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4<head>
5 <title>TableGen Fundamentals</title>
6 <link rel="stylesheet" href="llvm.css" type="text/css">
7</head>
8<body>
9
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 <li><a href="#multiclass">Multiclass definitions and instances</a></li>
34 </ol></li>
35 <li><a href="#filescope">File scope entities</a>
36 <ol>
37 <li><a href="#include">File inclusion</a></li>
38 <li><a href="#globallet">'let' expressions</a></li>
39 </ol></li>
40 </ol></li>
41 <li><a href="#backends">TableGen backends</a>
42 <ol>
43 <li><a href="#">todo</a></li>
44 </ol></li>
45</ul>
46</div>
47
48<div class="doc_author">
49 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
50</div>
51
52<!-- *********************************************************************** -->
53<div class="doc_section"><a name="introduction">Introduction</a></div>
54<!-- *********************************************************************** -->
55
56<div class="doc_text">
57
58<p>TableGen's purpose is to help a human develop and maintain records of
59domain-specific information. Because there may be a large number of these
60records, it is specifically designed to allow writing flexible descriptions and
61for common features of these records to be factored out. This reduces the
62amount of duplication in the description, reduces the chance of error, and
63makes it easier to structure domain specific information.</p>
64
65<p>The core part of TableGen <a href="#syntax">parses a file</a>, instantiates
66the declarations, and hands the result off to a domain-specific "<a
67href="#backends">TableGen backend</a>" for processing. The current major user
68of TableGen is the <a href="CodeGenerator.html">LLVM code generator</a>.</p>
69
70<p>Note that if you work on TableGen much, and use emacs or vim, that you can
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]71find an emacs "TableGen mode" and a vim language file in the
72<tt>llvm/utils/emacs</tt> and <tt>llvm/utils/vim</tt> directories of your LLVM
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]73distribution, respectively.</p>
74
75</div>
76
77<!-- ======================================================================= -->
78<div class="doc_subsection"><a name="concepts">Basic concepts</a></div>
79
80<div class="doc_text">
81
82<p>TableGen files consist of two key parts: 'classes' and 'definitions', both
83of which are considered 'records'.</p>
84
85<p><b>TableGen records</b> have a unique name, a list of values, and a list of
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]86superclasses. The list of values is the main data that TableGen builds for each
87record; it is this that holds the domain specific information for the
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]88application. The interpretation of this data is left to a specific <a
89href="#backends">TableGen backend</a>, but the structure and format rules are
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]90taken care of and are fixed by TableGen.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]91
92<p><b>TableGen definitions</b> are the concrete form of 'records'. These
93generally do not have any undefined values, and are marked with the
94'<tt>def</tt>' keyword.</p>
95
96<p><b>TableGen classes</b> are abstract records that are used to build and
97describe other records. These 'classes' allow the end-user to build
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]98abstractions for either the domain they are targeting (such as "Register",
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]99"RegisterClass", and "Instruction" in the LLVM code generator) or for the
100implementor to help factor out common properties of records (such as "FPInst",
101which is used to represent floating point instructions in the X86 backend).
102TableGen keeps track of all of the classes that are used to build up a
103definition, so the backend can find all definitions of a particular class, such
104as "Instruction".</p>
105
106<p><b>TableGen multiclasses</b> are groups of abstract records that are
David Greene60b5acc2009-04-22 16:42:54 +0000[diff] [blame]107instantiated all at once. Each instantiation can result in multiple
108TableGen definitions. If a multiclass inherits from another multiclass,
109the definitions in the sub-multiclass become part of the current
110multiclass, as if they were declared in the current multiclass.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]111
112</div>
113
114<!-- ======================================================================= -->
115<div class="doc_subsection"><a name="example">An example record</a></div>
116
117<div class="doc_text">
118
119<p>With no other arguments, TableGen parses the specified file and prints out
120all of the classes, then all of the definitions. This is a good way to see what
121the various definitions expand to fully. Running this on the <tt>X86.td</tt>
122file prints this (at the time of this writing):</p>
123
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]124<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]125<pre>
126...
