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  10 <div class="doc_title">TableGen Fundamentals</div>
  11
  12 <div class="doc_text">
  13 <ul>
  14   <li><a href="#introduction">Introduction</a>
  15   <ol>
  16     <li><a href="#concepts">Basic concepts</a></li>
  17     <li><a href="#example">An example record</a></li>
  18     <li><a href="#running">Running TableGen</a></li>
  19   </ol></li>
  20   <li><a href="#syntax">TableGen syntax</a>
  21   <ol>
  22     <li><a href="#primitives">TableGen primitives</a>
  23     <ol>
  24       <li><a href="#comments">TableGen comments</a></li>
  25       <li><a href="#types">The TableGen type system</a></li>
  26       <li><a href="#values">TableGen values and expressions</a></li>
  27     </ol></li>
  28     <li><a href="#classesdefs">Classes and definitions</a>
  29     <ol>
  30       <li><a href="#valuedef">Value definitions</a></li>
  31       <li><a href="#recordlet">'let' expressions</a></li>
  32       <li><a href="#templateargs">Class template arguments</a></li>
  33     </ol></li>
  34     <li><a href="#filescope">File scope entities</a>
  35     <ol>
  36       <li><a href="#include">File inclusion</a></li>
  37       <li><a href="#globallet">'let' expressions</a></li>
  38     </ol></li>
  39   </ol></li>
  40   <li><a href="#backends">TableGen backends</a>
  41   <ol>
  42     <li><a href="#">todo</a></li>
  43   </ol></li>
  44   <li><a href="#codegenerator">The LLVM code generator</a>
  45   <ol>
  46     <li><a href="#">todo</a></li>
  47   </ol></li>
  48 </ul>
  49 </div>
  50
  51 <div class="doc_author">
  52   <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
  53 </div>
  54
  55 <!-- *********************************************************************** -->
  56 <div class="doc_section"><a name="introduction">Introduction</a></div>
  57 <!-- *********************************************************************** -->
  58
  59 <div class="doc_text">
  60
  61 <p>TableGen's purpose is to help a human develop and maintain records of
  62 domain-specific information.  Because there may be a large number of these
  63 records, it is specifically designed to allow writing flexible descriptions and
  64 for common features of these records to be factored out.  This reduces the
  65 amount of duplication in the description, reduces the chance of error, and
  66 makes it easier to structure domain specific information.</p>
  67
  68 <p>The core part of TableGen <a href="#syntax">parses a file</a>, instantiates
  69 the declarations, and hands the result off to a domain-specific "<a
  70 href="#backends">TableGen backend</a>" for processing.  The current major user
  71 of TableGen is the <a href="#codegenerator">LLVM code generator</a>.</p>
  72
  73 <p>Note that if you work on TableGen much, and use emacs or vim, that you can
  74 find an emacs "TableGen mode" and a vim language file in
  75 <tt>llvm/utils/emacs</tt> and <tt>llvm/utils/vim</tt> directory of your LLVM
  76 distribution, respectively.</p>
  77
  78 </div>
  79
  80 <!-- ======================================================================= -->
  81 <div class="doc_subsection"><a name="running">Basic concepts</a></div>
  82
  83 <div class="doc_text">
  84
  85 <p>TableGen files consist of two key parts: 'classes' and 'definitions', both
  86 of which are considered 'records'.</p>
  87
  88 <p><b>TableGen records</b> have a unique name, a list of values, and a list of
  89 superclasses.  The list of values is main data that TableGen builds for each
  90 record, it is this that holds the domain specific information for the
  91 application.  The interpretation of this data is left to a specific <a
  92 href="#backends">TableGen backend</a>, but the structure and format rules are
  93 taken care of and fixed by TableGen.</p>
  94
  95 <p><b>TableGen definitions</b> are the concrete form of 'records'.  These
  96 generally do not have any undefined values, and are marked with the
  97 '<tt>def</tt>' keyword.</p>
  98
  99 <p><b>TableGen classes</b> are abstract records that are used to build and
 100 describe other records.  These 'classes' allow the end-user to build
 101 abstractions for either the domain they are targetting (such as "Register",
 102 "RegisterClass", and "Instruction" in the LLVM code generator) or for the
 103 implementor to help factor out common properties of records (such as "FPInst",
 104 which is used to represent floating point instructions in the X86 backend).
