HCoop / hcoop / debian / mlton.git / blame
| Commit | Line | Data |
|---|---|---|
| 7f918cf1 CE |
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>CommonBlock</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>CommonBlock</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="CommonBlock">CommonBlock</a> is an optimization pass for the <a href="SSA">SSA</a>\r | |
| 32 | <a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="SSASimplify">SSASimplify</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>It eliminates equivalent blocks in a <a href="SSA">SSA</a> function. The\r | |
| 39 | equivalence criteria requires blocks to have no arguments or\r | |
| 40 | statements and transfer via <span class="monospaced">Raise</span>, <span class="monospaced">Return</span>, or <span class="monospaced">Goto</span> of a single\r | |
| 41 | global variable.</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/common-block.fun"><span class="monospaced">common-block.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="ulist"><ul>\r | |
| 60 | <li>\r | |
| 61 | <p>\r | |
| 62 | Rewrites\r | |
| 63 | </p>\r | |
| 64 | <div class="listingblock">\r | |
| 65 | <div class="content monospaced">\r | |
| 66 | <pre>L_X ()\r | |
| 67 | raise (global_Y)</pre>\r | |
| 68 | </div></div>\r | |
| 69 | <div class="paragraph"><p>to</p></div>\r | |
| 70 | <div class="listingblock">\r | |
| 71 | <div class="content monospaced">\r | |
| 72 | <pre>L_X ()\r | |
| 73 | L_Y' ()</pre>\r | |
| 74 | </div></div>\r | |
| 75 | <div class="paragraph"><p>and adds</p></div>\r | |
| 76 | <div class="listingblock">\r | |
| 77 | <div class="content monospaced">\r | |
| 78 | <pre>L_Y' ()\r | |
| 79 | raise (global_Y)</pre>\r | |
| 80 | </div></div>\r | |
| 81 | <div class="paragraph"><p>to the <a href="SSA">SSA</a> function.</p></div>\r | |
| 82 | </li>\r | |
| 83 | <li>\r | |
| 84 | <p>\r | |
| 85 | Rewrites\r | |
| 86 | </p>\r | |
| 87 | <div class="listingblock">\r | |
| 88 | <div class="content monospaced">\r | |
| 89 | <pre>L_X ()\r | |
| 90 | return (global_Y)</pre>\r | |
| 91 | </div></div>\r | |
| 92 | <div class="paragraph"><p>to</p></div>\r | |
| 93 | <div class="listingblock">\r | |
| 94 | <div class="content monospaced">\r | |
| 95 | <pre>L_X ()\r | |
| 96 | L_Y' ()</pre>\r | |
| 97 | </div></div>\r | |
| 98 | <div class="paragraph"><p>and adds</p></div>\r | |
| 99 | <div class="listingblock">\r | |
| 100 | <div class="content monospaced">\r | |
| 101 | <pre>L_Y' ()\r | |
| 102 | return (global_Y)</pre>\r | |
| 103 | </div></div>\r | |
| 104 | <div class="paragraph"><p>to the <a href="SSA">SSA</a> function.</p></div>\r | |
| 105 | </li>\r | |
| 106 | <li>\r | |
| 107 | <p>\r | |
| 108 | Rewrites\r | |
| 109 | </p>\r | |
| 110 | <div class="listingblock">\r | |
| 111 | <div class="content monospaced">\r | |
| 112 | <pre>L_X ()\r | |
| 113 | L_Z (global_Y)</pre>\r | |
| 114 | </div></div>\r | |
| 115 | <div class="paragraph"><p>to</p></div>\r | |
| 116 | <div class="listingblock">\r | |
| 117 | <div class="content monospaced">\r | |
| 118 | <pre>L_X ()\r | |
| 119 | L_Y' ()</pre>\r | |
| 120 | </div></div>\r | |
| 121 | <div class="paragraph"><p>and adds</p></div>\r | |
| 122 | <div class="listingblock">\r | |
| 123 | <div class="content monospaced">\r | |
| 124 | <pre>L_Y' ()\r | |
| 125 | L_Z (global_Y)</pre>\r | |
| 126 | </div></div>\r | |
| 127 | <div class="paragraph"><p>to the <a href="SSA">SSA</a> function.</p></div>\r | |
| 128 | </li>\r | |
| 129 | </ul></div>\r | |
| 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>\r | |
| 131 | <div class="paragraph"><p>For example, all uncaught <span class="monospaced">Overflow</span> exceptions in a <a href="SSA">SSA</a> function\r | |
| 132 | share the same raising block.</p></div>\r | |
| 133 | </div>\r | |
| 134 | </div>\r | |
| 135 | </div>\r | |
| 136 | <div id="footnotes"><hr></div>\r | |
| 137 | <div id="footer">\r | |
| 138 | <div id="footer-text">\r | |
| 139 | </div>\r | |
| 140 | <div id="footer-badges">\r | |
| 141 | </div>\r | |
| 142 | </div>\r | |
| 143 | </body>\r | |
| 144 | </html>\r |