[turbofan] Improve representation selection for HeapObject checking.

src/machine-type.h

Index: src/machine-type.h
diff --git a/src/machine-type.h b/src/machine-type.h
index 69cb6d79fac6062e6771d68624ba0463385a5215..c9acd900371642825d551114f0f08970bd750116 100644
--- a/src/machine-type.h
+++ b/src/machine-type.h
@@ -234,6 +234,11 @@ inline bool CanBeTaggedPointer(MachineRepresentation rep) {
          rep == MachineRepresentation::kTaggedPointer;
 }
 
+inline bool CanBeTaggedSigned(MachineRepresentation rep) {
+  return rep == MachineRepresentation::kTagged ||
+         rep == MachineRepresentation::kTaggedSigned;
+}
+
 inline bool IsAnyTagged(MachineRepresentation rep) {
   return CanBeTaggedPointer(rep) || rep == MachineRepresentation::kTaggedSigned;
 }