 105 TableGen keeps track of all of the classes that are used to build up a
 106 definition, so the backend can find all definitions of a particular class, such
 107 as "Instruction".</p>
 108
 109 </div>
 110
 111 <!-- ======================================================================= -->
 112 <div class="doc_subsection"><a name="example">An example record</a></div>
 113
 114 <div class="doc_text">
 115
 116 <p>With no other arguments, TableGen parses the specified file and prints out
 117 all of the classes, then all of the definitions.  This is a good way to see what
 118 the various definitions expand to fully.  Running this on the <tt>X86.td</tt>
 119 file prints this (at the time of this writing):</p>
 120
 121 <pre>
 122 ...
 123 <b>def</b> ADDrr8 {    <i>// Instruction X86Inst I2A8 Pattern</i>
 124   <b>string</b> Name = "add";
 125   <b>string</b> Namespace = "X86";
 126   <b>list</b>&lt;Register&gt; Uses = [];
 127   <b>list</b>&lt;Register&gt; Defs = [];
 128   <b>bit</b> isReturn = 0;
 129   <b>bit</b> isBranch = 0;
 130   <b>bit</b> isCall = 0;
 131   <b>bit</b> isTwoAddress = 1;
 132   <b>bit</b> isTerminator = 0;
 133   <b>dag</b> Pattern = (set R8, (plus R8, R8));
 134   <b>bits</b>&lt;8&gt; Opcode = { 0, 0, 0, 0, 0, 0, 0, 0 };
 135   Format Form = MRMDestReg;
 136   <b>bits</b>&lt;5&gt; FormBits = { 0, 0, 0, 1, 1 };
 137   ArgType Type = Arg8;
 138   <b>bits</b>&lt;3&gt; TypeBits = { 0, 0, 1 };
 139   <b>bit</b> hasOpSizePrefix = 0;
 140   <b>bit</b> printImplicitUses = 0;
 141   <b>bits</b>&lt;4&gt; Prefix = { 0, 0, 0, 0 };
 142   FPFormat FPForm = ?;
 143   <b>bits</b>&lt;3&gt; FPFormBits = { 0, 0, 0 };
 144 }
 145 ...
 146 </pre>
 147
 148 <p>This definition corresponds to an 8-bit register-register add instruction in
 149 the X86.  The string after the '<tt>def</tt>' string indicates the name of the
 150 record ("<tt>ADDrr8</tt>" in this case), and the comment at the end of the line
 151 indicates the superclasses of the definition.  The body of the record contains
 152 all of the data that TableGen assembled for the record, indicating that the
 153 instruction is part of the "X86" namespace, should be printed as "<tt>add</tt>"
 154 in the assembly file, it is a two-address instruction, has a particular
 155 encoding, etc.  The contents and semantics of the information in the record is
 156 specific to the needs of the X86 backend, and is only shown as an example.</p>
 157
 158 <p>As you can see, a lot of information is needed for every instruction
 159 supported by the code generator, and specifying it all manually would be
 160 unmaintainble, prone to bugs, and tiring to do in the first place.  Because we
 161 are using TableGen, all of the information was derived from the following
 162 definition:</p>
 163
 164 <pre>
 165 <b>def</b> ADDrr8   : I2A8&lt;"add", 0x00, MRMDestReg&gt;,
 166                Pattern&lt;(set R8, (plus R8, R8))&gt;;
 167 </pre>
 168
 169 <p>This definition makes use of the custom I2A8 (two address instruction with
 170 8-bit operand) class, which is defined in the X86-specific TableGen file to
 171 factor out the common features that instructions of its class share.  A key
 172 feature of TableGen is that it allows the end-user to define the abstractions
 173 they prefer to use when describing their information.</p>
 174
 175 </div>
 176
 177 <!-- ======================================================================= -->
 178 <div class="doc_subsection"><a name="running">Running TableGen</a></div>
 179
 180 <div class="doc_text">
 181
 182 <p>TableGen runs just like any other LLVM tool.  The first (optional) argument
 183 specifies the file to read.  If a filename is not specified, <tt>tblgen</tt>
 184 reads from standard input.</p>
 185
 186 <p>To be useful, one of the <a href="#backends">TableGen backends</a> must be
 187 used.  These backends are selectable on the command line (type '<tt>tblgen
 188 --help</tt>' for a list).  For example, to get a list of all of the definitions
