spasm

An experimental multi-target assembler assembler.

Preparser

The preparser functions to provide many quality-of-life features that were previously introduced in a single backend. These include:

• Origin and byte offsetting
• Constants
  • Sized
• Labels
• Comment parsing

This feature-set is small to begin with but functions to standardize and consolidate the grammar accross multiple backends, leaving the backend to only handle the mapping to opcodes.

Grammar

program         = ( whitespace | newline )* ( origin | statement )+ ;

statements      = statement+ ;

statement       = ( whitespace | newline )* ( labeldef | symboldef | expression | instruction | comment ) comment?  ( newline | EOF );

instruction     = alphabetic ( alphabetic | digit | special | ";"! )+ ;

comment         = ";" ( whitespace | character )* ;

referenceid     = alphabetic* ;

labeldef        = referenceid ":" ;

definition      = .define whitespace+ referenceid whitespace+ expression ;

expression      = literal | referenceid;

literal         = (byte (byte (byte byte?)?)?) ;

origin          = ".origin" whitespace+ byte (byte (byte byte?)?)? ;

character       = lower|upper|digit|special ;
whitespace      = " " | "\t" ;
newline         = "\n" ;
alphabetic      = (lower|upper) ;
lower           = "a"|"b"|"c"|"d"|"e"|"f"|"g"|"h"|"i"|"j"|"k"|"l"|"m"
                |"n"|"o"|"p"|"q"|"r"|"s"|"t"|"u"|"v"|"w"|"x"|"y"|"z" ;
upper           = "A"|"B"|"C"|"D"|"E"|"F"|"G"|"H"|"I"|"J"|"K"|"L"|"M"
                |"N"|"O"|"P"|"Q"|"R"|"S"|"T"|"U"|"V"|"W"|"X"|"Y"|"Z" ;
byte            = ( "0x" hex hex ) | digit+ | ( "0b" binarybyte ) | "'" alphabetic "'" ;
hex             = "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9"|"a"|"b"|"c"
                |"d"|"e"|"f"|"A"|"B"|"C"|"D"|"E"|"F" ;
binarybyte      = binary binary binary binary binary binary binary binary ;
binary          = "0" | "1" ;
digit           = "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9" ;
special         = "-"|"_"|"\""|"#"|"&"|"’"|"("|")"|"*"|"+"|","|"."|"/"
                |":"|";"|"<"|"="|">" ;

Supported Backends

• MOS6502

Warnings

Please nobody use this. This is entirely an experiment to support insane restrictions I've imposed on myself to build a computer from first principles.

Instead, please use the wonderful vasm project that is better supported, better engineered and WAY more mature... frankly I don't even know why you are even looking at this.