/* * yosys -- Yosys Open SYnthesis Suite * * Copyright (C) 2012 Clifford Wolf * * 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 "opt_status.h" #include "kernel/register.h" #include "kernel/sigtools.h" #include "kernel/log.h" #include "kernel/celltypes.h" #include #include #include #include using RTLIL::id2cstr; struct OptMuxtreeWorker { RTLIL::Design *design; RTLIL::Module *module; SigMap assign_map; int removed_count; typedef std::pair bitDef_t; struct bitinfo_t { int num; bitDef_t bit; bool seen_non_mux; std::vector mux_users; std::vector mux_drivers; }; std::map bit2num; std::vector bit2info; struct portinfo_t { std::vector ctrl_sigs; std::vector input_sigs; std::vector input_muxes; bool const_activated; bool enabled; }; struct muxinfo_t { RTLIL::Cell *cell; std::vector ports; }; std::vector mux2info; OptMuxtreeWorker(RTLIL::Design *design, RTLIL::Module *module) : design(design), module(module), assign_map(module), removed_count(0) { log("Running muxtree optimizier on module %s..\n", module->name.c_str()); log(" Creating internal representation of mux trees.\n"); // Populate bit2info[]: // .seen_non_mux // .mux_users // .mux_drivers // Populate mux2info[].ports[]: // .ctrl_sigs // .input_sigs // .const_activated for (auto &cell_it : module->cells) { RTLIL::Cell *cell = cell_it.second; if (cell->type == "$mux" || cell->type == "$pmux" || cell->type == "$safe_pmux") { RTLIL::SigSpec sig_a = cell->connections["\\A"]; RTLIL::SigSpec sig_b = cell->connections["\\B"]; RTLIL::SigSpec sig_s = cell->connections["\\S"]; RTLIL::SigSpec sig_y = cell->connections["\\Y"]; muxinfo_t muxinfo; muxinfo.cell = cell; for (int i = 0; i < sig_s.size(); i++) { RTLIL::SigSpec sig = sig_b.extract(i*sig_a.size(), sig_a.size()); RTLIL::SigSpec ctrl_sig = assign_map(sig_s.extract(i, 1)); portinfo_t portinfo; for (int idx : sig2bits(sig)) { add_to_list(bit2info[idx].mux_users, mux2info.size()); add_to_list(portinfo.input_sigs, idx); } for (int idx : sig2bits(ctrl_sig)) add_to_list(portinfo.ctrl_sigs, idx); portinfo.const_activated = ctrl_sig.is_fully_const() && ctrl_sig.as_bool(); portinfo.enabled = false; muxinfo.ports.push_back(portinfo); } portinfo_t portinfo; for (int idx : sig2bits(sig_a)) { add_to_list(bit2info[idx].mux_users, mux2info.size()); add_to_list(portinfo.input_sigs, idx); } portinfo.const_activated = false; portinfo.enabled = false; muxinfo.ports.push_back(portinfo); for (int idx : sig2bits(sig_y)) add_to_list(bit2info[idx].mux_drivers, mux2info.size()); for (int idx : sig2bits(sig_s)) bit2info[idx].seen_non_mux = true; mux2info.push_back(muxinfo); } else { for (auto &it : cell->connections) { for (int idx : sig2bits(it.second)) bit2info[idx].seen_non_mux = true; } } } for (auto &it : module->wires) { if (it.second->port_output) for (int idx : sig2bits(RTLIL::SigSpec(it.second))) bit2info[idx].seen_non_mux = true; } if (mux2info.size() == 0) { log(" No muxes found in this module.\n"); return; } // Populate mux2info[].ports[]: // .input_muxes for (size_t i = 0; i < bit2info.size(); i++) for (int j : bit2info[i].mux_users) for (auto &p : mux2info[j].ports) { if (is_in_list(p.input_sigs, i)) for (int k : bit2info[i].mux_drivers) add_to_list(p.input_muxes, k); } log(" Evaluating internal representation of mux trees.\n"); std::set root_muxes; for (auto &bi : bit2info) { if (!bi.seen_non_mux) continue; for (int mux_idx : bi.mux_drivers) root_muxes.insert(mux_idx); } for (int mux_idx : root_muxes) eval_root_mux(mux_idx); log(" Analyzing evaluation results.\n"); for (auto &mi : mux2info) { std::vector live_ports; for (size_t port_idx = 0; port_idx < mi.ports.size(); port_idx++) { portinfo_t &pi = mi.ports[port_idx]; if (pi.enabled) { live_ports.push_back(port_idx); } else { log(" dead port %zd/%zd on %s %s.