//===- 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