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simplify_acc: fix an infinite loop

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* spot/twaalgos/cleanacc.cc (fuse_mark_here): Fix incorrect cancelling
of n-ary subterms, causing an invalid acceptance condition, and then
an infinite loop.
* tests/python/simplacc.py: Add test case.
This commit is contained in:
Alexandre Duret-Lutz 2020-04-16 22:40:49 +02:00
parent 68012e6a85
commit b62e1bb13c
2 changed files with 28 additions and 9 deletions
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21
spot/twaalgos/cleanacc.cc
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@ -367,7 +367,7 @@ namespace spot
return {};
}
acc_cond::mark_t find_interm_rec(acc_cond::acc_word* pos)
acc_cond::mark_t find_interm_rec(const acc_cond::acc_word* pos)
{
acc_cond::acc_op wanted;
auto topop = pos->sub.op;
@ -489,13 +489,13 @@ namespace spot
assert(topop == acc_cond::acc_op::Or);
}
// Return a vector of "singleton-sets" of
// Build a vector of "singleton-sets" of
// the wanted type in the operand of the
// pointed Or/And operator. For instance,
// assuming wanted=Inf and pos points to
//
// Inf({1})|Inf({2,3})|Fin({4})
// |Inf({5})|Inf({5})|Inf({6})
// |Inf({5})|Inf({5,6})
//
// This returns [({1}, Inf({1})),
// ({5}, Inf({5}))]].
@ -522,9 +522,8 @@ namespace spot
break;
case acc_cond::acc_op::And:
case acc_cond::acc_op::Or:
// On
// Fin(a)&(Fin(b)&Inf(c)|Fin(d))
// where we'd like to return [({a},...),
// On Fin(a)&(Fin(b)&Inf(c)|Fin(d))
// we'd like to build [({a},...),
// ({b,d},...)] and decide later that
// {b,d} can receive {a} if they
// (b and d) are both used once.
@ -556,12 +555,18 @@ namespace spot
if (p.first != can_receive &&
p.first.lowest() == p.first)
{
to_fuse.emplace_back(p.first, can_receive);
// Mark fused singletons as false,
// so that a future call to
// find_fusable() ignores them.
if (p.second->sub.op == acc_cond::acc_op::Fin)
p.second->sub.op = acc_cond::acc_op::Inf;
else
else if (p.second->sub.op ==
acc_cond::acc_op::Inf)
p.second->sub.op = acc_cond::acc_op::Fin;
else
continue;
p.second[-1].mark = {};
to_fuse.emplace_back(p.first, can_receive);
}
};