CutRewriter.cpp

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements a DAG-based boolean matching cut rewriting algorithm for
// applications like technology/LUT mapping and combinational logic
// optimization. The algorithm uses priority cuts and NPN
// (Negation-Permutation-Negation) canonical forms to efficiently match cuts
// against rewriting patterns.
//
// References:
//  "Combinational and Sequential Mapping with Priority Cuts", Alan Mishchenko,
//  Sungmin Cho, Satrajit Chatterjee and Robert Brayton, ICCAD 2007
//  "Improvements to technology mapping for LUT-based FPGAs", Alan Mishchenko,
//  Satrajit Chatterjee and Robert Brayton, FPGA 2006
//
//===----------------------------------------------------------------------===//
 
#include "circt/Dialect/Synth/Transforms/CutRewriter.h"
 
#include "circt/Dialect/Comb/CombOps.h"
#include "circt/Dialect/HW/HWOps.h"
#include "circt/Dialect/Synth/SynthOpInterfaces.h"
#include "circt/Dialect/Synth/SynthOps.h"
#include "circt/Support/LLVM.h"
#include "circt/Support/TruthTable.h"
#include "circt/Support/UnusedOpPruner.h"
#include "mlir/Analysis/TopologicalSortUtils.h"
#include "mlir/IR/Builders.h"
#include "mlir/IR/Operation.h"
#include "mlir/IR/RegionKindInterface.h"
#include "mlir/IR/Value.h"
#include "mlir/IR/ValueRange.h"
#include "mlir/IR/Visitors.h"
#include "mlir/Support/LLVM.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/Bitset.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/TypeSwitch.h"
#include "llvm/ADT/iterator.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LogicalResult.h"
#include <algorithm>
#include <functional>
#include <memory>
#include <optional>
#include <string>
 
#define DEBUG_TYPE "synth-cut-rewriter"
 
using namespace circt;
using namespace circt::synth;
 
//===----------------------------------------------------------------------===//
// LogicNetwork
//===----------------------------------------------------------------------===//
 
uint32_t LogicNetwork::getOrCreateIndex(Value value) {
  auto [it, inserted] = valueToIndex.try_emplace(value, gates.size());
  if (inserted) {
    indexToValue.push_back(value);
    gates.emplace_back(); // Will be filled in later
  }
  return it->second;
}
 
uint32_t LogicNetwork::getIndex(Value value) const {
  const auto it = valueToIndex.find(value);
  assert(it != valueToIndex.end() &&
         "Value not found in LogicNetwork - use getOrCreateIndex or check with "
         "hasIndex first");
  return it->second;
}
 
bool LogicNetwork::hasIndex(Value value) const {
  return valueToIndex.contains(value);
}
 
Value LogicNetwork::getValue(uint32_t index) const {
  // Index 0 and 1 are reserved for constants, they have no associated Value
  if (index == kConstant0 || index == kConstant1)
    return Value();
 
  assert(index < indexToValue.size() &&
         "Index out of bounds in LogicNetwork::getValue");
  return indexToValue[index];
}
 
void LogicNetwork::getValues(ArrayRef<uint32_t> indices,
                             SmallVectorImpl<Value> &values) const {
  values.clear();
  values.reserve(indices.size());
  for (uint32_t idx : indices)
    values.push_back(getValue(idx));
}
 
uint32_t LogicNetwork::addPrimaryInput(Value value) {
  const uint32_t index = getOrCreateIndex(value);
  gates[index] = LogicNetworkGate(nullptr, LogicNetworkGate::PrimaryInput);
  return index;
}
 
uint32_t LogicNetwork::addGate(Operation *op, LogicNetworkGate::Kind kind,
                               Value result, ArrayRef<Signal> operands) {
  const uint32_t index = getOrCreateIndex(result);
  gates[index] = LogicNetworkGate(op, kind, operands);
  return index;
}
 
LogicalResult LogicNetwork::buildFromBlock(Block *block) {
  // Pre-size vectors to reduce reallocations (rough estimate)
  const size_t estimatedSize =
      block->getArguments().size() + block->getOperations().size();
  indexToValue.reserve(estimatedSize);
  gates.reserve(estimatedSize);
 
  auto handleSingleInputGate = [&](Operation *op, Value result,
                                   const Signal &inputSignal) {
    if (!inputSignal.isInverted()) {
      // Non-inverted buffer: directly alias the result to the input
      valueToIndex[result] = inputSignal.getIndex();
      return;
    }
    // Inverted operation: create a NOT gate
    addGate(op, LogicNetworkGate::Identity, result, {inputSignal});
  };
 
  // Ensure all block arguments are indexed as primary inputs first
  for (Value arg : block->getArguments()) {
    if (!hasIndex(arg))
      addPrimaryInput(arg);
  }
 
  auto handleOtherResults = [&](Operation *op) {
    for (Value result : op->getResults()) {
      if (result.getType().isInteger(1) && !hasIndex(result))
        addPrimaryInput(result);
    }
  };
 
  auto getInvertibleSignal = [&](auto op, unsigned index) {
    return getOrCreateSignal(op.getOperand(index), op.isInverted(index));
  };
 
  auto handleInvertibleBinaryGate = [&](auto logicOp,
                                        LogicNetworkGate::Kind kind) {
    // The cut rewriter only has dedicated nodes for single-bit unary/binary
    // gates. Wider or variadic forms stay as opaque cut inputs for now.
    const auto inputs = logicOp.getInputs();
    if (inputs.size() == 1) {
      const Signal inputSignal = getInvertibleSignal(logicOp, 0);
      handleSingleInputGate(logicOp, logicOp.getResult(), inputSignal);
      return success();
    }
    if (inputs.size() == 2) {
      const Signal lhsSignal = getInvertibleSignal(logicOp, 0);
      const Signal rhsSignal = getInvertibleSignal(logicOp, 1);
      addGate(logicOp, kind, {lhsSignal, rhsSignal});
    }
    // Variadic gates with >2 inputs are treated as primary
    // inputs for now.
    handleOtherResults(logicOp);
    return success();
  };
 
  auto handleInvertibleTernaryGate = [&](auto logicOp,
                                         LogicNetworkGate::Kind kind) {
    if (!logicOp.getType().isInteger(1)) {
      handleOtherResults(logicOp);
      return success();
    }
    const Signal aSignal = getInvertibleSignal(logicOp, 0);
    const Signal bSignal = getInvertibleSignal(logicOp, 1);
    const Signal cSignal = getInvertibleSignal(logicOp, 2);
    addGate(logicOp, kind, {aSignal, bSignal, cSignal});
    return success();
  };
 
