d43ad8738c
The radix tree code will need the code to find 8-bit value in an array of some fixed size, so here are the helpers. Those that allow for SIMD implementations are such for x86_64 TODO: Add aarch64 Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
74 lines
2.1 KiB
C++
74 lines
2.1 KiB
C++
/*
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* Copyright (C) 2020 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <cstdint>
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#include <limits>
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namespace utils {
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static constexpr int64_t simple_key_unused_value = std::numeric_limits<int64_t>::min();
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/*
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* array_search_gt(value, array, capacity, size)
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*
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* Returns the index of the first element in the array that's greater
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* than the given value.
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*
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* To accomodate the single-instruction-multiple-data variant, observe
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* the following:
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* - capacity must be a multiple of 4
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* - any items with indexes in [size, capacity) must be initialized
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* to std::numeric_limits<int64_t>::min()
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*/
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int array_search_gt(int64_t val, const int64_t* array, const int capacity, const int size);
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static inline unsigned array_search_4_eq(uint8_t val, const uint8_t* array) {
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// Unrolled loop is few %s faster
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if (array[0] == val) {
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return 0;
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} else if (array[1] == val) {
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return 1;
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} else if (array[2] == val) {
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return 2;
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} else if (array[3] == val) {
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return 3;
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} else {
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return 4;
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}
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}
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static inline unsigned array_search_8_eq(uint8_t val, const uint8_t* array) {
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for (unsigned i = 0; i < 8; i++) {
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if (array[i] == val) {
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return i;
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}
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}
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return 8;
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}
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unsigned array_search_16_eq(uint8_t val, const uint8_t* array);
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unsigned array_search_32_eq(uint8_t val, const uint8_t* array);
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unsigned array_search_x32_eq(uint8_t val, const uint8_t* array, int nr);
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}
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