Visual C ++ arithmetic with `const` slower than a regular variable

Question

So, I was messing around with Visual C ++ 2015, and I noticed that there is a problem with how Visual C ++ seems to compile constants and their access.

Consider the following:

#include "stdafx.h"
#include <stdio.h>
#include <Windows.h>

#define ITERATIONS 500000
#define GET_START_TIME QueryPerformanceCounter(&StartingTime);
#define GET_END_TIME QueryPerformanceCounter(&EndingTime);
#define CALC_DIFF_TIME ElapsedMicroseconds.QuadPart = EndingTime.QuadPart - StartingTime.QuadPart; ElapsedMicroseconds.QuadPart *= 1000000; ElapsedMicroseconds.QuadPart /= Frequency.QuadPart;

int main()
{
    short results[ITERATIONS];
    const int n = 5;
    int m = 5;
    LARGE_INTEGER StartingTime, EndingTime, ElapsedMicroseconds;
    LARGE_INTEGER Frequency;

    QueryPerformanceFrequency(&Frequency);

    // This loop seems to take about 1400 us on my computer.
    printf("Beginning loop over %i iterations with n constant.\n", ITERATIONS);

    GET_START_TIME;

    for (int i = 0; i < ITERATIONS; i++)
    {
        int statement = i % 10;

        if (statement == 0)
            results[i] = n * 0;
        else if (statement == 4)
            results[i] = n * 4;
        else if (statement == 2)
            results[i] = n * 2;
        else if (statement == 5)
            results[i] = n * 5;
        else if (statement == 7)
            results[i] = n * 7;
        else if (statement == 6)
            results[i] = n * 6;
        else if (statement == 1)
            results[i] = n * 1;
        else if (statement == 3)
            results[i] = n * 3;
        else if (statement == 9)
            results[i] = n * 9;
        else if (statement == 8)
            results[i] = n * 8;
    }

    GET_END_TIME;
    CALC_DIFF_TIME;

    printf("Finished in %lld us.\n", ElapsedMicroseconds.QuadPart);

    // This one takes about 800 us on my computer.
    printf("Beginning loop over %i iterations with m variable.\n", ITERATIONS);

    GET_START_TIME;

    for (int i = 0; i < ITERATIONS; i++)
    {
        int statement = i % 10;

        if (statement == 0)
            results[i] = m * 0;
        else if (statement == 4)
            results[i] = m * 4;
        else if (statement == 2)
            results[i] = m * 2;
        else if (statement == 5)
            results[i] = m * 5;
        else if (statement == 7)
            results[i] = m * 7;
        else if (statement == 6)
            results[i] = m * 6;
        else if (statement == 1)
            results[i] = m * 1;
        else if (statement == 3)
            results[i] = m * 3;
        else if (statement == 9)
            results[i] = m * 9;
        else if (statement == 8)
            results[i] = m * 8;
    }

    GET_END_TIME;
    CALC_DIFF_TIME;

    printf("Finished in %lld us.\n", ElapsedMicroseconds.QuadPart);

    getchar();

    return 0;
}

The upper part is slower (about 75% of the extra time) than the lower section, and the only difference is that it nis const intinstead of the usual one int.

My questions are: is it design or bug / error in Visual C ++? Is this because I am assigning a result short?

After further debugging, it seems that if I change the array shortto an array int, then the speed for the regular variable will increase from ~ 800us to 1400us using the value const.

, : , int, short, const int ?

---

: , Release, .

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