What to remove after tree-ssa is merged?

[Richard Kenner]

    It _can_ be made explicit. We may not know the actual value, but for a
    given expression we do know which instance we want to extract it from
    (by walking back to a corresponding WITH_RECORD_EXPR). 

But there *is* no corresponding WITH_RECORD_EXPR when the expression
is used as a size, offset or bound: that's precisely the point.

Sure, when there is such an expression it can indeed be folded (or not even
generated at all).