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| author | Chris Lattner <sabre@nondot.org> | 2007-05-06 23:21:05 +0000 |
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| committer | Chris Lattner <sabre@nondot.org> | 2007-05-06 23:21:05 +0000 |
| commit | c9bafdaa752db1cbfe0354fd50b1735187980cdb (patch) | |
| tree | bc5fb543c2c7d5e16ee0759e3a9d888ebe1fc0d5 /docs/BytecodeFormat.html | |
| parent | de36ffd2ca8304ddaf189cf3b1ef97f7b57c2cb3 (diff) | |
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diff --git a/docs/BytecodeFormat.html b/docs/BytecodeFormat.html deleted file mode 100644 index 1dc9c742bd..0000000000 --- a/docs/BytecodeFormat.html +++ /dev/null @@ -1,2158 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> -<html> -<head> - <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> - <title>LLVM Bytecode File Format</title> - <link rel="stylesheet" href="llvm.css" type="text/css"> - <style type="text/css"> - TR, TD { border: 2px solid gray; padding-left: 4pt; padding-right: 4pt; - padding-top: 2pt; padding-bottom: 2pt; } - TH { border: 2px solid gray; font-weight: bold; font-size: 105%; } - TABLE { text-align: center; border: 2px solid black; - border-collapse: collapse; margin-top: 1em; margin-left: 1em; - margin-right: 1em; margin-bottom: 1em; } - .td_left { border: 2px solid gray; text-align: left; } - </style> -</head> -<body> -<div class="doc_title"> LLVM Bytecode File Format </div> -<ol> - <li><a href="#abstract">Abstract</a></li> - <li><a href="#concepts">Concepts</a> - <ol> - <li><a href="#blocks">Blocks</a></li> - <li><a href="#lists">Lists</a></li> - <li><a href="#fields">Fields</a></li> - <li><a href="#align">Alignment</a></li> - <li><a href="#vbr">Variable Bit-Rate Encoding</a></li> - <li><a href="#encoding">Encoding Primitives</a></li> - <li><a href="#slots">Slots</a></li> - </ol> - </li> - <li><a href="#general">General Structure</a> </li> - <li><a href="#blockdefs">Block Definitions</a> - <ol> - <li><a href="#signature">Signature Block</a></li> - <li><a href="#module">Module Block</a></li> - <li><a href="#globaltypes">Global Type Pool</a></li> - <li><a href="#globalinfo">Module Info Block</a></li> - <li><a href="#constantpool">Global Constant Pool</a></li> - <li><a href="#functiondefs">Function Definition</a></li> - <li><a href="#instructionlist">Instructions List</a></li> - <li><a href="#instructions">Instructions</a></li> - <li><a href="#symtab">Symbol Table</a></li> - </ol> - </li> - <li><a href="#versiondiffs">Version Differences</a> - <ol> - <li><a href="#vers13">Version 1.3 Differences From 1.4</a></li> - <li><a href="#vers12">Version 1.2 Differences From 1.3</a></li> - <li><a href="#vers11">Version 1.1 Differences From 1.2</a></li> - <li><a href="#vers10">Version 1.0 Differences From 1.1</a></li> - </ol> - </li> -</ol> -<div class="doc_author"> -<p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a> -</p> -</div> -<!-- *********************************************************************** --> -<div class="doc_section"> <a name="abstract">Abstract </a></div> -<!-- *********************************************************************** --> -<div class="doc_text"> -<p>This document describes the LLVM bytecode file format. It specifies -the binary encoding rules of the bytecode file format so that -equivalent systems can encode bytecode files correctly. The LLVM -bytecode representation is used to store the intermediate -representation on disk in compacted form.</p> -<p>The LLVM bytecode format may change in the future, but LLVM will -always be backwards compatible with older formats. This document will -only describe the most current version of the bytecode format. See <a - href="#versiondiffs">Version Differences</a> for the details on how -the current version is different from previous versions.</p> -</div> -<!-- *********************************************************************** --> -<div class="doc_section"> <a name="concepts">Concepts</a> </div> -<!-- *********************************************************************** --> -<div class="doc_text"> -<p>This section describes the general concepts of the bytecode file -format without getting into specific layout details. It is recommended -that you read this section thoroughly before interpreting the detailed -descriptions.