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Summary: It concatenates two or more lists. In addition to the !strconcat semantics the lists must have the same element type. My overall aim is to make it easy to append to Instruction.Predicates rather than override it. This can be done by concatenating lists passed as arguments, or by concatenating lists passed in additional fields. Reviewers: dsanders Reviewed By: dsanders Subscribers: hfinkel, llvm-commits Differential Revision: http://reviews.llvm.org/D3506 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208183 91177308-0d34-0410-b5e6-96231b3b80d8
385 lines
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ReStructuredText
385 lines
11 KiB
ReStructuredText
===========================
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TableGen Language Reference
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===========================
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.. contents::
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:local:
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.. warning::
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This document is extremely rough. If you find something lacking, please
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fix it, file a documentation bug, or ask about it on llvmdev.
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Introduction
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============
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This document is meant to be a normative spec about the TableGen language
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in and of itself (i.e. how to understand a given construct in terms of how
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it affects the final set of records represented by the TableGen file). If
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you are unsure if this document is really what you are looking for, please
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read the :doc:`introduction to TableGen <index>` first.
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Notation
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========
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The lexical and syntax notation used here is intended to imitate
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`Python's`_. In particular, for lexical definitions, the productions
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operate at the character level and there is no implied whitespace between
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elements. The syntax definitions operate at the token level, so there is
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implied whitespace between tokens.
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.. _`Python's`: http://docs.python.org/py3k/reference/introduction.html#notation
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Lexical Analysis
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================
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TableGen supports BCPL (``// ...``) and nestable C-style (``/* ... */``)
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comments.
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The following is a listing of the basic punctuation tokens::
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- + [ ] { } ( ) < > : ; . = ? #
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Numeric literals take one of the following forms:
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.. TableGen actually will lex some pretty strange sequences an interpret
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them as numbers. What is shown here is an attempt to approximate what it
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"should" accept.
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.. productionlist::
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TokInteger: `DecimalInteger` | `HexInteger` | `BinInteger`
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DecimalInteger: ["+" | "-"] ("0"..."9")+
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HexInteger: "0x" ("0"..."9" | "a"..."f" | "A"..."F")+
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BinInteger: "0b" ("0" | "1")+
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One aspect to note is that the :token:`DecimalInteger` token *includes* the
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``+`` or ``-``, as opposed to having ``+`` and ``-`` be unary operators as
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most languages do.
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TableGen has identifier-like tokens:
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.. productionlist::
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ualpha: "a"..."z" | "A"..."Z" | "_"
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TokIdentifier: ("0"..."9")* `ualpha` (`ualpha` | "0"..."9")*
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TokVarName: "$" `ualpha` (`ualpha` | "0"..."9")*
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Note that unlike most languages, TableGen allows :token:`TokIdentifier` to
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begin with a number. In case of ambiguity, a token will be interpreted as a
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numeric literal rather than an identifier.
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TableGen also has two string-like literals:
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.. productionlist::
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TokString: '"' <non-'"' characters and C-like escapes> '"'
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TokCodeFragment: "[{" <shortest text not containing "}]"> "}]"
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:token:`TokCodeFragment` is essentially a multiline string literal
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delimited by ``[{`` and ``}]``.
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.. note::
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The current implementation accepts the following C-like escapes::
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\\ \' \" \t \n
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TableGen also has the following keywords::
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bit bits class code dag
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def foreach defm field in
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int let list multiclass string
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TableGen also has "bang operators" which have a
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wide variety of meanings:
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.. productionlist::
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BangOperator: one of
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:!eq !if !head !tail !con
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:!add !shl !sra !srl
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:!cast !empty !subst !foreach !listconcat !strconcat
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Syntax
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======
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TableGen has an ``include`` mechanism. It does not play a role in the
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syntax per se, since it is lexically replaced with the contents of the
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included file.
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.. productionlist::
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IncludeDirective: "include" `TokString`
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TableGen's top-level production consists of "objects".
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.. productionlist::
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TableGenFile: `Object`*
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Object: `Class` | `Def` | `Defm` | `Let` | `MultiClass` | `Foreach`
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``class``\es
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------------
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.. productionlist::
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Class: "class" `TokIdentifier` [`TemplateArgList`] `ObjectBody`
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A ``class`` declaration creates a record which other records can inherit
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from. A class can be parametrized by a list of "template arguments", whose
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values can be used in the class body.
