3.5.4. Assembly time substitution of variables

You can use a string variable for a whole line of assembly language, or any part of a line. Use the variable with a $ prefix in the places where the value is to be substituted for the variable. The dollar character instructs the assembler to substitute the string into the source code line before checking the syntax of the line.

Numeric and logical variables can also be substituted. The current value of the variable is converted to a hexadecimal string (or T or F for logical variables) before substitution.

Use a dot to mark the end of the variable name if the following character would be permissible in a symbol name (see Symbol naming rules). You must set the contents of the variable before you can use it.

If you require a $ that you do not want to be substituted, use $$. This is converted to a single $.

You can include a variable with a $ prefix in a string. Substitution occurs in the same way as anywhere else.

Substitution does not occur within vertical bars, except that vertical bars within double quotes do not affect substitution.


    ; straightforward substitution
        GBLS    add4ff
add4ff  SETS    "ADD  r4,r4,#0xFF"    ; set up add4ff
        $add4ff.00                    ; invoke add4ff
        ; this produces
        ADD  r4,r4,#0xFF00

    ; elaborate substitution
            GBLS    s1
            GBLS    s2
            GBLS    fixup
            GBLA    count
count       SETA    14
s1          SETS    "a$$b$count" ; s1 now has value a$b0000000E
s2          SETS    "abc"
fixup       SETS    "|xy$s2.z|"  ; fixup now has value |xyabcz|
|C$$code|   MOV     r4,#16       ; but the label here is C$$code

Copyright © 2002-2005 ARM Limited. All rights reserved.ARM DUI 0204F