static void add_pointed_to_var (struct alias_info *, tree, tree);
static void create_global_var (void);
static void collect_points_to_info_for (struct alias_info *, tree);
-static bool ptr_is_dereferenced_by (tree, tree, bool *);
static void maybe_create_global_var (struct alias_info *ai);
static void group_aliases (struct alias_info *);
static void set_pt_anything (tree ptr);
0 /* letter */
};
+
+/* Data structure used to count the number of dereferences to PTR
+ inside an expression. */
+struct count_ptr_d
+{
+ tree ptr;
+ unsigned count;
+};
+
+
+/* Helper for count_uses_and_derefs. Called by walk_tree to look for
+ (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
+
+static tree
+count_ptr_derefs (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data)
+{
+ struct count_ptr_d *count_p = (struct count_ptr_d *) data;
+
+ if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr)
+ count_p->count++;
+
+ return NULL_TREE;
+}
+
+
+/* Count the number of direct and indirect uses for pointer PTR in
+ statement STMT. The two counts are stored in *NUM_USES_P and
+ *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at
+ least one of those dereferences is a store operation. */
+
+static void
+count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p,
+ unsigned *num_derefs_p, bool *is_store)
+{
+ ssa_op_iter i;
+ tree use;
+
+ *num_uses_p = 0;
+ *num_derefs_p = 0;
+ *is_store = false;
+
+ /* Find out the total number of uses of PTR in STMT. */
+ FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE)
+ if (use == ptr)
+ (*num_uses_p)++;
+
+ /* Now count the number of indirect references to PTR. This is
+ truly awful, but we don't have much choice. There are no parent
+ pointers inside INDIRECT_REFs, so an expression like
+ '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to
+ find all the indirect and direct uses of x_1 inside. The only
+ shortcut we can take is the fact that GIMPLE only allows
+ INDIRECT_REFs inside the expressions below. */
+ if (TREE_CODE (stmt) == MODIFY_EXPR
+ || (TREE_CODE (stmt) == RETURN_EXPR
+ && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
+ || TREE_CODE (stmt) == ASM_EXPR
+ || TREE_CODE (stmt) == CALL_EXPR)
+ {
+ tree lhs, rhs;
+
+ if (TREE_CODE (stmt) == MODIFY_EXPR)
+ {
+ lhs = TREE_OPERAND (stmt, 0);
+ rhs = TREE_OPERAND (stmt, 1);
+ }
+ else if (TREE_CODE (stmt) == RETURN_EXPR)
+ {
+ tree e = TREE_OPERAND (stmt, 0);
+ lhs = TREE_OPERAND (e, 0);
+ rhs = TREE_OPERAND (e, 1);
+ }
+ else if (TREE_CODE (stmt) == ASM_EXPR)
+ {
+ lhs = ASM_OUTPUTS (stmt);
+ rhs = ASM_INPUTS (stmt);
+ }
+ else
+ {
+ lhs = NULL_TREE;
+ rhs = stmt;
+ }
+
+ if (lhs && EXPR_P (lhs))
+ {
+ struct count_ptr_d count;
+ count.ptr = ptr;
+ count.count = 0;
+ walk_tree (&lhs, count_ptr_derefs, &count, NULL);
+ *is_store = true;
+ *num_derefs_p = count.count;
+ }
+
+ if (rhs && EXPR_P (rhs))
+ {
+ struct count_ptr_d count;
+ count.ptr = ptr;
+ count.count = 0;
+ walk_tree (&rhs, count_ptr_derefs, &count, NULL);
+ *num_derefs_p += count.count;
+ }
+ }
+
+ gcc_assert (*num_uses_p >= *num_derefs_p);
+}
+
+
/* Count the number of calls in the function and conditionally
create GLOBAL_VAR. This is performed before translation
into SSA (and thus before alias analysis) to avoid compile time
tag will need to be created in create_name_tags. */
pi->pt_anything = 0;
pi->pt_malloc = 0;
+ pi->pt_null = 0;
pi->value_escapes_p = 0;
pi->is_dereferenced = 0;
if (pi->pt_vars)
}
-/* Helper for ptr_is_dereferenced_by. Called by walk_tree to look for
- (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
-
-static tree
-find_ptr_dereference (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data)
-{
- tree ptr = (tree) data;
-
- if (INDIRECT_REF_P (*tp)
- && TREE_OPERAND (*tp, 0) == ptr)
- return *tp;
-
- return NULL_TREE;
-}
-
-
-/* Return true if STMT contains (ALIGN/MISALIGNED_)INDIRECT_REF <PTR>.
