The assembler back-end for most architectures needs to know if a jump is
backwards in order to emit optimised machine code, and they do this by
checking if the destination label has been set or not. So always reset
label offsets to -1 (this reverts partially the previous commit, with some
minor optimisation for the if-logic with the pass variable).
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