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//===- llvm/ADT/SmallPtrSet.cpp - 'Normally small' pointer set ------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the SmallPtrSet class. See SmallPtrSet.h for an
// overview of the algorithm.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/MemAlloc.h"
#include <algorithm>
#include <cassert>
#include <cstdlib>
using namespace llvm;
void SmallPtrSetImplBase::shrink_and_clear() {
assert(!isSmall() && "Can't shrink a small set!");
free(CurArray);
// Reduce the number of buckets.
unsigned Size = size();
CurArraySize = Size > 16 ? 1 << (Log2_32_Ceil(Size) + 1) : 32;
NumNonEmpty = NumTombstones = 0;
// Install the new array. Clear all the buckets to empty.
CurArray = (const void**)safe_malloc(sizeof(void*) * CurArraySize);
memset(CurArray, -1, CurArraySize*sizeof(void*));
}
std::pair<const void *const *, bool>
SmallPtrSetImplBase::insert_imp_big(const void *Ptr) {
if (LLVM_UNLIKELY(size() * 4 >= CurArraySize * 3)) {
// If more than 3/4 of the array is full, grow.
Grow(CurArraySize < 64 ? 128 : CurArraySize * 2);
} else if (LLVM_UNLIKELY(CurArraySize - NumNonEmpty < CurArraySize / 8)) {
// If fewer of 1/8 of the array is empty (meaning that many are filled with
// tombstones), rehash.
Grow(CurArraySize);
}
// Okay, we know we have space. Find a hash bucket.
const void **Bucket = const_cast<const void**>(FindBucketFor(Ptr));
if (*Bucket == Ptr)
return std::make_pair(Bucket, false); // Already inserted, good.
// Otherwise, insert it!
if (*Bucket == getTombstoneMarker())
--NumTombstones;
else
++NumNonEmpty; // Track density.
*Bucket = Ptr;
incrementEpoch();
return std::make_pair(Bucket, true);
}
const void * const *SmallPtrSetImplBase::FindBucketFor(const void *Ptr) const {
unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1);
unsigned ArraySize = CurArraySize;
unsigned ProbeAmt = 1;
const void *const *Array = CurArray;
const void *const *Tombstone = nullptr;
while (true) {
// If we found an empty bucket, the pointer doesn't exist in the set.
// Return a tombstone if we've seen one so far, or the empty bucket if
// not.
if (LLVM_LIKELY(Array[Bucket] == getEmptyMarker()))
return Tombstone ? Tombstone : Array+Bucket;
// Found Ptr's bucket?
if (LLVM_LIKELY(Array[Bucket] == Ptr))
return Array+Bucket;
// If this is a tombstone, remember it. If Ptr ends up not in the set, we
// prefer to return it than something that would require more probing.
if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
Tombstone = Array+Bucket; // Remember the first tombstone found.
// It's a hash collision or a tombstone. Reprobe.
Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
}
}
/// Grow - Allocate a larger backing store for the buckets and move it over.
///
void SmallPtrSetImplBase::Grow(unsigned NewSize) {
const void **OldBuckets = CurArray;
const void **OldEnd = EndPointer();
bool WasSmall = isSmall();
// Install the new array. Clear all the buckets to empty.
const void **NewBuckets = (const void**) safe_malloc(sizeof(void*) * NewSize);
// Reset member only if memory was allocated successfully
CurArray = NewBuckets;
CurArraySize = NewSize;
memset(CurArray, -1, NewSize*sizeof(void*));
// Copy over all valid entries.
for (const void **BucketPtr = OldBuckets; BucketPtr != OldEnd; ++BucketPtr) {
// Copy over the element if it is valid.
const void *Elt = *BucketPtr;
if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
*const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
}
if (!WasSmall)
free(OldBuckets);
NumNonEmpty -= NumTombstones;
NumTombstones = 0;
}
SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
const SmallPtrSetImplBase &that) {
SmallArray = SmallStorage;
// If we're becoming small, prepare to insert into our stack space
if (that.isSmall()) {
CurArray = SmallArray;
// Otherwise, allocate new heap space (unless we were the same size)
} else {
CurArray = (const void**)safe_malloc(sizeof(void*) * that.CurArraySize);
}
// Copy over the that array.
