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| 1 : | anton | 1.4 | 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. | ||
| 4 : | |||
| 5 : | This file is about Vmgen-specific issues. Issues affecting both | ||
| 6 : | Gforth and Vmgen (e.g., platform compatibility) are discussed in | ||
| 7 : | README. | ||
| 8 : | |||
| 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: | ||
| 13 : | anton | 1.1 | |
| 14 : | add ( i1 i2 -- i ) | ||
| 15 : | i = i1+i2; | ||
| 16 : | |||
| 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. | ||
| 24 : | |||
| 25 : | Vmgen has special support for stack-based VMs (but it can also be | ||
| 26 : | used to advantage when implementing a register-based VM). | ||
| 27 : | |||
| 28 : | anton | 1.4 | Changes in Vmgen from earlier releases are explained in NEWS.vmgen. |
| 29 : | anton | 1.1 | |
| 30 : | anton | 1.4 | After installation the documentation is available in info form and in |
| 31 : | printable form (doc/vmgen.ps). | ||
| 32 : | |||
| 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. | ||
| 35 : | |||
| 36 : | To report a bug, use | ||
| 37 : | <https://savannah.gnu.org/bugs/?func=addbug&group_id=2672>. For | ||
| 38 : | discussion on Vmgen (e.g., how to use it), use the | ||
| 39 : | bug-vmgen@mail.freesoftware.fsf.org mailing list (use | ||
| 40 : | <http://mail.gnu.org/mailman/listinfo/help-vmgen> to subscribe). | ||
| 41 : | anton | 1.1 | |
| 42 : | You can find vmgen at http://www.complang.tuwien.ac.at/anton/vmgen/. | ||
| 43 : | |||
| 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 : | anton | 1.4 | Gforth (read INSTALL for instructions). |
| 47 : | anton | 1.1 | |
| 48 : | anton | 1.4 | Note that future versions of vmgen may require small changes in |
| 49 : | programs written for the present version (e.g., requiring a few | ||
| 50 : | anton | 1.1 | additional macro definitions). |
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