Add lock-free fastpath to callable_method_entry...

Author: jhawthorn

vm_method.c

@@ -1822,6 +1822,25 @@ callable_method_entry_or_negative(VALUE klass, ID mid, VALUE *defined_class_ptr)
     const rb_callable_method_entry_t *cme;
 
     VM_ASSERT_TYPE2(klass, T_CLASS, T_ICLASS);
+
+    /* Fast path: lock-free read from cache */
+    VALUE cc_tbl = RUBY_ATOMIC_VALUE_LOAD(RCLASS_WRITABLE_CC_TBL(klass));
+    if (cc_tbl) {
+        VALUE ccs_data;
+        if (rb_managed_id_table_lookup(cc_tbl, mid, &ccs_data)) {
+            struct rb_class_cc_entries *ccs = (struct rb_class_cc_entries *)ccs_data;
+            VM_ASSERT(vm_ccs_p(ccs));
+
+            if (LIKELY(!METHOD_ENTRY_INVALIDATED(ccs->cme))) {
+                VM_ASSERT(ccs->cme->called_id == mid);
+                if (defined_class_ptr != NULL) *defined_class_ptr = ccs->cme->defined_class;
+                RB_DEBUG_COUNTER_INC(ccs_found);
+                return ccs->cme;
+            }
+        }
+    }
+
+    /* Slow path: need to lock and potentially populate cache */
     RB_VM_LOCKING() {
         cme = cached_callable_method_entry(klass, mid);