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//===- llvm/ADT/PointerIntPair.h - Pair for pointer and int -----*- 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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file defines the PointerIntPair class.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_POINTERINTPAIR_H
#define LLVM_ADT_POINTERINTPAIR_H
#include "llvm/Support/Compiler.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
#include "llvm/Support/type_traits.h"
#include <cassert>
#include <cstdint>
#include <cstring>
#include <limits>
namespace llvm {
namespace detail {
template <typename Ptr> struct PunnedPointer {
static_assert(sizeof(Ptr) == sizeof(intptr_t), "");
// Asserts that allow us to let the compiler implement the destructor and
// copy/move constructors
static_assert(std::is_trivially_destructible<Ptr>::value, "");
static_assert(std::is_trivially_copy_constructible<Ptr>::value, "");
static_assert(std::is_trivially_move_constructible<Ptr>::value, "");
explicit constexpr PunnedPointer(intptr_t i = 0) { *this = i; }
constexpr intptr_t asInt() const {
intptr_t R = 0;
std::memcpy(&R, Data, sizeof(R));
return R;
}
constexpr operator intptr_t() const { return asInt(); }
constexpr PunnedPointer &operator=(intptr_t V) {
std::memcpy(Data, &V, sizeof(Data));
return *this;
}
Ptr *getPointerAddress() { return reinterpret_cast<Ptr *>(Data); }
const Ptr *getPointerAddress() const { return reinterpret_cast<Ptr *>(Data); }
private:
alignas(Ptr) unsigned char Data[sizeof(Ptr)];
};
} // namespace detail
template <typename T, typename Enable> struct DenseMapInfo;
template <typename PointerT, unsigned IntBits, typename PtrTraits>
struct PointerIntPairInfo;
/// PointerIntPair - This class implements a pair of a pointer and small
/// integer. It is designed to represent this in the space required by one
/// pointer by bitmangling the integer into the low part of the pointer. This
/// can only be done for small integers: typically up to 3 bits, but it depends
/// on the number of bits available according to PointerLikeTypeTraits for the
/// type.
///
/// Note that PointerIntPair always puts the IntVal part in the highest bits
/// possible. For example, PointerIntPair<void*, 1, bool> will put the bit for
/// the bool into bit #2, not bit #0, which allows the low two bits to be used
/// for something else. For example, this allows:
/// PointerIntPair<PointerIntPair<void*, 1, bool>, 1, bool>
/// ... and the two bools will land in different bits.
template <typename PointerTy, unsigned IntBits, typename IntType = unsigned,
typename PtrTraits = PointerLikeTypeTraits<PointerTy>,
typename Info = PointerIntPairInfo<PointerTy, IntBits, PtrTraits>>
class PointerIntPair {
// Used by MSVC visualizer and generally helpful for debugging/visualizing.
using InfoTy = Info;
detail::PunnedPointer<PointerTy> Value;
public:
constexpr PointerIntPair() = default;
PointerIntPair(PointerTy PtrVal, IntType IntVal) {
setPointerAndInt(PtrVal, IntVal);
}
explicit PointerIntPair(PointerTy PtrVal) { initWithPointer(PtrVal); }
PointerTy getPointer() const { return Info::getPointer(Value); }
IntType getInt() const { return (IntType)Info::getInt(Value); }
void setPointer(PointerTy PtrVal) & {
Value = Info::updatePointer(Value, PtrVal);
}
void setInt(IntType IntVal) & {
Value = Info::updateInt(Value, static_cast<intptr_t>(IntVal));
}
void initWithPointer(PointerTy PtrVal) & {
Value = Info::updatePointer(0, PtrVal);
}
void setPointerAndInt(PointerTy PtrVal, IntType IntVal) & {
Value = Info::updateInt(Info::updatePointer(0, PtrVal),
static_cast<intptr_t>(IntVal));
}
PointerTy const *getAddrOfPointer() const {
return const_cast<PointerIntPair *>(this)->getAddrOfPointer();
}
PointerTy *getAddrOfPointer() {
assert(Value == reinterpret_cast<intptr_t>(getPointer()) &&
"Can only return the address if IntBits is cleared and "
"PtrTraits doesn't change the pointer");
return Value.getPointerAddress();
}
void *getOpaqueValue() const {
return reinterpret_cast<void *>(Value.asInt());
}
void setFromOpaqueValue(void *Val) & {
Value = reinterpret_cast<intptr_t>(Val);
}
static PointerIntPair getFromOpaqueValue(void *V) {
PointerIntPair P;
P.setFromOpaqueValue(V);
return P;
}
// Allow PointerIntPairs to be created from const void * if and only if the
// pointer type could be created from a const void *.
static PointerIntPair getFromOpaqueValue(const void *V) {
(void)PtrTraits::getFromVoidPointer(V);
return getFromOpaqueValue(const_cast<void *>(V));
}
bool operator==(const PointerIntPair &RHS) const {
return Value == RHS.Value;
}
bool operator!=(const PointerIntPair &RHS) const {
return Value != RHS.Value;
}
bool operator<(const PointerIntPair &RHS) const { return Value < RHS.Value; }
bool operator>(const PointerIntPair &RHS) const { return Value > RHS.Value; }
bool operator<=(const PointerIntPair &RHS) const {
return Value <= RHS.Value;
}
bool operator>=(const PointerIntPair &RHS) const {
return Value >= RHS.Value;
}
};
template <typename PointerT, unsigned IntBits, typename PtrTraits>
struct PointerIntPairInfo {
static_assert(PtrTraits::NumLowBitsAvailable <
std::numeric_limits<uintptr_t>::digits,
"cannot use a pointer type that has all bits free");
static_assert(IntBits <= PtrTraits::NumLowBitsAvailable,
"PointerIntPair with integer size too large for pointer");
enum MaskAndShiftConstants : uintptr_t {
/// PointerBitMask - The bits that come from the pointer.
