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QuFY
2025-09-20 17:13:38 +08:00
parent 7787b3ee30
commit 28ff2b0264
5251 changed files with 345029 additions and 285168 deletions
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Pods/abseil/absl/container/internal/raw_hash_set.h generated
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@@ -80,7 +80,7 @@
// slot_type slots[capacity];
// };
//
// The length of this array is computed by `AllocSize()` below.
// The length of this array is computed by `RawHashSetLayout::alloc_size` below.
//
// Control bytes (`ctrl_t`) are bytes (collected into groups of a
// platform-specific size) that define the state of the corresponding slot in
@@ -100,6 +100,13 @@
// Storing control bytes in a separate array also has beneficial cache effects,
// since more logical slots will fit into a cache line.
//
// # Small Object Optimization (SOO)
//
// When the size/alignment of the value_type and the capacity of the table are
// small, we enable small object optimization and store the values inline in
// the raw_hash_set object. This optimization allows us to avoid
// allocation/deallocation as well as cache/dTLB misses.
//
// # Hashing
//
// We compute two separate hashes, `H1` and `H2`, from the hash of an object.
@@ -233,9 +240,10 @@ namespace container_internal {
#ifdef ABSL_SWISSTABLE_ENABLE_GENERATIONS
#error ABSL_SWISSTABLE_ENABLE_GENERATIONS cannot be directly set
#elif defined(ABSL_HAVE_ADDRESS_SANITIZER) || \
defined(ABSL_HAVE_HWADDRESS_SANITIZER) || \
defined(ABSL_HAVE_MEMORY_SANITIZER)
#elif (defined(ABSL_HAVE_ADDRESS_SANITIZER) || \
defined(ABSL_HAVE_HWADDRESS_SANITIZER) || \
defined(ABSL_HAVE_MEMORY_SANITIZER)) && \
!defined(NDEBUG_SANITIZER) // If defined, performance is important.
// When compiled in sanitizer mode, we add generation integers to the backing
// array and iterators. In the backing array, we store the generation between
// the control bytes and the slots. When iterators are dereferenced, we assert
@@ -374,6 +382,9 @@ uint32_t TrailingZeros(T x) {
return static_cast<uint32_t>(countr_zero(x));
}
// 8 bytes bitmask with most significant bit set for every byte.
constexpr uint64_t kMsbs8Bytes = 0x8080808080808080ULL;
// An abstract bitmask, such as that emitted by a SIMD instruction.
//
// Specifically, this type implements a simple bitset whose representation is
@@ -423,27 +434,35 @@ class NonIterableBitMask {
// an ordinary 16-bit bitset occupying the low 16 bits of `mask`. When
// `SignificantBits` is 8 and `Shift` is 3, abstract bits are represented as
// the bytes `0x00` and `0x80`, and it occupies all 64 bits of the bitmask.
// If NullifyBitsOnIteration is true (only allowed for Shift == 3),
// non zero abstract bit is allowed to have additional bits
// (e.g., `0xff`, `0x83` and `0x9c` are ok, but `0x6f` is not).
//
// For example:
// for (int i : BitMask<uint32_t, 16>(0b101)) -> yields 0, 2
// for (int i : BitMask<uint64_t, 8, 3>(0x0000000080800000)) -> yields 2, 3
template <class T, int SignificantBits, int Shift = 0>
template <class T, int SignificantBits, int Shift = 0,
bool NullifyBitsOnIteration = false>
class BitMask : public NonIterableBitMask<T, SignificantBits, Shift> {
using Base = NonIterableBitMask<T, SignificantBits, Shift>;
static_assert(std::is_unsigned<T>::value, "");
static_assert(Shift == 0 || Shift == 3, "");
static_assert(!NullifyBitsOnIteration || Shift == 3, "");
public:
explicit BitMask(T mask) : Base(mask) {}
explicit BitMask(T mask) : Base(mask) {
if (Shift == 3 && !NullifyBitsOnIteration) {
assert(this->mask_ == (this->mask_ & kMsbs8Bytes));
}
}
// BitMask is an iterator over the indices of its abstract bits.
using value_type = int;
using iterator = BitMask;
using const_iterator = BitMask;
BitMask& operator++() {
if (Shift == 3) {
constexpr uint64_t msbs = 0x8080808080808080ULL;
this->mask_ &= msbs;
if (Shift == 3 && NullifyBitsOnIteration) {
this->mask_ &= kMsbs8Bytes;
}
this->mask_ &= (this->mask_ - 1);
return *this;
@@ -520,10 +539,24 @@ ABSL_DLL extern const ctrl_t kEmptyGroup[32];
// Returns a pointer to a control byte group that can be used by empty tables.
inline ctrl_t* EmptyGroup() {
// Const must be cast away here; no uses of this function will actually write
// to it, because it is only used for empty tables.
// to it because it is only used for empty tables.
return const_cast<ctrl_t*>(kEmptyGroup + 16);
}
// For use in SOO iterators.
// TODO(b/289225379): we could potentially get rid of this by adding an is_soo
// bit in iterators. This would add branches but reduce cache misses.
ABSL_DLL extern const ctrl_t kSooControl[17];
// Returns a pointer to a full byte followed by a sentinel byte.
inline ctrl_t* SooControl() {
// Const must be cast away here; no uses of this function will actually write
// to it because it is only used for SOO iterators.
return const_cast<ctrl_t*>(kSooControl);
}
// Whether ctrl is from the SooControl array.
inline bool IsSooControl(const ctrl_t* ctrl) { return ctrl == SooControl(); }
// Returns a pointer to a generation to use for an empty hashtable.
GenerationType* EmptyGeneration();
@@ -535,7 +568,37 @@ inline bool IsEmptyGeneration(const GenerationType* generation) {
// Mixes a randomly generated per-process seed with `hash` and `ctrl` to
// randomize insertion order within groups.
bool ShouldInsertBackwards(size_t hash, const ctrl_t* ctrl);
bool ShouldInsertBackwardsForDebug(size_t capacity, size_t hash,
const ctrl_t* ctrl);
ABSL_ATTRIBUTE_ALWAYS_INLINE inline bool ShouldInsertBackwards(
ABSL_ATTRIBUTE_UNUSED size_t capacity, ABSL_ATTRIBUTE_UNUSED size_t hash,
ABSL_ATTRIBUTE_UNUSED const ctrl_t* ctrl) {
#if defined(NDEBUG)
return false;
#else
return ShouldInsertBackwardsForDebug(capacity, hash, ctrl);
#endif
}
// Returns insert position for the given mask.
// We want to add entropy even when ASLR is not enabled.
// In debug build we will randomly insert in either the front or back of
// the group.
// TODO(kfm,sbenza): revisit after we do unconditional mixing
template <class Mask>
ABSL_ATTRIBUTE_ALWAYS_INLINE inline auto GetInsertionOffset(
Mask mask, ABSL_ATTRIBUTE_UNUSED size_t capacity,
ABSL_ATTRIBUTE_UNUSED size_t hash,
ABSL_ATTRIBUTE_UNUSED const ctrl_t* ctrl) {
#if defined(NDEBUG)
return mask.LowestBitSet();
#else
return ShouldInsertBackwardsForDebug(capacity, hash, ctrl)
? mask.HighestBitSet()
: mask.LowestBitSet();
#endif
}
// Returns a per-table, hash salt, which changes on resize. This gets mixed into
// H1 to randomize iteration order per-table.
@@ -560,7 +623,12 @@ inline h2_t H2(size_t hash) { return hash & 0x7F; }
// Helpers for checking the state of a control byte.
inline bool IsEmpty(ctrl_t c) { return c == ctrl_t::kEmpty; }
inline bool IsFull(ctrl_t c) { return c >= static_cast<ctrl_t>(0); }
inline bool IsFull(ctrl_t c) {
// Cast `c` to the underlying type instead of casting `0` to `ctrl_t` as `0`
// is not a value in the enum. Both ways are equivalent, but this way makes
// linters happier.
return static_cast<std::underlying_type_t<ctrl_t>>(c) >= 0;
}
inline bool IsDeleted(ctrl_t c) { return c == ctrl_t::kDeleted; }
inline bool IsEmptyOrDeleted(ctrl_t c) { return c < ctrl_t::kSentinel; }
@@ -646,6 +714,14 @@ struct GroupSse2Impl {
static_cast<uint16_t>(_mm_movemask_epi8(ctrl) ^ 0xffff));
}
// Returns a bitmask representing the positions of non full slots.
// Note: this includes: kEmpty, kDeleted, kSentinel.
// It is useful in contexts when kSentinel is not present.
auto MaskNonFull() const {
return BitMask<uint16_t, kWidth>(
static_cast<uint16_t>(_mm_movemask_epi8(ctrl)));
}
// Returns a bitmask representing the positions of empty or deleted slots.
NonIterableBitMask<uint16_t, kWidth> MaskEmptyOrDeleted() const {
auto special = _mm_set1_epi8(static_cast<char>(ctrl_t::kSentinel));
@@ -685,10 +761,11 @@ struct GroupAArch64Impl {
ctrl = vld1_u8(reinterpret_cast<const uint8_t*>(pos));
}
BitMask<uint64_t, kWidth, 3> Match(h2_t hash) const {
auto Match(h2_t hash) const {
uint8x8_t dup = vdup_n_u8(hash);
auto mask = vceq_u8(ctrl, dup);
return BitMask<uint64_t, kWidth, 3>(
return BitMask<uint64_t, kWidth, /*Shift=*/3,
/*NullifyBitsOnIteration=*/true>(
vget_lane_u64(vreinterpret_u64_u8(mask), 0));
}
@@ -704,12 +781,25 @@ struct GroupAArch64Impl {
// Returns a bitmask representing the positions of full slots.
// Note: for `is_small()` tables group may contain the "same" slot twice:
// original and mirrored.
BitMask<uint64_t, kWidth, 3> MaskFull() const {
auto MaskFull() const {
uint64_t mask = vget_lane_u64(
vreinterpret_u64_u8(vcge_s8(vreinterpret_s8_u8(ctrl),
vdup_n_s8(static_cast<int8_t>(0)))),
0);
return BitMask<uint64_t, kWidth, 3>(mask);
return BitMask<uint64_t, kWidth, /*Shift=*/3,
/*NullifyBitsOnIteration=*/true>(mask);
}
// Returns a bitmask representing the positions of non full slots.
// Note: this includes: kEmpty, kDeleted, kSentinel.
// It is useful in contexts when kSentinel is not present.
auto MaskNonFull() const {
uint64_t mask = vget_lane_u64(
vreinterpret_u64_u8(vclt_s8(vreinterpret_s8_u8(ctrl),
vdup_n_s8(static_cast<int8_t>(0)))),
0);
return BitMask<uint64_t, kWidth, /*Shift=*/3,
/*NullifyBitsOnIteration=*/true>(mask);
}
NonIterableBitMask<uint64_t, kWidth, 3> MaskEmptyOrDeleted() const {
@@ -736,11 +826,10 @@ struct GroupAArch64Impl {
void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
uint64_t mask = vget_lane_u64(vreinterpret_u64_u8(ctrl), 0);
constexpr uint64_t msbs = 0x8080808080808080ULL;
constexpr uint64_t slsbs = 0x0202020202020202ULL;
constexpr uint64_t midbs = 0x7e7e7e7e7e7e7e7eULL;
auto x = slsbs & (mask >> 6);
auto res = (x + midbs) | msbs;
auto res = (x + midbs) | kMsbs8Bytes;
little_endian::Store64(dst, res);
}
@@ -768,30 +857,33 @@ struct GroupPortableImpl {
// v = 0x1716151413121110
// hash = 0x12
// retval = (v - lsbs) & ~v & msbs = 0x0000000080800000
constexpr uint64_t msbs = 0x8080808080808080ULL;
constexpr uint64_t lsbs = 0x0101010101010101ULL;
auto x = ctrl ^ (lsbs * hash);
return BitMask<uint64_t, kWidth, 3>((x - lsbs) & ~x & msbs);
return BitMask<uint64_t, kWidth, 3>((x - lsbs) & ~x & kMsbs8Bytes);
}
NonIterableBitMask<uint64_t, kWidth, 3> MaskEmpty() const {
constexpr uint64_t msbs = 0x8080808080808080ULL;
return NonIterableBitMask<uint64_t, kWidth, 3>((ctrl & ~(ctrl << 6)) &
msbs);
kMsbs8Bytes);
}
// Returns a bitmask representing the positions of full slots.
// Note: for `is_small()` tables group may contain the "same" slot twice:
// original and mirrored.
BitMask<uint64_t, kWidth, 3> MaskFull() const {
constexpr uint64_t msbs = 0x8080808080808080ULL;
return BitMask<uint64_t, kWidth, 3>((ctrl ^ msbs) & msbs);
return BitMask<uint64_t, kWidth, 3>((ctrl ^ kMsbs8Bytes) & kMsbs8Bytes);
}
// Returns a bitmask representing the positions of non full slots.
// Note: this includes: kEmpty, kDeleted, kSentinel.
// It is useful in contexts when kSentinel is not present.
auto MaskNonFull() const {
return BitMask<uint64_t, kWidth, 3>(ctrl & kMsbs8Bytes);
}
NonIterableBitMask<uint64_t, kWidth, 3> MaskEmptyOrDeleted() const {
constexpr uint64_t msbs = 0x8080808080808080ULL;
return NonIterableBitMask<uint64_t, kWidth, 3>((ctrl & ~(ctrl << 7)) &
msbs);
kMsbs8Bytes);
}
uint32_t CountLeadingEmptyOrDeleted() const {
@@ -803,9 +895,8 @@ struct GroupPortableImpl {
}
void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
constexpr uint64_t msbs = 0x8080808080808080ULL;
constexpr uint64_t lsbs = 0x0101010101010101ULL;
auto x = ctrl & msbs;
auto x = ctrl & kMsbs8Bytes;
auto res = (~x + (x >> 7)) & ~lsbs;
little_endian::Store64(dst, res);
}
@@ -815,21 +906,21 @@ struct GroupPortableImpl {
#ifdef ABSL_INTERNAL_HAVE_SSE2
using Group = GroupSse2Impl;
using GroupEmptyOrDeleted = GroupSse2Impl;
using GroupFullEmptyOrDeleted = GroupSse2Impl;
#elif defined(ABSL_INTERNAL_HAVE_ARM_NEON) && defined(ABSL_IS_LITTLE_ENDIAN)
using Group = GroupAArch64Impl;
// For Aarch64, we use the portable implementation for counting and masking
// empty or deleted group elements. This is to avoid the latency of moving
// full, empty or deleted group elements. This is to avoid the latency of moving
// between data GPRs and Neon registers when it does not provide a benefit.
