[PATCH] [libcxx] Optimize vectors uninitialized construction of trivial types from an iterator range.

[Marshall Clow]

================
Comment at: include/vector:1393
@@ -1396,3 +1392,3 @@
 {
-    typename iterator_traits<_ForwardIterator>::difference_type __new_size = _VSTD::distance(__first, __last);
-    if (static_cast<size_type>(__new_size) <= capacity())
+    typename iterator_traits<_ForwardIterator>::difference_type __new_size_diff = _VSTD::distance(__first, __last);
+    size_type __new_size = static_cast<size_type>(__new_size_diff);
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This requires traversing the sequence (in the case of non-RA iterators). Do we really want to do that?  Is it worth having a separate version for RA iterators?

http://reviews.llvm.org/D8109

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