LLHDOps.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
//
//===----------------------------------------------------------------------===//
 
#include "circt/Dialect/LLHD/LLHDOps.h"
 
#include "circt/Dialect/Comb/CombOps.h"
#include "circt/Dialect/HW/HWOps.h"
#include "circt/Support/CustomDirectiveImpl.h"
#include "mlir/IR/Attributes.h"
#include "mlir/IR/BuiltinDialect.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/IR/Matchers.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/IR/Region.h"
#include "mlir/IR/Types.h"
#include "mlir/IR/Value.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallVector.h"
 
using namespace circt;
using namespace mlir;
using namespace llhd;
 
unsigned circt::llhd::getLLHDTypeWidth(Type type) {
  if (auto sig = dyn_cast<RefType>(type))
    type = sig.getNestedType();
  if (auto array = dyn_cast<hw::ArrayType>(type))
    return array.getNumElements();
  if (auto tup = dyn_cast<hw::StructType>(type))
    return tup.getElements().size();
  return type.getIntOrFloatBitWidth();
}
 
Type circt::llhd::getLLHDElementType(Type type) {
  if (auto sig = dyn_cast<RefType>(type))
    type = sig.getNestedType();
  if (auto array = dyn_cast<hw::ArrayType>(type))
    return array.getElementType();
  return type;
}
 
template <typename... OpTypes>
static bool hasUserOfKind(Operation *op) {
  for (auto *user : op->getUsers()) {
    if (isa<OpTypes...>(user))
      return true;
  }
  return false;
}
 
//===----------------------------------------------------------------------===//
// ConstantTimeOp
//===----------------------------------------------------------------------===//
 
OpFoldResult llhd::ConstantTimeOp::fold(FoldAdaptor adaptor) {
  assert(adaptor.getOperands().empty() && "const has no operands");
  return getValueAttr();
}
 
void llhd::ConstantTimeOp::build(OpBuilder &builder, OperationState &result,
                                 uint64_t time, const StringRef &timeUnit,
                                 unsigned delta, unsigned epsilon) {
  auto *ctx = builder.getContext();
  auto attr = TimeAttr::get(ctx, time, timeUnit, delta, epsilon);
  return build(builder, result, TimeType::get(ctx), attr);
}
 
//===----------------------------------------------------------------------===//
// SignalOp
//===----------------------------------------------------------------------===//
 
static Value getValueAtIndex(OpBuilder &builder, Location loc, Value val,
                             unsigned index, Type resultType) {
  return TypeSwitch<Type, Value>(val.getType())
      .Case<hw::StructType>([&](hw::StructType ty) -> Value {
        return hw::StructExtractOp::create(builder, loc, val,
                                           ty.getElements()[index].name);
      })
      .Case<hw::ArrayType>([&](hw::ArrayType ty) -> Value {
        Value idx = hw::ConstantOp::create(
            builder, loc,
            builder.getIntegerType(llvm::Log2_64_Ceil(ty.getNumElements())),
            index);
        return hw::ArrayGetOp::create(builder, loc, val, idx);
      })
      .Case<IntegerType>([&](IntegerType ty) -> Value {
        return comb::ExtractOp::create(builder, loc, val, index,
                                       resultType.getIntOrFloatBitWidth());
      });
}
 
void SignalOp::getAsmResultNames(OpAsmSetValueNameFn setNameFn) {
  if (getName() && !getName()->empty())
    setNameFn(getResult(), *getName());
}
 
// Calculates the destructured subelements for an integer type.
//
// Typically, subelements are determined by only looking at the type. For an
// IntegerType this would mean bit-blasting every bit of the type, so we instead
// take the value that we're destructuring into account by looking at its users.
static std::optional<DenseMap<Attribute, Type>>
getIntegerSubelementIndexMap(Type type, Value value) {
  int width = type.getIntOrFloatBitWidth();
  if (width <= 1)
    return {};
 
  // Calculate the intervals of bits demanded by users. If a user's interval
  // is unknown, we return nullopt.
  SmallVector<bool> startIndices(width, false);
  for (Operation *user : value.getUsers()) {
    if (auto extract = dyn_cast<SigExtractOp>(user)) {
      APInt lowBit;
      if (matchPattern(extract.getLowBit(), m_ConstantInt(&lowBit))) {
        startIndices[lowBit.getZExtValue()] = true;
        int64_t highBit = lowBit.getZExtValue() + extract.getResultWidth();
        if (highBit < width)
          startIndices[highBit] = true;
        continue;
      }
    }
    if (isa<ProbeOp, DriveOp>(user)) {
      // Probe and Drive require the entire interval but don't need to be
      // bit-blasted.
      continue;
    }
    // Potentially dynamic start index.
    return {};
  }
 
