Replication -O3 optimizations manually

Hi Stefano,

Thank you for the suggestions!

Actually, I tried to compile the same input file with and without -O3 at llc level, and I noticed no difference (the binary was the same), but I will double check it with a different input code.

I will also collapse step 3, 4, 5 as you suggested.

Thanks again!

Best regards

Emanuele Del Sozzo