What is Neon?

Neon is the implementation of Arm’s Advanced SIMD architecture. 

The purpose of Neon is to accelerate data manipulation by providing:

  • Thirty-two 128-bit vector registers, each capable of containing multiple lanes of data.
  • SIMD instructions to operate simultaneously on those multiple lanes of data.

Applications that can benefit from Neon technology include multimedia and signal processing, 3D graphics, speech, image processing, or other applications where fixed and floating-point performance is critical.

As a programmer, there are a number of ways you can make use of Neon technology:

  • Neon-enabled open source libraries such as the Arm Compute Library provide one of the easiest ways to take advantage of Neon.
  • Auto-vectorization features in your compiler can automatically optimize your code to take advantage of Neon.
  • Neon intrinsics are function calls that the compiler replaces with appropriate Neon instructions. This gives you direct, low-level access to the exact Neon instructions you want, all from C, or C++ code.
  • For very high performance, hand-coded Neon assembler can be the best approach for experienced programmers.

In this guide we will focus on using the Neon intrinsics for AArch64, but they can be compiled for AArch32 also. For more information about AArch32 Neon see Introducing Neon for Armv8-A. First we will look at a simplified image processing example and matrix multiplication. Then we will move on to a more general discussion about the intrinsics themselves.

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