HCoop / hcoop / debian / mlton.git / blame
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|---|---|---|
| 7f918cf1 CE |
1 | <!DOCTYPE html>\r |
| 2 | <html lang="en">\r | |
| 3 | <head>\r | |
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| 5 | <meta name="generator" content="AsciiDoc 8.6.9">\r | |
| 6 | <title>RedundantTests</title>\r | |
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| 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>RedundantTests</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="RedundantTests">RedundantTests</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>This pass simplifies conditionals whose results are implied by a\r | |
| 39 | previous conditional test.</p></div>\r | |
| 40 | </div>\r | |
| 41 | </div>\r | |
| 42 | <div class="sect1">\r | |
| 43 | <h2 id="_implementation">Implementation</h2>\r | |
| 44 | <div class="sectionbody">\r | |
| 45 | <div class="ulist"><ul>\r | |
| 46 | <li>\r | |
| 47 | <p>\r | |
| 48 | <a href="https://github.com/MLton/mlton/blob/master/mlton/ssa/redundant-tests.fun"><span class="monospaced">redundant-tests.fun</span></a>\r | |
| 49 | </p>\r | |
| 50 | </li>\r | |
| 51 | </ul></div>\r | |
| 52 | </div>\r | |
| 53 | </div>\r | |
| 54 | <div class="sect1">\r | |
| 55 | <h2 id="_details_and_notes">Details and Notes</h2>\r | |
| 56 | <div class="sectionbody">\r | |
| 57 | <div class="paragraph"><p>An additional test will sometimes eliminate the overflow test when\r | |
| 58 | adding or subtracting 1. In particular, it will eliminate it in the\r | |
| 59 | following cases:</p></div>\r | |
| 60 | <div class="listingblock">\r | |
| 61 | <div class="content"><div class="highlight"><pre><span class="k">if</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="n"><</span><span class="w"> </span><span class="n">y</span><span class="w"></span>\r | |
| 62 | <span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="n">+</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">...</span><span class="w"></span>\r | |
| 63 | <span class="k">else</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="n">y</span><span class="w"> </span><span class="n">-</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">...</span><span class="w"></span>\r | |
| 64 | </pre></div></div></div>\r | |
| 65 | </div>\r | |
| 66 | </div>\r | |
| 67 | </div>\r | |
| 68 | <div id="footnotes"><hr></div>\r | |
| 69 | <div id="footer">\r | |
| 70 | <div id="footer-text">\r | |
| 71 | </div>\r | |
| 72 | <div id="footer-badges">\r | |
| 73 | </div>\r | |
| 74 | </div>\r | |
| 75 | </body>\r | |
| 76 | </html>\r |