Gather and Scatter intrinsics in the Loop Vectorizer with llvm

I am trying to generate scatter/gather example in with llvm with no success. I am running the next example as mentioned in the llvm doc:

int foo(int * A, int * B, int n) {
  for (intptr_t i = 0; i < n; ++i)
      A[i] += B[i * 4];
}

I am compiler with the next command line:

clang ./test.cpp -save-temps -O3 -march=skylake-avx512 -mllvm -force-vector-width=512

What am I doing wrong ?