  // Process operations in topological order
  for (Operation &op : block->getOperations()) {
    LogicalResult result =
        llvm::TypeSwitch<Operation *, LogicalResult>(&op)
            .Case<aig::AndInverterOp>([&](aig::AndInverterOp andOp) {
              return handleInvertibleBinaryGate(andOp, LogicNetworkGate::And2);
            })
            .Case<synth::XorInverterOp>([&](synth::XorInverterOp xorOp) {
              return handleInvertibleBinaryGate(xorOp, LogicNetworkGate::Xor2);
            })
            .Case<synth::MuxInverterOp>([&](synth::MuxInverterOp muxOp) {
              return handleInvertibleTernaryGate(muxOp, LogicNetworkGate::Mux3);
            })
            .Case<synth::DotOp>([&](synth::DotOp dotOp) {
              return handleInvertibleTernaryGate(dotOp, LogicNetworkGate::Dot3);
            })
            .Case<synth::MajorityOp>([&](synth::MajorityOp majOp) {
              return handleInvertibleTernaryGate(majOp, LogicNetworkGate::Maj3);
            })
            .Case<synth::OneHotOp>([&](synth::OneHotOp oneHotOp) {
              return handleInvertibleTernaryGate(oneHotOp,
                                                 LogicNetworkGate::OneHot3);
            })
            .Case<comb::XorOp>([&](comb::XorOp xorOp) {
              if (xorOp->getNumOperands() != 2) {
                handleOtherResults(xorOp);
                return success();
              }
              const Signal lhsSignal =
                  getOrCreateSignal(xorOp.getOperand(0), false);
              const Signal rhsSignal =
                  getOrCreateSignal(xorOp.getOperand(1), false);
              addGate(xorOp, LogicNetworkGate::Xor2, {lhsSignal, rhsSignal});
              return success();
            })
            .Case<hw::ConstantOp>([&](hw::ConstantOp constOp) {
              Value result = constOp.getResult();
              if (!result.getType().isInteger(1)) {
                handleOtherResults(constOp);
                return success();
              }
              uint32_t constIdx =
                  constOp.getValue().isZero() ? kConstant0 : kConstant1;
              valueToIndex[result] = constIdx;
              return success();
            })
            .Case<synth::ChoiceOp>([&](synth::ChoiceOp choiceOp) {
              if (!choiceOp.getType().isInteger(1)) {
                handleOtherResults(choiceOp);
                return success();
              }
              addGate(choiceOp, LogicNetworkGate::Choice, choiceOp.getResult(),
                      {});
              return success();
            })
            .Default([&](Operation *defaultOp) {
              handleOtherResults(defaultOp);
              return success();
            });
 
    if (failed(result))
      return result;
  }
 
  return success();
}
 
void LogicNetwork::clear() {
  valueToIndex.clear();
  indexToValue.clear();
  gates.clear();
  // Re-add the constant nodes (index 0 = const0, index 1 = const1)
  gates.emplace_back(nullptr, LogicNetworkGate::Constant);
  gates.emplace_back(nullptr, LogicNetworkGate::Constant);
  // Placeholders for constants in indexToValue
  indexToValue.push_back(Value()); // const0
  indexToValue.push_back(Value()); // const1
}
 
//===----------------------------------------------------------------------===//
// Helper functions
//===----------------------------------------------------------------------===//
 
// Return true if the gate at the given index is always a cut input.
static bool isAlwaysCutInput(const LogicNetwork &network, uint32_t index) {
  const auto &gate = network.getGate(index);
  return gate.isAlwaysCutInput();
}
 
// Return true if the new area/delay is better than the old area/delay in the
// context of the given strategy.
static bool compareDelayAndArea(OptimizationStrategy strategy, double newArea,
                                ArrayRef<DelayType> newDelay, double oldArea,
                                ArrayRef<DelayType> oldDelay) {
  if (strategy == OptimizationStrategyArea)
    return newArea < oldArea || (newArea == oldArea && newDelay < oldDelay);
  if (strategy == OptimizationStrategyTiming)
    return newDelay < oldDelay || (newDelay == oldDelay && newArea < oldArea);
  llvm_unreachable("Unknown mapping strategy");
}
 
LogicalResult circt::synth::topologicallySortLogicNetwork(Operation *topOp) {
  const auto isOperationReady = [](Value value, Operation *op) -> bool {
    // Topologically sort AIG ops and dataflow ops. Other operations
    // can be scheduled.
    return !circt::synth::isLogicNetworkOp(op);
  };
 
  if (failed(topologicallySortGraphRegionBlocks(topOp, isOperationReady)))
    return emitError(topOp->getLoc(),
                     "failed to sort operations topologically");
  return success();
}
 
/// Get the truth table for operations within a block.
FailureOr<BinaryTruthTable> circt::synth::getTruthTable(ValueRange values,
                                                        Block *block) {
  llvm::SmallSetVector<Value, 4> inputArgs;
  for (Value arg : block->getArguments())
    inputArgs.insert(arg);
 
  if (inputArgs.empty())
    return BinaryTruthTable();
 
  const int64_t numInputs = inputArgs.size();
  const int64_t numOutputs = values.size();
  if (LLVM_UNLIKELY(numOutputs != 1 || numInputs >= maxTruthTableInputs)) {
    if (numOutputs == 0)
      return BinaryTruthTable(numInputs, 0);
    if (numInputs >= maxTruthTableInputs)
      return mlir::emitError(values.front().getLoc(),
                             "Truth table is too large");
    return mlir::emitError(values.front().getLoc(),
                           "Multiple outputs are not supported yet");
  }
 
  // Create a map to evaluate the operation
  DenseMap<Value, APInt> eval;
  for (uint32_t i = 0; i < numInputs; ++i)
    eval[inputArgs[i]] = circt::createVarMask(numInputs, i, true);
 
  // Simulate the operations in the block
  for (Operation &op : block->without_terminator()) {
    if (op.getNumResults() != 1 ||
        hw::getBitWidth(op.getResult(0).getType()) != 1)
      return op.emitError("Unsupported operation for truth table simulation");
 
    if (auto choiceOp = dyn_cast<synth::ChoiceOp>(&op)) {
      auto it = eval.find(choiceOp.getInputs().front());
      if (it == eval.end())
        return choiceOp.emitError("Input value not found in evaluation map");
      eval[choiceOp.getResult()] = it->second;
    } else if (auto logicOp = dyn_cast<BooleanLogicOpInterface>(&op)) {
      for (auto value : logicOp.getInputs())
        if (!eval.contains(value))
          return logicOp->emitError("Input value not found in evaluation map");
 
      eval[logicOp.getResult()] =
          logicOp.evaluateBooleanLogic([&](unsigned i) -> const APInt & {
            return eval.find(logicOp.getInput(i))->second;
          });
    } else if (auto xorOp = dyn_cast<comb::XorOp>(&op)) {
      // TODO: Define Xor as Synth op.
      auto it = eval.find(xorOp.getOperand(0));
      if (it == eval.end())
        return xorOp.emitError("Input value not found in evaluation map");
      llvm::APInt result = it->second;
      for (unsigned i = 1; i < xorOp.getNumOperands(); ++i) {
        it = eval.find(xorOp.getOperand(i));
        if (it == eval.end())
          return xorOp.emitError("Input value not found in evaluation map");
        result ^= it->second;
      }
      eval[xorOp.getResult()] = result;
    } else if (auto constantOp = dyn_cast<hw::ConstantOp>(&op)) {
      auto tableSize = 1ULL << numInputs;
      eval[constantOp.getResult()] = constantOp.getValue().isZero()
                                         ? llvm::APInt::getZero(tableSize)
                                         : llvm::APInt::getAllOnes(tableSize);
    } else {
      return op.emitError("Unsupported operation for truth table simulation");
    }
  }
 
  return BinaryTruthTable(numInputs, 1, eval[values[0]]);
}
 
//===----------------------------------------------------------------------===//
// Cut
//===----------------------------------------------------------------------===//
 
bool Cut::isTrivialCut() const {
  // A cut is a trivial cut if it has no root (rootIndex == 0 sentinel)
  // and only one input
  return rootIndex == 0 && inputs.size() == 1;
}
 
const NPNClass &Cut::getNPNClass() const { return getNPNClass(nullptr); }
 
const NPNClass &Cut::getNPNClass(const NPNTable *npnTable) const {
  if (npnClass)
    return *npnClass;
 
  const auto &truthTable = *getTruthTable();
  NPNClass canonicalForm;
  if (!npnTable || !npnTable->lookup(truthTable, canonicalForm))
    canonicalForm = NPNClass::computeNPNCanonicalForm(truthTable);
 
  npnClass.emplace(std::move(canonicalForm));
  return *npnClass;
}
 
void Cut::getPermutatedInputIndices(
    const NPNTable *npnTable, const NPNClass &patternNPN,
    SmallVectorImpl<unsigned> &permutedIndices) const {
  const auto &npnClass = getNPNClass(npnTable);
  npnClass.getInputPermutation(patternNPN, permutedIndices);
}
 
