From: Ralf Baechle <ralf@linux-mips.org>
To: ?$B9uDE ?$B4pLo <mips4700@yahoo.co.jp>
Cc: linux-mips@linux-mips.org
Subject: Re: mips inline asm question
Date: Tue, 23 Sep 2003 23:22:09 -0700 [thread overview]
Message-ID: <20030924062209.GA24923@linux-mips.org> (raw)
In-Reply-To: <20030924060456.11903.qmail@web2307.mail.yahoo.co.jp>
On Wed, Sep 24, 2003 at 03:04:56PM +0900, ?$B9uDE ?$B4pLo wrote:
> The following code is from
> linux-2.4.20/include/asm-mips/mipsregs.h.
> Could anyone tell how the difference between %z0 ("Jr")
> and %0 ("r") is?
> I compiled this code and deassemble the object, but I
> can't find any
> difference with my toolchains(gcc-2.95.3, binutils-2.11).
>
> static inline void set_context(unsigned long val)
> {
> __asm__ __volatile__(
> ".set push\n\t"
> ".set reorder\n\t"
> "mtc0 %z0, $4\n\t"
> ".set pop"
> : : "Jr" (val));
> }
%z0 is just like %0 except if %0 has the value of 0 the compiler will insert
register $0. "Jr" mean the compiler can either use a register or the
constant zero. Both combined mean the compiler will not waste a real
register but use $zero.
Ralf
prev parent reply other threads:[~2003-09-24 6:22 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-24 6:04 mips inline asm question 黒津 基弥
2003-09-24 6:22 ` Ralf Baechle [this message]
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