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Differential D70621

Add __default_init_tag to basic_string constructors
ClosedPublic

Authored by mvels on Nov 22 2019, 2:58 PM.

Details

Reviewers
mclow.lists
EricWF
Group Reviewers
Restricted Project
Summary

This removes unneeded zero initialization of string data.

For example, given the below code:

void Init(void *mem) {

new (mem) std::string("Hello World");

}

Assembly before:

Init(void*):

xorps   xmm0, xmm0
movups  xmmword ptr [rdi], xmm0
mov     qword ptr [rdi + 16], 0
mov     byte ptr [rdi], 22
movabs  rax, 8022916924116329800
mov     qword ptr [rdi + 1], rax
mov     dword ptr [rdi + 8], 1684828783
mov     byte ptr [rdi + 12], 0
ret

Assembly after:

Init():

mov     byte ptr [rdi], 22
movabs  rax, 8022916924116329800
mov     qword ptr [rdi + 1], rax
mov     dword ptr [rdi + 8], 1684828783
mov     byte ptr [rdi + 12], 0
ret

Diff Detail

Event Timeline

mvels created this revision.Nov 22 2019, 2:58 PM
Herald added a project: Restricted Project. · View Herald TranscriptNov 22 2019, 2:58 PM
Herald added subscribers: libcxx-commits, christof. · View Herald Transcript
Harbormaster completed remote builds in B41397: Diff 230730.Nov 22 2019, 3:01 PM
Herald added a reviewer: mclow.lists. · View Herald TranscriptNov 22 2019, 3:01 PM
mvels added a reviewer: EricWF.Nov 25 2019, 7:02 AM
mvels added a parent revision: D70617: Add default initialization to compressed_pair..Nov 25 2019, 7:10 AM
mvels added a comment.Dec 4 2019, 2:41 PM

Friendly ping

EricWF accepted this revision.Dec 12 2019, 11:45 AM
This revision is now accepted and ready to land.Dec 12 2019, 11:45 AM
EricWF closed this revision.Dec 16 2019, 4:04 PM

Committed as a53534a9f6404d1727fd6e9b13b6dc3089523e10.

nick added a subscriber: nick.Jun 14 2021, 2:42 PM

This change introduced an MSAN error https://bugs.llvm.org/show_bug.cgi?id=50112

Herald added a reviewer: Restricted Project. · View Herald TranscriptJun 14 2021, 2:42 PM

