cocom.sgml.in

<!doctype linuxdoc system>
<article>

<!-- Title information -->

<title>COCOM tool set
<author>Vladimir Makarov, <tt>vmakarov@gcc.gnu.org</tt>
<date>Apr 2, 2016
<abstract>
This document describes COCOM tool set oriented towards the creation
of compilers, cross-compilers, interpreters, and other language
processors.
</abstract>


<p>
COCOM tool set is oriented towards the creation of compilers,
cross-compilers, interpreters, and other language processors.  Now
COCOM tool set consists of the following components:

    <itemize>
    <item>Ammunition (reusable packages)
    <item>Sprut (internal representation description translator)
    <item>Nona (code selector description translator)
    <item>Msta (syntax description translator)
    <item>Oka (pipeline hazards description translator)
    <item>Shilka (keywords description translator)
    </itemize>
 
All of these components are written in ANSI C and have common style
input languages (a la YACC).  All code generated by the components is
in also strict ANSI C and in standard C++.  All documentation exists
in ASCII, Acrobat Reader, TeX dvi, Postsrcipt, HTML, and GNU info
formats.


<bf>1. Ammunition (reusable packages)</bf>

Currently there are the following packages:

   <descrip>
   <tag>allocate</tag>
        Allocating and freeing memory with automatic fixing some
        allocation errors.
   <tag>vlobject</tag>
        Work with variable length objects (VLO).  Any number of bytes
        may be added to and removed from the end of VLO.  If it is
        needed the memory allocated for storing variable length object
        may be expanded possibly with changing the object place.  But
        between any additions of the bytes (or tailoring) the object
        place is not changed.  To decrease number of changes of the
        object place the memory being allocated for the object is
        longer than the current object length.
   <tag>objstack</tag>
        Work with stacks of objects (OS).  Work with the object on the
        stack top is analogous to one with a variable length object.
        One motivation for the package is the problem of growing char
        strings in symbol tables.  Memory for OS is allocated by
        segments.  A segment may contain more one objects.  The most
        recently allocated segment contains object on the top of OS.
        If there is not sufficient free memory for the top object than
        new segment is created and the top object is transferred into
        the new segment, i.e. there is not any memory reallocation.
        Therefore the top object may change its address. But other
        objects never change address.
   <tag>hashtab</tag>
        Work with hash tables.  The package permits to work
        simultaneously with several expandable hash tables.  Besides
        insertion and search of elements the elements from the hash
        tables can be also removed.  The table element can be only a
        pointer.  The size of hash tables is not fixed.  The hash
        table will be automatically expanded when its occupancy will
        became big.
   <tag>position</tag>
        Work with source code positions.  The package serves to
        support information about source positions of compiled files
        taking all included files into account.
   <tag>errors</tag>
        Output of compiler messages.  The package serves output
        one-pass or multi-pass compiler messages of various modes
        (errors, warnings, fatal, system errors and appended messages)
        in Unix style or for traditional listing.  The package also
        permits adequate error reporting for included files.
   <tag>commline</tag>
        Work with command line.  The package implements features
        analogous to ones of public domain function `getopt'.  The
        goal of the package creation is to use more readable language
        of command line description and to use command line
        description as help output of program.
   <tag>ticker</tag>
        Simultaneous work with several tickers (timers).
   <tag>bits</tag>
        Work with bit strings (copying, moving, setting, testing,
        comparison).
   <tag>spset</tag>
        Work with expandable sparse sets of numbers.  The
        implementation is based on one descibed in "An Efficient
        Representation for Sparse Sets" by Preston Briggs and Linda
        Torczon.  Memory needed for the set is proportional to maximal
        element value in the set.
   <tag>cspset</tag>
        Work with expandable compact sparse sets of numbers.  It has
        very similar interface with `spset'.  The algorithm
        complexities of set operations in practice is the same as for
        package `spset' but have bigger constants.  Memory needed for
        the set is proportional to number of elements in the set and
        is node depended on element value.  It is implemented by
        special case hash tables.
   <tag>arithm</tag>
        Implementing host machine-independently arbitrary precision
        integer numbers arithmetic.  The implementation of the package
        functions are not sufficiently efficient in order to use for
        run-time.  The package functions are oriented to implement
        constant-folding in compilers, cross-compilers.
   <tag>IEEE</tag>
        Implementing host machine-independently IEEE floating point
        arithmetic.  The implementation of the package functions are
        not sufficiently efficient in order to use for run-time.  The
        package functions are oriented to implement constant-folding
        in compilers, cross-compilers.
   <tag>earley</tag>
        The package `earley' implements earley parser.  The earley
        parser implementation has the following features:
        <itemize>
        <item>It is sufficiently fast and does not require much
          memory.  This is the fastest implementation of Earley parser
          which I know.  The main design goal is to achieve speed and
          memory requirements which are necessary to use it in
          prototype compilers and language processors.  It parses 30K
          lines of C program per second on 500 MHz Pentium III and
          allocates about 5Mb memory for 10K line C program.
    
