HCoop / hcoop / debian / mlton.git / blame
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1 | <!DOCTYPE html>\r |
| 2 | <html lang="en">\r | |
| 3 | <head>\r | |
| 4 | <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">\r | |
| 5 | <meta name="generator" content="AsciiDoc 8.6.9">\r | |
| 6 | <title>DeepFlatten</title>\r | |
| 7 | <link rel="stylesheet" href="./asciidoc.css" type="text/css">\r | |
| 8 | <link rel="stylesheet" href="./pygments.css" type="text/css">\r | |
| 9 | \r | |
| 10 | \r | |
| 11 | <script type="text/javascript" src="./asciidoc.js"></script>\r | |
| 12 | <script type="text/javascript">\r | |
| 13 | /*<![CDATA[*/\r | |
| 14 | asciidoc.install();\r | |
| 15 | /*]]>*/\r | |
| 16 | </script>\r | |
| 17 | <link rel="stylesheet" href="./mlton.css" type="text/css">\r | |
| 18 | </head>\r | |
| 19 | <body class="article">\r | |
| 20 | <div id="banner">\r | |
| 21 | <div id="banner-home">\r | |
| 22 | <a href="./Home">MLton 20180207</a>\r | |
| 23 | </div>\r | |
| 24 | </div>\r | |
| 25 | <div id="header">\r | |
| 26 | <h1>DeepFlatten</h1>\r | |
| 27 | </div>\r | |
| 28 | <div id="content">\r | |
| 29 | <div id="preamble">\r | |
| 30 | <div class="sectionbody">\r | |
| 31 | <div class="paragraph"><p><a href="DeepFlatten">DeepFlatten</a> is an optimization pass for the <a href="SSA2">SSA2</a>\r | |
| 32 | <a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="SSA2Simplify">SSA2Simplify</a>.</p></div>\r | |
| 33 | </div>\r | |
| 34 | </div>\r | |
| 35 | <div class="sect1">\r | |
| 36 | <h2 id="_description">Description</h2>\r | |
| 37 | <div class="sectionbody">\r | |
| 38 | <div class="paragraph"><p>This pass flattens into mutable fields of objects and into vectors.</p></div>\r | |
| 39 | <div class="paragraph"><p>For example, an <span class="monospaced">(int * int) ref</span> is represented by a 2 word\r | |
| 40 | object, and an <span class="monospaced">(int * int) array</span> contains pairs of <span class="monospaced">int</span>-s,\r | |
| 41 | rather than pointers to pairs of <span class="monospaced">int</span>-s.</p></div>\r | |
| 42 | </div>\r | |
| 43 | </div>\r | |
| 44 | <div class="sect1">\r | |
| 45 | <h2 id="_implementation">Implementation</h2>\r | |
| 46 | <div class="sectionbody">\r | |
| 47 | <div class="ulist"><ul>\r | |
| 48 | <li>\r | |
| 49 | <p>\r | |
| 50 | <a href="https://github.com/MLton/mlton/blob/master/mlton/ssa/deep-flatten.fun"><span class="monospaced">deep-flatten.fun</span></a>\r | |
| 51 | </p>\r | |
| 52 | </li>\r | |
| 53 | </ul></div>\r | |
| 54 | </div>\r | |
| 55 | </div>\r | |
| 56 | <div class="sect1">\r | |
| 57 | <h2 id="_details_and_notes">Details and Notes</h2>\r | |
| 58 | <div class="sectionbody">\r | |
| 59 | <div class="paragraph"><p>There are some performance issues with the deep flatten pass, where it\r | |
| 60 | consumes an excessive amount of memory.</p></div>\r | |
| 61 | <div class="ulist"><ul>\r | |
| 62 | <li>\r | |
| 63 | <p>\r | |
| 64 | <a href="http://www.mlton.org/pipermail/mlton/2005-April/026990.html">http://www.mlton.org/pipermail/mlton/2005-April/026990.html</a>\r | |
| 65 | </p>\r | |
| 66 | </li>\r | |
| 67 | <li>\r | |
| 68 | <p>\r | |
| 69 | <a href="http://www.mlton.org/pipermail/mlton-user/2010-June/001626.html">http://www.mlton.org/pipermail/mlton-user/2010-June/001626.html</a>\r | |
| 70 | </p>\r | |
| 71 | </li>\r | |
| 72 | <li>\r | |
| 73 | <p>\r | |
| 74 | <a href="http://www.mlton.org/pipermail/mlton/2010-December/030876.html">http://www.mlton.org/pipermail/mlton/2010-December/030876.html</a>\r | |
| 75 | </p>\r | |
| 76 | </li>\r | |
| 77 | </ul></div>\r | |
| 78 | <div class="paragraph"><p>A number of applications require compilation with\r | |
| 79 | <span class="monospaced">-disable-pass deepFlatten</span> to avoid exceeding available memory. It is\r | |
| 80 | often asked whether the deep flatten pass usually has a significant\r | |
| 81 | impact on performance. The standard benchmark suite was run with and\r | |
| 82 | without the deep flatten pass enabled when the pass was first\r | |
| 83 | introduced:</p></div>\r | |
| 84 | <div class="ulist"><ul>\r | |
| 85 | <li>\r | |
| 86 | <p>\r | |
| 87 | <a href="http://www.mlton.org/pipermail/mlton/2004-August/025760.html">http://www.mlton.org/pipermail/mlton/2004-August/025760.html</a>\r | |
| 88 | </p>\r | |
| 89 | </li>\r | |
| 90 | </ul></div>\r | |
| 91 | <div class="paragraph"><p>The conclusion is that it does not have a significant impact.\r | |
| 92 | However, these are micro benchmarks; other applications may derive\r | |
| 93 | greater benefit from the pass.</p></div>\r | |
| 94 | </div>\r | |
| 95 | </div>\r | |
| 96 | </div>\r | |
| 97 | <div id="footnotes"><hr></div>\r | |
| 98 | <div id="footer">\r | |
| 99 | <div id="footer-text">\r | |
| 100 | </div>\r | |
| 101 | <div id="footer-badges">\r | |
| 102 | </div>\r | |
| 103 | </div>\r | |
| 104 | </body>\r | |
| 105 | </html>\r |