Expressions.cpp

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//===- Expressions.cpp - Slang expression conversion ----------------------===//
//
// 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 "ImportVerilogInternals.h"
#include "slang/ast/EvalContext.h"
#include "slang/ast/SystemSubroutine.h"
#include "slang/syntax/AllSyntax.h"
 
using namespace circt;
using namespace ImportVerilog;
using moore::Domain;
 
/// Convert a Slang `SVInt` to a CIRCT `FVInt`.
static FVInt convertSVIntToFVInt(const slang::SVInt &svint) {
  if (svint.hasUnknown()) {
    unsigned numWords = svint.getNumWords() / 2;
    auto value = ArrayRef<uint64_t>(svint.getRawPtr(), numWords);
    auto unknown = ArrayRef<uint64_t>(svint.getRawPtr() + numWords, numWords);
    return FVInt(APInt(svint.getBitWidth(), value),
                 APInt(svint.getBitWidth(), unknown));
  }
  auto value = ArrayRef<uint64_t>(svint.getRawPtr(), svint.getNumWords());
  return FVInt(APInt(svint.getBitWidth(), value));
}
 
/// Map an index into an array, with bounds `range`, to a bit offset of the
/// underlying bit storage. This is a dynamic version of
/// `slang::ConstantRange::translateIndex`.
static Value getSelectIndex(Context &context, Location loc, Value index,
                            const slang::ConstantRange &range) {
  auto &builder = context.builder;
  auto indexType = cast<moore::UnpackedType>(index.getType());
  auto bw = std::max(llvm::Log2_32_Ceil(std::max(std::abs(range.lower()),
                                                 std::abs(range.upper()))),
                     indexType.getBitSize().value());
 
  auto offset = range.isLittleEndian() ? range.lower() : range.upper();
  bool isSigned = (offset < 0);
  auto intType =
      moore::IntType::get(index.getContext(), bw, indexType.getDomain());
  index = context.materializeConversion(intType, index, isSigned, loc);
 
  if (offset == 0) {
    if (range.isLittleEndian())
      return index;
    else
      return moore::NegOp::create(builder, loc, index);
  }
 
  auto offsetConst =
      moore::ConstantOp::create(builder, loc, intType, offset, isSigned);
  if (range.isLittleEndian())
    return moore::SubOp::create(builder, loc, index, offsetConst);
  else
    return moore::SubOp::create(builder, loc, offsetConst, index);
}
 
/// Get the currently active timescale as an integer number of femtoseconds.
static uint64_t getTimeScaleInFemtoseconds(Context &context) {
  static_assert(int(slang::TimeUnit::Seconds) == 0);
  static_assert(int(slang::TimeUnit::Milliseconds) == 1);
  static_assert(int(slang::TimeUnit::Microseconds) == 2);
  static_assert(int(slang::TimeUnit::Nanoseconds) == 3);
  static_assert(int(slang::TimeUnit::Picoseconds) == 4);
  static_assert(int(slang::TimeUnit::Femtoseconds) == 5);
 
  static_assert(int(slang::TimeScaleMagnitude::One) == 1);
  static_assert(int(slang::TimeScaleMagnitude::Ten) == 10);
  static_assert(int(slang::TimeScaleMagnitude::Hundred) == 100);
 
  auto exp = static_cast<unsigned>(context.timeScale.base.unit);
  assert(exp <= 5);
  exp = 5 - exp;
  auto scale = static_cast<uint64_t>(context.timeScale.base.magnitude);
  while (exp-- > 0)
    scale *= 1000;
  return scale;
}
 
namespace {
/// A visitor handling expressions that can be lowered as lvalue and rvalue.
struct ExprVisitor {
  Context &context;
  Location loc;
  OpBuilder &builder;
  bool isLvalue;
 
  ExprVisitor(Context &context, Location loc, bool isLvalue)
      : context(context), loc(loc), builder(context.builder),
        isLvalue(isLvalue) {}
 
  /// Convert an expression either as an lvalue or rvalue, depending on whether
  /// this is an lvalue or rvalue visitor. This is useful for projections such
  /// as `a[i]`, where you want `a` as an lvalue if you want `a[i]` as an
  /// lvalue, or `a` as an rvalue if you want `a[i]` as an rvalue.
  Value convertLvalueOrRvalueExpression(const slang::ast::Expression &expr) {
    if (isLvalue)
      return context.convertLvalueExpression(expr);
    return context.convertRvalueExpression(expr);
  }
 
  /// Handle single bit selections.
  Value visit(const slang::ast::ElementSelectExpression &expr) {
    auto type = context.convertType(*expr.type);
    auto value = convertLvalueOrRvalueExpression(expr.value());
    if (!type || !value)
      return {};
 
    // We only support indexing into a few select types for now.
    auto derefType = value.getType();
    if (isLvalue)
      derefType = cast<moore::RefType>(derefType).getNestedType();
    if (!isa<moore::IntType, moore::ArrayType, moore::UnpackedArrayType>(
            derefType)) {
      mlir::emitError(loc) << "unsupported expression: element select into "
                           << expr.value().type->toString() << "\n";
      return {};
    }
 
    auto resultType =
        isLvalue ? moore::RefType::get(cast<moore::UnpackedType>(type)) : type;
    auto range = expr.value().type->getFixedRange();
    if (auto *constValue = expr.selector().getConstant();
        constValue && constValue->isInteger()) {
      assert(!constValue->hasUnknown());
      assert(constValue->size() <= 32);
 
      auto lowBit = constValue->integer().as<uint32_t>().value();
      if (isLvalue)
        return moore::ExtractRefOp::create(builder, loc, resultType, value,
                                           range.translateIndex(lowBit));
      else
        return moore::ExtractOp::create(builder, loc, resultType, value,
                                        range.translateIndex(lowBit));
    }
 
    auto lowBit = context.convertRvalueExpression(expr.selector());
    if (!lowBit)
      return {};
    lowBit = getSelectIndex(context, loc, lowBit, range);
    if (isLvalue)
      return moore::DynExtractRefOp::create(builder, loc, resultType, value,
                                            lowBit);
    else
      return moore::DynExtractOp::create(builder, loc, resultType, value,
                                         lowBit);
  }
 
  /// Handle range bit selections.
  Value visit(const slang::ast::RangeSelectExpression &expr) {
    auto type = context.convertType(*expr.type);
    auto value = convertLvalueOrRvalueExpression(expr.value());
    if (!type || !value)
      return {};
 
    std::optional<int32_t> constLeft;
    std::optional<int32_t> constRight;
    if (auto *constant = expr.left().getConstant())
      constLeft = constant->integer().as<int32_t>();
    if (auto *constant = expr.right().getConstant())
      constRight = constant->integer().as<int32_t>();
 
    // We currently require the right-hand-side of the range to be constant.
    // This catches things like `[42:$]` which we don't support at the moment.
    if (!constRight) {
      mlir::emitError(loc)
          << "unsupported expression: range select with non-constant bounds";
      return {};
    }
 
    // We need to determine the right bound of the range. This is the address of
    // the least significant bit of the underlying bit storage, which is the
    // offset we want to pass to the extract op.
    //
    // The arrays [6:2] and [2:6] both have 5 bits worth of underlying storage.
    // The left and right bound of the range only determine the addressing
    // scheme of the storage bits:
    //
    // Storage bits:   4  3  2  1  0  <-- extract op works on storage bits
    // [6:2] indices:  6  5  4  3  2  ("little endian" in Slang terms)
    // [2:6] indices:  2  3  4  5  6  ("big endian" in Slang terms)
    //
    // Before we can extract, we need to map the range select left and right
    // bounds from these indices to actual bit positions in the storage.
 