</p> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="blocks">Blocks</a> </div> -<div class="doc_text"> -<p>LLVM bytecode files consist simply of a sequence of blocks of bytes -using a binary encoding Each block begins with an header of two -unsigned integers. The first value identifies the type of block and the -second value provides the size of the block in bytes. The block -identifier is used because it is possible for entire blocks to be -omitted from the file if they are empty. The block identifier helps the -reader determine which kind of block is next in the file. Note that -blocks can be nested within other blocks.</p> -<p> All blocks are variable length, and the block header specifies the -size of the block. All blocks begin on a byte index that is aligned to -an even 32-bit boundary. That is, the first block is 32-bit aligned -because it starts at offset 0. Each block is padded with zero fill -bytes to ensure that the next block also starts on a 32-bit boundary.</p> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="lists">Lists</a> </div> -<div class="doc_text"> -<p>LLVM Bytecode blocks often contain lists of things of a similar -type. For example, a function contains a list of instructions and a -function type contains a list of argument types. There are two basic -types of lists: length lists (<a href="#llist">llist</a>), and null -terminated lists (<a href="#zlist">zlist</a>), as described below in -the <a href="#encoding">Encoding Primitives</a>.</p> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="fields">Fields</a> </div> -<div class="doc_text"> -<p>Fields are units of information that LLVM knows how to write atomically. Most -fields have a uniform length or some kind of length indication built into their -encoding. For example, a constant string (array of bytes) is written simply as -the length followed by the characters. Although this is similar to a list, -constant strings are treated atomically and are thus fields.</p> -<p>Fields use a condensed bit format specific to the type of information -they must contain. As few bits as possible are written for each field. The -sections that follow will provide the details on how these fields are -written and how the bits are to be interpreted.</p> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="align">Alignment</a> </div> -<div class="doc_text"> - <p>To support cross-platform differences, the bytecode file is aligned on - certain boundaries. This means that a small amount of padding (at most 3 - bytes) will be added to ensure that the next entry is aligned to a 32-bit - boundary.</p> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="vbr">Variable Bit-Rate Encoding</a> -</div> -<div class="doc_text"> -<p>Most of the values written to LLVM bytecode files are small integers. To -minimize the number of bytes written for these quantities, an encoding scheme -similar to UTF-8 is used to write integer data. The scheme is known as -variable bit rate (vbr) encoding. In this encoding, the high bit of -each byte is used to indicate if more bytes follow. If (byte & -0x80) is non-zero in any given byte, it means there is another byte -immediately following that also contributes to the value. For the final -byte (byte & 0x80) is false (the high bit is not set). In each byte -only the low seven bits contribute to the value. Consequently 32-bit -quantities can take from one to <em>five</em> bytes to encode. In -general, smaller quantities will encode in fewer bytes, as follows:</p> -<table> - <tbody> - <tr> - <th>Byte #</th> - <th>Significant Bits</th> - <th>Maximum Value</th> - </tr> - <tr> - <td>1</td> - <td>0-6</td> - <td>127</td> - </tr> - <tr> - <td>2</td> - <td>7-13</td> - <td>16,383</td> - </tr> - <tr> - <td>3</td> - <td>14-20</td> - <td>2,097,151</td> - </tr> - <tr> - <td>4</td> - <td>21-27</td> - <td>268,435,455</td> - </tr> - <tr> - <td>5</td> - <td>28-34</td> - <td>34,359,738,367</td> - </tr> - <tr> - <td>6</td> - <td>35-41</td> - <td>4,398,046,511,103</td> - </tr> - <tr> - <td>7</td> - <td>42-48</td> - <td>562,949,953,421,311</td> - </tr> - <tr> - <td>8</td> - <td>49-55</td> - <td>72,057,594,037,927,935</td> - </tr> - <tr> - <td>9</td> - <td>56-62</td> - <td>9,223,372,036,854,775,807</td> - </tr> - <tr> - <td>10</td> - <td>63-69</td> - <td>1,180,591,620,717,411,303,423</td> - </tr> - </tbody> -</table> -<p>Note that in practice, the tenth byte could only encode bit 63 since -the maximum quantity to use this encoding is a 64-bit integer.