From mboxrd@z Thu Jan 1 00:00:00 1970 From: felipe.contreras@gmail.com (Felipe Contreras) Date: Mon, 14 Sep 2009 15:59:52 +0300 Subject: 'bx lr' vs 'mov pc,lr' In-Reply-To: <20090914073514.GA15883@pengutronix.de> References: <94a0d4530909131455x7a33cbaaw402642fb2e63c6d6@mail.gmail.com> <20090913225835.GB30169@n2100.arm.linux.org.uk> <94a0d4530909131711hf068509x900f19b5dfe8141d@mail.gmail.com> <20090914002005.GC30621@shareable.org> <94a0d4530909131847g2295b93by47de1785cc2f34b4@mail.gmail.com> <20090914073514.GA15883@pengutronix.de> Message-ID: <94a0d4530909140559l27ec5fddof3102a519e30819@mail.gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 2009/9/14 Uwe Kleine-K?nig : > On Mon, Sep 14, 2009 at 04:47:35AM +0300, Felipe Contreras wrote: >> On Mon, Sep 14, 2009 at 3:20 AM, Jamie Lokier wrote: >> > Felipe Contreras wrote: >> >> > Why do you want bx? ?bx isn't available on older CPUs. >> >> >> >> Isn't it faster? I don't know if it would make sense to try it on >> >> newer CPUs. >> > >> > That's interesting. ?Do you know if it's faster? >> >> Nope, I'm assuming because of this: >> http://newsgroups.derkeiler.com/Archive/Comp/comp.sys.arm/2006-04/msg00031.html > > For ARM9EJ-S the docs can be found at > > ? ? ? ?http://infocenter.arm.com/help/topic/com.arm.doc.ddi0222b/I1028171.html > > . ?bx takes 3 cycles, mov (with dest=pc) takes 4 cycles. Couldn't we have a 'return' macro that uses the relevant one? -- Felipe Contreras