[turbofan] Initial version of the new LoadElimination.

src/compiler/pipeline.cc

Index: src/compiler/pipeline.cc
diff --git a/src/compiler/pipeline.cc b/src/compiler/pipeline.cc
index ec57f4a52651dc90a86c71c625471665c1700d12..c4e5032b7b719bb13756d7c2101e49337223c122 100644
--- a/src/compiler/pipeline.cc
+++ b/src/compiler/pipeline.cc
@@ -872,8 +872,6 @@ struct TypedLoweringPhase {
     JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
     DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
                                               data->common());
-    LoadElimination load_elimination(&graph_reducer, data->graph(),
-                                     data->jsgraph()->simplified());
     JSBuiltinReducer builtin_reducer(&graph_reducer, data->jsgraph());
     MaybeHandle<LiteralsArray> literals_array =
         data->info()->is_native_context_specializing()
@@ -912,7 +910,6 @@ struct TypedLoweringPhase {
     }
     AddReducer(data, &graph_reducer, &typed_lowering);
     AddReducer(data, &graph_reducer, &intrinsic_lowering);
-    AddReducer(data, &graph_reducer, &load_elimination);
     AddReducer(data, &graph_reducer, &value_numbering);
     AddReducer(data, &graph_reducer, &simple_reducer);
     AddReducer(data, &graph_reducer, &checkpoint_elimination);
@@ -1043,6 +1040,22 @@ struct StoreStoreEliminationPhase {
   }
 };
 
+struct LoadEliminationPhase {
+  static const char* phase_name() { return "load elimination"; }
+
+  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());
+
+    // Eliminate redundant loads.
+    LoadElimination load_elimination(data->graph(), temp_zone);
+    load_elimination.Run();
+  }
+};
+
 struct MemoryOptimizationPhase {
   static const char* phase_name() { return "memory optimization"; }
 
@@ -1446,6 +1459,11 @@ bool PipelineImpl::CreateGraph() {
       Run<EscapeAnalysisPhase>();
       RunPrintAndVerify("Escape Analysed");
     }
+
+    if (FLAG_turbo_load_elimination) {
+      Run<LoadEliminationPhase>();
+      RunPrintAndVerify("Load eliminated");
+    }
   }
 
   // Select representations. This has to run w/o the Typer decorator, because