From: Valentine <vbarshak@ru•mvista.com>
To: HongWoo Lee <hongwoo7@gmail•com>
Cc: linuxppc-dev@lists•ozlabs.org
Subject: Re: Simple question about powerpc asm.
Date: Sat, 18 Jul 2009 14:31:41 +0400 [thread overview]
Message-ID: <4A61A48D.8060601@ru.mvista.com> (raw)
In-Reply-To: <4A6194D8.9090602@gmail.com>
HongWoo Lee wrote:
> Hi all,
>
> I was reading kernel level source and found this macro.
>
> #define SET_REG_TO_LABEL(reg, label) \
> lis reg,(label)@highest; \
> ori reg,reg,(label)@higher; \
> rldicr reg,reg,32,31; \
> oris reg,reg,(label)@h; \
> ori reg,reg,(label)@l;
>
> But, I couldn't find any clue related with @highest, @higher, @h, @l.
>
> If anybody know about this directives(?), please explain it.
> Or just let me know the keyword, so I can search with those keyword.
>
PowerPC instructions are 32-bit long. So, there are only 16 bits
available within the instruction for constant values. Since address can
be up to 64 bits, we have to load it a piece at a time. The "@" within
the assembler instruct it to give a specially-processed form of a symbol
value:
@highest -- refers to bits 48-63 of a constant
@higher -- refers to bits 32-47 of a constant
@h -- refers to bits 16-31 of a constant
@l -- refers to bits 0-15 of a constant
> Thanks in advance.
>
> HongWoo.
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists•ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
next prev parent reply other threads:[~2009-07-18 10:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-18 9:24 Simple question about powerpc asm HongWoo Lee
2009-07-18 10:31 ` Valentine [this message]
2009-07-18 12:54 ` Wolfgang Denk
2009-07-18 13:55 ` Valentine
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