FIRRTLFolds.cpp

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//===- FIRRTLFolds.cpp - Implement folds and canonicalizations for ops ----===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implement the folding and canonicalizations for FIRRTL ops.
//
//===----------------------------------------------------------------------===//
 
#include "circt/Dialect/FIRRTL/FIRRTLAttributes.h"
#include "circt/Dialect/FIRRTL/FIRRTLOps.h"
#include "circt/Dialect/FIRRTL/FIRRTLTypes.h"
#include "circt/Dialect/FIRRTL/FIRRTLUtils.h"
#include "circt/Support/APInt.h"
#include "circt/Support/LLVM.h"
#include "circt/Support/Naming.h"
#include "mlir/IR/Matchers.h"
#include "mlir/IR/PatternMatch.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/TypeSwitch.h"
 
using namespace circt;
using namespace firrtl;
 
// Drop writes to old and pass through passthrough to make patterns easier to
// write.
static Value dropWrite(PatternRewriter &rewriter, OpResult old,
                       Value passthrough) {
  SmallPtrSet<Operation *, 8> users;
  for (auto *user : old.getUsers())
    users.insert(user);
  for (Operation *user : users)
    if (auto connect = dyn_cast<FConnectLike>(user))
      if (connect.getDest() == old)
        rewriter.eraseOp(user);
  return passthrough;
}
 
// Move a name hint from a soon to be deleted operation to a new operation.
// Pass through the new operation to make patterns easier to write.  This cannot
// move a name to a port (block argument), doing so would require rewriting all
// instance sites as well as the module.
static Value moveNameHint(OpResult old, Value passthrough) {
  Operation *op = passthrough.getDefiningOp();
  // This should handle ports, but it isn't clear we can change those in
  // canonicalizers.
  assert(op && "passthrough must be an operation");
  Operation *oldOp = old.getOwner();
  auto name = oldOp->getAttrOfType<StringAttr>("name");
  if (name && !name.getValue().empty())
    op->setAttr("name", name);
  return passthrough;
}
 
// Declarative canonicalization patterns
namespace circt {
namespace firrtl {
namespace patterns {
#include "circt/Dialect/FIRRTL/FIRRTLCanonicalization.h.inc"
} // namespace patterns
} // namespace firrtl
} // namespace circt
 
/// Return true if this operation's operands and results all have a known width.
/// This only works for integer types.
static bool hasKnownWidthIntTypes(Operation *op) {
  auto resultType = type_cast<IntType>(op->getResult(0).getType());
  if (!resultType.hasWidth())
    return false;
  for (Value operand : op->getOperands())
    if (!type_cast<IntType>(operand.getType()).hasWidth())
      return false;
  return true;
}
 
/// Return true if this value is 1 bit UInt.
static bool isUInt1(Type type) {
  auto t = type_dyn_cast<UIntType>(type);
  if (!t || !t.hasWidth() || t.getWidth() != 1)
    return false;
  return true;
}
 
/// Set the name of an op based on the best of two names:  The current name, and
/// the name passed in.
static void updateName(PatternRewriter &rewriter, Operation *op,
                       StringAttr name) {
  // Should never rename InstanceOp
  assert(!isa<InstanceOp>(op));
  if (!name || name.getValue().empty())
    return;
  auto newName = name.getValue(); // old name is interesting
  auto newOpName = op->getAttrOfType<StringAttr>("name");
  // new name might not be interesting
  if (newOpName)
    newName = chooseName(newOpName.getValue(), name.getValue());
  // Only update if needed
  if (!newOpName || newOpName.getValue() != newName)
    rewriter.modifyOpInPlace(
        op, [&] { op->setAttr("name", rewriter.getStringAttr(newName)); });
}
 
/// A wrapper of `PatternRewriter::replaceOp` to propagate "name" attribute.
/// If a replaced op has a "name" attribute, this function propagates the name
/// to the new value.
static void replaceOpAndCopyName(PatternRewriter &rewriter, Operation *op,
                                 Value newValue) {
  if (auto *newOp = newValue.getDefiningOp()) {
    auto name = op->getAttrOfType<StringAttr>("name");
    updateName(rewriter, newOp, name);
  }
  rewriter.replaceOp(op, newValue);
}
 
/// A wrapper of `PatternRewriter::replaceOpWithNewOp` to propagate "name"
/// attribute. If a replaced op has a "name" attribute, this function propagates
/// the name to the new value.
template <typename OpTy, typename... Args>
static OpTy replaceOpWithNewOpAndCopyName(PatternRewriter &rewriter,
                                          Operation *op, Args &&...args) {
  auto name = op->getAttrOfType<StringAttr>("name");
  auto newOp =
      rewriter.replaceOpWithNewOp<OpTy>(op, std::forward<Args>(args)...);
  updateName(rewriter, newOp, name);
  return newOp;
}
 
/// Return true if the name is droppable. Note that this is different from
/// `isUselessName` because non-useless names may be also droppable.
bool circt::firrtl::hasDroppableName(Operation *op) {
  if (auto namableOp = dyn_cast<firrtl::FNamableOp>(op))
    return namableOp.hasDroppableName();
  return false;
}
 
/// Implicitly replace the operand to a constant folding operation with a const
/// 0 in case the operand is non-constant but has a bit width 0, or if the
/// operand is an invalid value.
///
/// This makes constant folding significantly easier, as we can simply pass the
/// operands to an operation through this function to appropriately replace any
/// zero-width dynamic values or invalid values with a constant of value 0.
static std::optional<APSInt>
getExtendedConstant(Value operand, Attribute constant, int32_t destWidth) {
  assert(type_cast<IntType>(operand.getType()) &&
         "getExtendedConstant is limited to integer types");
 
  // We never support constant folding to unknown width values.
  if (destWidth < 0)
    return {};
 
  // Extension signedness follows the operand sign.
  if (IntegerAttr result = dyn_cast_or_null<IntegerAttr>(constant))
    return extOrTruncZeroWidth(result.getAPSInt(), destWidth);
 
  // If the operand is zero bits, then we can return a zero of the result
  // type.
  if (type_cast<IntType>(operand.getType()).getWidth() == 0)
    return APSInt(destWidth,
                  type_cast<IntType>(operand.getType()).isUnsigned());
  return {};
}
 
/// Determine the value of a constant operand for the sake of constant folding.
static std::optional<APSInt> getConstant(Attribute operand) {
  if (!operand)
    return {};
  if (auto attr = dyn_cast<BoolAttr>(operand))
    return APSInt(APInt(1, attr.getValue()));
  if (auto attr = dyn_cast<IntegerAttr>(operand))
    return attr.getAPSInt();
  return {};
}
 
/// Determine whether a constant operand is a zero value for the sake of
/// constant folding. This considers `invalidvalue` to be zero.
static bool isConstantZero(Attribute operand) {
  if (auto cst = getConstant(operand))
    return cst->isZero();
  return false;
}
 
/// Determine whether a constant operand is a one value for the sake of constant
/// folding.
static bool isConstantOne(Attribute operand) {
  if (auto cst = getConstant(operand))
    return cst->isOne();
  return false;
}
 
/// This is the policy for folding, which depends on the sort of operator we're
/// processing.
enum class BinOpKind {
  Normal,
  Compare,
  DivideOrShift,
};
 
/// Applies the constant folding function `calculate` to the given operands.
///
/// Sign or zero extends the operands appropriately to the bitwidth of the
/// result type if \p useDstWidth is true, else to the larger of the two operand
/// bit widths and depending on whether the operation is to be performed on
/// signed or unsigned operands.
static Attribute constFoldFIRRTLBinaryOp(
    Operation *op, ArrayRef<Attribute> operands, BinOpKind opKind,
    const function_ref<APInt(const APSInt &, const APSInt &)> &calculate) {
  assert(operands.size() == 2 && "binary op takes two operands");
 
  // We cannot fold something to an unknown width.
  auto resultType = type_cast<IntType>(op->getResult(0).getType());
  if (resultType.getWidthOrSentinel() < 0)
    return {};
 
  // Any binary op returning i0 is 0.
  if (resultType.getWidthOrSentinel() == 0)
    return getIntAttr(resultType, APInt(0, 0, resultType.isSigned()));
 
  // Determine the operand widths. This is either dictated by the operand type,
  // or if that type is an unsized integer, by the actual bits necessary to
  // represent the constant value.
  auto lhsWidth =
      type_cast<IntType>(op->getOperand(0).getType()).getWidthOrSentinel();
  auto rhsWidth =
      type_cast<IntType>(op->getOperand(1).getType()).getWidthOrSentinel();
  if (auto lhs = dyn_cast_or_null<IntegerAttr>(operands[0]))
    lhsWidth = std::max<int32_t>(lhsWidth, lhs.getValue().getBitWidth());
  if (auto rhs = dyn_cast_or_null<IntegerAttr>(operands[1]))
    rhsWidth = std::max<int32_t>(rhsWidth, rhs.getValue().getBitWidth());
 
  // Compares extend the operands to the widest of the operand types, not to the
  // result type.
  int32_t operandWidth;
  switch (opKind) {
  case BinOpKind::Normal:
    operandWidth = resultType.getWidthOrSentinel();
    break;
  case BinOpKind::Compare:
    // Compares compute with the widest operand, not at the destination type
    // (which is always i1).
    operandWidth = std::max(1, std::max(lhsWidth, rhsWidth));
    break;
  case BinOpKind::DivideOrShift:
    operandWidth =
        std::max(std::max(lhsWidth, rhsWidth), resultType.getWidthOrSentinel());
    break;
  }
 
  auto lhs = getExtendedConstant(op->getOperand(0), operands[0], operandWidth);
  if (!lhs)
    return {};
  auto rhs = getExtendedConstant(op->getOperand(1), operands[1], operandWidth);
  if (!rhs)
    return {};
 
  APInt resultValue = calculate(*lhs, *rhs);
 
  // If the result type is smaller than the computation then we need to
  // narrow the constant after the calculation.
  if (opKind == BinOpKind::DivideOrShift)
    resultValue = resultValue.trunc(resultType.getWidthOrSentinel());
 
  assert((unsigned)resultType.getWidthOrSentinel() ==
         resultValue.getBitWidth());
  return getIntAttr(resultType, resultValue);
}
 
/// Applies the canonicalization function `canonicalize` to the given operation.
///
/// Determines which (if any) of the operation's operands are constants, and
/// provides them as arguments to the callback function. Any `invalidvalue` in
/// the input is mapped to a constant zero. The value returned from the callback
/// is used as the replacement for `op`, and an additional pad operation is
/// inserted if necessary. Does nothing if the result of `op` is of unknown
/// width, in which case the necessity of a pad cannot be determined.
static LogicalResult canonicalizePrimOp(
    Operation *op, PatternRewriter &rewriter,
    const function_ref<OpFoldResult(ArrayRef<Attribute>)> &canonicalize) {
  // Can only operate on FIRRTL primitive operations.
  if (op->getNumResults() != 1)
    return failure();
  auto type = type_dyn_cast<FIRRTLBaseType>(op->getResult(0).getType());
  if (!type)
    return failure();
 
  // Can only operate on operations with a known result width.
  auto width = type.getBitWidthOrSentinel();
  if (width < 0)
    return failure();
 
  // Determine which of the operands are constants.
  SmallVector<Attribute, 3> constOperands;
  constOperands.reserve(op->getNumOperands());
  for (auto operand : op->getOperands()) {
    Attribute attr;
    if (auto *defOp = operand.getDefiningOp())
      TypeSwitch<Operation *>(defOp).Case<ConstantOp, SpecialConstantOp>(
          [&](auto op) { attr = op.getValueAttr(); });
    constOperands.push_back(attr);
  }
 
  // Perform the canonicalization and materialize the result if it is a
  // constant.
  auto result = canonicalize(constOperands);
  if (!result)
    return failure();
  Value resultValue;
  if (auto cst = dyn_cast<Attribute>(result))
    resultValue = op->getDialect()
                      ->materializeConstant(rewriter, cst, type, op->getLoc())
                      ->getResult(0);
  else
    resultValue = cast<Value>(result);
 
  // Insert a pad if the type widths disagree.
  if (width !=
      type_cast<FIRRTLBaseType>(resultValue.getType()).getBitWidthOrSentinel())
    resultValue = rewriter.create<PadPrimOp>(op->getLoc(), resultValue, width);
 
  // Insert a cast if this is a uint vs. sint or vice versa.
  if (type_isa<SIntType>(type) && type_isa<UIntType>(resultValue.getType()))
    resultValue = rewriter.create<AsSIntPrimOp>(op->getLoc(), resultValue);
  else if (type_isa<UIntType>(type) &&
           type_isa<SIntType>(resultValue.getType()))
    resultValue = rewriter.create<AsUIntPrimOp>(op->getLoc(), resultValue);
 
  assert(type == resultValue.getType() && "canonicalization changed type");
  replaceOpAndCopyName(rewriter, op, resultValue);
  return success();
}
 
/// Get the largest unsigned value of a given bit width. Returns a 1-bit zero
/// value if `bitWidth` is 0.
static APInt getMaxUnsignedValue(unsigned bitWidth) {
  return bitWidth > 0 ? APInt::getMaxValue(bitWidth) : APInt();
}
 
/// Get the smallest signed value of a given bit width. Returns a 1-bit zero
/// value if `bitWidth` is 0.
static APInt getMinSignedValue(unsigned bitWidth) {
  return bitWidth > 0 ? APInt::getSignedMinValue(bitWidth) : APInt();
}
 
/// Get the largest signed value of a given bit width. Returns a 1-bit zero
/// value if `bitWidth` is 0.
static APInt getMaxSignedValue(unsigned bitWidth) {
  return bitWidth > 0 ? APInt::getSignedMaxValue(bitWidth) : APInt();
}
 
//===----------------------------------------------------------------------===//
// Fold Hooks
//===----------------------------------------------------------------------===//
 
OpFoldResult ConstantOp::fold(FoldAdaptor adaptor) {
  assert(adaptor.getOperands().empty() && "constant has no operands");
  return getValueAttr();
}
 
OpFoldResult SpecialConstantOp::fold(FoldAdaptor adaptor) {
  assert(adaptor.getOperands().empty() && "constant has no operands");
  return getValueAttr();
}
 
OpFoldResult AggregateConstantOp::fold(FoldAdaptor adaptor) {
  assert(adaptor.getOperands().empty() && "constant has no operands");
  return getFieldsAttr();
}
 
OpFoldResult StringConstantOp::fold(FoldAdaptor adaptor) {
  assert(adaptor.getOperands().empty() && "constant has no operands");
  return getValueAttr();
}
 
OpFoldResult FIntegerConstantOp::fold(FoldAdaptor adaptor) {
  assert(adaptor.getOperands().empty() && "constant has no operands");
  return getValueAttr();
}
 
OpFoldResult BoolConstantOp::fold(FoldAdaptor adaptor) {
  assert(adaptor.getOperands().empty() && "constant has no operands");
  return getValueAttr();
}
 
OpFoldResult DoubleConstantOp::fold(FoldAdaptor adaptor) {
  assert(adaptor.getOperands().empty() && "constant has no operands");
  return getValueAttr();
}
 
//===----------------------------------------------------------------------===//
// Binary Operators
//===----------------------------------------------------------------------===//
 
OpFoldResult AddPrimOp::fold(FoldAdaptor adaptor) {
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Normal,
      [=](const APSInt &a, const APSInt &b) { return a + b; });
}
 
void AddPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::moveConstAdd, patterns::AddOfZero,
                 patterns::AddOfSelf, patterns::AddOfPad>(context);
}
 
