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Make return type of set_l*_indices be a renamedt [blocks: #4333] #3986

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Merged
merged 3 commits into from
Mar 6, 2019
+34 −48
Merged

Make return type of set_l*_indices be a renamedt [blocks: #4333] #3986

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b49354d
Make set_l0_indices return a renamedt
romainbrenguier Mar 5, 2019
2265305
Make set_l1_indices return a renamedt
romainbrenguier Mar 5, 2019
1bb05b6
Make set_l2_indices return a renamedt
romainbrenguier Mar 5, 2019
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68 changes: 24 additions & 44 deletions src/goto-symex/goto_symex_state.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -188,7 +188,7 @@ void goto_symex_statet::assignment(
const auto level2_it =
level2.current_names.emplace(l1_identifier, std::make_pair(lhs, 0)).first;
symex_renaming_levelt::increase_counter(level2_it);
set_l2_indices(lhs, ns);
lhs = set_l2_indices(std::move(lhs), ns).get();

// in case we happen to be multi-threaded, record the memory access
bool is_shared=l2_thread_write_encoding(lhs, ns);
Expand Down Expand Up @@ -235,37 +235,22 @@ void goto_symex_statet::assignment(
#endif
}

void goto_symex_statet::set_l0_indices(
ssa_exprt &ssa_expr,
const namespacet &ns)
renamedt<ssa_exprt, L0>
goto_symex_statet::set_l0_indices(ssa_exprt ssa_expr, const namespacet &ns)
{
renamedt<ssa_exprt, L0> renamed =
level0(std::move(ssa_expr), ns, source.thread_nr);
ssa_expr = renamed.get();
return level0(std::move(ssa_expr), ns, source.thread_nr);
}

void goto_symex_statet::set_l1_indices(
ssa_exprt &ssa_expr,
const namespacet &ns)
renamedt<ssa_exprt, L1>
goto_symex_statet::set_l1_indices(ssa_exprt ssa_expr, const namespacet &ns)
{
if(!ssa_expr.get_level_2().empty())
return;
if(!ssa_expr.get_level_1().empty())
return;
renamedt<ssa_exprt, L1> l1 =
level1(level0(std::move(ssa_expr), ns, source.thread_nr));
ssa_expr = l1.get();
return level1(level0(std::move(ssa_expr), ns, source.thread_nr));
}

void goto_symex_statet::set_l2_indices(
ssa_exprt &ssa_expr,
const namespacet &ns)
renamedt<ssa_exprt, L2>
goto_symex_statet::set_l2_indices(ssa_exprt ssa_expr, const namespacet &ns)
{
if(!ssa_expr.get_level_2().empty())
return;
renamedt<ssa_exprt, L2> l2 =
level2(level1(level0(std::move(ssa_expr), ns, source.thread_nr)));
ssa_expr = l2.get();
return level2(level1(level0(std::move(ssa_expr), ns, source.thread_nr)));
}

template <levelt level>
Expand All @@ -275,9 +260,9 @@ ssa_exprt goto_symex_statet::rename_ssa(ssa_exprt ssa, const namespacet &ns)
level == L0 || level == L1,
"rename_ssa can only be used for levels L0 and L1");
if(level == L0)
set_l0_indices(ssa, ns);
ssa = set_l0_indices(std::move(ssa), ns).get();
else if(level == L1)
set_l1_indices(ssa, ns);
ssa = set_l1_indices(std::move(ssa), ns).get();
else
UNREACHABLE;

Expand Down Expand Up @@ -312,7 +297,7 @@ exprt goto_symex_statet::rename(exprt expr, const namespacet &ns)
}
else if(level==L2)
{
set_l1_indices(ssa, ns);
ssa = set_l1_indices(std::move(ssa), ns).get();
rename<level>(expr.type(), ssa.get_identifier(), ns);
ssa.update_type();

Expand All @@ -333,7 +318,7 @@ exprt goto_symex_statet::rename(exprt expr, const namespacet &ns)
if(p_it != propagation.end())
expr=p_it->second; // already L2
else
set_l2_indices(ssa, ns);
ssa = set_l2_indices(std::move(ssa), ns).get();
}
}
}
Expand Down Expand Up @@ -447,8 +432,7 @@ bool goto_symex_statet::l2_thread_read_encoding(
if(!no_write.op().is_false())
cond |= guardt{no_write.op()};

if_exprt tmp(cond.as_expr(), ssa_l1, ssa_l1);
set_l2_indices(to_ssa_expr(tmp.true_case()), ns);
const renamedt<ssa_exprt, L2> l2_true_case = set_l2_indices(ssa_l1, ns);

if(a_s_read.second.empty())
{
Expand All @@ -458,14 +442,13 @@ bool goto_symex_statet::l2_thread_read_encoding(
symex_renaming_levelt::increase_counter(level2_it);
a_s_read.first=level2.current_count(l1_identifier);
}
const renamedt<ssa_exprt, L2> l2_false_case = set_l2_indices(ssa_l1, ns);

