Skip to content

Commit

Permalink
Refactor raw_hash_set deallocation to pass CommonFields instead of pa…
Browse files Browse the repository at this point in the history 
…ssing the results of a bunch of accessors of CommonFields.

Motivation: this makes it easier to refactor CommonFields to be smaller.
PiperOrigin-RevId: 551616928
Change-Id: I3710443fb156537d716944584bea02f945559e99
  • Loading branch information
@ezbr
ezbr authored and Copybara-Service committed Jul 27, 2023
1 parent 8f4fcc6 commit c9c0fd5
Show file tree
Hide file tree
Showing 2 changed files with 53 additions and 51 deletions.
4 changes: 1 addition & 3 deletions absl/container/internal/raw_hash_set.cc
View file
Expand Up @@ -247,9 +247,7 @@ void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,
ResetCtrl(c, policy.slot_size);
c.infoz().RecordStorageChanged(0, c.capacity());
} else {
void* set = &c;
(*policy.dealloc)(set, policy, c.backing_array_start(), c.slot_array(),
c.capacity());
(*policy.dealloc)(c, policy);
c.set_control(EmptyGroup());
c.set_generation_ptr(EmptyGeneration());
c.set_slots(nullptr);
Expand Down
100 changes: 52 additions & 48 deletions absl/container/internal/raw_hash_set.h
View file
Expand Up @@ -909,6 +909,39 @@ using HashSetIteratorGenerationInfo = HashSetIteratorGenerationInfoDisabled;
// 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 the control
// bytes. growth_left is stored at the beginning of the backing array.
inline size_t ControlOffset() { return sizeof(size_t); }

// Returns the number of "cloned control bytes".
//
// This is the number of control bytes that are present both at the beginning
// of the control byte array and at the end, such that we can create a
// `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) {
assert(IsValidCapacity(capacity));
const size_t num_control_bytes = capacity + 1 + NumClonedBytes();
return ControlOffset() + num_control_bytes;
}

// 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) {
assert(IsValidCapacity(capacity));
return (GenerationOffset(capacity) + NumGenerationBytes() + slot_align - 1) &
(~slot_align + 1);
}

// 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) {
return SlotOffset(capacity, slot_align) + capacity * slot_size;
}

// 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.
Expand Down Expand Up @@ -982,6 +1015,11 @@ class CommonFields : public CommonFieldsGenerationInfo {
CommonFieldsGenerationInfo::reset_reserved_growth(reservation, size());
}

// 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);
}

// Returns the number of control bytes set to kDeleted. For testing only.
size_t TombstonesCount() const {
return static_cast<size_t>(
Expand Down Expand Up @@ -1014,13 +1052,6 @@ class CommonFields : public CommonFieldsGenerationInfo {
compressed_tuple_{0u, HashtablezInfoHandle{}};
};

// Returns the number of "cloned control bytes".
//
// This is the number of control bytes that are present both at the beginning
// of the control byte array and at the end, such that we can create a
// `Group::kWidth`-width probe window starting from any control byte.
constexpr size_t NumClonedBytes() { return Group::kWidth - 1; }

template <class Policy, class Hash, class Eq, class Alloc>
class raw_hash_set;

Expand Down Expand Up @@ -1355,32 +1386,6 @@ constexpr size_t BackingArrayAlignment(size_t align_of_slot) {
return (std::max)(align_of_slot, alignof(size_t));
}

// Computes the offset from the start of the backing allocation of the control
// bytes. growth_left is stored at the beginning of the backing array.
inline size_t ControlOffset() { return sizeof(size_t); }

// 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) {
assert(IsValidCapacity(capacity));
const size_t num_control_bytes = capacity + 1 + NumClonedBytes();
return ControlOffset() + num_control_bytes;
}

// 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) {
assert(IsValidCapacity(capacity));
return (GenerationOffset(capacity) + NumGenerationBytes() + slot_align - 1) &
(~slot_align + 1);
}

// 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) {
return SlotOffset(capacity, slot_align) + capacity * slot_size;
}

template <typename Alloc, size_t SizeOfSlot, size_t AlignOfSlot>
ABSL_ATTRIBUTE_NOINLINE void InitializeSlots(CommonFields& c, Alloc alloc) {
assert(c.capacity());
Expand Down Expand Up @@ -1426,9 +1431,8 @@ struct PolicyFunctions {
// Transfer the contents of src_slot to dst_slot.
void (*transfer)(void* set, void* dst_slot, void* src_slot);

// Deallocate the specified backing store which is sized for n slots.
void (*dealloc)(void* set, const PolicyFunctions& policy,
void* backing_array_start, void* slot_array, size_t n);
// Deallocate the backing store from common.
void (*dealloc)(CommonFields& common, const PolicyFunctions& policy);
};

// ClearBackingArray clears the backing array, either modifying it in place,
Expand All @@ -1445,16 +1449,16 @@ void EraseMetaOnly(CommonFields& c, ctrl_t* it, size_t slot_size);
// function body for raw_hash_set instantiations that have the
// same slot alignment.
template <size_t AlignOfSlot>
ABSL_ATTRIBUTE_NOINLINE void DeallocateStandard(void*,
const PolicyFunctions& policy,
void* backing_array_start,
void* slot_array, size_t n) {
ABSL_ATTRIBUTE_NOINLINE void DeallocateStandard(CommonFields& common,
const PolicyFunctions& policy) {
// Unpoison before returning the memory to the allocator.
SanitizerUnpoisonMemoryRegion(slot_array, policy.slot_size * n);
SanitizerUnpoisonMemoryRegion(common.slot_array(),
policy.slot_size * common.capacity());

std::allocator<char> alloc;
Deallocate<BackingArrayAlignment(AlignOfSlot)>(
&alloc, backing_array_start, AllocSize(n, policy.slot_size, AlignOfSlot));
&alloc, common.backing_array_start(),
common.alloc_size(policy.slot_size, AlignOfSlot));
}

// For trivially relocatable types we use memcpy directly. This allows us to
Expand Down Expand Up @@ -2763,16 +2767,16 @@ class raw_hash_set {
static_cast<slot_type*>(src));
}
// Note: dealloc_fn will only be used if we have a non-standard allocator.
static void dealloc_fn(void* set, const PolicyFunctions&,
void* backing_array_start, void* slot_mem, size_t n) {
auto* h = static_cast<raw_hash_set*>(set);
static void dealloc_fn(CommonFields& common, const PolicyFunctions&) {
auto* set = reinterpret_cast<raw_hash_set*>(&common);

// Unpoison before returning the memory to the allocator.
SanitizerUnpoisonMemoryRegion(slot_mem, sizeof(slot_type) * n);
SanitizerUnpoisonMemoryRegion(common.slot_array(),
sizeof(slot_type) * common.capacity());

Deallocate<BackingArrayAlignment(alignof(slot_type))>(
&h->alloc_ref(), backing_array_start,
AllocSize(n, sizeof(slot_type), alignof(slot_type)));
&set->alloc_ref(), common.backing_array_start(),
common.alloc_size(sizeof(slot_type), alignof(slot_type)));
}

static const PolicyFunctions& GetPolicyFunctions() {
Expand Down

0 comments on commit c9c0fd5

Please sign in to comment.