// Using Neon is profitable when we call Match(), but is not when we don't,
// which is the case when we do *EmptyOrDeleted operations. It is difficult to
// make a similar approach beneficial on other architectures such as x86 since
// they have much lower GPR <-> vector register transfer latency and 16-wide
// Groups.
using GroupEmptyOrDeleted = GroupPortableImpl;
// which is the case when we do *EmptyOrDeleted and MaskFull operations.
// It is difficult to make a similar approach beneficial on other architectures
// such as x86 since they have much lower GPR <-> vector register transfer
// latency and 16-wide Groups.
using GroupFullEmptyOrDeleted = GroupPortableImpl;
#else
using Group = GroupPortableImpl;
using GroupEmptyOrDeleted = GroupPortableImpl;
using GroupFullEmptyOrDeleted = GroupPortableImpl;
#endif
// When there is an insertion with no reserved growth, we rehash with
@@ -978,17 +1069,96 @@ using CommonFieldsGenerationInfo = CommonFieldsGenerationInfoDisabled;
using HashSetIteratorGenerationInfo = HashSetIteratorGenerationInfoDisabled;
#endif
// Stored the information regarding number of slots we can still fill
// without needing to rehash.
//
// We want to ensure sufficient number of empty slots in the table in order
// to keep probe sequences relatively short. Empty slot in the probe group
// is required to stop probing.
//
// Tombstones (kDeleted slots) are not included in the growth capacity,
// because we'd like to rehash when the table is filled with tombstones and/or
// full slots.
//
// GrowthInfo also stores a bit that encodes whether table may have any
// deleted slots.
// Most of the tables (>95%) have no deleted slots, so some functions can
// be more efficient with this information.
//
// Callers can also force a rehash via the standard `rehash(0)`,
// which will recompute this value as a side-effect.
//
// See also `CapacityToGrowth()`.
class GrowthInfo {
public:
// Leaves data member uninitialized.
GrowthInfo() = default;
// Initializes the GrowthInfo assuming we can grow `growth_left` elements
// and there are no kDeleted slots in the table.
void InitGrowthLeftNoDeleted(size_t growth_left) {
growth_left_info_ = growth_left;
}
// Overwrites single full slot with an empty slot.
void OverwriteFullAsEmpty() { ++growth_left_info_; }
// Overwrites single empty slot with a full slot.
void OverwriteEmptyAsFull() {
assert(GetGrowthLeft() > 0);
--growth_left_info_;
}
// Overwrites several empty slots with full slots.
void OverwriteManyEmptyAsFull(size_t cnt) {
assert(GetGrowthLeft() >= cnt);
growth_left_info_ -= cnt;
}
// Overwrites specified control element with full slot.
void OverwriteControlAsFull(ctrl_t ctrl) {
assert(GetGrowthLeft() >= static_cast<size_t>(IsEmpty(ctrl)));
growth_left_info_ -= static_cast<size_t>(IsEmpty(ctrl));
}
// Overwrites single full slot with a deleted slot.
void OverwriteFullAsDeleted() { growth_left_info_ |= kDeletedBit; }
// Returns true if table satisfies two properties:
// 1. Guaranteed to have no kDeleted slots.
// 2. There is a place for at least one element to grow.
bool HasNoDeletedAndGrowthLeft() const {
return static_cast<std::make_signed_t<size_t>>(growth_left_info_) > 0;
}
// Returns true if the table satisfies two properties:
// 1. Guaranteed to have no kDeleted slots.
// 2. There is no growth left.
bool HasNoGrowthLeftAndNoDeleted() const { return growth_left_info_ == 0; }
// Returns true if table guaranteed to have no k
bool HasNoDeleted() const {
return static_cast<std::make_signed_t<size_t>>(growth_left_info_) >= 0;
}
// Returns the number of elements left to grow.
size_t GetGrowthLeft() const { return growth_left_info_ & kGrowthLeftMask; }
private:
static constexpr size_t kGrowthLeftMask = ((~size_t{}) >> 1);
static constexpr size_t kDeletedBit = ~kGrowthLeftMask;
// Topmost bit signal whenever there are deleted slots.
size_t growth_left_info_;
};
static_assert(sizeof(GrowthInfo) == sizeof(size_t), "");
static_assert(alignof(GrowthInfo) == alignof(size_t), "");
// Returns whether `n` is a valid capacity (i.e., number of slots).
//
// A valid capacity is a non-zero integer `2^m - 1`.
inline bool IsValidCapacity(size_t n) { return ((n + 1) & n) == 0 && n > 0; }
// Computes the offset from the start of the backing allocation of control.
// infoz and growth_left are stored at the beginning of the backing array.
inline size_t ControlOffset(bool has_infoz) {
return (has_infoz ? sizeof(HashtablezInfoHandle) : 0) + sizeof(size_t);
}
// Returns the number of "cloned control bytes".
//
// This is the number of control bytes that are present both at the beginning
@@ -996,36 +1166,157 @@ inline size_t ControlOffset(bool has_infoz) {
// `Group::kWidth`-width probe window starting from any control byte.
constexpr size_t NumClonedBytes() { return Group::kWidth - 1; }
// Given the capacity of a table, computes the offset (from the start of the
// backing allocation) of the generation counter (if it exists).
inline size_t GenerationOffset(size_t capacity, bool has_infoz) {
assert(IsValidCapacity(capacity));
const size_t num_control_bytes = capacity + 1 + NumClonedBytes();
return ControlOffset(has_infoz) + num_control_bytes;
// Returns the number of control bytes including cloned.
constexpr size_t NumControlBytes(size_t capacity) {
return capacity + 1 + NumClonedBytes();
}
// Given the capacity of a table, computes the offset (from the start of the
// backing allocation) at which the slots begin.
inline size_t SlotOffset(size_t capacity, size_t slot_align, bool has_infoz) {
assert(IsValidCapacity(capacity));
return (GenerationOffset(capacity, has_infoz) + NumGenerationBytes() +
slot_align - 1) &
(~slot_align + 1);
// Computes the offset from the start of the backing allocation of control.
// infoz and growth_info are stored at the beginning of the backing array.
inline static size_t ControlOffset(bool has_infoz) {
return (has_infoz ? sizeof(HashtablezInfoHandle) : 0) + sizeof(GrowthInfo);
}
// Given the capacity of a table, computes the total size of the backing
// array.
inline size_t AllocSize(size_t capacity, size_t slot_size, size_t slot_align,
bool has_infoz) {
return SlotOffset(capacity, slot_align, has_infoz) + capacity * slot_size;
}
// Helper class for computing offsets and allocation size of hash set fields.
class RawHashSetLayout {
public:
explicit RawHashSetLayout(size_t capacity, size_t slot_align, bool has_infoz)
: capacity_(capacity),
control_offset_(ControlOffset(has_infoz)),
generation_offset_(control_offset_ + NumControlBytes(capacity)),
slot_offset_(
(generation_offset_ + NumGenerationBytes() + slot_align - 1) &
(~slot_align + 1)) {
assert(IsValidCapacity(capacity));
}
// Returns the capacity of a table.
size_t capacity() const { return capacity_; }
// Returns precomputed offset from the start of the backing allocation of
// control.
size_t control_offset() const { return control_offset_; }
// Given the capacity of a table, computes the offset (from the start of the
// backing allocation) of the generation counter (if it exists).
size_t generation_offset() const { return generation_offset_; }
// Given the capacity of a table, computes the offset (from the start of the
// backing allocation) at which the slots begin.
size_t slot_offset() const { return slot_offset_; }
// Given the capacity of a table, computes the total size of the backing
// array.
size_t alloc_size(size_t slot_size) const {
return slot_offset_ + capacity_ * slot_size;
}
private:
size_t capacity_;
size_t control_offset_;
size_t generation_offset_;
size_t slot_offset_;
};
struct HashtableFreeFunctionsAccess;
// We only allow a maximum of 1 SOO element, which makes the implementation
// much simpler. Complications with multiple SOO elements include:
// - Satisfying the guarantee that erasing one element doesn't invalidate
// iterators to other elements means we would probably need actual SOO
// control bytes.
// - In order to prevent user code from depending on iteration order for small
// tables, we would need to randomize the iteration order somehow.
constexpr size_t SooCapacity() { return 1; }
// Sentinel type to indicate SOO CommonFields construction.
struct soo_tag_t {};
// Sentinel type to indicate SOO CommonFields construction with full size.
struct full_soo_tag_t {};
// Suppress erroneous uninitialized memory errors on GCC. For example, GCC
// thinks that the call to slot_array() in find_or_prepare_insert() is reading
// uninitialized memory, but slot_array is only called there when the table is
// non-empty and this memory is initialized when the table is non-empty.
#if !defined(__clang__) && defined(__GNUC__)
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED(x) \
_Pragma("GCC diagnostic push") \
_Pragma("GCC diagnostic ignored \"-Wmaybe-uninitialized\"") \
_Pragma("GCC diagnostic ignored \"-Wuninitialized\"") x; \
_Pragma("GCC diagnostic pop")
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(x) \
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED(return x)
#else
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED(x) x
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(x) return x
#endif
// This allows us to work around an uninitialized memory warning when
// constructing begin() iterators in empty hashtables.
union MaybeInitializedPtr {
void* get() const { ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(p); }
void set(void* ptr) { p = ptr; }
void* p;
};
struct HeapPtrs {
HeapPtrs() = default;
explicit HeapPtrs(ctrl_t* c) : control(c) {}
// The control bytes (and, also, a pointer near to the base of the backing
// array).
//
// This contains `capacity + 1 + NumClonedBytes()` entries, even
// when the table is empty (hence EmptyGroup).
//
// Note that growth_info is stored immediately before this pointer.
// May be uninitialized for SOO tables.
ctrl_t* control;
// The beginning of the slots, located at `SlotOffset()` bytes after
// `control`. May be uninitialized for empty tables.
// Note: we can't use `slots` because Qt defines "slots" as a macro.
MaybeInitializedPtr slot_array;
};
// Manages the backing array pointers or the SOO slot. When raw_hash_set::is_soo
// is true, the SOO slot is stored in `soo_data`. Otherwise, we use `heap`.
union HeapOrSoo {
HeapOrSoo() = default;
explicit HeapOrSoo(ctrl_t* c) : heap(c) {}
ctrl_t*& control() {
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(heap.control);
}
ctrl_t* control() const {
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(heap.control);
}
MaybeInitializedPtr& slot_array() {
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(heap.slot_array);
}
MaybeInitializedPtr slot_array() const {
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(heap.slot_array);
}
void* get_soo_data() {
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(soo_data);
}
const void* get_soo_data() const {
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(soo_data);
}
HeapPtrs heap;
unsigned char soo_data[sizeof(HeapPtrs)];
};
// CommonFields hold the fields in raw_hash_set that do not depend
// on template parameters. This allows us to conveniently pass all
// of this state to helper functions as a single argument.
class CommonFields : public CommonFieldsGenerationInfo {
public:
CommonFields() = default;
CommonFields() : capacity_(0), size_(0), heap_or_soo_(EmptyGroup()) {}
explicit CommonFields(soo_tag_t) : capacity_(SooCapacity()), size_(0) {}
explicit CommonFields(full_soo_tag_t)
: capacity_(SooCapacity()), size_(size_t{1} << HasInfozShift()) {}
// Not copyable
CommonFields(const CommonFields&) = delete;
@@ -1035,23 +1326,44 @@ class CommonFields : public CommonFieldsGenerationInfo {
CommonFields(CommonFields&& that) = default;
CommonFields& operator=(CommonFields&&) = default;
ctrl_t* control() const { return control_; }
void set_control(ctrl_t* c) { control_ = c; }
template <bool kSooEnabled>
static CommonFields CreateDefault() {
return kSooEnabled ? CommonFields{soo_tag_t{}} : CommonFields{};
}
// The inline data for SOO is written on top of control_/slots_.
const void* soo_data() const { return heap_or_soo_.get_soo_data(); }
void* soo_data() { return heap_or_soo_.get_soo_data(); }
HeapOrSoo heap_or_soo() const { return heap_or_soo_; }
const HeapOrSoo& heap_or_soo_ref() const { return heap_or_soo_; }
ctrl_t* control() const { return heap_or_soo_.control(); }
void set_control(ctrl_t* c) { heap_or_soo_.control() = c; }
void* backing_array_start() const {
// growth_left (and maybe infoz) is stored before control bytes.
// growth_info (and maybe infoz) is stored before control bytes.
assert(reinterpret_cast<uintptr_t>(control()) % alignof(size_t) == 0);
return control() - ControlOffset(has_infoz());
}
// Note: we can't use slots() because Qt defines "slots" as a macro.
void* slot_array() const { return slots_; }
void set_slots(void* s) { slots_ = s; }
void* slot_array() const { return heap_or_soo_.slot_array().get(); }
MaybeInitializedPtr slots_union() const { return heap_or_soo_.slot_array(); }
void set_slots(void* s) { heap_or_soo_.slot_array().set(s); }
// The number of filled slots.
size_t size() const { return size_ >> HasInfozShift(); }
void set_size(size_t s) {
size_ = (s << HasInfozShift()) | (size_ & HasInfozMask());
}
void set_empty_soo() {
AssertInSooMode();
size_ = 0;
}
void set_full_soo() {
AssertInSooMode();
size_ = size_t{1} << HasInfozShift();
}
void increment_size() {
assert(size() < capacity());
size_ += size_t{1} << HasInfozShift();
@@ -1070,15 +1382,17 @@ class CommonFields : public CommonFieldsGenerationInfo {
// The number of slots we can still fill without needing to rehash.
