Question

Generate code for the following three-address statements assuming a and b are arrays whose elements are 4-byte values. Also, compute the cost involved.

(a) x=a[i]+b[j]
(b) x=a[i]∗b[j]
(c) x=a[i]/b[j]
(d) x=a[i]−b[j]

Answer 1

The correct code for the three-address statement Option A. x = a[i] + b[j] involves loading the addresses of a and b, adding the indexes multiplied by the size of each element, loading the values from memory, adding them together, and storing the sum in the register holding x.

Step-by-step explanation:

The correct answer is option (a)

The three-address code for the statement x = a[i] + b[j] would be:

1. Load the address of a into a register (e.g., R1)
2. Add the index i multiplied by the size of each element (4 bytes) to the register holding the address of a to get the address of a[i] (e.g., R2)
3. Load the value from the address in R2 into a register (e.g., R3)
4. Load the address of b into a register (e.g., R4)
5. Add the index j multiplied by the size of each element (4 bytes) to the register holding the address of b to get the address of b[j] (e.g., R5)
6. Load the value from the address in R5 into a register (e.g., R6)
7. Add the values in R3 and R6
8. Store the sum in the register holding x (e.g., R7)

The cost involved in this operation would be the cost of loading the addresses and values from memory, which depends on the architecture being used.