<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <meta name="robots" content="index,nofollow"> <title>CommonBlock - MLton Standard ML Compiler (SML Compiler)</title> <link rel="stylesheet" type="text/css" charset="iso-8859-1" media="all" href="common.css"> <link rel="stylesheet" type="text/css" charset="iso-8859-1" media="screen" href="screen.css"> <link rel="stylesheet" type="text/css" charset="iso-8859-1" media="print" href="print.css"> <link rel="Start" href="Home"> </head> <body lang="en" dir="ltr"> <script src="http://www.google-analytics.com/urchin.js" type="text/javascript"> </script> <script type="text/javascript"> _uacct = "UA-833377-1"; urchinTracker(); </script> <table bgcolor = lightblue cellspacing = 0 style = "border: 0px;" width = 100%> <tr> <td style = " border: 0px; color: darkblue; font-size: 150%; text-align: left;"> <a class = mltona href="Home">MLton MLTONWIKIVERSION</a> <td style = " border: 0px; font-size: 150%; text-align: center; width: 50%;"> CommonBlock <td style = " border: 0px; text-align: right;"> <table cellspacing = 0 style = "border: 0px"> <tr style = "vertical-align: middle;"> </table> <tr style = "background-color: white;"> <td colspan = 3 style = " border: 0px; font-size:70%; text-align: right;"> <a href = "Home">Home</a> <a href = "TitleIndex">Index</a> </table> <div id="content" lang="en" dir="ltr"> CommonBlock is an optimization pass for the <a href="SSA">SSA</a> <a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="SSASimplify">SSASimplify</a>. <h2 id="head-55f8ebc805e65b5b71ddafdae390e3be2bcd69af">Description</h2> <p> It eliminates equivalent blocks in a <a href="SSA">SSA</a> function. The equivalence criteria requires blocks to have no arguments or statements and transfer via <tt>Raise</tt>, <tt>Return</tt>, or <tt>Goto</tt> of a single global variable. </p> <h2 id="head-8781d615fd77be9578225c40ac67b9471394cced">Implementation</h2> <a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-MLTONWIKIVERSION-release/mlton/ssa/common-block.sig?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">common-block.sig</a> <a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-MLTONWIKIVERSION-release/mlton/ssa/common-block.fun?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">common-block.fun</a> <h2 id="head-35ec00231a68203708e39f0e2cc10b50c6bf62de">Details and Notes</h2> <ul> <li> <p> Rewrites <pre> L_X () raise (global_Y) </pre> to <pre> L_X () L_Y' () </pre> and adds <pre> L_Y' () raise (global_Y) </pre> to the <a href="SSA">SSA</a> function. </p> </li> <li> <p> Rewrites <pre> L_X () return (global_Y) </pre> to <pre> L_X () L_Y' () </pre> and adds <pre> L_Y' () return (global_Y) </pre> to the <a href="SSA">SSA</a> function. </p> </li> <li> <p> Rewrites <pre> L_X () L_Z (global_Y) </pre> to <pre> L_X () L_Y' () </pre> and adds <pre> L_Y' () L_Z (global_Y) </pre> to the <a href="SSA">SSA</a> function. </p> </li> </ul> <p> The <a href="Shrink">Shrink</a> pass rewrites all uses of <tt>L_X</tt> to <tt>L_Y'</tt> and drops <tt>L_X</tt>. </p> <p> For example, all uncaught <tt>Overflow</tt> exceptions in a <a href="SSA">SSA</a> function share the same raising block. </p> </div> <p> <hr> Last edited on 2006-11-02 17:56:13 by <span title="76.16.241.4"><a href="MatthewFluet">MatthewFluet</a></span>. </body></html>