text: /* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  ==============================================================================*/
  
  #include "tensorflow/compiler/mlir/lite/ir/tfl_ops.h"
  
  #include <algorithm>
  #include <cstddef>
  #include <cstdint>
  #include <iterator>
  #include <numeric>
  
  #include "third_party/eigen3/Eigen/Core"
  #include "llvm/ADT/APFloat.h"
  #include "llvm/ADT/APInt.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SetVector.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/Support/FormatVariadic.h"
  #include "llvm/Support/raw_ostream.h"
  #include "mlir/Dialect/StandardOps/IR/Ops.h"  // from @llvm-project
  #include "mlir/IR/Attributes.h"  // from @llvm-project
  #include "mlir/IR/Builders.h"  // from @llvm-project
  #include "mlir/IR/BuiltinTypes.h"  // from @llvm-project
  #include "mlir/IR/Location.h"  // from @llvm-project
  #include "mlir/IR/Matchers.h"  // from @llvm-project
  #include "mlir/IR/OpImplementation.h"  // from @llvm-project
  #include "mlir/IR/PatternMatch.h"  // from @llvm-project
  #include "mlir/IR/TypeUtilities.h"  // from @llvm-project
  #include "mlir/Support/LLVM.h"  // from @llvm-project
  #include "mlir/Support/LogicalResult.h"  // from @llvm-project
  #include "mlir/Transforms/FoldUtils.h"  // from @llvm-project
  #include "mlir/Transforms/InliningUtils.h"  // from @llvm-project
  #include "mlir/Transforms/RegionUtils.h"  // from @llvm-project
  #include "tensorflow/compiler/mlir/lite/ir/tfl_structs.cc.inc"
  #include "tensorflow/compiler/mlir/tensorflow/ir/tf_ops.h"
  #include "tensorflow/compiler/mlir/tensorflow/ir/tf_ops_a_m.h"
  #include "tensorflow/compiler/mlir/tensorflow/ir/tf_types.h"
  #include "tensorflow/core/framework/kernel_shape_util.h"
  
  namespace mlir {
  namespace TFL {
  
  // Returns true when the given operand arguments have the same shape or
  // broadcastable shape within the given rank. If any given shapes are
  // non-static and maximum rank is within the given rank, this method returns
  // true.
  bool VerifyOperandsHaveSameShapesOrBroadcastableShape(
      Operation *op, ArrayRef<unsigned> indices, int max_bcast_rank) {
    if (indices.empty()) return true;
  
    // First, it checks there are any inputs that has unknown rank.
    bool has_unknown_shape_input = false;
    bool has_same_shape = true;
    bool reach_first_known_shape = false;
    int64_t max_rank = -1;
  
    ArrayRef<int64_t> pivot_shape;
    SmallVector<int64_t, 4> current_shape;
    SmallVector<int64_t, 4> result_shape;
  
    for (unsigned index : indices) {
      ShapedType shaped_type =
          op->getOperand(index).getType().dyn_cast<ShapedType>();
      if (!shaped_type || !shaped_type.hasRank()) {
        // Marks that we have an unknown rank input.
        has_unknown_shape_input = true;
        continue;
      }
      max_rank = std::max(max_rank, shaped_type.getRank());
      if (!shaped_type.hasStaticShape()) {
        // Marks that we have an unknown shape input.
        has_unknown_shape_input = true;
        continue;
      }
  
      ArrayRef<int64_t> shape = shaped_type.getShape();
      if (!reach_first_known_shape) {
        pivot_shape = shape;
        current_shape.assign(shape.begin(), shape.end());
        reach_first_known_shape = true;
        continue;
      }
  
      if (!pivot_shape.equals(shape)) {
        has_same_shape = false;
      }
      //  Checks if all the inputs are broadcastable since they have not all the
      //  same shapes.
      if (!OpTrait::util::getBroadcastedShape(current_shape, shape,
                                              result_shape)) {
        return false;
      }
      current_shape = result_shape;
    }
  
    // It will treat the unknown shape inputs as acceptable inputs for model
    // compatibility unless there is an known rank that is bigger than the allowed
    // broadcast maximum rank.
    if (has_unknown_shape_input) return max_rank <= max_bcast_rank;
  
    // If all the shape is known and same, CPU kernels are able to handle inputs
    // regardless of dimension size.
    return has_same_shape || max_rank <= max_bcast_rank;
  }
  
  // Return true when the given element_type is QI8.
  bool IsQI8Type(Type element_type) {
    auto quantized_type = element_type.dyn_cast<QuantizedType>();
    return quantized_type != nullptr &&
           quantized_type.getStorageTypeIntegralWidth() == 8 &&
           quantized_type.isSigned();
  }
  
  // Return true when the given element_type is QUI8.
  bool IsQUI8Type(Type element_type) {
    auto quantized_type = element_type.dyn_cast<QuantizedType>();
    return quantized_type != nullptr &&
           quantized_type.getStorageTypeIntegralWidth() == 8 &&
           !quantized_type.isSigned();
  }
  
  // Return true when the given element_type is QI16.
  bool IsQI16Type(Type element_type) {
    auto quantized_type = element_type.dyn_cast<QuantizedType>();
    return quantized_type != nullptr &&
           quantized_type.getStorageTypeIntegralWidth() == 16 &&
           quantized_type.isSigned();
  }
  
  // Return true when the given element_type is I32.
  bool IsI32Type(Type element_type) {
    return element_type.isInteger(32) && !element_type.isUnsignedInteger();
  }
  
  // Return true when the given element_type is I64.
  bool IsI64Type(Type element_type) {
    return element_type.isInteger(64) && !element_type.isUnsignedInteger();
  }
  
  // Return true if the value is a splat tensor constant zero.
  bool EqualsZero(Value value) {
    DenseElementsAttr constant;
    if (!matchPattern(value, m_Constant(&constant)) || !constant.isSplat()) {
      return false;
    }
  
    Type element_type = value.getType().cast<ShapedType>().getElementType();
    if (element_type.isa<FloatType>()) {
      return constant.getSplatValue<APFloat>().isZero();
    } else {
      return false;
    }
  }
  
  // Replaces the bias operand with a "none" type value if the bias value is
  // constant zero.
  // `ConcreteOpType` must be an concrete MLIR op class that has an optional
  // bias operand named 'bias'.
  template <typename ConcreteOpType>
  struct RemoveOptionalZeroBias : public OpRewritePattern<ConcreteOpType> {
    using OpRewritePattern<ConcreteOpType>::OpRewritePattern;
  
    LogicalResult matchAndRewrite(ConcreteOpType op,
                                  PatternRewriter &rewriter) const override {
      if (EqualsZero(op.bias())) {
        auto none_value = rewriter.create<mlir::ConstantOp>(
            rewriter.getUnknownLoc(), rewriter.getUnitAttr());
        op.biasMutable().assign(none_value);
      }
  
      return success();
    }
  };
  
  // Return true if the given Add operation has the CPU kernel supported shapes.
  bool VerifyAddOpShapeConstraints(AddOp op) {
    auto element_type = getElementTypeOrSelf(op.output().getType());
  
    // Allows F32, QI8, QUI8 and I32 outputs when the operands have valid shapes,
    // which are broadcastable shapes up to five dimension or have same shapes.
    if (element_type.isF32() || IsQI8Type(element_type) ||
        IsQUI8Type(element_type) || IsI32Type(element_type)) {
      return VerifyOperandsHaveSameShapesOrBroadcastableShape(
          /*op=*/op.getOperation(), /*indices=*/ArrayRef<unsigned>{0, 1},
          /*max_bcast_rank=*/4);
    }
  
    // Allows QI16 output when operands have the same shape.
    if (IsQI16Type(element_type)) {
      return succeeded(
          mlir::verifyCompatibleShape(op.lhs().getType(), op.rhs().getType()));
    }
    return false;
  }
  
  // Return true if the given Sub operation has the CPU kernel supported shapes.
  bool VerifySubOpShapeConstraints(SubOp op) {
    auto element_type = getElementTypeOrSelf(op.output().getType());
  
    // Allows F32, QUI8, and QI16 outputs when the operands have valid shapes,
    // which are broadcastable shapes up to five dimension or have same shapes.
    if (element_type.isF32() || IsI32Type(element_type) ||
        IsI64Type(element_type) || IsQUI8Type(element_type) ||
        IsQI16Type(element_type)) {
      return VerifyOperandsHaveSameShapesOrBroadcastableShape(
          /*op=*/op.getOperation(), /*indices=*/ArrayRef<unsigned>{0, 1},
          /*max_bcast_rank=*/5);
    }
  
    // Allows QI8 output when the operands have valid shapes, which are
    // broadcastable shapes up to four dimension or have same shapes.
    if (IsQI8Type(element_type)) {
      return VerifyOperandsHaveSameShapesOrBroadcastableShape(
          /*op=*/op.getOperation(), /*indices=*/ArrayRef<unsigned>{0, 1},
          /*max_bcast_rank=*/4);
    }
    return false;
  }
  
  // Return true if the given Mul operation has the CPU kernel supported shapes.
  bool VerifyMulOpShapeConstraints(MulOp op) {
    auto element_type = getElementTypeOrSelf(op.output().getType());
  
    // Allows QI8 and QUI8 inputs up to five dimension broadcasting unless the
    // output type is not QI16. If the output type is Q16, allows only the same
    // shape operands.
    if (IsQI8Type(element_type) || IsQUI8Type(element_type)) {
      if (IsQI16Type(getElementTypeOrSelf(op.lhs().getType()))) {
        return succeeded(
            mlir::verifyCompatibleShape(op.lhs().getType(), op.rhs().getType()));
      }
      return VerifyOperandsHaveSameShapesOrBroadcastableShape(
          /*op=*/op.getOperation(), /*indices=*/ArrayRef<unsigned>{0, 1},
          /*max_bcast_rank=*/4);
    }
  
    // Allows I32, QI16 and F32 outputs when the operands have valid shapes, which
    // are broadcastable shapes up to four dimension or have same shapes.
    if (IsI32Type(element_type) || IsQI16Type(element_type) ||
        element_type.isF32()) {
      return VerifyOperandsHaveSameShapesOrBroadcastableShape(
          /*op=*/op.getOperation(), /*indices=*/ArrayRef<unsigned>{0, 1},
          /*max_bcast_rank=*/4);
    }
    return false;
  }
  
  //===----------------------------------------------------------------------===//
  // TensorFlowLiteDialect
  //===----------------------------------------------------------------------===//
  
  struct TensorFlowLiteInlinerInterface : public DialectInlinerInterface {
    using DialectInlinerInterface::DialectInlinerInterface;
  
    //===--------------------------------------------------------------------===//
    // Analysis Hooks
    //===--------------------------------------------------------------------===//
  
    // Allow all call operations to be inlined.
    bool isLegalToInline(Operation *call, Operation *callable,
                         bool wouldBeCloned) const final {
      return true;
    }
    bool isLegalToInline(Operation *op, Region *dest, bool wouldBeCloned,
                         BlockAndValueMapping &) const final {
      // No TFLite op restricts inlining today, revise as needed in the future.
      return true;
    }
    bool isLegalToInline(Region *dest, Region *src, bool wouldBeCloned,
                         BlockAndValueMapping &valueMapping) const final {
      return isa<WhileOp>(dest->getParentOp());
    }
  };
  
  struct TensorFlowLiteDialectFoldInterface : public DialectFoldInterface {
    using DialectFoldInterface::DialectFoldInterface;
  
    // Registered hook to check if the given region, which is attached to an
    // operation that is *not* isolated from above (i.e. no internal regions
    // reference values defined in an enclosing region), should be used when
    // materializing constants.
    // In the TFLite dialect we materialize inside a while regions as slightly
    // more efficient computationally.
    bool shouldMaterializeInto(Region *region) const final {
      return isa<WhileOp>(region->getParentOp());
    }
  };
  
  TensorFlowLiteDialect::TensorFlowLiteDialect(mlir::MLIRContext *context)
      : Dialect(/*name=*/"tfl", context, TypeID::get<TensorFlowLiteDialect>()) {
    addOperations<
  #define GET_OP_LIST
  #include "tensorflow/compiler/mlir/lite/ir/tfl_ops.cc.inc"
        >();
    addInterfaces<TensorFlowLiteInlinerInterface,
                  TensorFlowLiteDialectFoldInterface>();
  }
  
  //===----------------------------------------------------------------------===//
  // Common support logic
  //===----------------------------------------------------------------------===//
  
  namespace {
  
  // Returns true if the dimensions in `a` is a suffix of the ones in `b`.
  // For example, dimensions {2}, {1, 2}, and {3, 1, 2} are all suffixes to
  // {5, 4, 3, 1, 2}, while {1}, {5, 4}, and {1, 3, 2} are all not.
  inline bool IsTrailingDimensions(ArrayRef<int64_t> a, ArrayRef<int64_t> b) {
    if (a.size() > b.size()) return false;
  
    return std::equal(a.rbegin(), a.rend(), b.rbegin());
  }
  
  // Returns true if it is a shaped type of f32 elements.
  inline bool IsF32ShapedType(Type t) {
    if (auto shaped_type = t.dyn_cast_or_null<ShapedType>()) {
      return shaped_type.getElementType().isF32();
    }
    return false;
  }
  
  // Returns true if it is a shaped type of bf16 elements.
  inline bool IsBF16ShapedType(Type t) {
    if (auto shaped_type = t.dyn_cast_or_null<ShapedType>()) {
      return shaped_type.getElementType().isBF16();
    }
    return false;
  }
  
  // Returns new shape with rank 'new_dims' with padded ones on the
  // left if needed.
  inline std::vector<int64_t> GetPaddedShape(ArrayRef<int64_t> old_shape,
                                             int new_dims) {
    std::vector<int64_t> new_shape(new_dims, 1);
    std::copy_backward(old_shape.begin(), old_shape.end(), new_shape.end());
    return new_shape;
  }
  
  // Helper method that given and 'current_index' representing
  // index in broadcasted tensor, get the index in the flat original tensor.
  // 'shape' is the original shape with padding to match result shape.
  int64_t GetElementIndex(const std::vector<int64_t> &shape,
                          const std::vector<int64_t> &current_index) {
    int64_t ind = 0;
    int64_t mul = 1;
    for (int i = shape.size() - 1; i >= 0; --i) {
      ind += (current_index[i] % shape[i]) * mul;
      mul *= shape[i];
    }
    return ind;
  }
  
  // Helper method that increment index represented in 'current_index_ptr'
  // in the shape of 'result_shape'.
  void IncrementIndex(ArrayRef<int64_t> result_shape,
                      std::vector<int64_t> *current_index_ptr) {
    std::vector<int64_t> &current_index = *current_index_ptr;
    for (int i = result_shape.size() - 1; i >= 0; --i) {
      current_index[i]++;
      if (current_index[i] == result_shape[i]) {
        current_index[i] = 0;
      } else {
        break;
      }
    }
  }
  
