[virtmach] Virtual Machines and Code Representation

[Stephen Pelc]

> The rationale for using a parse tree rather than byte-codes
> is that more information is available to a specific compiler to generate
> "better" machine code, in whatever way "better" is defined
> (faster/smaller/safer/more parrallel/etc...).
If you haven't already seen it, look at the ANDF (Architecture 
Neutral Distribution Format) system developed by the UK Defence 
Research Agency, adopted by OSF at one stage, and exploited by 
Etnoteam as far as I remember.

ANDF was designed to support multiple source languages. It used 
the model of an ANDF producer (convert source to ANDF) and 
consumer (ANDF to native code). It was assumed that the consumer 
ran on a workstation class machine. Together with the need for a 
back-end linker. This prevented its adoption for direct 
compilation on small targets.

The problem with the use of higher level descriptions has always 
been that it places higher CPU requirements on the back end, 
which usually rules out use on small embedded CPUs.

--
Stephen Pelc, sfp@mpeltd.demon.co.uk
MicroProcessor Engineering Ltd - More Real, Less Time
133 Hill Lane, Southampton SO15 5AF, England
tel: +44 23 80 631441, fax: +44 23 80 339691
web: http://www.mpeltd.demon.co.uk