It can in fact make predictions in a number of circumstances. The most common case is FDO (https://gcc.gnu.org/wiki/AutoFDO https://gcc.gnu.org/wiki/AutoFDO) -

It can in fact make predictions in a number of circumstances. The most common case is FDO (https://gcc.gnu.org/wiki/AutoFDO https://gcc.gnu.org/wiki/AutoFDO) - with FDO coverage GCC can easily demonstrate a particular vcall is ~always a particular type and emit exactly the code you describe. (To be clear, this isn't just in theory, but is actually happening in a wide variety of binaries I use.) This is perhaps not fully "ahead of time", granted, but it's extremely easy to deploy and highly effective, and entirely accessible to C++.