How to understand ARMv8 'SEVL' instruction in spin-lock?

hi experts,    

    ARMv7 spin-lock use 'WFE' instruction to wait for lock release and use 'SEV' in spin-unlock to notify all cores.   

    but ARMv8 use 'SEVL; WFE' instructions in spin-lock, and no 'SEV' in lock release.

    Why v8 use 'SEVL' in spin-lock instead of 'SEV' in lock release? what's the advantage using 'SEVL' in spin-lock?   

    Thanks for your attention!