[MLIR] Attribute and type formats in ODS

[Mogball]

Summary

Declarative attribute and type formats with assembly formats. Define an
assemblyFormat field in attribute and type defs with a mnemonic to
generate a parser and printer.

tablegen
def MyAttr : AttrDef<MyDialect, "MyAttr"> {
  let parameters = (ins "int64_t":$count, "AffineMap":$map);
  let mnemonic = "my_attr";
  let assemblyFormat = "`<` $count `,` $map `>`";
}

Use struct to define a comma-separated list of key-value pairs:

tablegen
def MyType : TypeDef<MyDialect, "MyType"> {
  let parameters = (ins "int":$one, "int":$two, "int":$three);
  let mnemonic = "my_attr";
  let assemblyFormat = "`<` $three `:` struct($one, $two) `>`";
}

Use struct(*) to capture all parameters.

[mehdi_amini]

I have one more feature request please: can we support "default values", like omitting an entry if it matches the default value and setting the default value when it is missing from the text?

[Mogball]

In D111594#3056877, @mehdi_amini wrote:

I have one more feature request please: can we support "default values", like omitting an entry if it matches the default value and setting the default value when it is missing from the text?

You're talking about for struct directive right?

[mehdi_amini]

In D111594#3056930, @Mogball wrote:

In D111594#3056877, @mehdi_amini wrote:

I have one more feature request please: can we support "default values", like omitting an entry if it matches the default value and setting the default value when it is missing from the text?

You're talking about for struct directive right?

I think it'd be applicable to struct somehow, but also more widely. I'm not sure what would be the best syntax in the declarative assembly for that. But also I wonder if the concept of a default value isn't in itself something to include on the let parameters = instead. This could impact the builder as well maybe.

[rriddle]

Took a quick glance, looks pretty good.

mlir/include/mlir/IR/DialectImplementation.h

105–112

nit: Can you move this lambda into a separate variable?

mlir/include/mlir/TableGen/Dialect.h

6

Nice

mlir/include/mlir/TableGen/FormatGen.h

1 ↗

(On Diff #378845)

Do we need this in the public Tablegen API? Can we move this to mlir-tblgen instead? I don't think we want this exposes in the public facing API.

mlir/lib/TableGen/FormatGen.cpp

21–22 ↗

(On Diff #378845)

mlir/test/lib/Dialect/Test/TestAttributes.cpp

136–153

Mark these as static and drop the anonymous namespace. Only classes should really be placed in those.

mlir/tools/mlir-tblgen/FormatParser.h

1 ↗

(On Diff #378845)

Unused?

[Mogball]

mlir/test/lib/Dialect/Test/TestAttributes.cpp

136–153

I need to stop forgetting about this rule

mlir/tools/mlir-tblgen/FormatParser.h

1 ↗

(On Diff #378845)

Indeed

[Mogball]

In D111594#3056931, @mehdi_amini wrote:

In D111594#3056930, @Mogball wrote:

In D111594#3056877, @mehdi_amini wrote:

I have one more feature request please: can we support "default values", like omitting an entry if it matches the default value and setting the default value when it is missing from the text?

You're talking about for struct directive right?

I think it'd be applicable to struct somehow, but also more widely. I'm not sure what would be the best syntax in the declarative assembly for that. But also I wonder if the concept of a default value isn't in itself something to include on the let parameters = instead. This could impact the builder as well maybe.

I was thinking purely in terms of struct: struct($one = 5, $two = "foo") which would be cleanest to implement IMO.

But of course default-valued parameters should extend beyond that. In which case it could be implemented much the same way default/optional attributes in ops are:

let parameters = (ins DefaultValuedParam<"int", "5">:$one, 
                      DefaultValuedParam<StringRefParameter, "\"foo\"">:$two);

[rriddle]

In D111594#3057166, @Mogball wrote:

In D111594#3056931, @mehdi_amini wrote:

In D111594#3056930, @Mogball wrote:

In D111594#3056877, @mehdi_amini wrote:

I have one more feature request please: can we support "default values", like omitting an entry if it matches the default value and setting the default value when it is missing from the text?

You're talking about for struct directive right?

I think it'd be applicable to struct somehow, but also more widely. I'm not sure what would be the best syntax in the declarative assembly for that. But also I wonder if the concept of a default value isn't in itself something to include on the let parameters = instead. This could impact the builder as well maybe.

I was thinking purely in terms of struct: struct($one = 5, $two = "foo") which would be cleanest to implement IMO.

But of course default-valued parameters should extend beyond that. In which case it could be implemented much the same way default/optional attributes in ops are:

let parameters = (ins DefaultValuedParam<"int", "5">:$one, 
                      DefaultValuedParam<StringRefParameter, "\"foo\"">:$two);

Yeah, I think the cleanest thing would be to incorporate this in the parameters themselves (i.e. on the attribute definition). The assembly format could then be taught to understand defaults (it might be cleanest to work this into how parameters get anchored for "optional groups").

[Mogball]

Fixes for review comments

[Mogball]

Will follow-up with a CL implementing default-valued parameters + optional groups in formats

[jpienaar]

mlir/test/mlir-tblgen/attr-or-type-format.mlir

110

Nit: could you name the functions to reflect what you are testing?

[Mogball]

Describing/naming test cases for attr-or-type-format

[Mogball]

Fix test cases

[Mogball]

This comment was removed by Mogball.

[Mogball]

pushed wrong diff...

[Mogball]

parsers of attributes or types with verifiers should call
getChecked

[rriddle]

mlir/test/lib/Dialect/Test/TestTypeDefs.td

217

Is this wrapped at 80?

mlir/test/mlir-tblgen/attr-or-type-format.mlir

5

Can you move all of these expected-error to the previous line and use either expected-error@+1 or expected-error@below?

mlir/test/mlir-tblgen/attr-or-type-format.td

36–48

Can you clean these up? Splitting them into different lines doesn't really help understand what this is supposed to be testing. (Same applies throughout this file).

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

109

110

Can this method be const?

183

Please document this.

208

Include mlir/Support/LLVM.h and you can drop the llvm:: on all of these raw_ostream.

231–232

Please document these.

243–244

You don't need to specify the comment with the definition, especially if it is in the same file.

260–261

Spell out auto here.

273

Spell out auto here.

286

same here.

367

I'd drop all of these hardcoded indents honestly. They don't provide much over explicitly specifying the spaces.

378–384

Is it really important to let them be in any order as opposed to say always alphabetical order (or order as specified in the directive)?

465–469

642–643

These methods should be defined top-level. Only the class should be in the namespace.

655

Spell out auto here.

691–701

I would have expected this to be defined with the ODS gen, as opposed to the format generator.

716

Spell out auto here.

718

It's kind of weird seeing the format namespace next to the variable name.

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.h

25

Please document this.

[Mogball]

mlir/test/lib/Dialect/Test/TestTypeDefs.td

217

This line's 76 characters.

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

378–384

If this were a fresh feature, I'd say "probably not", but since the struct directive is meant as a gateway to deprecate StructAttr, which is a DictionaryAttr, it needs to allow the parameters in any order (or else all the test cases will need to be fixed).

642–643

Ah, didn't know it also applied to member function definitions of anonymous-namespaced classes

[Mogball]

Review comments

[rriddle]

Can you document this in Tutorials/DefiningAttributesAndTypes.md?

mlir/test/mlir-tblgen/attr-or-type-format.td

155–157

Can you trim this down to 2? Or is there something being tested for 4 params?

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

527–528

Please remove the format token here. It makes the parser less local, because it relies on someone else having parsed the next token. This should use a similar form (i.e. have a currentToken, consumeToken, etc) as the other parser.

565–566

When does this happen? Why not let it be caught in the next call to parseElement?

571–576

Given that you need the index, why not llvm::enumerate?

655–656

Nit: You could just use SmallVector here (and give it a hint for the size, or let it pick one which would honestly be a pretty good choice here).

662–670

llvm::enumerate?

674

nit: Spell out auto here.

[Mogball]

• Change FormatParser to use curToken and consumeToken instead of passing tokens around
• Other review comments

[Mogball]

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

527–528

This "paradigm" personally made more sense to me, but I will change it to match the other parser. If I ever have to write a third format parser like this one, I will definitely try to abstract a lot of this duplicated logic away.

571–576

Because I didn't know it existed :)

[rriddle]

Did a scan and code looks alright, but still missing documentation?

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

593

Leftover debugging?

624–626

Drop the trivial braces here.

[Mogball]

Add documentation for attribute and type assembly formats
(and fixing review comments)

[rriddle]

LGTM after resolving the last comment.

mlir/docs/Tutorials/DefiningAttributesAndTypes.md

521

Would it be better to have a directive that represents all parameters? This seems a bit magical to me, and having a parameters/params directive also better matches the op format.

[Mogball]

mlir/docs/Tutorials/DefiningAttributesAndTypes.md

521

Personally, params, drawing a parallel with op formats, would intuitively expand to a comma-separated list of the parameters. But struct(...) indicates that the parameters captured inside the directive will be parsed and printed in a key-value list form, where order doesn't matter, and the * is just a shorthand for "capture all the parameters".

I debated with just using struct instead of struct(*) but struct on its own doesn't do enough to indicate what's going on.

[rriddle]

mlir/docs/Tutorials/DefiningAttributesAndTypes.md

521

But struct(...) indicates that the parameters captured inside the directive will be parsed and printed in a key-value list form, where order doesn't matter, and the * is just a shorthand for "capture all the parameters".

I'm not sure I agree here. Why would struct(params) be different from struct($a, $b, $c)?

[Mogball]

mlir/docs/Tutorials/DefiningAttributesAndTypes.md

521

Oh, I thought you meant params entirely instead of struct(*). I'm okay with struct(params)

[Mogball]

struct(*) -> struct(params)

And added params directive.

[rriddle]

mlir/docs/Tutorials/DefiningAttributesAndTypes.md

499

Can we have it just mean a comma list of parameter values when used outside of struct?

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

684–686

Drop trivial braces here.

698–700

Can we move this to the parser for the params directive instead? It feels like it would compose better, especially if the params directive is usable outside of struct.

[Mogball]

mlir/docs/Tutorials/DefiningAttributesAndTypes.md

499

Very well.

[Mogball]

Make params directive functional.

[rriddle]

LG, let's land and then iterate in tree.

[silvas]

Yay!!

[mehdi_amini]

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

511

I'm a bit puzzled by the conditional here, the emitted code isn't just "insert a space" like the comment indicates. What am I misunderstanding here?

[mehdi_amini]

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

511

Scratch it, I misread the code, to many meta levels here...

mlir/docs/Tutorials/DefiningAttributesAndTypes.md

 the things named `*Type` are generally now named `*Attr`.
 
 *   `Type::TypeBase` -> `Attribute::AttrBase`
 *   `TypeStorageAllocator` -> `AttributeStorageAllocator`
 *   `addTypes` -> `addAttributes`
 
 Aside from that, all of the interfaces for uniquing and storage construction are
 all the same.
+
+## Defining Custom Parsers and Printers using Assembly Formats
+
+Attributes and types defined in ODS with a mnemonic can define an
+`assemblyFormat` to declaratively describe custom parsers and printers. The
+assembly format consists of literals, variables, and directives.
+
+* A literal is a keyword or valid punctuation enclosed in backticks, e.g.
+  `` `keyword` `` or `` `<` ``.
+* A variable is a parameter name preceeded by a dollar sign, e.g. `$param0`,
+  which captures one attribute or type parameter.
+* A directive is a keyword followed by an optional argument list that defines
+  special parser and printer behaviour.
+
+```tablegen
+// An example type with an assembly format.
+def MyType : TypeDef<My_Dialect, "MyType"> {
+  // Define a mnemonic to allow the dialect's parser hook to call into the
+  // generated parser.
+  let mnemonic = "my_type";
+
+  // Define two parameters whose C++ types are indicated in string literals.
+  let parameters = (ins "int":$count, "AffineMap":$map);
+
+  // Define the assembly format. Surround the format with less `<` and greater
+  // `>` so that MLIR's printers use the pretty format.
+  let assemblyFormat = "`<` $count `,` `map` `=` $map `>`";
+}
+```
+
+The declarative assembly format for `MyType` results in the following format
+in the IR:
+
+```mlir
+!my_dialect.my_type<42, map = affine_map<(i, j) -> (j, i)>
+```
+
+### Parameter Parsing and Printing
+
+For many basic parameter types, no additional work is needed to define how
+these parameters are parsed or printerd.
+
+* The default printer for any parameter is `$_printer << $_self`,
+  where `$_self` is the C++ value of the parameter and `$_printer` is a
+  `DialectAsmPrinter`.
+* The default parser for a parameter is
+  `FieldParser<$cppClass>::parse($_parser)`, where `$cppClass` is the C++ type
+  of the parameter and `$_parser` is a `DialectAsmParser`.
+
+Printing and parsing behaviour can be added to additional C++ types by
+overloading these functions or by defining a `parser` and `printer` in an ODS
+parameter class.
+
+Example of overloading:
+
+```c++
+using MyParameter = std::pair<int, int>;
+
+DialectAsmPrinter &operator<<(DialectAsmPrinter &printer, MyParameter param) {
+  printer << param.first << " * " << param.second;
+}
+
+template <> struct FieldParser<MyParameter> {
+  static FailureOr<MyParameter> parse(DialectAsmParser &parser) {
+    int a, b;
+    if (parser.parseInteger(a) || parser.parseStar() ||
+        parser.parseInteger(b))
+      return failure();
+    return MyParameter(a, b);
+  }
+};
+```
+
+Example of using ODS parameter classes:
+
+```
+def MyParameter : TypeParameter<"std::pair<int, int>", "pair of ints"> {
+  let printer = [{ $_printer << $_self.first << " * " << $_self.second }];
+  let parser = [{ [&] -> FailureOr<std::pair<int, int>> {
+    int a, b;
+    if ($_parser.parseInteger(a) || $_parser.parseStar() ||
+        $_parser.parseInteger(b))
+      return failure();
+    return std::make_pair(a, b);
+  }() }];
+}
+```
+
+A type using this parameter with the assembly format `` `<` $myParam `>` ``
+will look as follows in the IR:
+
+```mlir
+!my_dialect.my_type<42 * 24>
+```
+
+#### Non-POD Parameters
+
+Parameters that aren't plain-old-data (e.g. references) may need to define a
+`cppStorageType` to contain the data until it is copied into the allocator.
+For example, `StringRefParameter` uses `std::string` as its storage type,
+whereas `ArrayRefParameter` uses `SmallVector` as its storage type. The parsers
+for these parameters are expected to return `FailureOr<$cppStorageType>`.
+
+### Assembly Format Directives
+
+Attribute and type assembly formats have the following directives:
+
+* `params`: capture all parameters of an attribute or type.
+* `struct`: generate a "struct-like" parser and printer for a list of key-value
+  pairs.
+
+#### `params` Directive
+
+This directive is used to refer to all parameters of an attribute or type.
+Currently, it can only be used as an argument to `struct`.
+
+#### `struct` Directive
+
+The `struct` directive accepts a list of variables to capture and will generate
+a parser and printer for a comma-separated list of key-value pairs. The
+variables are printed in the order they are specified in the argument list **but
+can be parsed in any order**. For example:
+
+```tablegen
+def MyStructType : TypeDef<My_Dialect, "MyStructType"> {
+  let parameters = (ins StringRefParameter<>:$sym_name,
+                        "int":$a, "int":$b, "int":$c);
+  let mnemonic = "struct";
+  let assemblyFormat = "`<` $sym_name `->` struct($a, $b, $c) `>`";
+}
+```
+
+In the IR, this type can appear with any permutation of the order of the
+parameters captured in the directive.
+
+```mlir
+!my_dialect.struct<"foo" -> a = 1, b = 2, c = 3>
+!my_dialect.struct<"foo" -> b = 2, c = 3, a = 1>
+```
+
+Passing `params` as the only argument to `struct` makes the directive capture
+all the parameters of the attribute or type. For the same type above, an
+assembly format of `` `<` struct(params) `>` `` will result in:
+
+```mlir
+!my_dialect.struct<b = 2, sym_name = "foo", c = 3, a = 1>
+```
+
+The order in which the parameters are printed is the order in which they are
+declared in the attribute's or type's `parameter` list.

mlir/include/mlir/IR/DialectImplementation.h

public:
   using AsmParser::AsmParser;
   ~DialectAsmParser() override;
 
   /// Returns the full specification of the symbol being parsed. This allows for
   /// using a separate parser if necessary.
   virtual StringRef getFullSymbolSpec() const = 0;
 };
 
+//===----------------------------------------------------------------------===//
+// Parse Fields
+//===----------------------------------------------------------------------===//
+
+/// Provide a template class that can be specialized by users to dispatch to
+/// parsers. Auto-generated parsers generate calls to `FieldParser<T>::parse`,
+/// where `T` is the parameter storage type, to parse custom types.
+template <typename T, typename = T>
+struct FieldParser;
+
+/// Parse an attribute.
+template <typename AttributeT>
+struct FieldParser<
+    AttributeT, std::enable_if_t<std::is_base_of<Attribute, AttributeT>::value,
+                                 AttributeT>> {
+  static FailureOr<AttributeT> parse(DialectAsmParser &parser) {
+    AttributeT value;
+    if (parser.parseAttribute(value))
+      return failure();
+    return value;
+  }
+};
+
+/// Parse any integer.
+template <typename IntT>
+struct FieldParser<IntT,
+                   std::enable_if_t<std::is_integral<IntT>::value, IntT>> {
+  static FailureOr<IntT> parse(DialectAsmParser &parser) {
+    IntT value;
+    if (parser.parseInteger(value))
+      return failure();
+    return value;
+  }
+};
+
+/// Parse a string.
+template <>
+struct FieldParser<std::string> {
+  static FailureOr<std::string> parse(DialectAsmParser &parser) {
+    std::string value;
+    if (parser.parseString(&value))
+      return failure();
+    return value;
+  }
+};
+
+/// Parse any container that supports back insertion as a list.
+template <typename ContainerT>
+struct FieldParser<
+    ContainerT, std::enable_if_t<std::is_member_function_pointer<
+                                     decltype(&ContainerT::push_back)>::value,
+                                 ContainerT>> {
+  using ElementT = typename ContainerT::value_type;
+  static FailureOr<ContainerT> parse(DialectAsmParser &parser) {
+    ContainerT elements;
+    auto elementParser = [&]() {
+      auto element = FieldParser<ElementT>::parse(parser);
+      if (failed(element))
+        return failure();
+      elements.push_back(element.getValue());
+      return success();
+    };
+    if (parser.parseCommaSeparatedList(elementParser))
+      return failure();
+    return elements;
+  }
+};
+
 } // end namespace mlir
 
