[mlir][CAPI] Introduce standard source layout for mlir-c dialect registration.

[stellaraccident]

Summary

• Registers a small set of sample dialects.
• NFC with respect to existing C-API symbols but some headers have been moved down a level to the Dialect/ sub-directory.
• Adds an additional entry point per dialect that is needed for dynamic discovery/loading.
• See discussion: https://llvm.discourse.group/t/dialects-and-the-c-api/2306/16

[stellaraccident]

Fix typo.

[GeorgeLyon]

It is great to see a unified approach to dialects, this will make further improvements much easier. Thanks, Stella!

[mehdi_amini]

mlir/include/mlir-c/Dialect/Linalg.h

26

Why isn't this all TableGen generated?

[lattner]

nice

[stellaraccident]

mlir/include/mlir-c/Dialect/Linalg.h

26

Because once George and I wrote it, we felt that tablegen would add a lot of complexity and opacity for no benefit.

mlir/include/mlir-c/Dialect/Linalg.h

+//===-- mlir-c/Dialect/Linalg.h - C API for Linalg dialect --------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_C_DIALECT_LINALG_H
+#define MLIR_C_DIALECT_LINALG_H
+
+#include "mlir-c/Registration.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+MLIR_DECLARE_CAPI_DIALECT_REGISTRATION(Linalg, linalg);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // MLIR_C_DIALECT_LINALG_H

mlir/include/mlir-c/Dialect/SCF.h

+//===-- mlir-c/Dialect/SCF.h - C API for SCF dialect --------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_C_DIALECT_SCF_H
+#define MLIR_C_DIALECT_SCF_H
+
+#include "mlir-c/Registration.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+MLIR_DECLARE_CAPI_DIALECT_REGISTRATION(SCF, scf);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // MLIR_C_DIALECT_SCF_H

mlir/include/mlir-c/Dialect/Shape.h

+//===-- mlir-c/Dialect/Shape.h - C API for Shape dialect ----------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_C_DIALECT_SHAPE_H
+#define MLIR_C_DIALECT_SHAPE_H
+
+#include "mlir-c/Registration.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+MLIR_DECLARE_CAPI_DIALECT_REGISTRATION(Shape, shape);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // MLIR_C_DIALECT_SHAPE_H

mlir/include/mlir-c/Dialect/Standard.h

-//===-- mlir-c/StandardDialect.h - C API for Standard dialect -----*- C -*-===//
+//===-- mlir-c/Dialect/Standard.h - C API for Standard dialect ----*- 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 header declares the C interface for registering and accessing the
 // Standard dialect. A dialect should be registered with a context to make it
 // available to users of the context. These users must load the dialect
 // before using any of its attributes, operations or types. Parser and pass
 // manager can load registered dialects automatically.
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef MLIR_C_STANDARDDIALECT_H
-#define MLIR_C_STANDARDDIALECT_H
+#ifndef MLIR_C_DIALECT_STANDARD_H
+#define MLIR_C_DIALECT_STANDARD_H
 
-#include "mlir-c/IR.h"
+#include "mlir-c/Registration.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-/** Registers the Standard dialect with the given context. This allows the
- * dialect to be loaded dynamically if needed when parsing. */
-MLIR_CAPI_EXPORTED void mlirContextRegisterStandardDialect(MlirContext context);
-
-/** Loads the Standard dialect into the given context. The dialect does _not_
- * have to be registered in advance. */
-MLIR_CAPI_EXPORTED MlirDialect
-mlirContextLoadStandardDialect(MlirContext context);
-
-/// Returns the namespace of the Standard dialect, suitable for loading it.
-MLIR_CAPI_EXPORTED MlirStringRef mlirStandardDialectGetNamespace();
+MLIR_DECLARE_CAPI_DIALECT_REGISTRATION(Standard, std);
 
