RTEMS GNU Tools On-Line Library

Variables

GASP

3.3: Preprocessor variables

You can use variables in GASP to represent strings, registers, or the results of expressions.

You must distinguish two kinds of variables:

Variables defined with .EQU or .ASSIGN. To evaluate this kind of variable in your assembly output, simply mention its name. For example, these two lines define and use a variable `eg':
```
eg     .EQU   FLIP-64
       ...
       mov.l  eg,r0
```
Do not use this kind of variable in conditional expressions or while loops; GASP only evaluates these variables when writing assembly output.
Variables for use during preprocessing. You can define these with .ASSIGNC or .ASSIGNA. To evaluate this kind of variable, write `\&' before the variable name; for example,
```
opcit  .ASSIGNA  47
       ...
       .AWHILE  \&opcit GT 0
       ...
       .AENDW
```
GASP treats macro arguments almost the same way, but to evaluate them you use the prefix `\' rather than `\&'. See Macros.

pvar .EQU expr: Assign preprocessor variable pvar the value of the expression expr. There are no restrictions on redefinition; use `.EQU' with the same pvar as often as you find it convenient.
pvar .ASSIGN expr: Almost the same as .EQU, save that you may not redefine pvar using .ASSIGN once it has a value.
pvar .ASSIGNA aexpr: Define a variable with a numeric value, for use during preprocessing. aexpr must be an absolute expression. You can redefine variables with .ASSIGNA at any time.
pvar .ASSIGNC "str": Define a variable with a string value, for use during preprocessing. You can redefine variables with .ASSIGNC at any time.
pvar .REG (register): Use .REG to define a variable that represents a register. In particular, register is not evaluated as an expression. You may use .REG at will to redefine register variables.

All these directives accept the variable name in the ``label'' position, that is at the left margin. You may specify a colon after the variable name if you wish; the first example above could have started `eg:' with the same effect.

GASP