333 lines
9.2 KiB
C++
333 lines
9.2 KiB
C++
// OpenSTA, Static Timing Analyzer
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// Copyright (c) 2025, Parallax Software, Inc.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//
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// The origin of this software must not be misrepresented; you must not
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// claim that you wrote the original software.
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//
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// Altered source versions must be plainly marked as such, and must not be
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// misrepresented as being the original software.
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//
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// This notice may not be removed or altered from any source distribution.
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#include "CheckFanoutLimits.hh"
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#include "Fuzzy.hh"
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#include "Liberty.hh"
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#include "Network.hh"
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#include "Sdc.hh"
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#include "InputDrive.hh"
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#include "Sim.hh"
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#include "PortDirection.hh"
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#include "Graph.hh"
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#include "Search.hh"
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namespace sta {
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class PinFanoutLimitSlackLess
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{
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public:
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PinFanoutLimitSlackLess(const MinMax *min_max,
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CheckFanoutLimits *check_fanout_limit,
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const StaState *sta);
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bool operator()(const Pin *pin1,
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const Pin *pin2) const;
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private:
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const MinMax *min_max_;
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CheckFanoutLimits *check_fanout_limit_;
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const StaState *sta_;
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};
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PinFanoutLimitSlackLess::PinFanoutLimitSlackLess(const MinMax *min_max,
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CheckFanoutLimits *check_fanout_limit,
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const StaState *sta) :
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min_max_(min_max),
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check_fanout_limit_(check_fanout_limit),
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sta_(sta)
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{
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}
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bool
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PinFanoutLimitSlackLess::operator()(const Pin *pin1,
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const Pin *pin2) const
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{
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float fanout1, fanout2;
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float limit1, limit2, slack1, slack2;
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check_fanout_limit_->checkFanout(pin1, min_max_,
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fanout1, limit1, slack1);
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check_fanout_limit_->checkFanout(pin2, min_max_,
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fanout2, limit2, slack2);
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return fuzzyLess(slack1, slack2)
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|| (fuzzyEqual(slack1, slack2)
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// Break ties for the sake of regression stability.
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&& sta_->network()->pinLess(pin1, pin2));
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}
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////////////////////////////////////////////////////////////////
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CheckFanoutLimits::CheckFanoutLimits(const Sta *sta) :
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sta_(sta)
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{
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}
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void
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CheckFanoutLimits::checkFanout(const Pin *pin,
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const MinMax *min_max,
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// Return values.
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float &fanout,
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float &limit,
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float &slack) const
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{
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fanout = 0.0;
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limit = min_max->initValue();
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slack = MinMax::min()->initValue();
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float limit1;
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bool limit1_exists;
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findLimit(pin, min_max, limit1, limit1_exists);
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if (limit1_exists)
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checkFanout(pin, min_max, limit1,
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fanout, limit, slack);
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}
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// return the tightest limit.
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void
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CheckFanoutLimits::findLimit(const Pin *pin,
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const MinMax *min_max,
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// Return values.
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float &limit,
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bool &exists) const
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{
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const Network *network = sta_->network();
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Sdc *sdc = sta_->sdc();
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limit = min_max->initValue();
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exists = false;
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// Default to top ("design") limit.
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// Applies to input ports as well as instance outputs.
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Cell *top_cell = network->cell(network->topInstance());
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sdc->fanoutLimit(top_cell, min_max,
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limit, exists);
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float limit1;
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bool exists1;
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if (network->isTopLevelPort(pin)) {
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Port *port = network->port(pin);
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sdc->fanoutLimit(port, min_max, limit1, exists1);
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if (exists1
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&& (!exists
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|| min_max->compare(limit, limit1))) {
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limit = limit1;
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exists = true;
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}
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InputDrive *drive = sdc->findInputDrive(port);
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if (drive) {
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for (auto rf : RiseFall::range()) {
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const LibertyCell *cell;
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const LibertyPort *from_port;
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float *from_slews;
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const LibertyPort *to_port;
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drive->driveCell(rf, min_max, cell, from_port, from_slews, to_port);
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if (to_port) {
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to_port->fanoutLimit(min_max, limit1, exists1);
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if (!exists1
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&& min_max == MinMax::max()
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&& to_port->direction()->isAnyOutput())
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to_port->libertyLibrary()->defaultMaxFanout(limit1, exists1);
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if (exists1
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&& (!exists
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|| min_max->compare(limit, limit1))) {
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limit = limit1;
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exists = true;
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}
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}
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}
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}
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}
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else {
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Cell *cell = network->cell(network->instance(pin));
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sdc->fanoutLimit(cell, min_max,
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limit1, exists1);
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if (exists1
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&& (!exists
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|| min_max->compare(limit, limit1))) {
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limit = limit1;
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exists = true;
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}
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LibertyPort *port = network->libertyPort(pin);
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if (port) {
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port->fanoutLimit(min_max, limit1, exists1);
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if (!exists1
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&& min_max == MinMax::max()
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&& port->direction()->isAnyOutput())
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port->libertyLibrary()->defaultMaxFanout(limit1, exists1);
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if (exists1
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&& (!exists
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|| min_max->compare(limit, limit1))) {
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limit = limit1;
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exists = true;
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}
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}
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}
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}
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void
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CheckFanoutLimits::checkFanout(const Pin *pin,
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const MinMax *min_max,
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float limit1,
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// Return values.
