Well, if you extend the call ICs to record multiple callees at the site, I'm assuming it would be pretty straightforward to do this for all calls.

Not sure if it's worth the effort, though.

I think most of the reason SM has polymorphic inlining for all callsites is that we added it first as a stop-gap for methodcall inlining, and then later went back and added support for method callsites (guarding directly on the receiver object's type and eliding the property lookup - which I assume is what V8 did from the start).

If you already have methodcall polymorphic inlining, the return on investment in expanding that to all callsites is perhaps pretty low.

Would be interesting to measure though..