[mlir][TypeDefGen] Add support for adding builders when generating a TypeDef

[rriddle]

Summary

This allows for specifying additional get/getChecked methods that should be generated on the type, and acts similarly to how OpBuilders work. TypeBuilders have two additional components though:

• InferredContextParam
  • Bit indicating that the context parameter of a get method is inferred from one of the builder parameters
• checkedBody
  • A code block representing the body of the equivalent getChecked method.

Depends On D94273

[rriddle]

+Chris as I think you also ran into a need for this.

[lattner]

Awesome, thank you for implementing this. The documentation and implementation look really really great, I'm excited to see this River!

[lattner]

@jdd fyi

[jdd]

Nice! Was this change being discussed in a bug which can now be closed? I seem to recall that but cannot find the bug.

[lattner]

It looks like I didn't file a PR about this

mlir/docs/OpDefinitions.md

-   If the `genVerifyInvariantsDecl` field is set, a declaration for a method
     method which gets the result of `verifyConstructionInvariants` before
     calling `get`.
 -   The `storageClass` field can be used to set the name of the storage class.
 -   The `storageNamespace` field is used to set the namespace where the storage
     class should sit. Defaults to "detail".
 -   The `extraClassDeclaration` field is used to include extra code in the class
     declaration.
 
+### Type builder methods
+
+For each type, there are a few builders(`get`/`getChecked`) automatically
+generated based on the parameters of the type. For example, given the following
+type definition:
+
+```tablegen
+def MyType : ... {
+  let parameters = (ins "int":$intParam);
+}
+```
+
+The following builders are generated:
+
+```c++
+// Type builders are named `get`, and return a new instance of a type for a
+// given set of parameters.
+static MyType get(MLIRContext *context, int intParam);
+
+// If `genVerifyInvariantsDecl` is set to 1, the following method is also
+// generated.
+static MyType getChecked(Location loc, int intParam);
+```
+
+If these autogenerated methods are not desired, such as when they conflict with
+a custom builder method, a type can set `skipDefaultBuilders` to 1 to signal
+that they should not be generated.
+
+#### Custom type builder methods
+
+The default build methods may cover a majority of the simple cases related to
+type construction, but when they cannot satisfy a type's needs, you can define
+additional convenience get methods in the `builders` field as follows:
+
+```tablegen
+def MyType : ... {
+  let parameters = (ins "int":$intParam);
+
+  let builders = [
+    TypeBuilder<(ins "int":$intParam)>,
+    TypeBuilder<(ins CArg<"int", "0">:$intParam)>,
+    TypeBuilder<(ins CArg<"int", "0">:$intParam), [{
+      // Write the body of the `get` builder inline here.
+      return Base::get($_ctxt, intParam);
+    }]>,
+    TypeBuilderWithInferredContext<(ins "Type":$typeParam), [{
+      // This builder states that it can infer an MLIRContext instance from
+      // its arguments.
+      return Base::get(typeParam.getContext(), ...);
+    }]>,
+  ];
+}
+```
+
+The `builders` field is a list of custom builders that are added to the type
+class. In this example, we provide a several different convenience builders that
+are useful in different scenarios. The `ins` prefix is common to many function
+declarations in ODS, which use a TableGen [`dag`](#tablegen-syntax). What
+follows is a comma-separated list of types (quoted string or CArg) and names
+prefixed with the `$` sign. The use of `CArg` allows for providing a default
+value to that argument. Let's take a look at each of these builders individually
+
+The first builder will generate the declaration of a builder method that looks
+like:
+
+```tablegen
+  let builders = [
+    TypeBuilder<(ins "int":$intParam)>,
+  ];
+```
+
+```c++
+class MyType : /*...*/ {
+  /*...*/
+  static MyType get(::mlir::MLIRContext *context, int intParam);
+};
+```
+
+This builder is identical to the one that will be automatically generated for
+`MyType`. The `context` parameter is implicitly added by the generator, and is
+used when building the file Type instance (with `Base::get`). The distinction
+here is that we can provide the implementation of this `get` method. With this
+style of builder definition only the declaration is generated, the implementor
+of MyType will need to provide a definition of `MyType::get`.
+
+The second builder will generate the declaration of a builder method that looks
+like:
+
+```tablegen
+  let builders = [
+    TypeBuilder<(ins CArg<"int", "0">:$intParam)>,
+  ];
+```
+
+```c++
+class MyType : /*...*/ {
+  /*...*/
+  static MyType get(::mlir::MLIRContext *context, int intParam = 0);
+};
+```
+
+The constraints here are identical to the first builder example except for the
+fact that `intParam` now has a default value attached.
+
+The third builder will generate the declaration of a builder method that looks
+like:
+
+```tablegen
+  let builders = [
+    TypeBuilder<(ins CArg<"int", "0">:$intParam), [{
+      // Write the body of the `get` builder inline here.
+      return Base::get($_ctxt, intParam);
+    }]>,
+  ];
+```
+
+```c++
+class MyType : /*...*/ {
+  /*...*/
+  static MyType get(::mlir::MLIRContext *context, int intParam = 0);
+};
+
+MyType MyType::get(::mlir::MLIRContext *context, int intParam) {
+  // Write the body of the `get` builder inline here.
+  return Base::get(context, intParam);
+}
+```
+
+This is identical to the second builder example. The difference is that now, a
+definition for the builder method will be generated automatically using the
+provided code block as the body. When specifying the body inline, `$_ctxt` may
+be used to access the `MLIRContext *` parameter.
+
+The fourth builder will generate the declaration of a builder method that looks
+like:
+
+```tablegen
+  let builders = [
+    TypeBuilderWithInferredContext<(ins "Type":$typeParam), [{
+      // This builder states that it can infer an MLIRContext instance from
+      // its arguments.
+      return Base::get(typeParam.getContext(), ...);
+    }]>,
+  ];
+```
+
+```c++
+class MyType : /*...*/ {
+  /*...*/
+  static MyType get(Type typeParam);
+};
+
+MyType MyType::get(Type typeParam) {
+  // This builder states that it can infer an MLIRContext instance from its
+  // arguments.
+  return Base::get(typeParam.getContext(), ...);
+}
+```
+
+In this builder example, the main difference from the third builder example
+three is that the `MLIRContext` parameter is no longer added. This is because
+the builder type used `TypeBuilderWithInferredContext` implies that the context
+parameter is not necessary as it can be inferred from the arguments to the
+builder.
+
 ## Debugging Tips
 
