[cfe-dev] Objective-C: methods, ivars, and cleanup

David Chisnall csdavec at swansea.ac.uk
Wed Mar 26 10:15:05 PDT 2008

On 26 Mar 2008, at 16:40, Devang Patel wrote:

> On Mar 26, 2008, at 8:09 AM, David Chisnall wrote:
>>> In this method you do a field lookup by iterating over all ObjectTy
>>> ivars. Would not it be more efficient to keep a map just like  
>>> normal C
>>> struct fields ?
>> You'd need to generate the map at some point, possibly the first  
>> time it's called?
> The map is collected for C structure while determining its layout  
> (in ConvertType()).
>> Since it works as-is, I'd rather do this later if profiling  
>> indicates this is a bottleneck.
> A class is defined once but its fields are referenced multiple  
> times, so it makes sense to avoid lookups during field access.  
> That's what we do for C structures. Let's not diverge here.

I have added a map from decls to field numbers which is filled in when  
the LLVM type of the object is generated.  This isn't quite ideal,  
since subclasses have the same ivars at the same locations and this is  
not taken into account, but is simpler (and might be faster) than  
calculating the offset every lookup.

>> +  assert(!verifyFunction(*CurFn));
> nit-pick, add a message here.

That code was copied-and-pasted from the GenerateCode method used for  
generating functions.  For completeness I've added a message in to  
where I originally copied it from as well.


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