    Value offsetDyn;
    int32_t offsetConst = 0;
    auto range = expr.value().type->getFixedRange();
 
    using slang::ast::RangeSelectionKind;
    if (expr.getSelectionKind() == RangeSelectionKind::Simple) {
      // For a constant range [a:b], we want the offset of the lowest storage
      // bit from which we are starting the extract. For a range [5:3] this is
      // bit index 3; for a range [3:5] this is bit index 5. Both of these are
      // later translated map to bit offset 1 (see bit indices above).
      assert(constRight && "constness checked in slang");
      offsetConst = *constRight;
    } else {
      // For an indexed range [a+:b] or [a-:b], determining the lowest storage
      // bit is a bit more complicated. We start out with the base index `a`.
      // This is the lower *index* of the range, but not the lower *storage bit
      // position*.
      //
      // The range [a+:b] expands to [a+b-1:a] for a [6:2] range, or [a:a+b-1]
      // for a [2:6] range. The range [a-:b] expands to [a:a-b+1] for a [6:2]
      // range, or [a-b+1:a] for a [2:6] range.
      if (constLeft) {
        offsetConst = *constLeft;
      } else {
        offsetDyn = context.convertRvalueExpression(expr.left());
        if (!offsetDyn)
          return {};
      }
 
      // For a [a-:b] select on [2:6] and a [a+:b] select on [6:2], the range
      // expands to [a-b+1:a] and [a+b-1:a]. In this case, the right bound which
      // corresponds to the lower *storage bit offset*, is just `a` and there's
      // no further tweaking to do.
      int32_t offsetAdd = 0;
 
      // For a [a-:b] select on [6:2], the range expands to [a:a-b+1]. We
      // therefore have to take the `a` from above and adjust it by `-b+1` to
      // arrive at the right bound.
      if (expr.getSelectionKind() == RangeSelectionKind::IndexedDown &&
          range.isLittleEndian()) {
        assert(constRight && "constness checked in slang");
        offsetAdd = 1 - *constRight;
      }
 
      // For a [a+:b] select on [2:6], the range expands to [a:a+b-1]. We
      // therefore have to take the `a` from above and adjust it by `+b-1` to
      // arrive at the right bound.
      if (expr.getSelectionKind() == RangeSelectionKind::IndexedUp &&
          !range.isLittleEndian()) {
        assert(constRight && "constness checked in slang");
        offsetAdd = *constRight - 1;
      }
 
      // Adjust the offset such that it matches the right bound of the range.
      if (offsetAdd != 0) {
        if (offsetDyn)
          offsetDyn = moore::AddOp::create(
              builder, loc, offsetDyn,
              moore::ConstantOp::create(
                  builder, loc, cast<moore::IntType>(offsetDyn.getType()),
                  offsetAdd,
                  /*isSigned=*/offsetAdd < 0));
        else
          offsetConst += offsetAdd;
      }
    }
 
    // Create a dynamic or constant extract. Use `getSelectIndex` and
    // `ConstantRange::translateIndex` to map from the bit indices provided by
    // the user to the actual storage bit position. Since `offset*` corresponds
    // to the right bound of the range, which provides the index of the least
    // significant selected storage bit, we get the bit offset at which we want
    // to start extracting.
    auto resultType =
        isLvalue ? moore::RefType::get(cast<moore::UnpackedType>(type)) : type;
 
    if (offsetDyn) {
      offsetDyn = getSelectIndex(context, loc, offsetDyn, range);
      if (isLvalue) {
        return moore::DynExtractRefOp::create(builder, loc, resultType, value,
                                              offsetDyn);
      } else {
        return moore::DynExtractOp::create(builder, loc, resultType, value,
                                           offsetDyn);
      }
    } else {
      offsetConst = range.translateIndex(offsetConst);
      if (isLvalue) {
        return moore::ExtractRefOp::create(builder, loc, resultType, value,
                                           offsetConst);
      } else {
        return moore::ExtractOp::create(builder, loc, resultType, value,
                                        offsetConst);
      }
    }
  }
 
  /// Handle concatenations.
  Value visit(const slang::ast::ConcatenationExpression &expr) {
    SmallVector<Value> operands;
    for (auto *operand : expr.operands()) {
      // Handle empty replications like `{0{...}}` which may occur within
      // concatenations. Slang assigns them a `void` type which we can check for
      // here.
      if (operand->type->isVoid())
        continue;
      auto value = convertLvalueOrRvalueExpression(*operand);
      if (!value)
        return {};
      if (!isLvalue)
        value = context.convertToSimpleBitVector(value);
      if (!value)
        return {};
      operands.push_back(value);
    }
    if (isLvalue)
      return moore::ConcatRefOp::create(builder, loc, operands);
    else
      return moore::ConcatOp::create(builder, loc, operands);
  }
 
  /// Handle member accesses.
  Value visit(const slang::ast::MemberAccessExpression &expr) {
    auto type = context.convertType(*expr.type);
    auto valueType = expr.value().type;
    auto value = convertLvalueOrRvalueExpression(expr.value());
    if (!type || !value)
      return {};
 
    auto resultType =
        isLvalue ? moore::RefType::get(cast<moore::UnpackedType>(type)) : type;
    auto memberName = builder.getStringAttr(expr.member.name);
 
    // Handle structs.
    if (valueType->isStruct()) {
      if (isLvalue)
        return moore::StructExtractRefOp::create(builder, loc, resultType,
                                                 memberName, value);
      else
        return moore::StructExtractOp::create(builder, loc, resultType,
                                              memberName, value);
    }
 
    // Handle unions.
    if (valueType->isPackedUnion() || valueType->isUnpackedUnion()) {
      if (isLvalue)
        return moore::UnionExtractRefOp::create(builder, loc, resultType,
                                                memberName, value);
      else
        return moore::UnionExtractOp::create(builder, loc, type, memberName,
                                             value);
    }
 
    mlir::emitError(loc, "expression of type ")
        << value.getType() << " has no member fields";
    return {};
  }
};
} // namespace
 
//===----------------------------------------------------------------------===//
// Rvalue Conversion
//===----------------------------------------------------------------------===//
 
// NOLINTBEGIN(misc-no-recursion)
namespace {
struct RvalueExprVisitor : public ExprVisitor {
  RvalueExprVisitor(Context &context, Location loc)
      : ExprVisitor(context, loc, /*isLvalue=*/false) {}
  using ExprVisitor::visit;
 
  // Handle references to the left-hand side of a parent assignment.
  Value visit(const slang::ast::LValueReferenceExpression &expr) {
    assert(!context.lvalueStack.empty() && "parent assignments push lvalue");
    auto lvalue = context.lvalueStack.back();
    return moore::ReadOp::create(builder, loc, lvalue);
  }
 
  // Handle named values, such as references to declared variables.
  Value visit(const slang::ast::NamedValueExpression &expr) {
    if (auto value = context.valueSymbols.lookup(&expr.symbol)) {
      if (isa<moore::RefType>(value.getType())) {
        auto readOp = moore::ReadOp::create(builder, loc, value);
        if (context.rvalueReadCallback)
          context.rvalueReadCallback(readOp);
        value = readOp.getResult();
      }
      return value;
    }
 
    // Try to materialize constant values directly.
    auto constant = context.evaluateConstant(expr);
    if (auto value = context.materializeConstant(constant, *expr.type, loc))
      return value;
 
    // Otherwise some other part of ImportVerilog should have added an MLIR
    // value for this expression's symbol to the `context.valueSymbols` table.
    auto d = mlir::emitError(loc, "unknown name `") << expr.symbol.name << "`";
    d.attachNote(context.convertLocation(expr.symbol.location))
        << "no rvalue generated for " << slang::ast::toString(expr.symbol.kind);
    return {};
  }
 
  // Handle hierarchical values, such as `x = Top.sub.var`.
  Value visit(const slang::ast::HierarchicalValueExpression &expr) {
    auto hierLoc = context.convertLocation(expr.symbol.location);
    if (auto value = context.valueSymbols.lookup(&expr.symbol)) {
      if (isa<moore::RefType>(value.getType())) {
        auto readOp = moore::ReadOp::create(builder, hierLoc, value);
        if (context.rvalueReadCallback)
          context.rvalueReadCallback(readOp);
        value = readOp.getResult();
      }
      return value;
    }
 
    // Emit an error for those hierarchical values not recorded in the
    // `valueSymbols`.
    auto d = mlir::emitError(loc, "unknown hierarchical name `")
             << expr.symbol.name << "`";
    d.attachNote(hierLoc) << "no rvalue generated for "
                          << slang::ast::toString(expr.symbol.kind);
    return {};
  }
 
  // Handle type conversions (explicit and implicit).
  Value visit(const slang::ast::ConversionExpression &expr) {
    auto type = context.convertType(*expr.type);
    if (!type)
      return {};
    return context.convertRvalueExpression(expr.operand(), type);
  }
 
  // Handle blocking and non-blocking assignments.
  Value visit(const slang::ast::AssignmentExpression &expr) {
    auto lhs = context.convertLvalueExpression(expr.left());
    if (!lhs)
      return {};
 
    context.lvalueStack.push_back(lhs);
    auto rhs = context.convertRvalueExpression(
        expr.right(), cast<moore::RefType>(lhs.getType()).getNestedType());
    context.lvalueStack.pop_back();
    if (!rhs)
      return {};
 
    if (expr.timingControl) {
      auto loc = context.convertLocation(expr.timingControl->sourceRange);
      mlir::emitError(loc, "delayed assignments not supported");
      return {};
    }
 
    if (expr.isNonBlocking())
      moore::NonBlockingAssignOp::create(builder, loc, lhs, rhs);
    else
      moore::BlockingAssignOp::create(builder, loc, lhs, rhs);
    return rhs;
  }
 