 ### Run `mlir-tblgen` to see the generated content
 
 TableGen syntax sometimes can be obscure; reading the generated content can be a
 very helpful way to understand and debug issues. To build `mlir-tblgen`, run
 `cmake --build . --target mlir-tblgen` in your build directory and find the
 `mlir-tblgen` binary in the `bin/` subdirectory. All the supported generators

mlir/include/mlir/Dialect/ArmSVE/ArmSVE.td

for (int64_t dim : getShape())
       $_printer << dim << 'x';
     $_printer << getElementType() << '>';
   }];
 
   let parser = [{
     VectorType vector;
     if ($_parser.parseType(vector))
       return Type();
-    return get(ctxt, vector.getShape(), vector.getElementType());
+    return get($_ctxt, vector.getShape(), vector.getElementType());
   }];
 
   let extraClassDeclaration = [{
     bool hasStaticShape() const {
       return llvm::none_of(getShape(), ShapedType::isDynamic);
     }
     int64_t getNumElements() const {
       assert(hasStaticShape() &&

mlir/include/mlir/IR/OpBase.td

 // so to replace the matched DAG with an existing SSA value.
 def replaceWithValue;
 
 
 //===----------------------------------------------------------------------===//
 // Data type generation
 //===----------------------------------------------------------------------===//
 
+// Class for defining a custom type getter.
+//
+// TableGen generates several generic getter methods for each type by default,
+// corresponding to the specified dag parameters. If the default generated ones
+// cannot cover some use case, custom getters can be defined using instances of
+// this class.
+//
+// The signature of the `get` is always either:
+//
+// ```c++
+// static <Type-Name> get(MLIRContext *context, <other-parameters>...) {
+//   <body>...
+// }
+// ```
+//
+// or:
+//
+// ```c++
+// static <TypeName> get(MLIRContext *context, <parameters>...);
+// ```
+//
+// To define a custom getter, the parameter list and body should be passed
+// in as separate template arguments to this class. The parameter list is a
+// TableGen DAG with `ins` operation with named arguments, which has either:
+//   - string initializers ("Type":$name) to represent a typed parameter, or
+//   - CArg-typed initializers (CArg<"Type", "default">:$name) to represent a
+//     typed parameter that may have a default value.
+// The type string is used verbatim to produce code and, therefore, must be a
+// valid C++ type. It is used inside the C++ namespace of the parent Type's
+// dialect; explicit namespace qualification like `::mlir` may be necessary if
+// Types are not placed inside the `mlir` namespace. The default value string is
+// used verbatim to produce code and must be a valid C++ initializer the given
+// type. For example, the following signature specification
+//
+// ```
+// TypeBuilder<(ins "int":$integerArg, CArg<"float", "3.0f">:$floatArg)>
+// ```
+//
+// has an integer parameter and a float parameter with a default value.
+//
+// If an empty string is passed in for `body`, then *only* the builder
+// declaration will be generated; this provides a way to define complicated
+// builders entirely in C++.
+//
+// `checkedBody` is similar to `body`, but is the code block used when
+// generating a `getChecked` method.
+class TypeBuilder<dag parameters, code bodyCode = "",
+                  code checkedBodyCode = ""> {
+  dag dagParams = parameters;
+  code body = bodyCode;
+  code checkedBody = checkedBodyCode;
+
+  // The context parameter can be inferred from one of the other parameters and
+  // is not implicitly added to the parameter list.
+  bit hasInferredContextParam = 0;
+}
+
+// A class of TypeBuilder that is able to infer the MLIRContext parameter from
+// one of the other builder parameters. Instances of this builder do not have
+// `MLIRContext *` implicitly added to the parameter list.
+class TypeBuilderWithInferredContext<dag parameters, code bodyCode = "",
+                                     code checkedBodyCode = "">
+  : TypeBuilder<parameters, bodyCode> {
+  code checkedBody = checkedBodyCode;
+  let hasInferredContextParam = 1;
+}
+
 // Define a new type, named `name`, belonging to `dialect` that inherits from
 // the given C++ base class.
 class TypeDef<Dialect dialect, string name,
               string baseCppClass = "::mlir::Type">
     : DialectType<dialect, CPred<"">, /*descr*/"", name # "Type"> {
   // The name of the C++ base class to use for this Type.
   string cppBaseClassName = baseCppClass;
 
class TypeDef<Dialect dialect, string name,
   //    (ins
   //        "int":$width,
   //        ArrayRefParameter<"bool", "list of bools">:$yesNoArray)
   //
   // (ArrayRefParameter is a subclass of TypeParameter which has allocation code
   // for re-allocating ArrayRefs. It is defined below.)
   dag parameters = (ins);
 
+  // Custom type builder methods.
+  // In addition to the custom builders provided here, and unless
+  // skipDefaultBuilders is set, a default builder is generated with the
+  // following signature:
+  //
+  // ```c++
+  // static <TypeName> get(MLIRContext *, <parameters>);
+  // ```
+  //
+  // Note that builders should only be provided when a type has parameters.
+  list<TypeBuilder> builders = ?;
+
   // Use the lowercased name as the keyword for parsing/printing. Specify only
   // if you want tblgen to generate declarations and/or definitions of
   // printer/parser for this type.
   string mnemonic = ?;
   // 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 = ?;
 
   // If set, generate accessors for each Type parameter.
   bit genAccessors = 1;
+  // Avoid generating default get/getChecked functions. Custom get methods must
+  // be provided.
+  bit skipDefaultBuilders = 0;
   // Generate the verifyConstructionInvariants declaration and getChecked
   // method.
   bit genVerifyInvariantsDecl = 0;
   // Extra code to include in the class declaration.
   code extraClassDeclaration = [{}];
 
