Add C bindings for mlir::ExecutionEngine

[mehdi_amini]

Summary

This adds minimalistic bindings for the execution engine, allowing to
invoke the JIT from the C API. This is still quite early and
experimental and shouldn't be considered stable in any way.

[mehdi_amini]

Remove unusued type

[stellaraccident]

mlir/lib/CAPI/ExecutionEngine/ExecutionEngine.cpp

22

I feel like you are going to run into trouble eventually by making the LLVM initialization implicit (as soon as being used in a context that also initializes LLVM differently). In things I've written, I've eventually had to lift all such default initialization sequences to custom functions that the top level can choose to use or not.

[mehdi_amini]

mlir/lib/CAPI/ExecutionEngine/ExecutionEngine.cpp

22

Yeah this is tricky and I'm not fond of these init in general...

In this case is there an issue to initializing the native target? I expect that you can call multiple times the initialization and LLVM will just ignore future calls. But I may miss some adversary effect that you have in mind with a client that would "initializes LLVM differently"?

[stellaraccident]

mlir/lib/CAPI/ExecutionEngine/ExecutionEngine.cpp

22

Honestly, I can't remember in this case - just memories of issues. Let's just stick with this for the moment to get started?

[mehdi_amini]

Fix memory leak and add missing implementation for mlirExecutionEngineDestroy()

mlir/include/mlir-c/Conversion.h

+//===-- mlir-c/Conversion.h - Conversion passes initialization ----*- 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 registration and creation method for conversion
+// passes.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_C_CONVERSIONS_H
+#define MLIR_C_CONVERSIONS_H
+
+#include "mlir-c/Support.h"
+
+#include "mlir/Conversion/Passes.capi.h.inc"
+
+#endif // MLIR_C_CONVERSIONS_H

mlir/include/mlir-c/ExecutionEngine.h

+//===-- mlir-c/ExecutionEngine.h - Execution engine management ---*- 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 provides basic access to the MLIR JIT. This is minimalist and
+// experimental at the moment.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_C_EXECUTIONENGINE_H
+#define MLIR_C_EXECUTIONENGINE_H
+
+#include "mlir-c/IR.h"
+#include "mlir-c/Support.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define DEFINE_C_API_STRUCT(name, storage)                                     \
+  struct name {                                                                \
+    storage *ptr;                                                              \
+  };                                                                           \
+  typedef struct name name
+
+DEFINE_C_API_STRUCT(MlirExecutionEngine, void);
+
+#undef DEFINE_C_API_STRUCT
+
+/// Creates an ExecutionEngine for the provided ModuleOp. The ModuleOp is
+/// expected to be "translatable" to LLVM IR (only contains operations in
+/// dialects that implement the `LLVMTranslationDialectInterface`). The module
+/// ownership stays with the client and can be destroyed as soon as the call
+/// returns.
+/// TODO: figure out options (optimization level, etc.).
+MLIR_CAPI_EXPORTED MlirExecutionEngine mlirExecutionEngineCreate(MlirModule op);
+
+/// Destroy an ExecutionEngine instance.
+MLIR_CAPI_EXPORTED void mlirExecutionEngineDestroy(MlirExecutionEngine jit);
+
+/// Checks whether an execution engine is null.
+static inline bool mlirExecutionEngineIsNull(MlirExecutionEngine jit) {
+  return !jit.ptr;
+}
+
+/// Invoke a native function in the execution engine by name with the arguments
+/// and result of the invoked function passed as an array of pointers. The
+/// function must have been tagged with the `llvm.emit_c_interface` attribute.
+/// Returns a failure if the execution fails for any reason (the function name
+/// can't be resolved for instance).
+MLIR_CAPI_EXPORTED MlirLogicalResult mlirExecutionEngineInvokePacked(
+    MlirExecutionEngine jit, MlirStringRef name, void **arguments);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // EXECUTIONENGINE_H

mlir/include/mlir-c/Registration.h

 MLIR_CAPI_EXPORTED MlirDialect mlirDialectHandleLoadDialect(MlirDialectHandle,
                                                             MlirContext);
 
 /// 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);
 
+/// Register all translations to LLVM IR for dialects that can support it.
+MLIR_CAPI_EXPORTED void mlirRegisterAllLLVMTranslations(MlirContext context);
+
 #ifdef __cplusplus
 }
 #endif
 
