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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - r600/sb: clobbers gl_Position -> gl_FragCoord"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=104143">104143</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>r600/sb: clobbers gl_Position -> gl_FragCoord
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>Mesa
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>git
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>x86-64 (AMD64)
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux (All)
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Drivers/Gallium/r600
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>dri-devel@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>gw.fossdev@gmail.com
          </td>
        </tr>

        <tr>
          <th>QA Contact</th>
          <td>dri-devel@lists.freedesktop.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=135998" name="attach_135998" title="piglit drawing output with sb enabled">attachment 135998</a> <a href="attachment.cgi?id=135998&action=edit" title="piglit drawing output with sb enabled">[details]</a></span>
piglit drawing output with sb enabled

With a variation of the piglit 

    spec/glsl-1.10/execution/variable-indexing/vs-output-array-vec2-index-wr

r600/sb clobbers the gl_Position/gl_FragCoord.

The variation consists in replacing two arrays of vec2 by one array of vec4 and
swizzling the elements to achieve the same result (by effectively interleaving
the two arrays). 

A few observations: 

* As can be seen from the colour coding screen shots, the array content is  
correctly passed from the vertex shader to the fragment shader. 

* The error only occurs for the uniform index value 0. 

* When passing an additional parameter that contains a copy of gl_Position,
then   this parameter seems to have the correct value (i.e. the vertex shader
correctly evaluates gl_Position).

* The byte code doesn't doesn't give any obvious indication why things go wrong
with the optimized shader. 

My mesa is at fa8c1b92b7. 

best, 
Gert</pre>
        </div>
      </p>


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