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//===- llvm/User.h - User class definition ----------------------*- 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 class defines the interface that one who uses a Value must implement.

// Each instance of the Value class keeps track of what User's have handles

// to it.

//

//  * Instructions are the largest class of Users.

//  * Constants may be users of other constants (think arrays and stuff)

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_IR_USER_H

#define LLVM_IR_USER_H

#include "llvm/ADT/iterator.h"

#include "llvm/ADT/iterator_range.h"

#include "llvm/IR/Use.h"

#include "llvm/IR/Value.h"

#include "llvm/Support/Casting.h"

#include "llvm/Support/Compiler.h"

#include "llvm/Support/ErrorHandling.h"

#include <cassert>

#include <cstddef>

#include <cstdint>

#include <iterator>

namespace llvm {

template <typename T> class ArrayRef;

template <typename T> class MutableArrayRef;

/// Compile-time customization of User operands.

///

/// Customizes operand-related allocators and accessors.

template <class>

struct OperandTraits;

class User : public Value {

  template <unsigned>

  friend struct HungoffOperandTraits;

  LLVM_ATTRIBUTE_ALWAYS_INLINE static void *

  allocateFixedOperandUser(size_t, unsigned, unsigned);

protected:

  /// Allocate a User with an operand pointer co-allocated.

  ///

  /// This is used for subclasses which need to allocate a variable number

  /// of operands, ie, 'hung off uses'.

  void *operator new(size_t Size);

  /// Allocate a User with the operands co-allocated.

  ///

  /// This is used for subclasses which have a fixed number of operands.

  void *operator new(size_t Size, unsigned Us);

  /// Allocate a User with the operands co-allocated.  If DescBytes is non-zero

  /// then allocate an additional DescBytes bytes before the operands. These

  /// bytes can be accessed by calling getDescriptor.

  ///

  /// DescBytes needs to be divisible by sizeof(void *).  The allocated

  /// descriptor, if any, is aligned to sizeof(void *) bytes.

  ///

  /// This is used for subclasses which have a fixed number of operands.

  void *operator new(size_t Size, unsigned Us, unsigned DescBytes);

  User(Type *ty, unsigned vty, Use *, unsigned NumOps)

      : Value(ty, vty) {

    assert(NumOps < (1u << NumUserOperandsBits) && "Too many operands");

    NumUserOperands = NumOps;

    // If we have hung off uses, then the operand list should initially be

    // null.

    assert((!HasHungOffUses || !getOperandList()) &&

           "Error in initializing hung off uses for User");

  }

  /// Allocate the array of Uses, followed by a pointer

  /// (with bottom bit set) to the User.

  /// \param IsPhi identifies callers which are phi nodes and which need

  /// N BasicBlock* allocated along with N

  void allocHungoffUses(unsigned N, bool IsPhi = false);

  /// Grow the number of hung off uses.  Note that allocHungoffUses

  /// should be called if there are no uses.

  void growHungoffUses(unsigned N, bool IsPhi = false);

protected:

  ~User() = default; // Use deleteValue() to delete a generic Instruction.

public:

  User(const User &) = delete;

  /// Free memory allocated for User and Use objects.

  void operator delete(void *Usr);

  /// Placement delete - required by std, called if the ctor throws.

  void operator delete(void *Usr, unsigned) {

    // Note: If a subclass manipulates the information which is required to calculate the

    // Usr memory pointer, e.g. NumUserOperands, the operator delete of that subclass has

    // to restore the changed information to the original value, since the dtor of that class

    // is not called if the ctor fails.

    User::operator delete(Usr);

#ifndef LLVM_ENABLE_EXCEPTIONS

    llvm_unreachable("Constructor throws?");

#endif

  }

  /// Placement delete - required by std, called if the ctor throws.

  void operator delete(void *Usr, unsigned, unsigned) {

    // Note: If a subclass manipulates the information which is required to calculate the

    // Usr memory pointer, e.g. NumUserOperands, the operator delete of that subclass has

    // to restore the changed information to the original value, since the dtor of that class

    // is not called if the ctor fails.

