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Reformatting. Adding "doc_code" divisions for code examples. Updated some

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of the examples to reflect the current .TD files.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46995 91177308-0d34-0410-b5e6-96231b3b80d8
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Bill Wendling 2008-02-12 07:06:19 +00:00
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@ -68,8 +68,8 @@ href="#backends">TableGen backend</a>" for processing. The current major user
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
find an emacs "TableGen mode" and a vim language file in the
<tt>llvm/utils/emacs</tt> and <tt>llvm/utils/vim</tt> directories of your LLVM
distribution, respectively.</p>
</div>
@ -83,11 +83,11 @@ distribution, respectively.</p>
of which are considered 'records'.</p>
<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
superclasses. The list of values is the 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>
taken care of and are 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
@ -95,7 +95,7 @@ generally do not have any undefined values, and are marked with the
<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",
abstractions for either the domain they are targeting (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).
@ -119,42 +119,71 @@ 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>
<div class="doc_code">
<pre>
...
<b>def</b> ADDrr8 { <i>// Instruction X86Inst I2A8 Pattern</i>
<b>string</b> Name = "add";
<b>def</b> ADD32rr { <i>// Instruction X86Inst I</i>
<b>string</b> Namespace = "X86";
<b>dag</b> OutOperandList = (outs GR32:$dst);
<b>dag</b> InOperandList = (ins GR32:$src1, GR32:$src2);
<b>string</b> AsmString = "add{l}\t{$src2, $dst|$dst, $src2}";
<b>list</b>&lt;dag&gt; Pattern = [(set GR32:$dst, (add GR32:$src1, GR32:$src2))];
<b>list</b>&lt;Register&gt; Uses = [];
<b>list</b>&lt;Register&gt; Defs = [];
<b>list</b>&lt;Register&gt; Defs = [EFLAGS];
<b>list</b>&lt;Predicate&gt; Predicates = [];
<b>int</b> CodeSize = 3;
<b>int</b> AddedComplexity = 0;
<b>bit</b> isReturn = 0;
<b>bit</b> isBranch = 0;
<b>bit</b> isIndirectBranch = 0;
<b>bit</b> isBarrier = 0;
<b>bit</b> isCall = 0;
<b>bit</b> isSimpleLoad = 0;
<b>bit</b> mayLoad = 0;
<b>bit</b> mayStore = 0;
<b>bit</b> isImplicitDef = 0;
<b>bit</b> isTwoAddress = 1;
<b>bit</b> isConvertibleToThreeAddress = 1;
<b>bit</b> isCommutable = 1;
<b>bit</b> isTerminator = 0;
<b>dag</b> Pattern = (set R8, (plus R8, R8));
<b>bits</b>&lt;8&gt; Opcode = { 0, 0, 0, 0, 0, 0, 0, 0 };
<b>bit</b> isReMaterializable = 0;
<b>bit</b> isPredicable = 0;
<b>bit</b> hasDelaySlot = 0;
<b>bit</b> usesCustomDAGSchedInserter = 0;
<b>bit</b> hasCtrlDep = 0;
<b>bit</b> isNotDuplicable = 0;
<b>bit</b> hasSideEffects = 0;
<b>bit</b> mayHaveSideEffects = 0;
<b>bit</b> neverHasSideEffects = 0;
InstrItinClass Itinerary = NoItinerary;
<b>string</b> Constraints = "";
<b>string</b> DisableEncoding = "";
<b>bits</b>&lt;8&gt; Opcode = { 0, 0, 0, 0, 0, 0, 0, 1 };
Format Form = MRMDestReg;
<b>bits</b>&lt;5&gt; FormBits = { 0, 0, 0, 1, 1 };
ArgType Type = Arg8;
<b>bits</b>&lt;3&gt; TypeBits = { 0, 0, 1 };
<b>bits</b>&lt;6&gt; FormBits = { 0, 0, 0, 0, 1, 1 };
ImmType ImmT = NoImm;
<b>bits</b>&lt;3&gt; ImmTypeBits = { 0, 0, 0 };
<b>bit</b> hasOpSizePrefix = 0;
<b>bit</b> printImplicitUses = 0;
<b>bit</b> hasAdSizePrefix = 0;
<b>bits</b>&lt;4&gt; Prefix = { 0, 0, 0, 0 };
<b>bit</b> hasREX_WPrefix = 0;
FPFormat FPForm = ?;
<b>bits</b>&lt;3&gt; FPFormBits = { 0, 0, 0 };
}
...
