Sure; I don't think anyone raised concerns about introducing SSA nodes per se. The issue is mostly about whether the rest of this MR (and by extension future dxil patches) should depend on that (and by extension the 1.9 release).
That makes more sense to me. Personally I wasn't even considering 1.9, and if I was, I would figure that if we're late enough in the release process to be that concerned, we wouldn't want to accept this anyway. I can see why we'd accept isolated changes to the sm6 stuff, though.
[I also did not consider GLSL or MSL, although having done so, I feel like we can translate those to an appropriately-namespaced temp? I.e. it shouldn't be that hard? It's not taking advantage of the SSA part, but it'd at least work.]
I think there is a bit of a tradeoff here, if we do use SSA eventually... namely, the unused complexity it adds to vsir, versus the cost of asking Conor to rewrite his patches just so he can un-rewrite them later. I'm still inclined to say the latter outweighs the former, and if that means we have to wait for 1.9 so be it. But I won't belabor the argument.