</p> -<p><em>Signed</em> VBR values are encoded with the standard vbr -encoding, but with the sign bit as the low order bit instead of the -high order bit. This allows small negative quantities to be encoded -efficiently. For example, -3 -is encoded as "((3 << 1) | 1)" and 3 is encoded as "(3 << -1) | 0)", emitted with the standard vbr encoding above.</p> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="encoding">Encoding Primitives</a> </div> -<div class="doc_text"> -<p>Each field in the bytecode format is encoded into the file using a -small set of primitive formats. The table below defines the encoding -rules for the various primitives used and gives them each a type name. -The type names used in the descriptions of blocks and fields in the <a - href="#details">Detailed Layout</a>next section. Any type name with -the suffix <em>_vbr</em> indicates a quantity that is encoded using -variable bit rate encoding as described above.</p> -<table class="doc_table"> - <tbody> - <tr> - <th><b>Type</b></th> - <th class="td_left"><b>Rule</b></th> - </tr> - <tr> - <td><a name="unsigned"><b>unsigned</b></a></td> - <td class="td_left">A 32-bit unsigned integer that always occupies four - consecutive bytes. The unsigned integer is encoded using LSB first - ordering. That is bits 2<sup>0</sup> through 2<sup>7</sup> are in the - byte with the lowest file offset (little endian).</td> - </tr> - <tr> - <td style="vertical-align: top;"><a name="uint24_vbr"> - <b>uint24_vbr</b></a></td> - <td style="vertical-align: top; text-align: left;">A 24-bit unsigned - integer that occupies from one to four bytes using variable bit rate - encoding.</td> - </tr> - <tr> - <td><a name="uint32_vbr"><b>uint32_vbr</b></a></td> - <td class="td_left">A 32-bit unsigned integer that occupies from one to - five bytes using variable bit rate encoding.</td> - </tr> - <tr> - <td><a name="uint64_vbr"><b>uint64_vbr</b></a></td> - <td class="td_left">A 64-bit unsigned integer that occupies from one to - ten bytes using variable bit rate encoding.</td> - </tr> - <tr> - <td><a name="int64_vbr"><b>int64_vbr</b></a></td> - <td class="td_left">A 64-bit signed integer that occupies from one to ten - bytes using the signed variable bit rate encoding.</td> - </tr> - <tr> - <td><a name="char"><b>char</b></a></td> - <td class="td_left">A single unsigned character encoded into one byte</td> - </tr> - <tr> - <td><a name="bit"><b>bit(n-m)</b></a></td> - <td class="td_left">A set of bit within some larger integer field. The - values of <code>n</code> and <code>m</code> specify the inclusive range - of bits that define the subfield. The value for <code>m</code> may be - omitted if its the same as <code>n</code>.</td> - </tr> - <tr> - <td style="vertical-align: top;"><b><a name="float"><b>float</b></a></b> - </td> - <td style="vertical-align: top; text-align: left;">A floating point - value encoded as a 32-bit IEEE value written in little-endian form.<br> - </td> - </tr> - <tr> - <td style="vertical-align: top;"><b><b><a name="double"><b>double</b></a> - </b></b></td> - <td style="vertical-align: top; text-align: left;">A floating point value - encoded as a64-bit IEEE value written in little-endian form</td> - </tr> - <tr> - <td><a name="string"><b>string</b></a></td> - <td class="td_left">A uint32_vbr indicating the type of the constant - string which also includes its length, immediately followed by the - characters of the string. There is no terminating null byte in the - string.</td> - </tr> - <tr> - <td><a name="data"><b>data</b></a></td> - <td class="td_left">An arbitrarily long segment of data to which no - interpretation is implied. This is used for constant initializers.<br> - </td> - </tr> - <tr> - <td><a name="llist"><b>llist(x)</b></a></td> - <td class="td_left">A length list of x. This means the list is encoded - as an <a href="#uint32_vbr">uint32_vbr</a> providing the length of the - list, followed by a sequence of that many "x" items. This implies that - the reader should iterate the number of times provided by the length. - </td> - </tr> - <tr> - <td><a name="zlist"><b>zlist(x)</b></a></td> - <td class="td_left">A zero-terminated list of x. This means the list is - encoded as a sequence of an indeterminate number of "x" items, followed - by an <a href="#uint32_vbr">uint32_vbr</a> terminating value. This - implies that none of the "x" items can have a zero value (or else the - list terminates).