FullReset.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 defines the FullReset pass.
//
//===----------------------------------------------------------------------===//
 
#include "circt/Analysis/FIRRTLInstanceInfo.h"
#include "circt/Dialect/FIRRTL/AnnotationDetails.h"
#include "circt/Dialect/FIRRTL/FIRRTLAnnotations.h"
#include "circt/Dialect/FIRRTL/FIRRTLInstanceGraph.h"
#include "circt/Dialect/FIRRTL/FIRRTLOps.h"
#include "circt/Dialect/FIRRTL/FIRRTLTypes.h"
#include "circt/Dialect/FIRRTL/FIRRTLUtils.h"
#include "circt/Dialect/FIRRTL/Passes.h"
#include "circt/Support/Debug.h"
#include "mlir/IR/Threading.h"
#include "mlir/Pass/Pass.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/LogicalResult.h"
#include <atomic>
 
#define DEBUG_TYPE "firrtl-full-reset"
 
namespace circt {
namespace firrtl {
#define GEN_PASS_DEF_FULLRESET
#include "circt/Dialect/FIRRTL/Passes.h.inc"
} // namespace firrtl
} // namespace circt
 
using namespace circt;
using namespace firrtl;
 
using circt::igraph::InstanceOpInterface;
using circt::igraph::InstancePath;
using circt::igraph::InstancePathCache;
using llvm::SmallDenseSet;
using llvm::SmallSetVector;
using mlir::FailureOr;
 
/// Return the name and parent module of a reset. The reset value must either be
/// a module port or a wire/node operation.
static std::pair<StringAttr, FModuleOp> getResetNameAndModule(Value reset) {
  if (auto arg = dyn_cast<BlockArgument>(reset)) {
    auto module = cast<FModuleOp>(arg.getParentRegion()->getParentOp());
    return {module.getPortNameAttr(arg.getArgNumber()), module};
  }
  auto *op = reset.getDefiningOp();
  return {op->getAttrOfType<StringAttr>("name"),
          op->getParentOfType<FModuleOp>()};
}
 
/// Return the name of a reset. The reset value must either be a module port or
/// a wire/node operation.
static StringAttr getResetName(Value reset) {
  return getResetNameAndModule(reset).first;
}
 
namespace {
/// A reset domain.
struct ResetDomain {
  /// Whether this is the root of the reset domain.
  bool isTop = false;
 
  /// The reset signal for this domain. A null value indicates that this domain
  /// explicitly has no reset.
  Value rootReset;
 
  /// The name of this reset signal.
  StringAttr resetName;
  /// The type of this reset signal.
  Type resetType;
 
  /// Implementation details for this domain. This will be the module local
  /// signal for this domain.
  Value localReset;
  /// If this module already has a port with the matching name, this holds the
  /// index of the port.
  std::optional<unsigned> existingPort;
 
  /// Create a reset domain without any reset.
  ResetDomain() = default;
 
  /// Create a reset domain associated with the root reset.
  ResetDomain(Value rootReset)
      : rootReset(rootReset), resetName(getResetName(rootReset)),
        resetType(rootReset.getType()) {}
 
  /// Returns true if this is in a reset domain, false if this is not a domain.
  explicit operator bool() const { return static_cast<bool>(rootReset); }
};
} // namespace
 
inline bool operator==(const ResetDomain &a, const ResetDomain &b) {
  return (a.isTop == b.isTop && a.resetName == b.resetName &&
          a.resetType == b.resetType);
}
inline bool operator!=(const ResetDomain &a, const ResetDomain &b) {
  return !(a == b);
}
 
/// Construct a zero value of the given type using the given builder.
static Value createZeroValue(ImplicitLocOpBuilder &builder, FIRRTLBaseType type,
                             SmallDenseMap<FIRRTLBaseType, Value> &cache) {
  // The zero value's type is a const version of `type`.
  type = type.getConstType(true);
  auto it = cache.find(type);
  if (it != cache.end())
    return it->second;
  auto nullBit = [&]() {
    return createZeroValue(
        builder, UIntType::get(builder.getContext(), 1, /*isConst=*/true),
        cache);
  };
  auto value =
      FIRRTLTypeSwitch<FIRRTLBaseType, Value>(type)
          .Case<ClockType>([&](auto type) {
            return AsClockPrimOp::create(builder, nullBit());
          })
          .Case<AsyncResetType>([&](auto type) {
            return AsAsyncResetPrimOp::create(builder, nullBit());
          })
          .Case<SIntType, UIntType>([&](auto type) {
            return ConstantOp::create(
                builder, type, APInt::getZero(type.getWidth().value_or(1)));
          })
          .Case<FEnumType>([&](auto type) -> Value {
            // There might not be a variant that corresponds to 0, in which case
            // we have to create a 0 value and bitcast it to the enum.
            if (type.getNumElements() != 0 &&
                type.getElement(0).value.getValue().isZero()) {
              const auto &element = type.getElement(0);
              auto value = createZeroValue(builder, element.type, cache);
              return FEnumCreateOp::create(builder, type, element.name, value);
            }
            auto value = ConstantOp::create(builder,
                                            UIntType::get(builder.getContext(),
                                                          type.getBitWidth(),
                                                          /*isConst=*/true),
                                            APInt::getZero(type.getBitWidth()));
            return BitCastOp::create(builder, type, value);
          })
          .Case<BundleType>([&](auto type) {
            auto wireOp = WireOp::create(builder, type);
            for (unsigned i = 0, e = type.getNumElements(); i < e; ++i) {
              auto fieldType = type.getElementTypePreservingConst(i);
              auto zero = createZeroValue(builder, fieldType, cache);
              auto acc =
                  SubfieldOp::create(builder, fieldType, wireOp.getResult(), i);
              emitConnect(builder, acc, zero);
            }
            return wireOp.getResult();
          })
          .Case<FVectorType>([&](auto type) {
            auto wireOp = WireOp::create(builder, type);
            auto zero = createZeroValue(
                builder, type.getElementTypePreservingConst(), cache);
            for (unsigned i = 0, e = type.getNumElements(); i < e; ++i) {
              auto acc = SubindexOp::create(builder, zero.getType(),
                                            wireOp.getResult(), i);
              emitConnect(builder, acc, zero);
            }
            return wireOp.getResult();
          })
          .Case<ResetType, AnalogType>(
              [&](auto type) { return InvalidValueOp::create(builder, type); })
          .Default([](auto) {
            llvm_unreachable("switch handles all types");
            return Value{};
          });
  cache.insert({type, value});
  return value;
}
 
/// Construct a null value of the given type using the given builder.
static Value createZeroValue(ImplicitLocOpBuilder &builder,
                             FIRRTLBaseType type) {
  SmallDenseMap<FIRRTLBaseType, Value> cache;
  return createZeroValue(builder, type, cache);
}
 
