Comment by wren6991

I feel like the author might be slightly missing the point here:

> The whole premise of fusion is predicated on the idea that it is valid for a core to transform code similar to the branchy code on the left into code similar to the branch-free code on the right.

The idea of Zicond afaict is that the compiler transforms select sequences into (usually multiple) Zicond instructions, and cores with more register ports available can fuse Zicond compounds into more complex select macro-ops. It's a 2R1W vocabulary for describing selects which require more than 2 read ports.

As an aside I evaluated Zicond on my scalar 3-stage implementation and found that at 1 CPI for ALU ops and 2-cycle taken branch cost, the branchless sequences GCC produced for Zicond were never better and sometimes worse than the equivalent branching sequence. It really does seem to be targeting bigger cores, or constant-time execution