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 @@ -72,12 +73,10 @@ find an emacs "TableGen mode" and a vim language file in the llvm/utils/emacs and llvm/utils/vim directories of your LLVM distribution, respectively.
-TableGen files consist of two key parts: 'classes' and 'definitions', both of which are considered 'records'.
@@ -112,9 +111,9 @@ multiclass, as if they were declared in the current multiclass.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 @@ -209,12 +208,20 @@ 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.
+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.
+TableGen runs just like any other LLVM tool. The first (optional) argument specifies the file to read. If a filename is not specified, tblgen @@ -256,27 +263,28 @@ what you need and formats it in the appropriate way.
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.
-TableGen supports BCPL style "//" comments, which run to the end of the line, and it also supports nestable "/* */" comments.
@@ -284,11 +292,11 @@ the line, and it also supports nestable "/* */" comments.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 @@ -344,11 +352,11 @@ needed.
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 @@ -400,6 +408,10 @@ which case the user must specify it explicitly.
As mentioned in the intro, classes and definitions (collectively known as 'records') in TableGen are the main high-level unit of @@ -473,14 +487,12 @@ 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.
-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 @@ -492,11 +504,11 @@ equal sign. Value definitions require terminating semicolons.
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 @@ -519,11 +531,11 @@ because the D class overrode its value.
TableGen permits the definition of parameterized classes as well as normal concrete classes. Parameterized TableGen classes specify a list of variable @@ -610,11 +622,11 @@ X86 backend.
While classes with template arguments are a good way to factor commonality @@ -772,17 +784,21 @@ before them.
TableGen supports the 'include' 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 'include' @@ -797,11 +813,11 @@ keyword. Example:
"Let" expressions at file scope are similar to "let" expressions within a record, except they can specify a value binding for @@ -864,11 +880,15 @@ several levels of multiclass instanciations. This also avoids the need of using
Expressions used by code generator to describe instructions and isel patterns:
@@ -882,10 +902,10 @@ patterns: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.