diff options
Diffstat (limited to 'passes/opt/wreduce.cc')
| -rw-r--r-- | passes/opt/wreduce.cc | 129 |
1 files changed, 126 insertions, 3 deletions
diff --git a/passes/opt/wreduce.cc b/passes/opt/wreduce.cc index 0164f58d..52245ce3 100644 --- a/passes/opt/wreduce.cc +++ b/passes/opt/wreduce.cc @@ -38,7 +38,8 @@ struct WreduceConfig "$shl", "$shr", "$sshl", "$sshr", "$shift", "$shiftx", "$lt", "$le", "$eq", "$ne", "$eqx", "$nex", "$ge", "$gt", "$add", "$sub", "$mul", // "$div", "$mod", "$pow", - "$mux", "$pmux" + "$mux", "$pmux", + "$dff", "$adff" }); } }; @@ -52,6 +53,8 @@ struct WreduceWorker std::set<Cell*, IdString::compare_ptr_by_name<Cell>> work_queue_cells; std::set<SigBit> work_queue_bits; pool<SigBit> keep_bits; + dict<SigBit, State> init_bits; + pool<SigBit> remove_init_bits; WreduceWorker(WreduceConfig *config, Module *module) : config(config), module(module), mi(module) { } @@ -134,6 +137,91 @@ struct WreduceWorker module->connect(sig_y.extract(n_kept, n_removed), sig_removed); } + void run_cell_dff(Cell *cell) + { + // Reduce size of FF if inputs are just sign/zero extended or output bit is not used + + SigSpec sig_d = mi.sigmap(cell->getPort("\\D")); + SigSpec sig_q = mi.sigmap(cell->getPort("\\Q")); + Const initval; + + int width_before = GetSize(sig_q); + + if (width_before == 0) + return; + + bool zero_ext = sig_d[GetSize(sig_d)-1] == State::S0; + bool sign_ext = !zero_ext; + + for (int i = 0; i < GetSize(sig_q); i++) { + SigBit bit = sig_q[i]; + if (init_bits.count(bit)) + initval.bits.push_back(init_bits.at(bit)); + else + initval.bits.push_back(State::Sx); + } + + for (int i = GetSize(sig_q)-1; i >= 0; i--) + { + if (zero_ext && sig_d[i] == State::S0 && (initval[i] == State::S0 || initval[i] == State::Sx)) { + module->connect(sig_q[i], State::S0); + remove_init_bits.insert(sig_q[i]); + sig_d.remove(i); + sig_q.remove(i); + continue; + } + + if (sign_ext && i > 0 && sig_d[i] == sig_d[i-1] && initval[i] == initval[i-1]) { + module->connect(sig_q[i], sig_q[i-1]); + remove_init_bits.insert(sig_q[i]); + sig_d.remove(i); + sig_q.remove(i); + continue; + } + + auto info = mi.query(sig_q[i]); + if (!info->is_output && GetSize(info->ports) == 1 && !keep_bits.count(mi.sigmap(sig_q[i]))) { + remove_init_bits.insert(sig_q[i]); + sig_d.remove(i); + sig_q.remove(i); + zero_ext = false; + sign_ext = false; + continue; + } + + break; + } + + if (width_before == GetSize(sig_q)) + return; + + if (GetSize(sig_q) == 0) { + log("Removed cell %s.%s (%s).\n", log_id(module), log_id(cell), log_id(cell->type)); + module->remove(cell); + return; + } + + log("Removed top %d bits (of %d) from FF cell %s.%s (%s).\n", width_before - GetSize(sig_q), width_before, + log_id(module), log_id(cell), log_id(cell->type)); + + for (auto bit : sig_d) + work_queue_bits.insert(bit); + + for (auto bit : sig_q) + work_queue_bits.insert(bit); + + // Narrow ARST_VALUE parameter to new size. + if (cell->parameters.count("\\ARST_VALUE")) { + Const arst_value = cell->getParam("\\ARST_VALUE"); + arst_value.bits.resize(GetSize(sig_q)); + cell->setParam("\\ARST_VALUE", arst_value); + } + + cell->setPort("\\D", sig_d); + cell->setPort("\\Q", sig_q); + cell->fixup_parameters(); + } + void run_reduce_inport(Cell *cell, char port, int max_port_size, bool &port_signed, bool &did_something) { port_signed = cell->getParam(stringf("\\%c_SIGNED", port)).as_bool(); @@ -176,6 +264,9 @@ struct WreduceWorker if (cell->type.in("$mux", "$pmux")) return run_cell_mux(cell); + if (cell->type.in("$dff", "$adff")) + return run_cell_dff(cell); + SigSpec sig = mi.sigmap(cell->getPort("\\Y")); if (sig.has_const()) @@ -235,8 +326,11 @@ struct WreduceWorker } else { while (GetSize(sig) > 0) { - auto info = mi.query(sig[GetSize(sig)-1]); + auto bit = sig[GetSize(sig)-1]; + if (keep_bits.count(bit)) + break; + auto info = mi.query(bit); if (info->is_output || GetSize(info->ports) > 1) break; @@ -297,10 +391,21 @@ struct WreduceWorker void run() { - for (auto w : module->wires()) + // create a copy as mi.sigmap will be updated as we process the module + SigMap init_attr_sigmap = mi.sigmap; + + for (auto w : module->wires()) { if (w->get_bool_attribute("\\keep")) for (auto bit : mi.sigmap(w)) keep_bits.insert(bit); + if (w->attributes.count("\\init")) { + Const initval = w->attributes.at("\\init"); + SigSpec initsig = init_attr_sigmap(w); + int width = std::min(GetSize(initval), GetSize(initsig)); + for (int i = 0; i < width; i++) + init_bits[initsig[i]] = initval[i]; + } + } for (auto c : module->selected_cells()) work_queue_cells.insert(c); @@ -348,6 +453,24 @@ struct WreduceWorker module->connect(nw, SigSpec(w).extract(0, GetSize(nw))); module->swap_names(w, nw); } + + if (!remove_init_bits.empty()) { + for (auto w : module->wires()) { + if (w->attributes.count("\\init")) { + Const initval = w->attributes.at("\\init"); + Const new_initval(State::Sx, GetSize(w)); + SigSpec initsig = init_attr_sigmap(w); + int width = std::min(GetSize(initval), GetSize(initsig)); + for (int i = 0; i < width; i++) { + log_dump(initsig[i], remove_init_bits.count(initsig[i])); + if (!remove_init_bits.count(initsig[i])) + new_initval[i] = initval[i]; + } + w->attributes.at("\\init") = new_initval; + log_dump(w->name, initval, new_initval); + } + } + } } }; |