 #ifdef __cplusplus
 }
 #endif
 
-#endif // MLIR_C_STANDARDDIALECT_H
+#endif // MLIR_C_DIALECT_STANDARD_H

mlir/include/mlir-c/Dialect/Tensor.h

+//===-- mlir-c/Dialect/Tensor.h - C API for Tensor dialect --------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_C_DIALECT_TENSOR_H
+#define MLIR_C_DIALECT_TENSOR_H
+
+#include "mlir-c/Registration.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+MLIR_DECLARE_CAPI_DIALECT_REGISTRATION(Tensor, tensor);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // MLIR_C_DIALECT_TENSOR_H

mlir/include/mlir-c/Registration.h

 #define MLIR_C_REGISTRATION_H
 
 #include "mlir-c/IR.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-/** Registers all dialects known to core MLIR with the provided Context.
- * This is needed before creating IR for these Dialects.
- */
+//===----------------------------------------------------------------------===//
+// Dialect registration declarations.
+// Registration entry-points for each dialect are declared using the common
+// MLIR_DECLARE_DIALECT_REGISTRATION_CAPI macro, which takes the dialect
+// API name (i.e. "Standard", "Tensor", "Linalg") and namespace (i.e. "std",
+// "tensor", "linalg"). The following declarations are produced:
+//
+//   /// Registers the dialect with the given context. This allows the
+//   /// dialect to be loaded dynamically if needed when parsing. */
+//   void mlirContextRegister{NAME}Dialect(MlirContext);
+//
+//   /// Loads the dialect into the given context. The dialect does _not_
+//   /// have to be registered in advance.
+//   MlirDialect mlirContextLoad{NAME}Dialect(MlirContext context);
+//
+//   /// Returns the namespace of the Standard dialect, suitable for loading it.
+//   MlirStringRef mlir{NAME}DialectGetNamespace();
+//
+//   /// Gets the above hook methods in struct form for a dialect by namespace.
+//   /// This is intended to facilitate dynamic lookup and registration of
+//   /// dialects via a plugin facility based on shared library symbol lookup.
+//   const MlirDialectRegistrationHooks *mlirGetDialectHooks__{NAMESPACE}__();
+//
+// This is done via a common macro to facilitate future expansion to
+// registration schemes.
+//===----------------------------------------------------------------------===//
+
+#define MLIR_DECLARE_CAPI_DIALECT_REGISTRATION(Name, Namespace)                \
+  MLIR_CAPI_EXPORTED void mlirContextRegister##Name##Dialect(                  \
+      MlirContext context);                                                    \
+  MLIR_CAPI_EXPORTED MlirDialect mlirContextLoad##Name##Dialect(               \
+      MlirContext context);                                                    \
+  MLIR_CAPI_EXPORTED MlirStringRef mlir##Name##DialectGetNamespace();          \
+  MLIR_CAPI_EXPORTED const MlirDialectRegistrationHooks                        \
+      *mlirGetDialectHooks__##Namespace##__()
+
+/// Hooks for dynamic discovery of dialects.
+typedef void (*MlirContextRegisterDialectHook)(MlirContext context);
+typedef MlirDialect (*MlirContextLoadDialectHook)(MlirContext context);
+typedef MlirStringRef (*MlirDialectGetNamespaceHook)();
+
+/// Structure of dialect registration hooks.
+struct MlirDialectRegistrationHooks {
+  MlirContextRegisterDialectHook registerHook;
+  MlirContextLoadDialectHook loadHook;
+  MlirDialectGetNamespaceHook getNamespaceHook;
+};
+typedef struct MlirDialectRegistrationHooks MlirDialectRegistrationHooks;
+
+/// Registers all dialects known to core MLIR with the provided Context.
+/// This is needed before creating IR for these Dialects.
+/// TODO: Remove this function once the real registration API is finished.
 MLIR_CAPI_EXPORTED void mlirRegisterAllDialects(MlirContext context);
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif // MLIR_C_REGISTRATION_H

