Ángel González wrote: > > I got good results (code apparently better) using -O3 in avr instead of > -Os. Just the skipped instructions in the prologue and epiloques may be > worth it. It may that since on avr you have one cycle per instruction > (except branches), when optimizing for speed, you indirectly also > optimize the number of instructions. However, I was using C, not C++, so > the different way of coding could lead to worse optimizations. > I recommend giving gcc as much information as possible, and watch the > generated code. I got gcc to perform a few tricky optimizations, and in > one case, I manually unrolled a loop for him (otherwise, it didn't > notice it could be optimized). If you see a very bad instance of code > generation, open a bug. :) > What difference do you have from -Os to -O3 ? Very often I also prefer O3 over Os, but this time Os seems to generate beter results. That's probably because I leart how to program on avr using c++ (templates rules ;) ) and my program is almost always perfectly optimized. Only sometimes I get some weird behaviour when code becomes bigger. regards -- Michał Walenciak gmail.com kicer86 http://kicer.sileman.net.pl gg: 3729519
