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				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
				59	domain-specific information. Because there may be a large number of these
				60	records, it is specifically designed to allow writing flexible descriptions and
				61	for common features of these records to be factored out. This reduces the
				62	amount of duplication in the description, reduces the chance of error, and
				63	makes it easier to structure domain specific information.</p>
				64
				65	<p>The core part of TableGen <a href="#syntax">parses a file</a>, instantiates
				66	the declarations, and hands the result off to a domain-specific "<a
				67	href="#backends">TableGen backend</a>" for processing. The current major user
				68	of 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 Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	71	find 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 Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	73	distribution, 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
				83	of 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 Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	86	superclasses. The list of values is the main data that TableGen builds for each
				87	record; it is this that holds the domain specific information for the
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	88	application. The interpretation of this data is left to a specific <a
				89	href="#backends">TableGen backend</a>, but the structure and format rules are
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	90	taken care of and are fixed by TableGen.</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	91
				92	<p><b>TableGen definitions</b> are the concrete form of 'records'. These
				93	generally 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
				97	describe other records. These 'classes' allow the end-user to build
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	98	abstractions for either the domain they are targeting (such as "Register",
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	99	"RegisterClass", and "Instruction" in the LLVM code generator) or for the
				100	implementor to help factor out common properties of records (such as "FPInst",
				101	which is used to represent floating point instructions in the X86 backend).
				102	TableGen keeps track of all of the classes that are used to build up a
				103	definition, so the backend can find all definitions of a particular class, such
				104	as "Instruction".</p>
				105
				106	<p><b>TableGen multiclasses</b> are groups of abstract records that are
David Greene	60b5acc	2009-04-22 16:42:54 +0000	[diff] [blame]	107	instantiated all at once. Each instantiation can result in multiple
				108	TableGen definitions. If a multiclass inherits from another multiclass,
				109	the definitions in the sub-multiclass become part of the current
				110	multiclass, as if they were declared in the current multiclass.</p>
Dan Gohman	f17a25c	2007-07-18 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
				120	all of the classes, then all of the definitions. This is a good way to see what
				121	the various definitions expand to fully. Running this on the <tt>X86.td</tt>
				122	file prints this (at the time of this writing):</p>
				123
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	124	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	125	<pre>
				126	...
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	127	<b>def</b> ADD32rr { <i>// Instruction X86Inst I</i>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	128	<b>string</b> Namespace = "X86";
Bill Wendling	707b6ab	2008-02-12 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, $src2}";
				132	<b>list</b><dag> Pattern = [(set GR32:$dst, (add GR32:$src1, GR32:$src2))];
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	133	<b>list</b><Register> Uses = [];
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	134	<b>list</b><Register> Defs = [EFLAGS];
				135	<b>list</b><Predicate> Predicates = [];
				136	<b>int</b> CodeSize = 3;
				137	<b>int</b> AddedComplexity = 0;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	138	<b>bit</b> isReturn = 0;
				139	<b>bit</b> isBranch = 0;
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	140	<b>bit</b> isIndirectBranch = 0;
				141	<b>bit</b> isBarrier = 0;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	142	<b>bit</b> isCall = 0;
Dan Gohman	5574cc7	2008-12-03 18:15:48 +0000	[diff] [blame]	143	<b>bit</b> canFoldAsLoad = 0;
Bill Wendling	707b6ab	2008-02-12 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 Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	147	<b>bit</b> isTwoAddress = 1;
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	148	<b>bit</b> isConvertibleToThreeAddress = 1;
				149	<b>bit</b> isCommutable = 1;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	150	<b>bit</b> isTerminator = 0;
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	151	<b>bit</b> isReMaterializable = 0;
				152	<b>bit</b> isPredicable = 0;
				153	<b>bit</b> hasDelaySlot = 0;
Dan Gohman	30afe01	2009-10-29 18:10:34 +0000	[diff] [blame]	154	<b>bit</b> usesCustomInserter = 0;
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	155	<b>bit</b> hasCtrlDep = 0;
				156	<b>bit</b> isNotDuplicable = 0;
				157	<b>bit</b> hasSideEffects = 0;
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	158	<b>bit</b> neverHasSideEffects = 0;
				159	InstrItinClass Itinerary = NoItinerary;
				160	<b>string</b> Constraints = "";
				161	<b>string</b> DisableEncoding = "";
				162	<b>bits</b><8> Opcode = { 0, 0, 0, 0, 0, 0, 0, 1 };
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	163	Format Form = MRMDestReg;
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	164	<b>bits</b><6> FormBits = { 0, 0, 0, 0, 1, 1 };
				165	ImmType ImmT = NoImm;
				166	<b>bits</b><3> ImmTypeBits = { 0, 0, 0 };
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	167	<b>bit</b> hasOpSizePrefix = 0;
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	168	<b>bit</b> hasAdSizePrefix = 0;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	169	<b>bits</b><4> Prefix = { 0, 0, 0, 0 };
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	170	<b>bit</b> hasREX_WPrefix = 0;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	171	FPFormat FPForm = ?;
				172	<b>bits</b><3> FPFormBits = { 0, 0, 0 };
				173	}
				174	...