</td> - </tr> - <tr> - <td><a name="block"><b>block</b></a></td> - <td class="td_left">A block of data that is logically related. A block - is an unsigned 32-bit integer that encodes the type of the block in - the low 5 bits and the size of the block in the high 27 bits. The - length does not include the block header or any alignment bytes at the - end of the block. Blocks may compose other blocks. </td> - </tr> - </tbody> -</table> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="notation">Field Notation</a> </div> -<div class="doc_text"> -<p>In the detailed block and field descriptions that follow, a regex -like notation is used to describe optional and repeated fields. A very -limited subset of regex is used to describe these, as given in the -following table: </p> -<table class="doc_table"> - <tbody> - <tr> - <th><b>Character</b></th> - <th class="td_left"><b>Meaning</b></th> - </tr> - <tr> - <td><b><code>?</code></b></td> - <td class="td_left">The question mark indicates 0 or 1 occurrences of - the thing preceding it.</td> - </tr> - <tr> - <td><b><code>*</code></b></td> - <td class="td_left">The asterisk indicates 0 or more occurrences of the - thing preceding it.</td> - </tr> - <tr> - <td><b><code>+</code></b></td> - <td class="td_left">The plus sign indicates 1 or more occurrences of the - thing preceding it.</td> - </tr> - <tr> - <td><b><code>()</code></b></td> - <td class="td_left">Parentheses are used for grouping.</td> - </tr> - <tr> - <td><b><code>,</code></b></td> - <td class="td_left">The comma separates sequential fields.</td> - </tr> - </tbody> -</table> -<p>So, for example, consider the following specifications:</p> -<div class="doc_code"> -<ol> - <li><code>string?</code></li> - <li><code>(uint32_vbr,uin32_vbr)+</code></li> - <li><code>(unsigned?,uint32_vbr)*</code></li> - <li><code>(llist(unsigned))?</code></li> -</ol> -</div> -<p>with the following interpretations:</p> -<ol> - <li>An optional string. Matches either nothing or a single string</li> - <li>One or more pairs of uint32_vbr.</li> - <li>Zero or more occurrences of either an unsigned followed by a uint32_vbr - or just a uint32_vbr.</li> - <li>An optional length list of unsigned values.</li> -</ol> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="slots">Slots</a> </div> -<div class="doc_text"> -<p>The bytecode format uses the notion of a "slot" to reference Types -and Values. Since the bytecode file is a <em>direct</em> representation of -LLVM's intermediate representation, there is a need to represent pointers in -the file. Slots are used for this purpose. For example, if one has the -following assembly: -</p> -<div class="doc_code"><code> %MyType = type { int, sbyte }<br> -%MyVar = external global %MyType -</code></div> -<p>there are two definitions. The definition of <tt>%MyVar</tt> uses -<tt>%MyType</tt>. -In the C++ IR this linkage between <tt>%MyVar</tt> and <tt>%MyType</tt> -is explicit through the use of C++ pointers. In bytecode, however, there's no -ability to store memory addresses. Instead, we compute and write out -slot numbers for every Type and Value written to the file.</p> -<p>A slot number is simply an unsigned 32-bit integer encoded in the variable -bit rate scheme (see <a href="#encoding">encoding</a>). This ensures that -low slot numbers are encoded in one byte. Through various bits of magic LLVM -attempts to always keep the slot numbers low. The first attempt is to associate -slot numbers with their "type plane". That is, Values of the same type -are written to the bytecode file in a list (sequentially). Their order in -that list determines their slot number. This means that slot #1 doesn't mean -anything unless you also specify for which type you want slot #1. Types are -always written to the file first (in the <a href="#globaltypes">Global Type -Pool</a>) and in such a way that both forward and backward references of the -types can often be resolved with a single pass through the type pool. </p> -<p>In summary then, a slot number can be thought of as just a vbr encoded index -into a list of Type* or Value*. To keep slot numbers low, Value* are indexed by -two slot numbers: the "type plane index" (type slot) and the "value index" -(value slot).