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https://github.com/YosysHQ/yosys
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Fold nested tristate hidden behind mux/tribuf data input.
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nella
nella
parent
a5af9d690a
commit
e2d589a9d5
1 changed files with 142 additions and 42 deletions
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@ -52,9 +52,116 @@ struct TribufWorker {
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return true;
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}
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static IdString tribuf_en_id(Cell *cell)
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{
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return cell->type == ID($tribuf) ? ID::EN : ID::E;
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}
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static SigSpec tribuf_en(Cell *cell)
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{
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return cell->getPort(tribuf_en_id(cell));
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}
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Cell *inner_tribuf(SigSpec sig, dict<SigBit, Cell*> &tribuf_driver, dict<SigBit, int> &fanout)
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{
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Cell *c = nullptr;
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for (auto bit : sigmap(sig)) {
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auto it = tribuf_driver.find(bit);
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if (it == tribuf_driver.end() || fanout[bit] != 1)
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return nullptr;
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if (c && c != it->second)
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return nullptr;
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c = it->second;
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}
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if (c && sigmap(c->getPort(ID::Y)) == sigmap(sig))
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return c;
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return nullptr;
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}
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// Fold tri-state that is hidden behind an ordinary $mux (or behind the data input of another tribuf)
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// into a single tribuf, so nested z like cond ? val : (en ? z : x) is not lost before iopadmap can see it
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bool fold_tristate()
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{
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dict<SigBit, Cell*> tribuf_driver;
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dict<SigBit, int> fanout;
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for (auto cell : module->cells()) {
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for (auto &conn : cell->connections())
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if (!cell->output(conn.first))
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for (auto bit : sigmap(conn.second))
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fanout[bit]++;
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if (cell->type.in(ID($tribuf), ID($_TBUF_)))
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for (auto bit : sigmap(cell->getPort(ID::Y)))
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tribuf_driver[bit] = cell;
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}
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// Ports keep their nets alive, so never fold them away
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for (auto wire : module->wires())
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if (wire->port_id)
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for (auto bit : sigmap(wire))
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fanout[bit]++;
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struct MuxJob { Cell *mux, *ta, *tb; };
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struct TriJob { Cell *outer, *inner; };
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std::vector<MuxJob> mux_jobs;
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std::vector<TriJob> tri_jobs;
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for (auto cell : module->selected_cells()) {
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if (cell->type.in(ID($mux), ID($_MUX_))) {
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Cell *ta = inner_tribuf(cell->getPort(ID::A), tribuf_driver, fanout);
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Cell *tb = inner_tribuf(cell->getPort(ID::B), tribuf_driver, fanout);
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if (ta || tb)
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mux_jobs.push_back({cell, ta, tb});
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} else if (cell->type.in(ID($tribuf), ID($_TBUF_))) {
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Cell *inner = inner_tribuf(cell->getPort(ID::A), tribuf_driver, fanout);
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if (inner)
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tri_jobs.push_back({cell, inner});
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}
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}
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for (auto &job : mux_jobs) {
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SigSpec s = job.mux->getPort(ID::S);
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SigSpec en_a = job.ta ? tribuf_en(job.ta) : SigSpec(State::S1);
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SigSpec en_b = job.tb ? tribuf_en(job.tb) : SigSpec(State::S1);
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SigSpec val_a = job.ta ? job.ta->getPort(ID::A) : job.mux->getPort(ID::A);
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SigSpec val_b = job.tb ? job.tb->getPort(ID::A) : job.mux->getPort(ID::B);
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SigSpec en = module->Mux(NEW_ID, en_a, en_b, s);
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SigSpec val = module->Mux(NEW_ID, val_a, val_b, s);
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SigSpec y = job.mux->getPort(ID::Y);
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if (job.ta) module->remove(job.ta);
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if (job.tb) module->remove(job.tb);
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module->remove(job.mux);
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module->addTribuf(NEW_ID, val, en, y);
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module->design->scratchpad_set_bool("tribuf.added_something", true);
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}
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// A tribuf whose data is another tribuf drives its value only while both are enabled
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pool<Cell*> folded_inner;
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for (auto &job : mux_jobs) {
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if (job.ta) folded_inner.insert(job.ta);
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if (job.tb) folded_inner.insert(job.tb);
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}
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for (auto &job : tri_jobs)
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folded_inner.insert(job.inner);
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bool tri_changed = false;
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for (auto &job : tri_jobs) {
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if (folded_inner.count(job.outer))
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continue;
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SigSpec en = module->And(NEW_ID, tribuf_en(job.outer), tribuf_en(job.inner));
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job.outer->setPort(ID::A, job.inner->getPort(ID::A));
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job.outer->setPort(tribuf_en_id(job.outer), en);
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module->remove(job.inner);
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module->design->scratchpad_set_bool("tribuf.added_something", true);
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tri_changed = true;
