OpenSTA/search/PathExpanded.cc

// OpenSTA, Static Timing Analyzer
// Copyright (c) 2026, 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 "PathExpanded.hh"

#include "Clock.hh"
#include "Genclks.hh"
#include "Latches.hh"
#include "Mode.hh"
#include "Network.hh"
#include "Path.hh"
#include "PortDirection.hh"
#include "Search.hh"
#include "TimingRole.hh"

namespace sta {

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

PathExpanded::PathExpanded(const Path *path,
                           // Expand generated clk source paths.
                           bool expand_genclks,
                           const StaState *sta) :
  sta_(sta)
{
  expand(path, expand_genclks);
}

PathExpanded::PathExpanded(const Path *path,
                           const StaState *sta) :
  sta_(sta)
{
  expand(path, false);
}

void
PathExpanded::expand(const Path *path,
                     bool expand_genclks)
{
  const Latches *latches = sta_->latches();
  const Mode *mode = path->mode(sta_);
  // Push the paths from the end into an array of Paths.
  const Path *p = path;
  const Path *last_path = nullptr;
  size_t i = 0;
  bool found_start = false;
  while (p) {
    const Path *prev_path = p->prevPath();
    if (!found_start) {
      if (prev_path) {
        const TimingArc *prev_arc = p->prevArc(sta_);
        const TimingRole *prev_role = prev_arc->role();
        if (prev_role == TimingRole::regClkToQ()
            || prev_role == TimingRole::latchEnToQ()) {
          start_index_ = i;
          found_start = true;
        }
        else if (prev_role->isLatchDtoQ()) {
          const Edge *prev_edge = p->prevEdge(sta_);
          if (prev_edge && latches->isLatchDtoQ(prev_edge, mode)) {
            start_index_ = i;
            found_start = true;

            paths_.push_back(p);
            // Push latch D path.
            paths_.push_back(prev_path);
            // This breaks latch loop paths.
            break;
          }
        }
      }
    }
    paths_.push_back(p);
    last_path = p;
    p = prev_path;
    i++;
  }
  if (!found_start)
    start_index_ = i - 1;

  if (expand_genclks)
    expandGenclk(last_path);
}

void
PathExpanded::expandGenclk(const Path *clk_path)
{
  if (clk_path) {
    const Clock *src_clk = clk_path->clock(sta_);
    if (src_clk && src_clk->isGenerated()) {
      const Mode *mode = clk_path->mode(sta_);
      const Path *src_path = mode->genclks()->srcPath(clk_path);
      if (src_path) {
        // The head of the genclk src path is already in paths_,
        // so skip past it.
        Path *prev_path = src_path->prevPath();
        Path *p = prev_path;
        Path *last_path = nullptr;
        while (p) {
          prev_path = p->prevPath();
          paths_.push_back(p);
          last_path = p;
          p = prev_path;
        }
        expandGenclk(last_path);
      }
    }
  }
}

// Convert external index that starts at the path root
// and increases to an index for paths_ (reversed).
size_t
PathExpanded::pathsIndex(size_t index) const
{
  return paths_.size() - index - 1;
}

size_t
PathExpanded::startIndex() const
{
  return pathsIndex(start_index_);
}

const Path *
PathExpanded::path(size_t index) const
{
  if (index < paths_.size())
    return paths_[pathsIndex(index)];
  else
    return nullptr;
}

const Path *
PathExpanded::startPath() const
{
  return paths_[start_index_];
}

const Path *
PathExpanded::endPath() const
{
  return paths_[0];
}

const TimingArc *
PathExpanded::startPrevArc() const
{
  return paths_[start_index_]->prevArc(sta_);
}

const Path *
PathExpanded::startPrevPath() const
{
  size_t start1 = start_index_ + 1;
  if (start1 < paths_.size())
    return paths_[start1];
  else
    return nullptr;
}

const Path *
PathExpanded::clkPath() const
{
  const Latches *latches = sta_->latches();
  const Path *start = startPath();
  const TimingArc *prev_arc = startPrevArc();
  if (start && prev_arc) {
    const TimingRole *role = prev_arc->role();
    if (role->isLatchDtoQ()) {
      Edge *prev_edge = start->prevEdge(sta_);
      const Mode *mode = start->mode(sta_);
      if (prev_edge && latches->isLatchDtoQ(prev_edge, mode)) {
        return latches->latchEnablePath(start, prev_edge);
      }
    }
    else if (role == TimingRole::regClkToQ()
             || role == TimingRole::latchEnToQ()) {
      const Path *start_prev = startPrevPath();
      if (start_prev)
        return start_prev;
    }
  }
  else if (start && start->isClock(sta_))
    return start;
  return nullptr;
}

void
PathExpanded::latchPaths(// Return values.
                         const Path *&d_path,
                         const Path *&q_path,
                         Edge *&d_q_edge) const
{
  d_path = nullptr;
  q_path = nullptr;
  d_q_edge = nullptr;
  const Path *start = startPath();
  const TimingArc *prev_arc = startPrevArc();
  if (start
      && prev_arc
      && prev_arc->role() == TimingRole::latchDtoQ()) {
    Edge *prev_edge = start->prevEdge(sta_);
    const Mode *mode = start->mode(sta_);
    // This breaks latch loop paths.
    if (prev_edge
        && sta_->latches()->isLatchDtoQ(prev_edge, mode)) {
      d_path = startPrevPath();
      q_path = start;
      d_q_edge = prev_edge;
    }
  }
}

} // namespace sta