[turbofan] Optimize certain chains of Branch into a Switch.

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/platform/elapsed-timer.h"
 #include "src/bootstrapper.h"  // TODO(mstarzinger): Only temporary.
 #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/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/control-reducer.h"
 #include "src/compiler/graph-replay.h"
 #include "src/compiler/graph-visualizer.h"
 #include "src/compiler/instruction.h"
 #include "src/compiler/instruction-selector.h"
 #include "src/compiler/js-builtin-reducer.h"
 #include "src/compiler/js-context-specialization.h"
 #include "src/compiler/js-generic-lowering.h"
 #include "src/compiler/js-inlining.h"
 #include "src/compiler/js-intrinsic-lowering.h"
@@ skipping 507 matching lines @@
     GraphReducer graph_reducer(data->graph(), temp_zone);
     AddReducer(data, &graph_reducer, &vn_reducer);
     AddReducer(data, &graph_reducer, &simple_reducer);
     AddReducer(data, &graph_reducer, &machine_reducer);
     AddReducer(data, &graph_reducer, &common_reducer);
     graph_reducer.ReduceGraph();
   }
 };
 
 
+struct ControlFlowOptimizationPhase {
+  static const char* phase_name() { return "control flow optimization"; }
+
+  void Run(PipelineData* data, Zone* temp_zone) {
+    ControlFlowOptimizer optimizer(data->jsgraph(), temp_zone);
+    optimizer.Optimize();
+  }
+};
+
+
 struct ChangeLoweringPhase {
   static const char* phase_name() { return "change lowering"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
     SourcePositionTable::Scope pos(data->source_positions(),
                                    SourcePosition::Unknown());
     ValueNumberingReducer vn_reducer(temp_zone);
     SimplifiedOperatorReducer simple_reducer(data->jsgraph());
     ChangeLowering lowering(data->jsgraph());
     MachineOperatorReducer machine_reducer(data->jsgraph());
@@ skipping 397 matching lines @@
     if (info()->is_osr()) {
       Run<OsrDeconstructionPhase>();
       if (info()->bailout_reason() != kNoReason) return Handle<Code>::null();
       RunPrintAndVerify("OSR deconstruction");
     }
 
     // Lower simplified operators and insert changes.
     Run<SimplifiedLoweringPhase>();
     RunPrintAndVerify("Lowered simplified");
 
+    // 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);
 
     Run<LateControlReductionPhase>();
     RunPrintAndVerify("Late Control reduced");
   } else {
     if (info()->is_osr()) {
       Run<OsrDeconstructionPhase>();
@@ skipping 220 matching lines @@
 
   if (FLAG_trace_turbo && !data->MayHaveUnverifiableGraph()) {
     TurboCfgFile tcf(data->isolate());
     tcf << AsC1VAllocator("CodeGen", data->register_allocator());
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8