-#endif
+#endif // MLIR_IR_DIALECTIMPLEMENTATION_H

mlir/include/mlir/IR/OpBase.td

class AttrOrTypeDef<string valueType, string name, list<Trait> defTraits,
 
   // If 'mnemonic' specified,
   //   If null, generate just the declarations.
   //   If a non-empty code block, just use that code as the definition code.
   //   Error if an empty code block.
   code printer = ?;
   code parser = ?;
 
+  // Custom assembly format. Requires 'mnemonic' to be specified. Cannot be
+  // specified at the same time as either 'printer' or 'parser'. The generated
+  // printer requires 'genAccessors' to be true.
+  string assemblyFormat = ?;
+
   // If set, generate accessors for each parameter.
   bit genAccessors = 1;
 
   // Avoid generating default get/getChecked functions. Custom get methods must
   // be provided.
   bit skipDefaultBuilders = 0;
 
   // Generate the verify and getChecked methods.
class AttrOrTypeParameter<string type, string desc, string accessorType = ""> {
   // Custom memory allocation code for storage constructor.
   code allocator = ?;
   // Custom comparator used to compare two instances for equality.
   code comparator = ?;
   // The C++ type of this parameter.
   string cppType = type;
   // The C++ type of the accessor for this parameter.
   string cppAccessorType = !if(!empty(accessorType), type, accessorType);
+  // The C++ storage type of of this parameter if it is a reference, e.g.
+  // `std::string` for `StringRef` or `SmallVector` for `ArrayRef`.
+  string cppStorageType = ?;
   // One-line human-readable description of the argument.
   string summary = desc;
   // The format string for the asm syntax (documentation only).
   string syntax = ?;
+  // The default parameter parser is `::mlir::parseField<T>($_parser)`, which
+  // returns `FailureOr<T>`. Overload `parseField` to support parsing for your
+  // type. Or you can provide a customer printer. For attributes, "$_type" will
+  // be replaced with the required attribute type.
+  string parser = ?;
+  // The default parameter printer is `$_printer << $_self`. Overload the stream
+  // operator of `DialectAsmPrinter` as necessary to print your type. Or you can
+  // provide a custom printer.
+  string printer = ?;
 }
 class AttrParameter<string type, string desc, string accessorType = "">
  : AttrOrTypeParameter<type, desc, accessorType>;
 class TypeParameter<string type, string desc, string accessorType = "">
  : AttrOrTypeParameter<type, desc, accessorType>;
 
 // For StringRefs, which require allocation.
 class StringRefParameter<string desc = ""> :
     AttrOrTypeParameter<"::llvm::StringRef", desc> {
   let allocator = [{$_dst = $_allocator.copyInto($_self);}];
+  let printer = [{$_printer << '"' << $_self << '"';}];
+  let cppStorageType = "std::string";
 }
 
 // For APFloats, which require comparison.
 class APFloatParameter<string desc> :
     AttrOrTypeParameter<"::llvm::APFloat", desc> {
   let comparator = "$_lhs.bitwiseIsEqual($_rhs)";
 }
 
 // For standard ArrayRefs, which require allocation.
 class ArrayRefParameter<string arrayOf, string desc = ""> :
     AttrOrTypeParameter<"::llvm::ArrayRef<" # arrayOf # ">", desc> {
   let allocator = [{$_dst = $_allocator.copyInto($_self);}];
+  let cppStorageType = "::llvm::SmallVector<" # arrayOf # ">";
 }
 
 // For classes which require allocation and have their own allocateInto method.
 class SelfAllocationParameter<string type, string desc> :
     AttrOrTypeParameter<type, desc> {
   let allocator = [{$_dst = $_self.allocateInto($_allocator);}];
 }
 

mlir/include/mlir/IR/OpImplementation.h

 }
 template <typename AsmPrinterT>
 inline std::enable_if_t<std::is_base_of<AsmPrinter, AsmPrinterT>::value,
                         AsmPrinterT &>
 operator<<(AsmPrinterT &p, const TypeRange &types) {
   llvm::interleaveComma(types, p);
   return p;
 }
-template <typename AsmPrinterT>
+template <typename AsmPrinterT, typename ElementT>
 inline std::enable_if_t<std::is_base_of<AsmPrinter, AsmPrinterT>::value,
                         AsmPrinterT &>
-operator<<(AsmPrinterT &p, ArrayRef<Type> types) {
+operator<<(AsmPrinterT &p, ArrayRef<ElementT> types) {
   llvm::interleaveComma(types, p);
   return p;
 }
 
 //===----------------------------------------------------------------------===//
 // OpAsmPrinter
 //===----------------------------------------------------------------------===//
 

mlir/include/mlir/TableGen/AttrOrTypeDef.h

public:
   // Returns the code to use as the types printer method. If not specified,
   // return a non-value. Otherwise, return the contents of that code block.
   Optional<StringRef> getPrinterCode() const;
 
   // Returns the code to use as the parser method. If not specified, returns
   // None. Otherwise, returns the contents of that code block.
   Optional<StringRef> getParserCode() const;
 
+  // Returns the custom assembly format, if one was specified.
+  Optional<StringRef> getAssemblyFormat() const;
+
   // Returns true if the accessors based on the parameters should be generated.
   bool genAccessors() const;
 
   // Return true if we need to generate the verify declaration and getChecked
   // method.
   bool genVerifyDecl() const;
 
   // Returns the def's extra class declaration code.
public:
   Optional<StringRef> getComparator() const;
 
   // Get the C++ type of this parameter.
   StringRef getCppType() const;
 
   // Get the C++ accessor type of this parameter.
   StringRef getCppAccessorType() const;
 
+  // Get the C++ storage type of this parameter.
+  StringRef getCppStorageType() const;
+
+  // Get an optional C++ parameter parser.
+  Optional<StringRef> getParser() const;
+
+  // Get an optional C++ parameter printer.
+  Optional<StringRef> getPrinter() const;
+
   // Get a description of this parameter for documentation purposes.
   Optional<StringRef> getSummary() const;
 
   // Get the assembly syntax documentation.
   StringRef getSyntax() const;
 
   // Return the underlying def of this parameter.
   const llvm::Init *getDef() const;

mlir/include/mlir/TableGen/Dialect.h

+//===- Dialect.h - Dialect class --------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // Dialect wrapper to simplify using TableGen Record defining a MLIR dialect.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef MLIR_TABLEGEN_DIALECT_H_
 #define MLIR_TABLEGEN_DIALECT_H_

mlir/lib/TableGen/AttrOrTypeDef.cpp

 Optional<StringRef> AttrOrTypeDef::getPrinterCode() const {
   return def->getValueAsOptionalString("printer");
 }
 
 Optional<StringRef> AttrOrTypeDef::getParserCode() const {
   return def->getValueAsOptionalString("parser");
 }
 
+Optional<StringRef> AttrOrTypeDef::getAssemblyFormat() const {
+  return def->getValueAsOptionalString("assemblyFormat");
+}
+
 bool AttrOrTypeDef::genAccessors() const {
   return def->getValueAsBit("genAccessors");
 }
 
 bool AttrOrTypeDef::genVerifyDecl() const {
   return def->getValueAsBit("genVerifyDecl");
 }
 
StringRef AttrOrTypeParameter::getCppAccessorType() const {
   if (auto *param = dyn_cast<llvm::DefInit>(def->getArg(index))) {
     if (Optional<StringRef> type =
             param->getDef()->getValueAsOptionalString("cppAccessorType"))
       return *type;
   }
   return getCppType();
 }
 
+StringRef AttrOrTypeParameter::getCppStorageType() const {
+  if (auto *param = dyn_cast<llvm::DefInit>(def->getArg(index))) {
+    if (auto type = param->getDef()->getValueAsOptionalString("cppStorageType"))
+      return *type;
+  }
+  return getCppType();
+}
+
+Optional<StringRef> AttrOrTypeParameter::getParser() const {
+  auto *parameterType = def->getArg(index);
+  if (auto *param = dyn_cast<llvm::DefInit>(parameterType)) {
+    if (auto parser = param->getDef()->getValueAsOptionalString("parser"))
+      return *parser;
+  }
+  return {};
+}
+
+Optional<StringRef> AttrOrTypeParameter::getPrinter() const {
+  auto *parameterType = def->getArg(index);
+  if (auto *param = dyn_cast<llvm::DefInit>(parameterType)) {
+    if (auto printer = param->getDef()->getValueAsOptionalString("printer"))
+      return *printer;
+  }
+  return {};
+}
+
 Optional<StringRef> AttrOrTypeParameter::getSummary() const {
   auto *parameterType = def->getArg(index);
   if (auto *param = dyn_cast<llvm::DefInit>(parameterType)) {
     const auto *desc = param->getDef()->getValue("summary");
     if (llvm::StringInit *ci = dyn_cast<llvm::StringInit>(desc->getValue()))
       return ci->getValue();
   }
   return Optional<StringRef>();

mlir/test/lib/Dialect/Test/TestAttrDefs.td

auto value_begin_impl(OverloadToken<llvm::APInt>) const {
       return llvm::map_range(getElements(), [=](uint64_t value) {
         return llvm::APInt(/*numBits=*/64, value);
       }).begin();
     }
   }];
   let genVerifyDecl = 1;
 }
 
+def TestParamOne : AttrParameter<"int64_t", ""> {}
+
+def TestParamTwo : AttrParameter<"std::string", "", "llvm::StringRef"> {
+  let printer = "$_printer << '\"' << $_self << '\"'";
+}
+
+def TestParamFour : ArrayRefParameter<"int", ""> {
+  let cppStorageType = "llvm::SmallVector<int>";
+  let parser = "::parseIntArray($_parser)";
+  let printer = "::printIntArray($_printer, $_self)";
+}
+
+def TestAttrWithFormat : Test_Attr<"TestAttrWithFormat"> {
+  let parameters = (
+    ins
+    TestParamOne:$one,
+    TestParamTwo:$two,
+    "::mlir::IntegerAttr":$three,
+    TestParamFour:$four
+  );
+
+  let mnemonic = "attr_with_format";
+  let assemblyFormat = "`<` $one `:` struct($two, $four) `:` $three `>`";
+  let genVerifyDecl = 1;
+}
+
+def TestAttrUgly : Test_Attr<"TestAttrUgly"> {
+  let parameters = (ins "::mlir::Attribute":$attr);
+
+  let mnemonic = "attr_ugly";
+  let assemblyFormat = "`begin` $attr `end`";
+}
+
 #endif // TEST_ATTRDEFS

mlir/test/lib/Dialect/Test/TestAttributes.cpp

 //
 //===----------------------------------------------------------------------===//
 
 #include "TestAttributes.h"
 #include "TestDialect.h"
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/DialectImplementation.h"
 #include "mlir/IR/Types.h"
+#include "mlir/Support/LogicalResult.h"
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/TypeSwitch.h"
+#include "llvm/ADT/bit.h"
 
 using namespace mlir;
 using namespace test;
 
 //===----------------------------------------------------------------------===//
 // AttrWithSelfTypeParamAttr
 //===----------------------------------------------------------------------===//
 
return emitError()
            << elements.size() << ", but expected: " << type.getNumElements();
   }
   if (type.getRank() != 1 || !type.getElementType().isSignlessInteger(64))
     return emitError() << "expected single rank 64-bit shape type, but got: "
                        << type;
   return success();
 }
 
+LogicalResult
+TestAttrWithFormatAttr::verify(function_ref<InFlightDiagnostic()> emitError,
+                               int64_t one, std::string two, IntegerAttr three,
+                               ArrayRef<int> four) {
+  if (four.size() != static_cast<unsigned>(one))
+    return emitError() << "expected 'one' to equal 'four.size()'";
+  return success();
+}
+
+//===----------------------------------------------------------------------===//
+// Utility Functions for Generated Attributes
+//===----------------------------------------------------------------------===//
+
+static FailureOr<SmallVector<int>> parseIntArray(DialectAsmParser &parser) {
+  SmallVector<int> ints;
+  if (parser.parseLSquare() || parser.parseCommaSeparatedList([&]() {
+        ints.push_back(0);
+        return parser.parseInteger(ints.back());
+      }) ||
+      parser.parseRSquare())
+    return failure();
+  return ints;
+}
+
+static void printIntArray(DialectAsmPrinter &printer, ArrayRef<int> ints) {
+  printer << '[';
+  llvm::interleaveComma(ints, printer);
+  printer << ']';
+}
+
 //===----------------------------------------------------------------------===//
 // Tablegen Generated Definitions
 //===----------------------------------------------------------------------===//
 
 #include "TestAttrInterfaces.cpp.inc"
 
 #define GET_ATTRDEF_CLASSES
 #include "TestAttrDefs.cpp.inc"

mlir/test/lib/Dialect/Test/TestTypeDefs.td

 //
 //===----------------------------------------------------------------------===//
 
 #ifndef TEST_TYPEDEFS
 #define TEST_TYPEDEFS
 
 // To get the test dialect def.
 include "TestOps.td"
+include "TestAttrDefs.td"
 include "mlir/IR/BuiltinTypes.td"
 include "mlir/Interfaces/DataLayoutInterfaces.td"
 
 // All of the types will extend this class.
 class Test_Type<string name, list<Trait> traits = []>
   : TypeDef<Test_Dialect, name, traits>;
 
 def SimpleTypeA : Test_Type<"SimpleA"> {

 
 def TestTypeTrait : NativeTypeTrait<"TestTypeTrait">;
 
 // The definition of a singleton type that has a trait.
 def TestTypeWithTrait : Test_Type<"TestTypeWithTrait", [TestTypeTrait]> {
   let mnemonic = "test_type_with_trait";
 }
 
+// Type with assembly format.
+def TestTypeWithFormat : Test_Type<"TestTypeWithFormat"> {
+  let parameters = (
+    ins
+    TestParamOne:$one,
+    TestParamTwo:$two,
+    "::mlir::Attribute":$three
+  );
+
+  let mnemonic = "type_with_format";
+  let assemblyFormat = "`<` $one `,` struct($three, $two) `>`";
+}
+
+// Test dispatch to parseField
+def TestTypeNoParser : Test_Type<"TestTypeNoParser"> {
+  let parameters = (
+    ins
+    "uint32_t":$one,
+    ArrayRefParameter<"int64_t">:$two,
+    StringRefParameter<>:$three,
+    "::test::CustomParam":$four
+  );
+
+  let mnemonic = "no_parser";
+  let assemblyFormat = "`<` $one `,` `[` $two `]` `,` $three `,` $four `>`";
+}
+
+def TestTypeStructCaptureAll : Test_Type<"TestStructTypeCaptureAll"> {
+  let parameters = (
+    ins
+    "int":$v0,
+    "int":$v1,
+    "int":$v2,
+    "int":$v3
+  );
+
+  let mnemonic = "struct_capture_all";
+  let assemblyFormat = "`<` struct(params) `>`";
+}
+
 #endif // TEST_TYPEDEFS

mlir/test/lib/Dialect/Test/TestTypes.h

struct FieldInfo {
   ::mlir::Type type;
 
   // Custom allocation called from generated constructor code
   FieldInfo allocateInto(::mlir::TypeStorageAllocator &alloc) const {
     return FieldInfo{alloc.copyInto(name), type};
   }
 };
 
+/// A custom type for a test type parameter.
+struct CustomParam {
+  int value;
+
+  bool operator==(const CustomParam &other) const {
+    return other.value == value;
+  }
+};
+
+inline llvm::hash_code hash_value(const test::CustomParam &param) {
+  return llvm::hash_value(param.value);
+}
+
 } // namespace test
 
+namespace mlir {
+template <>
+struct FieldParser<test::CustomParam> {
+  static FailureOr<test::CustomParam> parse(DialectAsmParser &parser) {
+    auto value = FieldParser<int>::parse(parser);
+    if (failed(value))
+      return failure();
+    return test::CustomParam{value.getValue()};
+  }
+};
+} // end namespace mlir
+
+inline mlir::DialectAsmPrinter &operator<<(mlir::DialectAsmPrinter &printer,
+                                           const test::CustomParam &param) {
+  return printer << param.value;
+}
+
 #include "TestTypeInterfaces.h.inc"
 
 #define GET_TYPEDEF_CLASSES
 #include "TestTypeDefs.h.inc"
 
 namespace test {
 
 /// Storage for simple named recursive types, where the type is identified by
 /// its name and can "contain" another type, including itself.
 struct TestRecursiveTypeStorage : public ::mlir::TypeStorage {
   using KeyTy = ::llvm::StringRef;
 
-  explicit TestRecursiveTypeStorage(::llvm::StringRef key) : name(key), body(::mlir::Type()) {}
+  explicit TestRecursiveTypeStorage(::llvm::StringRef key)
+      : name(key), body(::mlir::Type()) {}
 
   bool operator==(const KeyTy &other) const { return name == other; }
 
-  static TestRecursiveTypeStorage *construct(::mlir::TypeStorageAllocator &allocator,
-                                             const KeyTy &key) {
+  static TestRecursiveTypeStorage *
+  construct(::mlir::TypeStorageAllocator &allocator, const KeyTy &key) {
     return new (allocator.allocate<TestRecursiveTypeStorage>())
         TestRecursiveTypeStorage(allocator.copyInto(key));
   }
 
