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/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2021 gatecat <gatecat@ds0.me>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#include "log.h"
#include "nextpnr.h"
#include "util.h"
#include <queue>
NEXTPNR_NAMESPACE_BEGIN
namespace {
struct GlobalVist
{
PipId downhill = PipId();
int total_hops = 0;
int global_hops = 0;
bool operator<(const GlobalVist &other) const
{
return (total_hops < other.total_hops) ||
((total_hops == other.total_hops) && (global_hops > other.global_hops));
}
};
static bool route_global_arc(Context *ctx, NetInfo *net, size_t usr_idx, size_t phys_port_idx, int max_hops)
{
auto &usr = net->users.at(usr_idx);
WireId src = ctx->getNetinfoSourceWire(net);
WireId dest = ctx->getNetinfoSinkWire(net, usr, phys_port_idx);
if (dest == WireId()) {
log_error("Arc %d.%d (%s.%s) of net %s has no sink wire!\n", int(usr_idx), int(phys_port_idx),
ctx->nameOf(usr.cell), ctx->nameOf(usr.port), ctx->nameOf(net));
}
// Consider any existing routing put in place by the site router, etc
int start_hops = 0;
while (net->wires.count(dest) && dest != src) {
dest = ctx->getPipSrcWire(net->wires.at(dest).pip);
++start_hops;
}
// The main BFS implementation
// Currently this is a backwards-BFS from sink to source (or pre-existing routing) that avoids general routing. It
// currently aims for minimum hops as a primary goal and maximum global resource usage as a secondary goal. More
// advanced heuristics will likely be needed for more complex situation
WireId startpoint;
GlobalVist best_visit;
std::queue<WireId> visit_queue;
std::unordered_map<WireId, GlobalVist> visits;
visit_queue.push(dest);
visits[dest].downhill = PipId();
visits[dest].total_hops = start_hops;
while (!visit_queue.empty()) {
WireId cursor = visit_queue.front();
visit_queue.pop();
auto &curr_visit = visits.at(cursor);
// We're now at least one layer deeper than a valid visit, any further exploration is futile
if (startpoint != WireId() && curr_visit.total_hops > best_visit.total_hops)
break;
// Valid end of routing
if ((cursor == src) || (ctx->getBoundWireNet(cursor) == net)) {
if (startpoint == WireId() || curr_visit < best_visit) {
startpoint = cursor;
best_visit = curr_visit;
}
}
// Explore uphill
for (auto pip : ctx->getPipsUphill(cursor)) {
if (!ctx->checkPipAvailForNet(pip, net))
continue;
WireId pip_src = ctx->getPipSrcWire(pip);
if (!ctx->checkWireAvail(pip_src) && ctx->getBoundWireNet(pip_src) != net)
continue;
auto cat = ctx->get_wire_category(pip_src);
if (cat == WIRE_CAT_GENERAL)
continue; // never allow general routing
GlobalVist next_visit;
next_visit.downhill = pip;
next_visit.total_hops = curr_visit.total_hops + 1;
if (max_hops != -1 && next_visit.total_hops > max_hops)
continue;
next_visit.global_hops = curr_visit.global_hops + ((cat == WIRE_CAT_GLOBAL) ? 1 : 0);
auto fnd_src = visits.find(pip_src);
if (fnd_src == visits.end() || next_visit < fnd_src->second) {
visit_queue.push(pip_src);
visits[pip_src] = next_visit;
}
}
}
if (startpoint == WireId())
return false;
if (ctx->getBoundWireNet(startpoint) == nullptr)
ctx->bindWire(startpoint, net, STRENGTH_LOCKED);
WireId cursor = startpoint;
std::vector<PipId> pips;
// Create a list of pips on the routed path
while (true) {
PipId pip = visits.at(cursor).downhill;
if (pip == PipId())
break;
pips.push_back(pip);
cursor = ctx->getPipDstWire(pip);
}
// Reverse that list
std::reverse(pips.begin(), pips.end());
// Bind pips until we hit already-bound routing
for (PipId pip : pips) {
WireId dst = ctx->getPipDstWire(pip);
if (ctx->getBoundWireNet(dst) == net)
break;
ctx->bindPip(pip, net, STRENGTH_LOCKED);
}
return true;
}
}; // namespace
const GlobalCellPOD *Arch::global_cell_info(IdString cell_type) const
{
for (const auto &glb_cell : chip_info->global_cells)
if (IdString(glb_cell.cell_type) == cell_type)
return &glb_cell;
return nullptr;
}
void Arch::route_globals()
{
log_info("Routing globals...\n");
Context *ctx = getCtx();
IdString gnd_net_name(chip_info->constants->gnd_net_name);
IdString vcc_net_name(chip_info->constants->vcc_net_name);
for (auto cell : sorted(ctx->cells)) {
CellInfo *ci = cell.second;
const GlobalCellPOD *glb_cell = global_cell_info(ci->type);
if (glb_cell == nullptr)
continue;
for (const auto &pin : glb_cell->pins) {
IdString pin_name(pin.name);
if (!ci->ports.count(pin_name))
continue;
auto &port = ci->ports.at(pin_name);
// TOOD: routing of input ports, too
// output ports are generally the first priority though
if (port.type != PORT_OUT)
continue;
NetInfo *net = port.net;
if (net == nullptr || net->name == gnd_net_name || net->name == vcc_net_name)
continue;
int total_sinks = 0;
int global_sinks = 0;
for (size_t i = 0; i < net->users.size(); i++) {
auto &usr = net->users.at(i);
for (size_t j = 0; j < ctx->getNetinfoSinkWireCount(net, usr); j++) {
bool routed_global = route_global_arc(ctx, net, i, j, pin.max_hops);
++total_sinks;
if (routed_global)
++global_sinks;
if (!routed_global && pin.force_routing)
log_error("Failed to route arc %d.%d (%s.%s) of net %s using dedicated global routing!\n",
int(i), int(j), ctx->nameOf(usr.cell), ctx->nameOf(usr.port), ctx->nameOf(net));
}
}
log_info(" routed %d/%d sinks of net %s using dedicated routing.\n", global_sinks, total_sinks,
ctx->nameOf(net));
}
}
}
NEXTPNR_NAMESPACE_END
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