</pre>
</div>
<p>This definition corresponds to an 8-bit register-register add instruction in
<p>This definition corresponds to a 32-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>
record&mdash;"<tt>ADD32rr</tt>" in this case&mdash;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, the pattern indicating how the
the instruction should be emitted into the assembly file, that 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>
<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
@ -162,16 +191,23 @@ 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>
<div class="doc_code">
<pre>
<b>def</b> ADDrr8 : I2A8&lt;"add", 0x00, MRMDestReg&gt;,
Pattern&lt;(set R8, (plus R8, R8))&gt;;
let Defs = [EFLAGS],
isCommutable = 1, <i>// X = ADD Y,Z --&gt; X = ADD Z,Y</i>
isConvertibleToThreeAddress = 1 <b>in</b> <i>// Can transform into LEA.</i>
def ADD32rr : I&lt;0x01, MRMDestReg, (outs GR32:$dst),
(ins GR32:$src1, GR32:$src2),
"add{l}\t{$src2, $dst|$dst, $src2}",
[(set GR32:$dst, (add GR32:$src1, GR32:$src2))]&gt;;
</pre>
</div>
<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 class <tt>I</tt> (extended from the
custom class <tt>X86Inst</tt>), 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>
@ -186,28 +222,37 @@ 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
-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>
list of these records), use the <tt>-print-enums</tt> option:</p>
<div class="doc_code">
<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,
SI, SP, ST0, ST1, ST2, ST3, ST4, ST5, ST6, ST7,
AH, AL, AX, BH, BL, BP, BPL, BX, CH, CL, CX, DH, DI, DIL, DL, DX, EAX, EBP, EBX,
ECX, EDI, EDX, EFLAGS, EIP, ESI, ESP, FP0, FP1, FP2, FP3, FP4, FP5, FP6, IP,
MM0, MM1, MM2, MM3, MM4, MM5, MM6, MM7, R10, R10B, R10D, R10W, R11, R11B, R11D,
R11W, R12, R12B, R12D, R12W, R13, R13B, R13D, R13W, R14, R14B, R14D, R14W, R15,
R15B, R15D, R15W, R8, R8B, R8D, R8W, R9, R9B, R9D, R9W, RAX, RBP, RBX, RCX, RDI,
RDX, RIP, RSI, RSP, SI, SIL, SP, SPL, ST0, ST1, ST2, ST3, ST4, ST5, ST6, ST7,
XMM0, XMM1, XMM10, XMM11, XMM12, XMM13, XMM14, XMM15, XMM2, XMM3, XMM4, XMM5,
XMM6, XMM7, XMM8, XMM9,
$ tblgen X86.td -print-enums -class=Instruction
ADCrr32, ADDri16, ADDri16b, ADDri32, ADDri32b, ADDri8, ADDrr16, ADDrr32,
ADDrr8, ADJCALLSTACKDOWN, ADJCALLSTACKUP, ANDri16, ANDri16b, ANDri32, ANDri32b,
ANDri8, ANDrr16, ANDrr32, ANDrr8, BSWAPr32, CALLm32, CALLpcrel32, ...
ABS_F, ABS_Fp32, ABS_Fp64, ABS_Fp80, ADC32mi, ADC32mi8, ADC32mr, ADC32ri,
ADC32ri8, ADC32rm, ADC32rr, ADC64mi32, ADC64mi8, ADC64mr, ADC64ri32, ADC64ri8,
ADC64rm, ADC64rr, ADD16mi, ADD16mi8, ADD16mr, ADD16ri, ADD16ri8, ADD16rm,
ADD16rr, ADD32mi, ADD32mi8, ADD32mr, ADD32ri, ADD32ri8, ADD32rm, ADD32rr,
ADD64mi32, ADD64mi8, ADD64mr, ADD64ri32, ...
</pre>
</div>
<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, 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>
@ -217,10 +262,12 @@ to what you need and formats it in the appropriate way.</p>
<!-- *********************************************************************** -->
<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>
<!-- ======================================================================= -->
@ -230,8 +277,10 @@ This section describes the syntax and the constructs allowed in a TableGen file.
<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>
<!-- -------------------------------------------------------------------------->
@ -240,6 +289,7 @@ the line, and it also supports <b>nestable</b> "<tt>/* */</tt>" comments.</p>
</div>
<div class="doc_text">
<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
@ -252,34 +302,41 @@ allows it to describe a wide range of information conveniently and compactly.
