doc/guide/localhost/DeadCode

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  26 <h1>DeadCode</h1>
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  29 <div id="preamble">
  30 <div class="sectionbody">
  31 <div class="paragraph"><p><a href="DeadCode">DeadCode</a> is an optimization pass for the <a href="CoreML">CoreML</a>
  32 <a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="CoreMLSimplify">CoreMLSimplify</a>.</p></div>
  33 </div>
  34 </div>
  35 <div class="sect1">
  36 <h2 id="_description">Description</h2>
  37 <div class="sectionbody">
  38 <div class="paragraph"><p>This pass eliminates declarations from the
  39 <a href="BasisLibrary">Basis Library</a> not needed by the user program.</p></div>
  40 </div>
  41 </div>
  42 <div class="sect1">
  43 <h2 id="_implementation">Implementation</h2>
  44 <div class="sectionbody">
  45 <div class="ulist"><ul>
  46 <li>
  47 <p>
  48 <a href="https://github.com/MLton/mlton/blob/master/mlton/core-ml/dead-code.sig"><span class="monospaced">dead-code.sig</span></a>
  49 </p>
  50 </li>
  51 <li>
  52 <p>
  53 <a href="https://github.com/MLton/mlton/blob/master/mlton/core-ml/dead-code.fun"><span class="monospaced">dead-code.fun</span></a>
  54 </p>
  55 </li>
  56 </ul></div>
  57 </div>
  58 </div>
  59 <div class="sect1">
  60 <h2 id="_details_and_notes">Details and Notes</h2>
  61 <div class="sectionbody">
  62 <div class="paragraph"><p>In order to compile small programs rapidly, a pass of dead code
  63 elimination is run in order to eliminate as much of the Basis Library
  64 as possible.  The dead code elimination algorithm used is not safe in
  65 general, and only works because the Basis Library implementation has
  66 special properties:</p></div>
  67 <div class="ulist"><ul>
  68 <li>
  69 <p>
  70 it terminates
  71 </p>
  72 </li>
  73 <li>
  74 <p>
  75 it performs no I/O
  76 </p>
  77 </li>
  78 </ul></div>
  79 <div class="paragraph"><p>The dead code elimination includes the minimal set of
  80 declarations from the Basis Library so that there are no free
  81 variables in the user program (or remaining Basis Library
  82 implementation).  It has a special hack to include all
  83 bindings of the form:</p></div>
  84 <div class="listingblock">
  85 <div class="content"><div class="highlight"><pre><span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="p">...</span><span class="w"></span>
  86 </pre></div></div></div>
  87 <div class="paragraph"><p>There is an <a href="MLBasisAnnotations">ML Basis annotation</a>,
  88 <span class="monospaced">deadCode true</span>, that governs which code is subject to this unsafe
  89 dead-code elimination.</p></div>
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