gc-object-models.txt

V3 Object model:
====================================================================================================
                                                                    Value   <-------+
									            |
HeapTypeDecl<---------------+        +-------> Array<Value>: { typeid , length , e0 o , e1 , ... }
                            |        |
HeapObject: { typeid , decl x , vals x }


SPC support:

Level -1:
   no SPC support, interpreter only
Level 0:
   Runtime call for all STRUCT/ARRAY operations
Level 1:
   Runtime call for allocations
   STRUCT/ARRAY.get/set loads obj->vals and calls
     - Runtime.get_val_i(Array<Value>, index) -> i32
               get_val_l                      -> i64
               get_val_f                      -> i64
               get_val_d                      -> i64
               get_val_r                      -> Object
               get_val_s                      -> (i64, i64)
     - Runtime.set_val_i(Array<Value>, index, val: i32)
               set_val_l(Array<Value>, index, val: i64)

Level 1l:
  Inline array.len
Level 1r:
  Inline i31 ref operations
Level 1c:
  Inline all ref.cast operations

Level 2:
  STRUCT/ARRAY.get directly loads field from (boxed) Value.I32/I64/F32/Ref cases

Level 3:
   Values are unboxed but still tagged for I32, I64, F32, F64, Ref,
   STRUCT/ARRAY.get/set directly updates value array
   (what about write barriers?)
Level 3b:
   Values are unboxed and use same layout as Value stack array

Level 4:
   Object model uses Virgil runtime extensions

Level 5:
   Inline allocation via bump pointer of TLAB