Fix a bug with the cache in the BDD to exprt conversion #5005
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romainbrenguier
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allredj
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peterschrammel
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kroening
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src/solvers/prop/bdd_expr.cpp
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| return a.op0(); | ||
| return not_exprt{a}; | ||
| } | ||
|
|
danpoe
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Aug 13, 2019
Because of how the cache is handled, the expression for one node and its complement will collide in the cache. It is better to get rid of the complement argument and only reason about nodes.
This is more robust as the expression a&!b could equivalently be written !b&a, !(!a|b), !(b|!a)...
This tests a few more cases with BDDs. In particular, the last case would have failed before the bugfix for the BDD cache.
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Passed Diffblue compatibility checks (cbmc commit: b8850ed).
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There was a bug in which the result for a node and for it's complement would have been stored in the same map entry, this happens with the Cudd library which uses complemented nodes (a node and it's negation are stored at the same address).