Why Strings as Classes?

[Jb]

"Walter Bright" <newshound1 at digitalmars.com> wrote in message 
news:g90iia$2jc4$3 at digitalmars.com...
> Yigal Chripun wrote:
>> a) people here said that a virtual call will make it slow. How much
>> slow? how much of an overhead is it on modern hardware considering also
>> that this is a place where hardware manufacturers spend time on
>> optimizations?
>
> Virtual function calls have been a problem for hardware optimization. 
> Direct function calls can be speculatively executed, but not virtual ones, 
> because the hardware cannot predict where it will go. This means virtual 
> calls can be much slower than direct function calls.

Modern x86 branch prediction treats indirect calls the same as conditional 
branches. They get a slot in the branch target buffer, so they do get 
speculatively executed. And if correctly predicted it's only a couple of 
cycles more costly direct calls.

See the thread "Feature Request: nontrivial functions and vtable 
optimizations" about 2 weeks ago.

I cited the technical docs and a few doubters ran benchmarks, which proved 
that virtual methods are not as evil as many people think. In fact they are 
no more evil than a conditional branch.