The TableGen types are:</p>
<ul>
<li>"<tt><b>bit</b></tt>" - A 'bit' is a boolean value that can hold either 0 or
1.</li>
<dl>
<li>"<tt><b>int</b></tt>" - The 'int' type represents a simple 32-bit integer
value, such as 5.</li>
<di><tt><b>bit</b></tt></di>
<dd>A 'bit' is a boolean value that can hold either 0 or 1.</dd>
<li>"<tt><b>string</b></tt>" - The 'string' type represents an ordered sequence
of characters of arbitrary length.</li>
<di><tt><b>int</b></tt></di>
<dd>The 'int' type represents a simple 32-bit integer value, such as 5.</dd>
<li>"<tt><b>bits</b>&lt;n&gt;</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>
<di><tt><b>string</b></tt></di>
<dd>The 'string' type represents an ordered sequence of characters of
arbitrary length.</dd>
<li>"<tt><b>list</b>&lt;ty&gt;</tt>" - This type represents a list whose
elements are some other type. The contained type is arbitrary: it can even be
another list type.</li>
<di><tt><b>bits</b>&lt;n&gt;</tt></di>
<dd>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.</dd>
<li>Class type - Specifying a class name in a type context means that the
defined value must be a subclass of the specified class. This is useful in
conjunction with the "list" type, for example, to constrain the elements of the
list to a common base class (e.g., a <tt><b>list</b>&lt;Register&gt;</tt> can
only contain definitions derived from the "<tt>Register</tt>" class).</li>
<di><tt><b>list</b>&lt;ty&gt;</tt></di>
<dd>This type represents a list whose elements are some other type. The
contained type is arbitrary: it can even be another list type.</dd>
<li>"<tt><b>code</b></tt>" - This represents a big hunk of text. NOTE: I don't
remember why this is distinct from string!</li>
<di>Class type</di>
<dd>Specifying a class name in a type context means that the defined value
must be a subclass of the specified class. This is useful in conjunction with
the <b><tt>list</tt></b> type, for example, to constrain the elements of the
list to a common base class (e.g., a <tt><b>list</b>&lt;Register&gt;</tt> can
only contain definitions derived from the "<tt>Register</tt>" class).</dd>
<li>"<tt><b>dag</b></tt>" - This type represents a nestable directed graph of
elements.</li>
<di><tt><b>dag</b></tt></di>
<dd>This type represents a nestable directed graph of elements.</dd>
<di><tt><b>code</b></tt></di>
<dd>This represents a big hunk of text. NOTE: I don't remember why this is
distinct from string!</dd>
</dl>
</ul>
<p>To date, these types have been sufficient for describing things that
@ -301,34 +358,54 @@ natural syntax and flavor for the application. The current expression forms
supported include:</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&lt;3&gt;" 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&lt;val list&gt;</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>
<dl>
<di><tt>?</tt></di>
<dd>uninitialized field</dd>
<di><tt>0b1001011</tt></di>
<dd>binary integer value</dd>
<di><tt>07654321</tt></di>
<dd>octal integer value (indicated by a leading 0)</dd>
<di><tt>7</tt></di>
<dd>decimal integer value</dd>
<di><tt>0x7F</tt></di>
<dd>hexadecimal integer value</dd>
<di><tt>"foo"</tt></di>
<dd>string value</dd>
<di><tt>[{ ... }]</tt></di>
<dd>code fragment</dd>
<di><tt>[ X, Y, Z ]</tt></di>
<dd>list value.</dd>
<di><tt>{ a, b, c }</tt></di>
<dd>initializer for a "bits&lt;3&gt;" value</dd>
<di><tt>value</tt></di>
<dd>value reference</dd>
<di><tt>value{17}</tt></di>
<dd>access to one bit of a value</dd>
<di><tt>value{15-17}</tt></di>
<dd>access to multiple bits of a value</dd>
<di><tt>DEF</tt></di>
<dd>reference to a record definition</dd>
<di><tt>CLASS&lt;val list&gt;</tt></di>
<dd>reference to a new anonymous definition of CLASS with the specified
template arguments.</dd>
<di><tt>X.Y</tt></di>
<dd>reference to the subfield of a value</dd>
<di><tt>list[4-7,17,2-3]</tt></di>
<dd>A slice of the 'list' list, including elements 4,5,6,7,17,2, and 3 from
it. Elements may be included multiple times.</dd>
