diff options
Diffstat (limited to 'nexus/pack.cc')
-rw-r--r-- | nexus/pack.cc | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/nexus/pack.cc b/nexus/pack.cc index 96b48da9..7ba1ef7f 100644 --- a/nexus/pack.cc +++ b/nexus/pack.cc @@ -699,6 +699,83 @@ struct NexusPacker } } + // Find the nearest bel of a given type; matching a closure predicate + template <typename Tpred> BelId find_nearest_bel(const CellInfo *cell, IdString dest_type, Tpred predicate) + { + BelId origin = get_bel_attr(cell); + if (origin == BelId()) + return BelId(); + Loc origin_loc = ctx->getBelLocation(origin); + int best_distance = std::numeric_limits<int>::max(); + BelId best_bel = BelId(); + + for (BelId bel : ctx->getBels()) { + if (ctx->getBelType(bel) != dest_type) + continue; + if (!predicate(bel)) + continue; + Loc bel_loc = ctx->getBelLocation(bel); + int dist = std::abs(origin_loc.x - bel_loc.x) + std::abs(origin_loc.y - bel_loc.y); + if (dist < best_distance) { + best_distance = dist; + best_bel = bel; + } + } + return best_bel; + } + + std::unordered_set<BelId> used_bels; + + // Pre-place a primitive based on routeability first and distance second + BelId preplace_prim(CellInfo *cell, IdString pin, bool strict_routing) + { + std::vector<BelId> routeability_candidates; + + NetInfo *pin_net = get_net_or_empty(cell, pin); + if (pin_net == nullptr) + return BelId(); + + CellInfo *pin_drv = pin_net->driver.cell; + if (pin_drv == nullptr) + return BelId(); + + // Check based on routeability + find_connected_bels(pin_drv, pin_net->driver.port, cell->type, pin, 25000, routeability_candidates); + + for (BelId cand : routeability_candidates) { + if (used_bels.count(cand)) + continue; + cell->attrs[id_BEL] = ctx->getBelName(cand).str(ctx); + used_bels.insert(cand); + return cand; + } + + // Unless in strict mode; check based on simple distance too + BelId nearest = find_nearest_bel(pin_drv, cell->type, [&](BelId bel) { return !used_bels.count(bel); }); + + if (nearest != BelId()) { + cell->attrs[id_BEL] = ctx->getBelName(nearest).str(ctx); + used_bels.insert(nearest); + return nearest; + } + + return BelId(); + } + + // Pre-place a singleton primitive; so decisions can be made on routeability downstream of it + void preplace_singleton(CellInfo *cell) + { + if (cell->attrs.count(id_BEL)) + return; + for (BelId bel : ctx->getBels()) { + if (ctx->getBelType(bel) != cell->type) + continue; + // Check that the bel really is a singleton... + NPNR_ASSERT(!cell->attrs.count(id_BEL)); + cell->attrs[id_BEL] = ctx->getBelName(bel).str(ctx); + } + } + explicit NexusPacker(Context *ctx) : ctx(ctx) {} void operator()() |