linux-kernel - Re: [PATCH v2] compiler: prevent dead store elimination

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Message-ID: <20100302122421.GB19208@basil.fritz.box>
Date:	Tue, 2 Mar 2010 13:24:22 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Roel Kluin <roel.kluin@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	"David S. Miller" <davem@...emloft.net>,
	Mikael Pettersson <mikpe@...uu.se>, penberg@...helsinki.fi,
	Brian Gerst <brgerst@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-crypto@...r.kernel.org, Herbert@...dor.apana.org.au
Subject: Re: [PATCH v2] compiler: prevent dead store elimination

> 
> >> +#define ARRAY_PREVENT_DSE(p, n)
> > 
> > Who says the Intel compiler doesn't need this?
> 
> There was a comment in include/linux/compiler-intel.h that it's not supported.

That's true for the ia64 version, but not for the x86 version which supports
gcc compatible inline assembler. So on x86 you can use it. On Itanium
it probably would need some other compiler built in.

Also in any case some form of memory clobber is needed because it'll surely
do dead-store-optimization.

-Andi

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