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Added bv*mul_no*flow handling in bv_rewriter.

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Fixes #657.
This commit is contained in:
Christoph M. Wintersteiger 2016-06-24 16:25:11 +01:00
parent e9eb88e1b3
commit 70301ad3c8
2 changed files with 62 additions and 1 deletions
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60
src/ast/rewriter/bv_rewriter.cpp
View file

@ -189,6 +189,12 @@ br_status bv_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * cons
return mk_bv_comp(args[0], args[1], result);
case OP_MKBV:
return mk_mkbv(num_args, args, result);
case OP_BSMUL_NO_OVFL:
return mk_bvsmul_no_overflow(num_args, args, result);
case OP_BUMUL_NO_OVFL:
return mk_bvumul_no_overflow(num_args, args, result);
case OP_BSMUL_NO_UDFL:
return mk_bvsmul_no_underflow(num_args, args, result);
default:
return BR_FAILED;
}
@ -2186,6 +2192,58 @@ br_status bv_rewriter::mk_mkbv(unsigned num, expr * const * args, expr_ref & res
return BR_FAILED;
}
br_status bv_rewriter::mk_bvsmul_no_overflow(unsigned num, expr * const * args, expr_ref & result) {
SASSERT(num == 2);
unsigned bv_sz;
rational a0_val, a1_val;
if (m_util.is_numeral(args[0], a0_val, bv_sz) &&
m_util.is_numeral(args[1], a1_val, bv_sz)) {
rational mr = a0_val * a1_val;
rational lim = rational::power_of_two(bv_sz-1);
result = (mr < lim) ? m().mk_true() : m().mk_false();
return BR_DONE;
}
return BR_FAILED;
}
br_status bv_rewriter::mk_bvumul_no_overflow(unsigned num, expr * const * args, expr_ref & result) {
SASSERT(num == 2);
unsigned bv_sz;
rational a0_val, a1_val;
if (m_util.is_numeral(args[0], a0_val, bv_sz) &&
m_util.is_numeral(args[1], a1_val, bv_sz)) {
rational mr = a0_val * a1_val;
rational lim = rational::power_of_two(bv_sz);
result = (mr < lim) ? m().mk_true() : m().mk_false();
return BR_DONE;
}
return BR_FAILED;
}
br_status bv_rewriter::mk_bvsmul_no_underflow(unsigned num, expr * const * args, expr_ref & result) {
SASSERT(num == 2);
unsigned bv_sz;
rational a0_val, a1_val;
if (m_util.is_numeral(args[0], a0_val, bv_sz) &&
m_util.is_numeral(args[1], a1_val, bv_sz)) {
rational ul = rational::power_of_two(bv_sz);
rational lim = rational::power_of_two(bv_sz-1);
if (a0_val >= lim) a0_val -= ul;
if (a1_val >= lim) a1_val -= ul;
rational mr = a0_val * a1_val;
rational neg_lim = -lim;
TRACE("bv_rewriter_bvsmul_no_underflow", tout << "a0:" << a0_val << " a1:" << a1_val << " mr:" << mr << " neg_lim:" << neg_lim << std::endl;);
result = (mr >= neg_lim) ? m().mk_true() : m().mk_false();
return BR_DONE;
}
return BR_FAILED;
}
template class poly_rewriter<bv_rewriter_core>;

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

@ -123,6 +123,9 @@ class bv_rewriter : public poly_rewriter<bv_rewriter_core> {
br_status mk_blast_eq_value(expr * lhs, expr * rhs, expr_ref & result);
br_status mk_eq_concat(expr * lhs, expr * rhs, expr_ref & result);
br_status mk_mkbv(unsigned num, expr * const * args, expr_ref & result);
br_status mk_bvsmul_no_overflow(unsigned num, expr * const * args, expr_ref & result);
br_status mk_bvumul_no_overflow(unsigned num, expr * const * args, expr_ref & result);
br_status mk_bvsmul_no_underflow(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);