  // Create subelements for each interval.
  DenseMap<Attribute, Type> destructured;
  for (int start = 0; start < width;) {
    int end = start + 1;
    while (end < width && !startIndices[end])
      ++end;
 
    int runLength = end - start;
 
    destructured.insert(
        {IntegerAttr::get(IndexType::get(type.getContext()), start),
         IntegerType::get(type.getContext(), runLength)});
    start = end;
  }
 
  return destructured;
}
 
static std::optional<DenseMap<Attribute, Type>>
getSubelementIndexMap(Type type, Value value) {
  // Handle IntegerType specially; destructuring integers into individual
  // bits can create an explosion of ops, so instead we determine the subelement
  // map dynamically.
  if (auto intType = dyn_cast<IntegerType>(type)) {
    return getIntegerSubelementIndexMap(intType, value);
  } else {
    auto destructurable = llvm::dyn_cast<DestructurableTypeInterface>(type);
    if (!destructurable)
      return {};
    return destructurable.getSubelementIndexMap();
  }
}
 
SmallVector<DestructurableMemorySlot> SignalOp::getDestructurableSlots() {
  auto type = getType().getNestedType();
 
  // It only makes sense to destructure a SignalOp if it has one or more users
  // that access the destructured elements.
  if (!hasUserOfKind<SigExtractOp, SigArrayGetOp, SigStructExtractOp,
                     SigArraySliceOp>(*this))
    return {};
 
  auto destructuredType = getSubelementIndexMap(type, getResult());
  if (!destructuredType)
    return {};
  return {DestructurableMemorySlot{{getResult(), type}, *destructuredType}};
}
 
DenseMap<Attribute, MemorySlot> SignalOp::destructure(
    const DestructurableMemorySlot &slot,
    const SmallPtrSetImpl<Attribute> &usedIndices, OpBuilder &builder,
    SmallVectorImpl<DestructurableAllocationOpInterface> &newAllocators) {
  assert(slot.ptr == getResult());
  builder.setInsertionPointAfter(*this);
 
  DenseMap<Attribute, Type> subelementTypes = slot.subelementTypes;
  DenseMap<Attribute, MemorySlot> slotMap;
  SmallVector<std::pair<unsigned, Type>> indices;
  for (auto attr : usedIndices) {
    assert(isa<IntegerAttr>(attr));
    auto elemType = subelementTypes.at(attr);
    assert(elemType && "used index must exist");
    indices.push_back({cast<IntegerAttr>(attr).getInt(), elemType});
  }
 
  llvm::sort(indices, [](auto a, auto b) { return a.first < b.first; });
 
  for (auto [index, type] : indices) {
    Value init = getValueAtIndex(builder, getLoc(), getInit(), index, type);
    auto sigOp = SignalOp::create(builder, getLoc(), getNameAttr(), init);
    newAllocators.push_back(sigOp);
    slotMap.try_emplace<MemorySlot>(
        IntegerAttr::get(IndexType::get(getContext()), index),
        {sigOp.getResult(), type});
  }
 
  return slotMap;
}
 
std::optional<DestructurableAllocationOpInterface>
SignalOp::handleDestructuringComplete(const DestructurableMemorySlot &slot,
                                      OpBuilder &builder) {
  assert(slot.ptr == getResult());
  this->erase();
  return std::nullopt;
}
 
//===----------------------------------------------------------------------===//
// SigExtractOp
//===----------------------------------------------------------------------===//
 
template <class Op>
static OpFoldResult foldSigPtrExtractOp(Op op, ArrayRef<Attribute> operands) {
 
  if (!operands[1])
    return nullptr;
 
  // llhd.sig.extract(input, 0) with inputWidth == resultWidth => input
  if (op.getResultWidth() == op.getInputWidth() &&
      cast<IntegerAttr>(operands[1]).getValue().isZero())
    return op.getInput();
 
  return nullptr;
}
 
OpFoldResult llhd::SigExtractOp::fold(FoldAdaptor adaptor) {
  return foldSigPtrExtractOp(*this, adaptor.getOperands());
}
 
