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fix: Bitwise operations on signed integers (Part-2) #12238

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fix: Bitwise operations on signed integers (Part-2) #12238

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e16aaf7
fix: Bitwise operations on signed integers (Part-2)
anandamideShakyan Jan 29, 2025
c7c6342
fix: Bitwise operations on signed integers (Part-2)
anandamideShakyan Jan 29, 2025
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66 changes: 37 additions & 29 deletions velox/common/hyperloglog/DenseHll.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,8 @@
*/
#include "velox/common/hyperloglog/DenseHll.h"

#include <sys/stat.h>

#include <exception>
#include <sstream>
#include "velox/common/base/IOUtils.h"
Expand All @@ -24,8 +26,8 @@
namespace facebook::velox::common::hll {
namespace {
const int kBitsPerBucket = 4;
const int8_t kMaxDelta = (1 << kBitsPerBucket) - 1;
const int8_t kBucketMask = (1 << kBitsPerBucket) - 1;
const int8_t kMaxDelta = (1u << kBitsPerBucket) - 1;
const int8_t kBucketMask = (1u << kBitsPerBucket) - 1;
constexpr double kLinearCountingMinEmptyBuckets = 0.4;

/// Buckets are stored in a byte array. Each byte stored 2 buckets, 4 bits each.
Expand All @@ -34,7 +36,7 @@ constexpr double kLinearCountingMinEmptyBuckets = 0.4;
/// the byte for a given bucket, e.g. 0 for even and 4 for odd buckets.
int8_t shiftForBucket(int32_t index) {
// ((1 - bucket) % 2) * kBitsPerBucket
return ((~index) & 1) << 2;
return ((~static_cast<uint32_t>(index)) & 1) << 2;
}

/// Returns the value of alpha constant. See "Practical considerations" section
Expand All @@ -48,7 +50,7 @@ double alpha(int32_t indexBitLength) {
case 6:
return 0.709;
default:
return (0.7213 / (1 + 1.079 / (1 << indexBitLength)));
return (0.7213 / (1 + 1.079 / (1u << indexBitLength)));
}
}

Expand Down Expand Up @@ -132,7 +134,7 @@ void DenseHll::initialize(int8_t indexBitLength) {

indexBitLength_ = indexBitLength;

auto numBuckets = 1 << indexBitLength;
auto numBuckets = 1u << indexBitLength;
baselineCount_ = numBuckets;
deltas_.resize(numBuckets * kBitsPerBucket / 8);
}
Expand Down Expand Up @@ -186,8 +188,8 @@ struct DenseHllView {
const int8_t* overflowValues;

int8_t getDelta(int32_t index) const {
int slot = index >> 1;
return (deltas[slot] >> shiftForBucket(index)) & kBucketMask;
unsigned int slot = static_cast<uint32_t>(index) >> 1;
return (static_cast<uint32_t>(deltas[slot]) >> shiftForBucket(index)) & kBucketMask;
}

int8_t getValue(int32_t index) const {
Expand All @@ -203,7 +205,7 @@ struct DenseHllView {
};

int64_t cardinalityImpl(const DenseHllView& hll) {
auto numBuckets = 1 << hll.indexBitLength;
auto numBuckets = 1u << hll.indexBitLength;

int32_t baselineCount = 0;
for (int i = 0; i < numBuckets; i++) {
Expand All @@ -222,7 +224,7 @@ int64_t cardinalityImpl(const DenseHllView& hll) {
double sum = 0;
for (int i = 0; i < numBuckets; i++) {
int value = hll.getValue(i);
sum += 1.0 / (1L << value);
sum += 1.0 / (1UL << value);
}

double estimate = (alpha(hll.indexBitLength) * numBuckets * numBuckets) / sum;
Expand All @@ -240,7 +242,7 @@ DenseHllView deserialize(const char* serialized) {
auto indexBitLength = stream.read<int8_t>();
auto baseline = stream.read<int8_t>();

auto numBuckets = 1 << indexBitLength;
auto numBuckets = 1u << indexBitLength;
// next numBuckets / 2 bytes are deltas
const int8_t* deltas = stream.read<int8_t>(numBuckets / 2);

