This is an alternate version of D115914 that handles/tests all binary opcodes. I think it is close to the same logic, but I was having a hard time making sense of the diffs/comments in that patch, so I just wrote the patch from scratch.
I suspect that we don't see these patterns too often because -simplifycfg would convert the minimal cases into selects rather than leave them in phi form (note: instcombine has logic holes for combining the select patterns too though, so that's another potential patch).
We only create a new binop in a predecessor that unconditionally branches to the final block.
https://alive2.llvm.org/ce/z/WHwAoU (not safe to speculate an sdiv for example)
https://alive2.llvm.org/ce/z/rdVUvW (but it is ok on this path)