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Add compute_fmax() with refactoring, plus print out Fmax estimate post-place and post-route

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This commit is contained in:
Eddie Hung 2018-07-25 18:21:39 -07:00
parent a21cc4dd5b
commit 760a47779a
4 changed files with 49 additions and 40 deletions
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1
common/placer1.cc
View File

@ -276,6 +276,7 @@ class SAPlacer
}
}
}
log_info("estimated Fmax = %.2f MHz\n", compute_fmax(ctx) / 1e6);
ctx->unlock();
return true;
}

1
common/router1.cc
View File

@ -815,6 +815,7 @@ bool router1(Context *ctx)
ctx->check();
ctx->unlock();
#endif
log_info("estimated Fmax = %.2f MHz\n", compute_fmax(ctx) / 1e6);
return true;
} catch (log_execution_error_exception) {
#ifndef NDEBUG

84
common/timing.cc
View File

@ -76,10 +76,35 @@ static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t s
return net_budget;
}
void assign_budget(Context *ctx)
static UpdateMap compute_min_slack(Context *ctx, delay_t &min_slack)
{
UpdateMap updates;
delay_t min_slack = delay_t(1.0e12 / ctx->target_freq);
delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
// Go through all clocked drivers and distribute the available path
// slack evenly into the budget of every sink on the path ---
// record this value into the UpdateMap
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
delay_t clkToQ;
if (ctx->getCellDelay(cell.second.get(), clock_domain, port.first, clkToQ))
slack -= clkToQ;
if (port.second.net)
follow_net(ctx, port.second.net, 0, slack, updates, min_slack);
}
}
}
}
return updates;
}
void assign_budget(Context *ctx)
{
log_break();
log_info("Annotating ports with timing budgets\n");
@ -90,26 +115,12 @@ void assign_budget(Context *ctx)
usr.budget = default_slack;
}
}
min_slack = default_slack;
// Go through all clocked drivers and set up paths
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 = delay_t(1.0e12 / ctx->target_freq); // TODO: clock constraints
delay_t clkToQ;
if (ctx->getCellDelay(cell.second.get(), clock_domain, port.first, clkToQ))
slack -= clkToQ;
if (port.second.net) {
log_break();
follow_net(ctx, port.second.net, 0, slack, updates, min_slack);
}
}
}
}
}
delay_t min_slack = default_slack;
auto updates = compute_min_slack(ctx, min_slack);
// If user has not specified a frequency, adjust the target frequency
// to be equivalent to the critical path
if (!ctx->user_freq) {
ctx->target_freq = 1e12 / (default_slack - min_slack);
if (ctx->verbose)
@ -145,27 +156,12 @@ void assign_budget(Context *ctx)
void update_budget(Context *ctx)
{
UpdateMap updates;
delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
delay_t min_slack = delay_t(1.0e12 / ctx->target_freq);
// Go through all clocked drivers and distribute the available path slack evenly into every budget
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
delay_t clkToQ;
if (ctx->getCellDelay(cell.second.get(), clock_domain, port.first, clkToQ))
slack -= clkToQ;
if (port.second.net)
follow_net(ctx, port.second.net, 0, slack, updates, min_slack);
}
}
}
}
delay_t min_slack = default_slack;
auto updates = compute_min_slack(ctx, min_slack);
// If user has not specified a frequency, adjust the target frequency
// to be +5% higher than the current critical path
if (!ctx->user_freq) {
ctx->target_freq = 1.05 * (1e12 / (default_slack - min_slack));
if (ctx->verbose)
@ -199,4 +195,12 @@ void update_budget(Context *ctx)
}
}
float compute_fmax(Context *ctx)
{
delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
delay_t min_slack = default_slack;
compute_min_slack(ctx, min_slack);
return 1e12 / (default_slack - min_slack);
}
NEXTPNR_NAMESPACE_END

3
common/timing.h
View File

@ -27,8 +27,11 @@ NEXTPNR_NAMESPACE_BEGIN
// Assign "budget" values for all user ports in the design
void assign_budget(Context *ctx);
// Evenly redistribute the total path slack amongst all sinks on each path
void update_budget(Context *ctx);
float compute_fmax(Context *ctx);
NEXTPNR_NAMESPACE_END
#endif