/// Helper function that inserts reset multiplexer into all `ConnectOp`s
/// with the given target. Looks through `SubfieldOp`, `SubindexOp`,
/// and `SubaccessOp`, and inserts multiplexers into connects to
/// these subaccesses as well. Modifies the insertion location of the builder.
/// Returns true if the `resetValue` was used in any way, false otherwise.
static bool insertResetMux(ImplicitLocOpBuilder &builder, Value target,
                           Value reset, Value resetValue) {
  // Indicates whether the `resetValue` was assigned to in some way. We use this
  // to erase unused subfield/subindex/subaccess ops on the reset value if they
  // end up unused.
  bool resetValueUsed = false;
 
  for (auto &use : target.getUses()) {
    Operation *useOp = use.getOwner();
    builder.setInsertionPoint(useOp);
    TypeSwitch<Operation *>(useOp)
        // Insert a mux on the value connected to the target:
        // connect(dst, src) -> connect(dst, mux(reset, resetValue, src))
        .Case<ConnectOp, MatchingConnectOp>([&](auto op) {
          if (op.getDest() != target)
            return;
          LLVM_DEBUG(llvm::dbgs() << "  - Insert mux into " << op << "\n");
          auto muxOp =
              MuxPrimOp::create(builder, reset, resetValue, op.getSrc());
          op.getSrcMutable().assign(muxOp);
          resetValueUsed = true;
        })
        // Look through subfields.
        .Case<SubfieldOp>([&](auto op) {
          auto resetSubValue =
              SubfieldOp::create(builder, resetValue, op.getFieldIndexAttr());
          if (insertResetMux(builder, op, reset, resetSubValue))
            resetValueUsed = true;
          else
            resetSubValue.erase();
        })
        // Look through subindices.
        .Case<SubindexOp>([&](auto op) {
          auto resetSubValue =
              SubindexOp::create(builder, resetValue, op.getIndexAttr());
          if (insertResetMux(builder, op, reset, resetSubValue))
            resetValueUsed = true;
          else
            resetSubValue.erase();
        })
        // Look through subaccesses.
        .Case<SubaccessOp>([&](auto op) {
          if (op.getInput() != target)
            return;
          auto resetSubValue =
              SubaccessOp::create(builder, resetValue, op.getIndex());
          if (insertResetMux(builder, op, reset, resetSubValue))
            resetValueUsed = true;
          else
            resetSubValue.erase();
        });
  }
  return resetValueUsed;
}
 
//===----------------------------------------------------------------------===//
// Reset Network
//===----------------------------------------------------------------------===//
 
/// A reset signal.
///
 
namespace {
enum class ResetKind { Async, Sync };
 
static StringRef resetKindToStringRef(const ResetKind &kind) {
  switch (kind) {
  case ResetKind::Async:
    return "async";
  case ResetKind::Sync:
    return "sync";
  }
  llvm_unreachable("unhandled reset kind");
}
} // namespace
 
namespace {
struct MemToRegOfVecConverter {
  explicit MemToRegOfVecConverter(bool ignoreReadEnable)
      : ignoreReadEnable(ignoreReadEnable) {}
 
  void runOnModule(FModuleOp mod) {
 
    mod.getBodyBlock()->walk([&](MemOp memOp) {
      LLVM_DEBUG(llvm::dbgs() << "\n Memory op:" << memOp);
 
      auto firMem = memOp.getSummary();
      // Ignore if the memory is a sequential memory, i.e., something that is
      // supposed to be an SRAM.  In either possible eventual lowering by later
      // passes (blackboxing or lowering to a behavioral model) we don't want to
      // blow this out here as it both breaks expectations about later passes
      // that may add asynchronous resets (InferResets) or that expect metadata
      // on SRAMs to not be split up (LowerClasses).
      if (firMem.isSeqMem())
        return;
 
      generateMemory(memOp, firMem);
      ++numConverted;
      memOp.erase();
    });
  }
  Value addPipelineStages(ImplicitLocOpBuilder &b, size_t stages, Value clock,
                          Value pipeInput, StringRef name, Value gate = {}) {
    if (!stages)
      return pipeInput;
 
    while (stages--) {
      auto reg = RegOp::create(b, pipeInput.getType(), clock, name).getResult();
      if (gate) {
        WhenOp::create(b, gate, /*withElseRegion*/ false,
                       [&]() { MatchingConnectOp::create(b, reg, pipeInput); });
      } else
        MatchingConnectOp::create(b, reg, pipeInput);
 
      pipeInput = reg;
    }
 
    return pipeInput;
  }
 
  Value getClock(ImplicitLocOpBuilder &builder, Value bundle) {
    return SubfieldOp::create(builder, bundle, "clk");
  }
 
  Value getAddr(ImplicitLocOpBuilder &builder, Value bundle) {
    return SubfieldOp::create(builder, bundle, "addr");
  }
 
  Value getWmode(ImplicitLocOpBuilder &builder, Value bundle) {
    return SubfieldOp::create(builder, bundle, "wmode");
  }
 
  Value getEnable(ImplicitLocOpBuilder &builder, Value bundle) {
    return SubfieldOp::create(builder, bundle, "en");
  }
 
  Value getMask(ImplicitLocOpBuilder &builder, Value bundle) {
    auto bType = type_cast<BundleType>(bundle.getType());
    if (bType.getElement("mask"))
      return SubfieldOp::create(builder, bundle, "mask");
    return SubfieldOp::create(builder, bundle, "wmask");
  }
 
  Value getData(ImplicitLocOpBuilder &builder, Value bundle,
                bool getWdata = false) {
    auto bType = type_cast<BundleType>(bundle.getType());
    if (bType.getElement("data"))
      return SubfieldOp::create(builder, bundle, "data");
    if (bType.getElement("rdata") && !getWdata)
      return SubfieldOp::create(builder, bundle, "rdata");
    return SubfieldOp::create(builder, bundle, "wdata");
  }
 
  void generateRead(const FirMemory &firMem, Value clock, Value addr,
                    Value enable, Value data, Value regOfVec,
                    ImplicitLocOpBuilder &builder) {
    if (ignoreReadEnable) {
      // If read enable is ignored, then guard the address update with read
      // enable.
      for (size_t j = 0, e = firMem.readLatency; j != e; ++j) {
        auto enLast = enable;
        if (j < e - 1)
          enable = addPipelineStages(builder, 1, clock, enable, "en");
        addr = addPipelineStages(builder, 1, clock, addr, "addr", enLast);
      }
    } else {
      // Add pipeline stages to respect the read latency. One register for each
      // latency cycle.
      enable =
          addPipelineStages(builder, firMem.readLatency, clock, enable, "en");
      addr =
          addPipelineStages(builder, firMem.readLatency, clock, addr, "addr");
    }
 
    // Read the register[address] into a temporary.
    Value rdata = SubaccessOp::create(builder, regOfVec, addr);
    if (!ignoreReadEnable) {
      // Initialize read data out with invalid.
      MatchingConnectOp::create(
          builder, data, InvalidValueOp::create(builder, data.getType()));
      // If enable is true, then connect the data read from memory register.
      WhenOp::create(builder, enable, /*withElseRegion*/ false, [&]() {
        MatchingConnectOp::create(builder, data, rdata);
      });
    } else {
      // Ignore read enable signal.
      MatchingConnectOp::create(builder, data, rdata);
    }
  }
 
  void generateWrite(const FirMemory &firMem, Value clock, Value addr,
                     Value enable, Value maskBits, Value wdataIn,
                     Value regOfVec, ImplicitLocOpBuilder &builder) {
 
    auto numStages = firMem.writeLatency - 1;
    // Add pipeline stages to respect the write latency. Intermediate registers
    // for each stage.
    addr = addPipelineStages(builder, numStages, clock, addr, "addr");
    enable = addPipelineStages(builder, numStages, clock, enable, "en");
    wdataIn = addPipelineStages(builder, numStages, clock, wdataIn, "wdata");
    maskBits = addPipelineStages(builder, numStages, clock, maskBits, "wmask");
    // Create the register access.
    FIRRTLBaseValue rdata = SubaccessOp::create(builder, regOfVec, addr);
 
