blob: 3d2f0deac54b677f4006079a25dd9ed7a1941543 [file] [log] [blame]
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "bit_vector.h"
#include "allocator.h"
#include "bit_vector-inl.h"
namespace art {
// The number of words necessary to encode bits.
static constexpr uint32_t BitsToWords(uint32_t bits) {
return RoundUp(bits, 32) / 32;
}
// TODO: replace excessive argument defaulting when we are at gcc 4.7
// or later on host with delegating constructor support. Specifically,
// starts_bits and storage_size/storage are mutually exclusive.
BitVector::BitVector(uint32_t start_bits,
bool expandable,
Allocator* allocator,
uint32_t storage_size,
uint32_t* storage)
: storage_(storage),
storage_size_(storage_size),
allocator_(allocator),
expandable_(expandable) {
COMPILE_ASSERT(sizeof(*storage_) == kWordBytes, check_word_bytes);
COMPILE_ASSERT(sizeof(*storage_) * 8u == kWordBits, check_word_bits);
if (storage_ == nullptr) {
storage_size_ = BitsToWords(start_bits);
storage_ = static_cast<uint32_t*>(allocator_->Alloc(storage_size_ * kWordBytes));
}
}
BitVector::~BitVector() {
allocator_->Free(storage_);
}
bool BitVector::SameBitsSet(const BitVector *src) const {
int our_highest = GetHighestBitSet();
int src_highest = src->GetHighestBitSet();
// If the highest bit set is different, we are different.
if (our_highest != src_highest) {
return false;
}
// If the highest bit set is -1, both are cleared, we are the same.
// If the highest bit set is 0, both have a unique bit set, we are the same.
if (our_highest <= 0) {
return true;
}
// Get the highest bit set's cell's index
// No need of highest + 1 here because it can't be 0 so BitsToWords will work here.
int our_highest_index = BitsToWords(our_highest);
// This memcmp is enough: we know that the highest bit set is the same for both:
// - Therefore, min_size goes up to at least that, we are thus comparing at least what we need to, but not less.
// ie. we are comparing all storage cells that could have difference, if both vectors have cells above our_highest_index,
// they are automatically at 0.
return (memcmp(storage_, src->GetRawStorage(), our_highest_index * kWordBytes) == 0);
}
void BitVector::Intersect(const BitVector* src) {
uint32_t src_storage_size = src->storage_size_;
// Get the minimum size between us and source.
uint32_t min_size = (storage_size_ < src_storage_size) ? storage_size_ : src_storage_size;
uint32_t idx;
for (idx = 0; idx < min_size; idx++) {
storage_[idx] &= src->GetRawStorageWord(idx);
}
// Now, due to this being an intersection, there are two possibilities:
// - Either src was larger than us: we don't care, all upper bits would thus be 0.
// - Either we are larger than src: we don't care, all upper bits would have been 0 too.
// So all we need to do is set all remaining bits to 0.
for (; idx < storage_size_; idx++) {
storage_[idx] = 0;
}
}
bool BitVector::Union(const BitVector* src) {
// Get the highest bit to determine how much we need to expand.
int highest_bit = src->GetHighestBitSet();
bool changed = false;
// If src has no bit set, we are done: there is no need for a union with src.
if (highest_bit == -1) {
return changed;
}
// Update src_size to how many cells we actually care about: where the bit is + 1.
uint32_t src_size = BitsToWords(highest_bit + 1);
// Is the storage size smaller than src's?
if (storage_size_ < src_size) {
changed = true;
EnsureSize(highest_bit);
// Paranoid: storage size should be big enough to hold this bit now.
DCHECK_LT(static_cast<uint32_t> (highest_bit), storage_size_ * kWordBits);
}
for (uint32_t idx = 0; idx < src_size; idx++) {
uint32_t existing = storage_[idx];
uint32_t update = existing | src->GetRawStorageWord(idx);
if (existing != update) {
changed = true;
storage_[idx] = update;
}
}
return changed;
}
bool BitVector::UnionIfNotIn(const BitVector* union_with, const BitVector* not_in) {
// Get the highest bit to determine how much we need to expand.
int highest_bit = union_with->GetHighestBitSet();
bool changed = false;
// If src has no bit set, we are done: there is no need for a union with src.
if (highest_bit == -1) {
return changed;
}
// Update union_with_size to how many cells we actually care about: where the bit is + 1.
uint32_t union_with_size = BitsToWords(highest_bit + 1);
// Is the storage size smaller than src's?
if (storage_size_ < union_with_size) {
changed = true;
// Set it to reallocate.
SetBit(highest_bit);
// Paranoid: storage size should be big enough to hold this bit now.