</p> -</div> -<!-- *********************************************************************** --> -<div class="doc_section"> <a name="general">General Structure</a> </div> -<!-- *********************************************************************** --> -<div class="doc_text"> -<p>This section provides the general structure of the LLVM bytecode -file format. The bytecode file format requires blocks to be in a -certain order and nested in a particular way so that an LLVM module can -be constructed efficiently from the contents of the file. This ordering -defines a general structure for bytecode files as shown below. The -table below shows the order in which all block types may appear. Please -note that some of the blocks are optional and some may be repeated. The -structure is fairly loose because optional blocks, if empty, are -completely omitted from the file.</p> -<table> - <tbody> - <tr> - <th>ID</th> - <th>Parent</th> - <th>Optional?</th> - <th>Repeated?</th> - <th>Level</th> - <th>Block Type</th> - <th>Description</th> - </tr> - <tr> - <td>N/A</td> - <td>File</td> - <td>No</td> - <td>No</td> - <td>0</td> - <td class="td_left"><a href="#signature">Signature</a></td> - <td class="td_left">This contains the file signature (magic -number) that identifies the file as LLVM bytecode.</td> - </tr> - <tr> - <td>0x01</td> - <td>File</td> - <td>No</td> - <td>No</td> - <td>0</td> - <td class="td_left"><a href="#module">Module</a></td> - <td class="td_left">This is the top level block in a bytecode -file. It contains all the other blocks. </td> - </tr> - <tr> - <td>0x06</td> - <td>Module</td> - <td>No</td> - <td>No</td> - <td>1</td> - <td class="td_left"> <a href="#globaltypes">Global Type Pool</a></td> - <td class="td_left">This block contains all the global (module) -level types.</td> - </tr> - <tr> - <td>0x05</td> - <td>Module</td> - <td>No</td> - <td>No</td> - <td>1</td> - <td class="td_left"> <a href="#globalinfo">Module Globals Info</a></td> - <td class="td_left">This block contains the type, constness, and -linkage for each of the global variables in the module. It also -contains the type of the functions and the constant initializers.</td> - </tr> - <tr> - <td>0x03</td> - <td>Module</td> - <td>Yes</td> - <td>No</td> - <td>1</td> - <td class="td_left"> <a href="#constantpool">Module Constant Pool</a></td> - <td class="td_left">This block contains all the global constants -except function arguments, global values and constant strings.</td> - </tr> - <tr> - <td>0x02</td> - <td>Module</td> - <td>Yes</td> - <td>Yes</td> - <td>1</td> - <td class="td_left"> <a href="#functiondefs">Function Definitions</a>*</td> - <td class="td_left">One function block is written for each -function in the module. The function block contains the instructions, -type constant pool, and symbol table for the function.</td> - </tr> - <tr> - <td>0x03</td> - <td>Function</td> - <td>Yes</td> - <td>No</td> - <td>2</td> - <td class="td_left"> <a - href="#constantpool">Function Constant Pool</a></td> - <td class="td_left">Any constants (including types) used solely within - the function are emitted here in the function constant pool. </td> - </tr> - <tr> - <td>0x07</td> - <td>Function</td> - <td>No</td> - <td>No</td> - <td>2</td> - <td class="td_left"> <a - href="#instructionlist">Instruction List</a></td> - <td class="td_left">This block contains all the instructions of the - function. The basic blocks are inferred by terminating instructions. - </td> - </tr> - <tr> - <td>0x04</td> - <td>Function</td> - <td>Yes</td> - <td>No</td> - <td>2</td> - <td class="td_left"> <a - href="#symtab">Function Symbol Table</a></td> - <td class="td_left">This symbol table provides the names for the function - specific values used (basic block labels mostly).</td> - </tr> - <tr> - <td>0x04</td> - <td>Module</td> - <td>Yes</td> - <td>No</td> - <td>1</td> - <td class="td_left"> <a href="#symtab">Module Symbol Table</a></td> - <td class="td_left">This symbol table provides the names for the various - entries in the file that are not function specific (global vars, and - functions mostly).</td> - </tr> - </tbody> -</table> -<p>Use the links in the table for details about the contents of each of -the block types.</p> -</div> -<!