 189 that subclass a particular type (which can be useful for building up an enum
 190 list of these records), use the <tt>--print-enums</tt> option:</p>
 191
 192 <pre>
 193 $ tblgen X86.td -print-enums -class=Register
 194 AH, AL, AX, BH, BL, BP, BX, CH, CL, CX, DH, DI, DL, DX,
 195 EAX, EBP, EBX, ECX, EDI, EDX, ESI, ESP, FP0, FP1, FP2, FP3, FP4, FP5, FP6,
 196 SI, SP, ST0, ST1, ST2, ST3, ST4, ST5, ST6, ST7,
 197
 198 $ tblgen X86.td -print-enums -class=Instruction
 199 ADCrr32, ADDri16, ADDri16b, ADDri32, ADDri32b, ADDri8, ADDrr16, ADDrr32,
 200 ADDrr8, ADJCALLSTACKDOWN, ADJCALLSTACKUP, ANDri16, ANDri16b, ANDri32, ANDri32b,
 201 ANDri8, ANDrr16, ANDrr32, ANDrr8, BSWAPr32, CALLm32, CALLpcrel32, ...
 202 </pre>
 203
 204 <p>The default backend prints out all of the records, as described <a
 205 href="#example">above</a>.</p>
 206
 207 <p>If you plan to use TableGen for some purpose, you will most likely have to
 208 <a href="#backends">write a backend</a> that extracts the information specific
 209 to what you need and formats it in the appropriate way.</p>
 210
 211 </div>
 212
 213
 214 <!-- *********************************************************************** -->
 215 <div class="doc_section"><a name="syntax">TableGen syntax</a></div>
 216 <!-- *********************************************************************** -->
 217
 218 <div class="doc_text">
 219 <p>TableGen doesn't care about the meaning of data (that is up to the backend
 220 to define), but it does care about syntax, and it enforces a simple type system.
 221 This section describes the syntax and the constructs allowed in a TableGen file.
 222 </p>
 223 </div>
 224
 225 <!-- ======================================================================= -->
 226 <div class="doc_subsection"><a name="primitives">TableGen primitives</a></div>
 227
 228 <!-- -------------------------------------------------------------------------->
 229 <div class="doc_subsubsection"><a name="comments">TableGen comments</a></div>
 230
 231 <div class="doc_text">
 232 <p>TableGen supports BCPL style "<tt>//</tt>" comments, which run to the end of
 233 the line, and it also supports <b>nestable</b> "<tt>/* */</tt>" comments.</p>
 234 </div>
 235
 236 <!-- -------------------------------------------------------------------------->
 237 <div class="doc_subsubsection">
 238   <a name="types">The TableGen type system</a>
 239 </div>
 240
 241 <div class="doc_text">
 242 <p>TableGen files are strongly typed, in a simple (but complete) type-system.
 243 These types are used to perform automatic conversions, check for errors, and to
 244 help interface designers constrain the input that they allow.  Every <a
 245 href="#valuedef">value definition</a> is required to have an associated type.
 246 </p>
 247
 248 <p>TableGen supports a mixture of very low-level types (such as <tt>bit</tt>)
 249 and very high-level types (such as <tt>dag</tt>).  This flexibility is what
 250 allows it to describe a wide range of information conveniently and compactly.
