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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>
David Greenecde43742009-06-08 22:38:07 +0000[diff] [blame]374<dt><tt>[ X, Y, Z ]<type></tt></dt>
375 <dd>list value. <type> is the type of the list
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>
Evan Chengfb071382009-05-18 22:14:45 +0000[diff] [blame]401<dt><tt>(implicit a)</tt></dt>
402 <dd>an implicitly defined physical register. This tells the dag instruction
403 selection emitter the input pattern's extra definitions matches implicit
404 physical register definitions.</dd>
405<dt><tt>(parallel (a), (b))</tt></dt>
406 <dd>a list of dags specifying parallel operations which map to the same
407 instruction.</dd>
Bill Wendlingd5f12012008-02-12 07:09:05 +0000[diff] [blame]408<dt><tt>!strconcat(a, b)</tt></dt>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]409 <dd>A string value that is the result of concatenating the 'a' and 'b'
410 strings.</dd>
David Greene4fd89a02009-05-14 21:22:49 +0000[diff] [blame]411<dt><tt>!cast<type>(a)</tt></dt>
412 <dd>A symbol of type <em>type</em> obtained by looking up the string 'a' in
413the symbol table. If the type of 'a' does not match <em>type</em>, TableGen
David Greene1aa38cb2009-06-29 20:05:29 +0000[diff] [blame^]414aborts with an error. !cast<string> is a special case in that the argument must
415be an object defined by a 'def' construct.</dd>
David Greenef02acf02009-04-23 21:27:58 +0000[diff] [blame]416<dt><tt>!nameconcat&lt;type&gt;(a, b)</tt></dt>
David Greene4fd89a02009-05-14 21:22:49 +0000[diff] [blame]417 <dd>Shorthand for !cast<type>(!strconcat(a, b))</dd>
David Greene4f124db2009-05-14 21:54:42 +0000[diff] [blame]418<dt><tt>!subst(a, b, c)</tt></dt>
419 <dd>If 'a' and 'b' are of string type or are symbol references, substitute
420'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]421<dt><tt>!foreach(a, b, c)</tt></dt>
422 <dd>For each member 'b' of dag or list 'a' apply operator 'c.' 'b' is a
423dummy variable that should be declared as a member variable of an instantiated
424class. This operation is analogous to $(foreach) in GNU make.</dd>
David Greene04c89a12009-05-14 22:38:31 +0000[diff] [blame]425<dt><tt>!car(a)</tt></dt>
426 <dd>The first element of list 'a.'</dd>
427<dt><tt>!cdr(a)</tt></dt>
428 <dd>The 2nd-N elements of list 'a.'</dd>
429<dt><tt>!null(a)</tt></dt>
430 <dd>An integer {0,1} indicating whether list 'a' is empty.</dd>
David Greene70037ea2009-05-14 23:26:46 +0000[diff] [blame]431<dt><tt>!if(a,b,c)</tt></dt>
432 <dd>'b' if the result of integer operator 'a' is nonzero, 'c' otherwise.</dd>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]433</dl>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]434
435<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]436for different types. These rules allow you to assign a value like "<tt>7</tt>"
437to a "<tt>bits&lt;4&gt;</tt>" value, for example.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]438
439</div>
440
441<!-- ======================================================================= -->
442<div class="doc_subsection">
443 <a name="classesdefs">Classes and definitions</a>
444</div>
445
446<div class="doc_text">
447
448<p>As mentioned in the <a href="#concepts">intro</a>, classes and definitions
449(collectively known as 'records') in TableGen are the main high-level unit of
450information that TableGen collects. Records are defined with a <tt>def</tt> or
451<tt>class</tt> keyword, the record name, and an optional list of "<a
452href="#templateargs">template arguments</a>". If the record has superclasses,
453they are specified as a comma separated list that starts with a colon character
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]454("<tt>:</tt>"). If <a href="#valuedef">value definitions</a> or <a
455href="#recordlet">let expressions</a> are needed for the class, they are
456enclosed in curly braces ("<tt>{}</tt>"); otherwise, the record ends with a
457semicolon.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]458
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]459<p>Here is a simple TableGen file:</p>
460
461<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]462<pre>
463<b>class</b> C { <b>bit</b> V = 1; }
464<b>def</b> X : C;
465<b>def</b> Y : C {
466 <b>string</b> Greeting = "hello";
467}
468</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]469</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]470
471<p>This example defines two definitions, <tt>X</tt> and <tt>Y</tt>, both of
472which derive from the <tt>C</tt> class. Because of this, they both get the
473<tt>V</tt> bit value. The <tt>Y</tt> definition also gets the Greeting member
474as well.</p>
475
476<p>In general, classes are useful for collecting together the commonality
477between a group of records and isolating it in a single place. Also, classes
478permit the specification of default values for their subclasses, allowing the
479subclasses to override them as they wish.</p>
480
481</div>
482
483<!---------------------------------------------------------------------------->
484<div class="doc_subsubsection">
485 <a name="valuedef">Value definitions</a>
486</div>
487
488<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]489
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]490<p>Value definitions define named entries in records. A value must be defined
491before it can be referred to as the operand for another value definition or
492before the value is reset with a <a href="#recordlet">let expression</a>. A
493value is defined by specifying a <a href="#types">TableGen type</a> and a name.