LogicalResult
Cut::getInputArrivalTimes(CutEnumerator &enumerator,
                          SmallVectorImpl<DelayType> &results) const {
  results.reserve(getInputSize());
  const auto &network = enumerator.getLogicNetwork();
 
  // Compute arrival times for each input.
  for (auto inputIndex : inputs) {
    if (isAlwaysCutInput(network, inputIndex)) {
      // If the input is a primary input, it has no delay.
      results.push_back(0);
      continue;
    }
    auto *cutSet = enumerator.getCutSet(inputIndex);
    assert(cutSet && "Input must have a valid cut set");
 
    // If there is no matching pattern, it means it's not possible to use the
    // input in the cut rewriting. Return empty vector to indicate failure.
    auto *bestCut = cutSet->getBestMatchedCut();
    if (!bestCut)
      return failure();
 
    const auto &matchedPattern = *bestCut->getMatchedPattern();
 
    // Get the value for result number lookup
    mlir::Value inputValue = network.getValue(inputIndex);
    // Otherwise, the cut input is an op result. Get the arrival time
    // from the matched pattern.
    results.push_back(matchedPattern.getArrivalTime(
        cast<mlir::OpResult>(inputValue).getResultNumber()));
  }
 
  return success();
}
 
void Cut::dump(llvm::raw_ostream &os, const LogicNetwork &network) const {
  os << "// === Cut Dump ===\n";
  os << "Cut with " << getInputSize() << " inputs";
  if (rootIndex != 0) {
    auto *rootOp = network.getGate(rootIndex).getOperation();
    if (rootOp)
      os << " and root: " << *rootOp;
  }
  os << "\n";
 
  if (isTrivialCut()) {
    mlir::Value inputVal = network.getValue(inputs[0]);
    os << "Primary input cut: " << inputVal << "\n";
    return;
  }
 
  os << "Inputs (indices): \n";
  for (auto [idx, inputIndex] : llvm::enumerate(inputs)) {
    mlir::Value inputVal = network.getValue(inputIndex);
    os << "  Input " << idx << " (index " << inputIndex << "): " << inputVal
       << "\n";
  }
 
  if (rootIndex != 0) {
    os << "\nRoot operation: \n";
    if (auto *rootOp = network.getGate(rootIndex).getOperation())
      rootOp->print(os);
    os << "\n";
  }
 
  auto &npnClass = getNPNClass();
  npnClass.dump(os);
 
  os << "// === Cut End ===\n";
}
 
unsigned Cut::getInputSize() const { return inputs.size(); }
 
unsigned Cut::getOutputSize(const LogicNetwork &network) const {
  if (rootIndex == 0)
    return 1; // Trivial cut has 1 output
  auto *rootOp = network.getGate(rootIndex).getOperation();
  return rootOp ? rootOp->getNumResults() : 1;
}
 
/// Simulate a gate and return its truth table.
static inline llvm::APInt applyGateSemantics(LogicNetworkGate::Kind kind,
                                             const llvm::APInt &a) {
  switch (kind) {
  case LogicNetworkGate::Identity:
    return a;
  default:
    llvm_unreachable("Unsupported unary operation for truth table computation");
  }
}
 
static inline llvm::APInt applyGateSemantics(LogicNetworkGate::Kind kind,
                                             const llvm::APInt &a,
                                             const llvm::APInt &b) {
  switch (kind) {
  case LogicNetworkGate::And2:
    return a & b;
  case LogicNetworkGate::Xor2:
    return a ^ b;
  default:
    llvm_unreachable(
        "Unsupported binary operation for truth table computation");
  }
}
 
static inline llvm::APInt applyGateSemantics(LogicNetworkGate::Kind kind,
                                             const llvm::APInt &a,
                                             const llvm::APInt &b,
                                             const llvm::APInt &c) {
  switch (kind) {
  case LogicNetworkGate::Mux3:
    return evaluateMuxLogic(a, b, c);
  case LogicNetworkGate::Maj3:
    return evaluateMajorityLogic(a, b, c);
  case LogicNetworkGate::Dot3:
    return evaluateDotLogic(a, b, c);
  case LogicNetworkGate::OneHot3:
    return evaluateOneHotLogic(a, b, c);
  default:
    llvm_unreachable(
        "Unsupported ternary operation for truth table computation");
  }
}
 
namespace {
 
// Helper class to build a merged truth table for a cut based on its operand
// cuts
struct MergedTruthTableBuilder {
  MergedTruthTableBuilder(ArrayRef<uint32_t> mergedInputs,
                          ArrayRef<const Cut *> operandCuts)
      : mergedInputs(mergedInputs), numMergedInputs(mergedInputs.size()),
        operandCuts(operandCuts) {
    assert(llvm::is_sorted(mergedInputs) && "merged inputs must be sorted");
    assert(llvm::adjacent_find(mergedInputs) == mergedInputs.end() &&
           "merged inputs must be unique");
  }
 
  ArrayRef<uint32_t> mergedInputs;
  unsigned numMergedInputs;
  ArrayRef<const Cut *> operandCuts;
 
  std::optional<unsigned> findMergedInputPosition(uint32_t operandIdx) const {
    auto *it = llvm::find(mergedInputs, operandIdx);
    if (it == mergedInputs.end())
      return std::nullopt;
    return static_cast<unsigned>(std::distance(mergedInputs.begin(), it));
  }
 
  const Cut *findOperandCut(uint32_t operandIdx) const {
    for (const Cut *cut : operandCuts) {
      if (!cut)
        continue;
      uint32_t cutOutput =
          cut->isTrivialCut() ? cut->inputs[0] : cut->getRootIndex();
      if (cutOutput == operandIdx)
        return cut;
    }
    return nullptr;
  }
 
  void getInputMapping(const Cut *cut,
                       SmallVectorImpl<unsigned> &mapping) const {
    mapping.clear();
    mapping.reserve(cut->inputs.size());
    for (uint32_t idx : cut->inputs) {
      auto *it = llvm::find(mergedInputs, idx);
      assert(it != mergedInputs.end() &&
             "cut input must exist in merged inputs");
      mapping.push_back(static_cast<unsigned>(it - mergedInputs.begin()));
    }
  }
 
