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iverilog/xnfio.cc

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/*
* Copyright (c) 1998-2000 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT) && !defined(macintosh)
#ident "$Id: xnfio.cc,v 1.17 2000/11/20 00:58:40 steve Exp $"
#endif
# include "functor.h"
# include "netlist.h"
# include "netmisc.h"
# include <strstream>
class xnfio_f : public functor_t {
public:
void signal(Design*des, NetNet*sig);
void lpm_compare(Design*des, NetCompare*dev);
private:
bool compare_sideb_const(Design*des, NetCompare*dev);
};
static bool is_a_pad(const NetNet*net)
{
if (net->attribute("PAD") == "")
return false;
return true;
}
/*
* The xnfio function looks for the PAD signals in the design, and
* generates the needed IOB devices to handle being connected to the
* actual FPGA PAD. This will add items to the netlist if needed.
*
* FIXME: If there is a DFF connected to the pad, try to convert it
* to an IO DFF instead. This would save a CLB, and it is
* really lame to not do the obvious optimization.
*/
static NetLogic* make_obuf(Design*des, NetNet*net)
{
NetScope* scope = net->scope();
assert(scope);
assert(net->pin_count() == 1);
/* FIXME: If there is nothing internally driving this PAD, I
can connect the PAD to a pullup and disconnect it from the
rest of the circuit. This would save routing resources. */
if (count_outputs(net->pin(0)) <= 0) {
cerr << net->get_line() << ":warning: No outputs to OPAD: "
<< net->name() << endl;
return 0;
}
assert(count_outputs(net->pin(0)) > 0);
/* Look for an existing OBUF connected to this signal. If it
is there, then no need to add one. */
Nexus*nex = net->pin(0).nexus();
for (Link*idx = nex->first_nlink()
; idx ; idx = idx->next_nlink()) {
NetLogic*tmp;
if ((tmp = dynamic_cast<NetLogic*>(idx->get_obj())) == 0)
continue;
// Try to use an existing BUF as an OBUF. This moves the
// BUF into the IOB.
if ((tmp->type() == NetLogic::BUF)
&& (count_inputs(tmp->pin(0)) == 0)
&& (count_outputs(tmp->pin(0)) == 1)
&& (idx->get_pin() == 0) ) {
tmp->attribute("XNF-LCA", "OBUF:O,I");
return tmp;
}
// Try to use an existing INV as an OBUF. Certain
// technologies support inverting the input of an OBUF,
// which looks just like an inverter. This uses the
// available resources of an IOB to optimize away an
// otherwise expensive inverter.
if ((tmp->type() == NetLogic::NOT)
&& (count_inputs(tmp->pin(0)) == 0)
&& (count_outputs(tmp->pin(0)) == 1)
&& (idx->get_pin() == 0) ) {
tmp->attribute("XNF-LCA", "OBUF:O,~I");
return tmp;
}
// Try to use an existing bufif1 as an OBUFT. Of course
// this will only work if the output of the bufif1 is
// connected only to the pad. Handle bufif0 the same
// way, but the T input is inverted.
if ((tmp->type() == NetLogic::BUFIF1)
&& (count_inputs(tmp->pin(0)) == 0)
&& (count_outputs(tmp->pin(0)) == 1)
&& (idx->get_pin() == 0) ) {
tmp->attribute("XNF-LCA", "OBUFT:O,I,~T");
return tmp;
}
if ((tmp->type() == NetLogic::BUFIF0)
&& (count_inputs(tmp->pin(0)) == 0)
&& (count_outputs(tmp->pin(0)) == 1)
&& (idx->get_pin() == 0) ) {
tmp->attribute("XNF-LCA", "OBUFT:O,I,T");
return tmp;
}
}
// Can't seem to find a way to rearrange the existing netlist,
// so I am stuck creating a new buffer, the OBUF.
