WIP for new assign_budget() using topographical ordering
This commit is contained in:
Eddie Hung
parent
8a6ff4b261
commit
e314ea761a
171
common/timing.cc
171
common/timing.cc
@ -23,6 +23,7 @@
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#include <utility>
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#include "log.h"
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#include "util.h"
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#include <boost/range/adaptor/reversed.hpp>
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NEXTPNR_NAMESPACE_BEGIN
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@ -38,6 +39,14 @@ struct Timing
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PortRefVector *crit_path;
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DelayFrequency *slack_histogram;
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struct TimingData {
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TimingData() : max_arrival(), max_path_length(), min_remaining_budget() {}
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TimingData(delay_t max_arrival) : max_arrival(max_arrival), max_path_length(), min_remaining_budget() {}
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delay_t max_arrival;
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unsigned max_path_length = 0;
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delay_t min_remaining_budget;
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};
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Timing(Context *ctx, bool update, PortRefVector *crit_path = nullptr, DelayFrequency *slack_histogram = nullptr)
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: ctx(ctx), update(update), min_slack(1.0e12 / ctx->target_freq), crit_path(crit_path),
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slack_histogram(slack_histogram)
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@ -53,8 +62,8 @@ struct Timing
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// If budget override is less than existing budget, then do not increment
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// path length
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int pl = path_length + 1;
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auto budget = ctx->getBudgetOverride(net, usr, net_budget);
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if (budget < net_budget) {
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auto budget = net_budget;
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if (ctx->getBudgetOverride(net, usr, budget) && budget < net_budget) {
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net_budget = budget;
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pl = std::max(1, path_length);
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}
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@ -109,16 +118,17 @@ struct Timing
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delay_t walk_paths()
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{
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delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
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const auto clk_period = delay_t(1.0e12 / ctx->target_freq);
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// Go through all clocked drivers and distribute the available path
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// slack evenly into the budget of every sink on the path
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#if 0
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for (auto &cell : ctx->cells) {
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for (auto port : cell.second->ports) {
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if (port.second.type == PORT_OUT) {
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IdString clock_domain = ctx->getPortClock(cell.second.get(), port.first);
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if (clock_domain != IdString()) {
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delay_t slack = default_slack; // TODO: clock constraints
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delay_t slack = clk_period; // TODO: clock constraints
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DelayInfo clkToQ;
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if (ctx->getCellDelay(cell.second.get(), clock_domain, port.first, clkToQ))
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slack -= clkToQ.maxDelay();
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@ -128,16 +138,165 @@ struct Timing
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}
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}
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}
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#else
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std::vector<NetInfo*> topographical_order;
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std::unordered_map<const PortInfo*, unsigned> port_fanin;
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std::unordered_map<const NetInfo*, TimingData> net_data;
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std::vector<IdString> input_ports;
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std::vector<const PortInfo*> output_ports;
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for (auto &cell : ctx->cells) {
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input_ports.clear();
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output_ports.clear();
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bool is_io = cell.second->type == ctx->id_sb_io;
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for (auto& port : cell.second->ports) {
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if (!port.second.net) continue;
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if (port.second.type == PORT_OUT)
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output_ports.push_back(&port.second);
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else
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input_ports.push_back(port.first);
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}
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for (auto o : output_ports) {
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IdString clock_domain = ctx->getPortClock(cell.second.get(), o->name);
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if (clock_domain != IdString()) {
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DelayInfo clkToQ;
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ctx->getCellDelay(cell.second.get(), clock_domain, o->name, clkToQ);
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topographical_order.emplace_back(o->net);
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net_data.emplace(o->net, TimingData{ clkToQ.maxDelay() });
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}
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else {
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if (is_io) {
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topographical_order.emplace_back(o->net);
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net_data.emplace(o->net, TimingData{});
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}
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for (auto i : input_ports) {
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DelayInfo comb_delay;
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bool is_path = ctx->getCellDelay(cell.second.get(), i, o->name, comb_delay);
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if (is_path)
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port_fanin[o]++;
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}
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}
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}
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}
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std::deque<NetInfo*> queue(topographical_order.begin(), topographical_order.end());
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while (!queue.empty()) {
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const auto net = queue.front();
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queue.pop_front();
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for (auto &usr : net->users) {
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if (ctx->getPortClock(usr.cell, usr.port) != IdString()) {
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} else {
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// Follow outputs of the user
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for (auto& port : usr.cell->ports) {
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if (port.second.type == PORT_OUT && port.second.net) {
