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

src/compiler/simplified-lowering.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/simplified-lowering.h"
 
 #include <limits>
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 483 matching lines @@
         return VisitLeaf(node, kRepWord64);
       case IrOpcode::kFloat64Constant:
         return VisitLeaf(node, kRepFloat64);
       case IrOpcode::kExternalConstant:
         return VisitLeaf(node, kMachPtr);
       case IrOpcode::kNumberConstant:
         return VisitLeaf(node, kRepTagged);
       case IrOpcode::kHeapConstant:
         return VisitLeaf(node, kRepTagged);
 
-      case IrOpcode::kEnd:
-      case IrOpcode::kIfTrue:
-      case IrOpcode::kIfFalse:
-      case IrOpcode::kReturn:
-      case IrOpcode::kMerge:
-      case IrOpcode::kThrow:
-        return VisitInputs(node);  // default visit for all node inputs.
-
       case IrOpcode::kBranch:
         ProcessInput(node, 0, kRepBit);
         Enqueue(NodeProperties::GetControlInput(node, 0));
         break;
+      case IrOpcode::kSwitch:
+        ProcessInput(node, 0, kRepWord32);
+        Enqueue(NodeProperties::GetControlInput(node, 0));
+        break;
       case IrOpcode::kSelect:
         return VisitSelect(node, use, lowering);
       case IrOpcode::kPhi:
         return VisitPhi(node, use, lowering);
 
 //------------------------------------------------------------------
 // JavaScript operators.
 //------------------------------------------------------------------
 // For now, we assume that all JS operators were too complex to lower
 // to Simplified and that they will always require tagged value inputs
@@ skipping 1009 matching lines @@
 
 void SimplifiedLowering::DoStringLessThanOrEqual(Node* node) {
   node->set_op(machine()->IntLessThanOrEqual());
   node->ReplaceInput(0, StringComparison(node, true));
   node->ReplaceInput(1, jsgraph()->SmiConstant(EQUAL));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8