Differentiate T_OBJECT shapes from other objects

We would like to differentiate types of objects via their shape.  This
commit adds a special T_OBJECT shape when we allocate an instance of
T_OBJECT.  This allows us to avoid testing whether an object is an
instance of a T_OBJECT or not, we can just check the shape.

1 files changed, 2 insertions, 1 deletions

diff --git a/shape.h b/shape.h
index a2cbd7c482..9bbc5d35f9 100644
--- a/shape.h
+++ b/shape.h
@@ -42,7 +42,7 @@ typedef uint16_t shape_id_t;
 # define ROOT_SHAPE_ID 0x0
 // We use SIZE_POOL_COUNT number of shape IDs for transitions out of different size pools
 // The next available shapd ID will be the SPECIAL_CONST_SHAPE_ID
-# define SPECIAL_CONST_SHAPE_ID SIZE_POOL_COUNT
+# define SPECIAL_CONST_SHAPE_ID (SIZE_POOL_COUNT * 2)
 
 struct rb_shape {
     struct rb_id_table * edges; // id_table from ID (ivar) to next shape
@@ -63,6 +63,7 @@ enum shape_type {
     SHAPE_CAPACITY_CHANGE,
     SHAPE_IVAR_UNDEF,
     SHAPE_INITIAL_CAPACITY,
+    SHAPE_T_OBJECT,
 };
 
 #if SHAPE_IN_BASIC_FLAGS