[turbofan] Remove another premature optimization from ControlReducer.

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/graph-reducer.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-marker.h"
@@ skipping 69 matching lines @@
         result = ReduceEnd(node);
         break;
       default:
         break;
     }
 
     return result == node ? NoChange() : Replace(result);
   }
 
   // Try to statically fold a condition.
-  Decision DecideCondition(Node* cond, bool recurse = true) {
+  Decision DecideCondition(Node* cond) {
     switch (cond->opcode()) {
       case IrOpcode::kInt32Constant:
         return Int32Matcher(cond).Is(0) ? kFalse : kTrue;
       case IrOpcode::kInt64Constant:
         return Int64Matcher(cond).Is(0) ? kFalse : kTrue;
       case IrOpcode::kHeapConstant: {
         Handle<Object> object =
             HeapObjectMatcher<Object>(cond).Value().handle();
         return object->BooleanValue() ? kTrue : kFalse;
       }
-      case IrOpcode::kPhi: {
-        if (!recurse) return kUnknown;  // Only go one level deep checking phis.
-        Decision result = kUnknown;
-        // Check if all inputs to a phi result in the same decision.
-        for (int i = cond->op()->ValueInputCount() - 1; i >= 0; i--) {
-          // Recurse only one level, since phis can be involved in cycles.
-          Decision decision = DecideCondition(cond->InputAt(i), false);
-          if (decision == kUnknown) return kUnknown;
-          if (result == kUnknown) result = decision;
-          if (result != decision) return kUnknown;
-        }
-        return result;
-      }
       default:
         break;
     }
     return kUnknown;
   }
 
   // Reduce redundant selects.
   Node* ReduceSelect(Node* const node) {
     Node* const tvalue = node->InputAt(1);
     Node* const fvalue = node->InputAt(2);
@@ skipping 249 matching lines @@
     case IrOpcode::kIfFalse:
       return impl.ReduceIfProjection(node, kFalse);
     default:
       return node;
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8