Labels

In every assembly program, we need a way to refer to specific locations in our code. This is where labels come in!

You’ve already seen two labels in the last few examples: main: and stop:.

.text
main:
    # main code goes here

stop:
    li a7, 10
    ecall

What are labels?

A label is just a way of naming a specific ‘line’ in our code. When we put a label before a line of code, we’re saying “this line of code can be referred to by this name”.

Syntax

We can define a label by writing a name followed by a colon (:). For example:

loop_start:
    # code for the loop goes here

We can also put the label on the same line as an instruction:

loop_start: addi t0, t0, -1

Uses of labels

We’ll get into the main usage of labels in the next chapter when we learn about branching and jumping. The main uses of them are:

• for marking the start of functions (like main:)
• for marking locations to jump to (like stop:)
• for use in selection (assembly’s equivalent of if statements)
• for iteration (loops)
• for marking data locations in the .data section, e.g. memory variables and constants.