  /// Performs const folding `calculate` with broadcast behavior on the two
  /// attributes `operand1` and `operand2` and returns the result if possible.
  /// This function assumes the both operands are verified to have value
  /// attributes of broadcastable types.
  template <class AttrElementT,
            class ElementValueT = typename AttrElementT::ValueType,
            class CalculationT =
                llvm::function_ref<ElementValueT(ElementValueT, ElementValueT)>>
  Attribute ConstFoldBinaryOpDenseDense(Type result_type, DenseElementsAttr lhs,
                                        DenseElementsAttr rhs,
                                        const CalculationT &calculate) {
    auto type = OpTrait::util::getBroadcastedType(lhs.getType(), rhs.getType())
                    .dyn_cast_or_null<ShapedType>();
    if (!type) {
      return {};
    }
  
    const bool rhs_is_splat = rhs.isSplat();
    const bool lhs_is_splat = lhs.isSplat();
  
    // If both of them are splat, compute and return.
    if (lhs_is_splat && rhs_is_splat) {
      auto element_result = AttrElementT::get(
          type.getElementType(), calculate(lhs.getSplatValue<ElementValueT>(),
                                           rhs.getSplatValue<ElementValueT>()));
      if (!element_result) return {};
  
      return DenseElementsAttr::get(type, element_result);
    }
  
    auto num_elements = type.getNumElements();
  
    SmallVector<ElementValueT, 16> new_values;
    new_values.reserve(num_elements);
    const auto result_shape = type.getShape();
    std::vector<int64_t> current_index(type.getRank(), 0);
    // Create the new shape with ones padded to the left.
    const std::vector<int64_t> lhs_new_shape =
        GetPaddedShape(lhs.getType().getShape(), type.getRank());
    const std::vector<int64_t> rhs_new_shape =
        GetPaddedShape(rhs.getType().getShape(), type.getRank());
  
    auto lhs_old_values = lhs.getValues<ElementValueT>();
    auto rhs_old_values = rhs.getValues<ElementValueT>();
  
    // Add each pair of the corresponding values in the dense elements
    // attributes.
    for (int64_t i = 0; i < num_elements; ++i) {
      // current_index represents the index
      // in the N-dimension tensor. GetElementIndex returns
      // the index in the flat representation of the original tensor
      // to use.
      const int64_t lhs_index =
          lhs_is_splat ? 0 : GetElementIndex(lhs_new_shape, current_index);
      const int64_t rhs_index =
          rhs_is_splat ? 0 : GetElementIndex(rhs_new_shape, current_index);
  
      new_values.push_back(calculate(*(lhs_old_values.begin() + lhs_index),
                                     *(rhs_old_values.begin() + rhs_index)));
      IncrementIndex(result_shape, &current_index);
    }
    return DenseElementsAttr::get(type, ArrayRef<ElementValueT>(new_values));
  }
  
  /// Performs const folding `calculate` with broadcast behavior on the two
  /// attributes `operand1` and `operand2` and returns the result if possible.
  /// This function assumes the two operands are verified to have value
  /// attributes of broadcastable types.
  template <class AttrElementT,
            class ElementValueT = typename AttrElementT::ValueType,
            class CalculationT =
                llvm::function_ref<ElementValueT(ElementValueT, ElementValueT)>>
  Attribute ConstFoldBinaryOp(Type result_type, Attribute operand1,
                              Attribute operand2, const CalculationT &calculate) {
    if (operand1.dyn_cast_or_null<DenseElementsAttr>() &&
        operand2.dyn_cast_or_null<DenseElementsAttr>()) {
      return ConstFoldBinaryOpDenseDense<AttrElementT, ElementValueT>(
          result_type, operand1.cast<DenseElementsAttr>(),
          operand2.cast<DenseElementsAttr>(), calculate);
    }
  
    // TODO: support other attribute kinds
  
    return {};
  }
  
  /// Performs const folding with broadcast behavior on the two attributes in
  /// `operands` and returns the result if possible.
  /// Depending on the given `resultType`, either `floatCalculate` or
  /// `intCalculate` is chosen to conduct the calculate.
  Attribute ConstFoldBinaryOp(
      Type result_type, ArrayRef<Attribute> operands,
      llvm::function_ref<APFloat(APFloat, APFloat)> float_calculate,
      llvm::function_ref<APInt(APInt, APInt)> int_calculate) {
    // Note: All types are wrapped in tensor types in TFlite. E.g., f32 is
    // represented as tensor<f32>. So we are only handling tensor types here.
    auto type = result_type.dyn_cast<ShapedType>();
    if (!type) return {};
  
    auto elemType = type.getElementType();
  
    if (elemType.isa<FloatType>())
      return ConstFoldBinaryOp<FloatAttr>(result_type, operands[0], operands[1],
                                          float_calculate);
  
    if (elemType.isSignlessInteger())
      return ConstFoldBinaryOp<IntegerAttr>(result_type, operands[0], operands[1],
                                            int_calculate);
  
    return {};
  }
  
  /// Performs const folding a attributes `operand` and returns the result if
  /// possible.
  /// The function currently asserts that the `result_type` to be a f32 tensor
  /// type.
  /// TODO: Extend this function to handle integral tensor for ops like
  /// "tfl.logical_not".
  Attribute ConstFoldUnaryOp(Type result_type, Attribute operand,
                             llvm::function_ref<APFloat(APFloat)> calculate) {
    assert(IsF32ShapedType(result_type) || IsBF16ShapedType(result_type));
    auto result_shape_type = result_type.cast<ShapedType>();
  
    if (!result_shape_type.hasStaticShape()) return {};
  
    if (auto dense_elements = operand.dyn_cast_or_null<DenseElementsAttr>()) {
      SmallVector<APFloat, 16> new_values;
      const int num_elements = result_shape_type.getNumElements();
      new_values.reserve(num_elements);
  
      for (const APFloat &old_value : dense_elements.getValues<APFloat>()) {
        new_values.push_back(calculate(old_value));
      }
  
      return DenseElementsAttr::get(result_shape_type, new_values);
    }
  
    return {};
  }
  
  void buildComparisonBinOp(Builder *builder, OperationState &result, Value lhs,
                            Value rhs) {
    auto result_type =
        OpTrait::util::getBroadcastedType(lhs.getType(), rhs.getType());
    if (!result_type)
      emitError(result.location)
          << "non-broadcastable operands: " << lhs.getType() << " and "
          << rhs.getType();
    result.addOperands({lhs, rhs});
    // Comparison binary ops always return i1 tensor.
    if (auto shaped_type = result_type.dyn_cast<RankedTensorType>()) {
      auto result_shape = shaped_type.getShape();
      result.types.push_back(
          RankedTensorType::get(result_shape, builder->getI1Type()));
    } else {
      result.types.push_back(UnrankedTensorType::get(builder->getI1Type()));
    }
  }
  
  void buildFusedBroadcastableBinOp(Builder *builder, OperationState &result,
                                    Value lhs, Value rhs,
                                    StringAttr fused_activation_function) {
    auto result_type =
        OpTrait::util::getBroadcastedType(lhs.getType(), rhs.getType());
  
    if (!result_type)
      emitError(result.location)
          << "non-broadcastable operands: " << lhs.getType() << " and "
          << rhs.getType();
  
    result.addOperands({lhs, rhs});
    result.addAttribute("fused_activation_function", fused_activation_function);
    result.types.push_back(result_type);
  }
  
  }  // end anonymous namespace
  
  //===----------------------------------------------------------------------===//
  // AddOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult AddOp::fold(ArrayRef<Attribute> operands) {
    // TODO(b/142478136): Handle fused ops.
    if (fused_activation_function() != "NONE") return {};
    return ConstFoldBinaryOp(
        getType(), operands, [](APFloat a, APFloat b) { return a + b; },
        [](APInt a, APInt b) { return a + b; });
  }
  
  //===----------------------------------------------------------------------===//
  // ConcatenationOp
  //===----------------------------------------------------------------------===//
  // TODO(ashwinm): Implement shape inference for Concatenation
  
  namespace {
  
  int64_t GetConcatenationOpAxis(ConcatenationOp op) {
    auto output_type = op.output().getType().cast<RankedTensorType>();
    int32_t axis = op.axis();
    if (axis < 0) axis += output_type.getRank();
    return axis;
  }
  
  // Verify operand types and the result type:
  //
  // 1. Operand type ranks must be equal to the output type rank.
  //
  // 2. Operand dimension sizes (except dimension `axis`) must be equal to
  //    previously seen dimension sizes of the same dimension.
  //
  // 3. Sum of operand dimension sizes of the `axis` dimension must be equal to
  //    the dimension size of the `axis` dimension of output.
  //
  // Note: If an operand has unranked tensor type or has dynamic dimension size,
  // those dimensions will be skipped.
  LogicalResult VerifyConcatenationOpTypes(Operation *op,
                                           RankedTensorType output_type,
                                           ArrayRef<TensorType> operand_types,
                                           int64_t axis) {
    const int64_t output_rank = output_type.getRank();
  
    constexpr int64_t kDynamicSize = -1;
    SmallVector<int64_t, 4> result_dim_sizes_loc(output_rank, -1);
    SmallVector<int64_t, 4> result_dim_sizes(output_type.getShape().begin(),
                                             output_type.getShape().end());
    result_dim_sizes[axis] = 0;
  
    auto FormatLoc = [&result_dim_sizes_loc](int64_t dim) {
      const int64_t loc = result_dim_sizes_loc[dim];
      if (loc == -1) return std::string("output");
      return llvm::formatv("operand #{0}", loc).str();
    };
  
    for (auto operand : llvm::enumerate(operand_types)) {
      auto operand_type = operand.value().dyn_cast<RankedTensorType>();
      if (!operand_type) {
        result_dim_sizes[axis] = kDynamicSize;
        continue;
      }
  
      const int64_t operand_rank = operand_type.getRank();
      if (operand_rank != output_rank)
        return op->emitOpError() << "rank of operand #" << operand.index()
                                 << " must be equal to rank of output, expected "
                                 << output_rank << ", got " << operand_rank;
  
      for (int64_t dim = 0; dim < output_rank; ++dim) {
        const int64_t operand_dim_size = operand_type.getDimSize(dim);
        const int64_t result_dim_size = result_dim_sizes[dim];
  
        if (dim == axis) {
          if (RankedTensorType::isDynamic(operand_dim_size) ||
              RankedTensorType::isDynamic(result_dim_size))
            result_dim_sizes[axis] = kDynamicSize;
          else
            result_dim_sizes[axis] += operand_dim_size;
          continue;
        }
  
        if (RankedTensorType::isDynamic(operand_dim_size)) continue;
  
        if (RankedTensorType::isDynamic(result_dim_size)) {
          result_dim_sizes[dim] = operand_dim_size;
          result_dim_sizes_loc[dim] = operand.index();
          continue;
        }
  
        if (result_dim_size != operand_dim_size)
          return op->emitOpError()
                 << "dimension size of dimension #" << dim << " of operand #"
                 << operand.index() << " must be equal to "
                 << "dimension size of dimension #" << dim << " of "
                 << FormatLoc(dim) << ", expected " << result_dim_size << ", got "
                 << operand_dim_size;
      }
    }
  
    const int64_t output_concated_dim_size = output_type.getDimSize(axis);
    if (!RankedTensorType::isDynamic(output_concated_dim_size) &&
        !RankedTensorType::isDynamic(result_dim_sizes[axis]) &&
        result_dim_sizes[axis] != output_concated_dim_size)
      return op->emitOpError()
             << "dimension size of dimension #" << axis << " of output "
             << "must be equal to the sum of dimension sizes of dimension #"
             << axis << ", expected " << result_dim_sizes[axis] << ", got "
             << output_concated_dim_size;
  
    return success();
  }
  
  LogicalResult Verify(ConcatenationOp op) {
    auto output_type = op.output().getType().dyn_cast<RankedTensorType>();
  
    // If the output type is unranked, there is nothing else to be verified.
    if (!output_type) return success();
  
    const int64_t axis = GetConcatenationOpAxis(op);
    if (axis < 0 || axis >= output_type.getRank())
      return op.emitOpError("concatenation dimension must be in [-rank, rank)");
  
    SmallVector<TensorType, 4> operand_types;
    for (Value operand : op.values())
      operand_types.push_back(operand.getType().cast<TensorType>());
  
    return VerifyConcatenationOpTypes(op.getOperation(), output_type,
                                      operand_types, axis);
  }
  
  // Returns true when all operands are instances of DenseElementsAttr and the
  // output type has a static shape.
  bool IsConcatenationOpConstFoldable(ConcatenationOp op,
                                      ArrayRef<Attribute> operands,
                                      RankedTensorType output_type,
                                      int64_t axis) {
    if (operands.empty()) return false;
    if (!output_type.hasStaticShape()) return false;
    if (axis < 0) return false;
  
    return llvm::all_of(operands, [](Attribute operand) {
      return operand && operand.isa<DenseElementsAttr>();
    });
  }
  
  DenseElementsAttr ConstFoldConcatenateOpDense(ArrayRef<Attribute> operands,
                                                RankedTensorType output_type,
                                                int64_t axis) {
    const auto outer_dims = output_type.getShape().take_front(axis);
    const int64_t outer_size = std::accumulate(
        outer_dims.begin(), outer_dims.end(), 1, std::multiplies<int64_t>());
  
    const auto base_inner_dims = output_type.getShape().drop_front(axis + 1);
    const int64_t base_inner_size =
        std::accumulate(base_inner_dims.begin(), base_inner_dims.end(), 1,
                        std::multiplies<int64_t>());
  
    // Splits each input operand into outer_size pieces and combines them in
    // round-robin ordering.
    std::vector<Attribute> out_attrs(output_type.getNumElements());
    int64_t out = 0;
    for (int64_t outer = 0; outer < outer_size; ++outer) {
      for (auto op : operands) {
        const int64_t dim_size =
            op.getType().cast<RankedTensorType>().getDimSize(axis);
        const int64_t inner_size = dim_size * base_inner_size;
  
        auto input_attrs = op.cast<DenseElementsAttr>().getValues<Attribute>();
        auto input_iter = input_attrs.begin() + outer * inner_size;
        for (int64_t inner = 0; inner < inner_size; ++inner)
          out_attrs[out++] = *input_iter++;
      }
    }
  
    return DenseElementsAttr::get(output_type, out_attrs);
  }
  
  }  // end anonymous namespace
  
  OpFoldResult ConcatenationOp::fold(ArrayRef<Attribute> operands) {
    if (fused_activation_function() == "NONE") {
      if (auto output_type = output().getType().dyn_cast<RankedTensorType>()) {
        const int64_t axis = GetConcatenationOpAxis(*this);
        if (IsConcatenationOpConstFoldable(*this, operands, output_type, axis))
          return ConstFoldConcatenateOpDense(operands, output_type, axis);
      }
    }
  
