[crankshaft] Make sure +x is as fast as Number(x).

src/crankshaft/hydrogen-instructions.cc

 // Copyright 2012 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/crankshaft/hydrogen-instructions.h"
 
 #include "src/base/bits.h"
 #include "src/base/safe_math.h"
 #include "src/crankshaft/hydrogen-infer-representation.h"
 #include "src/double.h"
@@ skipping 2940 matching lines @@
                                                    Zone* zone) {
   HConstant* res = NULL;
   Handle<Object> handle = this->handle(isolate);
   if (handle->IsBoolean()) {
     res = handle->BooleanValue() ?
       new(zone) HConstant(1) : new(zone) HConstant(0);
   } else if (handle->IsUndefined()) {
     res = new (zone) HConstant(std::numeric_limits<double>::quiet_NaN());
   } else if (handle->IsNull()) {
     res = new(zone) HConstant(0);
+  } else if (handle->IsString()) {
+    res = new(zone) HConstant(String::ToNumber(Handle<String>::cast(handle)));
   }
   return res != NULL ? Just(res) : Nothing<HConstant*>();
 }
 
 
 std::ostream& HConstant::PrintDataTo(std::ostream& os) const {  // NOLINT
   if (HasInteger32Value()) {
     os << int32_value_ << " ";
   } else if (HasDoubleValue()) {
     os << double_value_ << " ";
@@ skipping 1684 matching lines @@
     case HObjectAccess::kExternalMemory:
       os << "[external-memory]";
       break;
   }
 
   return os << "@" << access.offset();
 }
 
 }  // namespace internal
 }  // namespace v8