SSA for all architectures, then delete the old compiler backend and optimize the frontend which can then assume an SSA backend and do less work. (Currently the frontend assumes a less-capable backend so has to do more work, which actually makes SSA slower)

You can read through this thread to see what people want to work on for Go 1.8.

https://groups.google.com/forum/#!topic/golang-dev/098vr4999...