-  ::mlir::LogicalResult mutate(::mlir::TypeStorageAllocator &allocator, ::mlir::Type newBody) {
+  ::mlir::LogicalResult mutate(::mlir::TypeStorageAllocator &allocator,
+                               ::mlir::Type newBody) {
     // Cannot set a different body than before.
     if (body && body != newBody)
       return ::mlir::failure();
 
     body = newBody;
     return ::mlir::success();
   }
 
   ::llvm::StringRef name;
   ::mlir::Type body;
 };
 
 /// Simple recursive type identified by its name and pointing to another named
 /// type, potentially itself. This requires the body to be mutated separately
 /// from type creation.
 class TestRecursiveType
-    : public ::mlir::Type::TypeBase<TestRecursiveType, ::mlir::Type, TestRecursiveTypeStorage> {
+    : public ::mlir::Type::TypeBase<TestRecursiveType, ::mlir::Type,
+                                    TestRecursiveTypeStorage> {
 public:
   using Base::Base;
 
-  static TestRecursiveType get(::mlir::MLIRContext *ctx, ::llvm::StringRef name) {
+  static TestRecursiveType get(::mlir::MLIRContext *ctx,
+                               ::llvm::StringRef name) {
     return Base::get(ctx, name);
   }
 
   /// Body getter and setter.
   ::mlir::LogicalResult setBody(Type body) { return Base::mutate(body); }
   ::mlir::Type getBody() { return getImpl()->body; }
 
   /// Name/key getter.
   ::llvm::StringRef getName() { return getImpl()->name; }
 };
 
 } // namespace test
 
 #endif // MLIR_TESTTYPES_H

mlir/test/mlir-tblgen/attr-or-type-format-invalid.td

+// RUN: mlir-tblgen -gen-typedef-defs -I %S/../../include -asmformat-error-is-fatal=false %s 2>&1 | FileCheck %s
+
+include "mlir/IR/OpBase.td"
+
+def Test_Dialect : Dialect {
+  let name = "TestDialect";
+  let cppNamespace = "::test";
+}
+
+class InvalidType<string name, string asm> : TypeDef<Test_Dialect, name> {
+  let mnemonic = asm;
+}
+
+/// Test format is missing a parameter capture.
+def InvalidTypeA : InvalidType<"InvalidTypeA", "invalid_a"> {
+  let parameters = (ins "int":$v0, "int":$v1);
+  // CHECK: format is missing reference to parameter: v1
+  let assemblyFormat = "`<` $v0 `>`";
+}
+
+/// Test format has duplicate parameter captures.
+def InvalidTypeB : InvalidType<"InvalidTypeB", "invalid_b"> {
+  let parameters = (ins "int":$v0, "int":$v1);
+  // CHECK: duplicate parameter 'v0'
+  let assemblyFormat = "`<` $v0 `,` $v1 `,` $v0 `>`";
+}
+
+/// Test format has invalid syntax.
+def InvalidTypeC : InvalidType<"InvalidTypeC", "invalid_c"> {
+  let parameters = (ins "int":$v0, "int":$v1);
+  // CHECK: expected literal, directive, or variable
+  let assemblyFormat = "`<` $v0, $v1 `>`";
+}
+
+/// Test struct directive has invalid syntax.
+def InvalidTypeD : InvalidType<"InvalidTypeD", "invalid_d"> {
+  let parameters = (ins "int":$v0);
+  // CHECK: literals may only be used in the top-level section of the format
+  // CHECK: expected a variable in `struct` argument list
+  let assemblyFormat = "`<` struct($v0, `,`) `>`";
+}
+
+/// Test struct directive cannot capture zero parameters.
+def InvalidTypeE : InvalidType<"InvalidTypeE", "invalid_e"> {
+  let parameters = (ins "int":$v0);
+  // CHECK: `struct` argument list expected a variable or directive
+  let assemblyFormat = "`<` struct() $v0 `>`";
+}
+
+/// Test capture parameter that does not exist.
+def InvalidTypeF : InvalidType<"InvalidTypeF", "invalid_f"> {
+  let parameters = (ins "int":$v0);
+  // CHECK: InvalidTypeF has no parameter named 'v1'
+  let assemblyFormat = "`<` $v0 $v1 `>`";
+}
+
+/// Test duplicate capture of parameter in capture-all struct.
+def InvalidTypeG : InvalidType<"InvalidTypeG", "invalid_g"> {
+  let parameters = (ins "int":$v0, "int":$v1, "int":$v2);
+  // CHECK: duplicate parameter 'v0'
+  let assemblyFormat = "`<` struct(params) $v0 `>`";
+}
+
+/// Test capture-all struct duplicate capture.
+def InvalidTypeH : InvalidType<"InvalidTypeH", "invalid_h"> {
+  let parameters = (ins "int":$v0, "int":$v1, "int":$v2);
+  // CHECK: struct(params) captures duplicate parameter: v0
+  let assemblyFormat = "`<` $v0 struct(params) `>`";
+}
+
+/// Test `params` cannot be used at the top-level.
+def InvalidTypeI : InvalidType<"InvalidTypeI", "invalid_i"> {
+  // CHECK: `params` may not be used in the top-level section of the format
+  let assemblyFormat = "`<` params `>`";
+}

mlir/test/mlir-tblgen/attr-or-type-format-roundtrip.mlir

+// RUN: mlir-opt %s | mlir-opt | FileCheck %s
+
+// CHECK-LABEL: @test_roundtrip_parameter_parsers
+// CHECK: !test.type_with_format<111, three = #test<"attr_ugly begin 5 : index end">, two = "foo">
+// CHECK: !test.type_with_format<2147, three = "hi", two = "hi">
+func private @test_roundtrip_parameter_parsers(!test.type_with_format<111, three = #test<"attr_ugly begin 5 : index end">, two = "foo">) -> !test.type_with_format<2147, two = "hi", three = "hi">
+attributes {
+  // CHECK: #test.attr_with_format<3 : two = "hello", four = [1, 2, 3] : 42 : i64>
+  attr0 = #test.attr_with_format<3 : two = "hello", four = [1, 2, 3] : 42 : i64>,
+  // CHECK: #test.attr_with_format<5 : two = "a_string", four = [4, 5, 6, 7, 8] : 8 : i8>
+  attr1 = #test.attr_with_format<5 : two = "a_string", four = [4, 5, 6, 7, 8] : 8 : i8>,
+  // CHECK: #test<"attr_ugly begin 5 : index end">
+  attr2 = #test<"attr_ugly begin 5 : index end">
+}
+
+// CHECK-LABEL: @test_roundtrip_default_parsers_struct
+// CHECK: !test.no_parser<255, [1, 2, 3, 4, 5], "foobar", 4>
+// CHECK: !test.struct_capture_all<v0 = 0, v1 = 1, v2 = 2, v3 = 3>
+func private @test_roundtrip_default_parsers_struct(!test.no_parser<255, [1, 2, 3, 4, 5], "foobar", 4>) -> !test.struct_capture_all<v3 = 3, v1 = 1, v2 = 2, v0 = 0>

mlir/test/mlir-tblgen/attr-or-type-format.mlir

+// RUN: mlir-opt --split-input-file %s --verify-diagnostics
+
+func private @test_ugly_attr_cannot_be_pretty() -> () attributes {
+  // expected-error@+1 {{expected 'begin'}}
+  attr = #test.attr_ugly
+}
+
+// -----
+
+func private @test_ugly_attr_no_mnemonic() -> () attributes {
+  // expected-error@+1 {{expected valid keyword}}
+  attr = #test<"">
+}
+
+// -----
+
+func private @test_ugly_attr_parser_dispatch() -> () attributes {
+  // expected-error@+1 {{expected 'begin'}}
+  attr = #test<"attr_ugly">
+}
+
+// -----
+
+func private @test_ugly_attr_missing_parameter() -> () attributes {
+  // expected-error@+2 {{failed to parse TestAttrUgly parameter 'attr'}}
+  // expected-error@+1 {{expected non-function type}}
+  attr = #test<"attr_ugly begin">
+}
+
+// -----
+
+func private @test_ugly_attr_missing_literal() -> () attributes {
+  // expected-error@+1 {{expected 'end'}}
+  attr = #test<"attr_ugly begin \"string_attr\"">
+}
+
+// -----
+
+func private @test_pretty_attr_expects_less() -> () attributes {
+  // expected-error@+1 {{expected '<'}}
+  attr = #test.attr_with_format
+}
+
+// -----
+
+func private @test_pretty_attr_missing_param() -> () attributes {
+  // expected-error@+2 {{expected integer value}}
+  // expected-error@+1 {{failed to parse TestAttrWithFormat parameter 'one'}}
+  attr = #test.attr_with_format<>
+}
+
+// -----
+
+func private @test_parse_invalid_param() -> () attributes {
+  // Test parameter parser failure is propagated
+  // expected-error@+2 {{expected integer value}}
+  // expected-error@+1 {{failed to parse TestAttrWithFormat parameter 'one'}}
+  attr = #test.attr_with_format<"hi">
+}
+
+// -----
+
+func private @test_pretty_attr_invalid_syntax() -> () attributes {
+  // expected-error@+1 {{expected ':'}}
+  attr = #test.attr_with_format<42>
+}
+
+// -----
+
+func private @test_struct_missing_key() -> () attributes {
+  // expected-error@+2 {{expected valid keyword}}
+  // expected-error@+1 {{expected a parameter name in struct}}
+  attr = #test.attr_with_format<42 :>
+}
+
+// -----
+
+func private @test_struct_unknown_key() -> () attributes {
+  // expected-error@+1 {{duplicate or unknown struct parameter}}
+  attr = #test.attr_with_format<42 : nine = "foo">
+}
+
+// -----
+
+func private @test_struct_duplicate_key() -> () attributes {
+  // expected-error@+1 {{duplicate or unknown struct parameter}}
+  attr = #test.attr_with_format<42 : two = "foo", two = "bar">
+}
+
+// -----
+
+func private @test_struct_not_enough_values() -> () attributes {
+  // expected-error@+1 {{expected ','}}
+  attr = #test.attr_with_format<42 : two = "foo">
+}
+
+// -----
+
+func private @test_parse_param_after_struct() -> () attributes {
+  // expected-error@+2 {{expected non-function type}}
+  // expected-error@+1 {{failed to parse TestAttrWithFormat parameter 'three'}}
+  attr = #test.attr_with_format<42 : two = "foo", four = [1, 2, 3] : >
+}
+
+// -----
+
+// expected-error@+1 {{expected '<'}}
+func private @test_invalid_type() -> !test.type_with_format
+
+// -----
+
+// expected-error@+2 {{expected integer value}}
+// expected-error@+1 {{failed to parse TestTypeWithFormat parameter 'one'}}
+func private @test_pretty_type_invalid_param() -> !test.type_with_format<>
+
+// -----
+
+// expected-error@+2 {{expected ':'}}
+// expected-error@+1 {{failed to parse TestTypeWithFormat parameter 'three'}}
+func private @test_type_syntax_error() -> !test.type_with_format<42, two = "hi", three = #test.attr_with_format<42>>
+
+// -----
+
+func private @test_verifier_fails() -> () attributes {
+  // expected-error@+1 {{expected 'one' to equal 'four.size()'}}
+  attr = #test.attr_with_format<42 : two = "hello", four = [1, 2, 3] : 42 : i64>
+}

