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-<div class="doc_title"> LLVM Bitcode File Format </div>
+<h1> LLVM Bitcode File Format</h1>
<ol>
<li><a href="#abstract">Abstract</a></li>
- <li><a href="#concepts">Concepts</a></li>
+ <li><a href="#overview">Overview</a></li>
+ <li><a href="#bitstream">Bitstream Format</a>
+ <ol>
+ <li><a href="#magic">Magic Numbers</a></li>
+ <li><a href="#primitives">Primitives</a></li>
+ <li><a href="#abbrevid">Abbreviation IDs</a></li>
+ <li><a href="#blocks">Blocks</a></li>
+ <li><a href="#datarecord">Data Records</a></li>
+ <li><a href="#abbreviations">Abbreviations</a></li>
+ <li><a href="#stdblocks">Standard Blocks</a></li>
+ </ol>
+ </li>
+ <li><a href="#wrapper">Bitcode Wrapper Format</a>
+ </li>
+ <li><a href="#llvmir">LLVM IR Encoding</a>
+ <ol>
+ <li><a href="#basics">Basics</a></li>
+ <li><a href="#MODULE_BLOCK">MODULE_BLOCK Contents</a></li>
+ <li><a href="#PARAMATTR_BLOCK">PARAMATTR_BLOCK Contents</a></li>
+ <li><a href="#TYPE_BLOCK">TYPE_BLOCK Contents</a></li>
+ <li><a href="#CONSTANTS_BLOCK">CONSTANTS_BLOCK Contents</a></li>
+ <li><a href="#FUNCTION_BLOCK">FUNCTION_BLOCK Contents</a></li>
+ <li><a href="#TYPE_SYMTAB_BLOCK">TYPE_SYMTAB_BLOCK Contents</a></li>
+ <li><a href="#VALUE_SYMTAB_BLOCK">VALUE_SYMTAB_BLOCK Contents</a></li>
+ <li><a href="#METADATA_BLOCK">METADATA_BLOCK Contents</a></li>
+ <li><a href="#METADATA_ATTACHMENT">METADATA_ATTACHMENT Contents</a></li>
+ </ol>
+ </li>
</ol>
<div class="doc_author">
- <p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a> and
- <a href="mailto:sabre@nondot.org">Chris Lattner</a>.
+ <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
+ <a href="http://www.reverberate.org">Joshua Haberman</a>,
+ and <a href="mailto:housel@acm.org">Peter S. Housel</a>.
</p>
</div>
+
<!-- *********************************************************************** -->
-<div class="doc_section"> <a name="abstract">Abstract </a></div>
+<h2><a name="abstract">Abstract</a></h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
-<p>This document describes the LLVM bitcode file format. It specifies
-the binary encoding rules of the bitcode file format so that
-equivalent systems can encode bitcode files correctly. The LLVM
-bitcode representation is used to store the intermediate
-representation on disk in a compacted form.</p>
-<p>This document supercedes the LLVM bytecode file format for the 2.0
-release.</p>
+
+<div>
+
+<p>This document describes the LLVM bitstream file format and the encoding of
+the LLVM IR into it.</p>
+
</div>
+
<!-- *********************************************************************** -->
-<div class="doc_section"> <a name="concepts">Concepts</a> </div>
+<h2><a name="overview">Overview</a></h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
-<p>This section describes the general concepts of the bitcode file
-format without getting into specific layout details. It is recommended
-that you read this section thoroughly before interpreting the detailed
-descriptions.</p>
+
+<div>
+
+<p>
+What is commonly known as the LLVM bitcode file format (also, sometimes
+anachronistically known as bytecode) is actually two things: a <a
+href="#bitstream">bitstream container format</a>
+and an <a href="#llvmir">encoding of LLVM IR</a> into the container format.</p>
+
+<p>
+The bitstream format is an abstract encoding of structured data, very
+similar to XML in some ways. Like XML, bitstream files contain tags, and nested
+structures, and you can parse the file without having to understand the tags.
+Unlike XML, the bitstream format is a binary encoding, and unlike XML it
+provides a mechanism for the file to self-describe "abbreviations", which are
+effectively size optimizations for the content.</p>
+
+<p>LLVM IR files may be optionally embedded into a <a
+href="#wrapper">wrapper</a> structure that makes it easy to embed extra data
+along with LLVM IR files.</p>
+
+<p>This document first describes the LLVM bitstream format, describes the
+wrapper format, then describes the record structure used by LLVM IR files.
+</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<h2><a name="bitstream">Bitstream Format</a></h2>
+<!-- *********************************************************************** -->
+
+<div>
+
+<p>
+The bitstream format is literally a stream of bits, with a very simple
+structure. This structure consists of the following concepts:
+</p>
+
+<ul>
+<li>A "<a href="#magic">magic number</a>" that identifies the contents of
+ the stream.</li>
+<li>Encoding <a href="#primitives">primitives</a> like variable bit-rate
+ integers.</li>
+<li><a href="#blocks">Blocks</a>, which define nested content.</li>
+<li><a href="#datarecord">Data Records</a>, which describe entities within the
+ file.</li>
+<li>Abbreviations, which specify compression optimizations for the file.</li>
+</ul>
+
+<p>Note that the <a
+href="CommandGuide/html/llvm-bcanalyzer.html">llvm-bcanalyzer</a> tool can be
+used to dump and inspect arbitrary bitstreams, which is very useful for
+understanding the encoding.</p>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="magic">Magic Numbers</a>
+</h3>
+
+<div>
+
+<p>The first two bytes of a bitcode file are 'BC' (0x42, 0x43).
+The second two bytes are an application-specific magic number. Generic
+bitcode tools can look at only the first two bytes to verify the file is
+bitcode, while application-specific programs will want to look at all four.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="primitives">Primitives</a>
+</h3>
+
+<div>
+
+<p>
+A bitstream literally consists of a stream of bits, which are read in order
+starting with the least significant bit of each byte. The stream is made up of a
+number of primitive values that encode a stream of unsigned integer values.
+These integers are encoded in two ways: either as <a href="#fixedwidth">Fixed
+Width Integers</a> or as <a href="#variablewidth">Variable Width
+Integers</a>.
+</p>
+
+<!-- _______________________________________________________________________ -->
+<h4>
+ <a name="fixedwidth">Fixed Width Integers</a>
+</h4>
+
+<div>
+
+<p>Fixed-width integer values have their low bits emitted directly to the file.
