From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: 'bx lr' vs 'mov pc,lr'
Date: Mon, 14 Sep 2009 00:01:03 +0100 [thread overview]
Message-ID: <20090913230103.GD30169@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <94a0d4530909131556j49824b84ubddc13237f2d0bdd@mail.gmail.com>
On Mon, Sep 14, 2009 at 01:56:16AM +0300, Felipe Contreras wrote:
> On Mon, Sep 14, 2009 at 1:15 AM, Daniel Silverstone
> <dsilvers@simtec.co.uk> wrote:
> > On Mon, Sep 14, 2009 at 12:55:24AM +0300, Felipe Contreras wrote:
> >> I noticed that in 'arch/arm/lib/delay.S' we are using 'mov pc, lr'
> >> instead of 'bx lr'. Why? It looks like 'mov pc, lr' is used all over
> >> the place, but I can't find out what's the reason.
> >
> > I'd guess at the reason being that not all ARM processors whose ports use
> > arch/arm/lib/delay.S support the bx instruction, whereas the 'mov pc, lr'
> > instruction is universally supported.
>
> Are there really processors that don't support 'bx'? Can you give some examples?
Any ARMv3 CPU and any ARMv4 which doesn't support Thumb. Eg, StrongARM.
next prev parent reply other threads:[~2009-09-13 23:01 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-13 21:55 'bx lr' vs 'mov pc,lr' Felipe Contreras
2009-09-13 22:15 ` Daniel Silverstone
2009-09-13 22:56 ` Felipe Contreras
2009-09-13 23:01 ` Russell King - ARM Linux [this message]
2009-09-14 0:11 ` Felipe Contreras
2009-09-13 22:58 ` Russell King - ARM Linux
2009-09-14 0:11 ` Felipe Contreras
2009-09-14 0:20 ` Jamie Lokier
2009-09-14 1:47 ` Felipe Contreras
2009-09-14 7:35 ` Uwe Kleine-König
2009-09-14 12:59 ` Felipe Contreras
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