<!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>DeepFlatten - 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%;"> DeepFlatten <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"> Deep flatten is an optimization pass for the <a href="SSA2">SSA2</a> <a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="SSA2Simplify">SSA2Simplify</a>. <h2 id="head-55f8ebc805e65b5b71ddafdae390e3be2bcd69af">Description</h2> <p> This pass flattens into mutable fields of objects and into vectors. </p> <p> For example, an <tt>(int * int) ref</tt> is represented by a 2 word object, and an <tt>(int * int) array</tt> contains pairs of <tt>int</tt>s, rather than pointers to pairs of <tt>int</tt>s. </p> <h2 id="head-8781d615fd77be9578225c40ac67b9471394cced">Implementation</h2> <a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-MLTONWIKIVERSION-release/mlton/ssa/deep-flatten.sig?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">deep-flatten.sig</a> <a href = "http://mlton.org/cgi-bin/viewsvn.cgi/mlton/tags/on-MLTONWIKIVERSION-release/mlton/ssa/deep-flatten.fun?view=markup"><img src="moin-www.png" alt="[WWW]" height="11" width="11">deep-flatten.fun</a> <h2 id="head-35ec00231a68203708e39f0e2cc10b50c6bf62de">Details and Notes</h2> <p> There are some performance issues with the deep flatten pass, where it consumes an excessive amount of memory. </p> <ul> <li> <p> <a href="http://mlton.org/pipermail/mlton/2005-April/026990.html"><img src="moin-www.png" alt="[WWW]" height="11" width="11">http://mlton.org/pipermail/mlton/2005-April/026990.html</a> </p> </li> <li> <p> <a href="http://mlton.org/pipermail/mlton-user/2010-June/001626.html"><img src="moin-www.png" alt="[WWW]" height="11" width="11">http://mlton.org/pipermail/mlton-user/2010-June/001626.html</a> </p> </li> </ul> <p> A number of applications require compilation with <tt>-drop-pass deepFlatten</tt> to avoid exceeding available memory. It is often asked whether the deep flatten pass usually has a significant impact on performance. The standard benchmark suite was run with and without the deep flatten pass enabled when the pass was first introduced: </p> <ul> <li> <p> <a href="http://mlton.org/pipermail/mlton/2004-August/025760.html"><img src="moin-www.png" alt="[WWW]" height="11" width="11">http://mlton.org/pipermail/mlton/2004-August/025760.html</a> </p> </li> </ul> <p> The conclusion is that it does not have a significant impact. However, these are micro benchmarks; other applications may derive greater benefit from the pass. </p> </div> <p> <hr> Last edited on 2010-06-01 17:13:13 by <span title="fenrir.cs.rit.edu"><a href="MatthewFluet">MatthewFluet</a></span>. </body></html>