[turbofan] Add backend support for signed loads.

src/compiler/machine-type.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/machine-type.h"
 #include "src/ostreams.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 #define PRINT(bit)         \
   if (type & bit) {        \
-    if (before) os << "+"; \
+    if (before) os << "|"; \
     os << #bit;            \
     before = true;         \
   }
 
+
 OStream& operator<<(OStream& os, const MachineType& type) {
   bool before = false;
   PRINT(kRepBit);
   PRINT(kRepWord8);
   PRINT(kRepWord16);
   PRINT(kRepWord32);
   PRINT(kRepWord64);
   PRINT(kRepFloat64);
   PRINT(kRepTagged);
 
   PRINT(kTypeBool);
   PRINT(kTypeInt32);
   PRINT(kTypeUint32);
   PRINT(kTypeInt64);
   PRINT(kTypeUint64);
   PRINT(kTypeNumber);
   PRINT(kTypeAny);
   return os;
 }
-}
-}
-}  // namespace v8::internal::compiler
+
+
+#undef PRINT
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8