[interpreter] Ensure optimizations preserve source positions.

test/cctest/interpreter/source-position-matcher.h

Index: test/cctest/interpreter/source-position-matcher.h
diff --git a/test/cctest/interpreter/source-position-matcher.h b/test/cctest/interpreter/source-position-matcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..eea53542b43552db45e9fdd0de5a55c6387696b8
--- /dev/null
+++ b/test/cctest/interpreter/source-position-matcher.h
@@ -0,0 +1,52 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TEST_CCTEST_INTERPRETER_SOURCE_POSITION_COMPARER_H_
+#define TEST_CCTEST_INTERPRETER_SOURCE_POSITION_COMPARER_H_
+
+#include "src/interpreter/source-position-table.h"
+#include "src/objects.h"
+#include "src/v8.h"
+
+namespace v8 {
+namespace internal {
+namespace interpreter {
+
+class SourcePositionMatcher final {
+ public:
+  explicit SourcePositionMatcher(int number_of_locals)
+      : number_of_locals_(number_of_locals) {}
+
+  bool Match(Handle<BytecodeArray> original, Handle<BytecodeArray> optimized);
+
+ private:
+  bool NewExpressionPositionsInOptimized(
+      const std::vector<PositionTableEntry>* const original_positions,
+      const std::vector<PositionTableEntry>* const optimized_positions);
+
+  bool CompareExpressionPositions(
+      const std::vector<PositionTableEntry>* const original_positions,
+      const std::vector<PositionTableEntry>* const optimized_positions);
+
+  void StripUnneededExpressionPositions(
+      Handle<BytecodeArray> bytecode_array,
+      std::vector<PositionTableEntry>* positions);
+
+  bool ExpressionPositionIsNeeded(Handle<BytecodeArray> bytecode_array,
+                                  int start_offset, int end_offset);
+
+  void MoveToNextStatement(
+      SourcePositionTableIterator* iterator,
+      std::vector<PositionTableEntry>* expression_positions);
+
+  int number_of_locals() const { return number_of_locals_; }

[rmcilroy, 2016/06/07 09:46:11]

This seems unused. Are you intending to add a test based on whether locals are
updated?

[oth, 2016/06/07 13:46:18]

Removed, at least for now. I think the check is pretty hard.

+
+  const int number_of_locals_;
+};
+
+}  // namespace interpreter
+}  // namespace internal
+}  // namespace v8
+
+#endif  // TEST_CCTEST_INTERPRETER_SOURCE_POSITION_COMPARER_H_