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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <arm_neon.h>
#include <cstdint>
#include "mongo/platform/bits.h"
namespace mongo {
namespace unicode {
/**
* A sequence of bytes that can be manipulated using vectorized instructions.
*
* This is specific to the use case in mongo::unicode::String and not intended as a general purpose
* vector class.
*
* This specialization offers acceleration for aarch64.
*/
class ByteVector {
public:
using Native = uint8x16_t;
using Mask = uint16_t;
using Scalar = int8_t;
static const int size = sizeof(Native);
/**
* Sets all bytes to 0.
*/
ByteVector() : _data(vdupq_n_u8(0)) {}
/**
* Sets all bytes to val.
*/
explicit ByteVector(Scalar val) : _data(vdupq_n_u8(val)) {}
/**
* Load a vector from a potentially unaligned location.
*/
static ByteVector load(const void* ptr) {
// This function is documented as taking an unaligned pointer.
return vld1q_u8(reinterpret_cast<const uint8_t*>(ptr));
}
/**
* Store this vector to a potentially unaligned location.
*/
void store(void* ptr) const {
// This function is documented as taking an unaligned pointer.
vst1q_u8(reinterpret_cast<uint8_t*>(ptr), _data);
}
/**
* Returns a bitmask with the high bit from each byte.
*/
Mask maskHigh() const {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wuninitialized"
uint64x1_t p;
// vset_lane_u64 initializes p but the compiler does not understand this and considers p
// uninitialized.
p = vset_lane_u64(0x8040201008040201, p, 0);
#pragma GCC diagnostic pop
uint8x16_t powers = vcombine_u8(vreinterpret_u8_u64(p), vreinterpret_u8_u64(p));
int8x16_t zero8x16 = vdupq_n_s8(0);
uint8x16_t input = vcltq_s8(vreinterpretq_s8_u8(_data), zero8x16);
uint64x2_t mask = vpaddlq_u32(vpaddlq_u16(vpaddlq_u8(vandq_u8(input, powers))));
uint16_t output;
output = ((vgetq_lane_u8(vreinterpretq_u8_u64(mask), 8) << 8) |
(vgetq_lane_u8(vreinterpretq_u8_u64(mask), 0) << 0));
return output;
}
/**
* Returns a bitmask with any bit from each byte.
*
* This operation only makes sense if all bytes are either 0x00 or 0xff, such as the result from
* comparison operations.
*/
Mask maskAny() const {
return maskHigh(); // Other archs may be more efficient here.
}
/**
* Counts zero bits in mask from whichever side corresponds to the lowest memory address.
*/
static uint32_t countInitialZeros(Mask mask) {
return mask == 0 ? size : countTrailingZeros64(mask);
}
/**
* Sets each byte to 0xff if it is ==(EQ), <(LT), or >(GT), otherwise 0x00.
*
* May use either signed or unsigned comparisons since this use case doesn't care about bytes
* with high bit set.
*/
ByteVector compareEQ(Scalar val) const {
return vceqq_u8(_data, ByteVector(val)._data);
}
ByteVector compareLT(Scalar val) const {
return vcltq_u8(_data, ByteVector(val)._data);
}
ByteVector compareGT(Scalar val) const {
return vcgtq_u8(_data, ByteVector(val)._data);
}
ByteVector operator|(ByteVector other) const {
return vorrq_u8(_data, other._data);
}
ByteVector& operator|=(ByteVector other) {
return (*this = (*this | other));
}
ByteVector operator&(ByteVector other) const {
return vandq_u8(_data, other._data);
}
ByteVector& operator&=(ByteVector other) {
return (*this = (*this & other));
}
private:
ByteVector(Native data) : _data(data) {}
Native _data;
};
} // namespace unicode
} // namespace mongo
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