linux-kernel - Question about missing "cld" in x86 string assembly code

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Message-Id: <201112172258.24221.nai.xia@gmail.com>
Date:	Sat, 17 Dec 2011 22:58:24 +0800
From:	Nai Xia <nai.xia@...il.com>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Linux-MM" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Question about missing "cld" in x86 string assembly code

Hi Andi, 

Seems I used a stale email address of you from a related git commit log,
so this is a resend, sorry.

=======
Hi, 

I notice that all x86 assembly code for string operations containing
"scasb, lodsb", etc does not have "cld" at the beginning.
Is this 100% safe? 
Or in other words, how could we be sure that
there is no "std" generated by compiler somewhere just before
the string operations? 

Thanks,

Nai
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