title: Vectorize for output buffers with mismatching width
body: <p>I have generator that uses a <code>.vectorize(x, 8)</code> in its schedule. The issue that I face is that, if my output buffer width is not a power of 8, I'll get accesses outside the buffer! I can certainly clamp the input <code>x, y</code> to the size of the image, but I'm wondering if there's any way to do this with the <code>Output&lt;Func&gt;</code> in my generator. Perhaps I'm not looking at the problem the right way?</p>
  
  <pre><code>class BasicGenerator : public Generator&lt;BasicGenerator&gt;
  {
  public:
      Var x, y;
  
      Input&lt;Func&gt; input { "input", UInt(8), 2 }
      Output&lt;Func&gt; output { "output", UInt(8), 2 }
  
      void generate()
      {
          output(x, y) = input(x, y);
      }
  
      void schedule()
      {
          output.vectorize(x, 8).parallel(y);
      }
  };
  </code></pre>