Well, kind of. The problem is that ARM is not as incremental as x86 is (in order to provide minimum silicon that can do the job), so in each generation you have several processors with different feature sets, with a basic common functionality. Even if you restrict yourself to ARMv6 in general, you have to drop VFP, Thumb2 and whatnot as not all ARMv6-es have them (not to mention you're compiling for the wrong pipeline and cache sizes). The point is that on mobile devices overhead directly translates to lower battery life, so, unlike x86, you really want the best optimized code in there for that particular unit.