unable to vectorize copy statement

I am trying to vectorize copy statement in LLVM but unable to do so why? my code is follows:

int main()


int c[2048], a[2048];

for (int j=0; j<2048; j++)

{ a[j]=2;
c[j] = a[j];



the command is follows:
opt -S -O3 -force-vector-width=64 s.ll -o s_o3.ll

how to do this?

Nothing uses the array after the loop and the program exits after that. Thus the compiler optimized out the loop because the computation was unnecessary. It had not affect on the observable behavior of the program.

This seems to work, although I'm not entirely sure about the -force-vector-width=64.