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[libc++] Optimize std::find if types are integral and have the same signedness #70345

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Merged
merged 1 commit into from
Dec 23, 2023
Merged

[libc++] Optimize std::find if types are integral and have the same signedness #70345

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19 changes: 19 additions & 0 deletions libcxx/include/__algorithm/find.h
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Original file line number Diff line number Diff line change
Expand Up @@ -21,8 +21,11 @@
#include <__fwd/bit_reference.h>
#include <__iterator/segmented_iterator.h>
#include <__string/constexpr_c_functions.h>
#include <__type_traits/is_integral.h>
#include <__type_traits/is_same.h>
#include <__type_traits/is_signed.h>
#include <__utility/move.h>
#include <limits>

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
# include <cwchar>
Expand Down Expand Up @@ -76,6 +79,22 @@ __find_impl(_Tp* __first, _Tp* __last, const _Up& __value, _Proj&) {
}
#endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS

// TODO: This should also be possible to get right with different signedness
// cast integral types to allow vectorization
template <class _Tp,
class _Up,
class _Proj,
__enable_if_t<__is_identity<_Proj>::value && !__libcpp_is_trivially_equality_comparable<_Tp, _Up>::value &&
is_integral<_Tp>::value && is_integral<_Up>::value &&
is_signed<_Tp>::value == is_signed<_Up>::value,
int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp*
__find_impl(_Tp* __first, _Tp* __last, const _Up& __value, _Proj& __proj) {
if (__value < numeric_limits<_Tp>::min() || __value > numeric_limits<_Tp>::max())
return __last;
return std::__find_impl(__first, __last, _Tp(__value), __proj);
}

// __bit_iterator implementation
template <bool _ToFind, class _Cp, bool _IsConst>
_LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, _IsConst>
Expand Down
42 changes: 42 additions & 0 deletions libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
//
//===----------------------------------------------------------------------===//

// ADDITIONAL_COMPILE_FLAGS(gcc): -Wno-bool-compare
// ADDITIONAL_COMPILE_FLAGS(gcc-style-warnings): -Wno-sign-compare
// MSVC warning C4389: '==': signed/unsigned mismatch
// ADDITIONAL_COMPILE_FLAGS(cl-style-warnings): /wd4389
Expand Down Expand Up @@ -162,6 +163,45 @@ void test_deque() {
}
}

template <class T>
struct TestIntegerPromotions1 {
template <class U>
TEST_CONSTEXPR_CXX20 void test(T val, U to_find) {
bool expect_match = val == to_find;
assert(std::find(&val, &val + 1, to_find) == (expect_match ? &val : &val + 1));
}

template <class U>
TEST_CONSTEXPR_CXX20 void operator()() {
test<U>(0, 0);
test<U>(0, 1);
test<U>(1, 1);
test<U>(0, -1);
test<U>(-1, -1);
test<U>(0, U(-127));
test<U>(T(-127), U(-127));
test<U>(T(-128), U(-128));
test<U>(T(-129), U(-129));
test<U>(T(255), U(255));
test<U>(T(256), U(256));
test<U>(T(257), U(257));
test<U>(0, std::numeric_limits<U>::min());
test<U>(T(std::numeric_limits<U>::min()), std::numeric_limits<U>::min());
test<U>(0, std::numeric_limits<U>::min() + 1);
test<U>(T(std::numeric_limits<U>::min() + 1), std::numeric_limits<U>::min() + 1);
test<U>(0, std::numeric_limits<U>::max());
test<U>(T(std::numeric_limits<U>::max()), std::numeric_limits<U>::max());
test<U>(T(std::numeric_limits<U>::max() - 1), std::numeric_limits<U>::max() - 1);
}
};

struct TestIntegerPromotions {
template <class T>
TEST_CONSTEXPR_CXX20 void operator()() {
types::for_each(types::integral_types(), TestIntegerPromotions1<T>());
}
};

TEST_CONSTEXPR_CXX20 bool test() {
types::for_each(types::integer_types(), TestTypes<char>());
types::for_each(types::integer_types(), TestTypes<int>());
Expand All @@ -181,6 +221,8 @@ TEST_CONSTEXPR_CXX20 bool test() {
}
#endif

types::for_each(types::integral_types(), TestIntegerPromotions());

return true;
}

Expand Down