// Returns the number of elements that overlap between [a1, a2) and [b1, b2).
static int64_t intervalOverlap(int64_t a1, int64_t a2, int64_t b1, int64_t b2) {
  return std::max<int64_t>(0, std::min(a2, b2) - std::max(a1, b1));
}
 
static void getSortedPtrs(DenseMap<Attribute, MemorySlot> &subslots,
                          SmallVectorImpl<std::pair<unsigned, Value>> &sorted) {
  for (auto [attr, mem] : subslots) {
    assert(isa<IntegerAttr>(attr));
    sorted.push_back({cast<IntegerAttr>(attr).getInt(), mem.ptr});
  }
 
  llvm::sort(sorted, [](auto a, auto b) { return a.first < b.first; });
}
 
static void getSortedPtrs(const DenseMap<Attribute, Type> &subslots,
                          SmallVectorImpl<std::pair<unsigned, Type>> &sorted) {
  for (auto [attr, mem] : subslots) {
    assert(isa<IntegerAttr>(attr));
    sorted.push_back({cast<IntegerAttr>(attr).getInt(), mem});
  }
 
  llvm::sort(sorted, [](auto a, auto b) { return a.first < b.first; });
}
 
bool SigExtractOp::canRewire(const DestructurableMemorySlot &slot,
                             SmallPtrSetImpl<Attribute> &usedIndices,
                             SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
                             const DataLayout &dataLayout) {
  if (slot.ptr != getInput())
    return false;
  APInt idx;
  Type type = getLLHDElementType(getResult().getType());
  if (!type.isSignlessInteger())
    return false;
  if (!matchPattern(getLowBit(), m_ConstantInt(&idx)))
    return false;
 
  // We rewire by pushing subslot values down to users, so we only support
  // ProbeOp and DriveOp users as these can deal with the naked (non-ref) types
  // produced by SROA.
  for (Operation *user : getResult().getUsers()) {
    if (!isa<ProbeOp, DriveOp>(user))
      return false;
  }
 
  SmallVector<std::pair<unsigned, Type>> elements;
  getSortedPtrs(slot.subelementTypes, elements);
 
  int64_t index = idx.getZExtValue();
  int64_t width = getLLHDTypeWidth(type);
  int64_t coveredBits = 0;
  for (auto [start, type] : elements) {
    int64_t subslotWidth = type.getIntOrFloatBitWidth();
    int64_t overlap =
        intervalOverlap(index, index + width, start, start + subslotWidth);
    if (overlap == 0)
      continue;
    usedIndices.insert(IntegerAttr::get(IndexType::get(getContext()), start));
    coveredBits += overlap;
  }
 
  if (coveredBits != width)
    return false;
 
  mustBeSafelyUsed.emplace_back<MemorySlot>({getResult(), type});
  return true;
}
 
DeletionKind SigExtractOp::rewire(const DestructurableMemorySlot &slot,
                                  DenseMap<Attribute, MemorySlot> &subslots,
                                  OpBuilder &builder,
                                  const DataLayout &dataLayout) {
  APInt idx;
  [[maybe_unused]] bool result = matchPattern(getLowBit(), m_ConstantInt(&idx));
  assert(result);
  int64_t width = getLLHDTypeWidth(getResult().getType());
  int64_t idxVal = idx.getZExtValue();
 
  SmallVector<std::pair<unsigned, Value>> elements;
  getSortedPtrs(subslots, elements);
 
  for (Operation *user : llvm::make_early_inc_range(getResult().getUsers())) {
    builder.setInsertionPoint(user);
    // Decompose a ProbeOp into a concatenation of ProbeOps, one per subslot.
    if (auto probeOp = dyn_cast<ProbeOp>(user)) {
      SmallVector<Value> values;
      for (auto [start, value] : elements) {
        int64_t subslotWidth = cast<RefType>(value.getType())
                                   .getNestedType()
                                   .getIntOrFloatBitWidth();
        int64_t overlap = intervalOverlap(idxVal, idxVal + width, start,
                                          start + subslotWidth);
        if (overlap == 0)
          continue;
        values.push_back(ProbeOp::create(builder, probeOp.getLoc(), value));
      }
      std::reverse(values.begin(), values.end());
      Value value = comb::ConcatOp::create(builder, probeOp.getLoc(), values);
      probeOp.replaceAllUsesWith(value);
      probeOp.erase();
      continue;
    }
 