// This is stored in the heap allocation before the control bytes.
size_t growth_left() const {
const size_t* gl_ptr = reinterpret_cast<size_t*>(control()) - 1;
assert(reinterpret_cast<uintptr_t>(gl_ptr) % alignof(size_t) == 0);
// TODO(b/289225379): experiment with moving growth_info back inline to
// increase room for SOO.
size_t growth_left() const { return growth_info().GetGrowthLeft(); }
GrowthInfo& growth_info() {
auto* gl_ptr = reinterpret_cast<GrowthInfo*>(control()) - 1;
assert(reinterpret_cast<uintptr_t>(gl_ptr) % alignof(GrowthInfo) == 0);
return *gl_ptr;
}
void set_growth_left(size_t gl) {
size_t* gl_ptr = reinterpret_cast<size_t*>(control()) - 1;
assert(reinterpret_cast<uintptr_t>(gl_ptr) % alignof(size_t) == 0);
*gl_ptr = gl;
GrowthInfo growth_info() const {
return const_cast<CommonFields*>(this)->growth_info();
}
bool has_infoz() const {
@@ -1103,12 +1417,8 @@ class CommonFields : public CommonFieldsGenerationInfo {
should_rehash_for_bug_detection_on_insert(control(), capacity());
}
bool should_rehash_for_bug_detection_on_move() const {
return CommonFieldsGenerationInfo::
should_rehash_for_bug_detection_on_move(control(), capacity());
}
void maybe_increment_generation_on_move() {
if (capacity() == 0) return;
increment_generation();
return CommonFieldsGenerationInfo::should_rehash_for_bug_detection_on_move(
control(), capacity());
}
void reset_reserved_growth(size_t reservation) {
CommonFieldsGenerationInfo::reset_reserved_growth(reservation, size());
@@ -1116,7 +1426,16 @@ class CommonFields : public CommonFieldsGenerationInfo {
// The size of the backing array allocation.
size_t alloc_size(size_t slot_size, size_t slot_align) const {
return AllocSize(capacity(), slot_size, slot_align, has_infoz());
return RawHashSetLayout(capacity(), slot_align, has_infoz())
.alloc_size(slot_size);
}
// Move fields other than heap_or_soo_.
void move_non_heap_or_soo_fields(CommonFields& that) {
static_cast<CommonFieldsGenerationInfo&>(*this) =
std::move(static_cast<CommonFieldsGenerationInfo&>(that));
capacity_ = that.capacity_;
size_ = that.size_;
}
// Returns the number of control bytes set to kDeleted. For testing only.
@@ -1132,21 +1451,12 @@ class CommonFields : public CommonFieldsGenerationInfo {
return (size_t{1} << HasInfozShift()) - 1;
}
// TODO(b/182800944): Investigate removing some of these fields:
// - control/slots can be derived from each other
// The control bytes (and, also, a pointer near to the base of the backing
// array).
//
// This contains `capacity + 1 + NumClonedBytes()` entries, even
// when the table is empty (hence EmptyGroup).
//
// Note that growth_left is stored immediately before this pointer.
ctrl_t* control_ = EmptyGroup();
// The beginning of the slots, located at `SlotOffset()` bytes after
// `control`. May be null for empty tables.
void* slots_ = nullptr;
// We can't assert that SOO is enabled because we don't have SooEnabled(), but
// we assert what we can.
void AssertInSooMode() const {
assert(capacity() == SooCapacity());
assert(!has_infoz());
}
// The number of slots in the backing array. This is always 2^N-1 for an
// integer N. NOTE: we tried experimenting with compressing the capacity and
@@ -1154,10 +1464,16 @@ class CommonFields : public CommonFieldsGenerationInfo {
// power (N in 2^N-1), and (b) storing 2^N as the most significant bit of
// size_ and storing size in the low bits. Both of these experiments were
// regressions, presumably because we need capacity to do find operations.
size_t capacity_ = 0;
size_t capacity_;
// The size and also has one bit that stores whether we have infoz.
size_t size_ = 0;
// TODO(b/289225379): we could put size_ into HeapOrSoo and make capacity_
// encode the size in SOO case. We would be making size()/capacity() more
// expensive in order to have more SOO space.
size_t size_;
// Either the control/slots pointers or the SOO slot.
HeapOrSoo heap_or_soo_;
};
template <class Policy, class Hash, class Eq, class Alloc>
@@ -1320,6 +1636,10 @@ inline bool AreItersFromSameContainer(const ctrl_t* ctrl_a,
const void* const& slot_b) {
// If either control byte is null, then we can't tell.
if (ctrl_a == nullptr || ctrl_b == nullptr) return true;
const bool a_is_soo = IsSooControl(ctrl_a);
if (a_is_soo != IsSooControl(ctrl_b)) return false;
if (a_is_soo) return slot_a == slot_b;
const void* low_slot = slot_a;
const void* hi_slot = slot_b;
if (ctrl_a > ctrl_b) {
@@ -1343,41 +1663,45 @@ inline void AssertSameContainer(const ctrl_t* ctrl_a, const ctrl_t* ctrl_b,
// - use `ABSL_PREDICT_FALSE()` to provide a compiler hint for code layout
// - use `ABSL_RAW_LOG()` with a format string to reduce code size and improve
// the chances that the hot paths will be inlined.
// fail_if(is_invalid, message) crashes when is_invalid is true and provides
// an error message based on `message`.
const auto fail_if = [](bool is_invalid, const char* message) {
if (ABSL_PREDICT_FALSE(is_invalid)) {
ABSL_RAW_LOG(FATAL, "Invalid iterator comparison. %s", message);
}
};
const bool a_is_default = ctrl_a == EmptyGroup();
const bool b_is_default = ctrl_b == EmptyGroup();
if (ABSL_PREDICT_FALSE(a_is_default != b_is_default)) {
ABSL_RAW_LOG(
FATAL,
"Invalid iterator comparison. Comparing default-constructed iterator "
"with non-default-constructed iterator.");
}
if (a_is_default && b_is_default) return;
fail_if(a_is_default != b_is_default,
"Comparing default-constructed hashtable iterator with a "
"non-default-constructed hashtable iterator.");
if (SwisstableGenerationsEnabled()) {
if (ABSL_PREDICT_TRUE(generation_ptr_a == generation_ptr_b)) return;
// Users don't need to know whether the tables are SOO so don't mention SOO
// in the debug message.
const bool a_is_soo = IsSooControl(ctrl_a);
const bool b_is_soo = IsSooControl(ctrl_b);
fail_if(a_is_soo != b_is_soo || (a_is_soo && b_is_soo),
"Comparing iterators from different hashtables.");
const bool a_is_empty = IsEmptyGeneration(generation_ptr_a);
const bool b_is_empty = IsEmptyGeneration(generation_ptr_b);
if (a_is_empty != b_is_empty) {
ABSL_RAW_LOG(FATAL,
"Invalid iterator comparison. Comparing iterator from a "
"non-empty hashtable with an iterator from an empty "
"hashtable.");
}
if (a_is_empty && b_is_empty) {
ABSL_RAW_LOG(FATAL,
"Invalid iterator comparison. Comparing iterators from "
"different empty hashtables.");
}
fail_if(a_is_empty != b_is_empty,
"Comparing an iterator from an empty hashtable with an iterator "
"from a non-empty hashtable.");
fail_if(a_is_empty && b_is_empty,
"Comparing iterators from different empty hashtables.");
const bool a_is_end = ctrl_a == nullptr;
const bool b_is_end = ctrl_b == nullptr;
if (a_is_end || b_is_end) {
ABSL_RAW_LOG(FATAL,
"Invalid iterator comparison. Comparing iterator with an "
"end() iterator from a different hashtable.");
}
ABSL_RAW_LOG(FATAL,
"Invalid iterator comparison. Comparing non-end() iterators "
"from different hashtables.");
fail_if(a_is_end || b_is_end,
"Comparing iterator with an end() iterator from a different "
"hashtable.");
fail_if(true, "Comparing non-end() iterators from different hashtables.");
} else {
ABSL_HARDENING_ASSERT(
AreItersFromSameContainer(ctrl_a, ctrl_b, slot_a, slot_b) &&
@@ -1432,20 +1756,17 @@ template <typename = void>
inline FindInfo find_first_non_full(const CommonFields& common, size_t hash) {
auto seq = probe(common, hash);
const ctrl_t* ctrl = common.control();
if (IsEmptyOrDeleted(ctrl[seq.offset()]) &&
!ShouldInsertBackwards(common.capacity(), hash, ctrl)) {
return {seq.offset(), /*probe_length=*/0};
}
while (true) {
GroupEmptyOrDeleted g{ctrl + seq.offset()};
GroupFullEmptyOrDeleted g{ctrl + seq.offset()};
auto mask = g.MaskEmptyOrDeleted();
if (mask) {
#if !defined(NDEBUG)
// We want to add entropy even when ASLR is not enabled.
// In debug build we will randomly insert in either the front or back of
// the group.
// TODO(kfm,sbenza): revisit after we do unconditional mixing
if (!is_small(common.capacity()) && ShouldInsertBackwards(hash, ctrl)) {
return {seq.offset(mask.HighestBitSet()), seq.index()};
}
#endif
return {seq.offset(mask.LowestBitSet()), seq.index()};
return {
seq.offset(GetInsertionOffset(mask, common.capacity(), hash, ctrl)),
seq.index()};
}
seq.next();
assert(seq.index() <= common.capacity() && "full table!");
@@ -1462,7 +1783,8 @@ extern template FindInfo find_first_non_full(const CommonFields&, size_t);
FindInfo find_first_non_full_outofline(const CommonFields&, size_t);
inline void ResetGrowthLeft(CommonFields& common) {
common.set_growth_left(CapacityToGrowth(common.capacity()) - common.size());
common.growth_info().InitGrowthLeftNoDeleted(
CapacityToGrowth(common.capacity()) - common.size());
}
// Sets `ctrl` to `{kEmpty, kSentinel, ..., kEmpty}`, marking the entire
@@ -1476,43 +1798,140 @@ inline void ResetCtrl(CommonFields& common, size_t slot_size) {
SanitizerPoisonMemoryRegion(common.slot_array(), slot_size * capacity);
}
// Sets `ctrl[i]` to `h`.
//
// Unlike setting it directly, this function will perform bounds checks and
// mirror the value to the cloned tail if necessary.
inline void SetCtrl(const CommonFields& common, size_t i, ctrl_t h,
size_t slot_size) {
const size_t capacity = common.capacity();
assert(i < capacity);
auto* slot_i = static_cast<const char*>(common.slot_array()) + i * slot_size;
// Sets sanitizer poisoning for slot corresponding to control byte being set.
inline void DoSanitizeOnSetCtrl(const CommonFields& c, size_t i, ctrl_t h,
size_t slot_size) {
assert(i < c.capacity());
auto* slot_i = static_cast<const char*>(c.slot_array()) + i * slot_size;
if (IsFull(h)) {
SanitizerUnpoisonMemoryRegion(slot_i, slot_size);
} else {
SanitizerPoisonMemoryRegion(slot_i, slot_size);
}
ctrl_t* ctrl = common.control();
ctrl[i] = h;
ctrl[((i - NumClonedBytes()) & capacity) + (NumClonedBytes() & capacity)] = h;
}
// Overload for setting to an occupied `h2_t` rather than a special `ctrl_t`.
inline void SetCtrl(const CommonFields& common, size_t i, h2_t h,
// Sets `ctrl[i]` to `h`.
//
// Unlike setting it directly, this function will perform bounds checks and
// mirror the value to the cloned tail if necessary.
inline void SetCtrl(const CommonFields& c, size_t i, ctrl_t h,
size_t slot_size) {
SetCtrl(common, i, static_cast<ctrl_t>(h), slot_size);
DoSanitizeOnSetCtrl(c, i, h, slot_size);
ctrl_t* ctrl = c.control();
ctrl[i] = h;
ctrl[((i - NumClonedBytes()) & c.capacity()) +
(NumClonedBytes() & c.capacity())] = h;
}
// Overload for setting to an occupied `h2_t` rather than a special `ctrl_t`.
inline void SetCtrl(const CommonFields& c, size_t i, h2_t h, size_t slot_size) {
SetCtrl(c, i, static_cast<ctrl_t>(h), slot_size);
}
// growth_left (which is a size_t) is stored with the backing array.
// Like SetCtrl, but in a single group table, we can save some operations when
// setting the cloned control byte.
inline void SetCtrlInSingleGroupTable(const CommonFields& c, size_t i, ctrl_t h,
size_t slot_size) {
assert(is_single_group(c.capacity()));
DoSanitizeOnSetCtrl(c, i, h, slot_size);
ctrl_t* ctrl = c.control();
ctrl[i] = h;
ctrl[i + c.capacity() + 1] = h;
}
// Overload for setting to an occupied `h2_t` rather than a special `ctrl_t`.
inline void SetCtrlInSingleGroupTable(const CommonFields& c, size_t i, h2_t h,
size_t slot_size) {
SetCtrlInSingleGroupTable(c, i, static_cast<ctrl_t>(h), slot_size);
}
// growth_info (which is a size_t) is stored with the backing array.
constexpr size_t BackingArrayAlignment(size_t align_of_slot) {
return (std::max)(align_of_slot, alignof(size_t));
return (std::max)(align_of_slot, alignof(GrowthInfo));
}
// Returns the address of the ith slot in slots where each slot occupies
// slot_size.
inline void* SlotAddress(void* slot_array, size_t slot, size_t slot_size) {
return reinterpret_cast<void*>(reinterpret_cast<char*>(slot_array) +
(slot * slot_size));
return static_cast<void*>(static_cast<char*>(slot_array) +
(slot * slot_size));
}
// Iterates over all full slots and calls `cb(const ctrl_t*, SlotType*)`.
