The loop body to optimize is:
        for (int i = 0; i < size; i++) {
            long j = i * UNSAFE.ARRAY_INT_INDEX_SCALE;

            j = Objects.checkIndex(j, size * 4);

            if (((base + j) & 3) != 0) {
                throw new RuntimeException();
            }

            v += UNSAFE.getInt(base + j);
        }

loop iv is first scaled, result is then casted to long, range checked and finally address of memory location is computed.