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323 lines
11 KiB
HTML
<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Additional P-CODE Operations</title>
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<link rel="stylesheet" type="text/css" href="Frontpage.css">
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<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
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<link rel="home" href="pcoderef.html" title="P-Code Reference Manual">
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<link rel="prev" href="pseudo-ops.html" title="Pseudo P-CODE Operations">
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<link rel="next" href="reference.html" title="Syntax Reference">
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</head>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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<div class="navheader">
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<table width="100%" summary="Navigation header">
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<tr><th colspan="3" align="center">Additional P-CODE Operations</th></tr>
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<tr>
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<td width="20%" align="left">
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<a accesskey="p" href="pseudo-ops.html">Prev</a> </td>
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<th width="60%" align="center"> </th>
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<td width="20%" align="right"> <a accesskey="n" href="reference.html">Next</a>
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</td>
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</tr>
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</table>
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<hr>
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</div>
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<div class="sect1">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="additionalpcode"></a>Additional P-CODE Operations</h2></div></div></div>
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<p>
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The following opcodes are not generated as part of the raw translation
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of a machine instruction into p-code operations, so none of them can be used
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in a processor specification. But, they may be
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introduced at a later stage by various analysis algorithms.
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</p>
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<div class="sect2">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="cpui_multiequal"></a>MULTIEQUAL</h3></div></div></div>
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<div class="informalexample"><div class="table">
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<a name="multiequal.htmltable"></a><table frame="above" width="80%" rules="groups">
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<col width="23%">
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<col width="15%">
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<col width="61%">
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<thead><tr>
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<td align="center" colspan="2"><span class="bold"><strong>Parameters</strong></span></td>
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<td><span class="bold"><strong>Description</strong></span></td>
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</tr></thead>
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<tbody>
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<tr>
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<td align="right">input0</td>
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<td></td>
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<td>Varnode to merge from first basic block.</td>
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</tr>
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<tr>
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<td align="right">input1</td>
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<td></td>
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<td>Varnode to merge from second basic block.</td>
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</tr>
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<tr>
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<td align="right">[...]</td>
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<td></td>
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<td>Varnodes to merge from additional basic blocks.</td>
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</tr>
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<tr>
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<td align="right">output</td>
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<td></td>
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<td>Merged varnode for basic block containing op.</td>
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</tr>
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</tbody>
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<tfoot>
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<tr>
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<td align="center" colspan="2"><span class="bold"><strong>Semantic statement</strong></span></td>
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<td></td>
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</tr>
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<tr>
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<td></td>
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<td colspan="2"><span class="emphasis"><em>Cannot be explicitly coded.</em></span></td>
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</tr>
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</tfoot>
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</table>
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</div></div>
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<p>
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This operation represents a copy from one or more possible
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locations. From the compiler theory concept of Static Single Assignment form, this is
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a <span class="bold"><strong>phi-node</strong></span>. Each input corresponds to a control-flow path
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flowing into the basic block containing the <span class="bold"><strong>MULTIEQUAL</strong></span>.
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The operator copies a particular input into the output varnode depending on what path
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was last executed. All inputs and outputs must be the same size.
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</p>
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</div>
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<div class="sect2">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="cpui_indirect"></a>INDIRECT</h3></div></div></div>
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<div class="informalexample"><div class="table">
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<a name="indirect.htmltable"></a><table frame="above" width="80%" rules="groups">
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<col width="23%">
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<col width="15%">
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<col width="61%">
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<thead><tr>
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<td align="center" colspan="2"><span class="bold"><strong>Parameters</strong></span></td>
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<td><span class="bold"><strong>Description</strong></span></td>
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</tr></thead>
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<tbody>
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<tr>
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<td align="right">input0</td>
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<td></td>
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<td>Varnode on which output may depend.</td>
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</tr>
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<tr>
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<td align="right">input1</td>
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<td>(<span class="bold"><strong>special</strong></span>)</td>
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<td>Code iop of instruction causing effect.</td>
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</tr>
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<tr>
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<td align="right">output</td>
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<td></td>
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<td>Varnode containing result of effect.</td>
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</tr>
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</tbody>
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<tfoot>
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<tr>
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<td align="center" colspan="2"><span class="bold"><strong>Semantic statement</strong></span></td>
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<td></td>
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</tr>
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<tr>
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<td></td>
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<td colspan="2"><span class="emphasis"><em>Cannot be explicitly coded.</em></span></td>
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</tr>
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</tfoot>
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</table>
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</div></div>
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<p>
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An <span class="bold"><strong>INDIRECT</strong></span> operator copies input0 into output,
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but the value may be altered in an indirect way
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by the operation referred to by input1. The varnode input1 is not part of the
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machine state but is really an internal reference to a specific p-code operator that
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may be affecting the value of the output varnode. A special address space indicates
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input1's use as an internal reference encoding.
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An <span class="bold"><strong>INDIRECT</strong></span> op is a placeholder for possible
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indirect effects (such as pointer aliasing or missing code) when data-flow
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algorithms do not have enough information to follow the data-flow directly. Like
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the <span class="bold"><strong>MULTIEQUAL</strong></span>, this op is used
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for generating Static Single Assignment form.
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</p>
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<p>
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A constant varnode (zero) for input0 is used by analysis to indicate that the output
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of the <span class="bold"><strong>INDIRECT</strong></span> is produced solely by the p-code operation
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producing the indirect effect, and there is no possibility that the value existing prior
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to the operation was used or preserved.
