SSA usage question

[Richard Kenner]

    > Then I propose that we allow VIEW_CONVERT_EXPR in a nested tree of
    > references if it doesn't change TYPE_MODE.  It will be treated as a NOP,
    > just there for type-correctness purposes.

    TYPE_MODE shouldn't matter.  Let me think about this one.

I think it does matter because if you are doing a "real" view conversion
(say a scalar to a record), you *probably* want to make a temporary of the
VIEW_CONVERSION.  But maybe not.  I'd need to think about that too.

I suggested same mode just to be safer: I'm sure that's safe, but I'm
not sure it's safe to include it if the mode changes and we don't do
that now.   I was trying to be conservative here.