[cfe-dev] Objective-C tidy up

Chris Lattner clattner at apple.com
Tue Jun 3 09:49:16 PDT 2008

On Jun 3, 2008, at 4:39 AM, David Chisnall wrote:

> On 3 Jun 2008, at 07:33, Chris Lattner wrote:
>> On Jun 1, 2008, at 10:07 AM, David Chisnall wrote:
>>> Hi,
>>> Here's the next installment of my ObjC changes.  This is fairly  
>>> minor, although the diff is quite large.  The biggest change is  
>>> that I've moved common code used to generate Objective-C methods  
>>> and C functions out into a separate method in CodeGenFunction and  
>>> I've moved GenerateObjCMethod from CodeGenFunction.cpp into  
>>> CGObjC.cpp where it should probably have been from the start.
>>> This diff also includes small changes to Sema to make self and  
>>> _cmd implicit parameters.  At some point, I imagine these will be  
>>> pulled out into a superclass for method decls that can be used for  
>>> both Objective-C and C++ methods.
>> Why should self and _cmd be ParmVarDecls?  Shouldn't they be  
>> PredefinedExprs?
> That's what I did to start with, but PredefinedExprs need special  
> handling in codegen, while ParmVarDecls are automatically turned  
> into loads of %var.addr.  Since they are parameters, and since it  
> simplifies the rest of the implementation, it seemed like a  
> ParmVarDecl would be the right thing to choose.

ParmVarDecl is an artifact of common implementations, not the way the  
language works.  They are not parameters, as they obviously don't have  
location info etc.

>> +++ include/clang/AST/DeclObjC.h	(working copy)
>> @@ -91,7 +91,8 @@
>>  // The following are only used for method definitions, null  
>> otherwise.
>>  // FIXME: space savings opportunity, consider a sub-class.
>>  Stmt *Body;
>> -  ParmVarDecl *SelfDecl;
>> +  // Decls for implicit parameters
>> +  llvm::SmallVector<ParmVarDecl *, 2> ImplicitParamInfo;
>> If there are always exactly two of these, just use:
>> ParmVarDecl *ImplicitParamInfo[2];
> There will be three for the √Čtoil√© runtime.  Someone expressed  
> interest in porting Objective-C to the COLA runtime from the  
> Viewpoints Research Institute as well, and this would have somewhere  
> between one and four depending on how they did it.

Please use a fixed size array.  That is cheaper than a smallvector<4>.


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