How do I Perform Integer SIMD operations on the iPad A4 Processor?

StackOverflow https://stackoverflow.com/questions/3847210

  •  27-09-2019
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Question

I feel the need for speed. Double for loops are killing my iPad apps performance. I need SIMD. How do I perform integer SIMD operations on the iPad A4 processor?

Thanks,
Doug

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Solution

To get the fastest speed, you will have to write ARM Assembly language code that uses NEON SIMD operations, because the C compilers generally don't make very good SIMD code, so hand-written Assembly will make a big difference. I have a brief intro here: http://www.shervinemami.co.cc/iphoneAssembly.html

Note that the iPad A4 uses the ARMv7-A CPU, so the reference manual for the NEON SIMD instructions is at: http://infocenter.arm.com/help/topic/com.arm.doc.ddi0406b/index.html (but its 2000 pages long and requires the understanding of Assembly code and perhaps SIMD in general!).

OTHER TIPS

The instruction set is NEON, intrinsics reference

I've never been able to find good documentation on what they all actually are. But you pick it up pretty quickly if you've had any exposure to SSE

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