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Optimize equality comparison for small str with fixed size
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,125 @@ | ||
| // Copyright 2022 PingCAP, Ltd. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
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| #pragma once | ||
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| #include <common/defines.h> | ||
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| #include <cstddef> | ||
| #include <cstdint> | ||
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| namespace mem_utils | ||
| { | ||
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| FLATTEN_INLINE_PURE | ||
| constexpr inline bool memcmp_eq0(const char *, const char *) | ||
| { | ||
| return true; | ||
| } | ||
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| FLATTEN_INLINE_PURE | ||
| inline bool memcmp_eq1(const char * a, const char * b) | ||
| { | ||
| return a[0] == b[0]; | ||
| } | ||
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| FLATTEN_INLINE_PURE | ||
| inline bool memcmp_eq2(const char * a, const char * b) | ||
| { | ||
| const uint16_t ax = *reinterpret_cast<const uint16_t *>(a); | ||
| const uint16_t bx = *reinterpret_cast<const uint16_t *>(b); | ||
| return ax == bx; | ||
| } | ||
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| FLATTEN_INLINE_PURE | ||
| inline bool memcmp_eq3(const char * a, const char * b) | ||
| { | ||
| return memcmp_eq2(a, b) & memcmp_eq2(a + 1, b + 1); | ||
| } | ||
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| FLATTEN_INLINE_PURE | ||
| inline bool memcmp_eq4(const char * a, const char * b) | ||
| { | ||
| const uint32_t ax = *reinterpret_cast<const uint32_t *>(a); | ||
| const uint32_t bx = *reinterpret_cast<const uint32_t *>(b); | ||
| return ax == bx; | ||
| } | ||
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| FLATTEN_INLINE_PURE | ||
| inline bool memcmp_eq8(const char * a, const char * b) | ||
| { | ||
| const uint64_t ax = *reinterpret_cast<const uint64_t *>(a); | ||
| const uint64_t bx = *reinterpret_cast<const uint64_t *>(b); | ||
| return ax == bx; | ||
| } | ||
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| template <size_t k> | ||
| ALWAYS_INLINE inline bool memcmp_eq_fixed_size(const char * a, const char * b) | ||
| { | ||
| #ifdef M | ||
| static_assert(false, "`M` is defined"); | ||
| #else | ||
| #define M(s) \ | ||
| else if constexpr (k == (s)) \ | ||
| { \ | ||
| return memcmp_eq##s(a, b); \ | ||
| } | ||
| #endif | ||
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| static_assert(k >= 0); | ||
| static_assert(k <= 32); | ||
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| if constexpr (k > 16) | ||
| { | ||
| return memcmp_eq_fixed_size<16>(a, b) & memcmp_eq_fixed_size<k - 16>(a + 16, b + 16); | ||
| } | ||
| else if constexpr (k > 8) | ||
| { | ||
| return memcmp_eq8(a, b) & memcmp_eq8(a + k - 8, b + k - 8); | ||
| } | ||
| else if constexpr (k > 4) | ||
| { | ||
| if constexpr (k == 8) | ||
| return memcmp_eq8(a, b); | ||
| else | ||
| return memcmp_eq_fixed_size<4>(a, b) & memcmp_eq_fixed_size<4>(a + k - 4, b + k - 4); | ||
| } | ||
| M(1) | ||
| M(2) | ||
| M(3) | ||
| M(4) | ||
| M(0) | ||
| #undef M | ||
| } | ||
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| /* | ||
| - with cxx flag `-mavx2` | ||
| - memcmp_eq_fixed_size<32>: | ||
| vmovdqu ymm0, ymmword ptr [rdi] | ||
| vpcmpeqq ymm0, ymm0, ymmword ptr [rsi] | ||
| vmovmskpd eax, ymm0 | ||
| cmp al, 15 | ||
| sete al | ||
| vzeroupper | ||
| ret | ||
| - memcmp_eq_fixed_size<16>: | ||
| vmovdqu xmm0, xmmword ptr [rdi] | ||
| vpcmpeqq xmm0, xmm0, xmmword ptr [rsi] | ||
| vmovmskpd eax, xmm0 | ||
| cmp al, 3 | ||
| sete al | ||
| ret | ||
| */ | ||
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| } // namespace mem_utils |