mirror of
https://github.com/YosysHQ/yosys
synced 2025-10-31 11:42:30 +00:00
419 lines
13 KiB
C++
419 lines
13 KiB
C++
#include "kernel/yosys.h"
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#include "kernel/ff.h"
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#include "kernel/gzip.h"
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#include "libparse.h"
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#include <optional>
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USING_YOSYS_NAMESPACE
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PRIVATE_NAMESPACE_BEGIN
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struct ClockGateCell {
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IdString name;
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IdString ce_pin;
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IdString clk_in_pin;
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IdString clk_out_pin;
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std::vector<IdString> tie_lo_pins;
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};
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ClockGateCell icg_from_arg(std::string& name, std::string& str) {
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ClockGateCell c;
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c.name = RTLIL::escape_id(name);
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char delimiter = ':';
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size_t pos1 = str.find(delimiter);
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if (pos1 == std::string::npos)
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log_cmd_error("Not enough ports in descriptor string");
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size_t pos2 = str.find(delimiter, pos1 + 1);
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if (pos2 == std::string::npos)
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log_cmd_error("Not enough ports in descriptor string");
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size_t pos3 = str.find(delimiter, pos2 + 1);
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if (pos3 != std::string::npos)
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log_cmd_error("Too many ports in descriptor string");
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std::string ce = str.substr(0, pos1);
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c.ce_pin = RTLIL::escape_id(ce);
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std::string clk_in = str.substr(pos1 + 1, pos2 - (pos1 + 1));
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c.clk_in_pin = RTLIL::escape_id(clk_in);
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std::string clk_out = str.substr(pos2 + 1, str.size() - (pos2 + 1));
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c.clk_out_pin = RTLIL::escape_id(clk_out);
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return c;
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}
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static std::pair<std::optional<ClockGateCell>, std::optional<ClockGateCell>>
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find_icgs(std::vector<const LibertyAst *> cells, std::vector<std::string> const& dont_use_cells) {
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// We will pick the most suitable ICG absed on tie_lo count and area
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struct ICGRankable : public ClockGateCell { double area; };
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std::optional<ICGRankable> best_pos;
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std::optional<ICGRankable> best_neg;
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// This is a lot of boilerplate, isn't it?
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for (auto cell : cells)
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{
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const LibertyAst *dn = cell->find("dont_use");
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if (dn != nullptr && dn->value == "true")
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continue;
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bool dont_use = false;
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for (auto dont_use_cell : dont_use_cells)
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{
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if (patmatch(dont_use_cell.c_str(), cell->args[0].c_str()))
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{
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dont_use = true;
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break;
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}
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}
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if (dont_use)
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continue;
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const LibertyAst *icg_kind_ast = cell->find("clock_gating_integrated_cell");
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if (icg_kind_ast == nullptr)
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continue;
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auto cell_name = cell->args[0];
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auto icg_kind = icg_kind_ast->value;
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auto starts_with = [&](std::string prefix) {
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return icg_kind.compare(0, prefix.size(), prefix) == 0;
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};
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bool clk_pol;
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if (icg_kind == "latch_posedge" || starts_with("latch_posedge_")) {
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clk_pol = true;
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} else if (icg_kind == "latch_negedge" || starts_with("latch_negedge_")) {
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clk_pol = false;
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} else {
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log("Ignoring ICG primitive %s of kind '%s'\n", cell_name, icg_kind);
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continue;
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}
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log_debug("maybe valid icg: %s\n", cell_name);
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ClockGateCell icg_interface;
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icg_interface.name = RTLIL::escape_id(cell_name);
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for (auto pin : cell->children) {
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if (pin->id != "pin" || pin->args.size() != 1)
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continue;
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if (pin->find("clock_gate_clock_pin")) {
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if (!icg_interface.clk_in_pin.empty()) {
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log_warning("Malformed liberty file - multiple clock_gate_clock_pin in cell %s\n",
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cell_name.c_str());
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continue;
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} else
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icg_interface.clk_in_pin = RTLIL::escape_id(pin->args[0]);
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} else if (pin->find("clock_gate_out_pin")) {
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if (!icg_interface.clk_out_pin.empty()) {
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log_warning("Malformed liberty file - multiple clock_gate_out_pin in cell %s\n",
