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  19     <label>OpenMP Info</label>
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  24     <label>Quick Links</label>
  25     <a href="https://lists.llvm.org/mailman/listinfo/openmp-dev">openmp-dev</a>
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  33   <!--*********************************************************************-->
  34   <h1>OpenMP&reg;: Support for the OpenMP language</h1>
  35   <!--*********************************************************************-->
  36
  37   <p>The OpenMP subproject of LLVM contains the
  38      components required to build an executable OpenMP program that are
  39      outside the compiler itself.
  40   </p>
  41
  42   <p>Here you can find :-
  43     <ul>
  44       <li>
  45         the code for the runtime library against which
  46         code compiled by <tt>clang -fopenmp</tt> must be linked before it
  47         can run.
  48       </li>
  49       <li>
  50         the library that supports offload to target devices (in
  51         "libomptarget")
  52       </li>
  53     </ul>
  54   </p>
  55
  56   <p>Support for the parts of the OpenMP 4.0 (and later) language that are not
  57   associated with the "target" constructs are contained in the
  58   "runtime" directory. Support for offloading computation via the
  59   "target" directive is in the separate "libomptarget" directory.
  60   </p>
  61
  62   <p>All of the code here is <a
  63      href="https://llvm.org/docs/DeveloperPolicy.html#copyright-license-and-patents">dual licensed</a>
  64      under the MIT license and the UIUC License (a BSD-like license).
  65      The LICENSE.txt file at the top of the OpenMP project contains
  66      the license text and associated patent grants.
  67   </p>
  68
  69   <!--=====================================================================-->
  70   <h2 id="dir-structure">Status</h2>
  71   <!--=====================================================================-->
  72
  73    <p>With the release of Clang 3.8.0, OpenMP 3.1 support is enabled in
  74    Clang by default, and the OpenMP runtime is therefore built as a
  75    normal part of the Clang build, and distributed with the binary
  76    distributions.You do not, therefore, need explicitly to check out this code, or
  77    build it out of tree; a normal Clang check out and build will
  78    automatically include building these runtime libraries.
  79    </p>
  80
  81   <!--=====================================================================-->
  82   <h2 id="goals">Features and Goals</h2>
  83   <!--=====================================================================-->
  84
  85     <ul>
  86         <li>Support for the <a href="https://www.openmp.org/wp-content/uploads/OpenMP3.1.pdf">OpenMP
  87           3.1 standard (PDF)</a> has been achieved in the Clang 3.8.0
  88           release.
  89         </li>
  90
  91         <li>Support for the
  92  <a href="https://www.openmp.org/wp-content/uploads/OpenMP4.0.0.pdf">OpenMP
  93           4.0 standard (PDF)</a> and <a href="https://www.openmp.org/wp-content/uploads/openmp-4.5.pdf">OpenMP
  94           4.5 standard (PDF)</a> is now being implemented. (Some OpenMP 4.0
  95           and 4.5 features are already available).
  96         <li>High performance.</li>
  97         <li>ABI compatibility with <a href="https://gcc.gnu.org">Gcc</a> and
  98         <a href="https://software.intel.com/en-us/compilers">Intel's
  99         existing OpenMP compilers.</a>
 100         We currently have binary compatibility with OpenMP
 101         3.1 code compiled by gcc 4.9, however we do not have support
 102         for OpenMP 4.0 code that uses task cancellation when compiled
 103         by gcc 4.9. How we will support such code remains a research issue.
 104         </li>
 105     </ul>
 106
 107   <!--=====================================================================-->
 108   <h2 id="why">Why have the runtime code here?</h2>
 109   <!--=====================================================================-->
 110
 111   <p>It makes sense to have the runtime sources in the same place
 112     (and with the same license) as the compiler.
 113   </p>
 114
 115   <!--=====================================================================-->
 116   <h2 id="requirements">Platform Support</h2>
 117   <!--=====================================================================-->
 118
 119    <p>The runtime can be built with gcc, icc or clang. However, note
 120    that a runtime built with clang cannot be guaranteed to work with
 121    OpenMP code compiled by the other compilers, since clang does not support
 122    a 128-bit float type, and cannot therefore generate the code used
 123    for reductions of that type (which may occur in user code compiled
 124    by the other compilers).
