[turbofan] MemoryOptimizer cannot deal with dead nodes in use lists.

src/compiler/pipeline.cc

 // Copyright 2014 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/compiler/pipeline.h"
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
 
 #include "src/base/adapters.h"
@@ skipping 1014 matching lines @@
     // - introduce effect phis and rewire effects to get SSA again.
     EffectControlLinearizer linearizer(data->jsgraph(), schedule, temp_zone);
     linearizer.Run();
   }
 };
 
 struct MemoryOptimizationPhase {
   static const char* phase_name() { return "memory optimization"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
+    // The memory optimizer requires the graphs to be trimmed, so trim now.
+    GraphTrimmer trimmer(temp_zone, data->graph());
+    NodeVector roots(temp_zone);
+    data->jsgraph()->GetCachedNodes(&roots);
+    trimmer.TrimGraph(roots.begin(), roots.end());
+
+    // Optimize allocations and load/store operations.
     MemoryOptimizer optimizer(data->jsgraph(), temp_zone);
     optimizer.Optimize();
   }
 };
 
 struct LateOptimizationPhase {
   static const char* phase_name() { return "late optimization"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
     JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
@@ skipping 760 matching lines @@
   data->DeleteRegisterAllocationZone();
 }
 
 CompilationInfo* PipelineImpl::info() const { return data_->info(); }
 
 Isolate* PipelineImpl::isolate() const { return info()->isolate(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8