[flang] correctly deal with bind(c) derived type result ABI (#111969)

Derived type results of BIND(C) function should be returned according
the the C ABI for returning the related C struct type.

This currently did not happen since the abstract-result pass was forcing
the Fortran ABI for all derived type results.
use the bind_c attribute that was added on call/func/dispatch in FIR to
prevent such rewrite in the abstract result pass, and update the
target-rewrite pass to deal with the struct return ABI.

So far, the target specific part of the target-rewrite is only
implemented for X86-64 according to the "System V Application Binary
Interface AMD64 v1", the other targets will hit a TODO, just like for
BIND(C), VALUE derived type arguments.

This intends to deal with #102113.

This is a re-land of #111678 with an extra commit to keep rewriting `type(c_ptr)`
results to `!fir.ref<none>` in the abstract result pass regardless of the ABIs.

0 files changed, 0 insertions, 0 deletions