You can just try the instructions with an off-the-shelf assembler. They're not supported.

Unless you have to toggle an MSR, of course…

I’m kind of interested about what happens if you throw random opcodes at processors now!

You might be interested in sandsifter [0], which does precisely that!

[0]: https://github.com/xoreaxeaxeax/sandsifter

I would guess the processor would just cause an exception/interrupt and it would just call an OS level exception/interrupt handler which would probably tell the user what the exception/interrupt was that occured; in this case an unsupported instruction.

I believe most processors have undocumented opcodes. Often used for internal debugging or similar.

Your program will crash with SIGILL.