[interpreter] Bytecode register 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) {
+  if (!entry.is_valid()) return;
+
   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 146 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