mlir/test/mlir-tblgen/attr-or-type-format.td

+// RUN: mlir-tblgen -gen-attrdef-defs -I %S/../../include %s | FileCheck %s --check-prefix=ATTR
+// RUN: mlir-tblgen -gen-typedef-defs -I %S/../../include %s | FileCheck %s --check-prefix=TYPE
+
+include "mlir/IR/OpBase.td"
+
+/// Test that attribute and type printers and parsers are correctly generated.
+def Test_Dialect : Dialect {
+  let name = "TestDialect";
+  let cppNamespace = "::test";
+}
+
+class TestAttr<string name> : AttrDef<Test_Dialect, name>;
+class TestType<string name> : TypeDef<Test_Dialect, name>;
+
+def AttrParamA : AttrParameter<"TestParamA", "an attribute param A"> {
+  let parser = "::parseAttrParamA($_parser, $_type)";
+  let printer = "::printAttrParamA($_printer, $_self)";
+}
+
+def AttrParamB : AttrParameter<"TestParamB", "an attribute param B"> {
+  let parser = "$_type ? ::parseAttrWithType($_parser, $_type) : ::parseAttrWithout($_parser)";
+  let printer = "::printAttrB($_printer, $_self)";
+}
+
+def TypeParamA : TypeParameter<"TestParamC", "a type param C"> {
+  let parser = "::parseTypeParamC($_parser)";
+  let printer = "$_printer << $_self";
+}
+
+def TypeParamB : TypeParameter<"TestParamD", "a type param D"> {
+  let parser = "someFcnCall()";
+  let printer = "myPrinter($_self)";
+}
+
+/// Check simple attribute parser and printer are generated correctly.
+
+// ATTR: ::mlir::Attribute TestAAttr::parse(::mlir::DialectAsmParser &parser,
+// ATTR:                                    ::mlir::Type attrType) {
+// ATTR:   FailureOr<IntegerAttr> _result_value;
+// ATTR:   FailureOr<TestParamA> _result_complex;
+// ATTR:   if (parser.parseKeyword("hello"))
+// ATTR:     return {};
+// ATTR:   if (parser.parseEqual())
+// ATTR:     return {};
+// ATTR:   _result_value = ::mlir::FieldParser<IntegerAttr>::parse(parser);
+// ATTR:   if (failed(_result_value))
+// ATTR:     return {};
+// ATTR:   if (parser.parseComma())
+// ATTR:     return {};
+// ATTR:   _result_complex = ::parseAttrParamA(parser, attrType);
+// ATTR:   if (failed(_result_complex))
+// ATTR:     return {};
+// ATTR:   if (parser.parseRParen())
+// ATTR:     return {};
+// ATTR:   return TestAAttr::get(parser.getContext(),
+// ATTR:                         _result_value.getValue(),
+// ATTR:                         _result_complex.getValue());
+// ATTR: }
+
+// ATTR: void TestAAttr::print(::mlir::DialectAsmPrinter &printer) const {
+// ATTR:   printer << "attr_a";
+// ATTR:   printer << ' ' << "hello";
+// ATTR:   printer << ' ' << "=";
+// ATTR:   printer << ' ';
+// ATTR:   printer << getValue();
+// ATTR:   printer << ",";
+// ATTR:   printer << ' ';
+// ATTR:   ::printAttrParamA(printer, getComplex());
+// ATTR:   printer << ")";
+// ATTR: }
+
+def AttrA : TestAttr<"TestA"> {
+  let parameters = (ins
+      "IntegerAttr":$value,
+      AttrParamA:$complex
+  );
+
+  let mnemonic = "attr_a";
+  let assemblyFormat = "`hello` `=` $value `,` $complex `)`";
+}
+
+/// Test simple struct parser and printer are generated correctly.
+
+// ATTR: ::mlir::Attribute TestBAttr::parse(::mlir::DialectAsmParser &parser,
+// ATTR:                                    ::mlir::Type attrType) {
+// ATTR:   bool _seen_v0 = false;
+// ATTR:   bool _seen_v1 = false;
+// ATTR:   for (unsigned _index = 0; _index < 2; ++_index) {
+// ATTR:     StringRef _paramKey;
+// ATTR:     if (parser.parseKeyword(&_paramKey))
+// ATTR:       return {};
+// ATTR:     if (parser.parseEqual())
+// ATTR:       return {};
+// ATTR:     if (!_seen_v0 && _paramKey == "v0") {
+// ATTR:       _seen_v0 = true;
+// ATTR:       _result_v0 = ::parseAttrParamA(parser, attrType);
+// ATTR:       if (failed(_result_v0))
+// ATTR:         return {};
+// ATTR:     } else if (!_seen_v1 && _paramKey == "v1") {
+// ATTR:       _seen_v1 = true;
+// ATTR:       _result_v1 = attrType ? ::parseAttrWithType(parser, attrType) : ::parseAttrWithout(parser);
+// ATTR:       if (failed(_result_v1))
+// ATTR:         return {};
+// ATTR:     } else {
+// ATTR:       return {};
+// ATTR:     }
+// ATTR:     if ((_index != 2 - 1) && parser.parseComma())
+// ATTR:       return {};
+// ATTR:   }
+// ATTR:   return TestBAttr::get(parser.getContext(),
+// ATTR:                         _result_v0.getValue(),
+// ATTR:                         _result_v1.getValue());
+// ATTR: }
+
+// ATTR: void TestBAttr::print(::mlir::DialectAsmPrinter &printer) const {
+// ATTR:   printer << "v0";
+// ATTR:   printer << ' ' << "=";
+// ATTR:   printer << ' ';
+// ATTR:   ::printAttrParamA(printer, getV0());
+// ATTR:   printer << ",";
+// ATTR:   printer << ' ' << "v1";
+// ATTR:   printer << ' ' << "=";
+// ATTR:   printer << ' ';
+// ATTR:   ::printAttrB(printer, getV1());
+// ATTR: }
+
+def AttrB : TestAttr<"TestB"> {
+  let parameters = (ins
+      AttrParamA:$v0,
+      AttrParamB:$v1
+  );
+
+  let mnemonic = "attr_b";
+  let assemblyFormat = "`{` struct($v0, $v1) `}`";
+}
+
+/// Test type parser and printer that mix variables and struct are generated
+/// correctly.
+
+// TYPE: ::mlir::Type TestCType::parse(::mlir::DialectAsmParser &parser) {
+// TYPE:  FailureOr<IntegerAttr> _result_value;
+// TYPE:  FailureOr<TestParamC> _result_complex;
+// TYPE:  if (parser.parseKeyword("foo"))
+// TYPE:    return {};
+// TYPE:  if (parser.parseComma())
+// TYPE:    return {};
+// TYPE:  if (parser.parseColon())
+// TYPE:    return {};
+// TYPE:  if (parser.parseKeyword("bob"))
+// TYPE:    return {};
+// TYPE:  if (parser.parseKeyword("bar"))
+// TYPE:    return {};
+// TYPE:  _result_value = ::mlir::FieldParser<IntegerAttr>::parse(parser);
+// TYPE:  if (failed(_result_value))
+// TYPE:    return {};
+// TYPE:  bool _seen_complex = false;
+// TYPE:  for (unsigned _index = 0; _index < 1; ++_index) {
+// TYPE:    StringRef _paramKey;
+// TYPE:    if (parser.parseKeyword(&_paramKey))
+// TYPE:      return {};
+// TYPE:    if (!_seen_complex && _paramKey == "complex") {
+// TYPE:      _seen_complex = true;
+// TYPE:      _result_complex = ::parseTypeParamC(parser);
+// TYPE:      if (failed(_result_complex))
+// TYPE:        return {};
+// TYPE:    } else {
+// TYPE:      return {};
+// TYPE:    }
+// TYPE:    if ((_index != 1 - 1) && parser.parseComma())
+// TYPE:      return {};
+// TYPE:  }
+// TYPE:  if (parser.parseRParen())
+// TYPE:    return {};
+// TYPE:  }
+
+// TYPE: void TestCType::print(::mlir::DialectAsmPrinter &printer) const {
+// TYPE:   printer << "type_c";
+// TYPE:   printer << ' ' << "foo";
+// TYPE:   printer << ",";
+// TYPE:   printer << ' ' << ":";
+// TYPE:   printer << ' ' << "bob";
+// TYPE:   printer << ' ' << "bar";
+// TYPE:   printer << ' ';
+// TYPE:   printer << getValue();
+// TYPE:   printer << ' ' << "complex";
+// TYPE:   printer << ' ' << "=";
+// TYPE:   printer << ' ';
+// TYPE:   printer << getComplex();
+// TYPE:   printer << ")";
+// TYPE: }
+
+def TypeA : TestType<"TestC"> {
+  let parameters = (ins
+      "IntegerAttr":$value,
+      TypeParamA:$complex
+  );
+
+  let mnemonic = "type_c";
+  let assemblyFormat = "`foo` `,` `:` `bob` `bar` $value struct($complex) `)`";
+}
+
+/// Test type parser and printer with mix of variables and struct are generated
+/// correctly.
+
+// TYPE: ::mlir::Type TestDType::parse(::mlir::DialectAsmParser &parser) {
+// TYPE:   _result_v0 = ::parseTypeParamC(parser);
+// TYPE:   if (failed(_result_v0))
+// TYPE:     return {};
+// TYPE:   bool _seen_v1 = false;
+// TYPE:   bool _seen_v2 = false;
+// TYPE:   for (unsigned _index = 0; _index < 2; ++_index) {
+// TYPE:     StringRef _paramKey;
+// TYPE:     if (parser.parseKeyword(&_paramKey))
+// TYPE:       return {};
+// TYPE:     if (parser.parseEqual())
+// TYPE:       return {};
+// TYPE:     if (!_seen_v1 && _paramKey == "v1") {
+// TYPE:       _seen_v1 = true;
+// TYPE:       _result_v1 = someFcnCall();
+// TYPE:       if (failed(_result_v1))
+// TYPE:         return {};
+// TYPE:     } else if (!_seen_v2 && _paramKey == "v2") {
+// TYPE:       _seen_v2 = true;
+// TYPE:       _result_v2 = ::parseTypeParamC(parser);
+// TYPE:       if (failed(_result_v2))
+// TYPE:         return {};
+// TYPE:     } else  {
+// TYPE:       return {};
+// TYPE:     }
+// TYPE:     if ((_index != 2 - 1) && parser.parseComma())
+// TYPE:       return {};
+// TYPE:   }
+// TYPE:   _result_v3 = someFcnCall();
+// TYPE:   if (failed(_result_v3))
+// TYPE:     return {};
+// TYPE:   return TestDType::get(parser.getContext(),
+// TYPE:                         _result_v0.getValue(),
+// TYPE:                         _result_v1.getValue(),
+// TYPE:                         _result_v2.getValue(),
+// TYPE:                         _result_v3.getValue());
+// TYPE: }
+
+// TYPE: void TestDType::print(::mlir::DialectAsmPrinter &printer) const {
+// TYPE:   printer << getV0();
+// TYPE:   myPrinter(getV1());
+// TYPE:   printer << ' ' << "v2";
+// TYPE:   printer << ' ' << "=";
+// TYPE:   printer << ' ';
+// TYPE:   printer << getV2();
+// TYPE:   myPrinter(getV3());
+// TYPE: }
+
+def TypeB : TestType<"TestD"> {
+  let parameters = (ins
+      TypeParamA:$v0,
+      TypeParamB:$v1,
+      TypeParamA:$v2,
+      TypeParamB:$v3
+  );
+
+  let mnemonic = "type_d";
+  let assemblyFormat = "`<` `foo` `:` $v0 `,` struct($v1, $v2) `,` $v3 `>`";
+}
+
+/// Type test with two struct directives has correctly generated parser and
+/// printer.
+
+// TYPE: ::mlir::Type TestEType::parse(::mlir::DialectAsmParser &parser) {
+// TYPE:   FailureOr<IntegerAttr> _result_v0;
+// TYPE:   FailureOr<IntegerAttr> _result_v1;
+// TYPE:   FailureOr<IntegerAttr> _result_v2;
+// TYPE:   FailureOr<IntegerAttr> _result_v3;
+// TYPE:   bool _seen_v0 = false;
+// TYPE:   bool _seen_v2 = false;
+// TYPE:   for (unsigned _index = 0; _index < 2; ++_index) {
+// TYPE:     StringRef _paramKey;
+// TYPE:     if (parser.parseKeyword(&_paramKey))
+// TYPE:       return {};
+// TYPE:     if (parser.parseEqual())
+// TYPE:       return {};
+// TYPE:     if (!_seen_v0 && _paramKey == "v0") {
+// TYPE:       _seen_v0 = true;
+// TYPE:       _result_v0 = ::mlir::FieldParser<IntegerAttr>::parse(parser);
+// TYPE:       if (failed(_result_v0))
+// TYPE:         return {};
+// TYPE:     } else if (!_seen_v2 && _paramKey == "v2") {
+// TYPE:       _seen_v2 = true;
+// TYPE:       _result_v2 = ::mlir::FieldParser<IntegerAttr>::parse(parser);
+// TYPE:       if (failed(_result_v2))
+// TYPE:         return {};
+// TYPE:     } else  {
+// TYPE:       return {};
+// TYPE:     }
+// TYPE:     if ((_index != 2 - 1) && parser.parseComma())
+// TYPE:       return {};
+// TYPE:   }
+// TYPE:   bool _seen_v1 = false;
+// TYPE:   bool _seen_v3 = false;
+// TYPE:   for (unsigned _index = 0; _index < 2; ++_index) {
+// TYPE:     StringRef _paramKey;
+// TYPE:     if (parser.parseKeyword(&_paramKey))
+// TYPE:       return {};
+// TYPE:     if (parser.parseEqual())
+// TYPE:       return {};
+// TYPE:     if (!_seen_v1 && _paramKey == "v1") {
+// TYPE:       _seen_v1 = true;
+// TYPE:       _result_v1 = ::mlir::FieldParser<IntegerAttr>::parse(parser);
+// TYPE:       if (failed(_result_v1))
+// TYPE:         return {};
+// TYPE:     } else if (!_seen_v3 && _paramKey == "v3") {
+// TYPE:       _seen_v3 = true;
+// TYPE:       _result_v3 = ::mlir::FieldParser<IntegerAttr>::parse(parser);
+// TYPE:       if (failed(_result_v3))
+// TYPE:         return {};
+// TYPE:     } else  {
+// TYPE:       return {};
+// TYPE:     }
+// TYPE:     if ((_index != 2 - 1) && parser.parseComma())
+// TYPE:       return {};
+// TYPE:   }
+// TYPE:   return TestEType::get(parser.getContext(),
+// TYPE:     _result_v0.getValue(),
+// TYPE:     _result_v1.getValue(),
+// TYPE:     _result_v2.getValue(),
+// TYPE:     _result_v3.getValue());
+// TYPE: }
+
+// TYPE: void TestEType::print(::mlir::DialectAsmPrinter &printer) const {
+// TYPE:   printer << "v0";
+// TYPE:   printer << ' ' << "=";
+// TYPE:   printer << ' ';
+// TYPE:   printer << getV0();
+// TYPE:   printer << ",";
+// TYPE:   printer << ' ' << "v2";
+// TYPE:   printer << ' ' << "=";
+// TYPE:   printer << ' ';
+// TYPE:   printer << getV2();
+// TYPE:   printer << "v1";
+// TYPE:   printer << ' ' << "=";
+// TYPE:   printer << ' ';
+// TYPE:   printer << getV1();
+// TYPE:   printer << ",";
+// TYPE:   printer << ' ' << "v3";
+// TYPE:   printer << ' ' << "=";
+// TYPE:   printer << ' ';
+// TYPE:   printer << getV3();
+// TYPE: }
+
+def TypeC : TestType<"TestE"> {
+  let parameters = (ins
+      "IntegerAttr":$v0,
+      "IntegerAttr":$v1,
+      "IntegerAttr":$v2,
+      "IntegerAttr":$v3
+  );
+
+  let mnemonic = "type_e";
+  let assemblyFormat = "`{` struct($v0, $v2) `}` `{` struct($v1, $v3) `}`";
+}

mlir/tools/mlir-tblgen/AttrOrTypeDefGen.cpp

 //===- AttrOrTypeDefGen.cpp - MLIR AttrOrType definitions generator -------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
+#include "AttrOrTypeFormatGen.h"
 #include "mlir/Support/LogicalResult.h"
 #include "mlir/TableGen/AttrOrTypeDef.h"
 #include "mlir/TableGen/CodeGenHelpers.h"
 #include "mlir/TableGen/Format.h"
 #include "mlir/TableGen/GenInfo.h"
 #include "mlir/TableGen/Interfaces.h"
 #include "llvm/ADT/Sequence.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/TableGenBackend.h"
 
 #define DEBUG_TYPE "mlir-tblgen-attrortypedefgen"
 
 using namespace mlir;
 using namespace mlir::tblgen;
 
+//===----------------------------------------------------------------------===//
+// Utility Functions
+//===----------------------------------------------------------------------===//
+
+std::string mlir::tblgen::getParameterAccessorName(StringRef name) {
+  assert(!name.empty() && "parameter has empty name");
+  auto ret = "get" + name.str();
+  ret[3] = llvm::toUpper(ret[3]); // uppercase first letter of the name
+  return ret;
+}
+
 /// Find all the AttrOrTypeDef for the specified dialect. If no dialect
 /// specified and can only find one dialect's defs, use that.
 static void collectAllDefs(StringRef selectedDialect,
                            std::vector<llvm::Record *> records,
                            SmallVectorImpl<AttrOrTypeDef> &resultDefs) {
   auto defs = llvm::map_range(
       records, [&](const llvm::Record *rec) { return AttrOrTypeDef(rec); });
   if (defs.empty())
void DefGenerator::emitDefDecl(const AttrOrTypeDef &def) {
 
   // Emit the mnenomic, if specified.
   if (auto mnenomic = def.getMnemonic()) {
     os << "    static constexpr ::llvm::StringLiteral getMnemonic() {\n"
        << "      return ::llvm::StringLiteral(\"" << mnenomic << "\");\n"
        << "    }\n";
 
     // If mnemonic specified, emit print/parse declarations.
-    if (def.getParserCode() || def.getPrinterCode() || !params.empty()) {
+    if (def.getParserCode() || def.getPrinterCode() ||
+        def.getAssemblyFormat() || !params.empty()) {
       os << llvm::formatv(defDeclParsePrintStr, valueType,
                           isAttrGenerator ? ", ::mlir::Type type" : "");
     }
   }
 
   if (def.genAccessors()) {
     SmallVector<AttrOrTypeParameter, 4> parameters;
     def.getParameters(parameters);
 
     for (AttrOrTypeParameter &parameter : parameters) {
-      SmallString<16> name = parameter.getName();
-      name[0] = llvm::toUpper(name[0]);
-      os << formatv("    {0} get{1}() const;\n", parameter.getCppAccessorType(),
-                    name);
+      os << formatv("    {0} {1}() const;\n", parameter.getCppAccessorType(),
+                    getParameterAccessorName(parameter.getName()));
     }
   }
 
   // Emit any interface method declarations.
   for (const Trait &trait : def.getTraits()) {
     if (const auto *traitDef = dyn_cast<InterfaceTrait>(&trait)) {
       if (traitDef->shouldDeclareMethods())
         emitInterfaceMethodDecls(traitDef, os);
if (!isa<AttributeSelfTypeParameter>(parameter))
          << ";\n";
   }
   os << "  };\n";
 
   os << "} // namespace " << def.getStorageNamespace() << "\n";
 }
 
 void DefGenerator::emitParsePrint(const AttrOrTypeDef &def) {
+  auto printerCode = def.getPrinterCode();
+  auto parserCode = def.getParserCode();
+  auto assemblyFormat = def.getAssemblyFormat();
+  if (assemblyFormat && (printerCode || parserCode)) {
+    // Custom assembly format cannot be specified at the same time as either
+    // custom printer or parser code.
+    PrintFatalError(def.getLoc(),
+                    def.getName() + ": assembly format cannot be specified at "
+                                    "the same time as printer or parser code");
+  }
+
+  // Generate a parser and printer based on the assembly format, if specified.
+  if (assemblyFormat) {
+    // A custom assembly format requires accessors to be generated for the
+    // generated printer.
+    if (!def.genAccessors()) {
+      PrintFatalError(def.getLoc(),
+                      def.getName() +
+                          ": the generated printer from 'assemblyFormat' "
+                          "requires 'genAccessors' to be true");
+    }
+    return generateAttrOrTypeFormat(def, os);
+  }
+
   // Emit the printer code, if specified.
-  if (Optional<StringRef> printerCode = def.getPrinterCode()) {
+  if (printerCode) {
     // Both the mnenomic and printerCode must be defined (for parity with
     // parserCode).
     os << "void " << def.getCppClassName()
        << "::print(::mlir::DialectAsmPrinter &printer) const {\n";
     if (printerCode->empty()) {
       // If no code specified, emit error.
       PrintFatalError(def.getLoc(),
                       def.getName() +
                           ": printer (if specified) must have non-empty code");
     }
     FmtContext fmtCtxt = FmtContext().addSubst("_printer", "printer");
     os << tgfmt(*printerCode, &fmtCtxt) << "\n}\n";
   }
 
   // Emit the parser code, if specified.
-  if (Optional<StringRef> parserCode = def.getParserCode()) {
+  if (parserCode) {
     FmtContext fmtCtxt;
     fmtCtxt.addSubst("_parser", "parser")
         .addSubst("_ctxt", "parser.getContext()");
 
     // The mnenomic must be defined so the dispatcher knows how to dispatch.
     os << llvm::formatv("::mlir::{0} {1}::parse("
                         "::mlir::DialectAsmParser &parser",
                         valueType, def.getCppClassName());
if (def.genAccessors() && def.genStorageClass()) {
         SmallString<32> paramStorageName;
         if (isa<AttributeSelfTypeParameter>(param)) {
           Twine("getType().cast<" + param.getCppType() + ">()")
               .toVector(paramStorageName);
         } else {
           paramStorageName = param.getName();
         }
 
-        SmallString<16> name = param.getName();
-        name[0] = llvm::toUpper(name[0]);
-        os << formatv("{0} {3}::get{1}() const {{ return getImpl()->{2}; }\n",
-                      param.getCppAccessorType(), name, paramStorageName,
-                      def.getCppClassName());
+        os << formatv("{0} {3}::{1}() const {{ return getImpl()->{2}; }\n",
+                      param.getCppAccessorType(),
+                      getParameterAccessorName(param.getName()),
+                      paramStorageName, def.getCppClassName());
       }
     }
   }
 
   // If mnemonic is specified maybe print definitions for the parser and printer
   // code, if they're specified.
   if (def.getMnemonic())
     emitParsePrint(def);

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.h

+//===- AttrOrTypeFormatGen.h - MLIR attribute and type format generator ---===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TOOLS_MLIRTBLGEN_ATTRORTYPEFORMATGEN_H_
+#define MLIR_TOOLS_MLIRTBLGEN_ATTRORTYPEFORMATGEN_H_
+
+#include "llvm/Support/raw_ostream.h"
+
+#include <string>
+
+namespace mlir {
+namespace tblgen {
+class AttrOrTypeDef;
+
+/// Generate a parser and printer based on a custom assembly format for an
+/// attribute or type.
+void generateAttrOrTypeFormat(const AttrOrTypeDef &def, llvm::raw_ostream &os);
+
+/// From the parameter name, get the name of the accessor function in camelcase.
+/// The first letter of the parameter is upper-cased and prefixed with "get".
+/// E.g. 'value' -> 'getValue'.
+std::string getParameterAccessorName(llvm::StringRef name);
+
+} // end namespace tblgen
+} // end namespace mlir
+
+#endif // MLIR_TOOLS_MLIRTBLGEN_ATTRORTYPEFORMATGEN_H_

