[mlir][EmitC] Refactor MLIR Translate To Cpp

This refactors the MLIR TranslateToCpp part by introducing CppTranslationInterface
that breaks down the overall translation into different dialects. This majorly helps
the readability of the code and extensibility for future c++ translation addition.

Author: weizchen

mlir/include/mlir/Target/Cpp/CppEmitter.h

@@ -14,21 +14,15 @@
 #define MLIR_TARGET_CPP_CPPEMITTER_H
 
 #include "mlir/IR/BuiltinTypes.h"
-#include "mlir/IR/Value.h"
-#include "llvm/ADT/ScopedHashTable.h"
-#include "llvm/Support/raw_ostream.h"
-#include <stack>
 
 namespace mlir {
-namespace emitc {
 
 /// Translates the given operation to C++ code. The operation or operations in
 /// the region of 'op' need almost all be in EmitC dialect. The parameter
 /// 'declareVariablesAtTop' enforces that all variables for op results and block
 /// arguments are declared at the beginning of the function.
 LogicalResult translateToCpp(Operation *op, raw_ostream &os,
                              bool declareVariablesAtTop = false);
-} // namespace emitc
 } // namespace mlir
 
 #endif // MLIR_TARGET_CPP_CPPEMITTER_H

mlir/include/mlir/Target/Cpp/CppTranslationInterface.h

@@ -0,0 +1,55 @@
+//===--- CppTranslationInterface.h - Translation to Cpp iface ---*- 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 dialect interfaces for translation to Cpp.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TARGET_CPP_CPPTRANSLATIONINTERFACE_H
+#define MLIR_TARGET_CPP_CPPTRANSLATIONINTERFACE_H
+
+#include "mlir/IR/DialectInterface.h"
+#include "mlir/Support/LogicalResult.h"
+
+namespace mlir {
+struct CppEmitter;
+
+/// Base class for dialect interfaces providing translation to Cpp. Dialects
+/// should implement this interface with supported operation translations to
+/// be registered and used with translate-to-cpp.
+class CppTranslationDialectInterface
+    : public DialectInterface::Base<CppTranslationDialectInterface> {
+public:
+  CppTranslationDialectInterface(Dialect *dialect) : Base(dialect) {}
+
+  /// Hook for derived dialect interface to provide op translation to Cpp.
+  virtual LogicalResult emitOperation(Operation *op, CppEmitter &cppEmitter,
+                                      bool trailingSemicolon) const {
+    return failure();
+  }
+};
+
+/// Interface collection for translation to Cpp, dispatches to a concrete
+/// interface implementation based on the dialect to which the given op belongs.
+class CppTranslationInterface
+    : public DialectInterfaceCollection<CppTranslationDialectInterface> {
+public:
+  using Base::Base;
+
+  /// Translates the given operation to Cpp using the derived dialect interface.
+  virtual LogicalResult emitOperation(Operation *op, CppEmitter &cppEmitter,
+                                      bool trailingSemicolon) const {
+    if (const CppTranslationDialectInterface *iface = getInterfaceFor(op))
+      return iface->emitOperation(op, cppEmitter, trailingSemicolon);
+    return failure();
+  }
+};
+
+} // namespace mlir
+
+#endif // MLIR_TARGET_CPP_CPPTRANSLATIONINTERFACE_H