    // The tuple for the access to individual fields of an aggregate data type.
    // Tuple::<register, data, mask>
    // The logic:
    // if (mask)
    //  register = data
    SmallVector<std::tuple<Value, Value, Value>, 8> loweredRegDataMaskFields;
 
    // Write to each aggregate data field is guarded by the corresponding mask
    // field. This means we have to generate read and write access for each
    // individual field of the aggregate type.
    // There are two options to handle this,
    // 1. FlattenMemory: cast the aggregate data into a UInt and generate
    // appropriate mask logic.
    // 2. Create access for each individual field of the aggregate type.
    // Here we implement the option 2 using getFields.
    // getFields, creates an access to each individual field of the data and
    // mask, and the corresponding field into the register.  It populates
    // the loweredRegDataMaskFields vector.
    // This is similar to what happens in LowerTypes.
    //
    if (!getFields(rdata, wdataIn, maskBits, loweredRegDataMaskFields,
                   builder)) {
      wdataIn.getDefiningOp()->emitOpError(
          "Cannot convert memory to bank of registers");
      return;
    }
    // If enable:
    WhenOp::create(builder, enable, /*withElseRegion*/ false, [&]() {
      // For each data field. Only one field if not aggregate.
      for (auto regDataMask : loweredRegDataMaskFields) {
        auto regField = std::get<0>(regDataMask);
        auto dataField = std::get<1>(regDataMask);
        auto maskField = std::get<2>(regDataMask);
        // If mask, then update the register field.
        WhenOp::create(builder, maskField, /*withElseRegion*/ false, [&]() {
          MatchingConnectOp::create(builder, regField, dataField);
        });
      }
    });
  }
 
  void generateReadWrite(const FirMemory &firMem, Value clock, Value addr,
                         Value enable, Value maskBits, Value wdataIn,
                         Value rdataOut, Value wmode, Value regOfVec,
                         ImplicitLocOpBuilder &builder) {
 
    // Add pipeline stages to respect the write latency. Intermediate registers
    // for each stage. Number of pipeline stages, max of read/write latency.
    auto numStages = std::max(firMem.readLatency, firMem.writeLatency) - 1;
    addr = addPipelineStages(builder, numStages, clock, addr, "addr");
    enable = addPipelineStages(builder, numStages, clock, enable, "en");
    wdataIn = addPipelineStages(builder, numStages, clock, wdataIn, "wdata");
    maskBits = addPipelineStages(builder, numStages, clock, maskBits, "wmask");
 
    // Read the register[address] into a temporary.
    Value rdata = SubaccessOp::create(builder, regOfVec, addr);
 
    SmallVector<std::tuple<Value, Value, Value>, 8> loweredRegDataMaskFields;
    if (!getFields(rdata, wdataIn, maskBits, loweredRegDataMaskFields,
                   builder)) {
      wdataIn.getDefiningOp()->emitOpError(
          "Cannot convert memory to bank of registers");
      return;
    }
    // Initialize read data out with invalid.
    MatchingConnectOp::create(
        builder, rdataOut, InvalidValueOp::create(builder, rdataOut.getType()));
    // If enable:
    WhenOp::create(builder, enable, /*withElseRegion*/ false, [&]() {
      // If write mode:
      WhenOp::create(
          builder, wmode, true,
          // Write block:
          [&]() {
            // For each data field. Only one field if not aggregate.
            for (auto regDataMask : loweredRegDataMaskFields) {
              auto regField = std::get<0>(regDataMask);
              auto dataField = std::get<1>(regDataMask);
              auto maskField = std::get<2>(regDataMask);
              // If mask true, then set the field.
              WhenOp::create(
                  builder, maskField, /*withElseRegion*/ false, [&]() {
                    MatchingConnectOp::create(builder, regField, dataField);
                  });
            }
          },
          // Read block:
          [&]() { MatchingConnectOp::create(builder, rdataOut, rdata); });
    });
  }
 
  // Generate individual field accesses for an aggregate type. Return false if
  // it fails. Which can happen if invalid fields are present of the mask and
  // input types donot match. The assumption is that, \p reg and \p input have
  // exactly the same type. And \p mask has the same bundle fields, but each
  // field is of type UInt<1> So, populate the \p results with each field
  // access. For example, the first entry should be access to first field of \p
  // reg, first field of \p input and first field of \p mask.
  bool getFields(Value reg, Value input, Value mask,
                 SmallVectorImpl<std::tuple<Value, Value, Value>> &results,
                 ImplicitLocOpBuilder &builder) {
 
    // Check if the number of fields of mask and input type match.
    auto isValidMask = [&](FIRRTLType inType, FIRRTLType maskType) -> bool {
      if (auto bundle = type_dyn_cast<BundleType>(inType)) {
        if (auto mBundle = type_dyn_cast<BundleType>(maskType))
          return mBundle.getNumElements() == bundle.getNumElements();
      } else if (auto vec = type_dyn_cast<FVectorType>(inType)) {
        if (auto mVec = type_dyn_cast<FVectorType>(maskType))
          return mVec.getNumElements() == vec.getNumElements();
      } else
        return true;
      return false;
    };
 
    std::function<bool(Value, Value, Value)> flatAccess =
        [&](Value reg, Value input, Value mask) -> bool {
      FIRRTLType inType = type_cast<FIRRTLType>(input.getType());
      if (!isValidMask(inType, type_cast<FIRRTLType>(mask.getType()))) {
        input.getDefiningOp()->emitOpError("Mask type is not valid");
        return false;
      }
      return FIRRTLTypeSwitch<FIRRTLType, bool>(inType)
          .Case<BundleType>([&](BundleType bundle) {
            for (size_t i = 0, e = bundle.getNumElements(); i != e; ++i) {
              auto regField = SubfieldOp::create(builder, reg, i);
              auto inputField = SubfieldOp::create(builder, input, i);
              auto maskField = SubfieldOp::create(builder, mask, i);
              if (!flatAccess(regField, inputField, maskField))
                return false;
            }
            return true;
          })
          .Case<FVectorType>([&](auto vector) {
            for (size_t i = 0, e = vector.getNumElements(); i != e; ++i) {
              auto regField = SubindexOp::create(builder, reg, i);
              auto inputField = SubindexOp::create(builder, input, i);
              auto maskField = SubindexOp::create(builder, mask, i);
              if (!flatAccess(regField, inputField, maskField))
                return false;
            }
            return true;
          })
          .Case<IntType>([&](auto iType) {
            results.push_back({reg, input, mask});
            return iType.getWidth().has_value();
          })
          .Default([&](auto) { return false; });
    };
    if (flatAccess(reg, input, mask))
      return true;
    return false;
  }
 