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]127<b>def</b> ADD32rr { <i>// Instruction X86Inst I</i>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]128 <b>string</b> Namespace = "X86";
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]129 <b>dag</b> OutOperandList = (outs GR32:$dst);
130 <b>dag</b> InOperandList = (ins GR32:$src1, GR32:$src2);
131 <b>string</b> AsmString = "add{l}\t{$src2, $dst|$dst, $src2}";
132 <b>list</b>&lt;dag&gt; Pattern = [(set GR32:$dst, (add GR32:$src1, GR32:$src2))];
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]133 <b>list</b>&lt;Register&gt; Uses = [];
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]134 <b>list</b>&lt;Register&gt; Defs = [EFLAGS];
135 <b>list</b>&lt;Predicate&gt; Predicates = [];
136 <b>int</b> CodeSize = 3;
137 <b>int</b> AddedComplexity = 0;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]138 <b>bit</b> isReturn = 0;
139 <b>bit</b> isBranch = 0;
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]140 <b>bit</b> isIndirectBranch = 0;
141 <b>bit</b> isBarrier = 0;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]142 <b>bit</b> isCall = 0;
Dan Gohman5574cc72008-12-03 18:15:48 +0000[diff] [blame]143 <b>bit</b> canFoldAsLoad = 0;
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]144 <b>bit</b> mayLoad = 0;
145 <b>bit</b> mayStore = 0;
146 <b>bit</b> isImplicitDef = 0;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]147 <b>bit</b> isTwoAddress = 1;
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]148 <b>bit</b> isConvertibleToThreeAddress = 1;
149 <b>bit</b> isCommutable = 1;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]150 <b>bit</b> isTerminator = 0;
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]151 <b>bit</b> isReMaterializable = 0;
152 <b>bit</b> isPredicable = 0;
153 <b>bit</b> hasDelaySlot = 0;
154 <b>bit</b> usesCustomDAGSchedInserter = 0;
155 <b>bit</b> hasCtrlDep = 0;
156 <b>bit</b> isNotDuplicable = 0;
157 <b>bit</b> hasSideEffects = 0;
158 <b>bit</b> mayHaveSideEffects = 0;
159 <b>bit</b> neverHasSideEffects = 0;
160 InstrItinClass Itinerary = NoItinerary;
161 <b>string</b> Constraints = "";
162 <b>string</b> DisableEncoding = "";
163 <b>bits</b>&lt;8&gt; Opcode = { 0, 0, 0, 0, 0, 0, 0, 1 };
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]164 Format Form = MRMDestReg;
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]165 <b>bits</b>&lt;6&gt; FormBits = { 0, 0, 0, 0, 1, 1 };
166 ImmType ImmT = NoImm;
167 <b>bits</b>&lt;3&gt; ImmTypeBits = { 0, 0, 0 };
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]168 <b>bit</b> hasOpSizePrefix = 0;
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]169 <b>bit</b> hasAdSizePrefix = 0;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]170 <b>bits</b>&lt;4&gt; Prefix = { 0, 0, 0, 0 };
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]171 <b>bit</b> hasREX_WPrefix = 0;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]172 FPFormat FPForm = ?;
173 <b>bits</b>&lt;3&gt; FPFormBits = { 0, 0, 0 };
174}
175...
176</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]177</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]178
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]179<p>This definition corresponds to a 32-bit register-register add instruction in
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]180the X86. The string after the '<tt>def</tt>' string indicates the name of the
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]181record&mdash;"<tt>ADD32rr</tt>" in this case&mdash;and the comment at the end of
182the line indicates the superclasses of the definition. The body of the record
183contains all of the data that TableGen assembled for the record, indicating that
184the instruction is part of the "X86" namespace, the pattern indicating how the
185the instruction should be emitted into the assembly file, that it is a
186two-address instruction, has a particular encoding, etc. The contents and
187semantics of the information in the record is specific to the needs of the X86
188backend, and is only shown as an example.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]189
190<p>As you can see, a lot of information is needed for every instruction
191supported by the code generator, and specifying it all manually would be
192unmaintainble, prone to bugs, and tiring to do in the first place. Because we
193are using TableGen, all of the information was derived from the following
194definition:</p>
195
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]196<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]197<pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]198let Defs = [EFLAGS],
199 isCommutable = 1, <i>// X = ADD Y,Z --&gt; X = ADD Z,Y</i>
200 isConvertibleToThreeAddress = 1 <b>in</b> <i>// Can transform into LEA.</i>
201def ADD32rr : I&lt;0x01, MRMDestReg, (outs GR32:$dst),
202 (ins GR32:$src1, GR32:$src2),
203 "add{l}\t{$src2, $dst|$dst, $src2}",
204 [(set GR32:$dst, (add GR32:$src1, GR32:$src2))]&gt;;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]205</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]206</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]207
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]208<p>This definition makes use of the custom class <tt>I</tt> (extended from the
