Refactor / document instance variable debug counters

This commit is refactoring and documenting the debug counters related to
instance variables.

debug_counter.h

@@ -127,29 +127,22 @@ RB_DEBUG_COUNTER(frame_R2C)
 RB_DEBUG_COUNTER(frame_C2C)
 RB_DEBUG_COUNTER(frame_C2R)
 
-/* instance variable counts
- *
- * * ivar_get_ic_hit/miss: ivar_get inline cache (ic) hit/miss counts (VM insn)
- * * ivar_get_ic_miss_unset:                      ... by unset (VM insn)
- * * ivar_get_ic_miss_noobject:                   ... by "not T_OBJECT" (VM insn)
- * * ivar_set_...: same counts with ivar_set (VM insn)
- * * ivar_get/set_base: call counts of "rb_ivar_get/set()".
- *                      because of (1) ic miss.
- *                                 (2) direct call by C extensions.
- */
-RB_DEBUG_COUNTER(ivar_get_ic_hit)
-RB_DEBUG_COUNTER(ivar_get_ic_miss)
-RB_DEBUG_COUNTER(ivar_get_ic_miss_noobject)
-RB_DEBUG_COUNTER(ivar_set_ic_hit)
-RB_DEBUG_COUNTER(ivar_set_ic_miss)
-RB_DEBUG_COUNTER(ivar_set_ic_miss_iv_hit)
-RB_DEBUG_COUNTER(ivar_set_ic_miss_noobject)
-RB_DEBUG_COUNTER(ivar_get_base)
-RB_DEBUG_COUNTER(ivar_set_base)
-RB_DEBUG_COUNTER(ivar_get_ic_miss_set)
-RB_DEBUG_COUNTER(ivar_get_cc_miss_set)
-RB_DEBUG_COUNTER(ivar_get_ic_miss_unset)
-RB_DEBUG_COUNTER(ivar_get_cc_miss_unset)
+/* instance variable counts */
+RB_DEBUG_COUNTER(ivar_get_obj_hit)  // Only T_OBJECT hits
+RB_DEBUG_COUNTER(ivar_get_obj_miss) // Only T_OBJECT misses
+RB_DEBUG_COUNTER(ivar_get_ic_hit)   // All hits
+RB_DEBUG_COUNTER(ivar_get_ic_miss)  // All misses
+RB_DEBUG_COUNTER(ivar_set_ic_hit)   // All hits
+RB_DEBUG_COUNTER(ivar_set_obj_hit)  // Only T_OBJECT hits
+RB_DEBUG_COUNTER(ivar_set_obj_miss) // Only T_OBJECT misses
+RB_DEBUG_COUNTER(ivar_set_ic_miss)  // All misses
+RB_DEBUG_COUNTER(ivar_set_ic_miss_noobject)  // Miss because non T_OBJECT
+RB_DEBUG_COUNTER(ivar_get_base) // Calls to `rb_ivar_get` (very slow path)
+RB_DEBUG_COUNTER(ivar_set_base) // Calls to `ivar_set` (very slow path)
+RB_DEBUG_COUNTER(ivar_get_ic_miss_set)   // Misses on IV reads where the cache was wrong
+RB_DEBUG_COUNTER(ivar_get_cc_miss_set)   // Misses on attr_reader where the cache was wrong
+RB_DEBUG_COUNTER(ivar_get_ic_miss_unset) // Misses on IV read where the cache wasn't set
+RB_DEBUG_COUNTER(ivar_get_cc_miss_unset) // Misses on attr_reader where the cache wasn't set
 
 /* local variable counts
  *

vm_insnhelper.c

@@ -1231,10 +1231,17 @@ vm_getivar(VALUE obj, ID id, const rb_iseq_t *iseq, IVC ic, const struct rb_call
         }
 
         val = ivar_list[index];
+#if USE_DEBUG_COUNTER
+        RB_DEBUG_COUNTER_INC(ivar_get_ic_hit);
+
+        if (RB_TYPE_P(obj, T_OBJECT)) {
+            RB_DEBUG_COUNTER_INC(ivar_get_obj_hit);
+        }
+#endif
         RUBY_ASSERT(!UNDEF_P(val));
     }
     else { // cache miss case
-#if RUBY_DEBUG
+#if USE_DEBUG_COUNTER
         if (is_attr) {
             if (cached_id != INVALID_SHAPE_ID) {
                 RB_DEBUG_COUNTER_INC(ivar_get_cc_miss_set);
@@ -1251,6 +1258,11 @@ vm_getivar(VALUE obj, ID id, const rb_iseq_t *iseq, IVC ic, const struct rb_call
                 RB_DEBUG_COUNTER_INC(ivar_get_ic_miss_unset);
             }
         }
+        RB_DEBUG_COUNTER_INC(ivar_get_ic_miss);
+
+        if (RB_TYPE_P(obj, T_OBJECT)) {
+            RB_DEBUG_COUNTER_INC(ivar_get_obj_miss);
+        }
 #endif
 
         rb_shape_t *shape = rb_shape_get_shape_by_id(shape_id);
@@ -1322,6 +1334,8 @@ static VALUE
 vm_setivar_slowpath(VALUE obj, ID id, VALUE val, const rb_iseq_t *iseq, IVC ic, const struct rb_callcache *cc, int is_attr)
 {
 #if OPT_IC_FOR_IVAR
+    RB_DEBUG_COUNTER_INC(ivar_set_ic_miss);
+
     switch (BUILTIN_TYPE(obj)) {
       case T_OBJECT:
         {
@@ -1335,7 +1349,7 @@ vm_setivar_slowpath(VALUE obj, ID id, VALUE val, const rb_iseq_t *iseq, IVC ic,
                 populate_cache(index, next_shape_id, id, iseq, ic, cc, is_attr);
             }
 
-            RB_DEBUG_COUNTER_INC(ivar_set_ic_miss_iv_hit);
+            RB_DEBUG_COUNTER_INC(ivar_set_obj_miss);
             return val;
         }
       case T_CLASS:
@@ -1363,7 +1377,6 @@ vm_setivar_slowpath(VALUE obj, ID id, VALUE val, const rb_iseq_t *iseq, IVC ic,
         }
     }
 #endif
-    RB_DEBUG_COUNTER_INC(ivar_set_ic_miss);
     return rb_ivar_set(obj, id, val);
 }
 
@@ -1469,6 +1482,7 @@ vm_setivar(VALUE obj, ID id, VALUE val, shape_id_t dest_shape_id, attr_index_t i
             RB_OBJ_WRITE(obj, &ptr[index], val);
 
             RB_DEBUG_COUNTER_INC(ivar_set_ic_hit);
+            RB_DEBUG_COUNTER_INC(ivar_set_obj_hit);
             return val;
         }
         break;