                            REDCODE REFERENCE

Simulator: pMARS
Version: 0.9.4
Standard: ICWS'94 draft (extended)

________________________________________
Opcodes:

    DAT     terminate process
    MOV     move from A to B
    ADD     add A to B, store result in B
    SUB     subtract A from B, store result in B
    MUL     multiply A by B, store result in B
    DIV     divide B by A, store result in B if A <> 0, else terminate
    MOD     divide B by A, store remainder in B if A <> 0, else terminate
    JMP     transfer execution to A
    JMZ     transfer execution to A if B is zero
    JMN     transfer execution to A if B is non-zero
    DJN     decrement B, if B is non-zero, transfer execution to A
    SPL     split off process to A
    SLT     skip next instruction if A is less than B
    CMP     same as SEQ
    SEQ     skip next instruction if A is equal to B
    SNE     skip next instruction if A is not equal to B
    NOP     no operation
    LDP     load P-space cell A into B
    STP     store A into P-space cell B

________________________________________
Pseudo opcodes:

    [labels] EQU text            replaces [labels] by text
            [EQU text]           multi-line EQU: text continues

             ORG start           specifies execution start

             END [start]         end of assembly (optional execution start)

    [count]  FOR expression      repeat enclosed instructions "expression"
             ROF                 times, counter is incremented starting with 01

             PIN number          P-space identification number, warriors
                                 with same number share P-space

________________________________________
Modifiers:

    .A   Instructions read and write A-fields.

    .B   Instructions read and write B-fields.

    .AB  Instructions read the A-field of the A-instruction  and
         the B-field of the B-instruction and write to B-fields.

    .BA  Instructions read the B-field of the A-instruction  and
         the A-field of the B-instruction and write to A-fields.

    .F   Instructions read both A- and B-fields of  the  the  A-
         and  B-instruction and write to both A- and B-fields (A
         to A and B to B).

    .X   Instructions read both A- and B-fields of  the  the  A-
         and  B-instruction  and  write  to both A- and B-fields
         exchanging fields (A to B and B to A).

    .I   Instructions read and write entire instructions.

________________________________________
Addressing modes:

    #       immediate
    $       direct
    @       indirect using B-field
    <       predecrement indirect using B-field
    >       postincrement indirect using B-field
    *       indirect using A-field
    {       predecrement indirect using A-field
    }       postincrement indirect using A-field

________________________________________
Directives:

    ;redcode                code follows, preceding text is ignored
    ;name                   name of warrior follows
    ;author                 name of author follows 
    ;assert                 expression that must evaluate to true
    ;trace [off]            toggle trace bit for following instructions
    ;break                  set trace bit for next instruction
    ;debug [static|off]     enable/disable setting [static] trace bits

________________________________________
Predefined variables:

    CORESIZE          value of -s parameter (default: 8000)
    MAXPROCESSES      value of -p parameter (default: 8000)
    MAXCYCLES         value of -c parameter (default: 80000)
    MAXLENGTH         value of -l parameter (default: 100)
    MINDISTANCE       value of -d parameter (default: 100)
    ROUNDS            value of -r parameter (default: 1)
    PSPACESIZE        value of -S parameter (default: 1/16th CORESIZE)
    CURLINE           current line in generated assembly (starts with 0)
    VERSION           pMARS version ("94" is v0.9.4)
    WARRIORS          number of warriors specified on command line
    READLIMIT         value of -R parameter
    WRITELIMIT        value of -W parameter
________________________________________
Expression operators:

    Arithmetic:
        +   addition or unary plus
        -   subtraction or unary minus
        *   multiplication
        /   division
        %   modulo (remainder of division)

    Comparison:
        ==  equality
        !=  inequality
        <   less than
        >   greater than
        <=  less than or equal
        >=  greater than or equal

    Logical:
        &&  and
        ||  or
        !   unary negation

    Assignment:
        =   (to register variables a..z)

    Comparison and logical operators return 1 for true and 0 for false.
    Parentheses can be used to override this precedence order:

        1)  ! - + (unary)
        2)  * / %
        3)  - + (binary)
        4)  == != < > <= >=
        5)  &&
        6)  ||
        7)  =

________________________________________
Redcode grammar:

statement_list :: statement statement_list | e ;
statement :: normal_stmt<1> |
             equ_stmt       |
             forrof_stmt    |
             comment_stmt   |
             substitution_stmt<2> ;

num       :: [0-9] ;
number    :: num number | num ;
alpha     :: [a-zA-Z] | "_" ;
alphanum  :: alpha | num ;
alphanums :: alphanum alphanums | e ;

label  :: alpha alphanums ;
label1 :: label label1 | label ;
labels :: label1 "\n" labels | label1 ;
stringization :: stringization"&"label | label ;

this_string :: (^\n)* ;
comment     :: ";" this_string "\n" | e ;

equ_stmt    :: labels equ_strings ;
equ_string  :: "equ" this_string comment "\n" ;
equ_strings :: equ_string "\n" equ_strings | equ_string ;

forrof_stmt :: labels index "for" expression<3> comment "\n"
               statement_list
               "rof" this_string "\n" ;
index       :: label

comment_stmt  :: info_comment | debug_comment | ignore ;
ignore        :: ";" this_string "\n" ;
info_comment  :: ";redcode" this_string "\n" |
                 ";" "name" this_string "\n" |
                 ";" "author" this_string "\n" |
                 ";" "date" this_string "\n" |
                 ";" "version" this_string "\n" |
                 ";" "assert" expression<4> "\n" ;
debug_comment :: ";" debug "\n" | ";" trace "\n" | ";" break "\n" ;
debug         :: "debug" | "debug" "off" | "debug" "static" ;
trace         :: "trace" | "trace" "off" ;
break         :: "break" ;

Note
----

1. Normal statements are statements in the following form:
   opcode [address mode] operand [, [address mode] operand] [comment]
   More details about the grammar are given in the '88 or '94 proposal.

