[gp2000]

And it could also save time. The Z-80 conditional return takes 5 cycles (or "T-States" in Zilog terminology) to execute if the condition is not met and 11 cycles otherwise. Quite worthwhile in testing for uncommon cases. Consider this routine to print a message that is terminated by nul or newline:

   PMESS  LD   A,(HL)     ; get character from message
          INC  HL         ; move message pointer to next character
          CP   10         ; newline?
          RET  Z          ; return if so
          OR   A          ; zero?
          RET  Z          ; done if so
          CALL PCHAR      ; print character
          JP   PMESS      ; keep looping

If instead of "RET Z" we had to do a conditional jump to a return it would be 10 cycles for each test instead of 5.

          CP   10
          JP   Z,DONE     ; 10 cycles, jump taken or not
          ...
          JP   PMESS
   DONE:  RET             ; 10 cycles, BTW

The conditional return just happens to be cheaper if not taken because it skips the work of popping the return address off the stack. Though purely an outcome of the implementation you can treat it as sort of a branch prediction.

Incidentally, the Z-80 also has relative branches (JR) that differ in execution time whether they are taken or not. The branch offset is a single byte so JR is only 2 bytes compared to JP's 3. A JR is 7 cycles if not taken, 12 otherwise. Again, we can treat it as a hard-coded branch prediction that predicts the branch is not taken. If space or distance to target is not a problem, a JR is faster if taken less than 60% of the time.