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[libcxx] Allow string to use SSO in constant evaluation. #66576

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Merged
merged 7 commits into from
Oct 10, 2023
Merged

[libcxx] Allow string to use SSO in constant evaluation. #66576

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209a8f9
[libcxx] Allow string to use SSO in constant evaluation.
jyknight Sep 16, 2023
e198d36
Address review comments.
jyknight Sep 18, 2023
cbe9209
Merge remote-tracking branch 'origin/main' into libcxx-sso-string
jyknight Sep 24, 2023
829978b
Add test, address comment, add doc note.
jyknight Sep 25, 2023
9d179b4
Address value_init_tag comment
jyknight Sep 26, 2023
db9f3b8
Tweak test per review comments.
jyknight Oct 6, 2023
98ca35e
Split off wchar bitset::to_string tests to avoid constexpr evaluation…
jyknight Oct 8, 2023
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54 changes: 15 additions & 39 deletions libcxx/include/string
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Original file line number Diff line number Diff line change
Expand Up @@ -830,8 +830,8 @@ private:
{
union
{
__long __l;
__short __s;
__long __l;
__raw __r;
};
};
Expand Down Expand Up @@ -1729,8 +1729,10 @@ private:

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
bool __is_long() const _NOEXCEPT {
if (__libcpp_is_constant_evaluated())
return true;
if (__libcpp_is_constant_evaluated()) {
if (__builtin_constant_p(__r_.first().__l.__is_long_))
return __r_.first().__l.__is_long_;
}
return __r_.first().__s.__is_long_;
}

Expand All @@ -1748,24 +1750,11 @@ private:

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __default_init() {
__r_.first() = __rep();
if (__libcpp_is_constant_evaluated()) {
size_type __sz = __recommend(0) + 1;
pointer __ptr = __alloc_traits::allocate(__alloc(), __sz);
__begin_lifetime(__ptr, __sz);
__set_long_pointer(__ptr);
__set_long_cap(__sz);
__set_long_size(0);
}
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __deallocate_constexpr() {
if (__libcpp_is_constant_evaluated() && __get_pointer() != nullptr)
__alloc_traits::deallocate(__alloc(), __get_pointer(), __get_long_cap());
}

_LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI static bool __fits_in_sso(size_type __sz) {
// SSO is disabled during constant evaluation because `__is_long` isn't constexpr friendly
return !__libcpp_is_constant_evaluated() && (__sz < __min_cap);
return (__sz < __min_cap);
}

template <class _Iterator, class _Sentinel>
Expand Down Expand Up @@ -1877,10 +1866,7 @@ private:
size_type __recommend(size_type __s) _NOEXCEPT
{
if (__s < __min_cap) {
if (__libcpp_is_constant_evaluated())
return static_cast<size_type>(__min_cap);
else
return static_cast<size_type>(__min_cap) - 1;
return static_cast<size_type>(__min_cap) - 1;
}
size_type __guess = __align_it<sizeof(value_type) < __alignment ?
__alignment/sizeof(value_type) : 1 > (__s+1) - 1;
Expand Down Expand Up @@ -1969,7 +1955,8 @@ private:
allocator_type __a = __str.__alloc();
auto __allocation = std::__allocate_at_least(__a, __str.__get_long_cap());
__begin_lifetime(__allocation.ptr, __allocation.count);
__alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
if (__is_long())
__alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
__alloc() = std::move(__a);
__set_long_pointer(__allocation.ptr);
__set_long_cap(__allocation.count);
Expand Down Expand Up @@ -2020,7 +2007,7 @@ private:
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& __assign_external(const value_type* __s, size_type __n);

// Assigns the value in __s, guaranteed to be __n < __min_cap in length.
inline basic_string& __assign_short(const value_type* __s, size_type __n) {
inline _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& __assign_short(const value_type* __s, size_type __n) {
pointer __p = __is_long()
? (__set_long_size(__n), __get_long_pointer())
: (__set_short_size(__n), __get_short_pointer());
Expand Down Expand Up @@ -2334,7 +2321,7 @@ basic_string<_CharT, _Traits, _Allocator>::__grow_by_and_replace
if (__sec_cp_sz != 0)
traits_type::copy(std::__to_address(__p) + __n_copy + __n_add,
std::__to_address(__old_p) + __n_copy + __n_del, __sec_cp_sz);
if (__old_cap+1 != __min_cap || __libcpp_is_constant_evaluated())
if (__old_cap+1 != __min_cap)
__alloc_traits::deallocate(__alloc(), __old_p, __old_cap+1);
__set_long_pointer(__p);
__set_long_cap(__allocation.count);
Expand Down Expand Up @@ -2374,7 +2361,7 @@ basic_string<_CharT, _Traits, _Allocator>::__grow_by(size_type __old_cap, size_t
traits_type::copy(std::__to_address(__p) + __n_copy + __n_add,
std::__to_address(__old_p) + __n_copy + __n_del,
__sec_cp_sz);
if (__libcpp_is_constant_evaluated() || __old_cap + 1 != __min_cap)
if (__old_cap + 1 != __min_cap)
__alloc_traits::deallocate(__alloc(), __old_p, __old_cap + 1);
__set_long_pointer(__p);
__set_long_cap(__allocation.count);
Expand Down Expand Up @@ -2537,12 +2524,8 @@ basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, tr
}
__move_assign_alloc(__str);
__r_.first() = __str.__r_.first();
if (__libcpp_is_constant_evaluated()) {
__str.__default_init();
} else {
__str.__set_short_size(0);
traits_type::assign(__str.__get_short_pointer()[0], value_type());
}
__str.__set_short_size(0);
traits_type::assign(__str.__get_short_pointer()[0], value_type());
}

#endif
Expand Down Expand Up @@ -2828,13 +2811,6 @@ basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, const value_t
if (__pos > __sz)
__throw_out_of_range();
size_type __cap = capacity();
if (__libcpp_is_constant_evaluated()) {
if (__cap - __sz >= __n)
__grow_by_and_replace(__cap, 0, __sz, __pos, 0, __n, __s);
else
__grow_by_and_replace(__cap, __sz + __n - __cap, __sz, __pos, 0, __n, __s);
return *this;
}
if (__cap - __sz >= __n)
{
if (__n)
Expand All @@ -2843,7 +2819,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, const value_t
size_type __n_move = __sz - __pos;
if (__n_move != 0)
{
if (__p + __pos <= __s && __s < __p + __sz)
if (std::__is_pointer_in_range(__p + __pos, __p + __sz, __s))
__s += __n;
traits_type::move(__p + __pos + __n, __p + __pos, __n_move);
}
Expand Down