[turbofan] Combine GenericLoweringPhase and ChangeLoweringPhase.

There's no need to use a dedicated ChangeLoweringPhase before we go to
GenericLoweringPhase; instead that change lowering (which is really
simplified lowering by now) should run together with generic lowering.

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/1697133002

Cr-Commit-Position: refs/heads/master@{#34008}

src/compiler/pipeline.cc

@@ -722,30 +722,6 @@ struct ControlFlowOptimizationPhase {
 };
 
 
-struct ChangeLoweringPhase {
-  static const char* phase_name() { return "change lowering"; }
-
-  void Run(PipelineData* data, Zone* temp_zone) {
-    JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
-    DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
-                                              data->common());
-    SimplifiedOperatorReducer simple_reducer(data->jsgraph());
-    ValueNumberingReducer value_numbering(temp_zone);
-    ChangeLowering lowering(data->jsgraph());
-    MachineOperatorReducer machine_reducer(data->jsgraph());
-    CommonOperatorReducer common_reducer(&graph_reducer, data->graph(),
-                                         data->common(), data->machine());
-    AddReducer(data, &graph_reducer, &dead_code_elimination);
-    AddReducer(data, &graph_reducer, &simple_reducer);
-    AddReducer(data, &graph_reducer, &value_numbering);
-    AddReducer(data, &graph_reducer, &lowering);
-    AddReducer(data, &graph_reducer, &machine_reducer);
-    AddReducer(data, &graph_reducer, &common_reducer);
-    graph_reducer.ReduceGraph();
-  }
-};
-
-
 struct EarlyGraphTrimmingPhase {
   static const char* phase_name() { return "early graph trimming"; }
   void Run(PipelineData* data, Zone* temp_zone) {
@@ -793,6 +769,10 @@ struct GenericLoweringPhase {
                                               data->common());
     CommonOperatorReducer common_reducer(&graph_reducer, data->graph(),
                                          data->common(), data->machine());
+    SimplifiedOperatorReducer simple_reducer(data->jsgraph());
+    ValueNumberingReducer value_numbering(temp_zone);
+    ChangeLowering change_lowering(data->jsgraph());
+    MachineOperatorReducer machine_reducer(data->jsgraph());
     JSGenericLowering generic_lowering(data->info()->is_typing_enabled(),
                                        data->jsgraph());
     SelectLowering select_lowering(data->jsgraph()->graph(),
@@ -801,6 +781,12 @@ struct GenericLoweringPhase {
     AddReducer(data, &graph_reducer, &context_relaxing);
     AddReducer(data, &graph_reducer, &dead_code_elimination);
     AddReducer(data, &graph_reducer, &common_reducer);
+    if (data->info()->is_typing_enabled()) {
+      AddReducer(data, &graph_reducer, &simple_reducer);
+      AddReducer(data, &graph_reducer, &value_numbering);
+      AddReducer(data, &graph_reducer, &change_lowering);
+      AddReducer(data, &graph_reducer, &machine_reducer);
+    }
     AddReducer(data, &graph_reducer, &generic_lowering);
     AddReducer(data, &graph_reducer, &select_lowering);
     AddReducer(data, &graph_reducer, &tco);
@@ -1192,14 +1178,9 @@ Handle<Code> Pipeline::GenerateCode() {
       Run<ControlFlowOptimizationPhase>();
       RunPrintAndVerify("Control flow optimized");
     }
-
-    // Lower changes that have been inserted before.
-    Run<ChangeLoweringPhase>();
-    // TODO(jarin, rossberg): Remove UNTYPED once machine typing works.
-    RunPrintAndVerify("Lowered changes", true);
   }
 
-  // Lower any remaining generic JSOperators.
+  // Lower changes inserted earlier and any remaining generic JSOperators.
   Run<GenericLoweringPhase>();
   // TODO(jarin, rossberg): Remove UNTYPED once machine typing works.
   RunPrintAndVerify("Lowered generic", true);