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-<div class="doc_title">TableGen Fundamentals</div>
+<h1>TableGen Fundamentals</h1>
-<div class="doc_text">
+<div>
<ul>
<li><a href="#introduction">Introduction</a>
<ol>
</div>
<!-- *********************************************************************** -->
-<div class="doc_section"><a name="introduction">Introduction</a></div>
+<h2><a name="introduction">Introduction</a></h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
+<div>
<p>TableGen's purpose is to help a human develop and maintain records of
domain-specific information. Because there may be a large number of these
<tt>llvm/utils/emacs</tt> and <tt>llvm/utils/vim</tt> directories of your LLVM
distribution, respectively.</p>
-</div>
-
<!-- ======================================================================= -->
-<div class="doc_subsection"><a name="concepts">Basic concepts</a></div>
+<h3><a name="concepts">Basic concepts</a></h3>
-<div class="doc_text">
+<div>
<p>TableGen files consist of two key parts: 'classes' and 'definitions', both
of which are considered 'records'.</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection"><a name="example">An example record</a></div>
+<h3><a name="example">An example record</a></h3>
-<div class="doc_text">
+<div>
<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
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>Each def record has a special entry called "NAME." This is the
+name of the def ("ADD32rr" above). In the general case def names can
+be formed from various kinds of string processing expressions and NAME
+resolves to the final value obtained after resolving all of those
+expressions. The user may refer to NAME anywhere she desires to use
+the ultimate name of the def. NAME should not be defined anywhere
+else in user code to avoid conflict problems.</p>
+
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection"><a name="running">Running TableGen</a></div>
+<h3><a name="running">Running TableGen</a></h3>
-<div class="doc_text">
+<div>
<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>
</div>
+</div>
<!-- *********************************************************************** -->
-<div class="doc_section"><a name="syntax">TableGen syntax</a></div>
+<h2><a name="syntax">TableGen syntax</a></h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
+<div>
<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</a></div>
+<h3><a name="primitives">TableGen primitives</a></h3>
+
+<div>
<!-- -------------------------------------------------------------------------->
-<div class="doc_subsubsection"><a name="comments">TableGen comments</a></div>
+<h4><a name="comments">TableGen comments</a></h4>
-<div class="doc_text">
+<div>
<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">
+<h4>
<a name="types">The TableGen type system</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<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
</div>
<!-- -------------------------------------------------------------------------->
-<div class="doc_subsubsection">
+<h4>
<a name="values">TableGen values and expressions</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<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
<dt><tt>!strconcat(a, b)</tt></dt>
<dd>A string value that is the result of concatenating the 'a' and 'b'
strings.</dd>
+<dt><tt>str1#str2</tt></dt>
+ <dd>"#" (paste) is a shorthand for !strconcat. It may concatenate
+ things that are not quoted strings, in which case an implicit
+ !cast<string> is done on the operand of the paste.</dd>
<dt><tt>!cast<type>(a)</tt></dt>
<dd>A symbol of type <em>type</em> obtained by looking up the string 'a' in
the symbol table. If the type of 'a' does not match <em>type</em>, TableGen
</div>
+</div>
+
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="classesdefs">Classes and definitions</a>
-</div>
+</h3>
-<div class="doc_text">
+<div>
<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
permit the specification of default values for their subclasses, allowing the
subclasses to override them as they wish.</p>
-</div>
-
<!---------------------------------------------------------------------------->
-<div class="doc_subsubsection">
+<h4>
<a name="valuedef">Value definitions</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<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
</div>
<!-- -------------------------------------------------------------------------->
-<div class="doc_subsubsection">
+<h4>
<a name="recordlet">'let' expressions</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<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
</div>
<!-- -------------------------------------------------------------------------->
-<div class="doc_subsubsection">
+<h4>
<a name="templateargs">Class template arguments</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<p>TableGen permits the definition of parameterized classes as well as normal
concrete classes. Parameterized TableGen classes specify a list of variable
</div>
<!-- -------------------------------------------------------------------------->
-<div class="doc_subsubsection">
+<h4>
<a name="multiclass">Multiclass definitions and instances</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<p>
While classes with template arguments are a good way to factor commonality
</div>
+</div>
+
<!-- ======================================================================= -->
-<div class="doc_subsection">
+<h3>
<a name="filescope">File scope entities</a>
-</div>
+</h3>
+
+<div>
<!-- -------------------------------------------------------------------------->
-<div class="doc_subsubsection">
+<h4>
<a name="include">File inclusion</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<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>'
</div>
<!-- -------------------------------------------------------------------------->
-<div class="doc_subsubsection">
+<h4>
<a name="globallet">'let' expressions</a>
-</div>
+</h4>
-<div class="doc_text">
+<div>
<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
</pre>
</div>
+</div>
+
+</div>
+
<!-- *********************************************************************** -->
-<div class="doc_section"><a name="codegen">Code Generator backend info</a></div>
+<h2><a name="codegen">Code Generator backend info</a></h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
+<div>
<p>Expressions used by code generator to describe instructions and isel
patterns:</p>
</div>
<!-- *********************************************************************** -->
-<div class="doc_section"><a name="backends">TableGen backends</a></div>
+<h2><a name="backends">TableGen backends</a></h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
+<div>
<p>TODO: How they work, how to write one. This section should not contain
details about any particular backend, except maybe -print-enums as an example.
projects / oota-llvm.git / blobdiff