    // Remove all empty values.
    SmallVector<Value, 4> non_empty_values;
    for (Value value : this->values()) {
      const auto shaped_type = value.getType().cast<ShapedType>();
      if (shaped_type.hasStaticShape() && shaped_type.getNumElements() == 0) {
        continue;
      }
      non_empty_values.push_back(value);
    }
  
    // All are not empty, do nothing.
    if (non_empty_values.size() == getNumOperands()) return nullptr;
  
    // If only one input is non-empty, just return it as the result of folding.
    if (non_empty_values.size() == 1) {
      return non_empty_values[0];
    }
  
    // Otherwise, build a new concatenation op with non-empty values.
    mlir::OpBuilder builder(getOperation());
    auto new_concat = builder.create<TFL::ConcatenationOp>(
        getLoc(), getType(), non_empty_values,
        builder.getIntegerAttr(builder.getIntegerType(32), axis()),
        builder.getStringAttr(fused_activation_function()));
    return new_concat.getResult();
  }
  
  //===----------------------------------------------------------------------===//
  // CustomOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(CustomOp op) {
    OpaqueElementsAttr opaque_attr =
        op.custom_option().cast<OpaqueElementsAttr>();
    if (!opaque_attr.getType().hasStaticShape())
      return op.emitOpError("custom_option should have a static shape.");
    const int attribute_size = opaque_attr.getValue().size();
    if (attribute_size != opaque_attr.getType().cast<ShapedType>().getDimSize(0))
      return op.emitOpError(
          "custom_option should have the same length of content with shape.");
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // CustomTfOp
  //===----------------------------------------------------------------------===//
  
  LogicalResult CustomTfOp::inferReturnTypes(
      MLIRContext *, Optional<Location> location, ValueRange operands,
      DictionaryAttr attr, RegionRange ranges,
      SmallVectorImpl<Type> &inferredReturnTypes) {
    CustomTfOpAdaptor op(operands, attr, ranges);
  
    if (op.getRegions().empty()) return success();
    auto *real_op = &op.body().front().front();
    if (llvm::isa<TF::FakeQuantWithMinMaxArgsOp, TF::FakeQuantWithMinMaxVarsOp,
                  TF::FakeQuantWithMinMaxVarsPerChannelOp>(real_op)) {
      Value input = *operands.begin();
      inferredReturnTypes.assign({input.getType()});
    }
    return success();
  }
  
  bool CustomTfOp::isCompatibleReturnTypes(TypeRange lhs, TypeRange rhs) {
    if (lhs.empty()) return true;
    if (lhs.size() != rhs.size() || lhs.size() != 1) return false;
    if (failed(mlir::verifyCompatibleShape(lhs[0], rhs[0]))) return false;
    return true;
  }
  
  //===----------------------------------------------------------------------===//
  // FullyConnectedOp
  //===----------------------------------------------------------------------===//
  
  LogicalResult Verify(FullyConnectedOp op) {
    ShapedType input_type = op.input().getType().cast<ShapedType>();
    ShapedType filter_type = op.filter().getType().cast<ShapedType>();
    if (filter_type.hasRank() && filter_type.getRank() != 2) {
      return op.emitOpError("expect 2d filter, got ") << filter_type;
    }
  
    if (!input_type.hasStaticShape() || !filter_type.hasStaticShape()) {
      return mlir::success();
    }
  
    // Input's element size must be multiple of parameter's z_in dimension.
    const int z_in = filter_type.getDimSize(1);
    const int num_input_elements = input_type.getNumElements();
    if (num_input_elements % z_in != 0) {
      return op.emitOpError(llvm::formatv(
                 "expect 'input' num_elements % {0} == 0, got input type ", z_in))
             << input_type;
    }
  
    // TODO(jpienaar): Include more shape verification for SHUFFLED4x16INT8
    // format.
    if (op.weights_format() == "DEFAULT") {
      ShapedType output_type =
          (*op.output().begin()).getType().cast<ShapedType>();
      if (!output_type.hasStaticShape()) {
        return mlir::success();
      }
  
      const int num_output_elements = output_type.getNumElements();
      const int z_out = filter_type.getDimSize(0);
      if (num_output_elements % z_out != 0) {
        return op.emitOpError(llvm::formatv(
                   "expect 'output' num_elements % {0} == 0, got ", z_out))
               << output_type;
      }
  
      if (num_input_elements / z_in != num_output_elements / z_out) {
        return op.emitOpError(
            "num_input_elements / z_in != num_output_elements / z_out");
      }
    }
  
    return mlir::success();
  }
  
  LogicalResult FullyConnectedOp::fold(ArrayRef<Attribute> operands,
                                       SmallVectorImpl<OpFoldResult> &results) {
    assert(operands.size() == 3);
  
    // Folding not implemented with any activation function or any weight type
    // besides the default.
    if (fused_activation_function() != "NONE") return failure();
    if (weights_format() != "DEFAULT") return failure();
  
    // Bias tensor is optional.
    const bool has_bias = !(!bias() || bias().getType().isa<NoneType>());
  
    // Get the tensors.
    DenseElementsAttr input_tensor, weights_tensor, bias_tensor;
    if (!matchPattern(input(), m_Constant(&input_tensor)) ||
        !matchPattern(filter(), m_Constant(&weights_tensor)) ||
        (has_bias && !matchPattern(bias(), m_Constant(&bias_tensor)))) {
      return failure();
    }
  
    // Get the tensor types.
    const auto input_type = input_tensor.getType().cast<ShapedType>();
    const auto weights_type = weights_tensor.getType().cast<ShapedType>();
    const auto bias_type =
        has_bias ? bias_tensor.getType().cast<ShapedType>() : ShapedType{};
  
    const auto output_type = getType(0).cast<ShapedType>();
  
    // Folding only implemented for float tensors.
    if (!input_type.getElementType().isF32() ||
        !weights_type.getElementType().isF32() ||
        !output_type.getElementType().isF32() ||
        (has_bias && !bias_type.getElementType().isF32())) {
      return failure();
    }
  
    // Folding only implemented for static shapes
    if (!input_type.hasStaticShape() || !weights_type.hasStaticShape() ||
        (has_bias && !bias_type.hasStaticShape())) {
      return failure();
    }
  
    // Folding only implemented for 1D input, 2D weights and 1D bias
    if (input_type.getShape().size() != 1 ||
        weights_type.getShape().size() != 2 ||
        (has_bias && bias_type.getShape().size() != 1)) {
      return failure();
    }
  
    // Get the sizes
    const auto input_size = input_type.getNumElements();
    const auto output_size = output_type.getNumElements();
  
    // Get iterators to the tensors.
    const auto input_values_it = input_tensor.getValues<float>().begin();
    const auto weights_values_ptr = weights_tensor.getValues<float>().begin();
    auto weights_row_it = weights_values_ptr;
    // The 'else' case could be nullptr, but the types don't match.
    auto bias_values_it =
        has_bias ? bias_tensor.getValues<float>().begin() : input_values_it;
  
    // Do the actual folding, one output at a time.
    std::vector<float> result_values;
    result_values.reserve(output_size);
  
    for (int i = 0; i < output_size; ++i) {
      // Dot product with Kahan/Neumaier summation to minimize numeric errors.
      float sum = has_bias ? *bias_values_it : 0.0f;
      float compensation = 0.0f;
      for (int j = 0; j < input_size; ++j) {
        const float addend = input_values_it[j] * weights_row_it[j];
        const float new_sum = sum + addend;
        // DO NOT enable -funsafe-math-optimizations here.
        // There is a test detecting unsafe optimizations.
        // Unsafe math optimizations can reorder float formulas, and set the
        // compensation to constant 0. The formula must be evaluated as written
        // for the algorithm to work.
        // (Note: -ffast-math is a superset of -funsafe-math-optimizations.)
        if (std::abs(sum) >= std::abs(addend)) {
          compensation += (sum - new_sum) + addend;
        } else {
          compensation += (addend - new_sum) + sum;
        }
        sum = new_sum;
      }
      result_values.push_back(sum + compensation);
      weights_row_it += input_size;
      bias_values_it++;
    }
  
    // Set result tensor
    const auto folded =
        DenseElementsAttr::get(output_type, ArrayRef<float>(result_values));
    results.assign({folded});
  
    return success();
  }
  
  void FullyConnectedOp::getCanonicalizationPatterns(
      OwningRewritePatternList &results, MLIRContext *context) {
    results.insert<RemoveOptionalZeroBias<FullyConnectedOp>>(context);
  }
  
  //===----------------------------------------------------------------------===//
  // Conv2DOp
  //===----------------------------------------------------------------------===//
  
  void Conv2DOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
                                             MLIRContext *context) {
    // TODO(b/180121750): Enable the pattern after the integration tests are
    // fixed.
    // results.insert<RemoveOptionalZeroBias<Conv2DOp>>(context);
  }
  
  static LogicalResult ComputeConvWindowedOutputSize(
      int64_t input_size, int64_t filter_size, int64_t dilation_rate,
      int64_t stride, tensorflow::Padding padding, int64_t *output_size) {
    int64_t pad_low;
    int64_t pad_high;
  
    tensorflow::Status status = tensorflow::GetWindowedOutputSizeVerboseV2(
        input_size, filter_size, dilation_rate, stride, padding, output_size,
        &pad_low, &pad_high);
    // Return failure if expected_output_size could not be calculated.
    if (!status.ok()) return failure();
    return success();
  }
  
  LogicalResult Conv2DOp::inferReturnTypes(
      MLIRContext *, Optional<Location> location, ValueRange operands,
      DictionaryAttr attr, RegionRange,
      SmallVectorImpl<Type> &inferredReturnTypes) {
    Conv2DOpAdaptor op(operands, attr);
  
    const Value input = op.input();
    const Value filter = op.filter();
  
    const RankedTensorType input_ty =
        input.getType().dyn_cast_or_null<RankedTensorType>();
    const RankedTensorType filter_ty =
        filter.getType().dyn_cast_or_null<RankedTensorType>();
    // If indeed both input type & filter type are ranked type and have ranks.
    // We will need to check their ranks are valid.
    if ((input_ty && input_ty.hasRank() && input_ty.getRank() != 4) ||
        (filter_ty && filter_ty.hasRank() && filter_ty.getRank() != 4)) {
      return emitOptionalError(location, "Invalid ranks");
    }
  
    // If either input or filter is unranked, we will just return unranked output
    // shape.
    if (!input_ty || !filter_ty || !input_ty.hasRank() || !filter_ty.hasRank()) {
      Type result_type;
      result_type = UnrankedTensorType::get(
          input.getType().cast<ShapedType>().getElementType());
      inferredReturnTypes.assign({result_type});
      return success();
    }
  
    auto stride_h = op.stride_h().getInt();
    auto stride_w = op.stride_w().getInt();
    auto dilation_h = op.dilation_h_factor().getInt();
    auto dilation_w = op.dilation_w_factor().getInt();
  
    // We don't have EXPLICIT PADDING in TfLite.
    auto paddings = op.padding().getValue();
    tensorflow::Padding padding;
    auto padding_is_valid = GetPaddingFromString(paddings.str(), &padding);
    if (!padding_is_valid.ok()) {
      return emitOptionalError(location, "invalid padding format provided");
    }
  
    // Output always have rank 4. All dimensions are initialized to
    // dynamic size and can be partially inferred.
    // TFL's conv2d is always NHWC format & the filter is OHWI.
    SmallVector<int64_t, 4> return_shape(4, ShapedType::kDynamicSize);
    return_shape[0] = input_ty.getDimSize(0);
    return_shape[3] = filter_ty.getDimSize(0);
  
    // Spatial dimensions can be inferred only when both input and filter are
    // ranked because we need to get their spatial dimensions.
  
    // Height.
    if (!input_ty.isDynamicDim(1) && !filter_ty.isDynamicDim(1)) {
      int64_t output_height;
      if (failed(ComputeConvWindowedOutputSize(
              input_ty.getDimSize(1), filter_ty.getDimSize(1), dilation_h,
              stride_h, padding, &output_height))) {
        return failure();
      }
      return_shape[1] = output_height;
    }
  
    // Width.
    if (!input_ty.isDynamicDim(2) && !filter_ty.isDynamicDim(2)) {
      int64_t output_width;
      if (failed(ComputeConvWindowedOutputSize(
              input_ty.getDimSize(2), filter_ty.getDimSize(2), dilation_w,
              stride_w, padding, &output_width))) {
        return failure();
      }
      return_shape[2] = output_width;
    }
  
    auto result_type =
        mlir::RankedTensorType::get(return_shape, input_ty.getElementType());
  
    inferredReturnTypes.assign({result_type});
    return success();
  }
  
  bool Conv2DOp::isCompatibleReturnTypes(TypeRange lhs, TypeRange rhs) {
    if (lhs.size() != rhs.size() || lhs.size() != 1) return false;
    if (failed(mlir::verifyCompatibleShape(lhs[0], rhs[0]))) return false;
    return true;
  }
  
  //===----------------------------------------------------------------------===//
  // DepthwiseConv2DO
  //===----------------------------------------------------------------------===//
  
  void DepthwiseConv2DOp::getCanonicalizationPatterns(
      OwningRewritePatternList &results, MLIRContext *context) {
    // TODO(b/180121750): Enable the pattern after the integration tests are
    // fixed.
    // results.insert<RemoveOptionalZeroBias<DepthwiseConv2DOp>>(context);
  }
  
  //===----------------------------------------------------------------------===//
  // GatherOp
  //===----------------------------------------------------------------------===//
  
  static void BuildGatherOp(OpBuilder *builder, OperationState &result,
                            Value params, Value indices, IntegerAttr axis,
                            IntegerAttr batch_dims) {
    auto params_type = params.getType().cast<TensorType>();
    auto indices_type = indices.getType().cast<TensorType>();
  
    // If params/indices is unranked, then output is unranked.
    if (!params_type.hasRank() || !indices_type.hasRank())
      return TFL::GatherOp::build(
          *builder, result, UnrankedTensorType::get(params_type.getElementType()),
          params, indices, axis, batch_dims);
  
    int64_t params_rank = params_type.getRank();
    int64_t indices_rank = indices_type.getRank();
  
    // params rank is guaranteed to be at least 1.
    // Produces an output tensor with shape:
    // params.shape[:axis] + indices.shape + params.shape[axis + 1:]
    std::vector<int64_t> shape(params_type.getShape());
    int64_t axis_i = axis.getInt();
  
    // For neg axis values, we wrap around params, e.g. axis = -1 => params[:-1]
    if (axis_i < 0) {
      axis_i += params_rank;
    }
  
