mirror of
https://github.com/matrix-construct/construct
synced 2024-06-26 22:08:20 +02:00
198 lines
4 KiB
C++
198 lines
4 KiB
C++
// The Construct
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//
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// Copyright (C) The Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2020 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_SIMD_LZCNT_H
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// This suite is for counting leading zero bits of a word T. It is not for
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// per-lane clz'ing; for this reason all overloads are explicitly instantiated
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// and optimal conversions are performed.
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namespace ircd::simd
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{
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template<class T> uint _lzcnt(const T) noexcept;
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template<class T> uint lzcnt(const T) noexcept = delete;
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template<> uint lzcnt(const u512x1) noexcept;
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template<> uint lzcnt(const u256x1) noexcept;
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template<> uint lzcnt(const u128x1) noexcept;
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template<> uint lzcnt(const u64x8) noexcept;
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template<> uint lzcnt(const u64x4) noexcept;
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template<> uint lzcnt(const u64x2) noexcept;
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template<> uint lzcnt(const u32x16) noexcept;
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template<> uint lzcnt(const u32x8) noexcept;
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template<> uint lzcnt(const u32x4) noexcept;
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template<> uint lzcnt(const u16x32) noexcept;
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template<> uint lzcnt(const u16x16) noexcept;
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template<> uint lzcnt(const u16x8) noexcept;
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template<> uint lzcnt(const u8x64) noexcept;
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template<> uint lzcnt(const u8x32) noexcept;
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template<> uint lzcnt(const u8x16) noexcept;
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}
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/// Convenience template. Unfortunately this drops to scalar until specific
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/// targets and specializations are created. The behavior can differ among
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/// platforms; we make use of lzcnt if available otherwise we account for bsr.
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template<class T>
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[[gnu::always_inline]]
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inline uint
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ircd::simd::_lzcnt(const T a)
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noexcept
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{
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uint ret(0);
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for(uint i(0); i < lanes<T>(); ++i)
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{
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const auto mask
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{
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boolmask(uint(ret == sizeof_lane<T>() * 8 * i))
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};
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if constexpr(sizeof_lane<T>() <= sizeof(u8))
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ret += mask & __builtin_clz((uint(a[i]) << 24) | 0x00ffffff);
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else if constexpr(sizeof_lane<T>() <= sizeof(u16))
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ret += mask & __builtin_clz((uint(__builtin_bswap16(a[i])) << 16) | 0x0000ffffU);
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else if constexpr(sizeof_lane<T>() <= sizeof(u32))
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ret += mask &
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(
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(boolmask(uint(a[i] != 0)) & __builtin_clz(__builtin_bswap32(a[i])))
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| (boolmask(uint(a[i] == 0)) & 32U)
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);
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else if constexpr(sizeof_lane<T>() <= sizeof(u64))
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ret += mask &
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(
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(boolmask(uint(a[i] != 0)) & __builtin_clzl(__builtin_bswap64(a[i])))
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| (boolmask(uint(a[i] == 0)) & 64U)
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);
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}
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return ret;
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u512x1 a)
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noexcept
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{
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return _lzcnt(u64x8(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u256x1 a)
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noexcept
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{
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return _lzcnt(u64x4(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u128x1 a)
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noexcept
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{
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return _lzcnt(u64x2(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u64x8 a)
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noexcept
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{
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return _lzcnt(u64x8(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u64x4 a)
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noexcept
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{
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return _lzcnt(u64x4(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u64x2 a)
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noexcept
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{
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return _lzcnt(u64x2(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u32x16 a)
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noexcept
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{
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return _lzcnt(u64x8(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u32x8 a)
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noexcept
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{
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return _lzcnt(u64x4(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u32x4 a)
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noexcept
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{
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return _lzcnt(u64x2(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u16x32 a)
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noexcept
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{
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return _lzcnt(u64x8(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u16x16 a)
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noexcept
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{
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return _lzcnt(u64x4(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u16x8 a)
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noexcept
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{
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return _lzcnt(u64x2(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u8x64 a)
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noexcept
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{
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return _lzcnt(u64x8(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u8x32 a)
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noexcept
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{
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return _lzcnt(u64x4(a));
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}
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template<>
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inline uint
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ircd::simd::lzcnt(const u8x16 a)
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noexcept
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{
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return _lzcnt(u64x2(a));
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}
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