<di><tt>(DEF a, b)</tt></di>
<dd>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.</dd>
<di><tt>!strconcat(a, b)</tt></di>
<dd>A string value that is the result of concatenating the 'a' and 'b'
strings.</dd>
</dl>
</ul>
<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&lt;4&gt;" value, for example.</p>
for different types. These rules allow you to assign a value like "<tt>7</tt>"
to a "<tt>bits&lt;4&gt;</tt>" value, for example.</p>
</div>
@ -345,11 +422,14 @@ 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 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>
("<tt>:</tt>"). 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 ("<tt>{}</tt>"); otherwise, the record ends with a
semicolon.</p>
<p>Here is a simple TableGen file:</p>
<div class="doc_code">
<pre>
<b>class</b> C { <b>bit</b> V = 1; }
<b>def</b> X : C;
@ -357,6 +437,7 @@ file:</p>
<b>string</b> Greeting = "hello";
}
</pre>
</div>
<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
@ -376,12 +457,14 @@ subclasses to override them as they wish.</p>
</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
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.</p>
</div>
<!-- -------------------------------------------------------------------------->
@ -390,17 +473,20 @@ equal sign. Value definitions require terminating semicolons.</p>
</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 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>
("<tt>=</tt>"), 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>
<div class="doc_code">
<pre>
<b>class</b> D : C { let V = 0; }
<b>def</b> Z : D;
</pre>
</div>
<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,
@ -414,11 +500,13 @@ because the <tt>D</tt> class overrode its value.</p>
</div>
<div class="doc_text">
<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>
<div class="doc_code">
<pre>
<b>class</b> FPFormat&lt;<b>bits</b>&lt;3&gt; val&gt; {
<b>bits</b>&lt;3&gt; Value = val;
@ -428,16 +516,20 @@ a simple example:</p>
<b>def</b> OneArgFP : FPFormat&lt;2&gt;;
<b>def</b> OneArgFPRW : FPFormat&lt;3&gt;;
<b>def</b> TwoArgFP : FPFormat&lt;4&gt;;
<b>def</b> SpecialFP : FPFormat&lt;5&gt;;
<b>def</b> CompareFP : FPFormat&lt;5&gt;;
<b>def</b> CondMovFP : FPFormat&lt;6&gt;;
<b>def</b> SpecialFP : FPFormat&lt;7&gt;;
</pre>
</div>
<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>
a list of "enumeration values", each with a "<tt>Value</tt>" 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>
<div class="doc_code">
<pre>
<b>class</b> ModRefVal&lt;<b>bits</b>&lt;2&gt; val&gt; {
<b>bits</b>&lt;2&gt; Value = val;
@ -449,7 +541,7 @@ useful in conjunction with template arguments. As an example:</p>
<b>def</b> ModRef : ModRefVal&lt;3&gt;;
<b>class</b> Value&lt;ModRefVal MR&gt; {
<i>// decode some information into a more convenient format, while providing
<i>// Decode some information into a more convenient format, while providing
// a nice interface to the user of the "Value" class.</i>
<b>bit</b> isMod = MR.Value{0};
<b>bit</b> isRef = MR.Value{1};
@ -462,12 +554,14 @@ useful in conjunction with template arguments. As an example:</p>
<b>def</b> zork : Value&lt;Ref&gt;;
<b>def</b> hork : Value&lt;ModRef&gt;;
</pre>
</div>
<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>
<div class="doc_code">
<pre>
<b>def</b> bork { <i>// Value</i>
<b>bit</b> isMod = 1;
@ -482,6 +576,7 @@ running <tt>tblgen</tt> on the example prints the following definitions:</p>
<b>bit</b> isRef = 1;
}
</pre>
</div>
<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.
@ -502,15 +597,16 @@ 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.
come in two forms: "<tt>reg = reg op reg</tt>" and "<tt>reg = reg op imm</tt>"
(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>
<div class="doc_code">
<pre>
<b>def</b> ops;
<b>def</b> GPR;
@ -524,18 +620,20 @@ Here is an example TableGen fragment that shows this idea:
(ops GPR:$dst, GPR:$src1, Imm:$src2)&gt;;
}
// Instantiations of the ri_inst multiclass.