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

+//===- AttrOrTypeFormatGen.cpp - MLIR attribute and type format generator -===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "AttrOrTypeFormatGen.h"
+#include "FormatGen.h"
+#include "mlir/Support/LLVM.h"
+#include "mlir/Support/LogicalResult.h"
+#include "mlir/TableGen/AttrOrTypeDef.h"
+#include "mlir/TableGen/Format.h"
+#include "mlir/TableGen/GenInfo.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/TableGen/Error.h"
+#include "llvm/TableGen/TableGenBackend.h"
+
+using namespace mlir;
+using namespace mlir::tblgen;
+
+using llvm::formatv;
+
+//===----------------------------------------------------------------------===//
+// Element
+//===----------------------------------------------------------------------===//
+
+namespace {
+
+/// This class represents a single format element.
+class Element {
+public:
+  /// LLVM-style RTTI.
+  enum class Kind {
+    /// This element is a directive.
+    ParamsDirective,
+    StructDirective,
+
+    /// This element is a literal.
+    Literal,
+
+    /// This element is a variable.
+    Variable,
+  };
+  Element(Kind kind) : kind(kind) {}
+  virtual ~Element() = default;
+
+  /// Return the kind of this element.
+  Kind getKind() const { return kind; }
+
+private:
+  /// The kind of this element.
+  Kind kind;
+};
+
+/// This class represents an instance of a literal element.
+class LiteralElement : public Element {
+public:
+  LiteralElement(StringRef literal)
+      : Element(Kind::Literal), literal(literal) {}
+
+  static bool classof(const Element *el) {
+    return el->getKind() == Kind::Literal;
+  }
+
+  /// Get the literal spelling.
+  StringRef getSpelling() const { return literal; }
+
+private:
+  /// The spelling of the literal for this element.
+  StringRef literal;
+};
+
+/// This class represents an instance of a variable element. A variable refers
+/// to an attribute or type parameter.
+class VariableElement : public Element {
+public:
+  VariableElement(AttrOrTypeParameter param)
+      : Element(Kind::Variable), param(param) {}
+
+  static bool classof(const Element *el) {
+    return el->getKind() == Kind::Variable;
+  }
+
+  /// Get the parameter in the element.
+  const AttrOrTypeParameter &getParam() const { return param; }
+
+private:
+  AttrOrTypeParameter param;
+};
+
+/// This class represents a `params` directive that refers to all parameters
+/// of an attribute or type.
+class ParamsDirective : public Element {
+public:
+  ParamsDirective() : Element(Kind::ParamsDirective) {}
+
+  static bool classof(const Element *el) {
+    return el->getKind() == Kind::ParamsDirective;
+  }
+};
+
+/// This class represents a `struct` directive that generates a struct format
+/// of the form:
+///
+///   `{` param-name `=` param-value (`,` param-name `=` param-value)* `}`
+///
+class StructDirective : public Element {
+public:
+  StructDirective(SmallVector<std::unique_ptr<Element>> &&params)
+      : Element(Kind::StructDirective), params(std::move(params)) {}
+
+  static bool classof(const Element *el) {
+    return el->getKind() == Kind::StructDirective;
+  }
+
+  /// Get the parameters contained within the struct.
+  auto getParams() const {
+    return llvm::map_range(params, [](auto &el) {
+      return cast<VariableElement>(el.get())->getParam();
+    });
+  }
+
+  /// Get the number of parameters.
+  unsigned getNumParams() const { return params.size(); }
+
+private:
+  SmallVector<std::unique_ptr<Element>> params;
+};
+
+} // end anonymous namespace
+
+//===----------------------------------------------------------------------===//
+// Format Strings
+//===----------------------------------------------------------------------===//
+
+/// Format for defining an attribute parser.
+///
+/// $0: The attribute C++ class name.
+static const char *const attrParserDefn = R"(
+::mlir::Attribute $0::parse(::mlir::DialectAsmParser &$_parser,
+                             ::mlir::Type $_type) {
+)";
+
+/// Format for defining a type parser.
+///
+/// $0: The type C++ class name.
+static const char *const typeParserDefn = R"(
+::mlir::Type $0::parse(::mlir::DialectAsmParser &$_parser) {
+)";
+
+/// Default parser for attribute or type parameters.
+static const char *const defaultParameterParser =
+    "::mlir::FieldParser<$0>::parse($_parser)";
+
+/// Default printer for attribute or type parameters.
+static const char *const defaultParameterPrinter = "$_printer << $_self";
+
+/// Print an error when failing to parse an element.
+///
+/// $0: The parameter C++ class name.
+static const char *const parseErrorStr =
+    "$_parser.emitError($_parser.getCurrentLocation(), ";
+
+/// Format for defining an attribute or type printer.
+///
+/// $0: The attribute or type C++ class name.
+/// $1: The attribute or type mnemonic.
+static const char *const attrOrTypePrinterDefn = R"(
+void $0::print(::mlir::DialectAsmPrinter &$_printer) const {
+  $_printer << "$1";
+)";
+
+/// Loop declaration for struct parser.
+///
+/// $0: Number of expected parameters.
+static const char *const structParseLoopStart = R"(
+  for (unsigned _index = 0; _index < $0; ++_index) {
+    StringRef _paramKey;
+    if ($_parser.parseKeyword(&_paramKey)) {
+      $_parser.emitError($_parser.getCurrentLocation(),
+                         "expected a parameter name in struct");
+      return {};
+    }
+)";
+
+/// Terminator code segment for the struct parser loop. Check for duplicate or
+/// unknown parameters. Parse a comma except on the last element.
+///
+/// {0}: Code template for printing an error.
+/// {1}: Number of elements in the struct.
+static const char *const structParseLoopEnd = R"({{
+      {0}"duplicate or unknown struct parameter name: ") << _paramKey;
+      return {{};
+    }
+    if ((_index != {1} - 1) && parser.parseComma())
+      return {{};
+  }
+)";
+
+/// Code format to parse a variable. Separate by lines because variable parsers
+/// may be generated inside other directives, which requires indentation.
+///
+/// {0}: The parameter name.
+/// {1}: The parse code for the parameter.
+/// {2}: Code template for printing an error.
+/// {3}: Name of the attribute or type.
+/// {4}: C++ class of the parameter.
+static const char *const variableParser[] = {
+    "  // Parse variable '{0}'",
+    "  _result_{0} = {1};",
+    "  if (failed(_result_{0})) {{",
+    "    {2}\"failed to parse {3} parameter '{0}' which is to be a `{4}`\");",
+    "    return {{};",
+    "  }",
+};
+
+//===----------------------------------------------------------------------===//
+// Utility Functions
+//===----------------------------------------------------------------------===//
+
+/// Get a list of an attribute's or type's parameters. These can be wrapper
+/// objects around `AttrOrTypeParameter` or string inits.
+static auto getParameters(const AttrOrTypeDef &def) {
+  SmallVector<AttrOrTypeParameter> params;
+  def.getParameters(params);
+  return params;
+}
+
+//===----------------------------------------------------------------------===//
+// AttrOrTypeFormat
+//===----------------------------------------------------------------------===//
+
+namespace {
+class AttrOrTypeFormat {
+public:
+  AttrOrTypeFormat(const AttrOrTypeDef &def,
+                   std::vector<std::unique_ptr<Element>> &&elements)
+      : def(def), elements(std::move(elements)) {}
+
+  /// Generate the attribute or type parser.
+  void genParser(raw_ostream &os);
+  /// Generate the attribute or type printer.
+  void genPrinter(raw_ostream &os);
+
+private:
+  /// Generate the parser code for a specific format element.
+  void genElementParser(Element *el, FmtContext &ctx, raw_ostream &os);
+  /// Generate the parser code for a literal.
+  void genLiteralParser(StringRef value, FmtContext &ctx, raw_ostream &os,
+                        unsigned indent = 0);
+  /// Generate the parser code for a variable.
+  void genVariableParser(const AttrOrTypeParameter &param, FmtContext &ctx,
+                         raw_ostream &os, unsigned indent = 0);
+  /// Generate the parser code for a `struct` directive.
+  void genStructParser(StructDirective *el, FmtContext &ctx, raw_ostream &os);
+
+  /// Generate the printer code for a specific format element.
+  void genElementPrinter(Element *el, FmtContext &ctx, raw_ostream &os);
+  /// Generate the printer code for a literal.
+  void genLiteralPrinter(StringRef value, FmtContext &ctx, raw_ostream &os);
+  /// Generate the printer code for a variable.
+  void genVariablePrinter(const AttrOrTypeParameter &param, FmtContext &ctx,
+                          raw_ostream &os);
+  /// Generate the printer code for a `struct` directive.
+  void genStructPrinter(StructDirective *el, FmtContext &ctx, raw_ostream &os);
+
+  /// The ODS definition of the attribute or type whose format is being used to
+  /// generate a parser and printer.
+  const AttrOrTypeDef &def;
+  /// The list of top-level format elements returned by the assembly format
+  /// parser.
+  std::vector<std::unique_ptr<Element>> elements;
+
+  /// Flags for printing spaces.
+  bool shouldEmitSpace;
+  bool lastWasPunctuation;
+};
+} // end anonymous namespace
+
+//===----------------------------------------------------------------------===//
+// ParserGen
+//===----------------------------------------------------------------------===//
+
+void AttrOrTypeFormat::genParser(raw_ostream &os) {
+  FmtContext ctx;
+  ctx.addSubst("_parser", "parser");
+
+  /// Generate the definition.
+  if (isa<AttrDef>(def)) {
+    ctx.addSubst("_type", "attrType");
+    os << tgfmt(attrParserDefn, &ctx, def.getCppClassName());
+  } else {
+    os << tgfmt(typeParserDefn, &ctx, def.getCppClassName());
+  }
+
+  /// Declare variables to store all of the parameters. Allocated parameters
+  /// such as `ArrayRef` and `StringRef` must provide a `storageType`. Store
+  /// FailureOr<T> to defer type construction for parameters that are parsed in
+  /// a loop (parsers return FailureOr anyways).
+  SmallVector<AttrOrTypeParameter> params = getParameters(def);
+  for (const AttrOrTypeParameter &param : params) {
+    os << formatv("  ::mlir::FailureOr<{0}> _result_{1};\n",
+                  param.getCppStorageType(), param.getName());
+  }
+
+  /// Store the initial location of the parser.
+  ctx.addSubst("_loc", "loc");
+  os << tgfmt("  ::llvm::SMLoc $_loc = $_parser.getCurrentLocation();\n"
+              "  (void) $_loc;\n",
+              &ctx);
+
+  /// Generate call to each parameter parser.
+  for (auto &el : elements)
+    genElementParser(el.get(), ctx, os);
+
+  /// Generate call to the attribute or type builder. Use the checked getter
+  /// if one was generated.
+  if (def.genVerifyDecl()) {
+    os << tgfmt("  return $_parser.getChecked<$0>($_loc, $_parser.getContext()",
+                &ctx, def.getCppClassName());
+  } else {
+    os << tgfmt("  return $0::get($_parser.getContext()", &ctx,
+                def.getCppClassName());
+  }
+  for (const AttrOrTypeParameter &param : params)
+    os << formatv(",\n    _result_{0}.getValue()", param.getName());
+  os << ");\n}\n\n";
+}
+
+void AttrOrTypeFormat::genElementParser(Element *el, FmtContext &ctx,
+                                        raw_ostream &os) {
+  if (auto *literal = dyn_cast<LiteralElement>(el))
+    return genLiteralParser(literal->getSpelling(), ctx, os);
+  if (auto *var = dyn_cast<VariableElement>(el))
+    return genVariableParser(var->getParam(), ctx, os);
+  if (auto *strct = dyn_cast<StructDirective>(el))
+    return genStructParser(strct, ctx, os);
+
+  llvm_unreachable("unknown format element");
+}
+
+void AttrOrTypeFormat::genLiteralParser(StringRef value, FmtContext &ctx,
+                                        raw_ostream &os, unsigned indent) {
+  os.indent(indent) << "  // Parse literal '" << value << "'\n";
+  os.indent(indent) << tgfmt("  if ($_parser.parse", &ctx);
+  if (value.front() == '_' || isalpha(value.front())) {
+    os << "Keyword(\"" << value << "\")";
+  } else {
+    os << StringSwitch<StringRef>(value)
+              .Case("->", "Arrow")
+              .Case(":", "Colon")
+              .Case(",", "Comma")
+              .Case("=", "Equal")
+              .Case("<", "Less")
+              .Case(">", "Greater")
+              .Case("{", "LBrace")
+              .Case("}", "RBrace")
+              .Case("(", "LParen")
+              .Case(")", "RParen")
+              .Case("[", "LSquare")
+              .Case("]", "RSquare")
+              .Case("?", "Question")
+              .Case("+", "Plus")
+              .Case("*", "Star")
+       << "()";
+  }
+  os << ")\n";
+  // Parser will emit an error
+  os.indent(indent) << "    return {};\n";
+}
+
+void AttrOrTypeFormat::genVariableParser(const AttrOrTypeParameter &param,
+                                         FmtContext &ctx, raw_ostream &os,
+                                         unsigned indent) {
+  /// Check for a custom parser. Use the default attribute parser otherwise.
+  auto customParser = param.getParser();
+  auto parser =
+      customParser ? *customParser : StringRef(defaultParameterParser);
+  for (const char *line : variableParser) {
+    os.indent(indent) << formatv(line, param.getName(),
+                                 tgfmt(parser, &ctx, param.getCppStorageType()),
+                                 tgfmt(parseErrorStr, &ctx), def.getName(),
+                                 param.getCppType())
+                      << "\n";
+  }
+}
+
+void AttrOrTypeFormat::genStructParser(StructDirective *el, FmtContext &ctx,
+                                       raw_ostream &os) {
+  os << "  // Parse parameter struct\n";
+
+  /// Declare a "seen" variable for each key.
+  for (const AttrOrTypeParameter &param : el->getParams())
+    os << formatv("  bool _seen_{0} = false;\n", param.getName());
+
+  /// Generate the parsing loop.
+  os << tgfmt(structParseLoopStart, &ctx, el->getNumParams());
+  genLiteralParser("=", ctx, os, 2);
+  os << "    ";
+  for (const AttrOrTypeParameter &param : el->getParams()) {
+    os << formatv("if (!_seen_{0} && _paramKey == \"{0}\") {\n"
+                  "      _seen_{0} = true;\n",
+                  param.getName());
+    genVariableParser(param, ctx, os, 4);
+    os << "    } else ";
+  }
+
+  /// Duplicate or unknown parameter.
+  os << formatv(structParseLoopEnd, tgfmt(parseErrorStr, &ctx),
+                el->getNumParams());
+
+  /// Because the loop loops N times and each non-failing iteration sets 1 of
+  /// N flags, successfully exiting the loop means that all parameters have been
+  /// seen. `parseOptionalComma` would cause issues with any formats that use
+  /// "struct(...) `,`" beacuse structs aren't sounded by braces.
+}
+
+//===----------------------------------------------------------------------===//
+// PrinterGen
+//===----------------------------------------------------------------------===//
+
+void AttrOrTypeFormat::genPrinter(raw_ostream &os) {
+  FmtContext ctx;
+  ctx.addSubst("_printer", "printer");
+
+  /// Generate the definition.
+  os << tgfmt(attrOrTypePrinterDefn, &ctx, def.getCppClassName(),
+              *def.getMnemonic());
+
+  /// Generate printers.
+  shouldEmitSpace = true;
+  lastWasPunctuation = false;
+  for (auto &el : elements)
+    genElementPrinter(el.get(), ctx, os);
+
+  os << "}\n\n";
+}
+
+void AttrOrTypeFormat::genElementPrinter(Element *el, FmtContext &ctx,
+                                         raw_ostream &os) {
+  if (auto *literal = dyn_cast<LiteralElement>(el))
+    return genLiteralPrinter(literal->getSpelling(), ctx, os);
+  if (auto *strct = dyn_cast<StructDirective>(el))
+    return genStructPrinter(strct, ctx, os);
+
+  /// Insert a space before the next element, if necessary.
+  if (shouldEmitSpace || !lastWasPunctuation)
+    os << tgfmt("  $_printer << ' ';\n", &ctx);
+  shouldEmitSpace = true;
+  lastWasPunctuation = false;
+
+  if (auto *var = dyn_cast<VariableElement>(el))
+    return genVariablePrinter(var->getParam(), ctx, os);
+
+  llvm_unreachable("unknown format element");
+}
+
+void AttrOrTypeFormat::genLiteralPrinter(StringRef value, FmtContext &ctx,
+                                         raw_ostream &os) {
+  /// Don't insert a space before certain punctuation.
+  bool needSpace =
+      shouldEmitSpace && shouldEmitSpaceBefore(value, lastWasPunctuation);
+  os << tgfmt("  $_printer$0 << \"$1\";\n", &ctx, needSpace ? " << ' '" : "",
+              value);
+
+  /// Update the flags.
+  shouldEmitSpace =
+      value.size() != 1 || !StringRef("<({[").contains(value.front());
+  lastWasPunctuation = !(value.front() == '_' || isalpha(value.front()));
+}
+
+void AttrOrTypeFormat::genVariablePrinter(const AttrOrTypeParameter &param,
+                                          FmtContext &ctx, raw_ostream &os) {
+  ctx.withSelf(getParameterAccessorName(param.getName()) + "()");
+  os << "  ";
+  if (auto printer = param.getPrinter())
+    os << tgfmt(*printer, &ctx) << ";\n";
+  else
+    os << tgfmt(defaultParameterPrinter, &ctx) << ";\n";
+}
+
+void AttrOrTypeFormat::genStructPrinter(StructDirective *el, FmtContext &ctx,
+                                        raw_ostream &os) {
+  llvm::interleave(
+      el->getParams(),
+      [&](auto param) {
+        genLiteralPrinter(param.getName(), ctx, os);
+        genLiteralPrinter("=", ctx, os);
+        os << tgfmt("  $_printer << ' ';\n", &ctx);
+        genVariablePrinter(param, ctx, os);
+      },
+      [&]() { genLiteralPrinter(",", ctx, os); });
+}
+
+//===----------------------------------------------------------------------===//
+// FormatParser
+//===----------------------------------------------------------------------===//
+
+namespace {
+class FormatParser {
+public:
+  FormatParser(llvm::SourceMgr &mgr, const AttrOrTypeDef &def)
+      : lexer(mgr, def.getLoc()[0]), curToken(lexer.lexToken()), def(def),
+        seenParams(def.getNumParameters()) {}
+
+  /// Parse the attribute or type format and create the format elements.
+  FailureOr<AttrOrTypeFormat> parse();
+
+private:
+  /// The current context of the parser when parsing an element.
+  enum ParserContext {
+    /// The element is being parsed in the default context - at the top of the
+    /// format
+    TopLevelContext,
+    /// The element is being parsed as a child to a `struct` directive.
+    StructDirective,
+  };
+
+  /// Emit an error.
+  LogicalResult emitError(const Twine &msg) {
+    lexer.emitError(curToken.getLoc(), msg);
+    return failure();
+  }
+
+  /// Parse an expected token.
+  LogicalResult parseToken(FormatToken::Kind kind, const Twine &msg) {
+    if (curToken.getKind() != kind)
+      return emitError(msg);
+    consumeToken();
+    return success();
+  }
+
+  /// Advance the lexer to the next token.
+  void consumeToken() {
+    assert(curToken.getKind() != FormatToken::eof &&
+           curToken.getKind() != FormatToken::error &&
+           "shouldn't advance past EOF or errors");
+    curToken = lexer.lexToken();
+  }
+
+  /// Parse any element.
+  FailureOr<std::unique_ptr<Element>> parseElement(ParserContext ctx);
+  /// Parse a literal element.
+  FailureOr<std::unique_ptr<Element>> parseLiteral(ParserContext ctx);
+  /// Parse a variable element.
+  FailureOr<std::unique_ptr<Element>> parseVariable(ParserContext ctx);
+  /// Parse a directive.
+  FailureOr<std::unique_ptr<Element>> parseDirective(ParserContext ctx);
+  /// Parse a `params` directive.
+  FailureOr<std::unique_ptr<Element>> parseParamsDirective();
+  /// Parse a `struct` directive.
+  FailureOr<std::unique_ptr<Element>> parseStructDirective();
+
+  /// The current format lexer.
+  FormatLexer lexer;
+  /// The current token in the stream.
+  FormatToken curToken;
+  /// Attribute or type tablegen def.
+  const AttrOrTypeDef &def;
+
+  /// Seen attribute or type parameters.
+  llvm::BitVector seenParams;
+};
+} // end anonymous namespace
+
+FailureOr<AttrOrTypeFormat> FormatParser::parse() {
+  std::vector<std::unique_ptr<Element>> elements;
+  elements.reserve(16);
+
+  /// Parse the format elements.
+  while (curToken.getKind() != FormatToken::eof) {
+    auto element = parseElement(TopLevelContext);
+    if (failed(element))
+      return failure();
+
+    /// Add the format element and continue.
+    elements.push_back(std::move(*element));
+  }
+
+  /// Check that all parameters have been seen.
+  SmallVector<AttrOrTypeParameter> params = getParameters(def);
+  for (auto it : llvm::enumerate(params)) {
+    if (!seenParams.test(it.index())) {
+      return emitError("format is missing reference to parameter: " +
+                       it.value().getName());
+    }
+  }
+
+  return AttrOrTypeFormat(def, std::move(elements));
+}
+
+FailureOr<std::unique_ptr<Element>>
+FormatParser::parseElement(ParserContext ctx) {
+  if (curToken.getKind() == FormatToken::literal)
+    return parseLiteral(ctx);
+  if (curToken.getKind() == FormatToken::variable)
+    return parseVariable(ctx);
+  if (curToken.isKeyword())
+    return parseDirective(ctx);
+
+  return emitError("expected literal, directive, or variable");
+}
+
+FailureOr<std::unique_ptr<Element>>
+FormatParser::parseLiteral(ParserContext ctx) {
+  if (ctx != TopLevelContext) {
+    return emitError(
+        "literals may only be used in the top-level section of the format");
+  }
+
+  /// Get the literal spelling without the surrounding "`".
+  auto value = curToken.getSpelling().drop_front().drop_back();
+  if (!isValidLiteral(value))
+    return emitError("literal '" + value + "' is not valid");
+
+  consumeToken();
+  return {std::make_unique<LiteralElement>(value)};
+}
+
+FailureOr<std::unique_ptr<Element>>
+FormatParser::parseVariable(ParserContext ctx) {
+  /// Get the parameter name without the preceding "$".
+  auto name = curToken.getSpelling().drop_front();
+
+  /// Lookup the parameter.
+  SmallVector<AttrOrTypeParameter> params = getParameters(def);
+  auto *it = llvm::find_if(
+      params, [&](auto &param) { return param.getName() == name; });
+
+  /// Check that the parameter reference is valid.
+  if (it == params.end())
+    return emitError(def.getName() + " has no parameter named '" + name + "'");
+  auto idx = std::distance(params.begin(), it);
+  if (seenParams.test(idx))
+    return emitError("duplicate parameter '" + name + "'");
+  seenParams.set(idx);
+
+  consumeToken();
+  return {std::make_unique<VariableElement>(*it)};
+}
+
+FailureOr<std::unique_ptr<Element>>
+FormatParser::parseDirective(ParserContext ctx) {
+
+  switch (curToken.getKind()) {
+  case FormatToken::kw_params:
+    if (ctx == TopLevelContext) {
+      return emitError(
+          "`params` may not be used in the top-level section of the format");
+    }
+    return parseParamsDirective();
+  case FormatToken::kw_struct:
+    if (ctx != TopLevelContext) {
+      return emitError(
+          "`struct` may only be used in the top-level section of the format");
+    }
+    return parseStructDirective();
+  default:
+    return emitError("unknown directive in format: " + curToken.getSpelling());
+  }
+}
+
+FailureOr<std::unique_ptr<Element>> FormatParser::parseParamsDirective() {
+  consumeToken();
+  return {std::make_unique<ParamsDirective>()};
+}
+
+FailureOr<std::unique_ptr<Element>> FormatParser::parseStructDirective() {
+  consumeToken();
+  if (failed(parseToken(FormatToken::l_paren,
+                        "expected '(' before `struct` argument list")))
+    return failure();
+
+  /// Parse variables captured by `struct`.
+  SmallVector<std::unique_ptr<Element>> vars;
+
+  /// Parse first captured parameter or a `params` directive.
+  FailureOr<std::unique_ptr<Element>> var = parseElement(StructDirective);
+  if (failed(var) || !isa<VariableElement, ParamsDirective>(*var)) {
+    return emitError("`struct` argument list expected a variable or directive");
+  }
+  if (isa<VariableElement>(*var)) {
+    /// Parse any other parameters.
+    vars.push_back(std::move(*var));
+    while (curToken.getKind() == FormatToken::comma) {
+      consumeToken();
+      var = parseElement(StructDirective);
+      if (failed(var) || !isa<VariableElement>(*var))
+        return emitError("expected a variable in `struct` argument list");
+      vars.push_back(std::move(*var));
+    }
+  } else {
+    /// `struct(params)` captures all parameters in the attribute or type.
+    SmallVector<AttrOrTypeParameter> params = getParameters(def);
+    for (auto it : llvm::enumerate(params)) {
+      if (seenParams.test(it.index())) {
+        return emitError("struct(params) captures duplicate parameter: " +
+                         it.value().getName());
+      }
+      seenParams.set(it.index());
+      vars.push_back(std::make_unique<VariableElement>(it.value()));
+    }
+  }
+
+  if (curToken.getKind() != FormatToken::r_paren)
+    return emitError("expected ')' at the end of an argument list");
+
+  consumeToken();
+  return {std::make_unique<::StructDirective>(std::move(vars))};
+}
+
+//===----------------------------------------------------------------------===//
+// Interface
+//===----------------------------------------------------------------------===//
+
+void mlir::tblgen::generateAttrOrTypeFormat(const AttrOrTypeDef &def,
+                                            raw_ostream &os) {
+  llvm::SourceMgr mgr;
+  mgr.AddNewSourceBuffer(
+      llvm::MemoryBuffer::getMemBuffer(*def.getAssemblyFormat()),
+      llvm::SMLoc());
+
+  /// Parse the custom assembly format>
+  FormatParser parser(mgr, def);
+  FailureOr<AttrOrTypeFormat> format = parser.parse();
+  if (failed(format)) {
+    if (formatErrorIsFatal)
+      PrintFatalError(def.getLoc(), "failed to parse assembly format");
+    return;
+  }
+
+  /// Generate the parser and printer.
+  format->genParser(os);
+  format->genPrinter(os);
+}