    // params must be at least rank axis + 1
    if (params_rank < axis_i + 1) {
      emitError(result.location, "params must be at least rank axis + 1");
    }
  
    int64_t batch_dims_i = batch_dims.getInt();
    if (batch_dims_i < 0) {
      batch_dims_i += indices_rank;
    }
  
    if (batch_dims_i > axis_i) {
      emitError(result.location,
                "axis should be bigger than or equal to batch_dims");
    }
    if (batch_dims_i >= params_rank || batch_dims_i > indices_rank) {
      emitError(result.location,
                "batch_dims must be smaller than params' rank and smaller than "
                "or equal to indices'rank");
    }
    for (int i = 0; i < batch_dims_i; ++i) {
      if (indices_type.getShape()[i] != params_type.getShape()[i]) {
        emitError(result.location,
                  "batch dimensions of params must be equal to batch dimensions "
                  "of indices");
      }
    }
  
    if ((indices_rank == 0) || (indices_rank == batch_dims_i)) {
      // Scalar indices (output is rank(params) - 1).
      // Erase shape[axis]
      shape.erase(shape.begin() + axis_i);
    } else if (indices_rank == 1) {
      // Vector indices (output is rank(params)).
      // Copy indices.shape into params.shape[axis]
      std::copy(std::begin(indices_type.getShape()),
                std::end(indices_type.getShape()), std::begin(shape) + axis_i);
    } else {
      // Higher rank indices (output is rank(params) + rank(indices) - 1).
      shape.resize(params_rank + indices_rank - 1 - batch_dims_i);
      // Copy params.shape[axis + 1: ] into shape[axis + indices_rank:]
      std::copy(std::begin(params_type.getShape()) + axis_i + 1,
                std::end(params_type.getShape()),
                std::begin(shape) + axis_i + indices_rank - batch_dims_i);
  
      // Copy indices.shape into params.shape[axis]
      std::copy(std::begin(indices_type.getShape()) + batch_dims_i,
                std::end(indices_type.getShape()), std::begin(shape) + axis_i);
    }
  
    TFL::GatherOp::build(
        *builder, result,
        RankedTensorType::get(shape, params_type.getElementType()), params,
        indices, axis, batch_dims);
  }
  
  //===----------------------------------------------------------------------===//
  // ScatterNdOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(ScatterNdOp op) {
    auto indices = op.indices();
    auto updates = op.updates();
    auto shape = op.shape();
    auto output = op.output();
  
    auto updates_type = updates.getType().cast<ShapedType>();
    auto indices_type = indices.getType().cast<ShapedType>();
  
    if (!indices_type.hasStaticShape() || !updates_type.hasStaticShape()) {
      return success();
    }
  
    // Checks if the shape of `updates` is a tensor of shape
    // `indices.shape[:-1] + shape[indices.shape[-1]:]`, as described in
    // ScatterNd op description.
  
    auto outer_dims = indices_type.getRank() - 1;
    auto outermost_dim = indices_type.getDimSize(outer_dims);
    // Checks whether the first `outer_dims` dimensions of `indices` and
    // `updates` are equal.
    for (auto i = 0; i < outer_dims; i++) {
      if (indices_type.getDimSize(i) != updates_type.getDimSize(i)) {
        return op.emitOpError()
               << "indices.Dims(" << i << ") == " << indices_type.getDimSize(i)
               << ", but updates.Dims(" << i
               << ") == " << updates_type.getDimSize(i);
      }
    }
  
    auto output_type = output.getType().cast<ShapedType>();
    auto shape_type = shape.getType().cast<ShapedType>();
    if (shape_type.hasStaticShape()) {
      // Check the rank of `shape`.
      auto output_rank = outermost_dim + updates_type.getRank() - outer_dims;
      if (shape_type.getDimSize(0) != output_rank) {
        return op.emitOpError()
               << "shape must be a vector of length " << output_rank;
      }
      if (output_type.hasRank()) {
        if (output_type.getRank() != output_rank) {
          return op.emitOpError()
                 << "output must have the same rank with the length of shape = "
                 << output_rank;
        }
      }
    }
  
    DenseIntElementsAttr shape_value;
    if (matchPattern(shape, m_Constant(&shape_value))) {
      for (const auto shape_elem : shape_value) {
        if (shape_elem.getSExtValue() <= 0) {
          return op.emitOpError("all elements of shape must be > 0");
        }
      }
  
      // Checks whether the last `(shape_type.getDimSize(0) - outermost_dim)`
      // dimensions of `updates` and `shape` are equal.
      for (auto shape_it : llvm::enumerate(shape_value)) {
        int64_t i = shape_it.index();
        auto value = shape_it.value().getSExtValue();
        if (i >= outermost_dim) {
          auto corresponding_dim = i - outermost_dim + outer_dims;
          if (value != updates_type.getDimSize(corresponding_dim)) {
            return op.emitOpError()
                   << "updates.Dims(" << i
                   << ") == " << updates_type.getDimSize(corresponding_dim)
                   << ", but shape[" << i << "] == " << value;
          }
        }
      }
  
      // Checks if the output has the shape specified by `shape`.
      if (output_type.hasStaticShape()) {
        for (auto shape_it : llvm::enumerate(shape_value)) {
          int i = shape_it.index();
          auto value = shape_it.value().getSExtValue();
          if (output_type.getDimSize(i) != value) {
            return op.emitOpError()
                   << "output shape [" << output_type.getShape()
                   << "] must be equal to the value of shape " << shape_value;
          }
        }
      }
    }
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // MulOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult MulOp::fold(ArrayRef<Attribute> operands) {
    // TODO(b/142478136): Handle fused ops.
    if (fused_activation_function() != "NONE") return {};
  
    // This function is performance critical for op fusion patterns, e.g.
    // FuseBinaryOpToPrecedingAffine and FuseMulOrDivWithConv2dOrDepthwiseConv2d.
    // So a few specializations are provided to evaluate the math operation
    // more efficiently.
  
    // Specialization for f32 type.
    if (getType().cast<ShapedType>().getElementType().isF32()) {
      return ConstFoldBinaryOp<FloatAttr, float>(
          getType(), operands[0], operands[1],
          [](float a, float b) { return a * b; });
    }
  
    // Specialization for bf16 type.
    if (getType().cast<ShapedType>().getElementType().isBF16()) {
      return ConstFoldBinaryOp<FloatAttr, Eigen::bfloat16>(
          getType(), operands[0], operands[1],
          [](Eigen::bfloat16 a, Eigen::bfloat16 b) { return a * b; });
    }
  
    // Generic fallback with APFloat
    return ConstFoldBinaryOp(
        getType(), operands, [](APFloat a, APFloat b) { return a * b; },
        [](APInt a, APInt b) { return a * b; });
  }
  
  //===----------------------------------------------------------------------===//
  // DivOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult DivOp::fold(ArrayRef<Attribute> operands) {
    // TODO(b/142478136): Handle fused ops.
    if (fused_activation_function() != "NONE") return {};
    return ConstFoldBinaryOp(
        getType(), operands, [](APFloat a, APFloat b) { return a / b; },
        [](APInt a, APInt b) { return a.sdiv(b); });
  }
  
  //===----------------------------------------------------------------------===//
  // PackOp
  //===----------------------------------------------------------------------===//
  
  // TODO(b/133486129): Implement shape inference for pack
  
  static LogicalResult Verify(PackOp op) {
    // TODO(antiagainst): Implement other checks as in
    // tensorflow/lite/kernels/pack.cc
  
    if (op.getOperation()->getNumOperands() != op.values_count())
      return op.emitOpError("input count should match 'values_count' attribute");
  
    Value operand0 = op.getOperand(0);
    auto input_type = operand0.getType().cast<ShapedType>();
  
    // Check axis bounds.
    if (input_type.hasRank()) {
      int32_t axis_value = op.axis();
      if (axis_value < 0) axis_value += input_type.getRank() + 1;
      if (axis_value < 0 || axis_value >= input_type.getRank() + 1)
        return op.emitOpError()
               << "op attribute 'axis' should be in range [-rank - 1, rank + 1), "
               << "got rank = " << input_type.getRank()
               << ", and axis = " << op.axis();
    }
  
    // Make sure all inputs have the same shape and element type.
    // TODO(b/135032063): Simplify once fixed.
    for (Type operand_type : op.getOperandTypes()) {
      if (failed(mlir::verifyCompatibleShape(input_type, operand_type)))
        return op.emitOpError("operands should be of the same type. got ")
               << input_type << ", " << operand_type;
    }
  
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // PReluOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(PReluOp op) {
    auto input_type = op.input().getType().cast<ShapedType>();
    auto alpha_type = op.alpha().getType().cast<ShapedType>();
    auto output_type = op.output().getType().cast<ShapedType>();
  
    if (input_type.hasStaticShape() && alpha_type.hasStaticShape()) {
      if (input_type.getRank() != alpha_type.getRank() + 1) {
        return op.emitOpError("'alpha' should have one less rank than 'input'.");
      }
  
      // Check if alpha is broadcastable
      for (int i = 0; i < alpha_type.getRank(); i++) {
        if (alpha_type.getDimSize(i) != input_type.getDimSize(i + 1) &&
            alpha_type.getDimSize(i) != 1) {
          return op.emitOpError(
              llvm::formatv("'alpha' is not broadcastable at dimension {0}.", i));
        }
      }
    }
  
    if (input_type.hasStaticShape() && output_type.hasStaticShape()) {
      if (input_type.getRank() != output_type.getRank()) {
        return op.emitOpError("'input' and 'output' should have the same rank.");
      }
  
      // Check if input and output shapes are same
      for (int i = 0; i < input_type.getRank(); i++) {
        if (input_type.getDimSize(i) != output_type.getDimSize(i)) {
          return op.emitOpError(
              "'input' and 'output' should have the same shape.");
        }
      }
    }
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // ReshapeOp
  //===----------------------------------------------------------------------===//
  
  namespace {
  // This pattern matches and merges a tfl.reshape under the following
  // condition:
  // * The input's defining op is another tfl.reshape.
  // TODO(antiagainst): This pattern probably should be moved to the peephole
  // category, after we have the infra for peephole passes.
  struct RemoveAdjacentReshape : public RewritePattern {
    RemoveAdjacentReshape(MLIRContext *context)
        : RewritePattern(ReshapeOp::getOperationName(), 1, context) {}
  
    LogicalResult match(Operation *op) const override {
      auto thisOp = cast<ReshapeOp>(op);
      auto prevOp = thisOp.getOperand(0).getDefiningOp();
      return isa_and_nonnull<ReshapeOp>(prevOp) ? success() : failure();
    }
  
    void rewrite(Operation *op, PatternRewriter &rewriter) const override {
      auto thisOp = cast<ReshapeOp>(op);
      auto prevOp = cast<ReshapeOp>(thisOp.getOperand(0).getDefiningOp());
  
      // Replace
      //   %1 = "tfl.reshape"(%0, %shape0)
      //   %2 = "tfl.reshape"(%1, %shape1)
      // With
      //   %2 = "tfl.reshape"(%0, %shape1)
      rewriter.replaceOpWithNewOp<ReshapeOp>(
          op, thisOp.getType(), prevOp.getOperand(0), thisOp.getOperand(1));
    }
  };
  
  // The kernel expects an 1-D tensor for the shape operand if it presents. If all
  // the dimensions are '1's except the last dimension, it will be reshaped to a
  // 1-D tensor.
  // Note that this pattern doesn't check or change the content of the shape
  // tensor.
  struct ConvertShapeTo1D : public OpRewritePattern<ReshapeOp> {
    using OpRewritePattern<ReshapeOp>::OpRewritePattern;
  
    LogicalResult matchAndRewrite(ReshapeOp reshape,
                                  PatternRewriter &rewriter) const override {
      if (!reshape.shape().hasOneUse()) return failure();
  
      DenseIntElementsAttr shape;
      if (!matchPattern(reshape.shape(), m_Constant(&shape))) {
        return failure();
      }
      // It is already a 1-D constant, no change.
      auto old_shape = shape.getType().getShape();
      if (old_shape.size() == 1) {
        return failure();
      }
      // Verify all the leading dimensions are length one, except the last one.
      for (auto it = ++old_shape.rbegin(); it != old_shape.rend(); ++it) {
        if (*it != 1) {
          reshape->emitError(
              "Non-vector shape input is used, might cause runtime error");
          return failure();
        }
      }
      auto new_shape = shape.reshape(RankedTensorType::get(
          {*old_shape.rbegin()}, shape.getType().getElementType()));
      rewriter.replaceOpWithNewOp<TFL::ConstOp>(reshape.shape().getDefiningOp(),
                                                new_shape);
      return success();
    }
  };
  
  }  // end anonymous namespace
  
  OpFoldResult ReshapeOp::fold(ArrayRef<Attribute> operands) {
    // Remove identity reshape with both static result and input shape.
    auto result_type = getType().cast<ShapedType>();
    auto input_type = getOperand(0).getType().cast<ShapedType>();
    if (result_type.hasStaticShape() && result_type == input_type) {
      return getOperand(0);
    }
  
    // Constant folding
    if (auto dense_elements = operands[0].dyn_cast_or_null<DenseElementsAttr>()) {
      // If the result type isn't static, tries to derive the result type from
      // the #2 operand.
      if (!result_type.hasStaticShape()) {
        auto shape_elements = operands[1].dyn_cast_or_null<DenseElementsAttr>();
        if (!shape_elements) return nullptr;
  
        SmallVector<int64_t, 4> shape_data;
        for (const auto &it : shape_elements.getValues<APInt>()) {
          shape_data.push_back(it.getSExtValue());
        }
        result_type =
            RankedTensorType::get(shape_data, input_type.getElementType());
      }
      return dense_elements.reshape(result_type);
    }
  
    return nullptr;
  }
  
  void ReshapeOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
                                              MLIRContext *context) {
    results.insert<RemoveAdjacentReshape, ConvertShapeTo1D>(context);
  }
  
  using ReshapeErrorHandler =
      llvm::function_ref<LogicalResult(const llvm::Twine &)>;
  
  LogicalResult GetReshapeOutputType(Value input, Value shape,
                                     ReshapeErrorHandler error_handler,
                                     TensorType &output_ty) {
    auto input_ty = input.getType().cast<TensorType>();
    auto element_ty = input_ty.getElementType();
    output_ty = UnrankedTensorType::get(element_ty);
  
    auto shape_ty = shape.getType().dyn_cast<RankedTensorType>();
    if (!shape_ty) return success();
    if (shape_ty.getRank() != 1)
      return error_handler(llvm::formatv(
          "requires 'shape' to be rank 1, but got {0}", shape_ty.getRank()));
  
    DenseIntElementsAttr shape_attr;
    if (!matchPattern(shape, m_Constant(&shape_attr))) {
      // If only shape of `shape` is known, return ranked but dynamic output
      // shape.
      if (shape_ty.hasStaticShape()) {
        llvm::SmallVector<int64_t, 8> dynamic_shape(shape_ty.getDimSize(0),
                                                    ShapedType::kDynamicSize);
        output_ty = RankedTensorType::get(dynamic_shape, element_ty);
      }
      return success();
    }
  
