[OpenBIOS] PATCH: Implement Forth source debugger for OpenBIOS

[Blue Swirl]

On Mon, Nov 2, 2009 at 8:15 PM, Segher Boessenkool
<segher at kernel.crashing.org> wrote:
>> Interesting - thanks for your comments on this. I'd like to get an idea as
>> to what kind of impact the patch has as it stands. Is there a standard
>> benchmark for Forth implementations?
>
> No standard, no.  It wouldn't matter anyway, you can measure this
> slowdown on _any_ code.
>
>> Or alternatively some word implementations that will stretch the kernel,
>> for example Fibonacci, Mandelbrot etc. that I can use for comparison?
>
> Sure, fib or mandel will do.
>
>> performance critical, I think it is acceptable to allow a slight
>> degradation in speed over the ease of use of debugging.
>
> Yes, but my point is your patch does not cause a "slight" slowdown
> (I haven't measured it though!), while standard techniques cause no
> slowdown at all.
>
>>> Did you try to change the actual compiled Forth code at runtime?  That's
>>> how
>>> all other Forth debuggers do it.
>>
>> Possibly; there are probably several ways in which you can implement
>> something like this.
>
> My point is that your strategy has some severe disadvantages.  Just run
> the benchmarks and then someone can decide if it's worthwhile.  My
> opinion would be that it is not worth it, since it inserts code into
> the "hot path" while that's not necessary at all.

The debug stuff could be made a compile time option. We could even
enable the debugging for non-release versions, so release versions
would not suffer.