1 files changed, 6 insertions, 19 deletions

diff --git a/iseq.c b/iseq.c
index 381bf6ed20..869ed4da6a 100644
--- a/iseq.c
+++ b/iseq.c
@@ -2509,33 +2509,20 @@ rb_iseq_disasm(const rb_iseq_t *iseq)
 attr_index_t
 rb_estimate_iv_count(VALUE klass, const rb_iseq_t * initialize_iseq)
 {
-    bool calls_super = false;
-
     struct rb_id_table * iv_names = rb_id_table_create(0);
 
-    VALUE * code = ISEQ_BODY(initialize_iseq)->iseq_encoded;
-
-    for (unsigned int i = 0; i < ISEQ_BODY(initialize_iseq)->iseq_size; ) {
-        VALUE insn = code[i];
-        int original_insn = rb_vm_insn_addr2insn((const void *)insn);
+    for (unsigned int i = 0; i < ISEQ_BODY(initialize_iseq)->ivc_size; i++) {
+        IVC cache = (IVC)&ISEQ_BODY(initialize_iseq)->is_entries[i];
 
-        if (BIN(setinstancevariable) == original_insn) {
-            ID name = (ID)code[i + 1];
-            rb_id_table_insert(iv_names, name, Qtrue);
+        if (cache->iv_set_name) {
+            rb_id_table_insert(iv_names, cache->iv_set_name, Qtrue);
         }
-        else if (BIN(invokesuper) == original_insn) {
-            calls_super = true;
-        }
-
-        i += insn_len(original_insn);
     }
 
     attr_index_t count = (attr_index_t)rb_id_table_size(iv_names);
 
-    if (calls_super) {
-        VALUE superclass = rb_class_superclass(klass);
-        count += RCLASS_EXT(superclass)->max_iv_count;
-    }
+    VALUE superclass = rb_class_superclass(klass);
+    count += RCLASS_EXT(superclass)->max_iv_count;
 
     rb_id_table_free(iv_names);