Should I use ELSE IF? for better performance?

Newbie here and I just want to know should I use ELSE IF for something like below:

(function)
IF x==1
IF x==2
IF x==3

That is the way I am using, because the x will not be anything else. However, I think that if the x is equal to 1, the program still gonna run through the following codes (which turn out to be FALSE FALSE FALSE ...). Should I use ELSE IF so it won't have to run the rest? Will that help the performance?

Why don't I want to use ELSE IF? because I'd like each code block (IF x==n) to be similar, not like this:

IF x==1
ELSE IF x==2
ELSE IF x==3

(each ELSE IF block is part of the block above it)

But the program will repeatedly call this function so I am worried about the performance or delay.