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30 <div class="sectionbody">
31 <div class="paragraph"><p><a href="CommonBlock">CommonBlock</a> is an optimization pass for the <a href="SSA">SSA</a>
32 <a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="SSASimplify">SSASimplify</a>.</p></div>
36 <h2 id="_description">Description</h2>
37 <div class="sectionbody">
38 <div class="paragraph"><p>It eliminates equivalent blocks in a <a href="SSA">SSA</a> function. The
39 equivalence criteria requires blocks to have no arguments or
40 statements and transfer via <span class="monospaced">Raise</span>, <span class="monospaced">Return</span>, or <span class="monospaced">Goto</span> of a single
41 global variable.</p></div>
45 <h2 id="_implementation">Implementation</h2>
46 <div class="sectionbody">
47 <div class="ulist"><ul>
50 <a href="https://github.com/MLton/mlton/blob/master/mlton/ssa/common-block.fun"><span class="monospaced">common-block.fun</span></a>
57 <h2 id="_details_and_notes">Details and Notes</h2>
58 <div class="sectionbody">
59 <div class="ulist"><ul>
64 <div class="listingblock">
65 <div class="content monospaced">
67 raise (global_Y)</pre>
69 <div class="paragraph"><p>to</p></div>
70 <div class="listingblock">
71 <div class="content monospaced">
75 <div class="paragraph"><p>and adds</p></div>
76 <div class="listingblock">
77 <div class="content monospaced">
79 raise (global_Y)</pre>
81 <div class="paragraph"><p>to the <a href="SSA">SSA</a> function.</p></div>
87 <div class="listingblock">
88 <div class="content monospaced">
90 return (global_Y)</pre>
92 <div class="paragraph"><p>to</p></div>
93 <div class="listingblock">
94 <div class="content monospaced">
98 <div class="paragraph"><p>and adds</p></div>
99 <div class="listingblock">
100 <div class="content monospaced">
102 return (global_Y)</pre>
104 <div class="paragraph"><p>to the <a href="SSA">SSA</a> function.</p></div>
110 <div class="listingblock">
111 <div class="content monospaced">
115 <div class="paragraph"><p>to</p></div>
116 <div class="listingblock">
117 <div class="content monospaced">
121 <div class="paragraph"><p>and adds</p></div>
122 <div class="listingblock">
123 <div class="content monospaced">
127 <div class="paragraph"><p>to the <a href="SSA">SSA</a> function.</p></div>
130 <div class="paragraph"><p>The <a href="Shrink">Shrink</a> pass rewrites all uses of <span class="monospaced">L_X</span> to <span class="monospaced">L_Y'</span> and drops <span class="monospaced">L_X</span>.</p></div>
131 <div class="paragraph"><p>For example, all uncaught <span class="monospaced">Overflow</span> exceptions in a <a href="SSA">SSA</a> function
132 share the same raising block.</p></div>
136 <div id="footnotes"><hr></div>
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