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router2: Special backwards mode for gnd/vcc-like nets

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Signed-off-by: David Shah <dave@ds0.me>
This commit is contained in:
David Shah 2019-11-11 12:57:05 +00:00
parent a4ab9b19d7
commit 599236bbc6
1 changed files with 67 additions and 3 deletions
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70
common/router2.cc
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@ -211,6 +211,10 @@ struct Router2
std::unordered_map<WireId, VisitInfo> visited;
// Special case where one net has multiple logical arcs to the same physical sink
std::unordered_set<WireId> processed_sinks;
// Backwards routing
std::queue<WireId> backwards_queue;
std::unordered_map<WireId, PipId> backwards_pip;
};
enum ArcRouteResult
@ -345,18 +349,78 @@ struct Router2
std::priority_queue<QueuedWire, std::vector<QueuedWire>, QueuedWire::Greater> new_queue;
t.queue.swap(new_queue);
}
t.visited.clear();
if (!t.backwards_queue.empty()) {
std::queue<WireId> new_queue;
t.backwards_queue.swap(new_queue);
}
// First try strongly iteration-limited routing backwards BFS
// this will deal with certain nets faster than forward A*
// and comes at a minimal performance cost for the others
// This could also be used to speed up forwards routing by a hybrid
// bidirectional approach
int backwards_iter = 0;
int backwards_limit = 125;
t.backwards_pip.clear();
t.backwards_queue.push(dst_wire);
while (!t.backwards_queue.empty() && backwards_iter < backwards_limit) {
WireId cursor = t.backwards_queue.front();
t.backwards_queue.pop();
auto &cwd = wires.at(cursor);
PipId cpip;
if (cwd.bound_nets.count(net->udata))
cpip = cwd.bound_nets.at(net->udata).second;
bool did_something = false;
for (auto uh : ctx->getPipsUphill(cursor)) {
did_something = true;
if (cpip != PipId() && cpip != uh)
continue; // don't allow multiple pips driving a wire with a net
WireId next = ctx->getPipSrcWire(uh);
if (t.backwards_pip.count(next))
continue; // skip wires that have already been visited
auto &wd = wires.at(next);
if (wd.unavailable)
continue;
if (wd.bound_nets.size() > 1 || (wd.bound_nets.size() == 1 && !wd.bound_nets.count(net->udata)))
continue; // never allow congestion in backwards routing
t.backwards_queue.push(next);
t.backwards_pip[next] = uh;
}
if (did_something)
++backwards_iter;
}
// Check if backwards routing succeeded in reaching source
if (t.backwards_pip.count(src_wire)) {
ROUTE_LOG_DBG(" Routed (backwards): ");
WireId cursor_fwd = src_wire;
bind_pip_internal(net, i, src_wire, PipId());
while (t.backwards_pip.count(cursor_fwd)) {
auto &v = t.backwards_pip.at(cursor_fwd);
cursor_fwd = ctx->getPipDstWire(v);
bind_pip_internal(net, i, cursor_fwd, v);
if (ctx->debug) {
auto &wd = wires.at(cursor_fwd);
ROUTE_LOG_DBG(" wire: %s (curr %d hist %f)\n", ctx->nameOfWire(cursor_fwd),
int(wd.bound_nets.size()) - 1, wd.hist_cong_cost);
}
}
NPNR_ASSERT(cursor_fwd == dst_wire);
t.processed_sinks.insert(dst_wire);
return ARC_SUCCESS;
}
// Add source wire to queue
// Normal forwards A* routing
t.visited.clear();
WireScore base_score;
base_score.cost = 0;
base_score.delay = ctx->getWireDelay(src_wire).maxDelay();
base_score.togo_cost = get_togo_cost(net, i, src_wire, dst_wire);
// Add source wire to queue
t.queue.push(QueuedWire(src_wire, PipId(), Loc(), base_score));
t.visited[src_wire].score = base_score;
t.visited[src_wire].pip = PipId();
int toexplore = 5000 * std::max(1, (ad.bb.x1 - ad.bb.x0) + (ad.bb.y1 - ad.bb.y0));
int toexplore = 25000 * std::max(1, (ad.bb.x1 - ad.bb.x0) + (ad.bb.y1 - ad.bb.y0));
int iter = 0;
while (!t.queue.empty() && (!is_bb || iter < toexplore)) {
auto curr = t.queue.top();