    // Detect if reshape output shape is folded.
    bool shape_ty_zero_dim = false;
    int unknown_index = -1;
    // The product of constant shape argument excluding unknown dimension.
    int64_t shape_ty_size = 1;
    llvm::SmallVector<int64_t, 8> output_ty_shape;
    output_ty_shape.reserve(shape_attr.getNumElements());
    for (const auto &dim : llvm::enumerate(shape_attr.getIntValues())) {
      const int64_t size = dim.value().getSExtValue();
      if (size == ShapedType::kDynamicSize) {
        if (unknown_index != -1)
          return error_handler(llvm::formatv(
              "requires 'shape' to have at most one dynamic dimension, but got "
              "multiple dynamic dimensions at indices {0} and {1}. You need to "
              "set up the unspecified size(s) to avoid this problem, for example,"
              "setting batch size in keras model or setting unspecified input "
              "size(s) with fixed ones.",
              unknown_index, dim.index()));
  
        unknown_index = dim.index();
      } else if (size == 0) {
        shape_ty_zero_dim = true;
      } else if (size > 0) {
        shape_ty_size *= size;
      } else {
        return error_handler(
            llvm::formatv("requires 'shape' to have dimensions greater than -1, "
                          "but got {0} at index {1}",
                          size, dim.index()));
      }
      output_ty_shape.push_back(size);
    }
  
    if (!input_ty.hasStaticShape()) {
      output_ty = RankedTensorType::get(output_ty_shape, element_ty);
      return success();
    }
  
    // Compute the value of the unknown dimension.
    if (unknown_index != -1) {
      // Compute number of elements in tensor shape.
      int64_t input_ty_size = 1;
      bool input_ty_zero_dim = false;
      for (const auto &dim : input_ty.getShape()) {
        if (dim > 0 || !shape_ty_zero_dim) {
          input_ty_size *= dim;
        } else {
          input_ty_zero_dim = true;
        }
      }
  
      const int64_t missing_dim = input_ty_size / shape_ty_size;
      if (!input_ty_zero_dim && shape_ty_size * missing_dim != input_ty_size)
        return error_handler(
            llvm::formatv("requires 'input' number of elements be a multiple of "
                          "{0}, but got {1}",
                          shape_ty_size, input_ty_size));
  
      // Set the unknown dimension such that total number of elements remain
      // constant.
      output_ty_shape[unknown_index] = missing_dim;
    }
  
    output_ty = RankedTensorType::get(output_ty_shape, element_ty);
  
    return success();
  }
  
  static LogicalResult Verify(ReshapeOp op) {
    auto error_handler = [&op](const llvm::Twine &message) -> LogicalResult {
      return op.emitOpError() << message;
    };
    TensorType expected_ty;
    if (failed(GetReshapeOutputType(op.input(), op.shape(), error_handler,
                                    expected_ty)))
      return failure();
  
    auto output_ty = op.getType().dyn_cast<RankedTensorType>();
    if (!output_ty) return success();
    auto input_ty = op.input().getType().cast<TensorType>();
    if (output_ty.hasStaticShape() && input_ty.hasStaticShape()) {
      const int64_t output_ty_size = output_ty.getNumElements();
      const int64_t input_ty_size = input_ty.getNumElements();
      if (input_ty_size != output_ty_size)
        return op.emitOpError() << "requires 'output' number of elements to "
                                   "match 'input' number of elements, but got "
                                << output_ty_size << " and " << input_ty_size;
    }
  
    if (!TF::AreCastCompatible({output_ty, expected_ty}))
      return op.emitOpError()
             << "requires 'output' type " << output_ty
             << " to be cast compatible with expected type " << expected_ty;
  
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // PackOp
  //===----------------------------------------------------------------------===//
  
  // Remove redundant unpack pack op.
  // If a unpack op is followed by a pack op, we can remove the pack op, if the
  // unpack op is only consumed by the pack op, it will be removed as well.
  // An example illustration is:
  //                  Unpack [5, 8, 9], axis = 1
  //                /       \
  //            value  ...  value [5, 9], 8 values in total
  //              \           /
  //                 pack,   axis = 1
  //                   |
  //               value   [5, 8, 9]
  //
  //   This can actually be simplified into just:
  //
  //           =>   Value [5, 8, 9]
  // TODO(b/133341698): Move to tablegen when variadic is supported.
  struct RemoveRedundantUnpackPack : public RewritePattern {
    explicit RemoveRedundantUnpackPack(MLIRContext *context)
        : RewritePattern(PackOp::getOperationName(), 2, context) {}
  
    LogicalResult matchAndRewrite(Operation *op,
                                  PatternRewriter &rewriter) const override {
      TFL::PackOp pack_op = cast<TFL::PackOp>(op);
      Operation *first_input = pack_op.getOperand(0).getDefiningOp();
      if (!first_input) return failure();
      auto input_unpack_op = dyn_cast_or_null<TFL::UnpackOp>(first_input);
      if (!input_unpack_op) return failure();
  
      // The unpack & pack should have the same axis & num inputs/outputs.
      if (pack_op.axis() != input_unpack_op.axis() ||
          pack_op.values_count() != input_unpack_op.num())
        return failure();
  
      const int total_pack_inputs = pack_op.getNumOperands();
      const int num_results = input_unpack_op.getNumResults();
      if (total_pack_inputs != num_results) return failure();
      for (auto input_output :
           llvm::zip(pack_op.getOperands(), input_unpack_op.getResults())) {
        Value pack_input = std::get<0>(input_output);
        Value unpack_output = std::get<1>(input_output);
        // Make sure the ordering is the same for the pack op & unpack op.
        if (pack_input != unpack_output) return failure();
      }
  
      // Replace the pack's output to the unpack's input.
      rewriter.replaceOp(pack_op, input_unpack_op.getOperand());
      // At this point, we don't manually remove the redundant pack op & unpack op
      // (we cannot actually), but trust the PatterRewriter to garbage collect
      // these two ops.
      return success();
    }
  };
  
  void PackOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
                                           MLIRContext *context) {
    results.insert<RemoveRedundantUnpackPack>(context);
  }
  
  //===----------------------------------------------------------------------===//
  // SliceOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(SliceOp op) {
    auto input_type = op.input().getType().cast<ShapedType>();
    auto begin_type = op.begin().getType().cast<ShapedType>();
    auto size_type = op.size().getType().cast<ShapedType>();
    if (input_type.hasStaticShape() && begin_type.hasStaticShape() &&
        size_type.hasStaticShape()) {
      if (input_type.getRank() != begin_type.getNumElements()) {
        return op.emitError(
            "begin tensor elements size is not equal to input tensor rank");
      }
  
      if (input_type.getRank() != size_type.getNumElements()) {
        return op.emitError(
            "size tensor elements size is not equal to input tensor rank");
      }
    }
  
    DenseIntElementsAttr begin;
    if (matchPattern(op.begin(), m_Constant(&begin))) {
      int axis = 0;
      for (auto begin_i : llvm::enumerate(begin)) {
        if (begin_i.value().getSExtValue() < 0) {
          return op.emitError(
              llvm::formatv("begin[{0}] cannot be negative", axis));
        }
        axis++;
      }
    }
  
    DenseIntElementsAttr size;
    if (matchPattern(op.size(), m_Constant(&size))) {
      int axis = 0;
      for (auto size_i : llvm::enumerate(size)) {
        if (size_i.value().getSExtValue() < -1) {
          return op.emitError(
              llvm::formatv("size[{0}] cannot be negative other than -1", axis));
        }
        axis++;
      }
    }
  
    if (begin && size && input_type.hasStaticShape()) {
      for (uint64_t i = 0, end = begin.getNumElements(); i < end; i++) {
        int begin_i =
            begin.getValue({i}).cast<IntegerAttr>().getValue().getSExtValue();
        int size_i =
            size.getValue({i}).cast<IntegerAttr>().getValue().getSExtValue();
        int dim_i = input_type.getShape()[i];
        if (begin_i > dim_i) {
          return op.emitOpError(llvm::formatv(
              "begin[{0}] cannot exceed dimension length: {1}", i, dim_i));
        }
        if (size_i >= 0 && begin_i + size_i > dim_i) {
          return op.emitError(llvm::formatv(
              "begin[{0}] + size[{0}] cannot exceed dimension length: {1}", i,
              dim_i));
        }
      }
    }
  
    return success();
  }
  
  TFL::ConstOp NarrowDownInt64InputValuesForOp(Operation *input_op,
                                               RankedTensorType value_type,
                                               Location loc, OpBuilder *builder) {
    if (input_op == nullptr) return nullptr;
  
    mlir::DenseIntElementsAttr attr;
    if (!matchPattern(input_op, m_Constant(&attr))) {
      return nullptr;
    }
  
    auto value_shape_type = mlir::RankedTensorType::get(
        value_type.getShape(), builder->getIntegerType(32));
  
    SmallVector<int32_t, 4> value_i32;
    value_i32.reserve(value_type.getRank());
    for (const auto &size : attr) {
      value_i32.push_back(static_cast<int32_t>(size.getSExtValue()));
    }
    auto new_value_i32_attr =
        mlir::DenseIntElementsAttr::get(value_shape_type, value_i32);
  
    return builder->create<TFL::ConstOp>(loc, new_value_i32_attr);
  }
  
  // This will cast down int64 values for TFL slice op.
  // This will require the begin & size are constants.
  struct CastDonwInt64BeginEndToInt32 : public OpRewritePattern<TFL::SliceOp> {
    using OpRewritePattern<TFL::SliceOp>::OpRewritePattern;
  
    LogicalResult matchAndRewrite(TFL::SliceOp slice_op,
                                  PatternRewriter &rewriter) const override {
      auto begin = slice_op.begin();
      auto size = slice_op.size();
      auto begin_type = begin.getType().dyn_cast_or_null<RankedTensorType>();
      auto size_type = size.getType().dyn_cast_or_null<RankedTensorType>();
      auto begin_op = begin.getDefiningOp();
      auto size_op = size.getDefiningOp();
  
      if (begin_op == nullptr && size_op == nullptr) return failure();
  
      if (begin_type == nullptr && size_type == nullptr) return failure();
  
      // Handle begin.
      if (begin_op && begin_type && begin_type.getElementType().isInteger(64)) {
        auto new_begin = NarrowDownInt64InputValuesForOp(
            begin_op, begin_type, slice_op.getLoc(), &rewriter);
        if (new_begin != nullptr) {
          slice_op.setOperand(1, new_begin);
        }
      }
  
      // Handle size.
      if (size_op && size_type && size_type.getElementType().isInteger(64)) {
        auto new_size = NarrowDownInt64InputValuesForOp(
            size_op, size_type, slice_op.getLoc(), &rewriter);
        if (new_size != nullptr) {
          slice_op.setOperand(2, new_size);
        }
      }
  
      return success();
    }
  };
  
  void SliceOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
                                            MLIRContext *context) {
    results.insert<CastDonwInt64BeginEndToInt32>(context);
  }
  
  //===----------------------------------------------------------------------===//
  // SubOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult SubOp::fold(ArrayRef<Attribute> operands) {
    // TODO(b/142478136): Handle fused ops.
    if (fused_activation_function() != "NONE") return {};
    return ConstFoldBinaryOp(
        getType(), operands, [](APFloat a, APFloat b) { return a - b; },
        [](APInt a, APInt b) { return a - b; });
  }
  
  //===----------------------------------------------------------------------===//
  // TopKOp
  //===----------------------------------------------------------------------===//
  
  static void BuildTopKOp(OpBuilder *builder, OperationState &result, Value input,
                          Value k) {
    // Output size is only known if k is constant value. A negative dimension is
    // considered dynamic so use -1 here if k is not a constant value.
    int const_k = -1;
    ElementsAttr cst;
    if (matchPattern(k, m_Constant(&cst)))
      // These casts should all be valid due to how Tensor constants are stored.
      // TODO(jpienaar): This should use a helper function.
      const_k = cst.getValue<IntegerAttr>({}).getValue().getSExtValue();
  
    auto val_type = input.getType().cast<TensorType>();
    // If value is unranked, then so is results.
    if (!val_type.hasRank())
      return TFL::TopKV2Op::build(
          *builder, result, UnrankedTensorType::get(val_type.getElementType()),
          UnrankedTensorType::get(builder->getIntegerType(32)), input, k);
  
    // Resultant shape is value.shape[:-1] + [k]
    std::vector<int64_t> shape(val_type.getShape());
    shape[shape.size() - 1] = const_k;
    TFL::TopKV2Op::build(
        *builder, result, RankedTensorType::get(shape, val_type.getElementType()),
        RankedTensorType::get(shape, builder->getIntegerType(32)), input, k);
  }
  
  //===----------------------------------------------------------------------===//
  // FakeQuantOp
  //===----------------------------------------------------------------------===//
  
  // Return true if the op has non-empty "minmax" attribute.
  static inline bool HasValidMinMaxAttribute(Operation *op) {
    auto minmax = op->getAttrOfType<ArrayAttr>("minmax");
    return minmax && minmax.getValue().size() == 2;
  }
  
  namespace {
  
  /// This pattern matches and remove a tfl.fake_quant if all the users of this op
  /// and itself have "minmax" attribute set.
  struct DropFakeQuant : public RewritePattern {
    explicit DropFakeQuant(MLIRContext *context)
        : RewritePattern(FakeQuantOp::getOperationName(), 1, context) {}
  
    LogicalResult match(Operation *op) const override {
      // We only match the op with valid "minmax" attribute.
      if (!HasValidMinMaxAttribute(op)) return failure();
  
      // If all the users of this op have valid "minmax" attributes, it is matched
      // and can be removed.
      auto fakeQuantOp = cast<FakeQuantOp>(op);
      for (auto *operand : fakeQuantOp.getResult().getUsers())
        if (!HasValidMinMaxAttribute(operand)) return failure();
  
      return success();
    }
  
    void rewrite(Operation *op, PatternRewriter &rewriter) const override {
      // Replace the matched FakeQuantOp by its primary operand.
      rewriter.replaceOp(op, op->getOperand(0));
    }
  };
  }  // end anonymous namespace
  
  void FakeQuantOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
                                                MLIRContext *context) {
    results.insert<DropFakeQuant>(context);
  }
  
  //===----------------------------------------------------------------------===//
  // UnpackOp
  //===----------------------------------------------------------------------===//
  