to_ssa_expr(tmp.false_case()).set_level_2(a_s_read.first);

exprt tmp;
if(cond.is_false())
{
exprt t=tmp.false_case();
t.swap(tmp);
}
tmp = l2_false_case.get();
else
tmp = if_exprt{cond.as_expr(), l2_true_case.get(), l2_false_case.get()};

const bool record_events_bak=record_events;
record_events=false;
Expand All @@ -481,8 +464,7 @@ bool goto_symex_statet::l2_thread_read_encoding(
source,
symex_targett::assignment_typet::PHI);

set_l2_indices(ssa_l1, ns);
expr=ssa_l1;
expr = set_l2_indices(std::move(ssa_l1), ns).get();

a_s_read.second.push_back(guard);
if(!no_write.op().is_false())
Expand All @@ -498,15 +480,13 @@ bool goto_symex_statet::l2_thread_read_encoding(
// No event and no fresh index, but avoid constant propagation
if(!record_events)
{
set_l2_indices(ssa_l1, ns);
expr=ssa_l1;
expr = set_l2_indices(std::move(ssa_l1), ns).get();
return true;
}

// produce a fresh L2 name
symex_renaming_levelt::increase_counter(level2_it);
set_l2_indices(ssa_l1, ns);
expr=ssa_l1;
expr = set_l2_indices(std::move(ssa_l1), ns).get();

// and record that
INVARIANT_STRUCTURED(
Expand Down Expand Up @@ -563,7 +543,7 @@ void goto_symex_statet::rename_address(exprt &expr, const namespacet &ns)
ssa_exprt &ssa=to_ssa_expr(expr);

// only do L1!
set_l1_indices(ssa, ns);
ssa = set_l1_indices(std::move(ssa), ns).get();

rename<level>(expr.type(), ssa.get_identifier(), ns);
ssa.update_type();
Expand Down
6 changes: 3 additions & 3 deletions src/goto-symex/goto_symex_state.h
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Expand Up @@ -114,13 +114,13 @@ class goto_symex_statet final : public goto_statet
void rename_address(exprt &expr, const namespacet &ns);

/// Update level 0 values.
void set_l0_indices(ssa_exprt &expr, const namespacet &ns);
renamedt<ssa_exprt, L0> set_l0_indices(ssa_exprt expr, const namespacet &ns);

/// Update level 0 and 1 values.
void set_l1_indices(ssa_exprt &expr, const namespacet &ns);
renamedt<ssa_exprt, L1> set_l1_indices(ssa_exprt expr, const namespacet &ns);

/// Update level 0, 1 and 2 values.
void set_l2_indices(ssa_exprt &expr, const namespacet &ns);
renamedt<ssa_exprt, L2> set_l2_indices(ssa_exprt expr, const namespacet &ns);

// this maps L1 names to (L2) types
typedef std::unordered_map<irep_idt, typet> l1_typest;
Expand Down
8 changes: 7 additions & 1 deletion src/goto-symex/renaming_level.cpp
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Expand Up @@ -46,8 +46,12 @@ operator()(ssa_exprt ssa_expr, const namespacet &ns, unsigned thread_nr) const
renamedt<ssa_exprt, L1> symex_level1t::
operator()(renamedt<ssa_exprt, L0> l0_expr) const
{
if(!l0_expr.get().get_level_1().empty())
if(
!l0_expr.get().get_level_1().empty() ||
!l0_expr.get().get_level_2().empty())
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To make sure there is no change in behaviour this will require an INVARIANT that !l0_expr.get().get_level_2().empty() implies !l0_expr.get().get_level_1().empty(). And I'm not convinced that holds, because a global variable would not need L1 renaming, even when L2 is non-empty.

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@romainbrenguier romainbrenguier Mar 6, 2019 •
edited
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Yes this does not hold, so we can't add an invariant. The reason this does not change the behaviour is that it is only called from set_l1_indices which had the same check until this commit.

{
return renamedt<ssa_exprt, L1>{std::move(l0_expr.value)};
}

const irep_idt l0_name = l0_expr.get().get_l1_object_identifier();

Expand All @@ -63,6 +67,8 @@ operator()(renamedt<ssa_exprt, L0> l0_expr) const
renamedt<ssa_exprt, L2> symex_level2t::
operator()(renamedt<ssa_exprt, L1> l1_expr) const
{
if(!l1_expr.get().get_level_2().empty())
return renamedt<ssa_exprt, L2>{std::move(l1_expr.value)};
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This change seems surprising to me, but I'm likely just missing something. Would you mind explaining?

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As for the symex_level1t case, it does not change the behaviour because it is only called from set_l2_indices which had the same check until this commit. We need the check to be here and not in set_l2_indices, because set_l2_indices cannot create renamedt expression, the constructor is private, this ensures we cannot make a renamedt without checking it has the right indices set.

l1_expr.value.set_level_2(current_count(l1_expr.get().get_identifier()));
return renamedt<ssa_exprt, L2>{std::move(l1_expr.value)};
}
Expand Down