[Vm-dev] Primitive 60 vs methods with more than one argument

[David T. Lewis]

I think you are suggesting to use the argumentCount to determine the
actual receiver and the first parameter, rather than assume that there
is exactly one argument so that the top two stack values are used. Is
that right?

The only cost that I can see associated with this would be related to 
finding the receiver and the first parameter based on argumentCount.
It might be a negligible difference, so it would be worth trying it to
find out.

Dave


On Sat, Oct 19, 2013 at 10:53:40PM +0200, Levente Uzonyi wrote:
> 
> Hi,
> 
> the code of primitive 60 seems to be assuming that the method has exactly 
> one argument, ignoring the actual number of arguments. This seems to be an 
> unnecessary restriction, which makes it cumbersome/impossible to use it in 
> methods which have more arguments, like #at:ifAbsent:.
> 
> Since the primitive uses two objects from the top of the stack, it's 
> possible to write a hackish method to see the potential benefits:
> 
> ifAbsent: aBlock receiver: receiver at: index
> 
> 	<primitive: 60>
> 	^aBlock value
> 
> The primitive will treat the variable receiver as the receiver, and index 
> as the index. The real receiver is not used at all.
> 
> This method performs 37% better than #at:ifAbsent for the case where 
> the index is valid.
> 
> Does it have any benefits not taking the actual number of arguments into 
> account in this primitive?
> 
> Cheers,
> Levente