I fought and lost a massive argument spanning years about this. There are very limited cases where the backend is able to do this successfully.

On 26 October 2014 20:37, via D.gnu <d.gnu@puremagic.com> wrote:

>  Bug ID 162 <http://bugzilla.gdcproject.org/show_bug.cgi?id=162>  Summary GDC
> unable to de-virtualise method calls  Product GDC  Version development
> Hardware All  OS All  Status NEW  Severity enhancement  Priority Normal
> Component gdc  Assignee ibuclaw@gdcproject.org  Reporter
> ibuclaw@gdcproject.org
>
>  Currently we emit method calls as the following:
>
>   *(c->__vptr + 40) (c, 1, 2, 3);
>
> Which translate directly into the following trees:
>
>   indirect_ref(pointer_plus(component_ref(c, __vptr), 40))
>
>
> GCC provides a more simplistic tree code called obj_type_ref, which represents a virtual method lookup, and given the binfo structure we already pass to the backed, this would give a chance for the optimiser passes to statically determine the dynamic type of the object and devirtualise the call.
>
>   obj_type_ref(component_ref(c, __vptr), c, 40)
>
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