    // Decompose a DriveOp into one DriveOp per subslot.
    auto driveOp = cast<DriveOp>(user);
    for (auto [start, sig] : elements) {
      int64_t subslotWidth =
          cast<RefType>(sig.getType()).getNestedType().getIntOrFloatBitWidth();
      int64_t overlap =
          intervalOverlap(idxVal, idxVal + width, start, start + subslotWidth);
      if (overlap == 0)
        continue;
      Value val =
          comb::ExtractOp::create(builder, driveOp.getLoc(), driveOp.getValue(),
                                  start - idxVal, subslotWidth);
      DriveOp::create(builder, driveOp.getLoc(), sig, val, driveOp.getTime(),
                      driveOp.getEnable());
    }
    driveOp.erase();
  }
 
  return DeletionKind::Delete;
}
 
LogicalResult SigExtractOp::ensureOnlySafeAccesses(
    const MemorySlot &slot, SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
    const DataLayout &dataLayout) {
  return success();
}
 
//===----------------------------------------------------------------------===//
// SigArraySliceOp
//===----------------------------------------------------------------------===//
 
OpFoldResult llhd::SigArraySliceOp::fold(FoldAdaptor adaptor) {
  auto lowIndex = dyn_cast_or_null<IntegerAttr>(adaptor.getLowIndex());
  if (!lowIndex)
    return {};
 
  // llhd.sig.array_slice(input, 0) with inputWidth == resultWidth => input
  if (getResultWidth() == getInputWidth() && lowIndex.getValue().isZero())
    return getInput();
 
  return {};
}
 
template <class Op>
static LogicalResult canonicalizeSigPtrArraySliceOp(Op op,
                                                    PatternRewriter &rewriter) {
  IntegerAttr indexAttr;
  if (!matchPattern(op.getLowIndex(), m_Constant(&indexAttr)))
    return failure();
 
  // llhd.sig.array_slice(llhd.sig.array_slice(target, a), b)
  //   => llhd.sig.array_slice(target, a+b)
  IntegerAttr a;
  if (matchPattern(op.getInput(),
                   m_Op<Op>(matchers::m_Any(), m_Constant(&a)))) {
    auto sliceOp = op.getInput().template getDefiningOp<Op>();
    rewriter.modifyOpInPlace(op, [&]() {
      op.getInputMutable().assign(sliceOp.getInput());
      Value newIndex = hw::ConstantOp::create(
          rewriter, op->getLoc(), a.getValue() + indexAttr.getValue());
      op.getLowIndexMutable().assign(newIndex);
    });
 
    return success();
  }
 
  return failure();
}
 
LogicalResult llhd::SigArraySliceOp::canonicalize(llhd::SigArraySliceOp op,
                                                  PatternRewriter &rewriter) {
  return canonicalizeSigPtrArraySliceOp(op, rewriter);
}
 
//===----------------------------------------------------------------------===//
// SigArrayGetOp
//===----------------------------------------------------------------------===//
 
bool SigArrayGetOp::canRewire(const DestructurableMemorySlot &slot,
                              SmallPtrSetImpl<Attribute> &usedIndices,
                              SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
                              const DataLayout &dataLayout) {
  if (slot.ptr != getInput())
    return false;
  APInt idx;
  if (!matchPattern(getIndex(), m_ConstantInt(&idx)))
    return false;
  auto index =
      IntegerAttr::get(IndexType::get(getContext()), idx.getZExtValue());
  if (!slot.subelementTypes.contains(index))
    return false;
  usedIndices.insert(index);
  mustBeSafelyUsed.emplace_back<MemorySlot>(
      {getResult(), cast<RefType>(getResult().getType()).getNestedType()});
  return true;
}
 
DeletionKind SigArrayGetOp::rewire(const DestructurableMemorySlot &slot,
                                   DenseMap<Attribute, MemorySlot> &subslots,
                                   OpBuilder &builder,
                                   const DataLayout &dataLayout) {
  APInt idx;
  bool result = matchPattern(getIndex(), m_ConstantInt(&idx));
  (void)result;
  assert(result);
  auto index =
      IntegerAttr::get(IndexType::get(getContext()), idx.getZExtValue());
  auto it = subslots.find(index);
  assert(it != subslots.end());
  replaceAllUsesWith(it->getSecond().ptr);
  return DeletionKind::Delete;
}
 
