title: vectorization : multiply _m256i elements
body: <p>I'm looking to multiply all 32 bits integers in a register at once using SIMD instructions, this is what I tried so far :</p>
  <pre><code>  int32_t a [8] = {1, 2, 3, 4, 5, 6, 7, 8};
    int32_t b [8] = {1, 2, 3, 4, 5, 6, 7, 8};
    __m256i tmp1 = _mm256_loadu_si256((__m256i*) a);
    __m256i tmp2 = _mm256_loadu_si256((__m256i*) b);
  
    __m256 tmp3 = _mm256_mul_epi32(tmp1,tmp2);
  </code></pre>
  <p>sadly it doesn't yield correct result, this is basically what I get :
  <em>1, 0, 9, 0, 25, 0, 49, 0</em></p>
  <p>I haven't found an alternative instruction yet, any help would be appreciated.</p>