diff --git a/src/script_opt/Reduce.cc b/src/script_opt/Reduce.cc
index bfb53f4aa2..ea69cf6353 100644
--- a/src/script_opt/Reduce.cc
+++ b/src/script_opt/Reduce.cc
@@ -90,7 +90,7 @@ bool Reducer::ID_IsReduced(const ID* id) const
 		IsNewLocal(id);
 	}
 
-NameExprPtr Reducer::GenInlineBlockName(IDPtr id)
+NameExprPtr Reducer::GenInlineBlockName(const IDPtr& id)
 	{
 	return make_intrusive<NameExpr>(GenLocal(id));
 	}
@@ -1004,7 +1004,7 @@ bool CSE_ValidityChecker::CheckID(const std::vector<const ID*>& ids,
 bool CSE_ValidityChecker::CheckAggrMod(const std::vector<const ID*>& ids,
 					const Expr* e) const
 	{
-	auto e_i_t = e->GetType();
+	const auto& e_i_t = e->GetType();
 	if ( IsAggr(e_i_t) )
 		{
 		// This assignment sets an aggregate value.
diff --git a/src/script_opt/Reduce.h b/src/script_opt/Reduce.h
index 59181f903f..ac62a61c0b 100644
--- a/src/script_opt/Reduce.h
+++ b/src/script_opt/Reduce.h
@@ -20,8 +20,8 @@ public:
 
 	StmtPtr Reduce(StmtPtr s)
 		{
-		reduction_root = s;
-		return s->Reduce(this);
+		reduction_root = std::move(s);
+		return reduction_root->Reduce(this);
 		}
 
 	const DefSetsMgr* GetDefSetsMgr() const		{ return mgr; }
@@ -45,7 +45,7 @@ public:
 
 	// This is called *prior* to pushing a new inline block, in
 	// order to generate the equivalent of function parameters.
-	NameExprPtr GenInlineBlockName(IDPtr id);
+	NameExprPtr GenInlineBlockName(const IDPtr& id);
 
 	int NumNewLocals() const	{ return new_locals.size(); }
 
@@ -141,7 +141,7 @@ public:
 	// one (meant for calls in an Expr context) does not, to avoid
 	// circularity.
 	ExprPtr OptExpr(Expr* e);
-	ExprPtr OptExpr(ExprPtr e)
+	ExprPtr OptExpr(const ExprPtr& e)
 		{ return OptExpr(e.get()); }
 
 	// This one for expressions appearing in an Expr context.
diff --git a/src/script_opt/TempVar.cc b/src/script_opt/TempVar.cc
index 10bb056e62..b385bb432a 100644
--- a/src/script_opt/TempVar.cc
+++ b/src/script_opt/TempVar.cc
@@ -11,7 +11,7 @@ TempVar::TempVar(int num, const TypePtr& t, ExprPtr _rhs) : type(t)
 	char buf[8192];
 	snprintf(buf, sizeof buf, "#%d", num);
 	name = buf;
-	rhs = _rhs;
+	rhs = std::move(_rhs);
 	}
 
 void TempVar::SetAlias(IDPtr _alias, const DefPoints* _dps)
@@ -28,7 +28,7 @@ void TempVar::SetAlias(IDPtr _alias, const DefPoints* _dps)
 	if ( alias == id )
 		reporter->InternalError("Creating alias loop");
 
-	alias = _alias;
+	alias = std::move(_alias);
 	dps = _dps;
 	}
 
diff --git a/src/script_opt/TempVar.h b/src/script_opt/TempVar.h
index dce8772751..446327c1bb 100644
--- a/src/script_opt/TempVar.h
+++ b/src/script_opt/TempVar.h
@@ -39,7 +39,7 @@ public:
 	void SetDPs(const DefPoints* _dps);
 
 	const RDPtr& MaxRDs() const	{ return max_rds; }
-	void SetMaxRDs(RDPtr rds)	{ max_rds = rds; }
+	void SetMaxRDs(RDPtr rds)	{ max_rds = std::move(rds); }
 
 protected:
 	std::string name;