Who can commit my changes? I have no rights to commit myself.

Can you add

else
  llvm_unreachable("Unexpected opcode!);

It should only be of the two shift opcodes and if for some reason that fails we should error. It also make the code behavior more obvious.

• Would you mind re-upping this with full context?

One more attempt: two commits are combined in one patch file.

Changes in code formatting and test cases according to the reviewer's comments.