Re: [PATCH 2/2] powerpc: cleanup hw_irq.h

From: Christophe Leroy
Date: Tue Aug 27 2019 - 14:33:49 EST

Le 27/08/2019 Ã 20:26, Segher Boessenkool a ÃcritÂ:
On Tue, Aug 27, 2019 at 07:36:35PM +0200, Christophe Leroy wrote:
Le 27/08/2019 Ã 19:29, Segher Boessenkool a ÃcritÂ:
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) :

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.

asm("add%I2 %0,%1,%2" : "=r"(dst) : "r"(src1), "ri"(src1));

"ri", not "n" as for wrtee ?


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?