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[libc++] Explicitly convert to masks
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@philnik777
philnik777 committed Sep 13, 2024
1 parent 1c334de commit 7007f4d
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Showing 2 changed files with 51 additions and 31 deletions.
8 changes: 4 additions & 4 deletions libcxx/include/__algorithm/mismatch.h
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,7 @@ __mismatch_vectorized(_Iter __first1, _Iter __last1, _Iter __first2) {
}

for (size_t __i = 0; __i != __unroll_count; ++__i) {
if (auto __cmp_res = __lhs[__i] == __rhs[__i]; !std::__all_of(__cmp_res)) {
if (auto __cmp_res = std::__as_mask(__lhs[__i] == __rhs[__i]); !std::__all_of(__cmp_res)) {
auto __offset = __i * __vec_size + std::__find_first_not_set(__cmp_res);
return {__first1 + __offset, __first2 + __offset};
}
Expand All @@ -89,7 +89,7 @@ __mismatch_vectorized(_Iter __first1, _Iter __last1, _Iter __first2) {

// check the remaining 0-3 vectors
while (static_cast<size_t>(__last1 - __first1) >= __vec_size) {
if (auto __cmp_res = std::__load_vector<__vec>(__first1) == std::__load_vector<__vec>(__first2);
if (auto __cmp_res = std::__as_mask(std::__load_vector<__vec>(__first1) == std::__load_vector<__vec>(__first2));
!std::__all_of(__cmp_res)) {
auto __offset = std::__find_first_not_set(__cmp_res);
return {__first1 + __offset, __first2 + __offset};
Expand All @@ -106,8 +106,8 @@ __mismatch_vectorized(_Iter __first1, _Iter __last1, _Iter __first2) {
if (static_cast<size_t>(__first1 - __orig_first1) >= __vec_size) {
__first1 = __last1 - __vec_size;
__first2 = __last2 - __vec_size;
auto __offset =
std::__find_first_not_set(std::__load_vector<__vec>(__first1) == std::__load_vector<__vec>(__first2));
auto __offset = std::__find_first_not_set(
std::__as_mask(std::__load_vector<__vec>(__first1) == std::__load_vector<__vec>(__first2)));
return {__first1 + __offset, __first2 + __offset};
} // else loop over the elements individually
}
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74 changes: 47 additions & 27 deletions libcxx/include/__algorithm/simd_utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -116,42 +116,62 @@ _LIBCPP_NODISCARD _LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _VecT __load_vecto
}(make_index_sequence<__simd_vector_size_v<_VecT>>{});
}

template <class _Tp, size_t _Np>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI bool __all_of(__simd_vector<_Tp, _Np> __vec) noexcept {
return __builtin_reduce_and(__builtin_convertvector(__vec, __simd_vector<bool, _Np>));
template <size_t _Np>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI bool __all_of(__simd_vector<bool, _Np> __vec) noexcept {
return __builtin_reduce_and(__vec);
}

template <class _Tp, size_t _Np>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI size_t __find_first_set(__simd_vector<_Tp, _Np> __vec) noexcept {
using __mask_vec = __simd_vector<bool, _Np>;
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI auto __as_mask(__simd_vector<_Tp, _Np> __vec) noexcept {
static_assert(!is_same<_Tp, bool>::value, "vector type should not be a bool!");
return __builtin_convertvector(__vec, __simd_vector<bool, _Np>);
}

// This has MSan disabled du to https://github.com/llvm/llvm-project/issues/85876
auto __impl = [&]<class _MaskT>(_MaskT) _LIBCPP_NO_SANITIZE("memory") noexcept {
# if defined(_LIBCPP_BIG_ENDIAN)
return std::min<size_t>(
_Np, std::__countl_zero(__builtin_bit_cast(_MaskT, __builtin_convertvector(__vec, __mask_vec))));
# else
return std::min<size_t>(
_Np, std::__countr_zero(__builtin_bit_cast(_MaskT, __builtin_convertvector(__vec, __mask_vec))));
# endif
};

if constexpr (sizeof(__mask_vec) == sizeof(uint8_t)) {
return __impl(uint8_t{});
} else if constexpr (sizeof(__mask_vec) == sizeof(uint16_t)) {
return __impl(uint16_t{});
} else if constexpr (sizeof(__mask_vec) == sizeof(uint32_t)) {
return __impl(uint32_t{});
} else if constexpr (sizeof(__mask_vec) == sizeof(uint64_t)) {
return __impl(uint64_t{});
// This uses __builtin_convertvector around the __builtin_shufflevector to work around #107981.
template <size_t _Np>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI __simd_vector<bool, 8>
__extend_vector(__simd_vector<bool, _Np> __vec) noexcept {
using _VecT = __simd_vector<bool, _Np>;
if constexpr (_Np == 4) {
return __builtin_convertvector(
__builtin_shufflevector(__vec, _VecT{}, 0, 1, 2, 3, 4, 5, 6, 7), __simd_vector<bool, 8>);
} else if constexpr (_Np == 2) {
return std::__extend_vector(
__builtin_convertvector(__builtin_shufflevector(__vec, _VecT{}, 0, 1, 2, 3), __simd_vector<bool, 4>));
} else {
static_assert(sizeof(__mask_vec) == 0, "unexpected required size for mask integer type");
static_assert(sizeof(_VecT) == 0, "Unexpected vector size");
}
}

template <size_t _Np>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI auto __to_int_mask(__simd_vector<bool, _Np> __vec) {
if constexpr (_Np < 8) {
return std::__bit_cast<uint8_t>(std::__extend_vector(__vec));
} else if constexpr (_Np == 8) {
return std::__bit_cast<uint8_t>(__vec);
} else if constexpr (_Np == 16) {
return std::__bit_cast<uint16_t>(__vec);
} else if constexpr (_Np == 32) {
return std::__bit_cast<uint32_t>(__vec);
} else if constexpr (_Np == 64) {
return std::__bit_cast<uint64_t>(__vec);
} else {
static_assert(sizeof(__simd_vector<bool, _Np>) == 0, "Unexpected vector size");
return 0;
}
}

template <class _Tp, size_t _Np>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI size_t __find_first_not_set(__simd_vector<_Tp, _Np> __vec) noexcept {
template <size_t _Np>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI size_t __find_first_set(__simd_vector<bool, _Np> __vec) noexcept {
# if defined(_LIBCPP_BIG_ENDIAN)
return std::min<size_t>(_Np, std::__countl_zero(std::__to_int_mask(__vec)));
# else
return std::min<size_t>(_Np, std::__countr_zero(std::__to_int_mask(__vec)));
# endif
}

template <size_t _Np>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI size_t __find_first_not_set(__simd_vector<bool, _Np> __vec) noexcept {
return std::__find_first_set(~__vec);
}

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