OpFoldResult SubPrimOp::fold(FoldAdaptor adaptor) {
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Normal,
      [=](const APSInt &a, const APSInt &b) { return a - b; });
}
 
void SubPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::SubOfZero, patterns::SubFromZeroSigned,
                 patterns::SubFromZeroUnsigned, patterns::SubOfSelf,
                 patterns::SubOfPadL, patterns::SubOfPadR>(context);
}
 
OpFoldResult MulPrimOp::fold(FoldAdaptor adaptor) {
  // mul(x, 0) -> 0
  //
  // This is legal because it aligns with the Scala FIRRTL Compiler
  // interpretation of lowering invalid to constant zero before constant
  // propagation.  Note: the Scala FIRRTL Compiler does NOT currently optimize
  // multiplication this way and will emit "x * 0".
  if (isConstantZero(adaptor.getRhs()) || isConstantZero(adaptor.getLhs()))
    return getIntZerosAttr(getType());
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Normal,
      [=](const APSInt &a, const APSInt &b) { return a * b; });
}
 
OpFoldResult DivPrimOp::fold(FoldAdaptor adaptor) {
  /// div(x, x) -> 1
  ///
  /// Division by zero is undefined in the FIRRTL specification.  This fold
  /// exploits that fact to optimize self division to one.  Note: this should
  /// supersede any division with invalid or zero.  Division of invalid by
  /// invalid should be one.
  if (getLhs() == getRhs()) {
    auto width = getType().base().getWidthOrSentinel();
    if (width == -1)
      width = 2;
    // Only fold if we have at least 1 bit of width to represent the `1` value.
    if (width != 0)
      return getIntAttr(getType(), APInt(width, 1));
  }
 
  // div(0, x) -> 0
  //
  // This is legal because it aligns with the Scala FIRRTL Compiler
  // interpretation of lowering invalid to constant zero before constant
  // propagation.  Note: the Scala FIRRTL Compiler does NOT currently optimize
  // division this way and will emit "0 / x".
  if (isConstantZero(adaptor.getLhs()) && !isConstantZero(adaptor.getRhs()))
    return getIntZerosAttr(getType());
 
  /// div(x, 1) -> x : (uint, uint) -> uint
  ///
  /// UInt division by one returns the numerator. SInt division can't
  /// be folded here because it increases the return type bitwidth by
  /// one and requires sign extension (a new op).
  if (auto rhsCst = dyn_cast_or_null<IntegerAttr>(adaptor.getRhs()))
    if (rhsCst.getValue().isOne() && getLhs().getType() == getType())
      return getLhs();
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::DivideOrShift,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        if (!!b)
          return a / b;
        return APInt(a.getBitWidth(), 0);
      });
}
 
OpFoldResult RemPrimOp::fold(FoldAdaptor adaptor) {
  // rem(x, x) -> 0
  //
  // Division by zero is undefined in the FIRRTL specification.  This fold
  // exploits that fact to optimize self division remainder to zero.  Note:
  // this should supersede any division with invalid or zero.  Remainder of
  // division of invalid by invalid should be zero.
  if (getLhs() == getRhs())
    return getIntZerosAttr(getType());
 
  // rem(0, x) -> 0
  //
  // This is legal because it aligns with the Scala FIRRTL Compiler
  // interpretation of lowering invalid to constant zero before constant
  // propagation.  Note: the Scala FIRRTL Compiler does NOT currently optimize
  // division this way and will emit "0 % x".
  if (isConstantZero(adaptor.getLhs()))
    return getIntZerosAttr(getType());
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::DivideOrShift,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        if (!!b)
          return a % b;
        return APInt(a.getBitWidth(), 0);
      });
}
 
OpFoldResult DShlPrimOp::fold(FoldAdaptor adaptor) {
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::DivideOrShift,
      [=](const APSInt &a, const APSInt &b) -> APInt { return a.shl(b); });
}
 
OpFoldResult DShlwPrimOp::fold(FoldAdaptor adaptor) {
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::DivideOrShift,
      [=](const APSInt &a, const APSInt &b) -> APInt { return a.shl(b); });
}
 
OpFoldResult DShrPrimOp::fold(FoldAdaptor adaptor) {
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::DivideOrShift,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        return getType().base().isUnsigned() || !a.getBitWidth() ? a.lshr(b)
                                                                 : a.ashr(b);
      });
}
 
// TODO: Move to DRR.
OpFoldResult AndPrimOp::fold(FoldAdaptor adaptor) {
  if (auto rhsCst = getConstant(adaptor.getRhs())) {
    /// and(x, 0) -> 0, 0 is largest or is implicit zero extended
    if (rhsCst->isZero())
      return getIntZerosAttr(getType());
 
    /// and(x, -1) -> x
    if (rhsCst->isAllOnes() && getLhs().getType() == getType() &&
        getRhs().getType() == getType())
      return getLhs();
  }
 
  if (auto lhsCst = getConstant(adaptor.getLhs())) {
    /// and(0, x) -> 0, 0 is largest or is implicit zero extended
    if (lhsCst->isZero())
      return getIntZerosAttr(getType());
 
    /// and(-1, x) -> x
    if (lhsCst->isAllOnes() && getLhs().getType() == getType() &&
        getRhs().getType() == getType())
      return getRhs();
  }
 
  /// and(x, x) -> x
  if (getLhs() == getRhs() && getRhs().getType() == getType())
    return getRhs();
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Normal,
      [](const APSInt &a, const APSInt &b) -> APInt { return a & b; });
}
 
void AndPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results
      .insert<patterns::extendAnd, patterns::moveConstAnd, patterns::AndOfZero,
              patterns::AndOfAllOne, patterns::AndOfSelf, patterns::AndOfPad,
              patterns::AndOfAsSIntL, patterns::AndOfAsSIntR>(context);
}
 
OpFoldResult OrPrimOp::fold(FoldAdaptor adaptor) {
  if (auto rhsCst = getConstant(adaptor.getRhs())) {
    /// or(x, 0) -> x
    if (rhsCst->isZero() && getLhs().getType() == getType())
      return getLhs();
 
    /// or(x, -1) -> -1
    if (rhsCst->isAllOnes() && getRhs().getType() == getType() &&
        getLhs().getType() == getType())
      return getRhs();
  }
 
  if (auto lhsCst = getConstant(adaptor.getLhs())) {
    /// or(0, x) -> x
    if (lhsCst->isZero() && getRhs().getType() == getType())
      return getRhs();
 
    /// or(-1, x) -> -1
    if (lhsCst->isAllOnes() && getLhs().getType() == getType() &&
        getRhs().getType() == getType())
      return getLhs();
  }
 
  /// or(x, x) -> x
  if (getLhs() == getRhs() && getRhs().getType() == getType())
    return getRhs();
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Normal,
      [](const APSInt &a, const APSInt &b) -> APInt { return a | b; });
}
 
void OrPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                           MLIRContext *context) {
  results.insert<patterns::extendOr, patterns::moveConstOr, patterns::OrOfZero,
                 patterns::OrOfAllOne, patterns::OrOfSelf, patterns::OrOfPad,
                 patterns::OrOrr>(context);
}
 
OpFoldResult XorPrimOp::fold(FoldAdaptor adaptor) {
  /// xor(x, 0) -> x
  if (auto rhsCst = getConstant(adaptor.getRhs()))
    if (rhsCst->isZero() &&
        firrtl::areAnonymousTypesEquivalent(getLhs().getType(), getType()))
      return getLhs();
 
  /// xor(x, 0) -> x
  if (auto lhsCst = getConstant(adaptor.getLhs()))
    if (lhsCst->isZero() &&
        firrtl::areAnonymousTypesEquivalent(getRhs().getType(), getType()))
      return getRhs();
 
  /// xor(x, x) -> 0
  if (getLhs() == getRhs())
    return getIntAttr(
        getType(),
        APInt(std::max(getType().base().getWidthOrSentinel(), 0), 0));
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Normal,
      [](const APSInt &a, const APSInt &b) -> APInt { return a ^ b; });
}
 
void XorPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::extendXor, patterns::moveConstXor,
                 patterns::XorOfZero, patterns::XorOfSelf, patterns::XorOfPad>(
      context);
}
 
void LEQPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::LEQWithConstLHS>(context);
}
 
OpFoldResult LEQPrimOp::fold(FoldAdaptor adaptor) {
  bool isUnsigned = getLhs().getType().base().isUnsigned();
 
  // leq(x, x) -> 1
  if (getLhs() == getRhs())
    return getIntAttr(getType(), APInt(1, 1));
 
  // Comparison against constant outside type bounds.
  if (auto width = getLhs().getType().base().getWidth()) {
    if (auto rhsCst = getConstant(adaptor.getRhs())) {
      auto commonWidth = std::max<int32_t>(*width, rhsCst->getBitWidth());
      commonWidth = std::max(commonWidth, 1);
 
      // leq(x, const) -> 0 where const < minValue of the unsigned type of x
      // This can never occur since const is unsigned and cannot be less than 0.
 
      // leq(x, const) -> 0 where const < minValue of the signed type of x
      if (!isUnsigned && sextZeroWidth(*rhsCst, commonWidth)
                             .slt(getMinSignedValue(*width).sext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 0));
 
      // leq(x, const) -> 1 where const >= maxValue of the unsigned type of x
      if (isUnsigned && rhsCst->zext(commonWidth)
                            .uge(getMaxUnsignedValue(*width).zext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 1));
 
      // leq(x, const) -> 1 where const >= maxValue of the signed type of x
      if (!isUnsigned && sextZeroWidth(*rhsCst, commonWidth)
                             .sge(getMaxSignedValue(*width).sext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 1));
    }
  }
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Compare,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        return APInt(1, a <= b);
      });
}
 
void LTPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                           MLIRContext *context) {
  results.insert<patterns::LTWithConstLHS>(context);
}
 
OpFoldResult LTPrimOp::fold(FoldAdaptor adaptor) {
  IntType lhsType = getLhs().getType();
  bool isUnsigned = lhsType.isUnsigned();
 
  // lt(x, x) -> 0
  if (getLhs() == getRhs())
    return getIntAttr(getType(), APInt(1, 0));
 
  // lt(x, 0) -> 0 when x is unsigned
  if (auto rhsCst = getConstant(adaptor.getRhs())) {
    if (rhsCst->isZero() && lhsType.isUnsigned())
      return getIntAttr(getType(), APInt(1, 0));
  }
 
  // Comparison against constant outside type bounds.
  if (auto width = lhsType.getWidth()) {
    if (auto rhsCst = getConstant(adaptor.getRhs())) {
      auto commonWidth = std::max<int32_t>(*width, rhsCst->getBitWidth());
      commonWidth = std::max(commonWidth, 1);
 
      // lt(x, const) -> 0 where const <= minValue of the unsigned type of x
      // Handled explicitly above.
 
      // lt(x, const) -> 0 where const <= minValue of the signed type of x
      if (!isUnsigned && sextZeroWidth(*rhsCst, commonWidth)
                             .sle(getMinSignedValue(*width).sext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 0));
 
      // lt(x, const) -> 1 where const > maxValue of the unsigned type of x
      if (isUnsigned && rhsCst->zext(commonWidth)
                            .ugt(getMaxUnsignedValue(*width).zext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 1));
 
      // lt(x, const) -> 1 where const > maxValue of the signed type of x
      if (!isUnsigned && sextZeroWidth(*rhsCst, commonWidth)
                             .sgt(getMaxSignedValue(*width).sext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 1));
    }
  }
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Compare,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        return APInt(1, a < b);
      });
}
 
void GEQPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::GEQWithConstLHS>(context);
}
 
OpFoldResult GEQPrimOp::fold(FoldAdaptor adaptor) {
  IntType lhsType = getLhs().getType();
  bool isUnsigned = lhsType.isUnsigned();
 
  // geq(x, x) -> 1
  if (getLhs() == getRhs())
    return getIntAttr(getType(), APInt(1, 1));
 
  // geq(x, 0) -> 1 when x is unsigned
  if (auto rhsCst = getConstant(adaptor.getRhs())) {
    if (rhsCst->isZero() && isUnsigned)
      return getIntAttr(getType(), APInt(1, 1));
  }
 
  // Comparison against constant outside type bounds.
  if (auto width = lhsType.getWidth()) {
    if (auto rhsCst = getConstant(adaptor.getRhs())) {
      auto commonWidth = std::max<int32_t>(*width, rhsCst->getBitWidth());
      commonWidth = std::max(commonWidth, 1);
 
      // geq(x, const) -> 0 where const > maxValue of the unsigned type of x
      if (isUnsigned && rhsCst->zext(commonWidth)
                            .ugt(getMaxUnsignedValue(*width).zext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 0));
 
      // geq(x, const) -> 0 where const > maxValue of the signed type of x
      if (!isUnsigned && sextZeroWidth(*rhsCst, commonWidth)
                             .sgt(getMaxSignedValue(*width).sext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 0));
 
      // geq(x, const) -> 1 where const <= minValue of the unsigned type of x
      // Handled explicitly above.
 
      // geq(x, const) -> 1 where const <= minValue of the signed type of x
      if (!isUnsigned && sextZeroWidth(*rhsCst, commonWidth)
                             .sle(getMinSignedValue(*width).sext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 1));
    }
  }
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Compare,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        return APInt(1, a >= b);
      });
}
 
void GTPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                           MLIRContext *context) {
  results.insert<patterns::GTWithConstLHS>(context);
}
 
OpFoldResult GTPrimOp::fold(FoldAdaptor adaptor) {
  IntType lhsType = getLhs().getType();
  bool isUnsigned = lhsType.isUnsigned();
 
  // gt(x, x) -> 0
  if (getLhs() == getRhs())
    return getIntAttr(getType(), APInt(1, 0));
 
  // Comparison against constant outside type bounds.
  if (auto width = lhsType.getWidth()) {
    if (auto rhsCst = getConstant(adaptor.getRhs())) {
      auto commonWidth = std::max<int32_t>(*width, rhsCst->getBitWidth());
      commonWidth = std::max(commonWidth, 1);
 
      // gt(x, const) -> 0 where const >= maxValue of the unsigned type of x
      if (isUnsigned && rhsCst->zext(commonWidth)
                            .uge(getMaxUnsignedValue(*width).zext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 0));
 
      // gt(x, const) -> 0 where const >= maxValue of the signed type of x
      if (!isUnsigned && sextZeroWidth(*rhsCst, commonWidth)
                             .sge(getMaxSignedValue(*width).sext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 0));
 
      // gt(x, const) -> 1 where const < minValue of the unsigned type of x
      // This can never occur since const is unsigned and cannot be less than 0.
 
