Update appendix for memory64 (#97)

Split out from WebAssembly/spec#1839

document/core/appendix/changes.rst

@@ -389,6 +389,44 @@ Added the ability to use multiple memories per module. [#proposal-multimem]_
 * :ref:`Data segments <syntax-elem>` take a :ref:`memory index <syntax-memidx>`
 
 
+.. index:: address type, number type, table, memory, instruction
+
+64-bit Address Space
+....................
+
+Added the ability to declare an :math:`\I64` :ref:`address type <syntax-addrtype>` for :ref:`tables <syntax-tabletype>` and :ref:`memories <syntax-memtype>`. [#proposal-addr64]_
+
+* :ref:`Address types <syntax-addrtype>` denote a subset of the integral :ref:`number types <syntax-numtype>`
+
+* :ref:`Table types <syntax-tabletype>` include an :ref:`address type <syntax-addrtype>`
+
+* :ref:`Memory types <syntax-memtype>` include an :ref:`address type <syntax-addrtype>`
+
+* Operand types of :ref:`table <syntax-instr-table>` and :ref:`memory <syntax-instr-memory>` instructions now depend on the subject's declared address type:
+
+  - |TABLEGET|
+  - |TABLESET|
+  - |TABLESIZE|
+  - |TABLEGROW|
+  - |TABLEFILL|
+  - |TABLECOPY|
+  - |TABLEINIT|
+  - |MEMORYSIZE|
+  - |MEMORYGROW|
+  - |MEMORYFILL|
+  - |MEMORYCOPY|
+  - |MEMORYINIT|
+  - :math:`t\K{.load}`
+  - :math:`t\K{.store}`
+  - :math:`t\K{.load}\!N\!\K{\_}\sx`
+  - :math:`t\K{.store}\!N`
+  - :math:`\K{v128.load}\!N\!\K{x}\!M\!\K{\_}\sx`
+  - :math:`\K{v128.load}\!N\!\K{\_zero}`
+  - :math:`\K{v128.load}\!N\!\K{\_splat}`
+  - :math:`\K{v128.load}\!N\!\K{\_lane}`
+  - :math:`\K{v128.store}\!N\!\K{\_lane}`
+
+
 .. index:: reference, reference type, heap type, value type, local, local type, instruction, instruction type, table, function, function type, matching, subtyping
 
 Typeful References
@@ -595,6 +633,9 @@ mirroring the role of custom sections in the binary format. [#proposal-annot]_
 .. [#proposal-multimem]
    https://github.com/WebAssembly/spec/blob/main/proposals/multi-memory/
 
+.. [#proposal-addr64]
+   https://github.com/WebAssembly/spec/blob/main/proposals/memory64/
+
 .. [#proposal-typedref]
    https://github.com/WebAssembly/spec/tree/main/proposals/function-references/