Clearing the labels to -1 is purely a debugging measure. For release
builds there is no need to do it as the label offset table should always
have the correct value assigned.
For all but the last pass the assembler only needs to count how much space
is needed for the machine code, it doesn't actually need to emit anything.
The dummy_data just uses unnecessary RAM and without it the code is not
any more complex (and code size does not increase for Thumb and Xtensa
archs).
Damien George