    User::operator delete(Usr);

#ifndef LLVM_ENABLE_EXCEPTIONS

    llvm_unreachable("Constructor throws?");

#endif

  }

protected:

  template <int Idx, typename U> static Use &OpFrom(const U *that) {

    return Idx < 0

      ? OperandTraits<U>::op_end(const_cast<U*>(that))[Idx]

      : OperandTraits<U>::op_begin(const_cast<U*>(that))[Idx];

  }

  template <int Idx> Use &Op() {

    return OpFrom<Idx>(this);

  }

  template <int Idx> const Use &Op() const {

    return OpFrom<Idx>(this);

  }

private:

  const Use *getHungOffOperands() const {

    return *(reinterpret_cast<const Use *const *>(this) - 1);

  }

  Use *&getHungOffOperands() { return *(reinterpret_cast<Use **>(this) - 1); }

  const Use *getIntrusiveOperands() const {

    return reinterpret_cast<const Use *>(this) - NumUserOperands;

  }

  Use *getIntrusiveOperands() {

    return reinterpret_cast<Use *>(this) - NumUserOperands;

  }

  void setOperandList(Use *NewList) {

    assert(HasHungOffUses &&

           "Setting operand list only required for hung off uses");

    getHungOffOperands() = NewList;

  }

public:

  const Use *getOperandList() const {

    return HasHungOffUses ? getHungOffOperands() : getIntrusiveOperands();

  }

  Use *getOperandList() {

    return const_cast<Use *>(static_cast<const User *>(this)->getOperandList());

  }

  Value *getOperand(unsigned i) const {

    assert(i < NumUserOperands && "getOperand() out of range!");

    return getOperandList()[i];

  }

  void setOperand(unsigned i, Value *Val) {

    assert(i < NumUserOperands && "setOperand() out of range!");

    assert((!isa<Constant>((const Value*)this) ||

            isa<GlobalValue>((const Value*)this)) &&

           "Cannot mutate a constant with setOperand!");

    getOperandList()[i] = Val;

  }

  const Use &getOperandUse(unsigned i) const {

    assert(i < NumUserOperands && "getOperandUse() out of range!");

    return getOperandList()[i];

  }

  Use &getOperandUse(unsigned i) {

    assert(i < NumUserOperands && "getOperandUse() out of range!");

    return getOperandList()[i];

  }

  unsigned getNumOperands() const { return NumUserOperands; }

  /// Returns the descriptor co-allocated with this User instance.

  ArrayRef<const uint8_t> getDescriptor() const;

  /// Returns the descriptor co-allocated with this User instance.

  MutableArrayRef<uint8_t> getDescriptor();

  /// Set the number of operands on a GlobalVariable.

  ///

  /// GlobalVariable always allocates space for a single operands, but

  /// doesn't always use it.

  ///

  /// FIXME: As that the number of operands is used to find the start of

  /// the allocated memory in operator delete, we need to always think we have

  /// 1 operand before delete.

  void setGlobalVariableNumOperands(unsigned NumOps) {

    assert(NumOps <= 1 && "GlobalVariable can only have 0 or 1 operands");

    NumUserOperands = NumOps;

  }

  /// Subclasses with hung off uses need to manage the operand count

  /// themselves.  In these instances, the operand count isn't used to find the

  /// OperandList, so there's no issue in having the operand count change.

  void setNumHungOffUseOperands(unsigned NumOps) {

    assert(HasHungOffUses && "Must have hung off uses to use this method");

    assert(NumOps < (1u << NumUserOperandsBits) && "Too many operands");

    NumUserOperands = NumOps;

  }

  /// A droppable user is a user for which uses can be dropped without affecting

  /// correctness and should be dropped rather than preventing a transformation

  /// from happening.

  bool isDroppable() const;

  // ---------------------------------------------------------------------------

  // Operand Iterator interface...