LogicalResult SigArrayGetOp::ensureOnlySafeAccesses(
    const MemorySlot &slot, SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
    const DataLayout &dataLayout) {
  return success();
}
 
//===----------------------------------------------------------------------===//
// SigStructExtractOp
//===----------------------------------------------------------------------===//
 
LogicalResult llhd::SigStructExtractOp::inferReturnTypes(
    MLIRContext *context, std::optional<Location> loc, ValueRange operands,
    DictionaryAttr attrs, mlir::OpaqueProperties properties,
    mlir::RegionRange regions, SmallVectorImpl<Type> &results) {
  typename SigStructExtractOp::Adaptor adaptor(operands, attrs, properties,
                                               regions);
  auto nestedType = cast<RefType>(adaptor.getInput().getType()).getNestedType();
  Type fieldType;
 
  // Support both StructType and UnionType
  if (auto structType = dyn_cast<hw::StructType>(nestedType)) {
    fieldType = structType.getFieldType(adaptor.getField());
  } else if (auto unionType = dyn_cast<hw::UnionType>(nestedType)) {
    fieldType = unionType.getFieldType(adaptor.getField());
  } else {
    context->getDiagEngine().emit(loc.value_or(UnknownLoc()),
                                  DiagnosticSeverity::Error)
        << "expected struct or union type";
    return failure();
  }
 
  if (!fieldType) {
    context->getDiagEngine().emit(loc.value_or(UnknownLoc()),
                                  DiagnosticSeverity::Error)
        << "invalid field name specified";
    return failure();
  }
  results.push_back(RefType::get(fieldType));
  return success();
}
 
bool SigStructExtractOp::canRewire(
    const DestructurableMemorySlot &slot,
    SmallPtrSetImpl<Attribute> &usedIndices,
    SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
    const DataLayout &dataLayout) {
  if (slot.ptr != getInput())
    return false;
 
  auto nestedType = cast<RefType>(getInput().getType()).getNestedType();
  std::optional<uint32_t> index;
 
  // Support both StructType and UnionType
  if (auto structType = dyn_cast<hw::StructType>(nestedType))
    index = structType.getFieldIndex(getFieldAttr());
  else if (auto unionType = dyn_cast<hw::UnionType>(nestedType))
    index = unionType.getFieldIndex(getFieldAttr());
  else
    return false;
 
  if (!index)
    return false;
  auto indexAttr = IntegerAttr::get(IndexType::get(getContext()), *index);
  if (!slot.subelementTypes.contains(indexAttr))
    return false;
  usedIndices.insert(indexAttr);
  mustBeSafelyUsed.emplace_back<MemorySlot>(
      {getResult(), cast<RefType>(getResult().getType()).getNestedType()});
  return true;
}
 
DeletionKind
SigStructExtractOp::rewire(const DestructurableMemorySlot &slot,
                           DenseMap<Attribute, MemorySlot> &subslots,
                           OpBuilder &builder, const DataLayout &dataLayout) {
  auto index =
      cast<hw::StructType>(cast<RefType>(getInput().getType()).getNestedType())
          .getFieldIndex(getFieldAttr());
  assert(index.has_value());
  auto indexAttr = IntegerAttr::get(IndexType::get(getContext()), *index);
  auto it = subslots.find(indexAttr);
  assert(it != subslots.end());
  replaceAllUsesWith(it->getSecond().ptr);
  return DeletionKind::Delete;
}
 
LogicalResult SigStructExtractOp::ensureOnlySafeAccesses(
    const MemorySlot &slot, SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
    const DataLayout &dataLayout) {
  return success();
}
 
//===----------------------------------------------------------------------===//
// ProbeOp
//===----------------------------------------------------------------------===//
 
bool ProbeOp::canRewire(const DestructurableMemorySlot &slot,
                        SmallPtrSetImpl<Attribute> &usedIndices,
                        SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
                        const DataLayout &dataLayout) {
  for (auto [key, _] : slot.subelementTypes)
    usedIndices.insert(key);
 
  return isa<hw::StructType, hw::ArrayType, IntegerType>(slot.elemType);
}
 
DeletionKind ProbeOp::rewire(const DestructurableMemorySlot &slot,
                             DenseMap<Attribute, MemorySlot> &subslots,
                             OpBuilder &builder, const DataLayout &dataLayout) {
  SmallVector<std::pair<unsigned, Value>> elements;
  SmallVector<Value> probed;
  getSortedPtrs(subslots, elements);
  for (auto [_, val] : elements)
    probed.push_back(ProbeOp::create(builder, getLoc(), val));
 