				175	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	176	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	177
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	178	<p>This definition corresponds to a 32-bit register-register add instruction in
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	179	the X86. The string after the '<tt>def</tt>' string indicates the name of the
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	180	record—"<tt>ADD32rr</tt>" in this case—and the comment at the end of
				181	the line indicates the superclasses of the definition. The body of the record
				182	contains all of the data that TableGen assembled for the record, indicating that
				183	the instruction is part of the "X86" namespace, the pattern indicating how the
				184	the instruction should be emitted into the assembly file, that it is a
				185	two-address instruction, has a particular encoding, etc. The contents and
				186	semantics of the information in the record is specific to the needs of the X86
				187	backend, and is only shown as an example.</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	188
				189	<p>As you can see, a lot of information is needed for every instruction
				190	supported by the code generator, and specifying it all manually would be
Dan Gohman	57bda1f	2010-02-26 02:15:17 +0000	[diff] [blame]	191	unmaintainable, prone to bugs, and tiring to do in the first place. Because we
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	192	are using TableGen, all of the information was derived from the following
				193	definition:</p>
				194
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	195	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	196	<pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	197	let Defs = [EFLAGS],
				198	isCommutable = 1, <i>// X = ADD Y,Z --> X = ADD Z,Y</i>
				199	isConvertibleToThreeAddress = 1 <b>in</b> <i>// Can transform into LEA.</i>
				200	def ADD32rr : I<0x01, MRMDestReg, (outs GR32:$dst),
				201	(ins GR32:$src1, GR32:$src2),
				202	"add{l}\t{$src2, $dst\|$dst, $src2}",
				203	[(set GR32:$dst, (add GR32:$src1, GR32:$src2))]>;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	204	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	205	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	206
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	207	<p>This definition makes use of the custom class <tt>I</tt> (extended from the
				208	custom class <tt>X86Inst</tt>), which is defined in the X86-specific TableGen
				209	file, to factor out the common features that instructions of its class share. A
				210	key feature of TableGen is that it allows the end-user to define the
				211	abstractions they prefer to use when describing their information.</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	212
				213	</div>
				214
				215	<!-- ======================================================================= -->
				216	<div class="doc_subsection"><a name="running">Running TableGen</a></div>
				217
				218	<div class="doc_text">
				219
				220	<p>TableGen runs just like any other LLVM tool. The first (optional) argument
				221	specifies the file to read. If a filename is not specified, <tt>tblgen</tt>
				222	reads from standard input.</p>
				223
				224	<p>To be useful, one of the <a href="#backends">TableGen backends</a> must be
				225	used. These backends are selectable on the command line (type '<tt>tblgen
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	226	-help</tt>' for a list). For example, to get a list of all of the definitions
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	227	that subclass a particular type (which can be useful for building up an enum
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	228	list of these records), use the <tt>-print-enums</tt> option:</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	229
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	230	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	231	<pre>
				232	$ tblgen X86.td -print-enums -class=Register
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	233	AH, AL, AX, BH, BL, BP, BPL, BX, CH, CL, CX, DH, DI, DIL, DL, DX, EAX, EBP, EBX,
				234	ECX, EDI, EDX, EFLAGS, EIP, ESI, ESP, FP0, FP1, FP2, FP3, FP4, FP5, FP6, IP,
				235	MM0, MM1, MM2, MM3, MM4, MM5, MM6, MM7, R10, R10B, R10D, R10W, R11, R11B, R11D,
				236	R11W, R12, R12B, R12D, R12W, R13, R13B, R13D, R13W, R14, R14B, R14D, R14W, R15,
				237	R15B, R15D, R15W, R8, R8B, R8D, R8W, R9, R9B, R9D, R9W, RAX, RBP, RBX, RCX, RDI,
				238	RDX, RIP, RSI, RSP, SI, SIL, SP, SPL, ST0, ST1, ST2, ST3, ST4, ST5, ST6, ST7,
				239	XMM0, XMM1, XMM10, XMM11, XMM12, XMM13, XMM14, XMM15, XMM2, XMM3, XMM4, XMM5,
				240	XMM6, XMM7, XMM8, XMM9,
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	241
				242	$ tblgen X86.td -print-enums -class=Instruction
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	243	ABS_F, ABS_Fp32, ABS_Fp64, ABS_Fp80, ADC32mi, ADC32mi8, ADC32mr, ADC32ri,