      // gt(x, const) -> 1 where const < minValue of the signed type of x
      if (!isUnsigned && sextZeroWidth(*rhsCst, commonWidth)
                             .slt(getMinSignedValue(*width).sext(commonWidth)))
        return getIntAttr(getType(), APInt(1, 1));
    }
  }
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Compare,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        return APInt(1, a > b);
      });
}
 
OpFoldResult EQPrimOp::fold(FoldAdaptor adaptor) {
  // eq(x, x) -> 1
  if (getLhs() == getRhs())
    return getIntAttr(getType(), APInt(1, 1));
 
  if (auto rhsCst = getConstant(adaptor.getRhs())) {
    /// eq(x, 1) -> x when x is 1 bit.
    /// TODO: Support SInt<1> on the LHS etc.
    if (rhsCst->isAllOnes() && getLhs().getType() == getType() &&
        getRhs().getType() == getType())
      return getLhs();
  }
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Compare,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        return APInt(1, a == b);
      });
}
 
LogicalResult EQPrimOp::canonicalize(EQPrimOp op, PatternRewriter &rewriter) {
  return canonicalizePrimOp(
      op, rewriter, [&](ArrayRef<Attribute> operands) -> OpFoldResult {
        if (auto rhsCst = getConstant(operands[1])) {
          auto width = op.getLhs().getType().getBitWidthOrSentinel();
 
          // eq(x, 0) ->  not(x) when x is 1 bit.
          if (rhsCst->isZero() && op.getLhs().getType() == op.getType() &&
              op.getRhs().getType() == op.getType()) {
            return rewriter.create<NotPrimOp>(op.getLoc(), op.getLhs())
                .getResult();
          }
 
          // eq(x, 0) -> not(orr(x)) when x is >1 bit
          if (rhsCst->isZero() && width > 1) {
            auto orrOp = rewriter.create<OrRPrimOp>(op.getLoc(), op.getLhs());
            return rewriter.create<NotPrimOp>(op.getLoc(), orrOp).getResult();
          }
 
          // eq(x, ~0) -> andr(x) when x is >1 bit
          if (rhsCst->isAllOnes() && width > 1 &&
              op.getLhs().getType() == op.getRhs().getType()) {
            return rewriter.create<AndRPrimOp>(op.getLoc(), op.getLhs())
                .getResult();
          }
        }
        return {};
      });
}
 
OpFoldResult NEQPrimOp::fold(FoldAdaptor adaptor) {
  // neq(x, x) -> 0
  if (getLhs() == getRhs())
    return getIntAttr(getType(), APInt(1, 0));
 
  if (auto rhsCst = getConstant(adaptor.getRhs())) {
    /// neq(x, 0) -> x when x is 1 bit.
    /// TODO: Support SInt<1> on the LHS etc.
    if (rhsCst->isZero() && getLhs().getType() == getType() &&
        getRhs().getType() == getType())
      return getLhs();
  }
 
  return constFoldFIRRTLBinaryOp(
      *this, adaptor.getOperands(), BinOpKind::Compare,
      [=](const APSInt &a, const APSInt &b) -> APInt {
        return APInt(1, a != b);
      });
}
 
LogicalResult NEQPrimOp::canonicalize(NEQPrimOp op, PatternRewriter &rewriter) {
  return canonicalizePrimOp(
      op, rewriter, [&](ArrayRef<Attribute> operands) -> OpFoldResult {
        if (auto rhsCst = getConstant(operands[1])) {
          auto width = op.getLhs().getType().getBitWidthOrSentinel();
 
          // neq(x, 1) -> not(x) when x is 1 bit
          if (rhsCst->isAllOnes() && op.getLhs().getType() == op.getType() &&
              op.getRhs().getType() == op.getType()) {
            return rewriter.create<NotPrimOp>(op.getLoc(), op.getLhs())
                .getResult();
          }
 
          // neq(x, 0) -> orr(x) when x is >1 bit
          if (rhsCst->isZero() && width > 1) {
            return rewriter.create<OrRPrimOp>(op.getLoc(), op.getLhs())
                .getResult();
          }
 
          // neq(x, ~0) -> not(andr(x))) when x is >1 bit
          if (rhsCst->isAllOnes() && width > 1 &&
              op.getLhs().getType() == op.getRhs().getType()) {
            auto andrOp = rewriter.create<AndRPrimOp>(op.getLoc(), op.getLhs());
            return rewriter.create<NotPrimOp>(op.getLoc(), andrOp).getResult();
          }
        }
 
        return {};
      });
}
 
OpFoldResult IntegerAddOp::fold(FoldAdaptor adaptor) {
  // TODO: implement constant folding, etc.
  // Tracked in https://github.com/llvm/circt/issues/6696.
  return {};
}
 
OpFoldResult IntegerMulOp::fold(FoldAdaptor adaptor) {
  // TODO: implement constant folding, etc.
  // Tracked in https://github.com/llvm/circt/issues/6724.
  return {};
}
 
OpFoldResult IntegerShrOp::fold(FoldAdaptor adaptor) {
  // TODO: implement constant folding, etc.
  // Tracked in https://github.com/llvm/circt/issues/6725.
  return {};
}
 
OpFoldResult IntegerShlOp::fold(FoldAdaptor adaptor) {
  if (auto rhsCst = getConstant(adaptor.getRhs())) {
    // Constant folding
    if (auto lhsCst = getConstant(adaptor.getLhs()))
 
      return IntegerAttr::get(
          IntegerType::get(getContext(), lhsCst->getBitWidth()),
          lhsCst->shl(*rhsCst));
 
    // integer.shl(x, 0) -> x
    if (rhsCst->isZero())
      return getLhs();
  }
 
  return {};
}
 
//===----------------------------------------------------------------------===//
// Unary Operators
//===----------------------------------------------------------------------===//
 
OpFoldResult SizeOfIntrinsicOp::fold(FoldAdaptor) {
  auto base = getInput().getType();
  auto w = getBitWidth(base);
  if (w)
    return getIntAttr(getType(), APInt(32, *w));
  return {};
}
 
OpFoldResult IsXIntrinsicOp::fold(FoldAdaptor adaptor) {
  // No constant can be 'x' by definition.
  if (auto cst = getConstant(adaptor.getArg()))
    return getIntAttr(getType(), APInt(1, 0));
  return {};
}
 
OpFoldResult AsSIntPrimOp::fold(FoldAdaptor adaptor) {
  // No effect.
  if (areAnonymousTypesEquivalent(getInput().getType(), getType()))
    return getInput();
 
  // Be careful to only fold the cast into the constant if the size is known.
  // Otherwise width inference may produce differently-sized constants if the
  // sign changes.
  if (getType().base().hasWidth())
    if (auto cst = getConstant(adaptor.getInput()))
      return getIntAttr(getType(), *cst);
 
  return {};
}
 
void AsSIntPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                               MLIRContext *context) {
  results.insert<patterns::StoUtoS>(context);
}
 
OpFoldResult AsUIntPrimOp::fold(FoldAdaptor adaptor) {
  // No effect.
  if (areAnonymousTypesEquivalent(getInput().getType(), getType()))
    return getInput();
 
  // Be careful to only fold the cast into the constant if the size is known.
  // Otherwise width inference may produce differently-sized constants if the
  // sign changes.
  if (getType().base().hasWidth())
    if (auto cst = getConstant(adaptor.getInput()))
      return getIntAttr(getType(), *cst);
 
  return {};
}
 
void AsUIntPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                               MLIRContext *context) {
  results.insert<patterns::UtoStoU>(context);
}
 
OpFoldResult AsAsyncResetPrimOp::fold(FoldAdaptor adaptor) {
  // No effect.
  if (getInput().getType() == getType())
    return getInput();
 
  // Constant fold.
  if (auto cst = getConstant(adaptor.getInput()))
    return BoolAttr::get(getContext(), cst->getBoolValue());
 
  return {};
}
 
OpFoldResult AsClockPrimOp::fold(FoldAdaptor adaptor) {
  // No effect.
  if (getInput().getType() == getType())
    return getInput();
 
  // Constant fold.
  if (auto cst = getConstant(adaptor.getInput()))
    return BoolAttr::get(getContext(), cst->getBoolValue());
 
  return {};
}
 
OpFoldResult CvtPrimOp::fold(FoldAdaptor adaptor) {
  if (!hasKnownWidthIntTypes(*this))
    return {};
 
  // Signed to signed is a noop, unsigned operands prepend a zero bit.
  if (auto cst = getExtendedConstant(getOperand(), adaptor.getInput(),
                                     getType().base().getWidthOrSentinel()))
    return getIntAttr(getType(), *cst);
 
  return {};
}
 
void CvtPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::CVTSigned, patterns::CVTUnSigned>(context);
}
 
OpFoldResult NegPrimOp::fold(FoldAdaptor adaptor) {
  if (!hasKnownWidthIntTypes(*this))
    return {};
 
  // FIRRTL negate always adds a bit.
  // -x ---> 0-sext(x) or 0-zext(x)
  if (auto cst = getExtendedConstant(getOperand(), adaptor.getInput(),
                                     getType().base().getWidthOrSentinel()))
    return getIntAttr(getType(), APInt((*cst).getBitWidth(), 0) - *cst);
 
  return {};
}
 
OpFoldResult NotPrimOp::fold(FoldAdaptor adaptor) {
  if (!hasKnownWidthIntTypes(*this))
    return {};
 
  if (auto cst = getExtendedConstant(getOperand(), adaptor.getInput(),
                                     getType().base().getWidthOrSentinel()))
    return getIntAttr(getType(), ~*cst);
 
  return {};
}
 
void NotPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::NotNot, patterns::NotEq, patterns::NotNeq,
                 patterns::NotLeq, patterns::NotLt, patterns::NotGeq,
                 patterns::NotGt>(context);
}
 
OpFoldResult AndRPrimOp::fold(FoldAdaptor adaptor) {
  if (!hasKnownWidthIntTypes(*this))
    return {};
 
  if (getInput().getType().getBitWidthOrSentinel() == 0)
    return getIntAttr(getType(), APInt(1, 1));
 
  // x == -1
  if (auto cst = getConstant(adaptor.getInput()))
    return getIntAttr(getType(), APInt(1, cst->isAllOnes()));
 
  // one bit is identity.  Only applies to UInt since we can't make a cast
  // here.
  if (isUInt1(getInput().getType()))
    return getInput();
 
  return {};
}
 
void AndRPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results
      .insert<patterns::AndRasSInt, patterns::AndRasUInt, patterns::AndRPadU,
              patterns::AndRPadS, patterns::AndRCatOneL, patterns::AndRCatOneR,
              patterns::AndRCatZeroL, patterns::AndRCatZeroR,
              patterns::AndRCatAndR_left, patterns::AndRCatAndR_right>(context);
}
 
OpFoldResult OrRPrimOp::fold(FoldAdaptor adaptor) {
  if (!hasKnownWidthIntTypes(*this))
    return {};
 
  if (getInput().getType().getBitWidthOrSentinel() == 0)
    return getIntAttr(getType(), APInt(1, 0));
 
  // x != 0
  if (auto cst = getConstant(adaptor.getInput()))
    return getIntAttr(getType(), APInt(1, !cst->isZero()));
 
  // one bit is identity.  Only applies to UInt since we can't make a cast
  // here.
  if (isUInt1(getInput().getType()))
    return getInput();
 
  return {};
}
 
void OrRPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::OrRasSInt, patterns::OrRasUInt, patterns::OrRPadU,
                 patterns::OrRCatZeroH, patterns::OrRCatZeroL,
                 patterns::OrRCatOrR_left, patterns::OrRCatOrR_right>(context);
}
 
OpFoldResult XorRPrimOp::fold(FoldAdaptor adaptor) {
  if (!hasKnownWidthIntTypes(*this))
    return {};
 
  if (getInput().getType().getBitWidthOrSentinel() == 0)
    return getIntAttr(getType(), APInt(1, 0));
 
  // popcount(x) & 1
  if (auto cst = getConstant(adaptor.getInput()))
    return getIntAttr(getType(), APInt(1, cst->popcount() & 1));
 
  // one bit is identity.  Only applies to UInt since we can't make a cast here.
  if (isUInt1(getInput().getType()))
    return getInput();
 
  return {};
}
 
void XorRPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results.insert<patterns::XorRasSInt, patterns::XorRasUInt, patterns::XorRPadU,
                 patterns::XorRCatZeroH, patterns::XorRCatZeroL,
                 patterns::XorRCatXorR_left, patterns::XorRCatXorR_right>(
      context);
}
 
//===----------------------------------------------------------------------===//
// Other Operators
//===----------------------------------------------------------------------===//
 
OpFoldResult CatPrimOp::fold(FoldAdaptor adaptor) {
  // cat(x, 0-width) -> x
  // cat(0-width, x) -> x
  // Limit to unsigned (result type), as cannot insert cast here.
  IntType lhsType = getLhs().getType();
  IntType rhsType = getRhs().getType();
  if (lhsType.getBitWidthOrSentinel() == 0 && rhsType.isUnsigned())
    return getRhs();
  if (rhsType.getBitWidthOrSentinel() == 0 && rhsType.isUnsigned())
    return getLhs();
 
  if (!hasKnownWidthIntTypes(*this))
    return {};
 
  // Constant fold cat.
  if (auto lhs = getConstant(adaptor.getLhs()))
    if (auto rhs = getConstant(adaptor.getRhs()))
      return getIntAttr(getType(), lhs->concat(*rhs));
 
  return {};
}
 
void DShlPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results.insert<patterns::DShlOfConstant>(context);
}
 
void DShrPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results.insert<patterns::DShrOfConstant>(context);
}
 
void CatPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::CatBitsBits, patterns::CatDoubleConst,
                 patterns::CatCast>(context);
}
 
OpFoldResult BitCastOp::fold(FoldAdaptor adaptor) {
  auto op = (*this);
  // BitCast is redundant if input and result types are same.
  if (op.getType() == op.getInput().getType())
    return op.getInput();
 
  // Two consecutive BitCasts are redundant if first bitcast type is same as the
  // final result type.
  if (BitCastOp in = dyn_cast_or_null<BitCastOp>(op.getInput().getDefiningOp()))
    if (op.getType() == in.getInput().getType())
      return in.getInput();
 
  return {};
}
 
OpFoldResult BitsPrimOp::fold(FoldAdaptor adaptor) {
  IntType inputType = getInput().getType();
  IntType resultType = getType();
  // If we are extracting the entire input, then return it.
  if (inputType == getType() && resultType.hasWidth())
    return getInput();
 
  // Constant fold.
  if (hasKnownWidthIntTypes(*this))
    if (auto cst = getConstant(adaptor.getInput()))
      return getIntAttr(resultType,
                        cst->extractBits(getHi() - getLo() + 1, getLo()));
 
  return {};
}
 
void BitsPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results
      .insert<patterns::BitsOfBits, patterns::BitsOfMux, patterns::BitsOfAsUInt,
              patterns::BitsOfAnd, patterns::BitsOfPad>(context);
}
 
/// Replace the specified operation with a 'bits' op from the specified hi/lo
/// bits.  Insert a cast to handle the case where the original operation
/// returned a signed integer.
static void replaceWithBits(Operation *op, Value value, unsigned hiBit,
                            unsigned loBit, PatternRewriter &rewriter) {
  auto resType = type_cast<IntType>(op->getResult(0).getType());
  if (type_cast<IntType>(value.getType()).getWidth() != resType.getWidth())
    value = rewriter.create<BitsPrimOp>(op->getLoc(), value, hiBit, loBit);
 
  if (resType.isSigned() && !type_cast<IntType>(value.getType()).isSigned()) {
    value = rewriter.createOrFold<AsSIntPrimOp>(op->getLoc(), resType, value);
  } else if (resType.isUnsigned() &&
             !type_cast<IntType>(value.getType()).isUnsigned()) {
    value = rewriter.createOrFold<AsUIntPrimOp>(op->getLoc(), resType, value);
  }
  rewriter.replaceOp(op, value);
}
 
template <typename OpTy>
static OpFoldResult foldMux(OpTy op, typename OpTy::FoldAdaptor adaptor) {
  // mux : UInt<0> -> 0
  if (op.getType().getBitWidthOrSentinel() == 0)
    return getIntAttr(op.getType(),
                      APInt(0, 0, op.getType().isSignedInteger()));
 
  // mux(cond, x, x) -> x
  if (op.getHigh() == op.getLow() && op.getHigh().getType() == op.getType())
    return op.getHigh();
 