209custom class <tt>X86Inst</tt>), which is defined in the X86-specific TableGen
210file, to factor out the common features that instructions of its class share. A
211key feature of TableGen is that it allows the end-user to define the
212abstractions they prefer to use when describing their information.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]213
214</div>
215
216<!-- ======================================================================= -->
217<div class="doc_subsection"><a name="running">Running TableGen</a></div>
218
219<div class="doc_text">
220
221<p>TableGen runs just like any other LLVM tool. The first (optional) argument
222specifies the file to read. If a filename is not specified, <tt>tblgen</tt>
223reads from standard input.</p>
224
225<p>To be useful, one of the <a href="#backends">TableGen backends</a> must be
226used. These backends are selectable on the command line (type '<tt>tblgen
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]227-help</tt>' for a list). For example, to get a list of all of the definitions
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]228that subclass a particular type (which can be useful for building up an enum
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]229list of these records), use the <tt>-print-enums</tt> option:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]230
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]231<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]232<pre>
233$ tblgen X86.td -print-enums -class=Register
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]234AH, AL, AX, BH, BL, BP, BPL, BX, CH, CL, CX, DH, DI, DIL, DL, DX, EAX, EBP, EBX,
235ECX, EDI, EDX, EFLAGS, EIP, ESI, ESP, FP0, FP1, FP2, FP3, FP4, FP5, FP6, IP,
236MM0, MM1, MM2, MM3, MM4, MM5, MM6, MM7, R10, R10B, R10D, R10W, R11, R11B, R11D,
237R11W, R12, R12B, R12D, R12W, R13, R13B, R13D, R13W, R14, R14B, R14D, R14W, R15,
238R15B, R15D, R15W, R8, R8B, R8D, R8W, R9, R9B, R9D, R9W, RAX, RBP, RBX, RCX, RDI,
239RDX, RIP, RSI, RSP, SI, SIL, SP, SPL, ST0, ST1, ST2, ST3, ST4, ST5, ST6, ST7,
240XMM0, XMM1, XMM10, XMM11, XMM12, XMM13, XMM14, XMM15, XMM2, XMM3, XMM4, XMM5,
241XMM6, XMM7, XMM8, XMM9,
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]242
243$ tblgen X86.td -print-enums -class=Instruction
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]244ABS_F, ABS_Fp32, ABS_Fp64, ABS_Fp80, ADC32mi, ADC32mi8, ADC32mr, ADC32ri,
245ADC32ri8, ADC32rm, ADC32rr, ADC64mi32, ADC64mi8, ADC64mr, ADC64ri32, ADC64ri8,
246ADC64rm, ADC64rr, ADD16mi, ADD16mi8, ADD16mr, ADD16ri, ADD16ri8, ADD16rm,
247ADD16rr, ADD32mi, ADD32mi8, ADD32mr, ADD32ri, ADD32ri8, ADD32rm, ADD32rr,
248ADD64mi32, ADD64mi8, ADD64mr, ADD64ri32, ...
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]249</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]250</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]251
252<p>The default backend prints out all of the records, as described <a
253href="#example">above</a>.</p>
254
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]255<p>If you plan to use TableGen, you will most likely have to <a
256href="#backends">write a backend</a> that extracts the information specific to
257what you need and formats it in the appropriate way.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]258
259</div>
260
261
262<!-- *********************************************************************** -->
263<div class="doc_section"><a name="syntax">TableGen syntax</a></div>
264<!-- *********************************************************************** -->
265
266<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]267
268<p>TableGen doesn't care about the meaning of data (that is up to the backend to
269define), but it does care about syntax, and it enforces a simple type system.
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]270This section describes the syntax and the constructs allowed in a TableGen file.
271</p>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]272
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]273</div>
274
275<!-- ======================================================================= -->
276<div class="doc_subsection"><a name="primitives">TableGen primitives</a></div>
277
278<!-- -------------------------------------------------------------------------->
279<div class="doc_subsubsection"><a name="comments">TableGen comments</a></div>
280
281<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]282
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]283<p>TableGen supports BCPL style "<tt>//</tt>" comments, which run to the end of
284the line, and it also supports <b>nestable</b> "<tt>/* */</tt>" comments.</p>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]285
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]286</div>
287
288<!-- -------------------------------------------------------------------------->
289<div class="doc_subsubsection">
290 <a name="types">The TableGen type system</a>
291</div>
292
293<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]294
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]295<p>TableGen files are strongly typed, in a simple (but complete) type-system.