NetLogic*buf = new NetLogic(scope, des->local_symbol(scope->name()),
2, NetLogic::BUF);
des->add_node(buf);
map<string,string>attr;
attr["XNF-LCA"] = "OBUF:O,I";
buf->set_attributes(attr);
// Put the buffer between this signal and the rest of the
// netlist.
connect(net->pin(0), buf->pin(1));
net->pin(0).unlink();
connect(net->pin(0), buf->pin(0));
// It is possible, in putting an OBUF between net and the rest
// of the netlist, to create a ring without a signal. Detect
// this case and create a new signal.
if (count_signals(buf->pin(1)) == 0) {
NetNet*tmp = new NetNet(scope, des->local_symbol(scope->name()),
NetNet::WIRE);
tmp->local_flag(true);
connect(buf->pin(1), tmp->pin(0));
}
return buf;
}
static void absorb_OFF(Design*des, NetLogic*buf)
{
/* If the nexus connects is not a simple point-to-point link,
then I can't drag it into the IOB. Give up. */
if (count_outputs(buf->pin(1)) != 1)
return;
if (count_inputs(buf->pin(1)) != 1)
return;
/* For now, only support OUTFF. */
if (buf->type() != NetLogic::BUF)
return;
Link*drv = find_next_output(&buf->pin(1));
assert(drv);
/* Make sure the device is a FF with width 1. */
NetFF*ff = dynamic_cast<NetFF*>(drv->get_obj());
if (ff == 0)
return;
if (ff->width() != 1)
return;
if (ff->attribute("LPM_FFType") != "DFF")
return;
/* Connect the flip-flop output to the buffer output and
delete the buffer. The XNF OUTFF can buffer the pin. */
connect(ff->pin_Q(0), buf->pin(0));
delete buf;
/* Finally, build up an XNF-LCA value that defines this
devices as an OUTFF and gives each pin an XNF name. */
char**names = new char*[ff->pin_count()];
for (unsigned idx = 0 ; idx < ff->pin_count() ; idx += 1)
names[idx] = "";
if (ff->attribute("Clock:LPM_Polarity") == "INVERT")
names[ff->pin_Clock().get_pin()] = "~C";
else
names[ff->pin_Clock().get_pin()] = "C";
names[ff->pin_Data(0).get_pin()] = "D";
names[ff->pin_Q(0).get_pin()] = "Q";
string lname = string("OUTFF:") + names[0];
for (unsigned idx = 1 ; idx < ff->pin_count() ; idx += 1)
lname = lname + "," + names[idx];
delete[]names;
ff->attribute("XNF-LCA", lname);
}
static void make_ibuf(Design*des, NetNet*net)
{
NetScope*scope = net->scope();
assert(scope);
assert(net->pin_count() == 1);
// XXXX For now, require at least one input.
assert(count_inputs(net->pin(0)) > 0);
/* Look for an existing BUF connected to this signal and
suitably connected that I can use it as an IBUF. */
Nexus*nex = net->pin(0).nexus();
for (Link*idx = nex->first_nlink()
; idx ; idx = idx->next_nlink()) {
NetLogic*tmp;
if ((tmp = dynamic_cast<NetLogic*>(idx->get_obj())) == 0)
continue;
if (tmp->attribute("XNF-LCA") != "")
continue;
// Found a BUF, it is only useable if the only input is
// the signal and there are no other inputs.
if ((tmp->type() == NetLogic::BUF) &&
(count_inputs(tmp->pin(1)) == 1) &&
(count_outputs(tmp->pin(1)) == 0)) {
tmp->attribute("XNF-LCA", "IBUF:O,I");
return;
}
}
// I give up, create an IBUF.
NetLogic*buf = new NetLogic(scope, des->local_symbol(scope->name()),
2, NetLogic::BUF);
des->add_node(buf);
map<string,string>attr;
attr["XNF-LCA"] = "IBUF:O,I";
buf->set_attributes(attr);
// Put the buffer between this signal and the rest of the
// netlist.
connect(net->pin(0), buf->pin(0));
net->pin(0).unlink();
connect(net->pin(0), buf->pin(1));
// It is possible, in putting an OBUF between net and the rest
// of the netlist, to create a ring without a signal. Detect
// this case and create a new signal.
if (count_signals(buf->pin(0)) == 0) {
NetNet*tmp = new NetNet(scope,
des->local_symbol(scope->name()),
NetNet::WIRE);
connect(buf->pin(0), tmp->pin(0));
}
}
void xnfio_f::signal(Design*des, NetNet*net)
{
NetNode*buf;
if (! is_a_pad(net))
return;
assert(net->pin_count() == 1);
string pattr = net->attribute("PAD");
switch (pattr[0]) {
case 'i':
case 'I':
make_ibuf(des, net);
break;
case 'o':
case 'O': {
NetLogic*buf = make_obuf(des, net);
if (buf == 0) break;
absorb_OFF(des, buf);
break;
}
// FIXME: Only IPAD and OPAD supported. Need to
// add support for IOPAD.
default:
assert(0);
break;
}
}
/*
* Attempt some XNF specific optimizations on comparators.
