代码

#include <iostream>
#include <immintrin.h>

#pragma GCC target("fma")
void my_memset(char *a, char c, unsigned n)
{
    size_t begin = reinterpret_cast<size_t>(a) % 32;
    std::cout << begin << "\n";
    char *p = a;
    while (p < a + begin && p < a + n)
    {
        *p = c;
        p++;
    }
    if (a + n - p >= 32)
    {
        __m256i data;
        static char ary[32] = {c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c};
        data = *(__m256i *)ary;
        size_t end = n - (n - begin) % 32;
        char *end_ptr = a + end;
        while (p < end_ptr)
        {
            _mm256_storeu_si256((__m256i *)p, data);
            p += 32;
        }
    }
    while (p < a + n)
    {
        *p = c;
        p++;
    }
}

评测结果