Re: RFC: New C++ Attribute: final

[Daniel Berlin <dberlin at dberlin dot org>]

> Certainly not.  But if such a pointer to member was final and bound to
> a known function, GCC might be able to short-curcuit function calls
> through it, and even inline them.  But since, for a virtual function,
> it is not possible to know the exact function that is going to be
> called unless you happen to know the dynamic type of the object, you
> lose.  With final, you'd win.

Compilers besides GCC have started to get good at determining the 
dynamic types of objects and "devirtualizing calls".  Some also 
implement more trivial methods (see if it must-alias a certain 
component of the virtual table object, and thus, must be pointing to 
that call) as a backup.
It's somewhere down on my list to implement some form of analysis 
(RTA/CHA/whatever) to be able to a determine a small set of actual 
calls a given virtual call can make.
No clue when i'll get to it. Probably around the same time we start 
doing other IPA things.