From: Segher Boessenkool <segher@kernel.crashing.org>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 2/2] powerpc/atomics: Use immediate operand when possible
Date: Mon, 12 Apr 2021 17:08:22 -0500 [thread overview]
Message-ID: <20210412220821.GN26583@gate.crashing.org> (raw)
In-Reply-To: <9f50b5fadeb090553e5c2fae025052d04d52f3c7.1617896018.git.christophe.leroy@csgroup.eu>
Hi!
On Thu, Apr 08, 2021 at 03:33:45PM +0000, Christophe Leroy wrote:
> +#define ATOMIC_OP(op, asm_op, dot, sign) \
> static __inline__ void atomic_##op(int a, atomic_t *v) \
> { \
> int t; \
> \
> __asm__ __volatile__( \
> "1: lwarx %0,0,%3 # atomic_" #op "\n" \
> - #asm_op " %0,%2,%0\n" \
> + #asm_op "%I2" dot " %0,%0,%2\n" \
> " stwcx. %0,0,%3 \n" \
> " bne- 1b\n" \
> - : "=&r" (t), "+m" (v->counter) \
> - : "r" (a), "r" (&v->counter) \
> + : "=&b" (t), "+m" (v->counter) \
> + : "r"#sign (a), "r" (&v->counter) \
> : "cc"); \
> } \
You need "b" (instead of "r") only for "addi". You can use "addic"
instead, which clobbers XER[CA], but *all* inline asm does, so that is
not a downside here (it is also not slower on any CPU that matters).
> @@ -238,14 +238,14 @@ static __inline__ int atomic_fetch_add_unless(atomic_t *v, int a, int u)
> "1: lwarx %0,0,%1 # atomic_fetch_add_unless\n\
> cmpw 0,%0,%3 \n\
> beq 2f \n\
> - add %0,%2,%0 \n"
> + add%I2 %0,%0,%2 \n"
> " stwcx. %0,0,%1 \n\
> bne- 1b \n"
> PPC_ATOMIC_EXIT_BARRIER
> -" subf %0,%2,%0 \n\
> +" sub%I2 %0,%0,%2 \n\
> 2:"
> - : "=&r" (t)
> - : "r" (&v->counter), "r" (a), "r" (u)
> + : "=&b" (t)
> + : "r" (&v->counter), "rI" (a), "r" (u)
> : "cc", "memory");
Same here.
Nice patches!
Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
Segher
next prev parent reply other threads:[~2021-04-12 22:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-08 15:33 [PATCH v1 1/2] powerpc/bitops: Use immediate operand when possible Christophe Leroy
2021-04-08 15:33 ` [PATCH v1 2/2] powerpc/atomics: " Christophe Leroy
2021-04-12 22:08 ` Segher Boessenkool [this message]
2021-04-13 16:36 ` Christophe Leroy
2021-04-12 21:54 ` [PATCH v1 1/2] powerpc/bitops: " Segher Boessenkool
2021-04-13 16:33 ` Christophe Leroy
2021-04-13 21:58 ` Segher Boessenkool
2021-04-14 2:01 ` Nicholas Piggin
2021-04-14 12:24 ` Segher Boessenkool
2021-04-14 12:42 ` Christophe Leroy
2021-04-14 15:19 ` Segher Boessenkool
2021-04-14 15:32 ` David Laight
2021-04-14 17:20 ` Segher Boessenkool
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