  Value repl =
      TypeSwitch<Type, Value>(getType())
          .Case<hw::StructType>([&](auto ty) {
            return hw::StructCreateOp::create(builder, getLoc(), getType(),
                                              probed);
          })
          .Case<hw::ArrayType>([&](auto ty) {
            std::reverse(probed.begin(), probed.end());
            return hw::ArrayCreateOp::create(builder, getLoc(), probed);
          })
          .Case<IntegerType>([&](auto ty) {
            std::reverse(probed.begin(), probed.end());
            return comb::ConcatOp::create(builder, getLoc(), probed);
          });
 
  replaceAllUsesWith(repl);
  return DeletionKind::Delete;
}
 
LogicalResult
ProbeOp::ensureOnlySafeAccesses(const MemorySlot &slot,
                                SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
                                const DataLayout &dataLayout) {
  return success();
}
 
void ProbeOp::getEffects(
    SmallVectorImpl<SideEffects::EffectInstance<MemoryEffects::Effect>>
        &effects) {
  if (mayHaveSSADominance(*getOperation()->getParentRegion()))
    effects.emplace_back(MemoryEffects::Read::get(), &getSignalMutable());
}
 
//===----------------------------------------------------------------------===//
// DriveOp
//===----------------------------------------------------------------------===//
 
LogicalResult llhd::DriveOp::fold(FoldAdaptor adaptor,
                                  SmallVectorImpl<OpFoldResult> &result) {
  if (!getEnable())
    return failure();
 
  if (matchPattern(getEnable(), m_One())) {
    getEnableMutable().clear();
    return success();
  }
 
  return failure();
}
 
LogicalResult llhd::DriveOp::canonicalize(llhd::DriveOp op,
                                          PatternRewriter &rewriter) {
  if (!op.getEnable())
    return failure();
 
  if (matchPattern(op.getEnable(), m_Zero())) {
    rewriter.eraseOp(op);
    return success();
  }
 
  return failure();
}
 
bool DriveOp::canRewire(const DestructurableMemorySlot &slot,
                        SmallPtrSetImpl<Attribute> &usedIndices,
                        SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
                        const DataLayout &dataLayout) {
  for (auto [key, _] : slot.subelementTypes)
    usedIndices.insert(key);
 
  return isa<hw::StructType, hw::ArrayType, IntegerType>(slot.elemType);
}
 
DeletionKind DriveOp::rewire(const DestructurableMemorySlot &slot,
                             DenseMap<Attribute, MemorySlot> &subslots,
                             OpBuilder &builder, const DataLayout &dataLayout) {
  SmallVector<std::pair<unsigned, Value>> driven;
  getSortedPtrs(subslots, driven);
 
  for (auto [idx, sig] : driven) {
    Type nestedType = cast<RefType>(sig.getType()).getNestedType();
    DriveOp::create(
        builder, getLoc(), sig,
        getValueAtIndex(builder, getLoc(), getValue(), idx, nestedType),
        getTime(), getEnable());
  }
 
  return DeletionKind::Delete;
}
 
LogicalResult
DriveOp::ensureOnlySafeAccesses(const MemorySlot &slot,
                                SmallVectorImpl<MemorySlot> &mustBeSafelyUsed,
                                const DataLayout &dataLayout) {
  return success();
}
 
//===----------------------------------------------------------------------===//
// ProcessOp
//===----------------------------------------------------------------------===//
 
LogicalResult ProcessOp::canonicalize(ProcessOp op, PatternRewriter &rewriter) {
  if (!op.getBody().hasOneBlock())
    return failure();
 
  auto &block = op.getBody().front();
  auto haltOp = dyn_cast<HaltOp>(block.getTerminator());
  if (!haltOp)
    return failure();
 
  if (op.getNumResults() == 0 && block.getOperations().size() == 1) {
    rewriter.eraseOp(op);
    return success();
  }
 
