OpenSTA/dcalc/DelayCalcBase.cc

// OpenSTA, Static Timing Analyzer
// Copyright (c) 2024, Parallax Software, Inc.
// 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

#include "DelayCalcBase.hh"

#include "Liberty.hh"
#include "TimingArc.hh"
#include "TimingModel.hh"
#include "TableModel.hh"
#include "Network.hh"
#include "Parasitics.hh"
#include "Sdc.hh"
#include "DcalcAnalysisPt.hh"

namespace sta {

using std::log;

DelayCalcBase::DelayCalcBase(StaState *sta) :
  ArcDelayCalc(sta)
{
}

TimingModel *
DelayCalcBase::model(const TimingArc *arc,
                     const DcalcAnalysisPt *dcalc_ap) const
{
  const OperatingConditions *op_cond = dcalc_ap->operatingConditions();
  const TimingArc *corner_arc = arc->cornerArc(dcalc_ap->libertyIndex());
  return corner_arc->model(op_cond);
}

GateTimingModel *
DelayCalcBase::gateModel(const TimingArc *arc,
                         const DcalcAnalysisPt *dcalc_ap) const
{
  return dynamic_cast<GateTimingModel*>(model(arc, dcalc_ap));
}

GateTableModel *
DelayCalcBase::gateTableModel(const TimingArc *arc,
                              const DcalcAnalysisPt *dcalc_ap) const
{
  return dynamic_cast<GateTableModel*>(model(arc, dcalc_ap));
}

CheckTimingModel *
DelayCalcBase::checkModel(const TimingArc *arc,
                          const DcalcAnalysisPt *dcalc_ap) const
{
  return dynamic_cast<CheckTimingModel*>(model(arc, dcalc_ap));
}

void
DelayCalcBase::finishDrvrPin()
{
  for (auto parasitic : unsaved_parasitics_)
    parasitics_->deleteUnsavedParasitic(parasitic);
  unsaved_parasitics_.clear();
  for (auto drvr_pin : reduced_parasitic_drvrs_)
    parasitics_->deleteDrvrReducedParasitics(drvr_pin);
  reduced_parasitic_drvrs_.clear();
}

// For DSPF on an input port the elmore delay is used as the time
// constant of an exponential waveform.  The delay to the logic
// threshold and slew are computed for the exponential waveform.
// Note that this uses the driver thresholds and relies on
// thresholdAdjust to convert the delay and slew to the load's thresholds.
void
DelayCalcBase::dspfWireDelaySlew(const Pin *load_pin,
                                 const RiseFall *rf,
                                 Slew drvr_slew,
                                 float elmore,
                                 ArcDelay &wire_delay,
                                 Slew &load_slew)
{
  
  LibertyLibrary *load_library = thresholdLibrary(load_pin);
  float vth = load_library->inputThreshold(rf);
  float vl = load_library->slewLowerThreshold(rf);
  float vh = load_library->slewUpperThreshold(rf);
  float slew_derate = load_library->slewDerateFromLibrary();
  wire_delay = -elmore * log(1.0 - vth);
  load_slew = drvr_slew + elmore * log((1.0 - vl) / (1.0 - vh)) / slew_derate;
  load_slew = drvr_slew + elmore * log((1.0 - vl) / (1.0 - vh)) / slew_derate;
}

void
DelayCalcBase::thresholdAdjust(const Pin *load_pin,
                               const LibertyLibrary *drvr_library,
                               const RiseFall *rf,
                               ArcDelay &load_delay,
                               Slew &load_slew)
{
  LibertyLibrary *load_library = thresholdLibrary(load_pin);
  if (load_library
      && drvr_library
      && load_library != drvr_library) {
    float drvr_vth = drvr_library->outputThreshold(rf);
    float load_vth = load_library->inputThreshold(rf);
    float drvr_slew_delta = drvr_library->slewUpperThreshold(rf)
      - drvr_library->slewLowerThreshold(rf);
    float load_delay_delta =
      delayAsFloat(load_slew) * ((load_vth - drvr_vth) / drvr_slew_delta);
    load_delay += (rf == RiseFall::rise())
      ? load_delay_delta
      : -load_delay_delta;
    float load_slew_delta = load_library->slewUpperThreshold(rf)
      - load_library->slewLowerThreshold(rf);
    float drvr_slew_derate = drvr_library->slewDerateFromLibrary();
    float load_slew_derate = load_library->slewDerateFromLibrary();
    load_slew = load_slew * ((load_slew_delta / load_slew_derate)
			     / (drvr_slew_delta / drvr_slew_derate));
  }
}

LibertyLibrary *
DelayCalcBase::thresholdLibrary(const Pin *load_pin)
{
  if (network_->isTopLevelPort(load_pin))
    // Input/output slews use the default (first read) library
    // for slew thresholds.
    return network_->defaultLibertyLibrary();
  else {
    LibertyPort *lib_port = network_->libertyPort(load_pin);
    if (lib_port)
      return lib_port->libertyCell()->libertyLibrary();
    else
      return network_->defaultLibertyLibrary();
  }
}

ArcDelay
DelayCalcBase::checkDelay(const Pin *check_pin,
                          const TimingArc *arc,
                          const Slew &from_slew,
                          const Slew &to_slew,
                          float related_out_cap,
                          const DcalcAnalysisPt *dcalc_ap)
{
  CheckTimingModel *model = checkModel(arc, dcalc_ap);
  if (model) {
    float from_slew1 = delayAsFloat(from_slew);
    float to_slew1 = delayAsFloat(to_slew);
    return model->checkDelay(pinPvt(check_pin, dcalc_ap), from_slew1, to_slew1,
                             related_out_cap, pocv_enabled_);
  }
  else
    return delay_zero;
}

string
DelayCalcBase::reportCheckDelay(const Pin *check_pin,
                                const TimingArc *arc,
                                const Slew &from_slew,
                                const char *from_slew_annotation,
                                const Slew &to_slew,
                                float related_out_cap,
                                const DcalcAnalysisPt *dcalc_ap,
                                int digits)
{
  CheckTimingModel *model = checkModel(arc, dcalc_ap);
  if (model) {
    float from_slew1 = delayAsFloat(from_slew);
    float to_slew1 = delayAsFloat(to_slew);
    return model->reportCheckDelay(pinPvt(check_pin, dcalc_ap), from_slew1,
                                   from_slew_annotation, to_slew1,
                                   related_out_cap, false, digits);
  }
  return "";
}

const Pvt *
DelayCalcBase::pinPvt(const Pin *pin,
                      const DcalcAnalysisPt *dcalc_ap)
{
  const Instance *drvr_inst = network_->instance(pin);
  const Pvt *pvt = sdc_->pvt(drvr_inst, dcalc_ap->constraintMinMax());
  if (pvt == nullptr)
    pvt = dcalc_ap->operatingConditions();
  return pvt;
}

} // namespace