linux-kernel - Re: [OpenRISC] [PATCH v3 09/25] openrisc: add optimized atomic operations

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Message-ID: <c775b4d1-fa98-c1b2-d212-1441343b62d4@twiddle.net>
Date:   Thu, 23 Feb 2017 04:31:34 +1100
From:   Richard Henderson <rth@...ddle.net>
To:     Stafford Horne <shorne@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Jonas Bonn <jonas@...thpole.se>, openrisc@...ts.librecores.org,
        linux-kernel@...r.kernel.org, linux@...ck-us.net
Subject: Re: [OpenRISC] [PATCH v3 09/25] openrisc: add optimized atomic
 operations

On 02/23/2017 01:22 AM, Stafford Horne wrote:
>> static inline int __atomic_add_unless(atomic_t *v, int a, int u)
>> {
>> 	int old, tmp;
>>
>> 	__asm__ __volatile__(
>> 		"1:     l.lwa %0, 0(%2)         \n"
>> 		"       l.sfeq %0, %4           \n"
>> 		"       l.bf 2f                 \n"
>> 		"        l.nop                  \n"
>> 		"	l.add %1, %0, %3	\n"

You can move this add into the delay slot and drop the preceding nop.


r~