   // The predicate for when this type is used as a type constraint.
   let predicate = CPred<"$_self.isa<" # dialect.cppNamespace #

mlir/include/mlir/TableGen/TypeDef.h

 //===-- TypeDef.h - Record wrapper for type definitions ---------*- 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
 //
 //===----------------------------------------------------------------------===//
 //
 // TypeDef wrapper to simplify using TableGen Record defining a MLIR type.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef MLIR_TABLEGEN_TYPEDEF_H
 #define MLIR_TABLEGEN_TYPEDEF_H
 
 #include "mlir/Support/LLVM.h"
-#include "mlir/TableGen/Dialect.h"
+#include "mlir/TableGen/Builder.h"
 
 namespace llvm {
-class Record;
 class DagInit;
+class Record;
 class SMLoc;
 } // namespace llvm
 
 namespace mlir {
 namespace tblgen {
-
+class Dialect;
 class TypeParameter;
 
+//===----------------------------------------------------------------------===//
+// TypeBuilder
+//===----------------------------------------------------------------------===//
+
+/// Wrapper class that represents a Tablegen TypeBuilder.
+class TypeBuilder : public Builder {
+public:
+  using Builder::Builder;
+
+  /// Return an optional code body used for the `getChecked` variant of this
+  /// builder.
+  Optional<StringRef> getCheckedBody() const;
+
+  /// Returns true if this builder is able to infer the MLIRContext parameter.
+  bool hasInferredContextParameter() const;
+};
+
+//===----------------------------------------------------------------------===//
+// TypeDef
+//===----------------------------------------------------------------------===//
+
 /// Wrapper class that contains a TableGen TypeDef's record and provides helper
 /// methods for accessing them.
 class TypeDef {
 public:
-  explicit TypeDef(const llvm::Record *def) : def(def) {}
+  explicit TypeDef(const llvm::Record *def);
 
   // Get the dialect for which this type belongs.
   Dialect getDialect() const;
 
   // Returns the name of this TypeDef record.
   StringRef getName() const;
 
   // Query functions for the documentation of the operator.
public:
   bool genVerifyInvariantsDecl() const;
 
   // Returns the dialects extra class declaration code.
   Optional<StringRef> getExtraDecls() const;
 
   // Get the code location (for error printing).
   ArrayRef<llvm::SMLoc> getLoc() const;
 
+  // Returns true if the default get/getChecked methods should be skipped during
+  // generation.
+  bool skipDefaultBuilders() const;
+
+  // Returns the builders of this type.
+  ArrayRef<TypeBuilder> getBuilders() const { return builders; }
+
   // Returns whether two TypeDefs are equal by checking the equality of the
   // underlying record.
   bool operator==(const TypeDef &other) const;
 
   // Compares two TypeDefs by comparing the names of the dialects.
   bool operator<(const TypeDef &other) const;
 
   // Returns whether the TypeDef is defined.
   operator bool() const { return def != nullptr; }
 
 private:
   const llvm::Record *def;
+
+  // The builders of this type definition.
+  SmallVector<TypeBuilder> builders;
 };
 
+//===----------------------------------------------------------------------===//
+// TypeParameter
+//===----------------------------------------------------------------------===//
+
 // A wrapper class for tblgen TypeParameter, arrays of which belong to TypeDefs
 // to parameterize them.
 class TypeParameter {
 public:
   explicit TypeParameter(const llvm::DagInit *def, unsigned num)
       : def(def), num(num) {}
 
   // Get the parameter name.

mlir/lib/TableGen/TypeDef.cpp

 //===- TypeDef.cpp - TypeDef wrapper class --------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // TypeDef wrapper to simplify using TableGen Record defining a MLIR dialect.
 //
 //===----------------------------------------------------------------------===//
 
 #include "mlir/TableGen/TypeDef.h"
+#include "mlir/TableGen/Dialect.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Record.h"
 
 using namespace mlir;
 using namespace mlir::tblgen;
 
+//===----------------------------------------------------------------------===//
+// TypeBuilder
+//===----------------------------------------------------------------------===//
+
+/// Return an optional code body used for the `getChecked` variant of this
+/// builder.
+Optional<StringRef> TypeBuilder::getCheckedBody() const {
+  Optional<StringRef> body = def->getValueAsOptionalString("checkedBody");
+  return body && !body->empty() ? body : llvm::None;
+}
+
+/// Returns true if this builder is able to infer the MLIRContext parameter.
+bool TypeBuilder::hasInferredContextParameter() const {
+  return def->getValueAsBit("hasInferredContextParam");
+}
+
+//===----------------------------------------------------------------------===//
+// TypeDef
+//===----------------------------------------------------------------------===//
+
 Dialect TypeDef::getDialect() const {
   auto *dialectDef =
       dyn_cast<llvm::DefInit>(def->getValue("dialect")->getValue());
   if (dialectDef == nullptr)
     return Dialect(nullptr);
   return Dialect(dialectDef->getDef());
 }
 

 bool TypeDef::genVerifyInvariantsDecl() const {
   return def->getValueAsBit("genVerifyInvariantsDecl");
 }
 llvm::Optional<StringRef> TypeDef::getExtraDecls() const {
   auto value = def->getValueAsString("extraClassDeclaration");
   return value.empty() ? llvm::Optional<StringRef>() : value;
 }
 llvm::ArrayRef<llvm::SMLoc> TypeDef::getLoc() const { return def->getLoc(); }
+
+bool TypeDef::skipDefaultBuilders() const {
+  return def->getValueAsBit("skipDefaultBuilders");
+}
+
 bool TypeDef::operator==(const TypeDef &other) const {
   return def == other.def;
 }
 
 bool TypeDef::operator<(const TypeDef &other) const {
   return getName() < other.getName();
 }
 
