Clean-up irep-id emptyness checks in pointer-analysis

Author: peterschrammel

src/pointer-analysis/add_failed_symbols.cpp

@@ -76,7 +76,7 @@ exprt get_failed_symbol(
   const symbolt &symbol=ns.lookup(expr);
   irep_idt failed_symbol_id=symbol.type.get(ID_C_failed_symbol);
 
-  if(failed_symbol_id==irep_idt())
+  if(failed_symbol_id.empty())
     return nil_exprt();
 
   const symbolt &failed_symbol=ns.lookup(failed_symbol_id);

src/pointer-analysis/goto_program_dereference.cpp

@@ -32,7 +32,7 @@ bool goto_program_dereferencet::has_failed_symbol(
     const irep_idt &failed_symbol=
       ptr_symbol.type.get("#failed_symbol");
 
-    if(failed_symbol==irep_idt())
+    if(failed_symbol.empty())
       return false;
 
     return !ns.lookup(failed_symbol, symbol);

src/pointer-analysis/value_set_analysis.cpp

@@ -44,7 +44,7 @@ void value_set_analysist::convert(
     if(location==previous_location)
       continue;
 
-    if(location.is_nil() || location.get_file()==irep_idt())
+    if(location.is_nil() || location.get_file().empty())
       continue;
 
     // find value set