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cell_name.c_str());
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continue;
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} else
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icg_interface.clk_out_pin = RTLIL::escape_id(pin->args[0]);
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} else if (pin->find("clock_gate_enable_pin")) {
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if (!icg_interface.ce_pin.empty()) {
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log_warning("Malformed liberty file - multiple clock_gate_enable_pin in cell %s\n",
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cell_name.c_str());
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continue;
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} else
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icg_interface.ce_pin = RTLIL::escape_id(pin->args[0]);
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} else if (pin->find("clock_gate_test_pin")) {
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icg_interface.tie_lo_pins.push_back(RTLIL::escape_id(pin->args[0]));
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} else {
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const LibertyAst *dir = pin->find("direction");
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if (dir->value == "internal")
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continue;
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log_warning("Malformed liberty file - extra pin %s in cell %s\n",
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pin->args[0].c_str(), cell_name.c_str());
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continue;
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}
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}
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if (icg_interface.clk_in_pin.empty()) {
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log_warning("Malformed liberty file - missing clock_gate_clock_pin in cell %s",
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cell_name.c_str());
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continue;
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}
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if (icg_interface.clk_out_pin.empty()) {
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log_warning("Malformed liberty file - missing clock_gate_out_pin in cell %s",
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cell_name.c_str());
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continue;
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}
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if (icg_interface.ce_pin.empty()) {
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log_warning("Malformed liberty file - missing clock_gate_enable_pin in cell %s",
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cell_name.c_str());
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continue;
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}
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double area = 0;
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const LibertyAst *ar = cell->find("area");
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if (ar != nullptr && !ar->value.empty())
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area = atof(ar->value.c_str());
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std::optional<ICGRankable>& icg_to_beat = clk_pol ? best_pos : best_neg;
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bool winning = false;
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if (icg_to_beat) {
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log_debug("ties: %zu ? %zu\n", icg_to_beat->tie_lo_pins.size(),
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icg_interface.tie_lo_pins.size());
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log_debug("area: %f ? %f\n", icg_to_beat->area, area);
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// Prefer fewer test enables over area reduction (unlikely to matter)
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auto goal = std::make_pair(icg_to_beat->tie_lo_pins.size(), icg_to_beat->area);
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auto cost = std::make_pair(icg_interface.tie_lo_pins.size(), area);
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winning = cost < goal;
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if (winning)
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log_debug("%s beats %s\n", icg_interface.name, icg_to_beat->name);
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} else {
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log_debug("%s is the first of its polarity\n", icg_interface.name);
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winning = true;
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}
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if (winning) {
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ICGRankable new_icg {icg_interface, area};
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icg_to_beat.emplace(new_icg);
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}
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}
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std::optional<ClockGateCell> pos;
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std::optional<ClockGateCell> neg;
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if (best_pos) {
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log("Selected rising edge ICG %s from Liberty file\n", best_pos->name);
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pos.emplace(*best_pos);
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}
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if (best_neg) {
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log("Selected falling edge ICG %s from Liberty file\n", best_neg->name);
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neg.emplace(*best_neg);
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}
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return std::make_pair(pos, neg);
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}
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struct ClockgatePass : public Pass {
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ClockgatePass() : Pass("clockgate", "extract clock gating out of flip flops") { }
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void help() override {
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// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
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log("\n");
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log(" clockgate [options] [selection]\n");
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log("\n");
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log("This pass transforms each set of FFs sharing the same clock and\n");
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log("enable signal into a clock-gating cell and a set of enable-less FFs.\n");
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log("Primarily a power-saving transformation on ASIC designs.\n");
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log("\n");
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log(" -pos <celltype> <ce>:<clk>:<gclk>\n");
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log(" If specified, rising-edge FFs will have CE inputs\n");
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log(" removed and a gated clock will be created by the\n");
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log(" user-specified <celltype> ICG (integrated clock gating)\n");
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log(" cell with ports named <ce>, <clk>, <gclk>.\n");
