[libcxx-commits] [libcxx] a53534a - [libc++] Add __default_init_tag to basic_string constructors
Eric Fiselier via libcxx-commits
libcxx-commits at lists.llvm.org
Mon Dec 16 16:04:29 PST 2019
Author: Eric Fiselier
Date: 2019-12-16T19:04:09-05:00
New Revision: a53534a9f6404d1727fd6e9b13b6dc3089523e10
URL: https://github.com/llvm/llvm-project/commit/a53534a9f6404d1727fd6e9b13b6dc3089523e10
DIFF: https://github.com/llvm/llvm-project/commit/a53534a9f6404d1727fd6e9b13b6dc3089523e10.diff
LOG: [libc++] Add __default_init_tag to basic_string constructors
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
Patch by Martijn Vels (mvels at google.com)
Reviewed as https://reviews.llvm.org/D70621
Added:
Modified:
libcxx/include/string
Removed:
################################################################################
diff --git a/libcxx/include/string b/libcxx/include/string
index 488c07a20cb8..8a0ac844470c 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -814,7 +814,7 @@ public:
template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
_LIBCPP_INLINE_VISIBILITY
- basic_string(const _CharT* __s) {
+ basic_string(const _CharT* __s) : __r_(__default_init_tag(), __default_init_tag()) {
_LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr");
__init(__s, traits_type::length(__s));
# if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1721,6 +1721,7 @@ template <class _CharT, class _Traits, class _Allocator>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string()
_NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
+ : __r_(__default_init_tag(), __default_init_tag())
{
#if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this);
@@ -1736,7 +1737,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __
#else
_NOEXCEPT
#endif
-: __r_(__value_init_tag(), __a)
+: __r_(__default_init_tag(), __a)
{
#if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__insert_c(this);
@@ -1796,7 +1797,7 @@ basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s, size_ty
template <class _CharT, class _Traits, class _Allocator>
template <class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const _Allocator& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
_LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
__init(__s, traits_type::length(__s));
@@ -1808,6 +1809,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const
template <class _CharT, class _Traits, class _Allocator>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n)
+ : __r_(__default_init_tag(), __default_init_tag())
{
_LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr");
__init(__s, __n);
@@ -1819,7 +1821,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_
template <class _CharT, class _Traits, class _Allocator>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n, const _Allocator& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
_LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n, allocator) detected nullptr");
__init(__s, __n);
@@ -1830,7 +1832,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_
template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str)
- : __r_(__value_init_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())
__r_.first().__r = __str.__r_.first().__r;
@@ -1844,7 +1846,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __st
template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(
const basic_string& __str, const allocator_type& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
if (!__str.__is_long())
__r_.first().__r = __str.__r_.first().__r;
@@ -1878,7 +1880,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str)
template <class _CharT, class _Traits, class _Allocator>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, const allocator_type& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
if (__str.__is_long() && __a != __str.__alloc()) // copy, not move
__init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
@@ -1923,6 +1925,7 @@ basic_string<_CharT, _Traits, _Allocator>::__init(size_type __n, value_type __c)
template <class _CharT, class _Traits, class _Allocator>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c)
+ : __r_(__default_init_tag(), __default_init_tag())
{
__init(__n, __c);
#if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1933,7 +1936,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __
template <class _CharT, class _Traits, class _Allocator>
template <class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c, const _Allocator& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
__init(__n, __c);
#if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1945,7 +1948,7 @@ template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str,
size_type __pos, size_type __n,
const _Allocator& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
size_type __str_sz = __str.size();
if (__pos > __str_sz)
@@ -1960,7 +1963,7 @@ template <class _CharT, class _Traits, class _Allocator>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos,
const _Allocator& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
size_type __str_sz = __str.size();
if (__pos > __str_sz)
@@ -1975,7 +1978,7 @@ template <class _CharT, class _Traits, class _Allocator>
template <class _Tp, class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(
const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
__self_view __sv0 = __t;
__self_view __sv = __sv0.substr(__pos, __n);
@@ -1988,6 +1991,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(
template <class _CharT, class _Traits, class _Allocator>
template <class _Tp, class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t)
+ : __r_(__default_init_tag(), __default_init_tag())
{
__self_view __sv = __t;
__init(__sv.data(), __sv.size());
@@ -1999,7 +2003,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t)
template <class _CharT, class _Traits, class _Allocator>
template <class _Tp, class>
basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t, const _Allocator& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
__self_view __sv = __t;
__init(__sv.data(), __sv.size());
@@ -2070,6 +2074,7 @@ template <class _CharT, class _Traits, class _Allocator>
template<class _InputIterator, class>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last)
+ : __r_(__default_init_tag(), __default_init_tag())
{
__init(__first, __last);
#if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2082,7 +2087,7 @@ template<class _InputIterator, class>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last,
const allocator_type& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
__init(__first, __last);
#if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2096,6 +2101,7 @@ template <class _CharT, class _Traits, class _Allocator>
inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(
initializer_list<_CharT> __il)
+ : __r_(__default_init_tag(), __default_init_tag())
{
__init(__il.begin(), __il.end());
#if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2108,7 +2114,7 @@ inline
basic_string<_CharT, _Traits, _Allocator>::basic_string(
initializer_list<_CharT> __il, const _Allocator& __a)
- : __r_(__value_init_tag(), __a)
+ : __r_(__default_init_tag(), __a)
{
__init(__il.begin(), __il.end());
#if _LIBCPP_DEBUG_LEVEL >= 2
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