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To: kernel mailz <kernelmailz@googlemail.com>
Subject: Re: Inline Assembly queries
References: <abe8a1fd0906271246q920124ard61422d9577e2d09@mail.gmail.com>
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	<abe8a1fd0906290849w1ba6bd33of60a9c2e110c10fd@mail.gmail.com>
From: Ian Lance Taylor <iant@google.com>
Date: Mon, 29 Jun 2009 14:29:38 -0700
In-Reply-To: <abe8a1fd0906290849w1ba6bd33of60a9c2e110c10fd@mail.gmail.com>
	(kernel mailz's message of "Mon\, 29 Jun 2009 21\:19\:57 +0530")
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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