+//===----------------------------------------------------------------------===//
+// TypeParameter
+//===----------------------------------------------------------------------===//
+
+TypeDef::TypeDef(const llvm::Record *def) : def(def) {
+  // Populate the builders.
+  auto *builderList =
+      dyn_cast_or_null<llvm::ListInit>(def->getValueInit("builders"));
+  if (builderList && !builderList->empty()) {
+    for (llvm::Init *init : builderList->getValues()) {
+      TypeBuilder builder(cast<llvm::DefInit>(init)->getDef(), def->getLoc());
+
+      // Ensure that all parameters have names.
+      for (const TypeBuilder::Parameter &param : builder.getParameters()) {
+        if (!param.getName())
+          PrintFatalError(def->getLoc(),
+                          "type builder parameters must have a name");
+      }
+      builders.emplace_back(builder);
+    }
+  } else if (skipDefaultBuilders()) {
+    PrintFatalError(
+        def->getLoc(),
+        "default builders are skipped and no custom builders provided");
+  }
+}
+
 StringRef TypeParameter::getName() const {
   return def->getArgName(num)->getValue();
 }
 Optional<StringRef> TypeParameter::getAllocator() const {
   llvm::Init *parameterType = def->getArg(num);
   if (isa<llvm::StringInit>(parameterType))
     return llvm::Optional<StringRef>();
 

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

 }
 
 // An example of how one could implement a standard integer.
 def IntegerType : Test_Type<"TestInteger"> {
   let mnemonic = "int";
   let genVerifyInvariantsDecl = 1;
   let parameters = (
     ins
+    "unsigned":$width,
     // SignednessSemantics is defined below.
-    "::mlir::test::TestIntegerType::SignednessSemantics":$signedness,
-    "unsigned":$width
+    "::mlir::test::TestIntegerType::SignednessSemantics":$signedness
   );
 
   // We define the printer inline.
   let printer = [{
     $_printer << "int<";
     printSignedness($_printer, getImpl()->signedness);
     $_printer << ", " << getImpl()->width << ">";
   }];
 
+  // Define custom builder methods.
+  let builders = [
+    TypeBuilder<(ins "unsigned":$width,
+                     CArg<"SignednessSemantics", "Signless">:$signedness), [{
+      return Base::get($_ctxt, width, signedness);
+    }], [{
+      return Base::getChecked($_loc, width, signedness);
+    }]>
+  ];
+  let skipDefaultBuilders = 1;
+
   // The parser is defined here also.
   let parser = [{
     if (parser.parseLess()) return Type();
     SignednessSemantics signedness;
     if (parseSignedness($_parser, signedness)) return mlir::Type();
     if ($_parser.parseComma()) return Type();
     int width;
     if ($_parser.parseInteger(width)) return Type();
     if ($_parser.parseGreater()) return Type();
     Location loc = $_parser.getEncodedSourceLoc($_parser.getNameLoc());
-    return getChecked(loc, signedness, width);
+    return getChecked(loc, width, signedness);
   }];
 
   // Any extra code one wants in the type's class declaration.
   let extraClassDeclaration = [{
     /// Signedness semantics.
     enum SignednessSemantics {
       Signless, /// No signedness semantics
       Signed,   /// Signed integer
       Unsigned, /// Unsigned integer
     };
 
-    /// This extra function is necessary since it doesn't include signedness
-    static IntegerType getChecked(unsigned width, Location location);
-
     /// Return true if this is a signless integer type.
     bool isSignless() const { return getSignedness() == Signless; }
     /// Return true if this is a signed integer type.
     bool isSigned() const { return getSignedness() == Signed; }
     /// Return true if this is an unsigned integer type.
     bool isUnsigned() const { return getSignedness() == Unsigned; }
   }];
 }

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

 
 // FieldInfo is used as part of a parameter, so a hash will be computed.
 static llvm::hash_code mlir::test::hash_value(const FieldInfo &fi) { // NOLINT
   return llvm::hash_combine(fi.name, fi.type);
 }
 
 // Example type validity checker.
 LogicalResult TestIntegerType::verifyConstructionInvariants(
-    Location loc, TestIntegerType::SignednessSemantics ss, unsigned int width) {
+    Location loc, unsigned width, TestIntegerType::SignednessSemantics ss) {
   if (width > 8)
     return failure();
   return success();
 }
 
 //===----------------------------------------------------------------------===//
 // Tablegen Generated Definitions
 //===----------------------------------------------------------------------===//

mlir/test/mlir-tblgen/typedefs.td

 // DEF: #ifdef GET_TYPEDEF_LIST
 // DEF: #undef GET_TYPEDEF_LIST
 // DEF: ::mlir::test::SimpleAType,
 // DEF: ::mlir::test::CompoundAType,
 // DEF: ::mlir::test::IndexType,
 // DEF: ::mlir::test::SingleParameterType,
 // DEF: ::mlir::test::IntegerType
 
-// DEF-LABEL: ::mlir::Type generatedTypeParser(::mlir::MLIRContext* ctxt, ::mlir::DialectAsmParser& parser, ::llvm::StringRef mnemonic)
-// DEF: if (mnemonic == ::mlir::test::CompoundAType::getMnemonic()) return ::mlir::test::CompoundAType::parse(ctxt, parser);
+// DEF-LABEL: ::mlir::Type generatedTypeParser(::mlir::MLIRContext *context, ::mlir::DialectAsmParser &parser, ::llvm::StringRef mnemonic)
+// DEF: if (mnemonic == ::mlir::test::CompoundAType::getMnemonic()) return ::mlir::test::CompoundAType::parse(context, parser);
 // DEF return ::mlir::Type();
 
 def Test_Dialect: Dialect {
 // DECL-NOT: TestDialect
 // DEF-NOT: TestDialect
     let name = "TestDialect";
     let cppNamespace = "::mlir::test";
 }
 
 class TestType<string name> : TypeDef<Test_Dialect, name> { }
 
 def A_SimpleTypeA : TestType<"SimpleA"> {
-// DECL: class SimpleAType: public ::mlir::Type
+// DECL: class SimpleAType : public ::mlir::Type
 }
 
 def RTLValueType : Type<CPred<"isRTLValueType($_self)">, "Type"> {
   string cppType = "::mlir::Type";
 }
 