  // Helper function to convert an argument to a simple bit vector type, pass it
  // to a reduction op, and optionally invert the result.
  template <class ConcreteOp>
  Value createReduction(Value arg, bool invert) {
    arg = context.convertToSimpleBitVector(arg);
    if (!arg)
      return {};
    Value result = ConcreteOp::create(builder, loc, arg);
    if (invert)
      result = moore::NotOp::create(builder, loc, result);
    return result;
  }
 
  // Helper function to create pre and post increments and decrements.
  Value createIncrement(Value arg, bool isInc, bool isPost) {
    auto preValue = moore::ReadOp::create(builder, loc, arg);
    Value postValue;
    // Catch the special case where a signed 1 bit value (i1) is incremented,
    // as +1 can not be expressed as a signed 1 bit value. For any 1-bit number
    // negating is equivalent to incrementing.
    if (moore::isIntType(preValue.getType(), 1)) {
      postValue = moore::NotOp::create(builder, loc, preValue).getResult();
    } else {
 
      auto one = moore::ConstantOp::create(
          builder, loc, cast<moore::IntType>(preValue.getType()), 1);
      postValue =
          isInc ? moore::AddOp::create(builder, loc, preValue, one).getResult()
                : moore::SubOp::create(builder, loc, preValue, one).getResult();
      moore::BlockingAssignOp::create(builder, loc, arg, postValue);
    }
    if (isPost)
      return preValue;
    return postValue;
  }
 
  // Handle unary operators.
  Value visit(const slang::ast::UnaryExpression &expr) {
    using slang::ast::UnaryOperator;
    Value arg;
    if (expr.op == UnaryOperator::Preincrement ||
        expr.op == UnaryOperator::Predecrement ||
        expr.op == UnaryOperator::Postincrement ||
        expr.op == UnaryOperator::Postdecrement)
      arg = context.convertLvalueExpression(expr.operand());
    else
      arg = context.convertRvalueExpression(expr.operand());
    if (!arg)
      return {};
 
    switch (expr.op) {
      // `+a` is simply `a`, but converted to a simple bit vector type since
      // this is technically an arithmetic operation.
    case UnaryOperator::Plus:
      return context.convertToSimpleBitVector(arg);
 
    case UnaryOperator::Minus:
      arg = context.convertToSimpleBitVector(arg);
      if (!arg)
        return {};
      return moore::NegOp::create(builder, loc, arg);
 
    case UnaryOperator::BitwiseNot:
      arg = context.convertToSimpleBitVector(arg);
      if (!arg)
        return {};
      return moore::NotOp::create(builder, loc, arg);
 
    case UnaryOperator::BitwiseAnd:
      return createReduction<moore::ReduceAndOp>(arg, false);
    case UnaryOperator::BitwiseOr:
      return createReduction<moore::ReduceOrOp>(arg, false);
    case UnaryOperator::BitwiseXor:
      return createReduction<moore::ReduceXorOp>(arg, false);
    case UnaryOperator::BitwiseNand:
      return createReduction<moore::ReduceAndOp>(arg, true);
    case UnaryOperator::BitwiseNor:
      return createReduction<moore::ReduceOrOp>(arg, true);
    case UnaryOperator::BitwiseXnor:
      return createReduction<moore::ReduceXorOp>(arg, true);
 
    case UnaryOperator::LogicalNot:
      arg = context.convertToBool(arg);
      if (!arg)
        return {};
      return moore::NotOp::create(builder, loc, arg);
 
    case UnaryOperator::Preincrement:
      return createIncrement(arg, true, false);
    case UnaryOperator::Predecrement:
      return createIncrement(arg, false, false);
    case UnaryOperator::Postincrement:
      return createIncrement(arg, true, true);
    case UnaryOperator::Postdecrement:
      return createIncrement(arg, false, true);
    }
 
    mlir::emitError(loc, "unsupported unary operator");
    return {};
  }
 
  // Helper function to convert two arguments to a simple bit vector type and
  // pass them into a binary op.
  template <class ConcreteOp>
  Value createBinary(Value lhs, Value rhs) {
    lhs = context.convertToSimpleBitVector(lhs);
    if (!lhs)
      return {};
    rhs = context.convertToSimpleBitVector(rhs);
    if (!rhs)
      return {};
    return ConcreteOp::create(builder, loc, lhs, rhs);
  }
 
  // Handle binary operators.
  Value visit(const slang::ast::BinaryExpression &expr) {
    auto lhs = context.convertRvalueExpression(expr.left());
    if (!lhs)
      return {};
    auto rhs = context.convertRvalueExpression(expr.right());
    if (!rhs)
      return {};
 
    // Determine the domain of the result.
    Domain domain = Domain::TwoValued;
    if (expr.type->isFourState() || expr.left().type->isFourState() ||
        expr.right().type->isFourState())
      domain = Domain::FourValued;
 
    using slang::ast::BinaryOperator;
    switch (expr.op) {
    case BinaryOperator::Add:
      return createBinary<moore::AddOp>(lhs, rhs);
    case BinaryOperator::Subtract:
      return createBinary<moore::SubOp>(lhs, rhs);
    case BinaryOperator::Multiply:
      return createBinary<moore::MulOp>(lhs, rhs);
    case BinaryOperator::Divide:
      if (expr.type->isSigned())
        return createBinary<moore::DivSOp>(lhs, rhs);
      else
        return createBinary<moore::DivUOp>(lhs, rhs);
    case BinaryOperator::Mod:
      if (expr.type->isSigned())
        return createBinary<moore::ModSOp>(lhs, rhs);
      else
        return createBinary<moore::ModUOp>(lhs, rhs);
    case BinaryOperator::Power: {
      // Slang casts the LHS and result of the `**` operator to a four-valued
      // type, since the operator can return X even for two-valued inputs. To
      // maintain uniform types across operands and results, cast the RHS to
      // that four-valued type as well.
      auto rhsCast = context.materializeConversion(
          lhs.getType(), rhs, expr.right().type->isSigned(), rhs.getLoc());
      if (expr.type->isSigned())
        return createBinary<moore::PowSOp>(lhs, rhsCast);
      else
        return createBinary<moore::PowUOp>(lhs, rhsCast);
    }
 
    case BinaryOperator::BinaryAnd:
      return createBinary<moore::AndOp>(lhs, rhs);
    case BinaryOperator::BinaryOr:
      return createBinary<moore::OrOp>(lhs, rhs);
    case BinaryOperator::BinaryXor:
      return createBinary<moore::XorOp>(lhs, rhs);
    case BinaryOperator::BinaryXnor: {
      auto result = createBinary<moore::XorOp>(lhs, rhs);
      if (!result)
        return {};
      return moore::NotOp::create(builder, loc, result);
    }
 
    case BinaryOperator::Equality:
      if (isa<moore::UnpackedArrayType>(lhs.getType()))
        return moore::UArrayCmpOp::create(
            builder, loc, moore::UArrayCmpPredicate::eq, lhs, rhs);
      else if (isa<moore::StringType>(lhs.getType()))
        return moore::StringCmpOp::create(
            builder, loc, moore::StringCmpPredicate::eq, lhs, rhs);
      else
        return createBinary<moore::EqOp>(lhs, rhs);
    case BinaryOperator::Inequality:
      if (isa<moore::UnpackedArrayType>(lhs.getType()))
        return moore::UArrayCmpOp::create(
            builder, loc, moore::UArrayCmpPredicate::ne, lhs, rhs);
      else if (isa<moore::StringType>(lhs.getType()))
        return moore::StringCmpOp::create(
            builder, loc, moore::StringCmpPredicate::ne, lhs, rhs);
      else
        return createBinary<moore::NeOp>(lhs, rhs);
    case BinaryOperator::CaseEquality:
      return createBinary<moore::CaseEqOp>(lhs, rhs);
    case BinaryOperator::CaseInequality:
      return createBinary<moore::CaseNeOp>(lhs, rhs);
    case BinaryOperator::WildcardEquality:
      return createBinary<moore::WildcardEqOp>(lhs, rhs);
    case BinaryOperator::WildcardInequality:
      return createBinary<moore::WildcardNeOp>(lhs, rhs);
 
    case BinaryOperator::GreaterThanEqual:
      if (expr.left().type->isSigned())
        return createBinary<moore::SgeOp>(lhs, rhs);
      else if (isa<moore::StringType>(lhs.getType()))
        return moore::StringCmpOp::create(
            builder, loc, moore::StringCmpPredicate::ge, lhs, rhs);
      else
        return createBinary<moore::UgeOp>(lhs, rhs);
    case BinaryOperator::GreaterThan:
      if (expr.left().type->isSigned())
        return createBinary<moore::SgtOp>(lhs, rhs);
      else if (isa<moore::StringType>(lhs.getType()))
        return moore::StringCmpOp::create(
            builder, loc, moore::StringCmpPredicate::gt, lhs, rhs);
      else
        return createBinary<moore::UgtOp>(lhs, rhs);
    case BinaryOperator::LessThanEqual:
      if (expr.left().type->isSigned())
        return createBinary<moore::SleOp>(lhs, rhs);
      else if (isa<moore::StringType>(lhs.getType()))
        return moore::StringCmpOp::create(
            builder, loc, moore::StringCmpPredicate::le, lhs, rhs);
      else
        return createBinary<moore::UleOp>(lhs, rhs);
    case BinaryOperator::LessThan:
      if (expr.left().type->isSigned())
        return createBinary<moore::SltOp>(lhs, rhs);
      else if (isa<moore::StringType>(lhs.getType()))
        return moore::StringCmpOp::create(
            builder, loc, moore::StringCmpPredicate::lt, lhs, rhs);
      else
        return createBinary<moore::UltOp>(lhs, rhs);
 
