0bd90b5465
This is used when generating the Barrett reduction tables, and also when applying the Barrett reduction at runtime, so we need it to be constexpr friendly.
70 lines
1.4 KiB
C++
70 lines
1.4 KiB
C++
/*
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* Copyright (C) 2018-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*
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*/
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#pragma once
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#include <cstdint>
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#include <type_traits>
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inline
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constexpr uint64_t clmul_u32_constexpr(uint32_t p1, uint32_t p2) {
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uint64_t result = 0;
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for (unsigned i = 0; i < 32; ++i) {
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result ^= (((p1 >> i) & 1) * uint64_t(p2)) << i;
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}
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return result;
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}
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// returns the low half of the result
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inline
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constexpr uint64_t clmul_u64_low_constexpr(uint64_t p1, uint64_t p2) {
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uint64_t result = 0;
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for (unsigned i = 0; i < 64; ++i) {
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result ^= (((p1 >> i) & 1) * p2) << i;
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}
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return result;
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}
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#if defined(__x86_64__) || defined(__i386__)
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#include <wmmintrin.h>
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#include <smmintrin.h>
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// Performs a carry-less multiplication of two integers.
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inline
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uint64_t clmul_u32(uint32_t p1, uint32_t p2) {
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__m128i p = _mm_set_epi64x(p1, p2);
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p = _mm_clmulepi64_si128(p, p, 0x01);
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return _mm_extract_epi64(p, 0);
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}
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constexpr
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inline
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uint64_t clmul(uint32_t p1, uint32_t p2) {
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return std::is_constant_evaluated() ? clmul_u32_constexpr(p1, p2) : clmul_u32(p1, p2);
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}
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#elif defined(__aarch64__)
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#include <arm_neon.h>
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// Performs a carry-less multiplication of two integers.
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inline
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uint64_t clmul_u32(uint32_t p1, uint32_t p2) {
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return vmull_p64(p1, p2);
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}
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constexpr
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inline
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uint64_t clmul(uint32_t p1, uint32_t p2) {
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return std::is_constant_evaluated() ? clmul_u32_constexpr(p1, p2) : clmul_u32(p1, p2);
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}
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#endif
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