From db8666322374d523784200a9c2288e5d82b8e865 Mon Sep 17 00:00:00 2001
From: Howard Hinnant <hhinnant@apple.com>
Date: Wed, 27 Jul 2011 23:19:59 +0000
Subject: [PATCH] Optimizing valarray::operator=(some-valarray-expression)

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@136291 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/valarray | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/valarray b/include/valarray
index 40c1fe120..d7a173cf6 100644
--- a/include/valarray
+++ b/include/valarray
@@ -817,6 +817,8 @@ public:
     valarray& operator=(const gslice_array<value_type>& __ga);
     valarray& operator=(const mask_array<value_type>& __ma);
     valarray& operator=(const indirect_array<value_type>& __ia);
+    template <class _ValExpr>
+        valarray& operator=(const __val_expr<_ValExpr>& __v);
 
     // element access:
     _LIBCPP_INLINE_VISIBILITY
@@ -2958,6 +2960,21 @@ valarray<_Tp>::operator=(const indirect_array<value_type>& __ia)
     return *this;
 }
 
+template <class _Tp>
+template <class _ValExpr>
+inline _LIBCPP_INLINE_VISIBILITY
+valarray<_Tp>&
+valarray<_Tp>::operator=(const __val_expr<_ValExpr>& __v)
+{
+    size_t __n = __v.size();
+    if (size() != __n)
+        resize(__n);
+    value_type* __t = __begin_;
+    for (size_t __i = 0; __i != __n; ++__t, ++__i)
+        *__t = result_type(__v[__i]);
+    return *this;
+}
+
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 __val_expr<__slice_expr<const valarray<_Tp>&> >