        <item>It makes simple syntax directed translation.  So an
          abstract tree is already the output of Earley parser.
    
        <item>It can parse input described by an ambiguous grammar.
          In this case the parse result can be an abstract tree or all
          possible abstract trees.  Moreover it produces the compact
          representation of all possible parse trees by using DAG
          instead of real trees.  This feature can be used to parse
          natural language sentences.
    
        <item>It can parse input described by an ambiguous grammar
          according to the abstract node costs.  In this case the
          parse result can be an minimal cost abstract tree or all
          possible minimal cost abstract trees.  This feature can be
          used to code selection task in compilers.

        <item>It can make syntax error recovery.  Moreover its error
          recovery algorithms finds error recovery with minimal number
          of ignored tokens.  It permits to implement parsers with
          very good error recovery and reporting.
    
        <item>It has fast startup.  There is no practically delay
          between processing grammar and start of parsing.
    
        <item>It has flexible interface.  The input grammar can be
          given by YACC-like description or providing functions
          returning terminals and rules.
    
        <item>It has good debugging features.  It can print huge
          amount of information about grammar, parsing, error
          recovery, translation.  You can even output the result
          translation in form for a graphic visualization program.
        </itemize>
   </descrip>

Current state: Implemented, documented, and tested.  All these
packages have been used in several products.

Under development: Design of some reusable packages for compilers.


<bf>2. SPRUT (internal representation description translator)</bf>

SPRUT is a translator of a compiler internal representation
description (IRD) into Standard Procedural Interface (SPI).  The most
convenient form of the internal representation is a directed graph.
IRD defines structure of the graph.  SPI provides general graph
manipulating functions.  The defined graph nodes can be decorated with
attributes of arbitrary types.

IRD declares types of nodes of the graph.  Nodes contains fields, part
of them represents links between nodes, and another part of them
stores attributes of arbitrary types.  To make easy describing
internal representation the IRD supports explicitly multiple
inheritance in node types.  There can be several levels of internal
representation description in separate files.  The nodes of one level
refer to the nodes of previous levels.  Therefore each next level
enriches source program internal representation.  For example, the
zero level representation may be internal representation for scanner,
the first level may be internal representation for parser, and so on.

SPI can contains functions to construct and destroy graphs and graph
nodes, to copy graphs or graph nodes, to read and write graphs or
graph nodes from (to) files, to print graphs or graph nodes, to check
up constraints on graph, to traverse graphs, and to transform acyclic
graphs in some commonly used manners.  SPI can also check up the most
important constraints on internal representation during work with node
fields.  SPI can automatically maintain back links between internal
representation nodes.

Using SPRUT has the following advantages:
     <enum>
     <item>brief and concise notation for internal representation
     <item>improving  maintainability  and  as consequence reliability of
        the compiler
     <item>user   is freed  from the  task  of writing large  amounts  of
        relatively simple code
     </enum>
Current state: Implemented, documented, and tested.  SPRUT has been
used in several products (the biggest one is extended Pascal
cross-compiler with moderate optimizations and with 3 different
internal representations).


<bf>3. NONA (code selector description translator)</bf>

NONA is a translator of a machine description (MD) into code for
solving code selection and possibly other back-end tasks.  The machine
description is mainly intended for describing code selection task
solution, i.e.  for determining by machine-independent way a
transformation of a low level internal representation of source
program into machine instruction level internal representation.  But
the machine description can be used also to locate machine dependent
code for solving other back-end task, e.g. register allocation.  To
describe machine description a special language is used.

An machine description describes mainly tree patterns of low level
internal representation with associated costs and semantic actions.
NONA generates the tree matcher which builds cover of low level
internal representation by the tree patterns with minimal cost on the
first bottom up pass and fulfills actions associated with the chosen
tree patterns on the second bottom up pass.  Usually the actions
contain code to output assembler instruction.

Analogous approach for solving code selection task is used by modern
generator generators such as BEG, Twig, Burg and Iburg.  The tree
matcher generated by NONA uses algorithm similar to one of BEG and
Iburg, i.e. the algorithm is based on dynamic programming during
fulfilling code selection.