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A given class can only be defined once. A ``class`` declaration is
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considered to define the class if any of the following is true:
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.. break ObjectBody into its consituents so that they are present here?
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#. The :token:`TemplateArgList` is present.
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#. The :token:`Body` in the :token:`ObjectBody` is present and is not empty.
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#. The :token:`BaseClassList` in the :token:`ObjectBody` is present.
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You can declare an empty class by giving and empty :token:`TemplateArgList`
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and an empty :token:`ObjectBody`. This can serve as a restricted form of
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forward declaration: note that records deriving from the forward-declared
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class will inherit no fields from it since the record expansion is done
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when the record is parsed.
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.. productionlist::
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TemplateArgList: "<" `Declaration` ("," `Declaration`)* ">"
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Declarations
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------------
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.. Omitting mention of arcane "field" prefix to discourage its use.
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The declaration syntax is pretty much what you would expect as a C++
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programmer.
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.. productionlist::
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Declaration: `Type` `TokIdentifier` ["=" `Value`]
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It assigns the value to the identifer.
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Types
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-----
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.. productionlist::
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Type: "string" | "code" | "bit" | "int" | "dag"
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:| "bits" "<" `TokInteger` ">"
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:| "list" "<" `Type` ">"
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:| `ClassID`
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ClassID: `TokIdentifier`
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Both ``string`` and ``code`` correspond to the string type; the difference
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is purely to indicate programmer intention.
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The :token:`ClassID` must identify a class that has been previously
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declared or defined.
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Values
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------
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.. productionlist::
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Value: `SimpleValue` `ValueSuffix`*
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ValueSuffix: "{" `RangeList` "}"
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:| "[" `RangeList` "]"
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:| "." `TokIdentifier`
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RangeList: `RangePiece` ("," `RangePiece`)*
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RangePiece: `TokInteger`
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:| `TokInteger` "-" `TokInteger`
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:| `TokInteger` `TokInteger`
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The peculiar last form of :token:`RangePiece` is due to the fact that the
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"``-``" is included in the :token:`TokInteger`, hence ``1-5`` gets lexed as
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two consecutive :token:`TokInteger`'s, with values ``1`` and ``-5``,
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instead of "1", "-", and "5".
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The :token:`RangeList` can be thought of as specifying "list slice" in some
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contexts.
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:token:`SimpleValue` has a number of forms:
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.. productionlist::
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SimpleValue: `TokIdentifier`
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The value will be the variable referenced by the identifier. It can be one
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of:
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.. The code for this is exceptionally abstruse. These examples are a
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best-effort attempt.
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* name of a ``def``, such as the use of ``Bar`` in::
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def Bar : SomeClass {
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int X = 5;
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}
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def Foo {
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SomeClass Baz = Bar;
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}
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* value local to a ``def``, such as the use of ``Bar`` in::
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def Foo {
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int Bar = 5;
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int Baz = Bar;
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}
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* a template arg of a ``class``, such as the use of ``Bar`` in::
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class Foo<int Bar> {
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int Baz = Bar;
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}
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* value local to a ``multiclass``, such as the use of ``Bar`` in::
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multiclass Foo {
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int Bar = 5;
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int Baz = Bar;
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}
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* a template arg to a ``multiclass``, such as the use of ``Bar`` in::
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multiclass Foo<int Bar> {
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int Baz = Bar;
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}
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.. productionlist::
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SimpleValue: `TokInteger`
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This represents the numeric value of the integer.
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.. productionlist::
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SimpleValue: `TokString`+
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Multiple adjacent string literals are concatenated like in C/C++. The value
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is the concatenation of the strings.
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.. productionlist::
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SimpleValue: `TokCodeFragment`
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The value is the string value of the code fragment.
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.. productionlist::
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SimpleValue: "?"
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``?`` represents an "unset" initializer.
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.. productionlist::
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SimpleValue: "{" `ValueList` "}"
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ValueList: [`ValueListNE`]
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ValueListNE: `Value` ("," `Value`)*
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This represents a sequence of bits, as would be used to initialize a
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``bits<n>`` field (where ``n`` is the number of bits).