// No insertion to the table allowed during Callback call.
// Erasure is allowed only for the element passed to the callback.
template <class SlotType, class Callback>
ABSL_ATTRIBUTE_ALWAYS_INLINE inline void IterateOverFullSlots(
const CommonFields& c, SlotType* slot, Callback cb) {
const size_t cap = c.capacity();
const ctrl_t* ctrl = c.control();
if (is_small(cap)) {
// Mirrored/cloned control bytes in small table are also located in the
// first group (starting from position 0). We are taking group from position
// `capacity` in order to avoid duplicates.
// Small tables capacity fits into portable group, where
// GroupPortableImpl::MaskFull is more efficient for the
// capacity <= GroupPortableImpl::kWidth.
assert(cap <= GroupPortableImpl::kWidth &&
"unexpectedly large small capacity");
static_assert(Group::kWidth >= GroupPortableImpl::kWidth,
"unexpected group width");
// Group starts from kSentinel slot, so indices in the mask will
// be increased by 1.
const auto mask = GroupPortableImpl(ctrl + cap).MaskFull();
--ctrl;
--slot;
for (uint32_t i : mask) {
cb(ctrl + i, slot + i);
}
return;
}
size_t remaining = c.size();
ABSL_ATTRIBUTE_UNUSED const size_t original_size_for_assert = remaining;
while (remaining != 0) {
for (uint32_t i : GroupFullEmptyOrDeleted(ctrl).MaskFull()) {
assert(IsFull(ctrl[i]) && "hash table was modified unexpectedly");
cb(ctrl + i, slot + i);
--remaining;
}
ctrl += Group::kWidth;
slot += Group::kWidth;
assert((remaining == 0 || *(ctrl - 1) != ctrl_t::kSentinel) &&
"hash table was modified unexpectedly");
}
// NOTE: erasure of the current element is allowed in callback for
// absl::erase_if specialization. So we use `>=`.
assert(original_size_for_assert >= c.size() &&
"hash table was modified unexpectedly");
}
template <typename CharAlloc>
constexpr bool ShouldSampleHashtablezInfo() {
// Folks with custom allocators often make unwarranted assumptions about the
// behavior of their classes vis-a-vis trivial destructability and what
// calls they will or won't make. Avoid sampling for people with custom
// allocators to get us out of this mess. This is not a hard guarantee but
// a workaround while we plan the exact guarantee we want to provide.
return std::is_same<CharAlloc, std::allocator<char>>::value;
}
template <bool kSooEnabled>
HashtablezInfoHandle SampleHashtablezInfo(size_t sizeof_slot, size_t sizeof_key,
size_t sizeof_value,
size_t old_capacity, bool was_soo,
HashtablezInfoHandle forced_infoz,
CommonFields& c) {
if (forced_infoz.IsSampled()) return forced_infoz;
// In SOO, we sample on the first insertion so if this is an empty SOO case
// (e.g. when reserve is called), then we still need to sample.
if (kSooEnabled && was_soo && c.size() == 0) {
return Sample(sizeof_slot, sizeof_key, sizeof_value, SooCapacity());
}
// For non-SOO cases, we sample whenever the capacity is increasing from zero
// to non-zero.
if (!kSooEnabled && old_capacity == 0) {
return Sample(sizeof_slot, sizeof_key, sizeof_value, 0);
}
return c.infoz();
}
// Helper class to perform resize of the hash set.
@@ -1521,17 +1940,21 @@ inline void* SlotAddress(void* slot_array, size_t slot, size_t slot_size) {
// See GrowIntoSingleGroupShuffleControlBytes for details.
class HashSetResizeHelper {
public:
explicit HashSetResizeHelper(CommonFields& c)
: old_ctrl_(c.control()),
old_capacity_(c.capacity()),
had_infoz_(c.has_infoz()) {}
explicit HashSetResizeHelper(CommonFields& c, bool was_soo, bool had_soo_slot,
HashtablezInfoHandle forced_infoz)
: old_capacity_(c.capacity()),
had_infoz_(c.has_infoz()),
was_soo_(was_soo),
had_soo_slot_(had_soo_slot),
forced_infoz_(forced_infoz) {}
// Optimized for small groups version of `find_first_non_full` applicable
// only right after calling `raw_hash_set::resize`.
// Optimized for small groups version of `find_first_non_full`.
// Beneficial only right after calling `raw_hash_set::resize`.
// It is safe to call in case capacity is big or was not changed, but there
// will be no performance benefit.
// It has implicit assumption that `resize` will call
// `GrowSizeIntoSingleGroup*` in case `IsGrowingIntoSingleGroupApplicable`.
// Falls back to `find_first_non_full` in case of big groups, so it is
// safe to use after `rehash_and_grow_if_necessary`.
// Falls back to `find_first_non_full` in case of big groups.
static FindInfo FindFirstNonFullAfterResize(const CommonFields& c,
size_t old_capacity,
size_t hash) {
@@ -1553,14 +1976,30 @@ class HashSetResizeHelper {
return FindInfo{offset, 0};
}
ctrl_t* old_ctrl() const { return old_ctrl_; }
HeapOrSoo& old_heap_or_soo() { return old_heap_or_soo_; }
void* old_soo_data() { return old_heap_or_soo_.get_soo_data(); }
ctrl_t* old_ctrl() const {
assert(!was_soo_);
return old_heap_or_soo_.control();
}
void* old_slots() const {
assert(!was_soo_);
return old_heap_or_soo_.slot_array().get();
}
size_t old_capacity() const { return old_capacity_; }
// Returns the index of the SOO slot when growing from SOO to non-SOO in a
// single group. See also InitControlBytesAfterSoo(). It's important to use
// index 1 so that when resizing from capacity 1 to 3, we can still have
// random iteration order between the first two inserted elements.
// I.e. it allows inserting the second element at either index 0 or 2.
static size_t SooSlotIndex() { return 1; }
// Allocates a backing array for the hashtable.
// Reads `capacity` and updates all other fields based on the result of
// the allocation.
//
// It also may do the folowing actions:
// It also may do the following actions:
// 1. initialize control bytes
// 2. initialize slots
// 3. deallocate old slots.
@@ -1590,45 +2029,45 @@ class HashSetResizeHelper {
//
// Returns IsGrowingIntoSingleGroupApplicable result to avoid recomputation.
template <typename Alloc, size_t SizeOfSlot, bool TransferUsesMemcpy,
size_t AlignOfSlot>
ABSL_ATTRIBUTE_NOINLINE bool InitializeSlots(CommonFields& c, void* old_slots,
Alloc alloc) {
bool SooEnabled, size_t AlignOfSlot>
ABSL_ATTRIBUTE_NOINLINE bool InitializeSlots(CommonFields& c, Alloc alloc,
ctrl_t soo_slot_h2,
size_t key_size,
size_t value_size) {
assert(c.capacity());
// Folks with custom allocators often make unwarranted assumptions about the
// behavior of their classes vis-a-vis trivial destructability and what
// calls they will or won't make. Avoid sampling for people with custom
// allocators to get us out of this mess. This is not a hard guarantee but
// a workaround while we plan the exact guarantee we want to provide.
const size_t sample_size =
(std::is_same<Alloc, std::allocator<char>>::value &&
c.slot_array() == nullptr)
? SizeOfSlot
: 0;
HashtablezInfoHandle infoz =
sample_size > 0 ? Sample(sample_size) : c.infoz();
ShouldSampleHashtablezInfo<Alloc>()
? SampleHashtablezInfo<SooEnabled>(SizeOfSlot, key_size, value_size,
old_capacity_, was_soo_,
forced_infoz_, c)
: HashtablezInfoHandle{};
const bool has_infoz = infoz.IsSampled();
const size_t cap = c.capacity();
const size_t alloc_size =
AllocSize(cap, SizeOfSlot, AlignOfSlot, has_infoz);
char* mem = static_cast<char*>(
Allocate<BackingArrayAlignment(AlignOfSlot)>(&alloc, alloc_size));
RawHashSetLayout layout(c.capacity(), AlignOfSlot, has_infoz);
char* mem = static_cast<char*>(Allocate<BackingArrayAlignment(AlignOfSlot)>(
&alloc, layout.alloc_size(SizeOfSlot)));
const GenerationType old_generation = c.generation();
c.set_generation_ptr(reinterpret_cast<GenerationType*>(
mem + GenerationOffset(cap, has_infoz)));
c.set_generation_ptr(
reinterpret_cast<GenerationType*>(mem + layout.generation_offset()));
c.set_generation(NextGeneration(old_generation));
c.set_control(reinterpret_cast<ctrl_t*>(mem + ControlOffset(has_infoz)));
c.set_slots(mem + SlotOffset(cap, AlignOfSlot, has_infoz));
c.set_control(reinterpret_cast<ctrl_t*>(mem + layout.control_offset()));
c.set_slots(mem + layout.slot_offset());
ResetGrowthLeft(c);
const bool grow_single_group =
IsGrowingIntoSingleGroupApplicable(old_capacity_, c.capacity());
if (old_capacity_ != 0 && grow_single_group) {
IsGrowingIntoSingleGroupApplicable(old_capacity_, layout.capacity());
if (SooEnabled && was_soo_ && grow_single_group) {
InitControlBytesAfterSoo(c.control(), soo_slot_h2, layout.capacity());
if (TransferUsesMemcpy && had_soo_slot_) {
TransferSlotAfterSoo(c, SizeOfSlot);
}
// SooEnabled implies that old_capacity_ != 0.
} else if ((SooEnabled || old_capacity_ != 0) && grow_single_group) {
if (TransferUsesMemcpy) {
GrowSizeIntoSingleGroupTransferable(c, old_slots, SizeOfSlot);
DeallocateOld<AlignOfSlot>(alloc, SizeOfSlot, old_slots);
GrowSizeIntoSingleGroupTransferable(c, SizeOfSlot);
DeallocateOld<AlignOfSlot>(alloc, SizeOfSlot);
} else {
GrowIntoSingleGroupShuffleControlBytes(c.control(), c.capacity());
GrowIntoSingleGroupShuffleControlBytes(c.control(), layout.capacity());
}
} else {
ResetCtrl(c, SizeOfSlot);
@@ -1636,8 +2075,8 @@ class HashSetResizeHelper {
c.set_has_infoz(has_infoz);
if (has_infoz) {
infoz.RecordStorageChanged(c.size(), cap);
if (grow_single_group || old_capacity_ == 0) {
infoz.RecordStorageChanged(c.size(), layout.capacity());
if ((SooEnabled && was_soo_) || grow_single_group || old_capacity_ == 0) {
infoz.RecordRehash(0);
}
c.set_infoz(infoz);
@@ -1651,21 +2090,22 @@ class HashSetResizeHelper {
// PRECONDITIONS:
// 1. GrowIntoSingleGroupShuffleControlBytes was already called.
template <class PolicyTraits, class Alloc>
void GrowSizeIntoSingleGroup(CommonFields& c, Alloc& alloc_ref,
typename PolicyTraits::slot_type* old_slots) {
void GrowSizeIntoSingleGroup(CommonFields& c, Alloc& alloc_ref) {
assert(old_capacity_ < Group::kWidth / 2);
assert(IsGrowingIntoSingleGroupApplicable(old_capacity_, c.capacity()));
using slot_type = typename PolicyTraits::slot_type;
assert(is_single_group(c.capacity()));
auto* new_slots = reinterpret_cast<slot_type*>(c.slot_array());
auto* new_slots = static_cast<slot_type*>(c.slot_array());
auto* old_slots_ptr = static_cast<slot_type*>(old_slots());
size_t shuffle_bit = old_capacity_ / 2 + 1;
for (size_t i = 0; i < old_capacity_; ++i) {
if (IsFull(old_ctrl_[i])) {
if (IsFull(old_ctrl()[i])) {
size_t new_i = i ^ shuffle_bit;
SanitizerUnpoisonMemoryRegion(new_slots + new_i, sizeof(slot_type));
PolicyTraits::transfer(&alloc_ref, new_slots + new_i, old_slots + i);
PolicyTraits::transfer(&alloc_ref, new_slots + new_i,
old_slots_ptr + i);
}
}
PoisonSingleGroupEmptySlots(c, sizeof(slot_type));
@@ -1673,11 +2113,12 @@ class HashSetResizeHelper {
// Deallocates old backing array.
template <size_t AlignOfSlot, class CharAlloc>
void DeallocateOld(CharAlloc alloc_ref, size_t slot_size, void* old_slots) {
SanitizerUnpoisonMemoryRegion(old_slots, slot_size * old_capacity_);
void DeallocateOld(CharAlloc alloc_ref, size_t slot_size) {
SanitizerUnpoisonMemoryRegion(old_slots(), slot_size * old_capacity_);
auto layout = RawHashSetLayout(old_capacity_, AlignOfSlot, had_infoz_);
Deallocate<BackingArrayAlignment(AlignOfSlot)>(
&alloc_ref, old_ctrl_ - ControlOffset(had_infoz_),
AllocSize(old_capacity_, slot_size, AlignOfSlot, had_infoz_));
&alloc_ref, old_ctrl() - layout.control_offset(),
layout.alloc_size(slot_size));
}
private:
@@ -1692,8 +2133,12 @@ class HashSetResizeHelper {
// Relocates control bytes and slots into new single group for
// transferable objects.
// Must be called only if IsGrowingIntoSingleGroupApplicable returned true.
void GrowSizeIntoSingleGroupTransferable(CommonFields& c, void* old_slots,
size_t slot_size);
void GrowSizeIntoSingleGroupTransferable(CommonFields& c, size_t slot_size);
// If there was an SOO slot and slots are transferable, transfers the SOO slot
// into the new heap allocation. Must be called only if
// IsGrowingIntoSingleGroupApplicable returned true.
void TransferSlotAfterSoo(CommonFields& c, size_t slot_size);
// Shuffle control bits deterministically to the next capacity.
