Do not pass-by-value if unnecessary

Remove unnecessary copying of expressions.

Author: peterschrammel

src/goto-symex/solver_hardness.cpp

@@ -44,7 +44,7 @@ bool solver_hardnesst::assertion_statst::empty() const
 
 void solver_hardnesst::register_ssa(
   std::size_t ssa_index,
-  const exprt ssa_expression,
+  const exprt &ssa_expression,
   goto_programt::const_targett pc)
 {
   PRECONDITION(ssa_index < hardness_stats.size());
@@ -73,7 +73,7 @@ void solver_hardnesst::register_ssa_size(std::size_t size)
 }
 
 void solver_hardnesst::register_assertion_ssas(
-  const exprt ssa_expression,
+  const exprt &ssa_expression,
   const std::vector<goto_programt::const_targett> &pcs)
 {
   if(assertion_stats.empty())
@@ -378,7 +378,7 @@ solver_hardnesst::goto_instruction2string(goto_programt::const_targett pc)
   return out.str();
 }
 
-std::string solver_hardnesst::expr2string(const exprt expr)
+std::string solver_hardnesst::expr2string(const exprt &expr)
 {
   std::stringstream ss;
   ss << format(expr);

src/goto-symex/solver_hardness.h

@@ -82,7 +82,7 @@ struct solver_hardnesst : public clause_hardness_collectort
   /// \param pc: the GOTO instruction iterator for this SSA step
   void register_ssa(
     std::size_t ssa_index,
-    const exprt ssa_expression,
+    const exprt &ssa_expression,
     goto_programt::const_targett pc);
 
   void register_ssa_size(std::size_t size);
@@ -95,7 +95,7 @@ struct solver_hardnesst : public clause_hardness_collectort
   /// \param pcs: all GOTO instruction iterators that contributed in the
   ///   disjunction
   void register_assertion_ssas(
-    const exprt ssa_expression,
+    const exprt &ssa_expression,
     const std::vector<goto_programt::const_targett> &pcs);
 
   /// Called e.g. from the `satcheck_minisat2::lcnf`, this function adds the
@@ -130,7 +130,7 @@ struct solver_hardnesst : public clause_hardness_collectort
   // A minor modification of \ref goto_programt::output_instruction
   static std::string goto_instruction2string(goto_programt::const_targett pc);
 
-  static std::string expr2string(const exprt expr);
+  static std::string expr2string(const exprt &expr);
 
   std::string outfile;
   std::vector<std::unordered_map<hardness_ssa_keyt, sat_hardnesst>>