mlir/include/mlir/CAPI/Registration.h

+//===- Registration.h - C API Registration implementation  ------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CAPI_REGISTRATION_H
+#define MLIR_CAPI_REGISTRATION_H
+
+#include "mlir-c/IR.h"
+#include "mlir-c/Registration.h"
+#include "mlir/CAPI/IR.h"
+#include "mlir/CAPI/Support.h"
+
+//===----------------------------------------------------------------------===//
+// Corrolary to MLIR_DECLARE_CAPI_DIALECT_REGISTRATION that defines an impl.
+// Takes the same name passed to the above and the fully qualified class name
+// of the dialect class.
+//===----------------------------------------------------------------------===//
+
+#define MLIR_DEFINE_CAPI_DIALECT_REGISTRATION(Name, Namespace, ClassName)      \
+  void mlirContextRegister##Name##Dialect(MlirContext context) {               \
+    unwrap(context)->getDialectRegistry().insert<ClassName>();                 \
+  }                                                                            \
+  MlirDialect mlirContextLoad##Name##Dialect(MlirContext context) {            \
+    return wrap(unwrap(context)->getOrLoadDialect<ClassName>());               \
+  }                                                                            \
+  MlirStringRef mlir##Name##DialectGetNamespace() {                            \
+    return wrap(ClassName::getDialectNamespace());                             \
+  }                                                                            \
+  const MlirDialectRegistrationHooks *mlirGetDialectHooks__##Namespace##__() { \
+    static MlirDialectRegistrationHooks hooks = {                              \
+        mlirContextRegister##Name##Dialect, mlirContextLoad##Name##Dialect,    \
+        mlir##Name##DialectGetNamespace};                                      \
+    return &hooks;                                                             \
+  }
+
+#endif // MLIR_CAPI_REGISTRATION_H

mlir/lib/CAPI/CMakeLists.txt

 add_subdirectory(IR)
 add_subdirectory(Registration)
-add_subdirectory(Standard)
+add_subdirectory(Dialect)
 add_subdirectory(Transforms)
 
 
 ################################################################################
 # libMLIRPublicAPI shared library/DLL.
 ################################################################################
 
 get_property(public_api_libs GLOBAL PROPERTY MLIR_PUBLIC_C_API_LIBS)

mlir/lib/CAPI/Dialect/CMakeLists.txt

+# TODO: Make the check source feature optional as an argument on *_add_library.
+set(LLVM_OPTIONAL_SOURCES
+  Linalg.cpp
+  SCF.cpp
+  Shape.cpp
+  Standard.cpp
+  Tensor.cpp
+)
+
+add_mlir_public_c_api_library(MLIRCAPILinalg
+  Linalg.cpp
+
+  LINK_LIBS PUBLIC
+  MLIRCAPIIR
+  MLIRLinalg
+)
+
+add_mlir_public_c_api_library(MLIRCAPISCF
+  SCF.cpp
+
+  LINK_LIBS PUBLIC
+  MLIRCAPIIR
+  MLIRSCF
+)
+
+add_mlir_public_c_api_library(MLIRCAPIShape
+  Shape.cpp
+
+  LINK_LIBS PUBLIC
+  MLIRCAPIIR
+  MLIRShape
+)
+
+add_mlir_public_c_api_library(MLIRCAPIStandard
+  Standard.cpp
+
+  LINK_LIBS PUBLIC
+  MLIRCAPIIR
+  MLIRStandard
+)
+
+add_mlir_public_c_api_library(MLIRCAPITensor
+  Tensor.cpp
+
+  LINK_LIBS PUBLIC
+  MLIRCAPIIR
+  MLIRTensor
+)

mlir/lib/CAPI/Dialect/Linalg.cpp

+//===- Linalg.cpp - C Interface for Linalg dialect ------------------------===//
+//
+// 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 "mlir-c/Dialect/Linalg.h"
+#include "mlir/CAPI/Registration.h"
+#include "mlir/Dialect/Linalg/IR/LinalgOps.h"
+
+MLIR_DEFINE_CAPI_DIALECT_REGISTRATION(Linalg, linalg,
+                                      mlir::linalg::LinalgDialect);