+ For example, a 3-bit integer value encodes 1 as 001. Fixed width integers
+ are used when there are a well-known number of options for a field. For
+ example, boolean values are usually encoded with a 1-bit wide integer.
+</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4>
+ <a name="variablewidth">Variable Width Integers</a>
+</h4>
+
+<div>
+
+<p>Variable-width integer (VBR) values encode values of arbitrary size,
+optimizing for the case where the values are small. Given a 4-bit VBR field,
+any 3-bit value (0 through 7) is encoded directly, with the high bit set to
+zero. Values larger than N-1 bits emit their bits in a series of N-1 bit
+chunks, where all but the last set the high bit.</p>
+
+<p>For example, the value 27 (0x1B) is encoded as 1011 0011 when emitted as a
+vbr4 value. The first set of four bits indicates the value 3 (011) with a
+continuation piece (indicated by a high bit of 1). The next word indicates a
+value of 24 (011 << 3) with no continuation. The sum (3+24) yields the value
+27.
+</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="char6">6-bit characters</a></h4>
+
+<div>
+
+<p>6-bit characters encode common characters into a fixed 6-bit field. They
+represent the following characters with the following 6-bit values:</p>
+
+<div class="doc_code">
+<pre>
+'a' .. 'z' — 0 .. 25
+'A' .. 'Z' — 26 .. 51
+'0' .. '9' — 52 .. 61
+ '.' — 62
+ '_' — 63
+</pre>
+</div>
+
+<p>This encoding is only suitable for encoding characters and strings that
+consist only of the above characters. It is completely incapable of encoding
+characters not in the set.</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="wordalign">Word Alignment</a></h4>
+
+<div>
+
+<p>Occasionally, it is useful to emit zero bits until the bitstream is a
+multiple of 32 bits. This ensures that the bit position in the stream can be
+represented as a multiple of 32-bit words.</p>
+
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="abbrevid">Abbreviation IDs</a>
+</h3>
+
+<div>
+
+<p>
+A bitstream is a sequential series of <a href="#blocks">Blocks</a> and
+<a href="#datarecord">Data Records</a>. Both of these start with an
+abbreviation ID encoded as a fixed-bitwidth field. The width is specified by
+the current block, as described below. The value of the abbreviation ID
+specifies either a builtin ID (which have special meanings, defined below) or
+one of the abbreviation IDs defined for the current block by the stream itself.
+</p>
+
+<p>
+The set of builtin abbrev IDs is:
+</p>
+
+<ul>
+<li><tt>0 - <a href="#END_BLOCK">END_BLOCK</a></tt> — This abbrev ID marks
+ the end of the current block.</li>
+<li><tt>1 - <a href="#ENTER_SUBBLOCK">ENTER_SUBBLOCK</a></tt> — This
+ abbrev ID marks the beginning of a new block.</li>
+<li><tt>2 - <a href="#DEFINE_ABBREV">DEFINE_ABBREV</a></tt> — This defines
+ a new abbreviation.</li>
+<li><tt>3 - <a href="#UNABBREV_RECORD">UNABBREV_RECORD</a></tt> — This ID
+ specifies the definition of an unabbreviated record.</li>
+</ul>
+
+<p>Abbreviation IDs 4 and above are defined by the stream itself, and specify
+an <a href="#abbrev_records">abbreviated record encoding</a>.</p>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="blocks">Blocks</a>
+</h3>
+
+<div>
+
+<p>
+Blocks in a bitstream denote nested regions of the stream, and are identified by
+a content-specific id number (for example, LLVM IR uses an ID of 12 to represent
+function bodies). Block IDs 0-7 are reserved for <a href="#stdblocks">standard blocks</a>
+whose meaning is defined by Bitcode; block IDs 8 and greater are
+application specific. Nested blocks capture the hierarchical structure of the data
+encoded in it, and various properties are associated with blocks as the file is
+parsed. Block definitions allow the reader to efficiently skip blocks
+in constant time if the reader wants a summary of blocks, or if it wants to
+efficiently skip data it does not understand. The LLVM IR reader uses this
+mechanism to skip function bodies, lazily reading them on demand.
+</p>
+
+<p>
+When reading and encoding the stream, several properties are maintained for the
+block. In particular, each block maintains:
+</p>
+
+<ol>
+<li>A current abbrev id width. This value starts at 2 at the beginning of
+ the stream, and is set every time a
+ block record is entered. The block entry specifies the abbrev id width for
+ the body of the block.</li>
+
+<li>A set of abbreviations. Abbreviations may be defined within a block, in
+ which case they are only defined in that block (neither subblocks nor
+ enclosing blocks see the abbreviation). Abbreviations can also be defined
+ inside a <tt><a href="#BLOCKINFO">BLOCKINFO</a></tt> block, in which case
+ they are defined in all blocks that match the ID that the BLOCKINFO block is
+ describing.
+</li>
+</ol>
+
+<p>
+As sub blocks are entered, these properties are saved and the new sub-block has
+its own set of abbreviations, and its own abbrev id width. When a sub-block is
+popped, the saved values are restored.
+</p>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="ENTER_SUBBLOCK">ENTER_SUBBLOCK Encoding</a></h4>
+
+<div>
+
+<p><tt>[ENTER_SUBBLOCK, blockid<sub>vbr8</sub>, newabbrevlen<sub>vbr4</sub>,
+ <align32bits>, blocklen<sub>32</sub>]</tt></p>
+
+<p>
+The <tt>ENTER_SUBBLOCK</tt> abbreviation ID specifies the start of a new block
+record. The <tt>blockid</tt> value is encoded as an 8-bit VBR identifier, and
+indicates the type of block being entered, which can be
+a <a href="#stdblocks">standard block</a> or an application-specific block.
+The <tt>newabbrevlen</tt> value is a 4-bit VBR, which specifies the abbrev id
+width for the sub-block. The <tt>blocklen</tt> value is a 32-bit aligned value
+that specifies the size of the subblock in 32-bit words. This value allows the
+reader to skip over the entire block in one jump.
+</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="END_BLOCK">END_BLOCK Encoding</a></h4>
+
+<div>
+
+<p><tt>[END_BLOCK, <align32bits>]</tt></p>
+
+<p>
+The <tt>END_BLOCK</tt> abbreviation ID specifies the end of the current block
+record. Its end is aligned to 32-bits to ensure that the size of the block is
+an even multiple of 32-bits.