				244	ADC32ri8, ADC32rm, ADC32rr, ADC64mi32, ADC64mi8, ADC64mr, ADC64ri32, ADC64ri8,
				245	ADC64rm, ADC64rr, ADD16mi, ADD16mi8, ADD16mr, ADD16ri, ADD16ri8, ADD16rm,
				246	ADD16rr, ADD32mi, ADD32mi8, ADD32mr, ADD32ri, ADD32ri8, ADD32rm, ADD32rr,
				247	ADD64mi32, ADD64mi8, ADD64mr, ADD64ri32, ...
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	248	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	249	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	250
				251	<p>The default backend prints out all of the records, as described <a
				252	href="#example">above</a>.</p>
				253
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	254	<p>If you plan to use TableGen, you will most likely have to <a
				255	href="#backends">write a backend</a> that extracts the information specific to
				256	what you need and formats it in the appropriate way.</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	257
				258	</div>
				259
				260
				261	<!-- *********************************************************************** -->
				262	<div class="doc_section"><a name="syntax">TableGen syntax</a></div>
				263	<!-- *********************************************************************** -->
				264
				265	<div class="doc_text">
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	266
				267	<p>TableGen doesn't care about the meaning of data (that is up to the backend to
				268	define), but it does care about syntax, and it enforces a simple type system.
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	269	This section describes the syntax and the constructs allowed in a TableGen file.
				270	</p>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	271
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	272	</div>
				273
				274	<!-- ======================================================================= -->
				275	<div class="doc_subsection"><a name="primitives">TableGen primitives</a></div>
				276
				277	<!-- -------------------------------------------------------------------------->
				278	<div class="doc_subsubsection"><a name="comments">TableGen comments</a></div>
				279
				280	<div class="doc_text">
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	281
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	282	<p>TableGen supports BCPL style "<tt>//</tt>" comments, which run to the end of
				283	the line, and it also supports <b>nestable</b> "<tt>/* */</tt>" comments.</p>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	284
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	285	</div>
				286
				287	<!-- -------------------------------------------------------------------------->
				288	<div class="doc_subsubsection">
				289	<a name="types">The TableGen type system</a>
				290	</div>
				291
				292	<div class="doc_text">
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	293
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	294	<p>TableGen files are strongly typed, in a simple (but complete) type-system.
				295	These types are used to perform automatic conversions, check for errors, and to
				296	help interface designers constrain the input that they allow. Every <a
				297	href="#valuedef">value definition</a> is required to have an associated type.
				298	</p>
				299
				300	<p>TableGen supports a mixture of very low-level types (such as <tt>bit</tt>)
				301	and very high-level types (such as <tt>dag</tt>). This flexibility is what
				302	allows it to describe a wide range of information conveniently and compactly.
