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Merge pull request #31 from eddiehung/slack_histogram

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Print slack histogram at end of placement and at end of routing
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Eddie Hung 2018-08-05 00:03:18 -07:00 committed by GitHub
commit 8a9b3626d3
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 148 additions and 102 deletions
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2
common/placer1.cc
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@ -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;
}

2
common/router1.cc
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@ -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) {

240
common/timing.cc
View File

@ -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)
*crit_path = *current_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)
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

6
common/timing.h
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@ -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