DCHECK_LT(static_cast<uint32_t> (highest_bit), storage_size_ * kWordBits);
}
uint32_t not_in_size = not_in->GetStorageSize();
uint32_t idx = 0;
for (; idx < std::min(not_in_size, union_with_size); idx++) {
uint32_t existing = storage_[idx];
uint32_t update = existing |
(union_with->GetRawStorageWord(idx) & ~not_in->GetRawStorageWord(idx));
if (existing != update) {
changed = true;
storage_[idx] = update;
}
}
for (; idx < union_with_size; idx++) {
uint32_t existing = storage_[idx];
uint32_t update = existing | union_with->GetRawStorageWord(idx);
if (existing != update) {
changed = true;
storage_[idx] = update;
}
}
return changed;
}
void BitVector::Subtract(const BitVector *src) {
uint32_t src_size = src->storage_size_;
// We only need to operate on bytes up to the smaller of the sizes of the two operands.
unsigned int min_size = (storage_size_ > src_size) ? src_size : storage_size_;
// Difference until max, we know both accept it:
// There is no need to do more:
// If we are bigger than src, the upper bits are unchanged.
// If we are smaller than src, the non-existant upper bits are 0 and thus can't get subtracted.
for (uint32_t idx = 0; idx < min_size; idx++) {
storage_[idx] &= (~(src->GetRawStorageWord(idx)));
}
}
uint32_t BitVector::NumSetBits() const {
uint32_t count = 0;
for (uint32_t word = 0; word < storage_size_; word++) {
count += POPCOUNT(storage_[word]);
}
return count;
}
uint32_t BitVector::NumSetBits(uint32_t end) const {
DCHECK_LE(end, storage_size_ * kWordBits);
return NumSetBits(storage_, end);
}
void BitVector::SetInitialBits(uint32_t num_bits) {
// If num_bits is 0, clear everything.
if (num_bits == 0) {
ClearAllBits();
return;
}
// Set the highest bit we want to set to get the BitVector allocated if need be.
SetBit(num_bits - 1);
uint32_t idx;
// We can set every storage element with -1.
for (idx = 0; idx < WordIndex(num_bits); idx++) {
storage_[idx] = -1;
}
// Handle the potentially last few bits.
uint32_t rem_num_bits = num_bits & 0x1f;
if (rem_num_bits != 0) {
storage_[idx] = (1 << rem_num_bits) - 1;
++idx;
}
// Now set the upper ones to 0.
for (; idx < storage_size_; idx++) {
storage_[idx] = 0;
}
}
int BitVector::GetHighestBitSet() const {
unsigned int max = storage_size_;
for (int idx = max - 1; idx >= 0; idx--) {
// If not 0, we have more work: check the bits.
uint32_t value = storage_[idx];
if (value != 0) {
// Return highest bit set in value plus bits from previous storage indexes.
return 31 - CLZ(value) + (idx * kWordBits);
}
}
// All zero, therefore return -1.
return -1;
}
void BitVector::Copy(const BitVector *src) {
// Get highest bit set, we only need to copy till then.
int highest_bit = src->GetHighestBitSet();
// If nothing is set, clear everything.
if (highest_bit == -1) {
ClearAllBits();
return;
}
// Set upper bit to ensure right size before copy.
SetBit(highest_bit);
// Now set until highest bit's storage.
uint32_t size = 1 + (highest_bit / kWordBits);
memcpy(storage_, src->GetRawStorage(), kWordBytes * size);
// Set upper bits to 0.
uint32_t left = storage_size_ - size;
if (left > 0) {
memset(storage_ + size, 0, kWordBytes * left);
}
}
uint32_t BitVector::NumSetBits(const uint32_t* storage, uint32_t end) {
uint32_t word_end = WordIndex(end);
uint32_t partial_word_bits = end & 0x1f;
uint32_t count = 0u;
for (uint32_t word = 0u; word < word_end; word++) {
count += POPCOUNT(storage[word]);
}
if (partial_word_bits != 0u) {
count += POPCOUNT(storage[word_end] & ~(0xffffffffu << partial_word_bits));
}
return count;
}
void BitVector::Dump(std::ostream& os, const char *prefix) const {
std::ostringstream buffer;
DumpHelper(prefix, buffer);
os << buffer.str() << std::endl;
}
void BitVector::DumpHelper(const char* prefix, std::ostringstream& buffer) const {
// Initialize it.
if (prefix != nullptr) {
buffer << prefix;
}
buffer << '(';
for (size_t i = 0; i < storage_size_ * kWordBits; i++) {
buffer << IsBitSet(i);
}
buffer << ')';
}
void BitVector::EnsureSize(uint32_t idx) {
if (idx >= storage_size_ * kWordBits) {
DCHECK(expandable_) << "Attempted to expand a non-expandable bitmap to position " << idx;
/* Round up to word boundaries for "idx+1" bits */
uint32_t new_size = BitsToWords(idx + 1);
DCHECK_GT(new_size, storage_size_);
uint32_t *new_storage =
static_cast<uint32_t*>(allocator_->Alloc(new_size * kWordBytes));
memcpy(new_storage, storage_, storage_size_ * kWordBytes);
// Zero out the new storage words.
memset(&new_storage[storage_size_], 0, (new_size - storage_size_) * kWordBytes);
// TOTO: collect stats on space wasted because of resize.
storage_ = new_storage;
storage_size_ = new_size;
}
}
} // namespace art