Transition shape when object's capacity changes

This commit adds a `capacity` field to shapes, and adds shape
transitions whenever an object's capacity changes. Objects which are
allocated out of a bigger size pool will also make a transition from the
root shape to the shape with the correct capacity for their size pool
when they are allocated.

This commit will allow us to remove numiv from objects completely, and
will also mean we can guarantee that if two objects share shapes, their
IVs are in the same positions (an embedded and extended object cannot
share shapes). This will enable us to implement ivar sets in YJIT using
object shapes.

Co-Authored-By: Aaron Patterson <[email protected]>

1 files changed, 4 insertions, 1 deletions

diff --git a/internal/gc.h b/internal/gc.h
index 84b7f9fa3e..5b2b9e8f70 100644
--- a/internal/gc.h
+++ b/internal/gc.h
@@ -14,6 +14,7 @@
 
 #include "internal/compilers.h" /* for __has_attribute */
 #include "ruby/ruby.h"          /* for rb_event_flag_t */
+#include "shape.h"
 
 struct rb_execution_context_struct; /* in vm_core.h */
 struct rb_objspace; /* in vm_core.h */
@@ -67,12 +68,14 @@ struct rb_objspace; /* in vm_core.h */
     rb_obj_write((VALUE)(a), UNALIGNED_MEMBER_ACCESS((VALUE *)(slot)), \
                  (VALUE)(b), __FILE__, __LINE__)
 
-#if USE_RVARGC
+#if USE_RVARGC && SHAPE_IN_BASIC_FLAGS
 # define SIZE_POOL_COUNT 5
 #else
 # define SIZE_POOL_COUNT 1
 #endif
 
+#define RCLASS_EXT_EMBEDDED (SIZE_POOL_COUNT > 1)
+
 typedef struct ractor_newobj_size_pool_cache {
     struct RVALUE *freelist;
     struct heap_page *using_page;