				303	The TableGen types are:</p>
				304
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	305	<dl>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	306	<dt><tt><b>bit</b></tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	307	<dd>A 'bit' is a boolean value that can hold either 0 or 1.</dd>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	308
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	309	<dt><tt><b>int</b></tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	310	<dd>The 'int' type represents a simple 32-bit integer value, such as 5.</dd>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	311
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	312	<dt><tt><b>string</b></tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	313	<dd>The 'string' type represents an ordered sequence of characters of
				314	arbitrary length.</dd>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	315
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	316	<dt><tt><b>bits</b><n></tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	317	<dd>A 'bits' type is an arbitrary, but fixed, size integer that is broken up
				318	into individual bits. This type is useful because it can handle some bits
				319	being defined while others are undefined.</dd>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	320
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	321	<dt><tt><b>list</b><ty></tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	322	<dd>This type represents a list whose elements are some other type. The
				323	contained type is arbitrary: it can even be another list type.</dd>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	324
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	325	<dt>Class type</dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	326	<dd>Specifying a class name in a type context means that the defined value
				327	must be a subclass of the specified class. This is useful in conjunction with
				328	the <b><tt>list</tt></b> type, for example, to constrain the elements of the
				329	list to a common base class (e.g., a <tt><b>list</b><Register></tt> can
				330	only contain definitions derived from the "<tt>Register</tt>" class).</dd>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	331
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	332	<dt><tt><b>dag</b></tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	333	<dd>This type represents a nestable directed graph of elements.</dd>
				334
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	335	<dt><tt><b>code</b></tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	336	<dd>This represents a big hunk of text. NOTE: I don't remember why this is
				337	distinct from string!</dd>
				338	</dl>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	339
				340	<p>To date, these types have been sufficient for describing things that
				341	TableGen has been used for, but it is straight-forward to extend this list if
				342	needed.</p>
				343
				344	</div>
				345
				346	<!-- -------------------------------------------------------------------------->
				347	<div class="doc_subsubsection">
				348	<a name="values">TableGen values and expressions</a>
				349	</div>
				350
				351	<div class="doc_text">
				352
				353	<p>TableGen allows for a pretty reasonable number of different expression forms
				354	when building up values. These forms allow the TableGen file to be written in a
				355	natural syntax and flavor for the application. The current expression forms
				356	supported include:</p>
				357
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	358	<dl>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	359	<dt><tt>?</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	360	<dd>uninitialized field</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	361	<dt><tt>0b1001011</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	362	<dd>binary integer value</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	363	<dt><tt>07654321</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	364	<dd>octal integer value (indicated by a leading 0)</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	365	<dt><tt>7</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	366	<dd>decimal integer value</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	367	<dt><tt>0x7F</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	368	<dd>hexadecimal integer value</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	369	<dt><tt>"foo"</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	370	<dd>string value</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	371	<dt><tt>[{ ... }]</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	372	<dd>code fragment</dd>
Benjamin Kramer	7b2136d	2009-08-05 15:42:44 +0000	[diff] [blame]	373	<dt><tt>[ X, Y, Z ]<type></tt></dt>
				374	<dd>list value. <type> is the type of the list
David Greene	cde4374	2009-06-08 22:38:07 +0000	[diff] [blame]	375	element and is usually optional. In rare cases,
				376	TableGen is unable to deduce the element type in
				377	which case the user must specify it explicitly.</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	378	<dt><tt>{ a, b, c }</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	379	<dd>initializer for a "bits<3>" value</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	380	<dt><tt>value</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	381	<dd>value reference</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	382	<dt><tt>value{17}</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	383	<dd>access to one bit of a value</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	384	<dt><tt>value{15-17}</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	385	<dd>access to multiple bits of a value</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	386	<dt><tt>DEF</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	387	<dd>reference to a record definition</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	388	<dt><tt>CLASS<val list></tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	389	<dd>reference to a new anonymous definition of CLASS with the specified
				390	template arguments.</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	391	<dt><tt>X.Y</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	392	<dd>reference to the subfield of a value</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	393	<dt><tt>list[4-7,17,2-3]</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	394	<dd>A slice of the 'list' list, including elements 4,5,6,7,17,2, and 3 from
