[libc++] Remove zero size branch from memmove

philnik777 · philnik777 · commit 2bc86be3decc · 2025-08-27T09:09:23.000+02:00
diff --git a/libcxx/include/__string/constexpr_c_functions.h b/libcxx/include/__string/constexpr_c_functions.h
@@ -22,7 +22,6 @@
 #include <__type_traits/is_equality_comparable.h>
 #include <__type_traits/is_integral.h>
 #include <__type_traits/is_same.h>
-#include <__type_traits/is_trivially_copyable.h>
 #include <__type_traits/is_trivially_lexicographically_comparable.h>
 #include <__type_traits/remove_cv.h>
 #include <__utility/element_count.h>
@@ -225,6 +224,8 @@ __constexpr_memmove(_Tp* __dest, _Up* __src, __element_count __n) {
           std::__assign_trivially_copyable(__dest[__i], __src[__i]);
       }
     }
+  } else if _LIBCPP_CONSTEXPR (sizeof(_Tp) == __datasizeof_v<_Tp>) {
+    ::__builtin_memmove(__dest, __src, __count * sizeof(_Tp));
   } else if (__count > 0) {
     ::__builtin_memmove(__dest, __src, (__count - 1) * sizeof(_Tp) + __datasizeof_v<_Tp>);
   }

Original file line number	Diff line number	Diff line change
`@@ -22,7 +22,6 @@`
`22`	`22`	`#include <__type_traits/is_equality_comparable.h>`
`23`	`23`	`#include <__type_traits/is_integral.h>`
`24`	`24`	`#include <__type_traits/is_same.h>`
`25`		`-#include <__type_traits/is_trivially_copyable.h>`
`26`	`25`	`#include <__type_traits/is_trivially_lexicographically_comparable.h>`
`27`	`26`	`#include <__type_traits/remove_cv.h>`
`28`	`27`	`#include <__utility/element_count.h>`
`@@ -225,6 +224,8 @@ __constexpr_memmove(_Tp* __dest, _Up* __src, __element_count __n) {`
`225`	`224`	`std::__assign_trivially_copyable(__dest[__i], __src[__i]);`
`226`	`225`	`}`
`227`	`226`	`}`
	`227`	`+ } else if _LIBCPP_CONSTEXPR (sizeof(_Tp) == __datasizeof_v<_Tp>) {`
	`228`	`+ ::__builtin_memmove(__dest, __src, __count * sizeof(_Tp));`
`228`	`229`	`} else if (__count > 0) {`
`229`	`230`	`::__builtin_memmove(__dest, __src, (__count - 1) * sizeof(_Tp) + __datasizeof_v<_Tp>);`
`230`	`231`	`}`