aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
Diffstat
-rw-r--r--common/placer1.cc2
-rw-r--r--common/router1.cc2
-rw-r--r--common/timing.cc240
-rw-r--r--common/timing.h6
4 files changed, 148 insertions, 102 deletions
diff --git a/common/placer1.cc b/common/placer1.cc
index 32074220..c4543e2a 100644
--- a/common/placer1.cc
+++ b/common/placer1.cc
@@ -276,7 +276,7 @@ class SAPlacer
if (get_constraints_distance(ctx, cell.second) != 0)
log_error("constraint satisfaction check failed for cell '%s' at Bel '%s'\n", cell.first.c_str(ctx),
ctx->getBelName(cell.second->bel).c_str(ctx));
- timing_analysis(ctx, true /* print_fmax */);
+ timing_analysis(ctx);
ctx->unlock();
return true;
}
diff --git a/common/router1.cc b/common/router1.cc
index 6e352866..dd338b35 100644
--- a/common/router1.cc
+++ b/common/router1.cc
@@ -933,7 +933,7 @@ bool router1(Context *ctx, const Router1Cfg &cfg)
#ifndef NDEBUG
ctx->check();
#endif
- timing_analysis(ctx, true /* print_fmax */, true /* print_path */);
+ timing_analysis(ctx, true /* slack_histogram */, true /* print_path */);
ctx->unlock();
return true;
} catch (log_execution_error_exception) {
diff --git a/common/timing.cc b/common/timing.cc
index f422ee91..f6c5f001 100644
--- a/common/timing.cc
+++ b/common/timing.cc
@@ -26,100 +26,124 @@
NEXTPNR_NAMESPACE_BEGIN
-typedef std::list<const PortRef *> PortRefList;
+typedef std::vector<const PortRef *> PortRefVector;
+typedef std::map<int, unsigned> DelayFrequency;
-static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack, bool update, delay_t &min_slack,
- PortRefList *current_path, PortRefList *crit_path);
-
-// Follow a path, returning budget to annotate
-static delay_t follow_user_port(Context *ctx, PortRef &user, int path_length, delay_t slack, bool update,
- delay_t &min_slack, PortRefList *current_path, PortRefList *crit_path)
+struct Timing
{
- delay_t value;
- if (ctx->getPortClock(user.cell, user.port) != IdString()) {
- // At the end of a timing path (arguably, should check setup time
- // here too)
- value = slack / path_length;
- if (slack < min_slack) {
- min_slack = slack;
+ Context *ctx;
+ bool update;
+ delay_t min_slack;
+ PortRefVector current_path;
+ PortRefVector *crit_path;
+ DelayFrequency *slack_histogram;
+
+ Timing(Context *ctx, bool update, PortRefVector *crit_path = nullptr, DelayFrequency *slack_histogram = nullptr)
+ : ctx(ctx), update(update), min_slack(1.0e12 / ctx->target_freq), crit_path(crit_path),
+ slack_histogram(slack_histogram)
+ {
+ }
+
+ delay_t follow_net(NetInfo *net, int path_length, delay_t slack)
+ {
+ delay_t net_budget = slack / (path_length + 1);
+ for (auto &usr : net->users) {
+ if (crit_path)
+ current_path.push_back(&usr);
+ // If budget override is less than existing budget, then do not increment
+ // path length
+ int pl = path_length + 1;
+ auto budget = ctx->getBudgetOverride(net, usr, net_budget);
+ if (budget < net_budget) {
+ net_budget = budget;
+ pl = std::max(1, path_length);
+ }
+ auto delay = ctx->getNetinfoRouteDelay(net, usr);
+ net_budget = std::min(net_budget, follow_user_port(usr, pl, slack - delay));
+ if (update)
+ usr.budget = std::min(usr.budget, delay + net_budget);
if (crit_path)
- *crit_path = *current_path;
+ current_path.pop_back();
}
- } else {
- // Default to the path ending here, if no further paths found
- value = slack / path_length;
- // Follow outputs of the user
- for (auto port : user.cell->ports) {
- if (port.second.type == PORT_OUT) {
- DelayInfo comb_delay;
- // Look up delay through this path
- bool is_path = ctx->getCellDelay(user.cell, user.port, port.first, comb_delay);
- if (is_path) {
- NetInfo *net = port.second.net;
- if (net) {
- delay_t path_budget = follow_net(ctx, net, path_length, slack - comb_delay.maxDelay(), update,
- min_slack, current_path, crit_path);
- value = std::min(value, path_budget);
+ return net_budget;
+ }
+
+ // Follow a path, returning budget to annotate
