[libc++] Remove not needed call to __is_long()

The string is known to be long since __grow_by unconditionally calls
__set_long_cap().

Differential Revision: https://reviews.llvm.org/D113910

diff --git a/libcxx/include/string b/libcxx/include/string
index 53b4e09..5d8473b 100644 (file)
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -2658,7 +2658,7 @@ basic_string<_CharT, _Traits, _Allocator>::push_back(value_type __c)
     if (__sz == __cap)
     {
         __grow_by(__cap, 1, __sz, __sz, 0);
-        __is_short = !__is_long();
+        __is_short = false;
     }
     pointer __p;
     if (__is_short)