[llvm-commits] [PATCH] SVR4 ABI support for the PowerPC backend

[Dale Johannesen]

On Jul 2, 2009, at 12:12 AMPDT, Tilmann Scheller wrote:

> Hi Dale,
>
> On Wed, Jul 1, 2009 at 11:26 PM, Dale Johannesen<dalej at apple.com>  
> wrote:
>> OK, I've looked these over.  They do not break any of the  
>> compatibility
>> tests on Darwin, and I'm pretty sure none of the code changes will  
>> break
>> Darwin.  I haven't looked over the SVR4-specific bits too  
>> carefully, but
>> didn't see anything obviously wrong.  PPCCallingConv.td and
>> PPCRegisterInfo.td say they have no newline at EOF, please fix those.
> Ok
>
>> One thing I'm concerned about is that you're replacing the existing  
>> "ELF"
>> ABI with the "SVR4" ABI.  They seem to be different in a few areas,  
>> like
>> callee-saved register usage.  Are you sure it is OK to destroy the  
>> older
>> one?  It looks to me like somebody familiar with a spec had set up  
>> the
>> register usage to be correct for their "ELF" target.  Nicolas  
>> Geoffray seems
>> to have done most of what I'm talking about, so I think he should  
>> comment.
>>  I think these might need to coexist as subdivisions of "elf", as  
>> on x86-32.
> Actually the old ELF ABI already was the SVR4 ABI, as mentioned by
> Nicolas in http://lists.cs.uiuc.edu/pipermail/llvmdev/2007-February/007911.html
>
> All differences are due to missing or incorrect things in the original
> implementation.

OK.  Register usage seemed like a surprising thing to get wrong, but  
if Nicolas is happy so am I.

> As ELF is not really an ABI but an object file format and there are
> other ELF-based ABIs for PowerPC, like the EABI or the AIX ABI for
> linux/ppc64, I did the rename from ELF to SVR4 to make this clear.

Right, I agree that's a good idea.  I suspect other ABIs that use ELF  
will have some things in common with this one, and an ELF abstraction  
might be useful, but we can leave that for whoever does such a port.

> Just to be sure, did you take a look at the llvm-gcc patch as well?

Yes I did.
Do you have commit access?

> Thanks for the fast review!
>
> Greetings,
>
> Tilmann
>
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