[MLIR] feat(mlir-tblgen): Add support for dialect interfaces #170046

aidint · 2025-11-30T18:50:56Z

Currently, Dialect Interfaces can't be defined in ODS. This PR adds the support for dialect interfaces. It follows the same approach with other interfaces and extends on top of Interface class defined in mlir/TableGen/Interfaces.h.

Given the following input:

#ifndef MY_INTERFACES
#define MY_INTERFACES

include "mlir/IR/Interfaces.td"

def DialectInlinerInterface : DialectInterface<"DialectInlinerInterface"> {
  let description = [{
     Define a base inlining interface class to allow for dialects to opt-in to the inliner.
  }];

  let cppNamespace = "::mlir";

  let methods = [
    InterfaceMethod<
      /*desc=*/        [{
        Returns true if the given region 'src' can be inlined into the region
        'dest' that is attached to an operation registered to the current dialect.
        'valueMapping' contains any remapped values from within the 'src' region.
        This can be used to examine what values will replace entry arguments into
        the 'src' region, for example.
      }],
      /*returnType=*/  "bool",
      /*methodName=*/  "isLegalToInline",
      /*args=*/        (ins "::mlir::Region *":$dest, "::mlir::Region *":$src, "::mlir::IRMapping &":$valueMapping),
      /*methodBody=*/  [{
        return true;
      }]
      >
  ];
}


#endif

It will generate the following code:

/*===- TableGen'erated file -------------------------------------*- C++ -*-===*\
|*                                                                            *|
|* Dialect Interface Declarations                                             *|
|*                                                                            *|
|* Automatically generated file, do not edit!                                 *|
|*                                                                            *|
\*===----------------------------------------------------------------------===*/

namespace mlir {

/// Define a base inlining interface class to allow for dialects to opt-in to the inliner.
class DialectInlinerInterface : public ::mlir::DialectInterface::Base<DialectInlinerInterface> {
public:

  /// Returns true if the given region 'src' can be inlined into the region
  /// 'dest' that is attached to an operation registered to the current dialect.
  /// 'valueMapping' contains any remapped values from within the 'src' region.
  /// This can be used to examine what values will replace entry arguments into
  /// the 'src' region, for example.
  virtual bool isLegalToInline(::mlir::Region * dest, ::mlir::Region * src, ::mlir::IRMapping & valueMapping) const;

protected:
  DialectInlinerInterface(::mlir::Dialect *dialect) : Base(dialect) {}
};

} // namespace mlir

bool ::mlir::DialectInlinerInterface::isLegalToInline(::mlir::Region * dest, ::mlir::Region * src, ::mlir::IRMapping & valueMapping) const {
  return true;
}

llvmbot · 2025-11-30T18:51:28Z

@llvm/pr-subscribers-mlir
@llvm/pr-subscribers-mlir-core

@llvm/pr-subscribers-mlir-ods

Author: AidinT (aidint)

Changes

Currently, Dialect Interfaces can't be defined in ODS. This PR adds the support for dialect interfaces. It follows the same approach with other interfaces and extends on top of Interface class defined in mlir/TableGen/Interfaces.h.

Given the following input:

#ifndef MY_INTERFACES
#define MY_INTERFACES

include "mlir/IR/Interfaces.td"

def DialectInlinerInterface : DialectInterface&lt;"DialectInlinerInterface"&gt; {
  let description = [{
     Define a base inlining interface class to allow for dialects to opt-in to the inliner.
  }];

  let cppNamespace = "::mlir";

  let methods = [
    InterfaceMethod&lt;
      /*desc=*/        [{
        Returns true if the given region 'src' can be inlined into the region
        'dest' that is attached to an operation registered to the current dialect.
        'valueMapping' contains any remapped values from within the 'src' region.
        This can be used to examine what values will replace entry arguments into
        the 'src' region, for example.
      }],
      /*returnType=*/  "bool",
      /*methodName=*/  "isLegalToInline",
      /*args=*/        (ins "::mlir::Region *":$dest, "::mlir::Region *":$src, "::mlir::IRMapping &amp;":$valueMapping),
      /*methodBody=*/  [{
        return true;
      }]
      &gt;
  ];
}


#endif

It will generate the following code:

