如何使用霓虹灯SIMD无符号字符转换为符号整数 [英] How to convert unsigned char to signed integer using Neon SIMD

问题描述

如何使用霓虹灯数据类型 uint8_t有的变量转换为 int32_t ？我找不到任何内在这样做的。

How to convert a variable of data type uint8_t to int32_t using Neon? I could not find any intrinsic for doing this.

推荐答案

假设你想要的16×8位整数向量转换为4×32位整数四个矢量，你可以先拆包到16位做到这一点然后再次以32位：

Assuming you want to convert a vector of 16 x 8 bit ints to four vectors of 4 x 32 bit ints, you can do this by first unpacking to 16 bits and then again to 32 bits:

// load 8 bit vector
uint8x16_t v = vld1q_u8(p);   // load vector of 16 x 8 bits ints from p

// unpack to 16 bits
int16x8_t vl =  vreinterpretq_s16_u16(vmovl_u8(vget_low_u8(v)));   // 0..7
int16x8_t vh =  vreinterpretq_s16_u16(vmovl_u8(vget_high_u8(v)));  // 8..15

// unpack to 32 bits
int32x4_t vll = vmovl_s16(vget_low_s16(vl));           // 0..3
int32x4_t vlh = vmovl_s16(vget_high_s16(vl));          // 4..7
int32x4_t vhl = vmovl_s16(vget_low_s16(vh));           // 8..11
int32x4_t vhh = vmovl_s16(vget_high_s16(vh));          // 12..15

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