在有效架构中使用armv7s支持的优势是什么？ [英] What is the advantage of using armv7s support In Valid Architecture?
问题描述
我正在开发支持iOS 4.3及更高版本的iOS应用。由于一些框架，我无法将其存档为armv7s，所以我已经删除了armv7s支持。它会降低应用程序性能吗？
使用armv7s有什么好处？
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?
推荐答案
令人惊讶的是，机器代码没有太大差异为两种不同的架构而制作;总的来说，armv7s代码与armv7代码没什么不同。然而，有两个具体的差异引起了我的注意。
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.
第一个差异影响整数除法。 armv7s架构有两个新的整数除法指令，这些指令在armv7架构中不存在。这些整数除法指令作为armv7上的函数实现，其至少比armv7上的等效指令慢一个数量级。整数除法在应用程序中很常见（它在Geekbench中被称为超过一百个），因此这些新指令应该可以显着提高所有应用程序的性能。
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.
第二个区别影响浮点运算。 Xcode对armv7使用不同的浮点算术指令而不是armv7。 Xcode用于armv7s的指令将多个操作组合成一个指令，这使得它们比Xcode用于armv7的几个独立指令更有效。令人惊讶的是，这些组合浮点指令存在于armv7架构中，但未被Xcode使用。目前还不清楚为什么会这样。对于armv7s，这些组合指令代表了所有浮点指令的一小部分，因此虽然它们可能提供优势，但很难确定它们将产生多大的影响。
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.
armv7和armv7s代码之间还存在其他差异，但与上面概述的整数除法和浮点算术更改相比，它们是次要的。使用armv7s可以使应用程序受益多少？通过检查生成的代码很难说，但如果您是开发人员，我认为值得花费时间和精力来发布应用程序的armv7s构建，特别是如果您的应用程序使用浮点运算。
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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