From 85234aca74411051406287a3b1991947feff6810 Mon Sep 17 00:00:00 2001 From: Misha Brukman Date: Wed, 12 May 2004 18:31:21 +0000 Subject: [PATCH] Make document HTML-4.01 (Strict) compliant. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13497 91177308-0d34-0410-b5e6-96231b3b80d8 --- docs/TableGenFundamentals.html | 449 ++++++++++++++------------------- 1 file changed, 184 insertions(+), 265 deletions(-) diff --git a/docs/TableGenFundamentals.html b/docs/TableGenFundamentals.html index a74ffe3f0e1..c63c5cef5fa 100644 --- a/docs/TableGenFundamentals.html +++ b/docs/TableGenFundamentals.html @@ -9,42 +9,44 @@
TableGen Fundamentals
+
+
Introduction
@@ -62,72 +64,56 @@ makes it easier to structure domain specific information.

The core part of TableGen parses a file, instantiates the declarations, and hands the result off to a domain-specific "TableGen backend" for processing. The current major user -of TableGen is the LLVM code generator. -

+of TableGen is the LLVM code generator.

-

-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 llvm/utils/emacs -and llvm/utils/vim directory of your LLVM distribution, respectively. -

+

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 +llvm/utils/emacs and llvm/utils/vim directory of your LLVM +distribution, respectively.

-
- Basic concepts -
+
Basic concepts
-

-TableGen files consist of two key parts: 'classes' and 'definitions', both of -which are considered 'records'. -

+

TableGen files consist of two key parts: 'classes' and 'definitions', both +of which are considered 'records'.

-

-TableGen records have a unique name, a list of values, and a list of +

TableGen records 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 TableGen backend, but the structure and format rules are -taken care of and fixed by TableGen. -

- -

-TableGen definitions are the concrete form of 'records'. These generally -do not have any undefined values, and are marked with the 'def' -keyword. -

- -

-TableGen classes 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". -

+taken care of and fixed by TableGen.

+ +

TableGen definitions are the concrete form of 'records'. These +generally do not have any undefined values, and are marked with the +'def' keyword.

+ +

TableGen classes 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".

-
- An example record -
+
An example record
-

-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 X86.td file -prints this (at the time of this writing): -

+

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 X86.td +file prints this (at the time of this writing):

-

 ...
 def ADDrr8 {    // Instruction X86Inst I2A8 Pattern
@@ -153,64 +139,53 @@ prints this (at the time of this writing):
   bits<3> FPFormBits = { 0, 0, 0 };
 }
 ...
-

+ -

-This definition corresponds to an 8-bit register-register add instruction in the -X86. The string after the 'def' string indicates the name of the +

This definition corresponds to an 8-bit register-register add instruction in +the X86. The string after the 'def' string indicates the name of the record ("ADDrr8" 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 "add" 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. -

+specific to the needs of the X86 backend, and is only shown as an example.

-

-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: -

+

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:

-

+
 def ADDrr8   : I2A8<"add", 0x00, MRMDestReg>,
                Pattern<(set R8, (plus R8, R8))>;
-

-
-

-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.
-

+
+ +

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.

-
- Running TableGen -
+
Running TableGen
-

-TableGen runs just like any other LLVM tool. The first (optional) argument +

TableGen runs just like any other LLVM tool. The first (optional) argument specifies the file to read. If a filename is not specified, tblgen -reads from standard input. -

+reads from standard input.

-

-To be useful, one of the TableGen backends must be used. -These backends are selectable on the command line (type 'tblgen --help' -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 --print-enums option: -

+

To be useful, one of the TableGen backends must be +used. These backends are selectable on the command line (type 'tblgen +--help' 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 --print-enums option:

-

+
 $ 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,
@@ -220,18 +195,14 @@ $ 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, ...
-

+
-

-The default backend prints out all of the records, as described above. -

+

The default backend prints out all of the records, as described above.

-

-If you plan to use TableGen for some purpose, you will most likely have to write a backend that extracts the information specific to -what you need and formats it in the appropriate way. -

+

If you plan to use TableGen for some purpose, you will most likely have to +write a backend that extracts the information specific +to what you need and formats it in the appropriate way.

@@ -241,54 +212,39 @@ 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. +

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 primitives -
+
TableGen primitives
- -
- TableGen comments -
+ +
TableGen comments
-

TableGen supports BCPL style "//" comments, which run to the end of the line, and it also supports nestable "/* */" comments.

-
- - -
- The TableGen type system + +
The TableGen type system
-

-TableGen files are strongly typed, in a simple (but complete) type-system. +

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 value definition is required to have an associated type.

-

-TableGen supports a mixture of very low-level types (such as bit) and -very high-level types (such as dag). This flexibility is what allows -it to describe a wide range of information conveniently and compactly. The -TableGen types are: -

+

TableGen supports a mixture of very low-level types (such as bit) +and very high-level types (such as dag). This flexibility is what +allows it to describe a wide range of information conveniently and compactly. +The TableGen types are:

-

  • "bit" - A 'bit' is a boolean value that can hold either 0 or 1.
    • @@ -319,29 +275,25 @@ remember why this is distinct from string!
  • "dag" - This type represents a nestable directed graph of elements.
-

-

-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. -

+

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.