+</p>
+
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="datarecord">Data Records</a>
+</h3>
+
+<div>
+<p>
+Data records consist of a record code and a number of (up to) 64-bit
+integer values. The interpretation of the code and values is
+application specific and may vary between different block types.
+Records can be encoded either using an unabbrev record, or with an
+abbreviation. In the LLVM IR format, for example, there is a record
+which encodes the target triple of a module. The code is
+<tt>MODULE_CODE_TRIPLE</tt>, and the values of the record are the
+ASCII codes for the characters in the string.
+</p>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="UNABBREV_RECORD">UNABBREV_RECORD Encoding</a></h4>
+
+<div>
+
+<p><tt>[UNABBREV_RECORD, code<sub>vbr6</sub>, numops<sub>vbr6</sub>,
+ op0<sub>vbr6</sub>, op1<sub>vbr6</sub>, ...]</tt></p>
+
+<p>
+An <tt>UNABBREV_RECORD</tt> provides a default fallback encoding, which is both
+completely general and extremely inefficient. It can describe an arbitrary
+record by emitting the code and operands as VBRs.
+</p>
+
+<p>
+For example, emitting an LLVM IR target triple as an unabbreviated record
+requires emitting the <tt>UNABBREV_RECORD</tt> abbrevid, a vbr6 for the
+<tt>MODULE_CODE_TRIPLE</tt> code, a vbr6 for the length of the string, which is
+equal to the number of operands, and a vbr6 for each character. Because there
+are no letters with values less than 32, each letter would need to be emitted as
+at least a two-part VBR, which means that each letter would require at least 12
+bits. This is not an efficient encoding, but it is fully general.
+</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="abbrev_records">Abbreviated Record Encoding</a></h4>
+
+<div>
+
+<p><tt>[<abbrevid>, fields...]</tt></p>
+
+<p>
+An abbreviated record is a abbreviation id followed by a set of fields that are
+encoded according to the <a href="#abbreviations">abbreviation definition</a>.
+This allows records to be encoded significantly more densely than records
+encoded with the <tt><a href="#UNABBREV_RECORD">UNABBREV_RECORD</a></tt> type,
+and allows the abbreviation types to be specified in the stream itself, which
+allows the files to be completely self describing. The actual encoding of
+abbreviations is defined below.
+</p>
+
+<p>The record code, which is the first field of an abbreviated record,
+may be encoded in the abbreviation definition (as a literal
+operand) or supplied in the abbreviated record (as a Fixed or VBR
+operand value).</p>
+
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="abbreviations">Abbreviations</a>
+</h3>
+
+<div>
+<p>
+Abbreviations are an important form of compression for bitstreams. The idea is
+to specify a dense encoding for a class of records once, then use that encoding
+to emit many records. It takes space to emit the encoding into the file, but
+the space is recouped (hopefully plus some) when the records that use it are
+emitted.
+</p>
+
+<p>
+Abbreviations can be determined dynamically per client, per file. Because the
+abbreviations are stored in the bitstream itself, different streams of the same
+format can contain different sets of abbreviations according to the needs
+of the specific stream.
+As a concrete example, LLVM IR files usually emit an abbreviation
+for binary operators. If a specific LLVM module contained no or few binary
+operators, the abbreviation does not need to be emitted.
+</p>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="DEFINE_ABBREV">DEFINE_ABBREV Encoding</a></h4>
+
+<div>
+
+<p><tt>[DEFINE_ABBREV, numabbrevops<sub>vbr5</sub>, abbrevop0, abbrevop1,
+ ...]</tt></p>
+
+<p>
+A <tt>DEFINE_ABBREV</tt> record adds an abbreviation to the list of currently
+defined abbreviations in the scope of this block. This definition only exists
+inside this immediate block — it is not visible in subblocks or enclosing
+blocks. Abbreviations are implicitly assigned IDs sequentially starting from 4
+(the first application-defined abbreviation ID). Any abbreviations defined in a
+<tt>BLOCKINFO</tt> record for the particular block type
+receive IDs first, in order, followed by any
+abbreviations defined within the block itself. Abbreviated data records
+reference this ID to indicate what abbreviation they are invoking.
+</p>
+
+<p>
+An abbreviation definition consists of the <tt>DEFINE_ABBREV</tt> abbrevid
+followed by a VBR that specifies the number of abbrev operands, then the abbrev
+operands themselves. Abbreviation operands come in three forms. They all start
+with a single bit that indicates whether the abbrev operand is a literal operand
+(when the bit is 1) or an encoding operand (when the bit is 0).
+</p>
+
+<ol>
+<li>Literal operands — <tt>[1<sub>1</sub>, litvalue<sub>vbr8</sub>]</tt>
+— Literal operands specify that the value in the result is always a single
+specific value. This specific value is emitted as a vbr8 after the bit
+indicating that it is a literal operand.</li>
+<li>Encoding info without data — <tt>[0<sub>1</sub>,
+ encoding<sub>3</sub>]</tt> — Operand encodings that do not have extra
+ data are just emitted as their code.
+</li>
+<li>Encoding info with data — <tt>[0<sub>1</sub>, encoding<sub>3</sub>,
+value<sub>vbr5</sub>]</tt> — Operand encodings that do have extra data are
+emitted as their code, followed by the extra data.
+</li>
+</ol>
+
+<p>The possible operand encodings are:</p>
+
+<ul>
+<li>Fixed (code 1): The field should be emitted as
+ a <a href="#fixedwidth">fixed-width value</a>, whose width is specified by
+ the operand's extra data.</li>
+<li>VBR (code 2): The field should be emitted as
+ a <a href="#variablewidth">variable-width value</a>, whose width is
+ specified by the operand's extra data.</li>
+<li>Array (code 3): This field is an array of values. The array operand
+ has no extra data, but expects another operand to follow it, indicating
+ the element type of the array. When reading an array in an abbreviated
+ record, the first integer is a vbr6 that indicates the array length,
+ followed by the encoded elements of the array. An array may only occur as
+ the last operand of an abbreviation (except for the one final operand that
+ gives the array's type).</li>
+<li>Char6 (code 4): This field should be emitted as
+ a <a href="#char6">char6-encoded value</a>. This operand type takes no
+ extra data. Char6 encoding is normally used as an array element type.