/*===- TableGen'erated file -------------------------------------*- C++ -*-===*\
|*                                                                            *|
|* Dialect Interface Declarations                                             *|
|*                                                                            *|
|* Automatically generated file, do not edit!                                 *|
|*                                                                            *|
\*===----------------------------------------------------------------------===*/

namespace mlir {

/// Define a base inlining interface class to allow for dialects to opt-in to the inliner.
class DialectInlinerInterface : public ::mlir::DialectInterface::Base&lt;DialectInlinerInterface&gt; {
public:

  /// Returns true if the given region 'src' can be inlined into the region
  /// 'dest' that is attached to an operation registered to the current dialect.
  /// 'valueMapping' contains any remapped values from within the 'src' region.
  /// This can be used to examine what values will replace entry arguments into
  /// the 'src' region, for example.
  virtual bool isLegalToInline(::mlir::Region * dest, ::mlir::Region * src, ::mlir::IRMapping &amp; valueMapping) const;

protected:
  DialectInlinerInterface(::mlir::Dialect *dialect) : Base(dialect) {}
};

} // namespace mlir

bool ::mlir::DialectInlinerInterface::isLegalToInline(::mlir::Region * dest, ::mlir::Region * src, ::mlir::IRMapping &amp; valueMapping) const {
  return true;
}

Full diff: https://github.com/llvm/llvm-project/pull/170046.diff

6 Files Affected:

(modified) mlir/include/mlir/IR/Interfaces.td (+5)
(modified) mlir/include/mlir/TableGen/Interfaces.h (+7)
(modified) mlir/lib/TableGen/Interfaces.cpp (+8)
(added) mlir/test/mlir-tblgen/dialect-interface.td (+66)
(modified) mlir/tools/mlir-tblgen/CMakeLists.txt (+1)
(added) mlir/tools/mlir-tblgen/DialectInterfacesGen.cpp (+176)

diff --git a/mlir/include/mlir/IR/Interfaces.td b/mlir/include/mlir/IR/Interfaces.td
index 0cbe3fa25c9e7..746ad3408f424 100644
--- a/mlir/include/mlir/IR/Interfaces.td
+++ b/mlir/include/mlir/IR/Interfaces.td
@@ -147,6 +147,11 @@ class TypeInterface<string name, list<Interface> baseInterfaces = []>
 			!if(!empty(cppNamespace),"", cppNamespace # "::") # name
     >;
 
+// DialectInterface represents an interface registered to an operation.
+class DialectInterface<string name, list<Interface> baseInterfaces = []>
+  : Interface<name, baseInterfaces>, OpInterfaceTrait<name>;
+
+
 // Whether to declare the interface methods in the user entity's header. This
 // class simply wraps an Interface but is used to indicate that the method
 // declarations should be generated. This class takes an optional set of methods
diff --git a/mlir/include/mlir/TableGen/Interfaces.h b/mlir/include/mlir/TableGen/Interfaces.h
index 7c36cbc1192ac..f62d21da467a1 100644
--- a/mlir/include/mlir/TableGen/Interfaces.h
+++ b/mlir/include/mlir/TableGen/Interfaces.h
@@ -157,6 +157,13 @@ struct TypeInterface : public Interface {
 
   static bool classof(const Interface *interface);
 };
+// An interface that is registered to a Dialect.
+struct DialectInterface : public Interface {
+  using Interface::Interface;
+
+  static bool classof(const Interface *interface);
+};
+
 } // namespace tblgen
 } // namespace mlir
 
