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re rewriter for loop

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2019-09-23 09:33:08 -07:00
parent 6041cb246f
commit 64d4e599c1
1 changed files with 16 additions and 8 deletions
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24
src/ast/rewriter/seq_rewriter.cpp
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@ -1820,31 +1820,39 @@ br_status seq_rewriter::mk_re_inter(expr* a, expr* b, expr_ref& result) {
br_status seq_rewriter::mk_re_loop(func_decl* f, unsigned num_args, expr* const* args, expr_ref& result) {
rational n1, n2;
unsigned lo, hi;
unsigned lo, hi, lo2, hi2, np;
expr* a = nullptr;
switch (num_args) {
case 1:
if (f->get_num_parameters() == 2 && f->get_parameter(0).get_int() > f->get_parameter(1).get_int()) {
result = m_util.re.mk_loop(args[0], f->get_parameter(1).get_int(), f->get_parameter(1).get_int());
np = f->get_num_parameters();
lo2 = np > 0 ? f->get_parameter(0).get_int() : 0;
hi2 = np > 1 ? f->get_parameter(1).get_int() : 0;
if (np == 2 && lo2 > hi2) {
result = m_util.re.mk_loop(args[0], hi2, hi2);
return BR_REWRITE1;
}
// (loop (loop a lo) lo2) = (loop lo*lo2)
if (m_util.re.is_loop(args[0], a, lo) && f->get_num_parameters() == 1) {
result = m_util.re.mk_loop(a, f->get_parameter(0).get_int() * lo);
if (m_util.re.is_loop(args[0], a, lo) && np == 1) {
result = m_util.re.mk_loop(a, lo2 * lo);
return BR_REWRITE1;
}
// (loop (loop a l l) h h) = (loop a l*h l*h)
if (m_util.re.is_loop(args[0], a, lo, hi) && np == 2 && lo == hi && lo2 == hi2) {
result = m_util.re.mk_loop(a, lo2 * lo, hi2 * hi);
return BR_REWRITE1;
}
// (loop a 0 0) = ""
if (f->get_num_parameters() == 2 && f->get_parameter(1).get_int() == 0) {
if (np == 2 && hi2 == 0) {
result = m_util.re.mk_to_re(m_util.str.mk_empty(m_util.re.to_seq(m().get_sort(args[0]))));
return BR_DONE;
}
// (loop a 1 1) = a
if (f->get_num_parameters() == 2 && f->get_parameter(0).get_int() == 1 && f->get_parameter(1).get_int() == 1) {
if (np == 2 && lo2 == 1 && hi2 == 1) {
result = args[0];
return BR_DONE;
}
// (loop a 0) = a*
if (f->get_num_parameters() == 1 && f->get_parameter(0).get_int() == 0) {
if (np == 1 && lo2 == 0) {
result = m_util.re.mk_star(args[0]);
return BR_DONE;
}