 // A more complex parameterized type
 def B_CompoundTypeA : TestType<"CompoundA"> {
   let summary = "A more complex parameterized type";
   let description = "This type is to test a reasonably complex type";
   let mnemonic = "cmpnd_a";
   let parameters = (
       ins
       "int":$widthOfSomething,
       "::mlir::test::SimpleTypeA": $exampleTdType,
       "SomeCppStruct": $exampleCppType,
       ArrayRefParameter<"int", "Matrix dimensions">:$dims,
       RTLValueType:$inner
   );
 
   let genVerifyInvariantsDecl = 1;
 
-// DECL-LABEL: class CompoundAType: public ::mlir::Type
+// DECL-LABEL: class CompoundAType : public ::mlir::Type
+// DECL: static CompoundAType getChecked(::mlir::Location loc, int widthOfSomething, ::mlir::test::SimpleTypeA exampleTdType, SomeCppStruct exampleCppType, ::llvm::ArrayRef<int> dims, ::mlir::Type inner);
 // DECL: static ::mlir::LogicalResult verifyConstructionInvariants(::mlir::Location loc, int widthOfSomething, ::mlir::test::SimpleTypeA exampleTdType, SomeCppStruct exampleCppType, ::llvm::ArrayRef<int> dims, ::mlir::Type inner);
-// DECL: static ::mlir::Type getChecked(::mlir::Location loc, int widthOfSomething, ::mlir::test::SimpleTypeA exampleTdType, SomeCppStruct exampleCppType, ::llvm::ArrayRef<int> dims, ::mlir::Type inner);
 // DECL: static ::llvm::StringRef getMnemonic() { return "cmpnd_a"; }
-// DECL: static ::mlir::Type parse(::mlir::MLIRContext* ctxt, ::mlir::DialectAsmParser& parser);
-// DECL: void print(::mlir::DialectAsmPrinter& printer) const;
+// DECL: static ::mlir::Type parse(::mlir::MLIRContext *context,
+// DECL-NEXT: ::mlir::DialectAsmParser &parser);
+// DECL: void print(::mlir::DialectAsmPrinter &printer) const;
 // DECL: int getWidthOfSomething() const;
 // DECL: ::mlir::test::SimpleTypeA getExampleTdType() const;
 // DECL: SomeCppStruct getExampleCppType() const;
 }
 
 def C_IndexType : TestType<"Index"> {
     let mnemonic = "index";
 
     let parameters = (
       ins
       StringRefParameter<"Label for index">:$label
     );
 
-// DECL-LABEL: class IndexType: public ::mlir::Type
+// DECL-LABEL: class IndexType : public ::mlir::Type
 // DECL: static ::llvm::StringRef getMnemonic() { return "index"; }
-// DECL: static ::mlir::Type parse(::mlir::MLIRContext* ctxt, ::mlir::DialectAsmParser& parser);
-// DECL: void print(::mlir::DialectAsmPrinter& printer) const;
+// DECL: static ::mlir::Type parse(::mlir::MLIRContext *context,
+// DECL-NEXT: ::mlir::DialectAsmParser &parser);
+// DECL: void print(::mlir::DialectAsmPrinter &printer) const;
 }
 
 def D_SingleParameterType : TestType<"SingleParameter"> {
   let parameters = (
     ins
     "int": $num
   );
 // DECL-LABEL: struct SingleParameterTypeStorage;
 // DECL-LABEL: class SingleParameterType
 // DECL-NEXT:                   detail::SingleParameterTypeStorage
 }
 
 def E_IntegerType : TestType<"Integer"> {
     let mnemonic = "int";
     let genVerifyInvariantsDecl = 1;
     let parameters = (
         ins
         "SignednessSemantics":$signedness,
         TypeParameter<"unsigned", "Bitwidth of integer">:$width
     );
 
-// DECL-LABEL: IntegerType: public ::mlir::Type
+// DECL-LABEL: IntegerType : public ::mlir::Type
 
     let extraClassDeclaration = [{
   /// Signedness semantics.
   enum SignednessSemantics {
     Signless, /// No signedness semantics
     Signed,   /// Signed integer
     Unsigned, /// Unsigned integer
   };

mlir/tools/mlir-tblgen/TypeDefGen.cpp

 )";
 
 /// The code block for the start of a typeDef class declaration -- singleton
 /// case.
 ///
 /// {0}: The name of the typeDef class.
 /// {1}: The name of the type base class.
 static const char *const typeDefDeclSingletonBeginStr = R"(
-  class {0}: public ::mlir::Type::TypeBase<{0}, {1}, ::mlir::TypeStorage> {{
+  class {0} : public ::mlir::Type::TypeBase<{0}, {1}, ::mlir::TypeStorage> {{
   public:
     /// Inherit some necessary constructors from 'TypeBase'.
     using Base::Base;
 
 )";
 
 /// The code block for the start of a typeDef class declaration -- parametric
 /// case.
 ///
 /// {0}: The name of the typeDef class.
 /// {1}: The name of the type base class.
 /// {2}: The typeDef storage class namespace.
 /// {3}: The storage class name.
 /// {4}: The list of parameters with types.
 static const char *const typeDefDeclParametricBeginStr = R"(
   namespace {2} {
     struct {3};
-  }
-  class {0}: public ::mlir::Type::TypeBase<{0}, {1},
+  } // end namespace {2}
+  class {0} : public ::mlir::Type::TypeBase<{0}, {1},
                                          {2}::{3}> {{
   public:
     /// Inherit some necessary constructors from 'TypeBase'.
     using Base::Base;
 
 )";
 
 /// The snippet for print/parse.
 static const char *const typeDefParsePrint = R"(
-    static ::mlir::Type parse(::mlir::MLIRContext* ctxt, ::mlir::DialectAsmParser& parser);
-    void print(::mlir::DialectAsmPrinter& printer) const;
+    static ::mlir::Type parse(::mlir::MLIRContext *context,
+                              ::mlir::DialectAsmParser &parser);
+    void print(::mlir::DialectAsmPrinter &printer) const;
 )";
 
