[llvm-commits] llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp

[Nicolas Geoffray]

Chris Lattner wrote:
>
> On Mar 12, 2007, at 7:57 AM, Nicolas Geoffray wrote:
>
>> Hi Chris,
>>
>> Chris Lattner wrote:
>>> Ahhh, ok.  I think I understand now what is going on.  Thank you for
>>> the very clear explanation.
>>>
>>> In this case, it seems like a clearly good thing to just call
>>> CreateFixedObject unconditionally early on (e.g.) when lowering the
>>> arguments.
>>>
>>
>> Unconditionally? I can do that, but do you mean without any check if R31
>> is actually used as frame pointer or we're compiling for linux/ppc?
>
> Sorry, I meant "without a check for r31", it should still only happen 
> on linux/ppc.
>

Actually why would you like to do this when lowering the arguments? It's 
possible that
R31 is never used in the function and calling CreateFixedObject 
unconditionnaly
will make the stack reservation for the function at least of 4 bytes, 
right? even if it doesn't
need to.

Both implementation work, but due to my small knowledge of what's going 
on in llvm :), I would
like to follow your idea, but I don't undestand why it's better during 
arguments lowering than before callee-saved
register scanning.

> Thanks Nicolas!
Thanks to you!

Nicolas
>
> -Chirs