				395	it. Elements may be included multiple times.</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	396	<dt><tt>(DEF a, b)</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	397	<dd>a dag value. The first element is required to be a record definition, the
				398	remaining elements in the list may be arbitrary other values, including nested
				399	`<tt>dag</tt>' values.</dd>
Bill Wendling	d5f1201	2008-02-12 07:09:05 +0000	[diff] [blame]	400	<dt><tt>!strconcat(a, b)</tt></dt>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	401	<dd>A string value that is the result of concatenating the 'a' and 'b'
				402	strings.</dd>
Benjamin Kramer	7b2136d	2009-08-05 15:42:44 +0000	[diff] [blame]	403	<dt><tt>!cast<type>(a)</tt></dt>
David Greene	4fd89a0	2009-05-14 21:22:49 +0000	[diff] [blame]	404	<dd>A symbol of type <em>type</em> obtained by looking up the string 'a' in
				405	the symbol table. If the type of 'a' does not match <em>type</em>, TableGen
Benjamin Kramer	7b2136d	2009-08-05 15:42:44 +0000	[diff] [blame]	406	aborts with an error. !cast<string> is a special case in that the argument must
David Greene	1aa38cb	2009-06-29 20:05:29 +0000	[diff] [blame]	407	be an object defined by a 'def' construct.</dd>
David Greene	f02acf0	2009-04-23 21:27:58 +0000	[diff] [blame]	408	<dt><tt>!nameconcat<type>(a, b)</tt></dt>
Benjamin Kramer	7b2136d	2009-08-05 15:42:44 +0000	[diff] [blame]	409	<dd>Shorthand for !cast<type>(!strconcat(a, b))</dd>
David Greene	4f124db	2009-05-14 21:54:42 +0000	[diff] [blame]	410	<dt><tt>!subst(a, b, c)</tt></dt>
				411	<dd>If 'a' and 'b' are of string type or are symbol references, substitute
				412	'b' for 'a' in 'c.' This operation is analogous to $(subst) in GNU make.</dd>
David Greene	2c38321	2009-05-14 22:23:47 +0000	[diff] [blame]	413	<dt><tt>!foreach(a, b, c)</tt></dt>
				414	<dd>For each member 'b' of dag or list 'a' apply operator 'c.' 'b' is a
				415	dummy variable that should be declared as a member variable of an instantiated
				416	class. This operation is analogous to $(foreach) in GNU make.</dd>
David Greene	04c89a1	2009-05-14 22:38:31 +0000	[diff] [blame]	417	<dt><tt>!car(a)</tt></dt>
				418	<dd>The first element of list 'a.'</dd>
				419	<dt><tt>!cdr(a)</tt></dt>
				420	<dd>The 2nd-N elements of list 'a.'</dd>
				421	<dt><tt>!null(a)</tt></dt>
				422	<dd>An integer {0,1} indicating whether list 'a' is empty.</dd>
David Greene	70037ea	2009-05-14 23:26:46 +0000	[diff] [blame]	423	<dt><tt>!if(a,b,c)</tt></dt>
				424	<dd>'b' if the result of integer operator 'a' is nonzero, 'c' otherwise.</dd>
David Greene	6366630	2010-01-05 19:11:42 +0000	[diff] [blame]	425	<dt><tt>!eq(a,b)</tt></dt>
				426	<dd>Integer one if string a is equal to string b, zero otherwise. This
				427	only operates on string objects. Use !cast<string> to compare other
				428	types of objects.</dd>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	429	</dl>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	430
				431	<p>Note that all of the values have rules specifying how they convert to values
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	432	for different types. These rules allow you to assign a value like "<tt>7</tt>"
				433	to a "<tt>bits<4></tt>" value, for example.</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	434
				435	</div>
				436
				437	<!-- ======================================================================= -->
				438	<div class="doc_subsection">
				439	<a name="classesdefs">Classes and definitions</a>
				440	</div>
				441
				442	<div class="doc_text">
				443
				444	<p>As mentioned in the <a href="#concepts">intro</a>, classes and definitions
				445	(collectively known as 'records') in TableGen are the main high-level unit of
				446	information that TableGen collects. Records are defined with a <tt>def</tt> or
				447	<tt>class</tt> keyword, the record name, and an optional list of "<a
				448	href="#templateargs">template arguments</a>". If the record has superclasses,
				449	they are specified as a comma separated list that starts with a colon character
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	450	("<tt>:</tt>"). If <a href="#valuedef">value definitions</a> or <a
				451	href="#recordlet">let expressions</a> are needed for the class, they are
				452	enclosed in curly braces ("<tt>{}</tt>"); otherwise, the record ends with a
				453	semicolon.</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	454
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	455	<p>Here is a simple TableGen file:</p>
				456
				457	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	458	<pre>
				459	<b>class</b> C { <b>bit</b> V = 1; }
				460	<b>def</b> X : C;
				461	<b>def</b> Y : C {
				462	<b>string</b> Greeting = "hello";
				463	}
				464	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	465	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	466
				467	<p>This example defines two definitions, <tt>X</tt> and <tt>Y</tt>, both of
				468	which derive from the <tt>C</tt> class. Because of this, they both get the
				469	<tt>V</tt> bit value. The <tt>Y</tt> definition also gets the Greeting member
				470	as well.</p>
				471
				472	<p>In general, classes are useful for collecting together the commonality
				473	between a group of records and isolating it in a single place. Also, classes
				474	permit the specification of default values for their subclasses, allowing the
				475	subclasses to override them as they wish.</p>
				476
				477	</div>
				478
				479	<!---------------------------------------------------------------------------->
				480	<div class="doc_subsubsection">
				481	<a name="valuedef">Value definitions</a>
				482	</div>
				483
				484	<div class="doc_text">
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	485
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	486	<p>Value definitions define named entries in records. A value must be defined
				487	before it can be referred to as the operand for another value definition or
				488	before the value is reset with a <a href="#recordlet">let expression</a>. A
				489	value is defined by specifying a <a href="#types">TableGen type</a> and a name.
