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Add flooring division operator

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The $div and $mod cells use truncating division semantics (rounding
towards 0), as defined by e.g. Verilog. Another rounding mode, flooring
(rounding towards negative infinity), can be used in e.g. VHDL. The
new $divfloor cell provides this flooring division.

This commit also fixes the handling of $div in opt_expr, which was
previously optimized as if it was $divfloor.
This commit is contained in:
Xiretza 2020-04-21 12:51:58 +02:00
parent 17163cf43a
commit edd8ff2c07
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GPG key ID: 17B78226F7139993
19 changed files with 213 additions and 24 deletions
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21
kernel/satgen.h
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@ -279,7 +279,7 @@ struct SatGen
bool arith_undef_handled = false;
bool is_arith_compare = cell->type.in(ID($lt), ID($le), ID($ge), ID($gt));
if (model_undef && (cell->type.in(ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($modfloor)) || is_arith_compare))
if (model_undef && (cell->type.in(ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($divfloor), ID($modfloor)) || is_arith_compare))
{
std::vector<int> undef_a = importUndefSigSpec(cell->getPort(ID::A), timestep);
std::vector<int> undef_b = importUndefSigSpec(cell->getPort(ID::B), timestep);
@ -293,7 +293,7 @@ struct SatGen
int undef_any_b = ez->expression(ezSAT::OpOr, undef_b);
int undef_y_bit = ez->OR(undef_any_a, undef_any_b);
if (cell->type.in(ID($div), ID($mod), ID($modfloor))) {
if (cell->type.in(ID($div), ID($mod), ID($divfloor), ID($modfloor))) {
std::vector<int> b = importSigSpec(cell->getPort(ID::B), timestep);
undef_y_bit = ez->OR(undef_y_bit, ez->NOT(ez->expression(ezSAT::OpOr, b)));
}
@ -935,7 +935,7 @@ struct SatGen
return true;
}
if (cell->type.in(ID($div), ID($mod), ID($modfloor)))
if (cell->type.in(ID($div), ID($mod), ID($divfloor), ID($modfloor)))
{
std::vector<int> a = importDefSigSpec(cell->getPort(ID::A), timestep);
std::vector<int> b = importDefSigSpec(cell->getPort(ID::B), timestep);
@ -990,6 +990,19 @@ struct SatGen
ez->assume(ez->vec_eq(y_tmp, y_u));
} else if (cell->type == ID($mod)) {
ez->assume(ez->vec_eq(y_tmp, modulo_trunc));
} else if (cell->type == ID($divfloor)) {
if (cell->parameters[ID::A_SIGNED].as_bool() && cell->parameters[ID::B_SIGNED].as_bool())
ez->assume(ez->vec_eq(y_tmp, ez->vec_ite(
ez->XOR(a.back(), b.back()),
ez->vec_neg(ez->vec_ite(
ez->vec_reduce_or(modulo_trunc),
ez->vec_add(y_u, ez->vec_const_unsigned(1, y_u.size())),
y_u
)),
y_u
)));
else
ez->assume(ez->vec_eq(y_tmp, y_u));
} else if (cell->type == ID($modfloor)) {
ez->assume(ez->vec_eq(y_tmp, ez->vec_ite(floored_eq_trunc, modulo_trunc, ez->vec_add(modulo_trunc, b))));
}
@ -998,7 +1011,7 @@ struct SatGen
ez->assume(ez->expression(ezSAT::OpOr, b));
} else {
std::vector<int> div_zero_result;
if (cell->type == ID($div)) {
if (cell->type.in(ID($div), ID($divfloor))) {
if (cell->parameters[ID::A_SIGNED].as_bool() && cell->parameters[ID::B_SIGNED].as_bool()) {
std::vector<int> all_ones(y.size(), ez->CONST_TRUE);
std::vector<int> only_first_one(y.size(), ez->CONST_FALSE);