[flang] add initial Burnside bridge code

Original-commit: flang-compiler/f18@0d387d1
Reviewed-on: flang-compiler/f18#720

flang/documentation/FortranIR.md

@@ -2,7 +2,7 @@
 
 ## Introduction
 
-After semantic analysis is complete and it has been determined that the compiler has a legal Fortran program as input, the parse tree will be lowered to an intermediate representation for the purposes of high-level analysis and optimization.  In this document, that intermediate representation will be called Fortran IR or FIR.
+After semantic analysis is complete and it has been determined that the compiler has a legal Fortran program as input, the parse tree will be lowered to an intermediate representation for the purposes of high-level analysis and optimization.  In this document, that intermediate representation will be called Fortran IR or FIR.  The pass that converts from the parse tree and other data structures of the front-end to FIR will be called the "Burnside bridge".
 
 FIR will be an explicit, operational, and strongly-typed representation, which shall encapsulate control-flow as graphs.
 

flang/lib/CMakeLists.txt

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+add_subdirectory(burnside)
 add_subdirectory(common)
 add_subdirectory(decimal)
 add_subdirectory(evaluate)

flang/lib/burnside/CMakeLists.txt

@@ -0,0 +1,25 @@
+# Copyright (c) 2019, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-parameter")
+
+add_library(FortranBurnside
+  flattened.cc
+)
+
+install (TARGETS FortranBurnside
+  ARCHIVE DESTINATION lib
+  LIBRARY DESTINATION lib
+  RUNTIME DESTINATION bin
+)

flang/lib/burnside/builder.h

@@ -0,0 +1,78 @@
+// Copyright (c) 2019, NVIDIA CORPORATION.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef FORTRAN_BURNSIDE_BUILDER_H_
+#define FORTRAN_BURNSIDE_BUILDER_H_
+
+#include "../semantics/symbol.h"
+#include "llvm/ADT/DenseMap.h"
+#include "mlir/IR/Builders.h"
+#include "mlir/IR/Function.h"
+#include "mlir/IR/Module.h"
+#include <string>
+
+namespace llvm {
+class StringRef;
+}
+
+namespace Fortran::burnside {
+
+/// Miscellaneous helper routines for building MLIR
+/// [Coding style](https://llvm.org/docs/CodingStandards.html)
+
+class SymMap {
+  llvm::DenseMap<const semantics::Symbol *, mlir::Value *> symbolMap;
+
+public:
+  void addSymbol(const semantics::Symbol *symbol, mlir::Value *value);
+
+  mlir::Value *lookupSymbol(const semantics::Symbol *symbol);
+};
+
+std::string applyNameMangling(llvm::StringRef parserName);
+
+/// Get the current Module
+inline mlir::ModuleOp getModule(mlir::OpBuilder *bldr) {
+  return bldr->getBlock()->getParent()->getParentOfType<mlir::ModuleOp>();
+}
+
+/// Get the current Function
+inline mlir::FuncOp getFunction(mlir::OpBuilder *bldr) {
+  return bldr->getBlock()->getParent()->getParentOfType<mlir::FuncOp>();
+}
+
+/// Get the entry block of the current Function
+inline mlir::Block *getEntryBlock(mlir::OpBuilder *bldr) {
+  return &getFunction(bldr).front();
+}
+
+/// Create a new basic block
+inline mlir::Block *createBlock(mlir::OpBuilder *bldr, mlir::Region *region) {
+  return bldr->createBlock(region, region->end());
+}
+
+inline mlir::Block *createBlock(mlir::OpBuilder *bldr) {
+  return createBlock(bldr, bldr->getBlock()->getParent());
+}
+
+/// Get a function by name (or null)
+mlir::FuncOp getNamedFunction(llvm::StringRef name);
+
+/// Create a new Function
+mlir::FuncOp createFunction(
+    mlir::ModuleOp module, llvm::StringRef name, mlir::FunctionType funcTy);
+
+}  // Fortran::burnside
+
+#endif  // FORTRAN_BURNSIDE_BUILDER_H_