				490	If an initial value is available, it may be specified after the type with an
				491	equal sign. Value definitions require terminating semicolons.</p>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	492
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	493	</div>
				494
				495	<!-- -------------------------------------------------------------------------->
				496	<div class="doc_subsubsection">
				497	<a name="recordlet">'let' expressions</a>
				498	</div>
				499
				500	<div class="doc_text">
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	501
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	502	<p>A record-level let expression is used to change the value of a value
				503	definition in a record. This is primarily useful when a superclass defines a
				504	value that a derived class or definition wants to override. Let expressions
				505	consist of the '<tt>let</tt>' keyword followed by a value name, an equal sign
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	506	("<tt>=</tt>"), and a new value. For example, a new class could be added to the
				507	example above, redefining the <tt>V</tt> field for all of its subclasses:</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	508
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	509	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	510	<pre>
				511	<b>class</b> D : C { let V = 0; }
				512	<b>def</b> Z : D;
				513	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	514	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	515
				516	<p>In this case, the <tt>Z</tt> definition will have a zero value for its "V"
				517	value, despite the fact that it derives (indirectly) from the <tt>C</tt> class,
				518	because the <tt>D</tt> class overrode its value.</p>
				519
				520	</div>
				521
				522	<!-- -------------------------------------------------------------------------->
				523	<div class="doc_subsubsection">
				524	<a name="templateargs">Class template arguments</a>
				525	</div>
				526
				527	<div class="doc_text">
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	528
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	529	<p>TableGen permits the definition of parameterized classes as well as normal
				530	concrete classes. Parameterized TableGen classes specify a list of variable
				531	bindings (which may optionally have defaults) that are bound when used. Here is
				532	a simple example:</p>
				533
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	534	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	535	<pre>
				536	<b>class</b> FPFormat<<b>bits</b><3> val> {
				537	<b>bits</b><3> Value = val;
				538	}
				539	<b>def</b> NotFP : FPFormat<0>;
				540	<b>def</b> ZeroArgFP : FPFormat<1>;
				541	<b>def</b> OneArgFP : FPFormat<2>;
				542	<b>def</b> OneArgFPRW : FPFormat<3>;
				543	<b>def</b> TwoArgFP : FPFormat<4>;
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	544	<b>def</b> CompareFP : FPFormat<5>;
				545	<b>def</b> CondMovFP : FPFormat<6>;
				546	<b>def</b> SpecialFP : FPFormat<7>;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	547	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	548	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	549
				550	<p>In this case, template arguments are used as a space efficient way to specify
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	551	a list of "enumeration values", each with a "<tt>Value</tt>" field set to the
				552	specified integer.</p>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	553
				554	<p>The more esoteric forms of <a href="#values">TableGen expressions</a> are
				555	useful in conjunction with template arguments. As an example:</p>
				556
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	557	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	558	<pre>
				559	<b>class</b> ModRefVal<<b>bits</b><2> val> {
				560	<b>bits</b><2> Value = val;
				561	}
				562
				563	<b>def</b> None : ModRefVal<0>;
				564	<b>def</b> Mod : ModRefVal<1>;
				565	<b>def</b> Ref : ModRefVal<2>;
				566	<b>def</b> ModRef : ModRefVal<3>;
				567
				568	<b>class</b> Value<ModRefVal MR> {
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	569	<i>// Decode some information into a more convenient format, while providing
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	570	// a nice interface to the user of the "Value" class.</i>
				571	<b>bit</b> isMod = MR.Value{0};
				572	<b>bit</b> isRef = MR.Value{1};
				573
				574	<i>// other stuff...</i>
				575	}
				576
				577	<i>// Example uses</i>
				578	<b>def</b> bork : Value<Mod>;
				579	<b>def</b> zork : Value<Ref>;
				580	<b>def</b> hork : Value<ModRef>;
				581	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	582	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	583
				584	<p>This is obviously a contrived example, but it shows how template arguments
				585	can be used to decouple the interface provided to the user of the class from the
				586	actual internal data representation expected by the class. In this case,
				587	running <tt>tblgen</tt> on the example prints the following definitions:</p>
				588
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	589	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	590	<pre>
				591	<b>def</b> bork { <i>// Value</i>
				592	<b>bit</b> isMod = 1;
				593	<b>bit</b> isRef = 0;
				594	}
				595	<b>def</b> hork { <i>// Value</i>
				596	<b>bit</b> isMod = 1;
				597	<b>bit</b> isRef = 1;
				598	}
				599	<b>def</b> zork { <i>// Value</i>
				600	<b>bit</b> isMod = 0;
				601	<b>bit</b> isRef = 1;
				602	}
				603	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	604	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	605
				606	<p> This shows that TableGen was able to dig into the argument and extract a
				607	piece of information that was requested by the designer of the "Value" class.
				608	For more realistic examples, please see existing users of TableGen, such as the
				609	X86 backend.</p>
				610
				611	</div>
				612
				613	<!-- -------------------------------------------------------------------------->
				614	<div class="doc_subsubsection">
				615	<a name="multiclass">Multiclass definitions and instances</a>
				616	</div>
				617
				618	<div class="doc_text">
				619
				620	<p>
				621	While classes with template arguments are a good way to factor commonality
				622	between two instances of a definition, multiclasses allow a convenient notation
				623	for defining multiple definitions at once (instances of implicitly constructed
				624	classes). For example, consider an 3-address instruction set whose instructions
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	625	come in two forms: "<tt>reg = reg op reg</tt>" and "<tt>reg = reg op imm</tt>"
				626	(e.g. SPARC). In this case, you'd like to specify in one place that this
				627	commonality exists, then in a separate place indicate what all the ops are.
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	628	</p>
				629
				630	<p>
				631	Here is an example TableGen fragment that shows this idea:
				632	</p>
				633
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	634	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	635	<pre>
				636	<b>def</b> ops;
				637	<b>def</b> GPR;
				638	<b>def</b> Imm;
				639	<b>class</b> inst<<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist>;
				640
				641	<b>multiclass</b> ri_inst<<b>int</b> opc, <b>string</b> asmstr> {
				642	def _rr : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"),
				643	(ops GPR:$dst, GPR:$src1, GPR:$src2)>;
				644	def _ri : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"),
				645	(ops GPR:$dst, GPR:$src1, Imm:$src2)>;
				646	}
				647
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	648	<i>// Instantiations of the ri_inst multiclass.</i>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	649	<b>defm</b> ADD : ri_inst<0b111, "add">;
				650	<b>defm</b> SUB : ri_inst<0b101, "sub">;
				651	<b>defm</b> MUL : ri_inst<0b100, "mul">;
				652	...
				653	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	654	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	655
				656	<p>The name of the resultant definitions has the multidef fragment names
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	657	appended to them, so this defines <tt>ADD_rr</tt>, <tt>ADD_ri</tt>,
David Greene	080d215	2009-04-22 22:17:51 +0000	[diff] [blame]	658	<tt>SUB_rr</tt>, etc. A defm may inherit from multiple multiclasses,
				659	instantiating definitions from each multiclass. Using a multiclass
				660	this way is exactly equivalent to instantiating the classes multiple
				661	times yourself, e.g. by writing:</p>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	662
				663	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	664	<pre>
				665	<b>def</b> ops;
				666	<b>def</b> GPR;
				667	<b>def</b> Imm;
				668	<b>class</b> inst<<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist>;
				669
				670	<b>class</b> rrinst<<b>int</b> opc, <b>string</b> asmstr>
				671	: inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"),
				672	(ops GPR:$dst, GPR:$src1, GPR:$src2)>;
				673
				674	<b>class</b> riinst<<b>int</b> opc, <b>string</b> asmstr>
				675	: inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"),
				676	(ops GPR:$dst, GPR:$src1, Imm:$src2)>;
				677
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	678	<i>// Instantiations of the ri_inst multiclass.</i>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	679	<b>def</b> ADD_rr : rrinst<0b111, "add">;
				680	<b>def</b> ADD_ri : riinst<0b111, "add">;
				681	<b>def</b> SUB_rr : rrinst<0b101, "sub">;
				682	<b>def</b> SUB_ri : riinst<0b101, "sub">;
				683	<b>def</b> MUL_rr : rrinst<0b100, "mul">;
				684	<b>def</b> MUL_ri : riinst<0b100, "mul">;
				685	...
				686	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	687	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	688
				689	</div>
				690
				691	<!-- ======================================================================= -->
				692	<div class="doc_subsection">
				693	<a name="filescope">File scope entities</a>
				694	</div>
				695
				696	<!-- -------------------------------------------------------------------------->
				697	<div class="doc_subsubsection">
				698	<a name="include">File inclusion</a>
				699	</div>
				700
				701	<div class="doc_text">
				702	<p>TableGen supports the '<tt>include</tt>' token, which textually substitutes
				703	the specified file in place of the include directive. The filename should be
				704	specified as a double quoted string immediately after the '<tt>include</tt>'
				705	keyword. Example:</p>
				706
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	707	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	708	<pre>
				709	<b>include</b> "foo.td"
				710	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	711	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	712
				713	</div>
				714
				715	<!-- -------------------------------------------------------------------------->
				716	<div class="doc_subsubsection">
				717	<a name="globallet">'let' expressions</a>
				718	</div>
				719
				720	<div class="doc_text">
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	721
				722	<p>"Let" expressions at file scope are similar to <a href="#recordlet">"let"
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	723	expressions within a record</a>, except they can specify a value binding for
				724	multiple records at a time, and may be useful in certain other cases.
