title: How to determine if memory is aligned?
body: <p>I am new to optimizing code with SSE/SSE2 instructions and until now I have not gotten very far. To my knowledge a common SSE-optimized function would look like this:</p>
  
  <pre><code>void sse_func(const float* const ptr, int len){
      if( ptr is aligned )
      {
          for( ... ){
              // unroll loop by 4 or 2 elements
          }
          for( ....){
              // handle the rest
              // (non-optimized code)
          }
      } else {
          for( ....){
              // regular C code to handle non-aligned memory
          }
      }
  }
  </code></pre>
  
  <p>However, how do I correctly determine if the memory <code>ptr</code> points to is aligned by e.g. 16 Bytes? I think I have to include the regular C code path for non-aligned memory as I cannot make sure that every memory passed to this function will be aligned. And using the intrinsics to load data from unaligned memory into the SSE registers seems to be horrible slow (Even slower than regular C code).</p>
  
  <p>Thank you in advance...</p>