Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> |
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| 5 | <title>LLVM Bitcode File Format</title> |
| 6 | <link rel="stylesheet" href="llvm.css" type="text/css"> |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 7 | </head> |
| 8 | <body> |
| 9 | <div class="doc_title"> LLVM Bitcode File Format </div> |
| 10 | <ol> |
| 11 | <li><a href="#abstract">Abstract</a></li> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 12 | <li><a href="#overview">Overview</a></li> |
| 13 | <li><a href="#bitstream">Bitstream Format</a> |
| 14 | <ol> |
| 15 | <li><a href="#magic">Magic Numbers</a></li> |
| 16 | </ol> |
| 17 | </li> |
| 18 | <li><a href="#llvmir">LLVM IR Encoding</a></li> |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 19 | </ol> |
| 20 | <div class="doc_author"> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 21 | <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>. |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 22 | </p> |
| 23 | </div> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 24 | |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 25 | <!-- *********************************************************************** --> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 26 | <div class="doc_section"> <a name="abstract">Abstract</a></div> |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 27 | <!-- *********************************************************************** --> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 28 | |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 29 | <div class="doc_text"> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 30 | |
| 31 | <p>This document describes the LLVM bitstream file format and the encoding of |
| 32 | the LLVM IR into it.</p> |
| 33 | |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 34 | </div> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 35 | |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 36 | <!-- *********************************************************************** --> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 37 | <div class="doc_section"> <a name="overview">Overview</a></div> |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 38 | <!-- *********************************************************************** --> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 39 | |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 40 | <div class="doc_text"> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 41 | |
| 42 | <p> |
| 43 | What is commonly known as the LLVM bitcode file format (also, sometimes |
| 44 | anachronistically known as bytecode) is actually two things: a <a |
| 45 | href="#bitstream">bitstream container format</a> |
| 46 | and an <a href="#llvmir">encoding of LLVM IR</a> into the container format.</p> |
| 47 | |
| 48 | <p> |
| 49 | The bitstream format is an abstract encoding of structured data, like very |
| 50 | similar to XML in some ways. Like XML, bitstream files contain tags, and nested |
| 51 | structures, and you can parse the file without having to understand the tags. |
| 52 | Unlike XML, the bitstream format is a binary encoding, and unlike XML it |
| 53 | provides a mechanism for the file to self-describe "abbreviations", which are |
| 54 | effectively size optimizations for the content.</p> |
| 55 | |
| 56 | <p>This document first describes the LLVM bitstream format, then describes the |
| 57 | record structure used by LLVM IR files. |
| 58 | </p> |
| 59 | |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 60 | </div> |
Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 61 | |
| 62 | <!-- *********************************************************************** --> |
| 63 | <div class="doc_section"> <a name="bitstream">Bitstream Format</a></div> |
| 64 | <!-- *********************************************************************** --> |
| 65 | |
| 66 | <div class="doc_text"> |
| 67 | |
| 68 | <p> |
| 69 | The bitstream format is literally a stream of bits, with a very simple |
| 70 | structure. This structure consists of the following concepts: |
| 71 | </p> |
| 72 | |
| 73 | <ul> |
| 74 | <li>A magic number that identifies the stream.</li> |
| 75 | <li>Encoding primitives like variable bit-rate integers.</li> |
| 76 | <li>Blocks, which define nested content.</li> |
| 77 | <li>Data Records, which describe entities within the file.</li> |
| 78 | <li>Abbreviations, which specify compression optimizations for the file.</li> |
| 79 | </ul> |
| 80 | |
| 81 | <p>Note that the <a |
| 82 | href="CommandGuide/html/llvm-bcanalyzer.html">llvm-bcanalyzer</a> tool can be |
| 83 | used to dump and inspect arbitrary bitstreams, which is very useful for |
| 84 | understanding the encoding.</p> |
| 85 | |
| 86 | </div> |
| 87 | |
| 88 | <!-- ======================================================================= --> |
| 89 | <div class="doc_subsection"><a name="magic">Magic Numbers</a> |
| 90 | </div> |
| 91 | |
| 92 | <div class="doc_text"> |
| 93 | |
| 94 | <p>LLVM </p> |
| 95 | |
| 96 | </div> |
| 97 | |
| 98 | |
| 99 | <!-- _______________________________________________________________________ --> |
| 100 | <div class="doc_subsubsection"> <a name="wellformed">Well-Formedness</a> </div> |
| 101 | |
| 102 | <div class="doc_text"> |
| 103 | |
| 104 | <p>blah |
| 105 | </p> |
| 106 | |
| 107 | </div> |
| 108 | |
| 109 | <!-- *********************************************************************** --> |
| 110 | <div class="doc_section"> <a name="llvmir">LLVM IR Encoding</a></div> |
| 111 | <!-- *********************************************************************** --> |
| 112 | |
| 113 | <div class="doc_text"> |
| 114 | |
| 115 | <p></p> |
| 116 | |
| 117 | </div> |
| 118 | |
| 119 | |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 120 | <!-- *********************************************************************** --> |
| 121 | <hr> |
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Chris Lattner | e9ef457 | 2007-05-12 03:23:40 +0000 | [diff] [blame^] | 126 | <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> |
Reid Spencer | 2c1ce4f | 2007-01-20 23:21:08 +0000 | [diff] [blame] | 127 | <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br> |
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