[brucehoult]

"impossible"?

It's a little easier than ARMv7, and orders of magnitude easier than x86, which doesn't seem to be preventing high performance x86 CPUs (at an energy use and surely silicon size penalty admittedly).

Everyone else in the RISC-V community except Qualcomm thinks the "C" extension is a good trade-off, and the reason Qualcomm don't is very likely because they're adapting Nuvia's Arm core to run RISC-V code instead, and of course that was designed for 4-byte instructions only.