  llvm::APInt expandCutTruthTable(const Cut *cut) const {
    const auto &cutTT = *cut->getTruthTable();
    SmallVector<unsigned, 8> inputMapping;
    getInputMapping(cut, inputMapping);
    return circt::detail::expandTruthTableToInputSpace(
        cutTT.table, inputMapping, numMergedInputs);
  }
 
  llvm::APInt expandOperand(uint32_t operandIdx, bool isInverted) const {
    llvm::APInt result(1, 0);
    if (operandIdx == LogicNetwork::kConstant0) {
      result = llvm::APInt::getZero(1U << numMergedInputs);
    } else if (operandIdx == LogicNetwork::kConstant1) {
      result = llvm::APInt::getAllOnes(1U << numMergedInputs);
    } else if (auto pos = findMergedInputPosition(operandIdx)) {
      // Direct cut inputs already live in the merged input space.
      result = circt::createVarMask(numMergedInputs, *pos, true);
    } else if (const Cut *cut = findOperandCut(operandIdx)) {
      // Internal operands reuse the operand cut truth table after expanding it
      // to this root cut's merged input space.
      result = expandCutTruthTable(cut);
    } else {
      llvm_unreachable("Operand not found in cuts or merged inputs");
    }
 
    if (isInverted)
      result.flipAllBits();
    return result;
  }
 
  BinaryTruthTable computeForGate(const LogicNetworkGate &rootGate) const {
    auto getEdgeTT = [&](unsigned edgeIdx) {
      const auto &edge = rootGate.edges[edgeIdx];
      return expandOperand(edge.getIndex(), edge.isInverted());
    };
 
    switch (rootGate.getKind()) {
    case LogicNetworkGate::And2:
    case LogicNetworkGate::Xor2:
      return BinaryTruthTable(
          numMergedInputs, 1,
          applyGateSemantics(rootGate.getKind(), getEdgeTT(0), getEdgeTT(1)));
    case LogicNetworkGate::Mux3:
      return BinaryTruthTable(numMergedInputs, 1,
                              applyGateSemantics(rootGate.getKind(),
                                                 getEdgeTT(0), getEdgeTT(1),
                                                 getEdgeTT(2)));
    case LogicNetworkGate::Maj3:
      return BinaryTruthTable(numMergedInputs, 1,
                              applyGateSemantics(rootGate.getKind(),
                                                 getEdgeTT(0), getEdgeTT(1),
                                                 getEdgeTT(2)));
    case LogicNetworkGate::Dot3:
      return BinaryTruthTable(numMergedInputs, 1,
                              applyGateSemantics(rootGate.getKind(),
                                                 getEdgeTT(0), getEdgeTT(1),
                                                 getEdgeTT(2)));
    case LogicNetworkGate::OneHot3:
      return BinaryTruthTable(numMergedInputs, 1,
                              applyGateSemantics(rootGate.getKind(),
                                                 getEdgeTT(0), getEdgeTT(1),
                                                 getEdgeTT(2)));
    case LogicNetworkGate::Identity:
      return BinaryTruthTable(
          numMergedInputs, 1,
          applyGateSemantics(rootGate.getKind(), getEdgeTT(0)));
    default:
      llvm_unreachable("Unsupported operation for truth table computation");
    }
  }
};
 
} // namespace
 
void Cut::computeTruthTableFromOperands(const LogicNetwork &network) {
  if (isTrivialCut()) {
    assert(truthTable && "trivial cuts should have their truth table pre-set");
    return;
  }
 
  assert(!operandCuts.empty() &&
         "non-trivial cuts must carry operand cuts for truth table expansion");
 
  const auto &rootGate = network.getGate(rootIndex);
  truthTable.emplace(
      MergedTruthTableBuilder(inputs, operandCuts).computeForGate(rootGate));
}
 
bool Cut::dominates(const Cut &other) const {
  return dominates(other.inputs, other.signature);
}
 
bool Cut::dominates(ArrayRef<uint32_t> otherInputs, uint64_t otherSig) const {
 
  if (getInputSize() > otherInputs.size())
    return false;
 
  if ((signature & otherSig) != signature)
    return false;
 
  return std::includes(otherInputs.begin(), otherInputs.end(), inputs.begin(),
                       inputs.end());
}
 
Cut Cut::getTrivialCut(uint32_t index) {
  Cut cut;
  cut.inputs.push_back(index);
  // The truth table for a trivial cut is just the identity function on its
  // single input.
  cut.setTruthTable(BinaryTruthTable(1, 1, llvm::APInt(2, 2)));
  cut.setSignature(1ULL << (index % 64)); // Set signature bit for this input
  return cut;
}
 
//===----------------------------------------------------------------------===//
// MatchedPattern
//===----------------------------------------------------------------------===//
 
ArrayRef<DelayType> MatchedPattern::getArrivalTimes() const {
  assert(pattern && "Pattern must be set to get arrival time");
  return arrivalTimes;
}
 
DelayType MatchedPattern::getArrivalTime(unsigned index) const {
  assert(pattern && "Pattern must be set to get arrival time");
  return arrivalTimes[index];
}
 
const CutRewritePattern *MatchedPattern::getPattern() const {
  assert(pattern && "Pattern must be set to get the pattern");
  return pattern;
}
 
double MatchedPattern::getArea() const {
  assert(pattern && "Pattern must be set to get area");
  return area;
}
 
//===----------------------------------------------------------------------===//
// CutSet
//===----------------------------------------------------------------------===//
 
Cut *CutSet::getBestMatchedCut() const { return bestCut; }
 
unsigned CutSet::size() const { return cuts.size(); }
 
void CutSet::addCut(Cut *cut) {
  assert(!isFrozen && "Cannot add cuts to a frozen cut set");
  cuts.push_back(cut);
}
 
ArrayRef<Cut *> CutSet::getCuts() const { return cuts; }
 
// Remove duplicate cuts and non-minimal cuts. A cut is non-minimal if there
// exists another cut that is a subset of it.
static void removeDuplicateAndNonMinimalCuts(SmallVectorImpl<Cut *> &cuts) {
  auto dumpInputs = [](llvm::raw_ostream &os,
                       const llvm::SmallVectorImpl<uint32_t> &inputs) {
    os << "{";
    llvm::interleaveComma(inputs, os);
    os << "}";
  };
  // Sort by size, then lexicographically by inputs. This enables cheap exact
  // duplicate elimination and tighter candidate filtering for subset checks.
  std::stable_sort(cuts.begin(), cuts.end(), [](const Cut *a, const Cut *b) {
    if (a->getInputSize() != b->getInputSize())
      return a->getInputSize() < b->getInputSize();
    return std::lexicographical_compare(a->inputs.begin(), a->inputs.end(),
                                        b->inputs.begin(), b->inputs.end());
  });
 
  // Group kept cuts by input size so subset checks only visit smaller cuts.
  unsigned maxCutSize = cuts.empty() ? 0 : cuts.back()->getInputSize();
  llvm::SmallVector<llvm::SmallVector<Cut *, 4>, 16> keptBySize(maxCutSize + 1);
 
  // Compact kept cuts in-place.
  unsigned uniqueCount = 0;
  for (Cut *cut : cuts) {
    unsigned cutSize = cut->getInputSize();
 
