search for: disablea

YOu have to look for which DAG fragments are not being matched. Then you can create patterns for those using alternate sequences. When you disablea given instruction, don't just disable it, but also look at what pattern it was matching. Then create a patten for that using remaining instructions or in some cases you might have to call a library function, as in the case of floating pointing or maybe even integer multiply if you don't...

Thanks for your reply. We are trying to implement a simple Mips-based CPU with just for teaching purpose, so we delete some instructions which are not commonly used, thus the task won't be too hard for students. I am responsible for modifying the compiler so that the compiler won't emit unsupported instructions. In order to avoid "can not select" error, I am trying to expand