diff --git a/mlir/lib/TableGen/Interfaces.cpp b/mlir/lib/TableGen/Interfaces.cpp
index b0ad3ee59a089..77a6cecebbeaf 100644
--- a/mlir/lib/TableGen/Interfaces.cpp
+++ b/mlir/lib/TableGen/Interfaces.cpp
@@ -208,3 +208,11 @@ bool OpInterface::classof(const Interface *interface) {
 bool TypeInterface::classof(const Interface *interface) {
   return interface->getDef().isSubClassOf("TypeInterface");
 }
+
+//===----------------------------------------------------------------------===//
+// DialectInterface
+//===----------------------------------------------------------------------===//
+
+bool DialectInterface::classof(const Interface *interface) {
+  return interface->getDef().isSubClassOf("DialectInterface");
+}
diff --git a/mlir/test/mlir-tblgen/dialect-interface.td b/mlir/test/mlir-tblgen/dialect-interface.td
new file mode 100644
index 0000000000000..9b424bf501be3
--- /dev/null
+++ b/mlir/test/mlir-tblgen/dialect-interface.td
@@ -0,0 +1,66 @@
+// RUN: mlir-tblgen -gen-dialect-interface-decls -I %S/../../include %s | FileCheck %s --check-prefix=DECL
+
+include "mlir/IR/Interfaces.td"
+
+def NoDefaultMethod : DialectInterface<"NoDefaultMethod"> {
+  let description = [{
+    This is an example dialect interface without default method body.
+  }];
+
+  let cppNamespace = "::mlir::example";
+
+  let methods = [
+    InterfaceMethod<
+      /*desc=*/        "Check if it's an example dialect",
+      /*returnType=*/  "bool",
+      /*methodName=*/  "isExampleDialect",
+      /*args=*/        (ins)
+      >,
+      InterfaceMethod<
+      /*desc=*/        "second method to check if multiple methods supported",
+      /*returnType=*/  "unsigned",
+      /*methodName=*/  "supportSecondMethod",
+      /*args=*/        (ins "::mlir::Type":$type)
+      >
+
+  ];
+}
+
+// DECL:   class NoDefaultMethod : public {{.*}}DialectInterface::Base<NoDefaultMethod>
+// DECL:   virtual bool isExampleDialect() const = 0;
+// DECL:   virtual unsigned supportSecondMethod(::mlir::Type type) const = 0;
+// DECL:   protected:
+// DECL-NEXT:   NoDefaultMethod(::mlir::Dialect *dialect) : Base(dialect) {}
+
+def WithDefaultMethodInterface : DialectInterface<"WithDefaultMethodInterface"> {
+  let description = [{
+    This is an example dialect interface with default method bodies.
+  }];
+
+  let cppNamespace = "::mlir::example";
+
+  let methods = [
+    InterfaceMethod<
+      /*desc=*/        "Check if it's an example dialect",
+      /*returnType=*/  "bool",
+      /*methodName=*/  "isExampleDialect",
+      /*args=*/        (ins),
+      /*methodBody=*/  [{
+          return true;
+         }]
+      >,
+      InterfaceMethod<
+      /*desc=*/        "second method to check if multiple methods supported",
+      /*returnType=*/  "unsigned",
+      /*methodName=*/  "supportSecondMethod",
+      /*args=*/        (ins "::mlir::Type":$type)
+      >
+
+  ];
+}
+
+// DECL:  virtual bool isExampleDialect() const;
+// DECL:  bool ::mlir::example::WithDefaultMethodInterface::isExampleDialect() const {
+// DECL-NEXT:  return true;
+// DECL-NEXT: }
+
diff --git a/mlir/tools/mlir-tblgen/CMakeLists.txt b/mlir/tools/mlir-tblgen/CMakeLists.txt
index 2a7ef7e0576c8..d7087cba3c874 100644
--- a/mlir/tools/mlir-tblgen/CMakeLists.txt
+++ b/mlir/tools/mlir-tblgen/CMakeLists.txt
@@ -12,6 +12,7 @@ add_tablegen(mlir-tblgen MLIR
   AttrOrTypeFormatGen.cpp
   BytecodeDialectGen.cpp
   DialectGen.cpp
+  DialectInterfacesGen.cpp
   DirectiveCommonGen.cpp
   EnumsGen.cpp
   EnumPythonBindingGen.cpp
diff --git a/mlir/tools/mlir-tblgen/DialectInterfacesGen.cpp b/mlir/tools/mlir-tblgen/DialectInterfacesGen.cpp
new file mode 100644
index 0000000000000..2fc500343501c
--- /dev/null
+++ b/mlir/tools/mlir-tblgen/DialectInterfacesGen.cpp
@@ -0,0 +1,176 @@
+//===- DialectInterfacesGen.cpp - MLIR dialect interface utility 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
+//
+//===----------------------------------------------------------------------===//
+//
+// DialectInterfaceGen generates definitions for Dialect interfaces.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CppGenUtilities.h"
+#include "DocGenUtilities.h"
+#include "mlir/TableGen/GenInfo.h"
+#include "mlir/TableGen/Interfaces.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/TableGen/CodeGenHelpers.h"
+#include "llvm/TableGen/Error.h"
+#include "llvm/TableGen/Record.h"
+#include "llvm/TableGen/TableGenBackend.h"
+
+using namespace mlir;
+using llvm::Record;
+using llvm::RecordKeeper;
+using mlir::tblgen::Interface;
+using mlir::tblgen::InterfaceMethod;
+
+/// Emit a string corresponding to a C++ type, followed by a space if necessary.
+static raw_ostream &emitCPPType(StringRef type, raw_ostream &os) {
+  type = type.trim();
+  os << type;
+  if (type.back() != '&' && type.back() != '*')
+    os << " ";
