Re: [Tinycc-devel] TCC code generation for a stack based VM

[Jim Peters]

Fabrice Bellard wrote:
> I really think that a register based VM target would be simpler to add 
> to TCC, and surely faster than a stack based VM.
> 
> I suggest the following parameters:
> 
> - 3 general integer registers, 3 general double registers, load and 
> store based.
> 
> - For each instruction you have at most 3x3 = 9 versions, which you can 
> generate easily with the C preprocessor.

This 3-register plus stack approach reminds me of the Transputer:

  http://en.wikipedia.org/wiki/Transputer

Three registers were considered optimal for that design.  When
evaluating an expression, there are lots of intermediate values which
don't really need to go to/from the stack memory.

In the Transputer, if I remember correctly, the registers were also
considered void at every branch point, allowing very quick context
switches between parallel Occam 'threads', although I guess this isn't
relevant to this particular situation.

Jim

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