1. This is x86-specific and does not go into cppmangle.
2. There is no equivalent type in D (``__float128 <-> real``), ``real`` has always been mapped to ``long double``, so this just wrong.
3. You'd have thought the name ``Tfloat80`` would give the hint as to what type this is. :)

For reference of C++ mangling ABI here.
```
<builtin-type>
  ::= e   # long double, __float80
  ::= g   # __float128          [not supported]
```