Fortran array slices and -frepack-arrays

[Wilco Dijkstra]

Hi,

I posted this on gcc-patches (https://gcc.gnu.org/ml/gcc/2018-04/msg00090.html) not realizing
there is a dedicated Fortran list:

I looked at a few performance anomalies between gfortran and Flang - it appears array slices
are treated differently. Using -frepack-arrays fixed a performance issue in gfortran and didn't
cause any regressions. Making input array slices contiguous helps both locality and enables
more vectorization.

So I wonder whether it should be made the default (-O3 or just -Ofast)? Alternatively would
it be feasible in Fortran to version functions or loops if all arguments are contiguous slices?

Wilco