[turbofan] Avoid unnecessary tagging of floating point values.

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 29 matching lines @@
     }
     case IrOpcode::kChangeBoolToBit: {
       HeapObjectMatcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceInt32(m.Value()->BooleanValue());
       if (m.IsChangeBitToBool()) return Replace(m.InputAt(0));
       break;
     }
     case IrOpcode::kChangeFloat64ToTagged: {
       Float64Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceNumber(m.Value());
+      if (m.IsChangeTaggedToFloat64()) return Replace(m.node()->InputAt(0));
       break;
     }
     case IrOpcode::kChangeInt32ToTagged: {
       Int32Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceNumber(m.Value());
       break;
     }
     case IrOpcode::kChangeTaggedToFloat64: {
       NumberMatcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceFloat64(m.Value());
@@ skipping 98 matching lines @@
 Graph* SimplifiedOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 
 MachineOperatorBuilder* SimplifiedOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8