feat: bv_decide short-circuit a * x = b * x
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This PR adds short-circuit support to bv_decide to accelerate certain multiplications. In particular, `a * x = b * x` can be extended to `a = b v (a * x = b * x)`. The latter is faster if `a = b` is indeed true.
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This PR adds short-circuit support to bv_decide to accelerate multiplications with shared coefficients. In particular,
a * x = b * xcan be extended toa = b v (a * x = b * x). The latter is faster ifa = bis true, asa = bmay be evaluated without considering the multiplication circuit. On the other hand, we require the multiplication circuit, asa * x = b * x -> a = bis not always true due to two's complement wrapping.We currently do not canonicalize sequences of multiplications by default. While the optional acNF mode does this, it does not take into account shared terms across an equality, such that it may canonicalize to
a * (b * c1) = a * (b * c2)instead of(a * b) * c1 = (a * b) * c2. As a result, the non-shared terms are not always lifted to the top. Consequently, a canonical rewrite for a single binary multiplication is not always sufficient. We commit a single test case that requires reasoning about three terms, and add the relevant theorem (with appropriate priority).To further generalize this, we may consider evolving acNf to take into account term structures across (in)equalities.