- avoid more platform specific behavior when using m_mk_extract,
- rename mk_eq in bool_rewriter to mk_eq_plain to distinguish it from mk_eq_rw
- rework bv_lookahead to be more closely based on sls_engine, which has much better heuristic behavior than attempt 1.
After introducing the rewriter.sort_disjunctions option (#6774), I
noticed a segfault in a Z3 run that was working fine for me before the
PR.
I traced the difference to a slight discrepancy between the first patch
I submitted and the one we ended up merging: my first version would skip
sorting the disjuncts in mk_nflat_core, but still return BR_DONE, while
the patch in master returns BR_FAILED instead.
This patch fixes that problem, and it makes slightly more sense to me to
return a BR_DONE since, if `s` is true, some disjunct (e.g. a `false`
or a repeat) might have been simplified away. However I don't fully
understand this code.
... and I can't say I understand why the segfault happens. Perhaps that
is a separate issue?
This is the file to reproduce:
https://gist.github.com/mtzguido/b7360c74d3d2e42d89f1bd9149ad26f6
Here's a stack trace of the failure, mk_nflat_or_core is not involved.
```
(gdb) where
#0 0x0000555555b98497 in smt::context::get_lit_assignment(unsigned int) const ()
#1 0x0000555555b984cb in smt::context::get_assignment(sat::literal) const ()
#2 0x0000555555b98504 in smt::context::get_assignment(unsigned int) const ()
#3 0x0000555555ca83b8 in smt::context::get_assignment_core(expr*) const ()
#4 0x0000555555c9af5a in smt::context::get_assignment(expr*) const ()
#5 0x0000555555d7bd1d in (anonymous namespace)::has_child_assigned_to(smt::context&, app*, lbool, expr*&, unsigned int) ()
#6 0x0000555555d7c413 in (anonymous namespace)::rel_case_split_queue::next_case_split_core(ptr_vector<expr>&, unsigned int&, unsigned int&, lbool&) ()
#7 0x0000555555d7c589 in (anonymous namespace)::rel_case_split_queue::next_case_split(unsigned int&, lbool&) ()
#8 0x0000555555c9c1b7 in smt::context::decide() ()
#9 0x0000555555ca39fd in smt::context::bounded_search() ()
#10 0x0000555555ca30c2 in smt::context::search() ()
#11 0x0000555555ca273d in smt::context::check(unsigned int, expr* const*, bool) ()
#12 0x0000555555cb166a in smt::kernel::check(unsigned int, expr* const*) ()
#13 0x0000555555cb9695 in (anonymous namespace)::smt_solver::check_sat_core2(unsigned int, expr* const*) ()
#14 0x00005555560dc0c6 in solver_na2as::check_sat_core(unsigned int, expr* const*) ()
#15 0x00005555560d73f3 in combined_solver::check_sat_core(unsigned int, expr* const*) ()
#16 0x00005555560d34e3 in solver::check_sat(unsigned int, expr* const*) ()
#17 0x0000555556097b26 in cmd_context::check_sat(unsigned int, expr* const*) ()
#18 0x0000555556082ff0 in smt2::parser::parse_check_sat() ()
#19 0x0000555556084dc0 in smt2::parser::parse_cmd() ()
#20 0x00005555560861b6 in smt2::parser::operator()() ()
#21 0x00005555560757e6 in parse_smt2_commands(cmd_context&, std::basic_istream<char, std::char_traits<char> >&, bool, params_ref const&, char const*) ()
#22 0x00005555555e8f68 in read_smtlib2_commands(char const*) ()
#23 0x00005555555ee6f6 in main ()
(gdb)
```
* patterns: add option for pattern decomposition (pi.decompose_patterns)
True by default, retaining current behavior.
* rewriter: add option for sorting of disjunctions (rewriter.sort_disjunctions)
True by default, retaining current behavior.
- ensure mk_extract performs simplification to distribute over extract and removing extract if the range is the entire bit-vector
- ensure bool_rewriter simplifeis disjunctions when applicable.