+ </li>
+<li>Blob (code 5): This field is emitted as a vbr6, followed by padding to a
+ 32-bit boundary (for alignment) and an array of 8-bit objects. The array of
+ bytes is further followed by tail padding to ensure that its total length is
+ a multiple of 4 bytes. This makes it very efficient for the reader to
+ decode the data without having to make a copy of it: it can use a pointer to
+ the data in the mapped in file and poke directly at it. A blob may only
+ occur as the last operand of an abbreviation.</li>
+</ul>
+
+<p>
+For example, target triples in LLVM modules are encoded as a record of the
+form <tt>[TRIPLE, 'a', 'b', 'c', 'd']</tt>. Consider if the bitstream emitted
+the following abbrev entry:
+</p>
+
+<div class="doc_code">
+<pre>
+[0, Fixed, 4]
+[0, Array]
+[0, Char6]
+</pre>
+</div>
+
+<p>
+When emitting a record with this abbreviation, the above entry would be emitted
+as:
+</p>
+
+<div class="doc_code">
+<p>
+<tt>[4<sub>abbrevwidth</sub>, 2<sub>4</sub>, 4<sub>vbr6</sub>, 0<sub>6</sub>,
+1<sub>6</sub>, 2<sub>6</sub>, 3<sub>6</sub>]</tt>
+</p>
+</div>
+
+<p>These values are:</p>
+
+<ol>
+<li>The first value, 4, is the abbreviation ID for this abbreviation.</li>
+<li>The second value, 2, is the record code for <tt>TRIPLE</tt> records within LLVM IR file <tt>MODULE_BLOCK</tt> blocks.</li>
+<li>The third value, 4, is the length of the array.</li>
+<li>The rest of the values are the char6 encoded values
+ for <tt>"abcd"</tt>.</li>
+</ol>
+
+<p>
+With this abbreviation, the triple is emitted with only 37 bits (assuming a
+abbrev id width of 3). Without the abbreviation, significantly more space would
+be required to emit the target triple. Also, because the <tt>TRIPLE</tt> value
+is not emitted as a literal in the abbreviation, the abbreviation can also be
+used for any other string value.
+</p>
+
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="stdblocks">Standard Blocks</a>
+</h3>
+
+<div>
+
+<p>
+In addition to the basic block structure and record encodings, the bitstream
+also defines specific built-in block types. These block types specify how the
+stream is to be decoded or other metadata. In the future, new standard blocks
+may be added. Block IDs 0-7 are reserved for standard blocks.
+</p>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="BLOCKINFO">#0 - BLOCKINFO Block</a></h4>
+
+<div>
+
+<p>
+The <tt>BLOCKINFO</tt> block allows the description of metadata for other
+blocks. The currently specified records are:
+</p>
+
+<div class="doc_code">
+<pre>
+[SETBID (#1), blockid]
+[DEFINE_ABBREV, ...]
+[BLOCKNAME, ...name...]
+[SETRECORDNAME, RecordID, ...name...]
+</pre>
+</div>
+
+<p>
+The <tt>SETBID</tt> record (code 1) indicates which block ID is being
+described. <tt>SETBID</tt> records can occur multiple times throughout the
+block to change which block ID is being described. There must be
+a <tt>SETBID</tt> record prior to any other records.
+</p>
+
+<p>
+Standard <tt>DEFINE_ABBREV</tt> records can occur inside <tt>BLOCKINFO</tt>
+blocks, but unlike their occurrence in normal blocks, the abbreviation is
+defined for blocks matching the block ID we are describing, <i>not</i> the
+<tt>BLOCKINFO</tt> block itself. The abbreviations defined
+in <tt>BLOCKINFO</tt> blocks receive abbreviation IDs as described
+in <tt><a href="#DEFINE_ABBREV">DEFINE_ABBREV</a></tt>.
+</p>
+
+<p>The <tt>BLOCKNAME</tt> record (code 2) can optionally occur in this block. The elements of
+the record are the bytes of the string name of the block. llvm-bcanalyzer can use
+this to dump out bitcode files symbolically.</p>
+
+<p>The <tt>SETRECORDNAME</tt> record (code 3) can also optionally occur in this block. The
+first operand value is a record ID number, and the rest of the elements of the record are
+the bytes for the string name of the record. llvm-bcanalyzer can use
+this to dump out bitcode files symbolically.</p>
+
+<p>
+Note that although the data in <tt>BLOCKINFO</tt> blocks is described as
+"metadata," the abbreviations they contain are essential for parsing records
+from the corresponding blocks. It is not safe to skip them.
+</p>
+
+</div>
+
+</div>
+
+</div>
+
+<!-- *********************************************************************** -->
+<h2><a name="wrapper">Bitcode Wrapper Format</a></h2>
+<!-- *********************************************************************** -->
+
+<div>
+
+<p>
+Bitcode files for LLVM IR may optionally be wrapped in a simple wrapper
+structure. This structure contains a simple header that indicates the offset
+and size of the embedded BC file. This allows additional information to be
+stored alongside the BC file. The structure of this file header is:
+</p>
+
+<div class="doc_code">
+<p>
+<tt>[Magic<sub>32</sub>, Version<sub>32</sub>, Offset<sub>32</sub>,
+Size<sub>32</sub>, CPUType<sub>32</sub>]</tt>
+</p>
+</div>
+
+<p>
+Each of the fields are 32-bit fields stored in little endian form (as with
+the rest of the bitcode file fields). The Magic number is always
+<tt>0x0B17C0DE</tt> and the version is currently always <tt>0</tt>. The Offset
+field is the offset in bytes to the start of the bitcode stream in the file, and
+the Size field is the size in bytes of the stream. CPUType is a target-specific
+value that can be used to encode the CPU of the target.
+</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<h2><a name="llvmir">LLVM IR Encoding</a></h2>
+<!-- *********************************************************************** -->
+
+<div>
+
+<p>
+LLVM IR is encoded into a bitstream by defining blocks and records. It uses
+blocks for things like constant pools, functions, symbol tables, etc. It uses
+records for things like instructions, global variable descriptors, type
+descriptions, etc. This document does not describe the set of abbreviations
+that the writer uses, as these are fully self-described in the file, and the
+reader is not allowed to build in any knowledge of this.
+</p>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="basics">Basics</a>
+</h3>
+
+<div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="ir_magic">LLVM IR Magic Number</a></h4>
+
+<div>
+
+<p>
+The magic number for LLVM IR files is:
+</p>
+
+<div class="doc_code">
+<p>
+<tt>[0x0<sub>4</sub>, 0xC<sub>4</sub>, 0xE<sub>4</sub>, 0xD<sub>4</sub>]</tt>
+</p>
+</div>
+
+<p>
+When combined with the bitcode magic number and viewed as bytes, this is
+<tt>"BC 0xC0DE"</tt>.
