From mboxrd@z Thu Jan 1 00:00:00 1970 From: mans@mansr.com (=?iso-8859-1?Q?M=E5ns_Rullg=E5rd?=) Date: Fri, 04 Jul 2014 23:06:57 +0100 Subject: Android and compatibility with deprecated armv7 instructions In-Reply-To: <6519224.oaibQ22oiI@wuerfel> (Arnd Bergmann's message of "Fri, 04 Jul 2014 21:33:24 +0200") References: <20140704132250.A2447C40ADD@trevor.secretlab.ca> <20140704192405.GE14896@sirena.org.uk> <6519224.oaibQ22oiI@wuerfel> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Arnd Bergmann writes: > On Friday 04 July 2014 20:24:05 Mark Brown wrote: >> >> Another question I think it's worth asking is what the use case for 32 >> bit mode is other than preexisting binaries - I guess there's a case for >> smaller binaries giving better cache utilisation? > > If you wanted that, you'd probably run x32-mode (or whatever it gets called > on ARM64), which I'd expect to also be more efficient ;-) > > Seriously, backwards-compatibility is the only reason I can think of > really, but that doesn't /have/ to mean existing binaries; there is a large > amount of source code that can readily be compiled to any CPU as long as > it's little-endian 32-bit. There's also a lot of code that has been heavily optimised for 32-bit ARM but doesn't (yet) have the same level of optimisation for ARM64, so even if it builds and works for ARM64, it won't be nearly as fast. -- M?ns Rullg?rd mans at mansr.com