代码

#include <cstring>

template <class Tp> void DoNotOptimize(Tp& value) {
    asm volatile("" : "+m,r"(value) : : "memory");
}

int main() {
    const int n = 1e6;
    static int a[n], b[n];
    for (int k = 0; k < 1000; k++) {
        memcpy(a, b, sizeof a);
        memcpy(a, b, sizeof a);
    }
    for (int i = 0; i < n; i++) DoNotOptimize(a[i]);
}

评测结果