Revision Contents

PathSize
libcxx/
include/
34 lines

Diff 230730

libcxx/include/string

Show First 20 Lines • Show All 808 Lines • ▼ Show 20 Lines
#endif #endif
_LIBCPP_INLINE_VISIBILITY _LIBCPP_INLINE_VISIBILITY
basic_string(basic_string&& __str, const allocator_type& __a); basic_string(basic_string&& __str, const allocator_type& __a);
#endif // _LIBCPP_CXX03_LANG #endif // _LIBCPP_CXX03_LANG
template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type> template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_INLINE_VISIBILITY
basic_string(const _CharT* __s) { basic_string(const _CharT* __s) : __r_(__default_init_tag()) {
_LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr"); _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr");
__init(__s, traits_type::length(__s)); __init(__s, traits_type::length(__s));
# if _LIBCPP_DEBUG_LEVEL >= 2 # if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
# endif # endif
} }
template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type> template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
▲ Show 20 Lines • Show All 890 Lines • ▼ Show 20 Lines#if _LIBCPP_DEBUG_LEVEL >= 2
} }
#endif // _LIBCPP_DEBUG_LEVEL >= 2 #endif // _LIBCPP_DEBUG_LEVEL >= 2
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string() basic_string<_CharT, _Traits, _Allocator>::basic_string()
_NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value) _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
: __r_(__default_init_tag())
{ {
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
__zero(); __zero();
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __a) basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __a)
#if _LIBCPP_STD_VER <= 14 #if _LIBCPP_STD_VER <= 14
_NOEXCEPT_(is_nothrow_copy_constructible<allocator_type>::value) _NOEXCEPT_(is_nothrow_copy_constructible<allocator_type>::value)
#else #else
_NOEXCEPT _NOEXCEPT
#endif #endif
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
__zero(); __zero();
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
▲ Show 20 Lines • Show All 43 Lines • ▼ Show 20 Linesbasic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s, size_type __sz)
} }
traits_type::copy(_VSTD::__to_address(__p), __s, __sz); traits_type::copy(_VSTD::__to_address(__p), __s, __sz);
traits_type::assign(__p[__sz], value_type()); traits_type::assign(__p[__sz], value_type());
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
template <class> template <class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const _Allocator& __a) basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const _Allocator& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
_LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr"); _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
__init(__s, traits_type::length(__s)); __init(__s, traits_type::length(__s));
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n) basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n)
: __r_(__default_init_tag())
{ {
_LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr"); _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr");
__init(__s, __n); __init(__s, __n);
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n, const _Allocator& __a) basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n, const _Allocator& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
_LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n, allocator) detected nullptr"); _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n, allocator) detected nullptr");
__init(__s, __n); __init(__s, __n);
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str) basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str)
: __r_(__second_tag(), __alloc_traits::select_on_container_copy_construction(__str.__alloc())) : __r_(__default_init_tag(), __alloc_traits::select_on_container_copy_construction(__str.__alloc()))
{ {
if (!__str.__is_long()) if (!__str.__is_long())
__r_.first().__r = __str.__r_.first().__r; __r_.first().__r = __str.__r_.first().__r;
else else
__init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size()); __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string( basic_string<_CharT, _Traits, _Allocator>::basic_string(
const basic_string& __str, const allocator_type& __a) const basic_string& __str, const allocator_type& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
if (!__str.__is_long()) if (!__str.__is_long())
__r_.first().__r = __str.__r_.first().__r; __r_.first().__r = __str.__r_.first().__r;
else else
__init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size()); __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
Show All 17 Lines#if _LIBCPP_DEBUG_LEVEL >= 2
if (__is_long()) if (__is_long())
__get_db()->swap(this, &__str); __get_db()->swap(this, &__str);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, const allocator_type& __a) basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, const allocator_type& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
if (__str.__is_long() && __a != __str.__alloc()) // copy, not move if (__str.__is_long() && __a != __str.__alloc()) // copy, not move
__init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size()); __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
else else
{ {
__r_.first().__r = __str.__r_.first().__r; __r_.first().__r = __str.__r_.first().__r;
__str.__zero(); __str.__zero();
} }
Show All 28 Linesbasic_string<_CharT, _Traits, _Allocator>::__init(size_type __n, value_type __c)
} }
traits_type::assign(_VSTD::__to_address(__p), __n, __c); traits_type::assign(_VSTD::__to_address(__p), __n, __c);
traits_type::assign(__p[__n], value_type()); traits_type::assign(__p[__n], value_type());
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c) basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c)
: __r_(__default_init_tag())
{ {
__init(__n, __c); __init(__n, __c);
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
template <class> template <class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c, const _Allocator& __a) basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c, const _Allocator& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
__init(__n, __c); __init(__n, __c);
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str,
size_type __pos, size_type __n, size_type __pos, size_type __n,
const _Allocator& __a) const _Allocator& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
size_type __str_sz = __str.size(); size_type __str_sz = __str.size();
if (__pos > __str_sz) if (__pos > __str_sz)
this->__throw_out_of_range(); this->__throw_out_of_range();
__init(__str.data() + __pos, _VSTD::min(__n, __str_sz - __pos)); __init(__str.data() + __pos, _VSTD::min(__n, __str_sz - __pos));
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos, basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos,
const _Allocator& __a) const _Allocator& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
size_type __str_sz = __str.size(); size_type __str_sz = __str.size();
if (__pos > __str_sz) if (__pos > __str_sz)
this->__throw_out_of_range(); this->__throw_out_of_range();
__init(__str.data() + __pos, __str_sz - __pos); __init(__str.data() + __pos, __str_sz - __pos);
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
template <class _Tp, class> template <class _Tp, class>
basic_string<_CharT, _Traits, _Allocator>::basic_string( basic_string<_CharT, _Traits, _Allocator>::basic_string(
const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a) const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
__self_view __sv0 = __t; __self_view __sv0 = __t;
__self_view __sv = __sv0.substr(__pos, __n); __self_view __sv = __sv0.substr(__pos, __n);
__init(__sv.data(), __sv.size()); __init(__sv.data(), __sv.size());
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
template <class _Tp, class> template <class _Tp, class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t) basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t)
: __r_(__default_init_tag())
{ {
__self_view __sv = __t; __self_view __sv = __t;
__init(__sv.data(), __sv.size()); __init(__sv.data(), __sv.size());
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
template <class _Tp, class> template <class _Tp, class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t, const _Allocator& __a) basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t, const _Allocator& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
__self_view __sv = __t; __self_view __sv = __t;
__init(__sv.data(), __sv.size()); __init(__sv.data(), __sv.size());
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
▲ Show 20 Lines • Show All 54 Lines • ▼ Show 20 Lines for (; __first != __last; ++__first, (void) ++__p)
traits_type::assign(*__p, *__first); traits_type::assign(*__p, *__first);
traits_type::assign(*__p, value_type()); traits_type::assign(*__p, value_type());
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator, class> template<class _InputIterator, class>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last) basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last)
: __r_(__default_init_tag())
{ {
__init(__first, __last); __init(__first, __last);
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator, class> template<class _InputIterator, class>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last, basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last,
const allocator_type& __a) const allocator_type& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
__init(__first, __last); __init(__first, __last);
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
#ifndef _LIBCPP_CXX03_LANG #ifndef _LIBCPP_CXX03_LANG
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string( basic_string<_CharT, _Traits, _Allocator>::basic_string(
initializer_list<_CharT> __il) initializer_list<_CharT> __il)
: __r_(__default_init_tag())
{ {
__init(__il.begin(), __il.end()); __init(__il.begin(), __il.end());
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
template <class _CharT, class _Traits, class _Allocator> template <class _CharT, class _Traits, class _Allocator>
inline inline
basic_string<_CharT, _Traits, _Allocator>::basic_string( basic_string<_CharT, _Traits, _Allocator>::basic_string(
initializer_list<_CharT> __il, const _Allocator& __a) initializer_list<_CharT> __il, const _Allocator& __a)
: __r_(__second_tag(), __a) : __r_(__default_init_tag(), __a)
{ {
__init(__il.begin(), __il.end()); __init(__il.begin(), __il.end());
#if _LIBCPP_DEBUG_LEVEL >= 2 #if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this); __get_db()->__insert_c(this);
#endif #endif
} }
#endif // _LIBCPP_CXX03_LANG #endif // _LIBCPP_CXX03_LANG
▲ Show 20 Lines • Show All 2,246 Lines • Show Last 20 Lines