296These types are used to perform automatic conversions, check for errors, and to
297help interface designers constrain the input that they allow. Every <a
298href="#valuedef">value definition</a> is required to have an associated type.
299</p>
300
301<p>TableGen supports a mixture of very low-level types (such as <tt>bit</tt>)
302and very high-level types (such as <tt>dag</tt>). This flexibility is what
303allows it to describe a wide range of information conveniently and compactly.
304The TableGen types are:</p>
305
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]306<dl>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]307<dt><tt><b>bit</b></tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]308 <dd>A 'bit' is a boolean value that can hold either 0 or 1.</dd>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]309
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]310<dt><tt><b>int</b></tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]311 <dd>The 'int' type represents a simple 32-bit integer value, such as 5.</dd>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]312
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]313<dt><tt><b>string</b></tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]314 <dd>The 'string' type represents an ordered sequence of characters of
315 arbitrary length.</dd>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]316
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]317<dt><tt><b>bits</b>&lt;n&gt;</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]318 <dd>A 'bits' type is an arbitrary, but fixed, size integer that is broken up
319 into individual bits. This type is useful because it can handle some bits
320 being defined while others are undefined.</dd>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]321
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]322<dt><tt><b>list</b>&lt;ty&gt;</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]323 <dd>This type represents a list whose elements are some other type. The
324 contained type is arbitrary: it can even be another list type.</dd>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]325
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]326<dt>Class type</dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]327 <dd>Specifying a class name in a type context means that the defined value
328 must be a subclass of the specified class. This is useful in conjunction with
329 the <b><tt>list</tt></b> type, for example, to constrain the elements of the
330 list to a common base class (e.g., a <tt><b>list</b>&lt;Register&gt;</tt> can
331 only contain definitions derived from the "<tt>Register</tt>" class).</dd>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]332
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]333<dt><tt><b>dag</b></tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]334 <dd>This type represents a nestable directed graph of elements.</dd>
335
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]336<dt><tt><b>code</b></tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]337 <dd>This represents a big hunk of text. NOTE: I don't remember why this is
338 distinct from string!</dd>
339</dl>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]340
341<p>To date, these types have been sufficient for describing things that
342TableGen has been used for, but it is straight-forward to extend this list if
343needed.</p>
344
345</div>
346
347<!-- -------------------------------------------------------------------------->
348<div class="doc_subsubsection">
349 <a name="values">TableGen values and expressions</a>
350</div>
351
352<div class="doc_text">
353
354<p>TableGen allows for a pretty reasonable number of different expression forms
355when building up values. These forms allow the TableGen file to be written in a
356natural syntax and flavor for the application. The current expression forms
357supported include:</p>
358
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]359<dl>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]360<dt><tt>?</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]361 <dd>uninitialized field</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]362<dt><tt>0b1001011</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]363 <dd>binary integer value</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]364<dt><tt>07654321</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]365 <dd>octal integer value (indicated by a leading 0)</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]366<dt><tt>7</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]367 <dd>decimal integer value</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]368<dt><tt>0x7F</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]369 <dd>hexadecimal integer value</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]370<dt><tt>"foo"</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]371 <dd>string value</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]372<dt><tt>[{ ... }]</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]373 <dd>code fragment</dd>
Benjamin Kramer7b2136d2009-08-05 15:42:44 +0000[diff] [blame]374<dt><tt>[ X, Y, Z ]&lt;type&gt;</tt></dt>
375 <dd>list value. &lt;type&gt; is the type of the list
David Greenecde43742009-06-08 22:38:07 +0000[diff] [blame]376element and is usually optional. In rare cases,
377TableGen is unable to deduce the element type in
378which case the user must specify it explicitly.</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]379<dt><tt>{ a, b, c }</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]380 <dd>initializer for a "bits&lt;3&gt;" value</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]381<dt><tt>value</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]382 <dd>value reference</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]383<dt><tt>value{17}</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]384 <dd>access to one bit of a value</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]385<dt><tt>value{15-17}</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]386 <dd>access to multiple bits of a value</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]387<dt><tt>DEF</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]388 <dd>reference to a record definition</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]389<dt><tt>CLASS&lt;val list&gt;</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]390 <dd>reference to a new anonymous definition of CLASS with the specified
