[turbofan] Redundant branch elimination.

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"
 #include "src/base/platform/elapsed-timer.h"
 #include "src/compiler/ast-graph-builder.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/basic-block-instrumentor.h"
+#include "src/compiler/branch-elimination.h"
 #include "src/compiler/bytecode-graph-builder.h"
 #include "src/compiler/change-lowering.h"
 #include "src/compiler/code-generator.h"
 #include "src/compiler/common-operator-reducer.h"
 #include "src/compiler/control-flow-optimizer.h"
 #include "src/compiler/dead-code-elimination.h"
 #include "src/compiler/frame-elider.h"
 #include "src/compiler/graph-replay.h"
 #include "src/compiler/graph-trimmer.h"
 #include "src/compiler/graph-visualizer.h"
@@ skipping 612 matching lines @@
     AddReducer(data, &graph_reducer, &typed_lowering);
     AddReducer(data, &graph_reducer, &intrinsic_lowering);
     AddReducer(data, &graph_reducer, &type_feedback_lowering);
     AddReducer(data, &graph_reducer, &load_elimination);
     AddReducer(data, &graph_reducer, &common_reducer);
     graph_reducer.ReduceGraph();
   }
 };
 
 
+struct BranchEliminationPhase {
+  static const char* phase_name() { return "branch condition elimination"; }
+
+  void Run(PipelineData* data, Zone* temp_zone) {
+    JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
+    BranchElimination branch_condition_elimination(&graph_reducer,
+                                                   data->jsgraph(), temp_zone);
+    DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
+                                              data->common());
+    AddReducer(data, &graph_reducer, &branch_condition_elimination);
+    AddReducer(data, &graph_reducer, &dead_code_elimination);
+    graph_reducer.ReduceGraph();
+  }
+};
+
+
 struct SimplifiedLoweringPhase {
   static const char* phase_name() { return "simplified lowering"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
     SimplifiedLowering lowering(data->jsgraph(), temp_zone,
                                 data->source_positions());
     lowering.LowerAllNodes();
     JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
     DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
                                               data->common());
@@ skipping 494 matching lines @@
 
     if (info()->is_type_feedback_enabled()) {
       Run<JSTypeFeedbackPhase>();
       RunPrintAndVerify("JSType feedback");
     }
 
     // Lower simplified operators and insert changes.
     Run<SimplifiedLoweringPhase>();
     RunPrintAndVerify("Lowered simplified");
 
+    Run<BranchEliminationPhase>();
+    RunPrintAndVerify("Branch conditions eliminated");
+
     // Optimize control flow.
     if (FLAG_turbo_cf_optimization) {
       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);
@@ skipping 280 matching lines @@
     tcf << AsC1VRegisterAllocationData("CodeGen",
                                        data->register_allocation_data());
   }
 
   data->DeleteRegisterAllocationZone();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8