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

Devang Patel dpatel at apple.com
Wed Mar 26 10:19:12 PDT 2008

On Mar 26, 2008, at 10:15 AM, David Chisnall wrote:

> 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.

Great!.  I'll apply this later today (or go ahead if you've commit  

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