+  return os;
+}
+
+/// Emit the method name and argument list for the given method.
+static void emitMethodNameAndArgs(const InterfaceMethod &method, StringRef name,
+                                  raw_ostream &os) {
+  os << name << '(';
+  llvm::interleaveComma(method.getArguments(), os,
+                        [&](const InterfaceMethod::Argument &arg) {
+                          os << arg.type << " " << arg.name;
+                        });
+  os << ") const";
+}
+
+/// Get an array of all Dialect Interface definitions
+static std::vector<const Record *>
+getAllInterfaceDefinitions(const RecordKeeper &records) {
+  std::vector<const Record *> defs =
+      records.getAllDerivedDefinitions("DialectInterface");
+
+  llvm::erase_if(defs, [&](const Record *def) {
+    // Ignore interfaces defined outside of the top-level file.
+    return llvm::SrcMgr.FindBufferContainingLoc(def->getLoc()[0]) !=
+           llvm::SrcMgr.getMainFileID();
+  });
+  return defs;
+}
+
+namespace {
+/// This struct is the generator used when processing tablegen dialect
+/// interfaces.
+class DialectInterfaceGenerator {
+public:
+  DialectInterfaceGenerator(const RecordKeeper &records, raw_ostream &os)
+      : defs(getAllInterfaceDefinitions(records)), os(os) {}
+
+  bool emitInterfaceDecls();
+
+protected:
+  void emitInterfaceDecl(const Interface &interface);
+  void emitInterfaceMethodsDef(const Interface &interface);
+
+  /// The set of interface records to emit.
+  std::vector<const Record *> defs;
+  // The stream to emit to.
+  raw_ostream &os;
+};
+} // namespace
+
+//===----------------------------------------------------------------------===//
+// GEN: Interface declarations
+//===----------------------------------------------------------------------===//
+
+static void emitInterfaceMethodDoc(const InterfaceMethod &method,
+                                   raw_ostream &os, StringRef prefix = "") {
+  if (std::optional<StringRef> description = method.getDescription())
+    tblgen::emitDescriptionComment(*description, os, prefix);
+}
+
+static void emitInterfaceDeclMethods(const Interface &interface,
+                                     raw_ostream &os) {
+  for (auto &method : interface.getMethods()) {
+    emitInterfaceMethodDoc(method, os, "  ");
+    os << "  virtual ";
+    emitCPPType(method.getReturnType(), os);
+    emitMethodNameAndArgs(method, method.getName(), os);
+    if (!method.getBody())
+      // no default method body
+      os << " = 0";
+    os << ";\n";
+  }
+}
+
+void DialectInterfaceGenerator::emitInterfaceDecl(const Interface &interface) {
+  llvm::NamespaceEmitter ns(os, interface.getCppNamespace());
+
+  StringRef interfaceName = interface.getName();
+
+  tblgen::emitSummaryAndDescComments(os, "",
+                                     interface.getDescription().value_or(""));
+
+  // Emit the main interface class declaration.
+  os << llvm::formatv(
+      "class {0} : public ::mlir::DialectInterface::Base<{0}> {{\n"
+      "public:\n",
+      interfaceName);
+
+  emitInterfaceDeclMethods(interface, os);
+  os << llvm::formatv("\nprotected:\n"
+                      "  {0}(::mlir::Dialect *dialect) : Base(dialect) {{}\n",
+                      interfaceName);
+
+  os << "};\n";
+}
+
+void DialectInterfaceGenerator::emitInterfaceMethodsDef(
+    const Interface &interface) {
+
+  for (auto &method : interface.getMethods()) {
+    if (auto body = method.getBody()) {
+      emitCPPType(method.getReturnType(), os);
+      os << interface.getCppNamespace() << "::";
+      os << interface.getName() << "::";
+      emitMethodNameAndArgs(method, method.getName(), os);
+      os << " {\n  " << body.value() << "\n}\n";
+    }
+  }
+}
+
+bool DialectInterfaceGenerator::emitInterfaceDecls() {
+
+  llvm::emitSourceFileHeader("Dialect Interface Declarations", os);
+
+  // Sort according to ID, so defs are emitted in the order in which they appear
+  // in the Tablegen file.
+  std::vector<const Record *> sortedDefs(defs);
+  llvm::sort(sortedDefs, [](const Record *lhs, const Record *rhs) {
+    return lhs->getID() < rhs->getID();
+  });
+
+  for (const Record *def : sortedDefs)
+    emitInterfaceDecl(Interface(def));
+
+  os << "\n";
+  for (const Record *def : sortedDefs)
+    emitInterfaceMethodsDef(Interface(def));
+
+  return false;
+}
+
+//===----------------------------------------------------------------------===//
+// GEN: Interface registration hooks
+//===----------------------------------------------------------------------===//
+
+static mlir::GenRegistration genDecls(
+    "gen-dialect-interface-decls",
+    "Generate dialect interface declarations.",
+    [](const RecordKeeper &records, raw_ostream &os) {
+      return DialectInterfaceGenerator(records, os).emitInterfaceDecls();
+    });

