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From: Ian Lance Taylor <iant@google.com>
To: kernel mailz <kernelmailz@googlemail.com>
Cc: gcc-help@gcc.gnu.org, linuxppc-dev@ozlabs.org
Subject: Re: Inline Assembly queries
Date: Mon, 29 Jun 2009 14:29:38 -0700	[thread overview]
Message-ID: <m3ljna20fx.fsf@google.com> (raw)
In-Reply-To: <abe8a1fd0906290849w1ba6bd33of60a9c2e110c10fd@mail.gmail.com> (kernel mailz's message of "Mon\, 29 Jun 2009 21\:19\:57 +0530")

kernel mailz <kernelmailz@googlemail.com> writes:

> I tried a small example
>
> int *p = 0x1000;
> int a = *p;
> asm("sync":::"memory");
> a = *p;
>
> and
>
> volatile int *p = 0x1000;
> int a = *p;
> asm("sync");
> a = *p
>
> Got the same assembly.
> Which is right.
>
> So does it mean, if proper use of volatile is done, there is no need
> of "memory" ?

You have to consider the effects of inlining, which may bring in other
memory loads and stores through non-volatile pointers.

Ian

  parent reply	other threads:[~2009-06-29 21:40 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-06-27 19:46 Inline Assembly queries kernel mailz
     [not found] ` <abe8a1fd0906271249k479e5a87gfe1ee9c02798a234@mail.gmail.com>
     [not found]   ` <m3ab3t4623.fsf@google.com>
2009-06-28  4:57     ` kernel mailz
2009-06-29 15:49       ` kernel mailz
2009-06-29 15:57         ` David Howells
2009-06-29 21:27           ` Ian Lance Taylor
2009-06-30 10:43           ` Benjamin Herrenschmidt
2009-06-29 19:27         ` Scott Wood
2009-06-30  5:27           ` kernel mailz
2009-06-30 10:41             ` Benjamin Herrenschmidt
2009-06-29 21:29         ` Ian Lance Taylor [this message]
2009-06-30  5:53           ` kernel mailz
2009-06-30  9:30             ` Andrew Haley
2009-06-30  9:52             ` Paul Mackerras

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