Labels

Labels are a way to store the position/address of a location in program memory for jumping or referring to elsewhere without having to use offsets or manually count instructions or addresses.

Labels are declared using a colon : character followed by letters, numbers, or underscores.

; Declare the :start label to jump back to later.
:start
swizzle r0.yzwx
mov r1.x [ri.x+]

...

; Use the label defined earlier to jump back to the start of the program.
jmp :start

Unlike other macros, labels perform a post-processing step on the program after the rest of the instructions have been generated, in order to track the correct memory locations and inject them into the necessary places.

Usage

Labels can be used in jump instructions as shown above, and can also be used in set instructions to assign the value of a label to a register, such as:

:begin
sub.w r0, r0, r0
set r1, :begin
set r2, $0010 ; nop
mov [r1.x], r2
jmp :begin

This program overwrites the instruction sub.w r0, r0, r0 with a nop by setting r1 to the address of the label :begin which itself contains the subtract instruction's memory address, and then using that as a pointer to write the value 0x0010 stored in r2, into the address pointed to by r1.x.