+</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="ir_signed_vbr">Signed VBRs</a></h4>
+
+<div>
+
+<p>
+<a href="#variablewidth">Variable Width Integer</a> encoding is an efficient way to
+encode arbitrary sized unsigned values, but is an extremely inefficient for
+encoding signed values, as signed values are otherwise treated as maximally large
+unsigned values.
+</p>
+
+<p>
+As such, signed VBR values of a specific width are emitted as follows:
+</p>
+
+<ul>
+<li>Positive values are emitted as VBRs of the specified width, but with their
+ value shifted left by one.</li>
+<li>Negative values are emitted as VBRs of the specified width, but the negated
+ value is shifted left by one, and the low bit is set.</li>
+</ul>
+
+<p>
+With this encoding, small positive and small negative values can both
+be emitted efficiently. Signed VBR encoding is used in
+<tt>CST_CODE_INTEGER</tt> and <tt>CST_CODE_WIDE_INTEGER</tt> records
+within <tt>CONSTANTS_BLOCK</tt> blocks.
+</p>
+
+</div>
+
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="ir_blocks">LLVM IR Blocks</a></h4>
+
+<div>
+
+<p>
+LLVM IR is defined with the following blocks:
+</p>
+
+<ul>
+<li>8 — <a href="#MODULE_BLOCK"><tt>MODULE_BLOCK</tt></a> — This is the top-level block that
+ contains the entire module, and describes a variety of per-module
+ information.</li>
+<li>9 — <a href="#PARAMATTR_BLOCK"><tt>PARAMATTR_BLOCK</tt></a> — This enumerates the parameter
+ attributes.</li>
+<li>10 — <a href="#TYPE_BLOCK"><tt>TYPE_BLOCK</tt></a> — This describes all of the types in
+ the module.</li>
+<li>11 — <a href="#CONSTANTS_BLOCK"><tt>CONSTANTS_BLOCK</tt></a> — This describes constants for a
+ module or function.</li>
+<li>12 — <a href="#FUNCTION_BLOCK"><tt>FUNCTION_BLOCK</tt></a> — This describes a function
+ body.</li>
+<li>13 — <a href="#TYPE_SYMTAB_BLOCK"><tt>TYPE_SYMTAB_BLOCK</tt></a> — This describes the type symbol
+ table.</li>
+<li>14 — <a href="#VALUE_SYMTAB_BLOCK"><tt>VALUE_SYMTAB_BLOCK</tt></a> — This describes a value symbol
+ table.</li>
+<li>15 — <a href="#METADATA_BLOCK"><tt>METADATA_BLOCK</tt></a> — This describes metadata items.</li>
+<li>16 — <a href="#METADATA_ATTACHMENT"><tt>METADATA_ATTACHMENT</tt></a> — This contains records associating metadata with function instruction values.</li>
+</ul>
+
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="MODULE_BLOCK">MODULE_BLOCK Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>MODULE_BLOCK</tt> block (id 8) is the top-level block for LLVM
+bitcode files, and each bitcode file must contain exactly one. In
+addition to records (described below) containing information
+about the module, a <tt>MODULE_BLOCK</tt> block may contain the
+following sub-blocks:
+</p>
+
+<ul>
+<li><a href="#BLOCKINFO"><tt>BLOCKINFO</tt></a></li>
+<li><a href="#PARAMATTR_BLOCK"><tt>PARAMATTR_BLOCK</tt></a></li>
+<li><a href="#TYPE_BLOCK"><tt>TYPE_BLOCK</tt></a></li>
+<li><a href="#TYPE_SYMTAB_BLOCK"><tt>TYPE_SYMTAB_BLOCK</tt></a></li>
+<li><a href="#VALUE_SYMTAB_BLOCK"><tt>VALUE_SYMTAB_BLOCK</tt></a></li>
+<li><a href="#CONSTANTS_BLOCK"><tt>CONSTANTS_BLOCK</tt></a></li>
+<li><a href="#FUNCTION_BLOCK"><tt>FUNCTION_BLOCK</tt></a></li>
+<li><a href="#METADATA_BLOCK"><tt>METADATA_BLOCK</tt></a></li>
+</ul>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_VERSION">MODULE_CODE_VERSION Record</a></h4>
+
+<div>
+
+<p><tt>[VERSION, version#]</tt></p>
+
+<p>The <tt>VERSION</tt> record (code 1) contains a single value
+indicating the format version. Only version 0 is supported at this
+time.</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_TRIPLE">MODULE_CODE_TRIPLE Record</a></h4>
+
+<div>
+<p><tt>[TRIPLE, ...string...]</tt></p>
+
+<p>The <tt>TRIPLE</tt> record (code 2) contains a variable number of
+values representing the bytes of the <tt>target triple</tt>
+specification string.</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_DATALAYOUT">MODULE_CODE_DATALAYOUT Record</a></h4>
+
+<div>
+<p><tt>[DATALAYOUT, ...string...]</tt></p>
+
+<p>The <tt>DATALAYOUT</tt> record (code 3) contains a variable number of
+values representing the bytes of the <tt>target datalayout</tt>
+specification string.</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_ASM">MODULE_CODE_ASM Record</a></h4>
+
+<div>
+<p><tt>[ASM, ...string...]</tt></p>
+
+<p>The <tt>ASM</tt> record (code 4) contains a variable number of
+values representing the bytes of <tt>module asm</tt> strings, with
+individual assembly blocks separated by newline (ASCII 10) characters.</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_SECTIONNAME">MODULE_CODE_SECTIONNAME Record</a></h4>
+
+<div>
+<p><tt>[SECTIONNAME, ...string...]</tt></p>
+
+<p>The <tt>SECTIONNAME</tt> record (code 5) contains a variable number
+of values representing the bytes of a single section name
+string. There should be one <tt>SECTIONNAME</tt> record for each
+section name referenced (e.g., in global variable or function
+<tt>section</tt> attributes) within the module. These records can be
+referenced by the 1-based index in the <i>section</i> fields of
+<tt>GLOBALVAR</tt> or <tt>FUNCTION</tt> records.</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_DEPLIB">MODULE_CODE_DEPLIB Record</a></h4>
+
+<div>
+<p><tt>[DEPLIB, ...string...]</tt></p>
+
+<p>The <tt>DEPLIB</tt> record (code 6) contains a variable number of
+values representing the bytes of a single dependent library name
+string, one of the libraries mentioned in a <tt>deplibs</tt>
+declaration. There should be one <tt>DEPLIB</tt> record for each
