linux-kernel - Re: PATCH] Use -mpreferred-stack-boundary=3 on x86-64 if supported

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Message-ID: <24bd04a1-1702-4d57-af64-af2381992789@email.android.com>
Date:	Sat, 23 Jun 2012 09:17:06 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>, "H.J. Lu" <hjl.tools@...il.com>
CC:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: PATCH] Use -mpreferred-stack-boundary=3 on x86-64 if supported

To keep gcc from paddong the stack to maintain a nonexistent alignment.

Andi Kleen <andi@...stfloor.org> wrote:

>> This patch uses -mpreferred-stack-boundary=3 on x86-64 if it is
>supported.
>> I have been running 3.4 kernel compiled with this option for weeks.
>
>But why? 
>
>All the SSE code in the kernel should adjust manually. And the other
>code doesn't need it.
>
>Besides the entry points do not guarantee alignment.
>
>For the kernel it would be probably more useful to have a attribute
>per function that forces alignment.
>
>-Andi
>-- 
>ak@...ux.intel.com -- Speaking for myself only.

-- 
Sent from my mobile phone. Please excuse brevity and lack of formatting.
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