  /// Generate the logic for implementing the memory using Registers.
  void generateMemory(MemOp memOp, FirMemory &firMem) {
    ImplicitLocOpBuilder builder(memOp.getLoc(), memOp);
    auto dataType = memOp.getDataType();
 
    auto innerSym = memOp.getInnerSym();
    SmallVector<Value> debugPorts;
 
    RegOp regOfVec = {};
    for (size_t index = 0, rend = memOp.getNumResults(); index < rend;
         ++index) {
      auto result = memOp.getResult(index);
      if (type_isa<RefType>(result.getType())) {
        debugPorts.push_back(result);
        continue;
      }
      // Create a temporary wire to replace the memory port. This makes it
      // simpler to delete the memOp.
      auto wire = WireOp::create(
          builder, result.getType(),
          (memOp.getName() + "_" + memOp.getPortName(index)).str(),
          memOp.getNameKind());
      result.replaceAllUsesWith(wire.getResult());
      result = wire.getResult();
      // Create an access to all the common subfields.
      auto adr = getAddr(builder, result);
      auto enb = getEnable(builder, result);
      auto clk = getClock(builder, result);
      auto dta = getData(builder, result);
      // IF the register is not yet created.
      if (!regOfVec) {
        // Create the register corresponding to the memory.
        regOfVec =
            RegOp::create(builder, FVectorType::get(dataType, firMem.depth),
                          clk, memOp.getNameAttr());
 
        // Copy all the memory annotations.
        if (!memOp.getAnnotationsAttr().empty())
          regOfVec.setAnnotationsAttr(memOp.getAnnotationsAttr());
        if (innerSym)
          regOfVec.setInnerSymAttr(memOp.getInnerSymAttr());
      }
      auto portKind = memOp.getPortKind(index);
      if (portKind == MemOp::PortKind::Read) {
        generateRead(firMem, clk, adr, enb, dta, regOfVec.getResult(), builder);
      } else if (portKind == MemOp::PortKind::Write) {
        auto mask = getMask(builder, result);
        generateWrite(firMem, clk, adr, enb, mask, dta, regOfVec.getResult(),
                      builder);
      } else {
        auto wmode = getWmode(builder, result);
        auto wDta = getData(builder, result, true);
        auto mask = getMask(builder, result);
        generateReadWrite(firMem, clk, adr, enb, mask, wDta, dta, wmode,
                          regOfVec.getResult(), builder);
      }
    }
    // If a valid register is created, then replace all the debug port users
    // with a RefType of the register. The RefType is obtained by using a
    // RefSend on the register.
    if (regOfVec)
      for (auto r : debugPorts)
        r.replaceAllUsesWith(RefSendOp::create(builder, regOfVec.getResult()));
  }
 
  bool ignoreReadEnable = false;
  unsigned numConverted = 0;
};
} // end anonymous namespace
 
void circt::firrtl::runCombMemsToRegOfVec(FModuleOp mod, bool ignoreReadEnable,
                                          unsigned &numConverted) {
  MemToRegOfVecConverter converter(ignoreReadEnable);
  converter.runOnModule(mod);
  numConverted += converter.numConverted;
}
 
namespace {
struct FullResetRunner {
  FullResetRunner(CircuitOp circuit, InstanceGraph &ig,
                  InstancePathCache &instancePathCache,
                  InstanceInfo &instanceInfo, bool convertAsyncDomainMems)
      : circuit(circuit), instanceGraph(&ig),
        instancePathCache(&instancePathCache), instanceInfo(&instanceInfo),
        convertAsyncDomainMems(convertAsyncDomainMems) {}
 
  LogicalResult run();
 
  //===--------------------------------------------------------------------===//
  // Full reset implementation
 
  LogicalResult collectAnnos();
  // Collect reset annotations in the module and return a reset signal.
  // Return `failure()` if there was an error in the annotation processing.
  // Return `std::nullopt` if there was no reset annotation.
  // Return `nullptr` if there was `ignore` annotation.
  // Return a non-null Value if the reset was actually provided.
  FailureOr<std::optional<Value>> collectAnnos(FModuleOp module);
 
  LogicalResult buildDomains();
  void buildDomains(FModuleOp module, const InstancePath &instPath,
                    Value parentReset, InstanceGraph &instGraph,
                    unsigned indent = 0);
 
  void convertMemsInAsyncDomains();
 
  LogicalResult determineImpl();
  LogicalResult determineImpl(FModuleOp module, ResetDomain &domain);
 
  LogicalResult implementFullReset();
  LogicalResult implementFullReset(FModuleOp module, ResetDomain &domain);
  LogicalResult implementFullReset(Operation *op, FModuleOp module,
                                   Value actualReset);
 
  // Helper to implement full reset for instance-like operations
  LogicalResult implementFullReset(FInstanceLike inst, StringAttr moduleName,
                                   Value actualReset);
 
  CircuitOp circuit;
 
  /// The annotated reset for a module. A null value indicates that the module
  /// is explicitly annotated with `ignore`. Otherwise the port/wire/node
  /// annotated as reset within the module is stored.
  DenseMap<Operation *, Value> annotatedResets;
 
  /// The reset domain for a module. In case of conflicting domain membership,
  /// the vector for a module contains multiple elements.
  MapVector<FModuleOp, SmallVector<std::pair<ResetDomain, InstancePath>, 1>>
      domains;
 
  /// Cache of modules symbols
  InstanceGraph *instanceGraph = nullptr;
 
  /// Cache of instance paths.
  InstancePathCache *instancePathCache = nullptr;
 
  InstanceInfo *instanceInfo = nullptr;
 
  bool convertAsyncDomainMems = false;
};
} // namespace
 
LogicalResult FullResetRunner::run() {
  if (failed(collectAnnos()))
    return failure();
  if (failed(buildDomains()))
    return failure();
  if (convertAsyncDomainMems)
    convertMemsInAsyncDomains();
  if (failed(determineImpl()))
    return failure();
  if (failed(implementFullReset()))
    return failure();
  return success();
}
 
void FullResetRunner::convertMemsInAsyncDomains() {
  SmallVector<FModuleOp> asyncDomainMods;
  for (auto &[mod, entries] : domains) {
    if (entries.empty())
      continue;
    auto &domain = entries.back().first;
    if (!domain.rootReset)
      continue;
    if (!type_isa<AsyncResetType>(domain.resetType))
      continue;
    if (!instanceInfo->anyInstanceInEffectiveDesign(mod))
      continue;
    asyncDomainMods.push_back(mod);
  }
  if (asyncDomainMods.empty())
    return;
 
  LLVM_DEBUG({
    llvm::dbgs() << "\n";
    debugHeader("Convert comb mems in async full-reset domains") << "\n\n";
    for (auto mod : asyncDomainMods)
      llvm::dbgs() << "- " << mod.getName() << "\n";
  });
 
  mlir::parallelForEach(
      circuit.getContext(), asyncDomainMods, [&](FModuleOp mod) {
        unsigned converted = 0;
        runCombMemsToRegOfVec(mod, /*ignoreReadEnable=*/false, converted);
      });
}
 