mlir/include/mlir/Target/Cpp/CppTranslationUtils.h

@@ -0,0 +1,86 @@
+//===- CppTranslationUtils.h - Helpers to used in C++ emitter ---*- 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 defines common helper functions used across different dialects
+// during the Cpp translation.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TARGET_CPP_CPPTRANSLATIONUTILS_H
+#define MLIR_TARGET_CPP_CPPTRANSLATIONUTILS_H
+
+#include "mlir/Dialect/EmitC/IR/EmitC.h"
+#include "mlir/Target/Cpp/TranslateToCpp.h"
+
+using namespace mlir;
+
+/// Convenience functions to produce interleaved output with functions returning
+/// a LogicalResult. This is different than those in STLExtras as functions used
+/// on each element doesn't return a string.
+template <typename ForwardIterator, typename UnaryFunctor,
+          typename NullaryFunctor>
+inline LogicalResult
+interleaveWithError(ForwardIterator begin, ForwardIterator end,
+                    UnaryFunctor eachFn, NullaryFunctor betweenFn) {
+  if (begin == end)
+    return success();
+  if (failed(eachFn(*begin)))
+    return failure();
+  ++begin;
+  for (; begin != end; ++begin) {
+    betweenFn();
+    if (failed(eachFn(*begin)))
+      return failure();
+  }
+  return success();
+}
+
+template <typename Container, typename UnaryFunctor, typename NullaryFunctor>
+inline LogicalResult interleaveWithError(const Container &c,
+                                         UnaryFunctor eachFn,
+                                         NullaryFunctor betweenFn) {
+  return interleaveWithError(c.begin(), c.end(), eachFn, betweenFn);
+}
+
+template <typename Container, typename UnaryFunctor>
+inline LogicalResult interleaveCommaWithError(const Container &c,
+                                              raw_ostream &os,
+                                              UnaryFunctor eachFn) {
+  return interleaveWithError(c.begin(), c.end(), eachFn, [&]() { os << ", "; });
+}
+
+
+/// Determine whether expression \p expressionOp should be emitted inline, i.e.
+/// as part of its user. This function recommends inlining of any expressions
+/// that can be inlined unless it is used by another expression, under the
+/// assumption that  any expression fusion/re-materialization was taken care of
+/// by transformations run by the backend.
+bool shouldBeInlined(emitc::ExpressionOp expressionOp);
+
+LogicalResult printConstantOp(CppEmitter &emitter, Operation *operation,
+                              Attribute value);
+
+LogicalResult printBinaryOperation(CppEmitter &emitter, Operation *operation,
+                                   StringRef binaryOperator);
+
+LogicalResult printUnaryOperation(CppEmitter &emitter, Operation *operation,
+                                  StringRef unaryOperator);
+
+LogicalResult printCallOperation(CppEmitter &emitter, Operation *callOp,
+                                 StringRef callee);
+
+LogicalResult printFunctionArgs(CppEmitter &emitter, Operation *functionOp,
+                                ArrayRef<Type> arguments);
+
+LogicalResult printFunctionArgs(CppEmitter &emitter, Operation *functionOp,
+                                Region::BlockArgListType arguments);
+
+LogicalResult printFunctionBody(CppEmitter &emitter, Operation *functionOp,
+                                Region::BlockListType &blocks);
+
+#endif // MLIR_TARGET_CPP_CPPTRANSLATIONUTILS_H

mlir/include/mlir/Target/Cpp/Dialect/All.h

@@ -0,0 +1,35 @@
+//===----- All.h - MLIR To Cpp Translation Registration ---------*- 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 defines a helper to register the all dialect translations to Cpp.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TARGET_CPP_DIALECT_ALL_H
+#define MLIR_TARGET_CPP_DIALECT_ALL_H
+
+#include "mlir/Target/Cpp/Dialect/Builtin/BuiltinToCppTranslation.h"
+#include "mlir/Target/Cpp/Dialect/ControlFlow/ControlFlowToCppTranslation.h"
+#include "mlir/Target/Cpp/Dialect/EmitC/EmitCToCppTranslation.h"
+#include "mlir/Target/Cpp/Dialect/Func/FuncToCppTranslation.h"
+
+namespace mlir {
+class DialectRegistry;
+
+/// Registers all dialects that can be translated to Cpp and the
+/// corresponding translation interfaces.
+static inline void registerAllToCppTranslations(DialectRegistry &registry) {
+  registerBuiltinDialectCppTranslation(registry);
+  registerControlFlowDialectCppTranslation(registry);
+  registerEmitCDialectCppTranslation(registry);
+  registerFuncDialectCppTranslation(registry);
+}
+
+} // namespace mlir
+
+#endif // MLIR_TARGET_CPP_DIALECT_ALL_H

