[CyberRabbi]

> If you're programming in C++, you probably do care about this level of performance, and in that case, it's nice to program in a style that guarantees it instead of hoping for a sufficiently smart compiler.

Neither implementation guarantees any particular sequence of assembly instructions. Both require hoping that a sufficiently smart compiler will compile it to a sufficiently optimal sequence of instructions.

[munificent]

Yes, in principle a compiler is free to generate arbitrarily horrendous code regardless of what you ask it to do.

In practice, non-virtual function calls are reliably compiled to fairly efficient code while virtual calls are much less reliable.

[CyberRabbi]

> In practice, non-virtual function calls are reliably compiled to fairly efficient code while virtual calls are much less reliable.

Like I said, this echoes the conventional wisdom that most C++ developers seem to retain. The compiler landscape has changed since that wisdom was formed, since the advent of LTO and devirtualization optimizations.