  // The following folds require that the result has a known width. Otherwise
  // the mux requires an additional padding operation to be inserted, which is
  // not possible in a fold.
  if (op.getType().getBitWidthOrSentinel() < 0)
    return {};
 
  // mux(0/1, x, y) -> x or y
  if (auto cond = getConstant(adaptor.getSel())) {
    if (cond->isZero() && op.getLow().getType() == op.getType())
      return op.getLow();
    if (!cond->isZero() && op.getHigh().getType() == op.getType())
      return op.getHigh();
  }
 
  // mux(cond, x, cst)
  if (auto lowCst = getConstant(adaptor.getLow())) {
    // mux(cond, c1, c2)
    if (auto highCst = getConstant(adaptor.getHigh())) {
      // mux(cond, cst, cst) -> cst
      if (highCst->getBitWidth() == lowCst->getBitWidth() &&
          *highCst == *lowCst)
        return getIntAttr(op.getType(), *highCst);
      // mux(cond, 1, 0) -> cond
      if (highCst->isOne() && lowCst->isZero() &&
          op.getType() == op.getSel().getType())
        return op.getSel();
 
      // TODO: x ? ~0 : 0 -> sext(x)
      // TODO: "x ? c1 : c2" -> many tricks
    }
    // TODO: "x ? a : 0" -> sext(x) & a
  }
 
  // TODO: "x ? c1 : y" -> "~x ? y : c1"
  return {};
}
 
OpFoldResult MuxPrimOp::fold(FoldAdaptor adaptor) {
  return foldMux(*this, adaptor);
}
 
OpFoldResult Mux2CellIntrinsicOp::fold(FoldAdaptor adaptor) {
  return foldMux(*this, adaptor);
}
 
OpFoldResult Mux4CellIntrinsicOp::fold(FoldAdaptor adaptor) { return {}; }
 
namespace {
 
// If the mux has a known output width, pad the operands up to this width.
// Most folds on mux require that folded operands are of the same width as
// the mux itself.
class MuxPad : public mlir::RewritePattern {
public:
  MuxPad(MLIRContext *context)
      : RewritePattern(MuxPrimOp::getOperationName(), 0, context) {}
 
  LogicalResult
  matchAndRewrite(Operation *op,
                  mlir::PatternRewriter &rewriter) const override {
    auto mux = cast<MuxPrimOp>(op);
    auto width = mux.getType().getBitWidthOrSentinel();
    if (width < 0)
      return failure();
 
    auto pad = [&](Value input) -> Value {
      auto inputWidth =
          type_cast<FIRRTLBaseType>(input.getType()).getBitWidthOrSentinel();
      if (inputWidth < 0 || width == inputWidth)
        return input;
      return rewriter
          .create<PadPrimOp>(mux.getLoc(), mux.getType(), input, width)
          .getResult();
    };
 
    auto newHigh = pad(mux.getHigh());
    auto newLow = pad(mux.getLow());
    if (newHigh == mux.getHigh() && newLow == mux.getLow())
      return failure();
 
    replaceOpWithNewOpAndCopyName<MuxPrimOp>(
        rewriter, op, mux.getType(), ValueRange{mux.getSel(), newHigh, newLow},
        mux->getAttrs());
    return success();
  }
};
 
// Find muxes which have conditions dominated by other muxes with the same
// condition.
class MuxSharedCond : public mlir::RewritePattern {
public:
  MuxSharedCond(MLIRContext *context)
      : RewritePattern(MuxPrimOp::getOperationName(), 0, context) {}
 
  static const int depthLimit = 5;
 
  Value updateOrClone(MuxPrimOp mux, Value high, Value low,
                      mlir::PatternRewriter &rewriter,
                      bool updateInPlace) const {
    if (updateInPlace) {
      rewriter.modifyOpInPlace(mux, [&] {
        mux.setOperand(1, high);
        mux.setOperand(2, low);
      });
      return {};
    }
    rewriter.setInsertionPointAfter(mux);
    return rewriter
        .create<MuxPrimOp>(mux.getLoc(), mux.getType(),
                           ValueRange{mux.getSel(), high, low})
        .getResult();
  }
 
  // Walk a dependent mux tree assuming the condition cond is true.
  Value tryCondTrue(Value op, Value cond, mlir::PatternRewriter &rewriter,
                    bool updateInPlace, int limit) const {
    MuxPrimOp mux = op.getDefiningOp<MuxPrimOp>();
    if (!mux)
      return {};
    if (mux.getSel() == cond)
      return mux.getHigh();
    if (limit > depthLimit)
      return {};
    updateInPlace &= mux->hasOneUse();
 
    if (Value v = tryCondTrue(mux.getHigh(), cond, rewriter, updateInPlace,
                              limit + 1))
      return updateOrClone(mux, v, mux.getLow(), rewriter, updateInPlace);
 
    if (Value v =
            tryCondTrue(mux.getLow(), cond, rewriter, updateInPlace, limit + 1))
      return updateOrClone(mux, mux.getHigh(), v, rewriter, updateInPlace);
    return {};
  }
 
  // Walk a dependent mux tree assuming the condition cond is false.
  Value tryCondFalse(Value op, Value cond, mlir::PatternRewriter &rewriter,
                     bool updateInPlace, int limit) const {
    MuxPrimOp mux = op.getDefiningOp<MuxPrimOp>();
    if (!mux)
      return {};
    if (mux.getSel() == cond)
      return mux.getLow();
    if (limit > depthLimit)
      return {};
    updateInPlace &= mux->hasOneUse();
 
    if (Value v = tryCondFalse(mux.getHigh(), cond, rewriter, updateInPlace,
                               limit + 1))
      return updateOrClone(mux, v, mux.getLow(), rewriter, updateInPlace);
 
    if (Value v = tryCondFalse(mux.getLow(), cond, rewriter, updateInPlace,
                               limit + 1))
      return updateOrClone(mux, mux.getHigh(), v, rewriter, updateInPlace);
 
    return {};
  }
 
  LogicalResult
  matchAndRewrite(Operation *op,
                  mlir::PatternRewriter &rewriter) const override {
    auto mux = cast<MuxPrimOp>(op);
    auto width = mux.getType().getBitWidthOrSentinel();
    if (width < 0)
      return failure();
 
    if (Value v = tryCondTrue(mux.getHigh(), mux.getSel(), rewriter, true, 0)) {
      rewriter.modifyOpInPlace(mux, [&] { mux.setOperand(1, v); });
      return success();
    }
 
    if (Value v = tryCondFalse(mux.getLow(), mux.getSel(), rewriter, true, 0)) {
      rewriter.modifyOpInPlace(mux, [&] { mux.setOperand(2, v); });
      return success();
    }
 
    return failure();
  }
};
} // namespace
 
void MuxPrimOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results
      .add<MuxPad, MuxSharedCond, patterns::MuxEQOperands,
           patterns::MuxEQOperandsSwapped, patterns::MuxNEQ, patterns::MuxNot,
           patterns::MuxSameTrue, patterns::MuxSameFalse,
           patterns::NarrowMuxLHS, patterns::NarrowMuxRHS, patterns::MuxPadSel>(
          context);
}
 
void Mux2CellIntrinsicOp::getCanonicalizationPatterns(
    RewritePatternSet &results, MLIRContext *context) {
  results.add<patterns::Mux2PadSel>(context);
}
 
void Mux4CellIntrinsicOp::getCanonicalizationPatterns(
    RewritePatternSet &results, MLIRContext *context) {
  results.add<patterns::Mux4PadSel>(context);
}
 
OpFoldResult PadPrimOp::fold(FoldAdaptor adaptor) {
  auto input = this->getInput();
 
  // pad(x) -> x  if the width doesn't change.
  if (input.getType() == getType())
    return input;
 
  // Need to know the input width.
  auto inputType = input.getType().base();
  int32_t width = inputType.getWidthOrSentinel();
  if (width == -1)
    return {};
 
  // Constant fold.
  if (auto cst = getConstant(adaptor.getInput())) {
    auto destWidth = getType().base().getWidthOrSentinel();
    if (destWidth == -1)
      return {};
 
    if (inputType.isSigned() && cst->getBitWidth())
      return getIntAttr(getType(), cst->sext(destWidth));
    return getIntAttr(getType(), cst->zext(destWidth));
  }
 
  return {};
}
 
OpFoldResult ShlPrimOp::fold(FoldAdaptor adaptor) {
  auto input = this->getInput();
  IntType inputType = input.getType();
  int shiftAmount = getAmount();
 
  // shl(x, 0) -> x
  if (shiftAmount == 0)
    return input;
 
  // Constant fold.
  if (auto cst = getConstant(adaptor.getInput())) {
    auto inputWidth = inputType.getWidthOrSentinel();
    if (inputWidth != -1) {
      auto resultWidth = inputWidth + shiftAmount;
      shiftAmount = std::min(shiftAmount, resultWidth);
      return getIntAttr(getType(), cst->zext(resultWidth).shl(shiftAmount));
    }
  }
  return {};
}
 
OpFoldResult ShrPrimOp::fold(FoldAdaptor adaptor) {
  auto input = this->getInput();
  IntType inputType = input.getType();
  int shiftAmount = getAmount();
  auto inputWidth = inputType.getWidthOrSentinel();
 
  // shr(x, 0) -> x
  // Once the shr width changes, do this: shiftAmount == 0 &&
  // (!inputType.isSigned() || inputWidth > 0)
  if (shiftAmount == 0 && inputWidth > 0)
    return input;
 
  if (inputWidth == -1)
    return {};
  if (inputWidth == 0)
    return getIntZerosAttr(getType());
 
  // shr(x, cst) where cst is all of x's bits and x is unsigned is 0.
  // If x is signed, it is the sign bit.
  if (shiftAmount >= inputWidth && inputType.isUnsigned())
    return getIntAttr(getType(), APInt(0, 0, false));
 
  // Constant fold.
  if (auto cst = getConstant(adaptor.getInput())) {
    APInt value;
    if (inputType.isSigned())
      value = cst->ashr(std::min(shiftAmount, inputWidth - 1));
    else
      value = cst->lshr(std::min(shiftAmount, inputWidth));
    auto resultWidth = std::max(inputWidth - shiftAmount, 1);
    return getIntAttr(getType(), value.trunc(resultWidth));
  }
  return {};
}
 
LogicalResult ShrPrimOp::canonicalize(ShrPrimOp op, PatternRewriter &rewriter) {
  auto inputWidth = op.getInput().getType().base().getWidthOrSentinel();
  if (inputWidth <= 0)
    return failure();
 
  // If we know the input width, we can canonicalize this into a BitsPrimOp.
  unsigned shiftAmount = op.getAmount();
  if (int(shiftAmount) >= inputWidth) {
    // shift(x, 32) => 0 when x has 32 bits.  This is handled by fold().
    if (op.getType().base().isUnsigned())
      return failure();
 
    // Shifting a signed value by the full width is actually taking the
    // sign bit. If the shift amount is greater than the input width, it
    // is equivalent to shifting by the input width.
    shiftAmount = inputWidth - 1;
  }
 
  replaceWithBits(op, op.getInput(), inputWidth - 1, shiftAmount, rewriter);
  return success();
}
 
LogicalResult HeadPrimOp::canonicalize(HeadPrimOp op,
                                       PatternRewriter &rewriter) {
  auto inputWidth = op.getInput().getType().base().getWidthOrSentinel();
  if (inputWidth <= 0)
    return failure();
 
  // If we know the input width, we can canonicalize this into a BitsPrimOp.
  unsigned keepAmount = op.getAmount();
  if (keepAmount)
    replaceWithBits(op, op.getInput(), inputWidth - 1, inputWidth - keepAmount,
                    rewriter);
  return success();
}
 
OpFoldResult HeadPrimOp::fold(FoldAdaptor adaptor) {
  if (hasKnownWidthIntTypes(*this))
    if (auto cst = getConstant(adaptor.getInput())) {
      int shiftAmount =
          getInput().getType().base().getWidthOrSentinel() - getAmount();
      return getIntAttr(getType(), cst->lshr(shiftAmount).trunc(getAmount()));
    }
 
  return {};
}
 
OpFoldResult TailPrimOp::fold(FoldAdaptor adaptor) {
  if (hasKnownWidthIntTypes(*this))
    if (auto cst = getConstant(adaptor.getInput()))
      return getIntAttr(getType(),
                        cst->trunc(getType().base().getWidthOrSentinel()));
  return {};
}
 
LogicalResult TailPrimOp::canonicalize(TailPrimOp op,
                                       PatternRewriter &rewriter) {
  auto inputWidth = op.getInput().getType().base().getWidthOrSentinel();
  if (inputWidth <= 0)
    return failure();
 
  // If we know the input width, we can canonicalize this into a BitsPrimOp.
  unsigned dropAmount = op.getAmount();
  if (dropAmount != unsigned(inputWidth))
    replaceWithBits(op, op.getInput(), inputWidth - dropAmount - 1, 0,
                    rewriter);
  return success();
}
 
void SubaccessOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                              MLIRContext *context) {
  results.add<patterns::SubaccessOfConstant>(context);
}
 
OpFoldResult MultibitMuxOp::fold(FoldAdaptor adaptor) {
  // If there is only one input, just return it.
  if (adaptor.getInputs().size() == 1)
    return getOperand(1);
 
  if (auto constIndex = getConstant(adaptor.getIndex())) {
    auto index = constIndex->getZExtValue();
    if (index < getInputs().size())
      return getInputs()[getInputs().size() - 1 - index];
  }
 
  return {};
}
 
LogicalResult MultibitMuxOp::canonicalize(MultibitMuxOp op,
                                          PatternRewriter &rewriter) {
  // If all operands are equal, just canonicalize to it. We can add this
  // canonicalization as a folder but it costly to look through all inputs so it
  // is added here.
  if (llvm::all_of(op.getInputs().drop_front(), [&](auto input) {
        return input == op.getInputs().front();
      })) {
    replaceOpAndCopyName(rewriter, op, op.getInputs().front());
    return success();
  }
 
  // If the index width is narrower than the size of inputs, drop front
  // elements.
  auto indexWidth = op.getIndex().getType().getBitWidthOrSentinel();
  uint64_t inputSize = op.getInputs().size();
  if (indexWidth >= 0 && indexWidth < 64 && 1ull << indexWidth < inputSize) {
    rewriter.modifyOpInPlace(op, [&]() {
      op.getInputsMutable().erase(0, inputSize - (1ull << indexWidth));
    });
    return success();
  }
 
  // If the op is a vector indexing (e.g. `multbit_mux idx, a[n-1], a[n-2], ...,
  // a[0]`), we can fold the op into subaccess op `a[idx]`.
  if (auto lastSubindex = op.getInputs().back().getDefiningOp<SubindexOp>()) {
    if (llvm::all_of(llvm::enumerate(op.getInputs()), [&](auto e) {
          auto subindex = e.value().template getDefiningOp<SubindexOp>();
          return subindex && lastSubindex.getInput() == subindex.getInput() &&
                 subindex.getIndex() + e.index() + 1 == op.getInputs().size();
        })) {
      replaceOpWithNewOpAndCopyName<SubaccessOp>(
          rewriter, op, lastSubindex.getInput(), op.getIndex());
      return success();
    }
  }
 
  // If the size is 2, canonicalize into a normal mux to introduce more folds.
  if (op.getInputs().size() != 2)
    return failure();
 
  // TODO: Handle even when `index` doesn't have uint<1>.
  auto uintType = op.getIndex().getType();
  if (uintType.getBitWidthOrSentinel() != 1)
    return failure();
 