LogicalResult circt::firrtl::runFullReset(CircuitOp circuit, InstanceGraph &ig,
                                          InstanceInfo &instanceInfo,
                                          bool convertAsyncDomainMems) {
  InstancePathCache instancePathCache(ig);
  return FullResetRunner(circuit, ig, instancePathCache, instanceInfo,
                         convertAsyncDomainMems)
      .run();
}
 
//===----------------------------------------------------------------------===//
// Reset Annotations
//===----------------------------------------------------------------------===//
 
LogicalResult FullResetRunner::collectAnnos() {
  LLVM_DEBUG({
    llvm::dbgs() << "\n";
    debugHeader("Gather reset annotations") << "\n\n";
  });
  SmallVector<std::pair<FModuleOp, std::optional<Value>>> results;
  for (auto module : circuit.getOps<FModuleOp>())
    results.push_back({module, {}});
  // Collect annotations parallelly.
  if (failed(mlir::failableParallelForEach(
          circuit.getContext(), results, [&](auto &moduleAndResult) {
            auto result = collectAnnos(moduleAndResult.first);
            if (failed(result))
              return failure();
            moduleAndResult.second = *result;
            return success();
          })))
    return failure();
 
  for (auto [module, reset] : results)
    if (reset.has_value())
      annotatedResets.insert({module, *reset});
  return success();
}
 
FailureOr<std::optional<Value>>
FullResetRunner::collectAnnos(FModuleOp module) {
  bool anyFailed = false;
  SmallSetVector<std::pair<Annotation, Location>, 4> conflictingAnnos;
 
  // Consume a possible "ignore" annotation on the module itself, which
  // explicitly assigns it no reset domain.
  bool ignore = false;
  AnnotationSet::removeAnnotations(module, [&](Annotation anno) {
    if (anno.isClass(excludeFromFullResetAnnoClass)) {
      ignore = true;
      conflictingAnnos.insert({anno, module.getLoc()});
      return true;
    }
    if (anno.isClass(fullResetAnnoClass)) {
      anyFailed = true;
      module.emitError("''FullResetAnnotation' cannot target module; must "
                       "target port or wire/node instead");
      return true;
    }
    return false;
  });
  if (anyFailed)
    return failure();
 
  // Consume any reset annotations on module ports.
  Value reset;
  // Helper for checking annotations and determining the reset
  auto checkAnnotations = [&](Annotation anno, Value arg) {
    if (anno.isClass(fullResetAnnoClass)) {
      ResetKind expectedResetKind;
      if (auto rt = anno.getMember<StringAttr>("resetType")) {
        if (rt == "sync") {
          expectedResetKind = ResetKind::Sync;
        } else if (rt == "async") {
          expectedResetKind = ResetKind::Async;
        } else {
          mlir::emitError(arg.getLoc(),
                          "'FullResetAnnotation' requires resetType == 'sync' "
                          "| 'async', but got resetType == ")
              << rt;
          anyFailed = true;
          return true;
        }
      } else {
        mlir::emitError(arg.getLoc(),
                        "'FullResetAnnotation' requires resetType == "
                        "'sync' | 'async', but got no resetType");
        anyFailed = true;
        return true;
      }
      // Check that the type is well-formed
      bool isAsync = expectedResetKind == ResetKind::Async;
      bool validUint = false;
      if (auto uintT = dyn_cast<UIntType>(arg.getType()))
        validUint = uintT.getWidth() == 1;
      if ((isAsync && !isa<AsyncResetType>(arg.getType())) ||
          (!isAsync && !validUint)) {
        auto kind = resetKindToStringRef(expectedResetKind);
        mlir::emitError(arg.getLoc(),
                        "'FullResetAnnotation' with resetType == '")
            << kind << "' must target " << kind << " reset, but targets "
            << arg.getType();
        anyFailed = true;
        return true;
      }
 
      reset = arg;
      conflictingAnnos.insert({anno, reset.getLoc()});
 
      return false;
    }
    if (anno.isClass(excludeFromFullResetAnnoClass)) {
      anyFailed = true;
      mlir::emitError(arg.getLoc(),
                      "'ExcludeFromFullResetAnnotation' cannot "
                      "target port/wire/node; must target module instead");
      return true;
    }
    return false;
  };
 
  AnnotationSet::removePortAnnotations(module,
                                       [&](unsigned argNum, Annotation anno) {
                                         Value arg = module.getArgument(argNum);
                                         return checkAnnotations(anno, arg);
                                       });
  if (anyFailed)
    return failure();
 
  // Consume any reset annotations on wires in the module body.
  module.getBody().walk([&](Operation *op) {
    // Reset annotations must target wire/node ops.
    if (!isa<WireOp, NodeOp>(op)) {
      if (AnnotationSet::hasAnnotation(op, fullResetAnnoClass,
                                       excludeFromFullResetAnnoClass)) {
        anyFailed = true;
        op->emitError(
            "reset annotations must target module, port, or wire/node");
      }
      return;
    }
 
    // At this point we know that we have a WireOp/NodeOp. Process the reset
    // annotations.
    AnnotationSet::removeAnnotations(op, [&](Annotation anno) {
      auto arg = op->getResult(0);
      return checkAnnotations(anno, arg);
    });
  });
  if (anyFailed)
    return failure();
 
  // If we have found no annotations, there is nothing to do. We just leave
  // this module unannotated, which will cause it to inherit a reset domain
  // from its instantiation sites.
  if (!ignore && !reset) {
    LLVM_DEBUG(llvm::dbgs()
               << "No reset annotation for " << module.getName() << "\n");
    return std::optional<Value>();
  }
 
  // If we have found multiple annotations, emit an error and abort.
  if (conflictingAnnos.size() > 1) {
    auto diag = module.emitError("multiple reset annotations on module '")
                << module.getName() << "'";
    for (auto &annoAndLoc : conflictingAnnos)
      diag.attachNote(annoAndLoc.second)
          << "conflicting " << annoAndLoc.first.getClassAttr() << ":";
    return failure();
  }
 
  // Dump some information in debug builds.
  LLVM_DEBUG({
    llvm::dbgs() << "Annotated reset for " << module.getName() << ": ";
    if (ignore)
      llvm::dbgs() << "no domain\n";
    else if (auto arg = dyn_cast<BlockArgument>(reset))
      llvm::dbgs() << "port " << module.getPortName(arg.getArgNumber()) << "\n";
    else
      llvm::dbgs() << "wire "
                   << reset.getDefiningOp()->getAttrOfType<StringAttr>("name")
                   << "\n";
  });
 
  // Store the annotated reset for this module.
  assert(ignore || reset);
  return std::optional<Value>(reset);
}
 
//===----------------------------------------------------------------------===//
// Domain Construction
//===----------------------------------------------------------------------===//
 