+library name referenced.</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_GLOBALVAR">MODULE_CODE_GLOBALVAR Record</a></h4>
+
+<div>
+<p><tt>[GLOBALVAR, pointer type, isconst, initid, linkage, alignment, section, visibility, threadlocal]</tt></p>
+
+<p>The <tt>GLOBALVAR</tt> record (code 7) marks the declaration or
+definition of a global variable. The operand fields are:</p>
+
+<ul>
+<li><i>pointer type</i>: The type index of the pointer type used to point to
+this global variable</li>
+
+<li><i>isconst</i>: Non-zero if the variable is treated as constant within
+the module, or zero if it is not</li>
+
+<li><i>initid</i>: If non-zero, the value index of the initializer for this
+variable, plus 1.</li>
+
+<li><a name="linkage"><i>linkage</i></a>: An encoding of the linkage
+type for this variable:
+ <ul>
+ <li><tt>external</tt>: code 0</li>
+ <li><tt>weak</tt>: code 1</li>
+ <li><tt>appending</tt>: code 2</li>
+ <li><tt>internal</tt>: code 3</li>
+ <li><tt>linkonce</tt>: code 4</li>
+ <li><tt>dllimport</tt>: code 5</li>
+ <li><tt>dllexport</tt>: code 6</li>
+ <li><tt>extern_weak</tt>: code 7</li>
+ <li><tt>common</tt>: code 8</li>
+ <li><tt>private</tt>: code 9</li>
+ <li><tt>weak_odr</tt>: code 10</li>
+ <li><tt>linkonce_odr</tt>: code 11</li>
+ <li><tt>available_externally</tt>: code 12</li>
+ <li><tt>linker_private</tt>: code 13</li>
+ </ul>
+</li>
+
+<li><i>alignment</i>: The logarithm base 2 of the variable's requested
+alignment, plus 1</li>
+
+<li><i>section</i>: If non-zero, the 1-based section index in the
+table of <a href="#MODULE_CODE_SECTIONNAME">MODULE_CODE_SECTIONNAME</a>
+entries.</li>
+
+<li><a name="visibility"><i>visibility</i></a>: If present, an
+encoding of the visibility of this variable:
+ <ul>
+ <li><tt>default</tt>: code 0</li>
+ <li><tt>hidden</tt>: code 1</li>
+ <li><tt>protected</tt>: code 2</li>
+ </ul>
+</li>
+
+<li><i>threadlocal</i>: If present and non-zero, indicates that the variable
+is <tt>thread_local</tt></li>
+
+<li><i>unnamed_addr</i>: If present and non-zero, indicates that the variable
+has <tt>unnamed_addr</tt></li>
+
+</ul>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_FUNCTION">MODULE_CODE_FUNCTION Record</a></h4>
+
+<div>
+
+<p><tt>[FUNCTION, type, callingconv, isproto, linkage, paramattr, alignment, section, visibility, gc]</tt></p>
+
+<p>The <tt>FUNCTION</tt> record (code 8) marks the declaration or
+definition of a function. The operand fields are:</p>
+
+<ul>
+<li><i>type</i>: The type index of the function type describing this function</li>
+
+<li><i>callingconv</i>: The calling convention number:
+ <ul>
+ <li><tt>ccc</tt>: code 0</li>
+ <li><tt>fastcc</tt>: code 8</li>
+ <li><tt>coldcc</tt>: code 9</li>
+ <li><tt>x86_stdcallcc</tt>: code 64</li>
+ <li><tt>x86_fastcallcc</tt>: code 65</li>
+ <li><tt>arm_apcscc</tt>: code 66</li>
+ <li><tt>arm_aapcscc</tt>: code 67</li>
+ <li><tt>arm_aapcs_vfpcc</tt>: code 68</li>
+ </ul>
+</li>
+
+<li><i>isproto</i>: Non-zero if this entry represents a declaration
+rather than a definition</li>
+
+<li><i>linkage</i>: An encoding of the <a href="#linkage">linkage type</a>
+for this function</li>
+
+<li><i>paramattr</i>: If nonzero, the 1-based parameter attribute index
+into the table of <a href="#PARAMATTR_CODE_ENTRY">PARAMATTR_CODE_ENTRY</a>
+entries.</li>
+
+<li><i>alignment</i>: The logarithm base 2 of the function's requested
+alignment, plus 1</li>
+
+<li><i>section</i>: If non-zero, the 1-based section index in the
+table of <a href="#MODULE_CODE_SECTIONNAME">MODULE_CODE_SECTIONNAME</a>
+entries.</li>
+
+<li><i>visibility</i>: An encoding of the <a href="#visibility">visibility</a>
+ of this function</li>
+
+<li><i>gc</i>: If present and nonzero, the 1-based garbage collector
+index in the table of
+<a href="#MODULE_CODE_GCNAME">MODULE_CODE_GCNAME</a> entries.</li>
+
+<li><i>unnamed_addr</i>: If present and non-zero, indicates that the function
+has <tt>unnamed_addr</tt></li>
+
+</ul>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_ALIAS">MODULE_CODE_ALIAS Record</a></h4>
+
+<div>
+
+<p><tt>[ALIAS, alias type, aliasee val#, linkage, visibility]</tt></p>
+
+<p>The <tt>ALIAS</tt> record (code 9) marks the definition of an
+alias. The operand fields are</p>
+
+<ul>
+<li><i>alias type</i>: The type index of the alias</li>
+
+<li><i>aliasee val#</i>: The value index of the aliased value</li>
+
+<li><i>linkage</i>: An encoding of the <a href="#linkage">linkage type</a>
+for this alias</li>
+
+<li><i>visibility</i>: If present, an encoding of the
+<a href="#visibility">visibility</a> of the alias</li>
+
+</ul>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_PURGEVALS">MODULE_CODE_PURGEVALS Record</a></h4>
+
+<div>
+<p><tt>[PURGEVALS, numvals]</tt></p>
+
+<p>The <tt>PURGEVALS</tt> record (code 10) resets the module-level
+value list to the size given by the single operand value. Module-level
+value list items are added by <tt>GLOBALVAR</tt>, <tt>FUNCTION</tt>,
+and <tt>ALIAS</tt> records. After a <tt>PURGEVALS</tt> record is seen,
+new value indices will start from the given <i>numvals</i> value.</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="MODULE_CODE_GCNAME">MODULE_CODE_GCNAME Record</a></h4>
+
+<div>
+<p><tt>[GCNAME, ...string...]</tt></p>
+
+<p>The <tt>GCNAME</tt> record (code 11) contains a variable number of
+values representing the bytes of a single garbage collector name
+string. There should be one <tt>GCNAME</tt> record for each garbage
+collector name referenced in function <tt>gc</tt> attributes within