494If an initial value is available, it may be specified after the type with an
495equal sign. Value definitions require terminating semicolons.</p>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]496
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]497</div>
498
499<!-- -------------------------------------------------------------------------->
500<div class="doc_subsubsection">
501 <a name="recordlet">'let' expressions</a>
502</div>
503
504<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]505
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]506<p>A record-level let expression is used to change the value of a value
507definition in a record. This is primarily useful when a superclass defines a
508value that a derived class or definition wants to override. Let expressions
509consist of the '<tt>let</tt>' keyword followed by a value name, an equal sign
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]510("<tt>=</tt>"), and a new value. For example, a new class could be added to the
511example above, redefining the <tt>V</tt> field for all of its subclasses:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]512
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]513<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]514<pre>
515<b>class</b> D : C { let V = 0; }
516<b>def</b> Z : D;
517</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]518</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]519
520<p>In this case, the <tt>Z</tt> definition will have a zero value for its "V"
521value, despite the fact that it derives (indirectly) from the <tt>C</tt> class,
522because the <tt>D</tt> class overrode its value.</p>
523
524</div>
525
526<!-- -------------------------------------------------------------------------->
527<div class="doc_subsubsection">
528 <a name="templateargs">Class template arguments</a>
529</div>
530
531<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]532
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]533<p>TableGen permits the definition of parameterized classes as well as normal
534concrete classes. Parameterized TableGen classes specify a list of variable
535bindings (which may optionally have defaults) that are bound when used. Here is
536a simple example:</p>
537
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]538<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]539<pre>
540<b>class</b> FPFormat&lt;<b>bits</b>&lt;3&gt; val&gt; {
541 <b>bits</b>&lt;3&gt; Value = val;
542}
543<b>def</b> NotFP : FPFormat&lt;0&gt;;
544<b>def</b> ZeroArgFP : FPFormat&lt;1&gt;;
545<b>def</b> OneArgFP : FPFormat&lt;2&gt;;
546<b>def</b> OneArgFPRW : FPFormat&lt;3&gt;;
547<b>def</b> TwoArgFP : FPFormat&lt;4&gt;;
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]548<b>def</b> CompareFP : FPFormat&lt;5&gt;;
549<b>def</b> CondMovFP : FPFormat&lt;6&gt;;
550<b>def</b> SpecialFP : FPFormat&lt;7&gt;;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]551</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]552</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]553
554<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]555a list of "enumeration values", each with a "<tt>Value</tt>" field set to the
556specified integer.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]557
558<p>The more esoteric forms of <a href="#values">TableGen expressions</a> are
559useful in conjunction with template arguments. As an example:</p>
560
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]561<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]562<pre>
563<b>class</b> ModRefVal&lt;<b>bits</b>&lt;2&gt; val&gt; {
564 <b>bits</b>&lt;2&gt; Value = val;
565}
566
567<b>def</b> None : ModRefVal&lt;0&gt;;
568<b>def</b> Mod : ModRefVal&lt;1&gt;;
569<b>def</b> Ref : ModRefVal&lt;2&gt;;
570<b>def</b> ModRef : ModRefVal&lt;3&gt;;
571
572<b>class</b> Value&lt;ModRefVal MR&gt; {
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]573 <i>// Decode some information into a more convenient format, while providing
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]574 // a nice interface to the user of the "Value" class.</i>
575 <b>bit</b> isMod = MR.Value{0};
576 <b>bit</b> isRef = MR.Value{1};
577
578 <i>// other stuff...</i>
579}
580
581<i>// Example uses</i>
582<b>def</b> bork : Value&lt;Mod&gt;;
583<b>def</b> zork : Value&lt;Ref&gt;;
584<b>def</b> hork : Value&lt;ModRef&gt;;
585</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]586</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]587
588<p>This is obviously a contrived example, but it shows how template arguments
589can be used to decouple the interface provided to the user of the class from the
590actual internal data representation expected by the class. In this case,
591running <tt>tblgen</tt> on the example prints the following definitions:</p>
592
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]593<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]594<pre>
595<b>def</b> bork { <i>// Value</i>
596 <b>bit</b> isMod = 1;
597 <b>bit</b> isRef = 0;
598}
599<b>def</b> hork { <i>// Value</i>
600 <b>bit</b> isMod = 1;
601 <b>bit</b> isRef = 1;
602}
603<b>def</b> zork { <i>// Value</i>
604 <b>bit</b> isMod = 0;
605 <b>bit</b> isRef = 1;
606}
607</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]608</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]609
610<p> This shows that TableGen was able to dig into the argument and extract a
611piece of information that was requested by the designer of the "Value" class.
