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graph delay calc N^2 from bidirect pad ring pins 

Signed-off-by: James Cherry <cherry@parallaxsw.com>
This commit is contained in:
James Cherry 2024-03-06 09:53:55 -07:00
parent 84d6735fa2
commit b4e58d5b74
2 changed files with 57 additions and 3 deletions
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56
graph/Graph.cc
View File

@ -276,10 +276,19 @@ Graph::makeWireEdgesFromPin(const Pin *drvr_pin,
{
// Find all drivers and loads on the net to avoid N*M run time
// for large fanin/fanout nets.
PinSeq loads, drvrs;
PinSeq drvrs, loads;
FindNetDrvrLoads visitor(drvr_pin, visited_drvrs, loads, drvrs, network_);
network_->visitConnectedPins(drvr_pin, visitor);
if (isIsolatedNet(drvrs, loads)) {
for (auto drvr_pin : drvrs) {
visited_drvrs.insert(drvr_pin);
debugPrint(debug_, "graph", 1, "ignoring isolated driver %s",
network_->pathName(drvr_pin));
}
return;
}
for (auto drvr_pin : drvrs) {
for (auto load_pin : loads) {
if (drvr_pin != load_pin)
@ -288,6 +297,35 @@ Graph::makeWireEdgesFromPin(const Pin *drvr_pin,
}
}
// Check for nets with bidirect drivers that have no fanin or
// fanout. One example of these nets are bidirect pad ring pins
// are connected together but have no function but are marked
// as signal nets.
// These nets tickle N^2 behaviors that have no function.
bool
Graph::isIsolatedNet(PinSeq &drvrs,
PinSeq &loads) const
{
if (drvrs.size() < 10)
return false;
// Check that all drivers have no fanin.
for (auto drvr_pin : drvrs) {
Vertex *drvr_vertex = pinDrvrVertex(drvr_pin);
if (network_->isTopLevelPort(drvr_pin)
|| drvr_vertex->hasFanin())
return false;
}
// Check for fanout on the load pins.
for (auto load_pin : loads) {
Vertex *load_vertex = pinLoadVertex(load_pin);
if (load_vertex->hasFanout()
|| load_vertex->hasChecks()) {
return false;
}
}
return true;
}
void
Graph::makeWireEdgesToPin(const Pin *to_pin)
{
@ -536,7 +574,7 @@ Graph::makeArrivals(Vertex *vertex,
uint32_t count)
{
if (vertex->arrivals() != arrival_null)
debugPrint(debug_, "leaks", 617, "arrival leak");
debugPrint(debug_, "graph", 1, "arrival leak");
Arrival *arrivals;
ArrivalId id;
{
@ -569,7 +607,7 @@ Graph::makeRequireds(Vertex *vertex,
uint32_t count)
{
if (vertex->requireds() != arrival_null)
debugPrint(debug_, "leaks", 617, "required leak");
debugPrint(debug_, "graph", 1, "required leak");
Required *requireds;
ArrivalId id;
{
@ -1281,6 +1319,18 @@ Vertex::setIsDisabledConstraint(bool disabled)
is_disabled_constraint_ = disabled;
}
bool
Vertex::hasFanin() const
{
return in_edges_ != edge_id_null;
}
bool
Vertex::hasFanout() const
{
return out_edges_ != edge_id_null;
}
void
Vertex::setHasChecks(bool has_checks)
{

4
include/sta/Graph.hh
View File

@ -221,6 +221,8 @@ protected:
void makePinVertices(const Instance *inst);
void makeWireEdgesFromPin(const Pin *drvr_pin,
PinSet &visited_drvrs);
bool isIsolatedNet(PinSeq &drvrs,
PinSeq &loads) const;
void makeWireEdges();
virtual void makeInstDrvrWireEdges(const Instance *inst,
PinSet &visited_drvrs);
@ -289,6 +291,8 @@ public:
Level level() const { return level_; }
void setLevel(Level level);
bool isRoot() const{ return level_ == 0; }
bool hasFanin() const;
bool hasFanout() const;
LevelColor color() const { return static_cast<LevelColor>(color_); }
void setColor(LevelColor color);
ArrivalId arrivals() { return arrivals_; }