Split the rename function according to the level and pass expression by copy instead of reference

src/goto-instrument/accelerate/scratch_program.cpp

@@ -69,11 +69,7 @@ bool scratch_programt::check_sat(bool do_slice)
 
 exprt scratch_programt::eval(const exprt &e)
 {
-  exprt ssa=e;
-
-  symex_state->rename<goto_symex_statet::L2>(ssa, ns);
-
-  return checker->get(ssa);
+  return checker->get(symex_state->rename<goto_symex_statet::L2>(e, ns));
 }
 
 void scratch_programt::append(goto_programt::instructionst &new_instructions)

src/goto-symex/goto_symex_state.cpp

@@ -282,7 +282,7 @@ goto_symex_statet::rename_level1_ssa(ssa_exprt ssa, const namespacet &ns)
 }
 
 template <goto_symex_statet::levelt level>
-void goto_symex_statet::rename(exprt &expr, const namespacet &ns)
+exprt goto_symex_statet::rename(exprt expr, const namespacet &ns)
 {
   // rename all the symbols with their last known value
 
@@ -330,13 +330,9 @@ void goto_symex_statet::rename(exprt &expr, const namespacet &ns)
   {
     // we never rename function symbols
     if(as_const(expr).type().id() == ID_code)
-    {
       rename<level>(expr.type(), to_symbol_expr(expr).get_identifier(), ns);
-      return;
-    }
-
-    expr=ssa_exprt(expr);
-    rename<level>(expr, ns);
+    else
+      expr = rename<level>(ssa_exprt(expr), ns);
   }
   else if(expr.id()==ID_address_of)
   {
@@ -351,7 +347,7 @@ void goto_symex_statet::rename(exprt &expr, const namespacet &ns)
 
     // do this recursively
     Forall_operands(it, expr)
-      rename<level>(*it, ns);
+      *it = rename<level>(std::move(*it), ns);
 
     const exprt &c_expr = as_const(expr);
     INVARIANT(
@@ -363,6 +359,7 @@ void goto_symex_statet::rename(exprt &expr, const namespacet &ns)
       "Type of renamed expr should be the same as operands for with_exprt and "
       "if_exprt");
   }
+  return expr;
 }
 
 /// thread encoding
@@ -572,13 +569,13 @@ void goto_symex_statet::rename_address(exprt &expr, const namespacet &ns)
       expr.type() = to_array_type(index_expr.array().type()).subtype();
 
       // the index is not an address
-      rename<level>(index_expr.index(), ns);
+      index_expr.index() = rename<level>(std::move(index_expr.index()), ns);
     }
     else if(expr.id()==ID_if)
     {
       // the condition is not an address
       if_exprt &if_expr=to_if_expr(expr);
-      rename<level>(if_expr.cond(), ns);
+      if_expr.cond() = rename<level>(std::move(if_expr.cond()), ns);
       rename_address<level>(if_expr.true_case(), ns);
       rename_address<level>(if_expr.false_case(), ns);
 
@@ -717,7 +714,7 @@ void goto_symex_statet::rename(
   {
     auto &array_type = to_array_type(type);
     rename<level>(array_type.subtype(), irep_idt(), ns);
-    rename<level>(array_type.size(), ns);
+    array_type.size() = rename<level>(std::move(array_type.size()), ns);
   }
   else if(type.id() == ID_struct || type.id() == ID_union)
   {
@@ -728,7 +725,10 @@ void goto_symex_statet::rename(
     {
       // be careful, or it might get cyclic
       if(component.type().id() == ID_array)
-        rename<level>(to_array_type(component.type()).size(), ns);
+      {
+        auto &array_type = to_array_type(component.type());
+        array_type.size() = rename<level>(std::move(array_type.size()), ns);
+      }
       else if(component.type().id() != ID_pointer)
         rename<level>(component.type(), irep_idt(), ns);
     }

src/goto-symex/goto_symex_state.h

@@ -180,7 +180,7 @@ class goto_symex_statet final : public goto_statet
   /// A full explanation of SSA (which is why we do this renaming) is in
   /// the SSA section of background-concepts.md.
   template <levelt level = L2>
-  void rename(exprt &expr, const namespacet &ns);
+  exprt rename(exprt expr, const namespacet &ns);
 
   ssa_exprt rename_level0_ssa(ssa_exprt ssa, const namespacet &ns);
 

src/goto-symex/symex_assign.cpp

@@ -212,13 +212,13 @@ void goto_symext::symex_assign_symbol(
     tmp_ssa_rhs.swap(ssa_rhs);
   }
 
