linux-kernel - Re: [RFC][PATCH 02/31] locking,alpha: Implement atomic{,64}_fetch

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Message-ID: <20160423015534.GW3430@twins.programming.kicks-ass.net>
Date:	Sat, 23 Apr 2016 03:55:34 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Richard Henderson <rth@...ddle.net>
Cc:	torvalds@...ux-foundation.org, mingo@...nel.org,
	tglx@...utronix.de, will.deacon@....com,
	paulmck@...ux.vnet.ibm.com, boqun.feng@...il.com,
	waiman.long@....com, fweisbec@...il.com,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	vgupta@...opsys.com, linux@....linux.org.uk, egtvedt@...fundet.no,
	realmz6@...il.com, ysato@...rs.sourceforge.jp, rkuo@...eaurora.org,
	tony.luck@...el.com, geert@...ux-m68k.org, james.hogan@...tec.com,
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	mpe@...erman.id.au, schwidefsky@...ibm.com, dalias@...c.org,
	davem@...emloft.net, cmetcalf@...lanox.com, jcmvbkbc@...il.com,
	arnd@...db.de, dbueso@...e.de, fengguang.wu@...el.com
Subject: Re: [RFC][PATCH 02/31] locking,alpha: Implement
 atomic{,64}_fetch_{add,sub,and,andnot,or,xor}()

On Fri, Apr 22, 2016 at 09:57:04AM -0700, Richard Henderson wrote:
> On 04/22/2016 02:04 AM, Peter Zijlstra wrote:
> > +	"1:	ldl_l %0,%1\n"						\
> > +	"       mov %0,%2\n"						\
> > +	"	" #asm_op " %0,%3,%0\n"					\
> > +	"	stl_c %0,%1\n"						\
> 
> No need for the extra mov.
> 
> 	ldl_l %2,%1
> 	asm_op %2,%3,%0
> 	stl_c %0,%1

Indeed, I got my head stuck in two operand (x86) asm. This is the second
such 'mistake', I'll go have a look at the rest too.

Thanks!