/// Gather the reset domains present in a circuit. This traverses the instance
/// hierarchy of the design, making instances either live in a new reset
/// domain if so annotated, or inherit their parent's domain. This can go
/// wrong in some cases, mainly when a module is instantiated multiple times
/// within different reset domains.
LogicalResult FullResetRunner::buildDomains() {
  LLVM_DEBUG({
    llvm::dbgs() << "\n";
    debugHeader("Build full reset domains") << "\n\n";
  });
 
  // Gather the domains.
  auto &instGraph = *instanceGraph;
  // Walk all top-level modules.
  instGraph.walkPostOrder([&](igraph::InstanceGraphNode &node) {
    if (!node.noUses())
      return;
    if (auto module =
            dyn_cast_or_null<FModuleOp>(node.getModule().getOperation()))
      buildDomains(module, InstancePath{}, Value{}, instGraph);
  });
 
  // Report any domain conflicts among the modules.
  bool anyFailed = false;
  for (auto &it : domains) {
    auto module = cast<FModuleOp>(it.first);
    auto &domainConflicts = it.second;
    if (domainConflicts.size() <= 1)
      continue;
 
    anyFailed = true;
    SmallDenseSet<Value> printedDomainResets;
    auto diag = module.emitError("module '")
                << module.getName()
                << "' instantiated in different reset domains";
    for (auto &it : domainConflicts) {
      ResetDomain &domain = it.first;
      const auto &path = it.second;
      auto inst = path.leaf();
      auto loc = path.empty() ? module.getLoc() : inst.getLoc();
      auto &note = diag.attachNote(loc);
 
      // Describe the instance itself.
      if (path.empty())
        note << "root instance";
      else {
        note << "instance '";
        llvm::interleave(
            path,
            [&](InstanceOpInterface inst) { note << inst.getInstanceName(); },
            [&]() { note << "/"; });
        note << "'";
      }
 
      // Describe the reset domain the instance is in.
      note << " is in";
      if (domain.rootReset) {
        auto nameAndModule = getResetNameAndModule(domain.rootReset);
        note << " reset domain rooted at '" << nameAndModule.first.getValue()
             << "' of module '" << nameAndModule.second.getName() << "'";
 
        // Show where the domain reset is declared (once per reset).
        if (printedDomainResets.insert(domain.rootReset).second) {
          diag.attachNote(domain.rootReset.getLoc())
              << "reset domain '" << nameAndModule.first.getValue()
              << "' of module '" << nameAndModule.second.getName()
              << "' declared here:";
        }
      } else
        note << " no reset domain";
    }
  }
  return failure(anyFailed);
}
 
void FullResetRunner::buildDomains(FModuleOp module,
                                   const InstancePath &instPath,
                                   Value parentReset, InstanceGraph &instGraph,
                                   unsigned indent) {
  LLVM_DEBUG({
    llvm::dbgs().indent(indent * 2) << "Visiting ";
    if (instPath.empty())
      llvm::dbgs() << "$root";
    else
      llvm::dbgs() << instPath.leaf().getInstanceName();
    llvm::dbgs() << " (" << module.getName() << ")\n";
  });
 
  // Assemble the domain for this module.
  ResetDomain domain;
  auto it = annotatedResets.find(module);
  if (it != annotatedResets.end()) {
    // If there is an actual reset, use it for our domain. Otherwise, our
    // module is explicitly marked to have no domain.
    if (auto localReset = it->second)
      domain = ResetDomain(localReset);
    domain.isTop = true;
  } else if (parentReset) {
    // Otherwise, we default to using the reset domain of our parent.
    domain = ResetDomain(parentReset);
  }
 
  // Associate the domain with this module. Only record non-null reset domains;
  // the `domains[module]` entry is created regardless, so modules in no-domain
  // contexts will have an empty entries list. If the module already has an
  // entry for this domain, don't add a duplicate.
  auto &entries = domains[module];
  if (domain.rootReset)
    if (llvm::all_of(entries,
                     [&](const auto &entry) { return entry.first != domain; }))
      entries.push_back({domain, instPath});
 
  // Traverse the child instances.
  for (auto *record : *instGraph[module]) {
    auto submodule = dyn_cast<FModuleOp>(*record->getTarget()->getModule());
    if (!submodule)
      continue;
    auto childPath =
        instancePathCache->appendInstance(instPath, record->getInstance());
    buildDomains(submodule, childPath, domain.rootReset, instGraph, indent + 1);
  }
}
 
/// Determine how the reset for each module shall be implemented.
LogicalResult FullResetRunner::determineImpl() {
  auto anyFailed = false;
  LLVM_DEBUG({
    llvm::dbgs() << "\n";
    debugHeader("Determine implementation") << "\n\n";
  });
  for (auto &it : domains) {
    auto module = cast<FModuleOp>(it.first);
    auto &entries = it.second;
    // Skip modules with no reset domain (empty entries).
    if (entries.empty())
      continue;
    auto &domain = entries.back().first;
    if (failed(determineImpl(module, domain)))
      anyFailed = true;
  }
  return failure(anyFailed);
}
 
/// Determine how the reset for a module shall be implemented. This function
/// fills in the `localReset` and `existingPort` fields of the given reset
/// domain.
///
/// Generally it does the following:
/// - If the domain has explicitly no reset ("ignore"), leaves everything
/// empty.
/// - If the domain is the place where the reset is defined ("top"), fills in
///   the existing port/wire/node as reset.
/// - If the module already has a port with the reset's name:
///   - If the port has the same name and type as the reset domain, reuses that
///   port.
///   - Otherwise errors out.
/// - Otherwise indicates that a port with the reset's name should be created.
///
LogicalResult FullResetRunner::determineImpl(FModuleOp module,
                                             ResetDomain &domain) {
  // Nothing to do if the module needs no reset.
  if (!domain)
    return success();
  LLVM_DEBUG(llvm::dbgs() << "Planning reset for " << module.getName() << "\n");
 
  // If this is the root of a reset domain, we don't need to add any ports
  // and can just simply reuse the existing values.
  if (domain.isTop) {
    LLVM_DEBUG(llvm::dbgs()
               << "- Rooting at local value " << domain.resetName << "\n");
    domain.localReset = domain.rootReset;
    if (auto blockArg = dyn_cast<BlockArgument>(domain.rootReset))
      domain.existingPort = blockArg.getArgNumber();
    return success();
  }
 
  // Otherwise, check if a port with this name and type already exists and
  // reuse that where possible.
  auto neededName = domain.resetName;
  auto neededType = domain.resetType;
  LLVM_DEBUG(llvm::dbgs() << "- Looking for existing port " << neededName
                          << "\n");
  auto portNames = module.getPortNames();
  auto *portIt = llvm::find(portNames, neededName);
 
  // If this port does not yet exist, record that we need to create it.
  if (portIt == portNames.end()) {
    LLVM_DEBUG(llvm::dbgs() << "- Creating new port " << neededName << "\n");
    domain.resetName = neededName;
    return success();
  }
 
  LLVM_DEBUG(llvm::dbgs() << "- Reusing existing port " << neededName << "\n");
 
  // If this port has the wrong type, then error out.
  auto portNo = std::distance(portNames.begin(), portIt);
  auto portType = module.getPortType(portNo);
  if (portType != neededType) {
    auto diag = emitError(module.getPortLocation(portNo), "module '")
                << module.getName() << "' is in reset domain requiring port '"
                << domain.resetName.getValue() << "' to have type "
                << domain.resetType << ", but has type " << portType;
    diag.attachNote(domain.rootReset.getLoc()) << "reset domain rooted here";
    return failure();
  }
 
