From: "Vladimir A. Gurevich" <vag@paulidav.org>
To: jbeisert@eurodsn.de
Cc: linuxppc-embedded@lists.linuxppc.org
Subject: Re: ppc405gp and GCC register usage
Date: Tue, 15 Jul 2003 03:42:23 -0700 [thread overview]
Message-ID: <3F13DA8F.4060403@paulidav.org> (raw)
In-Reply-To: <200307151224.04020.jbeisert@eurodsn.de>
Hi Juergen,
There is a standard, called ABI (Application Binary Interface) that
defines this.
ABIs are, obviuosly, CPU-specific. Compilers tend to respect ABI that
is defined for the CPU they generate code for.
The best documents specifying PPC ABI can be found on IBM's website:
PowerPC Compiler Writer's Guide
http://www-3.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF7785256996007558C6/$file/cwg.pdf
Developing PowerPC Embedded Application Binary Interface (EABI)
Compliant Programs
http://www-3.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF77852569970071B0D6/$file/eabi_app.pdf
They not only describe register usage, but stack layout, parameter
passing and many
other things. There are a couple of slightly different ABI's for
PowerPC, that differ
with regards to R2 and R13 usage to access the so-called small data
sections.
Also, depending on what you are doing you have 2 options:
-- do the whole function in assembly. You are free to do whatever (as
long as you
obey the ABI), but you've got to watch register allocation
yourself (among other
thing)
-- Use __asm__ in your C code. Then the compiler will do most of the
register
allocation for you and will help you with ABI issues as well.
Happy Hacking,
Vladimir
Juergen Beisert wrote:
>Hello all,
>
>does someone know, which register I can use in my own assembler routines
>without disturbing code generated by gcc (in kernel space)? I did not found
>any spec which registers gcc use, yet. Is such a document available?
>
>-- JB
>
>
>
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2003-07-15 10:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-15 10:24 ppc405gp and GCC register usage Juergen Beisert
2003-07-15 10:40 ` Wolfgang Denk
2003-07-15 10:42 ` Vladimir A. Gurevich [this message]
2003-07-15 11:31 ` Juergen Beisert
2003-07-15 10:51 ` Paul Mackerras
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