-- *********************************************************************** --> -<div class="doc_section"> <a name="blockdefs">Block Definitions</a> </div> -<!-- *********************************************************************** --> -<div class="doc_text"> -<p>This section provides the detailed layout of the individual block -types in the LLVM bytecode file format. </p> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="signature">Signature Block</a> </div> -<div class="doc_text"> -<p>The signature occurs in every LLVM bytecode file and is always first. -It simply provides a few bytes of data to identify the file as being an LLVM -bytecode file. This block is always four bytes in length and differs from the -other blocks because there is no identifier and no block length at the start -of the block. Essentially, this block is just the "magic number" for the file. -</p> -<p>There are two types of signatures for LLVM bytecode: uncompressed and -compressed as shown in the table below. </p> -<table> - <tbody> - <tr> - <th><b>Type</b></th> - <th class="td_left"><b>Uncompressed</b></th> - <th class="td_left"><b>Compressed</b></th> - </tr> - <tr> - <td><a href="#char">char</a></td> - <td class="td_left">Constant "l" (0x6C)</td> - <td class="td_left">Constant "l" (0x6C)</td> - </tr> - <tr> - <td><a href="#char">char</a></td> - <td class="td_left">Constant "l" (0x6C)</td> - <td class="td_left">Constant "l" (0x6C)</td> - </tr> - <tr> - <td><a href="#char">char</a></td> - <td class="td_left">Constant "v" (0x76)</td> - <td class="td_left">Constant "v" (0x76)</td> - </tr> - <tr> - <td><a href="#char">char</a></td> - <td class="td_left">Constant "m" (0x6D)</td> - <td class="td_left">Constant "c" (0x63)</td> - </tr> - <tr> - <td><a href="#char">char</a></td> - <td class="td_left">N/A</td> - <td class="td_left">'0'=null,'1'=gzip,'2'=bzip2</td> - </tr> - </tbody> -</table> -<p>In other words, the uncompressed signature is just the characters 'llvm' -while the compressed signature is the characters 'llvc' followed by an ascii -digit ('0', '1', or '2') that indicates the kind of compression used. A value of -'0' indicates that null compression was used. This can happen when compression -was requested on a platform that wasn't configured for gzip or bzip2. A value of -'1' means that the rest of the file is compressed using the gzip algorithm and -should be uncompressed before interpretation. A value of '2' means that the rest -of the file is compressed using the bzip2 algorithm and should be uncompressed -before interpretation. In all cases, the data resulting from uncompression -should be interpreted as if it occurred immediately after the 'llvm' -signature (i.e. the uncompressed data begins with the -<a href="#module">Module Block</a></p> -<p><b>NOTE:</b> As of LLVM 1.4, all bytecode files produced by the LLVM tools -are compressed by default. To disable compression, pass the -<tt>--disable-compression</tt> option to the tool, if it supports it. -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="module">Module Block</a> </div> -<div class="doc_text"> -<p>The module block contains a small pre-amble and all the other blocks in -the file. The table below shows the structure of the module block. Note that it -only provides the module identifier, size of the module block, and the format -information. Everything else is contained in other blocks, described in other -sections.</p> -<table> - <tbody> - <tr> - <th><b>Type</b></th> - <th class="td_left"><b>Field Description</b></th> - </tr> - <tr> - <td><a href="#unsigned">unsigned</a><br></td> - <td class="td_left"><a href="#mod_header">Module Block Identifier - (0x01)</a></td> - </tr> - <tr> - <td><a href="#unsigned">unsigned</a></td> - <td class="td_left"><a href="#mod_header">Module Block Size</a></td> - </tr> - <tr> - <td><a href="#uint32_vbr">uint32_vbr</a></td> - <td class="td_left"><a href="#format">Format Information</a></td> - </tr> - <tr> - <td><a href="#block">block</a></td> - <td class="td_left"><a href="#globaltypes">Global Type Pool</a></td> - </tr> - <tr> - <td><a href="#block">block</a></td> - <td class="td_left"><a href="#globalinfo">Module Globals Info</a></td> - </tr> - <tr> - <td><a href="#block">block</a></td> - <td class="td_left"><a href="#constantpool">Module Constant Pool</a></td> - </tr> - <tr> - <td><a href="#block">block</a>*</td> - <td class="td_left"><a href="#functiondefs">Function Definitions</a></td> - </tr> - <tr> - <td><a href="#block">block</a></td> - <td class="td_left"><a href="#symtab">Module Symbol Table</a></td> - </tr> - </tbody> -</table> -</div> - -<!