    // Fast exact duplicate check: with lexicographic sort, duplicates are
    // adjacent among cuts with equal size.
    if (uniqueCount > 0) {
      Cut *lastKept = cuts[uniqueCount - 1];
      if (lastKept->getInputSize() == cutSize &&
          lastKept->inputs == cut->inputs)
        continue;
    }
 
    bool isDominated = false;
    for (unsigned existingSize = 1; existingSize < cutSize && !isDominated;
         ++existingSize) {
      for (const Cut *existingCut : keptBySize[existingSize]) {
        if (!existingCut->dominates(*cut))
          continue;
 
        LLVM_DEBUG({
          llvm::dbgs() << "Dropping non-minimal cut ";
          dumpInputs(llvm::dbgs(), cut->inputs);
          llvm::dbgs() << " due to subset ";
          dumpInputs(llvm::dbgs(), existingCut->inputs);
          llvm::dbgs() << "\n";
        });
        isDominated = true;
        break;
      }
    }
 
    if (isDominated)
      continue;
 
    cuts[uniqueCount++] = cut;
    keptBySize[cutSize].push_back(cut);
  }
 
  LLVM_DEBUG(llvm::dbgs() << "Original cuts: " << cuts.size()
                          << " Unique cuts: " << uniqueCount << "\n");
 
  // Resize the cuts vector to the number of surviving cuts.
  cuts.resize(uniqueCount);
}
 
void CutSet::finalize(
    const CutRewriterOptions &options,
    llvm::function_ref<std::optional<MatchedPattern>(const Cut &)> matchCut,
    const LogicNetwork &logicNetwork) {
 
  // Remove duplicate/non-minimal cuts first so all follow-up work only runs on
  // survivors.
  removeDuplicateAndNonMinimalCuts(cuts);
 
  // Compute truth tables lazily, then match cuts to collect timing/area data.
  for (Cut *cut : cuts) {
    if (!cut->getTruthTable().has_value())
      cut->computeTruthTableFromOperands(logicNetwork);
 
    assert(cut->getInputSize() <= options.maxCutInputSize &&
           "Cut input size exceeds maximum allowed size");
 
    if (auto matched = matchCut(*cut))
      cut->setMatchedPattern(std::move(*matched));
  }
 
  // Sort cuts by priority to select the most promising ones.
  // Priority is determined by the optimization strategy:
  // - Trivial cuts (direct connections) have highest priority
  // - Among matched cuts, compare by area/delay based on the strategy
  // - Matched cuts are preferred over unmatched cuts
  // See "Combinational and Sequential Mapping with Priority Cuts" by Mishchenko
  // et al., ICCAD 2007 for more details.
  // TODO: Use a priority queue instead of sorting for better performance.
 
  // Partition the cuts into trivial and non-trivial cuts.
  auto *trivialCutsEnd =
      std::stable_partition(cuts.begin(), cuts.end(),
                            [](const Cut *cut) { return cut->isTrivialCut(); });
 
  auto isBetterCut = [&options](const Cut *a, const Cut *b) {
    assert(!a->isTrivialCut() && !b->isTrivialCut() &&
           "Trivial cuts should have been excluded");
    const auto &aMatched = a->getMatchedPattern();
    const auto &bMatched = b->getMatchedPattern();
 
    if (aMatched && bMatched)
      return compareDelayAndArea(
          options.strategy, aMatched->getArea(), aMatched->getArrivalTimes(),
          bMatched->getArea(), bMatched->getArrivalTimes());
 
    if (static_cast<bool>(aMatched) != static_cast<bool>(bMatched))
      return static_cast<bool>(aMatched);
 
    return a->getInputSize() < b->getInputSize();
  };
  std::stable_sort(trivialCutsEnd, cuts.end(), isBetterCut);
 
  // Keep only the top-K cuts to bound growth.
  if (cuts.size() > options.maxCutSizePerRoot)
    cuts.resize(options.maxCutSizePerRoot);
 
  // Select the best cut from the remaining candidates.
  bestCut = nullptr;
  for (Cut *cut : cuts) {
    const auto &currentMatch = cut->getMatchedPattern();
    if (!currentMatch)
      continue;
    bestCut = cut;
    break;
  }
 
  LLVM_DEBUG({
    llvm::dbgs() << "Finalized cut set with " << cuts.size() << " cuts and "
                 << (bestCut
                         ? "matched pattern to " + bestCut->getMatchedPattern()
                                                       ->getPattern()
                                                       ->getPatternName()
                         : "no matched pattern")
                 << "\n";
  });
 
  isFrozen = true; // Mark the cut set as frozen
}
 
//===----------------------------------------------------------------------===//
// CutRewritePattern
//===----------------------------------------------------------------------===//
 
bool CutRewritePattern::useTruthTableMatcher(
    SmallVectorImpl<NPNClass> &matchingNPNClasses) const {
  return false;
}
 
//===----------------------------------------------------------------------===//
// CutRewritePatternSet
//===----------------------------------------------------------------------===//
 
CutRewritePatternSet::CutRewritePatternSet(
    llvm::SmallVector<std::unique_ptr<CutRewritePattern>, 4> patterns)
    : patterns(std::move(patterns)) {
  // Initialize the NPN to pattern map
  for (auto &pattern : this->patterns) {
    SmallVector<NPNClass, 2> npnClasses;
    auto result = pattern->useTruthTableMatcher(npnClasses);
    if (result) {
      for (auto npnClass : npnClasses) {
        // Create a NPN class from the truth table
        npnToPatternMap[{npnClass.truthTable.table,
                         npnClass.truthTable.numInputs}]
            .push_back(std::make_pair(std::move(npnClass), pattern.get()));
      }
    } else {
      // If the pattern does not provide NPN classes, we use a special key
      // to indicate that it should be considered for all cuts.
      nonNPNPatterns.push_back(pattern.get());
    }
  }
}
 
//===----------------------------------------------------------------------===//
// CutEnumerator
//===----------------------------------------------------------------------===//
 
CutEnumerator::CutEnumerator(const CutRewriterOptions &options)
    : cutAllocator(stats.numCutsCreated),
      cutSetAllocator(stats.numCutSetsCreated), options(options) {}
 
CutSet *CutEnumerator::createNewCutSet(uint32_t index) {
  CutSet *cutSet = cutSetAllocator.create();
  auto [cutSetPtr, inserted] = cutSets.try_emplace(index, cutSet);
  assert(inserted && "Cut set already exists for this index");
  return cutSetPtr->second;
}
 
void CutEnumerator::clear() {
  cutSets.clear();
  processingOrder.clear();
  logicNetwork.clear();
  cutAllocator.DestroyAll();
  cutSetAllocator.DestroyAll();
}
 
LogicalResult CutEnumerator::visitLogicOp(uint32_t nodeIndex) {
  const auto &gate = logicNetwork.getGate(nodeIndex);
  auto *logicOp = gate.getOperation();
  assert(logicOp && logicOp->getNumResults() == 1 &&
         "Logic operation must have a single result");
 
  if (gate.getKind() == LogicNetworkGate::Choice) {
    auto choiceOp = cast<synth::ChoiceOp>(logicOp);
    auto *resultCutSet = createNewCutSet(nodeIndex);
    Cut *primaryInputCut = cutAllocator.create(Cut::getTrivialCut(nodeIndex));
    processingOrder.push_back(nodeIndex);
    resultCutSet->addCut(primaryInputCut);
 
    for (Value operand : choiceOp.getInputs()) {
      auto *operandCutSet = getCutSet(logicNetwork.getIndex(operand));
      if (!operandCutSet)
        return logicOp->emitError("Failed to get cut set for choice operand");
 