mlir/tools/mlir-tblgen/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Demangle
   Support
   TableGen
 )
 
 add_tablegen(mlir-tblgen MLIR
   AttrOrTypeDefGen.cpp
+  AttrOrTypeFormatGen.cpp
   CodeGenHelpers.cpp
   DialectGen.cpp
   DirectiveCommonGen.cpp
   EnumsGen.cpp
+  FormatGen.cpp
   LLVMIRConversionGen.cpp
   LLVMIRIntrinsicGen.cpp
   mlir-tblgen.cpp
   OpDefinitionsGen.cpp
   OpDocGen.cpp
   OpFormatGen.cpp
   OpGenHelpers.cpp
   OpInterfacesGen.cpp

mlir/tools/mlir-tblgen/FormatGen.h

+//===- FormatGen.h - Utilities for custom assembly formats ------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains common classes for building custom assembly format parsers
+// and generators.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TOOLS_MLIRTBLGEN_FORMATGEN_H_
+#define MLIR_TOOLS_MLIRTBLGEN_FORMATGEN_H_
+
+#include "mlir/Support/LLVM.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/SMLoc.h"
+
+namespace llvm {
+class SourceMgr;
+} // end namespace llvm
+
+namespace mlir {
+namespace tblgen {
+
+//===----------------------------------------------------------------------===//
+// FormatToken
+//===----------------------------------------------------------------------===//
+
+/// This class represents a specific token in the input format.
+class FormatToken {
+public:
+  /// Basic token kinds.
+  enum Kind {
+    // Markers.
+    eof,
+    error,
+
+    // Tokens with no info.
+    l_paren,
+    r_paren,
+    caret,
+    colon,
+    comma,
+    equal,
+    less,
+    greater,
+    question,
+    star,
+
+    // Keywords.
+    keyword_start,
+    kw_attr_dict,
+    kw_attr_dict_w_keyword,
+    kw_custom,
+    kw_functional_type,
+    kw_operands,
+    kw_params,
+    kw_ref,
+    kw_regions,
+    kw_results,
+    kw_struct,
+    kw_successors,
+    kw_type,
+    keyword_end,
+
+    // String valued tokens.
+    identifier,
+    literal,
+    variable,
+  };
+
+  FormatToken(Kind kind, StringRef spelling) : kind(kind), spelling(spelling) {}
+
+  /// Return the bytes that make up this token.
+  StringRef getSpelling() const { return spelling; }
+
+  /// Return the kind of this token.
+  Kind getKind() const { return kind; }
+
+  /// Return a location for this token.
+  llvm::SMLoc getLoc() const;
+
+  /// Return if this token is a keyword.
+  bool isKeyword() const {
+    return getKind() > Kind::keyword_start && getKind() < Kind::keyword_end;
+  }
+
+private:
+  /// Discriminator that indicates the kind of token this is.
+  Kind kind;
+
+  /// A reference to the entire token contents; this is always a pointer into
+  /// a memory buffer owned by the source manager.
+  StringRef spelling;
+};
+
+//===----------------------------------------------------------------------===//
+// FormatLexer
+//===----------------------------------------------------------------------===//
+
+/// This class implements a simple lexer for operation assembly format strings.
+class FormatLexer {
+public:
+  FormatLexer(llvm::SourceMgr &mgr, llvm::SMLoc loc);
+
+  /// Lex the next token and return it.
+  FormatToken lexToken();
+
+  /// Emit an error to the lexer with the given location and message.
+  FormatToken emitError(llvm::SMLoc loc, const Twine &msg);
+  FormatToken emitError(const char *loc, const Twine &msg);
+
+  FormatToken emitErrorAndNote(llvm::SMLoc loc, const Twine &msg,
+                               const Twine &note);
+
+private:
+  /// Return the next character in the stream.
+  int getNextChar();
+
+  /// Lex an identifier, literal, or variable.
+  FormatToken lexIdentifier(const char *tokStart);
+  FormatToken lexLiteral(const char *tokStart);
+  FormatToken lexVariable(const char *tokStart);
+
+  /// Create a token with the current pointer and a start pointer.
+  FormatToken formToken(FormatToken::Kind kind, const char *tokStart) {
+    return FormatToken(kind, StringRef(tokStart, curPtr - tokStart));
+  }
+
+  /// The source manager containing the format string.
+  llvm::SourceMgr &mgr;
+  /// Location of the format string.
+  llvm::SMLoc loc;
+  /// Buffer containing the format string.
+  StringRef curBuffer;
+  /// Current pointer in the buffer.
+  const char *curPtr;
+};
+
+/// Whether a space needs to be emitted before a literal. E.g., two keywords
+/// back-to-back require a space separator, but a keyword followed by '<' does
+/// not require a space.
+bool shouldEmitSpaceBefore(StringRef value, bool lastWasPunctuation);
+
+/// Returns true if the given string can be formatted as a keyword.
+bool canFormatStringAsKeyword(StringRef value);
+
+/// Returns true if the given string is valid format literal element.
+bool isValidLiteral(StringRef value);
+
+/// Whether a failure in parsing the assembly format should be a fatal error.
+extern llvm::cl::opt<bool> formatErrorIsFatal;
+
+} // end namespace tblgen
+} // end namespace mlir
+
+#endif // MLIR_TOOLS_MLIRTBLGEN_FORMATGEN_H_

mlir/tools/mlir-tblgen/FormatGen.cpp

+//===- FormatGen.cpp - Utilities for custom assembly formats ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "FormatGen.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/TableGen/Error.h"
+
+using namespace mlir;
+using namespace mlir::tblgen;
+
+//===----------------------------------------------------------------------===//
+// FormatToken
+//===----------------------------------------------------------------------===//
+
+llvm::SMLoc FormatToken::getLoc() const {
+  return llvm::SMLoc::getFromPointer(spelling.data());
+}
+
+//===----------------------------------------------------------------------===//
+// FormatLexer
+//===----------------------------------------------------------------------===//
+
+FormatLexer::FormatLexer(llvm::SourceMgr &mgr, llvm::SMLoc loc)
+    : mgr(mgr), loc(loc),
+      curBuffer(mgr.getMemoryBuffer(mgr.getMainFileID())->getBuffer()),
+      curPtr(curBuffer.begin()) {}
+
+FormatToken FormatLexer::emitError(llvm::SMLoc loc, const Twine &msg) {
+  mgr.PrintMessage(loc, llvm::SourceMgr::DK_Error, msg);
+  llvm::SrcMgr.PrintMessage(this->loc, llvm::SourceMgr::DK_Note,
+                            "in custom assembly format for this operation");
+  return formToken(FormatToken::error, loc.getPointer());
+}
+
+FormatToken FormatLexer::emitError(const char *loc, const Twine &msg) {
+  return emitError(llvm::SMLoc::getFromPointer(loc), msg);
+}
+
+FormatToken FormatLexer::emitErrorAndNote(llvm::SMLoc loc, const Twine &msg,
+                                          const Twine &note) {
+  mgr.PrintMessage(loc, llvm::SourceMgr::DK_Error, msg);
+  llvm::SrcMgr.PrintMessage(this->loc, llvm::SourceMgr::DK_Note,
+                            "in custom assembly format for this operation");
+  mgr.PrintMessage(loc, llvm::SourceMgr::DK_Note, note);
+  return formToken(FormatToken::error, loc.getPointer());
+}
+
+int FormatLexer::getNextChar() {
+  char curChar = *curPtr++;
+  switch (curChar) {
+  default:
+    return (unsigned char)curChar;
+  case 0: {
+    // A nul character in the stream is either the end of the current buffer or
+    // a random nul in the file. Disambiguate that here.
+    if (curPtr - 1 != curBuffer.end())
+      return 0;
+
+    // Otherwise, return end of file.
+    --curPtr;
+    return EOF;
+  }
+  case '\n':
+  case '\r':
+    // Handle the newline character by ignoring it and incrementing the line
+    // count. However, be careful about 'dos style' files with \n\r in them.
+    // Only treat a \n\r or \r\n as a single line.
+    if ((*curPtr == '\n' || (*curPtr == '\r')) && *curPtr != curChar)
+      ++curPtr;
+    return '\n';
+  }
+}
+
+FormatToken FormatLexer::lexToken() {
+  const char *tokStart = curPtr;
+
+  // This always consumes at least one character.
+  int curChar = getNextChar();
+  switch (curChar) {
+  default:
+    // Handle identifiers: [a-zA-Z_]
+    if (isalpha(curChar) || curChar == '_')
+      return lexIdentifier(tokStart);
+
+    // Unknown character, emit an error.
+    return emitError(tokStart, "unexpected character");
+  case EOF:
+    // Return EOF denoting the end of lexing.
+    return formToken(FormatToken::eof, tokStart);
+
+  // Lex punctuation.
+  case '^':
+    return formToken(FormatToken::caret, tokStart);
+  case ':':
+    return formToken(FormatToken::colon, tokStart);
+  case ',':
+    return formToken(FormatToken::comma, tokStart);
+  case '=':
+    return formToken(FormatToken::equal, tokStart);
+  case '<':
+    return formToken(FormatToken::less, tokStart);
+  case '>':
+    return formToken(FormatToken::greater, tokStart);
+  case '?':
+    return formToken(FormatToken::question, tokStart);
+  case '(':
+    return formToken(FormatToken::l_paren, tokStart);
+  case ')':
+    return formToken(FormatToken::r_paren, tokStart);
+  case '*':
+    return formToken(FormatToken::star, tokStart);
+
+  // Ignore whitespace characters.
+  case 0:
+  case ' ':
+  case '\t':
+  case '\n':
+    return lexToken();
+
+  case '`':
+    return lexLiteral(tokStart);
+  case '$':
+    return lexVariable(tokStart);
+  }
+}
+
+FormatToken FormatLexer::lexLiteral(const char *tokStart) {
+  assert(curPtr[-1] == '`');
+
+  // Lex a literal surrounded by ``.
+  while (const char curChar = *curPtr++) {
+    if (curChar == '`')
+      return formToken(FormatToken::literal, tokStart);
+  }
+  return emitError(curPtr - 1, "unexpected end of file in literal");
+}
+
+FormatToken FormatLexer::lexVariable(const char *tokStart) {
+  if (!isalpha(curPtr[0]) && curPtr[0] != '_')
+    return emitError(curPtr - 1, "expected variable name");
+
+  // Otherwise, consume the rest of the characters.
+  while (isalnum(*curPtr) || *curPtr == '_')
+    ++curPtr;
+  return formToken(FormatToken::variable, tokStart);
+}
+
+FormatToken FormatLexer::lexIdentifier(const char *tokStart) {
+  // Match the rest of the identifier regex: [0-9a-zA-Z_\-]*
+  while (isalnum(*curPtr) || *curPtr == '_' || *curPtr == '-')
+    ++curPtr;
+
+  // Check to see if this identifier is a keyword.
+  StringRef str(tokStart, curPtr - tokStart);
+  auto kind =
+      StringSwitch<FormatToken::Kind>(str)
+          .Case("attr-dict", FormatToken::kw_attr_dict)
+          .Case("attr-dict-with-keyword", FormatToken::kw_attr_dict_w_keyword)
+          .Case("custom", FormatToken::kw_custom)
+          .Case("functional-type", FormatToken::kw_functional_type)
+          .Case("operands", FormatToken::kw_operands)
+          .Case("params", FormatToken::kw_params)
+          .Case("ref", FormatToken::kw_ref)
+          .Case("regions", FormatToken::kw_regions)
+          .Case("results", FormatToken::kw_results)
+          .Case("struct", FormatToken::kw_struct)
+          .Case("successors", FormatToken::kw_successors)
+          .Case("type", FormatToken::kw_type)
+          .Default(FormatToken::identifier);
+  return FormatToken(kind, str);
+}
+
+//===----------------------------------------------------------------------===//
+// Utility Functions
+//===----------------------------------------------------------------------===//
+
+bool mlir::tblgen::shouldEmitSpaceBefore(StringRef value,
+                                         bool lastWasPunctuation) {
+  if (value.size() != 1 && value != "->")
+    return true;
+  if (lastWasPunctuation)
+    return !StringRef(">)}],").contains(value.front());
+  return !StringRef("<>(){}[],").contains(value.front());
+}
+
+bool mlir::tblgen::canFormatStringAsKeyword(StringRef value) {
+  if (!isalpha(value.front()) && value.front() != '_')
+    return false;
+  return llvm::all_of(value.drop_front(), [](char c) {
+    return isalnum(c) || c == '_' || c == '$' || c == '.';
+  });
+}
+
+bool mlir::tblgen::isValidLiteral(StringRef value) {
+  if (value.empty())
+    return false;
+  char front = value.front();
+
+  // If there is only one character, this must either be punctuation or a
+  // single character bare identifier.
+  if (value.size() == 1)
+    return isalpha(front) || StringRef("_:,=<>()[]{}?+*").contains(front);
+
+  // Check the punctuation that are larger than a single character.
+  if (value == "->")
+    return true;
+
+  // Otherwise, this must be an identifier.
+  return canFormatStringAsKeyword(value);
+}
+
+//===----------------------------------------------------------------------===//
+// Commandline Options
+//===----------------------------------------------------------------------===//
+
+llvm::cl::opt<bool> mlir::tblgen::formatErrorIsFatal(
+    "asmformat-error-is-fatal",
+    llvm::cl::desc("Emit a fatal error if format parsing fails"),
+    llvm::cl::init(true));

