From e2530b30df5ef4887683ca1a5b94cc417eaeec94 Mon Sep 17 00:00:00 2001 From: Akash Levy Date: Wed, 13 Nov 2024 15:45:43 -0800 Subject: [PATCH] Add `splitfanout` pass --- passes/cmds/Makefile.inc | 1 + passes/cmds/splitfanout.cc | 244 +++++++++++++++++++++++++++++++++++++ 2 files changed, 245 insertions(+) create mode 100644 passes/cmds/splitfanout.cc diff --git a/passes/cmds/Makefile.inc b/passes/cmds/Makefile.inc index 95c799f8f64..b5919dc3f5f 100644 --- a/passes/cmds/Makefile.inc +++ b/passes/cmds/Makefile.inc @@ -15,6 +15,7 @@ OBJS += passes/cmds/scatter.o OBJS += passes/cmds/setundef.o OBJS += passes/cmds/splitnets.o OBJS += passes/cmds/splitcells.o +OBJS += passes/cmds/splitfanout.o OBJS += passes/cmds/stat.o OBJS += passes/cmds/internal_stats.o OBJS += passes/cmds/setattr.o diff --git a/passes/cmds/splitfanout.cc b/passes/cmds/splitfanout.cc new file mode 100644 index 00000000000..c1630fe5e5c --- /dev/null +++ b/passes/cmds/splitfanout.cc @@ -0,0 +1,244 @@ +/* + * yosys -- Yosys Open SYnthesis Suite + * + * Copyright (C) 2012 Claire Xenia Wolf + * 2024 Akash Levy + * + * 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 "kernel/yosys.h" +#include "kernel/sigtools.h" +#include "kernel/utils.h" + +USING_YOSYS_NAMESPACE +PRIVATE_NAMESPACE_BEGIN + +struct SplitfanoutWorker +{ + Module *module; + SigMap sigmap; + dict> bit_drivers_db; + dict>> bit_users_db; + TopoSort toposort; + + SplitfanoutWorker(Module *module) : module(module), sigmap(module) + { + // Add nodes to topological sorter for all selected cells + log("Making toposort nodes for module %s...\n", log_id(module)); + for (auto cell : module->selected_cells()) + toposort.node(cell->name); + + // Build bit_drivers_db + log("Building bit_drivers_db...\n"); + for (auto cell : module->cells()) { + for (auto conn : cell->connections()) { + if (!cell->output(conn.first)) continue; + for (int i = 0; i < GetSize(conn.second); i++) { + SigBit bit(sigmap(conn.second[i])); + bit_drivers_db[bit] = tuple(cell->name, conn.first, i); + } + } + } + + // Build bit_users_db and add edges to topological sorter + log("Building bit_users_db and adding edges to toposort...\n"); + for (auto cell : module->cells()) { + for (auto conn : cell->connections()) { + if (!cell->input(conn.first)) continue; + for (int i = 0; i < GetSize(conn.second); i++) { + SigBit bit(sigmap(conn.second[i])); + if (!bit_drivers_db.count(bit)) continue; + bit_users_db[bit].insert(tuple(cell->name, + conn.first, i-std::get<2>(bit_drivers_db[bit]))); + IdString driver_cell = std::get<0>(bit_drivers_db[bit]); + if (toposort.has_node(driver_cell) && toposort.has_node(cell->name)) + // toposort.edge(driver_cell, cell->name); + toposort.edge(cell->name, driver_cell); + } + } + } + + // Build bit_users_db for output ports + log("Building bit_users_db for output ports...\n"); + for (auto wire : module->wires()) { + if (!wire->port_output) continue; + SigSpec sig(sigmap(wire)); + for (int i = 0; i < GetSize(sig); i++) { + SigBit bit(sig[i]); + if (!bit_drivers_db.count(bit)) continue; + bit_users_db[bit].insert(tuple(wire->name, + IdString(), i-std::get<2>(bit_drivers_db[bit]))); + } + } + + // Sort using the topological sorter + log("Sorting using toposort...\n"); + toposort.analyze_loops = false; + toposort.sort(); + } + + int split(Cell *cell, int limit) + { + // Get output signal/port + SigSpec outsig; + IdString outport; + int output_count = 0; + for (auto conn : cell->connections()) + if (cell->output(conn.first)) { + output_count++; + outport = conn.first; + outsig = conn.second; + } + if (output_count != 1) { + log("Skipping %s cell %s/%s with %d output ports.\n", log_id(cell->type), log_id(module), log_id(cell), output_count); + return 0; + } + + // Check if output signal is "bit-split", skip if so + auto bit_users = bit_users_db[outsig[0]]; + for (int i = 0; i < GetSize(outsig); i++) { + if (bit_users_db[outsig[i]] != bit_users) { + log("Skipping %s cell %s/%s with bit-split output.