  // TODO(b/133486129): Implement shape inference for unpack
  
  LogicalResult UnpackOp::inferReturnTypes(
      MLIRContext *context, Optional<Location> loc, ValueRange operands,
      DictionaryAttr attributes, RegionRange regions,
      SmallVectorImpl<Type> &inferredReturnTypes) {
    UnpackOpAdaptor op(operands, attributes);
    // TODO(jpienaar): Refactor verify
    if (failed(op.verify(loc.hasValue() ? *loc : UnknownLoc::get(context))))
      return failure();
  
    if (operands.size() != 1) {
      return emitOptionalError(loc, "input count should be equal to 1");
    }
  
    const int64_t num_value = op.num().getInt();
    auto input_type = operands[0].getType().dyn_cast<ShapedType>();
    if (!input_type || !input_type.hasRank()) {
      // If input is unranked, then so is output.
      inferredReturnTypes.assign(
          num_value, UnrankedTensorType::get(input_type.getElementType()));
      return success();
    }
  
    if (input_type.hasStaticShape() && input_type.getNumElements() <= 0) {
      return emitOptionalError(
          loc, "number of elements in input should be larger than 0");
    }
  
    const int64_t rank = input_type.getRank();
    if (rank <= 0) {
      return emitOptionalError(loc, "input should be of rank larger than 0");
    }
  
    int64_t axis_value = op.axis().getInt();
    if (axis_value < 0) {
      axis_value += rank;
    }
    if (axis_value < 0 || axis_value >= rank) {
      return emitOptionalError(
          loc, "attribute 'axis' should be in range [-rank, rank), got axis = ",
          op.axis().getInt(), ", and rank = ", rank);
    }
  
    if (!ShapedType::isDynamic(input_type.getDimSize(axis_value)) &&
        input_type.getDimSize(axis_value) != num_value) {
      return emitOptionalError(loc, "output count should match 'num' attribute");
    }
  
    auto output_shape = llvm::to_vector<4>(input_type.getShape());
    output_shape.erase(output_shape.begin() + axis_value);
  
    auto output_type =
        RankedTensorType::get(output_shape, input_type.getElementType());
    inferredReturnTypes.assign(num_value, output_type);
  
    return success();
  }
  
  bool UnpackOp::isCompatibleReturnTypes(TypeRange lhs, TypeRange rhs) {
    if (lhs.size() != rhs.size()) return false;
    for (auto pair : llvm::zip(lhs, rhs)) {
      if (failed(
              mlir::verifyCompatibleShape(std::get<0>(pair), std::get<1>(pair))))
        return false;
    }
    return true;
  }
  
  //===----------------------------------------------------------------------===//
  // SplitOp
  //===----------------------------------------------------------------------===//
  
  // Extracts and returns the signed integer constant in a 0-rank integer tensor
  // or 1-element 1-rank integer tensor if 'value' is a constant.
  static llvm::Optional<int64_t> ExtractConstantIntFromTensor(Value value) {
    ElementsAttr attr;
    if (!matchPattern(value, m_Constant(&attr))) return {};
    if (attr.getNumElements() != 1) return {};
    IntegerAttr int_attr = *attr.getValues<IntegerAttr>().begin();
    return int_attr.getValue().getSExtValue();
  }
  
  // Returns a RankedTensorType which is similar to `input_type` but replaces the
  // dimension size of `dim` with `dim_size`.  For example,
  // `SubstituteRankedTensorTypeDimSize(tensor<3x4xi32>, 1, 2)` returns
  // `tensor<3x2xi32>`.
  static RankedTensorType SubstituteRankedTensorTypeDimSize(
      RankedTensorType input_type, int64_t dim, int64_t dim_size) {
    auto shape = input_type.getShape().vec();
    shape[dim] = dim_size;
    return RankedTensorType::get(shape, input_type.getElementType());
  }
  
  // Verifies the output tensor types of SplitOp or SplitVOp.
  template <typename ExpectedOutputTypeGetter>
  static LogicalResult VerifySplitOpOutputTypes(
      Operation *op, int64_t num_splits,
      ExpectedOutputTypeGetter get_expected_output_type) {
    for (int64_t i = 0; i < num_splits; ++i) {
      auto expected_output_type = get_expected_output_type(i);
      Value output = op->getResult(i);
      if (failed(verifyCompatibleShape(output.getType(), expected_output_type)))
        return op->emitOpError()
               << "output #" << i << " should be " << expected_output_type
               << " instead got " << output.getType();
    }
    return success();
  }
  
  static LogicalResult Verify(SplitOp op) {
    int64_t num_splits = op.num_splits();
    if (op.getNumResults() != num_splits)
      return op.emitOpError("output count should match 'num_splits' attribute");
  
    // If 'split_dim' is not a constant, there are no other checks.
    llvm::Optional<int64_t> split_dim_opt =
        ExtractConstantIntFromTensor(op.split_dim());
    if (!split_dim_opt) return success();
  
    // If 'input' is not a ranked tensor, there are no other checks.
    auto input_type = op.value().getType().dyn_cast<RankedTensorType>();
    if (!input_type) return success();
  
    int64_t split_dim = split_dim_opt.getValue();
    const int64_t rank = input_type.getRank();
    if (split_dim < 0) split_dim += rank;
    if (split_dim < 0 || split_dim >= rank)
      return op.emitOpError("'split_dim' should be in [-rank, rank)");
  
    // If the 'split_dim' dimension of the 'input' tensor has a dynamic size,
    // there are no other checks.
    const int64_t dim_size = input_type.getDimSize(split_dim);
    if (ShapedType::isDynamic(dim_size)) return success();
  
    if (dim_size % num_splits != 0)
      return op.emitOpError("'num_splits' should evenly divide 'split_dim' axis");
  
    // Verifies output tensor types.
    RankedTensorType expected_output_type = SubstituteRankedTensorTypeDimSize(
        input_type, split_dim, dim_size / num_splits);
    return VerifySplitOpOutputTypes(
        op.getOperation(), num_splits,
        [expected_output_type](int64_t) { return expected_output_type; });
  }
  
  static LogicalResult Verify(SplitVOp op) {
    int64_t num_splits = op.num_splits();
    if (op.getNumResults() != num_splits)
      return op.emitOpError("output count should match 'num_splits' attribute");
  
    // If 'split_dim' is not a constant, there are no other checks.
    llvm::Optional<int64_t> split_dim_opt =
        ExtractConstantIntFromTensor(op.split_dim());
    if (!split_dim_opt) return success();
  
    // If 'input' is not a ranked tensor, there are no other checks.
    auto input_type = op.value().getType().dyn_cast<RankedTensorType>();
    if (!input_type) return success();
  
    int64_t split_dim = split_dim_opt.getValue();
    const int64_t rank = input_type.getRank();
    if (split_dim < 0) split_dim += rank;
    if (split_dim < 0 || split_dim >= rank)
      return op.emitOpError("'split_dim' should be in [-rank, rank)");
  
    // If the 'split_dim' dimension of the 'input' tensor has a dynamic size,
    // there are no other checks.
    const int64_t dim_size = input_type.getDimSize(split_dim);
    if (ShapedType::isDynamic(dim_size)) return success();
  
    // If 'size_splits' is not a constant, there are no other checks.
    ElementsAttr size_splits_attr;
    if (!matchPattern(op.size_splits(), m_Constant(&size_splits_attr)))
      return success();
  
    if (size_splits_attr.getNumElements() != num_splits) {
      auto size_splits_type = op.size_splits().getType().cast<RankedTensorType>();
      RankedTensorType expected_size_splits_type =
          RankedTensorType::get({num_splits}, size_splits_type.getElementType());
      return op.emitOpError("'size_splits' should be ")
             << expected_size_splits_type;
    }
  
    // Normalizes and verifies 'size_splits'.
    // Note: TensorFlow allows one -1 element in 'size_splits'.  The -1 element
    // means the rest of the dimension size.
    llvm::SmallVector<int64_t, 4> size_splits;
    size_splits.reserve(num_splits);
  
    int64_t negative_size_split_loc = -1;
    int64_t total_size_splits = 0;
  
    for (int64_t i = 0; i < num_splits; ++i) {
      auto size_split_attr = size_splits_attr.getValue<IntegerAttr>(i);
      int64_t size_split = size_split_attr.getValue().getSExtValue();
      size_splits.push_back(size_split);
      if (size_split >= 0) {
        total_size_splits += size_split;
        continue;
      }
      if (size_split < -1)
        return op.emitOpError(
            "elements of 'size_splits' should be greater than or equal to -1");
      if (negative_size_split_loc != -1)
        return op.emitOpError("'size_splits' can only have one -1");
      negative_size_split_loc = i;
    }
  
    if (negative_size_split_loc != -1) {
      if (total_size_splits > dim_size)
        return op.emitOpError(
            "sum of non-negative elements of 'size_splits' is greater than the "
            "dimension size of 'split_dim' axis");
      size_splits[negative_size_split_loc] = dim_size - total_size_splits;
      total_size_splits = dim_size;
    }
  
    if (total_size_splits != dim_size)
      return op.emitOpError(
          "sum of 'size_splits' should match the dimension size of 'split_dim' "
          "axis");
  
    // Verifies result tensor types.
    auto get_expected_output_type = [input_type, split_dim,
                                     &size_splits](int64_t i) {
      return SubstituteRankedTensorTypeDimSize(input_type, split_dim,
                                               size_splits[i]);
    };
    return VerifySplitOpOutputTypes(op.getOperation(), num_splits,
                                    get_expected_output_type);
  }
  
  //===----------------------------------------------------------------------===//
  // MeanOp
  //===----------------------------------------------------------------------===//
  
  // TODO(b/133854225): Implement shape inference to Mean
  
  //===----------------------------------------------------------------------===//
  // LSTMOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(LSTMOp op) {
    auto operands = op.GetStatefulOperands();
    if (operands.size() != 2 || operands[0] != 18 || operands[1] != 19) {
      return op.emitOpError("LSTMOp expected to have two stateful operands");
    }
  
    const auto input_type = op.input().getType().cast<ShapedType>();
    // Since TFLite runtime generally supports dynamic shape/rank, if `input_type`
    // doesn't have static shape, we skip the shape check below.
    if (!input_type.hasStaticShape()) return success();
    // The input should be at least 2D tensor since it will go through fully
    // connected layer.
    if (!input_type.hasRank() || input_type.getRank() < 2)
      return op.emitOpError(
          "the first input operand should have more than 2 dimensions.");
  
    const auto activation_state =
        op.input_activation_state().getType().cast<ShapedType>();
    const auto cell_state = op.input_cell_state().getType().cast<ShapedType>();
    const auto input_to_output_weights =
        op.input_to_output_weights().getType().cast<ShapedType>();
    const auto recurrent_to_output_weights =
        op.recurrent_to_output_weights().getType().cast<ShapedType>();
    if (activation_state.hasStaticShape() && cell_state.hasStaticShape() &&
        input_to_output_weights.hasStaticShape() &&
        recurrent_to_output_weights.hasStaticShape()) {
      const int n_input = input_type.getDimSize(input_type.getRank() - 1);
      const int n_cell = input_to_output_weights.getDimSize(0);
      const int n_output = recurrent_to_output_weights.getDimSize(1);
      const int output_state_size = activation_state.getNumElements();
      const int n_batch = input_type.getRank() == 2 ? input_type.getDimSize(0)
                                                    : input_type.getDimSize(1);
      const int state_size = cell_state.getNumElements();
  
      // Check if the dimension of the inputs matches.
      if ((output_state_size != n_batch * n_output) ||
          (state_size != n_batch * n_cell) ||
          (input_to_output_weights.getDimSize(1) != n_input) ||
          (recurrent_to_output_weights.getRank() != 2) ||
          (recurrent_to_output_weights.getDimSize(0) != n_cell) ||
          (input_to_output_weights.getRank() != 2)) {
        return op.emitOpError("inputs don't match with the dimensions.");
      }
  
      const bool is_layer_norm_lstm =
          !op.forget_layer_norm_coefficients().getType().isa<NoneType>();
      if (is_layer_norm_lstm) {
        const auto forget_layer_norm_coefficients =
            op.forget_layer_norm_coefficients().getType().cast<ShapedType>();
        // If this lstm has layer normalization, this input value,
        // "forget_layer_norm_coefficients" should be a 1D tensor.
        if (!forget_layer_norm_coefficients.hasRank() ||
            forget_layer_norm_coefficients.getRank() != 1 ||
            forget_layer_norm_coefficients.getDimSize(0) != n_cell)
          return op.emitOpError(
              "coefficient inputs have more than 2 dimensions or "
              "don't match the dimension with input operand "
              "`input_to_output_weights`.");
      }
    }
  
    return success();
  }
  
  namespace {
  
  // Replaces the optional bias operands with a "none" type value if the bias
  // values are constant zeros.
  struct RemoveLSTMOpZeroBias : public OpRewritePattern<LSTMOp> {
    using OpRewritePattern<LSTMOp>::OpRewritePattern;
  
    LogicalResult matchAndRewrite(LSTMOp op,
                                  PatternRewriter &rewriter) const override {
      if (EqualsZero(op.input_gate_bias())) {
        auto none_value = rewriter.create<mlir::ConstantOp>(
            rewriter.getUnknownLoc(), rewriter.getUnitAttr());
        op.input_gate_biasMutable().assign(none_value);
      }
  
      if (EqualsZero(op.projection_bias())) {
        auto none_value = rewriter.create<mlir::ConstantOp>(
            rewriter.getUnknownLoc(), rewriter.getUnitAttr());
        op.projection_biasMutable().assign(none_value);
      }
  
      return success();
    }
  };
  
  }  // namespace
  
  void LSTMOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
                                           MLIRContext *context) {
    results.insert<RemoveLSTMOpZeroBias>(context);
  }
  
  //===----------------------------------------------------------------------===//
  // UnidirectionalSequenceLSTMOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(UnidirectionalSequenceLSTMOp op) {
    auto operands = op.GetStatefulOperands();
    if (operands.size() == 2 && operands[0] == 18 && operands[1] == 19) {
      return success();
    }
    return op.emitError(
        "UnidirectionalSequenceLSTMOp expected to have two stateful operands");
  }
  
  LogicalResult UnidirectionalSequenceLSTMOp::inferReturnTypes(
      MLIRContext *, Optional<Location>, ValueRange operands, DictionaryAttr attr,
      RegionRange, SmallVectorImpl<Type> &inferredReturnTypes) {
    Value input = operands[0];
    auto input_type = input.getType().dyn_cast_or_null<RankedTensorType>();
  
    Value output_state = operands[18];
    auto output_state_type =
        output_state.getType().dyn_cast_or_null<RankedTensorType>();
  
    if (input_type && input_type.hasRank() && input_type.getRank() != 3) {
      return failure();
    }
  
    if (output_state_type && output_state_type.hasRank() &&
        output_state_type.getRank() != 2) {
      return failure();
    }
  
    if (!input_type || !input_type.hasRank() || !output_state_type ||
        !output_state_type.hasRank()) {
      // We cannot infer the output shape since we don't know the input shape or
      // the output state shape. We will set the output shape as unranked.
      Type result_type;
      result_type = UnrankedTensorType::get(
          input.getType().cast<ShapedType>().getElementType());
      inferredReturnTypes.assign({result_type});
      return success();
    }
  
