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/*
* Copyright (c) 2000-2016 Stephen Williams (steve@icarus.com)
*
* This source code is free software; you can redistribute it
* and/or modify it in source code form under the terms of the GNU
* General Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
# include "config.h"
# include "netlist.h"
# include "netmisc.h"
# include "ivl_assert.h"
/*
* Scan the link for drivers. If there are only constant drivers, then
* the nexus has a known constant value.
*/
bool Nexus::drivers_constant() const
{
if (driven_ == VAR)
return false;
if (driven_ != NO_GUESS)
return true;
unsigned constant_drivers = 0;
for (const Link*cur = first_nlink() ; cur ; cur = cur->next_nlink()) {
/* A target of a procedural assign or force statement
can't be treated as constant. */
const NetNet*sig = dynamic_cast<const NetNet*>(cur->get_obj());
if (sig && (sig->peek_lref() > 0)) {
driven_ = VAR;
return false;
}
/* If we are connected to a tran, there may be a driver
on the other side of the tran. We could try checking
for this, but for now, be pessimistic. */
if (dynamic_cast<const NetTran*>(cur->get_obj())) {
driven_ = VAR;
return false;
}
Link::DIR cur_dir = cur->get_dir();
if (cur_dir == Link::INPUT)
continue;
/* If this is an input or inout port of a root module,
then this is probably not a constant value. I
certainly don't know what the value is, anyhow. This
can happen in cases like this:
module main(sig);
input sig;
endmodule
If main is a root module (it has no parent) then sig
is not constant because it connects to an unspecified
outside world. */
if (cur_dir == Link::PASSIVE) {
if (sig == 0 || sig->scope()->parent() != 0)
continue;
if (sig->port_type() == NetNet::NOT_A_PORT)
continue;
if (sig->port_type() == NetNet::POUTPUT)
continue;
driven_ = VAR;
return false;
}
/* If there is an implicit pullup/pulldown on a net,
count it as a constant driver. */
if (sig)
switch (sig->type()) {
case NetNet::SUPPLY0:
case NetNet::TRI0:
constant_drivers += 1;
driven_ = V0;
continue;
case NetNet::SUPPLY1:
case NetNet::TRI1:
constant_drivers += 1;
driven_ = V1;
continue;
default:
break;
}
const NetSubstitute*ps = dynamic_cast<const NetSubstitute*>(cur->get_obj());
if (ps) {
if (ps->pin(1).nexus()->drivers_constant() &&
ps->pin(2).nexus()->drivers_constant() ) {
constant_drivers += 1;
continue;
}
driven_ = VAR;
return false;
}
if (! dynamic_cast<const NetConst*>(cur->get_obj())) {
driven_ = VAR;
return false;
}
constant_drivers += 1;
}
/* If there is more than one constant driver for this nexus, we
would need to resolve the constant value, taking into account
the drive strengths. This is a lot of work for something that
will rarely occur, so for now leave the resolution to be done
at run time. */
if (constant_drivers > 1) {
driven_ = VAR;
return false;
}
return true;
}
verinum::V Nexus::driven_value() const
{
switch (driven_) {
case V0:
return verinum::V0;
case V1:
return verinum::V1;
case Vx:
return verinum::Vx;
case Vz:
return verinum::Vz;
case VAR:
assert(0);
break;
case NO_GUESS:
break;
}
const Link*cur = list_;
verinum::V val = verinum::Vz;
for (cur = first_nlink() ; cur ; cur = cur->next_nlink()) {
const NetConst*obj;
const NetNet*sig;
if ((obj = dynamic_cast<const NetConst*>(cur->get_obj()))) {
// Multiple drivers are not currently supported.
ivl_assert(*obj, val == verinum::Vz);
val = obj->value(cur->get_pin());
} else if ((sig = dynamic_cast<const NetNet*>(cur->get_obj()))) {
// If we find an implicit pullup or pulldown on a
// net, this is a good guess for the driven value,
// but keep looking for other drivers.
if ((sig->type() == NetNet::SUPPLY0) ||
(sig->type() == NetNet::TRI0)) {
// Multiple drivers are not currently supported.
ivl_assert(*sig, val == verinum::Vz);
val = verinum::V0;
}
if ((sig->type() == NetNet::SUPPLY1) ||
(sig->type() == NetNet::TRI1)) {
// Multiple drivers are not currently supported.