\n", port_idx+1, mi.ports.size(), mi.cell->type.c_str(), mi.cell->name.c_str()); OPT_DID_SOMETHING = true; removed_count++; } } if (live_ports.size() == mi.ports.size()) continue; if (live_ports.size() == 0) { module->cells.erase(mi.cell->name); delete mi.cell; continue; } RTLIL::SigSpec sig_a = mi.cell->connections["\\A"]; RTLIL::SigSpec sig_b = mi.cell->connections["\\B"]; RTLIL::SigSpec sig_s = mi.cell->connections["\\S"]; RTLIL::SigSpec sig_y = mi.cell->connections["\\Y"]; RTLIL::SigSpec sig_ports = sig_b; sig_ports.append(sig_a); if (live_ports.size() == 1) { RTLIL::SigSpec sig_in = sig_ports.extract(live_ports[0]*sig_a.size(), sig_a.size()); module->connections.push_back(RTLIL::SigSig(sig_y, sig_in)); module->cells.erase(mi.cell->name); delete mi.cell; } else { RTLIL::SigSpec new_sig_a, new_sig_b, new_sig_s; for (size_t i = 0; i < live_ports.size(); i++) { RTLIL::SigSpec sig_in = sig_ports.extract(live_ports[i]*sig_a.size(), sig_a.size()); if (i == live_ports.size()-1) { new_sig_a = sig_in; } else { new_sig_b.append(sig_in); new_sig_s.append(sig_s.extract(live_ports[i], 1)); } } mi.cell->connections["\\A"] = new_sig_a; mi.cell->connections["\\B"] = new_sig_b; mi.cell->connections["\\S"] = new_sig_s; if (new_sig_s.size() == 1) { mi.cell->type = "$mux"; mi.cell->parameters.erase("\\S_WIDTH"); } else { mi.cell->parameters["\\S_WIDTH"] = RTLIL::Const(new_sig_s.size()); } } } } bool list_is_subset(const std::vector &sub, const std::vector &super) { for (int v : sub) if (!is_in_list(super, v)) return false; return true; } bool is_in_list(const std::vector &list, int value) { for (int v : list) if (v == value) return true; return false; } void add_to_list(std::vector &list, int value) { if (!is_in_list(list, value)) list.push_back(value); } std::vector sig2bits(RTLIL::SigSpec sig) { std::vector results; assign_map.apply(sig); sig.expand(); for (auto &c : sig.chunks()) if (c.wire != NULL) { bitDef_t bit(c.wire, c.offset); if (bit2num.count(bit) == 0) { bitinfo_t info; info.num = bit2info.size(); info.bit = bit; info.seen_non_mux = false; bit2info.push_back(info); bit2num[info.bit] = info.num; } results.push_back(bit2num[bit]); } return results; } struct knowledge_t { // database of known inactive signals // the 2nd integer is a reference counter used to manage the // list. when it is non-zero the signal in known to be inactive std::map known_inactive; // database of known active signals // the 2nd dimension is the list of or-ed signals. so we know that // for each i there is a j so that known_active[i][j] points to an // inactive control signal. std::vector> known_active; // this is just used to keep track of visited muxes in order to prohibit // endless recursion in mux loops std::set visited_muxes; }; void eval_mux_port(knowledge_t &knowledge, int mux_idx, int port_idx) { muxinfo_t &muxinfo = mux2info[mux_idx]; muxinfo.ports[port_idx].enabled = true; for (size_t i = 0; i < muxinfo.ports.size(); i++) { if (int(i) == port_idx) continue; for (int b : muxinfo.ports[i].ctrl_sigs) knowledge.known_inactive[b]++; } if (port_idx < int(muxinfo.ports.size())-1 && !muxinfo.ports[port_idx].const_activated) knowledge.known_active.push_back(muxinfo.ports[port_idx].ctrl_sigs); std::vector parent_muxes; for (int m : muxinfo.ports[port_idx].input_muxes) { if (knowledge.visited_muxes.count(m) > 0) continue; knowledge.visited_muxes.insert(m); parent_muxes.push_back(m); } for (int m : parent_muxes) eval_mux(knowledge, m); for (int m : parent_muxes) knowledge.visited_muxes.erase(m); if (port_idx < int(muxinfo.ports.size())-1 && !muxinfo.ports[port_idx].const_activated) knowledge.known_active.pop_back(); for (size_t i = 0; i < muxinfo.ports.size(); i++) { if (int(i) == port_idx) continue; for (int b : muxinfo.ports[i].ctrl_sigs) knowledge.known_inactive[b]--; } } void eval_mux(knowledge_t &knowledge, int mux_idx) { muxinfo_t &muxinfo = mux2info[mux_idx]; // if there is a constant activated port we just use it for (size_t port_idx = 0; port_idx < muxinfo.ports.size()-1; port_idx++) { portinfo_t &portinfo = muxinfo.ports[port_idx]; if (portinfo.const_activated) { eval_mux_port(knowledge, mux_idx, port_idx); return; } } // compare ports with known_active signals. if we find a match, only this // port can be active. do not include the last port (its the default port // that has no control signals). for (size_t port_idx = 0; port_idx < muxinfo.ports.size()-1; port_idx++) { portinfo_t &portinfo = muxinfo.ports[port_idx]; for (size_t i = 0; i < knowledge.known_active.size(); i++) { if (list_is_subset(knowledge.known_active[i], portinfo.ctrl_sigs)) { eval_mux_port(knowledge, mux_idx, port_idx); return; } } } // compare ports with known_inactive and known_active signals. If all control // signals of the port are know_inactive or if the control signals of all other // ports are known_active this port can't be activated. this loop includes the // default port but no known_inactive match is performed on the default port. for (size_t port_idx = 0; port_idx < muxinfo.ports.size(); port_idx++) { portinfo_t &portinfo = muxinfo.ports[port_idx]; if (port_idx < muxinfo.ports.size()-1) { bool found_non_known_inactive = false; for (int i : portinfo.ctrl_sigs) if (knowledge.known_inactive[i] == 0) found_non_known_inactive = true; if (!found_non_known_inactive) continue; } bool port_active = true; std::vector other_ctrl_sig; for (size_t i = 0; i < muxinfo.ports.size()-1; i++) { if (i == port_idx) continue; other_ctrl_sig.insert(other_ctrl_sig.end(), muxinfo.ports[i].ctrl_sigs.begin(), muxinfo.ports[i].ctrl_sigs.end()); } for (size_t i = 0; i < knowledge.known_active.size(); i++) { if (list_is_subset(knowledge.known_active[i], other_ctrl_sig)) port_active = false; } if (port_active) eval_mux_port(knowledge, mux_idx, port_idx); } } void eval_root_mux(int mux_idx) { knowledge_t knowledge; knowledge.visited_muxes.insert(mux_idx); eval_mux(knowledge, mux_idx); } }; struct OptMuxtreePass : public Pass { OptMuxtreePass() : Pass("opt_muxtree", "eliminate dead trees in multiplexer trees") { } virtual void help() { // |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---| log("\n"); log(" opt_muxtree [selection]\n"); log("\n"); log("This pass analyzes the control signals for the multiplexer trees in the design\n"); log("and identifies inputs that can never be active. It then removes this dead\n"); log("branches from the multiplexer trees.\n"); log("\n"); log("This pass only operates on completely selected modules without processes.\n"); log("\n"); } virtual void execute(std::vector args, RTLIL::Design *design) { log_header("Executing OPT_MUXTREE pass (detect dead branches in mux trees).\n"); extra_args(args, 1, design); int total_count = 0; for (auto &mod_it : design->modules) { if (!design->selected_whole_module(mod_it.first)) { if (design->selected(mod_it.second)) log("Skipping module %s as it is only partially selected.\n", id2cstr(mod_it.second->name)); continue; } if (mod_it.second->processes.size() > 0) { log("Skipping module %s as it contains processes.\n", id2cstr(mod_it.second->name)); } else { OptMuxtreeWorker worker(design, mod_it.second); total_count += worker.removed_count; } } log("Removed %d multiplexer ports.\n", total_count); } } OptMuxtreePass;