  // Only constants and halt terminator are expected in a single block.
  if (!llvm::all_of(block.without_terminator(), [](auto &bodyOp) {
        return bodyOp.template hasTrait<OpTrait::ConstantLike>();
      }))
    return failure();
 
  auto yieldOperands = haltOp.getYieldOperands();
  llvm::SmallDenseMap<Value, unsigned> uniqueOperands;
  llvm::SmallDenseMap<unsigned, unsigned> origToNewPos;
  llvm::BitVector operandsToErase(yieldOperands.size());
 
  for (auto [operandNo, operand] : llvm::enumerate(yieldOperands)) {
    auto *defOp = operand.getDefiningOp();
    if (defOp && defOp->hasTrait<OpTrait::ConstantLike>()) {
      // If the constant is available outside the process, use it directly;
      // otherwise move it outside.
      if (!defOp->getParentRegion()->isProperAncestor(&op.getBody())) {
        defOp->moveBefore(op);
      }
      rewriter.replaceAllUsesWith(op.getResult(operandNo), operand);
      operandsToErase.set(operandNo);
      continue;
    }
 
    // Identify duplicate operands to merge and compute updated result
    // positions for the process operation.
    if (!uniqueOperands.contains(operand)) {
      const auto newPos = uniqueOperands.size();
      uniqueOperands.insert(std::make_pair(operand, newPos));
      origToNewPos.insert(std::make_pair(operandNo, newPos));
    } else {
      auto firstOccurrencePos = uniqueOperands.lookup(operand);
      origToNewPos.insert(std::make_pair(operandNo, firstOccurrencePos));
      operandsToErase.set(operandNo);
    }
  }
 
  const auto countOperandsToErase = operandsToErase.count();
  if (countOperandsToErase == 0)
    return failure();
 
  // Remove the process operation if all its results have been replaced with
  // constants.
  if (countOperandsToErase == op.getNumResults()) {
    rewriter.eraseOp(op);
    return success();
  }
 
  rewriter.modifyOpInPlace(haltOp,
                           [&] { haltOp->eraseOperands(operandsToErase); });
 
  SmallVector<Type> resultTypes = llvm::to_vector(haltOp->getOperandTypes());
  auto newProcessOp = ProcessOp::create(rewriter, op.getLoc(), resultTypes,
                                        op->getOperands(), op->getAttrs());
  newProcessOp.getBody().takeBody(op.getBody());
 
  // Update old results with new values, accounting for pruned halt operands.
  for (auto oldResult : op.getResults()) {
    auto newResultPos = origToNewPos.find(oldResult.getResultNumber());
    if (newResultPos == origToNewPos.end())
      continue;
    auto newResult = newProcessOp.getResult(newResultPos->getSecond());
    rewriter.replaceAllUsesWith(oldResult, newResult);
  }
 
  rewriter.eraseOp(op);
  return success();
}
 
//===----------------------------------------------------------------------===//
// CombinationalOp
//===----------------------------------------------------------------------===//
 
LogicalResult CombinationalOp::canonicalize(CombinationalOp op,
                                            PatternRewriter &rewriter) {
  // Inline the combinational region if it consists of a single block and
  // contains no side-effecting operations.
  if (op.getBody().hasOneBlock() && isMemoryEffectFree(op)) {
    auto &block = op.getBody().front();
    auto *terminator = block.getTerminator();
    rewriter.inlineBlockBefore(&block, op, ValueRange{});
    rewriter.replaceOp(op, terminator->getOperands());
    rewriter.eraseOp(terminator);
    return success();
  }
  return failure();
}
 
//===----------------------------------------------------------------------===//
// WaitOp
//===----------------------------------------------------------------------===//
 
static LogicalResult verifyYieldResults(Operation *op,
                                        ValueRange yieldOperands) {
  // Determine the result values of the parent.
  auto *parentOp = op->getParentOp();
  SmallVector<Type> resultTypes;
  TypeSwitch<Operation *>(parentOp)
      .Case<ProcessOp, CombinationalOp>([&](auto op) {
        resultTypes.append(op.getResultTypes().begin(),
                           op.getResultTypes().end());
      })
      .Case<FinalOp>([](auto) {})
      .Case<GlobalSignalOp>(
          [&](auto op) { resultTypes.push_back(op.getType()); });
 
