LWASM Internals
===============

LWASM is a table-driven assembler that notionally uses two passes. However,
it implements its assembly in several passes as follows.

Pass 1
------

This pass reads the entire source code and parses each line into an internal
representation. Macros, file inclusions, and conditional assembly
instructions are resolved at this point as well. Instructions with known
sizes will have their sizes resolved at this point.

Pass 2
------

Check all exported symbols for validity and set them as imports if the
assembler state says so. Also resolve all symbol references in all
expressions to be direct references either to the symbol table or
to the import list.

Pass 3
------

This pass resolves all instruction sizes that can be resolved without
forcing any instruction sizes. This pass will run repeatedly until no
no new resolution occurs.

Pass 4
------

Work through all un-resolved instructions and force sizes. After each size
is forced, try re-resolving all other instructions. This is done starting
at the beginning of the source and working forward. If any instruction does
not resolve when forced, an error will be thrown.

Pass 5
------

Constantize all line addresses and throw errors if any cannot be. This
pass will repeat until no further lines addresses are reduced to constants
at which time all lines will be checked for constant-ness.

Pass 6
------

Finalize all expressions related to instructions. Carp about any that
cannot be reduced to a usable form. That means, for the non-object target
all expressions must resolve to a constant. For the object form, all
expressions must resolve to symbol references and constants. Those symbol
references may be internal or external.

Pass 7
------

Emit object code for each line for later output.