    // See IEEE 1800-2017 § 11.4.7 "Logical operators".
    case BinaryOperator::LogicalAnd: {
      // TODO: This should short-circuit. Put the RHS code into a separate
      // block.
      lhs = context.convertToBool(lhs, domain);
      if (!lhs)
        return {};
      rhs = context.convertToBool(rhs, domain);
      if (!rhs)
        return {};
      return moore::AndOp::create(builder, loc, lhs, rhs);
    }
    case BinaryOperator::LogicalOr: {
      // TODO: This should short-circuit. Put the RHS code into a separate
      // block.
      lhs = context.convertToBool(lhs, domain);
      if (!lhs)
        return {};
      rhs = context.convertToBool(rhs, domain);
      if (!rhs)
        return {};
      return moore::OrOp::create(builder, loc, lhs, rhs);
    }
    case BinaryOperator::LogicalImplication: {
      // `(lhs -> rhs)` equivalent to `(!lhs || rhs)`.
      lhs = context.convertToBool(lhs, domain);
      if (!lhs)
        return {};
      rhs = context.convertToBool(rhs, domain);
      if (!rhs)
        return {};
      auto notLHS = moore::NotOp::create(builder, loc, lhs);
      return moore::OrOp::create(builder, loc, notLHS, rhs);
    }
    case BinaryOperator::LogicalEquivalence: {
      // `(lhs <-> rhs)` equivalent to `(lhs && rhs) || (!lhs && !rhs)`.
      lhs = context.convertToBool(lhs, domain);
      if (!lhs)
        return {};
      rhs = context.convertToBool(rhs, domain);
      if (!rhs)
        return {};
      auto notLHS = moore::NotOp::create(builder, loc, lhs);
      auto notRHS = moore::NotOp::create(builder, loc, rhs);
      auto both = moore::AndOp::create(builder, loc, lhs, rhs);
      auto notBoth = moore::AndOp::create(builder, loc, notLHS, notRHS);
      return moore::OrOp::create(builder, loc, both, notBoth);
    }
 
    case BinaryOperator::LogicalShiftLeft:
      return createBinary<moore::ShlOp>(lhs, rhs);
    case BinaryOperator::LogicalShiftRight:
      return createBinary<moore::ShrOp>(lhs, rhs);
    case BinaryOperator::ArithmeticShiftLeft:
      return createBinary<moore::ShlOp>(lhs, rhs);
    case BinaryOperator::ArithmeticShiftRight: {
      // The `>>>` operator is an arithmetic right shift if the LHS operand is
      // signed, or a logical right shift if the operand is unsigned.
      lhs = context.convertToSimpleBitVector(lhs);
      rhs = context.convertToSimpleBitVector(rhs);
      if (!lhs || !rhs)
        return {};
      if (expr.type->isSigned())
        return moore::AShrOp::create(builder, loc, lhs, rhs);
      return moore::ShrOp::create(builder, loc, lhs, rhs);
    }
    }
 
    mlir::emitError(loc, "unsupported binary operator");
    return {};
  }
 
  // Handle `'0`, `'1`, `'x`, and `'z` literals.
  Value visit(const slang::ast::UnbasedUnsizedIntegerLiteral &expr) {
    return context.materializeSVInt(expr.getValue(), *expr.type, loc);
  }
 
  // Handle integer literals.
  Value visit(const slang::ast::IntegerLiteral &expr) {
    return context.materializeSVInt(expr.getValue(), *expr.type, loc);
  }
 
  // Handle time literals.
  Value visit(const slang::ast::TimeLiteral &expr) {
    // The time literal is expressed in the current time scale. Determine the
    // conversion factor to convert the literal from the current time scale into
    // femtoseconds, and round the scaled value to femtoseconds.
    double scale = getTimeScaleInFemtoseconds(context);
    double value = std::round(expr.getValue() * scale);
    assert(value >= 0.0);
 
    // Check that the value does not exceed what we can represent in the IR.
    // Casting the maximum uint64 value to double changes its value from
    // 18446744073709551615 to 18446744073709551616, which makes the comparison
    // overestimate the largest number we can represent. To avoid this, round
    // the maximum value down to the closest number that only has the front 53
    // bits set. This matches the mantissa of a double, plus the implicit
    // leading 1, ensuring that we can accurately represent the limit.
    static constexpr uint64_t limit =
        (std::numeric_limits<uint64_t>::max() >> 11) << 11;
    if (value > limit) {
      mlir::emitError(loc) << "time value is larger than " << limit << " fs";
      return {};
    }
 
    return moore::ConstantTimeOp::create(builder, loc,
                                         static_cast<uint64_t>(value));
  }
 
  // Handle replications.
  Value visit(const slang::ast::ReplicationExpression &expr) {
    auto type = context.convertType(*expr.type);
    auto value = context.convertRvalueExpression(expr.concat());
    if (!value)
      return {};
    return moore::ReplicateOp::create(builder, loc, type, value);
  }
 
  // Handle set membership operator.
  Value visit(const slang::ast::InsideExpression &expr) {
    auto lhs = context.convertToSimpleBitVector(
        context.convertRvalueExpression(expr.left()));
    if (!lhs)
      return {};
    // All conditions for determining whether it is inside.
    SmallVector<Value> conditions;
 
    // Traverse open range list.
    for (const auto *listExpr : expr.rangeList()) {
      Value cond;
      // The open range list on the right-hand side of the inside operator is a
      // comma-separated list of expressions or ranges.
      if (const auto *openRange =
              listExpr->as_if<slang::ast::ValueRangeExpression>()) {
        // Handle ranges.
        auto lowBound = context.convertToSimpleBitVector(
            context.convertRvalueExpression(openRange->left()));
        auto highBound = context.convertToSimpleBitVector(
            context.convertRvalueExpression(openRange->right()));
        if (!lowBound || !highBound)
          return {};
        Value leftValue, rightValue;
        // Determine if the expression on the left-hand side is inclusively
        // within the range.
        if (openRange->left().type->isSigned() ||
            expr.left().type->isSigned()) {
          leftValue = moore::SgeOp::create(builder, loc, lhs, lowBound);
        } else {
          leftValue = moore::UgeOp::create(builder, loc, lhs, lowBound);
        }
        if (openRange->right().type->isSigned() ||
            expr.left().type->isSigned()) {
          rightValue = moore::SleOp::create(builder, loc, lhs, highBound);
        } else {
          rightValue = moore::UleOp::create(builder, loc, lhs, highBound);
        }
        cond = moore::AndOp::create(builder, loc, leftValue, rightValue);
      } else {
        // Handle expressions.
        if (!listExpr->type->isIntegral()) {
          if (listExpr->type->isUnpackedArray()) {
            mlir::emitError(
                loc, "unpacked arrays in 'inside' expressions not supported");
            return {};
          }
          mlir::emitError(
              loc, "only simple bit vectors supported in 'inside' expressions");
          return {};
        }
 
        auto value = context.convertToSimpleBitVector(
            context.convertRvalueExpression(*listExpr));
        if (!value)
          return {};
        cond = moore::WildcardEqOp::create(builder, loc, lhs, value);
      }
      conditions.push_back(cond);
    }
 
    // Calculate the final result by `or` op.
    auto result = conditions.back();
    conditions.pop_back();
    while (!conditions.empty()) {
      result = moore::OrOp::create(builder, loc, conditions.back(), result);
      conditions.pop_back();
    }
    return result;
  }
 
  // Handle conditional operator `?:`.
  Value visit(const slang::ast::ConditionalExpression &expr) {
    auto type = context.convertType(*expr.type);
 
    // Handle condition.
    if (expr.conditions.size() > 1) {
      mlir::emitError(loc)
          << "unsupported conditional expression with more than one condition";
      return {};
    }
    const auto &cond = expr.conditions[0];
    if (cond.pattern) {
      mlir::emitError(loc) << "unsupported conditional expression with pattern";
      return {};
    }
    auto value =
        context.convertToBool(context.convertRvalueExpression(*cond.expr));
    if (!value)
      return {};
    auto conditionalOp =
        moore::ConditionalOp::create(builder, loc, type, value);
 
    // Create blocks for true region and false region.
    auto &trueBlock = conditionalOp.getTrueRegion().emplaceBlock();
    auto &falseBlock = conditionalOp.getFalseRegion().emplaceBlock();
 
    OpBuilder::InsertionGuard g(builder);
 
    // Handle left expression.
    builder.setInsertionPointToStart(&trueBlock);
    auto trueValue = context.convertRvalueExpression(expr.left(), type);
    if (!trueValue)
      return {};
    moore::YieldOp::create(builder, loc, trueValue);
 
    // Handle right expression.
    builder.setInsertionPointToStart(&falseBlock);
    auto falseValue = context.convertRvalueExpression(expr.right(), type);
    if (!falseValue)
      return {};
    moore::YieldOp::create(builder, loc, falseValue);
 
    return conditionalOp.getResult();
  }
 
  /// Handle calls.
  Value visit(const slang::ast::CallExpression &expr) {
    // Class method calls are currently not supported.
    if (expr.thisClass()) {
      mlir::emitError(loc, "unsupported class method call");
      return {};
    }
 
    // Try to materialize constant values directly.
    auto constant = context.evaluateConstant(expr);
    if (auto value = context.materializeConstant(constant, *expr.type, loc))
      return value;
 
    return std::visit(
        [&](auto &subroutine) { return visitCall(expr, subroutine); },
        expr.subroutine);
  }
 
  /// Handle subroutine calls.
  Value visitCall(const slang::ast::CallExpression &expr,
                  const slang::ast::SubroutineSymbol *subroutine) {
    auto *lowering = context.declareFunction(*subroutine);
    if (!lowering)
      return {};
 
    // Convert the call arguments. Input arguments are converted to an rvalue.
    // All other arguments are converted to lvalues and passed into the function
    // by reference.
    SmallVector<Value> arguments;
    for (auto [callArg, declArg] :
         llvm::zip(expr.arguments(), subroutine->getArguments())) {
 
      // Unpack the `<expr> = EmptyArgument` pattern emitted by Slang for output
      // and inout arguments.
      auto *expr = callArg;
      if (const auto *assign = expr->as_if<slang::ast::AssignmentExpression>())
        expr = &assign->left();
 
      Value value;
      if (declArg->direction == slang::ast::ArgumentDirection::In)
        value = context.convertRvalueExpression(*expr);
      else
        value = context.convertLvalueExpression(*expr);
      if (!value)
        return {};
      arguments.push_back(value);
    }
 
    // Create the call.
    auto callOp =
        mlir::func::CallOp::create(builder, loc, lowering->op, arguments);
 
    // For calls to void functions we need to have a value to return from this
    // function. Create a dummy `unrealized_conversion_cast`, which will get
    // deleted again later on.
    if (callOp.getNumResults() == 0)
      return mlir::UnrealizedConversionCastOp::create(
                 builder, loc, moore::VoidType::get(context.getContext()),
                 ValueRange{})
          .getResult(0);
 
    return callOp.getResult(0);
  }
 
  /// Handle system calls.
  Value visitCall(const slang::ast::CallExpression &expr,
                  const slang::ast::CallExpression::SystemCallInfo &info) {
    const auto &subroutine = *info.subroutine;
 
    // $rose, $fell, $stable, $changed, and $past are only valid in
    // the context of properties and assertions. Those are treated in the
    // LTLDialect; treat them there instead.
    bool isAssertionCall =
        llvm::StringSwitch<bool>(subroutine.name)
            .Cases("$rose", "$fell", "$stable", "$past", true)
            .Default(false);
 
    if (isAssertionCall)
      return context.convertAssertionCallExpression(expr, info, loc);
 
    auto args = expr.arguments();
 
    FailureOr<Value> result;
    Value value;
 
    // $sformatf() and $sformat look like system tasks, but we handle string
    // formatting differently from expression evaluation, so handle them
    // separately.
    // According to IEEE 1800-2023 Section 21.3.3 "Formatting data to a
    // string" $sformatf works just like the string formatting but returns
    // a StringType.
    if (!subroutine.name.compare("$sformatf")) {
      // Create the FormatString
      auto fmtValue = context.convertFormatString(
          expr.arguments(), loc, moore::IntFormat::Decimal, false);
      if (failed(fmtValue))
        return {};
      return fmtValue.value();
    }
 
    switch (args.size()) {
    case (0):
      result = context.convertSystemCallArity0(subroutine, loc);
      break;
 
    case (1):
      value = context.convertRvalueExpression(*args[0]);
      if (!value)
        return {};
      result = context.convertSystemCallArity1(subroutine, loc, value);
      break;
 
    default:
      mlir::emitError(loc)
          << "system call with more than 1 argument is not supported";
      break;
    }
 
    if (failed(result))
      return {};
    if (*result)
      return *result;
    mlir::emitError(loc) << "unsupported system call `" << subroutine.name
                         << "`";
    return {};
  }
 
  /// Handle string literals.
  Value visit(const slang::ast::StringLiteral &expr) {
    auto type = context.convertType(*expr.type);
    return moore::StringConstantOp::create(builder, loc, type, expr.getValue());
  }
 
  /// Handle real literals.
  Value visit(const slang::ast::RealLiteral &expr) {
    return moore::RealLiteralOp::create(
        builder, loc, builder.getF64FloatAttr(expr.getValue()));
  }
 
  /// Helper function to convert RValues at creation of a new Struct, Array or
  /// Int.
  FailureOr<SmallVector<Value>>
  convertElements(const slang::ast::AssignmentPatternExpressionBase &expr,
                  std::variant<Type, ArrayRef<Type>> expectedTypes,
                  unsigned replCount) {
    const auto &elts = expr.elements();
    const size_t elementCount = elts.size();
 
    // Inspect the variant.
    const bool hasBroadcast =
        std::holds_alternative<Type>(expectedTypes) &&
        static_cast<bool>(std::get<Type>(expectedTypes)); // non-null Type
 
    const bool hasPerElem =
        std::holds_alternative<ArrayRef<Type>>(expectedTypes) &&
        !std::get<ArrayRef<Type>>(expectedTypes).empty();
 
    // If per-element types are provided, enforce arity.
    if (hasPerElem) {
      auto types = std::get<ArrayRef<Type>>(expectedTypes);
      if (types.size() != elementCount) {
        mlir::emitError(loc)
            << "assignment pattern arity mismatch: expected " << types.size()
            << " elements, got " << elementCount;
        return failure();
      }
    }
 
    SmallVector<Value> converted;
    converted.reserve(elementCount * std::max(1u, replCount));
 
    // Convert each element heuristically, no type is expected
    if (!hasBroadcast && !hasPerElem) {
      // No expected type info.
      for (const auto *elementExpr : elts) {
        Value v = context.convertRvalueExpression(*elementExpr);
        if (!v)
          return failure();
        converted.push_back(v);
      }
    } else if (hasBroadcast) {
      // Same expected type for all elements.
      Type want = std::get<Type>(expectedTypes);
      for (const auto *elementExpr : elts) {
        Value v = want ? context.convertRvalueExpression(*elementExpr, want)
                       : context.convertRvalueExpression(*elementExpr);
        if (!v)
          return failure();
        converted.push_back(v);
      }
    } else { // hasPerElem, individual type is expected for each element
      auto types = std::get<ArrayRef<Type>>(expectedTypes);
      for (size_t i = 0; i < elementCount; ++i) {
        Type want = types[i];
        const auto *elementExpr = elts[i];
        Value v = want ? context.convertRvalueExpression(*elementExpr, want)
                       : context.convertRvalueExpression(*elementExpr);
        if (!v)
          return failure();
        converted.push_back(v);
      }
    }
 
    for (unsigned i = 1; i < replCount; ++i)
      converted.append(converted.begin(), converted.begin() + elementCount);
 
    return converted;
  }
 
  /// Handle assignment patterns.
  Value visitAssignmentPattern(
      const slang::ast::AssignmentPatternExpressionBase &expr,
      unsigned replCount = 1) {
    auto type = context.convertType(*expr.type);
    const auto &elts = expr.elements();
 
    // Handle integers.
    if (auto intType = dyn_cast<moore::IntType>(type)) {
      auto elements = convertElements(expr, {}, replCount);
 
      if (failed(elements))
        return {};
 
      assert(intType.getWidth() == elements->size());
      std::reverse(elements->begin(), elements->end());
      return moore::ConcatOp::create(builder, loc, intType, *elements);
    }
 
    // Handle packed structs.
    if (auto structType = dyn_cast<moore::StructType>(type)) {
      SmallVector<Type> expectedTy;
      expectedTy.reserve(structType.getMembers().size());
      for (auto member : structType.getMembers())
        expectedTy.push_back(member.type);
 
