使用sse内在函数时如何摆脱循环？

__m128* pSrc1 = (__m128*) string; __m128 m0 = _mm_set_ps1(0); //null character while(1) { __m128 result = __m128 _mm_cmpeq_ss(*pSrc1, m0); //if character is \0 then break //do some stuff here pSrc1++; } 

我有一个字符串，其长度可以是16的倍数。如果_mm_cmpeq_ss返回相等，我如何突破循环？

Answer 1

如果您在第一次遇到\0时试图突破循环，那么您需要执行以下操作：

 __m128i* pSrc1 = (__m128i *)string; // init pointer to start of string __m128i m0 = _mm_set1_epi8(0); // vector of 16 `\0` characters while (1) { __m128i v0 = _mm_loadu_si128(pSrc1); // get 16 chars from string __m128i v1 = _mm_cmpeq_epi8(v0, m0); // compare all 16 chars with '\0' int vmask = _mm_movemask_epi8(v1); // get 16 comparison result bits if (vmask != 0) // if any bit is 1 break; // we found a `\0`, break out of loop pSrc1++; // next 16 characters... } 

如果您只想在某些位置测试\0字符并忽略其他任何字符，那么您可以将if (vmask != 0)测试更改为符合您特定要求的测试。