1 files changed, 25 insertions, 68 deletions

diff --git a/include/ruby/internal/core/robject.h b/include/ruby/internal/core/robject.h
index f2028063a6..99f6470ac1 100644
--- a/include/ruby/internal/core/robject.h
+++ b/include/ruby/internal/core/robject.h
@@ -37,16 +37,15 @@
 /**
  * Convenient casting macro.
  *
- * @param   obj  An object, which is in fact an ::RRegexp.
- * @return  The passed object casted to ::RRegexp.
+ * @param   obj  An object, which is in fact an ::RObject.
+ * @return  The passed object casted to ::RObject.
  */
 #define ROBJECT(obj)          RBIMPL_CAST((struct RObject *)(obj))
 /** @cond INTERNAL_MACRO */
-#define ROBJECT_EMBED_LEN_MAX ROBJECT_EMBED_LEN_MAX
-#define ROBJECT_EMBED         ROBJECT_EMBED
-#define ROBJECT_NUMIV         ROBJECT_NUMIV
-#define ROBJECT_IVPTR         ROBJECT_IVPTR
-#define ROBJECT_IV_INDEX_TBL  ROBJECT_IV_INDEX_TBL
+#define ROBJECT_EMBED_LEN_MAX       ROBJECT_EMBED_LEN_MAX
+#define ROBJECT_HEAP                ROBJECT_HEAP
+#define ROBJECT_FIELDS_CAPACITY     ROBJECT_FIELDS_CAPACITY
+#define ROBJECT_FIELDS              ROBJECT_FIELDS
 /** @endcond */
 
 /**
@@ -56,10 +55,12 @@
  */
 enum ruby_robject_flags {
     /**
-     * This flag has  something to do with memory footprint.   If the object is
-     * "small"  enough, ruby  tries to  be creative  to abuse  padding bits  of
-     * struct ::RObject for storing instance variables.  This flag denotes that
-     * situation.
+     * This flag marks that the object's instance variables are stored in an
+     * external heap buffer.
+     * Normally, instance variable references are stored inside the object slot,
+     * but if it overflow, Ruby may have to allocate a separate buffer and spills
+     * the instance variables there.
+     * This flag denotes that situation.
      *
      * @warning  This  bit has  to be  considered read-only.   Setting/clearing
      *           this  bit without  corresponding fix  up must  cause immediate
@@ -72,16 +73,7 @@ enum ruby_robject_flags {
      * 3rd parties must  not be aware that  there even is more than  one way to
      * store instance variables.  Might better be hidden.
      */
-    ROBJECT_EMBED = RUBY_FL_USER1
-};
-
-/**
- * This is an enum because GDB wants it (rather than a macro).  People need not
- * bother.
- */
-enum ruby_robject_consts {
-    /** Max possible number of instance variables that can be embedded. */
-    ROBJECT_EMBED_LEN_MAX = RBIMPL_EMBED_LEN_MAX_OF(VALUE)
+    ROBJECT_HEAP = RUBY_FL_USER4
 };
 
 struct st_table;
@@ -103,60 +95,25 @@ struct RObject {
          * this pattern.
          */
         struct {
-
-            /**
-             * Number of instance variables.  This is per object; objects might
-             * differ in this field even if they have the identical classes.
-             */
-            uint32_t numiv;
-
             /** Pointer to a C array that holds instance variables. */
-            VALUE *ivptr;
-
-            /**
-             * This  is a  table that  holds  instance variable  name to  index
-             * mapping.  Used when accessing instance variables using names.
-             *
-             * @internal
-             *
-             * This is a shortcut for `RCLASS_IV_INDEX_TBL(rb_obj_class(obj))`.
-             */
-            struct st_table *iv_index_tbl;
+            VALUE *fields;
         } heap;
 
-        /**
-         * Embedded instance  variables.  When  an object  is small  enough, it
+        /* Embedded instance variables. When an object is small enough, it
          * uses this area to store the instance variables.
+         *
+         * This is a length 1 array because:
+         *   1. GCC has a bug that does not optimize C flexible array members
+         *      (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102452)
+         *   2. Zero length arrays are not supported by all compilers
          */
-        VALUE ary[ROBJECT_EMBED_LEN_MAX];
+        VALUE ary[1];
     } as;
 };
 
 RBIMPL_ATTR_PURE_UNLESS_DEBUG()
 RBIMPL_ATTR_ARTIFICIAL()
 /**
- * Queries the number of instance variables.
- *
- * @param[in]  obj  Object in question.
- * @return     Its number of instance variables.
- * @pre        `obj` must be an instance of ::RObject.
- */
-static inline uint32_t
-ROBJECT_NUMIV(VALUE obj)
-{
-    RBIMPL_ASSERT_TYPE(obj, RUBY_T_OBJECT);
-
-    if (RB_FL_ANY_RAW(obj, ROBJECT_EMBED)) {
-        return ROBJECT_EMBED_LEN_MAX;
-    }
-    else {
-        return ROBJECT(obj)->as.heap.numiv;
-    }
-}
-
-RBIMPL_ATTR_PURE_UNLESS_DEBUG()
-RBIMPL_ATTR_ARTIFICIAL()
-/**
  * Queries the instance variables.
  *
  * @param[in]  obj  Object in question.
@@ -168,17 +125,17 @@ RBIMPL_ATTR_ARTIFICIAL()
  * @shyouhei finds no reason for this to be visible from extension libraries.
  */
 static inline VALUE *
-ROBJECT_IVPTR(VALUE obj)
+ROBJECT_FIELDS(VALUE obj)
 {
     RBIMPL_ASSERT_TYPE(obj, RUBY_T_OBJECT);
 
     struct RObject *const ptr = ROBJECT(obj);
 
-    if (RB_FL_ANY_RAW(obj, ROBJECT_EMBED)) {
-        return ptr->as.ary;
+    if (RB_UNLIKELY(RB_FL_ANY_RAW(obj, ROBJECT_HEAP))) {
+        return ptr->as.heap.fields;
     }
     else {
-        return ptr->as.heap.ivptr;
+        return ptr->as.ary;
     }
 }