      FailureOr<SmallVector<Value>> elements;
      if (expectedTy.size() == elts.size())
        elements = convertElements(expr, expectedTy, replCount);
      else
        elements = convertElements(expr, {}, replCount);
 
      if (failed(elements))
        return {};
 
      assert(structType.getMembers().size() == elements->size());
      return moore::StructCreateOp::create(builder, loc, structType, *elements);
    }
 
    // Handle unpacked structs.
    if (auto structType = dyn_cast<moore::UnpackedStructType>(type)) {
      SmallVector<Type> expectedTy;
      expectedTy.reserve(structType.getMembers().size());
      for (auto member : structType.getMembers())
        expectedTy.push_back(member.type);
 
      FailureOr<SmallVector<Value>> elements;
      if (expectedTy.size() == elts.size())
        elements = convertElements(expr, expectedTy, replCount);
      else
        elements = convertElements(expr, {}, replCount);
 
      if (failed(elements))
        return {};
 
      assert(structType.getMembers().size() == elements->size());
 
      return moore::StructCreateOp::create(builder, loc, structType, *elements);
    }
 
    // Handle packed arrays.
    if (auto arrayType = dyn_cast<moore::ArrayType>(type)) {
      auto elements =
          convertElements(expr, arrayType.getElementType(), replCount);
 
      if (failed(elements))
        return {};
 
      assert(arrayType.getSize() == elements->size());
      return moore::ArrayCreateOp::create(builder, loc, arrayType, *elements);
    }
 
    // Handle unpacked arrays.
    if (auto arrayType = dyn_cast<moore::UnpackedArrayType>(type)) {
      auto elements =
          convertElements(expr, arrayType.getElementType(), replCount);
 
      if (failed(elements))
        return {};
 
      assert(arrayType.getSize() == elements->size());
      return moore::ArrayCreateOp::create(builder, loc, arrayType, *elements);
    }
 
    mlir::emitError(loc) << "unsupported assignment pattern with type " << type;
    return {};
  }
 
  Value visit(const slang::ast::SimpleAssignmentPatternExpression &expr) {
    return visitAssignmentPattern(expr);
  }
 
  Value visit(const slang::ast::StructuredAssignmentPatternExpression &expr) {
    return visitAssignmentPattern(expr);
  }
 
  Value visit(const slang::ast::ReplicatedAssignmentPatternExpression &expr) {
    auto count =
        context.evaluateConstant(expr.count()).integer().as<unsigned>();
    assert(count && "Slang guarantees constant non-zero replication count");
    return visitAssignmentPattern(expr, *count);
  }
 
  Value visit(const slang::ast::StreamingConcatenationExpression &expr) {
    SmallVector<Value> operands;
    for (auto stream : expr.streams()) {
      auto operandLoc = context.convertLocation(stream.operand->sourceRange);
      if (!stream.constantWithWidth.has_value() && stream.withExpr) {
        mlir::emitError(operandLoc)
            << "Moore only support streaming "
               "concatenation with fixed size 'with expression'";
        return {};
      }
      Value value;
      if (stream.constantWithWidth.has_value()) {
        value = context.convertRvalueExpression(*stream.withExpr);
        auto type = cast<moore::UnpackedType>(value.getType());
        auto intType = moore::IntType::get(
            context.getContext(), type.getBitSize().value(), type.getDomain());
        // Do not care if it's signed, because we will not do expansion.
        value = context.materializeConversion(intType, value, false, loc);
      } else {
        value = context.convertRvalueExpression(*stream.operand);
      }
 
      value = context.convertToSimpleBitVector(value);
      if (!value)
        return {};
      operands.push_back(value);
    }
    Value value;
 
    if (operands.size() == 1) {
      // There must be at least one element, otherwise slang will report an
      // error.
      value = operands.front();
    } else {
      value = moore::ConcatOp::create(builder, loc, operands).getResult();
    }
 
    if (expr.getSliceSize() == 0) {
      return value;
    }
 
    auto type = cast<moore::IntType>(value.getType());
    SmallVector<Value> slicedOperands;
    auto iterMax = type.getWidth() / expr.getSliceSize();
    auto remainSize = type.getWidth() % expr.getSliceSize();
 
    for (size_t i = 0; i < iterMax; i++) {
      auto extractResultType = moore::IntType::get(
          context.getContext(), expr.getSliceSize(), type.getDomain());
 
      auto extracted = moore::ExtractOp::create(builder, loc, extractResultType,
                                                value, i * expr.getSliceSize());
      slicedOperands.push_back(extracted);
    }
    // Handle other wire
    if (remainSize) {
      auto extractResultType = moore::IntType::get(
          context.getContext(), remainSize, type.getDomain());
 
      auto extracted =
          moore::ExtractOp::create(builder, loc, extractResultType, value,
                                   iterMax * expr.getSliceSize());
      slicedOperands.push_back(extracted);
    }
 
    return moore::ConcatOp::create(builder, loc, slicedOperands);
  }
 
  Value visit(const slang::ast::AssertionInstanceExpression &expr) {
    return context.convertAssertionExpression(expr.body, loc);
  }
 
  /// Emit an error for all other expressions.
  template <typename T>
  Value visit(T &&node) {
    mlir::emitError(loc, "unsupported expression: ")
        << slang::ast::toString(node.kind);
    return {};
  }
 
  Value visitInvalid(const slang::ast::Expression &expr) {
    mlir::emitError(loc, "invalid expression");
    return {};
  }
};
} // namespace
 
//===----------------------------------------------------------------------===//
// Lvalue Conversion
//===----------------------------------------------------------------------===//
 
namespace {
struct LvalueExprVisitor : public ExprVisitor {
  LvalueExprVisitor(Context &context, Location loc)
      : ExprVisitor(context, loc, /*isLvalue=*/true) {}
  using ExprVisitor::visit;
 
  // Handle named values, such as references to declared variables.
  Value visit(const slang::ast::NamedValueExpression &expr) {
    if (auto value = context.valueSymbols.lookup(&expr.symbol))
      return value;
    auto d = mlir::emitError(loc, "unknown name `") << expr.symbol.name << "`";
    d.attachNote(context.convertLocation(expr.symbol.location))
        << "no lvalue generated for " << slang::ast::toString(expr.symbol.kind);
    return {};
  }
 
  // Handle hierarchical values, such as `Top.sub.var = x`.
  Value visit(const slang::ast::HierarchicalValueExpression &expr) {
    if (auto value = context.valueSymbols.lookup(&expr.symbol))
      return value;
 
    // Emit an error for those hierarchical values not recorded in the
    // `valueSymbols`.
    auto d = mlir::emitError(loc, "unknown hierarchical name `")
             << expr.symbol.name << "`";
    d.attachNote(context.convertLocation(expr.symbol.location))
        << "no lvalue generated for " << slang::ast::toString(expr.symbol.kind);
    return {};
  }
 
  Value visit(const slang::ast::StreamingConcatenationExpression &expr) {
    SmallVector<Value> operands;
    for (auto stream : expr.streams()) {
      auto operandLoc = context.convertLocation(stream.operand->sourceRange);
      if (!stream.constantWithWidth.has_value() && stream.withExpr) {
        mlir::emitError(operandLoc)
            << "Moore only support streaming "
               "concatenation with fixed size 'with expression'";
        return {};
      }
      Value value;
      if (stream.constantWithWidth.has_value()) {
        value = context.convertLvalueExpression(*stream.withExpr);
        auto type = cast<moore::UnpackedType>(
            cast<moore::RefType>(value.getType()).getNestedType());
        auto intType = moore::RefType::get(moore::IntType::get(
            context.getContext(), type.getBitSize().value(), type.getDomain()));
        // Do not care if it's signed, because we will not do expansion.
        value = context.materializeConversion(intType, value, false, loc);
      } else {
        value = context.convertLvalueExpression(*stream.operand);
      }
 
      if (!value)
        return {};
      operands.push_back(value);
    }
    Value value;
    if (operands.size() == 1) {
      // There must be at least one element, otherwise slang will report an
      // error.
      value = operands.front();
    } else {
      value = moore::ConcatRefOp::create(builder, loc, operands).getResult();
    }
 
    if (expr.getSliceSize() == 0) {
      return value;
    }
 
    auto type = cast<moore::IntType>(
        cast<moore::RefType>(value.getType()).getNestedType());
    SmallVector<Value> slicedOperands;
    auto widthSum = type.getWidth();
    auto domain = type.getDomain();
    auto iterMax = widthSum / expr.getSliceSize();
    auto remainSize = widthSum % expr.getSliceSize();
 
    for (size_t i = 0; i < iterMax; i++) {
      auto extractResultType = moore::RefType::get(moore::IntType::get(
          context.getContext(), expr.getSliceSize(), domain));
 
      auto extracted = moore::ExtractRefOp::create(
          builder, loc, extractResultType, value, i * expr.getSliceSize());
      slicedOperands.push_back(extracted);
    }
    // Handle other wire
    if (remainSize) {
      auto extractResultType = moore::RefType::get(
          moore::IntType::get(context.getContext(), remainSize, domain));
 
      auto extracted =
          moore::ExtractRefOp::create(builder, loc, extractResultType, value,
                                      iterMax * expr.getSliceSize());
      slicedOperands.push_back(extracted);
    }
 
    return moore::ConcatRefOp::create(builder, loc, slicedOperands);
  }
 
  /// Emit an error for all other expressions.
  template <typename T>
  Value visit(T &&node) {
    return context.convertRvalueExpression(node);
  }
 
