//===- AttributeDetail.h - MLIR Affine Map details Class --------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This holds implementation details of Attribute.
//
//===----------------------------------------------------------------------===//

#ifndef ATTRIBUTEDETAIL_H_
#define ATTRIBUTEDETAIL_H_

#include "mlir/IR/AffineMap.h"
#include "mlir/IR/AttributeSupport.h"
#include "mlir/IR/BuiltinAttributes.h"
#include "mlir/IR/BuiltinTypeInterfaces.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/IR/IntegerSet.h"
#include "mlir/IR/MLIRContext.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/Support/Allocator.h"
#include <mutex>

namespace mlir {
namespace detail {

//===----------------------------------------------------------------------===//
// Elements Attributes
//===----------------------------------------------------------------------===//

/// Return the bit width which DenseElementsAttr should use for this type.
inline size_t getDenseElementBitWidth(Type eltType) {
  if (auto denseEltType = llvm::dyn_cast<DenseElementType>(eltType))
    return denseEltType.getDenseElementBitSize();
  llvm_unreachable("unsupported element type");
}

/// An attribute representing a reference to a dense vector or tensor object.
struct DenseElementsAttributeStorage : public AttributeStorage {
public:
  DenseElementsAttributeStorage(ShapedType type) : type(type) {}

  ShapedType type;
};

/// An attribute representing a reference to a dense vector or tensor object.
struct DenseTypedElementsAttrStorage : public DenseElementsAttributeStorage {
  DenseTypedElementsAttrStorage(ShapedType ty, ArrayRef<char> data)
      : DenseElementsAttributeStorage(ty), data(data) {}

  struct KeyTy {
    KeyTy(ShapedType type, ArrayRef<char> data, llvm::hash_code hashCode)
        : type(type), data(data), hashCode(hashCode) {}

    /// The type of the dense elements.
    ShapedType type;

    /// The raw buffer for the data storage.
    ArrayRef<char> data;

    /// The computed hash code for the storage data.
    llvm::hash_code hashCode;
  };

  /// Compare this storage instance with the provided key.
  bool operator==(const KeyTy &key) const {
    return key.type == type && key.data == data;
  }

  /// Construct a key from a shaped type and raw data buffer.
  static KeyTy getKey(ShapedType ty, ArrayRef<char> data) {
    // Handle an empty storage instance.
    if (data.empty())
      return KeyTy(ty, data, 0);

    size_t elementWidth = getDenseElementBitWidth(ty.getElementType());
    // Dense elements are padded to 8-bits.
    size_t storageSize = llvm::divideCeil(elementWidth, CHAR_BIT);

    // If the data buffer holds a single element, it is a known splat.
    if (data.size() == storageSize)
      return KeyTy(ty, data, llvm::hash_value(data));

    assert(((data.size() / storageSize) ==
            static_cast<size_t>(ty.getNumElements())) &&
           "data does not hold expected number of elements");

    // Create the initial hash value with just the first element.
    auto firstElt = data.take_front(storageSize);
    auto hashVal = llvm::hash_value(firstElt);

    // Check to see if this storage represents a splat. If it doesn't then
    // combine the hash for the data starting with the first non splat element.
    for (size_t i = storageSize, e = data.size(); i != e; i += storageSize)
      if (memcmp(data.data(), &data[i], storageSize))
        return KeyTy(ty, data, llvm::hash_combine(hashVal, data.drop_front(i)));

    // Otherwise, this is a splat so just return the hash of the first element.
    return KeyTy(ty, firstElt, hashVal);
  }

  /// Hash the key for the storage.
  static llvm::hash_code hashKey(const KeyTy &key) {
    return llvm::hash_combine(key.type, key.hashCode);
  }

  /// Construct a new storage instance.
  static DenseTypedElementsAttrStorage *
  construct(AttributeStorageAllocator &allocator, KeyTy key) {
    // If the data buffer is non-empty, we copy it into the allocator with a
    // 64-bit alignment.
    ArrayRef<char> copy, data = key.data;
    if (!data.empty()) {
      char *rawData = reinterpret_cast<char *>(
          allocator.allocate(data.size(), alignof(uint64_t)));
      std::memcpy(rawData, data.data(), data.size());
      copy = ArrayRef<char>(rawData, data.size());
    }

    return new (allocator.allocate<DenseTypedElementsAttrStorage>())
        DenseTypedElementsAttrStorage(key.type, copy);
  }

