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

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index 23c3e3294474949be02671fa18d96f4d7cf729ee..3084ef011e2154ba2dcd9132e24afb9e53c662a9 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -501,18 +501,14 @@ class RepresentationSelector {
       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: