From: Segher Boessenkool > Sent: 09 February 2021 13:51 > > On Tue, Feb 09, 2021 at 12:36:20PM +1000, Nicholas Piggin wrote: > > What if you did this? > > > +static inline struct task_struct *get_current(void) > > +{ > > + register struct task_struct *task asm ("r2"); > > + > > + return task; > > +} > > Local register asm variables are *only* guaranteed to live in that > register as operands to an asm. See > > https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html#Local-Register-Variables > ("The only supported use" etc.) > > You can do something like > > static inline struct task_struct *get_current(void) > { > register struct task_struct *task asm ("r2"); > > asm("" : "+r"(task)); > > return task; > } > > which makes sure that "task" actually is in r2 at the point of that asm.
If "r2" always contains current (and is never assigned by the compiler) why not use a global register variable for it? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)