Expand Down Expand Up @@ -279,20 +281,20 @@ int64_t DenseHll::cardinality(const char* serialized) {
}

int8_t DenseHll::getDelta(int32_t index) const {
int slot = index >> 1;
unsigned int slot = static_cast<uint32_t>(index) >> 1;
return (deltas_[slot] >> shiftForBucket(index)) & kBucketMask;
}

void DenseHll::setDelta(int32_t index, int8_t value) {
int slot = index >> 1;
unsigned int slot = static_cast<uint32_t>(index) >> 1;

// Clear the old value.
int8_t clearMask = static_cast<int8_t>(kBucketMask << shiftForBucket(index));
deltas_[slot] &= ~clearMask;
int8_t clearMask = static_cast<int8_t>(static_cast<uint8_t>(kBucketMask) << shiftForBucket(index));
deltas_[slot] = static_cast<uint8_t>(deltas_[slot]) & ~static_cast<uint8_t>(clearMask);

// Set the new value.
int8_t setMask = static_cast<int8_t>(value << shiftForBucket(index));
deltas_[slot] |= setMask;
int8_t setMask = static_cast<int8_t>(static_cast<uint8_t>(value) << shiftForBucket(index));
deltas_[slot] |= static_cast<uint8_t>(deltas_[slot]) | static_cast<uint8_t>(setMask);
}

int8_t DenseHll::getOverflow(int32_t index) const {
Expand All @@ -310,7 +312,7 @@ int DenseHll::findOverflowEntry(int32_t index) const {
}

void DenseHll::adjustBaselineIfNeeded() {
auto numBuckets = 1 << indexBitLength_;
auto numBuckets = 1u << indexBitLength_;

while (baselineCount_ == 0) {
baseline_++;
Expand Down Expand Up @@ -389,7 +391,7 @@ int32_t DenseHll::serializedSize() const {
return 1 /* type + version */
+ 1 /* indexBitLength */
+ 1 /* baseline */
+ (1 << indexBitLength_) / 2 /* buckets */
+ (1u << indexBitLength_) / 2 /* buckets */
+ 2 /* overflow bucket count */
+ 2 * overflows_ /* overflow bucket indexes */
+ overflows_ /* overflow bucket values */;
Expand Down Expand Up @@ -426,7 +428,7 @@ bool DenseHll::canDeserialize(const char* input, int size) {
return false;
}

auto numBuckets = 1 << indexBitLength;
auto numBuckets = 1u << indexBitLength;
const int8_t* deltas = stream.read<int8_t>(numBuckets / 2);
auto overflows = stream.read<int16_t>();

Expand Down Expand Up @@ -471,7 +473,7 @@ int32_t DenseHll::estimateInMemorySize(int8_t indexBitLength) {
// Note: we don't take into account overflow entries since their number can
// vary.
return sizeof(indexBitLength_) + sizeof(baseline_) + sizeof(baselineCount_) +
(1 << indexBitLength) / 2;
(1u << indexBitLength) / 2;
}

void DenseHll::serialize(char* output) {
Expand Down Expand Up @@ -500,7 +502,7 @@ DenseHll::DenseHll(const char* serialized, HashStringAllocator* allocator)
initialize(hll.indexBitLength);
baseline_ = hll.baseline;

auto numBuckets = 1 << indexBitLength_;
auto numBuckets = 1u << indexBitLength_;
std::copy(hll.deltas, hll.deltas + numBuckets / 2, deltas_.data());

overflows_ = hll.overflows;
Expand Down Expand Up @@ -553,7 +555,7 @@ void DenseHll::mergeWith(const char* serialized) {

auto baseline = stream.read<int8_t>();

auto numBuckets = 1 << indexBitLength_;
auto numBuckets = 1u << indexBitLength_;
auto deltas = stream.read<int8_t>(numBuckets / 2);
auto overflows = stream.read<int16_t>();
auto overflowBuckets = overflows ? stream.read<uint16_t>(overflows) : nullptr;
Expand Down Expand Up @@ -720,7 +722,9 @@ int32_t DenseHll::mergeWithSimd(const HllView& other, int8_t newBaseline) {