  // We have a pre-existing port which we should use.
  domain.existingPort = portNo;
  domain.localReset = module.getArgument(portNo);
  return success();
}
 
//===----------------------------------------------------------------------===//
// Full Reset Implementation
//===----------------------------------------------------------------------===//
 
/// Implement the annotated resets gathered in the pass' `domains` map.
LogicalResult FullResetRunner::implementFullReset() {
  LLVM_DEBUG({
    llvm::dbgs() << "\n";
    debugHeader("Implement full resets") << "\n\n";
  });
  for (auto &it : domains) {
    auto module = cast<FModuleOp>(it.first);
    auto &entries = it.second;
    // For modules with a real domain, use that domain. For no-domain modules,
    // use a default empty domain but still process for tie-off.
    ResetDomain domain;
    if (!entries.empty())
      domain = entries.back().first;
    if (failed(implementFullReset(module, domain)))
      return failure();
  }
  return success();
}
 
/// Implement the async resets for a specific module.
///
/// This will add ports to the module as appropriate, update the register ops
/// in the module, and update any instantiated submodules with their
/// corresponding reset implementation details.
LogicalResult FullResetRunner::implementFullReset(FModuleOp module,
                                                  ResetDomain &domain) {
  // For modules in no-domain contexts, we skip local transformations (adding
  // reset ports, converting registers) but still process instances to tie off
  // reset ports of children that have a real reset domain.
  if (!domain) {
    SmallVector<FInstanceLike> instances;
    module.walk([&](FInstanceLike instOp) { instances.push_back(instOp); });
    LLVM_DEBUG({
      if (!instances.empty())
        llvm::dbgs() << "Tie off instances in " << module.getName() << "\n";
    });
    for (auto instOp : instances)
      if (failed(implementFullReset(instOp, module, Value())))
        return failure();
    return success();
  }
 
  LLVM_DEBUG(llvm::dbgs() << "Implementing full reset for " << module.getName()
                          << "\n");
 
  // Add an annotation indicating that this module belongs to a reset domain.
  auto *context = module.getContext();
  AnnotationSet annotations(module);
  annotations.addAnnotations(DictionaryAttr::get(
      context, NamedAttribute(StringAttr::get(context, "class"),
                              StringAttr::get(context, fullResetAnnoClass))));
  annotations.applyToOperation(module);
 
  // If needed, add a reset port to the module.
  auto actualReset = domain.localReset;
  if (!domain.localReset) {
    PortInfo portInfo{domain.resetName,
                      domain.resetType,
                      Direction::In,
                      {},
                      domain.rootReset.getLoc()};
    module.insertPorts({{0, portInfo}});
    actualReset = module.getArgument(0);
    LLVM_DEBUG(llvm::dbgs() << "- Inserted port " << domain.resetName << "\n");
  }
 
  LLVM_DEBUG({
    llvm::dbgs() << "- Using ";
    if (auto blockArg = dyn_cast<BlockArgument>(actualReset))
      llvm::dbgs() << "port #" << blockArg.getArgNumber() << " ";
    else
      llvm::dbgs() << "wire/node ";
    llvm::dbgs() << getResetName(actualReset) << "\n";
  });
 
  // Gather a list of operations in the module that need to be updated with
  // the new reset.
  SmallVector<Operation *> opsToUpdate;
  module.walk([&](Operation *op) {
    if (isa<FInstanceLike, RegOp, RegResetOp>(op))
      opsToUpdate.push_back(op);
  });
 
  // If the reset is a local wire or node, move it upwards such that it
  // dominates all the operations that it will need to attach to. In the case
  // of a node this might not be easily possible, so we just spill into a wire
  // in that case.
  if (!isa<BlockArgument>(actualReset)) {
    mlir::DominanceInfo dom(module);
    // The first op in `opsToUpdate` is the top-most op in the module, since
    // the ops and blocks are traversed in a depth-first, top-to-bottom order
    // in `walk`. So we can simply check if the local reset declaration is
    // before the first op to find out if we need to move anything.
    auto *resetOp = actualReset.getDefiningOp();
    if (!opsToUpdate.empty() && !dom.dominates(resetOp, opsToUpdate[0])) {
      LLVM_DEBUG(llvm::dbgs()
                 << "- Reset doesn't dominate all uses, needs to be moved\n");
 
      // If the node can't be moved because its input doesn't dominate the
      // target location, convert it to a wire.
      auto nodeOp = dyn_cast<NodeOp>(resetOp);
      if (nodeOp && !dom.dominates(nodeOp.getInput(), opsToUpdate[0])) {
        LLVM_DEBUG(llvm::dbgs()
                   << "- Promoting node to wire for move: " << nodeOp << "\n");
        auto builder = ImplicitLocOpBuilder::atBlockBegin(nodeOp.getLoc(),
                                                          nodeOp->getBlock());
        auto wireOp = WireOp::create(
            builder, nodeOp.getResult().getType(), nodeOp.getNameAttr(),
            nodeOp.getNameKindAttr(), nodeOp.getAnnotationsAttr(),
            nodeOp.getInnerSymAttr(), nodeOp.getForceableAttr());
        // Don't delete the node, since it might be in use in worklists.
        nodeOp->replaceAllUsesWith(wireOp);
        nodeOp->removeAttr(nodeOp.getInnerSymAttrName());
        nodeOp.setName("");
        // Leave forcable alone, since we cannot remove a result.  It will be
        // cleaned up in canonicalization since it is dead.  As will this node.
        nodeOp.setNameKind(NameKindEnum::DroppableName);
        nodeOp.setAnnotationsAttr(ArrayAttr::get(builder.getContext(), {}));
        builder.setInsertionPointAfter(nodeOp);
        emitConnect(builder, wireOp.getResult(), nodeOp.getResult());
        resetOp = wireOp;
        actualReset = wireOp.getResult();
        domain.localReset = wireOp.getResult();
      }
 
      // Determine the block into which the reset declaration needs to be
      // moved.
      Block *targetBlock = dom.findNearestCommonDominator(
          resetOp->getBlock(), opsToUpdate[0]->getBlock());
      LLVM_DEBUG({
        if (targetBlock != resetOp->getBlock())
          llvm::dbgs() << "- Needs to be moved to different block\n";
      });
 
      // At this point we have to figure out in front of which operation in
      // the target block the reset declaration has to be moved. The reset
      // declaration and the first op it needs to dominate may be buried
      // inside blocks of other operations (e.g. `WhenOp`), so we have to look
      // through their parent operations until we find the one that lies
      // within the target block.
      auto getParentInBlock = [](Operation *op, Block *block) {
        while (op && op->getBlock() != block)
          op = op->getParentOp();
        return op;
      };
      auto *resetOpInTarget = getParentInBlock(resetOp, targetBlock);
      auto *firstOpInTarget = getParentInBlock(opsToUpdate[0], targetBlock);
 