// Returns offset for newly added element with given hash.
@@ -1726,6 +2171,13 @@ class HashSetResizeHelper {
void GrowIntoSingleGroupShuffleControlBytes(ctrl_t* new_ctrl,
size_t new_capacity) const;
// If the table was SOO, initializes new control bytes. `h2` is the control
// byte corresponding to the full slot. Must be called only if
// IsGrowingIntoSingleGroupApplicable returned true.
// Requires: `had_soo_slot_ || h2 == ctrl_t::kEmpty`.
void InitControlBytesAfterSoo(ctrl_t* new_ctrl, ctrl_t h2,
size_t new_capacity);
// Shuffle trivially transferable slots in the way consistent with
// GrowIntoSingleGroupShuffleControlBytes.
//
@@ -1739,8 +2191,7 @@ class HashSetResizeHelper {
// 1. new_slots are transferred from old_slots_ consistent with
// GrowIntoSingleGroupShuffleControlBytes.
// 2. Empty new_slots are *not* poisoned.
void GrowIntoSingleGroupShuffleTransferableSlots(void* old_slots,
void* new_slots,
void GrowIntoSingleGroupShuffleTransferableSlots(void* new_slots,
size_t slot_size) const;
// Poison empty slots that were transferred using the deterministic algorithm
@@ -1760,11 +2211,24 @@ class HashSetResizeHelper {
}
}
ctrl_t* old_ctrl_;
HeapOrSoo old_heap_or_soo_;
size_t old_capacity_;
bool had_infoz_;
bool was_soo_;
bool had_soo_slot_;
// Either null infoz or a pre-sampled forced infoz for SOO tables.
HashtablezInfoHandle forced_infoz_;
};
inline void PrepareInsertCommon(CommonFields& common) {
common.increment_size();
common.maybe_increment_generation_on_insert();
}
// Like prepare_insert, but for the case of inserting into a full SOO table.
size_t PrepareInsertAfterSoo(size_t hash, size_t slot_size,
CommonFields& common);
// PolicyFunctions bundles together some information for a particular
// raw_hash_set<T, ...> instantiation. This information is passed to
// type-erased functions that want to do small amounts of type-specific
@@ -1772,21 +2236,29 @@ class HashSetResizeHelper {
struct PolicyFunctions {
size_t slot_size;
// Returns the hash of the pointed-to slot.
size_t (*hash_slot)(void* set, void* slot);
// Returns the pointer to the hash function stored in the set.
const void* (*hash_fn)(const CommonFields& common);
// Transfer the contents of src_slot to dst_slot.
// Returns the hash of the pointed-to slot.
size_t (*hash_slot)(const void* hash_fn, void* slot);
// Transfers the contents of src_slot to dst_slot.
void (*transfer)(void* set, void* dst_slot, void* src_slot);
// Deallocate the backing store from common.
// Deallocates the backing store from common.
void (*dealloc)(CommonFields& common, const PolicyFunctions& policy);
// Resizes set to the new capacity.
// Arguments are used as in raw_hash_set::resize_impl.
void (*resize)(CommonFields& common, size_t new_capacity,
HashtablezInfoHandle forced_infoz);
};
// ClearBackingArray clears the backing array, either modifying it in place,
// or creating a new one based on the value of "reuse".
// REQUIRES: c.capacity > 0
void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,
bool reuse);
bool reuse, bool soo_enabled);
// Type-erased version of raw_hash_set::erase_meta_only.
void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size);
@@ -1817,9 +2289,26 @@ ABSL_ATTRIBUTE_NOINLINE void TransferRelocatable(void*, void* dst, void* src) {
memcpy(dst, src, SizeOfSlot);
}
// Type-erased version of raw_hash_set::drop_deletes_without_resize.
void DropDeletesWithoutResize(CommonFields& common,
const PolicyFunctions& policy, void* tmp_space);
// Type erased raw_hash_set::get_hash_ref_fn for the empty hash function case.
const void* GetHashRefForEmptyHasher(const CommonFields& common);
// Given the hash of a value not currently in the table and the first empty
// slot in the probe sequence, finds a viable slot index to insert it at.
//
// In case there's no space left, the table can be resized or rehashed
// (for tables with deleted slots, see FindInsertPositionWithGrowthOrRehash).
//
// In the case of absence of deleted slots and positive growth_left, the element
// can be inserted in the provided `target` position.
//
// When the table has deleted slots (according to GrowthInfo), the target
// position will be searched one more time using `find_first_non_full`.
//
// REQUIRES: Table is not SOO.
// REQUIRES: At least one non-full slot available.
// REQUIRES: `target` is a valid empty position to insert.
size_t PrepareInsertNonSoo(CommonFields& common, size_t hash, FindInfo target,
const PolicyFunctions& policy);
// A SwissTable.
//
@@ -1875,6 +2364,26 @@ class raw_hash_set {
using key_arg = typename KeyArgImpl::template type<K, key_type>;
private:
// TODO(b/289225379): we could add extra SOO space inside raw_hash_set
// after CommonFields to allow inlining larger slot_types (e.g. std::string),
// but it's a bit complicated if we want to support incomplete mapped_type in
// flat_hash_map. We could potentially do this for flat_hash_set and for an
// allowlist of `mapped_type`s of flat_hash_map that includes e.g. arithmetic
// types, strings, cords, and pairs/tuples of allowlisted types.
constexpr static bool SooEnabled() {
return PolicyTraits::soo_enabled() &&
sizeof(slot_type) <= sizeof(HeapOrSoo) &&
alignof(slot_type) <= alignof(HeapOrSoo);
}
// Whether `size` fits in the SOO capacity of this table.
bool fits_in_soo(size_t size) const {
return SooEnabled() && size <= SooCapacity();
}
// Whether this table is in SOO mode or non-SOO mode.
bool is_soo() const { return fits_in_soo(capacity()); }
bool is_full_soo() const { return is_soo() && !empty(); }
// Give an early error when key_type is not hashable/eq.
auto KeyTypeCanBeHashed(const Hash& h, const key_type& k) -> decltype(h(k));
auto KeyTypeCanBeEq(const Eq& eq, const key_type& k) -> decltype(eq(k, k));
@@ -1928,6 +2437,7 @@ class raw_hash_set {
class iterator : private HashSetIteratorGenerationInfo {
friend class raw_hash_set;
friend struct HashtableFreeFunctionsAccess;
public:
using iterator_category = std::forward_iterator_tag;
@@ -1958,6 +2468,7 @@ class raw_hash_set {
++ctrl_;
++slot_;
skip_empty_or_deleted();
if (ABSL_PREDICT_FALSE(*ctrl_ == ctrl_t::kSentinel)) ctrl_ = nullptr;
return *this;
}
// PRECONDITION: not an end() iterator.
@@ -1988,22 +2499,31 @@ class raw_hash_set {
// not equal to any end iterator.
ABSL_ASSUME(ctrl != nullptr);
}
// This constructor is used in begin() to avoid an MSan
// use-of-uninitialized-value error. Delegating from this constructor to
// the previous one doesn't avoid the error.
iterator(ctrl_t* ctrl, MaybeInitializedPtr slot,
const GenerationType* generation_ptr)
: HashSetIteratorGenerationInfo(generation_ptr),
ctrl_(ctrl),
slot_(to_slot(slot.get())) {
// This assumption helps the compiler know that any non-end iterator is
// not equal to any end iterator.
ABSL_ASSUME(ctrl != nullptr);
}
// For end() iterators.
explicit iterator(const GenerationType* generation_ptr)
: HashSetIteratorGenerationInfo(generation_ptr), ctrl_(nullptr) {}
// Fixes up `ctrl_` to point to a full by advancing it and `slot_` until
// they reach one.
//
// If a sentinel is reached, we null `ctrl_` out instead.
// Fixes up `ctrl_` to point to a full or sentinel by advancing `ctrl_` and
// `slot_` until they reach one.
void skip_empty_or_deleted() {
while (IsEmptyOrDeleted(*ctrl_)) {
uint32_t shift =
GroupEmptyOrDeleted{ctrl_}.CountLeadingEmptyOrDeleted();
GroupFullEmptyOrDeleted{ctrl_}.CountLeadingEmptyOrDeleted();
ctrl_ += shift;
slot_ += shift;
}
if (ABSL_PREDICT_FALSE(*ctrl_ == ctrl_t::kSentinel)) ctrl_ = nullptr;
}
ctrl_t* control() const { return ctrl_; }
@@ -2091,8 +2611,9 @@ class raw_hash_set {
size_t bucket_count, const hasher& hash = hasher(),
const key_equal& eq = key_equal(),
const allocator_type& alloc = allocator_type())
: settings_(CommonFields{}, hash, eq, alloc) {
if (bucket_count) {
: settings_(CommonFields::CreateDefault<SooEnabled()>(), hash, eq,
alloc) {
if (bucket_count > (SooEnabled() ? SooCapacity() : 0)) {
resize(NormalizeCapacity(bucket_count));
}
}
@@ -2193,22 +2714,69 @@ class raw_hash_set {
that.alloc_ref())) {}
raw_hash_set(const raw_hash_set& that, const allocator_type& a)
: raw_hash_set(0, that.hash_ref(), that.eq_ref(), a) {
: raw_hash_set(GrowthToLowerboundCapacity(that.size()), that.hash_ref(),
that.eq_ref(), a) {
const size_t size = that.size();
if (size == 0) return;
reserve(size);
// Because the table is guaranteed to be empty, we can do something faster
// than a full `insert`.
for (const auto& v : that) {
const size_t hash = PolicyTraits::apply(HashElement{hash_ref()}, v);
auto target = find_first_non_full_outofline(common(), hash);
SetCtrl(common(), target.offset, H2(hash), sizeof(slot_type));
emplace_at(target.offset, v);
common().maybe_increment_generation_on_insert();
infoz().RecordInsert(hash, target.probe_length);
if (size == 0) {
return;
}
// We don't use `that.is_soo()` here because `that` can have non-SOO
// capacity but have a size that fits into SOO capacity.
if (fits_in_soo(size)) {
assert(size == 1);
common().set_full_soo();
emplace_at(soo_iterator(), *that.begin());
const HashtablezInfoHandle infoz = try_sample_soo();
if (infoz.IsSampled()) resize_with_soo_infoz(infoz);
return;
}
assert(!that.is_soo());
const size_t cap = capacity();
// Note about single group tables:
// 1. It is correct to have any order of elements.
// 2. Order has to be non deterministic.
// 3. We are assigning elements with arbitrary `shift` starting from
// `capacity + shift` position.
// 4. `shift` must be coprime with `capacity + 1` in order to be able to use
// modular arithmetic to traverse all positions, instead if cycling
// through a subset of positions. Odd numbers are coprime with any
// `capacity + 1` (2^N).
size_t offset = cap;
const size_t shift =
is_single_group(cap) ? (PerTableSalt(control()) | 1) : 0;
IterateOverFullSlots(
that.common(), that.slot_array(),
[&](const ctrl_t* that_ctrl,
slot_type* that_slot) ABSL_ATTRIBUTE_ALWAYS_INLINE {
if (shift == 0) {
// Big tables case. Position must be searched via probing.
// The table is guaranteed to be empty, so we can do faster than
// a full `insert`.
const size_t hash = PolicyTraits::apply(
HashElement{hash_ref()}, PolicyTraits::element(that_slot));
FindInfo target = find_first_non_full_outofline(common(), hash);
infoz().RecordInsert(hash, target.probe_length);
offset = target.offset;
} else {
// Small tables case. Next position is computed via shift.
offset = (offset + shift) & cap;
}
const h2_t h2 = static_cast<h2_t>(*that_ctrl);
assert( // We rely that hash is not changed for small tables.
H2(PolicyTraits::apply(HashElement{hash_ref()},
PolicyTraits::element(that_slot))) == h2 &&
"hash function value changed unexpectedly during the copy");
SetCtrl(common(), offset, h2, sizeof(slot_type));
emplace_at(iterator_at(offset), PolicyTraits::element(that_slot));
common().maybe_increment_generation_on_insert();
});
if (shift != 0) {
// On small table copy we do not record individual inserts.
// RecordInsert requires hash, but it is unknown for small tables.
infoz().RecordStorageChanged(size, cap);
}
common().set_size(size);
set_growth_left(growth_left() - size);
growth_info().OverwriteManyEmptyAsFull(size);
}
ABSL_ATTRIBUTE_NOINLINE raw_hash_set(raw_hash_set&& that) noexcept(
@@ -2220,16 +2788,22 @@ class raw_hash_set {
// would create a nullptr functor that cannot be called.
// TODO(b/296061262): move instead of copying hash/eq/alloc.
// Note: we avoid using exchange for better generated code.
settings_(std::move(that.common()), that.hash_ref(), that.eq_ref(),
that.alloc_ref()) {
that.common() = CommonFields{};
settings_(PolicyTraits::transfer_uses_memcpy() || !that.is_full_soo()
? std::move(that.common())
: CommonFields{full_soo_tag_t{}},
that.hash_ref(), that.eq_ref(), that.alloc_ref()) {
if (!PolicyTraits::transfer_uses_memcpy() && that.is_full_soo()) {
transfer(soo_slot(), that.soo_slot());
}
that.common() = CommonFields::CreateDefault<SooEnabled()>();
maybe_increment_generation_or_rehash_on_move();
}
raw_hash_set(raw_hash_set&& that, const allocator_type& a)
: settings_(CommonFields{}, that.hash_ref(), that.eq_ref(), a) {
: settings_(CommonFields::CreateDefault<SooEnabled()>(), that.hash_ref(),
that.eq_ref(), a) {
if (a == that.alloc_ref()) {
std::swap(common(), that.common());
swap_common(that);
maybe_increment_generation_or_rehash_on_move();
} else {
move_elements_allocs_unequal(std::move(that));
@@ -2264,8 +2838,12 @@ class raw_hash_set {
~raw_hash_set() { destructor_impl(); }
iterator begin() ABSL_ATTRIBUTE_LIFETIME_BOUND {
auto it = iterator_at(0);
if (ABSL_PREDICT_FALSE(empty())) return end();
if (is_soo()) return soo_iterator();
iterator it = {control(), common().slots_union(),
common().generation_ptr()};
it.skip_empty_or_deleted();
assert(IsFull(*it.control()));
return it;
}
iterator end() ABSL_ATTRIBUTE_LIFETIME_BOUND {
@@ -2285,7 +2863,14 @@ class raw_hash_set {
bool empty() const { return !size(); }
size_t size() const { return common().size(); }
size_t capacity() const { return common().capacity(); }
size_t capacity() const {
const size_t cap = common().capacity();
// Compiler complains when using functions in assume so use local variables.