 125    </p>
 126
 127   <p>The OpenMP runtime is known to work on
 128     <ul>
 129       <li>ARM&reg;&nbsp; architecture processors</li>
 130       <li>PowerPC&trade;&nbsp; processors</li>
 131       <li>32 and 64 bit X86
 132         processors when compiled with clang, with the Intel compiler
 133         or with gcc, and also the Intel&reg;&nbsp;Xeon Phi&trade; product family, when compiled with
 134         the Intel compiler.
 135       </li>
 136       <li>MIPS and MIPS64</li>
 137       <li>RISC-V 64-bit</li>
 138     </ul>
 139     Ports to other architectures and operating systems are welcome.
 140   </p>
 141
 142   <p>A full OS and architecture compatibility matrix is in
 143     <a href="README.txt">README.txt</a>
 144   </p>
 145
 146
 147   <!--=====================================================================-->
 148   <h2>Get it and get involved!</h2>
 149   <!--=====================================================================-->
 150
 151   <p>First please review our
 152      <a href="https://llvm.org/docs/DeveloperPolicy.html">Developer's Policy</a>.
 153
 154   <p>To check out the code, use:</p>
 155
 156   <ul>
 157   <li><code>git clone https://github.com/llvm/llvm-project.git</code></li>
 158   </ul>
 159
 160   <p>In-tree build:</p>
 161   <ul>
 162     <li><code>cd llvm-project</code></li>
 163     <li><code>mkdir build &amp;&amp; cd build</code></li>
 164     <li><code>cmake ../llvm -DLLVM_ENABLE_PROJECTS=openmp -DCMAKE_C_COMPILER=&lt;C compiler&gt; -DCMAKE_CXX_COMPILER=&lt;C++ compiler&gt;</code></li>
 165     <li><code>make omp</code></li>
 166   </ul>
 167
 168   <p>Out-of-tree build:</p>
 169   <ul>
 170     <li><code>cd llvm-project</code></li>
 171     <li><code>mkdir build-openmp &amp;&amp; cd build-openmp</code></li>
 172     <li><code>cmake ../openmp -DCMAKE_C_COMPILER=&lt;C compiler&gt; -DCMAKE_CXX_COMPILER=&lt;C++ compiler&gt;</code></li>
 173     <li><code>make</code></li>
 174   </ul>
 175
 176   <p>Full details of how to build are in the
 177     <a href="README.txt">README.txt</a> and README.rst in the source code repository.
 178   </p>
 179
 180   <!--=====================================================================-->
 181   <h3>Notes</h3>
 182   <!--=====================================================================-->
 183
 184 <p>
 185
 186 </p>
 187
 188   <p>Send discussions to the
 189   (<a href="https://lists.llvm.org/mailman/listinfo/openmp-dev">OpenMP mailing list</a>).</p>
 190
 191
 192   <!--=====================================================================-->
 193   <h2>Design Documents</h2>
 194   <!--=====================================================================-->
 195
 196 <ul>
 197 <li><a href="Reference.pdf">Runtime design (PDF)</a></li>
 198 </ul>
 199
 200   <!--=====================================================================-->
 201   <h2>Copyright notices</h2>
 202   <!--=====================================================================-->
 203 <ul>
 204 <li>
 205   The OpenMP name and the OpenMP logo are registered trademarks of the
 206   OpenMP Architecture Review Board.
 207 </li>
 208 <li>
 209   Intel is a trademark of Intel Corporation in the U.S. and/or other
 210   countries.
 211 </li>
 212 <li>
 213   PowerPC is a trademark of IBM Corporation in the U.S. and/or other
 214   countries.
 215 </li>
 216 <li>
 217   ARM is a trademark of ARM Corporation in the U.S. and/or
 218   other countries.
 219 </li>
 220 <li>
 221   MIPS is a trademark of MIPS Computer Systems in the U.S. and/or
 222   other countries.
 223 </li>
 224 </ul>
 225 </div>
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