Feature Request: nontrivial functions and vtable optimizations

[Jb]

"Craig Black" <craigblack2 at cox.net> wrote in message 
news:g82rj4$1hqn$1 at digitalmars.com...
>>
>> The speedup you get from this is the inlining of the function, *not* the 
>> getting rid of the function pointer lookup. It still requires a lookup in 
>> the class info and a conditional branch to check that the "inlined 
>> function" is the correct match for the speculated object.
>>
>> That will still cost a whole pipline of cycles if wrongly predicted.
>
> You may be right in some cases.  Profile to be sure.  But experience has 
> taught me to be wary of function pointer invokations, even on modern 
> CPU's. If you want to believe that there is never a penalty for function 
> pointer invokation go right ahead.  After all, it's only two instructions 
> right? Must be real fast. ;)

I'm not saying there's no penalty, im saying it's a penalty you cant escape 
if you want virtual functions.

Function pointer invocations == conditional branches as far as modern branch 
predictors are concerned. You dont gain anything by replacing the former 
with the later.