[PATCH] Avoid introducing TREE_OVERFLOWs in (T)(x&cst) -> (T)x & (T)cst optimization (PR middle-end/19857)

[Richard Kenner]

    Sorry if this has already been mentioned, but I think your patch might
    be harmful to the Ada compiler, at least without specific
    counter-measures.  My understanding is that gigi relies on
    TREE_OVERFLOW being set by fold to issue warnings and detect
    CONSTRAINT_ERRORs at compile-time.  And, in some cases, that's vital
    (from Ada's viewpoint) because things would wrap around in the
    target's arithmetics, hence would go unnoticed at run-time.

I agree with you and have said that before. I was assured there'd be no
changed in the visible handling of TREE_OVERFLOW.