[turbofan] Remove another premature optimization from ControlReducer.

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 633dfe5abf0b31eb76b13478d43e029edbb0740b..6e085ad7c23a6347d6a4e668391feaba079186d2 100644
--- a/src/compiler/control-reducer.cc
+++ b/src/compiler/control-reducer.cc
@@ -87,7 +87,7 @@ class ControlReducerImpl final : public AdvancedReducer {
   }
 
   // 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;
@@ -98,19 +98,6 @@ class ControlReducerImpl final : public AdvancedReducer {
             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;
     }