[ODE] Report: performances, OPCODE, x86-64, GCC 4.0, etc.

[Adam D. Moss]

Tanguy Fautre wrote:
> Results:
> 32 bits: 4.2 fps
> 64 bits: 2.2 fps

Oh well, 'slower' is better than 'broken' IMHO!  And it's not
as if OPCODE is a slouch even at half the speed.

Is there a reason why this is only in the unstable branch?
I'm afraid that everything is ending up on the unstable
branch, ironically even non-dangerous stability fixes.

> So here are the new results:
> 32 bits GCC 3.3: 4.2 fps
> 64 bits GCC 3.3: 2.2 fps
> 64 bits GCC 4.0: 7.0 fps

That's amazing.  32 bits GCC 4.0 would be an interesting test
to see how much of that boost is 64-bit specific!

> Has anyone an idea why GCC is generating bad code for OPCODE?
> Is it a bug?
> from GCC?
> or from OPCODE?
> Or is it a GCC optimization being too agressive on float math?

I agree that this bug seems to have been prevailant through
enough big GCC releases now to indicate that this may be an OPCODE
problem.  The specific OPCODE code module which has the problem
has been isolated in the past (and I thought I added a GCC flag
workaround for that module, but now I can't find it; that may
have been clobbered when OPCODE ceased to need to be built
separately).  Anyway, a deep list archives search should
hopefully turn it up...

Regards,
--Adam
-- 
Adam D. Moss   -   adam at gimp.org