Benchmark of D against other languages

[lobo via Digitalmars-d]

On Thursday, 2 April 2015 at 09:06:52 UTC, Manu wrote:
> On 2 April 2015 at 08:15, Martin Nowak via Digitalmars-d
> <digitalmars-d at puremagic.com> wrote:
>> On 04/01/2015 10:31 PM, novice2 wrote:
>>> Can DMD compiler do it itself, as one of optimizations?
>>
>> You could do it as part of LTO or whole program optimization.
>> It requires another compiler/linker phase, so it's not easy to 
>> achieve,
>> maybe the LDC/GDC people have LTO running?
>>
>> GCC5 comes with a big announcement about devirtualization.
>> https://www.gnu.org/software/gcc/gcc-5/changes.html#general
>
> It is impossible to do a good job. There are 2 conditions that 
> break
> most opportunities that the compiler may have to improve this:
> 1) The class is a pointer (duh, in D, all classes are pointers, 
> so
> that condition is implicit).
> 2) That DLL's exist.
>
> If a DLL may exist, and a class is a pointer (it is), sourced 
> from an
> 'impure' location, then it is impossible for the compiler to 
> generally
> do anything at all about final.
> It may theoretically be able to do something in the case where 
> the
> class is proofably contained within a 'scope' confined 
> space/function,
> but that particular case is almost mutually exclusive with 
> cases where
> polymorphism is actually useful in the first place, so it's not 
> really
> practical. I also imagine the complexity in the compiler would 
> be off
> the charts.
>
> Basically, if it is _possible_ for a class pointer to come in 
> contact
> with dynamically loaded code, the compiler must conservatively 
> abandon
> any attempt to optimise.
>
> virtual by default is completely wrong for D.
>
> And don't say 'speculative' devirtualisation. What an 
> abomination!
> Just fix the problem; don't have every function be virtual in 
> the
> first place!

+1

Even an escape would be useful so one can do this:

final class Hack {
     virtual void func() {}
}

It would then be trivial to stick a final in front of the class.

It would also be required to declare final when instantiating the 
class, to work with third-party libraries that don't use final, 
i.e.

auto klass = new final Class();


I'm not a language developer and I don't know D that well yet so 
I'll stop there before I embarrass myself too much! :D

bye,
lobo