 251 The TableGen types are:</p>
 252
 253 <ul>
 254 <li>"<tt><b>bit</b></tt>" - A 'bit' is a boolean value that can hold either 0 or
 255 1.</li>
 256
 257 <li>"<tt><b>int</b></tt>" - The 'int' type represents a simple 32-bit integer
 258 value, such as 5.</li>
 259
 260 <li>"<tt><b>string</b></tt>" - The 'string' type represents an ordered sequence
 261 of characters of arbitrary length.</li>
 262
 263 <li>"<tt><b>bits</b>&lt;n&gt;</tt>" - A 'bits' type is an arbitrary, but fixed,
 264 size integer that is broken up into individual bits.  This type is useful
 265 because it can handle some bits being defined while others are undefined.</li>
 266
 267 <li>"<tt><b>list</b>&lt;ty&gt;</tt>" - This type represents a list whose
 268 elements are some other type.  The contained type is arbitrary: it can even be
 269 another list type.</li>
 270
 271 <li>Class type - Specifying a class name in a type context means that the
 272 defined value must be a subclass of the specified class.  This is useful in
 273 conjunction with the "list" type, for example, to constrain the elements of the
 274 list to a common base class (e.g., a <tt><b>list</b>&lt;Register&gt;</tt> can
 275 only contain definitions derived from the "<tt>Register</tt>" class).</li>
 276
 277 <li>"<tt><b>code</b></tt>" - This represents a big hunk of text.  NOTE: I don't
 278 remember why this is distinct from string!</li>
 279
 280 <li>"<tt><b>dag</b></tt>" - This type represents a nestable directed graph of
 281 elements.</li>
 282 </ul>
 283
 284 <p>To date, these types have been sufficient for describing things that
 285 TableGen has been used for, but it is straight-forward to extend this list if
 286 needed.</p>
 287
 288 </div>
 289
 290 <!-- -------------------------------------------------------------------------->
 291 <div class="doc_subsubsection">
 292   <a name="values">TableGen values and expressions</a>
 293 </div>
 294
 295 <div class="doc_text">
 296
 297 <p>TableGen allows for a pretty reasonable number of different expression forms
 298 when building up values.  These forms allow the TableGen file to be written in a
 299 natural syntax and flavor for the application.  The current expression forms
 300 supported include:</p>
 301
 302 <ul>
 303 <li>? - Uninitialized field.</li>
 304 <li>0b1001011 - Binary integer value.</li>
 305 <li>07654321 - Octal integer value (indicated by a leading 0).</li>
 306 <li>7 - Decimal integer value.</li>
 307 <li>0x7F - Hexadecimal integer value.</li>
 308 <li>"foo" - String value.</li>
 309 <li>[{ .... }] - Code fragment.</li>
 310 <li>[ X, Y, Z ] - List value.</li>
 311 <li>{ a, b, c } - Initializer for a "bits&lt;3&gt;" value.</li>
 312 <li>value - Value reference.</li>
 313 <li>value{17} - Access to one or more bits of a value.</li>
 314 <li>DEF - Reference to a record definition.</li>
 315 <li>X.Y - Reference to the subfield of a value.</li>
 316
 317 <li>(DEF a, b) - A dag value.  The first element is required to be a record
 318 definition, the remaining elements in the list may be arbitrary other values,
 319 including nested 'dag' values.</li>
 320
 321 </ul>
 322
 323 <p>Note that all of the values have rules specifying how they convert to values
 324 for different types.  These rules allow you to assign a value like "7" to a
 325 "bits&lt;4&gt;" value, for example.</p>
 326
 327 </div>
 328
 329 <!-- ======================================================================= -->
 330 <div class="doc_subsection">
 331   <a name="classesdefs">Classes and definitions</a>
 332 </div>
 333
 334 <div class="doc_text">
 335
 336 <p>As mentioned in the <a href="#concepts">intro</a>, classes and definitions
 337 (collectively known as 'records') in TableGen are the main high-level unit of
 338 information that TableGen collects.  Records are defined with a <tt>def</tt> or
 339 <tt>class</tt> keyword, the record name, and an optional list of "<a
 340 href="#templateargs">template arguments</a>".  If the record has superclasses,
 341 they are specified as a comma seperated list that starts with a colon character
 342 (":").  If <a href="#valuedef">value definitions</a> or <a href="#recordlet">let
 343 expressions</a> are needed for the class, they are enclosed in curly braces
 344 ("{}"); otherwise, the record ends with a semicolon.  Here is a simple TableGen
 345 file:</p>
 346
 347 <pre>
 348 <b>class</b> C { <b>bit</b> V = 1; }
 349 <b>def</b> X : C;
 350 <b>def</b> Y : C {
 351   <b>string</b> Greeting = "hello";
 352 }
 353 </pre>
 354
 355 <p>This example defines two definitions, <tt>X</tt> and <tt>Y</tt>, both of
 356 which derive from the <tt>C</tt> class.  Because of this, they both get the
 357 <tt>V</tt> bit value.  The <tt>Y</tt> definition also gets the Greeting member
 358 as well.</p>
 359
 360 <p>In general, classes are useful for collecting together the commonality
 361 between a group of records and isolating it in a single place.  Also, classes
 362 permit the specification of default values for their subclasses, allowing the
 363 subclasses to override them as they wish.</p>
 364
 365 </div>
 366
 367 <!---------------------------------------------------------------------------->
 368 <div class="doc_subsubsection">
 369   <a name="valuedef">Value definitions</a>
 370 </div>
 371
 372 <div class="doc_text">
 373 <p>Value definitions define named entries in records.  A value must be defined
 374 before it can be referred to as the operand for another value definition or
 375 before the value is reset with a <a href="#recordlet">let expression</a>.  A
 376 value is defined by specifying a <a href="#types">TableGen type</a> and a name.