391 template arguments.</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]392<dt><tt>X.Y</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]393 <dd>reference to the subfield of a value</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]394<dt><tt>list[4-7,17,2-3]</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]395 <dd>A slice of the 'list' list, including elements 4,5,6,7,17,2, and 3 from
396 it. Elements may be included multiple times.</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]397<dt><tt>(DEF a, b)</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]398 <dd>a dag value. The first element is required to be a record definition, the
399 remaining elements in the list may be arbitrary other values, including nested
400 `<tt>dag</tt>' values.</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]401<dt><tt>!strconcat(a, b)</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]402 <dd>A string value that is the result of concatenating the 'a' and 'b'
403 strings.</dd>
Benjamin Kramer7b2136d2009-08-05 15:42:44 +0000[diff] [blame]404<dt><tt>!cast&lt;type&gt;(a)</tt></dt>
David Greene4fd89a02009-05-14 21:22:49 +0000[diff] [blame]405 <dd>A symbol of type <em>type</em> obtained by looking up the string 'a' in
406the symbol table. If the type of 'a' does not match <em>type</em>, TableGen
Benjamin Kramer7b2136d2009-08-05 15:42:44 +0000[diff] [blame]407aborts with an error. !cast&lt;string&gt; is a special case in that the argument must
David Greene1aa38cb2009-06-29 20:05:29 +0000[diff] [blame]408be an object defined by a 'def' construct.</dd>
David Greenef02acf02009-04-23 21:27:58 +0000[diff] [blame]409<dt><tt>!nameconcat&lt;type&gt;(a, b)</tt></dt>
Benjamin Kramer7b2136d2009-08-05 15:42:44 +0000[diff] [blame]410 <dd>Shorthand for !cast&lt;type&gt;(!strconcat(a, b))</dd>
David Greene4f124db2009-05-14 21:54:42 +0000[diff] [blame]411<dt><tt>!subst(a, b, c)</tt></dt>
412 <dd>If 'a' and 'b' are of string type or are symbol references, substitute
413'b' for 'a' in 'c.' This operation is analogous to $(subst) in GNU make.</dd>
David Greene2c383212009-05-14 22:23:47 +0000[diff] [blame]414<dt><tt>!foreach(a, b, c)</tt></dt>
415 <dd>For each member 'b' of dag or list 'a' apply operator 'c.' 'b' is a
416dummy variable that should be declared as a member variable of an instantiated
417class. This operation is analogous to $(foreach) in GNU make.</dd>
David Greene04c89a12009-05-14 22:38:31 +0000[diff] [blame]418<dt><tt>!car(a)</tt></dt>
419 <dd>The first element of list 'a.'</dd>
420<dt><tt>!cdr(a)</tt></dt>
421 <dd>The 2nd-N elements of list 'a.'</dd>
422<dt><tt>!null(a)</tt></dt>
423 <dd>An integer {0,1} indicating whether list 'a' is empty.</dd>
David Greene70037ea2009-05-14 23:26:46 +0000[diff] [blame]424<dt><tt>!if(a,b,c)</tt></dt>
425 <dd>'b' if the result of integer operator 'a' is nonzero, 'c' otherwise.</dd>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]426</dl>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]427
428<p>Note that all of the values have rules specifying how they convert to values
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]429for different types. These rules allow you to assign a value like "<tt>7</tt>"
430to a "<tt>bits&lt;4&gt;</tt>" value, for example.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]431
432</div>
433
434<!-- ======================================================================= -->
435<div class="doc_subsection">
436 <a name="classesdefs">Classes and definitions</a>
437</div>
438
439<div class="doc_text">
440
441<p>As mentioned in the <a href="#concepts">intro</a>, classes and definitions
442(collectively known as 'records') in TableGen are the main high-level unit of
443information that TableGen collects. Records are defined with a <tt>def</tt> or
444<tt>class</tt> keyword, the record name, and an optional list of "<a
445href="#templateargs">template arguments</a>". If the record has superclasses,
446they are specified as a comma separated list that starts with a colon character
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]447("<tt>:</tt>"). If <a href="#valuedef">value definitions</a> or <a
448href="#recordlet">let expressions</a> are needed for the class, they are
449enclosed in curly braces ("<tt>{}</tt>"); otherwise, the record ends with a
450semicolon.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]451
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]452<p>Here is a simple TableGen file:</p>
453
454<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]455<pre>
456<b>class</b> C { <b>bit</b> V = 1; }
457<b>def</b> X : C;
458<b>def</b> Y : C {
459 <b>string</b> Greeting = "hello";
460}
461</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]462</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]463
464<p>This example defines two definitions, <tt>X</tt> and <tt>Y</tt>, both of
465which derive from the <tt>C</tt> class. Because of this, they both get the
466<tt>V</tt> bit value. The <tt>Y</tt> definition also gets the Greeting member
467as well.</p>
468
469<p>In general, classes are useful for collecting together the commonality
470between a group of records and isolating it in a single place. Also, classes
471permit the specification of default values for their subclasses, allowing the
472subclasses to override them as they wish.</p>
473
474</div>
475
476<!---------------------------------------------------------------------------->
477<div class="doc_subsubsection">
478 <a name="valuedef">Value definitions</a>
479</div>
480
481<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]482
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]483<p>Value definitions define named entries in records. A value must be defined
484before it can be referred to as the operand for another value definition or
485before the value is reset with a <a href="#recordlet">let expression</a>. A
486value is defined by specifying a <a href="#types">TableGen type</a> and a name.
