+ if (type && TREE_CODE (type) == TYPE_DECL)
+ type = TREE_TYPE (type);
+
+ /* NB: This function may be called before the ObjC front-end has
+ been initialized, in which case OBJC_OBJECT_TYPE will (still) be NULL. */
+ return (objc_object_type && type
+ && (IS_ID (type) || IS_CLASS (type) || IS_SUPER (type))
+ ? type
+ : NULL_TREE);
+}
+
+/* Check whether TYPE is either 'id', 'Class', or a pointer to an ObjC
+ class instance. This is needed by other parts of the compiler to
+ handle ObjC types gracefully. */
+
+tree
+objc_is_object_ptr (tree type)
+{
+ tree ret;
+
+ type = TYPE_MAIN_VARIANT (type);
+ if (!POINTER_TYPE_P (type))
+ return 0;
+
+ ret = objc_is_id (type);
+ if (!ret)
+ ret = objc_is_class_name (TREE_TYPE (type));
+
+ return ret;
+}
+
+static int
+objc_is_gcable_type (tree type, int or_strong_p)
+{
+ tree name;
+
+ if (!TYPE_P (type))
+ return 0;
+ if (objc_is_id (TYPE_MAIN_VARIANT (type)))
+ return 1;
+ if (or_strong_p && lookup_attribute ("objc_gc", TYPE_ATTRIBUTES (type)))
+ return 1;
+ if (TREE_CODE (type) != POINTER_TYPE && TREE_CODE (type) != INDIRECT_REF)
+ return 0;
+ type = TREE_TYPE (type);
+ if (TREE_CODE (type) != RECORD_TYPE)
+ return 0;
+ name = TYPE_NAME (type);
+ return (objc_is_class_name (name) != NULL_TREE);
+}
+
+static tree
+objc_substitute_decl (tree expr, tree oldexpr, tree newexpr)
+{
+ if (expr == oldexpr)
+ return newexpr;
+
+ switch (TREE_CODE (expr))
+ {
+ case COMPONENT_REF:
+ return objc_build_component_ref
+ (objc_substitute_decl (TREE_OPERAND (expr, 0),
+ oldexpr,
+ newexpr),
+ DECL_NAME (TREE_OPERAND (expr, 1)));
+ case ARRAY_REF:
+ return build_array_ref (objc_substitute_decl (TREE_OPERAND (expr, 0),
+ oldexpr,
+ newexpr),
+ TREE_OPERAND (expr, 1));
+ case INDIRECT_REF:
+ return build_indirect_ref (objc_substitute_decl (TREE_OPERAND (expr, 0),
+ oldexpr,
+ newexpr), "->");
+ default:
+ return expr;
+ }
+}
+
+static tree
+objc_build_ivar_assignment (tree outervar, tree lhs, tree rhs)
+{
+ tree func_params;
+ /* The LHS parameter contains the expression 'outervar->memberspec';
+ we need to transform it into '&((typeof(outervar) *) 0)->memberspec',
+ where memberspec may be arbitrarily complex (e.g., 'g->f.d[2].g[3]').
+ */
+ tree offs
+ = objc_substitute_decl
+ (lhs, outervar, convert (TREE_TYPE (outervar), integer_zero_node));
+ tree func
+ = (flag_objc_direct_dispatch
+ ? objc_assign_ivar_fast_decl
+ : objc_assign_ivar_decl);
+
+ offs = convert (integer_type_node, build_unary_op (ADDR_EXPR, offs, 0));
+ offs = fold (offs);
+ func_params = tree_cons (NULL_TREE,
+ convert (objc_object_type, rhs),
+ tree_cons (NULL_TREE, convert (objc_object_type, outervar),
+ tree_cons (NULL_TREE, offs,
+ NULL_TREE)));
+
+ assemble_external (func);
+ return build_function_call (func, func_params);
+}
+
+static tree
+objc_build_global_assignment (tree lhs, tree rhs)
+{
+ tree func_params = tree_cons (NULL_TREE,
+ convert (objc_object_type, rhs),
+ tree_cons (NULL_TREE, convert (build_pointer_type (objc_object_type),
+ build_unary_op (ADDR_EXPR, lhs, 0)),
+ NULL_TREE));
+
+ assemble_external (objc_assign_global_decl);
+ return build_function_call (objc_assign_global_decl, func_params);
+}
+
+static tree
+objc_build_strong_cast_assignment (tree lhs, tree rhs)
+{
+ tree func_params = tree_cons (NULL_TREE,
+ convert (objc_object_type, rhs),
+ tree_cons (NULL_TREE, convert (build_pointer_type (objc_object_type),
+ build_unary_op (ADDR_EXPR, lhs, 0)),
+ NULL_TREE));
+
+ assemble_external (objc_assign_strong_cast_decl);
+ return build_function_call (objc_assign_strong_cast_decl, func_params);
+}
+
+static int
+objc_is_gcable_p (tree expr)
+{
+ return (TREE_CODE (expr) == COMPONENT_REF
+ ? objc_is_gcable_p (TREE_OPERAND (expr, 1))
+ : TREE_CODE (expr) == ARRAY_REF
+ ? (objc_is_gcable_p (TREE_TYPE (expr))
