Yes, but if used as their own statement and not used as some bigger expression (parameter to function, etc.), any decent compiler will compile them the same way.

Yes, and thus a perfect example premature optimization; semantics should define default usage, not some possible micro optimization. This is exactly the kind of case Knuth is talking about, going around doing ++x because you think it's faster when the standard idiom is x++ is premature optimization.

x++ is not the "standard idiom".

In my experience x++ is far more common than ++x when it doesn't matter which you use, "for" statements for example.

Yes, it is.

I meant no more than ++x.

I know what you meant, I don't agree. Scour any large codebase, x++ is far more idiomatic than ++x.

What about top C++ books? Also when it comes to advancing iterators...

Well, there is no reason for any standard idiom there.

Those `++` and `--` operators are something to avoid anyway.

Notice how the asm changes here if changing it++ to ++it: https://godbolt.org/g/W5w7Dc

Looks like only thing that changes is label name which doesn't matter.

nope, there are less instructions

Except that those instructions are not actually called in either case from function foo(). So they're dead code and linker will remove them.