487If an initial value is available, it may be specified after the type with an
488equal sign. Value definitions require terminating semicolons.</p>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]489
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]490</div>
491
492<!-- -------------------------------------------------------------------------->
493<div class="doc_subsubsection">
494 <a name="recordlet">'let' expressions</a>
495</div>
496
497<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]498
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]499<p>A record-level let expression is used to change the value of a value
500definition in a record. This is primarily useful when a superclass defines a
501value that a derived class or definition wants to override. Let expressions
502consist of the '<tt>let</tt>' keyword followed by a value name, an equal sign
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]503("<tt>=</tt>"), and a new value. For example, a new class could be added to the
504example above, redefining the <tt>V</tt> field for all of its subclasses:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]505
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]506<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]507<pre>
508<b>class</b> D : C { let V = 0; }
509<b>def</b> Z : D;
510</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]511</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]512
513<p>In this case, the <tt>Z</tt> definition will have a zero value for its "V"
514value, despite the fact that it derives (indirectly) from the <tt>C</tt> class,
515because the <tt>D</tt> class overrode its value.</p>
516
517</div>
518
519<!-- -------------------------------------------------------------------------->
520<div class="doc_subsubsection">
521 <a name="templateargs">Class template arguments</a>
522</div>
523
524<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]525
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]526<p>TableGen permits the definition of parameterized classes as well as normal
527concrete classes. Parameterized TableGen classes specify a list of variable
528bindings (which may optionally have defaults) that are bound when used. Here is
529a simple example:</p>
530
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]531<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]532<pre>
533<b>class</b> FPFormat&lt;<b>bits</b>&lt;3&gt; val&gt; {
534 <b>bits</b>&lt;3&gt; Value = val;
535}
536<b>def</b> NotFP : FPFormat&lt;0&gt;;
537<b>def</b> ZeroArgFP : FPFormat&lt;1&gt;;
538<b>def</b> OneArgFP : FPFormat&lt;2&gt;;
539<b>def</b> OneArgFPRW : FPFormat&lt;3&gt;;
540<b>def</b> TwoArgFP : FPFormat&lt;4&gt;;
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]541<b>def</b> CompareFP : FPFormat&lt;5&gt;;
542<b>def</b> CondMovFP : FPFormat&lt;6&gt;;
543<b>def</b> SpecialFP : FPFormat&lt;7&gt;;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]544</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]545</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]546
547<p>In this case, template arguments are used as a space efficient way to specify
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]548a list of "enumeration values", each with a "<tt>Value</tt>" field set to the
549specified integer.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]550
551<p>The more esoteric forms of <a href="#values">TableGen expressions</a> are
552useful in conjunction with template arguments. As an example:</p>
553
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]554<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]555<pre>
556<b>class</b> ModRefVal&lt;<b>bits</b>&lt;2&gt; val&gt; {
557 <b>bits</b>&lt;2&gt; Value = val;
558}
559
560<b>def</b> None : ModRefVal&lt;0&gt;;
561<b>def</b> Mod : ModRefVal&lt;1&gt;;
562<b>def</b> Ref : ModRefVal&lt;2&gt;;
563<b>def</b> ModRef : ModRefVal&lt;3&gt;;
564
565<b>class</b> Value&lt;ModRefVal MR&gt; {
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]566 <i>// Decode some information into a more convenient format, while providing
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]567 // a nice interface to the user of the "Value" class.</i>
568 <b>bit</b> isMod = MR.Value{0};
569 <b>bit</b> isRef = MR.Value{1};
570
571 <i>// other stuff...</i>
572}
573
574<i>// Example uses</i>
575<b>def</b> bork : Value&lt;Mod&gt;;
576<b>def</b> zork : Value&lt;Ref&gt;;
577<b>def</b> hork : Value&lt;ModRef&gt;;
578</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]579</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]580
581<p>This is obviously a contrived example, but it shows how template arguments
582can be used to decouple the interface provided to the user of the class from the
583actual internal data representation expected by the class. In this case,
584running <tt>tblgen</tt> on the example prints the following definitions:</p>
585
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]586<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]587<pre>
588<b>def</b> bork { <i>// Value</i>
589 <b>bit</b> isMod = 1;
590 <b>bit</b> isRef = 0;
591}
592<b>def</b> hork { <i>// Value</i>
593 <b>bit</b> isMod = 1;
594 <b>bit</b> isRef = 1;
595}
596<b>def</b> zork { <i>// Value</i>
597 <b>bit</b> isMod = 0;
598 <b>bit</b> isRef = 1;
599}
600</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]601</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]602
603<p> This shows that TableGen was able to dig into the argument and extract a
604piece of information that was requested by the designer of the "Value" class.