 #endif // MLIR_C_REGISTRATION_H

mlir/include/mlir/CAPI/ExecutionEngine.h

+//===- IR.h - C API Utils for Core MLIR classes -----------------*- 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 declarations of implementation details of the C API for
+// core MLIR classes. This file should not be included from C++ code other than
+// C API implementation nor from C code.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CAPI_EXECUTIONENGINE_H
+#define MLIR_CAPI_EXECUTIONENGINE_H
+
+#include "mlir-c/ExecutionEngine.h"
+#include "mlir/CAPI/Wrap.h"
+#include "mlir/ExecutionEngine/ExecutionEngine.h"
+
+DEFINE_C_API_PTR_METHODS(MlirExecutionEngine, mlir::ExecutionEngine)
+
+#endif // MLIR_CAPI_EXECUTIONENGINE_H

mlir/include/mlir/Conversion/CMakeLists.txt

 
 set(LLVM_TARGET_DEFINITIONS Passes.td)
 mlir_tablegen(Passes.h.inc -gen-pass-decls -name Conversion)
+mlir_tablegen(Passes.capi.h.inc -gen-pass-capi-header --prefix Conversion)
+mlir_tablegen(Passes.capi.cpp.inc -gen-pass-capi-impl --prefix Conversion)
 add_public_tablegen_target(MLIRConversionPassIncGen)
 
 add_mlir_doc(Passes -gen-pass-doc ConversionPasses ./)

mlir/lib/CAPI/CMakeLists.txt

+add_subdirectory(Dialect)
+add_subdirectory(Conversion)
+add_subdirectory(ExecutionEngine)
 add_subdirectory(IR)
 add_subdirectory(Registration)
-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/Conversion/CMakeLists.txt

+get_property(conversion_libs GLOBAL PROPERTY MLIR_CONVERSION_LIBS)
+add_mlir_public_c_api_library(MLIRCAPIConversion
+  Passes.cpp
+
+  LINK_LIBS PUBLIC
+  ${conversion_libs}
+)

mlir/lib/CAPI/Conversion/Passes.cpp

+//===- Conversion.cpp - C API for Conversion Passes -----------------------===//
+//
+// 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/Conversion/Passes.h"
+#include "mlir/CAPI/Pass.h"
+#include "mlir/Pass/Pass.h"
+
+// Must include the declarations as they carry important visibility attributes.
+#include "mlir/Conversion/Passes.capi.h.inc"
+
+using namespace mlir;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "mlir/Conversion/Passes.capi.cpp.inc"
+
+#ifdef __cplusplus
+}
+#endif

mlir/lib/CAPI/ExecutionEngine/CMakeLists.txt

+# Main API shared library.
+add_mlir_public_c_api_library(MLIRCEXECUTIONENGINE
+  ExecutionEngine.cpp
+
+  LINK_LIBS PUBLIC
+  MLIRExecutionEngine
+)

mlir/lib/CAPI/ExecutionEngine/ExecutionEngine.cpp

+//===- ExecutionEngine.cpp - C API for MLIR JIT ---------------------------===//
+//
+// 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/ExecutionEngine.h"
+#include "mlir/CAPI/ExecutionEngine.h"
+#include "mlir/CAPI/IR.h"
+#include "mlir/CAPI/Support.h"
+#include "llvm/Support/TargetSelect.h"
+
+using namespace mlir;
+
+extern "C" MlirExecutionEngine mlirExecutionEngineCreate(MlirModule op) {
+  static bool init_once = [] {
+    llvm::InitializeNativeTarget();
+    llvm::InitializeNativeTargetAsmPrinter();
+    return true;
+  }();
+  (void)init_once;
+
+  auto jitOrError = ExecutionEngine::create(unwrap(op));
+  if (!jitOrError) {
+    consumeError(jitOrError.takeError());
+    return MlirExecutionEngine{nullptr};
+  }
+  return wrap(jitOrError->release());
+}
+
+extern "C" void mlirExecutionEngineDestroy(MlirExecutionEngine jit) {
+  delete (unwrap(jit));
+}
+
+extern "C" MlirLogicalResult
+mlirExecutionEngineInvokePacked(MlirExecutionEngine jit, MlirStringRef name,
+                                void **arguments) {
+  const std::string ifaceName = ("_mlir_ciface_" + unwrap(name)).str();
+  llvm::Error error = unwrap(jit)->invokePacked(
+      ifaceName, MutableArrayRef<void *>{arguments, (size_t)0});
+  if (error)
+    return wrap(failure());
+  return wrap(success());
+}

mlir/lib/CAPI/Registration/Registration.cpp

 //===- Registration.cpp - C Interface for MLIR Registration ---------------===//
 //
 // 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/Registration.h"
 
