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

[Fabrice Bellard]

Hi,

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.

- Each instruction is 16 bit wide, some are longer to integrate 16 or 32 
bit constants. 16 bit wide ops can be interesting to avoid one table 
indirection in the interpreter loop.

- Extend the ELF format for this virtual machine so that you can 
generate object and executables easily.

Fabrice.

Mirar wrote:
> > Unfortunately it is not in my hands to change the requirements.
>
>
> It was just an idea :)
>
>
> > On the other hand, if we would use TCC for JIT compiling then for
> > every new processor we would need to write a code generator wich we
> > would like to avoid.
>
>
> Nah, you would require TCC to work for every new processor. The code
> would stay the same (since it would be in C)? I didn't know you
> switched processors that often. 
>
> TCC is rather small though (a few 100k), quite comparable to an
> interpreter.
>
> Why not make a registered based byte code interpreter, it might be
> easier then rewriting tcc? (I haven't seen any answer whether tcc can
> do that yet, but...)
>
> /Mirar
>
>
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