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<title>SSA - MLton Standard ML Compiler (SML Compiler)</title>
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      SSA
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SSA is an <a href="IntermediateLanguage">IntermediateLanguage</a>,  translated from <a href="SXML">SXML</a> by <a href="ClosureConvert">ClosureConvert</a>,  optimized by <a href="SSASimplify">SSASimplify</a>, and  translated by <a href="ToSSA2">ToSSA2</a> to <a href="SSA2">SSA2</a>. <h2 id="head-55f8ebc805e65b5b71ddafdae390e3be2bcd69af">Description</h2>
<p>
SSA is a <a class="nonexistent" href="FirstOrder">FirstOrder</a>, <a class="nonexistent" href="SimplyTyped">SimplyTyped</a> <a href="IntermediateLanguage">IntermediateLanguage</a>. It is the main <a href="IntermediateLanguage">IntermediateLanguage</a> used for optimizations. 
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<p>
An SSA program consists of a collection of datatype declarations, a sequence of global statements, and a collection of functions, along with a distinguished "main" function.  Each function consists of a collection of basic blocks, where each basic block is a sequence of statements ending with some control transfer. 
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<h2 id="head-8781d615fd77be9578225c40ac67b9471394cced">Implementation</h2>

<a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-20051202-release/mlton/ssa/ssa.sig?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">ssa.sig</a>
 
<a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-20051202-release/mlton/ssa/ssa.fun?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">ssa.fun</a>
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<a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-20051202-release/mlton/ssa/ssa-tree.sig?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">ssa-tree.sig</a>
 
<a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-20051202-release/mlton/ssa/ssa-tree.fun?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">ssa-tree.fun</a>
 <h2 id="head-a6de4b535fedeaa8890bd890b60fe09f87b5f96a">Type Checking</h2>
<p>
Type checking of a SSA program verifies the following: 
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    <li>
<p>
 no duplicate definitions (tycons, cons, vars, labels, funcs) 
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</li>
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<p>
 no out of scope references (tycons, cons, vars, labels, funcs) 
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<p>
 variable definitions dominate variable uses 
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 case transfers are exhaustive and irredundant 
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    <li>
<p>
 <tt>Enter</tt>/<tt>Leave</tt> profile statements match 
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    <li>
<p>
 "traditional" well-typedness 
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    </ul>


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<a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-20051202-release/mlton/ssa/type-check.sig?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">type-check.sig</a>
 
<a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-20051202-release/mlton/ssa/type-check.fun?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">type-check.fun</a>
 
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<h2 id="head-35ec00231a68203708e39f0e2cc10b50c6bf62de">Details and Notes</h2>
<p>
SSA is an abbreviation for Static Single Assignment.   
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Last edited on 2005-12-02 04:25:39 by <span title="ppp-71-139-183-221.dsl.snfc21.pacbell.net"><a href="StephenWeeks">StephenWeeks</a></span>.
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