[LLVMdev] Linux/ppc backend

[Nicolas Geoffray]

Hi Chris,

>> It is marked callee saved. Because when it is not needed as frame 
>> pointer it is used like an ordinary register. But when it is used as 
>> frame pointer, the prologue and epilogue change its value, but the 
>> algorithm in llvm that finds clobbered register does not select it.
>>     
>
> Okay, I'm not sure.  If you describe the constraints better, perhaps Jim 
> or Evan will have an idea :)
>   
Well i believe the algorithm that finds clobbered registers does not 
look at the epilogue
and prologue, and therefore does not select R31.
Maybe all I need to do is to explicitly add R31 as a clobbered register 
when it is used
as a frame pointer. But I need some help to do that.

Thx,
Nicolas