  // multibit_mux(index, {lhs, rhs}) -> mux(index, lhs, rhs)
  replaceOpWithNewOpAndCopyName<MuxPrimOp>(
      rewriter, op, op.getIndex(), op.getInputs()[0], op.getInputs()[1]);
  return success();
}
 
//===----------------------------------------------------------------------===//
// Declarations
//===----------------------------------------------------------------------===//
 
/// Scan all the uses of the specified value, checking to see if there is
/// exactly one connect that has the value as its destination. This returns the
/// operation if found and if all the other users are "reads" from the value.
/// Returns null if there are no connects, or multiple connects to the value, or
/// if the value is involved in an `AttachOp`, or if the connect isn't matching.
///
/// Note that this will simply return the connect, which is located *anywhere*
/// after the definition of the value. Users of this function are likely
/// interested in the source side of the returned connect, the definition of
/// which does likely not dominate the original value.
MatchingConnectOp firrtl::getSingleConnectUserOf(Value value) {
  MatchingConnectOp connect;
  for (Operation *user : value.getUsers()) {
    // If we see an attach or aggregate sublements, just conservatively fail.
    if (isa<AttachOp, SubfieldOp, SubaccessOp, SubindexOp>(user))
      return {};
 
    if (auto aConnect = dyn_cast<FConnectLike>(user))
      if (aConnect.getDest() == value) {
        auto matchingConnect = dyn_cast<MatchingConnectOp>(*aConnect);
        // If this is not a matching connect, a second matching connect or in a
        // different block, fail.
        if (!matchingConnect || (connect && connect != matchingConnect) ||
            matchingConnect->getBlock() != value.getParentBlock())
          return {};
        else
          connect = matchingConnect;
      }
  }
  return connect;
}
 
// Forward simple values through wire's and reg's.
static LogicalResult canonicalizeSingleSetConnect(MatchingConnectOp op,
                                                  PatternRewriter &rewriter) {
  // While we can do this for nearly all wires, we currently limit it to simple
  // things.
  Operation *connectedDecl = op.getDest().getDefiningOp();
  if (!connectedDecl)
    return failure();
 
  // Only support wire and reg for now.
  if (!isa<WireOp>(connectedDecl) && !isa<RegOp>(connectedDecl))
    return failure();
  if (hasDontTouch(connectedDecl) || !AnnotationSet(connectedDecl).empty() ||
      !hasDroppableName(connectedDecl) ||
      cast<Forceable>(connectedDecl).isForceable())
    return failure();
 
  // Only forward if the types exactly match and there is one connect.
  if (getSingleConnectUserOf(op.getDest()) != op)
    return failure();
 
  // Only forward if there is more than one use
  if (connectedDecl->hasOneUse())
    return failure();
 
  // Only do this if the connectee and the declaration are in the same block.
  auto *declBlock = connectedDecl->getBlock();
  auto *srcValueOp = op.getSrc().getDefiningOp();
  if (!srcValueOp) {
    // Ports are ok for wires but not registers.
    if (!isa<WireOp>(connectedDecl))
      return failure();
 
  } else {
    // Constants/invalids in the same block are ok to forward, even through
    // reg's since the clocking doesn't matter for constants.
    if (!isa<ConstantOp>(srcValueOp))
      return failure();
    if (srcValueOp->getBlock() != declBlock)
      return failure();
  }
 
  // Ok, we know we are doing the transformation.
 
  auto replacement = op.getSrc();
  // This will be replaced with the constant source.  First, make sure the
  // constant dominates all users.
  if (srcValueOp && srcValueOp != &declBlock->front())
    srcValueOp->moveBefore(&declBlock->front());
 
  // Replace all things *using* the decl with the constant/port, and
  // remove the declaration.
  replaceOpAndCopyName(rewriter, connectedDecl, replacement);
 
  // Remove the connect
  rewriter.eraseOp(op);
  return success();
}
 
void ConnectOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                            MLIRContext *context) {
  results.insert<patterns::ConnectExtension, patterns::ConnectSameType>(
      context);
}
 
LogicalResult MatchingConnectOp::canonicalize(MatchingConnectOp op,
                                              PatternRewriter &rewriter) {
  // TODO: Canonicalize towards explicit extensions and flips here.
 
  // If there is a simple value connected to a foldable decl like a wire or reg,
  // see if we can eliminate the decl.
  if (succeeded(canonicalizeSingleSetConnect(op, rewriter)))
    return success();
  return failure();
}
 
//===----------------------------------------------------------------------===//
// Statements
//===----------------------------------------------------------------------===//
 
/// If the specified value has an AttachOp user strictly dominating by
/// "dominatingAttach" then return it.
static AttachOp getDominatingAttachUser(Value value, AttachOp dominatedAttach) {
  for (auto *user : value.getUsers()) {
    auto attach = dyn_cast<AttachOp>(user);
    if (!attach || attach == dominatedAttach)
      continue;
    if (attach->isBeforeInBlock(dominatedAttach))
      return attach;
  }
  return {};
}
 
LogicalResult AttachOp::canonicalize(AttachOp op, PatternRewriter &rewriter) {
  // Single operand attaches are a noop.
  if (op.getNumOperands() <= 1) {
    rewriter.eraseOp(op);
    return success();
  }
 
  for (auto operand : op.getOperands()) {
    // Check to see if any of our operands has other attaches to it:
    //    attach x, y
    //      ...
    //    attach x, z
    // If so, we can merge these into "attach x, y, z".
    if (auto attach = getDominatingAttachUser(operand, op)) {
      SmallVector<Value> newOperands(op.getOperands());
      for (auto newOperand : attach.getOperands())
        if (newOperand != operand) // Don't add operand twice.
          newOperands.push_back(newOperand);
      rewriter.create<AttachOp>(op->getLoc(), newOperands);
      rewriter.eraseOp(attach);
      rewriter.eraseOp(op);
      return success();
    }
 
    // If this wire is *only* used by an attach then we can just delete
    // it.
    // TODO: May need to be sensitive to "don't touch" or other
    // annotations.
    if (auto wire = dyn_cast_or_null<WireOp>(operand.getDefiningOp())) {
      if (!hasDontTouch(wire.getOperation()) && wire->hasOneUse() &&
          !wire.isForceable()) {
        SmallVector<Value> newOperands;
        for (auto newOperand : op.getOperands())
          if (newOperand != operand) // Don't the add wire.
            newOperands.push_back(newOperand);
 
        rewriter.create<AttachOp>(op->getLoc(), newOperands);
        rewriter.eraseOp(op);
        rewriter.eraseOp(wire);
        return success();
      }
    }
  }
  return failure();
}
 
/// Replaces the given op with the contents of the given single-block region.
static void replaceOpWithRegion(PatternRewriter &rewriter, Operation *op,
                                Region &region) {
  assert(llvm::hasSingleElement(region) && "expected single-region block");
  rewriter.inlineBlockBefore(&region.front(), op, {});
}
 
LogicalResult WhenOp::canonicalize(WhenOp op, PatternRewriter &rewriter) {
  if (auto constant = op.getCondition().getDefiningOp<firrtl::ConstantOp>()) {
    if (constant.getValue().isAllOnes())
      replaceOpWithRegion(rewriter, op, op.getThenRegion());
    else if (op.hasElseRegion() && !op.getElseRegion().empty())
      replaceOpWithRegion(rewriter, op, op.getElseRegion());
 
    rewriter.eraseOp(op);
 
    return success();
  }
 
  // Erase empty if-else block.
  if (!op.getThenBlock().empty() && op.hasElseRegion() &&
      op.getElseBlock().empty()) {
    rewriter.eraseBlock(&op.getElseBlock());
    return success();
  }
 
  // Erase empty whens.
 
  // If there is stuff in the then block, leave this operation alone.
  if (!op.getThenBlock().empty())
    return failure();
 
  // If not and there is no else, then this operation is just useless.
  if (!op.hasElseRegion() || op.getElseBlock().empty()) {
    rewriter.eraseOp(op);
    return success();
  }
  return failure();
}
 
namespace {
// Remove private nodes.  If they have an interesting names, move the name to
// the source expression.
struct FoldNodeName : public mlir::RewritePattern {
  FoldNodeName(MLIRContext *context)
      : RewritePattern(NodeOp::getOperationName(), 0, context) {}
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    auto node = cast<NodeOp>(op);
    auto name = node.getNameAttr();
    if (!node.hasDroppableName() || node.getInnerSym() ||
        !AnnotationSet(node).empty() || node.isForceable())
      return failure();
    auto *newOp = node.getInput().getDefiningOp();
    // Best effort, do not rename InstanceOp
    if (newOp && !isa<InstanceOp>(newOp))
      updateName(rewriter, newOp, name);
    rewriter.replaceOp(node, node.getInput());
    return success();
  }
};
 
// Bypass nodes.
struct NodeBypass : public mlir::RewritePattern {
  NodeBypass(MLIRContext *context)
      : RewritePattern(NodeOp::getOperationName(), 0, context) {}
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    auto node = cast<NodeOp>(op);
    if (node.getInnerSym() || !AnnotationSet(node).empty() ||
        node.use_empty() || node.isForceable())
      return failure();
    rewriter.replaceAllUsesWith(node.getResult(), node.getInput());
    return success();
  }
};
 
} // namespace
 
template <typename OpTy>
static LogicalResult demoteForceableIfUnused(OpTy op,
                                             PatternRewriter &rewriter) {
  if (!op.isForceable() || !op.getDataRef().use_empty())
    return failure();
 
  firrtl::detail::replaceWithNewForceability(op, false, &rewriter);
  return success();
}
 
// Interesting names and symbols and don't touch force nodes to stick around.
LogicalResult NodeOp::fold(FoldAdaptor adaptor,
                           SmallVectorImpl<OpFoldResult> &results) {
  if (!hasDroppableName())
    return failure();
  if (hasDontTouch(getResult())) // handles inner symbols
    return failure();
  if (getAnnotationsAttr() && !AnnotationSet(getAnnotationsAttr()).empty())
    return failure();
  if (isForceable())
    return failure();
  if (!adaptor.getInput())
    return failure();
 
  results.push_back(adaptor.getInput());
  return success();
}
 
void NodeOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                         MLIRContext *context) {
  results.insert<FoldNodeName>(context);
  results.add(demoteForceableIfUnused<NodeOp>);
}
 
namespace {
// For a lhs, find all the writers of fields of the aggregate type.  If there
// is one writer for each field, merge the writes
struct AggOneShot : public mlir::RewritePattern {
  AggOneShot(StringRef name, uint32_t weight, MLIRContext *context)
      : RewritePattern(name, 0, context) {}
 
  SmallVector<Value> getCompleteWrite(Operation *lhs) const {
    auto lhsTy = lhs->getResult(0).getType();
    if (!type_isa<BundleType, FVectorType>(lhsTy))
      return {};
 
    DenseMap<uint32_t, Value> fields;
    for (Operation *user : lhs->getResult(0).getUsers()) {
      if (user->getParentOp() != lhs->getParentOp())
        return {};
      if (auto aConnect = dyn_cast<MatchingConnectOp>(user)) {
        if (aConnect.getDest() == lhs->getResult(0))
          return {};
      } else if (auto subField = dyn_cast<SubfieldOp>(user)) {
        for (Operation *subuser : subField.getResult().getUsers()) {
          if (auto aConnect = dyn_cast<MatchingConnectOp>(subuser)) {
            if (aConnect.getDest() == subField) {
              if (subuser->getParentOp() != lhs->getParentOp())
                return {};
              if (fields.count(subField.getFieldIndex())) // duplicate write
                return {};
              fields[subField.getFieldIndex()] = aConnect.getSrc();
            }
            continue;
          }
          return {};
        }
      } else if (auto subIndex = dyn_cast<SubindexOp>(user)) {
        for (Operation *subuser : subIndex.getResult().getUsers()) {
          if (auto aConnect = dyn_cast<MatchingConnectOp>(subuser)) {
            if (aConnect.getDest() == subIndex) {
              if (subuser->getParentOp() != lhs->getParentOp())
                return {};
              if (fields.count(subIndex.getIndex())) // duplicate write
                return {};
              fields[subIndex.getIndex()] = aConnect.getSrc();
            }
            continue;
          }
          return {};
        }
      } else {
        return {};
      }
    }
 
    SmallVector<Value> values;
    uint32_t total = type_isa<BundleType>(lhsTy)
                         ? type_cast<BundleType>(lhsTy).getNumElements()
                         : type_cast<FVectorType>(lhsTy).getNumElements();
    for (uint32_t i = 0; i < total; ++i) {
      if (!fields.count(i))
        return {};
      values.push_back(fields[i]);
    }
    return values;
  }
 
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    auto values = getCompleteWrite(op);
    if (values.empty())
      return failure();
    rewriter.setInsertionPointToEnd(op->getBlock());
    auto dest = op->getResult(0);
    auto destType = dest.getType();
 
    // If not passive, cannot matchingconnect.
    if (!type_cast<FIRRTLBaseType>(destType).isPassive())
      return failure();
 
    Value newVal = type_isa<BundleType>(destType)
                       ? rewriter.createOrFold<BundleCreateOp>(op->getLoc(),
                                                               destType, values)
                       : rewriter.createOrFold<VectorCreateOp>(
                             op->getLoc(), destType, values);
    rewriter.createOrFold<MatchingConnectOp>(op->getLoc(), dest, newVal);
    for (Operation *user : dest.getUsers()) {
      if (auto subIndex = dyn_cast<SubindexOp>(user)) {
        for (Operation *subuser :
             llvm::make_early_inc_range(subIndex.getResult().getUsers()))
          if (auto aConnect = dyn_cast<MatchingConnectOp>(subuser))
            if (aConnect.getDest() == subIndex)
              rewriter.eraseOp(aConnect);
      } else if (auto subField = dyn_cast<SubfieldOp>(user)) {
        for (Operation *subuser :
             llvm::make_early_inc_range(subField.getResult().getUsers()))
          if (auto aConnect = dyn_cast<MatchingConnectOp>(subuser))
            if (aConnect.getDest() == subField)
              rewriter.eraseOp(aConnect);
      }
    }
    return success();
  }
};
 
struct WireAggOneShot : public AggOneShot {
  WireAggOneShot(MLIRContext *context)
      : AggOneShot(WireOp::getOperationName(), 0, context) {}
};
struct SubindexAggOneShot : public AggOneShot {
  SubindexAggOneShot(MLIRContext *context)
      : AggOneShot(SubindexOp::getOperationName(), 0, context) {}
};
struct SubfieldAggOneShot : public AggOneShot {
  SubfieldAggOneShot(MLIRContext *context)
      : AggOneShot(SubfieldOp::getOperationName(), 0, context) {}
};
} // namespace
 
void WireOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                         MLIRContext *context) {
  results.insert<WireAggOneShot>(context);
  results.add(demoteForceableIfUnused<WireOp>);
}
 
void SubindexOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results.insert<SubindexAggOneShot>(context);
}
 
OpFoldResult SubindexOp::fold(FoldAdaptor adaptor) {
  auto attr = dyn_cast_or_null<ArrayAttr>(adaptor.getInput());
  if (!attr)
    return {};
  return attr[getIndex()];
}
 
OpFoldResult SubfieldOp::fold(FoldAdaptor adaptor) {
  auto attr = dyn_cast_or_null<ArrayAttr>(adaptor.getInput());
  if (!attr)
    return {};
  auto index = getFieldIndex();
  return attr[index];
}
 
void SubfieldOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results.insert<SubfieldAggOneShot>(context);
}
 
static Attribute collectFields(MLIRContext *context,
                               ArrayRef<Attribute> operands) {
  for (auto operand : operands)
    if (!operand)
      return {};
  return ArrayAttr::get(context, operands);
}
 
