[turbofan] Fix control reducer with re-reducing branches.

src/compiler/control-reducer.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/common-operator.h"
 #include "src/compiler/control-reducer.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-marker.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 382 matching lines @@
       // If a node has only one control input and it is dead, replace with dead.
       Node* control = NodeProperties::GetControlInput(node);
       if (control->opcode() == IrOpcode::kDead) {
         TRACE(("ControlDead: #%d:%s\n", node->id(), node->op()->mnemonic()));
         return control;
       }
     }
 
     // Reduce branches, phis, and merges.
     switch (node->opcode()) {
+      case IrOpcode::kBranch:
+        return ReduceBranch(node);
       case IrOpcode::kIfTrue:
         return ReduceIfTrue(node);
       case IrOpcode::kIfFalse:
         return ReduceIfFalse(node);
       case IrOpcode::kLoop:
       case IrOpcode::kMerge:
         return ReduceMerge(node);
       case IrOpcode::kSelect:
         return ReduceSelect(node);
       case IrOpcode::kPhi:
@@ skipping 58 matching lines @@
       Node* input = *it;
       if (input->opcode() == IrOpcode::kDead) continue;  // ignore dead inputs.
       if (input != node && input != replacement) {       // non-redundant input.
         if (replacement != NULL) return node;
         replacement = input;
       }
     }
     return replacement == NULL ? dead() : replacement;
   }
 
+  // Reduce branches.
+  Node* ReduceBranch(Node* branch) {
+    if (DecideCondition(branch->InputAt(0)) != kUnknown) {
+      for (Node* use : branch->uses()) Revisit(use);
+    }
+    return branch;
+  }
+
   // Reduce merges by trimming away dead inputs from the merge and phis.
   Node* ReduceMerge(Node* node) {
     // Count the number of live inputs.
     int live = 0;
     int index = 0;
     int live_index = 0;
     for (Node* const input : node->inputs()) {
       if (input->opcode() != IrOpcode::kDead) {
         live++;
         live_index = index;
@@ skipping 143 matching lines @@
       return impl.ReduceIfTrue(node);
     case IrOpcode::kIfFalse:
       return impl.ReduceIfFalse(node);
     default:
       return node;
   }
 }
 }
 }
 }  // namespace v8::internal::compiler