2. Substitution statements are labels that have been declared by EQU.
   If a label is declared this way: "IMP_instr equ imp mov imp, imp + 
   1", the label name IMP_instr can be thought of as a statement.  
   Therefore, whenf IMP_instr is used after its declaration, it will 
   be replaced by "imp mov imp, imp + 1". It has effect of declaring 
   a label 'imp' and inserting the statement 'mov imp, imp + 1'.

3. Valid expressions for FOR statements are very close to C expressions
   in which operator '()' has the highest precedence, followed by 'unary
   +, unary -', '*, / and %', 'binary + and binary -', '<, <=, >, >=',
   '==, !=', '&&', '||', and the lowest '='.
   Beside numbers, it can also have labels as its terms. All of its labels
   have to be declared before the FOR statement is invoked.
4. Valid expressions for ASSERT statements are the same as those for FOR.

Case sensitivity
----------------

Opcode and pseudo-opcode names are case insensitive; labels are case
sensitive.

Label declaration
-----------------

Labels are declared in three ways:

 o Using EQU. When a label name that first appears (has not been declared)
   is declared with EQU, all subsequent occurences of that label name
   will be replaced by the strings following the EQU.

   The following equates label THIS with "num + 1". THIS equ num + 1.

   If the string substituting the label contains other labels, those labels
   are also replaced by their substituting string. Recursive reference of
   labels are flagged as error.

   More than one statement can be declared as a label name. To achieve this,
   use an EQU to continue the declaration on the lines following the line
   with the named EQU label. Thus, the declaration of the following:

   core_clear equ spl 0
              equ mov 2, <-1
              equ jmp -1

   causes three statements to be declared as strings of label core_clear.

 o As an offset relative to the current normal statement. If some labels 
   appear just before any '88 or '94 opcodes, they are automatically 
   declared as constants that are relative to the current statement.
   For example:

   first spl first                0000 spl 0
   imp   mov imp, imp + 1  -----> 0001 mov 0, 1

 o As an index belonging to FOR statement. Unlike other statements, labels
   declared with FOR consist of two ingredients: the last label serving
   as FOR index and the remaining labels serving as the same offset pointing
   at the first of the FOR statement. This allows the implementation of
   base[index] kind.

   This declaration:

   base
   index for 3
         mov base, base + index - 1
         rof

   translates into:

   0000 mov 0, 0
   0001 mov 0, 1
   0002 mov 0, 2

Stringization and declaration inside FOR/ROF
--------------------------------------------

FOR 5
imp mov imp, imp + 5
ROF

Declaration of the above example causes the assembler to complain for
duplicating declarations. pMARS however offers the stringization feature
to accomplish the same goal. Its syntax is: label"&"label"&"...
The first label can be any valid alphanums and it goes untranslated.
The rest of the labels have to be a FOR index and it is to be substituted
accordingly. Thus:

N FOR 5
  imp&N mov imp&N, imp&N + 5
  ROF

are expanded into:

imp01 mov imp01, imp01 + 5
imp02 mov imp02, imp02 + 5
imp03 mov imp03, imp03 + 5
imp04 mov imp04, imp04 + 5
imp05 mov imp05, imp05 + 5

It is then correctly compiled.

The following form is also valid:

prime01 equ 2
prime02 equ 3
prime03 equ 5
prime04 equ 7
prime05 equ 11

N FOR 5
  dat prime&N
  ROF

The conjunction of FOR statements and EQU statements
----------------------------------------------------

If labels that are not stringized are declared inside FOR/ROF statements,
the result is duplicate declarations. Although in the future it might be
allowed, it is well-advised that such labels are to be declared outside of
the FOR/ROF block.

If FOR statements are declared as strings of a label name using EQU such as:

THIS EQU N FOR 3
     EQU   mov 0, 3
     EQU   ROF

The expansion of such is feasible providing that both the FOR and ROF are
present in the same label name.

Therefore, the following will not work:

THIS EQU N FOR 3
THAT EQU   ROF

THIS
 mov 0, 3
THAT

or

TEST EQU N FOR 3
 mov 0, 3
 ROF

PMARS parsing background
------------------------

Parsing is done in three steps:

1. Reading from input

2. First pass assembly

3. Second pass assembly

 o During reading: info_comment is parsed, comments to be ignored are removed,
   the remaining are copied into memory. If the first ';redcode' appears,
   all the current contents are erased from memory. Reading is continued
   until it encounters the next ';redcode'. Reading always stops when it
   encounters a line containing a word END or end-of-file.

 o During the first pass, all labels are collected. All expansions and
   removals are done in this pass. All labels before opcodes are substituted
   if they have been declared or declared otherwise. All labels after opcode
   are preserved for the second pass. This allows forward declaration
   mechanism for labels after opcode.

 o During the second pass, no labels are declared and collected. There is
   no further statement expansions and removals. All labels that have not
   been substituted are substituted. Syntax checking to meet with '88 or '94
   requirement is done in this stage.

$Id: redcode.ref,v 1.1.1.2 2022/07/04 19:53:30 iltzu Exp $