OpFoldResult BundleCreateOp::fold(FoldAdaptor adaptor) {
  // bundle_create(%foo["a"], %foo["b"]) -> %foo when the type of %foo is
  // bundle<a:..., b:...>.
  if (getNumOperands() > 0)
    if (SubfieldOp first = getOperand(0).getDefiningOp<SubfieldOp>())
      if (first.getFieldIndex() == 0 &&
          first.getInput().getType() == getType() &&
          llvm::all_of(
              llvm::drop_begin(llvm::enumerate(getOperands())), [&](auto elem) {
                auto subindex =
                    elem.value().template getDefiningOp<SubfieldOp>();
                return subindex && subindex.getInput() == first.getInput() &&
                       subindex.getFieldIndex() == elem.index();
              }))
        return first.getInput();
 
  return collectFields(getContext(), adaptor.getOperands());
}
 
OpFoldResult VectorCreateOp::fold(FoldAdaptor adaptor) {
  // vector_create(%foo[0], %foo[1]) -> %foo when the type of %foo is
  // vector<..., 2>.
  if (getNumOperands() > 0)
    if (SubindexOp first = getOperand(0).getDefiningOp<SubindexOp>())
      if (first.getIndex() == 0 && first.getInput().getType() == getType() &&
          llvm::all_of(
              llvm::drop_begin(llvm::enumerate(getOperands())), [&](auto elem) {
                auto subindex =
                    elem.value().template getDefiningOp<SubindexOp>();
                return subindex && subindex.getInput() == first.getInput() &&
                       subindex.getIndex() == elem.index();
              }))
        return first.getInput();
 
  return collectFields(getContext(), adaptor.getOperands());
}
 
OpFoldResult UninferredResetCastOp::fold(FoldAdaptor adaptor) {
  if (getOperand().getType() == getType())
    return getOperand();
  return {};
}
 
namespace {
// A register with constant reset and all connection to either itself or the
// same constant, must be replaced by the constant.
struct FoldResetMux : public mlir::RewritePattern {
  FoldResetMux(MLIRContext *context)
      : RewritePattern(RegResetOp::getOperationName(), 0, context) {}
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    auto reg = cast<RegResetOp>(op);
    auto reset =
        dyn_cast_or_null<ConstantOp>(reg.getResetValue().getDefiningOp());
    if (!reset || hasDontTouch(reg.getOperation()) ||
        !AnnotationSet(reg).empty() || reg.isForceable())
      return failure();
    // Find the one true connect, or bail
    auto con = getSingleConnectUserOf(reg.getResult());
    if (!con)
      return failure();
 
    auto mux = dyn_cast_or_null<MuxPrimOp>(con.getSrc().getDefiningOp());
    if (!mux)
      return failure();
    auto *high = mux.getHigh().getDefiningOp();
    auto *low = mux.getLow().getDefiningOp();
    auto constOp = dyn_cast_or_null<ConstantOp>(high);
 
    if (constOp && low != reg)
      return failure();
    if (dyn_cast_or_null<ConstantOp>(low) && high == reg)
      constOp = dyn_cast<ConstantOp>(low);
 
    if (!constOp || constOp.getType() != reset.getType() ||
        constOp.getValue() != reset.getValue())
      return failure();
 
    // Check all types should be typed by now
    auto regTy = reg.getResult().getType();
    if (con.getDest().getType() != regTy || con.getSrc().getType() != regTy ||
        mux.getHigh().getType() != regTy || mux.getLow().getType() != regTy ||
        regTy.getBitWidthOrSentinel() < 0)
      return failure();
 
    // Ok, we know we are doing the transformation.
 
    // Make sure the constant dominates all users.
    if (constOp != &con->getBlock()->front())
      constOp->moveBefore(&con->getBlock()->front());
 
    // Replace the register with the constant.
    replaceOpAndCopyName(rewriter, reg, constOp.getResult());
    // Remove the connect.
    rewriter.eraseOp(con);
    return success();
  }
};
} // namespace
 
static bool isDefinedByOneConstantOp(Value v) {
  if (auto c = v.getDefiningOp<ConstantOp>())
    return c.getValue().isOne();
  if (auto sc = v.getDefiningOp<SpecialConstantOp>())
    return sc.getValue();
  return false;
}
 
static LogicalResult
canonicalizeRegResetWithOneReset(RegResetOp reg, PatternRewriter &rewriter) {
  if (!isDefinedByOneConstantOp(reg.getResetSignal()))
    return failure();
 
  // Ignore 'passthrough'.
  (void)dropWrite(rewriter, reg->getResult(0), {});
  replaceOpWithNewOpAndCopyName<NodeOp>(
      rewriter, reg, reg.getResetValue(), reg.getNameAttr(), reg.getNameKind(),
      reg.getAnnotationsAttr(), reg.getInnerSymAttr(), reg.getForceable());
  return success();
}
 
void RegResetOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results.add<patterns::RegResetWithZeroReset, FoldResetMux>(context);
  results.add(canonicalizeRegResetWithOneReset);
  results.add(demoteForceableIfUnused<RegResetOp>);
}
 
// Returns the value connected to a port, if there is only one.
static Value getPortFieldValue(Value port, StringRef name) {
  auto portTy = type_cast<BundleType>(port.getType());
  auto fieldIndex = portTy.getElementIndex(name);
  assert(fieldIndex && "missing field on memory port");
 
  Value value = {};
  for (auto *op : port.getUsers()) {
    auto portAccess = cast<SubfieldOp>(op);
    if (fieldIndex != portAccess.getFieldIndex())
      continue;
    auto conn = getSingleConnectUserOf(portAccess);
    if (!conn || value)
      return {};
    value = conn.getSrc();
  }
  return value;
}
 
// Returns true if the enable field of a port is set to false.
static bool isPortDisabled(Value port) {
  auto value = getPortFieldValue(port, "en");
  if (!value)
    return false;
  auto portConst = value.getDefiningOp<ConstantOp>();
  if (!portConst)
    return false;
  return portConst.getValue().isZero();
}
 
// Returns true if the data output is unused.
static bool isPortUnused(Value port, StringRef data) {
  auto portTy = type_cast<BundleType>(port.getType());
  auto fieldIndex = portTy.getElementIndex(data);
  assert(fieldIndex && "missing enable flag on memory port");
 
  for (auto *op : port.getUsers()) {
    auto portAccess = cast<SubfieldOp>(op);
    if (fieldIndex != portAccess.getFieldIndex())
      continue;
    if (!portAccess.use_empty())
      return false;
  }
 
  return true;
}
 
// Returns the value connected to a port, if there is only one.
static void replacePortField(PatternRewriter &rewriter, Value port,
                             StringRef name, Value value) {
  auto portTy = type_cast<BundleType>(port.getType());
  auto fieldIndex = portTy.getElementIndex(name);
  assert(fieldIndex && "missing field on memory port");
 
  for (auto *op : llvm::make_early_inc_range(port.getUsers())) {
    auto portAccess = cast<SubfieldOp>(op);
    if (fieldIndex != portAccess.getFieldIndex())
      continue;
    rewriter.replaceAllUsesWith(portAccess, value);
    rewriter.eraseOp(portAccess);
  }
}
 
// Remove accesses to a port which is used.
static void erasePort(PatternRewriter &rewriter, Value port) {
  // Helper to create a dummy 0 clock for the dummy registers.
  Value clock;
  auto getClock = [&] {
    if (!clock)
      clock = rewriter.create<SpecialConstantOp>(
          port.getLoc(), ClockType::get(rewriter.getContext()), false);
    return clock;
  };
 
  // Find the clock field of the port and determine whether the port is
  // accessed only through its subfields or as a whole wire.  If the port
  // is used in its entirety, replace it with a wire.  Otherwise,
  // eliminate individual subfields and replace with reasonable defaults.
  for (auto *op : port.getUsers()) {
    auto subfield = dyn_cast<SubfieldOp>(op);
    if (!subfield) {
      auto ty = port.getType();
      auto reg = rewriter.create<RegOp>(port.getLoc(), ty, getClock());
      rewriter.replaceAllUsesWith(port, reg.getResult());
      return;
    }
  }
 
  // Remove all connects to field accesses as they are no longer relevant.
  // If field values are used anywhere, which should happen solely for read
  // ports, a dummy register is introduced which replicates the behaviour of
  // memory that is never written, but might be read.
  for (auto *accessOp : llvm::make_early_inc_range(port.getUsers())) {
    auto access = cast<SubfieldOp>(accessOp);
    for (auto *user : llvm::make_early_inc_range(access->getUsers())) {
      auto connect = dyn_cast<FConnectLike>(user);
      if (connect && connect.getDest() == access) {
        rewriter.eraseOp(user);
        continue;
      }
    }
    if (access.use_empty()) {
      rewriter.eraseOp(access);
      continue;
    }
 
    // Replace read values with a register that is never written, handing off
    // the canonicalization of such a register to another canonicalizer.
    auto ty = access.getType();
    auto reg = rewriter.create<RegOp>(access.getLoc(), ty, getClock());
    rewriter.replaceOp(access, reg.getResult());
  }
  assert(port.use_empty() && "port should have no remaining uses");
}
 
namespace {
// If memory has known, but zero width, eliminate it.
struct FoldZeroWidthMemory : public mlir::RewritePattern {
  FoldZeroWidthMemory(MLIRContext *context)
      : RewritePattern(MemOp::getOperationName(), 0, context) {}
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    MemOp mem = cast<MemOp>(op);
    if (hasDontTouch(mem))
      return failure();
 
    if (!firrtl::type_isa<IntType>(mem.getDataType()) ||
        mem.getDataType().getBitWidthOrSentinel() != 0)
      return failure();
 
    // Make sure are users are safe to replace
    for (auto port : mem.getResults())
      for (auto *user : port.getUsers())
        if (!isa<SubfieldOp>(user))
          return failure();
 
    // Annoyingly, there isn't a good replacement for the port as a whole,
    // since they have an outer flip type.
    for (auto port : op->getResults()) {
      for (auto *user : llvm::make_early_inc_range(port.getUsers())) {
        SubfieldOp sfop = cast<SubfieldOp>(user);
        StringRef fieldName = sfop.getFieldName();
        auto wire = replaceOpWithNewOpAndCopyName<WireOp>(
                        rewriter, sfop, sfop.getResult().getType())
                        .getResult();
        if (fieldName.ends_with("data")) {
          // Make sure to write data ports.
          auto zero = rewriter.create<firrtl::ConstantOp>(
              wire.getLoc(), firrtl::type_cast<IntType>(wire.getType()),
              APInt::getZero(0));
          rewriter.create<MatchingConnectOp>(wire.getLoc(), wire, zero);
        }
      }
    }
    rewriter.eraseOp(op);
    return success();
  }
};
 
// If memory has no write ports and no file initialization, eliminate it.
struct FoldReadOrWriteOnlyMemory : public mlir::RewritePattern {
  FoldReadOrWriteOnlyMemory(MLIRContext *context)
      : RewritePattern(MemOp::getOperationName(), 0, context) {}
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    MemOp mem = cast<MemOp>(op);
    if (hasDontTouch(mem))
      return failure();
    bool isRead = false, isWritten = false;
    for (unsigned i = 0; i < mem.getNumResults(); ++i) {
      switch (mem.getPortKind(i)) {
      case MemOp::PortKind::Read:
        isRead = true;
        if (isWritten)
          return failure();
        continue;
      case MemOp::PortKind::Write:
        isWritten = true;
        if (isRead)
          return failure();
        continue;
      case MemOp::PortKind::Debug:
      case MemOp::PortKind::ReadWrite:
        return failure();
      }
      llvm_unreachable("unknown port kind");
    }
    assert((!isWritten || !isRead) && "memory is in use");
 
    // If the memory is read only, but has a file initialization, then we can't
    // remove it.  A write only memory with file initialization is okay to
    // remove.
    if (isRead && mem.getInit())
      return failure();
 
    for (auto port : mem.getResults())
      erasePort(rewriter, port);
 
    rewriter.eraseOp(op);
    return success();
  }
};
 
// Eliminate the dead ports of memories.
struct FoldUnusedPorts : public mlir::RewritePattern {
  FoldUnusedPorts(MLIRContext *context)
      : RewritePattern(MemOp::getOperationName(), 0, context) {}
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    MemOp mem = cast<MemOp>(op);
    if (hasDontTouch(mem))
      return failure();
    // Identify the dead and changed ports.
    llvm::SmallBitVector deadPorts(mem.getNumResults());
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      // Do not simplify annotated ports.
      if (!mem.getPortAnnotation(i).empty())
        continue;
 
      // Skip debug ports.
      auto kind = mem.getPortKind(i);
      if (kind == MemOp::PortKind::Debug)
        continue;
 
      // If a port is disabled, always eliminate it.
      if (isPortDisabled(port)) {
        deadPorts.set(i);
        continue;
      }
      // Eliminate read ports whose outputs are not used.
      if (kind == MemOp::PortKind::Read && isPortUnused(port, "data")) {
        deadPorts.set(i);
        continue;
      }
    }
    if (deadPorts.none())
      return failure();
 
    // Rebuild the new memory with the altered ports.
    SmallVector<Type> resultTypes;
    SmallVector<StringRef> portNames;
    SmallVector<Attribute> portAnnotations;
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      if (deadPorts[i])
        continue;
      resultTypes.push_back(port.getType());
      portNames.push_back(mem.getPortName(i));
      portAnnotations.push_back(mem.getPortAnnotation(i));
    }
 
    MemOp newOp;
    if (!resultTypes.empty())
      newOp = rewriter.create<MemOp>(
          mem.getLoc(), resultTypes, mem.getReadLatency(),
          mem.getWriteLatency(), mem.getDepth(), mem.getRuw(),
          rewriter.getStrArrayAttr(portNames), mem.getName(), mem.getNameKind(),
          mem.getAnnotations(), rewriter.getArrayAttr(portAnnotations),
          mem.getInnerSymAttr(), mem.getInitAttr(), mem.getPrefixAttr());
 
    // Replace the dead ports with dummy wires.
    unsigned nextPort = 0;
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      if (deadPorts[i])
        erasePort(rewriter, port);
      else
        rewriter.replaceAllUsesWith(port, newOp.getResult(nextPort++));
    }
 
    rewriter.eraseOp(op);
    return success();
  }
};
 
// Rewrite write-only read-write ports to write ports.
struct FoldReadWritePorts : public mlir::RewritePattern {
  FoldReadWritePorts(MLIRContext *context)
      : RewritePattern(MemOp::getOperationName(), 0, context) {}
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    MemOp mem = cast<MemOp>(op);
    if (hasDontTouch(mem))
      return failure();
 
    // Identify read-write ports whose read end is unused.
    llvm::SmallBitVector deadReads(mem.getNumResults());
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      if (mem.getPortKind(i) != MemOp::PortKind::ReadWrite)
        continue;
      if (!mem.getPortAnnotation(i).empty())
        continue;
      if (isPortUnused(port, "rdata")) {
        deadReads.set(i);
        continue;
      }
    }
    if (deadReads.none())
      return failure();
 