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DelayInfo comb_delay;
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bool is_path = ctx->getCellDelay(usr.cell, usr.port, port.first, comb_delay);
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if (is_path) {
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auto it = port_fanin.find(&port.second);
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NPNR_ASSERT(it != port_fanin.end());
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if (--it->second == 0) {
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topographical_order.emplace_back(port.second.net);
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queue.emplace_back(port.second.net);
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port_fanin.erase(it);
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}
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}
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}
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}
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}
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}
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}
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// Find the maximum arrival time and max path length for each net
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for (auto net : topographical_order) {
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auto &nd = net_data.at(net);
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const auto net_arrival = nd.max_arrival;
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const auto net_length_plus_one = nd.max_path_length + 1;
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nd.min_remaining_budget = clk_period;
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for (auto &usr : net->users) {
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if (ctx->getPortClock(usr.cell, usr.port) != IdString()) {
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} else {
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auto net_delay = ctx->getNetinfoRouteDelay(net, usr);
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delay_t budget;
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auto budget_override = ctx->getBudgetOverride(net, usr, budget);
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auto usr_arrival = net_arrival + net_delay;
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// Follow outputs of the user
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for (auto port : usr.cell->ports) {
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if (port.second.type == PORT_OUT && port.second.net) {
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DelayInfo comb_delay;
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// Look up delay through this path
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bool is_path = ctx->getCellDelay(usr.cell, usr.port, port.first, comb_delay);
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if (is_path) {
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auto& data = net_data[port.second.net];
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auto& arrival = data.max_arrival;
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arrival = std::max(arrival, usr_arrival + comb_delay.maxDelay());
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if (!budget_override) {
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auto& path_length = data.max_path_length;
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path_length = std::max(path_length, net_length_plus_one);
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}
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}
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}
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}
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}
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}
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}
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for (auto net : boost::adaptors::reverse(topographical_order)) {
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auto &nd = net_data.at(net);
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const delay_t net_length_plus_one = nd.max_path_length + 1;
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auto& net_min_remaining_budget = nd.min_remaining_budget;
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for (auto &usr : net->users) {
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const auto net_delay = ctx->getNetinfoRouteDelay(net, usr);
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auto budget_override = ctx->getBudgetOverride(net, usr, usr.budget);
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if (ctx->getPortClock(usr.cell, usr.port) != IdString()) {
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const auto net_arrival = nd.max_arrival;
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auto path_budget = clk_period - (net_arrival + net_delay);
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auto budget_share = path_budget / net_length_plus_one;
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if (budget_override)
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budget_share = 0;
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else
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usr.budget = std::min(usr.budget, net_delay + budget_share);
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net_min_remaining_budget = std::min(net_min_remaining_budget, path_budget - budget_share);
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min_slack = std::min(min_slack, path_budget);
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if (slack_histogram) {
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int slack_ps = ctx->getDelayNS(path_budget) * 1000;
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(*slack_histogram)[slack_ps]++;
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}
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} else {
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// Follow outputs of the user
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for (auto port : usr.cell->ports) {
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if (port.second.type == PORT_OUT && port.second.net) {
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DelayInfo comb_delay;
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// Look up delay through this path
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bool is_path = ctx->getCellDelay(usr.cell, usr.port, port.first, comb_delay);
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if (is_path) {
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auto path_budget = net_data.at(port.second.net).min_remaining_budget;
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auto budget_share = path_budget / net_length_plus_one;
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if (budget_override)
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budget_share = 0;
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else
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usr.budget = std::min(usr.budget, net_delay + budget_share);
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net_min_remaining_budget = std::min(net_min_remaining_budget, path_budget - budget_share);
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}
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}
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}
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}
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}
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}
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#endif
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return min_slack;
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}
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void assign_budget()
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{
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// Clear delays to a very high value first
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delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
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for (auto &net : ctx->nets) {
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for (auto &usr : net.second->users) {
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usr.budget = default_slack;
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usr.budget = std::numeric_limits<delay_t>::max();
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}
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}
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