[turbofan] Some strength reduction for ConvertTaggedHoleToUndefined.

src/compiler/simplified-operator-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/simplified-operator-reducer.h"
 
 #include "src/compiler/js-graph.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/operator-properties.h"
@@ skipping 116 matching lines @@
       break;
     }
     case IrOpcode::kCheckIf: {
       HeapObjectMatcher m(node->InputAt(0));
       if (m.Is(factory()->true_value())) {
         Node* const effect = NodeProperties::GetEffectInput(node);
         return Replace(effect);
       }
       break;
     }
+    case IrOpcode::kCheckNumber: {
+      NodeMatcher m(node->InputAt(0));
+      if (m.IsConvertTaggedHoleToUndefined()) {
+        node->ReplaceInput(0, m.InputAt(0));
+        return Changed(node);
+      }
+      break;
+    }
     case IrOpcode::kCheckTaggedPointer: {
       Node* const input = node->InputAt(0);
       if (DecideObjectIsSmi(input) == Decision::kFalse) {
         ReplaceWithValue(node, input);
         return Replace(input);
       }
       break;
     }
     case IrOpcode::kCheckTaggedSigned: {
       Node* const input = node->InputAt(0);
       if (DecideObjectIsSmi(input) == Decision::kTrue) {
         ReplaceWithValue(node, input);
         return Replace(input);
       }
+      NodeMatcher m(input);
+      if (m.IsConvertTaggedHoleToUndefined()) {
+        node->ReplaceInput(0, m.InputAt(0));
+        return Changed(node);
+      }
       break;
     }
     case IrOpcode::kObjectIsSmi: {
       Node* const input = node->InputAt(0);
       switch (DecideObjectIsSmi(input)) {
         case Decision::kTrue:
           return ReplaceBoolean(true);
         case Decision::kFalse:
           return ReplaceBoolean(false);
         case Decision::kUnknown:
@@ skipping 59 matching lines @@
   return jsgraph()->isolate();
 }
 
 MachineOperatorBuilder* SimplifiedOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8