代码

int binary_search(const unsigned *a, int n, unsigned x)
{
    const unsigned *base = a;
    int len = n;
    while (len > 1) {
        int half = len >> 1;
        const unsigned *mid = base + half;
        __builtin_prefetch(mid - (half >> 1));
        __builtin_prefetch(mid + (half >> 1));
        int less = (*mid <= x);
        base = less ? mid : base;
        len -= half;
    }
    return (int)(base - a);
}

评测结果