+ || objc_is_gcable_p (TREE_OPERAND (expr, 0)))
+ : TREE_CODE (expr) == ARRAY_TYPE
+ ? objc_is_gcable_p (TREE_TYPE (expr))
+ : TYPE_P (expr)
+ ? objc_is_gcable_type (expr, 1)
+ : (objc_is_gcable_p (TREE_TYPE (expr))
+ || (DECL_P (expr)
+ && lookup_attribute ("objc_gc", DECL_ATTRIBUTES (expr)))));
+}
+
+static int
+objc_is_ivar_reference_p (tree expr)
+{
+ return (TREE_CODE (expr) == ARRAY_REF
+ ? objc_is_ivar_reference_p (TREE_OPERAND (expr, 0))
+ : TREE_CODE (expr) == COMPONENT_REF
+ ? TREE_CODE (TREE_OPERAND (expr, 1)) == FIELD_DECL
+ : 0);
+}
+
+static int
+objc_is_global_reference_p (tree expr)
+{
+ return (TREE_CODE (expr) == INDIRECT_REF || TREE_CODE (expr) == PLUS_EXPR
+ ? objc_is_global_reference_p (TREE_OPERAND (expr, 0))
+ : DECL_P (expr)
+ ? (!DECL_CONTEXT (expr) || TREE_STATIC (expr))
+ : 0);
+}
+
+tree
+objc_generate_write_barrier (tree lhs, enum tree_code modifycode, tree rhs)
+{
+ tree result = NULL_TREE, outer;
+ int strong_cast_p = 0, outer_gc_p = 0, indirect_p = 0;
+
+ /* See if we have any lhs casts, and strip them out. NB: The lvalue casts
+ will have been transformed to the form '*(type *)&expr'. */
+ if (TREE_CODE (lhs) == INDIRECT_REF)
+ {
+ outer = TREE_OPERAND (lhs, 0);
+
+ while (!strong_cast_p
+ && (TREE_CODE (outer) == CONVERT_EXPR
+ || TREE_CODE (outer) == NOP_EXPR
+ || TREE_CODE (outer) == NON_LVALUE_EXPR))
+ {
+ tree lhstype = TREE_TYPE (outer);
+
+ /* Descend down the cast chain, and record the first objc_gc
+ attribute found. */
+ if (POINTER_TYPE_P (lhstype))
+ {
+ tree attr
+ = lookup_attribute ("objc_gc",
+ TYPE_ATTRIBUTES (TREE_TYPE (lhstype)));
+
+ if (attr)
+ strong_cast_p = 1;
+ }
+
+ outer = TREE_OPERAND (outer, 0);
+ }
+ }
+
+ /* If we have a __strong cast, it trumps all else. */
+ if (strong_cast_p)
+ {
+ if (modifycode != NOP_EXPR)
+ goto invalid_pointer_arithmetic;
+
+ if (warn_assign_intercept)
+ warning (0, "strong-cast assignment has been intercepted");
+
+ result = objc_build_strong_cast_assignment (lhs, rhs);
+
+ goto exit_point;
+ }
+
+ /* the lhs must be of a suitable type, regardless of its underlying
+ structure. */
+ if (!objc_is_gcable_p (lhs))
+ goto exit_point;
+
+ outer = lhs;
+
+ while (outer
+ && (TREE_CODE (outer) == COMPONENT_REF
+ || TREE_CODE (outer) == ARRAY_REF))
+ outer = TREE_OPERAND (outer, 0);
+
+ if (TREE_CODE (outer) == INDIRECT_REF)
+ {
+ outer = TREE_OPERAND (outer, 0);
+ indirect_p = 1;
+ }
+
+ outer_gc_p = objc_is_gcable_p (outer);
+
+ /* Handle ivar assignments. */
+ if (objc_is_ivar_reference_p (lhs))
+ {
+ /* if the struct to the left of the ivar is not an Objective-C object (__strong
+ doesn't cut it here), the best we can do here is suggest a cast. */
+ if (!objc_is_gcable_type (TREE_TYPE (outer), 0))
+ {
+ /* We may still be able to use the global write barrier... */
+ if (!indirect_p && objc_is_global_reference_p (outer))
+ goto global_reference;
+
+ suggest_cast:
+ if (modifycode == NOP_EXPR)
+ {
+ if (warn_assign_intercept)
+ warning (0, "strong-cast may possibly be needed");
+ }
+
+ goto exit_point;
+ }
+
+ if (modifycode != NOP_EXPR)
+ goto invalid_pointer_arithmetic;
+
+ if (warn_assign_intercept)
+ warning (0, "instance variable assignment has been intercepted");
+
+ result = objc_build_ivar_assignment (outer, lhs, rhs);
+
+ goto exit_point;
+ }
+
+ /* Likewise, intercept assignment to global/static variables if their type is
+ GC-marked. */
+ if (objc_is_global_reference_p (outer))
+ {
+ if (indirect_p)
+ goto suggest_cast;
+
+ global_reference:
+ if (modifycode != NOP_EXPR)
+ {
+ invalid_pointer_arithmetic:
+ if (outer_gc_p)
+ warning (0, "pointer arithmetic for garbage-collected objects not allowed");
+
+ goto exit_point;
+ }
+
+ if (warn_assign_intercept)
+ warning (0, "global/static variable assignment has been intercepted");