More precisely iterate over Object instance variables

Shapes provides us with an (almost) exact count of instance variables.
We only need to check for Qundef when an IV has been "undefined"
Prefer to use ROBJECT_IV_COUNT when iterating IVs

1 files changed, 4 insertions, 2 deletions

diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 3f1337c36c..8b19c6c10d 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1268,8 +1268,7 @@ vm_setivar_slowpath(VALUE obj, ID id, VALUE val, const rb_iseq_t *iseq, IVC ic,
 
             if (shape != next_shape) {
                 RUBY_ASSERT(next_shape->parent_id == rb_shape_id(shape));
-                rb_shape_set_shape(obj, next_shape);
-                next_shape_id = ROBJECT_SHAPE_ID(obj);
+                next_shape_id = rb_shape_id(next_shape);
             }
 
             if (rb_shape_get_iv_index(next_shape, id, &index)) { // based off the hash stored in the transition tree
@@ -1289,6 +1288,9 @@ vm_setivar_slowpath(VALUE obj, ID id, VALUE val, const rb_iseq_t *iseq, IVC ic,
                 rb_init_iv_list(obj);
             }
 
+            if (shape != next_shape) {
+                rb_shape_set_shape(obj, next_shape);
+            }
             VALUE *ptr = ROBJECT_IVPTR(obj);
             RB_OBJ_WRITE(obj, &ptr[index], val);
             RB_DEBUG_COUNTER_INC(ivar_set_ic_miss_iv_hit);