Why Strings as Classes?

[superdan]

Jb Wrote:

> 
> "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.

you're right. but direct calls don't speculate. they don't need speculation because they're direct jump. so they are loaded straight into the pipeline.

so walter was right but used the wrong term.