OpenSTA/search/SearchPred.cc

// OpenSTA, Static Timing Analyzer
// Copyright (c) 2025, 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/>.
// 
// The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software.
// 
// Altered source versions must be plainly marked as such, and must not be
// misrepresented as being the original software.
// 
// This notice may not be removed or altered from any source distribution.

#include "SearchPred.hh"

#include "TimingArc.hh"
#include "TimingRole.hh"
#include "Liberty.hh"
#include "Network.hh"
#include "Graph.hh"
#include "Sdc.hh"
#include "Levelize.hh"
#include "Search.hh"
#include "Latches.hh"
#include "Variables.hh"

namespace sta {

static bool
searchThruSimEdge(const Vertex *vertex, const RiseFall *rf);
static bool
searchThruTimingSense(const Edge *edge, const RiseFall *from_rf,
		      const RiseFall *to_rf);

SearchPred0::SearchPred0(const StaState *sta) :
  sta_(sta)
{
}

bool
SearchPred0::searchFrom(const Vertex *from_vertex)
{
  return !(from_vertex->isDisabledConstraint()
	   || from_vertex->isConstant());
}

bool
SearchPred0::searchThru(Edge *edge)
{
  const TimingRole *role = edge->role();
  const Sdc *sdc = sta_->sdc();
  const Variables *variables = sta_->variables();
  return !(edge->isDisabledConstraint()
	   // Constants disable edge cond expression.
	   || edge->isDisabledCond()
	   || sdc->isDisabledCondDefault(edge)
	   // Register/latch preset/clr edges are disabled by default.
	   || (role == TimingRole::regSetClr()
	       && !variables->presetClrArcsEnabled())
	   // Constants on other pins disable this edge (ie, a mux select).
	   || edge->simTimingSense() == TimingSense::none
	   || (edge->isBidirectInstPath()
	       && !variables->bidirectInstPathsEnabled())
	   || (edge->isBidirectNetPath()
	       && !variables->bidirectNetPathsEnabled())
	   || (role == TimingRole::latchDtoQ()
	       && sta_->latches()->latchDtoQState(edge)
	       == LatchEnableState::closed));
}

bool
SearchPred0::searchTo(const Vertex *to_vertex)
{
  return !to_vertex->isConstant();
}

////////////////////////////////////////////////////////////////

SearchPred1::SearchPred1(const StaState *sta) :
  SearchPred0(sta)
{
}

bool
SearchPred1::searchThru(Edge *edge)
{
  return SearchPred0::searchThru(edge)
    && !edge->isDisabledLoop();
}

////////////////////////////////////////////////////////////////

SearchPred2::SearchPred2(const StaState *sta) :
  SearchPred1(sta)
{
}

bool
SearchPred2::searchThru(Edge *edge)
{
  return SearchPred1::searchThru(edge)
    && !edge->role()->isTimingCheck();
}

////////////////////////////////////////////////////////////////

SearchPredNonLatch2::SearchPredNonLatch2(const StaState *sta) :
  SearchPred2(sta)
{
}

bool
SearchPredNonLatch2::searchThru(Edge *edge)
{
  return SearchPred2::searchThru(edge)
    && !sta_->latches()->isLatchDtoQ(edge);
}

////////////////////////////////////////////////////////////////

SearchPredNonReg2::SearchPredNonReg2(const StaState *sta) :
  SearchPred2(sta)
{
}

bool
SearchPredNonReg2::searchThru(Edge *edge)
{
  const TimingRole *role = edge->role();
  return SearchPred2::searchThru(edge)
    // Enqueue thru latches is handled explicitly by search.
    && !sta_->latches()->isLatchDtoQ(edge)
    && role->genericRole() != TimingRole::regClkToQ();
}

////////////////////////////////////////////////////////////////

ClkTreeSearchPred::ClkTreeSearchPred(const StaState *sta) :
  SearchPred1(sta)
{
}

bool
ClkTreeSearchPred::searchThru(Edge *edge)
{
  // Propagate clocks through constants.
  const TimingRole *role = edge->role();
  return (role->isWire()
	  || role == TimingRole::combinational())
    && (sta_->variables()->clkThruTristateEnabled()
	|| !(role == TimingRole::tristateEnable()
	     || role == TimingRole::tristateDisable()))
    && SearchPred1::searchThru(edge);
}

bool
isClkEnd(Vertex *vertex,
	 Graph *graph)
{
  ClkTreeSearchPred pred(graph);
  VertexOutEdgeIterator edge_iter(vertex, graph);
  while (edge_iter.hasNext()) {
    Edge *edge = edge_iter.next();
    if (pred.searchThru(edge))
      return false;
  }
  return true;
}

////////////////////////////////////////////////////////////////

bool
searchThru(const Edge *edge,
	   const TimingArc *arc,
	   const Graph *graph)
{
  const RiseFall *from_rf = arc->fromEdge()->asRiseFall();
  const RiseFall *to_rf = arc->toEdge()->asRiseFall();
  // Ignore transitions other than rise/fall.
  return from_rf && to_rf
    && searchThru(edge->from(graph), from_rf, edge, edge->to(graph), to_rf);
}

bool
searchThru(Vertex *from_vertex,
	   const RiseFall *from_rf,
	   const Edge *edge,
	   Vertex *to_vertex,
	   const RiseFall *to_rf)
{
  return searchThruTimingSense(edge, from_rf, to_rf)
    && searchThruSimEdge(from_vertex, from_rf)
    && searchThruSimEdge(to_vertex, to_rf);
}

// set_case_analysis rising/falling filters rise/fall edges during search.
static bool
searchThruSimEdge(const Vertex *vertex,
		  const RiseFall *rf)
{
  LogicValue sim_value = vertex->simValue();
  switch (sim_value) {
  case LogicValue::rise:
    return rf == RiseFall::rise();
  case LogicValue::fall:
    return rf == RiseFall::fall();
  default:
    return true;
  };
}

static bool
searchThruTimingSense(const Edge *edge, const RiseFall *from_rf,
		      const RiseFall *to_rf)
{
  switch (edge->simTimingSense()) {
  case TimingSense::unknown:
    return true;
  case TimingSense::positive_unate:
    return from_rf == to_rf;
  case TimingSense::negative_unate:
    return from_rf != to_rf;
  case TimingSense::non_unate:
    return true;
  case TimingSense::none:
    return false;
  default:
    return true;
  }
}

////////////////////////////////////////////////////////////////

bool
hasFanin(Vertex *vertex,
	 SearchPred *pred,
	 const Graph *graph)
{
  if (pred->searchTo(vertex)) {
    VertexInEdgeIterator edge_iter(vertex, graph);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      Vertex *from_vertex = edge->from(graph);
      if (pred->searchFrom(from_vertex)
	  && pred->searchThru(edge))
	return true;
    }
  }
  return false;
}

bool
hasFanout(Vertex *vertex,
	  SearchPred *pred,
	  const Graph *graph)
{
  if (pred->searchFrom(vertex)) {
    VertexOutEdgeIterator edge_iter(vertex, graph);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      Vertex *to_vertex = edge->to(graph);
      if (pred->searchTo(to_vertex)
	  && pred->searchThru(edge))
	return true;
    }
  }
  return false;
}

} // namespace