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

src/compiler/control-reducer.cc

Index: src/compiler/control-reducer.cc
diff --git a/src/compiler/control-reducer.cc b/src/compiler/control-reducer.cc
index 105bdfe2017115dc2c0a82cc62147b5ed146692d..9d74b8a6a4fb001f26f581b55c80019631cd0cd4 100644
--- a/src/compiler/control-reducer.cc
+++ b/src/compiler/control-reducer.cc
@@ -400,6 +400,8 @@ class ControlReducerImpl {
 
     // Reduce branches, phis, and merges.
     switch (node->opcode()) {
+      case IrOpcode::kBranch:
+        return ReduceBranch(node);
       case IrOpcode::kIfTrue:
         return ReduceIfTrue(node);
       case IrOpcode::kIfFalse:
@@ -478,6 +480,14 @@ class ControlReducerImpl {
     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.