+ delay_t follow_user_port(PortRef &user, int path_length, delay_t slack)
+ {
+ delay_t value;
+ if (ctx->getPortClock(user.cell, user.port) != IdString()) {
+ // At the end of a timing path (arguably, should check setup time
+ // here too)
+ value = slack / path_length;
+ if (slack < min_slack) {
+ min_slack = slack;
+ if (crit_path)
+ *crit_path = current_path;
+ }
+ if (slack_histogram) {
+ int slack_ps = ctx->getDelayNS(slack) * 1000;
+ (*slack_histogram)[slack_ps]++;
+ }
+ } else {
+ // Default to the path ending here, if no further paths found
+ value = slack / path_length;
+ // Follow outputs of the user
+ for (auto port : user.cell->ports) {
+ if (port.second.type == PORT_OUT) {
+ DelayInfo comb_delay;
+ // Look up delay through this path
+ bool is_path = ctx->getCellDelay(user.cell, user.port, port.first, comb_delay);
+ if (is_path) {
+ NetInfo *net = port.second.net;
+ if (net) {
+ delay_t path_budget = follow_net(net, path_length, slack - comb_delay.maxDelay());
+ value = std::min(value, path_budget);
+ }
}
}
}
}
+ return value;
}
- return value;
-}
-static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack, bool update, delay_t &min_slack,
- PortRefList *current_path, PortRefList *crit_path)
-{
- delay_t net_budget = slack / (path_length + 1);
- for (auto &usr : net->users) {
- if (crit_path)
- current_path->push_back(&usr);
- // If budget override is less than existing budget, then do not increment path length
- int pl = path_length + 1;
- auto budget = ctx->getBudgetOverride(net, usr, net_budget);
- if (budget < net_budget) {
- net_budget = budget;
- pl = std::max(1, path_length);
- }
- auto delay = ctx->getNetinfoRouteDelay(net, usr);
- net_budget = std::min(
- net_budget, follow_user_port(ctx, usr, pl, slack - delay, update, min_slack, current_path, crit_path));
- if (update)
- usr.budget = std::min(usr.budget, delay + net_budget);
- if (crit_path)
- current_path->pop_back();
- }
- return net_budget;
-}
+ delay_t walk_paths()
+ {
+ delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
-static delay_t walk_paths(Context *ctx, bool update, PortRefList *crit_path)
-{
- delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
- delay_t min_slack = default_slack;
-
- PortRefList current_path;
-
- // Go through all clocked drivers and distribute the available path
- // slack evenly into the budget of every sink on the path
- for (auto &cell : ctx->cells) {
- for (auto port : cell.second->ports) {
- if (port.second.type == PORT_OUT) {
- IdString clock_domain = ctx->getPortClock(cell.second.get(), port.first);
- if (clock_domain != IdString()) {
- delay_t slack = default_slack; // TODO: clock constraints
- DelayInfo clkToQ;
- if (ctx->getCellDelay(cell.second.get(), clock_domain, port.first, clkToQ))
- slack -= clkToQ.maxDelay();
- if (port.second.net)
- follow_net(ctx, port.second.net, 0, slack, update, min_slack, &current_path, crit_path);
+ // Go through all clocked drivers and distribute the available path
+ // slack evenly into the budget of every sink on the path
+ for (auto &cell : ctx->cells) {
+ for (auto port : cell.second->ports) {
+ if (port.second.type == PORT_OUT) {
+ IdString clock_domain = ctx->getPortClock(cell.second.get(), port.first);
+ if (clock_domain != IdString()) {
+ delay_t slack = default_slack; // TODO: clock constraints
+ DelayInfo clkToQ;
+ if (ctx->getCellDelay(cell.second.get(), clock_domain, port.first, clkToQ))
+ slack -= clkToQ.maxDelay();
+ if (port.second.net)
+ follow_net(port.second.net, 0, slack);
+ }
}
}
}
+ return min_slack;
}
- return min_slack;
-}
+ void assign_budget()
+ {
+ // Clear delays to a very high value first
+ delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
+ for (auto &net : ctx->nets) {
+ for (auto &usr : net.second->users) {
+ usr.budget = default_slack;
+ }
+ }
+
+ walk_paths();
+ }
+};
void assign_budget(Context *ctx, bool quiet)
{
@@ -128,15 +152,8 @@ void assign_budget(Context *ctx, bool quiet)
log_info("Annotating ports with timing budgets for target frequency %.2f MHz\n", ctx->target_freq/1e6);
}
- // Clear delays to a very high value first
- delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
- for (auto &net : ctx->nets) {
- for (auto &usr : net.second->users) {
- usr.budget = default_slack;
- }
- }
-
- delay_t min_slack = walk_paths(ctx, true, nullptr);
+ Timing timing(ctx, true /* update */);
+ timing.assign_budget();
if (!quiet || ctx->verbose) {
for (auto &net : ctx->nets) {
@@ -160,21 +177,27 @@ void assign_budget(Context *ctx, bool quiet)
// dynamically adjust the target frequency to be the currently
// achieved maximum
if (ctx->auto_freq && ctx->slack_redist_iter > 0) {
- ctx->target_freq = 1e12 / (default_slack - min_slack);
+ delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
+ ctx->target_freq = 1e12 / (default_slack - timing.min_slack);
if (ctx->verbose)
- log_info("minimum slack for this assign = %d, target Fmax for next update = %.2f MHz\n", min_slack,
- ctx->target_freq / 1e6);
+ log_info("minimum slack for this assign = %d, target Fmax for next "
+ "update = %.2f MHz\n",
+ timing.min_slack, ctx->target_freq / 1e6);
}
if (!quiet)
log_info("Checksum: 0x%08x\n", ctx->checksum());
}
-delay_t timing_analysis(Context *ctx, bool print_fmax, bool print_path)
+void timing_analysis(Context *ctx, bool print_histogram, bool print_path)
{
- delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
- PortRefList crit_path;
- delay_t min_slack = walk_paths(ctx, false, &crit_path);
+ PortRefVector crit_path;
+ DelayFrequency slack_histogram;
+
+ Timing timing(ctx, false /* update */, print_path ? &crit_path : nullptr,
+ print_histogram ? &slack_histogram : nullptr);
+ auto min_slack = timing.walk_paths();
+
if (print_path) {
if (crit_path.empty()) {
log_info("Design contains no timing paths\n");
@@ -211,9 +234,32 @@ delay_t timing_analysis(Context *ctx, bool print_fmax, bool print_path)
log_break();
}
}
- if (print_fmax)
- log_info("estimated Fmax = %.2f MHz\n", 1e6 / (default_slack - min_slack));
- return min_slack;
+
+ delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
+ log_info("estimated Fmax = %.2f MHz\n", 1e6 / (default_slack - min_slack));
+
+ if (print_histogram) {
+ constexpr unsigned num_bins = 20;
+ unsigned bar_width = 60;
+ auto min_slack = slack_histogram.begin()->first;
+ auto max_slack = slack_histogram.rbegin()->first;
+ auto bin_size = (max_slack - min_slack) / num_bins;
+ std::vector<unsigned> bins(num_bins + 1);
+ unsigned max_freq = 0;
+ for (const auto &i : slack_histogram) {
+ auto &bin = bins[(i.first - min_slack) / bin_size];
+ bin += i.second;
+ max_freq = std::max(max_freq, bin);
+ }
+ bar_width = std::min(bar_width, max_freq);
+
+ log_break();
+ log_info("Slack histogram:\n");
+ log_info(" legend: * represents %d endpoint(s)\n", max_freq / bar_width);
+ for (unsigned i = 0; i < bins.size(); ++i)
+ log_info("%6d < ps < %6d |%s\n", min_slack + bin_size * i, min_slack + bin_size * (i + 1),
+ std::string(bins[i] * bar_width / max_freq, '*').c_str());
+ }
}
NEXTPNR_NAMESPACE_END
diff --git a/common/timing.h b/common/timing.h
index d0159d5c..cfb71ae0 100644
--- a/common/timing.h
+++ b/common/timing.h
@@ -27,9 +27,9 @@ NEXTPNR_NAMESPACE_BEGIN
// Evenly redistribute the total path slack amongst all sinks on each path
void assign_budget(Context *ctx, bool quiet = false);
-// Perform timing analysis and return the minimum path slack,
-// optionally, print out the fmax and critical path
-delay_t timing_analysis(Context *ctx, bool print_fmax = false, bool print_path = false);
+// Perform timing analysis and print out the fmax, and optionally the
+// critical path
+void timing_analysis(Context *ctx, bool slack_histogram = true, bool print_path = false);
NEXTPNR_NAMESPACE_END
generated by cgit v1.2.3 (git 2.25.1) at 2025-04-21 18:08:16 +0000