Although the algorithm used by BURG and based on dynamic programming
during tree pattern matcher generation time is considerably more fast,
it is not acceptable for us.  Its main drawback which is to need usage
of less powerful machine description results in necessity of usage of
more machine-dependent low level internal representation.  For
example, the special internal representation node types for 8-bits,
16-bits constants besides 32-bits constants would be needed.  Also the
algorithm used by BURG is considerably more complex.

Tree pattern matchers generated by NONA also can work with directed
acyclic graphs besides trees.  This feature is useful when target
machine instruction is generated from the internal representation
which is result of some optimizations such as common sub-expression
elimination.

Current state: Implemented, documented (only plain text), and tested.
NONA has been used in several products (the biggest is extended Pascal
cross-compiler for superscalar RISC processor `AMD 29500' with
moderate optimizations).

Under development: Additional generation of the tree pattern matcher
based on dynamic programming during generation of the tree pattern
matcher.  Pascal implementation experience shows that time of the tree
pattern matcher work is practically the same as the time of all
front-end work.


<bf>4. MSTA (syntax description translator)</bf>

The MSTA can emulate YACC (Posix standard or System V Yacc).  The MSTA
have the following additional features:
    <itemize>
    <item>Fast LR(k) and LALR(k) grammars (with possibility resolution of
      conflicts).  Look ahead of only necessary depth (not necessary
      given k).  Originally LALR(k) parsers are generated by modified
      fast DeRemer's algorithm.  Parsers generated by MSTA are up to 50%
      faster than ones generated by BISON and BYACC but usually have
      bigger size.

    <item>Extended Backus-Naur Form (EBNF), and constructions for more
      convenient description of the scanners. More convenient
      naming attributes.

    <item>Optimizations (extracting LALR- and regular parts of grammars and
      implementing parsing them by adequate methods) which permit to
      use MSTA for generation of effective lexical analyzers.  As
      consequence MSTA permits to describe easily (by CFG) scanners
      which can not be described by regular expressions (i.e. nested
      comments).

    <item>More safe error recovery and reporting (the 1st additional
      error recovery method besides error recovery method of YACC).

    <item>A minimal error recovery and reporting (the 2nd additional
      error recovery method besides error recovery method of YACC).

    <item>Fast generation of fast parsers.
    </itemize>
Current state: Implemented, documented, and tested.  Now MSTA is
stable.  More verbose documentation is needed.

MSTA uses several methods (parser optimizations) nowhere described.


<bf>5. OKA (pipeline hazards description translator)</bf>

OKA is a translator of a processor pipeline hazards description (PHD)
into code for fast recognition of pipeline hazards.  A pipeline
hazards description describes mainly reservations of processor
functional units by an instruction during its execution.  The
instruction reservations are given by regular expression describing
nondeterministic finite state automaton (NDFA).  All analogous tools
are based only on deterministic finite state automaton (DFA).

OKA is accompanied with the scheduler on C and C++ for scheduling
basic blocks.

Current state: Implemented, documented, and tested.  OKA has been used
in experimental C/C++ compiler for Alpha.


<bf>6. SHILKA (keywords description translator)</bf>

SHILKA is oriented to fast recognition of keywords and standard
identifiers in compilers.  SHILKA is analogous to GNU package `gperf'
but based on minimal pruned O-trie which can take into account the
frequency of keyword occurrences in the program.  Gperf can not make
it.  SHILKA is up to 50% faster than Gperf.  SHILKA is also simpler
than Gperf in the usage.

Current state: Implemented, documented, and tested.

<bf>7. DINO interpreter</bf>

DINO is high level scripting dynamic-typed language.  DINO is oriented
on the same domain of applications as famous scripting languages perl,
tcl, python.  The most of programmers know C language.  Therefore Dino
aims to look like C language where it is possible.  Dino is an object
oriented languages with garbage collection.  Dino has possibilities of
concurrent execution, pattern matching, and exceptions handling.  Dino
is an extensible language with possibility of dynamic load of
libraries written on other languages.  The high level structures of
Dino are
    <itemize>
    <item>heterogenous extensible arrays
    <item>extensible associative tables with possibilities of deleting
      table elements
    <item>objects
    </itemize>
Originally, Dino was used in a russian graphics company ANIMATEK for
description of movement of dinosaurs in an project.  It has been
considerably redesigned and implemented with the aid of COCOM tool
set.

Current state: Implemented, documented, and tested.  Experimental
status.

</article>