Hi!
On Fri, Dec 20, 2013 at 6:49 PM, Masur Jonathan <jma...@bluewin.ch> wrote:
> Sorry if what I'm asking is dumb.
>
> I'd like to get started helping to develop SDCC. However the first thing
> is that I should understand as well as possible how its internal works.
> I downloaded the sources and managed to compile them just fine, however
> I'd like to know how I can find documentation about the internal
> workings of the compiler at a high level but still detailed enough
> (thigns like there's a front end, an ICode representation and a Back end
> is not detailed enough). The code itself isn't quite self-explanatory
> when it comes for the high level thing.
>
> Where can I look at the feature requests and bugs list Philip mentioned ?
>
Feature requests: http://sourceforge.net/p/sdcc/feature-requests/
Bugs: http://sourceforge.net/p/sdcc/bugs/
>
> As for the features Philip mentioned, many are platform specific to
> platforms I'm not familiar with so I can't take these. I'd be willing to
> add/improve/fix anything that is not platform specific though.
>
> As for Phillip's suggestions :
>
> Variables length arrays are nice, but clearly made for systems which
> creates arrays on their execution stacks. I believe that this is not the
> case of the majority of SDCC targets, so it'll simply not be technically
> feasible.
>
> Functions that takes structs and unions and return structs and unions
> could be nice, HOWEVER returning a struct/union will be dangerous as the
> # of bytes returned by a function is not bounded anymore. This will
> complicate the calling convention significantly, especially for return
> values. In the case of returning base types only, the # of bytes
> returned is limited to something like sizeof(long) or sizeof(long long)
> depending on whether long long is implemented.
>
> Speaking of types, I will probably be hated for stating the following,
> especially as a "newcommer"; however I still want to say that. I think
> it's crazy to support 64-bit basic types, but not supporting 24-bit.
> Unlike the majority of C compilers, SDCC targets 8-bit systems. We can
> assume distributions of variables range is somewhat exponential.
> This means that the user is :
> - Very likely to want to use 8-bit data types
> - Likely to use 16-bit data types
> - Somewhat likely to use 24-bit data types
> - Unlikely to use 32-bit data types
> - Much unlikely to use 40-bit data types
> etc...
> - Extremely unlikely to use 64-bit data types
>
> So in my opinion, "long" should be 24-bit, and "long long" 32-bit. Yes,
> I know the ANSI standard states that "long should be at least 32-bit"
> BUT we have to keep in mind that SDCC's goal is to make efficient code
> for 8-bit targets and that ANSI was NOT made with this goal. So by
> departing from ANSI when required we can make a better compiler overall.
>
> So that should be the end of the part I'll be hated for.
>
I agree with you... in the hate thing, hehe!
I think ANSI compliance is really usuful for portability and I would try as
hard as possible to be close to ANSI. My 2 cents.
>
> Now I think I'd like to contribute in the machine independent
> optimisation part, and I'd be interested in doing range analysis. In
> fact I'll have to do this at a school project, so if I success I could
> attempt to implement this into SDCC.
>
> However, in the meantime I should probably start by doing something mcuh
> simpler/shorter/easier in order to get started, right ? If I can get any
> pointers, that'd be great.
>
> Sorry for the very long post and best regards,
> Jonathan
>
Regards,
Diego
>
>
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