Re: [Mesa3d-dev] dynamic code generation with gcc

[Stephen J B. <sj...@li...>]

On 12 Mar 2001, Josh Vanderhoof wrote:

> Gareth Hughes <ga...@va...> writes:
> 
> > Compiling this with the code Josh sent takes around 70 msec on my 700MHz
> > PIII laptop.
> > 
> >    void codegen_test( void )
> >    {
> >       printf( "hello, world!\n" );
> >    }
> > 
> > That's a long time at 60fps...
> 
> I would think you would keep a cache of the stuff that you've compiled
> to avoid re-compiling every time you want to call the routine.  So
> you're really looking at a one time start up cost.  Is there something
> where the code would change on every single frame?
 
It depends what you use this code for.

If it's for something like varying the Z buffer depth - then a large
overhead might be acceptable (although I still maintain that creating
a dependence on a C compiler is a disasterously bad decision).

If it's something like catering for a particular combination of (say)
blend mode, texture type, dither and fogging (the kind of thing that
the SGI OpenGL-for-Windoze appears to do) - then taking even a couple
of milliseconds at runtime when you first happen to see a polygon with
that combination of states would be completely unacceptable - even with
caching.

----
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