Revert "Reserve 2 bits for expressing object layout (#17139)"HEADmaster

This reverts commit 63d9f090b5d9461cf0b9446e0039d9c56156b826.

1 files changed, 10 insertions, 44 deletions

diff --git a/shape.h b/shape.h
index a319449988..61fadca5ba 100644
--- a/shape.h
+++ b/shape.h
@@ -27,14 +27,12 @@ STATIC_ASSERT(shape_id_num_bits, SHAPE_ID_NUM_BITS == sizeof(shape_id_t) * CHAR_
 //      19-22 SHAPE_ID_HEAP_INDEX_MASK
 //              index in rb_shape_tree.capacities. Allow to access slot size.
 //              Currently always 0 except for T_OBJECT.
-//      23 SHAPE_ID_FL_COMPLEX
-//              The object is backed by a `st_table`.
-//      24 SHAPE_ID_FL_FROZEN
+//      23 SHAPE_ID_FL_FROZEN
 //              Whether the object is frozen or not.
-//      25 SHAPE_ID_FL_HAS_OBJECT_ID
+//      24 SHAPE_ID_FL_HAS_OBJECT_ID
 //              Whether the object has an `SHAPE_OBJ_ID` transition.
-//      26-27 SHAPE_ID_LAYOUT_MASK
-//              The object's physical field layout.
+//      25 SHAPE_ID_FL_COMPLEX
+//              The object is backed by a `st_table`.
 
 enum shape_id_fl_type {
 #define RBIMPL_SHAPE_ID_FL(n) (1<<(SHAPE_ID_FL_USHIFT+n))
@@ -45,26 +43,8 @@ enum shape_id_fl_type {
     SHAPE_ID_FL_FROZEN = RBIMPL_SHAPE_ID_FL(1),
     SHAPE_ID_FL_HAS_OBJECT_ID = RBIMPL_SHAPE_ID_FL(2),
 
-    // Means IVs are found at an offset from the object's addr, or in a
-    // malloc allocated side table
-    SHAPE_ID_LAYOUT_ROBJECT = 0,
-
-    // Means this object is a class/module that is NOT RCLASS_BOXABLE, and IV's
-    // are found in the fields_obj found on the rclass struct
-    SHAPE_ID_LAYOUT_RCLASS = RBIMPL_SHAPE_ID_FL(3),
-
-    // Means this object is an RData or RTypedData and IVs are found in the
-    // fields_obj found on the RData/RTypedData struct
-    SHAPE_ID_LAYOUT_RDATA = RBIMPL_SHAPE_ID_FL(4),
-
-    // Means this is a complicated object: boxable classes, structs, objects
-    // that store IVs on the geniv table
-    SHAPE_ID_LAYOUT_OTHER = SHAPE_ID_LAYOUT_RCLASS | SHAPE_ID_LAYOUT_RDATA,
-
-    SHAPE_ID_LAYOUT_MASK = SHAPE_ID_LAYOUT_OTHER,
-
     SHAPE_ID_FL_NON_CANONICAL_MASK = SHAPE_ID_FL_FROZEN | SHAPE_ID_FL_HAS_OBJECT_ID,
-    SHAPE_ID_FLAGS_MASK = SHAPE_ID_HEAP_INDEX_MASK | SHAPE_ID_FL_NON_CANONICAL_MASK | SHAPE_ID_FL_COMPLEX | SHAPE_ID_LAYOUT_MASK,
+    SHAPE_ID_FLAGS_MASK = SHAPE_ID_HEAP_INDEX_MASK | SHAPE_ID_FL_NON_CANONICAL_MASK | SHAPE_ID_FL_COMPLEX,
 
 #undef RBIMPL_SHAPE_ID_FL
 };
@@ -75,13 +55,12 @@ enum shape_id_mask {
     SHAPE_ID_HAS_IVAR_MASK = SHAPE_ID_FL_COMPLEX | (SHAPE_ID_OFFSET_MASK - 1),
 };
 
-// The interpreter doesn't care about frozen status, slot size, or object id, and
-// has its own checks for physical field layout when reading ivars.
+// The interpreter doesn't care about frozen status, slot size or object id when reading ivars.
 // So we normalize shape_id by clearing these bits to improve cache hits.
 // JITs however might care about some of it.
-#define SHAPE_ID_READ_ONLY_MASK (~(SHAPE_ID_FL_FROZEN | SHAPE_ID_HEAP_INDEX_MASK | SHAPE_ID_FL_HAS_OBJECT_ID | SHAPE_ID_LAYOUT_MASK))
+#define SHAPE_ID_READ_ONLY_MASK (~(SHAPE_ID_FL_FROZEN | SHAPE_ID_HEAP_INDEX_MASK | SHAPE_ID_FL_HAS_OBJECT_ID))
 // For write it's the same idea, but here we do care about frozen status.
-#define SHAPE_ID_WRITE_MASK (~(SHAPE_ID_HEAP_INDEX_MASK | SHAPE_ID_FL_HAS_OBJECT_ID | SHAPE_ID_LAYOUT_MASK))
+#define SHAPE_ID_WRITE_MASK (~(SHAPE_ID_HEAP_INDEX_MASK | SHAPE_ID_FL_HAS_OBJECT_ID))
 
 typedef uint32_t redblack_id_t;
 
@@ -174,18 +153,11 @@ RBASIC_SET_SHAPE_ID_NO_CHECKS(VALUE obj, shape_id_t shape_id)
 #endif
 }
 
-static inline shape_id_t
-rb_shape_layout(shape_id_t shape_id)
-{
-    return shape_id & SHAPE_ID_LAYOUT_MASK;
-}
-
 static inline void
 RBASIC_SET_SHAPE_ID(VALUE obj, shape_id_t shape_id)
 {
     RUBY_ASSERT(!RB_SPECIAL_CONST_P(obj));
     RUBY_ASSERT(!RB_TYPE_P(obj, T_IMEMO) || IMEMO_TYPE_P(obj, imemo_fields));
-    RUBY_ASSERT(!IMEMO_TYPE_P(obj, imemo_fields) || rb_shape_layout(shape_id) == SHAPE_ID_LAYOUT_ROBJECT);
 
     RBASIC_SET_SHAPE_ID_NO_CHECKS(obj, shape_id);
 
@@ -260,12 +232,6 @@ rb_shape_canonical_p(shape_id_t shape_id)
     return !(shape_id & SHAPE_ID_FL_NON_CANONICAL_MASK);
 }
 
-static inline shape_id_t
-rb_shape_id_with_robject_layout(shape_id_t shape_id)
-{
-    return (shape_id & ~SHAPE_ID_LAYOUT_MASK) | SHAPE_ID_LAYOUT_ROBJECT;
-}
-
 static inline uint8_t
 rb_shape_heap_index(shape_id_t shape_id)
 {
@@ -484,10 +450,10 @@ rb_shape_transition_frozen(shape_id_t shape_id)
 static inline shape_id_t
 rb_shape_transition_complex(shape_id_t shape_id)
 {
-    shape_id_t next_shape_id = rb_shape_layout(shape_id) | ROOT_COMPLEX_SHAPE_ID;
+    shape_id_t next_shape_id = ROOT_COMPLEX_SHAPE_ID;
 
     if (rb_shape_has_object_id(shape_id)) {
-        next_shape_id = rb_shape_layout(shape_id) | ROOT_COMPLEX_WITH_OBJ_ID;
+        next_shape_id = ROOT_COMPLEX_WITH_OBJ_ID;
     }
 
     uint8_t heap_index = rb_shape_heap_index(shape_id);