mlir/tools/mlir-tblgen/OpFormatGen.cpp

 //===- OpFormatGen.cpp - MLIR operation asm format generator --------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "OpFormatGen.h"
+#include "FormatGen.h"
 #include "mlir/Support/LogicalResult.h"
 #include "mlir/TableGen/Format.h"
 #include "mlir/TableGen/GenInfo.h"
 #include "mlir/TableGen/Interfaces.h"
 #include "mlir/TableGen/OpClass.h"
 #include "mlir/TableGen/Operator.h"
 #include "mlir/TableGen/Trait.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/Sequence.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/TypeSwitch.h"
-#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Record.h"
 
 #define DEBUG_TYPE "mlir-tblgen-opformatgen"
 
 using namespace mlir;
 using namespace mlir::tblgen;
 
-static llvm::cl::opt<bool> formatErrorIsFatal(
-    "asmformat-error-is-fatal",
-    llvm::cl::desc("Emit a fatal error if format parsing fails"),
-    llvm::cl::init(true));
-
-/// Returns true if the given string can be formatted as a keyword.
-static bool canFormatStringAsKeyword(StringRef value) {
-  if (!isalpha(value.front()) && value.front() != '_')
-    return false;
-  return llvm::all_of(value.drop_front(), [](char c) {
-    return isalnum(c) || c == '_' || c == '$' || c == '.';
-  });
-}
-
 //===----------------------------------------------------------------------===//
 // Element
 //===----------------------------------------------------------------------===//
 
 namespace {
 /// This class represents a single format element.
 class Element {
 public:
LiteralElement(StringRef literal)
       : Element{Kind::Literal}, literal(literal) {}
   static bool classof(const Element *element) {
     return element->getKind() == Kind::Literal;
   }
 
   /// Return the literal for this element.
   StringRef getLiteral() const { return literal; }
 
-  /// Returns true if the given string is a valid literal.
-  static bool isValidLiteral(StringRef value);
-
 private:
   /// The spelling of the literal for this element.
   StringRef literal;
 };
 } // end anonymous namespace
 
-bool LiteralElement::isValidLiteral(StringRef value) {
-  if (value.empty())
-    return false;
-  char front = value.front();
-
-  // If there is only one character, this must either be punctuation or a
-  // single character bare identifier.
-  if (value.size() == 1)
-    return isalpha(front) || StringRef("_:,=<>()[]{}?+*").contains(front);
-
-  // Check the punctuation that are larger than a single character.
-  if (value == "->")
-    return true;
-
-  // Otherwise, this must be an identifier.
-  return canFormatStringAsKeyword(value);
-}
-
 //===----------------------------------------------------------------------===//
 // WhitespaceElement
 
 namespace {
 /// This class represents a whitespace element, e.g. newline or space. It's a
 /// literal that is printed but never parsed.
 class WhitespaceElement : public Element {
 public:

 /// Generate the printer for a literal value. `shouldEmitSpace` is true if a
 /// space should be emitted before this element. `lastWasPunctuation` is true if
 /// the previous element was a punctuation literal.
 static void genLiteralPrinter(StringRef value, OpMethodBody &body,
                               bool &shouldEmitSpace, bool &lastWasPunctuation) {
   body << "  p";
 
   // Don't insert a space for certain punctuation.
-  auto shouldPrintSpaceBeforeLiteral = [&] {
-    if (value.size() != 1 && value != "->")
-      return true;
-    if (lastWasPunctuation)
-      return !StringRef(">)}],").contains(value.front());
-    return !StringRef("<>(){}[],").contains(value.front());
-  };
-  if (shouldEmitSpace && shouldPrintSpaceBeforeLiteral())
+  if (shouldEmitSpace && shouldEmitSpaceBefore(value, lastWasPunctuation))
     body << " << ' '";
   body << " << \"" << value << "\";\n";
 
   // Insert a space after certain literals.
   shouldEmitSpace =
       value.size() != 1 || !StringRef("<({[").contains(value.front());
   lastWasPunctuation = !(value.front() == '_' || isalpha(value.front()));
 }
void OperationFormat::genPrinter(Operator &op, OpClass &opClass) {
   // punctuation.
   bool shouldEmitSpace = true, lastWasPunctuation = false;
   for (auto &element : elements)
     genElementPrinter(element.get(), body, op, shouldEmitSpace,
                       lastWasPunctuation);
 }
 
 //===----------------------------------------------------------------------===//
-// FormatLexer
-//===----------------------------------------------------------------------===//
-
-namespace {
-/// This class represents a specific token in the input format.
-class Token {
-public:
-  enum Kind {
-    // Markers.
-    eof,
-    error,
-
-    // Tokens with no info.
-    l_paren,
-    r_paren,
-    caret,
-    colon,
-    comma,
-    equal,
-    less,
-    greater,
-    question,
-
-    // Keywords.
-    keyword_start,
-    kw_attr_dict,
-    kw_attr_dict_w_keyword,
-    kw_custom,
-    kw_functional_type,
-    kw_operands,
-    kw_ref,
-    kw_regions,
-    kw_results,
-    kw_successors,
-    kw_type,
-    keyword_end,
-
-    // String valued tokens.
-    identifier,
-    literal,
-    variable,
-  };
-  Token(Kind kind, StringRef spelling) : kind(kind), spelling(spelling) {}
-
-  /// Return the bytes that make up this token.
-  StringRef getSpelling() const { return spelling; }
-
-  /// Return the kind of this token.
-  Kind getKind() const { return kind; }
-
-  /// Return a location for this token.
-  llvm::SMLoc getLoc() const {
-    return llvm::SMLoc::getFromPointer(spelling.data());
-  }
-
-  /// Return if this token is a keyword.
-  bool isKeyword() const { return kind > keyword_start && kind < keyword_end; }
-
-private:
-  /// Discriminator that indicates the kind of token this is.
-  Kind kind;
-
-  /// A reference to the entire token contents; this is always a pointer into
-  /// a memory buffer owned by the source manager.
-  StringRef spelling;
-};
-
-/// This class implements a simple lexer for operation assembly format strings.
-class FormatLexer {
-public:
-  FormatLexer(llvm::SourceMgr &mgr, Operator &op);
-
-  /// Lex the next token and return it.
-  Token lexToken();
-
-  /// Emit an error to the lexer with the given location and message.
-  Token emitError(llvm::SMLoc loc, const Twine &msg);
-  Token emitError(const char *loc, const Twine &msg);
-
-  Token emitErrorAndNote(llvm::SMLoc loc, const Twine &msg, const Twine &note);
-
-private:
-  Token formToken(Token::Kind kind, const char *tokStart) {
-    return Token(kind, StringRef(tokStart, curPtr - tokStart));
-  }
-
-  /// Return the next character in the stream.
-  int getNextChar();
-
-  /// Lex an identifier, literal, or variable.
-  Token lexIdentifier(const char *tokStart);
-  Token lexLiteral(const char *tokStart);
-  Token lexVariable(const char *tokStart);
-
-  llvm::SourceMgr &srcMgr;
-  Operator &op;
-  StringRef curBuffer;
-  const char *curPtr;
-};
-} // end anonymous namespace
-
-FormatLexer::FormatLexer(llvm::SourceMgr &mgr, Operator &op)
-    : srcMgr(mgr), op(op) {
-  curBuffer = srcMgr.getMemoryBuffer(mgr.getMainFileID())->getBuffer();
-  curPtr = curBuffer.begin();
-}
-
-Token FormatLexer::emitError(llvm::SMLoc loc, const Twine &msg) {
-  srcMgr.PrintMessage(loc, llvm::SourceMgr::DK_Error, msg);
-  llvm::SrcMgr.PrintMessage(op.getLoc()[0], llvm::SourceMgr::DK_Note,
-                            "in custom assembly format for this operation");
-  return formToken(Token::error, loc.getPointer());
-}
-Token FormatLexer::emitErrorAndNote(llvm::SMLoc loc, const Twine &msg,
-                                    const Twine &note) {
-  srcMgr.PrintMessage(loc, llvm::SourceMgr::DK_Error, msg);
-  llvm::SrcMgr.PrintMessage(op.getLoc()[0], llvm::SourceMgr::DK_Note,
-                            "in custom assembly format for this operation");
-  srcMgr.PrintMessage(loc, llvm::SourceMgr::DK_Note, note);
-  return formToken(Token::error, loc.getPointer());
-}
-Token FormatLexer::emitError(const char *loc, const Twine &msg) {
-  return emitError(llvm::SMLoc::getFromPointer(loc), msg);
-}
-
-int FormatLexer::getNextChar() {
-  char curChar = *curPtr++;
-  switch (curChar) {
-  default:
-    return (unsigned char)curChar;
-  case 0: {
-    // A nul character in the stream is either the end of the current buffer or
-    // a random nul in the file. Disambiguate that here.
-    if (curPtr - 1 != curBuffer.end())
-      return 0;
-
-    // Otherwise, return end of file.
-    --curPtr;
-    return EOF;
-  }
-  case '\n':
-  case '\r':
-    // Handle the newline character by ignoring it and incrementing the line
-    // count. However, be careful about 'dos style' files with \n\r in them.
-    // Only treat a \n\r or \r\n as a single line.
-    if ((*curPtr == '\n' || (*curPtr == '\r')) && *curPtr != curChar)
-      ++curPtr;
-    return '\n';
-  }
-}
-
-Token FormatLexer::lexToken() {
-  const char *tokStart = curPtr;
-
-  // This always consumes at least one character.
-  int curChar = getNextChar();
-  switch (curChar) {
-  default:
-    // Handle identifiers: [a-zA-Z_]
-    if (isalpha(curChar) || curChar == '_')
-      return lexIdentifier(tokStart);
-
-    // Unknown character, emit an error.
-    return emitError(tokStart, "unexpected character");
-  case EOF:
-    // Return EOF denoting the end of lexing.
-    return formToken(Token::eof, tokStart);
-
-  // Lex punctuation.
-  case '^':
-    return formToken(Token::caret, tokStart);
-  case ':':
-    return formToken(Token::colon, tokStart);
-  case ',':
-    return formToken(Token::comma, tokStart);
-  case '=':
-    return formToken(Token::equal, tokStart);
-  case '<':
-    return formToken(Token::less, tokStart);
-  case '>':
-    return formToken(Token::greater, tokStart);
-  case '?':
-    return formToken(Token::question, tokStart);
-  case '(':
-    return formToken(Token::l_paren, tokStart);
-  case ')':
-    return formToken(Token::r_paren, tokStart);
-
-  // Ignore whitespace characters.
-  case 0:
-  case ' ':
-  case '\t':
-  case '\n':
-    return lexToken();
-
-  case '`':
-    return lexLiteral(tokStart);
-  case '$':
-    return lexVariable(tokStart);
-  }
-}
-
-Token FormatLexer::lexLiteral(const char *tokStart) {
-  assert(curPtr[-1] == '`');
-
-  // Lex a literal surrounded by ``.
-  while (const char curChar = *curPtr++) {
-    if (curChar == '`')
-      return formToken(Token::literal, tokStart);
-  }
-  return emitError(curPtr - 1, "unexpected end of file in literal");
-}
-
-Token FormatLexer::lexVariable(const char *tokStart) {
-  if (!isalpha(curPtr[0]) && curPtr[0] != '_')
-    return emitError(curPtr - 1, "expected variable name");
-
-  // Otherwise, consume the rest of the characters.
-  while (isalnum(*curPtr) || *curPtr == '_')
-    ++curPtr;
-  return formToken(Token::variable, tokStart);
-}
-
-Token FormatLexer::lexIdentifier(const char *tokStart) {
-  // Match the rest of the identifier regex: [0-9a-zA-Z_\-]*
-  while (isalnum(*curPtr) || *curPtr == '_' || *curPtr == '-')
-    ++curPtr;
-
-  // Check to see if this identifier is a keyword.
-  StringRef str(tokStart, curPtr - tokStart);
-  Token::Kind kind =
-      StringSwitch<Token::Kind>(str)
-          .Case("attr-dict", Token::kw_attr_dict)
-          .Case("attr-dict-with-keyword", Token::kw_attr_dict_w_keyword)
-          .Case("custom", Token::kw_custom)
-          .Case("functional-type", Token::kw_functional_type)
-          .Case("operands", Token::kw_operands)
-          .Case("ref", Token::kw_ref)
-          .Case("regions", Token::kw_regions)
-          .Case("results", Token::kw_results)
-          .Case("successors", Token::kw_successors)
-          .Case("type", Token::kw_type)
-          .Default(Token::identifier);
-  return Token(kind, str);
-}
-
-//===----------------------------------------------------------------------===//
 // FormatParser
 //===----------------------------------------------------------------------===//
 
 /// Function to find an element within the given range that has the same name as
 /// 'name'.
 template <typename RangeT>
 static auto findArg(RangeT &&range, StringRef name) {
   auto it = llvm::find_if(range, [=](auto &arg) { return arg.name == name; });
   return it != range.end() ? &*it : nullptr;
 }
 
 namespace {
 /// This class implements a parser for an instance of an operation assembly
 /// format.
 class FormatParser {
 public:
   FormatParser(llvm::SourceMgr &mgr, OperationFormat &format, Operator &op)
-      : lexer(mgr, op), curToken(lexer.lexToken()), fmt(format), op(op),
-        seenOperandTypes(op.getNumOperands()),
+      : lexer(mgr, op.getLoc()[0]), curToken(lexer.lexToken()), fmt(format),
+        op(op), seenOperandTypes(op.getNumOperands()),
         seenResultTypes(op.getNumResults()) {}
 
