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[timing] Restore and skip false startpoints

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This commit is contained in:
Eddie Hung 2018-09-15 15:17:37 -07:00
parent c9059fc7d0
commit 8749327f1e
1 changed files with 6 additions and 17 deletions
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23
common/timing.cc
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@ -48,6 +48,7 @@ struct Timing
delay_t max_arrival;
unsigned max_path_length = 0;
delay_t min_remaining_budget;
bool false_startpoint = false;
};
Timing(Context *ctx, bool net_delays, bool update, PortRefVector *crit_path = nullptr,
@ -93,12 +94,11 @@ struct Timing
topographical_order.emplace_back(o->net);
net_data.emplace(o->net, TimingData{clkToQ.maxDelay()});
} else {
// TODO(eddieh): Generated clocks and ignored ports are currently added into the ordering as if it
// was a regular timing start point in order to enable the full topographical order to be computed,
// however these false nets (and their downstream paths) should not be in the final ordering
if (portClass == TMG_STARTPOINT || portClass == TMG_GEN_CLOCK || portClass == TMG_IGNORE) {
topographical_order.emplace_back(o->net);
net_data.emplace(o->net, TimingData{});
TimingData td;
td.false_startpoint = (portClass == TMG_GEN_CLOCK || portClass == TMG_IGNORE);
net_data.emplace(o->net, std::move(td));
}
// Otherwise, for all driven input ports on this cell, if a timing arc exists between the input and
// the current output port, increment fanin counter
@ -112,19 +112,6 @@ struct Timing
}
}
// If these constant nets exist, add them to the topographical ordering too
// TODO(eddieh): Also false paths and should be removed from ordering
auto it = ctx->nets.find(ctx->id("$PACKER_VCC_NET"));
if (it != ctx->nets.end()) {
topographical_order.emplace_back(it->second.get());
net_data.emplace(it->second.get(), TimingData{});
}
it = ctx->nets.find(ctx->id("$PACKER_GND_NET"));
if (it != ctx->nets.end()) {
topographical_order.emplace_back(it->second.get());
net_data.emplace(it->second.get(), TimingData{});
}
std::deque<NetInfo *> queue(topographical_order.begin(), topographical_order.end());
// Now walk the design, from the start points identified previously, building up a topographical order
@ -208,6 +195,8 @@ struct Timing
// between all nets on the path
for (auto net : boost::adaptors::reverse(topographical_order)) {
auto &nd = net_data.at(net);
// Ignore false startpoints
if (nd.false_startpoint) continue;
const delay_t net_length_plus_one = nd.max_path_length + 1;
auto &net_min_remaining_budget = nd.min_remaining_budget;
for (auto &usr : net->users) {