dummyReferToProxy

I see this in SqueakVM souce, interp.c.

sqInt dummyReferToProxy(void) {
        interpreterProxy = interpreterProxy;
}

It looks strange to me. Can someone give me a clue?

Thanks.

Ang Beepeng

2009/7/30 Ang Beepeng <[hidden email]>:
>
> I see this in SqueakVM souce, interp.c.
>
> sqInt dummyReferToProxy(void) {
>        interpreterProxy = interpreterProxy;
> }
>
> It looks strange to me. Can someone give me a clue?
>
it is a dummy function, referring to proxy :)
It is done on purpose, because otherwise Code generator could decide
to not declare the interpreterProxy variable, because it is not used
anywhere.
Of course, it would be better if we could tell this explicitly to
codegen.. but dummy fn does the same..

> Thanks.
>
> Ang Beepeng
> --
> View this message in context: http://www.nabble.com/dummyReferToProxy-tp24733239p24733239.html
> Sent from the Squeak - Dev mailing list archive at Nabble.com.
>
>
>



--
Best regards,
Igor Stasenko AKA sig.

There is also a SLANG optimization step involved. It's exploited by  
the GC code.

The smalltalk code for the GC logic consists of a number of methods,  
mark & sweep for example.
Normally these would be translated into individual C procedure calls,  
but the first optimization the
SLANG translator does is fold small methods that follow certain rules  
into the caller, and deletes the method
in question. There is a method in the image that notes methods it  
should not delete since an outside caller would
use them. So most of the GC logic which is spread over a few methods  
in Smalltalk get nicely folded into a single C procedure.
By doing this C optimizing compiler are more happy about you.

Now the 2nd optimization is that after folding all these smaller  
methods into a particular caller and we find that the
scope of variables that would be global actually are *ONLY* used by  
this method then we make the variables local
versus global in scope.   As a side effect this would make a global  
variable then become a local variable used in a
particular method.  Of course if you are depending on this variable to  
actually be global in scope you now have a problem

To defeat that optimization you need a dummy method that refers to the  
variable so that SLANG then
thinks the global variable is used in two different methods, thus it  
cann't be made into a local.


On 30-Jul-09, at 3:07 AM, Igor Stasenko wrote:

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