blocks|key|235394|text|当您设置为64位时，得到的二进制文件是一个"+fat“二进制文件，它包含捆绑了一个瘦fat头部的所有三个Mach-O图像。您可以使用otool或jtool看到这一点。您可以查看包含在iOS+7.0SDK中的一些fat二进制文件，例如AVFoundation框架，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|235395|%25+cd++/Developer/Platforms/iPhoneOS.platform/DeviceSupport/7.0\+$11A465$/Symbols/System/Library/Frameworks/AVFoundation.framework/

%25otool+-V+-f+AVFoundation+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++9:36
Fat+headers
fat_magic+FAT_MAGIC
nfat_arch+3
architecture+arm64+++++#+The+64-bit+version+(A7)
++++cputype+CPU_TYPE_ARM64
++++cpusubtype+CPU_SUBTYPE_ARM64_ALL
++++capabilities+0x0
++++offset+16384
++++size+2329888
++++align+2%5E14+(16384)
architecture+armv7++++++++#+A5X+-+packaged+after+the+arm64version
++++cputype+CPU_TYPE_ARM
++++cpusubtype+CPU_SUBTYPE_ARM_V7
++++capabilities+0x0
++++offset+2359296
++++size+2046336
++++align+2%5E14+(16384)
architecture+armv7s+++++++#+A6+-+packaged+after+the+armv7+version
++++cputype+CPU_TYPE_ARM
++++cpusubtype+CPU_SUBTYPE_ARM_V7S
++++capabilities+0x0
++++offset+4407296
++++size+2046176
++++align+2%5E14+(16384)|code-block|syntax|javascript|235396|至于二进制文件本身，它使用ARM64位指令集，这是(主要与32位兼容，但)完全不同的指令集。这对于图形程序(使用霓虹灯指令和寄存器)尤其重要。同样，CPU有更多的寄存器，这对程序速度有相当大的影响。在http://blogs.barrons.com/techtraderdaily/2013/09/19/apple-the-64-bit-question/?mod=yahoobarrons中有一个关于这是否有影响的有趣讨论；到目前为止，基准测试已经清楚地表明是有影响的。|offset|length|235397|使用otool+-tV将转储程序集(如果您使用的是XCode+5或更高版本)，然后您可以自己查看指令集差异。大多数(但不是所有)开发人员将对这些更改保持不可知，因为大多数情况下，它们不会直接影响Obj-C+(尽管有CG*API)，并且必须在低级指针处理方面做更多工作。编译器将发挥它的魔力和优化功能。|235398|entityMap|0|LINK|mutability|MUTABLE|url|http://blogs.barrons.com/techtraderdaily/2013/09/19/apple-the-64-bit-question/?mod=yahoobarrons^0|0|0|2S|2N|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@$I|X|J|Y|1|Z]]|A|$]]|$1|K|3|L|5|6|7|10|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

When you set 64-bit the resulting binary is a "Fat" binary, which contains all three Mach-O images bundled with a thin fat header. You can see that using otool or jtool. You can check out some fat binaries included as part of the iOS 7.0 SDK, for example the AVFoundation Framework, like so:

<pre><code>% cd /Developer/Platforms/iPhoneOS.platform/DeviceSupport/7.0\ $11A465$/Symbols/System/Library/Frameworks/AVFoundation.framework/

%otool -V -f AVFoundation 9:36
Fat headers
fat_magic FAT_MAGIC
nfat_arch 3
architecture arm64 # The 64-bit version (A7)
 cputype CPU_TYPE_ARM64
 cpusubtype CPU_SUBTYPE_ARM64_ALL
 capabilities 0x0
 offset 16384
 size 2329888
 align 2^14 (16384)
architecture armv7 # A5X - packaged after the arm64version
 cputype CPU_TYPE_ARM
 cpusubtype CPU_SUBTYPE_ARM_V7
 capabilities 0x0
 offset 2359296
 size 2046336
 align 2^14 (16384)
architecture armv7s # A6 - packaged after the armv7 version
 cputype CPU_TYPE_ARM
 cpusubtype CPU_SUBTYPE_ARM_V7S
 capabilities 0x0
 offset 4407296
 size 2046176
 align 2^14 (16384)
</code></pre>

As for the binary itself, it uses the ARM64 bit instruction set, which is (mostly compatible with 32-bit, but) a totally different instruction set. This is especially important for graphics program (using NEON instructions and registers). Likewise, the CPU has more registers, which makes quite an impact on program speed. There's an interesting discussion in <a href="http://blogs.barrons.com/techtraderdaily/2013/09/19/apple-the-64-bit-question/?mod=yahoobarrons">http://blogs.barrons.com/techtraderdaily/2013/09/19/apple-the-64-bit-question/?mod=yahoobarrons</a> on whether or not this makes a difference; benchmarking tests have so far clearly indicated that it does.

Using otool -tV will dump the assembly (if you have XCode 5 and later), and then you can see the instruction set differences for yourself. Most (but not all) developers will remain agnostic to the changes, as for the most part they do not directly affect Obj-C (CG* APIs notwithstanding), and have to do more with low level pointer handling. The compiler will work its magic and optimizations.

I'm starting new project in Xcode 5. I want to develop application using <code>iOS SDK 7</code> but with deployment target <code>iOS 5.0</code>. As soon as I create new project in Xcode and try to change deployment target to 5.0, I've got this message:

<pre><code>Applications including an arm64 slice are not compatible with versions of iOS
prior to 6.0
Adjust your Architectures build setting to not include arm64 in order to deploy
to releases prior to iOS 6.0.
</code></pre>

So changed architectures to <code>Standard</code> (no 64bit). I compiles, runs but I do not really understand what just happend. What's the difference between <code>Architectures</code> and <code>Valid architectures</code> settings in Xcode project Build Settings? If I set <code>Architectures</code> to exclude 64-bit what happens when I run my app on 64-bit iPhone or iOS Simulator (I know it works, I'm just curious what hapens underneath)? Can you explain big mess with new 64-bit architecture?

<img src="https://i.stack.imgur.com/AZd2Q.png" alt="enter image description here">

Xcode 5 and iOS 7: Architecture and Valid architectures

编译器

Xcode

我在Xcode5中开始了一个新项目。我想使用iOS SDK 7开发应用程序，但要以部署目标iOS 5.0为目标。当我在Xcode中创建新项目并尝试将部署目标更改为5.0时，我收到了以下消息：Applications including an arm64 slice are not compatible with ver...

问Xcode5和iOS 7:架构和有效架构
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