[Interpreter] Preserve source positions in peephole optimizer.

src/interpreter/bytecode-pipeline.cc

 // 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.
 
 #include "src/interpreter/bytecode-pipeline.h"
 
 #include <iomanip>
 #include "src/interpreter/source-position-table.h"
 
 namespace v8 {
 namespace internal {
 namespace interpreter {
 
 void BytecodeSourceInfo::Update(const BytecodeSourceInfo& entry) {
-  DCHECK(entry.is_valid());
   if (!is_valid() || (entry.is_statement() && !is_statement()) ||
       (entry.is_statement() && is_statement() &&
        entry.source_position() > source_position())) {
     // Position is updated if any of the following conditions are met:
     //   (1) there is no existing position.
     //   (2) the incoming position is a statement and the current position
     //       is an expression.
     //   (3) the existing position is a statement and the incoming
     //       statement has a later source position.
     // Condition 3 is needed for the first statement in a function which
@@ skipping 83 matching lines @@
         Bytecodes::OperandScaleToPrefixBytecode(operand_scale_);
     os << '.' << Bytecodes::ToString(scale_prefix);
   }
 
   for (int i = 0; i < operand_count(); ++i) {
     os << ' ' << std::setw(8) << std::setfill('0') << std::hex << operands_[i];
   }
   os.copyfmt(saved_state);
 
   if (source_info_.is_valid()) {
-    os << source_info_;
+    os << ' ' << source_info_;
   }
   os << '\n';
 #else
   os << static_cast<const void*>(this);
 #endif  // DEBUG
 }
 
 void BytecodeNode::Clone(const BytecodeNode* const other) {
   memcpy(this, other, sizeof(*other));
 }
@@ skipping 23 matching lines @@
   if (info.is_valid()) {
     char description = info.is_statement() ? 'S' : 'E';
     os << info.source_position() << ' ' << description << '>';
   }
   return os;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8