Le 27/08/2019 à 20:26, Segher Boessenkool a écrit :
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.
Thinking about it once more, I'm not sure this form is possible, because wrteei expect 0 or 1. If someone calls wrtee(MSR_EE); (or any constant containing MSR_EE) wrteei 1 is expected. And any constant with MSR_EE cleared should result in wrteei 0.
So
asm("add%I2 %0,%1,%2" : "=r"(dst) : "r"(src1), "ri"(src1));
"ri", not "n" as for wrtee ? Christophe
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
