[turbofan] Add backend support for signed loads.

src/compiler/machine-type.cc

Index: src/compiler/machine-type.cc
diff --git a/src/compiler/machine-type.cc b/src/compiler/machine-type.cc
index 33ac20f36cf1a3abe7fcb45055d28a009d881bd8..b27727cb7a3b03c1f7bc4b559242533c9c119da0 100644
--- a/src/compiler/machine-type.cc
+++ b/src/compiler/machine-type.cc
@@ -11,11 +11,12 @@ 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);
@@ -35,6 +36,10 @@ OStream& operator<<(OStream& os, const MachineType& type) {
   PRINT(kTypeAny);
   return os;
 }
-}
-}
-}  // namespace v8::internal::compiler
+
+
+#undef PRINT
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8