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log(" The ICG's clock enable pin must be active high.\n");
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log(" -neg <celltype> <ce>:<clk>:<gclk>\n");
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log(" If specified, falling-edge FFs will have CE inputs\n");
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log(" removed and a gated clock will be created by the\n");
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log(" user-specified <celltype> ICG (integrated clock gating)\n");
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log(" cell with ports named <ce>, <clk>, <gclk>.\n");
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log(" The ICG's clock enable pin must be active high.\n");
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log(" -liberty <filename>\n");
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log(" If specified, ICGs will be selected from the liberty files\n");
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log(" if available. Priority is given to cells with fewer tie_lo\n");
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log(" inputs and smaller size. This removes the need to manually\n");
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log(" specify -pos or -neg and -tie_lo.\n");
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log(" -dont_use <celltype>\n");
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log(" Cells <celltype> won't be considered when searching for ICGs\n");
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log(" in the liberty file specified by -liberty.\n");
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log(" -tie_lo <port_name>\n");
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log(" Port <port_name> of the ICG will be tied to zero.\n");
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log(" Intended for DFT scan-enable pins.\n");
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log(" -min_net_size <n>\n");
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log(" Only transform sets of at least <n> eligible FFs.\n");
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log(" \n");
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}
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// One ICG will be generated per ClkNetInfo
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// if the number of FFs associated with it is sufficent
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struct ClkNetInfo {
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// Original, ungated clock into enabled FF
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SigBit clk_bit;
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// Original clock enable into enabled FF
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SigBit ce_bit;
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bool pol_clk;
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bool pol_ce;
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[[nodiscard]] Hasher hash_into(Hasher h) const {
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auto t = std::make_tuple(clk_bit, ce_bit, pol_clk, pol_ce);
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h.eat(t);
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return h;
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}
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bool operator==(const ClkNetInfo& other) const {
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return (clk_bit == other.clk_bit) &&
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(ce_bit == other.ce_bit) &&
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(pol_clk == other.pol_clk) &&
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(pol_ce == other.pol_ce);
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}
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};
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struct GClkNetInfo {
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// How many CE FFs on this CLK net have we seen?
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int net_size;
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// After ICG generation, we have new gated CLK signals
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Wire* new_net;
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};
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ClkNetInfo clk_info_from_ff(FfData& ff) {
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SigBit clk = ff.sig_clk[0];
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SigBit ce = ff.sig_ce[0];
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ClkNetInfo info{clk, ce, ff.pol_clk, ff.pol_ce};
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return info;
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}
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void execute(std::vector<std::string> args, RTLIL::Design *design) override {
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log_header(design, "Executing CLOCK_GATE pass (extract clock gating out of flip flops).\n");
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std::optional<ClockGateCell> pos_icg_desc;
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std::optional<ClockGateCell> neg_icg_desc;
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std::vector<std::string> tie_lo_pins;
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std::vector<std::string> liberty_files;
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std::vector<std::string> dont_use_cells;
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int min_net_size = 0;
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size_t argidx;
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for (argidx = 1; argidx < args.size(); argidx++) {
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if (args[argidx] == "-pos" && argidx+2 < args.size()) {
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auto name = args[++argidx];
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auto rest = args[++argidx];
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pos_icg_desc = icg_from_arg(name, rest);
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continue;
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}
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if (args[argidx] == "-neg" && argidx+2 < args.size()) {
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auto name = args[++argidx];
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auto rest = args[++argidx];
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neg_icg_desc = icg_from_arg(name, rest);
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continue;
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}
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if (args[argidx] == "-tie_lo" && argidx+1 < args.size()) {
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tie_lo_pins.push_back(RTLIL::escape_id(args[++argidx]));
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continue;
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}
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if (args[argidx] == "-liberty" && argidx+1 < args.size()) {
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std::string liberty_file = args[++argidx];
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rewrite_filename(liberty_file);
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liberty_files.push_back(liberty_file);
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continue;
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}
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if (args[argidx] == "-dont_use" && argidx+1 < args.size()) {
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dont_use_cells.push_back(args[++argidx]);
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continue;
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}