<i>// Instantiations of the ri_inst multiclass.</i>
<b>defm</b> ADD : ri_inst&lt;0b111, "add"&gt;;
<b>defm</b> SUB : ri_inst&lt;0b101, "sub"&gt;;
<b>defm</b> MUL : ri_inst&lt;0b100, "mul"&gt;;
...
</pre>
</div>
<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>
appended to them, so this defines <tt>ADD_rr</tt>, <tt>ADD_ri</tt>,
<tt>SUB_rr</tt>, etc. Using a multiclass this way is exactly equivalent to
instantiating the classes multiple times yourself, e.g. by writing:</p>
<div class="doc_code">
<pre>
<b>def</b> ops;
<b>def</b> GPR;
@ -550,7 +648,7 @@ Here is an example TableGen fragment that shows this idea:
: inst&lt;opc, !strconcat(asmstr, " $dst, $src1, $src2"),
(ops GPR:$dst, GPR:$src1, Imm:$src2)&gt;;
// Instantiations of the ri_inst multiclass.
<i>// Instantiations of the ri_inst multiclass.</i>
<b>def</b> ADD_rr : rrinst&lt;0b111, "add"&gt;;
<b>def</b> ADD_ri : riinst&lt;0b111, "add"&gt;;
<b>def</b> SUB_rr : rrinst&lt;0b101, "sub"&gt;;
@ -559,6 +657,7 @@ Here is an example TableGen fragment that shows this idea:
<b>def</b> MUL_ri : riinst&lt;0b100, "mul"&gt;;
...
</pre>
</div>
</div>
@ -578,9 +677,11 @@ 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:</p>
<div class="doc_code">
<pre>
<b>include</b> "foo.td"
</pre>
</div>
</div>
@ -590,7 +691,8 @@ keyword. Example:</p>
</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
@ -600,22 +702,30 @@ end-user to factor out commonality from the records.</p>
apply, and one of more records to bind the values in. Here are some
examples:</p>
<div class="doc_code">
<pre>
<b>let</b> isTerminator = 1, isReturn = 1 <b>in</b>
<b>def</b> RET : X86Inst&lt;"ret", 0xC3, RawFrm, NoArg&gt;;
<b>let</b> isTerminator = 1, isReturn = 1, isBarrier = 1, hasCtrlDep = 1 <b>in</b>
<b>def</b> RET : I&lt;0xC3, RawFrm, (outs), (ins), "ret", [(X86retflag 0)]&gt;;
<b>let</b> isCall = 1 <b>in</b>
<i>// All calls clobber the non-callee saved registers...</i>
<b>let</b> Defs = [EAX, ECX, EDX, FP0, FP1, FP2, FP3, FP4, FP5, FP6] in {
<b>def</b> CALLpcrel32 : X86Inst&lt;"call", 0xE8, RawFrm, NoArg&gt;;
<b>def</b> CALLr32 : X86Inst&lt;"call", 0xFF, MRMS2r, Arg32&gt;;
<b>def</b> CALLm32 : X86Inst&lt;"call", 0xFF, MRMS2m, Arg32&gt;;
<b>let</b> Defs = [EAX, ECX, EDX, FP0, FP1, FP2, FP3, FP4, FP5, FP6, ST0,
MM0, MM1, MM2, MM3, MM4, MM5, MM6, MM7,
XMM0, XMM1, XMM2, XMM3, XMM4, XMM5, XMM6, XMM7, EFLAGS] <b>in</b> {
<b>def</b> CALLpcrel32 : Ii32<0xE8, RawFrm, (outs), (ins i32imm:$dst,variable_ops),
"call\t${dst:call}", []>;
<b>def</b> CALL32r : I<0xFF, MRM2r, (outs), (ins GR32:$dst, variable_ops),
"call\t{*}$dst", [(X86call GR32:$dst)]>;
<b>def</b> CALL32m : I<0xFF, MRM2m, (outs), (ins i32mem:$dst, variable_ops),
"call\t{*}$dst", []>;
}
</pre>
</div>
<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>
opened, as in the case with the <tt>CALL*</tt> instructions above.</p>
</div>
<!-- *********************************************************************** -->
@ -623,9 +733,11 @@ opened, as in the case with the CALL* instructions above.</p>
<!-- *********************************************************************** -->
<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 <tt>TableGen/Record.h</tt>.</p>
<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.
This should highlight the APIs in <tt>TableGen/Record.h</tt>.</p>
</div>
<!-- *********************************************************************** -->