What does -O3 optimize above -O2?

if you run the monkey see command with no parameters, it lists them all.  of -O, there is this:

-O,--optimization <arg>    Optimization level [0=none, 1=basic, 2=fast
                           optimizations, 3=slow optimizations] [p=optimize
                           performance, z=optimize code space]

it could have been that -O3 was added/made functional since the GDVC last fall. or there was an old slide or something..

I'm talking about a breakdown of the various "slow optimizations.". For example, the linked video describes constant folding which is likely a part of -O2.  There are probably other additional optimizations part of -O3.

What it says to me, is that with -O3, it runs slower and looks at more things that can be optimized vs -O2.  What ends up different is based on your code. It could be there's no difference, but just takes longer

That much is obvious, which is why that is not what my question is asking.

Try running your app in the sim first with O2 then O3, using view memory and the profiler to see what's different.

Thanks, sounds like this is as good an answer as I'll get.  markw65's work is impressive.