Question

Write a program in LEGv8 assembly to copy a null-terminated ASCII string from array y to array x; converting every 'a' character in the source string to 'b' in the destination string. In other words, for each character in array y: else Assume that the base address of the arrays x and y are in registers X0 and X1, respectively. The ASCII code for characters 'a' and 'b' is 113 and 114 respectively [25 pts]. * Null-terminated means that a zero character shows the end of the string.

Answer 1

      ADD X9,XZR,XZR       // i = 0 + 0 = 0

L1: ADD X10,X9,X1       // X10 = addr of y[i]

      LDURB X11,[X1,#0] // X11 = y[i]

      ADD X12,X9,X0      // X12 = addr of x[i]

      SUBI X13,X11,#113

      B.NQ L2

      ADD X11,XZR, #114     //X11 = 'b'

L2: STURB X11,[X12,#0]      // x[i] = y[i]

      CBZ X11,L3 // if y[i] == 0 then exit

      ADDI X9,X9,#1   // i = i + 1

      B L1 // next iteration of loop

L3: HLT

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