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add rewrite for hoisting multipliers over modular inverses

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2022-04-18 14:29:16 +02:00
parent c727e2d048
commit 98c7069f75
2 changed files with 26 additions and 1 deletions

23
src/ast/rewriter/arith_rewriter.cpp
View file

@ -700,9 +700,32 @@ br_status arith_rewriter::mk_eq_core(expr * arg1, expr * arg2, expr_ref & result
else if (m_arith_lhs || is_arith_term(arg1) || is_arith_term(arg2)) {
st = mk_le_ge_eq_core(arg1, arg2, EQ, result);
}
if (st == BR_FAILED && mk_eq_mod(arg1, arg2, result))
st = BR_REWRITE2;
return st;
}
bool arith_rewriter::mk_eq_mod(expr* arg1, expr* arg2, expr_ref& result) {
expr* x = nullptr, *y = nullptr, *z = nullptr, *u = nullptr;
rational p, k, l;
// match k*u mod p = l, where k, p, l are integers
if (m_util.is_mod(arg1, x, y) && m_util.is_numeral(y, p) &&
m_util.is_mul(x, z, u) && m_util.is_numeral(z, k) &&
m_util.is_numeral(arg2, l) && 0 <= l && l < p) {
// a*p + k*b = g
rational a, b;
rational g = gcd(p, k, a, b);
if (g == 1) {
expr_ref nb(m_util.mk_numeral(b, true), m());
result = m().mk_eq(m_util.mk_mod(u, y),
m_util.mk_mod(m_util.mk_mul(nb, arg2), y));
return true;
}
}
return false;
}
expr_ref arith_rewriter::neg_monomial(expr* e) const {
expr_ref_vector args(m());
rational a1;

4
src/ast/rewriter/arith_rewriter.h
View file

@ -104,7 +104,9 @@ class arith_rewriter : public poly_rewriter<arith_rewriter_core> {
bool divides(expr* d, expr* n, expr_ref& result);
expr_ref remove_divisor(expr* arg, expr* num, expr* den);
void flat_mul(expr* e, ptr_buffer<expr>& args);
void remove_divisor(expr* d, ptr_buffer<expr>& args);
void remove_divisor(expr* d, ptr_buffer<expr>& args);
bool mk_eq_mod(expr* arg1, expr* arg2, expr_ref& result);
public:
arith_rewriter(ast_manager & m, params_ref const & p = params_ref()):
poly_rewriter<arith_rewriter_core>(m, p) {