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fix #7011

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2023-11-29 15:08:08 -08:00
parent 9efe6f6afa
commit e9abdbb7a4
2 changed files with 15 additions and 4 deletions
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16
src/ast/rewriter/bv_rewriter.cpp
View file

@ -216,7 +216,7 @@ br_status bv_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * cons
case OP_BUSUB_OVFL:
return mk_bvusub_underflow(num_args, args, result);
case OP_BSSUB_OVFL:
return mk_bvssub_overflow(num_args, args, result);
return mk_bvssub_under_overflow(num_args, args, result);
default:
return BR_FAILED;
}
@ -3081,19 +3081,29 @@ br_status bv_rewriter::mk_bvusub_underflow(unsigned num, expr * const * args, ex
return status;
}
br_status bv_rewriter::mk_bvssub_overflow(unsigned num, expr * const * args, expr_ref & result) {
//
// no_overflow := if t2 = min_int then t1 <s 0 else no_overflow(t1 + -t2)
// no_underflow := 0 <s -t2 => no_underflow(t1 + -t2)
// over_underflow := 0 <s -t2 & under_overflow+(t1 + -t2) || t2 = min_int & t1 >=s 0 || t2 != min_int & under_overflow+(t1 + -t2)
// := if t2 == min_int then t1 >=s 0 else under_overflow+(t1 + -t2)
// because when 0 <s min_int = false
//
br_status bv_rewriter::mk_bvssub_under_overflow(unsigned num, expr * const * args, expr_ref & result) {
SASSERT(num == 2);
SASSERT(get_bv_size(args[0]) == get_bv_size(args[1]));
auto sz = get_bv_size(args[0]);
auto minSigned = mk_numeral(rational::power_of_two(sz-1), sz);
expr_ref bvsaddo {m};
expr * args2[2] = { args[0], m_util.mk_bv_neg(args[1]) };
auto bvsaddo_stat = mk_bvsadd_overflow(2, args2, bvsaddo);
auto bvsaddo_stat = mk_bvsadd_over_underflow(2, args2, bvsaddo);
SASSERT(bvsaddo_stat != BR_FAILED); (void)bvsaddo_stat;
auto first_arg_ge_zero = m_util.mk_sle(mk_zero(sz), args[0]);
result = m.mk_ite(m.mk_eq(args[1], minSigned), first_arg_ge_zero, bvsaddo);
return BR_REWRITE_FULL;
}
//br_status bv_rewriter::mk_bvssub_overflow(unsigned num, expr * const * args, expr_ref & result) {
//}
br_status bv_rewriter::mk_bvsdiv_overflow(unsigned num, expr * const * args, expr_ref & result) {
SASSERT(num == 2);
SASSERT(get_bv_size(args[0]) == get_bv_size(args[1]));

3
src/ast/rewriter/bv_rewriter.h
View file

@ -153,7 +153,8 @@ class bv_rewriter : public poly_rewriter<bv_rewriter_core> {
br_status mk_bvsadd_over_underflow(unsigned num, expr * const * args, expr_ref & result);
br_status mk_bvusub_underflow(unsigned num, expr * const * args, expr_ref & result);
br_status mk_bvssub_overflow(unsigned num, expr * const * args, expr_ref & result);
// br_status mk_bvssub_overflow(unsigned num, expr * const * args, expr_ref & result);
br_status mk_bvssub_under_overflow(unsigned num, expr * const * args, expr_ref & result);
bool is_minus_one_times_t(expr * arg);
void mk_t1_add_t2_eq_c(expr * t1, expr * t2, expr * c, expr_ref & result);