ivl_assert(*sig, val == verinum::Vz);
val = verinum::V1;
}
}
}
/* Cache the result. */
switch (val) {
case verinum::V0:
driven_ = V0;
break;
case verinum::V1:
driven_ = V1;
break;
case verinum::Vx:
driven_ = Vx;
break;
case verinum::Vz:
driven_ = Vz;
break;
}
return val;
}
verinum Nexus::driven_vector() const
{
const Link*cur = list_;
verinum val;
verinum pval;
unsigned width = 0;
for (cur = first_nlink() ; cur ; cur = cur->next_nlink()) {
const NetSubstitute*ps;
const NetConst*obj;
const NetNet*sig;
if ((obj = dynamic_cast<const NetConst*>(cur->get_obj()))) {
// Multiple drivers are not currently supported.
ivl_assert(*obj, val.len() == 0);
ivl_assert(*obj, cur->get_pin() == 0);
val = obj->value();
width = val.len();
} else if ((ps = dynamic_cast<const NetSubstitute*>(cur->get_obj()))) {
if (cur->get_pin() != 0)
continue;
// Multiple drivers are not currently supported.
ivl_assert(*ps, val.len() == 0);
val = ps->pin(1).nexus()->driven_vector();
pval = ps->pin(2).nexus()->driven_vector();
for (unsigned idx = 0; idx < pval.len(); idx += 1)
val.set(ps->base() + idx, pval.get(idx));
width = val.len();
} else if ((sig = dynamic_cast<const NetNet*>(cur->get_obj()))) {
width = sig->vector_width();
// If we find an implicit pullup or pulldown on a
// net, this is a good guess for the driven value,
// but keep looking for other drivers.
if ((sig->type() == NetNet::SUPPLY0) ||
(sig->type() == NetNet::TRI0)) {
// Multiple drivers are not currently supported.
ivl_assert(*sig, val.len() == 0);
val = verinum(verinum::V0, width);
}
if ((sig->type() == NetNet::SUPPLY1) ||
(sig->type() == NetNet::TRI1)) {
// Multiple drivers are not currently supported.
ivl_assert(*sig, val.len() == 0);
val = verinum(verinum::V1, width);
}
}
}
// If we have a width but not a value, this must be an undriven net.
if (val.len() != width)
val = verinum(verinum::Vz, width);
return val;
}
/*
* Calculate a vector that represent all the bits of the vector, with
* each driven bit set to true, otherwise false.
*/
vector<bool> Nexus::driven_mask(void) const
{
vector<bool> mask (vector_width());
for (const Link*cur = first_nlink() ; cur ; cur = cur->next_nlink()) {
Link::DIR link_dir = cur->get_dir();
if (link_dir==Link::PASSIVE)
continue;
if (link_dir==Link::INPUT)
continue;
const NetPins*obj = cur->get_obj();
// If the link is to a variable (REG or INTEGER) then
// the variable is driving all the bits. We have our
// complete answer, mark all the bits as driven and
// finish. Otherwise, we are not going to get new
// information from this node, move on.
if (const NetNet*sig = dynamic_cast<const NetNet*> (obj)) {
NetNet::Type sig_type = sig->type();
if (sig_type==NetNet::INTEGER || sig_type==NetNet::REG) {
for (size_t idx = 0 ; idx < mask.size() ; idx += 1)
mask[idx] = true;
return mask;
}
continue;
}
const NetPartSelect*obj_ps = dynamic_cast<const NetPartSelect*>(obj);
if(obj_ps) {
if (obj_ps->dir()==NetPartSelect::VP) {
if(cur->get_pin() != 0)
continue;
for (size_t idx = 0 ; idx < mask.size() ; idx += 1)
mask[idx] = true;
return mask;
} else {
if (cur->get_pin() != 1)
continue;
}
for (unsigned idx = 0 ; idx < obj_ps->width() ; idx += 1) {
size_t bit = idx + obj_ps->base();
ivl_assert(*obj, bit < mask.size());
mask[bit] = true;
}
continue;
}
for (size_t idx = 0 ; idx < mask.size() ; idx += 1)
mask[idx] = true;
return mask;
}
return mask;
}
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