[hatari-devel] Hatari patches for bitplane conversion

[Eero Tamminen]

Hi,

On Tuesday 21 July 2009, Kåre Andersen wrote:
> Indeed. Which brings up another point: Why are the converters
> #include'd into one source file rather than being compiled as separate
> units as would make so much more sense? It really messes up the whole
> structure of the code, as they are neither inline functions nor simple
> headers...

As the functions are declared static, they're in practice the same and you
can consider them as inline.  With GCC, specifying "inline" is pretty much
redundant; if a function is static, with optimizations enabled GCC either
inlines or directly jumps to it (depending on in how many places it's
called in the code).  You cannot help noticing this when you debug GCC
optimized code with Gdb... :-)

If you would put them to separate object files, they would need to be global
functions and would have the normal function call overhead.  If I remember
correctly, a more important reason was that then the helper functions in
screen.c (which are called from the convertors) would then need to be global
and have the normal function call overhead too.

(GCC / GAS don't support (yet) inter-object optimizations.)


> > How do you want to detect that SDL feature? Hard-coding it with #ifdefs
> > is a bad idea, IMHO.
>
> I guess there are several ways to do this, including the check for
> hardware surfaces. The safest way should nevertheless be to do a bit
> of profiling on buffer creation (that is, program start _and_ screen
> mode changes). You can do a wait for vsync, and see how much time will 
> pass in between. If its shorter than a given threshold, say 50Hz, then
> you dont have any vsync... 

I like run-time detection, but isn't it possible to do it only on Hatari
startup, why it would need to be done on each screen mode change?

(Some programs, especially for Falcon do frequent mode changes.)


> A similar test is already done to get fine
> granularity cycle timing (and the comments about OS X in that part of
> the code are wrong mind you - we have HPET just as much as linux do).

On PowerPC?  (I think Thomas' Mac is PowerPC :-))


	- Eero