  ArrayRef<char> data;
};

/// An attribute representing a reference to a dense vector or tensor object
/// containing strings.
struct DenseStringElementsAttrStorage : public DenseElementsAttributeStorage {
  DenseStringElementsAttrStorage(ShapedType ty, ArrayRef<StringRef> data)
      : DenseElementsAttributeStorage(ty), data(data) {}

  struct KeyTy {
    KeyTy(ShapedType type, ArrayRef<StringRef> data, llvm::hash_code hashCode)
        : type(type), data(data), hashCode(hashCode) {}

    /// The type of the dense elements.
    ShapedType type;

    /// The raw buffer for the data storage.
    ArrayRef<StringRef> data;

    /// The computed hash code for the storage data.
    llvm::hash_code hashCode;
  };

  /// Compare this storage instance with the provided key.
  bool operator==(const KeyTy &key) const {
    if (key.type != type)
      return false;

    // Otherwise, we can default to just checking the data. StringRefs compare
    // by contents.
    return key.data == data;
  }

  /// Construct a key from a shaped type and StringRef data buffer.
  static KeyTy getKey(ShapedType ty, ArrayRef<StringRef> data) {
    // Handle an empty storage instance.
    if (data.empty())
      return KeyTy(ty, data, 0);

    // If the data buffer holds a single element, it is a known splat.
    if (data.size() == 1)
      return KeyTy(ty, data, llvm::hash_value(data.front()));

    // Create the initial hash value with just the first element.
    const auto &firstElt = data.front();
    auto hashVal = llvm::hash_value(firstElt);

    // Check to see if this storage represents a splat. If it doesn't then
    // combine the hash for the data starting with the first non splat element.
    for (size_t i = 1, e = data.size(); i != e; ++i)
      if (firstElt != data[i])
        return KeyTy(ty, data, llvm::hash_combine(hashVal, data.drop_front(i)));

    // Otherwise, this is a splat so just return the hash of the first element.
    return KeyTy(ty, data.take_front(), hashVal);
  }

  /// Hash the key for the storage.
  static llvm::hash_code hashKey(const KeyTy &key) {
    return llvm::hash_combine(key.type, key.hashCode);
  }

  /// Construct a new storage instance.
  static DenseStringElementsAttrStorage *
  construct(AttributeStorageAllocator &allocator, KeyTy key) {
    // If the data buffer is non-empty, we copy it into the allocator with a
    // 64-bit alignment.
    ArrayRef<StringRef> copy, data = key.data;
    if (data.empty()) {
      return new (allocator.allocate<DenseStringElementsAttrStorage>())
          DenseStringElementsAttrStorage(key.type, copy);
    }

    size_t numEntries = data.size();

    // Compute the amount data needed to store the ArrayRef and StringRef
    // contents.
    size_t dataSize = sizeof(StringRef) * numEntries;
    for (size_t i = 0; i < numEntries; ++i)
      dataSize += data[i].size();

    char *rawData = reinterpret_cast<char *>(
        allocator.allocate(dataSize, alignof(uint64_t)));

    // Setup a mutable array ref of our string refs so that we can update their
    // contents.
    auto mutableCopy = MutableArrayRef<StringRef>(
        reinterpret_cast<StringRef *>(rawData), numEntries);
    auto *stringData = rawData + numEntries * sizeof(StringRef);

    for (size_t i = 0; i < numEntries; ++i) {
      memcpy(stringData, data[i].data(), data[i].size());
      mutableCopy[i] = StringRef(stringData, data[i].size());
      stringData += data[i].size();
    }

    copy =
        ArrayRef<StringRef>(reinterpret_cast<StringRef *>(rawData), numEntries);

    return new (allocator.allocate<DenseStringElementsAttrStorage>())
        DenseStringElementsAttrStorage(key.type, copy);
  }

