File:  [gforth] / gforth / README.vmgen
Revision 1.4: download - view: text, annotated - select for diffs
Thu Aug 22 20:07:33 2002 UTC (19 years, 5 months ago) by anton
Branches: MAIN
CVS tags: HEAD
Getting ready for the Vmgen release
New snapshot dates, various documentation changes, Makefile and configure fixes

    1: Vmgen supports the construction of interpretive systems by generating
    2: the code for executing and dealing with virtual machine (VM)
    3: instructions from simple descriptions of the VM instructions.
    5: This file is about Vmgen-specific issues.  Issues affecting both
    6: Gforth and Vmgen (e.g., platform compatibility) are discussed in
    7: README.
    9: Vmgen generates code for executing VM instructions (with optional
   10: tracing), for generating VM code, for disassembling VM code, and for
   11: profiling VM instruction sequences.  A VM instruction description
   12: looks like this:
   14: add  ( i1 i2 -- i )
   15: i = i1+i2;
   17: Vmgen supports several techniques for writing efficient interpreters:
   18: virtual machine interpreters, threaded code, combining VM instructions
   19: into superinstructions, keeping the top-of-stack in a register,
   20: scheduling the dispatch of the next VM instruction, and a couple of
   21: minor optimizations.  Interpreters created with vmgen usually are
   22: faster than competing interpreters and are typically only a factor of
   23: 2-10 slower than the code generateed by native-code compilers.
   25: Vmgen has special support for stack-based VMs (but it can also be
   26: used to advantage when implementing a register-based VM).
   28: Changes in Vmgen from earlier releases are explained in NEWS.vmgen.
   30: After installation the documentation is available in info form and in
   31: printable form (doc/
   33: There is a simple usage example in vmgen-ex (and a variation on that
   34: in vmgen-ex2).  See the documentation for more information on that.
   36: To report a bug, use
   37: <>.  For
   38: discussion on Vmgen (e.g., how to use it), use the
   39: mailing list (use
   40: <> to subscribe).
   42: You can find vmgen at
   44: Vmgen is currently distributed with Gforth (because it needs Gforth to
   45: run, and Gforth needs it to build), and is installed together with
   46: Gforth (read INSTALL for instructions).
   48: Note that future versions of vmgen may require small changes in
   49: programs written for the present version (e.g., requiring a few
   50: additional macro definitions).

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