Flags -O1 -O2 -O3

I’ve found that in ‘opt’ command, the list of transformation passes used for -O0,-O1,-O2 and -O3, is a reduced subset from the list of all the available passes available in ‘opt’ command.

So, I have couple of questions regarding that:

  • How is defined the subset of passes/flags used for -O0,-O1,-O2 and -O3

  • And how to know which flags to discard from the whole list of passes available in ‘opt’ , as the flags of the family “X86” and more of this