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</p>
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</div>
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<div class="sect2">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="cpui_ptradd"></a>PTRADD</h3></div></div></div>
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<div class="informalexample"><div class="table">
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<a name="ptradd.htmltable"></a><table frame="above" width="80%" rules="groups">
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<col width="23%">
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<col width="15%">
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<col width="61%">
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<thead><tr>
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<td align="center" colspan="2"><span class="bold"><strong>Parameters</strong></span></td>
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<td><span class="bold"><strong>Description</strong></span></td>
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</tr></thead>
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<tbody>
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<tr>
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<td align="right">input0</td>
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<td></td>
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<td>Varnode containing pointer to an array.</td>
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</tr>
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<tr>
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<td align="right">input1</td>
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<td></td>
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<td>Varnode containing integer index.</td>
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</tr>
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<tr>
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<td align="right">input2</td>
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<td>(<span class="bold"><strong>constant</strong></span>)</td>
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<td>Constant varnode indicating element size.</td>
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</tr>
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<tr>
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<td align="right">output</td>
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<td></td>
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<td>Varnode result containing pointer to indexed array entry.</td>
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</tr>
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</tbody>
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<tfoot>
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<tr>
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<td align="center" colspan="2"><span class="bold"><strong>Semantic statement</strong></span></td>
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<td></td>
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</tr>
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<tr>
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<td></td>
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<td colspan="2"><span class="emphasis"><em>Cannot be explicitly coded.</em></span></td>
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</tr>
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</tfoot>
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</table>
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</div></div>
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<p>
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This operator serves as a more compact representation of the pointer calculation,
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input0 + input1 * input2, but also indicates explicitly that
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input0 is a reference to
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an array data-type. Input0 is a pointer to the beginning of the array, input1 is an
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index into the array, and input2 is a constant indicating the size of
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an element in the array. As an
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operation, <span class="bold"><strong>PTRADD</strong></span> produces the
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pointer value of the element at the indicated index in the array
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and stores it in output.
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</p>
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</div>
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<div class="sect2">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="cpui_ptrsub"></a>PTRSUB</h3></div></div></div>
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<div class="informalexample"><div class="table">
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<a name="ptrsub.htmltable"></a><table frame="above" width="80%" rules="groups">
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<col width="23%">
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<col width="15%">
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<col width="61%">
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<thead><tr>
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<td align="center" colspan="2"><span class="bold"><strong>Parameters</strong></span></td>
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<td><span class="bold"><strong>Description</strong></span></td>
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</tr></thead>
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<tbody>
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<tr>
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<td align="right">input0</td>
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<td></td>
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<td>Varnode containing pointer to structure.</td>
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</tr>
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<tr>
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<td align="right">input1</td>
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<td></td>
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<td>Varnode containing integer offset to a subcomponent.</td>
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</tr>
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<tr>
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<td align="right">output</td>
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<td></td>
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<td>Varnode result containing pointer to the subcomponent.</td>
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</tr>
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</tbody>
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<tfoot>
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<tr>
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<td align="center" colspan="2"><span class="bold"><strong>Semantic statement</strong></span></td>
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<td></td>
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</tr>
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<tr>
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<td></td>
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<td colspan="2"><span class="emphasis"><em>Cannot be explicitly coded.</em></span></td>
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</tr>
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</tfoot>
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</table>
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</div></div>
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<p>
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A <span class="bold"><strong>PTRSUB</strong></span> performs the simple pointer calculation,
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input0 + input1, but also indicates explicitly that input0 is a
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reference to a structured data-type
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and one of its subcomponents is being accessed. Input0 is a pointer
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to the beginning of the structure, and input1 is a byte offset to the subcomponent.
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As an operation, <span class="bold"><strong>PTRSUB</strong></span> produces a
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pointer to the subcomponent and stores it in output.
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</p>
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</div>
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<div class="sect2">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="cpui_cast"></a>CAST</h3></div></div></div>
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<div class="informalexample"><div class="table">
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<a name="cast.htmltable"></a><table frame="above" width="80%" rules="groups">
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<col width="23%">
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<col width="15%">
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<col width="61%">
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<thead><tr>
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<td align="center" colspan="2"><span class="bold"><strong>Parameters</strong></span></td>
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<td><span class="bold"><strong>Description</strong></span></td>
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</tr></thead>
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<tbody>
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<tr>
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<td align="right">input0</td>
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<td></td>
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<td>Varnode containing value to be copied.</td>
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</tr>
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<tr>
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<td align="right">output</td>
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<td></td>
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<td>Varnode result of copy.</td>
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</tr>
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</tbody>
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<tfoot>
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<tr>
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<td align="center" colspan="2"><span class="bold"><strong>Semantic statement</strong></span></td>
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<td></td>
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</tr>
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<tr>
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<td></td>
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<td colspan="2"><span class="emphasis"><em>Cannot be explicitly coded.</em></span></td>
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</tr>
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</tfoot>
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</table>
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</div></div>
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<p>
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A <span class="bold"><strong>CAST</strong></span> performs identically to the <span class="bold"><strong>COPY</strong></span>
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operator but also indicates that there is a forced change in the data-types associated with the varnodes
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at this point in the code. The value input0 is strictly copied into output; it is not a conversion cast.
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This operator is intended specifically for when the value doesn't change but its
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interpretation as a data-type changes at this point.
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</p>
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</div>
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</div>
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<div class="navfooter">
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<hr>
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left">
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<a accesskey="p" href="pseudo-ops.html">Prev</a> </td>
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<td width="20%" align="center"> </td>
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<td width="40%" align="right"> <a accesskey="n" href="reference.html">Next</a>
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</td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Pseudo P-CODE Operations </td>
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<td width="20%" align="center"><a accesskey="h" href="pcoderef.html">Home</a></td>
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<td width="40%" align="right" valign="top"> Syntax Reference</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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