On Fri, Nov 28, 2014 at 12:58:55PM +1100, Benjamin Herrenschmidt wrote:

quoted

Have you tested this with (upcoming) GCC 5.0?  GCC now uses CR5,
and it likes to use it very much, it might be more convenient to
use e.g. CR1 (which is allocated almost last, only before CR0).

We use CR1 all over the place in your asm code. Any other suggestion ?

What's the damage of -ffixed-cr5 on gcc5 ? won't it just use CR4 or 6
instead ?

Oh, it will work fine.  Not using CR5 would be more convenient so that
the register allocation for most code would not change when you use or
not use -ffixed-cr5, making code easier to read.  But your point about
asm code already using the other CR fields makes CR5 a better choice
actually, because people avoided it (because the compiler did) :-)


Segher