From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/4] msm: scm: Mark inline asm as volatile
Date: Sun, 27 Feb 2011 11:10:33 +0000 [thread overview]
Message-ID: <1298805034.4626.4.camel@jazzbox> (raw)
In-Reply-To: <8yapqqe3bs3.fsf@huya.qualcomm.com>
On Sat, 2011-02-26 at 18:12 +0000, David Brown wrote:
> On Fri, Feb 25 2011, Will Deacon wrote:
> > These asm blocks all have sensible looking output constraints. Why
> > do they need to be marked volatile?
>
> Without the volatile, the compiler is free to assume the only side
> effects of the asm are to modify the output registers. The volatile is
> needed to indicate to the compiler that the asm has other side effects.
As far as I know, volatile asm does two things:
(1) It stops the compiler from reordering the asm block with respect to
other volatile statements.
(2) It prevents the compiler from optimising the block away when
dataflow analysis indicates it's not required.
If side-effects need to be indicated, won't a memory clobber do the
trick?
Will
next prev parent reply other threads:[~2011-02-27 11:10 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-24 18:44 [PATCH 0/4] SCM fixes and updates Stephen Boyd
2011-02-24 18:44 ` [PATCH 1/4] msm: scm: Mark inline asm as volatile Stephen Boyd
2011-02-25 11:56 ` Will Deacon
2011-02-25 19:05 ` Stephen Boyd
2011-02-26 18:12 ` David Brown
2011-02-26 19:43 ` Nicolas Pitre
2011-02-27 17:41 ` David Brown
2011-02-28 2:21 ` Nicolas Pitre
2011-02-27 11:10 ` Will Deacon [this message]
2011-02-27 17:38 ` David Brown
2011-03-01 10:30 ` Will Deacon
2011-02-24 18:44 ` [PATCH 2/4] msm: scm: Fix improper register assignment Stephen Boyd
2011-02-25 13:23 ` Will Deacon
2011-02-25 19:22 ` Stephen Boyd
2011-02-26 5:09 ` Saravana Kannan
2011-02-26 8:47 ` Russell King - ARM Linux
2011-02-26 17:58 ` David Brown
2011-02-26 20:04 ` Nicolas Pitre
2011-03-01 10:37 ` Will Deacon
2011-03-01 21:29 ` Saravana Kannan
2011-03-02 0:02 ` Nicolas Pitre
2011-03-01 13:54 ` Will Deacon
2011-02-24 18:44 ` [PATCH 3/4] msm: scm: Check for interruption immediately Stephen Boyd
2011-02-24 18:44 ` [PATCH 4/4] msm: scm: Get cacheline size from CTR Stephen Boyd
2011-02-24 19:01 ` Thomas Gleixner
2011-02-24 19:44 ` Stephen Boyd
2011-02-24 19:56 ` Thomas Gleixner
2011-03-01 4:21 ` Stephen Boyd
2011-02-24 19:32 ` Sergei Shtylyov
2011-02-24 19:50 ` Stephen Boyd
2011-02-24 19:55 ` Russell King - ARM Linux
2011-03-09 19:29 ` [PATCH 0/4] SCM fixes and updates Stephen Boyd
2011-03-10 20:06 ` David Brown
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