On Tue, Aug 27, 2019 at 07:36:35PM +0200, Christophe Leroy wrote:
> Le 27/08/2019 à 19:29, Segher Boessenkool a écrit :
> >On Tue, Aug 27, 2019 at 10:48:24PM +1000, Nicholas Piggin wrote:
> >>Christophe Leroy's on August 27, 2019 6:13 pm:
> >>>+#define wrtee(val) asm volatile("wrtee %0" : : "r" (val) :
> >>>"memory")
> >>>+#define wrteei(val) asm volatile("wrteei %0" : : "i" (val) :
> >>>"memory")
> >>
> >>Can you implement just one macro that uses __builtin_constant_p to
> >>select between the imm and reg versions? I forgot if there's some
> >>corner cases that prevent that working with inline asm i constraints.
> >
> >static inline void wrtee(long val)
> >{
> > asm volatile("wrtee%I0 %0" : : "n"(val) : "memory");
> >}
>
> Great, didn't know that possibility.
>
> Can it be used with any insn, for instance with add/addi ?
> Or with mr/li ?
Any instruction, yes. %I<n> simply outputs an "i" if operand n is a
constant integer, and nothing otherwise.
So
asm("add%I2 %0,%1,%2" : "=r"(dst) : "r"(src1), "ri"(src1));
works well. I don't see how you would use it for li/mr... You can do
asm("add%I1 %0,0,%1" : "=r"(dst) : "ri"(src));
I suppose, but that is not really an mr.
> >(This output modifier goes back to the dark ages, some 2.4 or something).
>
> Hope Clang support it ...
I don't know, sorry. But it is used all over the place, see sfp-machine.h
for example, so maybe?
Segher
