Harikrishnan Harikrishnan - 5 months ago 23
iOS Question

What is the advantage of using armv7s support In Valid Architecture?

I'm working on an iOS app which supports iOS 4.3 and above. Due to some frameworks I cant Archive it for armv7s,so I have removed armv7s support. Will it reduce application performance?
What is the advantage of using armv7s?

Answer Source

Surprisingly there weren't a lot of differences in the machine code produced for the two different architectures; overall, the armv7s code does not look much different from the armv7 code. However, there were two specific differences that caught my eye.

The first difference affects integer division. The armv7s architecture has two new integer division instructions that aren't present on the armv7 architecture. These integer division instructions are implemented as a function on the armv7 that is at least an order of magnitude slower than the equivalent instruction on the armv7s. Integer division is common in applications (it's called in over a hundred places in Geekbench) so these new instructions should provide a significant increase in performance to all applications.

The second difference affect floating point arithmetic. Xcode uses different floating point arithmetic instructions for the armv7s than for the armv7. The instructions Xcode uses for the armv7s combine several operations into one instruction which should make them more efficient than the several independent instructions that Xcode uses for the armv7. Surprisingly these combined floating point instructions are present in the armv7 architecture but are unused by Xcode. It's unclear why this is the case. For armv7s these combined instructions represent a small proportion of all floating point instructions, so while they will probably provide an advantage it's hard to determine how much of an impact they will have.

There are other differences between the armv7 and the armv7s code, but they're minor in comparison to the integer division and the floating point arithmetic changes outlined above. How much will applications benefit from having an armv7s build? It's hard to say just from examining the generated code, but if you're a developer I think it's worth the time and the effort to ship an armv7s build of your application, especially if your application makes any use of floating point operations.

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Difference between armv7 and armv7s