[Interpreter] Preserve source positions in peephole optimizer.

src/interpreter/bytecode-pipeline.h

 // Copyright 2015 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 V8_INTERPRETER_BYTECODE_PIPELINE_H_
 #define V8_INTERPRETER_BYTECODE_PIPELINE_H_
 
 #include "src/interpreter/bytecode-register-allocator.h"
 #include "src/interpreter/bytecodes.h"
 #include "src/zone-containers.h"
@@ skipping 34 matching lines @@
 
   // Combine later source info with current.
   void Update(const BytecodeSourceInfo& entry);
 
   int source_position() const {
     DCHECK(is_valid());
     return source_position_;
   }
 
   bool is_statement() const { return is_valid() && is_statement_; }
+  bool is_expression() const { return is_valid() && !is_statement_; }
 
   bool is_valid() const { return source_position_ != kUninitializedPosition; }
   void set_invalid() { source_position_ = kUninitializedPosition; }
 
   bool operator==(const BytecodeSourceInfo& other) const {
     return source_position_ == other.source_position_ &&
            is_statement_ == other.is_statement_;
   }
   bool operator!=(const BytecodeSourceInfo& other) const {
     return source_position_ != other.source_position_ ||
@@ skipping 64 matching lines @@
 };
 
 std::ostream& operator<<(std::ostream& os, const BytecodeSourceInfo& info);
 std::ostream& operator<<(std::ostream& os, const BytecodeNode& node);
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_PIPELINE_H_