The behavior differs between (the present) nightly and rustc 1.45.2; the nightly available when this link was posted matched the 1.45.2 behavior.

The output with 1.45.2 is as follows:

  example::clone_concrete:
        mov     eax, edi
        ret

  example::clone_abstract:
        mov     ecx, edi
        and     ecx, -256
        xor     eax, eax
        xor     edx, edx
        cmp     dil, 1
        sete    dl
        cmove   eax, ecx
        or      eax, edx
        ret