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.. productionlist::
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SimpleValue: `ClassID` "<" `ValueListNE` ">"
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This generates a new anonymous record definition (as would be created by an
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unnamed ``def`` inheriting from the given class with the given template
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arguments) and the value is the value of that record definition.
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.. productionlist::
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SimpleValue: "[" `ValueList` "]" ["<" `Type` ">"]
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A list initializer. The optional :token:`Type` can be used to indicate a
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specific element type, otherwise the element type will be deduced from the
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given values.
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.. The initial `DagArg` of the dag must start with an identifier or
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!cast, but this is more of an implementation detail and so for now just
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leave it out.
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.. productionlist::
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SimpleValue: "(" `DagArg` `DagArgList` ")"
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DagArgList: `DagArg` ("," `DagArg`)*
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DagArg: `Value` [":" `TokVarName`] | `TokVarName`
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The initial :token:`DagArg` is called the "operator" of the dag.
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.. productionlist::
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SimpleValue: `BangOperator` ["<" `Type` ">"] "(" `ValueListNE` ")"
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Bodies
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------
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.. productionlist::
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ObjectBody: `BaseClassList` `Body`
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BaseClassList: [":" `BaseClassListNE`]
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BaseClassListNE: `SubClassRef` ("," `SubClassRef`)*
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SubClassRef: (`ClassID` | `MultiClassID`) ["<" `ValueList` ">"]
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DefmID: `TokIdentifier`
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The version with the :token:`MultiClassID` is only valid in the
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:token:`BaseClassList` of a ``defm``.
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The :token:`MultiClassID` should be the name of a ``multiclass``.
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.. put this somewhere else
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It is after parsing the base class list that the "let stack" is applied.
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.. productionlist::
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Body: ";" | "{" BodyList "}"
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BodyList: BodyItem*
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BodyItem: `Declaration` ";"
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:| "let" `TokIdentifier` [`RangeList`] "=" `Value` ";"
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The ``let`` form allows overriding the value of an inherited field.
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``def``
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-------
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.. TODO::
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There can be pastes in the names here, like ``#NAME#``. Look into that
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and document it (it boils down to ParseIDValue with IDParseMode ==
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ParseNameMode). ParseObjectName calls into the general ParseValue, with
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the only different from "arbitrary expression parsing" being IDParseMode
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== Mode.
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.. productionlist::
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Def: "def" `TokIdentifier` `ObjectBody`
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Defines a record whose name is given by the :token:`TokIdentifier`. The
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fields of the record are inherited from the base classes and defined in the
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body.
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Special handling occurs if this ``def`` appears inside a ``multiclass`` or
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a ``foreach``.
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``defm``
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--------
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.. productionlist::
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Defm: "defm" `TokIdentifier` ":" `BaseClassListNE` ";"
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Note that in the :token:`BaseClassList`, all of the ``multiclass``'s must
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precede any ``class``'s that appear.
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``foreach``
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-----------
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.. productionlist::
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Foreach: "foreach" `Declaration` "in" "{" `Object`* "}"
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:| "foreach" `Declaration` "in" `Object`
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The value assigned to the variable in the declaration is iterated over and
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the object or object list is reevaluated with the variable set at each
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iterated value.
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Top-Level ``let``
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-----------------
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.. productionlist::
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Let: "let" `LetList` "in" "{" `Object`* "}"
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:| "let" `LetList` "in" `Object`
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LetList: `LetItem` ("," `LetItem`)*
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LetItem: `TokIdentifier` [`RangeList`] "=" `Value`
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This is effectively equivalent to ``let`` inside the body of a record
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except that it applies to multiple records at a time. The bindings are
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applied at the end of parsing the base classes of a record.
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``multiclass``
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--------------
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.. productionlist::
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MultiClass: "multiclass" `TokIdentifier` [`TemplateArgList`]
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: [":" `BaseMultiClassList`] "{" `MultiClassObject`+ "}"
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BaseMultiClassList: `MultiClassID` ("," `MultiClassID`)*
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MultiClassID: `TokIdentifier`
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MultiClassObject: `Def` | `Defm` | `Let` | `Foreach`
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