fold_convert question

[Richard Kenner]

    What I don't understand is why have two different ARRAY types in the
    first place?

Two different subtypes, for example.

    This seems very inefficient.  As a new GCC developer I would like to
    see that types be correctly done in the front-end and middle-end.
    Saying two types are compatible but having a VIEW_CONVERT is just
    wrong.

No, it's not.  In the GENERIC tree, we require that the tree be precisely
type-correct.  The VIEW_CONVERT_EXPR serves that purpose.  For GIMPLE,
we weaken the type-correctness to compatible types.  At that point, the
VIEW_CONVERT_EXPR isn't needed and is removed.