+the module. These records can be referenced by 1-based index in the <i>gc</i>
+fields of <tt>FUNCTION</tt> records.</p>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="PARAMATTR_BLOCK">PARAMATTR_BLOCK Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>PARAMATTR_BLOCK</tt> block (id 9) contains a table of
+entries describing the attributes of function parameters. These
+entries are referenced by 1-based index in the <i>paramattr</i> field
+of module block <a name="MODULE_CODE_FUNCTION"><tt>FUNCTION</tt></a>
+records, or within the <i>attr</i> field of function block <a
+href="#FUNC_CODE_INST_INVOKE"><tt>INST_INVOKE</tt></a> and <a
+href="#FUNC_CODE_INST_CALL"><tt>INST_CALL</tt></a> records.</p>
+
+<p>Entries within <tt>PARAMATTR_BLOCK</tt> are constructed to ensure
+that each is unique (i.e., no two indicies represent equivalent
+attribute lists). </p>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="PARAMATTR_CODE_ENTRY">PARAMATTR_CODE_ENTRY Record</a></h4>
+
+<div>
+
+<p><tt>[ENTRY, paramidx0, attr0, paramidx1, attr1...]</tt></p>
+
+<p>The <tt>ENTRY</tt> record (code 1) contains an even number of
+values describing a unique set of function parameter attributes. Each
+<i>paramidx</i> value indicates which set of attributes is
+represented, with 0 representing the return value attributes,
+0xFFFFFFFF representing function attributes, and other values
+representing 1-based function parameters. Each <i>attr</i> value is a
+bitmap with the following interpretation:
+</p>
+
+<ul>
+<li>bit 0: <tt>zeroext</tt></li>
+<li>bit 1: <tt>signext</tt></li>
+<li>bit 2: <tt>noreturn</tt></li>
+<li>bit 3: <tt>inreg</tt></li>
+<li>bit 4: <tt>sret</tt></li>
+<li>bit 5: <tt>nounwind</tt></li>
+<li>bit 6: <tt>noalias</tt></li>
+<li>bit 7: <tt>byval</tt></li>
+<li>bit 8: <tt>nest</tt></li>
+<li>bit 9: <tt>readnone</tt></li>
+<li>bit 10: <tt>readonly</tt></li>
+<li>bit 11: <tt>noinline</tt></li>
+<li>bit 12: <tt>alwaysinline</tt></li>
+<li>bit 13: <tt>optsize</tt></li>
+<li>bit 14: <tt>ssp</tt></li>
+<li>bit 15: <tt>sspreq</tt></li>
+<li>bits 16–31: <tt>align <var>n</var></tt></li>
+<li>bit 32: <tt>nocapture</tt></li>
+<li>bit 33: <tt>noredzone</tt></li>
+<li>bit 34: <tt>noimplicitfloat</tt></li>
+<li>bit 35: <tt>naked</tt></li>
+<li>bit 36: <tt>inlinehint</tt></li>
+<li>bits 37–39: <tt>alignstack <var>n</var></tt>, represented as
+the logarithm base 2 of the requested alignment, plus 1</li>
+</ul>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="TYPE_BLOCK">TYPE_BLOCK Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>TYPE_BLOCK</tt> block (id 10) contains records which
+constitute a table of type operator entries used to represent types
+referenced within an LLVM module. Each record (with the exception of
+<a href="#TYPE_CODE_NUMENTRY"><tt>NUMENTRY</tt></a>) generates a
+single type table entry, which may be referenced by 0-based index from
+instructions, constants, metadata, type symbol table entries, or other
+type operator records.
+</p>
+
+<p>Entries within <tt>TYPE_BLOCK</tt> are constructed to ensure that
+each entry is unique (i.e., no two indicies represent structurally
+equivalent types). </p>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_NUMENTRY">TYPE_CODE_NUMENTRY Record</a></h4>
+
+<div>
+
+<p><tt>[NUMENTRY, numentries]</tt></p>
+
+<p>The <tt>NUMENTRY</tt> record (code 1) contains a single value which
+indicates the total number of type code entries in the type table of
+the module. If present, <tt>NUMENTRY</tt> should be the first record
+in the block.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_VOID">TYPE_CODE_VOID Record</a></h4>
+
+<div>
+
+<p><tt>[VOID]</tt></p>
+
+<p>The <tt>VOID</tt> record (code 2) adds a <tt>void</tt> type to the
+type table.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_FLOAT">TYPE_CODE_FLOAT Record</a></h4>
+
+<div>
+
+<p><tt>[FLOAT]</tt></p>
+
+<p>The <tt>FLOAT</tt> record (code 3) adds a <tt>float</tt> (32-bit
+floating point) type to the type table.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_DOUBLE">TYPE_CODE_DOUBLE Record</a></h4>
+
+<div>
+
+<p><tt>[DOUBLE]</tt></p>
+
+<p>The <tt>DOUBLE</tt> record (code 4) adds a <tt>double</tt> (64-bit
+floating point) type to the type table.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_LABEL">TYPE_CODE_LABEL Record</a></h4>
+
+<div>
+
+<p><tt>[LABEL]</tt></p>
+
+<p>The <tt>LABEL</tt> record (code 5) adds a <tt>label</tt> type to
+the type table.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_OPAQUE">TYPE_CODE_OPAQUE Record</a></h4>
+
+<div>
+
+<p><tt>[OPAQUE]</tt></p>
+
+<p>The <tt>OPAQUE</tt> record (code 6) adds an <tt>opaque</tt> type to
+the type table. Note that distinct <tt>opaque</tt> types are not
+unified.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_INTEGER">TYPE_CODE_INTEGER Record</a></h4>
+
+<div>
+
+<p><tt>[INTEGER, width]</tt></p>
+
+<p>The <tt>INTEGER</tt> record (code 7) adds an integer type to the
+type table. The single <i>width</i> field indicates the width of the
+integer type.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_POINTER">TYPE_CODE_POINTER Record</a></h4>
+
+<div>
+
+<p><tt>[POINTER, pointee type, address space]</tt></p>
+
+<p>The <tt>POINTER</tt> record (code 8) adds a pointer type to the
+type table. The operand fields are</p>
+
+<ul>
+<li><i>pointee type</i>: The type index of the pointed-to type</li>
+
+<li><i>address space</i>: If supplied, the target-specific numbered
+address space where the pointed-to object resides. Otherwise, the
+default address space is zero.
