vm_getivar: normalize shape_id to ignore frozen state

Freezing an object changes its `shape_id` This is necessary
so that `setivar` routines can use the `shape_id` as a cache key
and save on checking the frozen status every time.

However for `getivar` routines, this causes needless cache misses.
By clearing that bit we increase hit rate in codepaths that see
both frozen and mutable objects.

Author: byroot

id_table.c

@@ -381,6 +381,7 @@ managed_id_table_dup_i(ID id, VALUE val, void *data)
 VALUE
 rb_managed_id_table_dup(VALUE old_table)
 {
+    RUBY_ASSERT(RB_TYPE_P(old_table, T_DATA));
     RUBY_ASSERT(rb_typeddata_inherited_p(RTYPEDDATA_TYPE(old_table), &managed_id_table_type));
 
     struct rb_id_table *new_tbl;
@@ -394,6 +395,7 @@ rb_managed_id_table_dup(VALUE old_table)
 int
 rb_managed_id_table_lookup(VALUE table, ID id, VALUE *valp)
 {
+    RUBY_ASSERT(RB_TYPE_P(table, T_DATA));
     RUBY_ASSERT(rb_typeddata_inherited_p(RTYPEDDATA_TYPE(table), &managed_id_table_type));
 
     return rb_id_table_lookup(RTYPEDDATA_GET_DATA(table), id, valp);
@@ -402,6 +404,7 @@ rb_managed_id_table_lookup(VALUE table, ID id, VALUE *valp)
 int
 rb_managed_id_table_insert(VALUE table, ID id, VALUE val)
 {
+    RUBY_ASSERT(RB_TYPE_P(table, T_DATA));
     RUBY_ASSERT(rb_typeddata_inherited_p(RTYPEDDATA_TYPE(table), &managed_id_table_type));
 
     return rb_id_table_insert(RTYPEDDATA_GET_DATA(table), id, val);
@@ -410,6 +413,7 @@ rb_managed_id_table_insert(VALUE table, ID id, VALUE val)
 size_t
 rb_managed_id_table_size(VALUE table)
 {
+    RUBY_ASSERT(RB_TYPE_P(table, T_DATA));
     RUBY_ASSERT(rb_typeddata_inherited_p(RTYPEDDATA_TYPE(table), &managed_id_table_type));
 
     return rb_id_table_size(RTYPEDDATA_GET_DATA(table));
@@ -418,6 +422,7 @@ rb_managed_id_table_size(VALUE table)
 void
 rb_managed_id_table_foreach(VALUE table, rb_id_table_foreach_func_t *func, void *data)
 {
+    RUBY_ASSERT(RB_TYPE_P(table, T_DATA));
     RUBY_ASSERT(rb_typeddata_inherited_p(RTYPEDDATA_TYPE(table), &managed_id_table_type));
 
     rb_id_table_foreach(RTYPEDDATA_GET_DATA(table), func, data);

shape.c

@@ -303,7 +303,7 @@ static void
 shape_tree_mark(void *data)
 {
     rb_shape_t *cursor = rb_shape_get_root_shape();
-    rb_shape_t *end = RSHAPE(GET_SHAPE_TREE()->next_shape_id);
+    rb_shape_t *end = cursor + (GET_SHAPE_TREE()->next_shape_id - 1);
     while (cursor < end) {
         if (cursor->edges && !SINGLE_CHILD_P(cursor->edges)) {
             // FIXME: GC compaction may call `rb_shape_traverse_from_new_root`

shape.h

@@ -14,6 +14,7 @@ STATIC_ASSERT(shape_id_num_bits, SHAPE_ID_NUM_BITS == sizeof(shape_id_t) * CHAR_
 #define SHAPE_ID_OFFSET_MASK (SHAPE_BUFFER_SIZE - 1)
 #define SHAPE_ID_FLAGS_MASK (shape_id_t)(((1 << (SHAPE_ID_NUM_BITS - SHAPE_ID_OFFSET_NUM_BITS)) - 1) << SHAPE_ID_OFFSET_NUM_BITS)
 #define SHAPE_ID_FL_FROZEN (SHAPE_FL_FROZEN << SHAPE_ID_OFFSET_NUM_BITS)
+#define SHAPE_ID_READ_ONLY_MASK (~SHAPE_ID_FL_FROZEN)
 
 typedef uint32_t redblack_id_t;
 
@@ -110,6 +111,14 @@ RBASIC_SHAPE_ID(VALUE obj)
 #endif
 }
 
+// Same as RBASIC_SHAPE_ID but with flags that have no impact
+// on reads removed. e.g. Remove FL_FROZEN.
+static inline shape_id_t
+RBASIC_SHAPE_ID_FOR_READ(VALUE obj)
+{
+    return RBASIC_SHAPE_ID(obj) & SHAPE_ID_READ_ONLY_MASK;
+}
+
 static inline void
 RBASIC_SET_SHAPE_ID(VALUE obj, shape_id_t shape_id)
 {

vm_insnhelper.c

@@ -1215,14 +1215,13 @@ vm_getivar(VALUE obj, ID id, const rb_iseq_t *iseq, IVC ic, const struct rb_call
 {
 #if OPT_IC_FOR_IVAR
     VALUE val = Qundef;
-    shape_id_t shape_id;
     VALUE * ivar_list;
 
     if (SPECIAL_CONST_P(obj)) {
         return default_value;
     }
 
-    shape_id = RBASIC_SHAPE_ID(obj);
+    shape_id_t shape_id = RBASIC_SHAPE_ID_FOR_READ(obj);
 
     switch (BUILTIN_TYPE(obj)) {
       case T_OBJECT: