<div class="doc_title">TableGen Fundamentals</div>
+<div class="doc_text">
<ul>
- <li><a href="#introduction">Introduction</a></li>
+ <li><a href="#introduction">Introduction</a>
<ol>
<li><a href="#concepts">Basic concepts</a></li>
<li><a href="#example">An example record</a></li>
<li><a href="#running">Running TableGen</a></li>
- </ol>
- <li><a href="#syntax">TableGen syntax</a></li>
+ </ol></li>
+ <li><a href="#syntax">TableGen syntax</a>
<ol>
- <li><a href="#primitives">TableGen primitives</a></li>
+ <li><a href="#primitives">TableGen primitives</a>
<ol>
<li><a href="#comments">TableGen comments</a></li>
<li><a href="#types">The TableGen type system</a></li>
<li><a href="#values">TableGen values and expressions</a></li>
- </ol>
- <li><a href="#classesdefs">Classes and definitions</a></li>
+ </ol></li>
+ <li><a href="#classesdefs">Classes and definitions</a>
<ol>
<li><a href="#valuedef">Value definitions</a></li>
<li><a href="#recordlet">'let' expressions</a></li>
<li><a href="#templateargs">Class template arguments</a></li>
- </ol>
- <li><a href="#filescope">File scope entities</a></li>
+ <li><a href="#multiclass">Multiclass definitions and instances</a></li>
+ </ol></li>
+ <li><a href="#filescope">File scope entities</a>
<ol>
<li><a href="#include">File inclusion</a></li>
<li><a href="#globallet">'let' expressions</a></li>
- </ol>
- </ol>
- <li><a href="#backends">TableGen backends</a></li>
- <ol>
- <li><a href="#">todo</a></li>
- </ol>
- <li><a href="#codegenerator">The LLVM code generator</a></li>
+ </ol></li>
+ </ol></li>
+ <li><a href="#backends">TableGen backends</a>
<ol>
<li><a href="#">todo</a></li>
- </ol>
+ </ol></li>
</ul>
+</div>
+
+<div class="doc_author">
+ <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
+</div>
<!-- *********************************************************************** -->
<div class="doc_section"><a name="introduction">Introduction</a></div>
<p>The core part of TableGen <a href="#syntax">parses a file</a>, instantiates
the declarations, and hands the result off to a domain-specific "<a
href="#backends">TableGen backend</a>" for processing. The current major user
-of TableGen is the <a href="#codegenerator">LLVM code generator</a>.
-</p>
+of TableGen is the <a href="CodeGenerator.html">LLVM code generator</a>.</p>
-<p>
-Note that if you work on TableGen much, and use emacs or vim, that you can find
-an emacs "TableGen mode" and a vim language file in <tt>llvm/utils/emacs</tt>
-and <tt>llvm/utils/vim</tt> directory of your LLVM distribution, respectively.
-</p>
+<p>Note that if you work on TableGen much, and use emacs or vim, that you can
+find an emacs "TableGen mode" and a vim language file in
+<tt>llvm/utils/emacs</tt> and <tt>llvm/utils/vim</tt> directory of your LLVM
+distribution, respectively.</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="running">Basic concepts</a>
-</div>
+<div class="doc_subsection"><a name="concepts">Basic concepts</a></div>
<div class="doc_text">
-<p>
-TableGen files consist of two key parts: 'classes' and 'definitions', both of
-which are considered 'records'.
-</p>
+<p>TableGen files consist of two key parts: 'classes' and 'definitions', both
+of which are considered 'records'.</p>
-<p>
-<b>TableGen records</b> have a unique name, a list of values, and a list of
+<p><b>TableGen records</b> have a unique name, a list of values, and a list of
superclasses. The list of values is main data that TableGen builds for each
record, it is this that holds the domain specific information for the
application. The interpretation of this data is left to a specific <a
href="#backends">TableGen backend</a>, but the structure and format rules are
-taken care of and fixed by TableGen.
-</p>
-
-<p>
-<b>TableGen definitions</b> are the concrete form of 'records'. These generally
-do not have any undefined values, and are marked with the '<tt>def</tt>'
-keyword.
-</p>
-
-<p>
-<b>TableGen classes</b> are abstract records that are used to build and describe
-other records. These 'classes' allow the end-user to build abstractions for
-either the domain they are targetting (such as "Register", "RegisterClass", and
-"Instruction" in the LLVM code generator) or for the implementor to help factor
-out common properties of records (such as "FPInst", which is used to represent
-floating point instructions in the X86 backend). TableGen keeps track of all of
-the classes that are used to build up a definition, so the backend can find all
-definitions of a particular class, such as "Instruction".
-</p>
+taken care of and fixed by TableGen.</p>
+
+<p><b>TableGen definitions</b> are the concrete form of 'records'. These
+generally do not have any undefined values, and are marked with the
+'<tt>def</tt>' keyword.</p>
+
+<p><b>TableGen classes</b> are abstract records that are used to build and
+describe other records. These 'classes' allow the end-user to build
+abstractions for either the domain they are targetting (such as "Register",
+"RegisterClass", and "Instruction" in the LLVM code generator) or for the
+implementor to help factor out common properties of records (such as "FPInst",
+which is used to represent floating point instructions in the X86 backend).
+TableGen keeps track of all of the classes that are used to build up a
+definition, so the backend can find all definitions of a particular class, such
+as "Instruction".</p>
+
+<p><b>TableGen multiclasses</b> are groups of abstract records that are
+instantiated all at once. Each instantiation can result in multiple TableGen
+definitions.</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="example">An example record</a>
-</div>
+<div class="doc_subsection"><a name="example">An example record</a></div>
<div class="doc_text">
-<p>
-With no other arguments, TableGen parses the specified file and prints out all
-of the classes, then all of the definitions. This is a good way to see what the
-various definitions expand to fully. Running this on the <tt>X86.td</tt> file
-prints this (at the time of this writing):
-</p>
+<p>With no other arguments, TableGen parses the specified file and prints out
+all of the classes, then all of the definitions. This is a good way to see what
+the various definitions expand to fully. Running this on the <tt>X86.td</tt>
+file prints this (at the time of this writing):</p>
-<p>
<pre>
...
<b>def</b> ADDrr8 { <i>// Instruction X86Inst I2A8 Pattern</i>
<b>bits</b><3> FPFormBits = { 0, 0, 0 };
}
...
-</pre><p>
+</pre>
-<p>
-This definition corresponds to an 8-bit register-register add instruction in the
-X86. The string after the '<tt>def</tt>' string indicates the name of the
+<p>This definition corresponds to an 8-bit register-register add instruction in
+the X86. The string after the '<tt>def</tt>' string indicates the name of the
record ("<tt>ADDrr8</tt>" in this case), and the comment at the end of the line
indicates the superclasses of the definition. The body of the record contains
all of the data that TableGen assembled for the record, indicating that the
instruction is part of the "X86" namespace, should be printed as "<tt>add</tt>"
in the assembly file, it is a two-address instruction, has a particular
encoding, etc. The contents and semantics of the information in the record is
-specific to the needs of the X86 backend, and is only shown as an example.
-</p>
+specific to the needs of the X86 backend, and is only shown as an example.</p>
-<p>
-As you can see, a lot of information is needed for every instruction supported
-by the code generator, and specifying it all manually would be unmaintainble,
-prone to bugs, and tiring to do in the first place. Because we are using
-TableGen, all of the information was derived from the following definition:
-</p>
+<p>As you can see, a lot of information is needed for every instruction
+supported by the code generator, and specifying it all manually would be
+unmaintainble, prone to bugs, and tiring to do in the first place. Because we
+are using TableGen, all of the information was derived from the following
+definition:</p>
-<p><pre>
+<pre>
<b>def</b> ADDrr8 : I2A8<"add", 0x00, MRMDestReg>,
Pattern<(set R8, (plus R8, R8))>;
-</pre></p>
+</pre>
-<p>
-This definition makes use of the custom I2A8 (two address instruction with 8-bit
-operand) class, which is defined in the X86-specific TableGen file to factor out
-the common features that instructions of its class share. A key feature of
-TableGen is that it allows the end-user to define the abstractions they prefer
-to use when describing their information.
-</p>
+<p>This definition makes use of the custom I2A8 (two address instruction with
+8-bit operand) class, which is defined in the X86-specific TableGen file to
+factor out the common features that instructions of its class share. A key
+feature of TableGen is that it allows the end-user to define the abstractions
+they prefer to use when describing their information.</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="running">Running TableGen</a>
-</div>
+<div class="doc_subsection"><a name="running">Running TableGen</a></div>
<div class="doc_text">
-<p>
-TableGen runs just like any other LLVM tool. The first (optional) argument
+<p>TableGen runs just like any other LLVM tool. The first (optional) argument
specifies the file to read. If a filename is not specified, <tt>tblgen</tt>
-reads from standard input.
-</p>
+reads from standard input.</p>
-<p>
-To be useful, one of the <a href="#backends">TableGen backends</a> must be used.
-These backends are selectable on the command line (type '<tt>tblgen --help</tt>'
-for a list). For example, to get a list of all of the definitions that subclass
-a particular type (which can be useful for building up an enum list of these
-records), use the <tt>--print-enums</tt> option:
-</p>
+<p>To be useful, one of the <a href="#backends">TableGen backends</a> must be
+used. These backends are selectable on the command line (type '<tt>tblgen
+--help</tt>' for a list). For example, to get a list of all of the definitions
+that subclass a particular type (which can be useful for building up an enum
+list of these records), use the <tt>--print-enums</tt> option:</p>
-<p><pre>
+<pre>
$ tblgen X86.td -print-enums -class=Register
AH, AL, AX, BH, BL, BP, BX, CH, CL, CX, DH, DI, DL, DX,
EAX, EBP, EBX, ECX, EDI, EDX, ESI, ESP, FP0, FP1, FP2, FP3, FP4, FP5, FP6,
ADCrr32, ADDri16, ADDri16b, ADDri32, ADDri32b, ADDri8, ADDrr16, ADDrr32,
ADDrr8, ADJCALLSTACKDOWN, ADJCALLSTACKUP, ANDri16, ANDri16b, ANDri32, ANDri32b,
ANDri8, ANDrr16, ANDrr32, ANDrr8, BSWAPr32, CALLm32, CALLpcrel32, ...
-</pre></p>
+</pre>
-<p>
-The default backend prints out all of the records, as described <a
-href="#example">above</a>.
-</p>
+<p>The default backend prints out all of the records, as described <a
+href="#example">above</a>.</p>
-<p>
-If you plan to use TableGen for some purpose, you will most likely have to <a
-href="#backends">write a backend</a> that extracts the information specific to
-what you need and formats it in the appropriate way.
-</p>
+<p>If you plan to use TableGen for some purpose, you will most likely have to
+<a href="#backends">write a backend</a> that extracts the information specific
+to what you need and formats it in the appropriate way.</p>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
-
-<p>
-TableGen doesn't care about the meaning of data (that is up to the backend to
-define), but it does care about syntax, and it enforces a simple type system.
+<p>TableGen doesn't care about the meaning of data (that is up to the backend
+to define), but it does care about syntax, and it enforces a simple type system.
This section describes the syntax and the constructs allowed in a TableGen file.
</p>
-
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="primitives">TableGen primitives</tt></a>
-</div>
+<div class="doc_subsection"><a name="primitives">TableGen primitives</a></div>
-<!----------------------------------------------------------------------------->
-<div class="doc_subsubsection">
- <a name="comments">TableGen comments</tt></a>
-</div>
+<!-- -------------------------------------------------------------------------->
+<div class="doc_subsubsection"><a name="comments">TableGen comments</a></div>
<div class="doc_text">
-
<p>TableGen supports BCPL style "<tt>//</tt>" comments, which run to the end of
the line, and it also supports <b>nestable</b> "<tt>/* */</tt>" comments.</p>
-
</div>
-
-<!----------------------------------------------------------------------------->
+<!-- -------------------------------------------------------------------------->
<div class="doc_subsubsection">
- <a name="types">The TableGen type system</tt></a>
+ <a name="types">The TableGen type system</a>
</div>
<div class="doc_text">
-<p>
-TableGen files are strongly typed, in a simple (but complete) type-system.
+<p>TableGen files are strongly typed, in a simple (but complete) type-system.
These types are used to perform automatic conversions, check for errors, and to
help interface designers constrain the input that they allow. Every <a
href="#valuedef">value definition</a> is required to have an associated type.
</p>
-<p>
-TableGen supports a mixture of very low-level types (such as <tt>bit</tt>) and
-very high-level types (such as <tt>dag</tt>). This flexibility is what allows
-it to describe a wide range of information conveniently and compactly. The
-TableGen types are:
-</p>
+<p>TableGen supports a mixture of very low-level types (such as <tt>bit</tt>)
+and very high-level types (such as <tt>dag</tt>). This flexibility is what
+allows it to describe a wide range of information conveniently and compactly.
+The TableGen types are:</p>
-<p>
<ul>
<li>"<tt><b>bit</b></tt>" - A 'bit' is a boolean value that can hold either 0 or
1.</li>
<li>"<tt><b>string</b></tt>" - The 'string' type represents an ordered sequence
of characters of arbitrary length.</li>
-<li>"<tt><b>bits</b><n></tt>" - A 'bits' type is a arbitrary, but fixed,
+<li>"<tt><b>bits</b><n></tt>" - A 'bits' type is an arbitrary, but fixed,
size integer that is broken up into individual bits. This type is useful
because it can handle some bits being defined while others are undefined.</li>
<li>"<tt><b>dag</b></tt>" - This type represents a nestable directed graph of
elements.</li>
</ul>
-</p>
-<p>
-To date, these types have been sufficient for describing things that TableGen
-has been used for, but it is straight-forward to extend this list if needed.
-</p>
+<p>To date, these types have been sufficient for describing things that
+TableGen has been used for, but it is straight-forward to extend this list if
+needed.</p>
</div>
-<!----------------------------------------------------------------------------->
+<!-- -------------------------------------------------------------------------->
<div class="doc_subsubsection">
- <a name="values">TableGen values and expressions</tt></a>
+ <a name="values">TableGen values and expressions</a>
</div>
-<div>
-<p>
-TableGen allows for a pretty reasonable number of different expression forms
+<div class="doc_text">
+
+<p>TableGen allows for a pretty reasonable number of different expression forms
when building up values. These forms allow the TableGen file to be written in a
natural syntax and flavor for the application. The current expression forms
-supported include:
-</p>
+supported include:</p>
-<p><ul>
-<li>? - Uninitialized field.</li>
-<li>0b1001011 - Binary integer value.</li>
-<li>07654321 - Octal integer value (indicated by a leading 0).</li>
-<li>7 - Decimal integer value.</li>
-<li>0x7F - Hexadecimal integer value.</li>
-<li>"foo" - String value.</li>
-<li>[{ .... }] - Code fragment.</li>
-<li>[ X, Y, Z ] - List value.</li>
-<li>{ a, b, c } - Initializer for a "bits<3>" value.</li>
-<li>value - Value reference.</li>
-<li>value{17} - Access to one or more bits of a value.</li>
-<li>DEF - Reference to a record definition.</li>
-<li>X.Y - Reference to the subfield of a value.</li>
-
-<li>(DEF a, b) - A dag value. The first element is required to be a record
-definition, the remaining elements in the list may be arbitrary other values,
-including nested 'dag' values.</li>
-
-</ul></p>
+<ul>
+<li><tt>?</tt> - uninitialized field</li>
+<li><tt>0b1001011</tt> - binary integer value</li>
+<li><tt>07654321</tt> - octal integer value (indicated by a leading 0)</li>
+<li><tt>7</tt> - decimal integer value</li>
+<li><tt>0x7F</tt> - hexadecimal integer value</li>
+<li><tt>"foo"</tt> - string value</li>
+<li><tt>[{ ... }]</tt> - code fragment</li>
+<li><tt>[ X, Y, Z ]</tt> - list value.</li>
+<li><tt>{ a, b, c }</tt> - initializer for a "bits<3>" value</li>
+<li><tt>value</tt> - value reference</li>
+<li><tt>value{17}</tt> - access to one bit of a value</li>
+<li><tt>value{15-17}</tt> - access to multiple bits of a value</li>
+<li><tt>DEF</tt> - reference to a record definition</li>
+<li><tt>CLASS<val list></tt> - reference to a new anonymous definition of
+ CLASS with the specified template arguments.</li>
+<li><tt>X.Y</tt> - reference to the subfield of a value</li>
+<li><tt>list[4-7,17,2-3]</tt> - A slice of the 'list' list, including elements
+4,5,6,7,17,2, and 3 from it. Elements may be included multiple times.</li>
+<li><tt>(DEF a, b)</tt> - a dag value. The first element is required to be a
+record definition, the remaining elements in the list may be arbitrary other
+values, including nested `<tt>dag</tt>' values.</li>
+<li><tt>!strconcat(a, b)</tt> - A string value that is the result of
+ concatenating the 'a' and 'b' strings.</li>
+</ul>
-<p>
-Note that all of the values have rules specifying how they convert to to values
+<p>Note that all of the values have rules specifying how they convert to values
for different types. These rules allow you to assign a value like "7" to a
-"bits<4>" value, for example.
-</p>
-
-
+"bits<4>" value, for example.</p>
</div>
-
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="classesdefs">Classes and definitions</tt></a>
+ <a name="classesdefs">Classes and definitions</a>
</div>
-<div>
-<p>
-As mentioned in the <a href="#concepts">intro</a>, classes and definitions
+<div class="doc_text">
+
+
<p>As mentioned in the <a href="#concepts">intro</a>, classes and definitions
(collectively known as 'records') in TableGen are the main high-level unit of
information that TableGen collects. Records are defined with a <tt>def</tt> or
<tt>class</tt> keyword, the record name, and an optional list of "<a
-href="templateargs">template arguments</a>". If the record has superclasses,
-they are specified as a comma seperated list that starts with a colon character
+href="#templateargs">template arguments</a>". If the record has superclasses,
+they are specified as a comma separated list that starts with a colon character
(":"). If <a href="#valuedef">value definitions</a> or <a href="#recordlet">let
-expressions</a> are needed for the class they are enclosed in curly braces
-("{}"), otherwise the record ends with a semicolon. Here is a simple TableGen
-file:
-</p>
+expressions</a> are needed for the class, they are enclosed in curly braces
+("{}"); otherwise, the record ends with a semicolon. Here is a simple TableGen
+file:</p>
-<p><pre>
+<pre>
<b>class</b> C { <b>bit</b> V = 1; }
<b>def</b> X : C;
<b>def</b> Y : C {
<b>string</b> Greeting = "hello";
}
-</pre></p>
+</pre>
-<p>
-This example defines two definitions, <tt>X</tt> and <tt>Y</tt>, both of which
-derive from the <tt>C</tt> class. Because of this, they both get the <tt>V</tt>
-bit value. The <tt>Y</tt> definition also gets the Greeting member as well.
-</p>
+<p>This example defines two definitions, <tt>X</tt> and <tt>Y</tt>, both of
+which derive from the <tt>C</tt> class. Because of this, they both get the
+<tt>V</tt> bit value. The <tt>Y</tt> definition also gets the Greeting member
+as well.</p>
-<p>
-In general, classes are useful for collecting together the commonality between a
-group of records, and isolating it in a single places. Also, classes permit the
-specification of default values for their subclasses, allowing the subclasses to
-override them as they wish.
-</p>
+<p>In general, classes are useful for collecting together the commonality
+between a group of records and isolating it in a single place. Also, classes
+permit the specification of default values for their subclasses, allowing the
+subclasses to override them as they wish.</p>
</div>
-<!----------------------------------------------------------------------------->
+<!---------------------------------------------------------------------------->
<div class="doc_subsubsection">
- <a name="valuedef">Value definitions</tt></a>
+ <a name="valuedef">Value definitions</a>
</div>
<div class="doc_text">
-<p>
-Value definitions define named entries in records. A value must be defined
-before it can be referred to as the operand for another value definition, or
+<p>Value definitions define named entries in records. A value must be defined
+before it can be referred to as the operand for another value definition or
before the value is reset with a <a href="#recordlet">let expression</a>. A
value is defined by specifying a <a href="#types">TableGen type</a> and a name.
If an initial value is available, it may be specified after the type with an
-equal sign. Value definitions require terminating semicolons.
+equal sign. Value definitions require terminating semicolons.</p>
</div>
-<!----------------------------------------------------------------------------->
+<!-- -------------------------------------------------------------------------->
<div class="doc_subsubsection">
- <a name="recordlet">'let' expressions</tt></a>
+ <a name="recordlet">'let' expressions</a>
</div>
<div class="doc_text">
-<p>
-A record-level let expression is used to change the value of a value definition
-in a record. This is primarily useful when a superclass defines a value that a
-derived class or definitions wants to override. Let expressions consist of the
-'<tt>let</tt>' keyword, followed by a value name, an equal sign ("="), and a new
-value for example, a new class could be added to the example above, redefining
-the <tt>V</tt> field for all of its subclasses:</p>
-
-<p><pre>
+<p>A record-level let expression is used to change the value of a value
+definition in a record. This is primarily useful when a superclass defines a
+value that a derived class or definition wants to override. Let expressions
+consist of the '<tt>let</tt>' keyword followed by a value name, an equal sign
+("="), and a new value. For example, a new class could be added to the example
+above, redefining the <tt>V</tt> field for all of its subclasses:</p>
+
+<pre>
<b>class</b> D : C { let V = 0; }
<b>def</b> Z : D;
-</pre></p>
+</pre>
-<p>
-In this case, the <tt>Z</tt> definition will have a zero value for its "V"
+<p>In this case, the <tt>Z</tt> definition will have a zero value for its "V"
value, despite the fact that it derives (indirectly) from the <tt>C</tt> class,
-because the <tt>D</tt> class overrode its value.
-</p>
+because the <tt>D</tt> class overrode its value.</p>
</div>
-<!----------------------------------------------------------------------------->
+<!-- -------------------------------------------------------------------------->
<div class="doc_subsubsection">
- <a name="templateargs">Class template arguments</tt></a>
+ <a name="templateargs">Class template arguments</a>
</div>
<div class="doc_text">
-<p>
-TableGen permits the definition of parameterized classes as well as normal
+<p>TableGen permits the definition of parameterized classes as well as normal
concrete classes. Parameterized TableGen classes specify a list of variable
bindings (which may optionally have defaults) that are bound when used. Here is
a simple example:</p>
-<p><pre>
+<pre>
<b>class</b> FPFormat<<b>bits</b><3> val> {
<b>bits</b><3> Value = val;
}
<b>def</b> OneArgFPRW : FPFormat<3>;
<b>def</b> TwoArgFP : FPFormat<4>;
<b>def</b> SpecialFP : FPFormat<5>;
-</pre></p>
+</pre>
-<p>
-In this case, template arguments are used as a space efficient way to specify a
-list of "enumeration values", each with a "Value" field set to the specified
+<p>In this case, template arguments are used as a space efficient way to specify
+a list of "enumeration values", each with a "Value" field set to the specified
integer.</p>
<p>The more esoteric forms of <a href="#values">TableGen expressions</a> are
useful in conjunction with template arguments. As an example:</p>
-<p><pre>
+<pre>
<b>class</b> ModRefVal<<b>bits</b><2> val> {
<b>bits</b><2> Value = val;
}
<b>def</b> bork : Value<Mod>;
<b>def</b> zork : Value<Ref>;
<b>def</b> hork : Value<ModRef>;
-</pre></p>
+</pre>
-<p>
-This is obviously a contrived example, but it shows how template arguments can
-be used to decouple the interface provided to the user of the class from the
+<p>This is obviously a contrived example, but it shows how template arguments
+can be used to decouple the interface provided to the user of the class from the
actual internal data representation expected by the class. In this case,
running <tt>tblgen</tt> on the example prints the following definitions:</p>
-<p><pre>
+<pre>
<b>def</b> bork { <i>// Value</i>
- bit isMod = 1;
- bit isRef = 0;
+ <b>bit</b> isMod = 1;
+ <b>bit</b> isRef = 0;
}
<b>def</b> hork { <i>// Value</i>
- bit isMod = 1;
- bit isRef = 1;
+ <b>bit</b> isMod = 1;
+ <b>bit</b> isRef = 1;
}
<b>def</b> zork { <i>// Value</i>
- bit isMod = 0;
- bit isRef = 1;
+ <b>bit</b> isMod = 0;
+ <b>bit</b> isRef = 1;
}
-</pre></p>
+</pre>
-<p>
-This shows that TableGen was able to dig into the argument and extract a piece
-of information that was requested by the designer of the "Value" class. For
-more realistic examples, please see existing users of TableGen, such as the X86
-backend.</p>
+<p> This shows that TableGen was able to dig into the argument and extract a
+piece of information that was requested by the designer of the "Value" class.
+For more realistic examples, please see existing users of TableGen, such as the
+X86 backend.</p>
+
+</div>
+<!-- -------------------------------------------------------------------------->
+<div class="doc_subsubsection">
+ <a name="multiclass">Multiclass definitions and instances</a>
</div>
+<div class="doc_text">
+
+<p>
+While classes with template arguments are a good way to factor commonality
+between two instances of a definition, multiclasses allow a convenient notation
+for defining multiple definitions at once (instances of implicitly constructed
+classes). For example, consider an 3-address instruction set whose instructions
+come in two forms: "reg = reg op reg" and "reg = reg op imm" (e.g. SPARC). In
+this case, you'd like to specify in one place that this commonality exists, then
+in a separate place indicate what all the ops are.
+</p>
+
+<p>
+Here is an example TableGen fragment that shows this idea:
+</p>
+
+<pre>
+<b>def</b> ops;
+<b>def</b> GPR;
+<b>def</b> Imm;
+<b>class</b> inst<<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist>;
+
+<b>multiclass</b> ri_inst<<b>int</b> opc, <b>string</b> asmstr> {
+ def _rr : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"),
+ (ops GPR:$dst, GPR:$src1, GPR:$src2)>;
+ def _ri : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"),
+ (ops GPR:$dst, GPR:$src1, Imm:$src2)>;
+}
+// Instantiations of the ri_inst multiclass.
+<b>defm</b> ADD : ri_inst<0b111, "add">;
+<b>defm</b> SUB : ri_inst<0b101, "sub">;
+<b>defm</b> MUL : ri_inst<0b100, "mul">;
+...
+</pre>
+
+<p>The name of the resultant definitions has the multidef fragment names
+ appended to them, so this defines ADD_rr, ADD_ri, SUB_rr, etc. Using a
+ multiclass this way is exactly equivalent to instantiating the
+ classes multiple times yourself, e.g. by writing:</p>
+
+<pre>
+<b>def</b> ops;
+<b>def</b> GPR;
+<b>def</b> Imm;
+<b>class</b> inst<<b>int</b> opc, <b>string</b> asmstr, <b>dag</b> operandlist>;
+
+<b>class</b> rrinst<<b>int</b> opc, <b>string</b> asmstr>
+ : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"),
+ (ops GPR:$dst, GPR:$src1, GPR:$src2)>;
+
+<b>class</b> riinst<<b>int</b> opc, <b>string</b> asmstr>
+ : inst<opc, !strconcat(asmstr, " $dst, $src1, $src2"),
+ (ops GPR:$dst, GPR:$src1, Imm:$src2)>;
+
+// Instantiations of the ri_inst multiclass.
+<b>def</b> ADD_rr : rrinst<0b111, "add">;
+<b>def</b> ADD_ri : riinst<0b111, "add">;
+<b>def</b> SUB_rr : rrinst<0b101, "sub">;
+<b>def</b> SUB_ri : riinst<0b101, "sub">;
+<b>def</b> MUL_rr : rrinst<0b100, "mul">;
+<b>def</b> MUL_ri : riinst<0b100, "mul">;
+...
+</pre>
+
+</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="filescope">File scope entities</tt></a>
+ <a name="filescope">File scope entities</a>
</div>
-<!----------------------------------------------------------------------------->
+<!-- -------------------------------------------------------------------------->
<div class="doc_subsubsection">
- <a name="include">File inclusion</tt></a>
+ <a name="include">File inclusion</a>
</div>
<div class="doc_text">
-<p>
-TableGen supports the '<tt>include</tt>' token, which textually substitutes the
-specified file in place of the include directive. The filename should be
+<p>TableGen supports the '<tt>include</tt>' token, which textually substitutes
+the specified file in place of the include directive. The filename should be
specified as a double quoted string immediately after the '<tt>include</tt>'
-keyword. Example:
+keyword. Example:</p>
-<p><pre>
+<pre>
<b>include</b> "foo.td"
-</pre></p>
+</pre>
</div>
-<!----------------------------------------------------------------------------->
+<!-- -------------------------------------------------------------------------->
<div class="doc_subsubsection">
- <a name="globallet">'let' expressions</tt></a>
+ <a name="globallet">'let' expressions</a>
</div>
<div class="doc_text">
-<p>
-"let" expressions at file scope are similar to <a href="#recordlet">"let"
+<p> "let" expressions at file scope are similar to <a href="#recordlet">"let"
expressions within a record</a>, except they can specify a value binding for
multiple records at a time, and may be useful in certain other cases.
File-scope let expressions are really just another way that TableGen allows the
-end-user to factor out commonality from the records.
-</p>
+end-user to factor out commonality from the records.</p>
-<p>
-File-scope "let" expressions take a comma-seperated list of bindings to apply,
-and one of more records to bind the values in. Here are some examples:
-</p>
+<p>File-scope "let" expressions take a comma-separated list of bindings to
+apply, and one of more records to bind the values in. Here are some
+examples:</p>
-<p><pre>
+<pre>
<b>let</b> isTerminator = 1, isReturn = 1 <b>in</b>
<b>def</b> RET : X86Inst<"ret", 0xC3, RawFrm, NoArg>;
<b>def</b> CALLr32 : X86Inst<"call", 0xFF, MRMS2r, Arg32>;
<b>def</b> CALLm32 : X86Inst<"call", 0xFF, MRMS2m, Arg32>;
}
-</pre></p>
+</pre>
-<p>
-File-scope "let" expressions are often useful when a couple of definitions need
-to be added to several records, and the records do not otherwise need to be
-opened, as in the case with the CALL* instructions above.
-</p>
+<p>File-scope "let" expressions are often useful when a couple of definitions
+need to be added to several records, and the records do not otherwise need to be
+opened, as in the case with the CALL* instructions above.</p>
</div>
-
<!-- *********************************************************************** -->
<div class="doc_section"><a name="backends">TableGen backends</a></div>
<!-- *********************************************************************** -->
<div class="doc_text">
-
-<p>
-How they work, how to write one. This section should not contain details about
-any particular backend, except maybe -print-enums as an example. This should
-highlight the APIs in TableGen/Record.h.
-</p>
-
+<p>How they work, how to write one. This section should not contain details
+about any particular backend, except maybe -print-enums as an example. This
+should highlight the APIs in <tt>TableGen/Record.h</tt>.</p>
</div>
-
<!-- *********************************************************************** -->
-<div class="doc_section"><a name="codegenerator">The LLVM code generator</a></div>
-<!-- *********************************************************************** -->
-
-<div class="doc_text">
-<p>
-This is just a temporary, convenient, place to put stuff about the code
-generator before it gets its own document. This should describe all of the
-tablegen backends used by the code generator and the classes/definitions they
-expect.
-</p>
-
-</div>
-
-
-
-<!-- *********************************************************************** -->
<hr>
-<div class="doc_footer">
- <address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
- <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
- <br>
+<address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
+
+ <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
+ <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
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