    // Default to non-time_major.
    bool time_majored = attr.getNamed("time_major").hasValue()
                            ? attr.getNamed("time_major")
                                  .getValue()
                                  .second.cast<BoolAttr>()
                                  .getValue()
                            : false;
  
    int batch =
        time_majored ? input_type.getDimSize(1) : input_type.getDimSize(0);
    int time = time_majored ? input_type.getDimSize(0) : input_type.getDimSize(1);
    int n_output = output_state_type.getDimSize(1);
  
    // Build the output shape.
    SmallVector<int64_t, 3> output_shape;
    if (time_majored) {
      output_shape = {time, batch, n_output};
    } else {
      output_shape = {batch, time, n_output};
    }
    auto result_type =
        mlir::RankedTensorType::get(output_shape, input_type.getElementType());
  
    inferredReturnTypes.assign({result_type});
    return success();
  }
  
  bool UnidirectionalSequenceLSTMOp::isCompatibleReturnTypes(TypeRange lhs,
                                                             TypeRange rhs) {
    if (lhs.size() != rhs.size() || lhs.size() != 1) return false;
    if (failed(mlir::verifyCompatibleShape(lhs[0], rhs[0]))) return false;
    return true;
  }
  
  //===----------------------------------------------------------------------===//
  // BidirectionalSequenceLSTMOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(BidirectionalSequenceLSTMOp op) {
    auto operands = op.GetStatefulOperands();
    if (operands.size() == 4 && operands[0] == 35 && operands[1] == 36 &&
        operands[2] == 37 && operands[3] == 38) {
      return success();
    }
    return op.emitError(
        "BidirectionalSequenceLSTMOp expected to have four stateful operands");
  }
  
  //===----------------------------------------------------------------------===//
  // UnidirectionalSequenceRNNOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(UnidirectionalSequenceRNNOp op) {
    auto operands = op.GetStatefulOperands();
    if (operands.size() == 1 && operands[0] == 4) {
      return success();
    }
    return op.emitError(
        "UnidirectionalSequenceRNNOp expected to have one stateful operand");
  }
  
  //===----------------------------------------------------------------------===//
  // SvdfOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(SVDFOp op) {
    auto operands = op.GetStatefulOperands();
    if (operands.size() == 1 && operands[0] == 4) {
      return success();
    }
    return op.emitError("SvdfOp expected to have one stateful operand");
  }
  
  //===----------------------------------------------------------------------===//
  // AbsOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult AbsOp::fold(ArrayRef<Attribute> operands) {
    Type result_type = getType();
    // Only constant fold for tensor of f32 is implemented.
    if (!IsF32ShapedType(result_type)) return nullptr;
  
    auto compute = [](APFloat value) -> APFloat { return llvm::abs(value); };
    return ConstFoldUnaryOp(result_type, operands[0], compute);
  }
  
  //===----------------------------------------------------------------------===//
  // NegOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult NegOp::fold(ArrayRef<Attribute> operands) {
    Type result_type = getType();
    // Only constant fold for tensor of f32 is implemented.
    if (!IsF32ShapedType(result_type)) return nullptr;
  
    auto compute = [](APFloat value) -> APFloat { return llvm::neg(value); };
    return ConstFoldUnaryOp(result_type, operands[0], compute);
  }
  
  //===----------------------------------------------------------------------===//
  // SinOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult SinOp::fold(ArrayRef<Attribute> operands) {
    Type result_type = getType();
    // Only constant fold for tensor of f32 is implemented.
    if (!IsF32ShapedType(result_type)) return nullptr;
  
    auto compute = [](APFloat value) -> APFloat {
      float f = value.convertToFloat();
      float result = std::sin(f);
      return APFloat(result);
    };
    return ConstFoldUnaryOp(result_type, operands[0], compute);
  }
  
  //===----------------------------------------------------------------------===//
  // CosOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult CosOp::fold(ArrayRef<Attribute> operands) {
    Type result_type = getType();
    // Only constant fold for tensor of f32 is implemented.
    if (!IsF32ShapedType(result_type)) return nullptr;
  
    auto compute = [](APFloat value) -> APFloat {
      float f = value.convertToFloat();
      float result = std::cos(f);
      return APFloat(result);
    };
    return ConstFoldUnaryOp(result_type, operands[0], compute);
  }
  
  //===----------------------------------------------------------------------===//
  // LogOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult LogOp::fold(ArrayRef<Attribute> operands) {
    Type result_type = getType();
    // Only constant fold for tensor of f32 is implemented.
    if (!IsF32ShapedType(result_type)) return nullptr;
  
    auto compute = [](APFloat value) -> APFloat {
      float f = value.convertToFloat();
      float result = std::log(f);
      return APFloat(result);
    };
    return ConstFoldUnaryOp(result_type, operands[0], compute);
  }
  
  //===----------------------------------------------------------------------===//
  // SqrtOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult SqrtOp::fold(ArrayRef<Attribute> operands) {
    Type result_type = getType();
    // Only constant fold for tensor of f32 is implemented.
    if (!IsF32ShapedType(result_type)) return nullptr;
  
    auto compute = [](APFloat value) -> APFloat {
      float f = value.convertToFloat();
      float result = std::sqrt(f);
      return APFloat(result);
    };
    return ConstFoldUnaryOp(result_type, operands[0], compute);
  }
  
  //===----------------------------------------------------------------------===//
  // RsqrtOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult RsqrtOp::fold(ArrayRef<Attribute> operands) {
    Type result_type = getType();
    // Only constant fold for tensor of f32/bf16 is implemented.
    if (!IsF32ShapedType(result_type) && !IsBF16ShapedType(result_type))
      return nullptr;
  
    auto compute = [](APFloat value) -> APFloat {
      bool loseInfo;
      const llvm::fltSemantics &original_float_semantics = value.getSemantics();
      value.convert(APFloat::IEEEsingle(), APFloat::rmNearestTiesToEven,
                    &loseInfo);
      float f = value.convertToFloat();
      APFloat result(1.f / std::sqrt(f));
      result.convert(original_float_semantics, APFloat::rmNearestTiesToEven,
                     &loseInfo);
      return result;
    };
    return ConstFoldUnaryOp(result_type, operands[0], compute);
  }
  
  //===----------------------------------------------------------------------===//
  // SquareOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult SquareOp::fold(ArrayRef<Attribute> operands) {
    Type result_type = getType();
    // Only constant fold for tensor of f32 is implemented.
    if (!IsF32ShapedType(result_type)) return nullptr;
  
    auto compute = [](APFloat value) -> APFloat { return value * value; };
    return ConstFoldUnaryOp(result_type, operands[0], compute);
  }
  
  //===----------------------------------------------------------------------===//
  // RankOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult RankOp::fold(ArrayRef<Attribute> operands) {
    assert(operands.size() == 1);
    auto result_type = getType().cast<ShapedType>();
    if (auto elements_attr = operands[0].dyn_cast_or_null<ElementsAttr>()) {
      auto rank = static_cast<int32_t>(elements_attr.getType().getRank());
      return DenseElementsAttr::get(result_type, {rank});
    }
  
    // Also fold if `input` has a known rank.
    auto input_type = input().getType().cast<ShapedType>();
    // Do not fold if rank is zero because the TFLite converter doesn't
    // distinguish between unranked input and scalar input due to b/138865275.
    // TODO(b/138865275): Remove `input_type.getRank() != 0` in the following
    // predicate and fold the op when rank is zero.
    if (input_type.hasRank() && input_type.getRank() != 0) {
      auto rank = static_cast<int32_t>(input_type.getRank());
      return DenseElementsAttr::get(result_type, {rank});
    }
  
    return nullptr;
  }
  
  //===----------------------------------------------------------------------===//
  // ConstOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult ConstOp::fold(ArrayRef<Attribute> operands) {
    assert(operands.empty() && "constant has no operands");
    // Return the held attribute value.
    return value();
  }
  
  
  namespace {
  struct FoldPseudoConstOp
      : public OpRewritePattern<ConstOp> {
    using OpRewritePattern<ConstOp>::OpRewritePattern;
  
    LogicalResult matchAndRewrite(ConstOp const_op,
                                  PatternRewriter &rewriter) const override {
      if (!ConstantOp::isBuildableWith(const_op.value(), const_op.getType()))
        return failure();
      rewriter.replaceOpWithNewOp<ConstantOp>(const_op, const_op.value());
      return success();
    }
  };
  
  }  // namespace
  
  void ConstOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
                                            MLIRContext *context) {
    results.insert<FoldPseudoConstOp>(context);
  }
  
  
  
  //===----------------------------------------------------------------------===//
  // CastOp
  //===----------------------------------------------------------------------===//
  
  OpFoldResult CastOp::fold(ArrayRef<Attribute> operands) {
    assert(operands.size() == 1);
    if (getElementTypeOrSelf(input()) == getElementTypeOrSelf(getType())) {
      return input();
    }
  
    // For now, only supports cast between integer types.
    auto elements_attr = operands[0].dyn_cast_or_null<DenseIntElementsAttr>();
    if (!elements_attr) {
      return nullptr;
    }
  
    auto result_element_type =
        getType().cast<ShapedType>().getElementType().dyn_cast<IntegerType>();
    auto operand_element_type = input()
                                    .getType()
                                    .cast<ShapedType>()
                                    .getElementType()
                                    .dyn_cast<IntegerType>();
    // Returns nullptr if either result/operand element type is not integer.
    if (!result_element_type || !operand_element_type) {
      return nullptr;
    }
  
    const bool is_unsigned = operand_element_type.isUnsigned();
    const bool involves_bool = operand_element_type.getWidth() == 1 ||
                               result_element_type.getWidth() == 1;
    const int output_bitwidth = result_element_type.getWidth();
    // The integer cast op is the same as C integer cast. Depends on the operand
    // type's signedness, we will determine whether or not sign extension is
    // needed.
    auto cast = [&](APInt value) {
      if (involves_bool) {
        // Handle boolean inputs or outputs explicitly as it doesn't have the same
        // behavior as extension or truncation.
        // true input should always be cast to 1 and not -1 as the sign extension
        // would do for signed outputs. Similarly, non-zero inputs should be cast
        // to true. Truncating even numbers to one bit will result in `false`.
        return APInt(result_element_type.getWidth(), value != 0);
      }
      return is_unsigned ? value.zextOrTrunc(output_bitwidth)
                         : value.sextOrTrunc(output_bitwidth);
    };
  
    return elements_attr.mapValues(result_element_type, cast);
  }
  
  //===----------------------------------------------------------------------===//
  // SelectV2Op
  //===----------------------------------------------------------------------===//
  
  static void BuildSelectV2Op(Builder *builder, OperationState &result,
                              Value cond, Value x, Value y) {
    auto operand_type =
        OpTrait::util::getBroadcastedType(x.getType(), y.getType());
  
    if (!operand_type)
      emitError(result.location) << "non-broadcastable operands: " << x.getType()
                                 << " and " << y.getType();
  
    bool has_static_cond_shape = false;
    bool has_static_operand_shape = false;
    ArrayRef<int64_t> cond_shape;
    ArrayRef<int64_t> operand_shape;
  
    if (auto shaped_type = cond.getType().dyn_cast<ShapedType>()) {
      if (shaped_type.hasStaticShape()) {
        has_static_cond_shape = true;
        cond_shape = shaped_type.getShape();
      }
    }
    if (auto shaped_type = operand_type.dyn_cast<ShapedType>()) {
      if (shaped_type.hasStaticShape()) {
        has_static_operand_shape = true;
        operand_shape = shaped_type.getShape();
      }
    }
  
    SmallVector<int64_t, 4> broadcastedShape;
    if (has_static_cond_shape && has_static_operand_shape &&
        !OpTrait::util::getBroadcastedShape(cond_shape, operand_shape,
                                            broadcastedShape)) {
      emitError(result.location) << "non-broadcastable operands: " << operand_type
                                 << " and " << cond.getType();
    }
  
    result.addOperands({cond, x, y});
  
    auto elementType = x.getType().dyn_cast<ShapedType>().getElementType();
    if (has_static_cond_shape && has_static_operand_shape) {
      result.types.push_back(
          RankedTensorType::get(broadcastedShape, elementType));
    } else {
      result.types.push_back(UnrankedTensorType::get(elementType));
    }
  }
  
  //===----------------------------------------------------------------------===//
  // RangeOp
  //===----------------------------------------------------------------------===//
  
  namespace {
  
  // Compute the length of a range (1-D) tensor given `start`, `limit`, `delta`.
  // Template parameter `FloatOrInt` must be standard C integer or floating-point
  // types.
  template <typename FloatOrInt>
  int GetLengthOfRange(FloatOrInt start, FloatOrInt limit, FloatOrInt delta) {
    // Refer to the implementation in
    // tensorflow/lite/kernels/range.cc.
    return std::is_integral<FloatOrInt>::value
               ? ((std::abs(limit - start) + std::abs(delta) - 1) /
                  std::abs(delta))
               : std::ceil(std::abs((limit - start) / delta));
  }
  
  // Builds a constant range tensor of `result_elem_type` elements.
  // Template parameter `FloatOrIntAtrr` must be mlir::IntegerAttr or
  // mlir::FloatAttr.
  template <typename FloatOrIntAtrr>
  DenseElementsAttr BuildConstRangeTensor(Type result_elem_type, int num_elements,
                                          FloatOrIntAtrr start_attr,
                                          FloatOrIntAtrr delta_attr) {
    using ValueType = typename FloatOrIntAtrr::ValueType;  // APInt or APFloat
    ValueType start = start_attr.getValue();
    ValueType delta = delta_attr.getValue();
  
    SmallVector<ValueType, 16> new_values;
    new_values.reserve(num_elements);
    ValueType new_value = start;
    for (int i = 0; i < num_elements; ++i) {
      new_values.push_back(new_value);
      new_value = new_value + delta;
    }
    // Result is always a 1-D tensor.
    auto new_result_type =
        RankedTensorType::get({num_elements}, result_elem_type);
    return DenseElementsAttr::get(new_result_type, new_values);
  }
  }  // namespace
  