-- _______________________________________________________________________ --> -<div class="doc_subsubsection"><a name="mod_header">Module Block Header</a></div> -<div class="doc_text"> - <p>The block header for the module block uses a longer format than the other - blocks in a bytecode file. Specifically, instead of encoding the type and size - of the block into a 32-bit integer with 5-bits for type and 27-bits for size, - the module block header uses two 32-bit unsigned values, one for type, and one - for size. While the 2<sup>27</sup> byte limit on block size is sufficient - for the blocks contained in the module, it isn't sufficient for the module - block itself because we want to ensure that bytecode files as large as - 2<sup>32</sup> bytes are possible. For this reason, the module block (and - only the module block) uses a long format header.</p> -</div> - -<!-- _______________________________________________________________________ --> -<div class="doc_subsubsection"><a name="format">Format Information</a></div> -<div class="doc_text"> -<p>The format information field is encoded into a <a href="#uint32_vbr">uint32_vbr</a>.</p> - -<p>Of particular note, the bytecode format number is simply a 32-bit -monotonically increasing integer that identifies the version of the bytecode -format (which is not directly related to the LLVM release number). The -bytecode versions defined so far are (note that this document only -describes the latest version, 2.0):</p> -<ul> - <li>#0: LLVM 1.0 & 1.1</li> - <li>#1: LLVM 1.2</li> - <li>#2: LLVM 1.2.5 (not released)</li> - <li>#3: LLVM 1.3</li> - <li>#4: LLVM 1.3.x (not released)</li> - <li>#5: LLVM 1.4 through 1.8</li> - <li>#6: LLVM 1.9</li> - <li>#7: LLVM 2.0 and newer</li> -</ul> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsection"><a name="globaltypes">Global Type Pool</a> </div> -<div class="doc_text"> -<p>The global type pool consists of type definitions. Their order of appearance -in the file determines their type slot number (0 based). Slot numbers are -used to replace pointers in the intermediate representation. Each slot number -uniquely identifies one entry in a type plane (a collection of values of the -same type). Since all values have types and are associated with the order in -which the type pool is written, the global type pool <em>must</em> be written -as the first block of a module. If it is not, attempts to read the file will -fail because both forward and backward type resolution will not be possible.</p> -<p>The type pool is simply a list of type definitions, as shown in the -table below.</p> -<table> - <tbody> - <tr> - <th><b>Type</b></th> - <th class="td_left"><b>Field Description</b></th> - </tr> - <tr> - <td><a href="#unsigned">block</a></td> - <td class="td_left">Type Pool Identifier (0x06) + Size<br> - </td> - </tr> - <tr> - <td><a href="#llist">llist</a>(<a href="#type">type</a>)</td> - <td class="td_left">A length list of type definitions.</td> - </tr> - </tbody> -</table> -</div> -<!-- _______________________________________________________________________ --> -<div class="doc_subsubsection"><a name="type">Type Definitions</a></div> -<div class="doc_text"> -<p>Types in the type pool are defined using a different format for each kind -of type, as given in the following sections.</p> -<h3>Primitive Types</h3> -<p>The primitive types encompass the basic integer and floating point -types. They are encoded simply as their TypeID.</p> -<table> - <tbody> - <tr> - <th><b>Type</b></th> - <th class="td_left"><b>Description</b></th> - </tr> - <tr> - <td><a href="#uint24_vbr">uint24_vbr</a></td> - <td class="td_left">Type ID for the primitive types (values 1 to 11) - <sup>1</sup></td> - </tr> - </tbody> -</table> -Notes: -<ol> - <li>The values for the Type IDs for the primitive types are provided by the - definition of the <code>llvm::Type::TypeID</code> enumeration in - <code>include/llvm/Type.h</code>. The enumeration gives the following mapping: - <ol> - <li>bool</li> - <li>ubyte</li> - <li>sbyte</li> - <li>ushort</li> - <li>short</li> - <li>uint</li> - <li>int</li> - <li>ulong</li> - <li>long</li> - <li>float</li> - <li&g |