Question

1. For the following C statement, what is the corresponding RISC-V assembly code? Assume that the variables f, g, h, and i are given and could be considered 32-bit integers as declared in a C program. Assume your own memory addresses and registers to be used.

• f = g + (h − 5);
• B[8] = A[i−j];

addi $t0, $t1,-5

add $t2, $t0, $t3

A is in $S6, B is in $S7

Answer 1

Solution:

I am assuming  variables f, g, h, i, and j are assigned to registers x1, x2, x3, x4, and x5, and the base address of the arrays A and B are in registers s6 and s7, respectively.

1. RISC-V assembly code for f = g + (h − 5);

addi x0, x3, -5 #equivalent to x0 = h - 5 where x0 is temporary register

add x1, x2, x0 #equivalent to x1 = x2 + x0 that is f = g + ( h - 5)

2. RISC-V assembly code for B[8] = A[i−j];​​​​​​​

sub s0, x4, x5 #equivalent to x0 = i - j where s0 is temporary register

add s1, s6, s0 #equivalent to s1 = &A[i-j] where s1 is temporary register

lw s2, 0(s1) #equivalent to s2 = A[i-j] where s2 is temporary register

sw s2, 32(s7) #equivalent to B[8] = A[i-j]

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