>  > The TLS register, on the other hand must be fixed (since the value is 
>  > persistent across the whole thread).  If you pick r8 then you will 
>  > fragment the register ranges, particularly when not inside a shared 
>  > library.  There are different reasons why r9 or r10 might be the best 
>  > choice, but r8 certainly would be a bad choice.
> 
> Ah, okay.  Chris Gilbert suggested r11 to me after I posted my message.

*If* I had complete freedom to implement the ABI from scratch, then r11 
would probably be my choice too.  However, there is too much legacy use of 
r11 as a frame pointer to even consider that one now.

Note that the new ABI won't require a frame pointer, and I intend turning 
it's use in the compiler off, just as soon as we can make other tools 
(such as gdb) manage without it.

R.