Reply To: Introduction to the Mill CPU Programming Model

There are many types of “efficiency” and you got me thinking about power economy, which is a very important aspect to all this:

There is the opportunity for multi-cycle instructions to fast-path NaRs, and I’m particularly thinking about monsters like multiply… whereas a real multiply takes a lot of power especially for large operand widths and vectors, a NaR can cause a cheap short cicuit so you can make substantial gains in power efficiency with speculation verses the hardware needed to do prediction.