将 8bit uint8_t 加载为 uint32_t? [英] Load 8bit uint8_t as uint32_t?

问题描述

我的图像处理项目使用灰度图像.我有 ARM Cortex-A8 处理器平台.我想使用NEON.

my image processing project works with grayscale images. I have ARM Cortex-A8 processor platform. I want to make use of the NEON.

我有一个灰度图像(考虑下面的示例)，在我的算法中，我只需要添加列.

I have a grayscale image( consider the example below) and in my alogorithm, I have to add only the columns.

如何并行加载 四个 8 位像素值，它们是 uint8_t，作为 四个 uint32_t 到 128- 之一位 NEON 寄存器?我必须使用什么内在函数来做到这一点?

How can I load four 8-bit pixel values in parallel, which are uint8_t, as four uint32_t into one of the 128-bit NEON registers? What intrinsic do I have to use to do this?

我的意思是:

我必须将它们加载为 32 位，因为如果你仔细观察，我执行 255 + 255 的那一刻是 512，它不能保存在 8 位寄存器中.

I must load them as 32 bits because if you look carefully, the moment I do 255 + 255 is 512, which can't be held in a 8-bit register.

例如

255 255 255 255 ......... (640 pixels)
255 255 255 255
255 255 255 255
255 255 255 255
.
.
.
.
.
(480 pixels) 

推荐答案

我建议你花一点时间了解 SIMD 在 ARM 上的工作原理.看:

I will recommend that you spend a bit of time understanding how SIMD works on ARM. Look at:

看看:

1. http://blogs.arm.com/software-enablement/161-coding-for-neon-part-1-load-and-stores/
2. http://blogs.arm.com/software-enablement/196-coding-for-neon-part-2-dealing-with-leftovers/
3. http://blogs.arm.com/software-enablement/241-coding-for-neon-part-3-matrix-multiplication/
4. http://blogs.arm.com/software-enablement/277-coding-for-neon-part-4-shifting-left-and-right/

让你开始.然后，您可以使用内联汇编程序或 domen 推荐的相应 ARM 内部函数来实现您的 SIMD 代码.

to get you started. You can then implement your SIMD code using inline assembler or corresponding ARM intrinsics recommended by domen.

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