[Bug fortran/102043] [9/10/11/12 Regression] Wrong array types used for negative stride accesses, gfortran.dg/vector_subscript_1.f90 FAILs

[mikael at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102043

--- Comment #35 from Mikael Morin <mikael at gcc dot gnu.org> ---
A little status update.

I have pushed the latest patch attached to this PR a little further, but not
far enough to reduce the number of testsuite regressions to 0.

I plan to submit it for gcc-13, but it won’t make it for gcc-12.

(In reply to Richard Biener from comment #33)
> With
> a single dimension there's not much value in using ARRAY_REF over
> pointer arithmetic and dereference.

I have tried to fix this PR using pointer arithmetic too.
But there are so many places in the frontend where we expect to have an array
type when dereferencing a descriptor pointer, that it’s not as simple as it
seems and I finally convinced myself that the patch attached to this PR was the
best way to go.

For gcc-12, is there a way to add a middle-end workaround using annotations on
descriptor types (a lang flag or something) ?