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From: Thomas Koeller <thomas.koeller@baslerweb.com>
To: "Linux/MIPS Development" <linux-mips@linux-mips.org>
Cc: Manish Lachwani <mlachwani@mvista.com>
Subject: jump instruction in delay slot
Date: Tue, 19 Oct 2004 16:05:47 +0200	[thread overview]
Message-ID: <200410191605.47543.thomas.koeller@baslerweb.com> (raw)

Hi,

the following code snippet is from
arch/mips/pmc-sierra/yosemite/irq-handler.S:

ll_duart_irq:
		li	a0, 4
		move	a1, sp
		jal	do_IRQ
		j	ret_from_irq

I wonder if this is correct. AFAIK, a jump instruction
must not occupy the delay slot of another branch or
jump instruction. Since the 'jal' returns to the first
instruction after the delay slot, I would expect the
effect of the 'j' instruction to be cancelled. Or
is this some kind of trick I do not understand?

tk

-- 
--------------------------------------------------

Thomas Koeller, Software Development
Basler Vision Technologies

thomas dot koeller at baslerweb dot com
http://www.baslerweb.com

==============================

             reply	other threads:[~2004-10-19 14:02 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-10-19 14:05 Thomas Koeller [this message]
2004-10-19 14:25 ` jump instruction in delay slot Thiemo Seufer
     [not found] ` <000901c4b5e8$70141160$10eca8c0@grendel>
2004-10-19 15:48   ` Thomas Koeller
2004-10-19 17:06 ` Ralf Baechle
     [not found] <B482D8AA59BF244F99AFE7520D74BF961A5B71@server1.RightHand.righthandtech.com>
2004-10-19 17:00 ` Thomas Koeller
2004-10-19 17:02   ` Ralf Baechle

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