ABSL_ATTRIBUTE_UNUSED static constexpr bool kEnabled = SooEnabled();
ABSL_ATTRIBUTE_UNUSED static constexpr size_t kCapacity = SooCapacity();
ABSL_ASSUME(!kEnabled || cap >= kCapacity);
return cap;
}
size_t max_size() const { return (std::numeric_limits<size_t>::max)(); }
ABSL_ATTRIBUTE_REINITIALIZES void clear() {
@@ -2299,9 +2884,13 @@ class raw_hash_set {
const size_t cap = capacity();
if (cap == 0) {
// Already guaranteed to be empty; so nothing to do.
} else if (is_soo()) {
if (!empty()) destroy(soo_slot());
common().set_empty_soo();
} else {
destroy_slots();
ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/cap < 128);
ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/cap < 128,
SooEnabled());
}
common().set_reserved_growth(0);
common().set_reservation_size(0);
@@ -2432,7 +3021,7 @@ class raw_hash_set {
std::pair<iterator, bool> emplace(Args&&... args)
ABSL_ATTRIBUTE_LIFETIME_BOUND {
alignas(slot_type) unsigned char raw[sizeof(slot_type)];
slot_type* slot = reinterpret_cast<slot_type*>(&raw);
slot_type* slot = to_slot(&raw);
construct(slot, std::forward<Args>(args)...);
const auto& elem = PolicyTraits::element(slot);
@@ -2496,11 +3085,11 @@ class raw_hash_set {
F&& f) ABSL_ATTRIBUTE_LIFETIME_BOUND {
auto res = find_or_prepare_insert(key);
if (res.second) {
slot_type* slot = slot_array() + res.first;
slot_type* slot = res.first.slot();
std::forward<F>(f)(constructor(&alloc_ref(), &slot));
assert(!slot);
}
return iterator_at(res.first);
return res.first;
}
// Extension API: support for heterogeneous keys.
@@ -2524,7 +3113,7 @@ class raw_hash_set {
// this method returns void to reduce algorithmic complexity to O(1). The
// iterator is invalidated, so any increment should be done before calling
// erase. In order to erase while iterating across a map, use the following
// idiom (which also works for standard containers):
// idiom (which also works for some standard containers):
//
// for (auto it = m.begin(), end = m.end(); it != end;) {
// // `erase()` will invalidate `it`, so advance `it` first.
@@ -2540,7 +3129,11 @@ class raw_hash_set {
void erase(iterator it) {
AssertIsFull(it.control(), it.generation(), it.generation_ptr(), "erase()");
destroy(it.slot());
erase_meta_only(it);
if (is_soo()) {
common().set_empty_soo();
} else {
erase_meta_only(it);
}
}
iterator erase(const_iterator first,
@@ -2548,12 +3141,19 @@ class raw_hash_set {
// We check for empty first because ClearBackingArray requires that
// capacity() > 0 as a precondition.
if (empty()) return end();
if (first == last) return last.inner_;
if (is_soo()) {
destroy(soo_slot());
common().set_empty_soo();
return end();
}
if (first == begin() && last == end()) {
// TODO(ezb): we access control bytes in destroy_slots so it could make
// sense to combine destroy_slots and ClearBackingArray to avoid cache
// misses when the table is large. Note that we also do this in clear().
destroy_slots();
ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/true);
ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/true,
SooEnabled());
common().set_reserved_growth(common().reservation_size());
return end();
}
@@ -2568,13 +3168,21 @@ class raw_hash_set {
template <typename H, typename E>
void merge(raw_hash_set<Policy, H, E, Alloc>& src) { // NOLINT
assert(this != &src);
// Returns whether insertion took place.
const auto insert_slot = [this](slot_type* src_slot) {
return PolicyTraits::apply(InsertSlot<false>{*this, std::move(*src_slot)},
PolicyTraits::element(src_slot))
.second;
};
if (src.is_soo()) {
if (src.empty()) return;
if (insert_slot(src.soo_slot())) src.common().set_empty_soo();
return;
}
for (auto it = src.begin(), e = src.end(); it != e;) {
auto next = std::next(it);
if (PolicyTraits::apply(InsertSlot<false>{*this, std::move(*it.slot())},
PolicyTraits::element(it.slot()))
.second) {
src.erase_meta_only(it);
}
if (insert_slot(it.slot())) src.erase_meta_only(it);
it = next;
}
}
@@ -2588,7 +3196,11 @@ class raw_hash_set {
AssertIsFull(position.control(), position.inner_.generation(),
position.inner_.generation_ptr(), "extract()");
auto node = CommonAccess::Transfer<node_type>(alloc_ref(), position.slot());
erase_meta_only(position);
if (is_soo()) {
common().set_empty_soo();
} else {
erase_meta_only(position);
}
return node;
}
@@ -2605,7 +3217,7 @@ class raw_hash_set {
IsNoThrowSwappable<allocator_type>(
typename AllocTraits::propagate_on_container_swap{})) {
using std::swap;
swap(common(), that.common());
swap_common(that);
swap(hash_ref(), that.hash_ref());
swap(eq_ref(), that.eq_ref());
SwapAlloc(alloc_ref(), that.alloc_ref(),
@@ -2613,17 +3225,41 @@ class raw_hash_set {
}
void rehash(size_t n) {
if (n == 0 && capacity() == 0) return;
if (n == 0 && size() == 0) {
ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/false);
return;
const size_t cap = capacity();
if (n == 0) {
if (cap == 0 || is_soo()) return;
if (empty()) {
ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/false,
SooEnabled());
return;
}
if (fits_in_soo(size())) {
// When the table is already sampled, we keep it sampled.
if (infoz().IsSampled()) {
const size_t kInitialSampledCapacity = NextCapacity(SooCapacity());
if (capacity() > kInitialSampledCapacity) {
resize(kInitialSampledCapacity);
}
// This asserts that we didn't lose sampling coverage in `resize`.
assert(infoz().IsSampled());
return;
}
alignas(slot_type) unsigned char slot_space[sizeof(slot_type)];
slot_type* tmp_slot = to_slot(slot_space);
transfer(tmp_slot, begin().slot());
ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/false,
SooEnabled());
transfer(soo_slot(), tmp_slot);
common().set_full_soo();
return;
}
}
// bitor is a faster way of doing `max` here. We will round up to the next
// power-of-2-minus-1, so bitor is good enough.
auto m = NormalizeCapacity(n | GrowthToLowerboundCapacity(size()));
// n == 0 unconditionally rehashes as per the standard.
if (n == 0 || m > capacity()) {
if (n == 0 || m > cap) {
resize(m);
// This is after resize, to ensure that we have completed the allocation
@@ -2633,7 +3269,9 @@ class raw_hash_set {
}
void reserve(size_t n) {
if (n > size() + growth_left()) {
const size_t max_size_before_growth =
is_soo() ? SooCapacity() : size() + growth_left();
if (n > max_size_before_growth) {
size_t m = GrowthToLowerboundCapacity(n);
resize(NormalizeCapacity(m));
@@ -2666,6 +3304,7 @@ class raw_hash_set {
// specific benchmarks indicating its importance.
template <class K = key_type>
void prefetch(const key_arg<K>& key) const {
if (SooEnabled() ? is_soo() : capacity() == 0) return;
(void)key;
// Avoid probing if we won't be able to prefetch the addresses received.
#ifdef ABSL_HAVE_PREFETCH
@@ -2686,26 +3325,16 @@ class raw_hash_set {
template <class K = key_type>
iterator find(const key_arg<K>& key,
size_t hash) ABSL_ATTRIBUTE_LIFETIME_BOUND {
auto seq = probe(common(), hash);
slot_type* slot_ptr = slot_array();
const ctrl_t* ctrl = control();
while (true) {
Group g{ctrl + seq.offset()};
for (uint32_t i : g.Match(H2(hash))) {
if (ABSL_PREDICT_TRUE(PolicyTraits::apply(
EqualElement<K>{key, eq_ref()},
PolicyTraits::element(slot_ptr + seq.offset(i)))))
return iterator_at(seq.offset(i));
}
if (ABSL_PREDICT_TRUE(g.MaskEmpty())) return end();
seq.next();
assert(seq.index() <= capacity() && "full table!");
}
AssertHashEqConsistent(key);
if (is_soo()) return find_soo(key);
return find_non_soo(key, hash);
}
template <class K = key_type>
iterator find(const key_arg<K>& key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
AssertHashEqConsistent(key);
if (is_soo()) return find_soo(key);
prefetch_heap_block();
return find(key, hash_ref()(key));
return find_non_soo(key, hash_ref()(key));
}
template <class K = key_type>
@@ -2716,8 +3345,7 @@ class raw_hash_set {
template <class K = key_type>
const_iterator find(const key_arg<K>& key) const
ABSL_ATTRIBUTE_LIFETIME_BOUND {
prefetch_heap_block();
return find(key, hash_ref()(key));
return const_cast<raw_hash_set*>(this)->find(key);
}
template <class K = key_type>
@@ -2791,6 +3419,8 @@ class raw_hash_set {
friend struct absl::container_internal::hashtable_debug_internal::
HashtableDebugAccess;
friend struct absl::container_internal::HashtableFreeFunctionsAccess;
struct FindElement {
template <class K, class... Args>
const_iterator operator()(const K& key, Args&&...) const {
@@ -2824,7 +3454,7 @@ class raw_hash_set {
if (res.second) {
s.emplace_at(res.first, std::forward<Args>(args)...);
}
return {s.iterator_at(res.first), res.second};
return res;
}
raw_hash_set& s;
};
@@ -2835,11 +3465,11 @@ class raw_hash_set {
std::pair<iterator, bool> operator()(const K& key, Args&&...) && {
auto res = s.find_or_prepare_insert(key);
if (res.second) {
s.transfer(s.slot_array() + res.first, &slot);
s.transfer(res.first.slot(), &slot);
} else if (do_destroy) {
s.destroy(&slot);
}
return {s.iterator_at(res.first), res.second};
return res;
}
raw_hash_set& s;
// Constructed slot. Either moved into place or destroyed.
@@ -2858,17 +3488,55 @@ class raw_hash_set {
PolicyTraits::transfer(&alloc_ref(), to, from);
}
inline void destroy_slots() {
const size_t cap = capacity();
// TODO(b/289225379): consider having a helper class that has the impls for
// SOO functionality.
template <class K = key_type>
iterator find_soo(const key_arg<K>& key) {
assert(is_soo());
return empty() || !PolicyTraits::apply(EqualElement<K>{key, eq_ref()},
PolicyTraits::element(soo_slot()))
? end()
: soo_iterator();
}
template <class K = key_type>
iterator find_non_soo(const key_arg<K>& key, size_t hash) {
assert(!is_soo());
auto seq = probe(common(), hash);
const ctrl_t* ctrl = control();
slot_type* slot = slot_array();
for (size_t i = 0; i != cap; ++i) {
if (IsFull(ctrl[i])) {
destroy(slot + i);
while (true) {
Group g{ctrl + seq.offset()};
for (uint32_t i : g.Match(H2(hash))) {
if (ABSL_PREDICT_TRUE(PolicyTraits::apply(
EqualElement<K>{key, eq_ref()},
PolicyTraits::element(slot_array() + seq.offset(i)))))
return iterator_at(seq.offset(i));
}
if (ABSL_PREDICT_TRUE(g.MaskEmpty())) return end();
seq.next();
assert(seq.index() <= capacity() && "full table!");
}
}
// Conditionally samples hashtablez for SOO tables. This should be called on
// insertion into an empty SOO table and in copy construction when the size
// can fit in SOO capacity.
inline HashtablezInfoHandle try_sample_soo() {
assert(is_soo());
if (!ShouldSampleHashtablezInfo<CharAlloc>()) return HashtablezInfoHandle{};
return Sample(sizeof(slot_type), sizeof(key_type), sizeof(value_type),
SooCapacity());
}
inline void destroy_slots() {
assert(!is_soo());
if (PolicyTraits::template destroy_is_trivial<Alloc>()) return;
IterateOverFullSlots(
common(), slot_array(),
[&](const ctrl_t*, slot_type* slot)
ABSL_ATTRIBUTE_ALWAYS_INLINE { this->destroy(slot); });
}
inline void dealloc() {
assert(capacity() != 0);
// Unpoison before returning the memory to the allocator.
@@ -2881,6 +3549,12 @@ class raw_hash_set {
inline void destructor_impl() {
if (capacity() == 0) return;
if (is_soo()) {
if (!empty()) {
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED(destroy(soo_slot()));
}
return;
}
destroy_slots();
dealloc();
}
@@ -2890,10 +3564,16 @@ class raw_hash_set {
// This merely updates the pertinent control byte. This can be used in
// conjunction with Policy::transfer to move the object to another place.
void erase_meta_only(const_iterator it) {
assert(!is_soo());
EraseMetaOnly(common(), static_cast<size_t>(it.control() - control()),
sizeof(slot_type));
}
size_t hash_of(slot_type* slot) const {
return PolicyTraits::apply(HashElement{hash_ref()},
PolicyTraits::element(slot));
}
// Resizes table to the new capacity and move all elements to the new
// positions accordingly.
