[LLVMdev] Using LLVM to compile Objective-C on an Xbox 360

Thu May 27 10:15:27 PDT 2010

Please create a thread on DevNet to discuss this further.

Alex

On May 27, 2010, at 9:26 AM, Kevin Wooten wrote:

> By linux derivative I meant that it borrows the linux GCC ABI... and  
> it does.  You can compile with an off the shelf GCC cross compiler  
> and link the resultant object files ones compiled with the PS3  
> provided version.   We have done it.
>
> Also, as both an XBox 360 and PS3 developer, there seems to me to be  
> nothing in the TCRs/TRCs that preclude us from using a different  
> compiler.  There are rules about symbol inclusion and other  
> resultant binary requirements... but as of yet I have not found  
> specific ones stopping us from using a compiler that works.  In  
> either case the LLVM rewriter solves any other these issues as we  
> would be just be compiling C.
>
> On May 27, 2010, at 8:09 AM, Alex Rosenberg wrote:
>
>> PS3 is not "a Linux derivative." The compilers supplied by SCE for  
>> PS3 game development are highly customized and support a customized  
>> ABI that will take some time to adjust LLVM and Clang to support.
>>
>> You'd likely also run afoul of a TRC or two, similar to the  
>> problems you'll face with Microsoft TCRs mentioned earlier.
>>
>> Alex
>>
>> On May 27, 2010, at 12:15 AM, Kevin Wooten wrote:
>>
>>> Implementing the backend (or editing the current PPC backend as  
>>> needed) is a definite option.  This seems to be the real  
>>> question... which is easier... maintaining the PPC backend or  
>>> maintaining the rewriter.  Currently (in admittedly trivial tests)  
>>> I have gotten the rewriter to work and output C code.  There are  
>>> some outstanding issues to do with linking and accessing the  
>>> reflection information objective-c provides (and the rewriter  
>>> properly outputs) but I am sure the person/people who wrote the  
>>> rewriter can answer those fairly simply (or else the rewriter  
>>> would be fairly useless).
>>>
>>> As far as the runtime goes there is an implementation for windows,  
>>> linux and most likely the PS3 (since it is already a linux  
>>> derivative using GCC as mentioned).  If we have to create a  
>>> runtime for PS3 and XBox that seems trivial as the functions are  
>>> very basic in nature.
>>>
>>> My comments on OpenStep were more meant to point to the fact that  
>>> we would write our own library; really just throwing all notion of  
>>> OpenStep away.  Instead of NSObject we would create our own base  
>>> DObject or something along with a DString, DAarry, DSet, DMap,  
>>> etc.  Truthfully this would be our plan anyway because we want to  
>>> follow the lead of OSX and provide these objects "toll free  
>>> bridged"... meaning we would implement them using a std c++  
>>> library object (e.g. std::basic_string or std::vector) as the  
>>> first member of the object which will allow us to cast a DString  
>>> to std::string or DArray to std::vector without any manual or  
>>> automatic marshaling. As mentioned this is how OSX implements its  
>>> NS classes, by using the equivalent CF version which again allows  
>>> casting between the objects.
>>>
>>> On May 26, 2010, at 6:19 PM, Dale Johannesen wrote:
>>>
>>>> llvm can output C code, but that target has bitrotted severely  
>>>> over the last few months and nobody seems to be interested in  
>>>> fixing it.  You may need to do some work there.  Alternatively  
>>>> you could implement the PPC ABI that you need.  There are several  
>>>> examples of supporting multiple ABIs on the same hardware, x86  
>>>> being the most obvious.  A lot of simple stuff will probably Just  
>>>> Work with the existing PPC ABI, more complicated stuff may not.   
>>>> (Only 32-bit PPC is really maintained, though, there are probably  
>>>> lots of problems with 64-bit.)
>>>>
>>>> Objective C in llvm, AFAIK, is only used on the MacOSX targets  
>>>> and only tested there.   There are sufficient secret handshakes  
>>>> between the compiler and the ObjC runtime that it is unlikely to  
>>>> Just Work in an untested environment.  OpenStep has a familial  
>>>> relationship to MacOSX ObjC runtime, but they aren't the same and  
>>>> are unlikely to still be binary compatible at this point.  You  
>>>> may need to do some work there also.
>>>>
>>>> Summary, you can probably get this approach to work, but it's not  
>>>> as easy as you're hoping.
>>>>
>>>> On May 26, 2010, at 5:20 PMPDT, kdubb wrote:
>>>>
>>>>> We are looking at using Objective-C/C++ in a new game engine.   
>>>>> Objective C's duality of being both very dynamic and very "C"  
>>>>> gives us exactly what we need to make the SDK and engineering of  
>>>>> games simpler.
>>>>>
>>>>> This means that we will need a way to compile it on all  
>>>>> platforms our games will target.  Currently the major platforms  
>>>>> we are concerned with include... PC, Mac, XBox 360, PS3,  
>>>>> iPhone.  Now the PC, Mac, iPhone and PS3 are fairly simple.  If  
>>>>> we build our own OpenStep libraries we can simply use LLVM to  
>>>>> compile directly to these platforms; the PS3 although  
>>>>> proprietary uses GCC as a C/C++ compiler so I am assuming  
>>>>> Objective-C can be used fairly simply.  This leaves us with the  
>>>>> XBox 360.
>>>>>
>>>>> The 360 is a special chip (PowerPC based) with, as far as I have  
>>>>> researched, a special ABI (Windows derivative).  I haven't the  
>>>>> faintest clue of whether code from the LLVM PPC backend would  
>>>>> even work on the 360, much less interoperate with the system  
>>>>> libraries. So my formulated solution has become this: use an  
>>>>> LLVM backend to output C code and then compile that code with  
>>>>> using MS's XBox 360 compiler. I believe I have read that LLVM  
>>>>> has a C backend already but I don't know how to select it.
>>>>>
>>>>> If I can get a proof of concept showing Objective-C code running  
>>>>> on the 360 we are off to the races.  Any help is appreciated  
>>>>> just not sure if all the pieces/parts exist and/or what I am  
>>>>> missing.  So... is this feasible?  If so... how do I get LLVM to  
>>>>> output C code?
>>>>>
>>>>> Thanks,
>>>>> Kevin
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>>>>
>>>
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