253 lines
7.5 KiB
Plaintext
253 lines
7.5 KiB
Plaintext
GNU CHILL: A Complete CHILL Implementation
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CHILL (the CCITT High Level Language) is a strongly-typed, block
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structured language designed primarily for the implementation of large
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and complex embedded systems. Tens of millions of lines of CHILL code
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exist, and about 15,000 programmers world-wide use CHILL. Many
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central-office telephone switching systems use CHILL for their control
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software.
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CHILL was designed to
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- enhance reliability and run time efficiency by means of extensive
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compile time checking;
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- provide sufficient flexibility and power to encompass the required
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range of applications and to exploit a variety of hardware;
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_ provide facilities that encourage piecewise and modular development
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of large systems;
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- cater to real-time implementations by providing built-in concurrency
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and time supervision primitives;
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- permit the generation of highly efficient object code;
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- facilitate ease of use and a short learning curve.
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CHILL is specified in the "Blue Book":
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CCITT High Level Language (CHILL) Recommendation Z.200
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ISO/IEC 9496, Geneva 1989 ISBN 92-61-03801-8
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Cygnus Support has completed the first level implementation of the
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GNU CHILL compiler. Our compiler now supports the core features of
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the CHILL language. Our goal is a fully retargetable, complete
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implementation of the Z.200 specification. The next phase of
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implementation will include:
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. a minimal real-time kernel for demonstration use
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. more rigorous type checking
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. retargetable input/output
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. interprocess communications
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. fully compliant exception handling.
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The State of the Implementation
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The GNU CHILL compiler is in early beta state, performing correct
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compilation and execution of correctly coded programs. Like most
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CHILL compilers, the GNU compiler implements a large subset of the
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language (as described below).
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Since it uses the same compiler back-ends as the GNU C and C++
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compilers, GNU CHILL is almost instantly available on all
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platforms supported by GNU C, including the following:
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m680xx, i960, i80x86, AMD29K, R3000, R4000, SPARClite,
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Hitachi H8 and SH families, Z8001/2
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It has been specifically tested under SunOS on SPARCs and under
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SCO Unix on 80386s.
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All of the GCC optimizations apply to CHILL as well, including
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function inlining, dead code elimination, jump-to-jump elimination,
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cross-jumping (tail-merging), constant propagation, common
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subexpression elimination, loop-invariant code motion, strength
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reduction, loop unrolling, induction variable elimination, flow
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analysis (copy propagation, dead store elimination and elimination
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of unreachable code), dataflow-driven instruction scheduling, and
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many others.
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I/O statements are parsed. The anticipated timeframe for I/O code
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generation is Q1 1994.
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What's Next
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The multi-tasking functions require a small real time kernel.
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A free implementation of such a kernel is not yet available.
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We plan to offer a productized P-threads interface in Q2 1994.
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Other runtime functions involving strings and powersets are
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working.
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GDB, the GNU Debugger, has been modified to provide simple CHILL
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support. Some CHILL expressions are not yet recognized.
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For those who aren't familiar with CHILL, here's a small but
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useful example program:
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--
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-- Convert binary integers to decimal-coded ASCII string
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--
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vary1: MODULE
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-- include declarations so we can output the test results
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<> USE_SEIZE_FILE 'chprintf.grt' <>
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SEIZE chprintf;
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-- create a new name for the CHAR array mode
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SYNMODE dec_string = CHAR (6) VARYING;
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int_to_dec_char: PROC (decimal_num INT IN)
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RETURNS (dec_string);
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DCL neg_num BOOL := FALSE; -- save sign of parameter
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DCL out_string dec_string;
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IF decimal_num < 0 THEN -- positive numbers are easier
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decimal_num := -decimal_num;
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neg_num := TRUE;
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FI
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IF decimal_num = 0 THEN
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out_string := '0'; /* handle zero */
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ELSE
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out_string := '';
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DO WHILE decimal_num /= 0; -- loop until number is zero
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-- concatenate a new digit in front of the output string
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out_string := CHAR (ABS (decimal_num REM D'10) + H'30)
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// out_string;
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decimal_num := decimal_num / D'10;
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OD;
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IF neg_num THEN
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-- prepend a hyphen for numbers < zero
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out_string := '-' // out_string; -- restore sign
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FI;
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FI;
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RESULT out_string; -- remember result
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decimal_num := 0; -- reset for next call
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neg_num := FALSE;
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out_string := ' ';
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END int_to_dec_char;
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/* Try some test cases */
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chprintf (int_to_dec_char (123456), 0);
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chprintf ("^J", 0);
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chprintf (int_to_dec_char (-654321), 0);
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chprintf ("^J", 0);
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chprintf (int_to_dec_char (0), 0);
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chprintf ("^J", 0);
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END vary1;
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Completeness
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GNU CHILL currently supports the following features. This outline
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generally follows the structure of the Blue Book specification:
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CCITT High Level Language (CHILL) Recommendation Z.200
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ISO/IEC 9496, Geneva 1989 ISBN 92-61-03801-8
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Modes (types)
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no DYNAMIC modes yet
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discrete modes
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integer, boolean, character, real
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multiple integer/real precisions (an extension)
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set modes, range modes
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powersets
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references
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(no ROW modes)
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procedure modes
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instance modes
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event modes
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buffer modes
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(no input/output modes yet)
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(no timing modes yet)
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composite modes
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strings
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arrays
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structures
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VARYING string/array modes
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(type-checking is not fully rigorous yet)
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forward references
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Expressions
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literals
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tuples
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slices, ranges
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the standard operators
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Actions (statements)
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assignments
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if .. then .. else .. fi
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cases
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do action
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do .. with
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exits
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calls
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results/returns
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gotos
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assertions
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cause exception
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start/stop/continue process
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Input/Output
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(not yet)
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Exception handling
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fully compiled, but exceptions aren't
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generated in all of the required situations
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Time Supervision
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(syntax only)
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Inter-process communications
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delay/delay case actions
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send signal/receive case actions
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send buffer/receive case actions
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Multi-module programming
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Seize/grant processing
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multiple modules per source file
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Bibliography
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This list is included as an invitation. We'd appreciate hearing
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of CHILL-related documents (with ISBN if possible) which aren't
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described here. We're particularly interested in getting copies
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of other conference Proceedings.
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CCITT High Level Language (CHILL) Recommendation Z.200
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ISO/IEC 9496, Geneva 1989 ISBN 92-61-03801-8
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(The "blue book". The formal language definition; mostly a
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language-lawyer's document, but more readable than most.)
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Study Group X - Report R 34
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This is the May 1992 revision of Z.200.
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An Analytic Description of CHILL, the CCITT high-level
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language, Branquart, Louis & Wodon, Springer-Verlag 1981
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ISBN 3-540-11196-4
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CHILL User's Manual
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CCITT, Geneva 1986 ISBN 92-61-02601-X
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(Most readable, but doesn't cover the whole language).
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Introduction to CHILL
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CCITT, Geneva 1983 ISBN 92-61-017771-1
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CHILL CCITT High Level Language
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Proceedings of the 5th CHILL Conference
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North-Holland, 1991 ISBN 0 444 88904 3
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Introduction to the CHILL programming Language
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TELEBRAS, Campinas, Brazil 1990
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CHILL: A Self-Instruction Manual
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Telecommunication Institute - PITTC
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Available from KVATRO A/S, N-7005 Trondheim, Norway
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Phone: +47 7 52 00 90
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(Great discussion of novelty.)
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Some of these documents are available from Global Engineering
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Documents, in Irvine, CA, USA. +1 714 261 1455.
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