				725	File-scope let expressions are really just another way that TableGen allows the
				726	end-user to factor out commonality from the records.</p>
				727
				728	<p>File-scope "let" expressions take a comma-separated list of bindings to
Matthijs Kooijman	16bb03a	2008-10-20 08:45:34 +0000	[diff] [blame]	729	apply, and one or more records to bind the values in. Here are some
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	730	examples:</p>
				731
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	732	<div class="doc_code">
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	733	<pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	734	<b>let</b> isTerminator = 1, isReturn = 1, isBarrier = 1, hasCtrlDep = 1 <b>in</b>
				735	<b>def</b> RET : I<0xC3, RawFrm, (outs), (ins), "ret", [(X86retflag 0)]>;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	736
				737	<b>let</b> isCall = 1 <b>in</b>
				738	<i>// All calls clobber the non-callee saved registers...</i>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	739	<b>let</b> Defs = [EAX, ECX, EDX, FP0, FP1, FP2, FP3, FP4, FP5, FP6, ST0,
				740	MM0, MM1, MM2, MM3, MM4, MM5, MM6, MM7,
				741	XMM0, XMM1, XMM2, XMM3, XMM4, XMM5, XMM6, XMM7, EFLAGS] <b>in</b> {
Dan Gohman	8e58bc5	2008-10-14 17:00:38 +0000	[diff] [blame]	742	<b>def</b> CALLpcrel32 : Ii32<0xE8, RawFrm, (outs), (ins i32imm:$dst,variable_ops),
				743	"call\t${dst:call}", []>;
				744	<b>def</b> CALL32r : I<0xFF, MRM2r, (outs), (ins GR32:$dst, variable_ops),
				745	"call\t{*}$dst", [(X86call GR32:$dst)]>;
				746	<b>def</b> CALL32m : I<0xFF, MRM2m, (outs), (ins i32mem:$dst, variable_ops),
				747	"call\t{*}$dst", []>;
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	748	}
				749	</pre>
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	750	</div>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	751
				752	<p>File-scope "let" expressions are often useful when a couple of definitions
				753	need to be added to several records, and the records do not otherwise need to be
Bill Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	754	opened, as in the case with the <tt>CALL*</tt> instructions above.</p>
				755
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	756	</div>
				757
				758	<!-- *********************************************************************** -->
Evan Cheng	f68c8b6	2009-10-05 02:51:06 +0000	[diff] [blame]	759	<div class="doc_section"><a name="codegen">Code Generator backend info</a></div>
				760	<!-- *********************************************************************** -->
				761
				762	<p>Expressions used by code generator to describe instructions and isel
				763	patterns:</p>
				764
				765	<div class="doc_text">
				766
				767	<dt><tt>(implicit a)</tt></dt>
				768	<dd>an implicitly defined physical register. This tells the dag instruction
				769	selection emitter the input pattern's extra definitions matches implicit
				770	physical register definitions.</dd>
Evan Cheng	f68c8b6	2009-10-05 02:51:06 +0000	[diff] [blame]	771
				772	</div>
				773
				774	<!-- *********************************************************************** -->
Dan Gohman	f17a25c	2007-07-18 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 Wendling	707b6ab	2008-02-12 07:06:19 +0000	[diff] [blame]	779
				780	<p>TODO: How they work, how to write one. This section should not contain
				781	details about any particular backend, except maybe -print-enums as an example.
				782	This should highlight the APIs in <tt>TableGen/Record.h</tt>.</p>
				783
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	784	</div>
				785
				786	<!-- *********************************************************************** -->
				787
				788	<hr>
				789	<address>
				790	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman	947321d	2008-12-11 17:34:48 +0000	[diff] [blame]	791	src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Dan Gohman	f17a25c	2007-07-18 16:29:46 +0000	[diff] [blame]	792	<a href="http://validator.w3.org/check/referer"><img
Misha Brukman	947321d	2008-12-11 17:34:48 +0000	[diff] [blame]	793	src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
Dan Gohman	f17a25c	2007-07-18 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: $Date$
				798	</address>
				799
				800	</body>
				801	</html>