- +
- TableGen values and expressions + TableGen values and expressions
-

-TableGen allows for a pretty reasonable number of different expression forms +

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: -

+supported include:

-

    +
    • ? - Uninitialized field.
    • 0b1001011 - Binary integer value.
    • 07654321 - Octal integer value (indicated by a leading 0).
      • @@ -360,27 +312,20 @@ supported include: definition, the remaining elements in the list may be arbitrary other values, including nested 'dag' values. -

    +
-

-Note that all of the values have rules specifying how they convert to values +

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. -

- - +"bits<4>" value, for example.

- -
- Classes and definitions +
Classes and definitions
-

-As mentioned in the intro, classes and definitions +

As mentioned in the intro, 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 def or class keyword, the record name, and an optional list of "value definitions or let expressions are needed for the class, they are enclosed in curly braces ("{}"); otherwise, the record ends with a semicolon. Here is a simple TableGen -file: -

+file:

-

+
 class C { bit V = 1; }
 def X : C;
 def Y : C {
   string Greeting = "hello";
 }
-

+
-

-This example defines two definitions, X and Y, both of which -derive from the C class. Because of this, they both get the V -bit value. The Y definition also gets the Greeting member as well. -

+

This example defines two definitions, X and Y, both of +which derive from the C class. Because of this, they both get the +V bit value. The Y definition also gets the Greeting member +as well.

-

-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. -

+

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.

- +
- Value definitions + Value definitions
-

-Value definitions define named entries in records. A value must be defined +

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 let expression. A value is defined by specifying a TableGen type 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.

- +
- 'let' expressions + 'let' expressions
-

-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 -'let' 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 V field for all of its subclasses:

- -

+
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 'let' 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 V field for all of its subclasses:

+
+
 class D : C { let V = 0; }
 def Z : D;
-

+
-

-In this case, the Z definition will have a zero value for its "V" +

In this case, the Z definition will have a zero value for its "V" value, despite the fact that it derives (indirectly) from the C class, -because the D class overrode its value. -

+because the D class overrode its value.

- +
- Class template arguments + Class template arguments
-

-TableGen permits the definition of parameterized classes as well as normal +

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:

-

+
 class FPFormat<bits<3> val> {
   bits<3> Value = val;
 }
@@ -479,17 +415,16 @@ a simple example:

 def OneArgFPRW : FPFormat<3>;
 def TwoArgFP   : FPFormat<4>;
 def SpecialFP  : FPFormat<5>;
-

+
-

-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 +

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.

The more esoteric forms of TableGen expressions are useful in conjunction with template arguments. As an example:

-

+
 class ModRefVal<bits<2> val> {
   bits<2> Value = val;
 }
@@ -512,15 +447,14 @@ useful in conjunction with template arguments.  As an example:

 def bork : Value<Mod>;
 def zork : Value<Ref>;
 def hork : Value<ModRef>;
-

+
-

-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 +

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 tblgen on the example prints the following definitions:

-

+
 def bork {      // Value
   bit isMod = 1;
   bit isRef = 0;
@@ -533,61 +467,54 @@ running tblgen on the example prints the following definitions:

   bit isMod = 0;
   bit isRef = 1;
 }
-

+
-

-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.

+

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.

- -
- File scope entities + File scope entities
- +
- File inclusion + File inclusion
-

-TableGen supports the 'include' token, which textually substitutes the -specified file in place of the include directive. The filename should be +

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' -keyword. Example: +keyword. Example:

-

+
 include "foo.td"
-

+
- +
- 'let' expressions + 'let' expressions
-

-"let" expressions at file scope are similar to "let" +

"let" expressions at file scope are similar to "let" expressions within a record, 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. -

+end-user to factor out commonality from the records.

-

-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: -

+

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:

-

+
 let isTerminator = 1, isReturn = 1 in
   def RET : X86Inst<"ret", 0xC3, RawFrm, NoArg>;
 
@@ -598,56 +525,48 @@ and one of more records to bind the values in.  Here are some examples:
     def CALLr32     : X86Inst<"call", 0xFF, MRMS2r, Arg32>;
     def CALLm32     : X86Inst<"call", 0xFF, MRMS2m, Arg32>;
   }
-

+
-

-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. -

+

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.

-
TableGen backends
- -

-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. -

- +

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.

- -
The LLVM code generator
+
The LLVM code generator +
- -

-This is just a temporary, convenient, place to put stuff about the code +

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. -

- +expect.

- - +
-
-
Chris Lattner
- The LLVM Compiler Infrastructure -
+
+ Valid CSS! + Valid HTML 4.01! + + Chris Lattner
+ LLVM Compiler Infrastructure
Last modified: $Date$ -
+ -- 2.34.1