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Documentation updated to include upcoming support for bit vector support

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23063 91177308-0d34-0410-b5e6-96231b3b80d8
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Jim Laskey 2005-08-25 22:52:43 +00:00
parent 047b952e29
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@ -23,6 +23,7 @@
set of possibilities</a></li>
<li><a href="#namedalternatives">Named alternatives</a></li>
<li><a href="#list">Parsing a list of options</a></li>
<li><a href="#bits">Collecting options as a set of flags</a></li>
<li><a href="#description">Adding freeform text to help output</a></li>
</ol></li>
@ -61,6 +62,7 @@
<tt>cl::ParseEnvironmentOptions</tt> function</a></li>
<li><a href="#cl::opt">The <tt>cl::opt</tt> class</a></li>
<li><a href="#cl::list">The <tt>cl::list</tt> class</a></li>
<li><a href="#cl::bits">The <tt>cl::bits</tt> class</a></li>
<li><a href="#cl::alias">The <tt>cl::alias</tt> class</a></li>
<li><a href="#cl::extrahelp">The <tt>cl::extrahelp</tt> class</a></li>
</ul></li>
@ -691,6 +693,65 @@ checking we have to do.</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="bits">Collecting options as a set of flags</a>
</div>
<div class="doc_text">
<p>Instead of collecting sets of options in a list, it is also possible to
gather information for enum values in a bit vector. The represention used by
the <a href="#bits"><tt>cl::bits</tt></a> class is an <tt>unsigned long</tt>
integer. An enum value is represented by a 0/1 in the enum's ordinal value bit
position. 1 indicating that the enum was specified, 0 otherwise. As each
specified value is parsed, the resulting enum's bit is set in the option's bit
vector:</p>
<div class="doc_code"><pre>
<i>bits</i> |= 1 << (unsigned)<i>enum</i>;
</pre></div>
<p>An option specified more than once is redundant as far as the result is
concerned. The argument position information is however updated.</p>
<p>Reworking the above list example, we could replace <a href="#list">
<tt>cl::list</tt></a> with <a href="#bits"><tt>cl::bits</tt></a>:</p>
<div class="doc_code"><pre>
<a href="#cl::bits">cl::bits</a>&lt;Opts&gt; OptimizationBits(<a href="#cl::desc">cl::desc</a>("<i>Available Optimizations:</i>"),
<a href="#cl::values">cl::values</a>(
clEnumVal(dce , "<i>Dead Code Elimination</i>"),
clEnumVal(constprop , "<i>Constant Propagation</i>"),
clEnumValN(inlining, "<i>inline</i>", "<i>Procedure Integration</i>"),
clEnumVal(strip , "<i>Strip Symbols</i>"),
clEnumValEnd));
</pre></div>
<p>To test to see if <tt>constprop</tt> was specified, we can use the
<tt>cl:bits::isSet</tt> function:</p>
<div class="doc_code"><pre>
if (OptimizationBits.isSet(constprop)) {
...
}
</pre></div>
<p>It's also possible to get the raw bit vector using the
<tt>cl::bits::getBits</tt> function:</p>
<div class="doc_code"><pre>
unsigned long bits = OptimizationBits.getBits();
</pre></div>
<p>Finally, if external storage is used, then the location specified must be of
type <tt>unsigned long</tt>. In all other ways a <a
href="#bits"><tt>cl::bits</tt></a> option is morally equivalent to a <a
href="#list"> <tt>cl::list</tt></a> option</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="description">Adding freeform text to help output</a>
@ -1506,6 +1567,31 @@ be used.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="cl::bits">The <tt>cl::bits</tt> class</a>
</div>
<div class="doc_text">
<p>The <tt>cl::bits</tt> class is the class used to represent a list of command
line options in the form of a bit vector. It is also a templated class which
can take up to three arguments:</p>
<div class="doc_code"><pre>
<b>namespace</b> cl {
<b>template</b> &lt;<b>class</b> DataType, <b>class</b> Storage = <b>bool</b>,
<b>class</b> ParserClass = parser&lt;DataType&gt; &gt;
<b>class</b> bits;
}
</pre></div>
<p>This class works the exact same as the <a
href="#cl::opt"><tt>cl::lists</tt></a> class, except that the second argument
must be of <b>type</b> <tt>unsigned long</tt> if external storage is used.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="cl::alias">The <tt>cl::alias</tt> class</a>