//
@@ -2902,143 +3582,165 @@ class raw_hash_set {
// HashSetResizeHelper::FindFirstNonFullAfterResize(
// common(), old_capacity, hash)
// can be called right after `resize`.
ABSL_ATTRIBUTE_NOINLINE void resize(size_t new_capacity) {
void resize(size_t new_capacity) {
raw_hash_set::resize_impl(common(), new_capacity, HashtablezInfoHandle{});
}
// As above, except that we also accept a pre-sampled, forced infoz for
// SOO tables, since they need to switch from SOO to heap in order to
// store the infoz.
void resize_with_soo_infoz(HashtablezInfoHandle forced_infoz) {
assert(forced_infoz.IsSampled());
raw_hash_set::resize_impl(common(), NextCapacity(SooCapacity()),
forced_infoz);
}
// Resizes set to the new capacity.
// It is a static function in order to use its pointer in GetPolicyFunctions.
ABSL_ATTRIBUTE_NOINLINE static void resize_impl(
CommonFields& common, size_t new_capacity,
HashtablezInfoHandle forced_infoz) {
raw_hash_set* set = reinterpret_cast<raw_hash_set*>(&common);
assert(IsValidCapacity(new_capacity));
HashSetResizeHelper resize_helper(common());
auto* old_slots = slot_array();
common().set_capacity(new_capacity);
assert(!set->fits_in_soo(new_capacity));
const bool was_soo = set->is_soo();
const bool had_soo_slot = was_soo && !set->empty();
const ctrl_t soo_slot_h2 =
had_soo_slot ? static_cast<ctrl_t>(H2(set->hash_of(set->soo_slot())))
: ctrl_t::kEmpty;
HashSetResizeHelper resize_helper(common, was_soo, had_soo_slot,
forced_infoz);
// Initialize HashSetResizeHelper::old_heap_or_soo_. We can't do this in
// HashSetResizeHelper constructor because it can't transfer slots when
// transfer_uses_memcpy is false.
// TODO(b/289225379): try to handle more of the SOO cases inside
// InitializeSlots. See comment on cl/555990034 snapshot #63.
if (PolicyTraits::transfer_uses_memcpy() || !had_soo_slot) {
resize_helper.old_heap_or_soo() = common.heap_or_soo();
} else {
set->transfer(set->to_slot(resize_helper.old_soo_data()),
set->soo_slot());
}
common.set_capacity(new_capacity);
// Note that `InitializeSlots` does different number initialization steps
// depending on the values of `transfer_uses_memcpy` and capacities.
// Refer to the comment in `InitializeSlots` for more details.
const bool grow_single_group =
resize_helper.InitializeSlots<CharAlloc, sizeof(slot_type),
PolicyTraits::transfer_uses_memcpy(),
alignof(slot_type)>(
common(), const_cast<std::remove_const_t<slot_type>*>(old_slots),
CharAlloc(alloc_ref()));
SooEnabled(), alignof(slot_type)>(
common, CharAlloc(set->alloc_ref()), soo_slot_h2, sizeof(key_type),
sizeof(value_type));
if (resize_helper.old_capacity() == 0) {
// In the SooEnabled() case, capacity is never 0 so we don't check.
if (!SooEnabled() && resize_helper.old_capacity() == 0) {
// InitializeSlots did all the work including infoz().RecordRehash().
return;
}
assert(resize_helper.old_capacity() > 0);
// Nothing more to do in this case.
if (was_soo && !had_soo_slot) return;
slot_type* new_slots = set->slot_array();
if (grow_single_group) {
if (PolicyTraits::transfer_uses_memcpy()) {
// InitializeSlots did all the work.
return;
}
// We want GrowSizeIntoSingleGroup to be called here in order to make
// InitializeSlots not depend on PolicyTraits.
resize_helper.GrowSizeIntoSingleGroup<PolicyTraits>(common(), alloc_ref(),
old_slots);
if (was_soo) {
set->transfer(new_slots + resize_helper.SooSlotIndex(),
to_slot(resize_helper.old_soo_data()));
return;
} else {
// We want GrowSizeIntoSingleGroup to be called here in order to make
// InitializeSlots not depend on PolicyTraits.
resize_helper.GrowSizeIntoSingleGroup<PolicyTraits>(common,
set->alloc_ref());
}
} else {
// InitializeSlots prepares control bytes to correspond to empty table.
auto* new_slots = slot_array();
size_t total_probe_length = 0;
for (size_t i = 0; i != resize_helper.old_capacity(); ++i) {
if (IsFull(resize_helper.old_ctrl()[i])) {
size_t hash = PolicyTraits::apply(
HashElement{hash_ref()}, PolicyTraits::element(old_slots + i));
auto target = find_first_non_full(common(), hash);
size_t new_i = target.offset;
total_probe_length += target.probe_length;
SetCtrl(common(), new_i, H2(hash), sizeof(slot_type));
transfer(new_slots + new_i, old_slots + i);
const auto insert_slot = [&](slot_type* slot) {
size_t hash = PolicyTraits::apply(HashElement{set->hash_ref()},
PolicyTraits::element(slot));
auto target = find_first_non_full(common, hash);
SetCtrl(common, target.offset, H2(hash), sizeof(slot_type));
set->transfer(new_slots + target.offset, slot);
return target.probe_length;
};
if (was_soo) {
insert_slot(to_slot(resize_helper.old_soo_data()));
return;
} else {
auto* old_slots = static_cast<slot_type*>(resize_helper.old_slots());
size_t total_probe_length = 0;
for (size_t i = 0; i != resize_helper.old_capacity(); ++i) {
if (IsFull(resize_helper.old_ctrl()[i])) {
total_probe_length += insert_slot(old_slots + i);
}
}
common.infoz().RecordRehash(total_probe_length);
}
infoz().RecordRehash(total_probe_length);
}
resize_helper.DeallocateOld<alignof(slot_type)>(
CharAlloc(alloc_ref()), sizeof(slot_type),
const_cast<std::remove_const_t<slot_type>*>(old_slots));
resize_helper.DeallocateOld<alignof(slot_type)>(CharAlloc(set->alloc_ref()),
sizeof(slot_type));
}
// Prunes control bytes to remove as many tombstones as possible.
//
// See the comment on `rehash_and_grow_if_necessary()`.
inline void drop_deletes_without_resize() {
// Stack-allocate space for swapping elements.
alignas(slot_type) unsigned char tmp[sizeof(slot_type)];
DropDeletesWithoutResize(common(), GetPolicyFunctions(), tmp);
}
// Casting directly from e.g. char* to slot_type* can cause compilation errors
// on objective-C. This function converts to void* first, avoiding the issue.
static slot_type* to_slot(void* buf) { return static_cast<slot_type*>(buf); }
// Called whenever the table *might* need to conditionally grow.
//
// This function is an optimization opportunity to perform a rehash even when
// growth is unnecessary, because vacating tombstones is beneficial for
// performance in the long-run.
void rehash_and_grow_if_necessary() {
const size_t cap = capacity();
if (cap > Group::kWidth &&
// Do these calculations in 64-bit to avoid overflow.
size() * uint64_t{32} <= cap * uint64_t{25}) {
// Squash DELETED without growing if there is enough capacity.
//
// Rehash in place if the current size is <= 25/32 of capacity.
// Rationale for such a high factor: 1) drop_deletes_without_resize() is
// faster than resize, and 2) it takes quite a bit of work to add
// tombstones. In the worst case, seems to take approximately 4
// insert/erase pairs to create a single tombstone and so if we are
// rehashing because of tombstones, we can afford to rehash-in-place as
// long as we are reclaiming at least 1/8 the capacity without doing more
// than 2X the work. (Where "work" is defined to be size() for rehashing
// or rehashing in place, and 1 for an insert or erase.) But rehashing in
// place is faster per operation than inserting or even doubling the size
// of the table, so we actually afford to reclaim even less space from a
// resize-in-place. The decision is to rehash in place if we can reclaim
// at about 1/8th of the usable capacity (specifically 3/28 of the
// capacity) which means that the total cost of rehashing will be a small
// fraction of the total work.
//
// Here is output of an experiment using the BM_CacheInSteadyState
// benchmark running the old case (where we rehash-in-place only if we can
// reclaim at least 7/16*capacity) vs. this code (which rehashes in place
// if we can recover 3/32*capacity).
//
// Note that although in the worst-case number of rehashes jumped up from
// 15 to 190, but the number of operations per second is almost the same.
//
// Abridged output of running BM_CacheInSteadyState benchmark from
// raw_hash_set_benchmark. N is the number of insert/erase operations.
//
// | OLD (recover >= 7/16 | NEW (recover >= 3/32)
// size | N/s LoadFactor NRehashes | N/s LoadFactor NRehashes
// 448 | 145284 0.44 18 | 140118 0.44 19
// 493 | 152546 0.24 11 | 151417 0.48 28
// 538 | 151439 0.26 11 | 151152 0.53 38
// 583 | 151765 0.28 11 | 150572 0.57 50
// 628 | 150241 0.31 11 | 150853 0.61 66
// 672 | 149602 0.33 12 | 150110 0.66 90
// 717 | 149998 0.35 12 | 149531 0.70 129
// 762 | 149836 0.37 13 | 148559 0.74 190
// 807 | 149736 0.39 14 | 151107 0.39 14
// 852 | 150204 0.42 15 | 151019 0.42 15
drop_deletes_without_resize();
// Requires that lhs does not have a full SOO slot.
static void move_common(bool that_is_full_soo, allocator_type& rhs_alloc,
CommonFields& lhs, CommonFields&& rhs) {
if (PolicyTraits::transfer_uses_memcpy() || !that_is_full_soo) {
lhs = std::move(rhs);
} else {
// Otherwise grow the container.
resize(NextCapacity(cap));
lhs.move_non_heap_or_soo_fields(rhs);
// TODO(b/303305702): add reentrancy guard.
PolicyTraits::transfer(&rhs_alloc, to_slot(lhs.soo_data()),
to_slot(rhs.soo_data()));
}
}
// Swaps common fields making sure to avoid memcpy'ing a full SOO slot if we
// aren't allowed to do so.
void swap_common(raw_hash_set& that) {
using std::swap;
if (PolicyTraits::transfer_uses_memcpy()) {
swap(common(), that.common());
return;
}
CommonFields tmp = CommonFields::CreateDefault<SooEnabled()>();
const bool that_is_full_soo = that.is_full_soo();
move_common(that_is_full_soo, that.alloc_ref(), tmp,
std::move(that.common()));
move_common(is_full_soo(), alloc_ref(), that.common(), std::move(common()));
move_common(that_is_full_soo, that.alloc_ref(), common(), std::move(tmp));
}
void maybe_increment_generation_or_rehash_on_move() {
common().maybe_increment_generation_on_move();
if (!SwisstableGenerationsEnabled() || capacity() == 0 || is_soo()) {
return;
}
common().increment_generation();
if (!empty() && common().should_rehash_for_bug_detection_on_move()) {
resize(capacity());
}
}
template<bool propagate_alloc>
template <bool propagate_alloc>
raw_hash_set& assign_impl(raw_hash_set&& that) {
// We don't bother checking for this/that aliasing. We just need to avoid
// breaking the invariants in that case.
destructor_impl();
common() = std::move(that.common());
move_common(that.is_full_soo(), that.alloc_ref(), common(),
std::move(that.common()));
// TODO(b/296061262): move instead of copying hash/eq/alloc.
hash_ref() = that.hash_ref();
eq_ref() = that.eq_ref();
CopyAlloc(alloc_ref(), that.alloc_ref(),
std::integral_constant<bool, propagate_alloc>());
that.common() = CommonFields{};
that.common() = CommonFields::CreateDefault<SooEnabled()>();
maybe_increment_generation_or_rehash_on_move();
return *this;
}
@@ -3051,8 +3753,8 @@ class raw_hash_set {
insert(std::move(PolicyTraits::element(it.slot())));
that.destroy(it.slot());
}
that.dealloc();
that.common() = CommonFields{};
if (!that.is_soo()) that.dealloc();
that.common() = CommonFields::CreateDefault<SooEnabled()>();
maybe_increment_generation_or_rehash_on_move();
return *this;
}
@@ -3078,12 +3780,30 @@ class raw_hash_set {
return move_elements_allocs_unequal(std::move(that));
}
protected:
// Attempts to find `key` in the table; if it isn't found, returns a slot that
// the value can be inserted into, with the control byte already set to
// `key`'s H2.
template <class K>
std::pair<size_t, bool> find_or_prepare_insert(const K& key) {
std::pair<iterator, bool> find_or_prepare_insert_soo(const K& key) {
if (empty()) {
const HashtablezInfoHandle infoz = try_sample_soo();
if (infoz.IsSampled()) {
resize_with_soo_infoz(infoz);
} else {
common().set_full_soo();
return {soo_iterator(), true};
}
} else if (PolicyTraits::apply(EqualElement<K>{key, eq_ref()},
PolicyTraits::element(soo_slot()))) {
return {soo_iterator(), false};
} else {
resize(NextCapacity(SooCapacity()));
}
const size_t index =
PrepareInsertAfterSoo(hash_ref()(key), sizeof(slot_type), common());
return {iterator_at(index), true};
}
template <class K>
std::pair<iterator, bool> find_or_prepare_insert_non_soo(const K& key) {
assert(!is_soo());
prefetch_heap_block();
auto hash = hash_ref()(key);
auto seq = probe(common(), hash);
@@ -3094,65 +3814,92 @@ class raw_hash_set {
if (ABSL_PREDICT_TRUE(PolicyTraits::apply(
EqualElement<K>{key, eq_ref()},
PolicyTraits::element(slot_array() + seq.offset(i)))))
return {seq.offset(i), false};
return {iterator_at(seq.offset(i)), false};
}
auto mask_empty = g.MaskEmpty();
if (ABSL_PREDICT_TRUE(mask_empty)) {
size_t target = seq.offset(
GetInsertionOffset(mask_empty, capacity(), hash, control()));
return {iterator_at(PrepareInsertNonSoo(common(), hash,
FindInfo{target, seq.index()},
GetPolicyFunctions())),
true};
}
if (ABSL_PREDICT_TRUE(g.MaskEmpty())) break;
seq.next();
assert(seq.index() <= capacity() && "full table!");
}
return {prepare_insert(hash), true};
}
// Given the hash of a value not currently in the table, finds the next
// viable slot index to insert it at.
