[Bug fortran/81615] save-temps and gfortran produces *.f90 files instead of *.i or *i90 files

["barrowes at alum dot mit.edu" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81615

--- Comment #2 from Ben Barrowes <barrowes at alum dot mit.edu> ---
Then how does one get a preprocessed/savetemp file from an existing *.f90 file?

In the case of C, preprocessed and temp files have different extensions and are
thus easily identified after compiling. For gfortran,
preprocessing/saveingtemps of *.f files produces *.f90 files which is
confusing, and preprocessing/savetemps of *.f90 files produces no output.

Gfortran needs to produce preprocessed/savetemps that have unique and easily
identifiable extensions. If not *.i and *.i90, then something else like *.t and
*.t90 or similar.