add vs mul (IA32-Assembly)

Question

I know that add is faster as compared to mul function.

I want to know how to go about using add instead of mul in the following code in order to make it more efficient.

Sample code:

            mov eax, [ebp + 8]              #eax = x1
            mov ecx, [ebp + 12]             #ecx = x2
            mov edx, [ebp + 16]             #edx = y1
            mov ebx, [ebp + 20]             #ebx = y2

            sub eax,ecx                     #eax = x1-x2
            sub edx,ebx                     #edx = y1-y2

            mul edx                         #eax = (x1-x2)*(y1-y2)

Answer 1

add is faster than mul, but if you want to multiply two general values, mul is far faster than any loop iterating add operations.

You can't seriously use add to make that code go faster than it will with mul. If you needed to multiply by some small constant value (such as 2), then maybe you could use add to speed things up. But for the general case - no.