// Store newDelta in deltas_[deltaIndex].
auto slot1 = deltas_[deltaIndex];
deltas_[deltaIndex] = (newDelta << 4) | (slot1 & kBucketMask);
uint8_t highNibble = static_cast<uint8_t>(newDelta) << 4;
uint8_t lowNibble = static_cast<uint8_t>(slot1) & static_cast<uint8_t>(kBucketMask);
deltas_[deltaIndex] = deltas_[deltaIndex] = highNibble | lowNibble;
});
}

Expand All @@ -742,8 +746,10 @@ int32_t DenseHll::mergeWithSimd(const HllView& other, int8_t newBaseline) {
}

// Store newDelta.
auto slot1 = deltas_[deltaIndex];
deltas_[deltaIndex] = (((slot1 >> 4) & kBucketMask) << 4) | newDelta;
auto slot1 = static_cast<uint8_t>(deltas_[deltaIndex]);
uint8_t upperBits = (slot1 >> 4) & static_cast<uint8_t>(kBucketMask);
uint8_t shiftedUpperBits = upperBits << 4;
deltas_[deltaIndex] = shiftedUpperBits | static_cast<uint8_t>(newDelta);
});
}
}
Expand All @@ -762,8 +768,10 @@ int32_t DenseHll::mergeWithScalar(const HllView& other, int8_t newBaseline) {
int8_t slot2 = other.deltas[i];

for (int shift = 4; shift >= 0; shift -= 4) {
int8_t delta1 = (slot1 >> shift) & kBucketMask;
int8_t delta2 = (slot2 >> shift) & kBucketMask;
uint8_t maskedSlot1 = static_cast<uint8_t>(slot1) >> shift;
uint8_t maskedSlot2 = static_cast<uint8_t>(slot2) >> shift;
int8_t delta1 = maskedSlot1 & static_cast<uint8_t>(kBucketMask);
int8_t delta2 = maskedSlot2 & static_cast<uint8_t>(kBucketMask);

auto [newValue, overflowEntry] =
computeNewValue(delta1, delta2, bucket, other);
Expand All @@ -776,8 +784,8 @@ int32_t DenseHll::mergeWithScalar(const HllView& other, int8_t newBaseline) {

newDelta = updateOverflow(bucket, overflowEntry, newDelta);

newSlot <<= 4;
newSlot |= newDelta;
newSlot = static_cast<uint32_t>(newSlot) << 4;
newSlot = static_cast<uint32_t>(newSlot) | static_cast<uint32_t>(newDelta);
bucket++;
}

Expand Down
6 changes: 3 additions & 3 deletions velox/common/hyperloglog/SparseHll.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@ inline uint32_t decodeIndex(uint32_t entry) {
}

inline uint32_t decodeValue(uint32_t entry) {
return entry & ((1 << kValueBitLength) - 1);
return entry & ((1u << kValueBitLength) - 1);
}

int searchIndex(
Expand All @@ -41,7 +41,7 @@ int searchIndex(
int high = entries.size() - 1;

while (low <= high) {
int middle = (low + high) >> 1;
int middle = static_cast<uint32_t>(low + high) >> 1;

auto middleIndex = decodeIndex(entries[middle]);

Expand Down Expand Up @@ -93,7 +93,7 @@ int64_t SparseHll::cardinality() const {
// 2^kIndexBitLength buckets available due to the fact that we're
// recording the raw leading kIndexBitLength of the hash. This produces
// much better precision while in the sparse regime.
static const int kTotalBuckets = 1 << kIndexBitLength;
static const int kTotalBuckets = 1u << kIndexBitLength;

int zeroBuckets = kTotalBuckets - entries_.size();
return std::round(linearCounting(zeroBuckets, kTotalBuckets));
Expand Down