-  state.rename(ssa_rhs, ns);
-  do_simplify(ssa_rhs);
+  exprt l2_rhs = state.rename(std::move(ssa_rhs), ns);
+  do_simplify(l2_rhs);
 
   ssa_exprt ssa_lhs=lhs;
   state.assignment(
     ssa_lhs,
-    ssa_rhs,
+    l2_rhs,
     ns,
     symex_config.simplify_opt,
     symex_config.constant_propagation,
@@ -228,7 +228,7 @@ void goto_symext::symex_assign_symbol(
   ssa_full_lhs=add_to_lhs(ssa_full_lhs, ssa_lhs);
   const bool record_events=state.record_events;
   state.record_events=false;
-  state.rename(ssa_full_lhs, ns);
+  exprt l2_full_lhs = state.rename(std::move(ssa_full_lhs), ns);
   state.record_events=record_events;
 
   guardt tmp_guard(state.guard);
@@ -254,8 +254,9 @@ void goto_symext::symex_assign_symbol(
   target.assignment(
     tmp_guard.as_expr(),
     ssa_lhs,
-    ssa_full_lhs, add_to_lhs(full_lhs, ssa_lhs.get_original_expr()),
-    ssa_rhs,
+    l2_full_lhs,
+    add_to_lhs(full_lhs, ssa_lhs.get_original_expr()),
+    l2_rhs,
     state.source,
     assignment_type);
 }
@@ -406,8 +407,7 @@ void goto_symext::symex_assign_if(
 
   guardt old_guard=guard;
 
-  exprt renamed_guard=lhs.cond();
-  state.rename(renamed_guard, ns);
+  exprt renamed_guard = state.rename(lhs.cond(), ns);
   do_simplify(renamed_guard);
 
   if(!renamed_guard.is_false())

src/goto-symex/symex_builtin_functions.cpp

@@ -71,8 +71,8 @@ void goto_symext::symex_allocate(
   }
   else
   {
-    exprt tmp_size=size;
-    state.rename(tmp_size, ns); // to allow constant propagation
+    // to allow constant propagation
+    exprt tmp_size = state.rename(size, ns);
     simplify(tmp_size, ns);
 
     // special treatment for sizeof(T)*x
@@ -164,8 +164,8 @@ void goto_symext::symex_allocate(
 
   state.symbol_table.add(value_symbol);
 
-  exprt zero_init=code.op1();
-  state.rename(zero_init, ns); // to allow constant propagation
+  // to allow constant propagation
+  exprt zero_init = state.rename(code.op1(), ns);
   simplify(zero_init, ns);
 
   INVARIANT(
@@ -233,8 +233,8 @@ void goto_symext::symex_gcc_builtin_va_arg_next(
   if(lhs.is_nil())
     return; // ignore
 
-  exprt tmp=code.op0();
-  state.rename(tmp, ns); // to allow constant propagation
+  // to allow constant propagation
+  exprt tmp = state.rename(code.op0(), ns);
   do_simplify(tmp);
   irep_idt id=get_symbol(tmp);
 
@@ -311,8 +311,7 @@ void goto_symext::symex_printf(
 {
   PRECONDITION(!rhs.operands().empty());
 
-  exprt tmp_rhs=rhs;
-  state.rename(tmp_rhs, ns);
+  exprt tmp_rhs = state.rename(rhs, ns);
   do_simplify(tmp_rhs);
 
   const exprt::operandst &operands=tmp_rhs.operands();
@@ -336,17 +335,15 @@ void goto_symext::symex_input(
 {
   PRECONDITION(code.operands().size() >= 2);
 
-  exprt id_arg=code.op0();
-
-  state.rename(id_arg, ns);
+  exprt id_arg = state.rename(code.op0(), ns);
 
   std::list<exprt> args;
 
   for(std::size_t i=1; i<code.operands().size(); i++)
   {
-    args.push_back(code.operands()[i]);
-    state.rename(args.back(), ns);
-    do_simplify(args.back());
+    exprt l2_arg = state.rename(code.operands()[i], ns);
+    do_simplify(l2_arg);
+    args.emplace_back(std::move(l2_arg));
   }
 
   const irep_idt input_id=get_string_argument(id_arg, ns);
@@ -359,18 +356,15 @@ void goto_symext::symex_output(
   const codet &code)
 {
   PRECONDITION(code.operands().size() >= 2);
-
-  exprt id_arg=code.op0();
-
-  state.rename(id_arg, ns);
+  exprt id_arg = state.rename(code.op0(), ns);
 
   std::list<exprt> args;
 
   for(std::size_t i=1; i<code.operands().size(); i++)
   {
-    args.push_back(code.operands()[i]);
-    state.rename(args.back(), ns);
-    do_simplify(args.back());
+    exprt l2_arg = state.rename(code.operands()[i], ns);
+    do_simplify(l2_arg);
+    args.emplace_back(std::move(l2_arg));
   }
 
   const irep_idt output_id=get_string_argument(id_arg, ns);
@@ -481,11 +475,7 @@ void goto_symext::symex_trace(
     irep_idt event = to_string_constant(code.arguments()[1].op0()).get_value();
 
     for(std::size_t j=2; j<code.arguments().size(); j++)
-    {
-      exprt var(code.arguments()[j]);
-      state.rename(var, ns);
-      vars.push_back(var);
-    }
+      vars.push_back(state.rename(code.arguments()[j], ns));
 
     target.output(state.guard.as_expr(), state.source, event, vars);
   }

src/goto-symex/symex_dead.cpp

@@ -37,8 +37,9 @@ void goto_symext::symex_dead(statet &state)
     else
       rhs=exprt(ID_invalid);
 