 /// The code block for the verifyConstructionInvariants and getChecked.
 ///
-/// {0}: List of parameters, parameters style.
+/// {0}: The name of the typeDef class.
+/// {1}: List of parameters, parameters style.
 static const char *const typeDefDeclVerifyStr = R"(
-    static ::mlir::LogicalResult verifyConstructionInvariants(::mlir::Location loc{0});
-    static ::mlir::Type getChecked(::mlir::Location loc{0});
+    static ::mlir::LogicalResult verifyConstructionInvariants(::mlir::Location loc{1});
 )";
 
+/// Emit the builders for the given type.
+static void emitTypeBuilderDecls(const TypeDef &typeDef, raw_ostream &os,
+                                 TypeParamCommaFormatter &paramTypes) {
+  StringRef typeClass = typeDef.getCppClassName();
+  bool genCheckedMethods = typeDef.genVerifyInvariantsDecl();
+  if (!typeDef.skipDefaultBuilders()) {
+    os << llvm::formatv(
+        "    static {0} get(::mlir::MLIRContext *context{1});\n", typeClass,
+        paramTypes);
+    if (genCheckedMethods) {
+      os << llvm::formatv(
+          "    static {0} getChecked(::mlir::Location loc{1});\n", typeClass,
+          paramTypes);
+    }
+  }
+
+  // Generate the builders specified by the user.
+  for (const TypeBuilder &builder : typeDef.getBuilders()) {
+    std::string paramStr;
+    llvm::raw_string_ostream paramOS(paramStr);
+    llvm::interleaveComma(
+        builder.getParameters(), paramOS,
+        [&](const TypeBuilder::Parameter &param) {
+          // Note: TypeBuilder parameters are guaranteed to have names.
+          paramOS << param.getCppType() << " " << *param.getName();
+          if (Optional<StringRef> defaultParamValue = param.getDefaultValue())
+            paramOS << " = " << *defaultParamValue;
+        });
+    paramOS.flush();
+
+    // Generate the `get` variant of the builder.
+    os << "    static " << typeClass << " get(";
+    if (!builder.hasInferredContextParameter()) {
+      os << "::mlir::MLIRContext *context";
+      if (!paramStr.empty())
+        os << ", ";
+    }
+    os << paramStr << ");\n";
+
+    // Generate the `getChecked` variant of the builder.
+    if (genCheckedMethods) {
+      os << "    static " << typeClass << " getChecked(::mlir::Location loc";
+      if (!paramStr.empty())
+        os << ", " << paramStr;
+      os << ");\n";
+    }
+  }
+}
+
 /// Generate the declaration for the given typeDef class.
 static void emitTypeDefDecl(const TypeDef &typeDef, raw_ostream &os) {
   SmallVector<TypeParameter, 4> params;
   typeDef.getParameters(params);
 
   // Emit the beginning string template: either the singleton or parametric
   // template.
   if (typeDef.getNumParameters() == 0)
     os << formatv(typeDefDeclSingletonBeginStr, typeDef.getCppClassName(),
                   typeDef.getCppBaseClassName());
   else
     os << formatv(typeDefDeclParametricBeginStr, typeDef.getCppClassName(),
                   typeDef.getCppBaseClassName(), typeDef.getStorageNamespace(),
                   typeDef.getStorageClassName());
 
   // Emit the extra declarations first in case there's a type definition in
   // there.
   if (Optional<StringRef> extraDecl = typeDef.getExtraDecls())
     os << *extraDecl << "\n";
 
   TypeParamCommaFormatter emitTypeNamePairsAfterComma(
       TypeParamCommaFormatter::EmitFormat::TypeNamePairs, params);
   if (!params.empty()) {
-    os << llvm::formatv("    static {0} get(::mlir::MLIRContext* ctxt{1});\n",
-                        typeDef.getCppClassName(), emitTypeNamePairsAfterComma);
-  }
+    emitTypeBuilderDecls(typeDef, os, emitTypeNamePairsAfterComma);
 
     // Emit the verify invariants declaration.
     if (typeDef.genVerifyInvariantsDecl())
-    os << llvm::formatv(typeDefDeclVerifyStr, emitTypeNamePairsAfterComma);
+      os << llvm::formatv(typeDefDeclVerifyStr, typeDef.getCppClassName(),
+                          emitTypeNamePairsAfterComma);
+  }
 
   // Emit the mnenomic, if specified.
   if (auto mnenomic = typeDef.getMnemonic()) {
     os << "    static ::llvm::StringRef getMnemonic() { return \"" << mnenomic
        << "\"; }\n";
 
     // If mnemonic specified, emit print/parse declarations.
+    if (typeDef.getParserCode() || typeDef.getPrinterCode() || !params.empty())
       os << typeDefParsePrint;
   }
 
   if (typeDef.genAccessors()) {
     SmallVector<TypeParameter, 4> parameters;
     typeDef.getParameters(parameters);
 
     for (TypeParameter &parameter : parameters) {
       SmallString<16> name = parameter.getName();

 /// {0}: storage class name.
 /// {1}: list of parameters.
 static const char *const typeDefStorageClassConstructorReturn = R"(
       return new (allocator.allocate<{0}>())
           {0}({1});
     }
 )";
 
-/// The code block for the getChecked definition.
-///
-/// {0}: List of parameters, parameters style.
-/// {1}: C++ type class name.
-/// {2}: Comma separated list of parameter names.
-static const char *const typeDefDefGetCheckeStr = R"(
-    ::mlir::Type {1}::getChecked(Location loc{0}) {{
-      return Base::getChecked(loc{2});
-    }
-)";
-
 /// Use tgfmt to emit custom allocation code for each parameter, if necessary.
 static void emitParameterAllocationCode(TypeDef &typeDef, raw_ostream &os) {
   SmallVector<TypeParameter, 4> parameters;
   typeDef.getParameters(parameters);
   auto fmtCtxt = FmtContext().addSubst("_allocator", "allocator");
   for (TypeParameter &parameter : parameters) {
     auto allocCode = parameter.getAllocator();
     if (allocCode) {
static void emitStorageClass(TypeDef typeDef, raw_ostream &os) {
   // Then combine them all. This requires all the parameters types to have a
   // hash_value defined.
   os << llvm::formatv(
       "      return ::llvm::hash_combine({0});\n    }\n",
       TypeParamCommaFormatter(TypeParamCommaFormatter::EmitFormat::JustParams,
                               parameters, /* prependComma */ false));
 
   // 3) Emit the construct method.
-  if (typeDef.hasStorageCustomConstructor())
+  if (typeDef.hasStorageCustomConstructor()) {
     // If user wants to build the storage constructor themselves, declare it
     // here and then they can write the definition elsewhere.
     os << "    static " << typeDef.getStorageClassName()
        << " *construct(::mlir::TypeStorageAllocator &allocator, const KeyTy "
           "&key);\n";
-  else {
+  } else {
     // If not, autogenerate one.
 
