Limit maximum number of IVs on a shape on T_OBJECTS

Create SHAPE_MAX_NUM_IVS (currently 50) and limit all shapes of
T_OBJECTS to that number of IVs. When a shape with a T_OBJECT has more than 50 IVs, fall back to the
obj_too_complex shape which uses hash lookup for ivs.

Note that a previous version of this commit
78fcc9847a9db6d42c8c263154ec05903a370b6b was reverted in
88f2b94065be3fcd6769a3f132cfee8ecfb663b8 because it did not account for
non-T_OBJECTS

1 files changed, 12 insertions, 9 deletions

diff --git a/shape.c b/shape.c
index c2004d7b65..13441f3e71 100644
--- a/shape.c
+++ b/shape.c
@@ -114,7 +114,7 @@ rb_shape_get_shape(VALUE obj)
 }
 
 static rb_shape_t*
-get_next_shape_internal(rb_shape_t * shape, ID id, enum shape_type shape_type, bool * variation_created, bool new_shapes_allowed)
+get_next_shape_internal(rb_shape_t * shape, ID id, enum shape_type shape_type, bool * variation_created, bool new_shapes_allowed, bool new_shape_necessary)
 {
     rb_shape_t *res = NULL;
 
@@ -123,7 +123,7 @@ get_next_shape_internal(rb_shape_t * shape, ID id, enum shape_type shape_type, b
 
     *variation_created = false;
 
-    if (new_shapes_allowed) {
+    if (new_shape_necessary || (new_shapes_allowed && (shape->next_iv_index < SHAPE_MAX_NUM_IVS))) {
         RB_VM_LOCK_ENTER();
         {
             bool had_edges = !!shape->edges;
@@ -238,7 +238,7 @@ remove_shape_recursive(VALUE obj, ID id, rb_shape_t * shape, VALUE * removed)
             // has the same attributes as this shape.
             if (new_parent) {
                 bool dont_care;
-                rb_shape_t * new_child = get_next_shape_internal(new_parent, shape->edge_name, shape->type, &dont_care, true);
+                rb_shape_t * new_child = get_next_shape_internal(new_parent, shape->edge_name, shape->type, &dont_care, true, false);
                 new_child->capacity = shape->capacity;
                 if (new_child->type == SHAPE_IVAR) {
                     move_iv(obj, id, shape->next_iv_index - 1, new_child->next_iv_index - 1);
@@ -283,7 +283,7 @@ rb_shape_transition_shape_frozen(VALUE obj)
     }
 
     bool dont_care;
-    next_shape = get_next_shape_internal(shape, (ID)id_frozen, SHAPE_FROZEN, &dont_care, true);
+    next_shape = get_next_shape_internal(shape, (ID)id_frozen, SHAPE_FROZEN, &dont_care, true, false);
 
     RUBY_ASSERT(next_shape);
     rb_shape_set_shape(obj, next_shape);
@@ -298,7 +298,7 @@ rb_shape_get_next_iv_shape(rb_shape_t* shape, ID id)
 {
     RUBY_ASSERT(!is_instance_id(id) || RTEST(rb_sym2str(ID2SYM(id))));
     bool dont_care;
-    return get_next_shape_internal(shape, id, SHAPE_IVAR, &dont_care, true);
+    return get_next_shape_internal(shape, id, SHAPE_IVAR, &dont_care, true, false);
 }
 
 rb_shape_t *
@@ -314,7 +314,9 @@ rb_shape_get_next(rb_shape_t* shape, VALUE obj, ID id)
     }
 
     bool variation_created = false;
-    rb_shape_t * new_shape = get_next_shape_internal(shape, id, SHAPE_IVAR, &variation_created, allow_new_shape);
+    // For non T_OBJECTS, force a new shape
+    bool new_shape_necessary = BUILTIN_TYPE(obj) != T_OBJECT;
+    rb_shape_t * new_shape = get_next_shape_internal(shape, id, SHAPE_IVAR, &variation_created, allow_new_shape, new_shape_necessary);
 
     if (!new_shape) {
         RUBY_ASSERT(BUILTIN_TYPE(obj) == T_OBJECT);
@@ -341,7 +343,7 @@ rb_shape_transition_shape_capa(rb_shape_t* shape, uint32_t new_capacity)
 {
     ID edge_name = rb_make_temporary_id(new_capacity);
     bool dont_care;
-    rb_shape_t * new_shape = get_next_shape_internal(shape, edge_name, SHAPE_CAPACITY_CHANGE, &dont_care, true);
+    rb_shape_t * new_shape = get_next_shape_internal(shape, edge_name, SHAPE_CAPACITY_CHANGE, &dont_care, true, false);
     new_shape->capacity = new_capacity;
     return new_shape;
 }
@@ -751,7 +753,7 @@ Init_default_shapes(void)
         rb_shape_t * shape = rb_shape_get_shape_by_id(i);
         bool dont_care;
         rb_shape_t * t_object_shape =
-            get_next_shape_internal(shape, id_t_object, SHAPE_T_OBJECT, &dont_care, true);
+            get_next_shape_internal(shape, id_t_object, SHAPE_T_OBJECT, &dont_care, true, false);
         t_object_shape->edges = rb_id_table_create(0);
         RUBY_ASSERT(rb_shape_id(t_object_shape) == (shape_id_t)(i + SIZE_POOL_COUNT));
     }
@@ -761,7 +763,7 @@ Init_default_shapes(void)
 #if RUBY_DEBUG
     rb_shape_t * special_const_shape =
 #endif
-        get_next_shape_internal(root, (ID)id_frozen, SHAPE_FROZEN, &dont_care, true);
+        get_next_shape_internal(root, (ID)id_frozen, SHAPE_FROZEN, &dont_care, true, false);
     RUBY_ASSERT(rb_shape_id(special_const_shape) == SPECIAL_CONST_SHAPE_ID);
     RUBY_ASSERT(SPECIAL_CONST_SHAPE_ID == (GET_VM()->next_shape_id - 1));
     RUBY_ASSERT(rb_shape_frozen_shape_p(special_const_shape));
@@ -800,6 +802,7 @@ Init_shape(void)
     rb_define_const(rb_cShape, "SPECIAL_CONST_SHAPE_ID", INT2NUM(SPECIAL_CONST_SHAPE_ID));
     rb_define_const(rb_cShape, "OBJ_TOO_COMPLEX_SHAPE_ID", INT2NUM(OBJ_TOO_COMPLEX_SHAPE_ID));
     rb_define_const(rb_cShape, "SHAPE_MAX_VARIATIONS", INT2NUM(SHAPE_MAX_VARIATIONS));
+    rb_define_const(rb_cShape, "SHAPE_MAX_NUM_IVS", INT2NUM(SHAPE_MAX_NUM_IVS));
 
     rb_define_singleton_method(rb_cShape, "transition_tree", shape_transition_tree, 0);
     rb_define_singleton_method(rb_cShape, "find_by_id", rb_shape_find_by_id, 1);