  Value visitInvalid(const slang::ast::Expression &expr) {
    mlir::emitError(loc, "invalid expression");
    return {};
  }
};
} // namespace
 
//===----------------------------------------------------------------------===//
// Entry Points
//===----------------------------------------------------------------------===//
 
Value Context::convertRvalueExpression(const slang::ast::Expression &expr,
                                       Type requiredType) {
  auto loc = convertLocation(expr.sourceRange);
  auto value = expr.visit(RvalueExprVisitor(*this, loc));
  if (value && requiredType)
    value =
        materializeConversion(requiredType, value, expr.type->isSigned(), loc);
  return value;
}
 
Value Context::convertLvalueExpression(const slang::ast::Expression &expr) {
  auto loc = convertLocation(expr.sourceRange);
  return expr.visit(LvalueExprVisitor(*this, loc));
}
// NOLINTEND(misc-no-recursion)
 
/// Helper function to convert a value to its "truthy" boolean value.
Value Context::convertToBool(Value value) {
  if (!value)
    return {};
  if (auto type = dyn_cast_or_null<moore::IntType>(value.getType()))
    if (type.getBitSize() == 1)
      return value;
  if (auto type = dyn_cast_or_null<moore::UnpackedType>(value.getType()))
    return moore::BoolCastOp::create(builder, value.getLoc(), value);
  mlir::emitError(value.getLoc(), "expression of type ")
      << value.getType() << " cannot be cast to a boolean";
  return {};
}
 
/// Materialize a Slang integer literal as a constant op.
Value Context::materializeSVInt(const slang::SVInt &svint,
                                const slang::ast::Type &astType, Location loc) {
  auto type = convertType(astType);
  if (!type)
    return {};
 
  bool typeIsFourValued = false;
  if (auto unpackedType = dyn_cast<moore::UnpackedType>(type))
    typeIsFourValued = unpackedType.getDomain() == moore::Domain::FourValued;
 
  auto fvint = convertSVIntToFVInt(svint);
  auto intType = moore::IntType::get(getContext(), fvint.getBitWidth(),
                                     fvint.hasUnknown() || typeIsFourValued
                                         ? moore::Domain::FourValued
                                         : moore::Domain::TwoValued);
  auto result = moore::ConstantOp::create(builder, loc, intType, fvint);
  return materializeConversion(type, result, astType.isSigned(), loc);
}
 
Value Context::materializeFixedSizeUnpackedArrayType(
    const slang::ConstantValue &constant,
    const slang::ast::FixedSizeUnpackedArrayType &astType, Location loc) {
 
  auto type = convertType(astType);
  if (!type)
    return {};
 
  // Check whether underlying type is an integer, if so, get bit width
  unsigned bitWidth;
  if (astType.elementType.isIntegral())
    bitWidth = astType.elementType.getBitWidth();
  else
    return {};
 
  bool typeIsFourValued = false;
 
  // Check whether the underlying type is four-valued
  if (auto unpackedType = dyn_cast<moore::UnpackedType>(type))
    typeIsFourValued = unpackedType.getDomain() == moore::Domain::FourValued;
  else
    return {};
 
  auto domain =
      typeIsFourValued ? moore::Domain::FourValued : moore::Domain::TwoValued;
 
  // Construct the integer type this is an unpacked array of; if possible keep
  // it two-valued, unless any entry is four-valued or the underlying type is
  // four-valued
  auto intType = moore::IntType::get(getContext(), bitWidth, domain);
  // Construct the full array type from intType
  auto arrType = moore::UnpackedArrayType::get(
      getContext(), constant.elements().size(), intType);
 
  llvm::SmallVector<mlir::Value> elemVals;
  moore::ConstantOp constOp;
 
  mlir::OpBuilder::InsertionGuard guard(builder);
 
  // Add one ConstantOp for every element in the array
  for (auto elem : constant.elements()) {
    FVInt fvInt = convertSVIntToFVInt(elem.integer());
    constOp = moore::ConstantOp::create(builder, loc, intType, fvInt);
    elemVals.push_back(constOp.getResult());
  }
 
  // Take the result of each ConstantOp and concatenate them into an array (of
  // constant values).
  auto arrayOp = moore::ArrayCreateOp::create(builder, loc, arrType, elemVals);
 
  return arrayOp.getResult();
}
 
Value Context::materializeConstant(const slang::ConstantValue &constant,
                                   const slang::ast::Type &type, Location loc) {
 
  if (auto *arr = type.as_if<slang::ast::FixedSizeUnpackedArrayType>())
    return materializeFixedSizeUnpackedArrayType(constant, *arr, loc);
  if (constant.isInteger())
    return materializeSVInt(constant.integer(), type, loc);
 
  return {};
}
 
slang::ConstantValue
Context::evaluateConstant(const slang::ast::Expression &expr) {
  using slang::ast::EvalFlags;
  slang::ast::EvalContext evalContext(
      slang::ast::ASTContext(compilation.getRoot(),
                             slang::ast::LookupLocation::max),
      EvalFlags::CacheResults | EvalFlags::SpecparamsAllowed);
  return expr.eval(evalContext);
}
 
/// Helper function to convert a value to its "truthy" boolean value and
/// convert it to the given domain.
Value Context::convertToBool(Value value, Domain domain) {
  value = convertToBool(value);
  if (!value)
    return {};
  auto type = moore::IntType::get(getContext(), 1, domain);
  return materializeConversion(type, value, false, value.getLoc());
}
 
Value Context::convertToSimpleBitVector(Value value) {
  if (!value)
    return {};
  if (isa<moore::IntType>(value.getType()))
    return value;
 
  // Some operations in Slang's AST, for example bitwise or `|`, don't cast
  // packed struct/array operands to simple bit vectors but directly operate
  // on the struct/array. Since the corresponding IR ops operate only on
  // simple bit vectors, insert a conversion in this case.
  if (auto packed = dyn_cast<moore::PackedType>(value.getType()))
    if (auto sbvType = packed.getSimpleBitVector())
      return materializeConversion(sbvType, value, false, value.getLoc());
 
  mlir::emitError(value.getLoc()) << "expression of type " << value.getType()
                                  << " cannot be cast to a simple bit vector";
  return {};
}
 
/// Create the necessary operations to convert from a `PackedType` to the
/// corresponding simple bit vector `IntType`. This will apply special handling
/// to time values, which requires scaling by the local timescale.
static Value materializePackedToSBVConversion(Context &context, Value value,
                                              Location loc) {
  if (isa<moore::IntType>(value.getType()))
    return value;
 
  auto &builder = context.builder;
  auto packedType = cast<moore::PackedType>(value.getType());
  auto intType = packedType.getSimpleBitVector();
  assert(intType);
 
  // If we are converting from a time to an integer, divide the integer by the
  // timescale.
  if (isa<moore::TimeType>(packedType) &&
      moore::isIntType(intType, 64, moore::Domain::FourValued)) {
    value = builder.createOrFold<moore::TimeToLogicOp>(loc, value);
    auto scale = moore::ConstantOp::create(builder, loc, intType,
                                           getTimeScaleInFemtoseconds(context));
    return builder.createOrFold<moore::DivUOp>(loc, value, scale);
  }
 
  // If this is an aggregate type, make sure that it does not contain any
  // `TimeType` fields. These require special conversion to ensure that the
  // local timescale is in effect.
  if (packedType.containsTimeType()) {
    mlir::emitError(loc) << "unsupported conversion: " << packedType
                         << " cannot be converted to " << intType
                         << "; contains a time type";
    return {};
  }
 
  // Otherwise create a simple `PackedToSBVOp` for the conversion.
  return builder.createOrFold<moore::PackedToSBVOp>(loc, value);
}
 