      // Choice nodes do not introduce new logic. They forward each non-trivial
      // operand cut as an equivalent alternative for the same root.
      for (const Cut *operandCut : operandCutSet->getCuts()) {
        if (operandCut->isTrivialCut())
          continue;
 
        resultCutSet->addCut(cutAllocator.create(
            nodeIndex, operandCut->inputs, operandCut->getSignature(),
            ArrayRef<const Cut *>{operandCut}, *operandCut->getTruthTable()));
      }
    }
 
    // Finalize cut set: remove duplicates, limit size, and match patterns
    resultCutSet->finalize(options, matchCut, logicNetwork);
    return success();
  }
 
  unsigned numFanins = gate.getNumFanins();
 
  // Validate operation constraints
  // TODO: Variadic operations and non-single-bit results can be supported
  if (numFanins > 3)
    return logicOp->emitError("Cut enumeration supports at most 3 operands, "
                              "found: ")
           << numFanins;
  if (!logicOp->getOpResult(0).getType().isInteger(1))
    return logicOp->emitError()
           << "Supported logic operations must have a single bit "
              "result type but found: "
           << logicOp->getResult(0).getType();
 
  // A vector to hold cut sets for each operand along with their max cut input
  // size.
  SmallVector<std::pair<const CutSet *, unsigned>, 2> operandCutSets;
  operandCutSets.reserve(numFanins);
 
  // Collect cut sets for each fanin (using LogicNetwork edges)
  for (unsigned i = 0; i < numFanins; ++i) {
    uint32_t faninIndex = gate.edges[i].getIndex();
    auto *operandCutSet = getCutSet(faninIndex);
    if (!operandCutSet)
      return logicOp->emitError("Failed to get cut set for fanin index ")
             << faninIndex;
 
    // Find the largest cut size among the operand's cuts for sorting heuristic
    // later.
    unsigned maxInputCutSize = 0;
    for (auto *cut : operandCutSet->getCuts())
      maxInputCutSize = std::max(maxInputCutSize, cut->getInputSize());
    operandCutSets.push_back(std::make_pair(operandCutSet, maxInputCutSize));
  }
 
  // Create the trivial cut for this node's output
  Cut *primaryInputCut = cutAllocator.create(Cut::getTrivialCut(nodeIndex));
 
  auto *resultCutSet = createNewCutSet(nodeIndex);
  processingOrder.push_back(nodeIndex);
  resultCutSet->addCut(primaryInputCut);
 
  // Sort operand cut sets by their largest cut size in descending order. This
  // heuristic improves efficiency of the k-way merge when generating cuts for
  // the current node by maximizing the chance of early pruning when the merged
  // cut exceeds the input size limit.
  llvm::stable_sort(operandCutSets,
                    [](const std::pair<const CutSet *, unsigned> &a,
                       const std::pair<const CutSet *, unsigned> &b) {
                      return a.second > b.second;
                    });
 
  // Cache maxCutInputSize to avoid repeated access
  unsigned maxInputSize = options.maxCutInputSize;
 
  // This lambda generates nested loops at runtime to iterate over all
  // combinations of cuts from N operands
  auto enumerateCutCombinations = [&](auto &&self, unsigned operandIdx,
                                      SmallVector<const Cut *, 3> &cutPtrs,
                                      uint64_t currentSig) -> void {
    // Base case: all operands processed, create merged cut
    if (operandIdx == numFanins) {
      // Efficient k-way merge: inputs are sorted, so dedup and constant
      // filtering can be done while merging. Abort early once we exceed the
      // cut-size limit to avoid building doomed merged cuts.
      SmallVector<uint32_t, 6> mergedInputs;
      auto appendMergedInput = [&](uint32_t value) {
        if (value == LogicNetwork::kConstant0 ||
            value == LogicNetwork::kConstant1)
          return true;
        if (!mergedInputs.empty() && mergedInputs.back() == value)
          return true;
        mergedInputs.push_back(value);
        return mergedInputs.size() <= maxInputSize;
      };
 
      if (numFanins == 1) {
        // Single input: copy while filtering constants.
        mergedInputs.reserve(
            std::min<size_t>(cutPtrs[0]->inputs.size(), maxInputSize));
        for (uint32_t value : cutPtrs[0]->inputs)
          if (!appendMergedInput(value))
            return;
      } else if (numFanins == 2) {
        // Two-way merge (common case for AND gates)
        const auto &inputs0 = cutPtrs[0]->inputs;
        const auto &inputs1 = cutPtrs[1]->inputs;
        mergedInputs.reserve(
            std::min<size_t>(inputs0.size() + inputs1.size(), maxInputSize));
 
        unsigned i = 0, j = 0;
        while (i < inputs0.size() || j < inputs1.size()) {
          uint32_t next;
          if (j == inputs1.size() ||
              (i < inputs0.size() && inputs0[i] <= inputs1[j])) {
            next = inputs0[i++];
            if (j < inputs1.size() && inputs1[j] == next)
              ++j;
          } else {
            next = inputs1[j++];
          }
          if (!appendMergedInput(next))
            return;
        }
      } else {
        // Three-way merge (for MAJ/MUX gates)
        const SmallVectorImpl<uint32_t> &inputs0 = cutPtrs[0]->inputs;
        const SmallVectorImpl<uint32_t> &inputs1 = cutPtrs[1]->inputs;
        const SmallVectorImpl<uint32_t> &inputs2 = cutPtrs[2]->inputs;
        mergedInputs.reserve(std::min<size_t>(
            inputs0.size() + inputs1.size() + inputs2.size(), maxInputSize));
 
        unsigned i = 0, j = 0, k = 0;
        while (i < inputs0.size() || j < inputs1.size() || k < inputs2.size()) {
          // Find minimum among available elements
          uint32_t minVal = UINT32_MAX;
          if (i < inputs0.size())
            minVal = std::min(minVal, inputs0[i]);
          if (j < inputs1.size())
            minVal = std::min(minVal, inputs1[j]);
          if (k < inputs2.size())
            minVal = std::min(minVal, inputs2[k]);
 
          // Advance all iterators pointing to minVal (handles duplicates)
          if (i < inputs0.size() && inputs0[i] == minVal)
            i++;
          if (j < inputs1.size() && inputs1[j] == minVal)
            j++;
          if (k < inputs2.size() && inputs2[k] == minVal)
            k++;
 
          if (!appendMergedInput(minVal))
            return;
        }
      }
 
      // Create the merged cut.
      Cut *mergedCut = cutAllocator.create(nodeIndex, mergedInputs, currentSig,
                                           ArrayRef<const Cut *>(cutPtrs));
      resultCutSet->addCut(mergedCut);
 
      LLVM_DEBUG({
        if (mergedCut->inputs.size() >= 4) {
          llvm::dbgs() << "Generated cut for node " << nodeIndex;
          if (logicOp)
            llvm::dbgs() << " (" << logicOp->getName() << ")";
          llvm::dbgs() << " inputs=";
          llvm::interleaveComma(mergedCut->inputs, llvm::dbgs());
          llvm::dbgs() << "\n";
        }
      });
      return;
    }
 