+</li>
+</ul>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_FUNCTION">TYPE_CODE_FUNCTION Record</a></h4>
+
+<div>
+
+<p><tt>[FUNCTION, vararg, ignored, retty, ...paramty... ]</tt></p>
+
+<p>The <tt>FUNCTION</tt> record (code 9) adds a function type to the
+type table. The operand fields are</p>
+
+<ul>
+<li><i>vararg</i>: Non-zero if the type represents a varargs function</li>
+
+<li><i>ignored</i>: This value field is present for backward
+compatibility only, and is ignored</li>
+
+<li><i>retty</i>: The type index of the function's return type</li>
+
+<li><i>paramty</i>: Zero or more type indices representing the
+parameter types of the function</li>
+</ul>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_STRUCT">TYPE_CODE_STRUCT Record</a></h4>
+
+<div>
+
+<p><tt>[STRUCT, ispacked, ...eltty...]</tt></p>
+
+<p>The <tt>STRUCT </tt> record (code 10) adds a struct type to the
+type table. The operand fields are</p>
+
+<ul>
+<li><i>ispacked</i>: Non-zero if the type represents a packed structure</li>
+
+<li><i>eltty</i>: Zero or more type indices representing the element
+types of the structure</li>
+</ul>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_ARRAY">TYPE_CODE_ARRAY Record</a></h4>
+
+<div>
+
+<p><tt>[ARRAY, numelts, eltty]</tt></p>
+
+<p>The <tt>ARRAY</tt> record (code 11) adds an array type to the type
+table. The operand fields are</p>
+
+<ul>
+<li><i>numelts</i>: The number of elements in arrays of this type</li>
+
+<li><i>eltty</i>: The type index of the array element type</li>
+</ul>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_VECTOR">TYPE_CODE_VECTOR Record</a></h4>
+
+<div>
+
+<p><tt>[VECTOR, numelts, eltty]</tt></p>
+
+<p>The <tt>VECTOR</tt> record (code 12) adds a vector type to the type
+table. The operand fields are</p>
+
+<ul>
+<li><i>numelts</i>: The number of elements in vectors of this type</li>
+
+<li><i>eltty</i>: The type index of the vector element type</li>
+</ul>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_X86_FP80">TYPE_CODE_X86_FP80 Record</a></h4>
+
+<div>
+
+<p><tt>[X86_FP80]</tt></p>
+
+<p>The <tt>X86_FP80</tt> record (code 13) adds an <tt>x86_fp80</tt> (80-bit
+floating point) type to the type table.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_FP128">TYPE_CODE_FP128 Record</a></h4>
+
+<div>
+
+<p><tt>[FP128]</tt></p>
+
+<p>The <tt>FP128</tt> record (code 14) adds an <tt>fp128</tt> (128-bit
+floating point) type to the type table.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_PPC_FP128">TYPE_CODE_PPC_FP128 Record</a></h4>
+
+<div>
+
+<p><tt>[PPC_FP128]</tt></p>
+
+<p>The <tt>PPC_FP128</tt> record (code 15) adds a <tt>ppc_fp128</tt>
+(128-bit floating point) type to the type table.
+</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TYPE_CODE_METADATA">TYPE_CODE_METADATA Record</a></h4>
+
+<div>
+
+<p><tt>[METADATA]</tt></p>
+
+<p>The <tt>METADATA</tt> record (code 16) adds a <tt>metadata</tt>
+type to the type table.
+</p>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="CONSTANTS_BLOCK">CONSTANTS_BLOCK Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>CONSTANTS_BLOCK</tt> block (id 11) ...
+</p>
+
+</div>
+
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="FUNCTION_BLOCK">FUNCTION_BLOCK Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>FUNCTION_BLOCK</tt> block (id 12) ...
+</p>
+
+<p>In addition to the record types described below, a
+<tt>FUNCTION_BLOCK</tt> block may contain the following sub-blocks:
+</p>
+
+<ul>
+<li><a href="#CONSTANTS_BLOCK"><tt>CONSTANTS_BLOCK</tt></a></li>
+<li><a href="#VALUE_SYMTAB_BLOCK"><tt>VALUE_SYMTAB_BLOCK</tt></a></li>
+<li><a href="#METADATA_ATTACHMENT"><tt>METADATA_ATTACHMENT</tt></a></li>
+</ul>
+
+</div>
+
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="TYPE_SYMTAB_BLOCK">TYPE_SYMTAB_BLOCK Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>TYPE_SYMTAB_BLOCK</tt> block (id 13) contains entries which
+map between module-level named types and their corresponding type
+indices.
+</p>
+
+<!-- _______________________________________________________________________ -->
+<h4><a name="TST_CODE_ENTRY">TST_CODE_ENTRY Record</a></h4>
+
+<div>
+
+<p><tt>[ENTRY, typeid, ...string...]</tt></p>
+
+<p>The <tt>ENTRY</tt> record (code 1) contains a variable number of
+values, with the first giving the type index of the designated type,
+and the remaining values giving the character codes of the type
+name. Each entry corresponds to a single named type.
+</p>
+</div>
+
+</div>
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="VALUE_SYMTAB_BLOCK">VALUE_SYMTAB_BLOCK Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>VALUE_SYMTAB_BLOCK</tt> block (id 14) ...
+</p>
+
+</div>
+
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="METADATA_BLOCK">METADATA_BLOCK Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>METADATA_BLOCK</tt> block (id 15) ...
+</p>
+
+</div>
+
+
+<!-- ======================================================================= -->
+<h3>
+ <a name="METADATA_ATTACHMENT">METADATA_ATTACHMENT Contents</a>
+</h3>
+
+<div>
+
+<p>The <tt>METADATA_ATTACHMENT</tt> block (id 16) ...
+</p>
+
+</div>
+
</div>
+
<!-- *********************************************************************** -->
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- href="mailto:sabre@nondot.org">Chris Lattner</a><br>
-<a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
+ src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
+ <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
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projects / oota-llvm.git / blobdiff