    SmallVector<Type> resultTypes;
    SmallVector<StringRef> portNames;
    SmallVector<Attribute> portAnnotations;
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      if (deadReads[i])
        resultTypes.push_back(
            MemOp::getTypeForPort(mem.getDepth(), mem.getDataType(),
                                  MemOp::PortKind::Write, mem.getMaskBits()));
      else
        resultTypes.push_back(port.getType());
 
      portNames.push_back(mem.getPortName(i));
      portAnnotations.push_back(mem.getPortAnnotation(i));
    }
 
    auto newOp = rewriter.create<MemOp>(
        mem.getLoc(), resultTypes, mem.getReadLatency(), mem.getWriteLatency(),
        mem.getDepth(), mem.getRuw(), rewriter.getStrArrayAttr(portNames),
        mem.getName(), mem.getNameKind(), mem.getAnnotations(),
        rewriter.getArrayAttr(portAnnotations), mem.getInnerSymAttr(),
        mem.getInitAttr(), mem.getPrefixAttr());
 
    for (unsigned i = 0, n = mem.getNumResults(); i < n; ++i) {
      auto result = mem.getResult(i);
      auto newResult = newOp.getResult(i);
      if (deadReads[i]) {
        auto resultPortTy = type_cast<BundleType>(result.getType());
 
        // Rewrite accesses to the old port field to accesses to a
        // corresponding field of the new port.
        auto replace = [&](StringRef toName, StringRef fromName) {
          auto fromFieldIndex = resultPortTy.getElementIndex(fromName);
          assert(fromFieldIndex && "missing enable flag on memory port");
 
          auto toField = rewriter.create<SubfieldOp>(newResult.getLoc(),
                                                     newResult, toName);
          for (auto *op : llvm::make_early_inc_range(result.getUsers())) {
            auto fromField = cast<SubfieldOp>(op);
            if (fromFieldIndex != fromField.getFieldIndex())
              continue;
            rewriter.replaceOp(fromField, toField.getResult());
          }
        };
 
        replace("addr", "addr");
        replace("en", "en");
        replace("clk", "clk");
        replace("data", "wdata");
        replace("mask", "wmask");
 
        // Remove the wmode field, replacing it with dummy wires.
        auto wmodeFieldIndex = resultPortTy.getElementIndex("wmode");
        for (auto *op : llvm::make_early_inc_range(result.getUsers())) {
          auto wmodeField = cast<SubfieldOp>(op);
          if (wmodeFieldIndex != wmodeField.getFieldIndex())
            continue;
          rewriter.replaceOpWithNewOp<WireOp>(wmodeField, wmodeField.getType());
        }
      } else {
        rewriter.replaceAllUsesWith(result, newResult);
      }
    }
    rewriter.eraseOp(op);
    return success();
  }
};
 
// Eliminate the dead ports of memories.
struct FoldUnusedBits : public mlir::RewritePattern {
  FoldUnusedBits(MLIRContext *context)
      : RewritePattern(MemOp::getOperationName(), 0, context) {}
 
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    MemOp mem = cast<MemOp>(op);
    if (hasDontTouch(mem))
      return failure();
 
    // Only apply the transformation if the memory is not sequential.
    const auto &summary = mem.getSummary();
    if (summary.isMasked || summary.isSeqMem())
      return failure();
 
    auto type = type_dyn_cast<IntType>(mem.getDataType());
    if (!type)
      return failure();
    auto width = type.getBitWidthOrSentinel();
    if (width <= 0)
      return failure();
 
    llvm::SmallBitVector usedBits(width);
    DenseMap<unsigned, unsigned> mapping;
 
    // Find which bits are used out of the users of a read port. This detects
    // ports whose data/rdata field is used only through bit select ops. The
    // bit selects are then used to build a bit-mask. The ops are collected.
    SmallVector<BitsPrimOp> readOps;
    auto findReadUsers = [&](Value port, StringRef field) -> LogicalResult {
      auto portTy = type_cast<BundleType>(port.getType());
      auto fieldIndex = portTy.getElementIndex(field);
      assert(fieldIndex && "missing data port");
 
      for (auto *op : port.getUsers()) {
        auto portAccess = cast<SubfieldOp>(op);
        if (fieldIndex != portAccess.getFieldIndex())
          continue;
 
        for (auto *user : op->getUsers()) {
          auto bits = dyn_cast<BitsPrimOp>(user);
          if (!bits)
            return failure();
 
          usedBits.set(bits.getLo(), bits.getHi() + 1);
          if (usedBits.all())
            return failure();
 
          mapping[bits.getLo()] = 0;
          readOps.push_back(bits);
        }
      }
 
      return success();
    };
 
    // Finds the users of write ports. This expects all the data/wdata fields
    // of the ports to be used solely as the destination of matching connects.
    // If a memory has ports with other uses, it is excluded from optimisation.
    SmallVector<MatchingConnectOp> writeOps;
    auto findWriteUsers = [&](Value port, StringRef field) -> LogicalResult {
      auto portTy = type_cast<BundleType>(port.getType());
      auto fieldIndex = portTy.getElementIndex(field);
      assert(fieldIndex && "missing data port");
 
      for (auto *op : port.getUsers()) {
        auto portAccess = cast<SubfieldOp>(op);
        if (fieldIndex != portAccess.getFieldIndex())
          continue;
 
        auto conn = getSingleConnectUserOf(portAccess);
        if (!conn)
          return failure();
 
        writeOps.push_back(conn);
      }
      return success();
    };
 
    // Traverse all ports and find the read and used data fields.
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      // Do not simplify annotated ports.
      if (!mem.getPortAnnotation(i).empty())
        return failure();
 
      switch (mem.getPortKind(i)) {
      case MemOp::PortKind::Debug:
        // Skip debug ports.
        return failure();
      case MemOp::PortKind::Write:
        if (failed(findWriteUsers(port, "data")))
          return failure();
        continue;
      case MemOp::PortKind::Read:
        if (failed(findReadUsers(port, "data")))
          return failure();
        continue;
      case MemOp::PortKind::ReadWrite:
        if (failed(findWriteUsers(port, "wdata")))
          return failure();
        if (failed(findReadUsers(port, "rdata")))
          return failure();
        continue;
      }
      llvm_unreachable("unknown port kind");
    }
 
    // Unused memories are handled in a different canonicalizer.
    if (usedBits.none())
      return failure();
 
    // Build a mapping of existing indices to compacted ones.
    SmallVector<std::pair<unsigned, unsigned>> ranges;
    unsigned newWidth = 0;
    for (int i = usedBits.find_first(); 0 <= i && i < width;) {
      int e = usedBits.find_next_unset(i);
      if (e < 0)
        e = width;
      for (int idx = i; idx < e; ++idx, ++newWidth) {
        if (auto it = mapping.find(idx); it != mapping.end()) {
          it->second = newWidth;
        }
      }
      ranges.emplace_back(i, e - 1);
      i = e != width ? usedBits.find_next(e) : e;
    }
 
    // Create the new op with the new port types.
    auto newType = IntType::get(op->getContext(), type.isSigned(), newWidth);
    SmallVector<Type> portTypes;
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      portTypes.push_back(
          MemOp::getTypeForPort(mem.getDepth(), newType, mem.getPortKind(i)));
    }
    auto newMem = rewriter.replaceOpWithNewOp<MemOp>(
        mem, portTypes, mem.getReadLatency(), mem.getWriteLatency(),
        mem.getDepth(), mem.getRuw(), mem.getPortNames(), mem.getName(),
        mem.getNameKind(), mem.getAnnotations(), mem.getPortAnnotations(),
        mem.getInnerSymAttr(), mem.getInitAttr(), mem.getPrefixAttr());
 
    // Rewrite bundle users to the new data type.
    auto rewriteSubfield = [&](Value port, StringRef field) {
      auto portTy = type_cast<BundleType>(port.getType());
      auto fieldIndex = portTy.getElementIndex(field);
      assert(fieldIndex && "missing data port");
 
      rewriter.setInsertionPointAfter(newMem);
      auto newPortAccess =
          rewriter.create<SubfieldOp>(port.getLoc(), port, field);
 
      for (auto *op : llvm::make_early_inc_range(port.getUsers())) {
        auto portAccess = cast<SubfieldOp>(op);
        if (op == newPortAccess || fieldIndex != portAccess.getFieldIndex())
          continue;
        rewriter.replaceOp(portAccess, newPortAccess.getResult());
      }
    };
 
    // Rewrite the field accesses.
    for (auto [i, port] : llvm::enumerate(newMem.getResults())) {
      switch (newMem.getPortKind(i)) {
      case MemOp::PortKind::Debug:
        llvm_unreachable("cannot rewrite debug port");
      case MemOp::PortKind::Write:
        rewriteSubfield(port, "data");
        continue;
      case MemOp::PortKind::Read:
        rewriteSubfield(port, "data");
        continue;
      case MemOp::PortKind::ReadWrite:
        rewriteSubfield(port, "rdata");
        rewriteSubfield(port, "wdata");
        continue;
      }
      llvm_unreachable("unknown port kind");
    }
 
    // Rewrite the reads to the new ranges, compacting them.
    for (auto readOp : readOps) {
      rewriter.setInsertionPointAfter(readOp);
      auto it = mapping.find(readOp.getLo());
      assert(it != mapping.end() && "bit op mapping not found");
      // Create a new bit selection from the compressed memory. The new op may
      // be folded if we are selecting the entire compressed memory.
      auto newReadValue = rewriter.createOrFold<BitsPrimOp>(
          readOp.getLoc(), readOp.getInput(),
          readOp.getHi() - readOp.getLo() + it->second, it->second);
      rewriter.replaceAllUsesWith(readOp, newReadValue);
      rewriter.eraseOp(readOp);
    }
 
    // Rewrite the writes into a concatenation of slices.
    for (auto writeOp : writeOps) {
      Value source = writeOp.getSrc();
      rewriter.setInsertionPoint(writeOp);
 
      Value catOfSlices;
      for (auto &[start, end] : ranges) {
        Value slice = rewriter.createOrFold<BitsPrimOp>(writeOp.getLoc(),
                                                        source, end, start);
        if (catOfSlices) {
          catOfSlices = rewriter.createOrFold<CatPrimOp>(writeOp.getLoc(),
                                                         slice, catOfSlices);
        } else {
          catOfSlices = slice;
        }
      }
 
      // If the original memory held a signed integer, then the compressed
      // memory will be signed too. Since the catOfSlices is always unsigned,
      // cast the data to a signed integer if needed before connecting back to
      // the memory.
      if (type.isSigned())
        catOfSlices =
            rewriter.createOrFold<AsSIntPrimOp>(writeOp.getLoc(), catOfSlices);
 
      rewriter.replaceOpWithNewOp<MatchingConnectOp>(writeOp, writeOp.getDest(),
                                                     catOfSlices);
    }
 
    return success();
  }
};
 
// Rewrite single-address memories to a firrtl register.
struct FoldRegMems : public mlir::RewritePattern {
  FoldRegMems(MLIRContext *context)
      : RewritePattern(MemOp::getOperationName(), 0, context) {}
  LogicalResult matchAndRewrite(Operation *op,
                                PatternRewriter &rewriter) const override {
    MemOp mem = cast<MemOp>(op);
    const FirMemory &info = mem.getSummary();
    if (hasDontTouch(mem) || info.depth != 1)
      return failure();
 
    auto ty = mem.getDataType();
    auto loc = mem.getLoc();
    auto *block = mem->getBlock();
 
    // Find the clock of the register-to-be, all write ports should share it.
    Value clock;
    SmallPtrSet<Operation *, 8> connects;
    SmallVector<SubfieldOp> portAccesses;
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      if (!mem.getPortAnnotation(i).empty())
        continue;
 
      auto collect = [&, port = port](ArrayRef<StringRef> fields) {
        auto portTy = type_cast<BundleType>(port.getType());
        for (auto field : fields) {
          auto fieldIndex = portTy.getElementIndex(field);
          assert(fieldIndex && "missing field on memory port");
 
          for (auto *op : port.getUsers()) {
            auto portAccess = cast<SubfieldOp>(op);
            if (fieldIndex != portAccess.getFieldIndex())
              continue;
            portAccesses.push_back(portAccess);
            for (auto *user : portAccess->getUsers()) {
              auto conn = dyn_cast<FConnectLike>(user);
              if (!conn)
                return failure();
              connects.insert(conn);
            }
          }
        }
        return success();
      };
 
      switch (mem.getPortKind(i)) {
      case MemOp::PortKind::Debug:
        return failure();
      case MemOp::PortKind::Read:
        if (failed(collect({"clk", "en", "addr"})))
          return failure();
        continue;
      case MemOp::PortKind::Write:
        if (failed(collect({"clk", "en", "addr", "data", "mask"})))
          return failure();
        break;
      case MemOp::PortKind::ReadWrite:
        if (failed(collect({"clk", "en", "addr", "wmode", "wdata", "wmask"})))
          return failure();
        break;
      }
 
      Value portClock = getPortFieldValue(port, "clk");
      if (!portClock || (clock && portClock != clock))
        return failure();
      clock = portClock;
    }
    // Create a new wire where the memory used to be. This wire will dominate
    // all readers of the memory. Reads should be made through this wire.
    rewriter.setInsertionPointAfter(mem);
    auto memWire = rewriter.create<WireOp>(loc, ty).getResult();
 
    // The memory is replaced by a register, which we place at the end of the
    // block, so that any value driven to the original memory will dominate the
    // new register (including the clock). All other ops will be placed
    // after the register.
    rewriter.setInsertionPointToEnd(block);
    auto memReg =
        rewriter.create<RegOp>(loc, ty, clock, mem.getName()).getResult();
 
    // Connect the output of the register to the wire.
    rewriter.create<MatchingConnectOp>(loc, memWire, memReg);
 
    // Helper to insert a given number of pipeline stages through registers.
    // The pipelines are placed at the end of the block.
    auto pipeline = [&](Value value, Value clock, const Twine &name,
                        unsigned latency) {
      for (unsigned i = 0; i < latency; ++i) {
        std::string regName;
        {
          llvm::raw_string_ostream os(regName);
          os << mem.getName() << "_" << name << "_" << i;
        }
        auto reg = rewriter
                       .create<RegOp>(mem.getLoc(), value.getType(), clock,
                                      rewriter.getStringAttr(regName))
                       .getResult();
        rewriter.create<MatchingConnectOp>(value.getLoc(), reg, value);
        value = reg;
      }
      return value;
    };
 
    const unsigned writeStages = info.writeLatency - 1;
 
    // Traverse each port. Replace reads with the pipelined register, discarding
    // the enable flag and reading unconditionally. Pipeline the mask, enable
    // and data bits of all write ports to be arbitrated and wired to the reg.
    SmallVector<std::tuple<Value, Value, Value>> writes;
    for (auto [i, port] : llvm::enumerate(mem.getResults())) {
      Value portClock = getPortFieldValue(port, "clk");
      StringRef name = mem.getPortName(i);
 
      auto portPipeline = [&, port = port](StringRef field, unsigned stages) {
        Value value = getPortFieldValue(port, field);
        assert(value);
        return pipeline(value, portClock, name + "_" + field, stages);
      };
 
      switch (mem.getPortKind(i)) {
      case MemOp::PortKind::Debug:
        llvm_unreachable("unknown port kind");
      case MemOp::PortKind::Read: {
        // Read ports pipeline the addr and enable signals. However, the
        // address must be 0 for single-address memories and the enable signal
        // is ignored, always reading out the register. Under these constraints,
        // the read port can be replaced with the value from the register.
        replacePortField(rewriter, port, "data", memWire);
        break;
      }
      case MemOp::PortKind::Write: {
        auto data = portPipeline("data", writeStages);
        auto en = portPipeline("en", writeStages);
        auto mask = portPipeline("mask", writeStages);
        writes.emplace_back(data, en, mask);
        break;
      }
      case MemOp::PortKind::ReadWrite: {
        // Always read the register into the read end.
        replacePortField(rewriter, port, "rdata", memWire);
 