*/
void xnfio_f::lpm_compare(Design*des, NetCompare*dev)
{
if (compare_sideb_const(des, dev))
return;
return;
}
bool xnfio_f::compare_sideb_const(Design*des, NetCompare*dev)
{
/* Even if side B is all constant, if there are more then 4
signals on side A we will not be able to fit the operation
into a function unit, so we might as well accept a
comparator. Give up. */
if (dev->width() > 4)
return false;
NetScope*scope = des->find_root_scope();
verinum side (verinum::V0, dev->width());
/* Is the B side all constant? */
for (unsigned idx = 0 ; idx < dev->width() ; idx += 1) {
if (! link_drivers_constant(dev->pin_DataB(idx)))
return false;
side.set(idx, driven_value(dev->pin_DataB(idx)));
}
/* Handle the special case of comparing A to 0. Use an N-input
NOR gate to return 0 if any of the bits is not 0. */
if ((side.as_ulong() == 0) && (count_inputs(dev->pin_AEB()) > 0)) {
NetLogic*sub = new NetLogic(scope, dev->name(), dev->width()+1,
NetLogic::NOR);
connect(sub->pin(0), dev->pin_AEB());
for (unsigned idx = 0 ; idx < dev->width() ; idx += 1)
connect(sub->pin(idx+1), dev->pin_DataA(idx));
delete dev;
des->add_node(sub);
return true;
}
/* Handle the special case of comparing A to 0. Use an N-input
NOR gate to return 0 if any of the bits is not 0. */
if ((side.as_ulong() == 0) && (count_inputs(dev->pin_ANEB()) > 0)) {
NetLogic*sub = new NetLogic(scope, dev->name(), dev->width()+1,
NetLogic::OR);
connect(sub->pin(0), dev->pin_ANEB());
for (unsigned idx = 0 ; idx < dev->width() ; idx += 1)
connect(sub->pin(idx+1), dev->pin_DataA(idx));
delete dev;
des->add_node(sub);
return true;
}
return false;
}
void xnfio(Design*des)
{
xnfio_f xnfio_obj;
des->functor(&xnfio_obj);
}
/*
* $Log: xnfio.cc,v $
* Revision 1.17 2000/11/20 00:58:40 steve
* Add support for supply nets (PR#17)
*
* Revision 1.16 2000/10/07 19:45:43 steve
* Put logic devices into scopes.
*
* Revision 1.15 2000/06/25 19:59:42 steve
* Redesign Links to include the Nexus class that
* carries properties of the connected set of links.
*
* Revision 1.14 2000/05/07 04:37:56 steve
* Carry strength values from Verilog source to the
* pform and netlist for gates.
*
* Change vvm constants to use the driver_t to drive
* a constant value. This works better if there are
* multiple drivers on a signal.
*
* Revision 1.13 2000/05/02 00:58:12 steve
* Move signal tables to the NetScope class.
*
* Revision 1.12 2000/04/20 00:28:03 steve
* Catch some simple identity compareoptimizations.
*
* Revision 1.11 2000/02/23 02:56:56 steve
* Macintosh compilers do not support ident.
*
* Revision 1.10 1999/12/11 05:45:41 steve
* Fix support for attaching attributes to primitive gates.
*
* Revision 1.9 1999/11/27 19:07:58 steve
* Support the creation of scopes.
*
* Revision 1.8 1999/11/19 05:02:15 steve
* Handle inverted clock into OUTFF.
*
* Revision 1.7 1999/11/19 03:02:25 steve
* Detect flip-flops connected to opads and turn
* them into OUTFF devices. Inprove support for
* the XNF-LCA attribute in the process.
*
* Revision 1.6 1999/11/18 02:58:37 steve
* Handle (with a warning) unconnected opads.
*
* Revision 1.5 1999/11/02 04:55:01 steve
* repair the sense of T from bufif01
*
* Revision 1.4 1999/11/02 01:43:55 steve
* Fix iobuf and iobufif handling.
*
* Revision 1.3 1999/10/09 17:52:27 steve
* support XNF OBUFT devices.
*
* Revision 1.2 1999/07/17 22:01:14 steve
* Add the functor interface for functor transforms.
*
* Revision 1.1 1998/12/07 04:53:17 steve
* Generate OBUF or IBUF attributes (and the gates
* to garry them) where a wire is a pad. This involved
* figuring out enough of the netlist to know when such
* was needed, and to generate new gates and signales
* to handle what's missing.
*
*/
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