[MLIR][OpenMP] Set up MLIR transform pass infrastructure for the OpenMP dialect

[skatrak]

Summary

This patch sets up CMake and creates the TableGen/headers to enable the
addition of MLIR transform passes for the OpenMP dialect, as well as
registering them.

This is not intended to land on its own, but instead to agree on the right
approach to define transform passes and act as a dependency for a few related
passes that are under development, also reducing potential for diverging
approaches. This patch should land together with the first dependent patch that
gets accepted.

[skatrak]

After discussion in D154247, I will close this patch for the time being, since the patches that were intended to make use of this infrastructure will initially be defined as Flang-only transformation passes. This could serve as a reference later if/when some of these passes are moved to the OpenMP dialect.

mlir/include/mlir/Dialect/OpenMP/CMakeLists.txt

 add_dependencies(OpenMPDialectDocGen omp_common_td)
 add_mlir_interface(OpenMPOpsInterfaces)
 
 set(LLVM_TARGET_DEFINITIONS OpenMPTypeInterfaces.td)
 mlir_tablegen(OpenMPTypeInterfaces.h.inc -gen-type-interface-decls)
 mlir_tablegen(OpenMPTypeInterfaces.cpp.inc -gen-type-interface-defs)
 add_public_tablegen_target(MLIROpenMPTypeInterfacesIncGen)
 add_dependencies(mlir-generic-headers MLIROpenMPTypeInterfacesIncGen)
+
+set(LLVM_TARGET_DEFINITIONS OpenMPPasses.td)
+mlir_tablegen(OpenMPPasses.h.inc -gen-pass-decls -name OpenMP)
+mlir_tablegen(OpenMPPasses.capi.h.inc -gen-pass-capi-header --prefix OpenMP)
+mlir_tablegen(OpenMPPasses.capi.cpp.inc -gen-pass-capi-impl --prefix OpenMP)
+add_public_tablegen_target(MLIROpenMPPassIncGen)
+add_mlir_doc(Passes OpenMPPasses ./ -gen-pass-doc)

mlir/include/mlir/Dialect/OpenMP/OpenMPPasses.h

+//===- OpenMPPasses.h - OpenMP pass entry points ----------------*- 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 file defines prototypes that expose pass constructors.
+//
+//===----------------------------------------------------------------------===//
+#ifndef MLIR_DIALECT_OPENMP_OPENMPPASSES_H_
+#define MLIR_DIALECT_OPENMP_OPENMPPASSES_H_
+
+#include "mlir/Pass/Pass.h"
+
+namespace mlir {
+namespace omp {
+
+#define GEN_PASS_DECL
+#include "mlir/Dialect/OpenMP/OpenMPPasses.h.inc"
+
+// TODO Add "std::unique_ptr<Pass> create<Name>Pass();" declarations
+
+} // namespace omp
+
+//===----------------------------------------------------------------------===//
+// Registration
+//===----------------------------------------------------------------------===//
+
+/// Generate the code for registering passes.
+#define GEN_PASS_REGISTRATION
+#include "mlir/Dialect/OpenMP/OpenMPPasses.h.inc"
+
+} // namespace mlir
+
+#endif // MLIR_DIALECT_OPENMP_OPENMPPASSES_H_

mlir/include/mlir/Dialect/OpenMP/OpenMPPasses.td

+//===-- OpenMPPasses.td - OpenMp pass definition file ------*- tablegen -*-===//
+//
+// 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_DIALECT_OPENMP_OPENMPPASSES_TD_
+#define MLIR_DIALECT_OPENMP_OPENMPPASSES_TD_
+
+include "mlir/Pass/PassBase.td"
+
+// TODO Add transform pass definitions
+
+#endif // MLIR_DIALECT_OPENMP_OPENMPPASSES_TD_

mlir/include/mlir/InitAllPasses.h

 #include "mlir/Dialect/Bufferization/Transforms/Passes.h"
 #include "mlir/Dialect/Func/Transforms/Passes.h"
 #include "mlir/Dialect/GPU/Transforms/Passes.h"
 #include "mlir/Dialect/LLVMIR/Transforms/Passes.h"
 #include "mlir/Dialect/Linalg/Passes.h"
 #include "mlir/Dialect/Math/Transforms/Passes.h"
 #include "mlir/Dialect/MemRef/Transforms/Passes.h"
 #include "mlir/Dialect/NVGPU/Passes.h"
+#include "mlir/Dialect/OpenMP/OpenMPPasses.h"
 #include "mlir/Dialect/SCF/Transforms/Passes.h"
 #include "mlir/Dialect/SPIRV/Transforms/Passes.h"
 #include "mlir/Dialect/Shape/Transforms/Passes.h"
 #include "mlir/Dialect/SparseTensor/Pipelines/Passes.h"
 #include "mlir/Dialect/SparseTensor/Transforms/Passes.h"
 #include "mlir/Dialect/Tensor/Transforms/Passes.h"
 #include "mlir/Dialect/Tosa/Transforms/Passes.h"
 #include "mlir/Dialect/Transform/Transforms/Passes.h"
inline void registerAllPasses() {
   registerGpuSerializeToCubinPass();
   registerGpuSerializeToHsacoPass();
   registerLinalgPasses();
   registerNVGPUPasses();
   registerSparseTensorPasses();
   LLVM::registerLLVMPasses();
   math::registerMathPasses();
   memref::registerMemRefPasses();
+  registerOpenMPPasses();
   registerSCFPasses();
   registerShapePasses();
   spirv::registerSPIRVPasses();
   tensor::registerTensorPasses();
   tosa::registerTosaOptPasses();
   transform::registerTransformPasses();
   vector::registerVectorPasses();
   arm_sme::registerArmSMEPasses();
 
   // Dialect pipelines
   sparse_tensor::registerSparseTensorPipelines();
 }
 
 } // namespace mlir
 
 #endif // MLIR_INITALLPASSES_H_

mlir/lib/Dialect/OpenMP/CMakeLists.txt

 add_mlir_dialect_library(MLIROpenMPDialect
   IR/OpenMPDialect.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${MLIR_MAIN_INCLUDE_DIR}/mlir/Dialect/OpenMP
 
   DEPENDS
   MLIROpenMPOpsIncGen
   MLIROpenMPOpsInterfacesIncGen
   MLIROpenMPTypeInterfacesIncGen
 
   LINK_LIBS PUBLIC
   MLIRIR
   MLIRLLVMDialect
   MLIRFuncDialect
   )
+
+add_subdirectory(Transforms)

mlir/lib/Dialect/OpenMP/Transforms/CMakeLists.txt

+add_mlir_dialect_library(MLIROpenMPTransforms
+  # TODO Add a source file for each pass
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Dialect/OpenMP
+
+  DEPENDS
+  MLIROpenMPPassIncGen
+
+  LINK_LIBS PUBLIC
+  MLIRIR
+  MLIROpenMPDialect
+  MLIRPass
+  MLIRTransforms
+)