From 9a1cad85fe66138c6be2da0ad0a5349240f5a546 Mon Sep 17 00:00:00 2001 From: gatecat Date: Wed, 5 May 2021 10:36:32 +0100 Subject: interchange: Adding a basic global buffer placer Signed-off-by: gatecat --- fpga_interchange/arch.cc | 10 +++ fpga_interchange/arch.h | 2 + fpga_interchange/globals.cc | 152 ++++++++++++++++++++++++++++++++++---------- 3 files changed, 132 insertions(+), 32 deletions(-) diff --git a/fpga_interchange/arch.cc b/fpga_interchange/arch.cc index ee462848..938c4f2c 100644 --- a/fpga_interchange/arch.cc +++ b/fpga_interchange/arch.cc @@ -479,6 +479,14 @@ IdString Arch::getWireType(WireId wire) const return IdString(chip_info->wire_types[wire_type].name); } +bool Arch::is_site_wire(WireId wire) const +{ + if (wire.tile == -1) + return false; + const auto &tile_type = loc_info(chip_info, wire); + return tile_type.wire_data[wire.index].site != -1; +} + WireCategory Arch::get_wire_category(WireId wire) const { int tile = wire.tile, index = wire.index; @@ -791,6 +799,8 @@ bool Arch::place() getCtx()->check(); #endif + place_globals(); + std::string placer = str_or_default(settings, id("placer"), defaultPlacer); if (placer == "heap") { PlacerHeapCfg cfg(getCtx()); diff --git a/fpga_interchange/arch.h b/fpga_interchange/arch.h index 4dc64b05..7188fd36 100644 --- a/fpga_interchange/arch.h +++ b/fpga_interchange/arch.h @@ -533,6 +533,7 @@ struct Arch : ArchAPI return range; } + bool is_site_wire(WireId wire) const; WireCategory get_wire_category(WireId wire) const; // ------------------------------------------------- @@ -690,6 +691,7 @@ struct Arch : ArchAPI void decode_lut_cells(); const GlobalCellPOD *global_cell_info(IdString cell_type) const; + void place_globals(); void route_globals(); bool pack() final; diff --git a/fpga_interchange/globals.cc b/fpga_interchange/globals.cc index a4528c90..66d04f75 100644 --- a/fpga_interchange/globals.cc +++ b/fpga_interchange/globals.cc @@ -39,14 +39,20 @@ struct GlobalVist } }; -static bool route_global_arc(Context *ctx, NetInfo *net, size_t usr_idx, size_t phys_port_idx, int max_hops) +// This is our main global routing implementation. It is used both to actually route globals; and also to discover if +// global buffers have available short routes from their source for auto-placement +static int route_global_arc(Context *ctx, NetInfo *net, size_t usr_idx, size_t phys_port_idx, int max_hops, + bool dry_run) { 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)); + if (dry_run) + return -1; + else + 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; @@ -83,13 +89,13 @@ static bool route_global_arc(Context *ctx, NetInfo *net, size_t usr_idx, size_t } // Explore uphill for (auto pip : ctx->getPipsUphill(cursor)) { - if (!ctx->checkPipAvailForNet(pip, net)) + if (!dry_run && !ctx->checkPipAvailForNet(pip, net)) continue; WireId pip_src = ctx->getPipSrcWire(pip); - if (!ctx->checkWireAvail(pip_src) && ctx->getBoundWireNet(pip_src) != net) + if (!dry_run && !ctx->checkWireAvail(pip_src) && ctx->getBoundWireNet(pip_src) != net) continue; auto cat = ctx->get_wire_category(pip_src); - if (cat == WIRE_CAT_GENERAL) + if (!ctx->is_site_wire(pip_src) && cat == WIRE_CAT_GENERAL) continue; // never allow general routing GlobalVist next_visit; next_visit.downhill = pip; @@ -106,31 +112,32 @@ static bool route_global_arc(Context *ctx, NetInfo *net, size_t usr_idx, size_t } if (startpoint == WireId()) - return false; + return -1; + if (!dry_run) { + if (ctx->getBoundWireNet(startpoint) == nullptr) + ctx->bindWire(startpoint, net, STRENGTH_LOCKED); - if (ctx->getBoundWireNet(startpoint) == nullptr) - ctx->bindWire(startpoint, net, STRENGTH_LOCKED); - - WireId cursor = startpoint; - std::vector 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); + WireId cursor = startpoint; + std::vector 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; + return visits.at(startpoint).total_hops; } }; // namespace @@ -143,6 +150,87 @@ const GlobalCellPOD *Arch::global_cell_info(IdString cell_type) const return nullptr; } +void Arch::place_globals() +{ + log_info("Placing 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); + + // TODO: for more complex PLL type setups, we might want a toposort or iterative loop as the PLL must be placed + // before the GBs it drives + for (auto cell : sorted(ctx->cells)) { + CellInfo *ci = cell.second; + const GlobalCellPOD *glb_cell = global_cell_info(ci->type); + if (glb_cell == nullptr) + continue; + // Ignore if already placed + if (ci->bel != BelId()) + continue; + + for (const auto &pin : glb_cell->pins) { + if (!pin.guide_placement) + continue; + + IdString pin_name(pin.name); + if (!ci->ports.count(pin_name)) + continue; + auto &port = ci->ports.at(pin_name); + + // only input ports currently used for placement guidance + if (port.type != PORT_IN) + continue; + + NetInfo *net = port.net; + if (net == nullptr || net->name == gnd_net_name || net->name == vcc_net_name) + continue; + // Ignore if there is no driver; or the driver is not placed + if (net->driver.cell == nullptr || net->driver.cell->bel == BelId()) + continue; + size_t user_idx = 0; + bool found_user = false; + for (user_idx = 0; user_idx < net->users.size(); user_idx++) + if (net->users.at(user_idx).cell == ci && net->users.at(user_idx).port == pin_name) { + found_user = true; + break; + } + NPNR_ASSERT(found_user); + + // TODO: substantial performance improvements are probably possible, although of questionable benefit given + // the low number of globals in a typical device... + BelId best_bel; + int shortest_distance = std::numeric_limits::max(); + + for (auto bel : getBels()) { + int distance; + if (!isValidBelForCellType(ci->type, bel)) + continue; + if (!checkBelAvail(bel)) + continue; + // Provisionally place + bindBel(bel, ci, STRENGTH_WEAK); + if (!isBelLocationValid(bel)) + goto fail; + // Check distance + distance = route_global_arc(ctx, net, user_idx, 0, pin.max_hops, true); + if (distance != -1 && distance < shortest_distance) { + best_bel = bel; + shortest_distance = distance; + } + fail: + unbindBel(bel); + } + + if (best_bel != BelId()) { + bindBel(best_bel, ci, STRENGTH_LOCKED); + log_info(" placed %s:%s at %s\n", ctx->nameOf(ci), ctx->nameOf(ci->type), ctx->nameOfBel(best_bel)); + break; + } + } + } +} + void Arch::route_globals() { log_info("Routing globals...\n"); @@ -177,11 +265,11 @@ void Arch::route_globals() 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); + int result = route_global_arc(ctx, net, i, j, pin.max_hops, false); ++total_sinks; - if (routed_global) + if (result != -1) ++global_sinks; - if (!routed_global && pin.force_routing) + if ((result == -1) && 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)); 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