CopyHelper(that);
}
SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
unsigned SmallSize,
SmallPtrSetImplBase &&that) {
SmallArray = SmallStorage;
MoveHelper(SmallSize, std::move(that));
}
void SmallPtrSetImplBase::CopyFrom(const SmallPtrSetImplBase &RHS) {
assert(&RHS != this && "Self-copy should be handled by the caller.");
if (isSmall() && RHS.isSmall())
assert(CurArraySize == RHS.CurArraySize &&
"Cannot assign sets with different small sizes");
// If we're becoming small, prepare to insert into our stack space
if (RHS.isSmall()) {
if (!isSmall())
free(CurArray);
CurArray = SmallArray;
// Otherwise, allocate new heap space (unless we were the same size)
} else if (CurArraySize != RHS.CurArraySize) {
if (isSmall())
CurArray = (const void**)safe_malloc(sizeof(void*) * RHS.CurArraySize);
else {
const void **T = (const void**)safe_realloc(CurArray,
sizeof(void*) * RHS.CurArraySize);
CurArray = T;
}
}
CopyHelper(RHS);
}
void SmallPtrSetImplBase::CopyHelper(const SmallPtrSetImplBase &RHS) {
// Copy over the new array size
CurArraySize = RHS.CurArraySize;
// Copy over the contents from the other set
std::copy(RHS.CurArray, RHS.EndPointer(), CurArray);
NumNonEmpty = RHS.NumNonEmpty;
NumTombstones = RHS.NumTombstones;
}
void SmallPtrSetImplBase::MoveFrom(unsigned SmallSize,
SmallPtrSetImplBase &&RHS) {
if (!isSmall())
free(CurArray);
MoveHelper(SmallSize, std::move(RHS));
}
void SmallPtrSetImplBase::MoveHelper(unsigned SmallSize,
SmallPtrSetImplBase &&RHS) {
assert(&RHS != this && "Self-move should be handled by the caller.");
if (RHS.isSmall()) {
// Copy a small RHS rather than moving.
CurArray = SmallArray;
std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, CurArray);
} else {
CurArray = RHS.CurArray;
RHS.CurArray = RHS.SmallArray;
}
// Copy the rest of the trivial members.
CurArraySize = RHS.CurArraySize;
NumNonEmpty = RHS.NumNonEmpty;
NumTombstones = RHS.NumTombstones;
// Make the RHS small and empty.
RHS.CurArraySize = SmallSize;
assert(RHS.CurArray == RHS.SmallArray);
RHS.NumNonEmpty = 0;
RHS.NumTombstones = 0;
}
void SmallPtrSetImplBase::swap(SmallPtrSetImplBase &RHS) {
if (this == &RHS) return;
// We can only avoid copying elements if neither set is small.
if (!this->isSmall() && !RHS.isSmall()) {
std::swap(this->CurArray, RHS.CurArray);
std::swap(this->CurArraySize, RHS.CurArraySize);
std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
std::swap(this->NumTombstones, RHS.NumTombstones);
return;
}
// FIXME: From here on we assume that both sets have the same small size.
// If only RHS is small, copy the small elements into LHS and move the pointer
// from LHS to RHS.
if (!this->isSmall() && RHS.isSmall()) {
assert(RHS.CurArray == RHS.SmallArray);
std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, this->SmallArray);
std::swap(RHS.CurArraySize, this->CurArraySize);
std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
std::swap(this->NumTombstones, RHS.NumTombstones);
RHS.CurArray = this->CurArray;
this->CurArray = this->SmallArray;
return;
}
// If only LHS is small, copy the small elements into RHS and move the pointer
// from RHS to LHS.
if (this->isSmall() && !RHS.isSmall()) {
assert(this->CurArray == this->SmallArray);
std::copy(this->CurArray, this->CurArray + this->NumNonEmpty,
RHS.SmallArray);
std::swap(RHS.CurArraySize, this->CurArraySize);
std::swap(RHS.NumNonEmpty, this->NumNonEmpty);
std::swap(RHS.NumTombstones, this->NumTombstones);
this->CurArray = RHS.CurArray;
RHS.CurArray = RHS.SmallArray;
return;
}
// Both a small, just swap the small elements.
assert(this->isSmall() && RHS.isSmall());
unsigned MinNonEmpty = std::min(this->NumNonEmpty, RHS.NumNonEmpty);
std::swap_ranges(this->SmallArray, this->SmallArray + MinNonEmpty,
RHS.SmallArray);
if (this->NumNonEmpty > MinNonEmpty) {
std::copy(this->SmallArray + MinNonEmpty,
this->SmallArray + this->NumNonEmpty,
RHS.SmallArray + MinNonEmpty);
} else {
std::copy(RHS.SmallArray + MinNonEmpty, RHS.SmallArray + RHS.NumNonEmpty,
this->SmallArray + MinNonEmpty);
}
assert(this->CurArraySize == RHS.CurArraySize);
std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
std::swap(this->NumTombstones, RHS.NumTombstones);
}