 377 If an initial value is available, it may be specified after the type with an
 378 equal sign.  Value definitions require terminating semicolons.</p>
 379 </div>
 380
 381 <!-- -------------------------------------------------------------------------->
 382 <div class="doc_subsubsection">
 383   <a name="recordlet">'let' expressions</a>
 384 </div>
 385
 386 <div class="doc_text">
 387 <p>A record-level let expression is used to change the value of a value
 388 definition in a record.  This is primarily useful when a superclass defines a
 389 value that a derived class or definition wants to override.  Let expressions
 390 consist of the '<tt>let</tt>' keyword followed by a value name, an equal sign
 391 ("="), and a new value.  For example, a new class could be added to the example
 392 above, redefining the <tt>V</tt> field for all of its subclasses:</p>
 393
 394 <pre>
 395 <b>class</b> D : C { let V = 0; }
 396 <b>def</b> Z : D;
 397 </pre>
 398
 399 <p>In this case, the <tt>Z</tt> definition will have a zero value for its "V"
 400 value, despite the fact that it derives (indirectly) from the <tt>C</tt> class,
 401 because the <tt>D</tt> class overrode its value.</p>
 402
 403 </div>
 404
 405 <!-- -------------------------------------------------------------------------->
 406 <div class="doc_subsubsection">
 407   <a name="templateargs">Class template arguments</a>
 408 </div>
 409
 410 <div class="doc_text">
 411 <p>TableGen permits the definition of parameterized classes as well as normal
 412 concrete classes.  Parameterized TableGen classes specify a list of variable
 413 bindings (which may optionally have defaults) that are bound when used.  Here is
 414 a simple example:</p>
 415
 416 <pre>
 417 <b>class</b> FPFormat&lt;<b>bits</b>&lt;3&gt; val&gt; {
 418   <b>bits</b>&lt;3&gt; Value = val;
 419 }
 420 <b>def</b> NotFP      : FPFormat&lt;0&gt;;
 421 <b>def</b> ZeroArgFP  : FPFormat&lt;1&gt;;
 422 <b>def</b> OneArgFP   : FPFormat&lt;2&gt;;
 423 <b>def</b> OneArgFPRW : FPFormat&lt;3&gt;;
 424 <b>def</b> TwoArgFP   : FPFormat&lt;4&gt;;
 425 <b>def</b> SpecialFP  : FPFormat&lt;5&gt;;
 426 </pre>
 427
 428 <p>In this case, template arguments are used as a space efficient way to specify
 429 a list of "enumeration values", each with a "Value" field set to the specified
 430 integer.</p>
 431
 432 <p>The more esoteric forms of <a href="#values">TableGen expressions</a> are
 433 useful in conjunction with template arguments.  As an example:</p>
 434
 435 <pre>
 436 <b>class</b> ModRefVal&lt;<b>bits</b>&lt;2&gt; val&gt; {
 437   <b>bits</b>&lt;2&gt; Value = val;
 438 }
 439
 440 <b>def</b> None   : ModRefVal&lt;0&gt;;
 441 <b>def</b> Mod    : ModRefVal&lt;1&gt;;
 442 <b>def</b> Ref    : ModRefVal&lt;2&gt;;
 443 <b>def</b> ModRef : ModRefVal&lt;3&gt;;
 444
 445 <b>class</b> Value&lt;ModRefVal MR&gt; {
 446   <i>// decode some information into a more convenient format, while providing
 447   // a nice interface to the user of the "Value" class.</i>
 448   <b>bit</b> isMod = MR.Value{0};
 449   <b>bit</b> isRef = MR.Value{1};
 450
 451   <i>// other stuff...</i>
 452 }
 453
 454 <i>// Example uses</i>
 455 <b>def</b> bork : Value&lt;Mod&gt;;
 456 <b>def</b> zork : Value&lt;Ref&gt;;
 457 <b>def</b> hork : Value&lt;ModRef&gt;;
 458 </pre>
 459
 460 <p>This is obviously a contrived example, but it shows how template arguments
 461 can be used to decouple the interface provided to the user of the class from the
 462 actual internal data representation expected by the class.  In this case,
 463 running <tt>tblgen</tt> on the example prints the following definitions:</p>
 464
 465 <pre>
 466 <b>def</b> bork {      <i>// Value</i>
 467   bit isMod = 1;
 468   bit isRef = 0;
 469 }
 470 <b>def</b> hork {      <i>// Value</i>
 471   bit isMod = 1;
 472   bit isRef = 1;
 473 }
 474 <b>def</b> zork {      <i>// Value</i>
 475   bit isMod = 0;
 476   bit isRef = 1;
 477 }
 478 </pre>
 479
 480 <p> This shows that TableGen was able to dig into the argument and extract a
 481 piece of information that was requested by the designer of the "Value" class.