  // Check that the number of yield operands matches the process.
  if (yieldOperands.size() != resultTypes.size())
    return op->emitOpError()
           << "has " << yieldOperands.size()
           << " yield operands, but enclosing '" << parentOp->getName()
           << "' returns " << resultTypes.size();
 
  // Check that the types match.
  for (unsigned i = 0; i < yieldOperands.size(); ++i)
    if (yieldOperands[i].getType() != resultTypes[i])
      return op->emitError()
             << "type of yield operand " << i << " ("
             << yieldOperands[i].getType() << ") does not match enclosing '"
             << parentOp->getName() << "' result type (" << resultTypes[i]
             << ")";
 
  return success();
}
 
LogicalResult WaitOp::verify() {
  return verifyYieldResults(*this, getYieldOperands());
}
 
//===----------------------------------------------------------------------===//
// HaltOp
//===----------------------------------------------------------------------===//
 
LogicalResult HaltOp::verify() {
  return verifyYieldResults(*this, getYieldOperands());
}
 
//===----------------------------------------------------------------------===//
// YieldOp
//===----------------------------------------------------------------------===//
 
LogicalResult YieldOp::verify() {
  return verifyYieldResults(*this, getYieldOperands());
}
 
namespace {
struct IntegerTypeInterface
    : public DestructurableTypeInterface::ExternalModel<IntegerTypeInterface,
                                                        IntegerType> {
  std::optional<DenseMap<Attribute, Type>>
  getSubelementIndexMap(Type type) const {
    // We always return the empty map, indicating that IntegerType is not
    // destructurable.
    //
    // It is not always profitable to SROA an integer, so an extra cost model
    // is used by SignalOp::getDestructurableSlots() to determine the best
    // slot configuration for a given integer SignalOp.
    //
    // SROA demands that any destructured type must implement
    // DestructurableTypeInterface so we do nothing here.
    return {};
  }
 
  Type getTypeAtIndex(Type type, Attribute index) const {
    // As above, we never expect this to be called.
    llvm_unreachable("Not implemented");
  }
};
} // namespace
 
void llhd::registerDestructableIntegerExternalModel(DialectRegistry &registry) {
  registry.addExtension(+[](MLIRContext *ctx, BuiltinDialect *dialect) {
    IntegerType::attachInterface<IntegerTypeInterface>(*ctx);
    // SROA on the IntegerTypeInterface can cause comb::ExtractOps to be
    // created.
    ctx->loadDialect<comb::CombDialect>();
  });
}
 
//===----------------------------------------------------------------------===//
// GlobalSignalOp
//===----------------------------------------------------------------------===//
 
LogicalResult GlobalSignalOp::verifyRegions() {
  if (auto *block = getInitBlock()) {
    auto &terminator = block->back();
    if (!isa<YieldOp>(terminator))
      return emitOpError() << "must have a 'llhd.yield' terminator";
  }
  return success();
}
 
Block *GlobalSignalOp::getInitBlock() {
  if (getInitRegion().empty())
    return nullptr;
  return &getInitRegion().front();
}
 
//===----------------------------------------------------------------------===//
// GetGlobalSignalOp
//===----------------------------------------------------------------------===//
 
LogicalResult
GetGlobalSignalOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
  // Resolve the target symbol.
  auto *symbol =
      symbolTable.lookupNearestSymbolFrom(*this, getGlobalNameAttr());
  if (!symbol)
    return emitOpError() << "references unknown symbol " << getGlobalNameAttr();
 
  // Check that the symbol is a global signal.
  auto signal = dyn_cast<GlobalSignalOp>(symbol);
  if (!signal)
    return emitOpError() << "must reference a 'llhd.global_signal', but "
                         << getGlobalNameAttr() << " is a '"
                         << symbol->getName() << "'";
 
  // Check that the types match.
  auto expType = signal.getType();
  auto actType = getType().getNestedType();
  if (expType != actType)
    return emitOpError() << "returns a " << actType << " reference, but "
                         << getGlobalNameAttr() << " is of type " << expType;
 
  return success();
}
 
//===----------------------------------------------------------------------===//
// Auto-Generated Implementations
//===----------------------------------------------------------------------===//
 
#define GET_OP_CLASSES
#include "circt/Dialect/LLHD/LLHD.cpp.inc"
#include "circt/Dialect/LLHD/LLHDEnums.cpp.inc"