Add DebugStringHelper, which makes it easier to get a string from a dump method

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PiperOrigin-RevId: 243899072

mlir/include/mlir/Support/DebugStringHelper.h

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+//===- DebugStringHelper.h - helpers to generate debug strings --*- C++ -*-===//
+//
+// Copyright 2019 The MLIR Authors.
+//
+// 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.
+// =============================================================================
+//
+// Convenience functions to make it easier to get a string representation for
+// ops that have a print method. For use in debugging output and errors
+// returned.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_DEBUGSTRINGHELPER_H_
+#define MLIR_DEBUGSTRINGHELPER_H_
+
+#include <string>
+
+#include "llvm/ADT/Twine.h"
+#include "llvm/Support/raw_os_ostream.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace mlir {
+
+// Simple helper function that returns a string as printed from a op.
+template <typename T>
+static string debugString(T &op) {
+  std::string instr_str;
+  llvm::raw_string_ostream os(instr_str);
+  op.print(os);
+  return os.str();
+}
+
+} // namespace mlir
+
+inline std::ostream &operator<<(std::ostream &out, const llvm::Twine &twine) {
+  llvm::raw_os_ostream rout(out);
+  rout << twine;
+  return out;
+}
+
+#endif // MLIR_DEBUGSTRINGHELPER_H_