    // Recursive case: iterate over cuts for current operand
    const CutSet *currentCutSet = operandCutSets[operandIdx].first;
    for (const Cut *cut : currentCutSet->getCuts()) {
      uint64_t cutSig = cut->getSignature();
      uint64_t newSig = currentSig | cutSig;
      if (static_cast<unsigned>(llvm::popcount(newSig)) > maxInputSize)
        continue; // Early rejection based on signature
 
      cutPtrs.push_back(cut);
 
      // Recurse to next operand
      self(self, operandIdx + 1, cutPtrs, newSig);
 
      cutPtrs.pop_back();
    }
  };
 
  // Start the recursion with empty cut pointer list and zero signature
  SmallVector<const Cut *, 3> cutPtrs;
  cutPtrs.reserve(numFanins);
  enumerateCutCombinations(enumerateCutCombinations, 0, cutPtrs, 0ULL);
 
  // Finalize cut set: remove duplicates, limit size, and match patterns
  resultCutSet->finalize(options, matchCut, logicNetwork);
 
  return success();
}
 
LogicalResult CutEnumerator::enumerateCuts(
    Operation *topOp,
    llvm::function_ref<std::optional<MatchedPattern>(const Cut &)> matchCut) {
  LLVM_DEBUG(llvm::dbgs() << "Enumerating cuts for module: " << topOp->getName()
                          << "\n");
  // Topologically sort the logic network
  if (failed(topologicallySortLogicNetwork(topOp)))
    return failure();
 
  // Store the pattern matching function for use during cut finalization
  this->matchCut = matchCut;
 
  // Build the flat logic network representation for efficient simulation
  auto &block = topOp->getRegion(0).getBlocks().front();
  if (failed(logicNetwork.buildFromBlock(&block)))
    return failure();
 
  for (const auto &[index, gate] : llvm::enumerate(logicNetwork.getGates())) {
    // Skip non-logic gates.
    if (!gate.isLogicGate())
      continue;
 
    // Ensure cut set exists for each logic gate
    if (failed(visitLogicOp(index)))
      return failure();
  }
 
  LLVM_DEBUG(llvm::dbgs() << "Cut enumeration completed successfully\n");
  return success();
}
 
const CutSet *CutEnumerator::getCutSet(uint32_t index) {
  // Check if cut set already exists
  auto it = cutSets.find(index);
  if (it == cutSets.end()) {
    // Create new cut set for an unprocessed value (primary input or other)
    CutSet *cutSet = cutSetAllocator.create();
    Cut *trivialCut = cutAllocator.create(Cut::getTrivialCut(index));
    cutSet->addCut(trivialCut);
    auto [newIt, inserted] = cutSets.insert({index, cutSet});
    assert(inserted && "Cut set already exists for this index");
    it = newIt;
  }
 
  return it->second;
}
 
/// Generate a human-readable name for a value used in test output.
/// This function creates meaningful names for values to make debug output
/// and test results more readable and understandable.
static StringRef
getTestVariableName(Value value, DenseMap<OperationName, unsigned> &opCounter) {
  if (auto *op = value.getDefiningOp()) {
    // Handle values defined by operations
    // First, check if the operation already has a name hint attribute
    if (auto name = op->getAttrOfType<StringAttr>("sv.namehint"))
      return name.getValue();
 
    // For single-result operations, generate a unique name based on operation
    // type
    if (op->getNumResults() == 1) {
      auto opName = op->getName();
      auto count = opCounter[opName]++;
 
      // Create a unique name by appending a counter to the operation name
      SmallString<16> nameStr;
      nameStr += opName.getStringRef();
      nameStr += "_";
      nameStr += std::to_string(count);
 
      // Store the generated name as a hint attribute for future reference
      auto nameAttr = StringAttr::get(op->getContext(), nameStr);
      op->setAttr("sv.namehint", nameAttr);
      return nameAttr;
    }
 
    // Multi-result operations or other cases get a generic name
    return "<unknown>";
  }
 
  // Handle block arguments
  auto blockArg = cast<BlockArgument>(value);
  auto hwOp =
      dyn_cast<circt::hw::HWModuleOp>(blockArg.getOwner()->getParentOp());
  if (!hwOp)
    return "<unknown>";
 
  // Return the formal input name from the hardware module
  return hwOp.getInputName(blockArg.getArgNumber());
}
 
void CutEnumerator::dump() const {
  DenseMap<OperationName, unsigned> opCounter;
  for (auto index : processingOrder) {
    auto it = cutSets.find(index);
    if (it == cutSets.end())
      continue;
    auto &cutSet = *it->second;
    mlir::Value value = logicNetwork.getValue(index);
    llvm::outs() << getTestVariableName(value, opCounter) << " "
                 << cutSet.getCuts().size() << " cuts:";
    for (const Cut *cut : cutSet.getCuts()) {
      llvm::outs() << " {";
      llvm::interleaveComma(cut->inputs, llvm::outs(), [&](uint32_t inputIdx) {
        mlir::Value inputVal = logicNetwork.getValue(inputIdx);
        llvm::outs() << getTestVariableName(inputVal, opCounter);
      });
      auto &pattern = cut->getMatchedPattern();
      llvm::outs() << "}"
                   << "@t" << cut->getTruthTable()->table.getZExtValue() << "d";
      if (pattern) {
        llvm::outs() << *std::max_element(pattern->getArrivalTimes().begin(),
                                          pattern->getArrivalTimes().end());
      } else {
        llvm::outs() << "0";
      }
    }
    llvm::outs() << "\n";
  }
  llvm::outs() << "Cut enumeration completed successfully\n";
}
 
//===----------------------------------------------------------------------===//
// CutRewriter
//===----------------------------------------------------------------------===//
 
LogicalResult CutRewriter::run(Operation *topOp) {
  LLVM_DEBUG({
    llvm::dbgs() << "Starting Cut Rewriter\n";
    llvm::dbgs() << "Mode: "
                 << (OptimizationStrategyArea == options.strategy ? "area"
                                                                  : "timing")
                 << "\n";
    llvm::dbgs() << "Max input size: " << options.maxCutInputSize << "\n";
    llvm::dbgs() << "Max cut size: " << options.maxCutSizePerRoot << "\n";
  });
 
  // Currently we don't support patterns with multiple outputs.
  // So check that.
  // TODO: This must be removed when we support multiple outputs.
  for (auto &pattern : patterns.patterns) {
    if (pattern->getNumOutputs() > 1) {
      return mlir::emitError(pattern->getLoc(),
                             "Cut rewriter does not support patterns with "
                             "multiple outputs yet");
    }
  }
 
  // First sort the operations topologically to ensure we can process them
  // in a valid order.
  if (failed(topologicallySortLogicNetwork(topOp)))
    return failure();
 
  // Enumerate cuts for all nodes (initial delay-oriented selection)
  if (failed(enumerateCuts(topOp)))
    return failure();
 
  // Dump cuts if testing priority cuts.
  if (options.testPriorityCuts) {
    cutEnumerator.dump();
    return success();
  }
 
  // Select best cuts and perform mapping
  if (failed(runBottomUpRewrite(topOp)))
    return failure();
 
  return success();
}
 
LogicalResult CutRewriter::enumerateCuts(Operation *topOp) {
  LLVM_DEBUG(llvm::dbgs() << "Enumerating cuts...\n");
 
  return cutEnumerator.enumerateCuts(
      topOp, [&](const Cut &cut) -> std::optional<MatchedPattern> {
        // Match the cut against the patterns
        return patternMatchCut(cut);
      });
}
 
