type))
    return false;

  set_by_decl (base, off);
  return true;
}

cgraph_node *
cgraph_node::create_clone (....)
{
  ....
  new_node->icf_merged = icf_merged;
  new_node->merged_comdat = merged_comdat;   // <=
  new_node->thunk = thunk;
  new_node->unit_id = unit_id;
  new_node->merged_comdat = merged_comdat;   // <=
  new_node->merged_extern_inline = merged_extern_inline;
  ....
}

static void
complete_mode (struct mode_data *m)
{
  ....
  if (m->cl == MODE_COMPLEX_INT || m->cl == MODE_COMPLEX_FLOAT)
    alignment = m->component->bytesize;
  else
    alignment = m->bytesize;

  m->alignment = alignment & (~alignment + 1);

  if (m->component)
  ....
}

void
pointer_and_operator::wi_fold (value_range &r, tree type,
                               const wide_int &lh_lb,
                               const wide_int &lh_ub,
                               const wide_int &rh_lb ATTRIBUTE_UNUSED,
                               const wide_int &rh_ub ATTRIBUTE_UNUSED) const
{
  // For pointer types, we are really only interested in asserting
  // whether the expression evaluates to non-NULL.
  if (wi_zero_p (type, lh_lb, lh_ub) || wi_zero_p (type, lh_lb, lh_ub))
    r = range_zero (type);
  else 
    r = value_range (type);
}

if (wi_zero_p (type, lh_lb, lh_ub))
  r = range_zero (type);
else 
  r = value_range (type);

struct algorithm
{
  struct mult_cost cost;
  short ops;
  enum alg_code op[MAX_BITS_PER_WORD];
  char log[MAX_BITS_PER_WORD];
};

static void
synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
            const struct mult_cost *cost_limit, machine_mode mode)
{
  int m;
  struct algorithm *alg_in, *best_alg;
  ....
  /* Cache the result.  */
  if (!cache_hit)
  {
    entry_ptr->t = t;
    entry_ptr->mode = mode;
    entry_ptr->speed = speed;
    entry_ptr->alg = best_alg->op[best_alg->ops];
    entry_ptr->cost.cost = best_cost.cost;
    entry_ptr->cost.latency = best_cost.latency;
  }

  /* If we are getting a too long sequence for `struct algorithm'
     to record, make this search fail.  */
  if (best_alg->ops == MAX_BITS_PER_WORD)
    return;
  ....
}

if (!cache_hit)
{
  entry_ptr->alg = best_alg->op[best_alg->ops];
}
if (best_alg->ops == MAX_BITS_PER_WORD)

static bool
dw_val_equal_p (dw_val_node *a, dw_val_node *b)
{
  ....
  case dw_val_class_vms_delta:
    return (!strcmp (a->v.val_vms_delta.lbl1, b->v.val_vms_delta.lbl1)
            && !strcmp (a->v.val_vms_delta.lbl1, b->v.val_vms_delta.lbl1));
  ....
}

return (   !strcmp (a->v.val_vms_delta.lbl1, b->v.val_vms_delta.lbl1)
        && !strcmp (a->v.val_vms_delta.lbl2, b->v.val_vms_delta.lbl2));

return (!strcmp (a->v.val_vms_delta.lbl1, b->v.val_vms_delta.lbl1));

Kesimpulan

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