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Wow, the description of the 'switch' instruction was out of date.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11790 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2004-02-24 04:54:45 +00:00
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@ -748,40 +748,61 @@ control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p>
href="#i_ret">ret</a> int 1<br>IfUnequal:<br> <a href="#i_ret">ret</a> int 0<br></pre>
</div>
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<div class="doc_subsubsection"> <a name="i_switch">'<tt>switch</tt>'
Instruction</a> </div>
<div class="doc_subsubsection">
<a name="i_switch">'<tt>switch</tt>' Instruction</a>
</div>
<div class="doc_text">
<h5>Syntax:</h5>
<pre> switch uint &lt;value&gt;, label &lt;defaultdest&gt; [ int &lt;val&gt;, label &lt;dest&gt;, ... ]<br></pre>
<pre>
switch &lt;intty&gt; &lt;value&gt;, label &lt;defaultdest&gt; [ &lt;intty&gt; &lt;val&gt;, label &lt;dest&gt; ... ]
</pre>
<h5>Overview:</h5>
<p>The '<tt>switch</tt>' instruction is used to transfer control flow
to one of several different places. It is a generalization of the '<tt>br</tt>'
<p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of
several different places. It is a generalization of the '<tt>br</tt>'
instruction, allowing a branch to occur to one of many possible
destinations.</p>
<h5>Arguments:</h5>
<p>The '<tt>switch</tt>' instruction uses three parameters: a '<tt>uint</tt>'
comparison value '<tt>value</tt>', a default '<tt>label</tt>'
destination, and an array of pairs of comparison value constants and '<tt>label</tt>'s.</p>
<p>The '<tt>switch</tt>' instruction uses three parameters: an integer
comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, and
an array of pairs of comparison value constants and '<tt>label</tt>'s. The
table is not allowed to contain duplicate constant entries.</p>
<h5>Semantics:</h5>
<p>The <tt>switch</tt> instruction specifies a table of values and
destinations. When the '<tt>switch</tt>' instruction is executed, this
table is searched for the given value. If the value is found, the
corresponding destination is branched to, otherwise the default value
it transfered to.</p>
<h5>Implementation:</h5>
<p>Depending on properties of the target machine and the particular <tt>switch</tt>
instruction, this instruction may be code generated as a series of
chained conditional branches, or with a lookup table.</p>
<h5>Example:</h5>
<pre> <i>; Emulate a conditional br instruction</i>
%Val = <a
href="#i_cast">cast</a> bool %value to uint<br> switch uint %Val, label %truedest [int 0, label %falsedest ]<br><br> <i>; Emulate an unconditional br instruction</i>
switch uint 0, label %dest [ ]
<i>; Implement a jump table:</i>
switch uint %val, label %otherwise [ int 0, label %onzero,
int 1, label %onone,
int 2, label %ontwo ]
<h5>Implementation:</h5>
<p>Depending on properties of the target machine and the particular
<tt>switch</tt> instruction, this instruction may be code generated in different
ways, for example as a series of chained conditional branches, or with a lookup
table.</p>
<h5>Example:</h5>
<pre>
<i>; Emulate a conditional br instruction</i>
%Val = <a href="#i_cast">cast</a> bool %value to int
switch int %Val, label %truedest [int 0, label %falsedest ]
<i>; Emulate an unconditional br instruction</i>
switch uint 0, label %dest [ ]
<i>; Implement a jump table:</i>
switch uint %val, label %otherwise [ uint 0, label %onzero
uint 1, label %onone
uint 2, label %ontwo ]
</pre>
</div>
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