\n", log_id(cell->type), log_id(module), log_id(cell)); + return 0; + } + } + + // Skip if output signal has only one user + if (GetSize(bit_users) <= 1) + return 0; + + // Skip if fanout is above limit + if (limit != -1 && GetSize(bit_users) > limit) { + log("Skipping %s cell %s/%s with high fanout %d.\n", log_id(cell->type), log_id(module), log_id(cell), GetSize(bit_users)-1); + return 0; + } + + // Iterate over bit users and create a new cell for each one + log("Splitting %s cell %s/%s into %d copies based on fanout\n", log_id(cell->type), log_id(module), log_id(cell), GetSize(bit_users)-1); + int foi = 0; + cell->unsetPort(outport); + int num_new_cells = GetSize(bit_users)-1; + int bit_user_i = num_new_cells; + for (auto bit_user : bit_users) + { + // Configure the driver cell + IdString new_name; + Cell *new_cell; + if (bit_user_i-- != 0) { // create a new cell + new_name = module->uniquify(cell->name.str()); + new_cell = module->addCell(new_name, cell); + // Add new cell to the bit_users_db + for (auto conn : new_cell->connections()) { + if (!new_cell->input(conn.first)) continue; + for (int i = 0; i < GetSize(conn.second); i++) { + SigBit bit(sigmap(conn.second[i])); + if (!bit_drivers_db.count(bit)) continue; + bit_users_db[bit].insert(tuple(new_cell->name, + conn.first, i-std::get<2>(bit_drivers_db[bit]))); + } + } + } else { // if last cell, reuse the original cell + new_name = cell->name; + new_cell = cell; + } + + // Connect the new cell to the user + if (std::get<1>(bit_user) == IdString()) { // is wire + Wire *old_wire = module->wire(std::get<0>(bit_user)); + Wire *new_wire = module->addWire(NEW_ID, old_wire); + module->swap_names(old_wire, new_wire); + old_wire->port_input = false; + old_wire->port_output = false; + SigSpec sig(new_wire, std::get<2>(bit_user), GetSize(outsig)); + new_cell->setPort(outport, sig); + } + else { + Wire *new_wire = module->addWire(NEW_ID, GetSize(outsig)); + Cell *target_cell = module->cell(std::get<0>(bit_user)); + SigSpec sig = target_cell->getPort(std::get<1>(bit_user)); + sig.replace(std::get<2>(bit_user), new_wire); + module->cell(std::get<0>(bit_user))->setPort(std::get<1>(bit_user), sig); + new_cell->setPort(outport, new_wire); + } + + // Log the new cell + log_debug(" slice %d: %s => %s\n", foi++, log_id(new_name), log_signal(new_cell->getPort(outport))); + } + + // Fix up ports + module->fixup_ports(); + + // Return the number of new cells created + return num_new_cells; + } +}; + +struct SplitfanoutPass : public Pass { + SplitfanoutPass() : Pass("splitfanout", "split up cells with >1 fanout into copies") { } + void help() override + { + // |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---| + log("\n"); + log(" splitfanout [selection]\n"); + log("\n"); + log("This command copies selected cells with >1 fanout into cells with fanout 1. It\n"); + log("is effectively the opposite of the opt_merge pass.\n"); + log("\n"); + log("This command operates only on cells with 1 output and no 'bit split' on that\n"); + log("output.\n"); + log("\n"); + log(" -limit n\n"); + log(" max fanout to split.\n"); + log("\n"); + } + void execute(std::vector args, RTLIL::Design *design) override + { + int limit = -1; + log_header(design, "Executing SPLITFANOUT pass (splitting up cells with >1 fanout into copies).\n"); + + size_t argidx; + for (argidx = 1; argidx < args.size(); argidx++) + { + // No options currently. When adding in the future make sure to update docstring with [options] + if (args[argidx] == "-limit" && argidx+1 < args.size()) { + limit = std::stoi(args[++argidx]); + continue; + } + break; + } + extra_args(args, argidx, design); + + for (auto module : design->selected_modules()) + { + int count_split_pre = 0; + int count_split_post = 0; + + SplitfanoutWorker worker(module); + for (auto cell : worker.toposort.sorted) { + int n = worker.split(module->cell(cell), limit); + count_split_pre += (n != 0); + count_split_post += n; + } + + if (count_split_pre) + log("Split %d cells in module '%s' into %d copies based on fanout.\n", + count_split_pre, log_id(module), count_split_post); + } + + Pass::call(design, "clean *"); + } +} SplitfanoutPass; + +PRIVATE_NAMESPACE_END