mlir/lib/CAPI/Dialect/SCF.cpp

+//===- SCF.cpp - C Interface for SCF dialect ------------------------------===//
+//
+// 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 "mlir/Dialect/SCF/SCF.h"
+#include "mlir-c/Dialect/SCF.h"
+#include "mlir/CAPI/Registration.h"
+
+MLIR_DEFINE_CAPI_DIALECT_REGISTRATION(SCF, scf, mlir::scf::SCFDialect);

mlir/lib/CAPI/Dialect/Shape.cpp

+//===- Shape.cpp - C Interface for Shape dialect --------------------------===//
+//
+// 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 "mlir/Dialect/Shape/IR/Shape.h"
+#include "mlir-c/Dialect/Shape.h"
+#include "mlir/CAPI/Registration.h"
+
+MLIR_DEFINE_CAPI_DIALECT_REGISTRATION(Shape, shape, mlir::shape::ShapeDialect);

mlir/lib/CAPI/Dialect/Standard.cpp

+//===- Standard.cpp - C Interface for Standard dialect --------------------===//
+//
+// 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 "mlir-c/Dialect/Standard.h"
+#include "mlir/CAPI/Registration.h"
+#include "mlir/Dialect/StandardOps/IR/Ops.h"
+
+MLIR_DEFINE_CAPI_DIALECT_REGISTRATION(Standard, std, mlir::StandardOpsDialect);

mlir/lib/CAPI/Dialect/Tensor.cpp

+//===- Tensor.cpp - C Interface for Tensor dialect ------------------------===//
+//
+// 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 "mlir/Dialect/Tensor/IR/Tensor.h"
+#include "mlir-c/Dialect/Tensor.h"
+#include "mlir/CAPI/Registration.h"
+
+MLIR_DEFINE_CAPI_DIALECT_REGISTRATION(Tensor, tensor,
+                                      mlir::tensor::TensorDialect);

mlir/lib/CAPI/Standard/CMakeLists.txt

-add_mlir_public_c_api_library(MLIRCAPIStandard
-  StandardDialect.cpp
-
-  LINK_LIBS PUBLIC
-  MLIRCAPIIR
-  MLIRStandard
-)

mlir/lib/CAPI/Standard/StandardDialect.cpp

-//===- StandardDialect.cpp - C Interface for Standard dialect -------------===//
-//
-// 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 "mlir-c/StandardDialect.h"
-#include "mlir-c/IR.h"
-#include "mlir/CAPI/IR.h"
-#include "mlir/CAPI/Support.h"
-#include "mlir/Dialect/StandardOps/IR/Ops.h"
-
-void mlirContextRegisterStandardDialect(MlirContext context) {
-  unwrap(context)->getDialectRegistry().insert<mlir::StandardOpsDialect>();
-}
-
-MlirDialect mlirContextLoadStandardDialect(MlirContext context) {
-  return wrap(unwrap(context)->getOrLoadDialect<mlir::StandardOpsDialect>());
-}
-
-MlirStringRef mlirStandardDialectGetNamespace() {
-  return wrap(mlir::StandardOpsDialect::getDialectNamespace());
-}

mlir/test/CAPI/ir.c

  */
 
 #include "mlir-c/IR.h"
 #include "mlir-c/AffineExpr.h"
 #include "mlir-c/AffineMap.h"
 #include "mlir-c/BuiltinAttributes.h"
 #include "mlir-c/BuiltinTypes.h"
 #include "mlir-c/Diagnostics.h"
+#include "mlir-c/Dialect/Standard.h"
 #include "mlir-c/Registration.h"
-#include "mlir-c/StandardDialect.h"
 
 #include <assert.h>
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 void populateLoopBody(MlirContext ctx, MlirBlock loopBody,