If you really want to go into details, please see https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
I really like the template of this code and have seen this many times , so i need to understand this!
okayyyy thank you so much sir !! 
1 Like
also this blog has a very relevant discussion, you can take a look at it https://codeforces.com/blog/entry/66279
1 Like