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208 lines
6.4 KiB
C++
208 lines
6.4 KiB
C++
#pragma once
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#include <cstdint>
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#if defined(__SSE2__)
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#include <emmintrin.h>
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#endif
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#if defined(__SSE4_2__)
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#include <nmmintrin.h>
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#endif
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/** find_first_symbols<c1, c2, ...>(begin, end):
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*
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* Allow to search for next character from the set of 'symbols...' in a string.
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* It is similar to 'strpbrk', 'strcspn' (and 'strchr', 'memchr' in the case of one symbol and '\0'),
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* but with the following differencies:
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* - works with any memory ranges, including containing zero bytes;
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* - doesn't require terminating zero byte: end of memory range is passed explicitly;
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* - if not found, returns pointer to end instead of NULL;
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* - maximum number of symbols to search is 16.
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*
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* Uses SSE 2 in case of small number of symbols for search and SSE 4.2 in the case of large number of symbols,
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* that have more than 2x performance advantage over trivial loop
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* in the case of parsing tab-separated dump with (probably escaped) string fields.
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* In the case of parsing tab separated dump with short strings, there is no performance degradation over trivial loop.
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*
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* Note: the optimal threshold to choose between SSE 2 and SSE 4.2 may depend on CPU model.
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*
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* find_last_symbols_or_null<c1, c2, ...>(begin, end):
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*
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* Allow to search for the last matching character in a string.
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* If no such characters, returns nullptr.
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*/
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namespace detail
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{
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template <char s0>
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inline bool is_in(char x)
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{
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return x == s0;
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}
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template <char s0, char s1, char... tail>
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inline bool is_in(char x)
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{
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return x == s0 || is_in<s1, tail...>(x);
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}
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#if defined(__SSE2__)
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template <char s0>
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inline __m128i mm_is_in(__m128i bytes)
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{
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__m128i eq0 = _mm_cmpeq_epi8(bytes, _mm_set1_epi8(s0));
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return eq0;
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}
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template <char s0, char s1, char... tail>
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inline __m128i mm_is_in(__m128i bytes)
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{
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__m128i eq0 = _mm_cmpeq_epi8(bytes, _mm_set1_epi8(s0));
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__m128i eq = mm_is_in<s1, tail...>(bytes);
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return _mm_or_si128(eq0, eq);
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}
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#endif
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template <char... symbols>
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inline const char * find_first_symbols_sse2(const char * begin, const char * end)
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{
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#if defined(__SSE2__)
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for (; begin + 15 < end; begin += 16)
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{
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__m128i bytes = _mm_loadu_si128(reinterpret_cast<const __m128i *>(begin));
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__m128i eq = mm_is_in<symbols...>(bytes);
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uint16_t bit_mask = _mm_movemask_epi8(eq);
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if (bit_mask)
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return begin + __builtin_ctz(bit_mask);
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}
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#endif
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for (; begin < end; ++begin)
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if (is_in<symbols...>(*begin))
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return begin;
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return end;
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}
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template <char... symbols>
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inline const char * find_last_symbols_or_null_sse2(const char * begin, const char * end)
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{
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#if defined(__SSE2__)
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for (; end - 16 >= begin; end -= 16) /// Assuming the pointer cannot overflow. Assuming we can compare these pointers.
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{
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__m128i bytes = _mm_loadu_si128(reinterpret_cast<const __m128i *>(end - 16));
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__m128i eq = mm_is_in<symbols...>(bytes);
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uint16_t bit_mask = _mm_movemask_epi8(eq);
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if (bit_mask)
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return end - 1 - (__builtin_clz(bit_mask) - 16); /// because __builtin_clz works with mask as uint32.
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}
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#endif
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--end;
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for (; end >= begin; --end)
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if (is_in<symbols...>(*end))
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return end;
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return nullptr;
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}
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template <size_t num_chars,
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char c01, char c02 = 0, char c03 = 0, char c04 = 0,
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char c05 = 0, char c06 = 0, char c07 = 0, char c08 = 0,
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char c09 = 0, char c10 = 0, char c11 = 0, char c12 = 0,
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char c13 = 0, char c14 = 0, char c15 = 0, char c16 = 0>
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inline const char * find_first_symbols_sse42_impl(const char * begin, const char * end)
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{
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#if defined(__SSE4_2__)
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#define MODE (_SIDD_UBYTE_OPS | _SIDD_CMP_EQUAL_ANY | _SIDD_LEAST_SIGNIFICANT)
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__m128i set = _mm_setr_epi8(c01, c02, c03, c04, c05, c06, c07, c08, c09, c10, c11, c12, c13, c14, c15, c16);
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for (; begin + 15 < end; begin += 16)
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{
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__m128i bytes = _mm_loadu_si128(reinterpret_cast<const __m128i *>(begin));
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if (_mm_cmpestrc(set, num_chars, bytes, 16, MODE))
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return begin + _mm_cmpestri(set, num_chars, bytes, 16, MODE);
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}
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#undef MODE
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#endif
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for (; begin < end; ++begin)
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if ( (num_chars >= 1 && *begin == c01)
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|| (num_chars >= 2 && *begin == c02)
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|| (num_chars >= 3 && *begin == c03)
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|| (num_chars >= 4 && *begin == c04)
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|| (num_chars >= 5 && *begin == c05)
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|| (num_chars >= 6 && *begin == c06)
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|| (num_chars >= 7 && *begin == c07)
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|| (num_chars >= 8 && *begin == c08)
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|| (num_chars >= 9 && *begin == c09)
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|| (num_chars >= 10 && *begin == c10)
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|| (num_chars >= 11 && *begin == c11)
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|| (num_chars >= 12 && *begin == c12)
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|| (num_chars >= 13 && *begin == c13)
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|| (num_chars >= 14 && *begin == c14)
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|| (num_chars >= 15 && *begin == c15)
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|| (num_chars >= 16 && *begin == c16))
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return begin;
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return end;
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}
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template <char... symbols>
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inline const char * find_first_symbols_sse42(const char * begin, const char * end)
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{
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return find_first_symbols_sse42_impl<sizeof...(symbols), symbols...>(begin, end);
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}
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/// NOTE No SSE 4.2 implementation for find_last_symbols_or_null. Not worth to do.
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template <char... symbols>
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inline const char * find_first_symbols_dispatch(const char * begin, const char * end)
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{
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#if defined(__SSE4_2__)
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if (sizeof...(symbols) >= 5)
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return find_first_symbols_sse42<symbols...>(begin, end);
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else
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#endif
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return find_first_symbols_sse2<symbols...>(begin, end);
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}
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}
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template <char... symbols>
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inline const char * find_first_symbols(const char * begin, const char * end)
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{
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return detail::find_first_symbols_dispatch<symbols...>(begin, end);
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}
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/// Returning non const result for non const arguments.
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/// It is convenient when you are using this function to iterate through non-const buffer.
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template <char... symbols>
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inline char * find_first_symbols(char * begin, char * end)
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{
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return const_cast<char *>(detail::find_first_symbols_dispatch<symbols...>(begin, end));
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}
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template <char... symbols>
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inline const char * find_last_symbols_or_null(const char * begin, const char * end)
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{
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return detail::find_last_symbols_or_null_sse2<symbols...>(begin, end);
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}
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template <char... symbols>
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inline char * find_last_symbols_or_null(char * begin, char * end)
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{
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return const_cast<char *>(detail::find_last_symbols_or_null_sse2<symbols...>(begin, end));
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}
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