Mercurial > hg > index.cgi
view docs/internals.txt @ 460:3d53f2e8d0e0
Allow macros to shadow instructions that are not supported by current CPU.
When assembling in 6809 mode, 6309 instructions should be usable as macros.
When assembling in 6309 mode, instructions not valid on the 6309 should be
usable as macros.
author | William Astle <lost@l-w.ca> |
---|---|
date | Wed, 28 Feb 2018 20:43:14 -0700 |
parents | 2c24602be78f |
children |
line wrap: on
line source
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.