Equivalent gfort and ifort compilation

Overall, in many cases from my experience, on Linux, ifort and gfortran have similar performance. ifort usually 10-20% faster, but the difference are not very big. However, it seems on windows, with the same flags, gfortran can be 7 times slower than its performance on Linux. Intel’s performance is consistent on windows and Linux.
You may begin with the following flags.
For ifort,

-O3 -xHost

For gfortran

-O3 -march=native

Both can be used with perhaps one single flag,
For ifort,

-fast

For gfortran

-Ofast

See also,