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From: "Benoît Thébaudeau" <benoit.thebaudeau@advansee.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] why bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
Date: Sun, 17 Feb 2013 15:04:25 +0100 (CET)	[thread overview]
Message-ID: <658576869.1527675.1361109865699.JavaMail.root@advansee.com> (raw)
In-Reply-To: <1361095150115-147472.post@n7.nabble.com>

Hi,

On Sunday, February 17, 2013 10:59:10 AM, janpharm wrote:
> Hi All,
> 
> After searching via google,I still can not find the hint for
> 
> I understand the function of bic command,

http://infocenter.arm.com/help/topic/com.arm.doc.qrc0001l/QRC0001_UAL.pdf

Simple bit clear with bit-mask.

> but did not understand :
> 
> why "bic sp, sp, #7" can be implied for "8-byte alignment for ABI
> compliance" ?

http://infocenter.arm.com/help/topic/com.arm.doc.qrc0001l/QRC0001_UAL.pdf

5.2.1.2.

SP has to be double-word (64-bit, 8-byte) aligned, so since this is an
expand-down stack, its lower 3 bits have to be cleared in order to make
it a multiple of 8.

> can someone offer some example?

http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=blob;f=arch/arm/lib/crt0.S;h=4f60958b1dbf1782863cebd7ffe884733a452b26;hb=HEAD#l110

Best regards,
Beno?t

      parent reply	other threads:[~2013-02-17 14:04 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-02-17  9:59 [U-Boot] why bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ janpharm
2013-02-17 11:30 ` [U-Boot] u-boot recovery mode TigerLiu at viatech.com.cn
2013-02-17 14:34   ` Albert ARIBAUD
2013-02-18  1:44     ` TigerLiu at viatech.com.cn
2013-02-18  7:42       ` Albert ARIBAUD
2013-02-17 14:04 ` Benoît Thébaudeau [this message]

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