PointerBitMask =
~(uintptr_t)(((intptr_t)1 << PtrTraits::NumLowBitsAvailable) - 1),
/// IntShift - The number of low bits that we reserve for other uses, and
/// keep zero.
IntShift = (uintptr_t)PtrTraits::NumLowBitsAvailable - IntBits,
/// IntMask - This is the unshifted mask for valid bits of the int type.
IntMask = (uintptr_t)(((intptr_t)1 << IntBits) - 1),
// ShiftedIntMask - This is the bits for the integer shifted in place.
ShiftedIntMask = (uintptr_t)(IntMask << IntShift)
};
static PointerT getPointer(intptr_t Value) {
return PtrTraits::getFromVoidPointer(
reinterpret_cast<void *>(Value & PointerBitMask));
}
static intptr_t getInt(intptr_t Value) {
return (Value >> IntShift) & IntMask;
}
static intptr_t updatePointer(intptr_t OrigValue, PointerT Ptr) {
intptr_t PtrWord =
reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(Ptr));
assert((PtrWord & ~PointerBitMask) == 0 &&
"Pointer is not sufficiently aligned");
// Preserve all low bits, just update the pointer.
return PtrWord | (OrigValue & ~PointerBitMask);
}
static intptr_t updateInt(intptr_t OrigValue, intptr_t Int) {
intptr_t IntWord = static_cast<intptr_t>(Int);
assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
// Preserve all bits other than the ones we are updating.
return (OrigValue & ~ShiftedIntMask) | IntWord << IntShift;
}
};
// Provide specialization of DenseMapInfo for PointerIntPair.
template <typename PointerTy, unsigned IntBits, typename IntType>
struct DenseMapInfo<PointerIntPair<PointerTy, IntBits, IntType>, void> {
using Ty = PointerIntPair<PointerTy, IntBits, IntType>;
static Ty getEmptyKey() {
uintptr_t Val = static_cast<uintptr_t>(-1);
Val <<= PointerLikeTypeTraits<Ty>::NumLowBitsAvailable;
return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
}
static Ty getTombstoneKey() {
uintptr_t Val = static_cast<uintptr_t>(-2);
Val <<= PointerLikeTypeTraits<PointerTy>::NumLowBitsAvailable;
return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
}
static unsigned getHashValue(Ty V) {
uintptr_t IV = reinterpret_cast<uintptr_t>(V.getOpaqueValue());
return unsigned(IV) ^ unsigned(IV >> 9);
}
static bool isEqual(const Ty &LHS, const Ty &RHS) { return LHS == RHS; }
};
// Teach SmallPtrSet that PointerIntPair is "basically a pointer".
template <typename PointerTy, unsigned IntBits, typename IntType,
typename PtrTraits>
struct PointerLikeTypeTraits<
PointerIntPair<PointerTy, IntBits, IntType, PtrTraits>> {
static inline void *
getAsVoidPointer(const PointerIntPair<PointerTy, IntBits, IntType> &P) {
return P.getOpaqueValue();
}
static inline PointerIntPair<PointerTy, IntBits, IntType>
getFromVoidPointer(void *P) {
return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
}
static inline PointerIntPair<PointerTy, IntBits, IntType>
getFromVoidPointer(const void *P) {
return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
}
static constexpr int NumLowBitsAvailable =
PtrTraits::NumLowBitsAvailable - IntBits;
};
// Allow structured bindings on PointerIntPair.
template <std::size_t I, typename PointerTy, unsigned IntBits, typename IntType,
typename PtrTraits, typename Info>
decltype(auto)
get(const PointerIntPair<PointerTy, IntBits, IntType, PtrTraits, Info> &Pair) {
static_assert(I < 2);
if constexpr (I == 0)
return Pair.getPointer();
else
return Pair.getInt();
}
} // end namespace llvm
namespace std {
template <typename PointerTy, unsigned IntBits, typename IntType,
typename PtrTraits, typename Info>
struct tuple_size<
llvm::PointerIntPair<PointerTy, IntBits, IntType, PtrTraits, Info>>
: std::integral_constant<std::size_t, 2> {};
template <std::size_t I, typename PointerTy, unsigned IntBits, typename IntType,
typename PtrTraits, typename Info>
struct tuple_element<
I, llvm::PointerIntPair<PointerTy, IntBits, IntType, PtrTraits, Info>>
: std::conditional<I == 0, PointerTy, IntType> {};
} // namespace std
#endif // LLVM_ADT_POINTERINTPAIR_H
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