From: "David S. Miller" <davem@redhat.com>
To: sparclinux@vger.kernel.org
Subject: Re: why "mov %0, %0" after "rd %%tick, %0"?
Date: Fri, 23 Jan 2004 20:58:06 +0000 [thread overview]
Message-ID: <20040123125806.215b41da.davem@redhat.com> (raw)
On Fri, 23 Jan 2004 15:59:13 -0500
Ed L Cashin <ecashin@uga.edu> wrote:
> One thing I don't get is why there's a mov %0, %0 instruction after
> reading the tick register. Is this because of the delay slot?
No, there is a bug in some of the UltraSPARC processors in that if
you go:
rd %tick, %reg
cmp %reg, XXX
the compare will get an incorrect result. If we force the %tick result
into a simple move instruction this prevents the sequence that leads up
to the bug.
next reply other threads:[~2004-01-23 20:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-01-23 20:58 David S. Miller [this message]
2004-01-23 20:59 ` why "mov %0, %0" after "rd %%tick, %0"? Ed L Cashin
2004-01-23 21:31 ` Ed L Cashin
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