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CHC encoder: universally quantify nondeterministic choices #6958

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Merged
merged 1 commit into from
Jul 29, 2022
Merged

CHC encoder: universally quantify nondeterministic choices #6958

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4 changes: 2 additions & 2 deletions regression/goto-instrument-chc/basic/nondet1.desc
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,6 @@ nondet1.c
--horn
^EXIT=0$
^SIGNAL=0$
^\(assert \(forall \( \(|__CPROVER_rounding_mode| \(_ BitVec 32\)\) \(|main::1::x| \(_ BitVec 32\)\) \(|main::1::y| \(_ BitVec 32\)\) \(|return_value| \(_ BitVec 32\)\) \) \(=> \(|S30Entry| |__CPROVER_rounding_mode| |main::1::x| |main::1::y| |return_value|\) \(|S30\.2| |__CPROVER_rounding_mode| |nondet::S30\.2| |main::1::y| |return_value|\)\)\)\)$
^\(assert \(forall \( \(|__CPROVER_rounding_mode| \(_ BitVec 32\)\) \(|main::1::x| \(_ BitVec 32\)\) \(|main::1::y| \(_ BitVec 32\)\) \(|return_value| \(_ BitVec 32\)\) \) \(=> \(|S30\.2| |__CPROVER_rounding_mode| |main::1::x| |main::1::y| |return_value|\) \(= |main::1::x| \(_ bv20 32\)\)\)\)\)$
^\(assert \(forall \( \(__CPROVER_rounding_mode \(_ BitVec 32\)\) \(|main::1::x| \(_ BitVec 32\)\) \(|main::1::y| \(_ BitVec 32\)\) \(return_value \(_ BitVec 32\)\) \(|nondet::S30\.2| \(_ BitVec 32\)\) \) \(=> \(S30Entry __CPROVER_rounding_mode |main::1::x| |main::1::y| return_value\) \(S30\.2 __CPROVER_rounding_mode |nondet::S30\.2| |main::1::y| return_value\)\)\)\)$
^\(assert \(forall \( \(__CPROVER_rounding_mode \(_ BitVec 32\)\) \(|main::1::x| \(_ BitVec 32\)\) \(|main::1::y| \(_ BitVec 32\)\) \(return_value \(_ BitVec 32\)\) \) \(=> \(S30\.2 __CPROVER_rounding_mode |main::1::x| |main::1::y| return_value\) \(= |main::1::x| \(_ bv20 32\)\)\)\)\)$
--
22 changes: 17 additions & 5 deletions src/goto-instrument/horn_encoding.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -663,8 +663,14 @@ exprt state_encodingt::assignment_constraint(loct loc, exprt lhs, exprt rhs)

auto new_state = update_state_exprt(s, address, new_value);

return forall_states_expr(
loc, function_application_exprt(out_state_expr(loc), {new_state}));
forall_exprt::variablest binding = {state_expr()};
binding.insert(binding.end(), nondet_symbols.begin(), nondet_symbols.end());

return forall_exprt(
std::move(binding),
implies_exprt(
function_application_exprt(in_state_expr(loc), {state_expr()}),
function_application_exprt(out_state_expr(loc), {new_state})));
}

void state_encodingt::setup_incoming(const goto_functiont &goto_function)
Expand Down Expand Up @@ -1042,11 +1048,17 @@ exprt variable_encoding(exprt src, const binding_exprt::variablest &variables)
{
auto &forall_expr = to_forall_expr(src);
if(
forall_expr.variables().size() == 1 &&
forall_expr.symbol().type().id() == ID_state)
forall_expr.variables().size() >= 1 &&
forall_expr.variables().front().type().id() == ID_state)
{
// replace 'state' by the program variables
forall_exprt::variablest new_variables = variables;
new_variables.insert(
new_variables.end(),
forall_expr.variables().begin() + 1,
forall_expr.variables().end());
forall_expr
.variables() = variables;
.variables() = std::move(new_variables);
return std::move(forall_expr);
}
}
Expand Down