- *IS_STORE is set to 'true' if the dereference is on the LHS of an
- assignment. */
-
-static bool
-ptr_is_dereferenced_by (tree ptr, tree stmt, bool *is_store)
-{
- *is_store = false;
-
- if (TREE_CODE (stmt) == MODIFY_EXPR
- || (TREE_CODE (stmt) == RETURN_EXPR
- && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR))
- {
- tree e, lhs, rhs;
-
- e = (TREE_CODE (stmt) == RETURN_EXPR) ? TREE_OPERAND (stmt, 0) : stmt;
- lhs = TREE_OPERAND (e, 0);
- rhs = TREE_OPERAND (e, 1);
-
- if (EXPR_P (lhs)
- && walk_tree (&lhs, find_ptr_dereference, ptr, NULL))
- {
- *is_store = true;
- return true;
- }
- else if (EXPR_P (rhs)
- && walk_tree (&rhs, find_ptr_dereference, ptr, NULL))
- {
- return true;
- }
- }
- else if (TREE_CODE (stmt) == ASM_EXPR)
- {
- if (walk_tree (&ASM_OUTPUTS (stmt), find_ptr_dereference, ptr, NULL)
- || walk_tree (&ASM_CLOBBERS (stmt), find_ptr_dereference, ptr, NULL))
- {
- *is_store = true;
- return true;
- }
- else if (walk_tree (&ASM_INPUTS (stmt), find_ptr_dereference, ptr, NULL))
- {
- return true;
- }
- }
- else
- {
- /* CALL_EXPRs may also contain pointer dereferences for types
- that are not GIMPLE register types. If the CALL_EXPR is on
- the RHS of an assignment, it will be handled by the
- MODIFY_EXPR handler above. */
- tree call = get_call_expr_in (stmt);
- if (call && walk_tree (&call, find_ptr_dereference, ptr, NULL))
- return true;
- }
-
- return false;
-}
-
-
/* Traverse use-def links for all the pointers in the program to collect
address escape and points-to information.
var_ann_t v_ann = var_ann (SSA_NAME_VAR (op));
struct ptr_info_def *pi;
bool is_store;
+ unsigned num_uses, num_derefs;
/* If the operand's variable may be aliased, keep track
of how many times we've referenced it. This is used
collect_points_to_info_for (ai, op);
pi = SSA_NAME_PTR_INFO (op);
- if (ptr_is_dereferenced_by (op, stmt, &is_store))
+ count_uses_and_derefs (op, stmt, &num_uses, &num_derefs,
+ &is_store);
+
+ if (num_derefs > 0)
{
/* Mark OP as dereferenced. In a subsequent pass,
dereferenced pointers that point to a set of
else
bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid);
}
- else if (stmt_escapes_p)
+
+ if (stmt_escapes_p && num_derefs < num_uses)
{
- /* Note that even if STMT is an escape point, pointer OP
- will not escape if it is being dereferenced. That's
- why we only check for escape points if OP is not
- dereferenced by STMT. */
+ /* If STMT is an escape point and STMT contains at
+ least one direct use of OP, then the value of OP
+ escapes and so the pointed-to variables need to
+ be marked call-clobbered. */
pi->value_escapes_p = 1;
/* If the statement makes a function call, assume
if (orig_pi)
{
+ gcc_assert (orig_pi != dest_pi);
+
/* Notice that we never merge PT_MALLOC. This attribute is only
true if the pointer is the result of a malloc() call.
Otherwise, we can end up in this situation:
create_name_tags is not smart enough to determine that the
two come from the same malloc call. Copy propagation before
aliasing should cure this. */
- gcc_assert (orig_pi != dest_pi);
-
dest_pi->pt_malloc = 0;
-
if (orig_pi->pt_malloc || orig_pi->pt_anything)
set_pt_anything (dest);
+ dest_pi->pt_null |= orig_pi->pt_null;
+
if (!dest_pi->pt_anything
&& orig_pi->pt_vars
&& !bitmap_empty_p (orig_pi->pt_vars))
&& TREE_CODE (op1) != INTEGER_CST))
set_pt_anything (ptr);
}
+ else if (integer_zerop (expr))
+ {
+ /* EXPR is the NULL pointer. Mark PTR as pointing to NULL. */
+ SSA_NAME_PTR_INFO (ptr)->pt_null = 1;
+ }
else
{
/* If we can't recognize the expression, assume that PTR may
if (pi->pt_malloc)
fprintf (file, ", points-to malloc");
+ if (pi->pt_null)
+ fprintf (file, ", points-to NULL");
+
if (pi->pt_vars)
{
unsigned ix;
return true;
}
-
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