612For more realistic examples, please see existing users of TableGen, such as the
613X86 backend.</p>
614
615</div>
616
617<!-- -------------------------------------------------------------------------->
618<div class="doc_subsubsection">
619 <a name="multiclass">Multiclass definitions and instances</a>
620</div>
621
622<div class="doc_text">
623
624<p>
625While classes with template arguments are a good way to factor commonality
626between two instances of a definition, multiclasses allow a convenient notation
627for defining multiple definitions at once (instances of implicitly constructed
628classes). For example, consider an 3-address instruction set whose instructions
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]629come in two forms: "<tt>reg = reg op reg</tt>" and "<tt>reg = reg op imm</tt>"
630(e.g. SPARC). In this case, you'd like to specify in one place that this
631commonality exists, then in a separate place indicate what all the ops are.
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]632</p>
633
634<p>
635Here is an example TableGen fragment that shows this idea:
636</p>
637
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]638<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]639<pre>
640<b>def</b> ops;
641<b>def</b> GPR;
642<b>def</b> Imm;
643<b>class</b> inst&lt;<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist&gt;;
644
645<b>multiclass</b> ri_inst&lt;<b>int</b> opc, <b>string</b> asmstr&gt; {
646 def _rr : inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
647 (ops GPR:$dst, GPR:$src1, GPR:$src2)&gt;;
648 def _ri : inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
649 (ops GPR:$dst, GPR:$src1, Imm:$src2)&gt;;
650}
651
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]652<i>// Instantiations of the ri_inst multiclass.</i>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]653<b>defm</b> ADD : ri_inst&lt;0b111, "add"&gt;;
654<b>defm</b> SUB : ri_inst&lt;0b101, "sub"&gt;;
655<b>defm</b> MUL : ri_inst&lt;0b100, "mul"&gt;;
656...
657</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]658</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]659
660<p>The name of the resultant definitions has the multidef fragment names
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]661 appended to them, so this defines <tt>ADD_rr</tt>, <tt>ADD_ri</tt>,
David Greene080d2152009-04-22 22:17:51 +0000[diff] [blame]662 <tt>SUB_rr</tt>, etc. A defm may inherit from multiple multiclasses,
663 instantiating definitions from each multiclass. Using a multiclass
664 this way is exactly equivalent to instantiating the classes multiple
665 times yourself, e.g. by writing:</p>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]666
667<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]668<pre>
669<b>def</b> ops;
670<b>def</b> GPR;
671<b>def</b> Imm;
672<b>class</b> inst&lt;<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist&gt;;
673
674<b>class</b> rrinst&lt;<b>int</b> opc, <b>string</b> asmstr&gt;
675 : inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
676 (ops GPR:$dst, GPR:$src1, GPR:$src2)&gt;;
677
678<b>class</b> riinst&lt;<b>int</b> opc, <b>string</b> asmstr&gt;
679 : inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
680 (ops GPR:$dst, GPR:$src1, Imm:$src2)&gt;;
681
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]682<i>// Instantiations of the ri_inst multiclass.</i>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]683<b>def</b> ADD_rr : rrinst&lt;0b111, "add"&gt;;
684<b>def</b> ADD_ri : riinst&lt;0b111, "add"&gt;;
685<b>def</b> SUB_rr : rrinst&lt;0b101, "sub"&gt;;
686<b>def</b> SUB_ri : riinst&lt;0b101, "sub"&gt;;
687<b>def</b> MUL_rr : rrinst&lt;0b100, "mul"&gt;;
688<b>def</b> MUL_ri : riinst&lt;0b100, "mul"&gt;;
689...
