Keiko assembly language

Syntax

This section gives the syntax of Keiko assembly language programs in the form that is accepted by the bytecode assembler/linker oblink. The style of syntax description is similar to that used in the Kernighan & Ritchie book on C: a syntactic category is followed by a sequence of alternatives, each on a separate line. A subscript _opt indicates that a construct is optional.

=Lexical conventions

• Each element on its own line (nl used below to denote a line boundary)
• Blank lines and lines beginning # are ignored
• Identifiers can be any sequence of non-blank characters, including e.g. Files.Read.

Files

A Keiko file contains a heading that gives the name of the module and lists (in IMPORT directives) other modules that it depends upon. A compiler that outputs Keiko code can generate a checksum for the public interface of a module and embed this checksum in each other module that uses it, and the assembler/linker will then check across all modules in a program that the checksums are consistent. Unused checksums can be replaced by 0. The module header also contains a count of source lines in the module that is used to allocate counters for line-count profiling; this too can be replaced by 0 of profiling is not going to be used on the program.

file:
    heading bodyopt

heading:
    module-directive importsopt endhdr-directive

module-directive:
    MODULE ident checksum linecnt nl

imports:
    import-directive
    import-directive imports

import-directive:
    IMPORT ident checksum nl

endhdr-directive:
    ENDHDR nl

The body of a module constists of multi-line procedures interspersed with other single-line directives that (among other things) allocate global storage.

body:
    phrase
    phrase body

phrase:
    directive
    procedure

Directives

directive:
    DEFINE
    WORD
    LONG
    FLOAT
    DOUBLE
    STRING
    GLOVAR
    PRIMDEF

• a DEFINE directive defines a label at the current location in the data segment. That location is the address of any following data item created with another directive such as WORD, FLOAT or STRING.

Procedures

Each procedure has a heading that gives its name and some other information. This is followed by a sequence of mingled Keiko machine instructions and pseudo-operations. The pseudo-operations typically assemble into an entry in the procedure's constant pool, together with an instruction that loads the constant onto the stack.

procedure:
    proc-directive bodyopt end-directive

proc-directive:
    PROC ident 0 0 0

body:
    element
    element body

end-directive:
    END

element:
    pseudo-operation
    instruction

Pseudo-operations

LABEL
CONST
GLOBAL
FCONST
DCONST
QCONST
STKMAP
LINE