3.4. Labels, Arguments Labels and Multi Labels

Label declarations in Kick Assembler end with ‘:’ and have no postfix when referred to, as shown in the following program: 

loop:   inc $d020
        inc $d021
        jmp loop

You can put labels in front of mnemonic arguments. This can be useful when creating self modifying code: 

        stx tmpX
        ...
        ldx tmpX:#$00

Kick Assembler also supports multi labels, which are labels that can be declared more than once. These are useful to prevent name conflicts between labels. A multi label starts with a ‘!’ and when your reference it you have to end with a ‘+’ to refer to the next multi label or ‘-‘ to refer to the previous multi label: 

        ldx #100
!loop:  inc $d020
        dex
        bne !loop- // Jumps to the previous instance of !loop

        ldx #100
!loop:  inc $d021
        dex
        bne !loop- // Jumps to the previous instance of !loop

or

        ldx #10
!loop:
        jmp !+ // Jumps over the two next nops to the ! label
        nop
        nop
!:      jmp !+ // Jumps over the two next nops to the ! label
        nop
        nop
!:
        dex
        bne !loop- // Jumps to the previous !loop label

Applying more than one '+' or '-' will skip labels. E.g. '+++' will jump to the third label: 

        jmp !+++ // Jumps to the third '!' label
!:      nop
!:      nop
!:              // <- here!

Another way to avoid conflicting variables is to use user defined scopes, which are explained in the scoping section of Chapter 4, Introducing the Script Language.

A ‘*’ returns the value of the current memory location so instead of using labels you can write your jumps like this: 

// Jumps with '*'
        jmp *

        inc $d020
        inc $d021
        jmp *-6

// The same jumps with labels
this:   jmp this

!loop:  inc $d020
        inc $d021
        jmp !loop-

When referencing a label that is not yet resolved, the assembler will assume a two byte address, even though it later is found to be in the zeropage. You can mark labels as being in the zeropage with the .zp directive: 

        // Uses zeropage form of lda and sta eventhough the labels is first 
        // resolved later
        lda zpReg1
        sta zpReg2

*=$10 virtual 
.zp {
zpReg1: .byte 0
zpReg2: .byte 0
}

Note: Currently the .zp directive doesn't handle macros and pseudocommands called within the {}. Labels inside these will be in the form defined in the macro.

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