Integer declaration assembly difference

Question

Suppose you have this code:

static void Send(byte[] buffer, int offset, int count)
{
    while (count > 0)
    {
        int size = sock.Send(buffer, offset, count);

        if (size == 0) throw new EndOfStreamException();

        offset += size;
        count -= size;
    }
}

vs.

static void Send(byte[] buffer, int offset, int count)
{
    int size;

    while (count > 0)
    {
        size = sock.Send(buffer, offset, count);

        if (size == 0) throw new EndOfStreamException();

        offset += size;
        count -= size;
    }
}

My teacher told me the second one would be more efficient, but is that true?

I did some testing and compared the assembly code and it was equal.

But will this always be the case?

What if instead of a primitive type you used a reference type? (assuming you don't allocate)
What about using multiple variables?
Will there ever be differences between the two possibilities?

Thanks in advance for any answers, I apologize if this has been asked before but I didn't really know how to call it.

If you tested and you found the cases to be equal, why would you believe what a teacher says? — Camilo Terevinto, Dec 30 '15 at 22:41
Did you test with the compiler optimizations switched OFF and then ON again? — Grantly, Dec 30 '15 at 22:46
@cFrozenDeath I don't believe it, hence why I'm testing it myself and ask a question on stackoverflow, desperately trying to find if this could even be remotely true. — hl3mukkel, Dec 30 '15 at 22:50
It's a shame there are still people teaching based on outdated information... This may have been true in the last century, but any real modern compiler should be able to produce the same code in both cases. — Lucas Trzesniewski, Dec 30 '15 at 22:53

score 1 · Answer 1 · answered Dec 30 '15 at 22:42

1

Depends on the compiler optimizations - but since it's the same scope (function) - implementation would (usually) be the same.

As long as you don't instantiate anything new in that row, it's a local variable in the function scope.

answered Dec 30 '15 at 22:42

Raz Abramov

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Integer declaration assembly difference

1 Answers1