ArrayRef<std::pair<NPNClass, const CutRewritePattern *>>
CutRewriter::getMatchingPatternsFromTruthTable(const Cut &cut) const {
  if (patterns.npnToPatternMap.empty())
    return {};
 
  auto &npnClass = cut.getNPNClass(options.npnTable);
  auto it = patterns.npnToPatternMap.find(
      {npnClass.truthTable.table, npnClass.truthTable.numInputs});
  if (it == patterns.npnToPatternMap.end())
    return {};
  return it->getSecond();
}
 
std::optional<MatchedPattern> CutRewriter::patternMatchCut(const Cut &cut) {
  if (cut.isTrivialCut())
    return {};
 
  const auto &network = cutEnumerator.getLogicNetwork();
  const CutRewritePattern *bestPattern = nullptr;
  SmallVector<DelayType, 4> inputArrivalTimes;
  SmallVector<DelayType, 1> bestArrivalTimes;
  double bestArea = 0.0;
  inputArrivalTimes.reserve(cut.getInputSize());
  bestArrivalTimes.reserve(cut.getOutputSize(network));
 
  // Compute arrival times for each input.
  if (failed(cut.getInputArrivalTimes(cutEnumerator, inputArrivalTimes)))
    return {};
 
  auto computeArrivalTimeAndPickBest =
      [&](const CutRewritePattern *pattern, const MatchResult &matchResult,
          llvm::function_ref<unsigned(unsigned)> mapIndex) {
        SmallVector<DelayType, 1> outputArrivalTimes;
        // Compute the maximum delay for each output from inputs.
        for (unsigned outputIndex = 0, outputSize = cut.getOutputSize(network);
             outputIndex < outputSize; ++outputIndex) {
          // Compute the arrival time for this output.
          DelayType outputArrivalTime = 0;
          auto delays = matchResult.getDelays();
          for (unsigned inputIndex = 0, inputSize = cut.getInputSize();
               inputIndex < inputSize; ++inputIndex) {
            // Map pattern input i to cut input through NPN transformations
            unsigned cutOriginalInput = mapIndex(inputIndex);
            outputArrivalTime =
                std::max(outputArrivalTime,
                         delays[outputIndex * inputSize + inputIndex] +
                             inputArrivalTimes[cutOriginalInput]);
          }
 
          outputArrivalTimes.push_back(outputArrivalTime);
        }
 
        // Update the arrival time
        if (!bestPattern ||
            compareDelayAndArea(options.strategy, matchResult.area,
                                outputArrivalTimes, bestArea,
                                bestArrivalTimes)) {
          LLVM_DEBUG({
            llvm::dbgs() << "== Matched Pattern ==============\n";
            llvm::dbgs() << "Matching cut: \n";
            cut.dump(llvm::dbgs(), network);
            llvm::dbgs() << "Found better pattern: "
                         << pattern->getPatternName();
            llvm::dbgs() << " with area: " << matchResult.area;
            llvm::dbgs() << " and input arrival times: ";
            for (unsigned i = 0; i < inputArrivalTimes.size(); ++i) {
              llvm::dbgs() << " " << inputArrivalTimes[i];
            }
            llvm::dbgs() << " and arrival times: ";
 
            for (auto arrivalTime : outputArrivalTimes) {
              llvm::dbgs() << " " << arrivalTime;
            }
            llvm::dbgs() << "\n";
            llvm::dbgs() << "== Matched Pattern End ==============\n";
          });
 
          bestArrivalTimes = std::move(outputArrivalTimes);
          bestArea = matchResult.area;
          bestPattern = pattern;
        }
      };
 
  for (auto &[patternNPN, pattern] : getMatchingPatternsFromTruthTable(cut)) {
    assert(patternNPN.truthTable.numInputs == cut.getInputSize() &&
           "Pattern input size must match cut input size");
    auto matchResult = pattern->match(cutEnumerator, cut);
    if (!matchResult)
      continue;
    auto &cutNPN = cut.getNPNClass(options.npnTable);
 
    // Get the input mapping from pattern's NPN class to cut's NPN class
    SmallVector<unsigned> inputMapping;
    cutNPN.getInputPermutation(patternNPN, inputMapping);
    computeArrivalTimeAndPickBest(pattern, *matchResult,
                                  [&](unsigned i) { return inputMapping[i]; });
  }
 
  for (const CutRewritePattern *pattern : patterns.nonNPNPatterns) {
    if (auto matchResult = pattern->match(cutEnumerator, cut))
      computeArrivalTimeAndPickBest(pattern, *matchResult,
                                    [&](unsigned i) { return i; });
  }
 
  if (!bestPattern)
    return {}; // No matching pattern found
 
  return MatchedPattern(bestPattern, std::move(bestArrivalTimes), bestArea);
}
 
LogicalResult CutRewriter::runBottomUpRewrite(Operation *top) {
  LLVM_DEBUG(llvm::dbgs() << "Performing cut-based rewriting...\n");
  const auto &network = cutEnumerator.getLogicNetwork();
  const auto &cutSets = cutEnumerator.getCutSets();
  auto processingOrder = cutEnumerator.getProcessingOrder();
 
  // Note: Don't clear cutEnumerator yet - we need it during rewrite
  UnusedOpPruner pruner;
  PatternRewriter rewriter(top->getContext());
 
  // Process in reverse topological order
  for (auto index : llvm::reverse(processingOrder)) {
    auto it = cutSets.find(index);
    if (it == cutSets.end())
      continue;
 
    mlir::Value value = network.getValue(index);
    auto &cutSet = *it->second;
 
    if (value.use_empty()) {
      if (auto *op = value.getDefiningOp())
        pruner.eraseNow(op);
      continue;
    }
 
    if (isAlwaysCutInput(network, index)) {
      // If the value is a primary input, skip it
      LLVM_DEBUG(llvm::dbgs() << "Skipping inputs: " << value << "\n");
      continue;
    }
 
    LLVM_DEBUG(llvm::dbgs() << "Cut set for value: " << value << "\n");
    auto *bestCut = cutSet.getBestMatchedCut();
    if (!bestCut) {
      if (options.allowNoMatch)
        continue; // No matching pattern found, skip this value
      return emitError(value.getLoc(), "No matching cut found for value: ")
             << value;
    }
 
    // Get the root operation from LogicNetwork
    auto *rootOp = network.getGate(bestCut->getRootIndex()).getOperation();
    rewriter.setInsertionPoint(rootOp);
    const auto &matchedPattern = bestCut->getMatchedPattern();
    auto result = matchedPattern->getPattern()->rewrite(rewriter, cutEnumerator,
                                                        *bestCut);
    if (failed(result))
      return failure();
 
    rewriter.replaceOp(rootOp, *result);
    cutEnumerator.noteCutRewritten();
 
    if (options.attachDebugTiming) {
      auto array = rewriter.getI64ArrayAttr(matchedPattern->getArrivalTimes());
      (*result)->setAttr("test.arrival_times", array);
    }
  }
 
  // Clear the enumerator after rewriting is complete
  cutEnumerator.clear();
  return success();
}