Conditionalize ASan variables

Variables used only by ASan helper functions are conditionalized (put behind `#ifndef _LIBCPP_HAS_NO_ASAN`) after that commit.
That should remove any impact on performance.

Author: Advenam Tacet

libcxx/include/string

@@ -1368,7 +1368,9 @@ public:
   _LIBCPP_HIDE_FROM_ABI constexpr void __move_assign(basic_string&& __str, size_type __pos, size_type __len) {
     // Pilfer the allocation from __str.
     _LIBCPP_ASSERT_INTERNAL(__alloc() == __str.__alloc(), "__move_assign called with wrong allocator");
+#ifndef __LIBCPP_HAS_NO_ASAN
     size_type __old_sz = __str.size();
+#endif
     _LIBCPP_IF_ASAN() {
       if (!__str.__is_long())
         __str.__annotate_delete();
@@ -1382,11 +1384,13 @@ public:
     _Traits::assign(data()[__len], value_type());
 
     _LIBCPP_IF_ASAN() {
+#ifndef __LIBCPP_HAS_NO_ASAN
       if (!__is_long()) {
         __annotate_new(__len);
       } else if (__old_sz > __len) {
         __annotate_shrink(__old_sz);
       }
+#endif
     }
   }
 #endif
@@ -2091,35 +2095,43 @@ private:
 
   // Assigns the value in __s, guaranteed to be __n < __min_cap in length.
   inline _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& __assign_short(const value_type* __s, size_type __n) {
+#ifndef __LIBCPP_HAS_NO_ASAN
     size_type __old_size = size();
     _LIBCPP_IF_ASAN() {
       if (__n > __old_size)
         __annotate_increase(__n - __old_size);
     }
+#endif
     pointer __p =
         __is_long() ? (__set_long_size(__n), __get_long_pointer()) : (__set_short_size(__n), __get_short_pointer());
     traits_type::move(std::__to_address(__p), __s, __n);
     traits_type::assign(__p[__n], value_type());
+#ifndef __LIBCPP_HAS_NO_ASAN
     _LIBCPP_IF_ASAN() {
       if (__old_size > __n)
         __annotate_shrink(__old_size);
     }
+#endif
     return *this;
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string&
   __null_terminate_at(value_type* __p, size_type __newsz) {
+#ifndef __LIBCPP_HAS_NO_ASAN
     size_type __old_size = size();
     _LIBCPP_IF_ASAN() {
       if (__newsz > __old_size)
         __annotate_increase(__newsz - __old_size);
     }
+#endif
     __set_size(__newsz);
     traits_type::assign(__p[__newsz], value_type());
+#ifndef __LIBCPP_HAS_NO_ASAN
     _LIBCPP_IF_ASAN() {
       if (__old_size > __newsz)
         __annotate_shrink(__old_size);
     }
+#endif
     return *this;
   }
 
@@ -2463,19 +2475,23 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_NOINLINE basic_string<_CharT, _Traits, _Al
 basic_string<_CharT, _Traits, _Allocator>::__assign_no_alias(const value_type* __s, size_type __n) {
   size_type __cap = __is_short ? static_cast<size_type>(__min_cap) : __get_long_cap();
   if (__n < __cap) {
+#ifndef __LIBCPP_HAS_NO_ASAN
     size_type __old_size = __is_short ? __get_short_size() : __get_long_size();
     _LIBCPP_IF_ASAN() {
       if (__n > __old_size)
         __annotate_increase(__n - __old_size);
     }
+#endif
     pointer __p = __is_short ? __get_short_pointer() : __get_long_pointer();
     __is_short ? __set_short_size(__n) : __set_long_size(__n);
     traits_type::copy(std::__to_address(__p), __s, __n);
     traits_type::assign(__p[__n], value_type());
+#ifndef __LIBCPP_HAS_NO_ASAN
     _LIBCPP_IF_ASAN() {
       if (__old_size > __n)
         __annotate_shrink(__old_size);
     }
+#endif
   } else {
     size_type __sz = __is_short ? __get_short_size() : __get_long_size();
     __grow_by_and_replace(__cap - 1, __n - __cap + 1, __sz, 0, __sz, __n, __s);
@@ -2488,10 +2504,9 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_NOINLINE basic_string<_CharT, _Traits, _Al
 basic_string<_CharT, _Traits, _Allocator>::__assign_external(const value_type* __s, size_type __n) {
   size_type __cap = capacity();
   if (__cap >= __n) {
-    size_type __old_size = size();
     _LIBCPP_IF_ASAN() {
-      if (__n > __old_size)
-        __annotate_increase(__n - __old_size);
+      if (__n > size())
+        __annotate_increase(__n - size());
     }
     value_type* __p = std::__to_address(__get_pointer());
     traits_type::move(__p, __s, __n);
@@ -2514,14 +2529,13 @@ template <class _CharT, class _Traits, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::assign(size_type __n, value_type __c) {
   size_type __cap      = capacity();
-  size_type __old_size = size();
   if (__cap < __n) {
     size_type __sz = size();
     __grow_by_without_replace(__cap, __n - __cap, __sz, 0, __sz);
     _LIBCPP_IF_ASAN() { __annotate_increase(__n); }
   } else _LIBCPP_IF_ASAN() {
-      if (__n > __old_size)
-        __annotate_increase(__n - __old_size);
+      if (__n > size())
+        __annotate_increase(__n - size());
     }
   value_type* __p = std::__to_address(__get_pointer());
   traits_type::assign(__p, __n, __c);
@@ -2532,11 +2546,13 @@ template <class _CharT, class _Traits, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::operator=(value_type __c) {
   pointer __p;
+#ifndef _LIBCPP_HAS_NO_ASAN
   size_type __old_size = size();
   _LIBCPP_IF_ASAN() {
     if (__old_size == 0)
       __annotate_increase(1);
   }
+#endif
   if (__is_long()) {
     __p = __get_long_pointer();
     __set_long_size(1);
@@ -2546,10 +2562,12 @@ basic_string<_CharT, _Traits, _Allocator>::operator=(value_type __c) {
   }
   traits_type::assign(*__p, __c);
   traits_type::assign(*++__p, value_type());
+#ifndef _LIBCPP_HAS_NO_ASAN
   _LIBCPP_IF_ASAN() {
     if (__old_size > 1)
       __annotate_shrink(__old_size);
   }
+#endif
   return *this;
 }
 