  OpFoldResult RangeOp::fold(ArrayRef<Attribute> operands) {
    assert(operands.size() == 3);
    auto start_tensor = operands[0].dyn_cast_or_null<ElementsAttr>();
    auto limit_tensor = operands[1].dyn_cast_or_null<ElementsAttr>();
    auto delta_tensor = operands[2].dyn_cast_or_null<ElementsAttr>();
    if (start_tensor && limit_tensor && delta_tensor) {
      // Operands should all be scalars
      assert(start_tensor.getType().getRank() == 0 &&
             limit_tensor.getType().getRank() == 0 &&
             delta_tensor.getType().getRank() == 0);
      Type elem_type = getType().cast<ShapedType>().getElementType();
      if (elem_type.isSignlessInteger()) {
        auto start_attr = start_tensor.getValue<IntegerAttr>({});
        auto limit_attr = limit_tensor.getValue<IntegerAttr>({});
        auto delta_attr = delta_tensor.getValue<IntegerAttr>({});
        const int num_elements = GetLengthOfRange(
            start_attr.getInt(), limit_attr.getInt(), delta_attr.getInt());
        return BuildConstRangeTensor(elem_type, num_elements, start_attr,
                                     delta_attr);
      } else if (elem_type.isa<FloatType>()) {
        auto start_attr = start_tensor.getValue<FloatAttr>({});
        auto limit_attr = limit_tensor.getValue<FloatAttr>({});
        auto delta_attr = delta_tensor.getValue<FloatAttr>({});
        const int num_elements = GetLengthOfRange(start_attr.getValueAsDouble(),
                                                  limit_attr.getValueAsDouble(),
                                                  delta_attr.getValueAsDouble());
        return BuildConstRangeTensor(elem_type, num_elements, start_attr,
                                     delta_attr);
      }
    }
  
    return nullptr;
  }
  
  //===----------------------------------------------------------------------===//
  // TransposeConvOp
  //===----------------------------------------------------------------------===//
  
  static LogicalResult Verify(TransposeConvOp op) {
    ShapedType output_type = op.output().getType().cast<ShapedType>();
    ShapedType output_shape_type = op.output_shape().getType().cast<ShapedType>();
    if (output_type.hasRank() && output_shape_type.hasStaticShape()) {
      if (output_type.getRank() != output_shape_type.getDimSize(0)) {
        return op.emitOpError(llvm::formatv(
            "expect output type has rank = {0}, got output type {1}",
            output_shape_type.getDimSize(0), output_type));
      }
    }
  
    DenseIntElementsAttr output_shape_elements;
    if (!matchPattern(op.output_shape(), m_Constant(&output_shape_elements))) {
      return success();
    }
  
    llvm::SmallVector<int64_t, 4> output_shape;
    output_shape.reserve(output_shape_elements.getNumElements());
    for (auto dim : output_shape_elements.getValues<int>()) {
      output_shape.push_back(dim);
    }
  
    auto expected_output_type =
        RankedTensorType::get(output_shape, output_type.getElementType());
    if (failed(mlir::verifyCompatibleShape(output_type, expected_output_type))) {
      return op.emitOpError(llvm::formatv("expect output type {0}, got {1}",
                                          expected_output_type, output_type));
    }
  
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // StridedSliceOp
  //===----------------------------------------------------------------------===//
  
  LogicalResult Verify(StridedSliceOp op) {
    auto ranked_input_type = op.input().getType().dyn_cast<RankedTensorType>();
  
    // If input is unranked, there is nothing else to be verified.
    if (!ranked_input_type) return success();
    int num_input_dims = ranked_input_type.getRank();
  
    // The kernel will reshape the input tensor with new axis, it only supports
    // this reshaped tensor up to 5D.
    uint32_t ellipsis_mask = op.ellipsis_mask();
    uint32_t new_axis_mask = op.new_axis_mask();
    int num_added_axis = 0;
    for (int i = 0; i < 8; ++i) {
      if (!((1 << i) & ellipsis_mask) && ((1 << i) & new_axis_mask)) {
        num_added_axis++;
      }
    }
    if (num_input_dims + num_added_axis > 5) return failure();
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // TransposeOp
  //===----------------------------------------------------------------------===//
  
  namespace {
  
  // Computes the permutation of a constant `input_tensor` according to `perm`.
  // The function recursively traverses the dimensions of the output tensor in
  // a row-major order and writes the value in the output tensor into
  // `new_values`.
  void ComputePermutation(ElementsAttr input_tensor, ArrayRef<int32_t> perm,
                          ArrayRef<int64_t> output_shape, int num_dimensions,
                          int output_axis, std::vector<uint64_t> *input_indices,
                          std::vector<Attribute> *new_values) {
    // Refer to the implementation of `Transpose` function in
    // tensorflow/lite/kernels/internal/reference/reference_ops.h
    assert(output_axis < num_dimensions);
    const int input_axis = perm[output_axis];
    for (int i = 0; i < output_shape[output_axis]; ++i) {
      // Update the input indices on `input_axis`.
      input_indices->at(input_axis) = i;
      // Write the value from `input_tensor` if it is the last axis or
      // recurse into the next axis.
      const bool is_last_axis = output_axis == num_dimensions - 1;
      if (is_last_axis) {
        new_values->push_back(input_tensor.getValue(*input_indices));
      } else {
        ComputePermutation(input_tensor, perm, output_shape, num_dimensions,
                           output_axis + 1, input_indices, new_values);
      }
    }
  }
  
  }  // namespace
  
  OpFoldResult TransposeOp::fold(ArrayRef<Attribute> operands) {
    assert(operands.size() == 2);
    auto input_tensor = operands[0].dyn_cast_or_null<ElementsAttr>();
    auto perm_tensor = operands[1].dyn_cast_or_null<ElementsAttr>();
    if (!input_tensor || !perm_tensor) return nullptr;
  
    // Do not try to fold elements attr of a quant type because
    // DenseElementsAttr does not support it.
    if (!getType().cast<ShapedType>().getElementType().isSignlessIntOrFloat())
      return nullptr;
  
    assert(perm_tensor.getType().getRank() == 1);
    const int num_dimensions = input_tensor.getType().getRank();
    assert(perm_tensor.getType().getNumElements() == num_dimensions);
  
    ArrayRef<int64_t> input_shape = input_tensor.getType().getShape();
    auto output_type = getType().cast<ShapedType>();
  
    SmallVector<int32_t, 4> perm;
    SmallVector<int64_t, 4> output_shape;
    for (int i = 0; i < num_dimensions; ++i) {
      perm.push_back(
          perm_tensor.getValue<IntegerAttr>({static_cast<uint64_t>(i)}).getInt());
      output_shape.push_back(input_shape[perm[i]]);
  
      // Check that the derived output shape matches the static shape.
      assert(!output_type.hasStaticShape() ||
             output_type.getShape()[i] == output_shape[i]);
    }
  
    std::vector<Attribute> new_values;
    new_values.reserve(input_tensor.getType().getNumElements());
    std::vector<uint64_t> input_indices(num_dimensions);
    ComputePermutation(input_tensor, perm, output_shape, num_dimensions,
                       /*output_axis=*/0, &input_indices, &new_values);
    auto result_type =
        RankedTensorType::get(output_shape, output_type.getElementType());
    return DenseElementsAttr::get(result_type, new_values);
  }
  
  static LogicalResult Verify(TransposeOp op) {
    auto input_type = op.input().getType().cast<ShapedType>();
    auto perm_type = op.perm().getType().cast<ShapedType>();
    auto output_type = op.output().getType().cast<ShapedType>();
    if (input_type.hasStaticShape() && perm_type.hasStaticShape()) {
      if (perm_type.getNumElements() != input_type.getRank()) {
        return op.emitOpError(
            "perm tensor elements size is not equal to input tensor rank");
      }
    }
  
    DenseIntElementsAttr perm;
    if (!matchPattern(op.perm(), m_Constant(&perm))) {
      return success();
    }
  
    int index = 0;
    llvm::SmallVector<int64_t, 4> axes;
    for (const auto &axis_int : perm.getValues<APInt>()) {
      const int64_t axis = axis_int.getSExtValue();
      if (axis < 0 || (input_type.hasRank() && axis >= input_type.getRank())) {
        return op.emitOpError(
            llvm::formatv("perm[{0}] must be in [0, rank)", index));
      }
      if (std::count(axes.begin(), axes.end(), axis) > 0) {
        return op.emitOpError(
            llvm::formatv("perm[{0}] cannot have duplicated axis", index));
      }
      axes.push_back(axis);
      index++;
    }
  
    if (input_type.hasStaticShape() && output_type.hasStaticShape()) {
      llvm::SmallVector<int64_t, 4> transposed_shape;
      for (int64_t axis : axes) {
        transposed_shape.push_back(input_type.getDimSize(axis));
      }
      auto expected_output_type =
          RankedTensorType::get(transposed_shape, input_type.getElementType());
      if (failed(
              mlir::verifyCompatibleShape(output_type, expected_output_type))) {
        return op.emitOpError(llvm::formatv("expect output type {0}, got {1}",
                                            expected_output_type, output_type));
      }
    }
  
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // WhileOp
  //===----------------------------------------------------------------------===//
  
  LogicalResult Verify(WhileOp op) {
    if (op.getNumOperands() != op.getNumResults())
      return op.emitOpError(llvm::formatv(
          "number of operands does not match number of results ({0} != {1})",
          op.getNumOperands(), op.getNumResults()));
    // TODO(jpienaar): Verify operand, result & block arguments types
    return success();
  }
  
  namespace {
  // Canonicalize While op so that results and operands match and external values
  // are via implicit capture rather than via block args.
  struct WhileResultOperandsMatchAndImplicitCapture
      : public OpRewritePattern<WhileOp> {
    using OpRewritePattern<WhileOp>::OpRewritePattern;
  
    LogicalResult matchAndRewrite(WhileOp while_op,
                                  PatternRewriter &rewriter) const override {
      // Replace values simply passed through the body with extern values
      // (in both body and condition regions as well as while result). The
      // block arguments of body and while match and so the corresponding cond
      // argument can be easily found.
      bool unchanged = true;
      auto &body_block = while_op.body().front();
      auto &cond_block = while_op.cond().front();
      auto &yield = *body_block.getTerminator();
      for (auto ba : body_block.getArguments()) {
        int arg_no = ba.getArgNumber();
        // Skip removing resources that are not read-only variables.
        if (getElementTypeOrSelf(ba.getType()).isa<TF::ResourceType>()) {
          bool has_read_only_variables = true;
          for (auto user : ba.getUsers()) {
            // Ternimator ops, for example, tfl::yield op, should be ignored since
            // the argument can be used for yielding as the `body` function result
            // and that does not give any meaningful points to the decision
            // whether the given arugment is a read-only variable or not.
            if (user->hasTrait<OpTrait::IsTerminator>()) continue;
            if (!llvm::isa<mlir::TF::ReadVariableOp>(user)) {
              has_read_only_variables = false;
              break;
            }
          }
          if (!has_read_only_variables) continue;
        }
        if (ba == yield.getOperand(arg_no)) {
          unchanged = false;
          auto value = while_op.getOperand(arg_no);
          ba.replaceAllUsesWith(value);
          cond_block.getArgument(arg_no).replaceAllUsesWith(value);
  
          // This could be relaxed and casts inserted.
          if (while_op.getResult(arg_no).getType() == value.getType())
            while_op.getResult(arg_no).replaceAllUsesWith(value);
        }
      }
  
      // The While ops operands and result types need to match
      SmallVector<Value, 4> new_operands;
      SmallVector<Value, 4> new_body_yield;
      SmallVector<bool, 4> removed_operand(while_op.getNumOperands(), false);
      llvm::SmallVector<Type, 4> types;
      new_operands.reserve(while_op.getNumOperands());
      new_body_yield.reserve(while_op.getNumOperands());
      types.reserve(while_op.getNumOperands());
  
      // Remove block arguments not used in either cond or body. This leaves the
      // block arguments of body and cond matching still.
      int arg_index = 0;
      for (int while_index = 0, e = while_op.getNumOperands(); while_index < e;
           ++while_index) {
        auto value = while_op.getOperand(while_index);
        if (body_block.getArgument(arg_index).use_empty() &&
            cond_block.getArgument(arg_index).use_empty() &&
            // Note: since we are not erasing results, need to use while_index
            // to check if the corresponding result is unused.
            while_op.getResult(while_index).use_empty()) {
          unchanged = false;
          body_block.eraseArgument(arg_index);
          cond_block.eraseArgument(arg_index);
  
          // Mark operand for removal.
          removed_operand[while_index] = true;
        } else {
          new_operands.push_back(value);
          new_body_yield.push_back(yield.getOperand(while_index));
          auto type = while_op.getResult(while_index).getType();
          types.push_back(type);
          ++arg_index;
        }
      }
  
      // Done if no values removed from blocks and operands & results match.
      if (unchanged) return failure();
  
      // Replace with new While with matching operands and results.
      Operation *op = while_op.getOperation();
      Operation *new_op = rewriter.insert(
          Operation::create(op->getLoc(), op->getName(), types, new_operands,
                            op->getAttrs(), {}, /*numRegions=*/2));
  
      for (int i = 0; i < 2; ++i) new_op->getRegion(i).takeBody(op->getRegion(i));
      int new_index = 0;
      for (int op_index = 0, e = op->getNumResults(); op_index < e; ++op_index) {
        if (removed_operand[op_index]) continue;
        op->getResult(op_index).replaceAllUsesWith(new_op->getResult(new_index));
        ++new_index;
      }
      rewriter.eraseOp(op);
  
      Block &new_body_block = cast<WhileOp>(new_op).body().front();
      rewriter.setInsertionPointToEnd(&new_body_block);
      rewriter.replaceOpWithNewOp<YieldOp>(new_body_block.getTerminator(),
                                           new_body_yield);
  
      return success();
    }
  };
  
  }  // namespace
  
  void WhileOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
                                            MLIRContext *context) {
    results.insert<WhileResultOperandsMatchAndImplicitCapture>(context);
  }
  
  Region &WhileOp::getLoopBody() { return body(); }
  
  bool WhileOp::isDefinedOutsideOfLoop(Value value) {
    // TODO(jpienaar): This is to overly conservative and disables anything other
    // than constant hoisting initially.
    return false;
  }
  
  LogicalResult WhileOp::moveOutOfLoop(llvm::ArrayRef<mlir::Operation *> ops) {
    if (ops.empty()) return success();
  
    // Move the hoisted value to just before the while.
    Operation *while_op = this->getOperation();
    for (auto op : ops) op->moveBefore(while_op);
  
    return success();
  }
  
  //===----------------------------------------------------------------------===//
  // TableGen'd op method definitions
  //===----------------------------------------------------------------------===//
  
  #include "tensorflow/compiler/mlir/lite/ir/tfl_ops_interface.cc.inc"
  
  }  // namespace TFL
  }  // namespace mlir
  
  #define GET_OP_CLASSES
  #include "tensorflow/compiler/mlir/lite/ir/tfl_ops.cc.inc"
  
  namespace mlir {
  namespace TFL {
  
  #include "tensorflow/compiler/mlir/lite/runtime_verifiers.inc"
  
  Operation *TensorFlowLiteDialect::materializeConstant(OpBuilder &builder,
                                                        Attribute value,
                                                        Type type, Location loc) {
    // If this is an opaque elements attribute or the result type doesn't match
    // the attribute type, then generate a tfl.pseudo_const.
    if (value.isa<OpaqueElementsAttr>() ||
        (value.isa<ElementsAttr>() && value.getType() != type))
      return builder.create<ConstOp>(loc, type, value.cast<ElementsAttr>());
    if (ConstantOp::isBuildableWith(value, type))
      return builder.create<ConstantOp>(loc, type, value);
    return nullptr;
  }
  
  }  // namespace TFL
  }  // namespace mlir
  