github-actions · 2025-11-30T18:52:42Z

✅ With the latest revision this PR passed the C/C++ code formatter.

joker-eph

Could you convert an interface like DialectInlinerInterface for example here so we have a concrete working example as well.

aidint · 2025-12-02T22:27:21Z

Could you convert an interface like DialectInlinerInterface for example here so we have a concrete working example as well.

I converted DialectInlinerInterface in mlir/Transforms/InliningUtils.h to the tablegen version.

joker-eph

LGTM, thanks :)

joker-eph

Actually I suspect we need to update the documentation as well, can you do this?

aidint · 2025-12-03T22:08:15Z

@joker-eph I updated the documentation.

jpienaar · 2025-12-04T08:29:03Z

mlir/docs/Interfaces.md

Nit: newline above (certain markdown renders require separation between text and codeblock)

jpienaar · 2025-12-04T08:30:43Z

mlir/docs/Interfaces.md

Nit: the spacing here is different from the other interfaces, lets keep to something like how mlir/include/mlir/Interfaces/ControlFlowInterfaces.td does it.

jpienaar · 2025-12-04T08:30:56Z

mlir/docs/Interfaces.md

With that spacing change I think this fits on previous line.

jpienaar · 2025-12-04T08:31:37Z

mlir/docs/Interfaces.md

Newline above. You could perhaps even point to example in code / cmake usage.

jpienaar · 2025-12-04T08:31:48Z

mlir/docs/Interfaces.md

Wouldn't this be --gen-dialect-interface-decls?

jpienaar · 2025-12-04T08:32:07Z

mlir/include/mlir/Transforms/DialectInlinerInterface.td

jpienaar · 2025-12-04T08:32:29Z

mlir/include/mlir/Transforms/DialectInlinerInterface.td

Missing space before (

jpienaar · 2025-12-04T08:33:00Z

mlir/include/mlir/Transforms/DialectInlinerInterface.td

jpienaar · 2025-12-04T08:34:13Z

mlir/tools/mlir-tblgen/DialectInterfacesGen.cpp

No change needed, but you could also use indented ostream here

I used indented ostream. Can you please review again to see if that's the correct usage?

jpienaar · 2025-12-04T08:36:00Z

mlir/tools/mlir-tblgen/DialectInterfacesGen.cpp

I could have sworn I had this exposed somewhere :)

I grabbed this one from OpInterfacesGen.cpp. I haven't done any research if this has been implemented somewhere else. Do you remember where it might be implemented?

feat(mlir-tblgen): Add support for dialect interfaces

504bb5c

llvmbot added mlir:core MLIR Core Infrastructure mlir mlir:ods labels Nov 30, 2025

resolve clang-format problem

4ca9d25

joker-eph reviewed Dec 1, 2025

View reviewed changes

convert DialectInlinerInterface and use ODS

e3d4a43

joker-eph approved these changes Dec 3, 2025

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joker-eph reviewed Dec 3, 2025

View reviewed changes

add documentation for dialect interface ods support

3f0fc8b

aidint force-pushed the add-dialect-interface-mlir-tblgen branch from 813b84b to 3f0fc8b Compare December 3, 2025 22:06

remove extra line

aa94279

jpienaar approved these changes Dec 4, 2025

View reviewed changes

Resolve documentation issues and use indented ostream

0531140

[MLIR] feat(mlir-tblgen): Add support for dialect interfaces #170046

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[MLIR] feat(mlir-tblgen): Add support for dialect interfaces #170046

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llvmbot commented Nov 30, 2025 •

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