Please explain what

     MOV  AR0,#LOW(func) 
     MOV  AR1,#HIGH(func) 
     PUSH AR0 
     PUSH AR1 
     RET 

does for you which

     LJMP func

doesn't, besides
- destroying the contents of AR0 and AR1,
- using 2 bytes on the stack for a few microseconds,
- taking 11 instruction cycles in stead of the LJMP's 3, and
- take up 11 bytes of code memory in stead of the LJMP's 3.

Please explain. I fail to see the point.