From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Segher Boessenkool <segher@kernel.crashing.org>
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: Tue, 13 Apr 2021 18:36:04 +0200 [thread overview]
Message-ID: <063ca819-1276-8deb-0d9b-ea6ec33f9a98@csgroup.eu> (raw)
In-Reply-To: <20210412220821.GN26583@gate.crashing.org>
Le 13/04/2021 à 00:08, Segher Boessenkool a écrit :
> 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.
Yes, I thought about addic, I didn't find an early solution because I forgot the matching 'addc'.
Now with the couple addc/addic it works well.
Thanks
>
> Nice patches!
>
> Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
>
Christophe
WARNING: multiple messages have this Message-ID (diff)
From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 2/2] powerpc/atomics: Use immediate operand when possible
Date: Tue, 13 Apr 2021 18:36:04 +0200 [thread overview]
Message-ID: <063ca819-1276-8deb-0d9b-ea6ec33f9a98@csgroup.eu> (raw)
In-Reply-To: <20210412220821.GN26583@gate.crashing.org>
Le 13/04/2021 à 00:08, Segher Boessenkool a écrit :
> 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.
Yes, I thought about addic, I didn't find an early solution because I forgot the matching 'addc'.
Now with the couple addc/addic it works well.
Thanks
>
> Nice patches!
>
> Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
>
Christophe
next prev parent reply other threads:[~2021-04-13 16:36 UTC|newest]
Thread overview: 26+ 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 ` Christophe Leroy
2021-04-08 15:33 ` [PATCH v1 2/2] powerpc/atomics: " Christophe Leroy
2021-04-08 15:33 ` Christophe Leroy
2021-04-12 22:08 ` Segher Boessenkool
2021-04-12 22:08 ` Segher Boessenkool
2021-04-13 16:36 ` Christophe Leroy [this message]
2021-04-13 16:36 ` Christophe Leroy
2021-04-12 21:54 ` [PATCH v1 1/2] powerpc/bitops: " Segher Boessenkool
2021-04-12 21:54 ` Segher Boessenkool
2021-04-13 16:33 ` Christophe Leroy
2021-04-13 16:33 ` Christophe Leroy
2021-04-13 21:58 ` Segher Boessenkool
2021-04-13 21:58 ` Segher Boessenkool
2021-04-14 2:01 ` Nicholas Piggin
2021-04-14 2:01 ` Nicholas Piggin
2021-04-14 12:24 ` Segher Boessenkool
2021-04-14 12:24 ` Segher Boessenkool
2021-04-14 12:42 ` Christophe Leroy
2021-04-14 12:42 ` Christophe Leroy
2021-04-14 15:19 ` Segher Boessenkool
2021-04-14 15:19 ` Segher Boessenkool
2021-04-14 15:32 ` David Laight
2021-04-14 15:32 ` David Laight
2021-04-14 17:20 ` Segher Boessenkool
2021-04-14 17:20 ` Segher Boessenkool
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