 482 For more realistic examples, please see existing users of TableGen, such as the
 483 X86 backend.</p>
 484
 485 </div>
 486
 487 <!-- ======================================================================= -->
 488 <div class="doc_subsection">
 489   <a name="filescope">File scope entities</a>
 490 </div>
 491
 492 <!-- -------------------------------------------------------------------------->
 493 <div class="doc_subsubsection">
 494   <a name="include">File inclusion</a>
 495 </div>
 496
 497 <div class="doc_text">
 498 <p>TableGen supports the '<tt>include</tt>' token, which textually substitutes
 499 the specified file in place of the include directive.  The filename should be
 500 specified as a double quoted string immediately after the '<tt>include</tt>'
 501 keyword.  Example:</p>
 502
 503 <pre>
 504 <b>include</b> "foo.td"
 505 </pre>
 506
 507 </div>
 508
 509 <!-- -------------------------------------------------------------------------->
 510 <div class="doc_subsubsection">
 511   <a name="globallet">'let' expressions</a>
 512 </div>
 513
 514 <div class="doc_text">
 515 <p> "let" expressions at file scope are similar to <a href="#recordlet">"let"
 516 expressions within a record</a>, except they can specify a value binding for
 517 multiple records at a time, and may be useful in certain other cases.
 518 File-scope let expressions are really just another way that TableGen allows the
 519 end-user to factor out commonality from the records.</p>
 520
 521 <p>File-scope "let" expressions take a comma-seperated list of bindings to
 522 apply, and one of more records to bind the values in.  Here are some
 523 examples:</p>
 524
 525 <pre>
 526 <b>let</b> isTerminator = 1, isReturn = 1 <b>in</b>
 527   <b>def</b> RET : X86Inst&lt;"ret", 0xC3, RawFrm, NoArg&gt;;
 528
 529 <b>let</b> isCall = 1 <b>in</b>
 530   <i>// All calls clobber the non-callee saved registers...</i>
 531   <b>let</b> Defs = [EAX, ECX, EDX, FP0, FP1, FP2, FP3, FP4, FP5, FP6] in {
 532     <b>def</b> CALLpcrel32 : X86Inst&lt;"call", 0xE8, RawFrm, NoArg&gt;;
 533     <b>def</b> CALLr32     : X86Inst&lt;"call", 0xFF, MRMS2r, Arg32&gt;;
 534     <b>def</b> CALLm32     : X86Inst&lt;"call", 0xFF, MRMS2m, Arg32&gt;;
 535   }
 536 </pre>
 537
 538 <p>File-scope "let" expressions are often useful when a couple of definitions
 539 need to be added to several records, and the records do not otherwise need to be
 540 opened, as in the case with the CALL* instructions above.</p>
 541 </div>
 542
 543 <!-- *********************************************************************** -->
 544 <div class="doc_section"><a name="backends">TableGen backends</a></div>
 545 <!-- *********************************************************************** -->
 546
 547 <div class="doc_text">
 548 <p>How they work, how to write one.  This section should not contain details
 549 about any particular backend, except maybe -print-enums as an example.  This
 550 should highlight the APIs in <tt>TableGen/Record.h</tt>.</p>
 551 </div>
 552
 553 <!-- *********************************************************************** -->
 554 <div class="doc_section"><a name="codegenerator">The LLVM code generator</a>
 555 </div>
 556 <!-- *********************************************************************** -->
 557
 558 <div class="doc_text">
 559 <p>This is just a temporary, convenient, place to put stuff about the code
 560 generator before it gets its own document.  This should describe all of the
 561 tablegen backends used by the code generator and the classes/definitions they
 562 expect.</p>
 563 </div>
 564
 565 <!-- *********************************************************************** -->
 566
 567 <hr>
 568 <address>
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 574   <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
 575   <a href="http://llvm.cs.uiuc.edu">LLVM Compiler Infrastructure</a><br>
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