   /// Parse the operation assembly format.
   LogicalResult parse();
 
 private:
   /// The current context of the parser when parsing an element.
   enum ParserContext {
private:
   LogicalResult parseAttrDictDirective(std::unique_ptr<Element> &element,
                                        llvm::SMLoc loc, ParserContext context,
                                        bool withKeyword);
   LogicalResult parseCustomDirective(std::unique_ptr<Element> &element,
                                      llvm::SMLoc loc, ParserContext context);
   LogicalResult parseCustomDirectiveParameter(
       std::vector<std::unique_ptr<Element>> &parameters);
   LogicalResult parseFunctionalTypeDirective(std::unique_ptr<Element> &element,
-                                             Token tok, ParserContext context);
+                                             FormatToken tok,
+                                             ParserContext context);
   LogicalResult parseOperandsDirective(std::unique_ptr<Element> &element,
                                        llvm::SMLoc loc, ParserContext context);
   LogicalResult parseReferenceDirective(std::unique_ptr<Element> &element,
                                         llvm::SMLoc loc, ParserContext context);
   LogicalResult parseRegionsDirective(std::unique_ptr<Element> &element,
                                       llvm::SMLoc loc, ParserContext context);
   LogicalResult parseResultsDirective(std::unique_ptr<Element> &element,
                                       llvm::SMLoc loc, ParserContext context);
   LogicalResult parseSuccessorsDirective(std::unique_ptr<Element> &element,
                                          llvm::SMLoc loc,
                                          ParserContext context);
-  LogicalResult parseTypeDirective(std::unique_ptr<Element> &element, Token tok,
-                                   ParserContext context);
+  LogicalResult parseTypeDirective(std::unique_ptr<Element> &element,
+                                   FormatToken tok, ParserContext context);
   LogicalResult parseTypeDirectiveOperand(std::unique_ptr<Element> &element,
                                           bool isRefChild = false);
 
   //===--------------------------------------------------------------------===//
   // Lexer Utilities
   //===--------------------------------------------------------------------===//
 
   /// Advance the current lexer onto the next token.
   void consumeToken() {
-    assert(curToken.getKind() != Token::eof &&
-           curToken.getKind() != Token::error &&
+    assert(curToken.getKind() != FormatToken::eof &&
+           curToken.getKind() != FormatToken::error &&
            "shouldn't advance past EOF or errors");
     curToken = lexer.lexToken();
   }
-  LogicalResult parseToken(Token::Kind kind, const Twine &msg) {
+  LogicalResult parseToken(FormatToken::Kind kind, const Twine &msg) {
     if (curToken.getKind() != kind)
       return emitError(curToken.getLoc(), msg);
     consumeToken();
     return ::mlir::success();
   }
   LogicalResult emitError(llvm::SMLoc loc, const Twine &msg) {
     lexer.emitError(loc, msg);
     return ::mlir::failure();
   }
   LogicalResult emitErrorAndNote(llvm::SMLoc loc, const Twine &msg,
                                  const Twine &note) {
     lexer.emitErrorAndNote(loc, msg, note);
     return ::mlir::failure();
   }
 
   //===--------------------------------------------------------------------===//
   // Fields
   //===--------------------------------------------------------------------===//
 
   FormatLexer lexer;
-  Token curToken;
+  FormatToken curToken;
   OperationFormat &fmt;
   Operator &op;
 
   // The following are various bits of format state used for verification
   // during parsing.
   bool hasAttrDict = false;
   bool hasAllRegions = false, hasAllSuccessors = false;
   bool canInferResultTypes = false;
   llvm::SmallBitVector seenOperandTypes, seenResultTypes;
   llvm::SmallSetVector<const NamedAttribute *, 8> seenAttrs;
   llvm::DenseSet<const NamedTypeConstraint *> seenOperands;
   llvm::DenseSet<const NamedRegion *> seenRegions;
   llvm::DenseSet<const NamedSuccessor *> seenSuccessors;
 };
 } // end anonymous namespace
 
 LogicalResult FormatParser::parse() {
   llvm::SMLoc loc = curToken.getLoc();
 
   // Parse each of the format elements into the main format.
-  while (curToken.getKind() != Token::eof) {
+  while (curToken.getKind() != FormatToken::eof) {
     std::unique_ptr<Element> element;
     if (failed(parseElement(element, TopLevelContext)))
       return ::mlir::failure();
     fmt.elements.push_back(std::move(element));
   }
 
   // Check that the attribute dictionary is in the format.
   if (!hasAttrDict)

 }
 
 LogicalResult FormatParser::parseElement(std::unique_ptr<Element> &element,
                                          ParserContext context) {
   // Directives.
   if (curToken.isKeyword())
     return parseDirective(element, context);
   // Literals.
-  if (curToken.getKind() == Token::literal)
+  if (curToken.getKind() == FormatToken::literal)
     return parseLiteral(element, context);
   // Optionals.
-  if (curToken.getKind() == Token::l_paren)
+  if (curToken.getKind() == FormatToken::l_paren)
     return parseOptional(element, context);
   // Variables.
-  if (curToken.getKind() == Token::variable)
+  if (curToken.getKind() == FormatToken::variable)
     return parseVariable(element, context);
   return emitError(curToken.getLoc(),
                    "expected directive, literal, variable, or optional group");
 }
 
 LogicalResult FormatParser::parseVariable(std::unique_ptr<Element> &element,
                                           ParserContext context) {
-  Token varTok = curToken;
+  FormatToken varTok = curToken;
   consumeToken();
 
   StringRef name = varTok.getSpelling().drop_front();
   llvm::SMLoc loc = varTok.getLoc();
 
   // Check that the parsed argument is something actually registered on the
   // op.
   /// Attributes
if (const auto *successor = findArg(op.getSuccessors(), name)) {
     return ::mlir::success();
   }
   return emitError(loc, "expected variable to refer to an argument, region, "
                         "result, or successor");
 }
 
 LogicalResult FormatParser::parseDirective(std::unique_ptr<Element> &element,
                                            ParserContext context) {
-  Token dirTok = curToken;
+  FormatToken dirTok = curToken;
   consumeToken();
 
   switch (dirTok.getKind()) {
-  case Token::kw_attr_dict:
+  case FormatToken::kw_attr_dict:
     return parseAttrDictDirective(element, dirTok.getLoc(), context,
                                   /*withKeyword=*/false);
-  case Token::kw_attr_dict_w_keyword:
+  case FormatToken::kw_attr_dict_w_keyword:
     return parseAttrDictDirective(element, dirTok.getLoc(), context,
                                   /*withKeyword=*/true);
-  case Token::kw_custom:
+  case FormatToken::kw_custom:
     return parseCustomDirective(element, dirTok.getLoc(), context);
-  case Token::kw_functional_type:
+  case FormatToken::kw_functional_type:
     return parseFunctionalTypeDirective(element, dirTok, context);
-  case Token::kw_operands:
+  case FormatToken::kw_operands:
     return parseOperandsDirective(element, dirTok.getLoc(), context);
-  case Token::kw_regions:
+  case FormatToken::kw_regions:
     return parseRegionsDirective(element, dirTok.getLoc(), context);
-  case Token::kw_results:
+  case FormatToken::kw_results:
     return parseResultsDirective(element, dirTok.getLoc(), context);
-  case Token::kw_successors:
+  case FormatToken::kw_successors:
     return parseSuccessorsDirective(element, dirTok.getLoc(), context);
-  case Token::kw_ref:
+  case FormatToken::kw_ref:
     return parseReferenceDirective(element, dirTok.getLoc(), context);
-  case Token::kw_type:
+  case FormatToken::kw_type:
     return parseTypeDirective(element, dirTok, context);
 
   default:
     llvm_unreachable("unknown directive token");
   }
 }
 
 LogicalResult FormatParser::parseLiteral(std::unique_ptr<Element> &element,
                                          ParserContext context) {
-  Token literalTok = curToken;
+  FormatToken literalTok = curToken;
   if (context != TopLevelContext) {
     return emitError(
         literalTok.getLoc(),
         "literals may only be used in a top-level section of the format");
   }
   consumeToken();
 
   StringRef value = literalTok.getSpelling().drop_front().drop_back();
 
   // The parsed literal is a space element (`` or ` `).
   if (value.empty() || (value.size() == 1 && value.front() == ' ')) {
     element = std::make_unique<SpaceElement>(!value.empty());
     return ::mlir::success();
   }
   // The parsed literal is a newline element.
   if (value == "\\n") {
     element = std::make_unique<NewlineElement>();
     return ::mlir::success();
   }
 
   // Check that the parsed literal is valid.
-  if (!LiteralElement::isValidLiteral(value))
+  if (!isValidLiteral(value))
     return emitError(literalTok.getLoc(), "expected valid literal");
 
   element = std::make_unique<LiteralElement>(value);
   return ::mlir::success();
 }
 
 LogicalResult FormatParser::parseOptional(std::unique_ptr<Element> &element,
                                           ParserContext context) {
   llvm::SMLoc curLoc = curToken.getLoc();
   if (context != TopLevelContext)
     return emitError(curLoc, "optional groups can only be used as top-level "
                              "elements");
   consumeToken();
 
   // Parse the child elements for this optional group.
   std::vector<std::unique_ptr<Element>> thenElements, elseElements;
   Optional<unsigned> anchorIdx;
   do {
     if (failed(parseOptionalChildElement(thenElements, anchorIdx)))
       return ::mlir::failure();
-  } while (curToken.getKind() != Token::r_paren);
+  } while (curToken.getKind() != FormatToken::r_paren);
   consumeToken();
 
   // Parse the `else` elements of this optional group.
-  if (curToken.getKind() == Token::colon) {
+  if (curToken.getKind() == FormatToken::colon) {
     consumeToken();
-    if (failed(parseToken(Token::l_paren, "expected '(' to start else branch "
-                                          "of optional group")))
+    if (failed(parseToken(FormatToken::l_paren,
+                          "expected '(' to start else branch "
       return failure();
     do {
       llvm::SMLoc childLoc = curToken.getLoc();
       elseElements.push_back({});
       if (failed(parseElement(elseElements.back(), TopLevelContext)) ||
           failed(verifyOptionalChildElement(elseElements.back().get(), childLoc,
                                             /*isAnchor=*/false)))
         return failure();
-    } while (curToken.getKind() != Token::r_paren);
+    } while (curToken.getKind() != FormatToken::r_paren);
     consumeToken();
   }
 
-  if (failed(parseToken(Token::question, "expected '?' after optional group")))
+  if (failed(parseToken(FormatToken::question,
+                        "expected '?' after optional group")))
     return ::mlir::failure();
 
   // The optional group is required to have an anchor.
   if (!anchorIdx)
     return emitError(curLoc, "optional group specified no anchor element");
 
   // The first parsable element of the group must be able to be parsed in an
   // optional fashion.
LogicalResult FormatParser::parseOptionalChildElement(
     std::vector<std::unique_ptr<Element>> &childElements,
     Optional<unsigned> &anchorIdx) {
   llvm::SMLoc childLoc = curToken.getLoc();
   childElements.push_back({});
   if (failed(parseElement(childElements.back(), TopLevelContext)))
     return ::mlir::failure();
 
   // Check to see if this element is the anchor of the optional group.
-  bool isAnchor = curToken.getKind() == Token::caret;
+  bool isAnchor = curToken.getKind() == FormatToken::caret;
   if (isAnchor) {
     if (anchorIdx)
       return emitError(childLoc, "only one element can be marked as the anchor "
                                  "of an optional group");
     anchorIdx = childElements.size() - 1;
     consumeToken();
   }
 

 LogicalResult
 FormatParser::parseCustomDirective(std::unique_ptr<Element> &element,
                                    llvm::SMLoc loc, ParserContext context) {
   llvm::SMLoc curLoc = curToken.getLoc();
   if (context != TopLevelContext)
     return emitError(loc, "'custom' is only valid as a top-level directive");
 
   // Parse the custom directive name.
-  if (failed(
-          parseToken(Token::less, "expected '<' before custom directive name")))
+  if (failed(parseToken(FormatToken::less,
+                        "expected '<' before custom directive name")))
     return ::mlir::failure();
 
-  Token nameTok = curToken;
-  if (failed(parseToken(Token::identifier,
+  FormatToken nameTok = curToken;
+  if (failed(parseToken(FormatToken::identifier,
                         "expected custom directive name identifier")) ||
-      failed(parseToken(Token::greater,
+      failed(parseToken(FormatToken::greater,
                         "expected '>' after custom directive name")) ||
-      failed(parseToken(Token::l_paren,
+      failed(parseToken(FormatToken::l_paren,
                         "expected '(' before custom directive parameters")))
     return ::mlir::failure();
 
   // Parse the child elements for this optional group.=
   std::vector<std::unique_ptr<Element>> elements;
   do {
     if (failed(parseCustomDirectiveParameter(elements)))
       return ::mlir::failure();
-    if (curToken.getKind() != Token::comma)
+    if (curToken.getKind() != FormatToken::comma)
       break;
     consumeToken();
   } while (true);
 
-  if (failed(parseToken(Token::r_paren,
+  if (failed(parseToken(FormatToken::r_paren,
                         "expected ')' after custom directive parameters")))
     return ::mlir::failure();
 
   // After parsing all of the elements, ensure that all type directives refer
   // only to variables.
   for (auto &ele : elements) {
     if (auto *typeEle = dyn_cast<TypeDirective>(ele.get())) {
       if (!isa<OperandVariable, ResultVariable>(typeEle->getOperand())) {
if (!isa<RefDirective, TypeDirective, AttrDictDirective, AttributeVariable,
            OperandVariable, RegionVariable, SuccessorVariable>(
           parameters.back().get())) {
     return emitError(childLoc, "only variables and types may be used as "
                                "parameters to a custom directive");
   }
   return ::mlir::success();
 }
 
-LogicalResult
-FormatParser::parseFunctionalTypeDirective(std::unique_ptr<Element> &element,
-                                           Token tok, ParserContext context) {
+LogicalResult FormatParser::parseFunctionalTypeDirective(
+    std::unique_ptr<Element> &element, FormatToken tok, ParserContext context) {
   llvm::SMLoc loc = tok.getLoc();
   if (context != TopLevelContext)
     return emitError(
         loc, "'functional-type' is only valid as a top-level directive");
 
   // Parse the main operand.
   std::unique_ptr<Element> inputs, results;
-  if (failed(parseToken(Token::l_paren, "expected '(' before argument list")) ||
+  if (failed(parseToken(FormatToken::l_paren,
+                        "expected '(' before argument list")) ||
       failed(parseTypeDirectiveOperand(inputs)) ||
-      failed(parseToken(Token::comma, "expected ',' after inputs argument")) ||
+      failed(parseToken(FormatToken::comma,
+                        "expected ',' after inputs argument")) ||
       failed(parseTypeDirectiveOperand(results)) ||
-      failed(parseToken(Token::r_paren, "expected ')' after argument list")))
+      failed(
+          parseToken(FormatToken::r_paren, "expected ')' after argument list")))
     return ::mlir::failure();
   element = std::make_unique<FunctionalTypeDirective>(std::move(inputs),
                                                       std::move(results));
   return ::mlir::success();
 }
 
 LogicalResult
 FormatParser::parseOperandsDirective(std::unique_ptr<Element> &element,

 
 LogicalResult
 FormatParser::parseReferenceDirective(std::unique_ptr<Element> &element,
                                       llvm::SMLoc loc, ParserContext context) {
   if (context != CustomDirectiveContext)
     return emitError(loc, "'ref' is only valid within a `custom` directive");
 
   std::unique_ptr<Element> operand;
-  if (failed(parseToken(Token::l_paren, "expected '(' before argument list")) ||
+  if (failed(parseToken(FormatToken::l_paren,
+                        "expected '(' before argument list")) ||
       failed(parseElement(operand, RefDirectiveContext)) ||
-      failed(parseToken(Token::r_paren, "expected ')' after argument list")))
+      failed(
+          parseToken(FormatToken::r_paren, "expected ')' after argument list")))
     return ::mlir::failure();
 
   element = std::make_unique<RefDirective>(std::move(operand));
   return ::mlir::success();
 }
 
 LogicalResult
 FormatParser::parseRegionsDirective(std::unique_ptr<Element> &element,
if (hasAllSuccessors || !seenSuccessors.empty())
       return emitError(loc, "'successors' directive creates overlap in format");
     hasAllSuccessors = true;
   }
   element = std::make_unique<SuccessorsDirective>();
   return ::mlir::success();
 }
 
 LogicalResult
-FormatParser::parseTypeDirective(std::unique_ptr<Element> &element, Token tok,
-                                 ParserContext context) {
+FormatParser::parseTypeDirective(std::unique_ptr<Element> &element,
+                                 FormatToken tok, ParserContext context) {
   llvm::SMLoc loc = tok.getLoc();
   if (context == TypeDirectiveContext)
     return emitError(loc, "'type' cannot be used as a child of another `type`");
 
   bool isRefChild = context == RefDirectiveContext;
   std::unique_ptr<Element> operand;
-  if (failed(parseToken(Token::l_paren, "expected '(' before argument list")) ||
+  if (failed(parseToken(FormatToken::l_paren,
+                        "expected '(' before argument list")) ||
       failed(parseTypeDirectiveOperand(operand, isRefChild)) ||
-      failed(parseToken(Token::r_paren, "expected ')' after argument list")))
+      failed(
+          parseToken(FormatToken::r_paren, "expected ')' after argument list")))
     return ::mlir::failure();
 
   element = std::make_unique<TypeDirective>(std::move(operand));
   return ::mlir::success();
 }
 
 LogicalResult
 FormatParser::parseTypeDirectiveOperand(std::unique_ptr<Element> &element,

utils/bazel/llvm-project-overlay/mlir/test/BUILD.bazel

deps = [
         "//mlir:LLVMDialect",
         "//mlir:LinalgInterfaces",
         "//mlir:LinalgOps",
         "//mlir:Pass",
         "//mlir:Reducer",
         "//mlir:SideEffects",
         "//mlir:StandardOps",
         "//mlir:StandardOpsTransforms",
+        "//mlir:Support",
         "//mlir:TensorDialect",
         "//mlir:TransformUtils",
         "//mlir:Transforms",
     ],
 )
 
 cc_library(
     name = "TestIR",