Self Modifying Code 8051

Question

Let p0.0 be set to receive inputs and that it switches ON only once with an initial value 0f 0. Assuming that 8051 follows a regular Von Neumann Architecture , how can the number of cycles can be reduced? The code is:

BACK :JNB P0.0,SKIP
DO_SOMETHING: CALL FIRST
SKIP: CALL SECOND                
SJMP BACK

I just know that Self Modifying Code is to be used but don't know how to implement it.

Answer 1

I found the solution to it:

JNB P0.0,SKIP
DO_SOMETHING: CALL FIRST
SKIP: CALL SECOND                
NOP