[Issue 24333] New: Inline ClassInfo with the vtbl

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24333

          Issue ID: 24333
           Summary: Inline ClassInfo with the vtbl
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: bugzilla at digitalmars.com

deadalnix writes:

The current layout of objects is as follow:

+-----------+    +-----------+    +-----------+
|  __vtbl   +--->|  typeid   +--->| ClassInfo |
+-----------+    +-----------+    |           |
| __monitor |    |  method0  |    |    ...    |
+-----------+    +-----------+    |           |
|  field0   |    |  method1  |    +-----------+
+-----------+    +-----------+
|  field1   |    |    ...    |
+-----------+    +-----------+
|    ...    |
+-----------+
This causes a ton of extra indirections that are not necessary. instead the
following layout ought to be used:

+-----------+    +-----------+
|  __vtbl   +--->| ClassInfo |
+-----------+    |           |
| __monitor |    |    ...    |
+-----------+    |           |
|  field0   |    +-----------+
+-----------+    |  method0  |
|  field1   |    +-----------+
+-----------+    |  method1  |
|    ...    |    +-----------+
+-----------+    |    ...    |
                 +-----------+
Alternatively, it is possible to have the pointer point at the first method and
subtract to get the typeid. The important part is that there is only one
indirection now.

https://forum.dlang.org/post/hteuczyclxajakrisxjd@forum.dlang.org

--