Remove unnecessary if condition and comment

Author: winner245

libcxx/include/__vector/vector_bool.h

@@ -561,7 +561,7 @@ vector<bool, _Allocator>::__construct_at_end(size_type __n, bool __x) {
       capacity() >= size() + __n, "vector<bool>::__construct_at_end called with insufficient capacity");
   std::fill_n(end(), __n, __x);
   this->__size_ += __n;
-  if (end().__ctz_ != 0) // has uninitialized trailing bits in the last word
+  if (end().__ctz_ != 0) // Ensure uninitialized leading bits in the last word are set to zero
     std::fill_n(end(), __bits_per_word - end().__ctz_, 0);
 }
 
@@ -573,7 +573,7 @@ vector<bool, _Allocator>::__construct_at_end(_InputIterator __first, _Sentinel _
       capacity() >= size() + __n, "vector<bool>::__construct_at_end called with insufficient capacity");
   std::__copy(std::move(__first), std::move(__last), end());
   this->__size_ += __n;
-  if (end().__ctz_ != 0) // has uninitialized trailing bits in the last word
+  if (end().__ctz_ != 0) // Ensure uninitialized leading bits in the last word are set to zero
     std::fill_n(end(), __bits_per_word - end().__ctz_, 0);
 }
 
@@ -848,9 +848,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void vector<bool, _Allocator>::reserve(size_type _
       this->__throw_length_error();
     vector __v(this->get_allocator());
     __v.__vallocate(__n);
-    // Ensure that the call to __construct_at_end(first, last, n) meets the precondition of n > 0
-    if (this->size() > 0)
-      __v.__construct_at_end(this->begin(), this->end(), this->size());
+    __v.__construct_at_end(this->begin(), this->end(), this->size());
     swap(__v);
   }
 }