Chapter 13. ARM Dependent Features

89

 moabi

This indicates that the code should be assembled using the old ARM ELF conventions, based on

a beta release release of the ARM ELF specifications, rather than the default conventions which

are based on the final release of the ARM ELF specifications.

13.2. Syntax

13.2.1. Special Characters

The presence of a

@

on a line indicates the start of a comment that extends to the end of the current

line. If a

#

appears as the first character of a line, the whole line is treated as a comment.

The

;

character can be used instead of a newline to separate statements.

Either

#

or

$

can be used to indicate immediate operands.

*TODO* Explain about /data modifier on symbols.

13.2.2. Register Names

*TODO* Explain about ARM register naming, and the predefined names.

13.3. Floating Point

The ARM family uses ieee floating point numbers.

13.4. ARM Machine Directives

.align expression [, expression]

This is the generic

.align

directive. For the ARM however if the first argument is zero (ie no

alignment is needed) the assembler will behave as if the argument had been 2 (ie pad to the next

four byte boundary). This is for compatibility with ARM's own assembler.

name .req register name

This creates an alias for

register name

called

name

. For example:

foo .req r0

.unreq alias name

This undefines a register alias which was previously defined using the

req

directive. For example:

foo .req r0

.unreq foo

An error occurs if the name is undefined. Note   this pseudo op can be used to delete builtin in

register name aliases (eg 'r0'). This should only be done if it is really necessary.