     // First, unbox the parameters.
     os << formatv(typeDefStorageClassConstructorBegin,
                   typeDef.getStorageClassName());
     for (size_t i = 0; i < parameters.size(); ++i) {
       os << formatv("      auto {0} = std::get<{1}>(key);\n",
                     parameters[i].getName(), i);

 
 /// Emit the parser and printer for a particular type, if they're specified.
 void emitParserPrinter(TypeDef typeDef, raw_ostream &os) {
   // Emit the printer code, if specified.
   if (auto printerCode = typeDef.getPrinterCode()) {
     // Both the mnenomic and printerCode must be defined (for parity with
     // parserCode).
     os << "void " << typeDef.getCppClassName()
-       << "::print(::mlir::DialectAsmPrinter& printer) const {\n";
+       << "::print(::mlir::DialectAsmPrinter &printer) const {\n";
     if (*printerCode == "") {
       // If no code specified, emit error.
       PrintFatalError(typeDef.getLoc(),
                       typeDef.getName() +
                           ": printer (if specified) must have non-empty code");
     }
     auto fmtCtxt = FmtContext().addSubst("_printer", "printer");
     os << tgfmt(*printerCode, &fmtCtxt) << "\n}\n";
   }
 
   // emit a parser, if specified.
   if (auto parserCode = typeDef.getParserCode()) {
     // The mnenomic must be defined so the dispatcher knows how to dispatch.
     os << "::mlir::Type " << typeDef.getCppClassName()
-       << "::parse(::mlir::MLIRContext* ctxt, ::mlir::DialectAsmParser& "
+       << "::parse(::mlir::MLIRContext *context, ::mlir::DialectAsmParser &"
           "parser) "
           "{\n";
     if (*parserCode == "") {
       // if no code specified, emit error.
       PrintFatalError(typeDef.getLoc(),
                       typeDef.getName() +
                           ": parser (if specified) must have non-empty code");
     }
     auto fmtCtxt =
-        FmtContext().addSubst("_parser", "parser").addSubst("_ctxt", "ctxt");
+        FmtContext().addSubst("_parser", "parser").addSubst("_ctxt", "context");
     os << tgfmt(*parserCode, &fmtCtxt) << "\n}\n";
   }
 }
 
+/// Emit the builders for the given type.
+static void emitTypeBuilderDefs(const TypeDef &typeDef, raw_ostream &os,
+                                ArrayRef<TypeParameter> typeDefParams) {
+  bool genCheckedMethods = typeDef.genVerifyInvariantsDecl();
+  StringRef typeClass = typeDef.getCppClassName();
+  if (!typeDef.skipDefaultBuilders()) {
+    os << llvm::formatv(
+        "{0} {0}::get(::mlir::MLIRContext *context{1}) {{\n"
+        "  return Base::get(context{2});\n}\n",
+        typeClass,
+        TypeParamCommaFormatter(
+            TypeParamCommaFormatter::EmitFormat::TypeNamePairs, typeDefParams),
+        TypeParamCommaFormatter(TypeParamCommaFormatter::EmitFormat::JustParams,
+                                typeDefParams));
+    if (genCheckedMethods) {
+      os << llvm::formatv(
+          "{0} {0}::getChecked(::mlir::Location loc{1}) {{\n"
+          "  return Base::getChecked(loc{2});\n}\n",
+          typeClass,
+          TypeParamCommaFormatter(
+              TypeParamCommaFormatter::EmitFormat::TypeNamePairs,
+              typeDefParams),
+          TypeParamCommaFormatter(
+              TypeParamCommaFormatter::EmitFormat::JustParams, typeDefParams));
+    }
+  }
+
+  // Generate the builders specified by the user.
+  auto builderFmtCtx = FmtContext().addSubst("_ctxt", "context");
+  auto checkedBuilderFmtCtx = FmtContext()
+                                  .addSubst("_loc", "loc")
+                                  .addSubst("_ctxt", "loc.getContext()");
+  for (const TypeBuilder &builder : typeDef.getBuilders()) {
+    Optional<StringRef> body = builder.getBody();
+    Optional<StringRef> checkedBody =
+        genCheckedMethods ? builder.getCheckedBody() : llvm::None;
+    if (!body && !checkedBody)
+      continue;
+    std::string paramStr;
+    llvm::raw_string_ostream paramOS(paramStr);
+    llvm::interleaveComma(builder.getParameters(), paramOS,
+                          [&](const TypeBuilder::Parameter &param) {
+                            // Note: TypeBuilder parameters are guaranteed to
+                            // have names.
+                            paramOS << param.getCppType() << " "
+                                    << *param.getName();
+                          });
+    paramOS.flush();
+
+    // Emit the `get` variant of the builder.
+    if (body) {
+      os << llvm::formatv("{0} {0}::get(", typeClass);
+      if (!builder.hasInferredContextParameter()) {
+        os << "::mlir::MLIRContext *context";
+        if (!paramStr.empty())
+          os << ", ";
+        os << llvm::formatv("{0}) {{\n  {1};\n}\n", paramStr,
+                            tgfmt(*body, &builderFmtCtx).str());
+      } else {
+        os << llvm::formatv("{0}) {{\n  {1};\n}\n", paramStr, *body);
+      }
+    }
+
+    // Emit the `getChecked` variant of the builder.
+    if (checkedBody) {
+      os << llvm::formatv("{0} {0}::getChecked(::mlir::Location loc",
+                          typeClass);
+      if (!paramStr.empty())
+        os << ", " << paramStr;
+      os << llvm::formatv(") {{\n  {0};\n}\n",
+                          tgfmt(*checkedBody, &checkedBuilderFmtCtx));
+    }
+  }
+}
+
 /// Print all the typedef-specific definition code.
-static void emitTypeDefDef(TypeDef typeDef, raw_ostream &os) {
+static void emitTypeDefDef(const TypeDef &typeDef, raw_ostream &os) {
   NamespaceEmitter ns(os, typeDef.getDialect());
+
   SmallVector<TypeParameter, 4> parameters;
   typeDef.getParameters(parameters);
-
+  if (!parameters.empty()) {
     // Emit the storage class, if requested and necessary.
-  if (typeDef.genStorageClass() && typeDef.getNumParameters() > 0)
+    if (typeDef.genStorageClass())
       emitStorageClass(typeDef, os);
 
