[Bf-committers] Optimization flags. Even speedier blender.

[Robert Wenzlaff]

I know we need to stick with 1 set that will work for all the platforms for 
the official release.

But as an interesting side note, I found that setting the following gcc flags 
gave me about a 30% speed boost in rendering:

-march=athlon-xp -msse -mfpmath=sse

(Average of 3 renders of blacksmith.blend:
standard flags:  Old render: 23.11s, Unified: 29.23s
modified flags:  Old render: 17.68s,  Unified: 25.41s )

It's like a free CPU upgrade.  Overclocking without the smell of burning 
fiberglass...

The -mmmx and -m3dnow flags did next to nothing.

Going from -O2 to -O3 slowed the old renderer down just a bit, but sped the 
unified renderer up.  (Probably broke a few other things, though I only 
noticed the ones already known broken by -O2 with my gcc rev - I'd love to 
see the list of reasons that lead to -O2).

The speed difference between -O2 and -O1 was about 2-3% with with the standard 
switches, but 4-5% with the -march, -msse, and -mfpmath flags set as above.

No switch gave and significant change to my draw times, but I have a rather 
speedy accelerated gfx card, so the CPU probably has very little influence 
there.

I guess to be fully sure I didn't break anything, I'd have to wait for the 
regression suite.   I think I'll run highly optimized for a while and start 
making a list.

Maybe this is the topic for an article for the do-it-yourselfers out there.
And autoconf can certainly detect some of this and set the right flags.
-- 
********************************************
Robert Wenzlaff  rwenzlaff@soylent-green.com