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useful string rewrites

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2023-10-26 03:48:50 -07:00
parent 5622fd1362
commit 0b8d7b755d
1 changed files with 22 additions and 1 deletions
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23
src/ast/rewriter/seq_rewriter.cpp
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@ -828,6 +828,7 @@ br_status seq_rewriter::mk_seq_concat(expr* a, expr* b, expr_ref& result) {
br_status seq_rewriter::mk_seq_length(expr* a, expr_ref& result) {
zstring b;
rational r;
m_es.reset();
str().get_concat(a, m_es);
unsigned len = 0;
@ -867,6 +868,13 @@ br_status seq_rewriter::mk_seq_length(expr* a, expr_ref& result) {
result = str().mk_length(z);
return BR_REWRITE1;
}
// len(extract(x, 0, z)) = min(z, len(x))
if (str().is_extract(a, x, y, z) &&
m_autil.is_numeral(y, r) && r.is_zero()) {
expr* len_x = str().mk_length(x);
result = m().mk_ite(m_autil.mk_le(len_x, z), len_x, z);
return BR_REWRITE2;
}
#if 0
expr* s = nullptr, *offset = nullptr, *length = nullptr;
if (str().is_extract(a, s, offset, length)) {
@ -1209,6 +1217,11 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
constantPos &= pos.is_unsigned();
constantLen &= len.is_unsigned();
if (constantPos && constantLen && len == 1) {
result = str().mk_at(a, b);
return BR_REWRITE1;
}
if (constantPos && constantLen && constantBase) {
unsigned _pos = pos.get_unsigned();
unsigned _len = len.get_unsigned();
@ -1548,9 +1561,17 @@ bool seq_rewriter::reduce_by_char(expr_ref& r, expr* ch, unsigned depth) {
*/
br_status seq_rewriter::mk_seq_at(expr* a, expr* b, expr_ref& result) {
zstring c;
rational r;
rational r, offset_r, len_r;
expr* offset, *a1, *len;
expr_ref_vector lens(m());
sort* sort_a = a->get_sort();
if (str().is_extract(a, a1, offset, len) &&
m_autil.is_numeral(offset, offset_r) && offset_r.is_zero() &&
m_autil.is_numeral(len, len_r) && m_autil.is_numeral(b, r) &&
r < len_r) {
result = str().mk_at(a1, b);
return BR_REWRITE1;
}
if (!get_lengths(b, lens, r)) {
return BR_FAILED;
}