-    state.rename<goto_symex_statet::L1>(rhs, ns);
-    state.value_set.assign(ssa, rhs, ns, true, false);
+    const exprt l1_rhs =
+      state.rename<goto_symex_statet::L1>(std::move(rhs), ns);
+    state.value_set.assign(ssa, l1_rhs, ns, true, false);
   }
 
   const irep_idt &l1_identifier = ssa.get_identifier();

src/goto-symex/symex_decl.cpp

@@ -53,8 +53,8 @@ void goto_symext::symex_decl(statet &state, const symbol_exprt &expr)
     else
       rhs=exprt(ID_invalid);
 
-    state.rename<goto_symex_statet::L1>(rhs, ns);
-    state.value_set.assign(ssa, rhs, ns, true, false);
+    exprt l1_rhs = state.rename<goto_symex_statet::L1>(std::move(rhs), ns);
+    state.value_set.assign(ssa, l1_rhs, ns, true, false);
   }
 
   // prevent propagation
@@ -69,7 +69,11 @@ void goto_symext::symex_decl(statet &state, const symbol_exprt &expr)
   symex_renaming_levelt::increase_counter(level2_it);
   const bool record_events=state.record_events;
   state.record_events=false;
-  state.rename(ssa, ns);
+  exprt expr_l2 = state.rename(std::move(ssa), ns);
+  INVARIANT(
+    expr_l2.id() == ID_symbol && expr_l2.get_bool(ID_C_SSA_symbol),
+    "symbol to declare should not be replaced by constant propagation");
+  ssa = to_ssa_expr(expr_l2);
   state.record_events=record_events;
 
   // we hide the declaration of auxiliary variables

src/goto-symex/symex_dereference.cpp

@@ -357,11 +357,11 @@ void goto_symext::dereference(exprt &expr, statet &state)
   // from different frames. Would be enough to rename
   // symbols whose address is taken.
   PRECONDITION(!state.call_stack().empty());
-  state.rename<goto_symex_statet::L1>(expr, ns);
+  exprt l1_expr = state.rename<goto_symex_statet::L1>(expr, ns);
 
   // start the recursion!
-  dereference_rec(expr, state);
+  dereference_rec(l1_expr, state);
   // dereferencing may introduce new symbol_exprt
   // (like __CPROVER_memory)
-  state.rename<goto_symex_statet::L1>(expr, ns);
+  expr = state.rename<goto_symex_statet::L1>(std::move(l1_expr), ns);
 }

src/goto-symex/symex_function_call.cpp

@@ -261,7 +261,7 @@ void goto_symext::symex_function_call_code(
   // read the arguments -- before the locality renaming
   exprt::operandst arguments = call.arguments();
   for(auto &a : arguments)
-    state.rename(a, ns);
+    a = state.rename(std::move(a), ns);
 
   // we hide the call if the caller and callee are both hidden
   const bool hidden = state.top().hidden_function && goto_function.is_hidden();

src/goto-symex/symex_goto.cpp

@@ -37,8 +37,7 @@ void goto_symext::symex_goto(statet &state)
   exprt old_guard = instruction.get_condition();
   clean_expr(old_guard, state, false);
 
-  exprt new_guard=old_guard;
-  state.rename(new_guard, ns);
+  exprt new_guard = state.rename(old_guard, ns);
   do_simplify(new_guard);
 
   if(new_guard.is_false())
@@ -269,8 +268,7 @@ void goto_symext::symex_goto(statet &state)
         original_source,
         symex_targett::assignment_typet::GUARD);
 
-      guard_expr = boolean_negate(guard_symbol_expr);
-      state.rename(guard_expr, ns);
+      guard_expr = state.rename(boolean_negate(guard_symbol_expr), ns);
     }
 
     if(state.has_saved_jump_target)

src/goto-symex/symex_main.cpp

@@ -95,18 +95,18 @@ void goto_symext::vcc(
   }
 
   // now rename, enables propagation
-  state.rename(expr, ns);
+  exprt l2_expr = state.rename(std::move(expr), ns);
 
   // now try simplifier on it
-  do_simplify(expr);
+  do_simplify(l2_expr);
 
-  if(expr.is_true())
+  if(l2_expr.is_true())
     return;
 
-  state.guard.guard_expr(expr);
+  state.guard.guard_expr(l2_expr);
 
   state.remaining_vccs++;
-  target.assertion(state.guard.as_expr(), expr, msg, state.source);
+  target.assertion(state.guard.as_expr(), l2_expr, msg, state.source);
 }
 
 void goto_symext::symex_assume(statet &state, const exprt &cond)
@@ -410,8 +410,7 @@ void goto_symext::symex_step(
     {
       exprt tmp = instruction.get_condition();
       clean_expr(tmp, state, false);
-      state.rename(tmp, ns);
-      symex_assume(state, tmp);
+      symex_assume(state, state.rename(std::move(tmp), ns));
     }
 
     symex_transition(state);