[Vm-dev] macros (was: SiliconSqueak and RISC-V J Extension)

[Jecel Assumpcao Jr.]

David,

> If you replace the cpp macros with high level Smalltalk (slang), and rely
> on the inliner in CCodeGenertor to unroll the Smalltalk into inlined C code,
> then the performance of the resulting interpreter is essentially the same
> as that of the interpreter implemented with cpp macros.
> 
> This is important for two reasons:
> 
> 1) By getting rid of the cpp macros, you open up the possibility of doing
> profiling and debugging of low level functions directly with generated C code
> that is not obscured by cpp macros.

I agree it is better, but in terms of measurement inlined functions and
macros are equivalent. But:

> 2) If you want to look at time spent in individual functions that normally
> would be inlined (either because they are cpp macros, or because the
> slang inliner unrolled them in similar ways), then you can do so by
> disabling the inlining during C code generation. This produces a very
> slow VM, but one that can be easily profiled to see time spent in the
> individual functions.

Such results are way better than nothing but I think they will be
distorted. When a function is inlined you can do additional optimization
so the resulting code is not the same as in the function but without the
call/return overhead.

> I have only ever measured this in the interpreter VM (see package
> MemoryAccess in the VMMaker repository), but it would be reasonable to
> expect similar results with oscog, at least with respect to the base
> interpreter and primitive functions.

Like I said, I am interested both in the interpreter and in compiled
code. Thanks for the tip!

-- Jecel