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extend constant folding for bit-vector overflow/underflow operators, #657

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2016-06-24 07:43:05 -07:00
parent 41edf5f91e
commit 914bf2ff3b
10 changed files with 332 additions and 57 deletions
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96
src/ast/rewriter/bv_rewriter.cpp
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@ -20,6 +20,7 @@ Notes:
#include"bv_rewriter_params.hpp"
#include"poly_rewriter_def.h"
#include"ast_smt2_pp.h"
#include"bit_blaster/bit_blaster.h"
void bv_rewriter::updt_local_params(params_ref const & _p) {
@ -189,6 +190,15 @@ 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_BUMUL_NO_OVFL:
SASSERT(num_args == 2);
return mk_bv_umul_no_ovfl(args[0], args[1], result);
case OP_BSMUL_NO_OVFL:
SASSERT(num_args == 2);
return mk_bv_smul_no_ovfl(args[0], args[1], result);
case OP_BSMUL_NO_UDFL:
SASSERT(num_args == 2);
return mk_bv_smul_no_udfl(args[0], args[1], result);
default:
return BR_FAILED;
}
@ -1100,6 +1110,92 @@ br_status bv_rewriter::mk_concat(unsigned num_args, expr * const * args, expr_re
return BR_DONE;
}
br_status bv_rewriter::mk_bv_umul_no_ovfl(expr * arg1, expr * arg2, expr_ref& result) {
rational val1, val2;
unsigned bv_size;
bool is_num1 = is_numeral(arg1, val1, bv_size);
bool is_num2 = is_numeral(arg2, val2, bv_size);
if (is_num1 && (val1.is_zero() || val1.is_one())) {
result = m().mk_true();
return BR_DONE;
}
if (is_num2 && (val2.is_zero() || val2.is_one())) {
result = m().mk_true();
return BR_DONE;
}
if (is_num1 && is_num2) {
SASSERT(!val1.is_neg());
SASSERT(!val2.is_neg());
rational r = val1 * val2;
result = m().mk_bool_val(r < rational(2).expt(bv_size));
return BR_DONE;
}
return BR_FAILED;
}
br_status bv_rewriter::mk_bv_smul_no_ovfl(expr * arg1, expr * arg2, expr_ref& result) {
rational val1, val2;
unsigned bv_size;
bool is_num1 = is_numeral(arg1, val1, bv_size);
bool is_num2 = is_numeral(arg2, val2, bv_size);
if (is_num1 && (val1.is_zero() || val1.is_one())) {
result = m().mk_true();
return BR_DONE;
}
if (is_num2 && (val2.is_zero() || val2.is_one())) {
result = m().mk_true();
return BR_DONE;
}
if (is_num1 && is_num2) {
bit_blaster_params params;
bit_blaster blaster(m(), params);
SASSERT(!val1.is_neg());
SASSERT(!val2.is_neg());
expr_ref_vector bits1(m()), bits2(m());
for (unsigned i = 0; i < bv_size; ++i) {
bits1.push_back(m().mk_bool_val(!val1.is_even()));
bits2.push_back(m().mk_bool_val(!val2.is_even()));
val1 = div(val1, rational(2));
val2 = div(val2, rational(2));
}
blaster.mk_smul_no_overflow(bits1.size(), bits1.c_ptr(), bits2.c_ptr(), result);
return BR_DONE;
}
return BR_FAILED;
}
br_status bv_rewriter::mk_bv_smul_no_udfl(expr * arg1, expr * arg2, expr_ref& result) {
rational val1, val2;
unsigned bv_size;
bool is_num1 = is_numeral(arg1, val1, bv_size);
bool is_num2 = is_numeral(arg2, val2, bv_size);
if (is_num1 && (val1.is_zero() || val1.is_one())) {
result = m().mk_true();
return BR_DONE;
}
if (is_num2 && (val2.is_zero() || val2.is_one())) {
result = m().mk_true();
return BR_DONE;
}
if (is_num1 && is_num2) {
bit_blaster_params params;
bit_blaster blaster(m(), params);
SASSERT(!val1.is_neg());
SASSERT(!val2.is_neg());
expr_ref_vector bits1(m()), bits2(m());
for (unsigned i = 0; i < bv_size; ++i) {
bits1.push_back(m().mk_bool_val(!val1.is_even()));
bits2.push_back(m().mk_bool_val(!val2.is_even()));
val1 = div(val1, rational(2));
val2 = div(val2, rational(2));
}
blaster.mk_smul_no_underflow(bits1.size(), bits1.c_ptr(), bits2.c_ptr(), result);
return BR_DONE;
}
return BR_FAILED;
}
br_status bv_rewriter::mk_zero_extend(unsigned n, expr * arg, expr_ref & result) {
if (n == 0) {
result = arg;