//
// REQUIRES: At least one non-full slot available.
size_t prepare_insert(size_t hash) ABSL_ATTRIBUTE_NOINLINE {
const bool rehash_for_bug_detection =
common().should_rehash_for_bug_detection_on_insert();
if (rehash_for_bug_detection) {
// Move to a different heap allocation in order to detect bugs.
const size_t cap = capacity();
resize(growth_left() > 0 ? cap : NextCapacity(cap));
protected:
// Asserts that hash and equal functors provided by the user are consistent,
// meaning that `eq(k1, k2)` implies `hash(k1)==hash(k2)`.
template <class K>
void AssertHashEqConsistent(ABSL_ATTRIBUTE_UNUSED const K& key) {
#ifndef NDEBUG
if (empty()) return;
const size_t hash_of_arg = hash_ref()(key);
const auto assert_consistent = [&](const ctrl_t*, slot_type* slot) {
const value_type& element = PolicyTraits::element(slot);
const bool is_key_equal =
PolicyTraits::apply(EqualElement<K>{key, eq_ref()}, element);
if (!is_key_equal) return;
const size_t hash_of_slot =
PolicyTraits::apply(HashElement{hash_ref()}, element);
const bool is_hash_equal = hash_of_arg == hash_of_slot;
if (!is_hash_equal) {
// In this case, we're going to crash. Do a couple of other checks for
// idempotence issues. Recalculating hash/eq here is also convenient for
// debugging with gdb/lldb.
const size_t once_more_hash_arg = hash_ref()(key);
assert(hash_of_arg == once_more_hash_arg && "hash is not idempotent.");
const size_t once_more_hash_slot =
PolicyTraits::apply(HashElement{hash_ref()}, element);
assert(hash_of_slot == once_more_hash_slot &&
"hash is not idempotent.");
const bool once_more_eq =
PolicyTraits::apply(EqualElement<K>{key, eq_ref()}, element);
assert(is_key_equal == once_more_eq && "equality is not idempotent.");
}
assert((!is_key_equal || is_hash_equal) &&
"eq(k1, k2) must imply that hash(k1) == hash(k2). "
"hash/eq functors are inconsistent.");
};
if (is_soo()) {
assert_consistent(/*unused*/ nullptr, soo_slot());
return;
}
auto target = find_first_non_full(common(), hash);
if (!rehash_for_bug_detection &&
ABSL_PREDICT_FALSE(growth_left() == 0 &&
!IsDeleted(control()[target.offset]))) {
size_t old_capacity = capacity();
rehash_and_grow_if_necessary();
// NOTE: It is safe to use `FindFirstNonFullAfterResize`.
// `FindFirstNonFullAfterResize` must be called right after resize.
// `rehash_and_grow_if_necessary` may *not* call `resize`
// and perform `drop_deletes_without_resize` instead. But this
// could happen only on big tables.
// For big tables `FindFirstNonFullAfterResize` will always
// fallback to normal `find_first_non_full`, so it is safe to use it.
target = HashSetResizeHelper::FindFirstNonFullAfterResize(
common(), old_capacity, hash);
}
common().increment_size();
set_growth_left(growth_left() - IsEmpty(control()[target.offset]));
SetCtrl(common(), target.offset, H2(hash), sizeof(slot_type));
common().maybe_increment_generation_on_insert();
infoz().RecordInsert(hash, target.probe_length);
return target.offset;
// We only do validation for small tables so that it's constant time.
if (capacity() > 16) return;
IterateOverFullSlots(common(), slot_array(), assert_consistent);
#endif
}
// Attempts to find `key` in the table; if it isn't found, returns an iterator
// where the value can be inserted into, with the control byte already set to
// `key`'s H2. Returns a bool indicating whether an insertion can take place.
template <class K>
std::pair<iterator, bool> find_or_prepare_insert(const K& key) {
AssertHashEqConsistent(key);
if (is_soo()) return find_or_prepare_insert_soo(key);
return find_or_prepare_insert_non_soo(key);
}
// Constructs the value in the space pointed by the iterator. This only works
// after an unsuccessful find_or_prepare_insert() and before any other
// modifications happen in the raw_hash_set.
//
// PRECONDITION: i is an index returned from find_or_prepare_insert(k), where
// k is the key decomposed from `forward<Args>(args)...`, and the bool
// returned by find_or_prepare_insert(k) was true.
// PRECONDITION: iter was returned from find_or_prepare_insert(k), where k is
// the key decomposed from `forward<Args>(args)...`, and the bool returned by
// find_or_prepare_insert(k) was true.
// POSTCONDITION: *m.iterator_at(i) == value_type(forward<Args>(args)...).
template <class... Args>
void emplace_at(size_t i, Args&&... args) {
construct(slot_array() + i, std::forward<Args>(args)...);
void emplace_at(iterator iter, Args&&... args) {
construct(iter.slot(), std::forward<Args>(args)...);
assert(PolicyTraits::apply(FindElement{*this}, *iterator_at(i)) ==
iterator_at(i) &&
assert(PolicyTraits::apply(FindElement{*this}, *iter) == iter &&
"constructed value does not match the lookup key");
}
@@ -3160,7 +3907,7 @@ class raw_hash_set {
return {control() + i, slot_array() + i, common().generation_ptr()};
}
const_iterator iterator_at(size_t i) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
return {control() + i, slot_array() + i, common().generation_ptr()};
return const_cast<raw_hash_set*>(this)->iterator_at(i);
}
reference unchecked_deref(iterator it) { return it.unchecked_deref(); }
@@ -3178,13 +3925,25 @@ class raw_hash_set {
// side-effect.
//
// See `CapacityToGrowth()`.
size_t growth_left() const { return common().growth_left(); }
void set_growth_left(size_t gl) { return common().set_growth_left(gl); }
size_t growth_left() const {
assert(!is_soo());
return common().growth_left();
}
GrowthInfo& growth_info() {
assert(!is_soo());
return common().growth_info();
}
GrowthInfo growth_info() const {
assert(!is_soo());
return common().growth_info();
}
// Prefetch the heap-allocated memory region to resolve potential TLB and
// cache misses. This is intended to overlap with execution of calculating the
// hash for a key.
void prefetch_heap_block() const {
assert(!is_soo());
#if ABSL_HAVE_BUILTIN(__builtin_prefetch) || defined(__GNUC__)
__builtin_prefetch(control(), 0, 1);
#endif
@@ -3193,11 +3952,31 @@ class raw_hash_set {
CommonFields& common() { return settings_.template get<0>(); }
const CommonFields& common() const { return settings_.template get<0>(); }
ctrl_t* control() const { return common().control(); }
ctrl_t* control() const {
assert(!is_soo());
return common().control();
}
slot_type* slot_array() const {
assert(!is_soo());
return static_cast<slot_type*>(common().slot_array());
}
HashtablezInfoHandle infoz() { return common().infoz(); }
slot_type* soo_slot() {
assert(is_soo());
return static_cast<slot_type*>(common().soo_data());
}
const slot_type* soo_slot() const {
return const_cast<raw_hash_set*>(this)->soo_slot();
}
iterator soo_iterator() {
return {SooControl(), soo_slot(), common().generation_ptr()};
}
const_iterator soo_iterator() const {
return const_cast<raw_hash_set*>(this)->soo_iterator();
}
HashtablezInfoHandle infoz() {
assert(!is_soo());
return common().infoz();
}
hasher& hash_ref() { return settings_.template get<1>(); }
const hasher& hash_ref() const { return settings_.template get<1>(); }
@@ -3208,12 +3987,9 @@ class raw_hash_set {
return settings_.template get<3>();
}
// Make type-specific functions for this type's PolicyFunctions struct.
static size_t hash_slot_fn(void* set, void* slot) {
auto* h = static_cast<raw_hash_set*>(set);
return PolicyTraits::apply(
HashElement{h->hash_ref()},
PolicyTraits::element(static_cast<slot_type*>(slot)));
static const void* get_hash_ref_fn(const CommonFields& common) {
auto* h = reinterpret_cast<const raw_hash_set*>(&common);
return &h->hash_ref();
}
static void transfer_slot_fn(void* set, void* dst, void* src) {
auto* h = static_cast<raw_hash_set*>(set);
@@ -3236,13 +4012,18 @@ class raw_hash_set {
static const PolicyFunctions& GetPolicyFunctions() {
static constexpr PolicyFunctions value = {
sizeof(slot_type),
&raw_hash_set::hash_slot_fn,
// TODO(b/328722020): try to type erase
// for standard layout and alignof(Hash) <= alignof(CommonFields).
std::is_empty<hasher>::value ? &GetHashRefForEmptyHasher
: &raw_hash_set::get_hash_ref_fn,
PolicyTraits::template get_hash_slot_fn<hasher>(),
PolicyTraits::transfer_uses_memcpy()
? TransferRelocatable<sizeof(slot_type)>
: &raw_hash_set::transfer_slot_fn,
(std::is_same<SlotAlloc, std::allocator<slot_type>>::value
? &DeallocateStandard<alignof(slot_type)>
: &raw_hash_set::dealloc_fn),
&raw_hash_set::resize_impl,
};
return value;
}
@@ -3252,22 +4033,78 @@ class raw_hash_set {
// fields that occur after CommonFields.
absl::container_internal::CompressedTuple<CommonFields, hasher, key_equal,
allocator_type>
settings_{CommonFields{}, hasher{}, key_equal{}, allocator_type{}};
settings_{CommonFields::CreateDefault<SooEnabled()>(), hasher{},
key_equal{}, allocator_type{}};
};
// Friend access for free functions in raw_hash_set.h.
struct HashtableFreeFunctionsAccess {
template <class Predicate, typename Set>
static typename Set::size_type EraseIf(Predicate& pred, Set* c) {
if (c->empty()) {
return 0;
}
if (c->is_soo()) {
auto it = c->soo_iterator();
if (!pred(*it)) {
assert(c->size() == 1 && "hash table was modified unexpectedly");
return 0;
}
c->destroy(it.slot());
c->common().set_empty_soo();
return 1;
}
ABSL_ATTRIBUTE_UNUSED const size_t original_size_for_assert = c->size();
size_t num_deleted = 0;
IterateOverFullSlots(
c->common(), c->slot_array(), [&](const ctrl_t* ctrl, auto* slot) {
if (pred(Set::PolicyTraits::element(slot))) {
c->destroy(slot);
EraseMetaOnly(c->common(), static_cast<size_t>(ctrl - c->control()),
sizeof(*slot));
++num_deleted;
}
});
// NOTE: IterateOverFullSlots allow removal of the current element, so we
// verify the size additionally here.
assert(original_size_for_assert - num_deleted == c->size() &&
"hash table was modified unexpectedly");
return num_deleted;
}
template <class Callback, typename Set>
static void ForEach(Callback& cb, Set* c) {
if (c->empty()) {
return;
}
if (c->is_soo()) {
cb(*c->soo_iterator());
return;
}
using ElementTypeWithConstness = decltype(*c->begin());
IterateOverFullSlots(
c->common(), c->slot_array(), [&cb](const ctrl_t*, auto* slot) {
ElementTypeWithConstness& element = Set::PolicyTraits::element(slot);
cb(element);
});
}
};
// Erases all elements that satisfy the predicate `pred` from the container `c`.
template <typename P, typename H, typename E, typename A, typename Predicate>
typename raw_hash_set<P, H, E, A>::size_type EraseIf(
Predicate& pred, raw_hash_set<P, H, E, A>* c) {
const auto initial_size = c->size();
for (auto it = c->begin(), last = c->end(); it != last;) {
if (pred(*it)) {
c->erase(it++);
} else {
++it;
}
}
return initial_size - c->size();
return HashtableFreeFunctionsAccess::EraseIf(pred, c);
}
// Calls `cb` for all elements in the container `c`.
template <typename P, typename H, typename E, typename A, typename Callback>
void ForEach(Callback& cb, raw_hash_set<P, H, E, A>* c) {
return HashtableFreeFunctionsAccess::ForEach(cb, c);
}
template <typename P, typename H, typename E, typename A, typename Callback>
void ForEach(Callback& cb, const raw_hash_set<P, H, E, A>* c) {
return HashtableFreeFunctionsAccess::ForEach(cb, c);
}
namespace hashtable_debug_internal {
@@ -3278,6 +4115,7 @@ struct HashtableDebugAccess<Set, absl::void_t<typename Set::raw_hash_set>> {
static size_t GetNumProbes(const Set& set,
const typename Set::key_type& key) {
if (set.is_soo()) return 0;
size_t num_probes = 0;
size_t hash = set.hash_ref()(key);
auto seq = probe(set.common(), hash);
@@ -3301,7 +4139,8 @@ struct HashtableDebugAccess<Set, absl::void_t<typename Set::raw_hash_set>> {
static size_t AllocatedByteSize(const Set& c) {
size_t capacity = c.capacity();
if (capacity == 0) return 0;
size_t m = c.common().alloc_size(sizeof(Slot), alignof(Slot));
size_t m =
c.is_soo() ? 0 : c.common().alloc_size(sizeof(Slot), alignof(Slot));
size_t per_slot = Traits::space_used(static_cast<const Slot*>(nullptr));
if (per_slot != ~size_t{}) {
@@ -3321,5 +4160,7 @@ ABSL_NAMESPACE_END
} // namespace absl
#undef ABSL_SWISSTABLE_ENABLE_GENERATIONS
#undef ABSL_SWISSTABLE_IGNORE_UNINITIALIZED
#undef ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN
#endif // ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_