 #include "mlir/CAPI/IR.h"
 #include "mlir/InitAllDialects.h"
+#include "mlir/Target/LLVMIR.h"
 
 void mlirRegisterAllDialects(MlirContext context) {
   mlir::registerAllDialects(*unwrap(context));
   // TODO: we may not want to eagerly load here.
   unwrap(context)->loadAllAvailableDialects();
 }
+
+void mlirRegisterAllLLVMTranslations(MlirContext context) {
+  mlir::registerLLVMDialectTranslation(*unwrap(context));
+}

mlir/test/CAPI/CMakeLists.txt

 set(LLVM_OPTIONAL_SOURCES
+  execution_engine.c
   ir.c
   pass.c
 )
 
 set(LLVM_LINK_COMPONENTS
   )
 
 add_llvm_executable(mlir-capi-ir-test
add_llvm_executable(mlir-capi-pass-test
   )
 llvm_update_compile_flags(mlir-capi-pass-test)
 
 get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
 target_link_libraries(mlir-capi-pass-test
   PRIVATE
   MLIRPublicAPI
   )
+
+add_llvm_executable(mlir-capi-execution-engine-test
+  execution_engine.c
+DEPENDS
+  MLIRConversionPassIncGen
+  )
+llvm_update_compile_flags(mlir-capi-execution-engine-test)
+
+get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
+target_link_libraries(mlir-capi-execution-engine-test
+  PRIVATE
+  MLIRPublicAPI
+  )

mlir/test/CAPI/execution_engine.c

+//===- execution_engine.c - Test for the C bindings for the MLIR JIT-------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+/* RUN: mlir-capi-execution-engine-test 2>&1 | FileCheck %s
+ */
+
+#include "mlir-c/Conversion.h"
+#include "mlir-c/ExecutionEngine.h"
+#include "mlir-c/IR.h"
+#include "mlir-c/Registration.h"
+
+#include <assert.h>
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void lowerModuleToLLVM(MlirContext ctx, MlirModule module) {
+  MlirPassManager pm = mlirPassManagerCreate(ctx);
+  mlirPassManagerAddOwnedPass(pm, mlirCreateConversionConvertStandardToLLVM());
+  MlirLogicalResult status = mlirPassManagerRun(pm, module);
+  if (mlirLogicalResultIsFailure(status)) {
+    fprintf(stderr, "Unexpected failure running pass pipeline\n");
+    exit(2);
+  }
+  mlirPassManagerDestroy(pm);
+}
+
+// CHECK-LABEL: Running test 'testSimpleExecution'
+void testSimpleExecution() {
+  MlirContext ctx = mlirContextCreate();
+  mlirRegisterAllDialects(ctx);
+  MlirModule module = mlirModuleCreateParse(
+      ctx, mlirStringRefCreateFromCString(
+               // clang-format off
+"module {                                                                   \n"
+"  func @add(%arg0 : i32) -> i32 attributes { llvm.emit_c_interface } {     \n"
+"    %res = std.addi %arg0, %arg0 : i32                                     \n"
+"    return %res : i32                                                      \n"
+"  }                                                                        \n"
+"}"));
+  // clang-format on
+  lowerModuleToLLVM(ctx, module);
+  mlirRegisterAllLLVMTranslations(ctx);
+  MlirExecutionEngine jit = mlirExecutionEngineCreate(module);
+  if (mlirExecutionEngineIsNull(jit)) {
+    fprintf(stderr, "Execution engine creation failed");
+    exit(2);
+  }
+  int input = 42;
+  int result = -1;
+  void *args[2] = {&input, &result};
+  if (mlirLogicalResultIsFailure(mlirExecutionEngineInvokePacked(
+          jit, mlirStringRefCreateFromCString("add"), args))) {
+    fprintf(stderr, "Execution engine creation failed");
+    abort();
+  }
+  // CHECK: Input: 42 Result: 84
+  printf("Input: %d Result: %d\n", input, result);
+  mlirExecutionEngineDestroy(jit);
+  mlirModuleDestroy(module);
+  mlirContextDestroy(ctx);
+}
+
+int main() {
+
+#define _STRINGIFY(x) #x
+#define STRINGIFY(x) _STRINGIFY(x)
+#define TEST(test)                                                             \
+  printf("Running test '" STRINGIFY(test) "'\n");                              \
+  test();
+
+  TEST(testSimpleExecution);
+  return 0;
+}

mlir/test/CMakeLists.txt

configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/Unit/lit.site.cfg.py.in
   ${CMAKE_CURRENT_BINARY_DIR}/Unit/lit.site.cfg.py
   MAIN_CONFIG
   ${CMAKE_CURRENT_SOURCE_DIR}/Unit/lit.cfg.py
   )
 
 set(MLIR_TEST_DEPENDS
   FileCheck count not
+  mlir-capi-execution-engine-test
   mlir-capi-ir-test
   mlir-capi-pass-test
   mlir-cpu-runner
   mlir-edsc-builder-api-test
   mlir-linalg-ods-gen
   mlir-opt
   mlir-reduce
   mlir-sdbm-api-test