        // Create a write enable and pipeline stages.
        auto wdata = portPipeline("wdata", writeStages);
        auto wmask = portPipeline("wmask", writeStages);
 
        Value en = getPortFieldValue(port, "en");
        Value wmode = getPortFieldValue(port, "wmode");
 
        auto wen = rewriter.create<AndPrimOp>(port.getLoc(), en, wmode);
        auto wenPipelined =
            pipeline(wen, portClock, name + "_wen", writeStages);
        writes.emplace_back(wdata, wenPipelined, wmask);
        break;
      }
      }
    }
 
    // Regardless of `writeUnderWrite`, always implement PortOrder.
    Value next = memReg;
    for (auto &[data, en, mask] : writes) {
      Value masked;
 
      // If a mask bit is used, emit muxes to select the input from the
      // register (no mask) or the input (mask bit set).
      Location loc = mem.getLoc();
      unsigned maskGran = info.dataWidth / info.maskBits;
      for (unsigned i = 0; i < info.maskBits; ++i) {
        unsigned hi = (i + 1) * maskGran - 1;
        unsigned lo = i * maskGran;
 
        auto dataPart = rewriter.createOrFold<BitsPrimOp>(loc, data, hi, lo);
        auto nextPart = rewriter.createOrFold<BitsPrimOp>(loc, next, hi, lo);
        auto bit = rewriter.createOrFold<BitsPrimOp>(loc, mask, i, i);
        auto chunk = rewriter.create<MuxPrimOp>(loc, bit, dataPart, nextPart);
 
        if (masked) {
          masked = rewriter.create<CatPrimOp>(loc, chunk, masked);
        } else {
          masked = chunk;
        }
      }
 
      next = rewriter.create<MuxPrimOp>(next.getLoc(), en, masked, next);
    }
    Value typedNext = rewriter.createOrFold<BitCastOp>(next.getLoc(), ty, next);
    rewriter.create<MatchingConnectOp>(memReg.getLoc(), memReg, typedNext);
 
    // Delete the fields and their associated connects.
    for (Operation *conn : connects)
      rewriter.eraseOp(conn);
    for (auto portAccess : portAccesses)
      rewriter.eraseOp(portAccess);
    rewriter.eraseOp(mem);
 
    return success();
  }
};
} // namespace
 
void MemOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                        MLIRContext *context) {
  results
      .insert<FoldZeroWidthMemory, FoldReadOrWriteOnlyMemory,
              FoldReadWritePorts, FoldUnusedPorts, FoldUnusedBits, FoldRegMems>(
          context);
}
 
//===----------------------------------------------------------------------===//
// Declarations
//===----------------------------------------------------------------------===//
 
// Turn synchronous reset looking register updates to registers with resets.
// Also, const prop registers that are driven by a mux tree containing only
// instances of one constant or self-assigns.
static LogicalResult foldHiddenReset(RegOp reg, PatternRewriter &rewriter) {
  // reg ; connect(reg, mux(port, const, val)) ->
  // reg.reset(port, const); connect(reg, val)
 
  // Find the one true connect, or bail
  auto con = getSingleConnectUserOf(reg.getResult());
  if (!con)
    return failure();
 
  auto mux = dyn_cast_or_null<MuxPrimOp>(con.getSrc().getDefiningOp());
  if (!mux)
    return failure();
  auto *high = mux.getHigh().getDefiningOp();
  auto *low = mux.getLow().getDefiningOp();
  // Reset value must be constant
  auto constOp = dyn_cast_or_null<ConstantOp>(high);
 
  // Detect the case if a register only has two possible drivers:
  // (1) itself/uninit and (2) constant.
  // The mux can then be replaced with the constant.
  // r = mux(cond, r, 3) --> r = 3
  // r = mux(cond, 3, r) --> r = 3
  bool constReg = false;
 
  if (constOp && low == reg)
    constReg = true;
  else if (dyn_cast_or_null<ConstantOp>(low) && high == reg) {
    constReg = true;
    constOp = dyn_cast<ConstantOp>(low);
  }
  if (!constOp)
    return failure();
 
  // For a non-constant register, reset should be a module port (heuristic to
  // limit to intended reset lines). Replace the register anyway if constant.
  if (!isa<BlockArgument>(mux.getSel()) && !constReg)
    return failure();
 
  // Check all types should be typed by now
  auto regTy = reg.getResult().getType();
  if (con.getDest().getType() != regTy || con.getSrc().getType() != regTy ||
      mux.getHigh().getType() != regTy || mux.getLow().getType() != regTy ||
      regTy.getBitWidthOrSentinel() < 0)
    return failure();
 
  // Ok, we know we are doing the transformation.
 
  // Make sure the constant dominates all users.
  if (constOp != &con->getBlock()->front())
    constOp->moveBefore(&con->getBlock()->front());
 
  if (!constReg) {
    SmallVector<NamedAttribute, 2> attrs(reg->getDialectAttrs());
    auto newReg = replaceOpWithNewOpAndCopyName<RegResetOp>(
        rewriter, reg, reg.getResult().getType(), reg.getClockVal(),
        mux.getSel(), mux.getHigh(), reg.getNameAttr(), reg.getNameKindAttr(),
        reg.getAnnotationsAttr(), reg.getInnerSymAttr(),
        reg.getForceableAttr());
    newReg->setDialectAttrs(attrs);
  }
  auto pt = rewriter.saveInsertionPoint();
  rewriter.setInsertionPoint(con);
  auto v = constReg ? (Value)constOp.getResult() : (Value)mux.getLow();
  replaceOpWithNewOpAndCopyName<ConnectOp>(rewriter, con, con.getDest(), v);
  rewriter.restoreInsertionPoint(pt);
  return success();
}
 
LogicalResult RegOp::canonicalize(RegOp op, PatternRewriter &rewriter) {
  if (!hasDontTouch(op.getOperation()) && !op.isForceable() &&
      succeeded(foldHiddenReset(op, rewriter)))
    return success();
 
  if (succeeded(demoteForceableIfUnused(op, rewriter)))
    return success();
 
  return failure();
}
 
//===----------------------------------------------------------------------===//
// Verification Ops.
//===----------------------------------------------------------------------===//
 
static LogicalResult eraseIfZeroOrNotZero(Operation *op, Value predicate,
                                          Value enable,
                                          PatternRewriter &rewriter,
                                          bool eraseIfZero) {
  // If the verification op is never enabled, delete it.
  if (auto constant = enable.getDefiningOp<firrtl::ConstantOp>()) {
    if (constant.getValue().isZero()) {
      rewriter.eraseOp(op);
      return success();
    }
  }
 
  // If the verification op is never triggered, delete it.
  if (auto constant = predicate.getDefiningOp<firrtl::ConstantOp>()) {
    if (constant.getValue().isZero() == eraseIfZero) {
      rewriter.eraseOp(op);
      return success();
    }
  }
 
  return failure();
}
 
template <class Op, bool EraseIfZero = false>
static LogicalResult canonicalizeImmediateVerifOp(Op op,
                                                  PatternRewriter &rewriter) {
  return eraseIfZeroOrNotZero(op, op.getPredicate(), op.getEnable(), rewriter,
                              EraseIfZero);
}
 
void AssertOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                           MLIRContext *context) {
  results.add(canonicalizeImmediateVerifOp<AssertOp>);
}
 
void AssumeOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                           MLIRContext *context) {
  results.add(canonicalizeImmediateVerifOp<AssumeOp>);
}
 
void UnclockedAssumeIntrinsicOp::getCanonicalizationPatterns(
    RewritePatternSet &results, MLIRContext *context) {
  results.add(canonicalizeImmediateVerifOp<UnclockedAssumeIntrinsicOp>);
}
 
void CoverOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                          MLIRContext *context) {
  results.add(canonicalizeImmediateVerifOp<CoverOp, /* EraseIfZero = */ true>);
}
 
//===----------------------------------------------------------------------===//
// InvalidValueOp
//===----------------------------------------------------------------------===//
 
LogicalResult InvalidValueOp::canonicalize(InvalidValueOp op,
                                           PatternRewriter &rewriter) {
  // Remove `InvalidValueOp`s with no uses.
  if (op.use_empty()) {
    rewriter.eraseOp(op);
    return success();
  }
  // Propagate invalids through a single use which is a unary op.  You cannot
  // propagate through multiple uses as that breaks invalid semantics.  Nor
  // can you propagate through binary ops or generally any op which computes.
  // Not is an exception as it is a pure, all-bits inverse.
  if (op->hasOneUse() &&
      (isa<BitsPrimOp, HeadPrimOp, ShrPrimOp, TailPrimOp, SubfieldOp,
           SubindexOp, AsSIntPrimOp, AsUIntPrimOp, NotPrimOp, BitCastOp>(
           *op->user_begin()) ||
       (isa<CvtPrimOp>(*op->user_begin()) &&
        type_isa<SIntType>(op->user_begin()->getOperand(0).getType())) ||
       (isa<AndRPrimOp, XorRPrimOp, OrRPrimOp>(*op->user_begin()) &&
        type_cast<FIRRTLBaseType>(op->user_begin()->getOperand(0).getType())
                .getBitWidthOrSentinel() > 0))) {
    auto *modop = *op->user_begin();
    auto inv = rewriter.create<InvalidValueOp>(op.getLoc(),
                                               modop->getResult(0).getType());
    rewriter.replaceAllOpUsesWith(modop, inv);
    rewriter.eraseOp(modop);
    rewriter.eraseOp(op);
    return success();
  }
  return failure();
}
 
OpFoldResult InvalidValueOp::fold(FoldAdaptor adaptor) {
  if (getType().getBitWidthOrSentinel() == 0 && isa<IntType>(getType()))
    return getIntAttr(getType(), APInt(0, 0, isa<SIntType>(getType())));
  return {};
}
 
//===----------------------------------------------------------------------===//
// ClockGateIntrinsicOp
//===----------------------------------------------------------------------===//
 
OpFoldResult ClockGateIntrinsicOp::fold(FoldAdaptor adaptor) {
  // Forward the clock if one of the enables is always true.
  if (isConstantOne(adaptor.getEnable()) ||
      isConstantOne(adaptor.getTestEnable()))
    return getInput();
 
  // Fold to a constant zero clock if the enables are always false.
  if (isConstantZero(adaptor.getEnable()) &&
      (!getTestEnable() || isConstantZero(adaptor.getTestEnable())))
    return BoolAttr::get(getContext(), false);
 
  // Forward constant zero clocks.
  if (isConstantZero(adaptor.getInput()))
    return BoolAttr::get(getContext(), false);
 
  return {};
}
 
LogicalResult ClockGateIntrinsicOp::canonicalize(ClockGateIntrinsicOp op,
                                                 PatternRewriter &rewriter) {
  // Remove constant false test enable.
  if (auto testEnable = op.getTestEnable()) {
    if (auto constOp = testEnable.getDefiningOp<ConstantOp>()) {
      if (constOp.getValue().isZero()) {
        rewriter.modifyOpInPlace(op,
                                 [&] { op.getTestEnableMutable().clear(); });
        return success();
      }
    }
  }
 
  return failure();
}
 
//===----------------------------------------------------------------------===//
// Reference Ops.
//===----------------------------------------------------------------------===//
 
// refresolve(forceable.ref) -> forceable.data
static LogicalResult
canonicalizeRefResolveOfForceable(RefResolveOp op, PatternRewriter &rewriter) {
  auto forceable = op.getRef().getDefiningOp<Forceable>();
  if (!forceable || !forceable.isForceable() ||
      op.getRef() != forceable.getDataRef() ||
      op.getType() != forceable.getDataType())
    return failure();
  rewriter.replaceAllUsesWith(op, forceable.getData());
  return success();
}
 
void RefResolveOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                               MLIRContext *context) {
  results.insert<patterns::RefResolveOfRefSend>(context);
  results.insert(canonicalizeRefResolveOfForceable);
}
 
OpFoldResult RefCastOp::fold(FoldAdaptor adaptor) {
  // RefCast is unnecessary if types match.
  if (getInput().getType() == getType())
    return getInput();
  return {};
}
 
static bool isConstantZero(Value operand) {
  auto constOp = operand.getDefiningOp<ConstantOp>();
  return constOp && constOp.getValue().isZero();
}
 
template <typename Op>
static LogicalResult eraseIfPredFalse(Op op, PatternRewriter &rewriter) {
  if (isConstantZero(op.getPredicate())) {
    rewriter.eraseOp(op);
    return success();
  }
  return failure();
}
 
void RefForceOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
  results.add(eraseIfPredFalse<RefForceOp>);
}
void RefForceInitialOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                                    MLIRContext *context) {
  results.add(eraseIfPredFalse<RefForceInitialOp>);
}
void RefReleaseOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                               MLIRContext *context) {
  results.add(eraseIfPredFalse<RefReleaseOp>);
}
void RefReleaseInitialOp::getCanonicalizationPatterns(
    RewritePatternSet &results, MLIRContext *context) {
  results.add(eraseIfPredFalse<RefReleaseInitialOp>);
}
 
//===----------------------------------------------------------------------===//
// HasBeenResetIntrinsicOp
//===----------------------------------------------------------------------===//
 
OpFoldResult HasBeenResetIntrinsicOp::fold(FoldAdaptor adaptor) {
  // The folds in here should reflect the ones for `verif::HasBeenResetOp`.
 
  // Fold to zero if the reset is a constant. In this case the op is either
  // permanently in reset or never resets. Both mean that the reset never
  // finishes, so this op never returns true.
  if (adaptor.getReset())
    return getIntZerosAttr(UIntType::get(getContext(), 1));
 
  // Fold to zero if the clock is a constant and the reset is synchronous. In
  // that case the reset will never be started.
  if (isUInt1(getReset().getType()) && adaptor.getClock())
    return getIntZerosAttr(UIntType::get(getContext(), 1));
 
  return {};
}
 
//===----------------------------------------------------------------------===//
// FPGAProbeIntrinsicOp
//===----------------------------------------------------------------------===//
 
static bool isTypeEmpty(FIRRTLType type) {
  return FIRRTLTypeSwitch<FIRRTLType, bool>(type)
      .Case<FVectorType>(
          [&](auto ty) -> bool { return isTypeEmpty(ty.getElementType()); })
      .Case<BundleType>([&](auto ty) -> bool {
        for (auto elem : ty.getElements())
          if (!isTypeEmpty(elem.type))
            return false;
        return true;
      })
      .Case<IntType>([&](auto ty) { return ty.getWidth() == 0; })
      .Default([](auto) -> bool { return false; });
}
 
LogicalResult FPGAProbeIntrinsicOp::canonicalize(FPGAProbeIntrinsicOp op,
                                                 PatternRewriter &rewriter) {
  auto firrtlTy = type_dyn_cast<FIRRTLType>(op.getInput().getType());
  if (!firrtlTy)
    return failure();
 
  if (!isTypeEmpty(firrtlTy))
    return failure();
 
  rewriter.eraseOp(op);
  return success();
}
 
//===----------------------------------------------------------------------===//
// Layer Block Op
//===----------------------------------------------------------------------===//
 
LogicalResult LayerBlockOp::canonicalize(LayerBlockOp op,
                                         PatternRewriter &rewriter) {
 
  // If the layerblock is empty, erase it.
  if (op.getBody()->empty()) {
    rewriter.eraseOp(op);
    return success();
  }
 
  return failure();
}