605For more realistic examples, please see existing users of TableGen, such as the
606X86 backend.</p>
607
608</div>
609
610<!-- -------------------------------------------------------------------------->
611<div class="doc_subsubsection">
612 <a name="multiclass">Multiclass definitions and instances</a>
613</div>
614
615<div class="doc_text">
616
617<p>
618While classes with template arguments are a good way to factor commonality
619between two instances of a definition, multiclasses allow a convenient notation
620for defining multiple definitions at once (instances of implicitly constructed
621classes). For example, consider an 3-address instruction set whose instructions
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]622come in two forms: "<tt>reg = reg op reg</tt>" and "<tt>reg = reg op imm</tt>"
623(e.g. SPARC). In this case, you'd like to specify in one place that this
624commonality exists, then in a separate place indicate what all the ops are.
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]625</p>
626
627<p>
628Here is an example TableGen fragment that shows this idea:
629</p>
630
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]631<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]632<pre>
633<b>def</b> ops;
634<b>def</b> GPR;
635<b>def</b> Imm;
636<b>class</b> inst&lt;<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist&gt;;
637
638<b>multiclass</b> ri_inst&lt;<b>int</b> opc, <b>string</b> asmstr&gt; {
639 def _rr : inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
640 (ops GPR:$dst, GPR:$src1, GPR:$src2)&gt;;
641 def _ri : inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
642 (ops GPR:$dst, GPR:$src1, Imm:$src2)&gt;;
643}
644
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]645<i>// Instantiations of the ri_inst multiclass.</i>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]646<b>defm</b> ADD : ri_inst&lt;0b111, "add"&gt;;
647<b>defm</b> SUB : ri_inst&lt;0b101, "sub"&gt;;
648<b>defm</b> MUL : ri_inst&lt;0b100, "mul"&gt;;
649...
650</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]651</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]652
653<p>The name of the resultant definitions has the multidef fragment names
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]654 appended to them, so this defines <tt>ADD_rr</tt>, <tt>ADD_ri</tt>,
David Greene080d2152009-04-22 22:17:51 +0000[diff] [blame]655 <tt>SUB_rr</tt>, etc. A defm may inherit from multiple multiclasses,
656 instantiating definitions from each multiclass. Using a multiclass
657 this way is exactly equivalent to instantiating the classes multiple
658 times yourself, e.g. by writing:</p>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]659
660<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]661<pre>
662<b>def</b> ops;
663<b>def</b> GPR;
664<b>def</b> Imm;
665<b>class</b> inst&lt;<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist&gt;;
666
667<b>class</b> rrinst&lt;<b>int</b> opc, <b>string</b> asmstr&gt;
668 : inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
669 (ops GPR:$dst, GPR:$src1, GPR:$src2)&gt;;
670
671<b>class</b> riinst&lt;<b>int</b> opc, <b>string</b> asmstr&gt;
672 : inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
673 (ops GPR:$dst, GPR:$src1, Imm:$src2)&gt;;
674
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]675<i>// Instantiations of the ri_inst multiclass.</i>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]676<b>def</b> ADD_rr : rrinst&lt;0b111, "add"&gt;;
677<b>def</b> ADD_ri : riinst&lt;0b111, "add"&gt;;
678<b>def</b> SUB_rr : rrinst&lt;0b101, "sub"&gt;;
679<b>def</b> SUB_ri : riinst&lt;0b101, "sub"&gt;;
680<b>def</b> MUL_rr : rrinst&lt;0b100, "mul"&gt;;
681<b>def</b> MUL_ri : riinst&lt;0b100, "mul"&gt;;
682...