@@ -2560,16 +2578,20 @@ basic_string<_CharT, _Traits, _Allocator>::operator=(const basic_string& __str)
     __copy_assign_alloc(__str);
     if (!__is_long()) {
       if (!__str.__is_long()) {
+#ifndef _LIBCPP_HAS_NO_ASAN
         size_type __old_size = __get_short_size();
+#endif
         _LIBCPP_IF_ASAN() {
           if (__get_short_size() < __str.__get_short_size())
             __annotate_increase(__str.__get_short_size() - __get_short_size());
         }
         __r_.first() = __str.__r_.first();
+#ifndef _LIBCPP_HAS_NO_ASAN
         _LIBCPP_IF_ASAN() {
           if (__old_size > __get_short_size())
             __annotate_shrink(__old_size);
         }
+#endif
       } else {
         return __assign_no_alias<true>(__str.data(), __str.size());
       }
@@ -2612,13 +2634,16 @@ basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, tr
     }
 #  endif
   }
+#ifndef _LIBCPP_HAS_NO_ASAN
   size_type __str_old_size = __str.size();
+#endif
   bool __str_was_short     = !__str.__is_long();
 
   __move_assign_alloc(__str);
   __r_.first() = __str.__r_.first();
   __str.__set_short_size(0);
   traits_type::assign(__str.__get_short_pointer()[0], value_type());
+#ifndef _LIBCPP_HAS_NO_ASAN
   _LIBCPP_IF_ASAN() {
     if (__str_was_short && this != &__str)
       __str.__annotate_shrink(__str_old_size);
@@ -2638,6 +2663,7 @@ basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, tr
       // If it is long string, delete was never called on original __str's buffer.
       __annotate_new(__get_short_size());
   }
+#endif
 }
 
 #endif
@@ -2678,8 +2704,9 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void
 basic_string<_CharT, _Traits, _Allocator>::__assign_trivial(_Iterator __first, _Sentinel __last, size_type __n) {
   _LIBCPP_ASSERT_INTERNAL(
       __string_is_trivial_iterator<_Iterator>::value, "The iterator type given to `__assign_trivial` must be trivial");
-
+#ifndef _LIBCPP_HAS_NO_ASAN
   size_type __old_size = size();
+#endif
   size_type __cap      = capacity();
   if (__cap < __n) {
     // Unlike `append` functions, if the input range points into the string itself, there is no case that the input
@@ -2692,18 +2719,20 @@ basic_string<_CharT, _Traits, _Allocator>::__assign_trivial(_Iterator __first, _
     __grow_by_without_replace(__cap, __n - __cap, __sz, 0, __sz);
     _LIBCPP_IF_ASAN() { __annotate_increase(__n); }
   } else _LIBCPP_IF_ASAN() {
-    if (__n > __old_size)
-      __annotate_increase(__n - __old_size);
+    if (__n > size())
+      __annotate_increase(__n - size());
   }
   pointer __p = __get_pointer();
   for (; __first != __last; ++__p, (void)++__first)
     traits_type::assign(*__p, *__first);
   traits_type::assign(*__p, value_type());
   __set_size(__n);
+#ifndef _LIBCPP_HAS_NO_ASAN
   _LIBCPP_IF_ASAN() {
     if (__n < __old_size)
       __annotate_shrink(__old_size);
   }
+#endif
 }
 
 template <class _CharT, class _Traits, class _Allocator>
@@ -3208,15 +3237,19 @@ inline _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocat
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocator>::clear() _NOEXCEPT {
+#ifndef _LIBCPP_HAS_NO_ASAN
   size_type __old_size = size();
+#endif
   if (__is_long()) {
     traits_type::assign(*__get_long_pointer(), value_type());
     __set_long_size(0);
   } else {
     traits_type::assign(*__get_short_pointer(), value_type());
     __set_short_size(0);
   }
+#ifndef _LIBCPP_HAS_NO_ASAN
   _LIBCPP_IF_ASAN() { __annotate_shrink(__old_size); }
+#endif
 }
 
 template <class _CharT, class _Traits, class _Allocator>