What is the simplest, most readable and straightforward way to raise an illegal instruction in RISC-V on purpose?

I know that per spec any "full zero" instruction (so 32/16 bits only zeros) is a "Defined Illegal Instruction" (section 12.5, user spec). But I have no idea if there exists an asm shorthand for that (at least I could not find any) that I could then use in inline asm in C code.

There must surely be a portable and reliable way to always cause an illegal instruction exception? I personally find writing to read-only registers or similar hacks quite offputting, as they are not very explicit. But maybe this is just how its done?

Thank you in advance

CodePudding user response：

The mnemonic for it is unimp. It is documented in the RISC-V asm manual, so it should be portable.