/// Create the necessary operations to convert from a simple bit vector
/// `IntType` to an equivalent `PackedType`. This will apply special handling to
/// time values, which requires scaling by the local timescale.
static Value materializeSBVToPackedConversion(Context &context,
                                              moore::PackedType packedType,
                                              Value value, Location loc) {
  if (value.getType() == packedType)
    return value;
 
  auto &builder = context.builder;
  auto intType = cast<moore::IntType>(value.getType());
  assert(intType && intType == packedType.getSimpleBitVector());
 
  // If we are converting from an integer to a time, multiply the integer by the
  // timescale.
  if (isa<moore::TimeType>(packedType) &&
      moore::isIntType(intType, 64, moore::Domain::FourValued)) {
    auto scale = moore::ConstantOp::create(builder, loc, intType,
                                           getTimeScaleInFemtoseconds(context));
    value = builder.createOrFold<moore::MulOp>(loc, value, scale);
    return builder.createOrFold<moore::LogicToTimeOp>(loc, value);
  }
 
  // If this is an aggregate type, make sure that it does not contain any
  // `TimeType` fields. These require special conversion to ensure that the
  // local timescale is in effect.
  if (packedType.containsTimeType()) {
    mlir::emitError(loc) << "unsupported conversion: " << intType
                         << " cannot be converted to " << packedType
                         << "; contains a time type";
    return {};
  }
 
  // Otherwise create a simple `PackedToSBVOp` for the conversion.
  return builder.createOrFold<moore::SBVToPackedOp>(loc, packedType, value);
}
 
Value Context::materializeConversion(Type type, Value value, bool isSigned,
                                     Location loc) {
  // Nothing to do if the types are already equal.
  if (type == value.getType())
    return value;
 
  // Handle packed types which can be converted to a simple bit vector. This
  // allows us to perform resizing and domain casting on that bit vector.
  auto dstPacked = dyn_cast<moore::PackedType>(type);
  auto srcPacked = dyn_cast<moore::PackedType>(value.getType());
  auto dstInt = dstPacked ? dstPacked.getSimpleBitVector() : moore::IntType();
  auto srcInt = srcPacked ? srcPacked.getSimpleBitVector() : moore::IntType();
 
  if (dstInt && srcInt) {
    // Convert the value to a simple bit vector if it isn't one already.
    value = materializePackedToSBVConversion(*this, value, loc);
    if (!value)
      return {};
 
    // Create truncation or sign/zero extension ops depending on the source and
    // destination width.
    auto resizedType = moore::IntType::get(
        value.getContext(), dstInt.getWidth(), srcPacked.getDomain());
    if (dstInt.getWidth() < srcInt.getWidth()) {
      value = builder.createOrFold<moore::TruncOp>(loc, resizedType, value);
    } else if (dstInt.getWidth() > srcInt.getWidth()) {
      if (isSigned)
        value = builder.createOrFold<moore::SExtOp>(loc, resizedType, value);
      else
        value = builder.createOrFold<moore::ZExtOp>(loc, resizedType, value);
    }
 
    // Convert the domain if needed.
    if (dstInt.getDomain() != srcInt.getDomain()) {
      if (dstInt.getDomain() == moore::Domain::TwoValued)
        value = builder.createOrFold<moore::LogicToIntOp>(loc, value);
      else if (dstInt.getDomain() == moore::Domain::FourValued)
        value = builder.createOrFold<moore::IntToLogicOp>(loc, value);
    }
 
    // Convert the value from a simple bit vector back to the packed type.
    value = materializeSBVToPackedConversion(*this, dstPacked, value, loc);
    if (!value)
      return {};
 
    assert(value.getType() == type);
    return value;
  }
 
  // Convert from FormatStringType to StringType
  if (isa<moore::StringType>(type) &&
      isa<moore::FormatStringType>(value.getType())) {
    return builder.createOrFold<moore::FormatStringToStringOp>(loc, value);
  }
 
  // Convert from StringType to FormatStringType
  if (isa<moore::FormatStringType>(type) &&
      isa<moore::StringType>(value.getType())) {
    return builder.createOrFold<moore::FormatStringOp>(loc, value);
  }
 
  // TODO: Handle other conversions with dedicated ops.
  if (value.getType() != type)
    value = moore::ConversionOp::create(builder, loc, type, value);
  return value;
}
 
FailureOr<Value>
Context::convertSystemCallArity0(const slang::ast::SystemSubroutine &subroutine,
                                 Location loc) {
 
  auto systemCallRes =
      llvm::StringSwitch<std::function<FailureOr<Value>()>>(subroutine.name)
          .Case("$urandom",
                [&]() -> Value {
                  return moore::UrandomBIOp::create(builder, loc, nullptr);
                })
          .Case("$random",
                [&]() -> Value {
                  return moore::RandomBIOp::create(builder, loc, nullptr);
                })
          .Case(
              "$time",
              [&]() -> Value { return moore::TimeBIOp::create(builder, loc); })
          .Case(
              "$stime",
              [&]() -> Value { return moore::TimeBIOp::create(builder, loc); })
          .Case(
              "$realtime",
              [&]() -> Value { return moore::TimeBIOp::create(builder, loc); })
          .Default([&]() -> Value { return {}; });
  return systemCallRes();
}
 
FailureOr<Value>
Context::convertSystemCallArity1(const slang::ast::SystemSubroutine &subroutine,
                                 Location loc, Value value) {
  auto systemCallRes =
      llvm::StringSwitch<std::function<FailureOr<Value>()>>(subroutine.name)
          // Signed and unsigned system functions.
          .Case("$signed", [&]() { return value; })
          .Case("$unsigned", [&]() { return value; })
 
          // Math functions in SystemVerilog.
          .Case("$clog2",
                [&]() -> FailureOr<Value> {
                  value = convertToSimpleBitVector(value);
                  if (!value)
                    return failure();
                  return (Value)moore::Clog2BIOp::create(builder, loc, value);
                })
          .Case("$ln",
                [&]() -> Value {
                  return moore::LnBIOp::create(builder, loc, value);
                })
          .Case("$log10",
                [&]() -> Value {
                  return moore::Log10BIOp::create(builder, loc, value);
                })
          .Case("$sin",
                [&]() -> Value {
                  return moore::SinBIOp::create(builder, loc, value);
                })
          .Case("$cos",
                [&]() -> Value {
                  return moore::CosBIOp::create(builder, loc, value);
                })
          .Case("$tan",
                [&]() -> Value {
                  return moore::TanBIOp::create(builder, loc, value);
                })
          .Case("$exp",
                [&]() -> Value {
                  return moore::ExpBIOp::create(builder, loc, value);
                })
          .Case("$sqrt",
                [&]() -> Value {
                  return moore::SqrtBIOp::create(builder, loc, value);
                })
          .Case("$floor",
                [&]() -> Value {
                  return moore::FloorBIOp::create(builder, loc, value);
                })
          .Case("$ceil",
                [&]() -> Value {
                  return moore::CeilBIOp::create(builder, loc, value);
                })
          .Case("$asin",
                [&]() -> Value {
                  return moore::AsinBIOp::create(builder, loc, value);
                })
          .Case("$acos",
                [&]() -> Value {
                  return moore::AcosBIOp::create(builder, loc, value);
                })
          .Case("$atan",
                [&]() -> Value {
                  return moore::AtanBIOp::create(builder, loc, value);
                })
          .Case("$sinh",
                [&]() -> Value {
                  return moore::SinhBIOp::create(builder, loc, value);
                })
          .Case("$cosh",
                [&]() -> Value {
                  return moore::CoshBIOp::create(builder, loc, value);
                })
          .Case("$tanh",
                [&]() -> Value {
                  return moore::TanhBIOp::create(builder, loc, value);
                })
          .Case("$asinh",
                [&]() -> Value {
                  return moore::AsinhBIOp::create(builder, loc, value);
                })
          .Case("$acosh",
                [&]() -> Value {
                  return moore::AcoshBIOp::create(builder, loc, value);
                })
          .Case("$atanh",
                [&]() -> Value {
                  return moore::AtanhBIOp::create(builder, loc, value);
                })
          .Case("$urandom",
                [&]() -> Value {
                  return moore::UrandomBIOp::create(builder, loc, value);
                })
          .Case("$random",
                [&]() -> Value {
                  return moore::RandomBIOp::create(builder, loc, value);
                })
          .Case("$realtobits",
                [&]() -> Value {
                  return moore::RealtobitsBIOp::create(builder, loc, value);
                })
          .Case("$bitstoreal",
                [&]() -> Value {
                  return moore::BitstorealBIOp::create(builder, loc, value);
                })
          .Case("$shortrealtobits",
                [&]() -> Value {
                  return moore::ShortrealtobitsBIOp::create(builder, loc,
                                                            value);
                })
          .Case("$bitstoshortreal",
                [&]() -> Value {
                  return moore::BitstoshortrealBIOp::create(builder, loc,
                                                            value);
                })
          .Default([&]() -> Value { return {}; });
  return systemCallRes();
}