<div class="refentry" id="barrier">

<div class="titlepage"></div>

<div class="refnamediv">

<h2>Name</h2>

<p>barrier — synchronize execution of multiple shader invocations</p>

</div>

<div class="refsynopsisdiv">

<h2>Declaration</h2>

<div class="funcsynopsis">

<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">

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<td>

<code class="funcdef">void <strong class="fsfunc">barrier</strong>(</code>

</td>

<td>void<code>)</code>;</td>

</tr>

</table>

<div class="funcprototype-spacer"> </div>

</div>

</div>

<div class="refsect1" id="description">

<h2>Description</h2>

<p>

<span class="emphasis"><em>Available only in the Tessellation Control and Compute Shaders</em></span>, <code class="function">barrier</code> provides

a partially defined order of execution between shader invocations. For any given static instance of <code class="function">barrier</code>,

in a tessellation control shader, all invocations for a single input patch must enter it before any will be allowed

to continue beyond it. For any given static instance of <code class="function">barrier</code> in a compute shader, all invocations

within a single work group must enter it before any are allowed to continue beyond it.

This ensures that values written by one invocation prior to a given static instance

of <code class="function">barrier</code> can be safely read by other invocations after their call to the same static

instance of <code class="function">barrier</code>. Because invocations may execute in undefined order between these

<code class="function">barrier</code> calls, the values of a per-vertex or per-patch output variable, or any shared variable will be undefined

in a number of cases.

</p>

<p>

<code class="function">barrier</code> may only be placed inside the function <code class="code">main()</code> of the tessellation

control shader, but may be placed anywhere in a compute shader. Calls to <code class="function">barrier</code> may not

be placed within any control flow. Barriers are also disallowed after a return

statement in the function <code class="code">main()</code>.

</p>

</div>

{$pipelinestall}{$examples}

<div class="refsect1" id="versions">

<h2>Version Support</h2>

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<col style="text-align: center; " class="lastvers"/>

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<th style="text-align: left; border-right: 2px solid ; ">

</th>

<th style="text-align: center; border-bottom: 2px solid ; " colspan="12">

<span class="bold"><strong>OpenGL Shading Language Version</strong></span>

</th>

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<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>Function Name</strong></span>

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<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>1.10</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>1.20</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>1.30</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>1.40</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>1.50</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>3.30</strong></span>

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<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>4.00</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>4.10</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>4.20</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>4.30</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>4.40</strong></span>

</th>

<th style="text-align: center; border-bottom: 2px solid ; ">

<span class="bold"><strong>4.50</strong></span>

</th>

</tr>

</thead>

<tbody>

<tr>

<td style="text-align: left; border-right: 2px solid ; ">barrier</td>

<td style="text-align: center; border-right: 2px solid ; ">-</td>

<td style="text-align: center; border-right: 2px solid ; ">-</td>

<td style="text-align: center; border-right: 2px solid ; ">-</td>

<td style="text-align: center; border-right: 2px solid ; ">-</td>

<td style="text-align: center; border-right: 2px solid ; ">-</td>

<td style="text-align: center; border-right: 2px solid ; ">-</td>

<td style="text-align: center; border-right: 2px solid ; ">✔</td>

<td style="text-align: center; border-right: 2px solid ; ">✔</td>

<td style="text-align: center; border-right: 2px solid ; ">✔</td>

<td style="text-align: center; border-right: 2px solid ; ">✔</td>

<td style="text-align: center; border-right: 2px solid ; ">✔</td>

<td style="text-align: center; ">✔</td>

</tr>

</tbody>

</table>

</div>

</div>

<div class="refsect1" id="Copyright">

<h2>Copyright</h2>

<p>

Copyright © 2011-2014 Khronos Group.

This material may be distributed subject to the terms and conditions set forth in

the Open Publication License, v 1.0, 8 June 1999.

<a class="link" href="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.

</p>

</div>

</div>