683</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]684</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]685
686</div>
687
688<!-- ======================================================================= -->
689<div class="doc_subsection">
690 <a name="filescope">File scope entities</a>
691</div>
692
693<!-- -------------------------------------------------------------------------->
694<div class="doc_subsubsection">
695 <a name="include">File inclusion</a>
696</div>
697
698<div class="doc_text">
699<p>TableGen supports the '<tt>include</tt>' token, which textually substitutes
700the specified file in place of the include directive. The filename should be
701specified as a double quoted string immediately after the '<tt>include</tt>'
702keyword. Example:</p>
703
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]704<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]705<pre>
706<b>include</b> "foo.td"
707</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]708</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]709
710</div>
711
712<!-- -------------------------------------------------------------------------->
713<div class="doc_subsubsection">
714 <a name="globallet">'let' expressions</a>
715</div>
716
717<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]718
719<p>"Let" expressions at file scope are similar to <a href="#recordlet">"let"
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]720expressions within a record</a>, except they can specify a value binding for
721multiple records at a time, and may be useful in certain other cases.
722File-scope let expressions are really just another way that TableGen allows the
723end-user to factor out commonality from the records.</p>
724
725<p>File-scope "let" expressions take a comma-separated list of bindings to
Matthijs Kooijman16bb03a2008-10-20 08:45:34 +0000[diff] [blame]726apply, and one or more records to bind the values in. Here are some
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]727examples:</p>
728
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]729<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]730<pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]731<b>let</b> isTerminator = 1, isReturn = 1, isBarrier = 1, hasCtrlDep = 1 <b>in</b>
732 <b>def</b> RET : I&lt;0xC3, RawFrm, (outs), (ins), "ret", [(X86retflag 0)]&gt;;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]733
734<b>let</b> isCall = 1 <b>in</b>
735 <i>// All calls clobber the non-callee saved registers...</i>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]736 <b>let</b> Defs = [EAX, ECX, EDX, FP0, FP1, FP2, FP3, FP4, FP5, FP6, ST0,
737 MM0, MM1, MM2, MM3, MM4, MM5, MM6, MM7,
738 XMM0, XMM1, XMM2, XMM3, XMM4, XMM5, XMM6, XMM7, EFLAGS] <b>in</b> {
Dan Gohman8e58bc52008-10-14 17:00:38 +0000[diff] [blame]739 <b>def</b> CALLpcrel32 : Ii32&lt;0xE8, RawFrm, (outs), (ins i32imm:$dst,variable_ops),
740 "call\t${dst:call}", []&gt;;
741 <b>def</b> CALL32r : I&lt;0xFF, MRM2r, (outs), (ins GR32:$dst, variable_ops),
742 "call\t{*}$dst", [(X86call GR32:$dst)]&gt;;
743 <b>def</b> CALL32m : I&lt;0xFF, MRM2m, (outs), (ins i32mem:$dst, variable_ops),
744 "call\t{*}$dst", []&gt;;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]745 }
746</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]747</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]748
749<p>File-scope "let" expressions are often useful when a couple of definitions
750need to be added to several records, and the records do not otherwise need to be
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]751opened, as in the case with the <tt>CALL*</tt> instructions above.</p>
752
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]753</div>
754
755<!-- *********************************************************************** -->
Evan Chengf68c8b62009-10-05 02:51:06 +0000[diff] [blame]756<div class="doc_section"><a name="codegen">Code Generator backend info</a></div>
757<!-- *********************************************************************** -->
758
759<p>Expressions used by code generator to describe instructions and isel
760patterns:</p>
761
762<div class="doc_text">
763
764<dt><tt>(implicit a)</tt></dt>
765 <dd>an implicitly defined physical register. This tells the dag instruction
766 selection emitter the input pattern's extra definitions matches implicit
767 physical register definitions.</dd>
768<dt><tt>(parallel (a), (b))</tt></dt>
769 <dd>a list of dags specifying parallel operations which map to the same
770 instruction.</dd>
771
772</div>
773
774<!-- *********************************************************************** -->
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]775<div class="doc_section"><a name="backends">TableGen backends</a></div>
776<!-- *********************************************************************** -->
777
778<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]779
780<p>TODO: How they work, how to write one. This section should not contain
781details about any particular backend, except maybe -print-enums as an example.
782This should highlight the APIs in <tt>TableGen/Record.h</tt>.</p>
783
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]784</div>
785
786<!-- *********************************************************************** -->
787
788<hr>
789<address>
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Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]794
795 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
796 <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
797 Last modified: $Date$
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