690</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]691</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]692
693</div>
694
695<!-- ======================================================================= -->
696<div class="doc_subsection">
697 <a name="filescope">File scope entities</a>
698</div>
699
700<!-- -------------------------------------------------------------------------->
701<div class="doc_subsubsection">
702 <a name="include">File inclusion</a>
703</div>
704
705<div class="doc_text">
706<p>TableGen supports the '<tt>include</tt>' token, which textually substitutes
707the specified file in place of the include directive. The filename should be
708specified as a double quoted string immediately after the '<tt>include</tt>'
709keyword. Example:</p>
710
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]711<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]712<pre>
713<b>include</b> "foo.td"
714</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]715</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]716
717</div>
718
719<!-- -------------------------------------------------------------------------->
720<div class="doc_subsubsection">
721 <a name="globallet">'let' expressions</a>
722</div>
723
724<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]725
726<p>"Let" expressions at file scope are similar to <a href="#recordlet">"let"
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]727expressions within a record</a>, except they can specify a value binding for
728multiple records at a time, and may be useful in certain other cases.
729File-scope let expressions are really just another way that TableGen allows the
730end-user to factor out commonality from the records.</p>
731
732<p>File-scope "let" expressions take a comma-separated list of bindings to
Matthijs Kooijman16bb03a2008-10-20 08:45:34 +0000[diff] [blame]733apply, and one or more records to bind the values in. Here are some
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]734examples:</p>
735
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]736<div class="doc_code">
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]737<pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]738<b>let</b> isTerminator = 1, isReturn = 1, isBarrier = 1, hasCtrlDep = 1 <b>in</b>
739 <b>def</b> RET : I&lt;0xC3, RawFrm, (outs), (ins), "ret", [(X86retflag 0)]&gt;;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]740
741<b>let</b> isCall = 1 <b>in</b>
742 <i>// All calls clobber the non-callee saved registers...</i>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]743 <b>let</b> Defs = [EAX, ECX, EDX, FP0, FP1, FP2, FP3, FP4, FP5, FP6, ST0,
744 MM0, MM1, MM2, MM3, MM4, MM5, MM6, MM7,
745 XMM0, XMM1, XMM2, XMM3, XMM4, XMM5, XMM6, XMM7, EFLAGS] <b>in</b> {
Dan Gohman8e58bc52008-10-14 17:00:38 +0000[diff] [blame]746 <b>def</b> CALLpcrel32 : Ii32&lt;0xE8, RawFrm, (outs), (ins i32imm:$dst,variable_ops),
747 "call\t${dst:call}", []&gt;;
748 <b>def</b> CALL32r : I&lt;0xFF, MRM2r, (outs), (ins GR32:$dst, variable_ops),
749 "call\t{*}$dst", [(X86call GR32:$dst)]&gt;;
750 <b>def</b> CALL32m : I&lt;0xFF, MRM2m, (outs), (ins i32mem:$dst, variable_ops),
751 "call\t{*}$dst", []&gt;;
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]752 }
753</pre>
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]754</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]755
756<p>File-scope "let" expressions are often useful when a couple of definitions
757need 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]758opened, as in the case with the <tt>CALL*</tt> instructions above.</p>
759
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]760</div>
761
762<!-- *********************************************************************** -->
763<div class="doc_section"><a name="backends">TableGen backends</a></div>
764<!-- *********************************************************************** -->
765
766<div class="doc_text">
Bill Wendling707b6ab2008-02-12 07:06:19 +0000[diff] [blame]767
768<p>TODO: How they work, how to write one. This section should not contain
769details about any particular backend, except maybe -print-enums as an example.
770This should highlight the APIs in <tt>TableGen/Record.h</tt>.</p>
771
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]772</div>
773
774<!-- *********************************************************************** -->
775
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783 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
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