Fix std::__rotl and std::__rotr

2018-07-04  Jonathan Wakely  <jwakely@redhat.com>
	    Jakub Jelinek  <jakub@redhat.com>

	* include/std/bit (__rotl, __rotr): Fix for non-power of two sizes.

Co-Authored-By: Jakub Jelinek <jakub@redhat.com>

From-SVN: r262414

libstdc++-v3/ChangeLog

 2018-07-04  Jonathan Wakely  <jwakely@redhat.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	* include/std/bit (__rotl, __rotr): Fix for non-power of two sizes.
+
+2018-07-04  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/86398
 	* include/std/type_traits (is_trivially_constructible): Check

libstdc++-v3/include/std/bit

@@ -46,7 +46,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       constexpr auto _Nd = numeric_limits<_Tp>::digits;
       const unsigned __sN = __s % _Nd;
-      return (__x << __sN) | (__x >> ((-__sN) % _Nd));
+      return (__x << __sN) | (__x >> ((_Nd - __sN) % _Nd));
     }
 
   template<typename _Tp>
@@ -55,7 +55,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       constexpr auto _Nd = numeric_limits<_Tp>::digits;
       const unsigned __sN = __s % _Nd;
-      return (__x >> __sN) | (__x << ((-__sN) % _Nd));
+      return (__x >> __sN) | (__x << ((_Nd - __sN) % _Nd));
     }
 
   template<typename _Tp>