offset = 1*i    if A is a  byte typed array

  offset = 2*i    if A is a short typed array

  offset = 4*i    if A is an  int typed array

     x  <<  1   ≡    2 * x 
     x  <<  2   ≡    4 * x 

          x                  x << 1               x << 2 
     ----------------------------------------------------------
      00000011 (= 3)     00000110 (= 2*3)    00001100 (= 4*3)

   ldrXX  rN, [rN, rk, LSL #n] // Advanced load instruction for arrays

   strXX  rN, [rN, rk, LSL #n] // Advanced load instruction for arrays

        memory address = rN + ( rk << n )

 i.e.:  memory address = rN +   2n*rk  

  ldrsb  rN, [rN, rk, LSL #0]   // Load byte data at array index rk

  ldrsh  rN, [rN, rk, LSL #1]   // Load short data at array index rk

  ldr    rN, [rN, rk, LSL #2]   // Load int data at array index rk