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float &fanout,
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float &limit,
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float &slack) const
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{
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float fanout1 = fanoutLoad(pin);
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float slack1 = (min_max == MinMax::max())
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? limit1 - fanout1
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: fanout1 - limit1;
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if (fuzzyLessEqual(slack1, slack)) {
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fanout = fanout1;
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slack = slack1;
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limit = limit1;
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}
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}
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float
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CheckFanoutLimits::fanoutLoad(const Pin *pin) const
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{
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float fanout = 0;
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const Network *network = sta_->network();
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NetConnectedPinIterator *pin_iter = network->connectedPinIterator(pin);
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while (pin_iter->hasNext()) {
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const Pin *fanout_pin = pin_iter->next();
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if (network->isLoad(fanout_pin)
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&& !network->isTopLevelPort(fanout_pin)) {
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LibertyPort *port = network->libertyPort(fanout_pin);
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if (port) {
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float fanout_load;
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bool exists;
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port->fanoutLoad(fanout_load, exists);
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if (!exists) {
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LibertyLibrary *lib = port->libertyLibrary();
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lib->defaultFanoutLoad(fanout_load, exists);
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}
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if (exists)
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fanout += fanout_load;
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}
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else
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fanout += 1;
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}
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}
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delete pin_iter;
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return fanout;
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}
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////////////////////////////////////////////////////////////////
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PinSeq
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CheckFanoutLimits::checkFanoutLimits(const Net *net,
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bool violators,
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const MinMax *min_max)
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{
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const Network *network = sta_->network();
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PinSeq fanout_pins;
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float min_slack = MinMax::min()->initValue();
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if (net) {
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NetPinIterator *pin_iter = network->pinIterator(net);
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while (pin_iter->hasNext()) {
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const Pin *pin = pin_iter->next();
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checkFanoutLimits(pin, violators, min_max, fanout_pins, min_slack);
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}
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delete pin_iter;
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}
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else {
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LeafInstanceIterator *inst_iter = network->leafInstanceIterator();
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while (inst_iter->hasNext()) {
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const Instance *inst = inst_iter->next();
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checkFanoutLimits(inst, violators, min_max, fanout_pins, min_slack);
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}
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delete inst_iter;
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// Check top level ports.
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checkFanoutLimits(network->topInstance(), violators, min_max,
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fanout_pins, min_slack);
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}
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sort(fanout_pins, PinFanoutLimitSlackLess(min_max, this, sta_));
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// Keep the min slack pin unless all violators or net pins.
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if (!fanout_pins.empty() && !violators && net == nullptr)
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fanout_pins.resize(1);
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return fanout_pins;
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}
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void
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CheckFanoutLimits::checkFanoutLimits(const Instance *inst,
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bool violators,
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const MinMax *min_max,
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PinSeq &fanout_pins,
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float &min_slack)
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{
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const Network *network = sta_->network();
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InstancePinIterator *pin_iter = network->pinIterator(inst);
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while (pin_iter->hasNext()) {
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const Pin *pin = pin_iter->next();
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checkFanoutLimits(pin, violators, min_max, fanout_pins, min_slack);
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}
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delete pin_iter;
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}
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void
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CheckFanoutLimits::checkFanoutLimits(const Pin *pin,
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bool violators,
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const MinMax *min_max,
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PinSeq &fanout_pins,
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float &min_slack)
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{
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if (checkPin(pin)) {
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float fanout;
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float limit, slack;
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checkFanout(pin, min_max, fanout, limit, slack);
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if (!fuzzyInf(slack)) {
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if (violators) {
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if (slack < 0.0)
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fanout_pins.push_back(pin);
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}
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else {
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if (fanout_pins.empty()
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|| slack < min_slack) {
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fanout_pins.push_back(pin);
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min_slack = slack;
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}
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}
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}
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}
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}
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bool
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CheckFanoutLimits::checkPin(const Pin *pin)
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{
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const Network *network = sta_->network();
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const Sim *sim = sta_->sim();
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const Sdc *sdc = sta_->sdc();
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const Graph *graph = sta_->graph();
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Vertex *vertex = graph->pinDrvrVertex(pin);
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return network->isDriver(pin)
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&& !sim->logicZeroOne(pin)
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&& !sdc->isDisabled(pin)
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&& !(vertex && sta_->isIdealClock(pin));
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}
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} // namespace
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