  //

  using op_iterator = Use*;

  using const_op_iterator = const Use*;

  using op_range = iterator_range<op_iterator>;

  using const_op_range = iterator_range<const_op_iterator>;

  op_iterator       op_begin()       { return getOperandList(); }

  const_op_iterator op_begin() const { return getOperandList(); }

  op_iterator       op_end()         {

    return getOperandList() + NumUserOperands;

  }

  const_op_iterator op_end()   const {

    return getOperandList() + NumUserOperands;

  }

  op_range operands() {

    return op_range(op_begin(), op_end());

  }

  const_op_range operands() const {

    return const_op_range(op_begin(), op_end());

  }

  /// Iterator for directly iterating over the operand Values.

  struct value_op_iterator

      : iterator_adaptor_base<value_op_iterator, op_iterator,

                              std::random_access_iterator_tag, Value *,

                              ptrdiff_t, Value *, Value *> {

    explicit value_op_iterator(Use *U = nullptr) : iterator_adaptor_base(U) {}

    Value *operator*() const { return *I; }

    Value *operator->() const { return operator*(); }

  };

  value_op_iterator value_op_begin() {

    return value_op_iterator(op_begin());

  }

  value_op_iterator value_op_end() {

    return value_op_iterator(op_end());

  }

  iterator_range<value_op_iterator> operand_values() {

    return make_range(value_op_begin(), value_op_end());

  }

  struct const_value_op_iterator

      : iterator_adaptor_base<const_value_op_iterator, const_op_iterator,

                              std::random_access_iterator_tag, const Value *,

                              ptrdiff_t, const Value *, const Value *> {

    explicit const_value_op_iterator(const Use *U = nullptr) :

      iterator_adaptor_base(U) {}

    const Value *operator*() const { return *I; }

    const Value *operator->() const { return operator*(); }

  };

  const_value_op_iterator value_op_begin() const {

    return const_value_op_iterator(op_begin());

  }

  const_value_op_iterator value_op_end() const {

    return const_value_op_iterator(op_end());

  }

  iterator_range<const_value_op_iterator> operand_values() const {

    return make_range(value_op_begin(), value_op_end());

  }

  /// Drop all references to operands.

  ///

  /// This function is in charge of "letting go" of all objects that this User

  /// refers to.  This allows one to 'delete' a whole class at a time, even

  /// though there may be circular references...  First all references are

  /// dropped, and all use counts go to zero.  Then everything is deleted for

  /// real.  Note that no operations are valid on an object that has "dropped

  /// all references", except operator delete.

  void dropAllReferences() {

    for (Use &U : operands())

      U.set(nullptr);

  }

  /// Replace uses of one Value with another.

  ///

  /// Replaces all references to the "From" definition with references to the

  /// "To" definition. Returns whether any uses were replaced.

  bool replaceUsesOfWith(Value *From, Value *To);

  // Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const Value *V) {

    return isa<Instruction>(V) || isa<Constant>(V);

  }

};

// Either Use objects, or a Use pointer can be prepended to User.

static_assert(alignof(Use) >= alignof(User),

              "Alignment is insufficient after objects prepended to User");

static_assert(alignof(Use *) >= alignof(User),

              "Alignment is insufficient after objects prepended to User");

template<> struct simplify_type<User::op_iterator> {

  using SimpleType = Value*;

  static SimpleType getSimplifiedValue(User::op_iterator &Val) {

    return Val->get();

  }

};

template<> struct simplify_type<User::const_op_iterator> {

  using SimpleType = /*const*/ Value*;

  static SimpleType getSimplifiedValue(User::const_op_iterator &Val) {

    return Val->get();

  }

};

} // end namespace llvm

#endif // LLVM_IR_USER_H