如何使用SSE计算某些范围内的字节数？

Question

我想编写一个c程序，用以下代码计算范围a ... c中的字节数：

char a[16], b[16], c[16];  
int counter = 0; 
for(i = 0;  i < 16; i++)  
{  
  if((a[i] < b[i]) && (b[i] < c[i]))  
  counter++;  
}  
return counter;  

我打算做这样的事情

__m128i result1 = _mm_cmpgt_epi8 (b, a);  
__m128i result2 = _mm_cmplt_epi8 (b, c);  
unsigned short out1 = _mm_movemask_epi8(result1);  
unsigned short out2 = _mm_movemask_epi8(result2);  
unsigned short out3 = out1 & out2;  
unsigned short out4 = _mm_popcnt_u32(out3);   

我的方法是否正确？有更好的方法吗？

Answer 1

你的方法看起来很合理。我想你可以通过在SIMD寄存器中执行AND来保存指令，如下所示：

__m128i result1 = _mm_cmpgt_epi8 (b, a);
__m128i result2 = _mm_cmplt_epi8 (b, c);
__m128i mask = _mm_and_si128(result1, result2);
int mask2 = _mm_movemask_epi8(mask);
int counter = _mm_popcnt_u32(mask2);