Interface vs pure abstract class - speed.

[Maxim Fomin]

On Sunday, 12 May 2013 at 18:21:14 UTC, SundayMorningRunner wrote:
> On Sunday, 12 May 2013 at 18:14:51 UTC, Maxim Fomin wrote:
>> On Sunday, 12 May 2013 at 17:31:22 UTC, SundayMorningRunner 
>> wrote:
>>> Hello, let's say I have the choice between using an abstract 
>>> class or an interface to declare a "plan", a "template" for 
>>> the descendants.
>>> From the dmd compiler point of view, should I use the 
>>> abstract class version (so I guess that for each method call, 
>>> there will be a few MOV, in order to extract the relative 
>>> address from the vmt before a CALL) or the interface version 
>>> (are the CALL directly performed in this case). Are interface 
>>> faster ? (to get the address used by the CALL).
>>>
>>> Thx.
>>
>> I doubt that looking from buggy compiler POV is a good idea. 
>> Anyway you can take code and look into assembly.
> Which is exactly what you could have done before answering ;)

This is exactly what I *have done* before answering to get 
correct answer for me. I see no reasons to ask such questions if 
you can do the test yourself.

interface I
{
    void foo();
}

class A : I { void foo(){}}

abstract class B { void foo() {} }
class C : B {}

void bar(C c, I i)
{
    c.foo();
    i.foo();
}

void main()
{
    A a = new A;
    a.foo();
    C c = new C;
    c.foo();
    bar(c, a);
}
disas _Dmain
Dump of assembler code for function _Dmain:
    0x0000000000419cd8 <+0>:	push   %rbp
    0x0000000000419cd9 <+1>:	mov    %rsp,%rbp
    0x0000000000419cdc <+4>:	sub    $0x10,%rsp
    0x0000000000419ce0 <+8>:	movabs $0x639210,%rdi
    0x0000000000419cea <+18>:	callq  0x41becc <_d_newclass>
    0x0000000000419cef <+23>:	mov    %rax,-0x10(%rbp)
    0x0000000000419cf3 <+27>:	mov    %rax,%rdi
    0x0000000000419cf6 <+30>:	mov    (%rax),%rcx
    0x0000000000419cf9 <+33>:	rex.W callq *0x28(%rcx)
    0x0000000000419cfd <+37>:	movabs $0x639380,%rdi
    0x0000000000419d07 <+47>:	callq  0x41becc <_d_newclass>
    0x0000000000419d0c <+52>:	mov    %rax,-0x8(%rbp)
    0x0000000000419d10 <+56>:	mov    %rax,%rdi
    0x0000000000419d13 <+59>:	mov    (%rax),%rdx
    0x0000000000419d16 <+62>:	rex.W callq *0x28(%rdx)
    0x0000000000419d1a <+66>:	mov    -0x8(%rbp),%rsi
    0x0000000000419d1e <+70>:	cmpq   $0x0,-0x10(%rbp)
    0x0000000000419d23 <+75>:	je     0x419d2f <_Dmain+87>
    0x0000000000419d25 <+77>:	mov    -0x10(%rbp),%rax
    0x0000000000419d29 <+81>:	lea    0x10(%rax),%rdi
    0x0000000000419d2d <+85>:	jmp    0x419d32 <_Dmain+90>
    0x0000000000419d2f <+87>:	xor    %rdi,%rdi
---Type <return> to continue, or q <return> to quit---
    0x0000000000419d32 <+90>:	callq  0x419cb0 
<_D4main3barFC4main1CC4main1IZv>
    0x0000000000419d37 <+95>:	xor    %eax,%eax
    0x0000000000419d39 <+97>:	leaveq
    0x0000000000419d3a <+98>:	retq
End of assembler dump.
disas _D4main3barFC4main1CC4main1IZv
Dump of assembler code for function 
_D4main3barFC4main1CC4main1IZv:
    0x0000000000419cb0 <+0>:	push   %rbp
    0x0000000000419cb1 <+1>:	mov    %rsp,%rbp
    0x0000000000419cb4 <+4>:	sub    $0x10,%rsp
    0x0000000000419cb8 <+8>:	mov    %rdi,-0x10(%rbp)
    0x0000000000419cbc <+12>:	mov    %rsi,%rdi
    0x0000000000419cbf <+15>:	mov    (%rsi),%rax
    0x0000000000419cc2 <+18>:	rex.W callq *0x28(%rax)
    0x0000000000419cc6 <+22>:	mov    -0x10(%rbp),%rdi
    0x0000000000419cca <+26>:	mov    (%rdi),%rcx
    0x0000000000419ccd <+29>:	rex.W callq *0x8(%rcx)
    0x0000000000419cd1 <+33>:	leaveq
    0x0000000000419cd2 <+34>:	retq
End of assembler dump.