What to remove after tree-ssa is merged?

[Richard Kenner]

    For the record, I believe PLACEHOLDER_EXPR and WITH_RECORD_EXPR should
    be nodes in GENERIC, since Ada is not the only language that has variant
    records of this sort.

I'm not convinced that WITH_RECORD_EXPR needs to be there.  If you're going
to simplify the result by doing the substition, why have the node in the
first place: why not just do the substitution instead of making node?