Yeah, that's a legitimate use; it is (judging by the code) relying on the fact that it's glue between two calling conventions where the outer one has more calle

Yeah, that's a legitimate use; it is (judging by the code) relying on the fact that it's glue between two calling conventions where the outer one has more callee-saves registers, so we can save LR in a register rather than putting it on the stack.