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router2: Reserve wires in more complex cases

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Signed-off-by: gatecat <gatecat@ds0.me>
This commit is contained in:
gatecat 2021-05-06 21:20:09 +01:00
parent 62613cb266
commit 65c611da02
1 changed files with 39 additions and 13 deletions
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52
common/router2.cc
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@ -434,20 +434,35 @@ struct Router2
}
// Returns true if a wire contains no source ports or driving pips
bool is_wire_undriveable(WireId wire)
bool is_wire_undriveable(WireId wire, const NetInfo *net, int iter_count = 0)
{
// This is specifically designed to handle a particularly icky case that the current router struggles with in
// the nexus device,
// C -> C lut input only
// C; D; or F from another lut -> D lut input
// D or M -> M ff input
// without careful reservation of C for C lut input and D for D lut input, there is fighting for D between FF
// and LUT
if (iter_count > 7)
return false; // heuristic to assume we've hit general routing
if (wire_data(wire).reserved_net != -1 && wire_data(wire).reserved_net != net->udata)
return true; // reserved for another net
for (auto bp : ctx->getWireBelPins(wire))
if (ctx->getBelPinType(bp.bel, bp.pin) != PORT_IN)
if ((net->driver.cell == nullptr || bp.bel == net->driver.cell->bel) &&
ctx->getBelPinType(bp.bel, bp.pin) != PORT_IN)
return false;
for (auto p : ctx->getPipsUphill(wire))
if (ctx->checkPipAvail(p))
return false;
if (ctx->checkPipAvail(p)) {
if (!is_wire_undriveable(ctx->getPipSrcWire(p), net, iter_count + 1))
return false;
}
return true;
}
// Find all the wires that must be used to route a given arc
void reserve_wires_for_arc(NetInfo *net, size_t i)
bool reserve_wires_for_arc(NetInfo *net, size_t i)
{
bool did_something = false;
WireId src = ctx->getNetinfoSourceWire(net);
for (auto sink : ctx->getNetinfoSinkWires(net, net->users.at(i))) {
std::unordered_set<WireId> rsv;
@ -459,13 +474,14 @@ struct Router2
auto &wd = wire_data(cursor);
if (ctx->debug)
log(" %s\n", ctx->nameOfWire(cursor));
did_something |= (wd.reserved_net != net->udata);
wd.reserved_net = net->udata;
if (cursor == src)
break;
WireId next_cursor;
for (auto uh : ctx->getPipsUphill(cursor)) {
WireId w = ctx->getPipSrcWire(uh);
if (is_wire_undriveable(w))
if (is_wire_undriveable(w, net))
continue;
if (next_cursor != WireId()) {
done = true;
@ -478,17 +494,23 @@ struct Router2
cursor = next_cursor;
}
}
return did_something;
}
void find_all_reserved_wires()
{
for (auto net : nets_by_udata) {
WireId src = ctx->getNetinfoSourceWire(net);
if (src == WireId())
continue;
for (size_t i = 0; i < net->users.size(); i++)
reserve_wires_for_arc(net, i);
}
// Run iteratively, as reserving wires for one net might limit choices for another
bool did_something = false;
do {
did_something = false;
for (auto net : nets_by_udata) {
WireId src = ctx->getNetinfoSourceWire(net);
if (src == WireId())
continue;
for (size_t i = 0; i < net->users.size(); i++)
did_something |= reserve_wires_for_arc(net, i);
}
} while (did_something);
}
void reset_wires(ThreadContext &t)
@ -720,6 +742,7 @@ struct Router2
next_score.delay =
curr.score.delay + ctx->getPipDelay(dh).maxDelay() + ctx->getWireDelay(next).maxDelay();
next_score.togo_cost = cfg.estimate_weight * get_togo_cost(net, i, next_idx, dst_wire, &forward);
#if 0
ROUTE_LOG_DBG(
"src_wire = %s -> next %s -> dst_wire = %s (backward: %s, forward: %s, sum: %s, cost = %f, "
"togo_cost = %f, total = %f), dt = %02fs\n",
@ -728,6 +751,7 @@ struct Router2
std::to_string(next_score.delay + forward).c_str(), next_score.cost, next_score.togo_cost,
next_score.cost + next_score.togo_cost,
std::chrono::duration<float>(std::chrono::high_resolution_clock::now() - arc_start).count());
#endif
const auto &v = nwd.visit;
if (!v.visited || (v.score.total() > next_score.total())) {
++explored;
@ -809,7 +833,9 @@ struct Router2
// Ripup failed arcs to start with
// Check if arc is already legally routed
if (check_arc_routing(net, i, j)) {
#if 0
ROUTE_LOG_DBG("Arc '%s' (user %zu, arc %zu) already routed skipping.\n", ctx->nameOf(net), i, j);
#endif
continue;
}