      // Move the operation upwards. Since there are situations where the
      // reset declaration does not dominate the first use, but the `WhenOp`
      // it is nested within actually *does* come before that use, we have to
      // consider moving the reset declaration in front of its parent op.
      if (resetOpInTarget->isBeforeInBlock(firstOpInTarget))
        resetOp->moveBefore(resetOpInTarget);
      else
        resetOp->moveBefore(firstOpInTarget);
    }
  }
 
  // Update the operations.
  for (auto *op : opsToUpdate)
    if (failed(implementFullReset(op, module, actualReset)))
      return failure();
 
  return success();
}
 
/// Helper to implement full reset for instance-like operations.
/// This handles the common logic of adding reset ports and connecting them.
LogicalResult FullResetRunner::implementFullReset(FInstanceLike inst,
                                                  StringAttr moduleName,
                                                  Value actualReset) {
  // Lookup the reset domain of the default target module. If there is no
  // reset domain associated with that module, as indicated by an empty list
  // of domains, simply skip it.
  auto *node = instanceGraph->lookup(moduleName);
  auto refModule = dyn_cast<FModuleOp>(*node->getModule());
  if (!refModule)
    return success();
  auto *domainIt = domains.find(refModule);
  if (domainIt == domains.end() || domainIt->second.empty())
    return success();
  auto &domain = domainIt->second.back().first;
  assert(domain && "null domains should not be listed");
 
  ImplicitLocOpBuilder builder(inst.getLoc(), inst);
 
  LLVM_DEBUG(llvm::dbgs() << (actualReset ? "- Update " : "- Tie-off ")
                          << inst->getName() << " '" << inst.getInstanceName()
                          << "'\n");
 
  // If needed, add a reset port to the instance.
  Value instReset;
  if (!domain.localReset) {
    LLVM_DEBUG(llvm::dbgs() << "  - Adding new result as reset\n");
    auto newInstOp = inst.cloneWithInsertedPortsAndReplaceUses(
        {{/*portIndex=*/0,
          {domain.resetName, domain.resetType, Direction::In}}});
    instReset = newInstOp->getResult(0);
    instanceGraph->replaceInstance(inst, newInstOp);
    inst->erase();
    inst = newInstOp;
  } else if (domain.existingPort.has_value()) {
    auto idx = *domain.existingPort;
    instReset = inst->getResult(idx);
    LLVM_DEBUG(llvm::dbgs() << "  - Using result #" << idx << " as reset\n");
  }
 
  // If there's no reset port on the instance to connect, we're done. This
  // can happen if the instantiated module has a reset domain, but that
  // domain is e.g. rooted at an internal wire.
  if (!instReset)
    return success();
 
  builder.setInsertionPointAfter(inst);
 
  // If the module that contains the instance is not in a reset domain, as
  // indicated by actualReset being null, create a tie-off constant which
  // effectively turns the no-reset registers that had full resets added back
  // into no-reset registers.
  if (!actualReset) {
    LLVM_DEBUG(llvm::dbgs() << "  - Tying off reset to constant 0\n");
    if (type_isa<AsyncResetType>(domain.resetType))
      actualReset = SpecialConstantOp::create(builder, domain.resetType, false);
    else
      actualReset = ConstantOp::create(
          builder, UIntType::get(builder.getContext(), 1), APInt(1, 0));
  }
 
  // Connect the instance's reset to the actual reset or tie-off.
  assert(instReset && actualReset);
  emitConnect(builder, instReset, actualReset);
  return success();
}
 
/// Modify an operation in a module to implement an full reset for that
/// module. If actualReset is null and op is an `InstanceOp`, creates a tie-off
/// constant for added reset ports. If the op is not an instance, aborts.
LogicalResult FullResetRunner::implementFullReset(Operation *op,
                                                  FModuleOp module,
                                                  Value actualReset) {
  ImplicitLocOpBuilder builder(op->getLoc(), op);
 
  // Handle instances.
  if (auto instOp = dyn_cast<FInstanceLike>(op))
    return implementFullReset(
        instOp, cast<StringAttr>(instOp.getReferencedModuleNamesAttr()[0]),
        actualReset);
 
  // All other ops require an actual reset. We only ever call this function with
  // null actualReset to create tie-offs on instance ops.
  assert(actualReset);
 
  // Handle reset-less registers.
  if (auto regOp = dyn_cast<RegOp>(op)) {
    LLVM_DEBUG(llvm::dbgs() << "- Adding full reset to " << regOp << "\n");
    auto zero = createZeroValue(builder, regOp.getResult().getType());
    auto newRegOp = RegResetOp::create(
        builder, regOp.getResult().getType(), regOp.getClockVal(), actualReset,
        zero, regOp.getNameAttr(), regOp.getNameKindAttr(),
        regOp.getAnnotations(), regOp.getInnerSymAttr(),
        regOp.getForceableAttr(), regOp.getInitialAttr());
    regOp.getResult().replaceAllUsesWith(newRegOp.getResult());
    if (regOp.getForceable())
      regOp.getRef().replaceAllUsesWith(newRegOp.getRef());
    regOp->erase();
    return success();
  }
 
  // Handle registers with reset.
  if (auto regOp = dyn_cast<RegResetOp>(op)) {
    // If the register already has an async reset or if the type of the added
    // reset is sync, leave it alone.
    if (type_isa<AsyncResetType>(regOp.getResetSignal().getType()) ||
        type_isa<UIntType>(actualReset.getType())) {
      LLVM_DEBUG(llvm::dbgs() << "- Skipping (has reset) " << regOp << "\n");
      // The following performs the logic of `CheckResets` in the original
      // Scala source code.
      if (failed(regOp.verifyInvariants()))
        return failure();
      return success();
    }
    LLVM_DEBUG(llvm::dbgs() << "- Updating reset of " << regOp << "\n");
 
    auto reset = regOp.getResetSignal();
    auto value = regOp.getResetValue();
 
    // If we arrive here, the register has a sync reset and the added reset is
    // async. In order to add an async reset, we have to move the sync reset
    // into a mux in front of the register.
    insertResetMux(builder, regOp.getResult(), reset, value);
    builder.setInsertionPointAfterValue(regOp.getResult());
    auto mux = MuxPrimOp::create(builder, reset, value, regOp.getResult());
    emitConnect(builder, regOp.getResult(), mux);
 
    // Replace the existing reset with the async reset.
    builder.setInsertionPoint(regOp);
    auto zero = createZeroValue(builder, regOp.getResult().getType());
    regOp.getResetSignalMutable().assign(actualReset);
    regOp.getResetValueMutable().assign(zero);
  }
  return success();
}
 
namespace {
struct FullResetPass
    : public circt::firrtl::impl::FullResetBase<FullResetPass> {
  using FullResetBase::FullResetBase;
 
  void runOnOperation() override {
    auto &ig = getAnalysis<InstanceGraph>();
    auto &instanceInfo = getAnalysis<InstanceInfo>();
    if (failed(runFullReset(getOperation(), ig, instanceInfo,
                            convertAsyncDomainMems)))
      return signalPassFailure();
    markAnalysesPreserved<InstanceGraph, InstanceInfo>();
  }
};
} // namespace