mlir/include/mlir/Target/Cpp/Dialect/Builtin/BuiltinToCppTranslation.h

@@ -0,0 +1,31 @@
+//===---- BuiltinToCppTranslation.h - Builtin Dialect to Cpp ----*- 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 provides registration calls for Builtin dialect to Cpp translation.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TARGET_CPP_DIALECT_BUILTIN_BUILTINTOCPPTRANSLATION_H
+#define MLIR_TARGET_CPP_DIALECT_BUILTIN_BUILTINTOCPPTRANSLATION_H
+
+namespace mlir {
+
+class DialectRegistry;
+class MLIRContext;
+
+/// Register the Builtin dialect and the translation from it to the Cpp in the
+/// given registry;
+void registerBuiltinDialectCppTranslation(DialectRegistry &registry);
+
+/// Register the Builtin dialect and the translation from it in the registry
+/// associated with the given context.
+void registerBuiltinDialectCppTranslation(MLIRContext &context);
+
+} // namespace mlir
+
+#endif // MLIR_TARGET_CPP_DIALECT_BUILTIN_BUILTINTOCPPTRANSLATION_H

mlir/include/mlir/Target/Cpp/Dialect/ControlFlow/ControlFlowToCppTranslation.h

@@ -0,0 +1,31 @@
+//===- ControlFlowToCppTranslation.h - ControlFlow Dialect to Cpp -*-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 provides registration calls for ControlFlow dialect to Cpp translation.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TARGET_CPP_DIALECT_CONTROLFLOW_CONTROLFLOWTOCPPTRANSLATION_H
+#define MLIR_TARGET_CPP_DIALECT_CONTROLFLOW_CONTROLFLOWTOCPPTRANSLATION_H
+
+namespace mlir {
+
+class DialectRegistry;
+class MLIRContext;
+
+/// Register the ControlFlow dialect and the translation from it to the Cpp in
+/// the given registry;
+void registerControlFlowDialectCppTranslation(DialectRegistry &registry);
+
+/// Register the ControlFlow dialect and the translation from it in the registry
+/// associated with the given context.
+void registerControlFlowDialectCppTranslation(MLIRContext &context);
+
+} // namespace mlir
+
+#endif // MLIR_TARGET_CPP_DIALECT_CONTROLFLOW_CONTROLFLOWTOCPPTRANSLATION_H

mlir/include/mlir/Target/Cpp/Dialect/EmitC/EmitCToCppTranslation.h

@@ -0,0 +1,31 @@
+//===------ EmitCToCppTranslation.h - EmitC Dialect to Cpp-------*- 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 provides registration calls for EmitC dialect to Cpp translation.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TARGET_CPP_DIALECT_EMITC_EMITCTOCPPTRANSLATION_H
+#define MLIR_TARGET_CPP_DIALECT_EMITC_EMITCTOCPPTRANSLATION_H
+
+namespace mlir {
+
+class DialectRegistry;
+class MLIRContext;
+
+/// Register the EmitC dialect and the translation from it to the Cpp in the
+/// given registry;
+void registerEmitCDialectCppTranslation(DialectRegistry &registry);
+
+/// Register the EmitC dialect and the translation from it in the registry
+/// associated with the given context.
+void registerEmitCDialectCppTranslation(MLIRContext &context);
+
+} // namespace mlir
+
+#endif // MLIR_TARGET_CPP_DIALECT_EMITC_EMITCTOCPPTRANSLATION_H

mlir/include/mlir/Target/Cpp/Dialect/Func/FuncToCppTranslation.h

@@ -0,0 +1,31 @@
+//===------- FuncToCppTranslation.h - Func Dialect to Cpp -------*- 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 provides registration calls for Func dialect to Cpp translation.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TARGET_CPP_DIALECT_FUNC_FUNCTOCPPTRANSLATION_H
+#define MLIR_TARGET_CPP_DIALECT_FUNC_FUNCTOCPPTRANSLATION_H
+
+namespace mlir {
+
+class DialectRegistry;
+class MLIRContext;
+
+/// Register the Func dialect and the translation from it to the Cpp in the
+/// given registry;
+void registerFuncDialectCppTranslation(DialectRegistry &registry);
+
+/// Register the Func dialect and the translation from it in the registry
+/// associated with the given context.
+void registerFuncDialectCppTranslation(MLIRContext &context);
+
+} // namespace mlir
+
+#endif // MLIR_TARGET_CPP_DIALECT_FUNC_FUNCTOCPPTRANSLATION_H