For the sake of example, I will assume that you are working with
32-bit addressing and 32-bit words.
The same approach works for double-words, half-words, etc., but the exact instructions are different.
1) First allocate the Array.
For performance reasons make sure that it is aligned on a 4-byte boundary.
2) Make sure all the three variables are in registers.
I will assume that
x2 contains the starting address of Array
x3 contains the value of i
x4 contains the value of c
3) Rewrite the C array statement into indirect addressing of a char array
Array[i] = c; becomes *((char *)Array + 4*i) = c;
The reason for casting the array into (char *) is because RISC-V accesses memory using byte addresses.
In contrast, C would automatically provide access with 4-byte addresses.
4) Convert to instructions.
I choose to be wasteful with registers, assuming that you do not want to overwrite the contents of x2, x3, x4.
But if you can overwrite them, you could reuse the registers for temporary results.
SLLI x13,x3,2 # x13 = x3 << 2 which provides x13 = 4*i
ADD x12,x2,x13 # x12 = x2 + x13 which provides x12 = (char *)Array + 4*i
SW x4,0(x12) # *x12 = x4
