In a bunch of places where we had several calls to AddAllArgs, the new overload accepting an ArrayRef can be used.
But there is actually an observable difference: the old way re-ordered the rendered arguments across groups; but within a single group, they appear in-order as originally expressed.
The new behavior preserves original order throughout, and I assume that this is generally to be preferred.
It would be strange indeed if the driver was required to alter the order as written (at least not without a comment saying "We need to reorder these...").
Which is to say, I think that being faithful to what the user supplied should not be wrong.
Patch depends on http://reviews.llvm.org/D11597