  ArrayRef<StringRef> data;
};

//===----------------------------------------------------------------------===//
// StringAttr
//===----------------------------------------------------------------------===//

struct StringAttrStorage : public AttributeStorage {
  StringAttrStorage(StringRef value, Type type)
      : type(type), value(value), referencedDialect(nullptr) {}

  /// The hash key is a tuple of the parameter types.
  using KeyTy = std::pair<StringRef, Type>;
  bool operator==(const KeyTy &key) const {
    return value == key.first && type == key.second;
  }
  static ::llvm::hash_code hashKey(const KeyTy &key) {
    return DenseMapInfo<KeyTy>::getHashValue(key);
  }

  /// Define a construction method for creating a new instance of this
  /// storage.
  static StringAttrStorage *construct(AttributeStorageAllocator &allocator,
                                      const KeyTy &key) {
    return new (allocator.allocate<StringAttrStorage>())
        StringAttrStorage(allocator.copyInto(key.first), key.second);
  }

  /// Initialize the storage given an MLIRContext.
  void initialize(MLIRContext *context);

  /// The type of the string.
  Type type;
  /// The raw string value.
  StringRef value;
  /// If the string value contains a dialect namespace prefix (e.g.
  /// dialect.blah), this is the dialect referenced.
  Dialect *referencedDialect;
};

//===----------------------------------------------------------------------===//
// DistinctAttr
//===----------------------------------------------------------------------===//

/// An attribute to store a distinct reference to another attribute.
struct DistinctAttrStorage : public AttributeStorage {
  using KeyTy = Attribute;

  DistinctAttrStorage(Attribute referencedAttr)
      : referencedAttr(referencedAttr) {}

  /// Returns the referenced attribute as key.
  KeyTy getAsKey() const { return KeyTy(referencedAttr); }

  /// The referenced attribute.
  Attribute referencedAttr;
};

/// A specialized attribute uniquer for distinct attributes that always
/// allocates since the distinct attribute instances use the address of their
/// storage as unique identifier.
class DistinctAttributeUniquer {
public:
  /// Creates a distinct attribute storage. Allocates every time since the
  /// address of the storage serves as unique identifier.
  template <typename T, typename... Args>
  static T get(MLIRContext *context, Args &&...args) {
    static_assert(std::is_same_v<typename T::ImplType, DistinctAttrStorage>,
                  "expects a distinct attribute storage");
    DistinctAttrStorage *storage = DistinctAttributeUniquer::allocateStorage(
        context, std::forward<Args>(args)...);
    storage->initializeAbstractAttribute(
        AbstractAttribute::lookup(DistinctAttr::getTypeID(), context));
    return storage;
  }

private:
  /// Allocates a distinct attribute storage.
  static DistinctAttrStorage *allocateStorage(MLIRContext *context,
                                              Attribute referencedAttr);
};

/// An allocator for distinct attribute storage instances. Uses a synchronized
/// BumpPtrAllocator to ensure thread-safety. The allocated storage is deleted
/// when the DistinctAttributeAllocator is destroyed.
class DistinctAttributeAllocator final {
public:
  DistinctAttributeAllocator() = default;
  DistinctAttributeAllocator(DistinctAttributeAllocator &&) = delete;
  DistinctAttributeAllocator(const DistinctAttributeAllocator &) = delete;
  DistinctAttributeAllocator &
  operator=(const DistinctAttributeAllocator &) = delete;

  DistinctAttrStorage *allocate(Attribute referencedAttr) {
    std::scoped_lock<std::mutex> guard(allocatorMutex);
    return new (allocator.Allocate<DistinctAttrStorage>())
        DistinctAttrStorage(referencedAttr);
  };

private:
  /// Used to allocate distict attribute storages. The managed memory is freed
  /// automatically when the allocator instance is destroyed.
  llvm::BumpPtrAllocator allocator;

  /// Used to lock access to the allocator.
  std::mutex allocatorMutex;
};
} // namespace detail
} // namespace mlir

#endif // ATTRIBUTEDETAIL_H_