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if (args[argidx] == "-min_net_size" && argidx+1 < args.size()) {
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min_net_size = atoi(args[++argidx].c_str());
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continue;
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}
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break;
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}
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if (!liberty_files.empty()) {
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LibertyMergedCells merged;
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for (auto path : liberty_files) {
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std::istream* f = uncompressed(path);
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LibertyParser p(*f, path);
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merged.merge(p);
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delete f;
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}
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std::tie(pos_icg_desc, neg_icg_desc) =
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find_icgs(merged.cells, dont_use_cells);
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} else {
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for (auto pin : tie_lo_pins) {
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if (pos_icg_desc)
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pos_icg_desc->tie_lo_pins.push_back(pin);
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if (neg_icg_desc)
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neg_icg_desc->tie_lo_pins.push_back(pin);
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}
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}
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extra_args(args, argidx, design);
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pool<Cell*> ce_ffs;
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dict<ClkNetInfo, GClkNetInfo> clk_nets;
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int gated_flop_count = 0;
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for (auto module : design->selected_unboxed_whole_modules()) {
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for (auto cell : module->cells()) {
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if (!cell->is_builtin_ff())
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continue;
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FfData ff(nullptr, cell);
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// It would be odd to get constants, but we better handle it
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if (ff.has_ce) {
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if (!ff.sig_clk.is_bit() || !ff.sig_ce.is_bit())
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continue;
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if (!ff.sig_clk[0].is_wire() || !ff.sig_ce[0].is_wire())
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continue;
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ce_ffs.insert(cell);
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ClkNetInfo info = clk_info_from_ff(ff);
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auto it = clk_nets.find(info);
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if (it == clk_nets.end())
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clk_nets[info] = GClkNetInfo();
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clk_nets[info].net_size++;
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}
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}
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for (auto& clk_net : clk_nets) {
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auto& clk = clk_net.first;
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auto& gclk = clk_net.second;
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if (gclk.net_size < min_net_size)
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continue;
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std::optional<ClockGateCell> matching_icg_desc;
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if (pos_icg_desc && clk.pol_clk)
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matching_icg_desc = pos_icg_desc;
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else if (neg_icg_desc && !clk.pol_clk)
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matching_icg_desc = neg_icg_desc;
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if (!matching_icg_desc)
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continue;
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Cell* icg = module->addCell(NEW_ID, matching_icg_desc->name);
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icg->setPort(matching_icg_desc->ce_pin, clk.ce_bit);
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icg->setPort(matching_icg_desc->clk_in_pin, clk.clk_bit);
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gclk.new_net = module->addWire(NEW_ID);
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icg->setPort(matching_icg_desc->clk_out_pin, gclk.new_net);
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// Tie low DFT ports like scan chain enable
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for (auto port : matching_icg_desc->tie_lo_pins)
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icg->setPort(port, Const(0, 1));
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// Fix CE polarity if needed
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if (!clk.pol_ce) {
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SigBit ce_fixed_pol = module->NotGate(NEW_ID, clk.ce_bit);
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icg->setPort(matching_icg_desc->ce_pin, ce_fixed_pol);
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}
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}
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for (auto cell : ce_ffs) {
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FfData ff(nullptr, cell);
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ClkNetInfo info = clk_info_from_ff(ff);
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auto it = clk_nets.find(info);
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log_assert(it != clk_nets.end() && "Bug: desync ce_ffs and clk_nets");
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if (!it->second.new_net)
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continue;
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log_debug("Fix up FF %s\n", cell->name);
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// Now we start messing with the design
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ff.has_ce = false;
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// Construct the clock gate
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// ICG = integrated clock gate, industry shorthand
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ff.sig_clk = (*it).second.new_net;
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// Rebuild the flop
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(void)ff.emit();
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gated_flop_count++;
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}
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ce_ffs.clear();
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clk_nets.clear();
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}
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log("Converted %d FFs.\n", gated_flop_count);
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}
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} ClockgatePass;
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PRIVATE_NAMESPACE_END
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