[interpreter] Minor clean-up of BytecodeSourceInfo.

src/interpreter/bytecode-peephole-optimizer.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-peephole-optimizer.h"
 
 #include "src/interpreter/constant-array-builder.h"
 #include "src/objects-inl.h"
 #include "src/objects.h"
 
@@ skipping 279 matching lines @@
       // Preserve the source information by replacing the current bytecode
       // with a no op bytecode.
       current->set_bytecode(Bytecode::kNop);
     } else {
       current = nullptr;
     }
     return current;
   }
 
   if (CanElideLast(current) && CanElideLastBasedOnSourcePosition(current)) {
-    current->source_info().Update(last_.source_info());
+    if (last_.source_info().is_valid()) {
+      // Current can not be valid per CanElideLastBasedOnSourcePosition().
+      current->source_info().Clone(last_.source_info());
+    }
     InvalidateLast();
     return current;
   }
 
   return current;
 }
 
 BytecodeNode* BytecodePeepholeOptimizer::OptimizeAndEmitLast(
     BytecodeNode* current) {
   // Attempt optimization if there is an earlier node to optimize with.
   if (LastIsValid()) {
     current = Optimize(current);
     // Only output the last node if it wasn't invalidated by the optimization.
     if (LastIsValid()) {
       next_stage_->Write(&last_);
       InvalidateLast();
     }
   }
   return current;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8