如何使用Neon SIMD将unsigned char转换为有符号整数

如何使用Neon将数据类型uint8_t的变量转换为int32_t ？ 这样做我找不到任何内在的东西。

Answer 1

假设您想要将16 x 8位整数的向量转换为4 x 32位整数的四个向量，您可以通过首先解压缩到16位然后再转换为32位来执行此操作：

 // 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