-  if (!parameters.empty()) {
-    os << llvm::formatv(
-        "{0} {0}::get(::mlir::MLIRContext* ctxt{1}) {{\n"
-        "  return Base::get(ctxt{2});\n}\n",
-        typeDef.getCppClassName(),
-        TypeParamCommaFormatter(
-            TypeParamCommaFormatter::EmitFormat::TypeNamePairs, parameters),
-        TypeParamCommaFormatter(TypeParamCommaFormatter::EmitFormat::JustParams,
-                                parameters));
-  }
+    // Emit the builders for this type.
+    emitTypeBuilderDefs(typeDef, os, parameters);
 
+    // Generate accessor definitions only if we also generate the storage class.
+    // Otherwise, let the user define the exact accessor definition.
+    if (typeDef.genAccessors() && typeDef.genStorageClass()) {
       // Emit the parameter accessors.
-  if (typeDef.genAccessors())
       for (const TypeParameter &parameter : parameters) {
         SmallString<16> name = parameter.getName();
         name[0] = llvm::toUpper(name[0]);
         os << formatv("{0} {3}::get{1}() const { return getImpl()->{2}; }\n",
                       parameter.getCppType(), name, parameter.getName(),
                       typeDef.getCppClassName());
       }
-
-  // Generate getChecked() method.
-  if (typeDef.genVerifyInvariantsDecl()) {
-    os << llvm::formatv(
-        typeDefDefGetCheckeStr,
-        TypeParamCommaFormatter(
-            TypeParamCommaFormatter::EmitFormat::TypeNamePairs, parameters),
-        typeDef.getCppClassName(),
-        TypeParamCommaFormatter(TypeParamCommaFormatter::EmitFormat::JustParams,
-                                parameters));
+    }
   }
 
   // If mnemonic is specified maybe print definitions for the parser and printer
   // code, if they're specified.
   if (typeDef.getMnemonic())
     emitParserPrinter(typeDef, os);
 }
 
 /// Emit the dialect printer/parser dispatcher. User's code should call these
 /// functions from their dialect's print/parse methods.
 static void emitParsePrintDispatch(ArrayRef<TypeDef> types, raw_ostream &os) {
   if (llvm::none_of(types, [](const TypeDef &type) {
         return type.getMnemonic().hasValue();
       })) {
     return;
   }
 
   // The parser dispatch is just a list of if-elses, matching on the
   // mnemonic and calling the class's parse function.
-  os << "static ::mlir::Type generatedTypeParser(::mlir::MLIRContext* "
-        "ctxt, "
-        "::mlir::DialectAsmParser& parser, ::llvm::StringRef mnemonic) {\n";
+  os << "static ::mlir::Type generatedTypeParser(::mlir::MLIRContext *"
+        "context, ::mlir::DialectAsmParser &parser, "
+        "::llvm::StringRef mnemonic) {\n";
   for (const TypeDef &type : types) {
     if (type.getMnemonic()) {
       os << formatv("  if (mnemonic == {0}::{1}::getMnemonic()) return "
                     "{0}::{1}::",
                     type.getDialect().getCppNamespace(),
                     type.getCppClassName());
 
       // If the type has no parameters and no parser code, just invoke a normal
       // `get`.
       if (type.getNumParameters() == 0 && !type.getParserCode())
-        os << "get(ctxt);\n";
+        os << "get(context);\n";
       else
-        os << "parse(ctxt, parser);\n";
+        os << "parse(context, parser);\n";
     }
   }
   os << "  return ::mlir::Type();\n";
   os << "}\n\n";
 
   // The printer dispatch uses llvm::TypeSwitch to find and call the correct
   // printer.
   os << "static ::mlir::LogicalResult generatedTypePrinter(::mlir::Type "
         "type, "
-        "::mlir::DialectAsmPrinter& printer) {\n"
+        "::mlir::DialectAsmPrinter &printer) {\n"
      << "  return ::llvm::TypeSwitch<::mlir::Type, "
         "::mlir::LogicalResult>(type)\n";
   for (const TypeDef &type : types) {
     if (Optional<StringRef> mnemonic = type.getMnemonic()) {
       StringRef cppNamespace = type.getDialect().getCppNamespace();
       StringRef cppClassName = type.getCppClassName();
       os << formatv("    .Case<{0}::{1}>([&]({0}::{1} t) {{\n      ",
                     cppNamespace, cppClassName);
static bool emitTypeDefDefs(const llvm::RecordKeeper &recordKeeper,
   emitSourceFileHeader("TypeDef Definitions", os);
 
   SmallVector<TypeDef, 16> typeDefs;
   findAllTypeDefs(recordKeeper, typeDefs);
   emitTypeDefList(typeDefs, os);
 
   IfDefScope scope("GET_TYPEDEF_CLASSES", os);
   emitParsePrintDispatch(typeDefs, os);
-  for (auto typeDef : typeDefs)
+  for (const TypeDef &typeDef : typeDefs)
     emitTypeDefDef(typeDef, os);
 
   return false;
 }
 
 //===----------------------------------------------------------------------===//
 // GEN: TypeDef registration hooks
 //===----------------------------------------------------------------------===//