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}
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return !mux_jobs.empty() || tri_changed;
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}
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void run()
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{
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dict<SigSpec, vector<Cell*>> tribuf_cells;
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pool<SigBit> output_bits;
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if (config.logic_mode || config.formal_mode)
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@ -65,45 +172,44 @@ struct TribufWorker {
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for (auto cell : module->selected_cells())
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{
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if (cell->type == ID($tribuf))
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tribuf_cells[sigmap(cell->getPort(ID::Y))].push_back(cell);
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if (!cell->type.in(ID($mux), ID($_MUX_)))
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continue;
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if (cell->type == ID($_TBUF_))
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tribuf_cells[sigmap(cell->getPort(ID::Y))].push_back(cell);
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IdString en_port = cell->type == ID($mux) ? ID::EN : ID::E;
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IdString tri_type = cell->type == ID($mux) ? ID($tribuf) : ID($_TBUF_);
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if (cell->type.in(ID($mux), ID($_MUX_)))
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{
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IdString en_port = cell->type == ID($mux) ? ID::EN : ID::E;
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IdString tri_type = cell->type == ID($mux) ? ID($tribuf) : ID($_TBUF_);
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if (is_all_z(cell->getPort(ID::A)) && is_all_z(cell->getPort(ID::B))) {
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module->remove(cell);
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continue;
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}
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if (is_all_z(cell->getPort(ID::A)) && is_all_z(cell->getPort(ID::B))) {
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module->remove(cell);
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continue;
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}
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if (is_all_z(cell->getPort(ID::A))) {
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cell->setPort(ID::A, cell->getPort(ID::B));
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cell->setPort(en_port, cell->getPort(ID::S));
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cell->unsetPort(ID::B);
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cell->unsetPort(ID::S);
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cell->type = tri_type;
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module->design->scratchpad_set_bool("tribuf.added_something", true);
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continue;
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}
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if (is_all_z(cell->getPort(ID::A))) {
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cell->setPort(ID::A, cell->getPort(ID::B));
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cell->setPort(en_port, cell->getPort(ID::S));
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cell->unsetPort(ID::B);
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cell->unsetPort(ID::S);
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cell->type = tri_type;
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tribuf_cells[sigmap(cell->getPort(ID::Y))].push_back(cell);
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module->design->scratchpad_set_bool("tribuf.added_something", true);
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continue;
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}
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if (is_all_z(cell->getPort(ID::B))) {
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cell->setPort(en_port, module->Not(NEW_ID, cell->getPort(ID::S)));
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cell->unsetPort(ID::B);
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cell->unsetPort(ID::S);
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cell->type = tri_type;
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tribuf_cells[sigmap(cell->getPort(ID::Y))].push_back(cell);
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module->design->scratchpad_set_bool("tribuf.added_something", true);
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continue;
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}
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if (is_all_z(cell->getPort(ID::B))) {
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cell->setPort(en_port, module->Not(NEW_ID, cell->getPort(ID::S)));
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cell->unsetPort(ID::B);
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cell->unsetPort(ID::S);
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cell->type = tri_type;
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module->design->scratchpad_set_bool("tribuf.added_something", true);
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continue;
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}
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}
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while (fold_tristate()) {}
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dict<SigSpec, vector<Cell*>> tribuf_cells;
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for (auto cell : module->selected_cells())
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if (cell->type.in(ID($tribuf), ID($_TBUF_)))
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tribuf_cells[sigmap(cell->getPort(ID::Y))].push_back(cell);
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if (config.merge_mode || config.logic_mode || config.formal_mode)
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{
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for (auto &it : tribuf_cells)
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@ -130,13 +236,10 @@ struct TribufWorker {
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for (auto other_cell : it.second) {
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if (other_cell == cell)
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continue;
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else if (other_cell->type == ID($tribuf))
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others_s.append(other_cell->getPort(ID::EN));
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else
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others_s.append(other_cell->getPort(ID::E));
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others_s.append(tribuf_en(other_cell));
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}
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auto cell_s = cell->type == ID($tribuf) ? cell->getPort(ID::EN) : cell->getPort(ID::E);
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auto cell_s = tribuf_en(cell);
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auto other_s = module->ReduceOr(NEW_ID, others_s);
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@ -154,10 +257,7 @@ struct TribufWorker {
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SigSpec pmux_b, pmux_s;
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for (auto cell : it.second) {
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if (cell->type == ID($tribuf))
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pmux_s.append(cell->getPort(ID::EN));
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else
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pmux_s.append(cell->getPort(ID::E));
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pmux_s.append(tribuf_en(cell));
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pmux_b.append(cell->getPort(ID::A));
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module->remove(cell);
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}
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